SECONDARY ELECTROCHEMICAL CELL WITH HIGH RATE CAPABILITY

FIELD OF THE INVENTION

[0001] This invention relates to an electrochemical cell, and more

particularly to a secondary electrochemical cell employing a polyanion-based

active material in a first electrode, and a titanium-oxide-based material in a

second counter-electrode.

BACKGROUND OF THE INVENTION

[0002] A battery pack consists of one or more electrochemical cells or

batteries, wherein each cell typically includes a positive electrode, a negative

electrode, and an electrolyte or other material for facilitating movement of ionic

charge carriers between the negative electrode and positive electrode. As the

cell is charged, cations migrate from the positive electrode to the electrolyte

and, concurrently, from the electrolyte to the negative electrode. During

discharge, cations migrate from the negative electrode to the electrolyte and,

concurrently, from the electrolyte to the positive electrode.

SUMMARY OF THE INVENTION

[0003] The present invention provides a novel secondary electrochemical

cell employing a first electrode active material represented by the general

formula:

_{a b c d>}

wherein:

(i) A is selected from the group consisting of elements from Group ! of

the Periodic Table, and mixtures thereof, and 0 ≤ a < 9;

(ii) M includes at least one redox active element, and 0 < b ≤ 4;

(iii) L is selected from the group consisting of X'[O _4- χ Y ¹ J ₁ X'[O _4-y Y' _2y ],

X ¹¹ S ₄ , and mixtures thereof, wherein:

(a) X' and X ¹ " are each independently selected from the group

consisting of P, As, Sb, Si, Ge, V, S, and mixtures thereof;

(b) X" is selected from the group consisting of P, As, Sb, Si, Ge, V ₁

and mixtures thereof;

(c) Y ¹ is selected from the group consisting of halogens selected

from Group 17 of the Periodic Table, S, N, and mixtures thereof;

(d) 0 < x < 3, 0 < y ≤ 2, 0 < z < 1 and 0 < z < 3; and

(iv) Z is selected from the group consisting of a hydroxy! (OH), a

halogen selected from Group 17 of the Periodic Table, and

mixtures thereof, and 0 ≤ e ≤ 4;

wherein A, M, L, Z, a, b, c and d are selected so as to maintain

electroneutraiity of the first electrode active material in its nascent state.

[0004] The secondary electrochemical cell includes an electrode

assembly enclosed in a casing. The electrode assembly includes a separator

interposed between a first electrode (positive electrode) and a counter second

electrode (negative electrode), for electrically insulating the first electrode from

the second electrode. An electrolyte (preferably a non-aqueous electrolyte) is

vi i i w i e ec n

the second electrode during charge and discharge of the electrochemical cell.

[0005] The first and second electrodes each include an electrically

conductive current collector for providing electrical communication between the

electrodes and an external load. An electrode film is formed on at least one

side of each current collector, preferably both sides of the positive electrode

current collector.

[0006] A first electrode plate contacts an exposed portion of the first

electrode current collector in order to provide electrical communication between

the first electrode current collector and an external load. An opposing second

electrode plate contacts an exposed portion of the second electrode current

collector in order to provide electrical communication between the second

electrode current collector and an externa! load.

[0007] The counter-second electrode employs a counter-electrode active

material represented by the genera! formula:

E _f Ti _g D _h Oj _;

wherein:

(i) E is selected from the group consisting of elements from

Group I of the Periodic Table, and mixtures thereof, and 0 < f

< 12;

(ii) 0 < g < 6;

(iii) D is selected from the group consisting of Al, Zr, Mg, Ca, Zn,

Cd, Fe, Mn, Ni, Co, and mixtures thereof, and 0 ≤ h < 2; and

(iv) 2 < i < 12.

, , , , i y

of the second counter-electrode active material in its nascent state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic cross-sectional diagram illustrating the

structure of a non-aqueous electrolyte cylindrical electrochemical cell of the

present invention.

[0009] Figure 2 is a plot of cathode specific capacity vs. cell voltage for a

Li / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell.

[0010] Figure 3 is a plot of cathode specific capacity vs. cell voltage for a

Li / 1 M LiPF ₆ (EC/DMC) / Li ₂ Ti ₃ O ₇ cell.

[0011 ] Figure 4 shows the first cycle EVS results for a LiVPO ₄ F / 1 M LiPF ₆

(EC/DMC) / Li ₂ Ti ₃ O ₇ cell.

[0012] Figure 5 is an EVS differential capacity plot based on Figure 4.

[0013] Figure 6 is a plot of cathode specific capacity vs. cycle number for

LiVPO ₄ F / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cells.

[0014] Figure 7 shows the first cycle EVS results for a LiVPO ₄ F / 1 M LiPF ₆

(EC/DMC) / Li ₄ Ti ₅ O ₁₂ ceil.

[0015] Figure 8 is an EVS differential capacity plot based on Figure 7.

[0016] Figure 9 shows the voltage profile plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell.

[0017] Figure 10 shows the differential capacity plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ ) ₂ F ₃ / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell.

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell.

[0019] Figure 12 shows the differential capacity plot for the fifth cycle EVS

response of a Na ₃ V ₂ (Pθ ₄ ) ₂ F ₃ / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell.

[0020] Figure 13 shows the cycling behavior of the Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M

LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ ceil.

[0021 ] Figure 14 shows the voltage profile plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ CeII.

[0022] Figure 15 shows the differential capacity plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMCJ / Li ₄ Ti ₅ O ₁₂ cell.

[0023] Figure 16 shows the voltage profile plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ CeII.

[0024] Figure 17 shows the differentia! capacity plot for the first cycle EVS

response of a Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ CeII.

[0025] Figure 18 shows the cycling behavior of a first L ₃ V ₂ (PO ₄ J ₃ / 0.13M

LiPF ₆ (EC/DMC/EMCJ / Li ₄ Ti ₅ O ₁₂ CeII.

[0026] Figure 19 shows the cycling behavior of a second L ₃ V ₂ (PO ₄ J ₃ /

0.13M LiPF ₆ (EC/DMC/EMC) / Li ₄ Ti ₅ O ₁₂ CeII.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] It has been found that the novel electrochemical cells of this

invention afford benefits over such materials and devices among those known

in the art. Such benefits include, without limitation, one or more of increased

capacity, enhanced cycling capability, enhanced reversibility, enhanced ionic

_ _ _. u ivi y, con uc ivi y, en an ra e cap i y, an

reduced costs. Specific benefits and embodiments of the present invention are

apparent from the detailed description set forth herein below. It shouid be

understood, however, that the detailed description and specific examples, while

indicating embodiments among those preferred, are intended for purposes of

illustration only and are not intended to limit the scope of the invention.

[0028] Referring to Figure 1 , one embodiment of a secondary

electrochemical cell 10 having a positive electrode active material described

herein below as general formula (1 ), and a negative electrode active material

described herein below as general formula (9), is illustrated. The cell 10

includes a spirally coiled or wound electrode assembly 12 enclosed in a sealed

container, preferably a rigid cylindrical casing 14. The electrode assembly 12

includes; a positive electrode 16 consisting of, among other things, an electrode

active material described herein below; a counter negative electrode 18; and a

separator 20 interposed between the first and second electrodes 16,18. The

separator 20 is preferably an electrically insulating, ionically conductive

microporous film, and composed of a polymeric material selected from the

group consisting of polyethylene, polyethylene oxide, polyacrylonitrile and

polyvinylidene fluoride, polymethyl methacrylate, polysiloxane, copolymers

thereof, and admixtures thereof.

[0029] Each electrode 16,18 includes a current collector 22 and 24,

respectively, for providing electrical communication between the electrodes

16,18 and an external load. Each current collector 22,24 is a foil or grid of an

electrically conductive metal such as iron, copper, aluminum, titanium, nickel,

s a n ess s ee , or e e, av ng a c ness o e ween μm an μm,

preferably 5 μm and 20 μm. In one embodiment, each current collector is a foil

or grid of aluminum.

[0030] Optionally, the current collector may be treated with an oxide-

removing agent such as a mild acid and the like, and coated with an electrically

conductive coating for inhibiting the formation of electrically insulating oxides on

the surface of the current collector 22,24. Examples of suitable coatings

include polymeric materials comprising a homogenously dispersed electrically

conductive material (e.g. carbon), such polymeric materials including: acrylics

including acrylic acid and methacrylic acids and esters, including poly

(ethylene-coacrylic acid); vinylic materials including polyvinyl acetate) and

poly(vinylidene fiuoride-co-hexafluoropropylene); polyesters including

poly(adipic acid-coethylene glycol); poiyurethanes; fluoroelastomers; and

mixtures thereof.

[0031] The positive electrode 16 further includes a positive electrode film

26 formed on at least one side of the positive electrode current collector 22,

preferably both sides of the positive electrode current collector 22, each film 26

having a thickness of between 10 μm and 150 μm, preferably between 25 μm

an 125 μm, in order to realize the optimal capacity for the cell 10. The positive

electrode film 26 is preferably composed of between 80% and 99% by weight of

a positive electrode active materials described herein below by general formula

(1), between 1% and 10% by weight binder, and between 1% and 10% by

weight electrically conductive agent.

u a e n ers nc u e: po yacry c ac ; car oxyme y ce u ose;

diacetylceilulose; hydroxypropylceliulose; polyethylene; polypropylene;

ethylene-propylene-diene copolymer; polytetrafluoroethylene; polyvinylidene

fluoride; styrene-butadiene rubber; tetrafiuoroethylene-hexafluoropropyiene

copolymer; polyvinyl alcohol; polyvinyl chloride; polyvinyl pyrrolidone;

tetrafluoroethyiene-perfluoroalkylvinyl ether copolymer; vinylidene fluoride-

hexafiuoropropyiene copolymer; vinylidene fluoride-chlorotrifiuoroethylene

copolymer; ethylenetetrafluoroethylene copolymer; polychlorothfluoroethylene;

vinylidene fluoride-pentafluoropropylene copolymer; propylene-

tetrafluoroethylene copolymer; ethylene-chlorotrifluoroethylene copolymer;

vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer;

vinylidene fluoride-perfluoromethylvinyi ether-tetrafluoroethylene copolymer;

ethylene-acrylic acid copolymer; ethylene-methacrylic acid copolymer;

ethylene-methyl acrylate copolymer; ethylene-methyl methacrylate copolymer;

styrene-butadiene rubber; fluorinated rubber; polybutadiene; and admixtures

thereof. Of these materials, most preferred are polyvinylidene fluoride and

polytetrafluoroethylene.

[0033] Suitable electrically conductive agents include: natural graphite

(e.g. flaky graphite, and the like); manufactured graphite; carbon blacks such as

acetylene black, Ketzen black, channel black, furnace black, lamp black,

thermal black, and the like; conductive fibers such as carbon fibers and metallic

fibers; metal powders such as carbon fluoride, copper, nickel, and the like; and

organic conductive materials such as polyphenylene derivatives.

e nega ve e ec ro e s orme o a nega ve e ec ro e m

formed on at least one side of the negative electrode current collector 24,

preferably both sides of the negative electrode current collector 24. The

negative electrode film 28 is composed of between 80% and 95% of by weight

of a negative electrode active material described herein below by general

formula (9), and (optionaliy) between 1 % and 10% by of an weight electrically

conductive agent.

[0035] Referring again to Figure 1 , to ensure that the electrodes 16,18 do

not come into electrical contact with one another, in the event the electrodes

16,18 become offset during the winding operation during manufacture, the

separator 20 "overhangs" or extends a width "a" beyond each edge of the

negative electrode 18. In one embodiment, 50 μm < a < 2,000 μm. To ensure

alkali metal does not plate on the edges of the negative electrode 18 during

charging, the negative electrode 18 "overhangs" or extends a width "b" beyond

each edge of the positive electrode 16. In one embodiment, 50 μm < b ≤ 2,000

μm.

[0036] The cylindrical casing 14 includes a cylindrical body member 30

having a closed end 32 in electrical communication with the negative electrode

18 via a negative electrode lead 34, and an open end defined by crimped edge

36. In operation, the cylindrical body member 3O ₁ and more particularly the

closed end 32, is electrically conductive and provides electrical communication

between the negative electrode 18 and an externa! load (not illustrated). An

insulating member 38 is interposed between the spirally coiled or wound

electrode assembly 12 and the closed end 32.

pos ve erm na su assem y n e ec r ca commun ca on

with the positive electrode 16 via a positive electrode lead 42 provides electrical

communication between the positive electrode 16 and the external load (not

illustrated). Preferably, the positive terminal subassembly 40 is adapted to

sever electrical communication between the positive electrode 16 and an

external load/charging device in the event of an overcharge condition (e.g. by

way of positive temperature coefficient (PTC) element), elevated temperature

and/or in the event of excess gas generation within the cylindrical casing 14.

Suitable positive terminal assemblies 40 are disclosed in U.S. Patent No.

6,632,572 to Iwaizono, et al., issued October 14, 2003; and U.S. Patent No.

6,667,132 to Okochi, et al., issued December 23, 2003. A gasket member 42

seaiingly engages the upper portion of the cylindrical body member 30 to the

positive terminal subassembly 40.

[0038] In one embodiment, a non-aqueous electrolyte (not shown) is

provided for transferring ionic charge carriers between the positive electrode 16

and the negative electrode 18 during charge and discharge of the

electrochemical cell 10. The electrolyte includes a non-aqueous solvent and an

alkali metal salt dissolved therein (most preferably, a lithium salt). In the

electrochemical cell's nascent state (namely, before the cell undergoes

cycling), the non-aqueous electrolyte contains one or more metal-ion charge

carriers other than the element(s) selected from composition variables A and E

of general formulas (1) and (9), respectively.

[0039] Suitable solvents include: a cyclic carbonate such as ethylene

carbonate, propylene carbonate, butylene carbonate or vinylene carbonate; a

non-cyc c car ona e suc as me y car ona e, e y car ona e, e y

methyl carbonate or dipropyl carbonate; an aliphatic carboxylic acid ester such

as methyl formate, methyl acetate, methyl propionate or ethyl propionate; a

.gamma.-lactone such as γ-butyroiactone; a non-cyclic ether such as 1 ,2-

dimethoxyethane, 1 ,2-diethoxyethane or ethoxymethoxyethane; a cyciic ether

such as tetrahydrofuran or 2-methyltetrahydrofuran; an organic aprotic solvent

such as dimethylsulfoxide, 1 ,3-dioxolane, formamide, acetamide,

dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl

monoglyme, phospheric acid triester, trimethoxymethane, a dioxolane

derivative, sulfolane, methylsulfolane, 1 ,3-dimethyl-2-imidazolidinone, 3-methyl-

2-oxazoIidinone a propylene carbonate derivative, a tetrahydrofuran derivative,

ethyl ether, 1 ,3-propanesultone, anisole, dimethylsulfoxide and N-

methylpyrrolidone; and mixtures thereof. A mixture of a cyclic carbonate and a

non-cyclic carbonate or a mixture of a cyclic carbonate, a non-cyclic carbonate

and an aliphatic carboxylic acid ester, are preferred.

[0040] Suitable alkali metal salts, particularly alkali-metal salts, include:

RCiO ₄ ; RBF ₄ ; RPF ₆ ; RAICI ₄ ; RSbF ₆ ; RSCN; RCF ₃ SO ₃ ; RCF ₃ CO ₂ ; R(CF ₃ SO ₂ ) ₂ ;

RAsF ₆ ; RN(CF ₃ SO2) ₂ ; RB ₁₀ CI ₁₀ ; an alkali-metal lower aliphatic carboxylate;

RCI; RBr; Rl; a chloroboran of an alkali-metal; alkali-metal tetraphenylborate;

alkaii-metal imides (e.g. alkali metal bis(tπfluoromethanesulfonyl)imides); and

mixtures thereof, wherein R is selected from the group consisting of alkali-metal

from Group I of the Periodic Table. Preferably, the electrolyte contains at least

LiPF ₆ .

n ano er em o men , a room- empera ure on c qu

electrolyte (not shown) is provided for transferring ionic charge carriers

between the positive electrode 16 and the negative electrode 18 during charge

and discharge of the electrochemical celi 10. The RTIL electrolyte contains an

alkali metal salt described herein dissolved in an ionic liquid selected from the

group consisting of compounds represented by general formulas (A) through

(K):

and mixtures thereof, wherein:

(1 ) R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently selected from the

group consisting of: H; F; Cl; Br; and linear and branched aikyl, hydroxyalkyt,

enzy a y , a y a e, oxoa y , a oxya y , am noa y , car oxya y ,

sulfonylalkyl, phosphoalkyl, and sulfoalkyl groups of 1 to 7 carbon atoms; and

(2) X ^" is selected selected the group consisting of: Cl ^" ; BF ₄ ^" ; Br ^" ;

(CF ₃ ) _a PF _b ^" (wherein a+b=6 and a and b are each greater or equal to 0 (a,b >

0); compounds represented by general formulas (L) and (M):

and mixtures thereof; wherein:

(1) G ₁ and G ₂ , G ₃ , G ₄ , G ₅ , and G ₆ are each independently selected

from the group consisting of -CO- and SO ₂ -; and

(2) R ₇ , R ₈ , Rg, Rio, and Rn are each independently selected from the

group consisting of H, F, Cl, Br, halogenated alkyl groups of 1 to 5 carbon

atoms, and alkyl nitrile groups of 1 to 5 carbon atoms.

[0042] RTIL cations useful herein include, without limitation: 1-ethyl-3-

methylimidasolium; 1 ,2-dimethyl-3-propylimidazolium; 1 -propyl-2,3-

dimethylimidazolium; 1 -methyl-3-propylpyrrolidinium; 1 -methyl-3-

propylpiperidinium; λ/,/V-diethyl-λ/-methyl-N-(2-methoxyethyl)ammonium; 1 -

butyl-3-methylimidazolium tetrafiuoroborate; 1-butyl-3-methylimidazolium; 1 -

ethyl-3-methylimidazolium; λ/-methyl-λ/-alkyi piperidinium;

butyldimethylpropylammonium; and benzyldimethylethylammonium.

[0043] an ons use u ere n nc u e, wt out m tat on:

bis(trifluoromethanesulfonyl)imide; and (perfluoroalkylsulfonyl)imide.

[0044] As noted herein above, for all embodiments described herein, the

positive electrode film 26 contains a positive electrode active material

represented by the general formula (1):

A _a M _b L _c Z _d . (1)

[0045] The electrode active materials described herein are in their

nascent or as-synthesized state, prior to undergoing cycling in an

electrochemical cell. The components of the electrode active material are

selected so as to maintain electro neutrality of the electrode active material.

The stoichiometric values of one or more elements of the composition may take

on non-integer values.

[0046] For all embodiments described herein, composition variable A

contains at least one element capable of forming a positive ion and undergoing

deintercalation from the active material upon charge of an electrochemical cell

containing the same. In one embodiment, A is selected from the group

consisting of elements from Group I of the Periodic Table, and mixtures thereof

(e.g. A _a = A _a-a -A' _a >, wherein A and A' are each selected from the group

consisting of elements from Group I of the Periodic Table and are different from

one another, and a' < a). In one subembodiment, in the material's as-

synthesized or nascent state, A does not include lithium (Li). In another

subembodiment, in the material's as-synthesized or nascent state, A does not

include lithium (Li) or sodium (Na).

7 s re erre to ere n, roup re ers to e roup num ers .e.,

columns) of the Periodic Table as defined in the current IUPAC Periodic Table.

(See, e.g., U.S. Patent 6,136,472, Barker et al., issued October 24, 2000,

incorporated by reference herein.) In addition , the recitation of a genus of

elements, materials or other components, from which an individual component

or mixture of components can be selected, is intended to include all possible

sub-generic combinations of the listed components, and mixtures thereof.

[0048] Preferably, a sufficient quantity (a) of composition variable A

should be present so as to allow all of the "redox active" elements of

composition variable M (as defined herein below) to undergo

oxidation/reduction. Removal of an amount (a) of composition variable A from

the electrode active material is accompanied by a change in oxidation state of

at least one of the "redox active" elements in the active material, as defined

herein below. The amount of redox active material available for

oxidation/reduction in the active material determines the amount (a) of

composition variable A that may be removed. Such concepts are, in general

application, well known in the art, e.g., as disclosed in U.S. Patent 4,477,541 ,

Fraioli, issued October 16, 1984; and U.S. Patent 6,136,472, Barker, et al.,

issued October 24, 2000, both of which are incorporated by reference herein.

[0049] Referring again to general formula (1), in all embodiments

described herein, composition variable M is at least one redox active element.

As used herein, the term "redox active element" includes those elements

characterized as being capable of undergoing oxidation/reduction to another

oxidation state when the electrochemical cell is operating under normal

opera ng con t ons. s use ere n, e erm norma operat ng con t ons

refers to the intended voltage at which the cell is charged, which, in turn,

depends on the materials used to construct the cell.

[0050] Redox active elements useful herein with respect to composition

variable M include, without limitation, elements from Groups 4 through 11 of the

Periodic Table, as well as select non-transition metals, including, without

limitation, Ti (Titanium), V (Vanadium), Cr (Chromium), Mn (Manganese), Fe

(Iron), Co (Cobalt), Ni (Nickel), Cu (Copper), Nb (Niobium), Mo (Molybdenum),

Ru (Ruthenium), Rh (Rhodium), Pd (Palladium), Os (Osmium), Ir (Iridium), Pt

(Platinum), Au (Gold), Si (Silicon), Sn (Tin), Pb (Lead), and mixtures thereof.

For each embodiment described herein, M may comprise a mixture of oxidation

states for the selected element (e.g., M - Mn ²⁺ Mn ⁴⁺ ). Also, "include," and its

variants, is intended to be non-limiting, such that recitation of items in a list is

not to the exclusion of other like items that may also be useful in the materials,

compositions, devices, and methods of this invention.

[0051] In one embodiment, composition variable M is a redox active

element. In one subembodiment, M is a redox active element selected from the

group consisting of Ti ²⁺ , V ²⁺ , Cr ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Mo ²⁺ , Si ²⁺ , Sn ²⁺ ,

and Pb ²⁺ . In another subembodiment, M is a redox active element selected

from the group consisting Of Ti ³⁺ , V ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Mo ³⁺ , and

Nb ³⁺ .

[0052] In another embodiment, composition variable M includes one or

more redox active elements and (optionally) one or more non-redox active

elements. As referred to herein, "non-redox active elements" include elements

,. , . . . . .. . . . , . . that are capaDie o orming stable active materials, and do not undergo

oxidation/reduction when the electrode active material is operating under

normal operating conditions.

[0053] Among the non-redox active elements useful herein include,

without limitation, those selected from Group 2 elements, particularly Be

(Beryllium), Mg (Magnesium), Ca (Calcium), Sr (Strontium), Ba (Barium); Group

3 elements, particularly Sc (Scandium), Y (Yttrium), and the lanthanides,

particularly La (Lanthanum), Ce (Cerium), Pr (Praseodymium), Nd

(Neodymium), Sm (Samarium); Group 12 elements, particularly Zn (Zinc) and

Cd (Cadmium); Group 13 elements, particularly B (Boron), Al (Aluminum), Ga

(Gallium), In (Indium), Tl (Thallium); Group 14 elements, particularly C

(Carbon) and Ge (Germanium), Group 15 elements, particularly As (Arsenic),

Sb (Antimony), and Bi (Bismuth); Group 16 elements, particularly Te

(Tellurium); and mixtures thereof.

[0054] In one embodiment, M = MI _n MII ₀ , wherein 0 < o + n < 3 and each

of o and n is greater than zero (0 < o,n), wherein Ml and Mil are each

independently selected from the group consisting of redox active elements and

non-redox active elements, wherein at least one of Ml and Mil is redox active.

Ml may be partially substituted with Mil by isocharge or aliovalent substitution,

in equal or unequal stoichiometric amounts.

[0055] "Isocharge substitution" refers to a substitution of one element on a

given crystallographic site with an element having the same oxidation state

(e.g. substitution of Ca ²⁺ with Mg ²⁺ ). "Aliovalent substitution" refers to a

su s i u ion o one e emen on a given crys a ograp ic s e w an e emen o a

different oxidation state (e.g. substitution of Li ⁺ with Mg ²⁺ ).

[0056] For all embodiments described herein where Ml is partially

substituted by Mil by isocharge substitution, Ml may be substituted by an equal

stoichiometric amount of Mil, whereby M = MI _n-0 MII ₀ . Where Ml is partially

substituted by Mil by isocharge substitution and the stoichiometric amount of Ml

is not equal to the amount of Mil, whereby M = MI _n-0 MII _p and o ≠ p, then the

stoichiometric amount of one or more of the other components (e.g. A, L and Z)

in the active material must be adjusted in order to maintain electroneutrality,

[0057] For all embodiments described herein where Ml is partially

substituted by Mil by aliovalent substitution and an equal amount of Ml is

substituted by an equal amount of Mil, whereby M = Ml _n . _o MII _Ol then the

stoichiometric amount of one or more of the other components (e.g. A, L and Z)

in the active material must be adjusted in order to maintain electroneutrality.

However, Ml may be partially substituted by Mil by aliovalent substitution by

substituting an "oxidatively" equivalent amount of Mil for Ml, whereby

M = MI ₀ Mil ₀ , wherein V ^M! is the oxidation state of Ml, and V ^Mtl is the

7Mi

oxidation state of

[0058] In one subembodiment, Ml is selected from the group consisting of

Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Si, Pb, Mo, Nb, and mixtures thereof, and Mil

is selected from the group consisting of Be, Mg, Ca, Sr, Ba, Sc, Y, Zn, Cd, B,

Al ₁ Ga, In, C, Ge, and mixtures thereof. In this subembodiment, Ml may be

substituted by Mil by isocharge substitution or aliovalent substitution.

[0059] In another subembodiment, Mi is partially substituted by Mil by

isocharge substitution. In one aspect of this subembodiment, Ml is selected

from the group consisting of Ti ²⁺ , V ²⁺ , Cr ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Mo ²⁺ ,

Si ²⁺ , Sn ²⁺ , Pb ²⁺ , and mixtures thereof, and Mil is selected from the group

consisting of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ , Cd ²⁺ , Ge ²⁺ , and mixtures

thereof. In another aspect of this subembodiment, Ml is selected from the

group specified immediately above, and Mil is selected from the group

consisting of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and mixtures thereof. In another

aspect of this subembodiment, Ml is selected from the group specified above, .

and Mil is selected from the group consisting of Zn ²⁺ , Cd ²⁺ , and mixtures

thereof. In yet another aspect of this subembodiment, Ml is selected from the

group consisting of Ti ³⁺ , V ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Mo ³⁺ , Nb ³⁺ , and

mixtures thereof, and Mil is selected from the group consisting of Sc ³⁺ , Y ³⁺ , B ³⁺ ,

Al ³⁺ , Ga ³⁺ , In ³⁺ , and mixtures thereof.

[0060] In another embodiment, Ml is partially substituted by Mil by

aliovalent substitution. In one aspect of this subembodiment, Ml is selected

from the group consisting of Ti ²⁺ , V ²⁺ , Cr ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Mo ²⁺ ,

Si ²⁺ , Sn ²⁺ , Pb ²⁺ , and mixtures thereof, and Mil is selected from the group

consisting of Sc ³⁺ , Y ³⁺ , B ³⁺ , Al ³⁺ , Ga ³⁺ , In ³⁺ , and mixtures thereof. In another

aspect of this subembodiment, Ml is a 2+ oxidation state redox active element

selected from the group specified immediately above, and Mil is selected from

the group consisting of alkali metals, Cu ¹⁺ , Ag ¹⁺ and mixtures thereof. In

another aspect of this subembodiment, Ml is selected from the group consisting

of Ti ³⁺ , V ³⁺ , Cr ³⁺ , Mn ³⁺ , Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Mo ³⁺ , Nb ³⁺ , and mixtures thereof, and

Mil is selected from the group consisting of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ ,

Cd ²⁺ , Ge ²⁺ , and mixtures thereof. In another aspect of this subembodiment, Ml

is a 3+ oxidation state redox active element selected from the group specified

immediately above, and Mil is selected from the group consisting of alkali

metals, Cu ¹⁺ , Ag ¹⁺ and mixtures thereof.

[0061] In another embodiment, M = M1 _q M2 _r M3 _s , wherein;

(i) M1 is a redox active element with a 2+ oxidation state;

(ii) M2 is selected from the group consisting of redox and non-

redox active elements with a 1 + oxidation state;

(Hi) M3 is selected from the group consisting of redox and non-

redox active elements with a 3+ or greater oxidation state;

and

(iv) at least one of q, r and s is greater than 0, and at least one

of M1 , M2, and M3 is redox active.

[0062] In one subembodiment, M1 is substituted by an equal amount of

M2 and/or M3, whereby q = q - (r + s). In this subembodiment, then the

stoichiometric amount of one or more of the other components (e.g. A, L and Z)

in the active material must be adjusted in order to maintain electroneutrality.

[0063] In another subembodiment, M1 is substituted by an "oxidatively"

equivalent amount of M2 and/or M3, whereby M=M1 _{r s} M2 _r M3 _s , wherein

V ^M1 is the oxidation state of M1 , V ^M2 is the oxidation state of M2, and V ^M3 is the

oxidation state of M3.

[0064] In one subembodiment, M1 is selected from the group consisting of

Ti ²⁺ , V ²⁺ , Cr ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Mo ²⁺ , Si ²⁺ , Sn ²⁺ , Pb ²⁺ , and mixtures

thereof; M2 is selected from the group consisting of Cu ¹⁺ , Ag ¹⁺ and mixtures

thereof; and M3 is selected from the group consisting of Ti ³⁺ , V ³⁺ , Cr ³⁺ , Mn ³⁺ ,

Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Mo ³⁺ , Nb ³⁺ , and mixtures thereof. In another subembodiment,

M1 and M3 are selected from their respective preceding groups, and M2 is

selected from the group consisting of Li ¹⁺ , K ¹⁺ , Na ¹⁺ , Ru ¹⁺ , Cs ¹⁺ , and mixtures

thereof.

[0065] In another subembodiment, M1 is selected from the group

consisting of Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ , Cd ²⁺ , Ge ²⁺ , and mixtures

thereof; M2 is selected from the group consisting of Cu ¹⁺ , Ag ¹⁺ and mixtures

thereof; and M3 is selected from the group consisting of Ti ³⁺ , V ³⁺ , Cr ³⁺ , Mn ³⁺ ,

Fe ³⁺ , Co ³⁺ , Ni ³⁺ , Mo ³⁺ , Nb ³⁺ , and mixtures thereof. In another subembodiment,

M1 and M3 are selected from their respective preceding groups, and M2 is

selected from the group consisting of Li ¹⁺ , K ¹⁺ , Na ¹⁺ , Ru ¹⁺ , Cs ¹⁺ , and mixtures

thereof.

[0066] In another subembodiment, M1 is selected from the group

consisting of Ti ²⁺ , V ²⁺ , Cr ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ _r Mo ²⁺ , Si ²⁺ , Sn ²⁺ , Pb ²⁺ ,

and mixtures thereof; M2 is selected from the group consisting of Cu ¹⁺ , Ag ¹⁺ ,

and mixtures thereof; and M3 is selected from the group consisting of Sc ³⁺ , Y ³⁺ ,

B ³⁺ , Al ³⁺ , Ga ³⁺ , In ³⁺ , and mixtures thereof. In another subembodiment, M1 and

M3 are selected from their respective preceding groups, and M2 is selected

from the group consisting of Li ¹⁺ , K ¹⁺ , Na ¹⁺ , Ru ¹⁺ , Cs ¹⁺ , and mixtures thereof.

[0067] In all embodiments described herein, composition variable L is a

polyanion selected from the group consisting of X'[O ₄ . _X Y' _X ], X'[O ₄ . _y Y' _2y ], X"S ₄ ,

[X2 ^''' ,X' _1-2 ]O ₄ , and mixtures thereof, wherein:

consisting of P, As, Sb, Si, Ge, V, S, and mixtures thereof;

(b) X" is selected from the group consisting of P, As, Sb, Si, Ge,

V, and mixtures thereof;

(c) Y' is selected from the group consisting of a halogen, S, N,

and mixtures thereof; and

(d) 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1 , and 1 ≤ c ≤ 3.

[0068] In one embodiment, composition variable L is selected from the

group consisting of XO ₄ .χY' _x , XO _4-y Y' _2y , and mixtures thereof, and x and y are

both 0 (x,y = 0). Stated otherwise, composition variable L is a polyanion

selected from the group consisting of PO ₄ , SiO ₄ , GeO ₄ , VO ₄ , AsO ₄ , SbO ₄ , SO ₄ ,

and mixtures thereof. Preferably, composition variable L is PO ₄ (a phosphate

group) or a mixture of PO ₄ with another anion of the above-noted group (i.e.,

where X' is not P, Y' is not O, or both, as defined above). In one embodiment,

composition variable L includes about 80% or more phosphate and up to about

20% of one or more of the above-noted polyanions.

[0069] In another embodiment, composition variable L is selected from the

group consisting of X ¹ IO ₄ - _X1 Y ¹ J, X'[0 _4- y ₍ Y ^f ₂ y], and mixtures thereof, and O < x ≤ 3

and O < y < 2, wherein a portion of the oxygen (O) in the XY ₄ composition

variable is substituted with a halogen, S, N, or a mixture thereof.

[0070] In all embodiments described herein, composition variable Z (when

provided) is selected from the group consisting of a hydroxyl (OH), a halogen

selected from Group 17 of the Periodic Table, and mixtures thereof. In one

embodiment, Z is selected from the group consisting of OH, F (Fluorine), Cl

or ne , r romine , an mix ures ereo . n ano er em o imen , is

OH. In another embodiment, Z is F, or a mixture of F with OH, Ci, or Br.

[0071] In one particular subembodiment, the positive electrode film 26

contains a positive electrode active material represented by the general

formula (2):

A _a M _b PO ₄ Z _d , (2)

wherein composition variables A, M, and Z are as described herein above, 0.1

< a < 4, 8 < b < 1.2 and 0 < d < 4; and wherein A, M, Z, a, b, and d are selected

so as to maintain electroneutrality of the electrode active material in its nascent

or as-synthesized state. Specific examples of electrode active materials

represented by general formula (2), wherein d > 0, include Li ₂ Fe ₀ . ₉ Mgo.iP04F,

Li ₂ Fe ₀₁₈ Mg _C2 PO ₄ F, Li ₂ Fe _C95 Mg ₀ ^ ₅ PO ₄ F, Li ₂ CoPO ₄ F, Li ₂ FePO ₄ F, and

Li ₂ MnPO ₄ F.

[0072] In a subembodiment, M includes at least one element from Groups

4 to 11 of the Periodic Table, and at least one element from Groups 2, 3, and

12-16 of the Periodic Table. In a particular subembodiment, M includes an

element selected from the group consisting of Fe, Co, Mn, Cu, V, Cr, and

mixtures thereof; and a metal selected from the group consisting of Mg, Ca, Zn,

Ba, Al, and mixtures thereof.

[0073] In another subembodiment, the positive electrode film 26 contains

a positive electrode active material represented by the general formula (3):

wherein composition variable A is as described herein above, and wherein M' is

at least one transition metal from Groups 4 to 11 of the Periodic Table and has

a +2 valence state; M" is at least one metallic element which is from Group 2,

12, or 14 of the Periodic Table and has a +2 valence state; and 0 < j < 1. In

one subembodiment, M' is selected from the group consisting of Fe, Co, Mn ₁

Cu, V, Cr, Ni, and mixtures thereof; more preferably M' is selected from Fe, Co,

Ni, Mn and mixtures thereof. Preferably, M" is selected from the group

consisting of Mg, Ca, Zn, Ba, and mixtures thereof.

[0074] In another subembodiment, the positive electrode film 26 contains

a positive electrode active material represented by the general formula (4):

wherein M ^" is selected from the group consisting of Mg, Ca, Zn, Sr, Pb, Cd, Sn,

Ba, Be, and mixtures thereof; and 0 < k < Un one subembodiment, 0 < k ≤

0.2. In a another subembodiment, M ^" is selected from the group consisting of

Mg, Ca, Zn, Ba, and mixtures thereof, more preferably, M ^" is Mg. In another

subembodiment the electrode active material is represented by the formula

LiFe _1-k Mg _k PO _4l wherein 0 < k < 0.5. Specific examples of electrode active

materials represented by general formula (4) include LiFeo. ₈ Mgo. ₂ PO ₄ ,

LiFe _0-9 Mg ₀ .! PO ₄ , and LiFe _0-95 Mg ₀₁₀₅ PO ₄ .

[0075] In another subembodiment, the positive electrode film 26 contains

a positive electrode active material represented by the general formula (5):

A _a Co _u Fe _v M ¹³ _w M ¹⁴ _aa M ¹⁵ _bb L, (5)

wherein:

(i) composition variable A is as described herein above, 0 < a < 2

(ii) u > 0 and v > 0;

M ¹³ is one or more transition metals, wherein w > 0;

[V is one or more + oxi a ion s a e non- ransi ion me a s,

wherein aa > 0;

(v) M ¹⁵ is one or more +3 oxidation state non-transition metais,

wherein

bb ≥ O;

(vi) L is selected from the group consisting of X'O _4-X Y' _X ,

XO _4-y Y' _2y , X"S ₄ , and mixtures thereof, where X' is selected from

the group consisting of P, As, Sb, Si, Ge, V, S ₁ and mixtures

thereof; X" is selected from the group consisting of P, As, Sb, Si,

Ge, V and mixtures thereof; Y' is selected from the group

consisting of halogen, S, N, and mixtures thereof; 0 < x < 3; and 0

< y < 2; and

wherein 0 < (u + v + w + aa + bb) < 2, and M ¹³ , M ¹⁴ , M ¹⁵ , L, a, u, v, w, aa,

bb, x, and y are selected so as to maintain electroneutrality of the electrode

active material in its nascent or as-synthesized state. In one subembodiment,

0.8 < (u + v + w + aa + bb) < 1.2, wherein u > 0.8 and 0.05 < v < 0.15. In

another subembodiment, 0.8 < (u + v + w + aa + bb) < 1.2, wherein u > 0.5,

0.01 < v < 0.5, and 0.01 < w < 0.5.

[0076] In one subembodiment, M ¹³ is selected from the group consisting

of Ti, V, Cr, Mn, Ni, Cu and mixtures thereof. In another subembodiment, M ¹³

is selected from the group consisting of Mn, Ti, and mixtures thereof. In

another subembodiment, M ¹⁴ is selected from the group consisting of Be, Mg,

Ca, Sr, Ba, and mixtures thereof. In one particular subembodiment, M ¹⁴ is Mg

and 0.01 < bb < 0.2, preferably 0.01 < bb < 0.1. In another particular

su em o men , s se ec e rom e group cons s ng o , , a, n, an

mixtures thereof.

[0077] In another subembodiment, the positive electrode film 26 contains

a positive electrode active materia! represented by the general formula (6):

LiM(PO _4-X r _x ), (6)

wherein M is M ¹⁶ _cc M ¹⁷ _dd M ¹⁸ _ee M ¹⁹ _ff, and

(i) M ¹⁶ is one or more transition metals;

(ii) M ¹⁷ is one or more +2 oxidation state non-transition metals;

(iii) M ¹⁸ is one or more +3 oxidation state non-transition metals;

(iv) M ¹⁹ is one or more +1 oxidation state non-transition metals;

(v) Y' is halogen; and

wherein cc > 0, each of dd, ee, and ff > 0, (cc + dd + ee + ff) < 1 ,

and 0 < x < 0.2, and and M ¹⁶ , M ¹⁷ , M ¹⁸ , M ¹⁹ , Y, cc, dd, ee, ff, and x are selected

so as to maintain electroneutrality of the electrode active material in its nascent

or as-synthesized state. In one subembodiment, cc > 0.8. In another

subembodiment, 0.01 < (dd + ee) < 0.5, preferably 0.01 < dd < 0.2 and 0.01 <

ee < 0.2. In another subembodiment x = 0.

[0078] In one particular subembodiment, M ¹⁶ is a +2 oxidation state

transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Cu,

and mixtures thereof. In another subembodiment, M ¹⁶ is selected from the

group consisting of Fe ₁ Co, and mixtures thereof. In a preferred

subembodiment M ¹⁷ is selected from the group consisting of Be, Mg, Ca, Sr, Ba

and mixtures thereof. In a preferred subembodiment M ¹⁸ is Al. In one

subembodiment, M ¹⁹ is selected from the group consisting of Li, Na, and K,

w ere n . < < . . n a pre erre su em o men s . n one

preferred subembodiment x = O, (cc + dd + ee + ff) = 1 , M ¹⁷ is selected from the

group consisting of Be ₁ Mg ₁ Ca, Sr, Ba and mixtures thereof, preferably 0.01 <

dd < 0.1 , M ¹⁸ is Al, preferably 0.01 < ee < 0.1 , and M ¹⁹ is Li ₁ preferably 0.01 < ff

< 0.1. In another preferred subembodiment, 0 < x < 0, preferably 0.01 < x <

0.05, and (cc + dd + ee + ff) < 1 , wherein cc > 0.8, 0.01 < dd < 0.1 , 0.01 < ee <

0.1 and ff = 0, Preferably (cc + dd + ee) = 1 - x.

[0079] In another subembodiment, the positive electrode film 26 contains

a positive electrode active material represented by the general formula (7):

A ¹ _a (MO) _gg M' _1-gg XO ₄ , (7)

wherein

(i) A ¹ is independently selected from the group consisting of Li, Na, K

and mixtures thereof, 0.1 < a < 2;

(ii) M comprises at least one element, having a +4 oxidation state,

which is redox active; 0 < gg < 1 ;

(iii) M' is one or more metals selected from metals having a +2 and a

+3 oxidation state; and

(iv) X is selected from the group consisting of P, As, Sb, Si, Ge, V, S,

and mixtures thereof; and

wherein A ¹ , M, M , X, a and gg are selected so as to maintain

electroneutrality of the electrode active material in its nascent or as-synthesized

state.

[0080] In one subembodiment, A ¹ is Li. In another subembodiment, M is

selected from a group consisting of +4 oxidation state transition metals. In a

pre erre su em o imen , is se ec e rom e group comprising ana ium

(V), Tantaium (Ta), Niobium (Nb), molybdenum (Mo), and mixtures thereof. In

another preferred subembodiment M comprises V, and b = 1. M' may generally

be any +2 or +3 element, or mixture of elements. In one subembodiment, M' is

selected from the group consisting V, Cr, Mn, Fe, Co, Ni, Mo, Ti ₁ Al, Ga, In, Sb,

Bi, Sc, and mixtures thereof. In another subembodiment, M' is selected from

the group consisting of V, Cr, Mn, Fe, Co, Ni, Ti, Al, and mixtures thereof. In

one preferred subembodiment, M ^f comprises Al. Specific examples of

electrode active materials represented by general formula (7) include LiVOPO ₄ ,

Li(VO)o. ₇₅ Mno. ₂₅ P0 ₄ , Li _0-75 Na _0-2S VO PO ₄ , and mixtures thereof.

[0081] In another subembodiment, the positive electrode film 26 contains

a positive electrode active material represented by the general formula (8):

A _a M _b L ₃ Z _dl (8)

wherein composition variables A, M XY ₄ and Z are as described herein

above, 2 < a < 8, 1 < b < 3, and O < d < 6; and

wherein M, L, Z, a, b, d, x and y are selected so as to maintain

electroneutrality of the electrode active material in its nascent or as-synthesized

state.

[0082] In one subembodiment, A is Li, or a mixture of Li with Na or K. In

another preferred embodiment, A is Na, K, or a mixture thereof. In another

subembodiment, M is selected from the group consisting of Fe, Co, Ni, Mn, Cu,

V, Zr, Ti, Cr, and mixtures thereof. In another subembodiment, M comprises

two or more transition metals from Groups 4 to 1 1 of the Periodic Table,

preferably transition metals selected from the group consisting of Fe, Co, Ni,

₄ ;

0251

i _{O 7S} n _{025 4} ; an mix ures ereo . par icu ar y pre erre ac ive

material is LiCo0.8Fe0.1AI0.025Mg0.05PO3.975F0.025-

[0089] Active materials of general formulas (1) through (8) are readily

synthesized by reacting starting materials in a solid state reaction, with or

without simultaneous oxidation or reduction of the metal species involved.

Sources of composition variable A include any of a number of salts or ionic

compounds of lithium, sodium, potassium, rubidium or cesium. Lithium,

sodium, and potassium compounds are preferred. Preferably, the alkali metal

source is provided in powder or particulate form. A wide range of such

materials is well known in the field of inorganic chemistry. Non-limiting

examples include the lithium, sodium, and/or potassium fluorides, chlorides,

bromides, iodides, nitrates, nitrites, sulfates, hydrogen sulfates, sulfites,

bisuifites, carbonates, bicarbonates, borates, phosphates, hydrogen ammonium

phosphates, dihydrogen ammonium phosphates, silicates, antimonates,

arsenates, germinates, oxides, acetates, oxalates, and the like. Hydrates of the

above compounds may also be used, as well as mixtures. In particular, the

mixtures may contain more than one alkali metal so that a mixed alkali metal

active material will be produced in the reaction.

[0090] Sources of composition variable M include salts or compounds of

any of the transition metals, alkaline earth metals, or lanthanide metals, as well

as of non-transition metals such as aluminum, gallium, indium, thallium, tin,

lead, and bismuth. The metal compounds include, without limitation, fluorides,

chlorides, bromides, iodides, nitrates, nitrites, sulfates, hydrogen sulfates,

sulfites, bisuifites, carbonates, bicarbonates, borates, phosphates, hydrogen

ammon um p osp a es, y rogen ammonium p osp a es, s ca es,

antimonates, arsenates, germanates, oxides, hydroxides, acetates, oxalates,

and the like. Hydrates may also be used, as well as mixtures of metals, as with

the alkali metals, so that alkaϋ metal mixed metal active materials are

produced. The elements or elements comprising composition variable M in the

starting material may have any oxidation state, depending the oxidation state

required in the desired product and the oxidizing or reducing conditions

contemplated, as discussed below. The metal sources are chosen so that at

least one metal in the final reaction product is capable of being in an oxidation

state higher than it is in the reaction product.

[0091] Sources for composition variable L are provided by a number of

salts or compounds containing positively charged cations in addition to the

source of the polyanion or polyanions comprising composition variable L. Such

cations include, without limitation, metal ions such as the alkali metals, alkaline

metals, transition metals, or other non-transition metals, as well as complex

cations such as ammonium or quaternary ammonium. The phosphate anion in

such compounds may be phosphate, hydrogen ammonium phosphate, or

dihydrogen ammonium phosphate. As with the alkali metal source and metal

source discussed above, the phosphate or other XO ₄ species, starting materials

are preferably provided in particulate or powder form. Hydrates of any of the

above may be used, as can mixtures of the above.

[0092] Sources of composition variable Z include any of a number of salts

or ionic compounds of a halogen or hydroxyl. Non-limiting examples include

the alkali-metal halides and hydroxides, and ammonium halides and

y roxi es. y ra es o e a ove compoun s may a so e use , as we as

mixtures thereof. In particular, the mixtures may contain more than one alkali

metal so that a mixed aikali metal active material will be produced in the

reaction.

[0093] A starting material may provide more than one of composition

variables A, M, and L and Z as is evident in the list above. In various

embodiments of the invention, starting materials are provided that combine, for

example, composition variable M and L, thus requiring only composition

variable A and Z be added. In one embodiment, a starting material is provided

that contains alkali metal, a metal, and phosphate. Combinations of starting

materials providing each of the components may also be used. It is preferred

to select starting materials with counterions that give rise to volatile by¬

products. Thus, it is desirable to choose ammonium salts, carbonates, oxides,

and the like where possible. Starting materials with these counterions tend to

form volatile by-products such as water, ammonia, and carbon dioxide, which

can be readily removed from the reaction mixture. This concept is well

illustrated in the Examples below.

[0094] The sources of composition variables A ₁ M, L and Z, may be

reacted together in the solid state while heating for a time and temperature

sufficient to make a reaction product. The starting materials are provided in

powder or particulate form. The powders are mixed together with any of a

variety of procedures, such as by ball milling without attrition, blending in a

mortar and pestle, and the like. Thereafter the mixture of powdered starting

materials is compressed into a tablet and/or held together with a binder material

o orm a c ose y co ering reac ion mix ure. e reac ion mix ure is ea e in

an oven, generaliy at a temperature of about 400 ⁰ C or greater until a reaction

product forms. Exemplary times and temperatures for the reaction are given in

the Examples below.

[0095] Another means for carrying out the reaction at a lower temperature

is hydrothermally. In a hydrothermal reaction, the starting materials are mixed

with a small amount of a liquid such as water, and placed in a pressurized

bomb. The reaction temperature is limited to that which can be achieved by

heating the liquid water in a continued volume creating an increased pressure,

and the particular reaction vessel used.

[0096] The reaction may be carried out without redox, or if desired under

reducing or oxidizing conditions. When the reaction is done without redox, the

oxidation state of the metal or mixed metals in the reaction product is the same

as in the starting materials. Oxidizing conditions may be provided by running

the reaction in air. Thus, oxygen from the air is used to oxidize the starting

material containing the transition metal.

[0097] The reaction may also be carried out with reduction. For example,

the reaction may be carried out in a reducing atmosphere such as hydrogen,

ammonia, methane, or a mixture of reducing gases. Alternatively, the reduction

may be carried out in-situ by including in the reaction mixture a reductant that

will participate in the reaction to reduce the one or more elements comprising

composition variable M, but that will produce by-products that will not interfere

with the active material when used later in an electrode or an electrochemical

cell. One convenient reductant to use to make the active materials of the

inven on s a re ucing car on. n a pre erre em o imen , e reac ion is

carried out in an inert atmosphere such as argon, nitrogen, or carbon dioxide.

Such reducing carbon is conveniently provided by elemental carbon, or by an

organic material that can decompose under the reaction conditions to form

elementai carbon or a similar carbon containing species that has reducing

power. Such organic materials include, without limitation, glycerol, starch,

sugars, cokes, and organic polymers which carbonize or pyrolize under the

reaction conditions to produce a reducing form of carbon. A preferred source of

reducing carbon is elemental carbon.

[0098] It is usually easier to provide the reducing agent in stoichiometric

excess and remove the excess, if desired, after the reaction. In the case of the

reducing gases and the use of reducing carbon such as elemental carbon, any

excess reducing agent does not present a problem. In the former case, the gas

is volatile and is easily separated from the reaction mixture, while in the latter,

the excess carbon in the reaction product does not harm the properties of the

active material, because carbon is generally added to the active material to

form an electrode material for use in the electrochemical cells and batteries of

the invention. Conveniently also, the by-products carbon monoxide or carbon

dioxide (in the case of carbon) or water (in the case of hydrogen) are readily

removed from the reaction mixture.

[0099] The carbothermal reduction method of synthesis of mixed metal

phosphates has been described in PCT Publication WO01/53198, Barker et al.,

incorporated by reference herein. The carbothermal method may be used to

react starting materials in the presence of reducing carbon to form a variety of

pro uc s. e car on unc ions o re uce a me a ion in e s ar ing ma eria

source. The reducing carbon, for example in the form of elemental carbon

powder, is mixed with the other starting materials and heated. For best results,

the temperature should be about 400 ⁰ C or greater, and up to about 950 ⁰ C.

Higher temperatures may be used, but are usually not required.

[00100] Methods of making the electrode active materials described by

general formulas (1 ) through (8) are generally known in the art and described in

the literature, and are also described in: WO 01/54212 to Barker et al.,

published July 26, 2001 ; International Publication No. WO 98/12761 to Barker

et al., published March 26, 1998; WO 00/01024 to Barker et al., published

January 6, 2000; WO 00/31812 to Barker et al., published June 2, 2000; WO

00/57505 to Barker et al., published September 28, 2000; WO 02/44084 to

Barker et al., published June 6, 2002; WO 03/085757 to Saidi et a!., published

October 16, 2003; WO 03/085771 to Saidi et al., published October 16, 2003;

WO 03/088383 to Saidi et a!., published October 23, 2003; U.S. Patent No.

6,528,033 to Barker et ai., issued March 4, 2003; U.S. Patent No. 6,387,568 to

Barker et al., issued May 14, 2002; U.S. Publication No. 2003/0027049 to

Barker et al., published February 2, 2003; U.S. Publication No. 2002/0192553

to Barker et al., published December 19, 2002; U.S. Publication No.

2003/0170542 to Barker at al., published September 11 , 2003; and U.S.

Publication No. 2003/1029492 to Barker et al., published July 10, 2003; the

teachings of all of which are incorporated herein by reference.

S no e erein a ove, or a em o imen s escri e erein, e

negative electrode film 28 contains a negative electrode active material

represented by the general formula (9):

wherein:

(i) E is selected from the group consisting of elements from Group I of

the Periodic Table, and mixtures thereof, and 0 < f < 12;

(ϋ) 0 < g < 6;

(iii) D is selected from the group consisting of Al, Zr, Mg, Ca, Zn, Cd,

Fe, Mn, Ni, Co, and mixtures thereof, and 0 ≤ h < 2; and

(iv) 2 < i < 12.

wherein E, D, f, g, h and i are selected so as to maintain electroneutrality

of the second counter-electrode active material in its nascent state.

[00102] For all embodiments described herein, composition variable E is

selected from the group consisting of elements from Group I of the Periodic

Table, and mixtures thereof (e.g. E _f = E _M -EV, wherein E and E' are each

selected from the group consisting of elements from Group I of the Periodic

Table and are different from one another, and f < f). In one subembodiment, in

the positive and negative material's as-synthesized or nascent state, E and A

share at least one common element (e.g. both E and A include the alkali-metal

Li). In another subembodiment, in the positive and negative material's as-

synthesized or nascent state, E and A do not share a common element.

[00103] In one subembodiment, 0 < h < 2. In another subembodiment, 0 <

h < 2 and D is Al.

on- imi ing examp es o ac ive ma eria s represen e y genera

formula (10) include the following: Li ₄ Ti ₅ O ₁₂ ; Li ₅ Ti ₄ AIO ₁₂ ; rutile and anatase

forms of TiO ₂ , including magneli type phases having the general formula Ti _n O _2n -

_λ (4 < n < 9); TiO; Ti ₄ O ₅ ; Ti ₃ O ₅ ; LiTiO ₂ ; Ti ₄ O ₇ ; Li ₂ Ti ₃ O ₇ ; and LiTi ₂ O ₄ .

[00105] In one subembodiment, the negative electrode active material is

Li ₄ Ti ₅ O ₁₂ . The Li ₄ Ti ₅ O ₁₂ negative electrode active material is characterized has

having cubic spinel structure, space group Fd3m, the unit ceil parameter a =

8.3575(5) A.

[00106] To prepare materials represented by general formula (10), starting

materials are first selected to provide for composition variables A and

(optionally) D, as well as elements Ti and O. A starting material may provide

more than one of the components A, Ti, O and (optionally) D. In general, any

anion may be combined with the alkali metal cation (composition variable A) to

provide the alkali metal source starting material, with the Ti cation to provide a

Ti-containing starting material, or with the elements comprising composition

variable D to provide a D-containing starting material. It is preferred, however,

to select starting materials with counterions that give rise to the formation of

volatile by-products during the solid state reaction. Thus, it is desirable to

choose ammonium salts, carbonates, bicarbonates, oxides, hydroxides, and

the like where possible. Starting materials with these counterions tend to form

volatile by-products such as water, ammonia, and carbon dioxide, which can be

readily removed from the reaction mixture. Similarly, sulfur-containing anions

such as sulfate, bisulfate, sulfite, bisulfite and the like tend to result in volatile

su ur ox e y-pro uc s. rogen-con a n ng an ons suc as n ra e an n r e

also tend to give volatile NO _x by-products.

[00107] Sources of composition variable E include any of a number of salts

or ionic compounds of lithium, sodium, potassium, rubidium or cesium. Lithium,

sodium, and potassium compounds are preferred, with lithium being particularly

preferred. Preferably, the alkali metal source is provided in powder or

particulate form. A wide range of such materials is well known in the field of

inorganic chemistry. Examples include the lithium, sodium, and/or potassium

fluorides, chlorides, bromides, iodides, nitrates, nitrites, sulfates, hydrogen

sulfates, sulfites, bisulfites, carbonates, bicarbonates, borates, phosphates,

hydrogen ammonium phosphates, dihydrogen ammonium phosphates,

silicates, antimonates, arsenates, germinates, oxides, acetates, oxalates, and

the like. Hydrates of the above compounds may also be used, as well as

mixtures. In particular, the mixtures may contain more than one alkali metal so

that a mixed alkali metal active material will be produced in the reaction.

[00108] Suitable Ti-containing starting materials include TiO ₂ , Ti ₂ O ₃ , and

TiO. Suitable D-containing starting materials include fluorides, chlorides,

bromides, iodides, nitrates, nitrites, sulfates, hydrogen sulfates, sulfites,

bisulfites, carbonates, bicarbonates, borates, phosphates, hydrogen ammonium

phosphates, dihydrogen ammonium phosphates, silicates, antimonates,

arsenates, germanates, oxides, hydroxides, acetates, oxalates, and the iike.

Hydrates may also be used.

[00109] The mixture of starting materials is heated for a time and at a

temperature sufficient to form a reaction product. In one embodiment, the

reac on s carr e ou n an ox z ng a mosp ere so a an um n e

reaction product is present in the 4+ oxidation state. The temperature should

preferably be about 400°C or greater, and desirably between about 700 ⁰ C and

900 ⁰ C.

[00110] Methods of making the negative electrode active materials

described by general formula (9) are generally known in the art and described

in the literature, and are also described in: U.S. Patent No. 5,545,468 to

Koshiba et al., issued August 13, 1996; U.S. Patent No. 6,827,921 to Singhal et

al., issued December 7, 2004; and U.S. Patent No. 6,749,648 to Kumar et al.,

issued June 15, 2004.

[00111] The following non-limiting examples illustrate the compositions and

methods of the present invention.

EXAMPLE 1

[00112] A negative electrode active material of formula Li ₄ Ti ₅ O ₁₂ is made

according to the following reaction scheme.

2 Li ₂ CO ₃ + 5 TiO ₂ → Li ₄ Ti ₅ O ₁₂ + 2 CO ₂

[00113] To make Li ₄ Ti ₅ O ₁₂ , 4 g TiO ₂ and 1.48 g of Li ₂ CO ₃ are premixed,

pelletized, placed in an oven and heated in a flowing argon atmosphere at a

rate of 5°C/min to an ultimate temperature of 800 ⁰ C. The temperature is

maintained for 8 hours, after which the sample is cooled to room temperature

and removed from the oven.

EXAMPLE 2

n e ec ro e ac ve ma er a o ormu a _{4 5 12} was ma e

according to the following alternative reaction scheme.

2 Li ₂ CO ₃ + 5 TiO ₂ + C → Li ₄ Ti ₅ O ₁₂ + 2 CO ₂

[00115] To make Li ₄ Ti ₅ O ₁₂ , 7.98 grams TiO ₂ , 3.04 g of Li ₂ CO ₃ and 0.56 g of

Ensaco carbon black were micronized for 15 minutes, premixed, pelletized,

placed in an oven and heated in a flowing argon atmosphere at a rate of

2°C/min to an ultimate temperature of 850 ⁰ C. The temperature was maintained

for 1 hour, after which the sample was cooled to room temperature and

removed from the oven.

[00116] An electrode was made with -84% of the Li ₄ Ti ₅ O ₁₂ active material

(11.1 mg), 5% of Super P conductive carbon, and 11% PVdF-HFP co-po!ymer

(EIf Atochem) binder. A cell with that electrode as cathode and a lithium-metal

counter electrode was constructed with an electrolyte comprising 1 M LiPF ₆

solution in ethylene carbonate/dimethyl carbonate (2:1 by weight) while a dried

glass fiber filter (Whatman, Grade GF/A) was used as electrode separator.

[00117] Figure 2 is a plot of cathode specific capacity vs. cell voltage for

the Li / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell. The cell was cycled using constant

current cycling at 0.1 milliamps per square centimeter (mA/cm ² ) in a range of 1

to 3 volts (V) at ambient temperature (~23(C). The initial measured open circuit

voltage (OCV) was approximately 3.02V vs. Li. The cathode material exhibited

a 182 mA ^β h/g (miliiamp-hour per gram) lithium insertion capacity, and a 163

mA ^β h/g lithium extraction capacity.

EXAMPLE 3

n e ec ro e ac ve ma er a o ormu a _{2 3 7} was ma e

according to the following reaction scheme.

Li ₂ CO ₃ + 3 TiO ₂ → Li ₂ Ti ₃ O ₇ + CO ₂

[00119] To make Li ₂ Ti ₃ O ₇ , 9.56 g TiO ₂ , 2.96 g of Li ₂ CO ₃ and 0.62 g Ensaco

carbon black were micronized for 15 minutes, premixed, pelletized, placed in an

oven and heated in a flowing argon atmosphere at a rate of 2°C/min to an

ultimate temperature of 750 ⁰ C. The temperature was maintained for 4 hour,

after which the sample was cooled to room temperature and removed from the

oven.

[00120] An electrode was made with -84% of the Li ₂ Ti ₃ O ₇ active material

(10.7 mg), 5% of Super P conductive carbon, and 11% PVdF-HFP co-polymer

(EIf Atochem) binder. A cell with that electrode as cathode and a lithium-metal

counter electrode was constructed with an electrolyte comprising 1 M LiPF ₆

solution in ethylene carbonate/dimethyl carbonate (2:1 by weight) while a dried

glass fiber filter (Whatman, Grade GF/A) was used as electrode separator.

[00121] Figure 3 is a plot of cathode specific capacity vs. cell voltage for

the Li / 1 M LiPF ₆ (EC/DMC) / Li ₂ Ti ₃ O ₇ cell. The cell was cycled using constant

current cycling at 0.1 mϋliamps per square centimeter (mA/cm ² ) in a range of 1

to 3 volts (V) at ambient temperature (~23°C). The initial measured open circuit

voltage (OCV) was approximately 3.04V vs. Li. The cathode material exhibited

a 172 mA»h/g lithium insertion capacity, and a 159 mA ^β h/g lithium extraction

capacity.

EXAMPLE 4

n e ec ro e ac ve ma er a o ormu a _{2 3 7} was syn es ze

per the teachings of Example 3. A counter electrode active material of the

formula LiVPO ₄ F was made as follows. In a first step, a metal phosphate was

made by carbothermal reduction of a metal oxide, here exemplified by

vanadium pentoxide. The overall reaction scheme of the carbothermal

reduction is as follows.

0.5V ₂ O ₅ + NH ₄ H ₂ PO ₄ + C → VPO ₄ + x NH ₃ + x H ₂ O + x CO

[00123] 7.28 g V ₂ O ₅ , 10.56 g (NH ₄ ) ₂ HPO ₄ , and 0.96 g carbon black

(Ensaco) were premixed using a mortar and pestle and then pelletized. The

pellet was transferred to an oven equipped with a flowing argon atmosphere.

The sample was heated at a ramp rate of 2°C per minute to an ultimate

temperature of 700 ⁰ C and maintained at this temperature for sixteen hours.

The sample was cooled to room temperature, and then removed from the oven.

[00124] In a second step, the vanadium phosphate made in the first step

was reacted with additional reactants, according to the following reaction

scheme.

VPO ₄ + LiF → LiVPO ₄ F

[00125] To make LiVPO ₄ F, 2.04 g VPO ₄ and 0.36 g LiF were premixed,

peϋetized, placed in an oven and heated at a ramp rate of 2°C per minute to an

ultimate temperature of 700°C, and maintained at that temperature for one

hour, after which the sample was cooled to ambient temperature and removed

from the oven.

[00126] A first electrode was made with -84% of the Li ₂ Ti ₃ O ₇ active

material (11.7 mg), 5% of Super P conductive carbon, and 11% PVdF-HFP co-

po ymer oc em n er. secon coun er-e ec ro e e ec ro e was ma e

with -84% of the LiVPO ₄ F active material (11.5 mg), 5% of Super P conductive

carbon, and 11% PVdF-HFP co-poiymer (EIf Atochem) binder.

[00127] A cell was constructed using the first and second electrodes and

an electrolyte comprising 1 M LiPF ₆ solution in ethylene carbonate/dimethyl

carbonate (2:1 by weight), while a dried glass fiber filter (Whatman, Grade

GF/A) was used as electrode separator.

[00128] Figure 4 shows the first cycle EVS results for the LiVPO ₄ F / 1 M

LiPF ₆ (EC/DMC) / Li ₂ Ti ₃ O ₇ cell (voltage range: 2 - 3.2 V vs. Li; Critical current

density < 100 μA/cm ² ; voltage step = 10 mV). The testing was carried out at

ambient temperature (-23 ⁰ C). The initial measured open circuit voltage (OCV)

was approximately 1.55V . The fluorophosphate cathode material exhibited a

153 mA ^β h/g lithium extraction capacity, and a 142 mA ^β h/g lithium insertion

capacity capacity. The titanate anode material exhibited a 170 mA ^β h/g ϋthium

insertion capacity, and a 158 mA ^β h/g lithium extraction capacity. The generally

symmetrical nature of the charge-discharge curves further indicates the good

reversibility of the system.

[00129] Figure 5 is an EVS differential capacity plot based on Figure 4. As

can be seen from Figure 5, the relatively symmetrical nature of the peaks

indicates good electrical reversibility. There are small peak separations

(charge/discharge), and good correspondence between peaks above and

below the zero axis. There are essentially no peaks that can be related to

irreversible reactions, since peaks above the axis (cell charge) have

corresponding peaks below the axis (cell discharge), and there is very little

separa on e ween e pea s a ove an e ow e ax s. s s ows a e

LiVPO ₄ F / Li ₂ Ti ₃ O ₇ COUpIe is suitable for use in a cell.

EXAMPLE 5

[00130] An electrode active material of formula Li ₄ Ti ₅ O ₁₂ was synthesized

per the teachings of Example 2, and a counter-electrode active material of the

formula LiVPO ₄ F was synthesized per the teachings of Example 5,

[00131] Two LiVPO ₄ F / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cells were

constructed per the teachings of Example 5 (cell 1 : LiVPO ₄ F = 12.2 mg,

Li ₄ Ti ₅ O ₁₂ = 12.5 mg)(cell 2: LiVPO ₄ F = 10.3 mg, Li ₄ Ti ₅ O ₁₂ = 10.6 mg),

[00132] Figure 5 presents data obtained by multiple constant current

cycling at 0.1 milliamp hours per square centimeter of the two cells between 2

and 3 volts at ambient temperature (-23 ⁰ C), carried out at a charge/discharge

rate of C/2 (cell 1 = π, cell 2 = o). Figure 6 shows the excellent rechargeability

of the LiVPO ₄ F / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cells, and also shows good

cycling and capacity of the cells.

[00133] A third LiVPO ₄ F / 1 M LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell was

constructed per the teachings of Example 5 (LiVPO ₄ F = 11.2 mg, Li ₄ Ti ₅ O ₁₂ =

10.1 mg). Figure 7 shows the first cycle EVS results for the LiVPO ₄ F / 1 M

LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell (voltage range: 2 V -3 V; critical current density

< 100 μA/cm ² ; voltage step = 10 mV). The testing was carried out at ambient

temperature (-23 ⁰ C). The initial measured open circuit voltage (OCV) was

approximately 3.10 V. The fluorophosphate cathode material exhibited a 148

mA ^β h/g lithium extraction capacity, and a 142 mA*h/g iithium insertion capacity

capaci y. e i ana e ano e ma er a ex e a m ^® g um nser on

capacity, and a 158 mA ^β h/g lithium extraction capacity. The generally

symmetrical nature of the charge-discharge curves further indicates the good

reversibility of the system.

[00134] Figure 8 is an EVS differential capacity plot based on Figure 7. As

can be seen from Figure 8, the relatively symmetrical nature of the peaks

indicates good electrical reversibility. There are small peak separations

(charge/discharge), and good correspondence between peaks above and

below the zero axis. There are essentially no peaks that can be related to

irreversible reactions, since peaks above the axis (cell charge) have

corresponding peaks below the axis (cell discharge), and there is very little

separation between the peaks above and below the axis. This shows that the

LiVPO ₄ F / Li ₄ Ti ₅ O ₁₂ COUpIe is a suitable for use in a cell.

EXAMPLE 6

[00135] An electrode active material of formula Li ₄ Ti ₅ O- _I2 was synthesized

per the teachings of Example 1. A counter electrode active material of the

formula Na ₃ V ₂ (PO ₄ J ₂ F ₃ was made as follows. First, a VPO ₄ precursor was

made according to the following reaction scheme.

V ₂ O ₅ + 2 (NH ₄ J ₂ HPO ₄ + C → 2 VPO ₄

A mixture of 18.2 g (0.1 mol) V ₂ O ₅ , 26.4 g (0.2 mol) (NH ₄ J ₂ HPO ₄ , and 2.4 g (0.2

mol) of elemental carbon was made, using a mortar and pestle. The mixture

was pelletized, and transferred to a box oven equipped with an argon gas flow.

e mixture was nea e o a empera ure o a ou , an ma n a ne a

this temperature for 3 hours. The mixture was then heated to a temperature of

about 75O ⁰ C ₁ and maintained at this temperature for 8 hours. The product was

then cooled to ambient temperature (about 21 ⁰ C).

[00136] Na ₃ V ₂ (Pθ ₄ ) ₂ F ₃ was then made from the VPO ₄ precursor. The

material was made according to the following reaction scheme.

2 VPO ₄ + 3 NaF → Na ₃ V ₂ (PO ₄ J ₂ F ₃

[00137] A mixture of 2.92 g of VPO ₄ and 1.26 g of NaF was made, using a

mortar and pestle. The mixture was pelletized, and transferred to a

temperature-controlled tube furnace equipped with an argon gas flow. The

mixture was heated at a ramp rate of about 2°C/minute to an ultimate

temperature of about 75O ⁰ C for 1 hour. The product was then cooled to

ambient temperature (about 20 ⁰ C).

[00138] A first electrode was made with -84% of the Li ₄ Ti ₅ O ₁₂ active

material (11.1 mg), 5% of Super P conductive carbon, and 11% PVdF-HFP co¬

polymer (EIf Atochem) binder, A second counter-electrode electrode was made

with -84% of the Na ₃ V ₂ (PO ₄ J ₂ F ₃ active material (11.9 mg), 5% of Super P

conductive carbon, and 1 1% PVdF-HFP co-polymer (EIf Atochem) binder.

[00139] A cell was constructed using the first and second electrodes and

an electrolyte comprising 1 M LiPF ₆ solution in ethylene carbonate/dimethyl

carbonate (2:1 by weight), while a dried glass fiber filter (Whatman, Grade

GFfA) was used as electrode separator.

[00140] Figure sets 9/10 and 11/12 show the voltage profile and differential

capacity plots for the first and fifth cycle EVS responses, respectively, of the

a _{3 2} U _{2 3} 1 _{6 4 5 12} ce vo tage range: 1 ,5 - 3.2 ;

Critical current density < 100 μA/cm ² ; voitage step = 10 mV). The testing was

carried out at ambient temperature (-23 ⁰ C). The initial measured open circuit

voltage (OCV) was approximately 1.55V . The fluorophosphate cathode

material exhibited a 160 mA ^β h/g lithium extraction capacity, and a 156 mA»h/g

lithium insertion capacity for the first cycle. The first cycle results demonstrated

a first cycle charge efficiency of > 97%. The fluorophosphate cathode material

exhibited a 150 mA ^β h/g lithium extraction capacity, and a 150 mA ^» h/g lithium

insertion capacity for the fifth cycle.

[00141] The titanate anode material exhibited a 171 mA ^β h/g lithium

insertion capacity, and a 167 mA ^β h/g lithium extraction capacity for the first

cycle. The titanate anode material exhibited a 161 mA ^» h/g lithium insertion

capacity, and a 161 mA ^e h/g lithium extraction capacity for the fifth cycle. The

generally symmetrical nature of the charge-discharge curves further indicates

the good reversibility of the system.

[00142] The EVS differential capacity plots for the first and fifth cycles,

Figures 10 and 12, respectively, indicate good electrical reversibility. There are

small peak separations (charge/discharge), and good correspondence between

peaks above and below the zero axis. There are essentially no peaks that can

be related to irreversible reactions, since peaks above the axis (cell charge)

have corresponding peaks below the axis (cell discharge), and there is very

little separation between the peaks above and below the axis. This shows that

the Na ₃ V ₂ (PO^ ₂ F ₃ / Li ₄ Ti ₅ O ₁₂ COUpIe is suitable for use in a cell.

igu ws y vi _{3 2 4 2} - _S

LiPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ cell. The data was collected at approximate

charge/discharge rate of C/2. The initiai cathode reversible capacity was

approximately 110 mA ^β h/g and the cells cycle with relatively low capacity fade

behavior. The minor decrease in discharge capacity is indicative of the

excellent rate characteristics of this system.

[00144] A second cell was constructed per the teachings in this example,

comprising a 2:1 Na:Li salt mixture using a mixture of 2M NaPF ₆ and 1 M LiPF ₆

in ethylene carbonate/dimethyl carbonate (2:1 by weight) electrolyte

(Na ₃ V ₂ (PO ₄ ) _S F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMC) / Li ₄ Ti ₅ O ₁₂ ).

The first electrode was made with -84% of the Li ₄ Ti ₅ O ₁₂ active material (11.3

mg), 5% of Super P conductive carbon, and 11% PVdF-HFP co-polymer (EIf

Atochem) binder. The second counter-electrode electrode was made with

-84% of the Na ₃ V ₂ (PO ₄ J ₂ F ₃ active material (12.0 mg), 5% of Super P

conductive carbon, and 11% PVdF-HFP co-polymer (EIf Atochem) binder.

[00145] Figures sets 14/15 and 16/17 show the voltage profile and

differential capacity plots for the first and second cycle EVS responses,

respectively, of the Na ₃ V ₂ (PO ₄ J ₂ F ₃ / 1 M LiPF ₆ + 2M NaPF ₆ (EC/DMC) /

Li ₄ Ti ₅ Oi ₂ CeII (voltage range: 1.5 - 3.2 V; Critical current density < 100 μA/cm ² ;

voltage step = 10 mV). The testing was carried out at ambient temperature

(-23 ⁰ C). The initial measured open circuit voltage (OCV) was approximately

1.55V . The fluorophosphate cathode material exhibited a 130 mA ^β h/g lithium

extraction capacity, and a 120 mA ^β h/g lithium insertion capacity for the first

cycle. The fluorophosphate cathode material exhibited a 131 mA ^β h/g lithium

extraction capacity, and a 128 mA-h/g lithium insertion capacity for the second

cycle.

[00146] The titanate anode material exhibited a 138 mA*h/g lithium

insertion capacity, and a 128 mA ^» h/g iithium extraction capacity for the first

cycle. The titanate anode material exhibited a 139 mA ^« h/g lithium insertion

capacity, and a 136 mA ^» h/g lithium extraction capacity for the second cycle.

The generally symmetrical nature of the charge-discharge curves further

indicates the good reversibility of the system.

[00147] The EVS differential capacity plots for the first and second cycles,

Figures 15 and 17, respectively, indicate good electrical reversibility. There are

small peak separations (charge/discharge), and good correspondence between

peaks above and below the zero axis. There are essentially no peaks that can

be related to irreversible reactions, since peaks above the axis (cell charge)

have corresponding peaks below the axis (cell discharge), and there is very

little separation between the peaks above and below the axis. This shows that

the Na ₃ V ₂ (PO ₄ J ₂ F ₃ / Li ₄ Ti ₅ O ₁₂ COUpIe is suitable for use in a cell having a 1M

LiPF ₆ + ^" 2M NaPF ₆ (EC/DMC) electrolyte.

EXAMPLE 7

[00148] Active material of formula L ₃ V ₂ (PO ₄ J ₃ was made according to the

following reaction scheme.

3 LiH ₂ PO ₄ + V ₂ O ₃ + x C → L ₃ V ₂ (PO ₄ J ₃ + 2 CO ₂

[00149] To make L ₃ V ₂ (PO ₄ J ₃ , 15 g LiH ₂ PO ₄ (Aldrich), 7.25 g V ₂ O ₃ (Stratcor)

and 0.70 g of Super P carbon (Ensaco) are premixed, pelletized, placed in an

,

which the sample is cooled to room temperature and removed from the oven.

[00150] A first cell was constructed as follows. A first electrode was made

with 83% by weight Li ₄ Ti ₅ O ₁₂ active material (commercially available from Sud-

Chemie under the trade name EXM 1037), 10% by weight Super P conductive

carbon, and 7% by weight PVdF binder. A second counter-electrode electrode

was made with 84.5% by weight L ₃ V ₂ (PO ₄ ) _S active material, 8.5% of Super P

conductive carbon, and 7% PVdF binder. The first cell was constructed using

the first and second electrodes and an electrolyte comprising 0.13M LiPF ₆

solution in ethylene carbonate/dimethyl carbonate/ethyl-methyl carbonate (2:5:3

by weight), while a Celgard 2300 separator was used as electrode separator.

[00151] A second cell was constructed in the same manner as the first,

except formulation for the first electrode was as follows: 87% by weight

Li ₄ Ti ₅ O ₁₂ active material (commercially available from Sud-Chemie under the

trade name EXM 1037), 6% by weight Super P conductive carbon, and 7% by

weight PVdF binder.

[00152] To test the electrochemical performance of the cells, the cells were

initially cycled three times between 1 ,5V and 3.2V at C/5. Thereafter, for 2OC

charge cycling, the charge voltage was maintained at 3.8V until the current

dropped to 20% of its initial value. The testing was carried out at ambient

temperature (-23 ⁰ C).

[00153] Figures 18 and 19 shows the cycling behavior of the first and

second cells, respectively. The data was collected at a charge rate of 2OC

(after the initial three conditioning cycles), and a discharge rate of C/2. The

n a ca o e revers e sc arge capac y was m * g or e rs ce

and 133 mA ^® h/g for the second celi, and the capacity at the third cycle was 106

mA ^β h/g for the first cell and 1 10 mA ^β h/g for the second cell. After a 1 ,000

cycles, the first cell exhibited 77% of its initial capacity and the second cell

exhibited 76% of its initial capacity. The amount of decrease in discharge

capacity is indicative of the excellent high rate characteristics of this system.

[00154] In addition, both cells exhibited recoverable capacity. At

approximately the 500 ^th cycle, each cell was returned to a C/2 charge rate for

four consecutive cycles (referred to as "intermediate C/2 cycles" and indicated

by reference symbol "0" in Figures 18 and 19). The first cell exhibited a

discharge capacity of 87 mA ^β h/g immediately prior to the intermediate C/2

cycles, 125 mA ^β h/g for the intermediate C/2 cycles, and 95 mA ^β h/g immediately

after the celi was returned to the 2OC charge rate. The second cell exhibited a

capacity of 91 mA ^« h/g immediately prior to the intermediate C/2 cycles, 130

mA*h/g for the intermediate C/2 cycles, and 96 mA ^β h/g immediately after the

cell was returned to the 2OC charge rate.

[00155] The examples and other embodiments described herein are

exemplary and not intended to be limiting in describing the full scope of

compositions and methods of this invention. Equivalent changes, modifications

and variations of specific embodiments, materials, compositions and methods

may be made within the scope of the present invention, with substantially

similar results.