CATION CONDUCTIVE SOLID POLYMERS

Technical Field The present invention relates to a broad class of cation conductive solid polymers useful in batteries, fuel cells, sensors, supercapacitors, electrochromic devices and the like.

Background Of The Invention

A number cf solvent-free polymer electrolytes are known and there has been considerable interest in the possible utilization of the electrolytes in electrochemical devices such as batteries, fuel cells, sensors, supercapacitors and eiectrochromic devices. Among the pol -ers which have been tested for such use are those based upon the linear-chain polyethers, poly(ethylenecxice) and poly(propyieneoxide) with alkali metal salts. Cation conductive phosphazene and siloxane pol mers have also been reported which exhibit better conductivity at room temperature than do the linear-chain polyether electrolytes. One class of polymers of interest are the pclyphosphazene sulfonates as reported by S. Ganapathiappan, Kaisin Chen and D.F. Shriver,

Macromolecules , 1988, 21, 2299, in Journal of the American Chemical Society, 1989, 111. 4091' and Chemistry cf Materials, 1989, ___, 483. The polyether electrolytes reported in, for example, Polymer Communications, 1987, 23, 302. Polyester conductive

polymers are reported in, for example, Macromolecules 1988, 21, 96. Cation conductive siloxane comb polymers are reported in Polymer Communications, 1989, 30 , 52 and in Journal of Polymer Science: Part C: Polymer letters, 2_S, 187-191, 1990. Anion conductivity is also known in solid polymer electrolytes as is reported, for example, in Macromolecules 1984, __ _, 975. Single ion conductive polymers have an advantage over double (positive and negative) ion conductive polymers in that they can charge and discharge more completely as limitations on charging and discharging due to DC polarization is obviated.

While the various polymer electrolytes set forth in the above publications have shown promise, such promise has generally not been enough to make them practical choices for use in, for example high energy batteries and for other applications wherein it is desirable to have particularly high ionic conductivity for the polymer electrolyte and wherein it is desirable to use relatively thin films of the polymer electrolyte. Basically, the polymer electrolytes of the prior art do not exhibit sufficient ionic conductivity. Furthermore, the polymer electrolytes of the prior art have generally not exhibited desirable physical properties for incorporation in electrolytic devices. For example, the films may be too sticky, the polymers may be too close to being liquid, the polymers may be too brittle, or the polymers may be too heat sensitive.

The present invention is directed to overcoming one or -ore of the problems as set forth above.

Disclosure Of Invention

In accordance with an embodient of the present invention an amorphous lomcally conductive macromolecular solid is set forth which has improved ambient temperature ionic conductivity. The macromolecular solid carries a negative charge and has a positively charged ionic species associated with it. The macromolecular material comprises a polymer or copolymer having a polymer backbone having a plurality of side chains extending therefrom having distal constituents having the formula:

-x-y M ^* wherein

X = CF ₂ , CFCN, CFR, or CCNR or CgF.R _p where a s 1-4, b is 0-3 and a + b is 4 and wnere R is virtually any organic or substituted organic group, for example, alk l, alkenyl, aryl, aralkyl, haloalkyl , CN, a polymer such as a polyether, a polyester, a polyamme, a polyimine, etc. Y = S0 ₃ , C0 ₂ or PO _c where c is 2, 3 or , and

M = a cation.

An lomcally conductive aacrcroiecular solid m accordance with the present invention nas a number cf advantages over prior art lomcally conductive macromolecular solids. First of all, tr.e conductivity cf the macromolecular solid in accordance with the present invention is generally significantly higher than tnat of the prior art macromolecular solids. Second, the macromolecular solids of the present invention have desirable physical properties in that tney can be formulated in relatively th r. but still relatively highly conducting films whicr. hav*-** esiraole mechanical properties sucn as ou. . ess and lack of stickiness. Furthermore, side cnams of the

- A - nature required by the present invention can be relatively readily added to polymers of substantially any backbone so long as such polymers have at least one active or labile hydrogen. Or, alternatively, the required side chains of the present invention can be added to the monomers which are later polymerized or copolymerized to form a polymer system. Since any of a number of different polymer backbones can be utilized the designer of a battery, fuel cell, supercapacitor, electrochroπ _\ ic device, sensor or the like can, to a greater extent, choose the physical properties desired for the particular application thus providing significant added flexibility to the design of such devices. In accordance with a preferred embodiment of the present invention a plasticizer car- be added leading to a further increase m the conductivity of the macromolecular solid as well as adjustment of its mechanical properties as by adding flexibility.

Brief Description Of Drawings

The invention will be better understood by reference to the figures of the drawings wherein like partes denote like parts throughout and wherein: Figure 1 illustrates a cell assembly as used for measuring conductivity;

Figure 2 illustrates a cell and vacuum chamber as used for measuring conductivities; and Figure 3 illustrates, schematically, an experimental, setup as used for AC impedance (conductivity) measurements.

Best Mode For Carrying Out Invention

The present invention provides a broad class of iomcally conductive macromolecular solids. Such macromolecular solids (polymers or copolymers) can ^* 5 have any of a great number of polymer backbones (made up of repetitive units) but are all characterized by having a plurality of side chains which have distal constituents having the formula: -X-Y ^' M ^* 10 wherein

X = CF ₂ , CFCN, CFR, or CCNR or C ₆ F _a R-, where a is 1-4, b is 0-3 and a - b is 4 and where R is virtually any organic or substituted organic group, for example, alkyi, alkenyl, aryl, aralkyl, CN, 15 haloalkyl, a polymer such as a polyether, a polyester, a polyamine, a polyimine, etc.

Y = S0 ₃ , C0 ₂ or PO _c where c is 2, 3 or 4 , and M = a cation.

The term cation is used broadly herein to 20 include virtually every species which ca bear a positive charge and includes the elements of Groups IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, V3, VIA, VI3, VIIA, VII3, AND VIII of the Periodic Table of the Elements . 25 Examples of useful polymer backbones include polyether polymers, polyester polymers, poly(ethylene)imine polymers, polyphasphazene polymers, siloxane polymers, and the like. The just set forth list of polymer backbones is not meant to be 20 exhaustive buz is merely illustrative of a few of the . polymers to w.-.ich the side chains required by the present invention may be appended. The polymers which make up the backbone of the macromolecular solid of the invention can be polymerized by the methods of the

prior art. The polymer backbone may -also comprise a copolymer of two or more polymers with repeating units of the individual monomers.

Generally the number of side chains on the macromolecular solid should be such as to provide from 0.04 to about 4 side chains per monomer unit. More preferably, the number of side chains per monomer unit falls within the range from about 0.04 to about 2. The preferred compounds are those wherein X = CF ₂ or C ₆ F ₄

Alternatively, some, but not all of the fluorines may be replaced with an organic group. Virtually any organic or substituted organic group can be present, for example, alkyl, aikenyl, aryl, aralkyl , πaloalkyl, a polymer such as a polyether, a polyesrer, a polyamine, a polyimine, etc.

The cation, M, can be virtually any desired catioin for a desired use, e.g. , as a sensor, battery, fuel cell, supercapacitor, electrochromic device, ofr the like. Batteries can be based upon, for example, having the cation be an hydrogen, a quarternary ammonium ion (NR ¹ ₄ ^* where ¹ can be hydrogen, alkyl, aryl, aralkyl, aikenyl or the like), or an alkali metal cation, such as lithium, sodium, potassium, rubidium or cesium, with lithium and sodium generally being preferred.

In accordance with the present invention the _^ macromolecular solid can further include an effective amount for enhancing the ionic conductivity cf the solid of a plasticizer. Virtually any plasticizer which does not significantly lower the ionic conductivity can be utilized. However, the preferred plasticizer can be represented by the formula: R ² ₂ C(OC ₂ R ² „) _n CN

wherein each R ² const.tuent is independently hydrogen, alkyl, aryl, aikenyl ^" or aralkyl with hydrogen, methyl and ethyl being preferred and wherein n = 1 to 8 inclusive. One method of preparing polymers with the desired side chains is as follows: a desired polymer, for example, a poly(ethylene)i ine polymer, can be reacted with a compound of the formula R ³ C0C1 in an amount sufficient to react with only a portion of the imine hydrogen to add COR ³ groups. The remainder of the poly(ethylene) imine polymer backbone wili then still have imine hydrogens present. Thereafter, the -COR containing ethyleneimme polymer can be reacted to an excess of FS0 ₂ CF ₂ COF to provide the required side chains in accordance with the present invention, but with a fluorine attached to the terminal S0 ₂ group. Thereafter the polymer can be reacted with a metal carbonate, for example sodium carbonate, to convert it to its ionic form. The polymer can then be d alyzed in the presence of an excess of sodium chloride. All of the CO groups in the side chains can then be reduced using, for example, BH ₃ -SMe ₂ followed by HC1 and a base such as LiOH, NaOH or KOH. A typical R ³ group would be -CH ₂ 0(C ₂ H ₄ 0) _rτ ,CH ₃ but R ³ may have a multitude of other structures.

Cation conductive polymers with polyether side chains can be made by the following reaction scheme

1 . CH ₃ ( 0C,H ₄ ) ₂ 0H - CH ₃ OC ₂ H ₄ OCH ₂ CHO CH,C1,

( C0C1 ) ₂ I [ O ]

DMSϋ

N ( C„H _e ) ₃

CK ₃ OC ₂ H ₄ OCH ₂ COOK

2. CH ₃ (OC ₂ H ) ₂ OH - CH ₃ OC ₂ H ₄ OCH ₂ COOH

Mlt _> 0 ₇ -78 ^* C

CH ₃ (OC ₂ H ₄ ) _m OH + Na NaO(C ₂ H ₄ ) _m CH ₃

THF

NaO(C ₂ H ₄₀ ) _m CH ₃ - CH ₃ (OC ₂ H ₄ ) _m OCH ₂ COOCH ₃

BrCH ₂ COOCH ₃ 10 -NaBr

CH ₃ (OC ₂ H ₄ ) _m OCH ₂ COOCH ₃ - CH ₃ (OC ₂ H ₄ ) _m OCH ₂ COOH acid or base hydrolysis

- 0 where may be an integer or an average of integers

Single ion conductive ionic conducting polymers can also be prepared as set forth in following: RCOC1 - [C ₂ H ₄ NH] _n - [ (C ₂ H ₄ N) _x (C ₂ HNH)- _.x ] _n

COR

[(C _: H ₄ N) _x ;C ₂ H ₄ NH), n - [ (C ₂ H ₄ ) _x (C ₂ H ₄ N) ₁ . _n . I FS0 ₂ CF ₂ COF ; I

COR. (excess) COR C0CF ₂ S0 ₂ F

[ ( C ₂ H ₄ N ) { C ₂ H ₄ N ) ,. _x ] _n → [ ( C ₂ K ₄ N ) _x ( C ₂ H ₄ N ) ,, j _n

20 COR COR COCF ₂ S0 ₃ ^' M"

[ ( C,H ₄ N J _x ( C ₂ H ₄ N ) ] „ ^■ * [ ( C ₂ H ₄ N ) ( C ₂ H ₄ N ) ,. _x ] _π

COR COCF ₂ S0 ₃ ^{' τ} CH ₂ R CK,CF ₂ S0 ₃ ^" M

(i) BH ₃ .S(CH ₃ ) ₂ (ii) HC1 (iii) MOH

40 where R = CH ₂ 0 ( C ₂ K ₄ 0 ) _m CH ₃ , m is an integer or average o: integers and M can suitably be Li or Na.

As an alternative pol (ethylene) imine based electrolyte can ^" be synthesized from monomers as per the following reaction scheme:

Polvmeπze CF ₂ SO. _j F

[CH ₂ CH ₌ N] _n [CH ₂ CH ₂ N:

COR COCF ₂ SOF (i) 3H ₃ .S(CH,) ₂ (ii) HC1 (ii ) MOH

[CH ₂ CH ₂ N] _Π [CH ₂ CH ₂ N; ι-n

CH,R CH _^ CF ₂ S0 ₃ ^{' ,}

Poly (phosphazenef luorosulf cnate) home- anc copolymers can be prepared as fellows:

) [NPCl ₂ ] _n 2Na'[S0,CF ₂ CH.,0] 2-

THF

[NP(OCH ₂ CF ₂ S0 ₃ a ^* ) _x Cl ₂ . _n

NaOR (excess)

[NP(OCH ₂ CF ₂ S0 ₃ a ^* ) _χ (OR) ₂ . _x ] _n

LiCl (excess)

( NP ( 0CH ₂ CF ₂ SO ₃ ^' i ^* ) _χ ( OR ) ₂ . _x ] „ where R is C _c H ₄ OC ₂ K ₄ OCH ₃ and x lies between 0 and 1.

2) [NPCl ₂ ] _n + 2Na ^* [S0 ₃ CF ₂ CH ₂ 0] ^2"

THF

[NP(OCH ₂ CF ₂ S0 ₃ ^" Na ^* ) ₂ ] _n

Siloxane homo- and copolymers having the required side chains can be made as follows:

CH ₃

I

(CH ₃ ) ₃ SiO[SiO] _n Si(CH ₃ ) ₃ ♦ HOC ₂ H ₄ OCOCF ₂ S0 ₃ M ⁺

H

THF, N(C ₂ H,) ₃ , 80 ^* C/24 hours

ID CH, CH,

(CH ₃ ) ₃ SiO[ (SiO) _x (SiO),. _x ; _n Si(CH ₃ ) ₃ - (ROH, 80 ^* C/48 hours ) H OC ₂ H ₄ OCOCF,S0 ₃ ^' M ^T

20

25 (CH ₃ )

wherein M = Na or Li; 20

R = (C ₂ H ₄ 0) _m CH ₃ where m is an integer or average of integers; and

25 x = 0 to 1.

More generally, the compound

R-C X

40

0 I Y I, where X, Y and R are as previously defined can be reacted with virtually any polymer which has an available hydrogen, for example a hydrogen attached to nitrogen, sulfur or oxygen, to provide the desired side chains. As pointed out previously, the group R can be virtually any alkyl, aryl, aralkyl, aikenyl, fluoroalkvl, fluoroarvl or

fluoroalkenyl group or can be an oligomer such polyethyleneoxide or polypropyleneoxide.

An alternative side chain m accordance with the present invention can be added by reacting the compound

with an active hydrogen on a polymer backbone. Such might be carried out, for example, by converting the above compound to its acid chloride and then reacting the acid chloride with poly(ethyieneimine) as set forth previously.

The invention will be setter understood by reference to the illustrative examples which follow. It should be noted that these examples are meant to be illustrative only and are not exhaustive of the polymer backbones and side chains of the invention.

Eq ip ent And Measurement Technique

Conductivities of the polymers were evaluated by AC impedance spectroscopy. Referring to the Figures, a f lm 6 of the dried polymer electrolyte was sandwiched between two stainless steel blocking

2 electrodes ~,8 that each had an area of 0.7854 cm .

The thickness cf the polymer film 6, which typically varied between 0.51 mm ...id 1.02 mm, was measured with a micrometer. ^" e asse oly 9, composed of the blocking electrode-polymer sandwich cell 10 inside a

Delrin cup 12 (Figure 1), was transferred to a vacuun chamber 14 that had provision for heating (Figure 2) and for applying a constant pressure of 65-97 lb/in across the polymer film 6. The electrodes 7,8 were connected to a potentiostat (PAR 173) operating in the gaivanostatic mode.

The cell 10 was then perturbed with a small AC signal generated by a Solartron 1250 Frequency Response Analyzer, and the real and imaginary components of the cell impedance were measured as a function of frequency at each of the desired temperatures. The setup was allowed to stabilize overnight after the temperature was changed. The AC impedance data were plotted in both the Nyquist and 3ode planes to identify the high frequency relaxation arising due to the polymer electrolyte. Typically, the frequency of the AC signal was scanned from 65 KHz down to 10 mHz. The intercept at the real axis of the high frequency relaxation was assumed to represent the resistive component of the polymer electrolyte impedance. This was then converted to the resistivity of the polymer (the thickness and the area of the polymer film 6 were known) . The reciprocal of resistivity gave the conductivity, σ, having units of Ω-cm ^* ' . In cases where high frequency relaxation occurred above 65 KHz, a Hewlett Packard 4192A Impedance Analyzer was used to measure the polymer electrolyte resistance. This instrument has a frequency range capability of 13 MHz to 5 Hz. The experimental setup 16 used for conductivity measurements is shown in Figure 3.

Preparation Of Polymer Films

Solutions o ^" f polymer films were prepared by dissolving a known quantity of polymer in dry solvent. For conductivity measurements, the polymer solution ^" 5 was added dropwise into the Delrin cup to cast a film. The film was then dried for 3 days in a glass vacuum apparatus at 120'C at <0.01 torr. Film thickness was measured using a micrometer.

0 Example I

Poly(ethyleneimine) polymers in accordance with the present invention were synthesized as described herein and the ionic conductivity of their lithium and sodium salts were determined at 24 'C and 5 80'C. Table 1 reports the results of this study.

Example 2 The effects of the presence of the plasticizer CH ₃ (0C ₂ H ) ₄ CN were determined for lithium 0 forms of modified poly(ethyleneimine) polymers in accordance with the present invention. The results are recorded in Table 2. These can be compared viz: the entries in Table 1 wherein X = 0.66 and X = 2.9: and wherein M is Li. It will be noted that the 5 conductivity increased from low (which amounts to less than 10 ^'7 ) to the order of magnitude of 10 ^"5 to 10 . Thus, significant effect has been found for adding plasticizer.

Tahls_2

Variation Of Conductivity In The Presence Of Plasticizer Me(00,11,1

(C ₂ H ₄ N),. (C,H ₄ N) ,,

(C ₂ H«0) _ia3 CII ₃ CH _? CF ₂ S0 ₃ i'

Amount of Plasticizer (It of moles for 1 mole Ratio of ether oxygen Condu

X of polymer) to Li+ ion

66 2 69 47 2 88 49 3 36 55

4.72 379.1 1.0

Example 3 Polyphosphazene polymers in accordance with the invention in the manner previously described and the effect of the presence of a plasticizer on the conductivity of such polymers was determined. Table 3 presents the results of such experiments.

Example 4

The variation in the conductivity of siloxane polymers in accordance with the invention and synthesized as previously described was determined and is reported in Table 4 .

V V.

©

9\

B

Table 3

Ionic Conductivity Of Polyphosphazene Based PolyelectrolyteB 5 [ P(OCjH ₄ OC ₂ H ₄ OCH3) _1B (OCH ₂ CF ₂ Sθ3Li*)o ₂ )n ( lOOmg)

D«

Amount of PlaBtlciaerfrngl Conductivity at 24 'C (Ω-cπ .

10 0 3.2 x 10 ⁷

66 3.4 x 10 ^β

132 4.3 x 10

15 321 1.8 x 10

516 1.4 x 10 ^r "

Plasticizer used was C\l ₃ (OC._l\ _t ) CN

r- -fi i

Table 4

10 Amount of Plasticizer (mq) Conductivity at 24 ^" C (fl-cm) ¹

0 l.l x 10"

57 l .9 x l o

15

00 99 3.2 x 10

196 4.5 x 10

390 1.2 x 10

Plasticizer used was CH ₃ (OC.,H ₄ ) ₄ CN

Industrial Applicability

Cation conductive solid polymers are provided in accordance with the present invention which have good physical properties and which are relatively high in conductivity whereby they are useful in the manufacture of batteries, sensors, fuel cells and the like.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable cf further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention and the limits of the appended claims.