TITLE OF THE INVENTION

DODECABORATE SALT RADICAL ANION COMPOSITIONS AND METHODS FOR MAKING AND USING SUCH COMPOSITIONS

[0001] This application claims the benefit of Provisional Application No 60/991357, filed on November 30, 2007 The disclosure of the Provisional Application is hereby incorporated by reference

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The subject matter of the instant invention is related to the following copendtng and commonly assigned patent applications 10/655,476, filed September 04, 2003; 10/924,293, filed August 23, 2004; 11/372,907, filed March 10, 2006, 11/197,478, filed August 05, 2005 and 11/710,116, filed February 23, 2007. The disclosure of the foregoing patent applications ts hereby incorporated by reference

BACKGROUND OF THE INVENTION

[0003] The invention relates to a novel compound that can formed by the chemical or electrochemical oxidation of a Bi ₂ F _x Zi ₂ / salt to obtain a compound which can be characterized as:

M ^a* (B ₁₂ F _x Z _12-1 ), wherein a is 1 to 4 and x is at least 3, or at least 5, or at least 8, for the dodecaborate salts; 3 ≤ x ≤ 12; M comprises at least one electrochemically stable cations. Z represents H, Cl, Br, or OR, where R = H, C _{1 8} , preferably d ₃ alkyl or fluoroalkyl The subscript x can be 4 to 12, 7 to 12 or 7 to 11 , and mixtures of salts having x values from 4 to 12, 7 to 12 or 7 to 1 1. The subscripts "10-x" and "12-x" mean "10 minus x" and "12 minus x" respectively All other subscripts with the "-" indicate a range, e.g 1-3 means 1 through 3

[0004] The invention also relates compositions comprising the compound and to methods for making and using the compound and compositions.

[0005] Divalent salts based on the decaborate and dodecaborate closed cage structure (i.e., B ₁₀ Xi _O ^{2" ar|} d B ₁₂ Xi ₂ ^2' ), are known in the art. The use of these salts has been reported in battery electrolytes, fuel cell electrolytes and other applications.

Electrochemical oxidation of Bi ₀ Cli ₀ ^2" in acetonitrile gives a purple colored solution, (e.g., as described in Electrochemical Oxidation of Polyhedral Boron Halide Anions, Bowden, J. Electrochem Soc; Vo1 129, No. 6, Page 1249). Chemical oxidation of B ₁₀ Ch ₀ ^2" with TI(CF ₃ COO) ₃ in acetonitrile gives a purple product which by UV-vis spectroscopy is identical to the electrochemical oxidation product of B ₁₀ CI ₁₀ ^2" . Chemical oxidation with xenon difluoride was show to form neutral B ₉ CI ₉ .

[0006] Fluorinated B ₁₂ derivatives such as B ₁₂ F _x H ₁₂ - _X ^2" are described in the Cross Reference To Related Patents and Patent Applications above. It was reported (by Ivanov et. al., J. Amer. Chem. Soc, 2003, vol. 125, 4694.) that B ₁₂ F ₁₂ ^2" underwent a quasi-reversible oxidation at 4.9 V vs. LJ+/O (ca. 1 .9-2.0 V vs. NHE).

[0007] There is a need in this art for oxidized radical anion products such as B ₁₂ F _x Z ₁₂ -/ or Bi ₀ F _x Z _{1O x} ^" . Such products can impart desirable properties when employed alone or as additives when generated in conventional battery, capacitors or fuel cell electrolytes, or when prepared for use as reagents for carrying out chemical reactions..

BRIEF SUMMARY OF THE INVENTION

[0008] The invention solves problems associated with conventional compounds by providing a compound comprising at least one oxidized B ₁₂ F _x Zi _{2 x} ^2" salt which can be characterized as:

M ^a+ (B ₁₂ F _x Z ₁₂ ., ) _a

wherein a is 1 to 4 and x is at least 3, or at least 5, or at least 8, for the dodecaborate salts and; 3 < x < 12; M comprises at least one electrochemically stable cations. Z represents H, Cl, Br, or OR, where R = H, C _1-8 , preferably Ci _-3 alkyl or fluoroatkyl. The subscript x can be 4 to 12, 7 to 12 or 7 to 11 , and mixtures of salts having x values from 4 to 12, 7 to 12 or 7 to 11. The subscripts "10-x" and "12-x" mean "10 minus x" and "12

minus x" respectively All other subscripts with the "-" indicate a range, e g 1-3 means 1 through 3

[0009] One aspect of the invention relates to a method for producing oxidized salts that can be employed for carrying out a variety of chemical oxidations by employing an oxidant The oxidized salts can be isolated as solids or as part of oxidizing solutions for use in these applications In another aspect of the invention, the oxidized salts can be produced by using electrochemical oxidation Furthermore, because the oxidant ts typically stable in a range of non-aqueous solvents, the oxidized salt formation at elevated potentials during charging in electrochemical cells such as lithium ion batteries or ultracapacitors, can provide a voltage limiting capability in such cells thereby preventing the cells from reaching dangerous levels of overcharge

[0010] In another aspect of the invention relates to a method for producing a monovalent dodecaborate salt comprising exposing a salt of the formula

where x averages at least 4 but not more than 12 and Z represents H, Cl, Br, or OR, where R = H, C _{1 8} . to an oxidizing environment for a time and under conditions sufficient to form a salt of the formula

M ^a+ (B ₁₂ F _x Z ₁₂ J ₃ wherein a is 1 to 4, 3 ≤ x ≤ 12, and M comprises at least one electrochemically stable cations

[0011] A further aspect of the invention relates to electrolytes and electrochemical devices that incorporate the inventive salts

DETAILED DESCRIPTION OF THE INVENTION [0012] One aspect of the invention comprises one electron oxidants comprising monovalent dodecaborates salts of the form

M ³⁺ (B ₁₂ F _x Z _{12 x} ), {Compound 1 )

[0013] wherein x is at least 1 , or at least 3 for the decaborate, or at least 5, or at least 8, for the dodecaborate salts and a is 1 to 4, 3 ≤ x ≤ 12, M comprises at least one

electrochemical Iy stable cations Z represents H, Cl, Br, or OR, where R = H, C _1-8 , preferably C _1-3 alkyl or fluoroalkyl. The subscript x can be 4 to 12, 7 to 12 or 7 to 11 , and mixtures of salts having x values from 4 to 12, 7 to 12 or 7 to 11 The subscripts "10-x" and "12-x" mean "10 minus x" and "12 minus x" respectively. Alt other subscripts with the "-" indicate a range, e.g 1-3 means 1 through 3. M is selected from electrochemically stable cations and can comprise at least one member selected from the group consisting of alkali metal, alkaline earth metal, tetraalkylammonium, or imidazolium

[0014] In another aspect of the invention, Compound 1 may be obtained from divalent dodecaborate salts comprising those in the form'

M ³⁺ (B ₁₂ F _x Z _{12 s} ² ) _a/2 (Compound 2)

by electrochemical or chemical oxidation according to a process comprising.

B > ₁ 1 ₂ 2F ^r _x xZ~-i1 ₂ 2 _x x - ->» _x . + e or

B 51 ₁ 2 ₂ γR,-Z-12 X ^τ ^ O*x -> ° B1 ₁ 2 ₂ ^r F> _x /Z-1 122 : x + Ox ^"

[0015] Examples of chemical oxidizers include, without limitation, nitrosyl and nitrosonium salts such as NO ⁺ BF ₄ , NO ₂ ⁺ BF ₄ , fluorine and oxidative fiuorinators such as CIF, CIF ₃ , BrF ₃ , XeF ₂ , K ₂ NiF ₆ , CeF ₄ and Ce(IV) salts, mixtures thereof, among other suitable oxidizers

[0016] When employing electrochemical oxidation to form Compound (1), Compound (2) can be dissolved in an organic aprotic, or inorganic solvent, in a quantity ranging from about 0.1 to about 50 wt %, provided that the solvent is not substantially oxidized by Compound (1 ) Examples of organic aprotic solvents comprise nitriles, including acetonitrile, propionitrile and glutaronitπle; organic carbonates and fluorinated solvents such as fluorinated organic carbonates, esters, ethers; mixtures thereof, among others. Examples of inorganic solvents comprise HF (which is protic but oxidatively stable), halogen fluorides, sulfur fluorides, chlorides, oxychlorides and oxyfluondes; mixtures thereof, among others. Typically acceptable solvents will have an oxidiation potential greater than about 4.6 V vs Li/Lι ⁺ .

[0017] When employing chemical oxidation to form Compound (1 ), chemical oxidation may be carried out by reacting Compound (2) with at least one suitable oxidant in at least one solvent which either does not react with the oxidant or reacts more slowly with

the oxidant than Compound (2), Examples of suitable solvents comprise at least one of HF, acetonitrile, glutaronitrile, bromine trifluoride; mixtures thereof, among others. In one example of a chemical oxidation process, Compound (2) is suspended or dissolved in the solvent and the oxidizer added at between about 0.1 and about 2 MoI equivalents relative to Compound (1 ). When fluorine is used as the oxidant, fluorination of any of Bi ₂ F _x H ₁₂ -X ² typically produces the fully fluorinated radical anion B ₁₂ F ₁₂ ^1" . Without wishing to be bound by any theory or explanation it is believed that F ₂ and similar oxidizers can fully fluorinate the partially fluorinated salts before generating the fully fluorinated radical anion. [0018] In one aspect of the invention, the inventive salts can be used with or generated from a lithium based salt of the formula:

[0019] wherein x is at least 1 , or at least 3 for the decaborate, or at least 5, or at least 8, for the dodecaborate salts. Z represents H, Cl, Br, or OR, where R = H, C _1-8 , preferably C ₁ ^ alkyl or fluoroalkyl. The subscript x can be 4 to 12, 7 to 12 or 7 to 1 1 , and mixtures of salts having x values from 4 to 12, 7 to 12 or 7 to 11 The most preferred compounds are Li ₂ B ₁₂ F ₁₂ , and Li ₂ B ₁₂ F _x Zi ₂ -X where x is 6, 7, 8, 9, 10, 11 and 12 or where x is 7, 8, 9,10 and 11 and mixtures of Li ₂ B ₁₂ F _x Z _12- , where x is 6, 7, 8, 9, 10, 11 and 12 or where x is 7, 8, 9,10 and 11. For example, a mixture of Li ₂ B ₁₂ F ₈ H ₄ SaIt means Li ₂ B ₁₂ F _x H ₁₂ . _x where x is predominantly 8 with lesser amounts of x = 6, 7, 9, 10, 1 1 , and 12. The subscripts "10-x" and "12-x" mean "10 minus x" and "12 minus x" respectively. All other subscripts with the "-" indicate a range, e.g 1-3 means 1 through 3. Specific examples of suitable lithium fluoroborate compounds comprise at least one member selected from the group consisting of Li ₂ B ₁₂ F ₆ . ₁₂ Zo. ₄ where Z is Cl, Br, or OR where R is C ₁ ^, preferably C ₁ . ₃ . Typically, the salts include Li ₂ B ₁₀ F ₁₀ , Li ₂ B ₁₂ F ₁₂ , Li ₂ B ₁₂ F _10-12 (OH) _0-2 , Li ₂ B ₁₂ F _10-12 (CI) ₂ , Li ₂ B-| ₂ Fβ-io(H )o-2ι Li ₂ Bi ₂ Fβ-i ₂ (OCF3)o-4, Li ₂ Bi _O F@.ioBro- ₂ , Li ₂ B ₁₂ FsH/, Li ₂ Bi ₂ FeHg ₁ Li ₂ B ₁₂ F ₇ Hs, Li ₂ B ₁₂ F ₈ H ₄ , Li ₂ B ₁₂ FgH ₃ , Li ₂ B ₁₂ F ₁₀ H ₂ , Li ₂ B ₁₂ F ₁₁ H and mixtures of salts with varying x such that the average x is equal to or greater than 5, or equal to 9 or 10, or Li ₂ B ₁₂ F _x CI _12-X and Li ₂ B ₁₂ F _x Br _12-X where x is 10 or 11. Additional details of this lithium based salt as well as electrolytes and electrochemical devices in which the inventive salt can be employed, are disclosed in U.S. Patent Application No 10/924,293; hereby incorporated by reference.

[0020] In another aspect of the invention, the inventive salts and the lithium based salt can be employed with at least one additive, and in electrolytes and electrochemical devices Examples of suitable additives can comprise at least one member selected from the group consisting of inorganic salt additives and organic additives such as LiBOB, LiBF4, among others that are disclosed in U S Patent Application No

11/300287 , hereby incorporated by reference The concentration of such additives in an electrolyte is normally about 0 1 to 5 wt % based on the total weight of the electrolyte solution

[0021] While the inventive salts can be employed in any suitable application or end- use, examples of such applications comprise usage as ι) a stable one electron oxidant, particularly of neutral species to stable reactive cations with lower oxidation potentials than those of the inventive salts, n) an oxidative dopant in the polymerization of conductive polymers, and in in) electrochemical devices such as a battery, fuel cell and ultracapacitor In electrochemical cells such as batteries or ultracapacitors, the inventive salt can be added as a chemical passivating additive, or if generated in situ can serve to maintain the voltage in the cell at a safe upper limit thereby providing overcharge protection

[0022] When the oxidized salts of this invention are generated in solution by chemical or electrochemical oxidation they are they can be prepared at concentrations ranging from about 0 001 M to about 1 M, or about 0 01 M to about 1 M ₁ or about 0 1 to about 0 5M The oxidizied salts can be employed in such concentrations or diluted by being combined with a suitable solvent, among other components

[0023] In a further aspect of the invention, the oxidized compound and electrolytes containing the compound are substantially free of water. By substantially free it is meant that the compound or electrolyte contains less than about IOOppm of water and other hydroxyl moieties, and typically less than about 50 ppm of water and other hydroxyl moieties.

[0024] Certain aspects of the invention, for example, salt isolation as a solid and in a series of solutions, its characterization in solution and its quantification in solid and solutionare illustrated by the following Examples which shall not limit the scope of the claims appended hereto.

Example 1 Electrochemical Oxidation of Li ₂ B ₁₂ F ₉ H ₃

[0025] For the electrochemical oxidation of Li ₂ Bi ₂ F ₉ H ₃ an electrochemical cell based on a 0.07cm ² glassy carbon working electrode (Bioanalyttcal Systems lnc ) and Li metal foil (FMC Corp.) reference and counter electrodes was fabricated. A CH Instruments

CHI660a potenttostat was used as the power supply A current of 0.14 mA was applied to ~ 5 mL of a 0.4 M solution of Li ₂ B ₁₂ F ₉ H ₃ in ethylene carbonate/diethyl carbonate (EC/DEC) for ~ 1 hr red/orange species formed underneath the working electrode, which gradually diffused into the bulk solution Titration with thiosulfate indicated that ~ 0 002M of a 1 electron oxidant had been formed by electrolysis An aliquot of the solution was loaded into a Teflon™ Harrick liquid optical cell (part # DLC2) with sapphire windows spaced 0 1mm apart to enable full-scale observation of the absorption values without the need for dilution. The solution in the Harrick cell was analyzed by UV-visible spectroscopy on a Cary model 300 spectrophotometer from Vaπan, Inc. Single scans were run from 200-700 nm with a resolution of 1 nm at a scan rate of 4nm/s.Two new absorption peaks were observed in the Li ₂ B ₁₂ F ₉ H ₃ solution at 350 and 460 nm after electrochemical oxidation The color of the solution as well as these absorption bands gradually decreased and completely disappeared after 8-9 hrs

Comparative Example 1

UV spectrum of Li ₂ B ₁₂ F ₁₂

[0026] An untreated 0.4 M solution of Li ₂ B ₁₂ F ₁₂ in EC/DEC is clear and colorless UV- visible spectroscopy was performed on the solution as in example 1 which shows UV absorption peaks of Li ₂ B ₁₂ F ₁₂ occuring at 290 and 315 nm.

Example 2 Electrochemical Oxidation of Li ₂ Bi ₂ Fi ₂

[0027] A 0.4 M solution of Li ₂ Bi ₂ F ₁₂ in EC/DEC was electrochemically oxidized by the method described in example 1. On electrochemical oxidation, a lemon-yellow species was observed under the working electrode which gradually diffused into the solution UV- visible spectroscopy showed a new absorption peak at 410 nm in addition to the original UV absorption peaks of Li ₂ B ₁₂ F ₁₂ at 290 and 315 nm. The color of the solution as well as the new UV-visible peak gradually decreased, completely disappearing in 24 hr

Electrolysis of solutions at 5.0V for 2hrs gave similar results except a more deeply colored solutions were obtained which are indicative of higher concentrations of radical. Electrolysis currents were higher as expected. Mass susceptibility shift correlation (NMR and mass susctibility balance measurements) and iodometric titrations of solutions (anhydrous LiI added to the solution in the glove box followed by aqueous thiosulfate titration) indicated about 10% conversion of Bi ₂ F ₁₂ ^2' to the radical, or 0.03-0.04 M radical anion concentration. Coulometry correlated well with the quantitation studies. The same byproducts were observed over a long time period while the radical had completely decayed (UV-Vis) by the fourth day. [0028] Example 3

Chemical Oxidation of K ₂ B ₁₂ F ₁₂ with Xenon Difluoride

[0029] In an Ar-filied dry box, about 500 mg (1.1mmol) K ₂ B ₁₂ F ₁₂ was loaded into one arm of a 2-armed FEP reactor and ~ 200 mg XeF ₂ ( 1.2 mmol) was loaded into the other arm. On a vacuum line 3 mL of anhydrous hydrogen fluoride was distilled into each arm of the reactor thereby forming colorless solutions in each reactor arm. The XeF ₂ solution was poured into the K ₂ B ₁₂ F ₁₂ solution at ~ O ⁰ C. Slow gas evolution was observed and a gradual yellowing of the solution. After 1 hr. gas evolution ceased and the solution was a bright lemon yellow. The HF was evacuated at O ⁰ C leaving a pale yellow solid. In a dry box this solid was dissolved in EC/DEC giving a yellow solution. The UV-visible spectrum showed the new absorption peak at 410nm,in the same location as that observed for electrochemicatly oxidized Li ₂ Bi ₂ Fi ₂ ,

Example 4 Chemical Oxidation of (H ₃ O) ₂ B ₁₂ F ₁₂

[0030] In an Ar-filled dry box 5 g (11 mmol) of (H ₃ O) ₂ B ₁₂ F ₉ H ₃ was loaded into a single arm valved FEB reactor. Approximately 20 mL of anhydrous HF was distilled into the reactor and a 20%F ₂ /80% N ₂ stream was bubbled into the solution. Analysis of the solution by ¹⁹ F NMR after the addition of ~ 40 mmol F ₂ indicated that B ₁₂ F ₉ H ₃ ² had been converted completely to B ₁₂ F ₁₂ ^2" . An additional 40 mmol F ₂ was added to the solution over which time it turned deep blue in color. Removal of residual fluorine and HF by distillation left - 6 g of pale blue solid. A sample of the solid was treated with potassium iodide and gave a deep orange solution in acetonitriie, indicative of oxidizer. Back titration of this solution with Na ₂ S ₂ O ₃ solution was consistent with the solid consisting of 60 mol % of a one electron oxidizer. Another sample of this solid was dissolved in

acetonitπle and gave rise to a pale blue solution. UV analysis of this solution showed the 410 nm absorption peak at much higher intensity than was observed for the electrochemical or XeF ₂ chemical oxidation of B ₁₂ F ₁₂ ^2" .

Example 5

Characterization of solutions of Oxidized Li ₂ B ₁₂ F ₁₂ by Time of Flight Secondary Ion Mass

Spectrometry (ToF-SIMS)

[0031] A solution of the yellow oxidized product from example 3 was dissolved in acetonitrile and analyzed by Time of Flight Secondary Ion Mass Spectrometry (ToF- SIMS) on a PHI Trift Il TOFMS instrument In this experiment, the samples were ionized with a ⁶⁹ Ga liquid metal ion gun Positive and negative ions were analyzed via TOFMS (B3 instument file). The data were collected with 138 ps/bin, 1.5-2000 Daltons, 5kV post acceleration, 250 micron raster, 1.5 pA ion gun current and 1 5-5 mm collection times Under SIMS conditions, two phenomena are common recombination of preformed ions with electrons and neighboring ions in the near surface region as well as fragmentation of ion clusters In addition, doubly charged ion clusters are rarely maintained For example, the neutral divalent salt Li ₂ B ₁₂ F ₁₂ would be expected to give rise rise to both B ₁₂ F ₁₂ ^" and LiB ₁₂ F ₁₂ ions, while the neutral, oxidized radical monovalent salt LiBi ₂ F ₁₂ would be expected produces primarily B ₁₂ F ₁₂ , but not the divalent monoanion LiB ₁₂ F ₁₂ The ratio of B ₁₂ F ₁₂ to LiB ₁₂ F ₁₂ ^" should be close to 1 for the neutral divalent salt,

Li ₂ B ₁₂ Fi ₂ , which contains the divalent anion, B ₁₂ F ₁₂ ² This ratio is expected to be be significantly higher than 1 for the neutral, oxidized salt, LiB ₁₂ F ₁₂ , which contains the radical monovalent anion, B ₁₂ F ₁₂ . As expected, SIMS data on the unoxidized Li ₂ B ₁₂ F ₁₂ shows 2 primary sets of peaks centered at 358 D for B ₁₂ F ₁₂ and 365 D for LiB ₁₂ F ₁₂ , which are approximately the same intensity When the Li ₂ B ₁₂ F ₁₂ salt was oxidized with xenon difluoride in acetonitrile solution and the yellow solid product mixture analyzed by SIMS, the same primary sets of peaks were observed, but the B ₁₂ F ₁₂ peak centered at 358 D was nearly twice the intensity of the LiB ₁₂ F ₁₂ ^" peak centered at 365 D. This indicates that the LiBi ₂ F ₁₂ salt based on the radical anion B ₁₂ F ₁₂ ^" is one of the products of XeF ₂ oxidation of Li ₂ B ₁₂ Fi ₂ .

Example 6 Characterization of Solutions of Oxidized Li ₂ Bi ₂ F ₁₂ by EPR

[0032] A 0.4 M solution of Li ₂ B ₁₂ F ₁₂ in 7EC/3DEC was electrochemically oxidized in an optically flat cell, part # WG-81OA available from Wilmad-Labglass, by the method described in example 1 , with the exception that Pt wire working, counter and pseudo reference electrodes were used On electrochemical oxidation, a lemon-yellow species was observed under the working electrode which gradually diffused into the solution The solution was analyzed by EPR measurements on a Bruker ESP 580 X-Band EPR Spectrometer, A TE 102 mode resonator was used at 25 ⁰ C with 100kHz field modulation A total of 20 scans were collected A solution of 0 4M Li ₂ B ₁₂ F ₁₂ in 7 3 EC-DEC was used for the experiments because it was found to promote excellent lifetimes for the generated radical. Upon electrolysis, the steady growth of at single, broad, dysonian signal at a g- factor of approximately 2.0094 was observed which is consistent with a single unpaired electron of a radical species. Ex-situ generation of the radical anion in a glove bag followed by analysis of a colored solution gave the same signal.

Comparative Example 2 EPR of Inert Supporting Electrolyte in EC/DEC

[0033] A 0.4 M solution of tetrabutylammonium hexafluorophosphate in 7EC/3DEC was electrochemically oxidized by the method described in example 6 The solution was analyzed by EPR measurements as in example 6 No EPR signals were observed

[0034] The invention has been described with reference to certain aspects, but other aspects and embodiments are apparent to persons of skill in the art, and are included within the scope of the claims