CYANOALKYL SULFONYLFLUORIDES FOR ELECTROLYTE COMPOSITIONS FOR HIGH ENERGY LITHIUM-ION BATTERIES

Abstract

Compounds of formula (I), wherein q is 1, 2 or 3, r is 1, 2 or 3, and Y is a q+r valent non-fluorinated alkylene group Shaving 1 to 12 C-atoms, wherein one or more CH.sub.2-units of the alkylene group which are not directly bound to CN or SO.sub.2F may be replaced by O, for use in electrolyte compositions.

##STR00001##

Claims

1. An electrolyte composition, comprising at least one compound of formula (I): ##STR00005## wherein: q is 1, 2 or 3, r is 1, 2 or 3, and Y is a q+r valent non-fluorinated alkylene group having 1 to 12 C-atoms, wherein one or more CH.sub.2-units of the alkylene group which are not directly bound to CN or SO.sub.2F may be replaced by O.

2. The electrolyte composition according to claim 1, wherein the alkylene group Y has 2 to 6 C-atoms.

3. The electrolyte composition according to claim 1, wherein r is 2 and the two sulfonylfluoride groups are bound to the alkylene group Y at terminal positions.

4. The electrolyte composition according to claim 1, wherein q is 2 and both CN-groups are bound to the same C-atom of the alkylene group Y.

5. The electrolyte composition according to claim 1, wherein q is 2 and r is 2.

6. The electrolyte composition according to claim 1, wherein q is 1 and r is 1.

7. The electrolyte composition according to claim 1, wherein compound of formula (I) is selected from the group consisting of 2-cyanoethanesulfonyl fluoride and 3,3-dicyano-pentane-1,5-disulfonyl fluoride.

8. The electrolyte composition according to claim 1, comprising 0.01 to 10 wt.-% of the at least one compound of formula (I), based on a total weight of the electrolyte composition.

9. The electrolyte composition according to claim 1, further comprising at least one aprotic organic solvent selected from the group consisting of fluorinated and non-fluorinated cyclic and acyclic organic carbonates, di-C.sub.1-C.sub.10-alkylethers, di-C.sub.1-C.sub.4-alkyl-C.sub.2-C.sub.6-alkylene ethers and polyethers, cyclic ethers, cyclic and acyclic acetates and ketales, orthocarboxylic acids esters, cyclic and acyclic esters and diesters of carboxylic acids, cyclic and acyclic sulfones, cyclic and acyclic nitriles and dinitriles, and mixtures thereof.

10. The electrolyte composition according to claim 1, further comprising at least one lithium conducting salt.

11. The electrolyte composition according to claim 1, further comprising at least one conducting salt selected from the group consisting of LiPF.sub.6, LiAsF.sub.6, LiSbF.sub.6, LiCF.sub.3SO.sub.3, LiBF.sub.4, lithium bis(oxalato) borate, lithium difluoro(oxalato) borate, LiClO.sub.4, LiN(SO.sub.2C.sub.2F.sub.5).sub.2, LiN(SO.sub.2CF.sub.3).sub.2, LiN(SO.sub.2F).sub.2, and LiPF.sub.3(CF.sub.2CF.sub.3).sub.3.

12. The electrolyte composition according to claim 1, further comprising at least one further additive different from the compounds of formula (I) selected from the group consisting of polymers, film forming additives, flame retardants, overcharging additives, wetting agents, HF and/or H.sub.2O scavenger, stabilizer for LiPF.sub.6 salt, ionic solvation enhancer, corrosion inhibitors, and gelling agents.

13. The electrolyte composition according to claim 1, further comprising 0.01 to 10 wt.-% of at least one further additive selected from the group consisting of organic carbonates having at least one CC unsaturated bond, fluorinated organic carbonates, and inorganic fluoride salts.

14. An electrolyte composition, comprising a compound of formula (I): ##STR00006## wherein: q is 1, 2 or 3, r is 1, 2 or 3, and Y is a q+r valent non-fluorinated alkylene group having 1 to 12 C-atoms, wherein one or more CH.sub.2-units of the alkylene group which are not directly bound to CN or SO.sub.2F may be replaced by O.

15. An electrochemical cell, comprising the electrolyte composition according to claim 1.

Description

[0134] The present invention is further illustrated by the following examples that do not, however, restrict the invention.

1) Synthesis of Additives

(1-1) Synthesis of 2-chloroethanesulfonyl Fluoride

[0135] 2-Chloroethanesulfonyl chloride (500 g, 2910 mmol) was added to a saturated KHF.sub.2 solution in water (1700 ml) cooled by an ice bath, and the two phase mixture was stirred for 15 h at room temperature. The reaction mixture was diluted with water, extracted with dichloromethane (DCM), and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure to give the product (386 g, 86% yield).

(1-2) Synthesis of 2-Cyanoethanesulfonyl Fluoride (Method A)

[0136] Tetrabutylammonium fluoride trihydrate (29 g, 88 mmol, 1.1 eq) was added to a solution of 2-chloroethanesulfonyl fluoride prepared according to (1-1) (12 g, 80 mmol, 1.0 eq) in tetrahydro-furane (THF) (80 ml) cooled by an ice bath. The mixture was stirred for 30 min, and became a pale brown solution. Trimethylsilyl cyanide (11 ml, 88 mol, 1.1 eq) was added slowly, and the solution became dark brown. The reaction temperature was increased to 50 C., and stirred for 15 h. The reaction mixture was quenched with water, extracted with ethyl acetate, washed with brine, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was purified by silica gel chromatography. The obtained oil was purified again by distillation to give the product as a color less oil (6.0 g, 50% yield).

(1-3) Synthesis of 2-cyanoethanesulfonyl Fluoride (method B)

[0137] MgO (31 g, 773 mmol, 0.54 eq) was added to a solution of 2-chloroethanesulfonyl fluoride prepared according to (1-1) (221 g, 1433 mmol, 1.0 eq) in H.sub.2O/ethanol=1/1 (1200 ml) cooled by an ice bath, the mixture was stirred for 15 min, and became a white suspension. KCN (100 g, 1504 mol, 1.05 eq) was added slowly, and the reaction mixture became a dark brown suspension. The reaction temperature was kept under 35 C. The reaction mixture was stirred for 1 h in an ice bath. The reaction mixture was quenched with water, extracted with AcOEt, washed with brine, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was filtrated by short silica gel filter. The obtained oil was purified by distillation to give the product as a color less oil (130 g, 65% yield).

(1-4) Synthesis of Methanesulfonyl Fluoride

[0138] Methanesulfonyl chloride (115 g, 1.00 mol) was added to a saturated KHF.sub.2 solution in water 300 ml) in an ice bath was added, and the two phase mixture was stirred for 15 h at room temperature. The reaction mixture was diluted with water, extracted by DCM, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was purified by distillation to give the product as a color less oil (65 g, 66% yield).

(1-5) Synthesis of Methanedisulfonyl Fluoride

[0139] KF (26 g, 440 mmol, 8 eq) and 18-crown-6-ether (14.8 g, 55 mmol, 1 eq) were added to a suspension of methanedisulfonyl chloride (12 g, 55 mmol, 1.0 eq) in acetonitrile (300 ml) in an ice bath, the mixture was stirred for 15 h at room temperature. The reaction mixture was diluted with water, extracted by AcOEt, washed with brine, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was purified by distillation to give the product as a color less oil (3.0 g, 45% yield).

(1-6) Synthesis of Ethanedisulfonyl Fluoride

[0140] Ethanedisulfonyl fluoride (13 g, 58 mmol) was added to a saturated KHF.sub.2 solution in water (100 ml) cooled by an ice bath, and the two phase mixture was stirred for 15 h at room temperature. The reaction mixture was diluted with water, extracted by DCM, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was purified by distillation to give the product as a color less oil (2.6 g, 23% yield).

(1-7) Synthesis of 3,3-dicyano-pentane-1,5-disulfonyl Fluoride

[0141] Tetrabutylammonium fluoride trihydrate (1.63 g, 5 mmol, 0.05 eq) was added to a solution of malononitrile (6.7 g, 100 mmol, 1.0 eq) and vinylsulfonyl fluoride (12.2 g, 100 mmol, 1.0 eq) in EtOH (500 ml) at room temperature, the mixture was stirred for 3 h, and became white suspension. The reaction mixture was quenched with water, extracted with AcOEt, washed with brine, and dried over anhydrous Na.sub.2SO.sub.4. The solvent was removed under reduced pressure and the crude product was purified by silica gel chromatography to give the product as a color less solid (5.8 g, 20% yield).

2) Electrolyte Compositions

[0142] A base electrolyte composition was prepared containing 12.7 wt % of LiPF.sub.6, 26.2 wt % of ethylene carbonate (EC), and 61.1 wt % of ethyl methyl carbonate (EMC) (EL base 1), based on the total weight of ELbase1. To this ELbase1 formulation 2 wt % VC (EL base 2), 2 wt % FEC (EL base 3) and 10 wt % FEC (EL base 4) were added. To these base electrolyte compositions different amounts of additives were added. Vinyl sulfonylfluoride and methyl fluorosulfonate were purchased, the other additives were synthetized as described above. The exact compositions are summarized in Tables 1 to 10. In the Tables concentrations are given as wt.-% based on the total weight of the electrolyte composition. The molar concentration of the different additives was the same.

3) Silicon Suboxide/Graphite Anodes

[0143] Silicon suboxide, graphite and carbon black were thoroughly mixed. CMC (carboxymethyl cellulose) aqueous solution and SBR (styrene butadiene rubber) aqueous solution were used as binder. The mixture of silicon oxide, graphite and carbon black was mixed with the binder solutions and an adequate amount of water was added to prepare a suitable slurry for electrode preparation. The thus obtained slurry was coated by using a roll coater onto copper foil (thickness=18 m) and dried under ambient temperature. The sample loading for electrodes on Cu foil was fixed to be 5 mg cm.sup.2 for coin type cell testing and 7 mg cm.sup.2 for NCA//silicon suboxide/graphite pouch cell (200 mAh) testing.

4) Fabrication of Cathode Tapes

(4-1) Fabrication of NCM523 Cathode Tapes

[0144] Lithium containing mixed Ni, Co and Mn oxide (NCM 523, manufactured by BASF) was used as a cathode active material and mixed with carbon black. The mixture of NCM 523 and carbon black was mixed with polyvinylidene fluoride (PVdF) binders, and an adequate amount of N-methylpyrrolidinone (NMP) was added to prepare a suitable slurry for electrode preparation. The thus obtained slurry was coated by using a roll coater onto aluminum foil (thickness=15 m) and dried under ambient temperature. This electrode tape was then kept at 130 C. under vacuum for 8 h to be ready to be used. The thickness of the cathode active material was found to be 72 m, which was corresponding to 12.5 mg/cm.sup.2 of the loading amount.

(4-2) Fabrication of NCA Cathode Tapes

[0145] Lithium containing mixed Ni, Co and Al oxide (NCA) was used as a cathode active material. Method for fabricating the NCA tape is same as described above for NCM523. The thickness of the cathode active material was found to be 50 m, which was corresponding to 11 mg/cm.sup.2 of the loading amount.

5) Fabrication of the Test Cells

[0146] Coin-type full cells (20 mm in diameter and 3.2 mm in thickness) comprising a NCM 523 cathode prepared as described above under (4-1) and a silicon suboxide/graphite composite anode prepared as described above under 3) as cathode and anode electrode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode described above and a separator were superposed in order of cathode//separator//anode to produce a coin full cell. Thereafter, 0.15 mL of the different nonaqueous electrolyte compositions were introduced into the coin cell.

[0147] Pouch cells (350 mAh) comprising a NCM 523 electrode prepared as described above in (4-1) and a graphite electrode as cathode and anode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode described above and a separator were superposed in order of cathode//separator//anode to produce a several layers pouch cell. Thereafter, 3 mL of the different nonaqueous electrolyte compositions were introduced into the Laminate pouch cell.

[0148] Pouch cells (200 mAh) comprising a NCA electrode prepared as described above in (4-2) and a silicon suboxide/graphite electrode as cathode and anode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode described above and a separator were superposed in order of cathode//separator//anode to produce a several layers pouch cell. Thereafter, 0.7 mL of the different nonaqueous electrolyte compositions were introduced into the Laminate pouch cell.

6) Cycling Stability of Coin Full Cell Comprising NCM523//Silicon Suboxide/Graphite Composite Anode

[0149] Coin full cells prepared comprising a NCM523 cathode and silicon suboxide/graphite composite anode were tested in a voltage range between 4.2 V to 2.5 V at room temperature. For the initial 2 cycles, the initial charge was conducted in the CCCV mode, i.e., a constant current (CC) of 0.05 C was applied until reaching 0.01 C. After 5 min resting time, discharge was carried out at constant current of 0.05 C to 2.5 V. For the cycling, the current density increased to 0.5 C. The results are summarized in Table 1, 2, 3 and 4. [%] Discharge capacity after 200 cycles is based on the capacity of EL base 2 cell after 200 cycles as 100%.

TABLE-US-00001 TABLE 1 Initial irreversible capacity of the coin full cells at 25 C. 3,3- 2- dicyano- Cyano- pentane- ethane- 1,5- Methane Vinyl Methyl Methane Ethane EL base 2 sulfonyl disulfonyl sulfonyl- sulfonyl- fluoro- disulfonyl- disulfonyl- Initial EL base fluoride fluoride fluoride fluoride sulfonate fluoride fluoride irreversible Example Electrolyte 1 VC [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] capacity 1 (inventive) EL 1 95.4 2.0 2.6 0.0 0.0 0.0 0.0 0.0 0.0 18.7% 2 (inventive) EL 2 96.7 2.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 20.0% 3 (Comparative) EL 3 96.1 2.0 0.0 0.0 1.9 0.0 0.0 0.0 0.0 22.7% 4 (Comparative) EL 4 95.9 2.0 0.0 0.0 0.0 2.1 0.0 0.0 0.0 29.8% 5 (Comparative) EL 5 95.8 2.0 0.0 0.0 0.0 0.0 2.2 0.0 0.0 95.9% 6 (Comparative) EL 6 96.3 2.0 0.0 0.0 0.0 0.0 0.0 1.7 0.0 34.4% 7 (Comparative) EL 7 96.2 2.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 21.3% 8 (Comparative) EL 8 98.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20.2%

TABLE-US-00002 TABLE 2 Initial irreversible capacity of the coin full cells at 25 C. 2-Cyano- Initial EL base 3 ethanesulfonyl irre- Electro- EL fluoride versible Example lyte base 1 FEC [wt.-%] capacity 1 (inventive) EL 10 96.7 2 1.3 19.0% 2 (Comparative) EL 11 98 2 0 19.5%

TABLE-US-00003 TABLE 3 Initial irreversible capacity of the coin full cells at 25 C. 3,3- 2-Cyano- dicyanopentane- EL base 4 ethanesulfonyl 1,5-disulfonyl Initial EL fluoride fluoride irreversible Example Electrolyte base 1 FEC [wt.-%] [wt.-%] capacity 1 (inventive) EL 12 88.7 10 1.3 0 20.0% 2 (inventive) EL 13 87.4 10 2.6 0 20.0% 3 (inventive) EL 14 88.7 10 0 1.3 21.0% 4 (inventive) EL 15 87.4 10 0 2.6 21.0% 5 (Comparative) EL 16 90 10 0 0 22.0%

TABLE-US-00004 TABLE 4 Discharge capacity after the 200 cycles of the coin full cells at 25 C. 2-Cyano- Discharge ethane- Methane Vinyl Methyl Methane- Ethanedi- capacity sulfonyl sulfonyl- sulfonyl- fluoro- disulfonyl sulfonyl after EL base 2 fluoride fluoride fluoride sulfonate fluoride fluoride 200 Example Electrolyte ELbase1 VC [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] cycles 1 (inventive) EL 1 95.4 2.0 2.6 0.0 0.0 0.0 0.0 0.0 102.0% 2 (Comparative) EL 3 96.1 2.0 0.0 1.9 0.0 0.0 0.0 0.0 100.9% 3 (Comparative) EL 4 95.9 2.0 0.0 0.0 2.1 0.0 0.0 0.0 74.4% 4 (Comparative) EL 5 95.8 2.0 0.0 0.0 0.0 2.2 0.0 0.0 0.02% 5 (Comparative) EL 6 96.3 2.0 0.0 0.0 0.0 0.0 1.7 0.0 40.0% 6 (Comparative) EL 7 96.2 2.0 0.0 0.0 0.0 0.0 0.0 1.8 89.6% 7 (Comparative) EL 8 98.0 2.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0% 8 (Comparative) EL 9 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 78.8%

[0150] As can be seen from Tables 1, 2, 3 and 4, the inventive electrochemical cell shows the lowest initial irreversible capacity and shows the best discharge capacity after 200 charge/discharge cycles at 25 C.

7) Evaluation of High-Temperature Storability of Pouch Cell Comprising NCM523//Graphite Anode

7-1) AC Impedance at 3.1 V and at 4.25 V

[0151] The pouch cells (350 mAh) prepared comprising a NCM523 cathode and graphite anode were charged to 3.1 V at a constant current of 0.1 C and then charged at a constant voltage of 3.1 V until the current value reached 0.01 C at initial cycles. For these cells the AC impedance was measured at 25 C. Afterwards, the cells were degassed. After degassing, the pouch cells were charged to 4.2 V at the constant current of 0.1 C and then they were charged at a constant voltage of 4.2 V until the current value reached 0.01 C. These cells were stored at 45 C. for 5 days and then transferred to 25 C. to check the retention capacity and recover capacity. After the capacity check, the pouch cells was charged to 4.25 V at a constant current of 0.1 C and then charged at a constant voltage of 4.25 V until the current value reached 0.01 C after the formation cycles. For these cells the AC impedance was measured at 4.25 V at 25 C. The results are shown in Table 5.

7-2) Gas Amount after Storage at 60 C. for 30 Days at 4.25 V

[0152] These cells was stored at 60 C. for 30 days and then cooled. The cells was measured by Archimedes method to identify the volume change before and after storage. The gas amount of the cells is determined as the ratio of the volume change before and after storage of cells and is given in % based on the gas amount of pouch cell with EL 9 electrolyte (EL base 1). The results are summarized in Table 6.

8) Evaluation of High-Temperature Storability of Pouch Full Cell Comprising NCA//Silicon Suboxide/Graphite Composite Anode

(8-1) Gas Amount after Aging at 45 C. for 5 Days at 4.2V

[0153] The pouch cells (200 mAh) prepared comprising a NCA cathode and silicon suboxide/graphite anode were charged to 3.1 V at a constant current of 0.1 C and then charged at a constant voltage of 3.1 V until the current value reached 0.01 C at initial cycles. Afterwards, these cells were degassed. After degassing, cell volume was measured by Archimedes method. After then, the pouch cells charged to 4.2 V at the constant current of 0.1 C and then charged at a constant voltage of 4.2 V until the current value reached 0.01 C. These cells were stored at 45 C. for 5 days and then transferred to 25 C. to check the retention capacity and recover capacity. After the capacity check, cell volume was measured again. The aging gas amount of the cells is determined as the volume difference before and after aging of cells and is given in % based on the gas amount of pouch cell without 2-cyanoethane sulfonyl fluoride. The results are displayed in Tables 7 and 8.

(8-2) Gas Amount after Storage at 60 C. for 30 Days at 4.2 V

[0154] After the above formation step, these cells were stored at 60 C. for 30 days and cell volume was measured again. The storage gas amount of the cells is determined as the volume difference after degas and after storage of cells and is given in % based on the gas amount of pouch cell without 2-cyanoethane sulfonyl fluoride. The results are displayed in Tables 9 and 10.

TABLE-US-00005 TABLE 5 AC Impedance of pouch cells with different additives after CC-CV to 3.1 V. 2-Cyano- ethane- Methane Methane AC AC sulfonyl sulfonyl- disulfonyl- Impedance Impedance EL base 2 FEC fluoride fluoride fluoride at at Example Electrolyte EL base 1 VC [wt.-%] [wt.-%] [wt.-%] [wt.-%] 3.1 V 4.25 V 1 (inventive) EL 1 95.4 2.0 0.0 2.6 0.0 0.0 0.024 0.15 2 (Comparative) EL 3 96.1 2.0 0.0 0.0 1.9 0.0 0.024 0.22 3 (Comparative) EL 6 96.3 2.0 0.0 0.0 0.0 1.7 0.034 0.23 4 (Comparative) EL 8 98.0 2.0 0.0 0.0 0.0 0.0 0.036 0.23 5 (Comparative) EL 9 100.0 0.0 0.0 0.0 0.0 0.0 0.058 0.27 6 (Comparative) EL 11 98.0 0.0 2.0 0.0 0.0 0.0 0.035 0.22 7 (Comparative) EL 16 90.0 0.0 10.0 0.0 0.0 0.0 0.030 0.19 8 (Comparative) EL 17 96.0 2.0 2.0 0.0 0.0 1.7 0.046 0.25

[0155] Table 5 shows the impedance for an inventive electrolyte composition containing 2-cyanoethane sulfonyl fluoride and for seven comparative electrolyte compositions. The addition of the 2-cyanoethane sulfonyl fluoride shows lowest AC resistance at 3.1V and also at 4.25V after the formation. It is considered that adding 2-cyanoethane sulfonyl fluoride to VC containing electrolyte could reduce charge transfer resistance.

TABLE-US-00006 TABLE 6 Gas amount after 30 days at 60 C. storage. Volume 2- change Cyano- after ethane- Methane Methane 30 days EL base 2 sulfonyl sulfonyl- disulfonyl- at EL FEC fluoride fluoride fluoride 60 C. Example Electrolyte base 1 VC [wt.-%] [wt.-%] [wt.-%] [wt.-%] storage 1 (inventive) EL 1 95.4 2.0 0.0 2.6 0.0 0.0 96% 2 (Comparative) EL 3 96.1 2.0 0.0 0.0 1.9 0.0 100% 3 (Comparative) EL 6 96.3 2.0 0.0 0.0 0.0 1.7 115% 4 (Comparative) EL 8 98.0 2.0 0.0 0.0 0.0 0.0 115% 5 (Comparative) EL 9 100.0 0.0 0.0 0.0 0.0 0.0 100% 6 (Comparative) EL 11 98.0 0.0 2.0 0.0 0.0 0.0 120% 7 (Comparative) EL 16 90.0 0.0 10.0 0.0 0.0 0.0 165% 8 (Comparative) EL 17 96.0 2.0 2.0 0.0 0.0 1.7 140%

[0156] Table 6 shows that in the NCM523//graphite pouch cell, that by adding 2-cyanoethane sulfonyl fluoride to VC containing electrolyte the storage gas development is significantly reduced.

TABLE-US-00007 TABLE 7 Aging gas of pouch full cell comprising NCA//silicon suboxide/graphite composite anode. 2- 3,3- Cyano- dicyanopentane- ethane- 1,5- EL base 2 sulfonyl disulfonyl EL fluoride fluoride Aging Example Electrolyte base 1 VC [wt.-%] [wt.-%] gas 1 (inventive) EL 1 95.4 2 2.6 0 14% 2 (inventive) EL 2 96.7 2 0 1.3 26% 3 (Comparative) EL 8 98 2 0 0 100%

TABLE-US-00008 TABLE 8 Aging gas of pouch full cell comprising NCA//silicon suboxide/graphite composite anode. 2- 3,3-dicyano- Cyano- pentane- ethane- 1,5-di- EL base 4 sulfonyl sulfonyl EL fluoride fluoride Aging Example Electrolyte base 1 FEC [wt.-%] [wt.-%] gas 1 (inventive) EL 13 87.4 10 2.6 0 32% 2 (inventive) EL 15 87.4 10 0 2.6 68% 3 (Comparative) EL 16 90 10 0 0 100%

[0157] Tables 7 and 8 show that in the NCA//silicon suboxide/graphite pouch cell, the development of aging gas is significantly reduced by adding 2-cyanoethane sulfonyl fluoride and 3,3-dicyano-pentane-1,5-disulfonyl fluoride to a VC or FEC containing electrolyte.

TABLE-US-00009 TABLE 9 Storage gas of pouch full cell comprising NCA//silicon suboxide/graphite composite anode. 3,3- 2- dicyano Cyano- pentane- ethane- 1,5- EL base 2 sulfonyl disulfonyl EL fluoride fluoride Storage Example Electrolyte base 1 VC [wt.-%] [wt.-%] gas 1 (inventive) EL 1 95.4 2 2.6 0 14% 2 (inventive) EL 2 96.7 2 0 1.3 19% 3 (Comparative) EL 8 98 2 0 0 100%

TABLE-US-00010 TABLE 10 Storage gas of pouch full cell comprising NCA//silicon suboxide/graphite composite anode. 3,3- 2- dicyano- Cyano- pentane- ethane- 1,5-di- EL base 4 sulfonyl sulfonyl EL fluoride fluoride Storage Example Electrolyte base 1 FEC [wt.-%] [wt.-%] gas 1 (inventive) EL 13 87.4 10 2.6 0 29% 2 (inventive) EL 15 87.4 10 0 2.6 30% 3 (Comparative) EL 16 90 10 0 0 100%

[0158] Tables 9 and 10 show that in the NCA//silicon suboxide/graphite pouch cell, the development of storage gas is significantly reduced by adding 2-cyanoethane sulfonyl fluoride and 3,3-dicyano-pentane-1,5-disulfonyl fluoride to a VC or FEC containing electrolyte.