PHOSPHONATE BASED LITHIUM COMPLEXES

Abstract

Phosphonate based lithium complexes of formula (I) and their use in electrolyte compositions for electrochemical cells.

##STR00001##

Claims

1. A complex compound, wherein the complex compound satisfies formula (I): ##STR00039## wherein R.sup.1 is selected from H, F, R.sup.2, OR.sup.2, OSi(R.sup.3R.sup.4R.sup.5), and OX.sup.Li.sup.+; wherein R.sup.2 is selected from C.sub.1-C.sub.6 alkyl, C.sub.2-C.sub.6 alkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.6-C.sub.13 (hetero)aralkyl, which may be substituted by one or more substituents selected from OSi(CH.sub.3).sub.3 and F; R.sup.3, R.sup.4, and R.sup.5 are independently from each other selected from H, F, R.sup.2, OR.sup.2, and OSi(R.sup.6).sub.3; and R.sup.6 is independently at each occurrence selected from H, F, R.sup.2 and OR.sup.2; and X is selected from Y.sup.1(R.sup.7).sub.4-b and Y.sup.2(R.sup.8).sub.6-b; wherein Y.sup.1 is B or A1; Y.sup.2 is P, Sb, or As; if X is Y.sup.1(R.sup.7).sub.4-b, then b is an integer from 1 to 4; if X is Y.sup.2(R.sup.8).sub.6-b then b is an integer from 1 to 6; and R.sup.7 and R.sup.8 are independently at each occurrence selected from F, R.sup.9 and OR.sup.9; wherein R.sup.9 is selected from C.sub.1-C.sub.6 alkyl, C.sub.2-C.sub.6 alkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.6-C.sub.13 (hetero)aralkyl, which may be substituted by one or more F; one pair of R.sup.7 or one or two pairs of R.sup.8 may be combined and jointly be ##STR00040## forming a cycle with Y.sup.1 or Y.sup.2, respectively; wherein ##STR00041## is a bidentate radical derived from a 1,2-, 1,3- or 1,4-diol, from a 1,2-, 1,3- or 1,4-dicarboxylic acid or from a 1,2-, 1,3- or 1,4-hydroxycarboxylic acid; and R.sup.1 may be combined with one of R.sup.7 or R.sup.8, respectively, and jointly form a cycle.

2. The complex compound of claim 1, wherein R.sup.7 and R.sup.8 are independently at each occurrence selected from F, OC.sub.1OC.sub.6 alkyl, and C.sub.1-C.sub.6 alkyl substituted by at least one F, wherein one pair of R.sup.7 or one or two pairs of R.sup.8 may be combined and jointly be ##STR00042## forming a cycle with Y.sup.1 or Y.sup.2, respectively, and/or one or more of R.sup.7 or R.sup.8 may be combined with R.sup.1 and jointly form a cycle with the POX-group.

3. The complex compound of claim 1, wherein R.sup.1 is R.sup.2, OR.sup.2, OSi(R.sup.3R.sup.4R.sup.5) or OX.sup.Li.sup.+.

4. The complex compound of claim 1, wherein X comprises at least one ##STR00043## group derived from oxalic acid, maleic acid, malonic acid, or succinic acid.

5. The complex compound of claim 1, wherein X is B(R.sup.7).sub.3.

6. The complex compound of claim 1, wherein X is P(R.sup.8).sub.5.

7. A method of producing an electrochemical cell, the method comprising adding the complex compound of claim 1 to an electrochemical cell.

8. The method of claim 7, wherein the complex compound is a cathode active additive.

9. The method of claim 7, wherein the complex compound is an anode active additive.

10. The method of claim 7, wherein the adding comprises generating the complex compound in situ in an electrolyte composition of the electrochemical cell.

11. An electrolyte composition, comprising: (i) at least one aprotic organic solvent; (ii) at least one lithium ion-comprising conducting salt; (iii) at least one complex compound of claim 1; and (iv) optionally one or more additives.

12. The electrolyte composition of claim 11, which comprises 0.001 to 10 wt.-% of the at least one complex compound based on a total weight of the electrolyte composition.

13. The electrolyte composition of claim 11, which comprises LiPF.sub.6 or LiBF.sub.4.

14. The electrolyte composition of claim 11, wherein the at least one aprotic organic solvent is selected from optionally fluorinated cyclic and acyclic organic carbonates, optionally fluorinated ethers and polyethers, optionally fluorinated cyclic ethers, optionally fluorinated cyclic and acyclic acetales and ketales, optionally fluorinated orthocarboxylic acids esters, optionally fluorinated cyclic and acyclic esters and diesters of carboxylic acids, optionally fluorinated cyclic and acyclic sulfones, optionally fluorinated cyclic and acyclic nitriles and dinitriles, optionally fluorinated cyclic and acyclic phosphates, and mixtures thereof.

15. An electrochemical cell, comprising: (A) an anode comprising at least one anode active material, (B) a cathode comprising at least one cathode active material; and (C) the electrolyte composition of claim 11.

Description

EXPERIMENTAL SECTION

A) Electrolyte Compositions

A.1) Electrolyte Compositions for Electrochemical Investigations

[0180] The electrolyte compositions were prepared by dissolving different amounts of LiPF.sub.6, LiBF.sub.4, lithium difluoro (oxalato) borate (LiDFOB) or lithium bis(fluorosulfonyl) imide (LiFSI) in different mixtures of ethyl carbonate (EC, BASF), diethyl carbonate (DEC, BASF), monofluoroethylene carbonate (FEC, BASF), 1H,1H,5H-perfluoropentyl-1,1,2,2-tetrafluoroethylether (CF.sub.2H(CF.sub.2).sub.3CH.sub.2OCF.sub.2CF.sub.2H, FPEE, Foosung co., Ltd). Different comparative and inventive additives were added to these compositions as indicated in Tables 1 and 2. vol. % refers to the volume of the solvents in the electrolyte composition. The additive concentrations are expressed either in wt. %, which refers to the total weight of the electrolyte composition, or in mol/L, which corresponds to the molar concentration of the additive. The concentrations of the lithium salts are given in mol/L, also abbreviated as M. The additives were commercially available with the exception of compound A2 and A3. A2 was prepared according to R. Rabinowitz, J. Org. Chem., Vol. 28 (1963), pages 2975 to 2978. A3 was prepared according to M. Sekine et al., J. Org. Chem., Vol. 46 (1981), pages 2097 to 2107. All solvents were dry (water content <3 ppm). All electrolyte compositions were prepared and stored in an Ar-filled glovebox having oxygen and water levels below 1.0 ppm.

TABLE-US-00001 TABLE 1 Electrolyte additives employed [00031] VC [00032] PS [00033] A1 [00034] A2 [00035] A3

TABLE-US-00002 TABLE 2 Electrolyte formulations employed Conducting Salt Solvents Additives Electrolyte [M] [vol. %] [wt. %] [mol/L] composition LiPF.sub.6 LiBF.sub.4 LiDFOB LiFSI EC FEC DEC FPEE VC PS FEC A1 A2 A3 A3 EL 1 (comparative) 1 12 64 24 EL 2 (comparative) 1 12 64 24 2 EL 3 (comparative) 1 12 64 24 2 EL 4 (inventive) 1 12 64 24 2 EL 5 (comparative) 1 30 70 1 1.5 EL 6 (comparative) 1 30 70 1 1 1.5 EL 7 (inventive) 1 30 70 1 1.5 1 EL 8 (inventive) 1 12 64 24 4 EL 9 (comparative) 1 30 70 EL 10 (inventive) 1 30 70 4 EL 11 (inventive) 0.1 30 70 0.1 EL 12 (inventive) 0.05 30 70 0.1 EL 13 (inventive) 0.1 30 70 0.1 EL 14 (comparative) 0.1 30 70 0.1

B) Electrochemical Cells

C.1) HE-NCM/Graphite 2032 Full Coin Cells

[0181] The positive electrodes for the electrochemical cycling experiments were prepared by coating a slurry containing 92.5 wt. % of cathode active material, 2 wt. % Graphite, 2 wt. % Super C65 carbon black and 3.5 wt. % PVDF binder suspended in N-ethyl-2-pyrrolidinone (NEP) on aluminum foil. The cathode active material was the HE-NCM 0.33Li.sub.2MnO.sub.3. 0.67Li(Ni.sub.0.4Mn.sub.0.4Co.sub.0.2)O.sub.2, HE-NCM, BASF). Commercial graphite-coated tapes from Elexcel Corporation Ltd. were used as negative electrodes. The positive, negative composite electrodes, a polypropylene separator (Celgard) and the respective electrolyte were used to manufacture 2032 coin cells. All cells were assembled in an argon-filled glove box having oxygen and water levels below 1.0 ppm and their electrochemical testing carried out in a Maccor 4000 battery-test system.

B.2) NCM424/Graphite and NCM622/Graphite Pouch Cells

[0182] The positive electrodes for the electrochemical cycling experiments in pouch cells were prepared by coating on aluminum foil (thickness=17 m) using a roll coater a slurry containing cathode active material, carbon black and polyvinylidene fluoride (PVdF) binders suspended in N-methyl-2-pyrrolidinone (NMP). The electrode tapes were dried in a hot air chamber and dried further under vacuum at 130 C. for 8 h and the electrodes were pressed using a roll pressor. The cathode active materials employed were either Li(Ni.sub.0.4Co.sub.0.2Mn.sub.0.4)O.sub.2 (NCM424) or Li(Ni.sub.0.6 Co.sub.0.2Mn.sub.0.2)O.sub.2 (NCM622). For the negative electrodes, an aqueous slurry aqueous was prepared by mixing graphite and carbon black with CMC (carboxymethyl cellulose) and SBR (styrene butadiene rubber). The obtained slurry was coated onto copper foil (thickness=9 m) by using a roll coater and dried under hot air chamber (80 C. to 120 C.). The loading of the resulted electrode was found to be 10 mg/cm.sup.2. The electrodes was pressed by roll pressor to an approximate thickness of 72 m. Pouch cells (250 mAh) were assembled in Ar-filled glove box, comprising NCM positive electrodes and graphite negative electrodes with a separator superposed between cathode and anode. Thereafter, all cells were filled with electrolyte, as described in Tables 3, 4, 5 and 6, in an Argon-Filled Glove Box Having Oxygen and Water Levels below 1.0 ppm and their electrochemical testing carried out in a Maccor 4000 battery-test system.

C) Evaluation of Cycling and Cell Resistance in HE-NCM/Graphite 2032 Coin Full Cells at 25 C.

[0183] The cells were charged at a constant current of 0.067 C to a voltage of 4.7 V and discharged with a constant current of 0.067 C to a discharge voltage of 2.0 V (First activation cycle) at 25 C. The first cycle coulombic efficiency is defined as the ratio between the measured discharge and charge capacities.

[0184] Immediately after the cells are charged at 25 C. at a constant current of 0.1 C to a voltage of 4.6 V. The cells were further charged at 4.6 V until the current reached a value of 0.05 C and then discharged at a constant current of 0.1 C to a discharge voltage of 2.0 V (second cycle). The same procedure as in the second cycle was repeated 3 times (cycles 3 to 5). In the cycles 6 to 7, the cells are charged at 25 C. at a constant current of 0.2 C to a voltage of 4.6 V. The cells were further charged at 4.6 V until the current reached a value of 0.05 C and then discharged at a constant current of 0.5 C to a discharge voltage of 2.0 V. Then, the cells are charged at a constant current of 0.7 C to a voltage of 4.6 V, charged at 4.6 V until the current reached a value of 0.05 C and while keeping constant this charging conditions then the cells are discharged to a discharge voltage of 2.0 V at a constant current of 1 C (2 times, cycles 8 to 9), 2 C (2 times, cycles 10 to 11) and 3 C (2 times, cycles 12 to 13).

[0185] Following the variation of discharge rates, prolonged cycling was carried out by charging the cells at a constant current of 0.7 C to a voltage of 4.6 V, charging at 4.6 V until the current reached a value of 0.05 C and discharging to a discharge voltage of 2.0 V at a constant current of 1 C (Cycle 14). The discharge capacity measured for cycle 14 was recorded as the first discharge capacity at 1 C. This charge and discharge procedure was repeated at least 400 times or until the measured charge capacity is lower than 50% of the charge capacity of cycle 14. During the prolonged cycling experiments, DC internal resistance (DCIR) measurements were carried out at each cycle immediately after fully charging the cells (100% state-of-charge) by applying a 0.2 C current interrupt during 10 seconds. The results from the various examples are presented in Table 3.

TABLE-US-00003 TABLE 3 Results obtained from HE-NCM/Graphite cells cycling experiments at 25 C. Cell First Cycle Capacity Capacity Resistance Coulombic retention after Retention after after 200 Efficiency 200 400 1 C-cycles Electrolyte [%] 1 C-cycles [%] 1 C-cycles [%] [Ohm cm.sup.2] Comparative EL 1 87.8 80.5 329 Example 1 Comparative EL 2 87.2 87.2 81.1 242 Example 2 Comparative EL 3 86.5 86.7 77.0 280 Example 3 Inventive EL 4 88.1 95.6 90.5 163 Example 1

D) Evaluation of Cycling of Pouch Cell Comprising NCM424/Graphite Anode

D.1) Formation

[0186] Pouch full-cells prepared comprising a NCM424 cathode and graphite anode were charged at a constant current of 0.1 C either to a voltage of 3.7 V or during maximum 2 hours. Then, the cells were stored for 17 hours at 45 C. followed by degassing and initial volume measurements carried out via Archimedes measurements in water at ambient temperature.

D.2) Cycle Stability of Pouch Full-Cell Comprising NCM424//Graphite at 45 C.

[0187] After completing the formation procedure, the initial charge (CCCV charge, 0.2 C, 4.5V, 0.05 C cut-off) and discharge (CC discharge, 0.2 C, 3.0 V cut-off) capacities were measured. The cell resistance after formation was determined by charging the cells up to 50% SOC and carrying out DC internal resistance (DCIR) measurements by applying a current interrupt and the cells were discharged (CC discharge, 0.2 C, 3.0V cut-off). Then the cells were charged at a constant current of 0.6 C to a voltage of 4.5 V, charged at 4.5 V until the current reached a value of 0.05 C and discharged to a voltage of 3.0 V at a constant current of 1 C and the discharge capacity measured was set as the reference discharge capacity value and corresponding to 100%. This charge and discharge procedure was repeated 200 times. The discharge capacities in cycle 100 and 200 are reported in Table 4 and are expressed as a percentage of the reference discharge capacity. Then, the cells were charged up to 50% SOC to determine their resistance after cycling via DC internal resistance (DCIR) measurements by applying a current interrupt, discharged at a constant current of 0.2 C to a voltage of 3.0 V. Finally, volume measurements after cycling were carried out via Archimedes measurements in water at ambient temperature. The results from the various examples are presented in Table 4.

TABLE-US-00004 TABLE 4 Results obtained from NCM-424/Graphite cells cycling experiments at 45 C. Cell Cell Cell volume Capacity Capacity resistance resistance change after retention Retention after after 200 200 cycles after 100 after 200 formation cycles at 45 C. at 45 C. Electrolyte cycles [%] Cycles [%] [Ohm cm.sup.2] [Ohm cm.sup.2] [mL] Comparative EL 1 93.0 64.2 107.4 147.0 0.36 Example 4 Comparative EL 3 93.5 87.2 68.7 92.0 0.33 Example 5 Inventive EL 4 93.7 89.8 82.7 95.7 0.10 Example 6

E) Evaluation of Cycling and High-Temperature Storability of Pouch Cell Comprising NCM622/Graphite Anode

E.1) Formation

[0188] Pouch full-cells prepared comprising a NCM622 cathode and graphite anode were charged up to 10% SOC at ambient temperature. Degassing process was applied to the cells before charge (CCCV charge, 0.2 C, 4.2 V cut off 0.015 C) and discharge (CC discharge, 0.2 C, 2.5 V cut-off) at ambient temperature. Then, the cells were charged again up to 4.2V (CCCV charge, 0.2 C, 4.2 V cut off 0.015 C) and stored at 60 C. for 6 h. After formation, the initial charge (CCCV charge, 0.2 C, 4.2 V, 0.015 C cut-off) and discharge (CC discharge, 0.2 C, 2.5 V cut-off) capacities were measured. The cell resistance after formation was determined by charging the cells up to 50% SOC and DC internal resistance (DCIR) measurements by applying a current interrupt. The results from the various examples are presented in Table 5.

E.2) Cycle Stability of Pouch Full-Cell Comprising NCM622//Graphite at 45 C.

[0189] After completing the formation procedure, the cells were charged in CC/CV mode up to 4.2V with 1 C current and cut-off current of 0.015 C and discharged down to 2.5 V with 1 C at 45 C. This charge/discharge (one cycle) procedure was repeated 250 times. The final charge (CCCV charge, 0.2 C, 4.2 V, 0.015 C cut-off) and discharge (CC discharge, 0.2 C, 2.5 V cut-off) capacities were measured after cycling. The capacity retention after cycling is expressed as the ratio between the final and initial discharge capacity. The cell resistance after cycling was determined by charging the cells up to 50% SOC and DC internal resistance (DCIR) measurements by applying a current interrupt. The results from the various examples are presented in Table 5.

TABLE-US-00005 TABLE 5 Results obtained from NCM-622/Graphite cells cycling experiments at 45 C. Capacity Cell Resistance retention at Cell Resistance after cycling 0.2 C after after formation at 45 C. cycling at Electrolyte [Ohm cm.sup.2] [Ohm cm.sup.2] 45 C. [%] Comparative EL 5 86.9 285.8 75.0 Example 6 Comparative EL 6 81.3 182.4 85.9 Example 7 Inventive EL 7 75.6 126.0 86.4 Example 3

E.3) High Temperature Storage of Pouch Full-Cell Comprising NCM622//Graphite at 60 C.

[0190] After completing the formation procedure, the cells were charged up to 4.2 V at ambient temperature and then stored at 60 C. for 30 days. The generated gas amount (mL) during the storage was determined by Archimedes measurements in water at ambient temperature and the results are summarized in Table 6. The final charge (CCCV charge, 0.2 C, 4.2 V, 0.015 C cutoff) and discharge (CC discharge, 0.2 C, 2.5 V cut-off) capacities were measured after storage tests. The capacity retention after cycling is expressed as the ratio between the final and initial discharge capacity. The cell resistance after cycling was determined by charging the cells up to 50% SOC and DC internal resistance (DCIR) measurements by applying a current interrupt. The results from the various examples are presented in Table 6.

TABLE-US-00006 TABLE 6 Results obtained from NCM-622/Graphite cells storage experiments at 60 C. Cell volume Cell volume Cell volume Cell Resistance change change after change after after 30 days after 8 days 15 days 30 days storage at 60 C. storage at storage at storage at Electrolyte [Ohm cm.sup.2] 60 C. [mL] 60 C. [mL] 60 C. [mL] Comparative EL 5 101.5 1.90 1.82 1.75 Example 8 Comparative EL 6 107.2 0.49 0.49 0.61 Example 9 Inventive EL 7 90.2 0.27 0.30 0.43 Example 4

F) NMR Analysis

[0191] EL 8 was analyzed by .sup.1H NMR spectroscopy and .sup.19F NMR spectroscopy directly after preparation and after one week of storage at 25 C. The electrolytes were analyzed using .sup.1H, .sup.19F and .sup.31P NMR without any dilution. The spectra were recorded on a Bruker Avance III equipped with a CryoProbe Prodigy probe head or on a Varian NMR system 400 operating at a frequency of .sup.1H: 500.36 MHz, .sup.19F: 470.76 MHz, .sup.31P: 202.56 MHz. Bruker TopSpin software was used to analyze the spectra. All signals were referenced in .sup.1H NMR to d.sub.6-benzene (7.16 ppm) or d.sub.6-DMSO (2.50 ppm); placed in an internal capillary), in .sup.31P NMR to LiPF.sub.6 (145.88 ppm, septet, E. J. Cairns et al., J. Electrochem. Soc. Vol. 152 (2005), pages A1629 to A1632) within the electrolyte and in .sup.19F NMR to LiPF.sub.6 (73.18 ppm, d, reference same as for .sup.31P NMR). .sup.31P NMR data were collected for the sake of clarity decoupled from proton: {1H}: Quantitative analysis was performed in .sup.19F NMR using 3,5-bis(trifluoromethyl)benzoic acid as an internal standard.

[0192] In FIG. 1 parts of the 1H NMR spectrum and in FIG. 2 part of the 19F NMR spectrum of EL 8 directly after formation are shown. The spectra indicate the presence of additive A3 (formula (13)) and the inventive complex compound (formula (14)) and (CH.sub.3).sub.3SiF (formula (15)) formed in situ in the electrolyte composition by the reaction of additive A3 and LiPF.sub.6. In Table 7 the structures of these compounds are displayed and the different H/F-atoms are denoted H.sup.a to H.sup.e and F.sup.a and F.sup.b, respectively as indicated in the 1H/19F NMR spectra in FIGS. 1 and 2. Integration ratios are indicated in parentheses for each atomic species in FIGS. 1 and 2.

TABLE-US-00007 TABLE 7 Species found in EL 8 by 1H/19F NMR [00036] (13) [00037] (14) [00038] (15)

[0193] In FIG. 1 the typical upfield shifted signals of a methyl group bonded to a silicon atom is observed for three chemical species. A large PH coupling can be observed for two chemical species. The more upfield shifted signal is broad indicating a coordinated molecule.

[0194] The coordinated PF.sub.5 group of the compound of formula (9) exhibits an asymmetric configuration, four F-atoms being in one plane and the fifth is directed vertical on this plane. The .sup.19F NMR spectrum in FIG. 2 shows a characteristic coupling between the two non-equivalent fluorine nuclei in the molecule.

[0195] A quantitative analysis was performed by determining molar concentrations calculated from the integral of peak signals in reference to the internal standard from the .sup.1H or .sup.19F NMR spectrum. The results are summarized in Tables 8, 9, 10 and 11 for different ELY base formulations. Rel. concentration was evaluated by comparison of the integrals of H.sup.b (18 H for A3, see formula (13)) vs. Hd (9 H for (14)) in .sup.1H NMR or the integrated signals at 15.08 ppm (A3) and 13.98 ppm (14) in .sup.31P NMR.

TABLE-US-00008 TABLE 8 Quantification of formation of (14) in EL7 (DEC:EC 70:30, 1 wt. % VC, 1.5 wt. % FEC, 1M LiPF.sub.6 + 1 wt. % A3) Freshly prepared After storage of 1 week Species [mmol/L] [mmol/L] Formula (13) (A3) 27 12 Formula (14) based on 1H 23 31 NMR Formula (15) Not determined 30 Coordinated PF.sub.5 group 19 31 based on .sup.19F NMR

[0196] The added amount of additive A3 equaled a concentration of about 53 mmol/L in the electrolyte composition. Right after adding additive A3 to the electrolyte composition the reaction between the LiPF.sub.6 and additive A3 started. The reaction continued gradually overtime and also more coordinated PF.sub.5 groups were formed. The coordinated PF.sub.5 groups are assumed to belong to the complex compound of formula (14).

TABLE-US-00009 TABLE 9 Quantification of formation of (14) in EL7 (DEC:EC 70:30, 1 wt. % VC, 1.5 wt. % FEC, 1M LiPF.sub.6 + 1 wt. % A3) Rel. concentration of (14) Time Rel. concentration of A3 based on 1H NMR Freshly 1 0.84 prepared After 1 week 1 2.48 storage at 25 C.

TABLE-US-00010 TABLE 10 Quantification of formation of (14) in EL8 (DEC:FEC:FPEE 64:12:24, 1M LiPF.sub.6 + 4 wt. % A3), Rel. Rel. concentration Rel. concentration concentration of (14) based of (14) based Time of A3 on .sup.1H NMR on .sup.31P NMR Freshly prepared 1 0.10 0.10 After 24 h 1 0.48 0.42 storage at 25 C. After 4 days 1 1.02 1.13 storage at 25 C. After 1 week 1 1.32 1.32 storage at 25 C.

[0197] The NMR-signals used for the evaluation shown in Tables 8 to 10 are summarized below.

[0198] A3 in EL7 (DEC:EC 70:30, 1 wt. % VC, 1.5 wt. % FEC, 1 M LiPF.sub.6, initially 1 wt. % A3)

[0199] .sup.1H NMR (400 MHz, d.sub.6-DMSO): 6.58 (d, J=723.9 Hz, 1H), 0.03 (s, 18H)

[0200] (14) in EL7 (DEC:EC 70:30, 1 wt. % VC, 1.5 wt. % FEC, 1 M LiPF.sub.6, initially 1 wt. % A3)

[0201] .sup.1H NMR (400 MHz, d.sub.6-DMSO): 6.52 (d, J=711.5 Hz, 1H), 0.00 (s, 9H)

[0202] .sup.19F NMR (367 MHz, LiPF.sub.6): 59.55 (ddd, J=734.2, 51.5, 11.7 Hz), 74.26 (dp, J=722.1, 51.6 Hz)

[0203] (15) in EL7 (DEC:EC 70:30, 1 wt. % VC, 1.5 wt. % FEC, 1 M LiPF.sub.6, initially 1 wt. % A3)

[0204] .sup.1H NMR (400 MHz, d.sub.6-DMSO): 0.08 (d, J=7.4 Hz, 9H)

[0205] .sup.19F NMR (367 MHz, LiPF.sub.6): 157.11 (m)

[0206] A3 in EL8 (DEC:FEC:FPEE 64:12:24, 1 M LiPF.sub.6, initially 4 wt. % A3)

[0207] .sup.1H NMR (500 MHz, d.sub.6-benzene): 7.05 (d, J=722.2 Hz, 1H), 0.51 (s, 18H)

[0208] .sup.31P{.sup.1H} NMR (202 MHz, LiPF.sub.6): 15.08 (s)

[0209] (14) in EL8 (DEC:FEC:FPEE 64:12:24, 1 M LiPF.sub.6, initially 4 wt. % A3)

[0210] .sup.1H NMR (500 MHz, d.sub.6-benzene): 7.03 (d, J=714.2 Hz, 1H), 0.48 (s, 9H)

[0211] .sup.19F NMR (470 MHz, LiPF.sub.6): 59.42 (ddd, J=732.7, 50.4, 11.6 Hz), 74.25 (dp, J=717.2, 50.4 Hz)

[0212] .sup.31P{.sup.1H} NMR (202 MHz, LiPF.sub.6): 13.98 (h, J=11.9 Hz), 149.53 (h, J=733.0 Hz)

[0213] (15) in EL8 (DEC:FEC:FPEE 64:12:24, 1 M LiPF.sub.6, initially 4 wt. % A3)

[0214] .sup.1H NMR (400 MHz, d.sub.6-benzene): 0.39 (d, J=7.4 Hz, 9H)

[0215] .sup.19F NMR (367 MHz, LiPF.sub.6): 157.43 (m)

[0216] When LiBF.sub.4 or LiDFOB were used instead of LiPF.sub.6, a mixture of multiple species containing OPH(O)OTMS and/or OPH(O)O were obtained. The clear determination of the structure of the individual complexes formed via .sup.1H, .sup.19F or .sup.31P{.sup.1H} NMR was not possible due to overlapping signals. Instead of the evolution of signals of discrete complexes of formula (I) the generation of trimethyl silyl fluoride (15) and the degradation of A3 was used to quantify the formation reaction. The relative ratio of A3 vs (15) were quantified by the comparison of the relevant integrals in .sup.1H NMR for A3 at 0.63 ppm (s, 18H) and for (15) at 0.52 ppm (d, J=7.4 Hz, 9H). The data is summarized in table 11. Formation of trimethyl silyl fluoride (15) was not observed in case LiFSI was used instead of LiPF.sub.6. FIG. 3 shows parts of the .sup.19F NMR spectra of EL9, EL10, EL11 and EL12 freshly prepared and after storage for 1 week at 25 C.

[0217] A3 in (DEC:EC 70:30)

[0218] .sup.1H NMR (400 MHz, d.sub.6-benzene): 7.16 (d, J=716.2 Hz, 1H), 0.63 (s, 18H) (15) in (DEC:EC 70:30)

[0219] .sup.1H NMR (400 MHz, d.sub.6-benzene): 0.52 (d, J=7.4 Hz, 9H)

TABLE-US-00011 TABLE 11 Quantification of formation of complexes with various lithium salts Initial molar ratio Electrolyte lithium salt lithium salt:A3 Status Observation EL 9 1M LiBF.sub.4 100:0 Freshly No formation of (15) observed (.sup.1H and prepared .sup.19F NMR) EL 10 1M LiBF.sub.4 4:1 Freshly Quantitative formation of (15) observed prepared A3 quantitatively converted (.sup.1H and .sup.31P NMR) EL 11 0.1M 1:1 Freshly prepared Quantitative conversion of LiBF.sub.4 (.sup.19F LiBF.sub.4 NMR) Ratio A3:(15) = 1:12.5 (.sup.1H NMR) EL 12 0.05M 1:2 Freshly prepared Quantitative conversion of LiBF.sub.4 (.sup.19F LiBF.sub.4 NMR) Ratio A3:(15) = 1:5.4 (.sup.1H NMR) EL 12 0.05M 1:2 Stored 1 Quantitative conversion of LiBF.sub.4 (.sup.19F LiBF.sub.4 week at 25 C. NMR) Ratio A3:(15) = 1:99 (.sup.1H NMR) EL 13 0.1M 1:1 Freshly prepared Formation of (15) observed (.sup.1H and LiDFOB .sup.19F NMR) Ratio A3:(15) = 1:0.03 (.sup.1H NMR) EL 13 0.1M 1:1 Stored 1 Formation of (15) observed (.sup.1H and LiDFOB week at 25 C. .sup.19F NMR) Ratio A3:(15) = 1:0.12 (.sup.1H NMR) EL 14 0.1M 1:1 Freshly prepared No formation of (15) observed (.sup.1H and LiFSI .sup.19F NMR)