Heterocyclic sulfonyl fluoride additives for electrolyte composition for lithium batteries

Abstract

Heterocyclic sulfonyl fluoride additives for electrolyte composition for lithium batteries An electrolyte composition containing •(i) at least one aprotic organic solvent; •(ii) at least one conducting salt; •(iii) at least one compound of formula (I) wherein R.sup.1, R.sup.2, and R.sup.3 are each independently H or a C.sub.1-C.sub.20 hydrocarbon group which may be unsubstituted or substituted by one or more substituents selected from F, CN, OS(O).sub.2F, and S(O).sub.2F and which may contain one or more groups selected from —O—, —S—, —C(O)O—, —OC(O)—, and —OS(O).sub.2—; wherein at least one of R.sup.1, R.sup.2, and R.sup.3 is substituted by one or more S(O).sub.2F groups; and •(iv) optionally one or more additives. ##STR00001##

Claims

1. An electrolyte composition comprising: (i) at least one aprotic organic solvent; (ii) at least one conducting salt; (iii) at least one compound of formula (I) ##STR00014## wherein R.sup.1, R.sup.2, and R.sup.3 may each independently be H or a C.sub.1-C.sub.20 hydrocarbon group which may be unsubstituted or substituted by one or more substituents selected from the group consisting of F, CN, OS(O).sub.2F, and S(O).sub.2F and which may comprise one or more groups selected from the group consisting of —O—, —S—, —C(O)O—, —OC(O)—, and —OS(O).sub.2—; wherein at least two of R.sup.1, R.sup.2, and R.sup.3 are substituted by one or more S(O).sub.2F groups; and (iv) optionally one or more additives.

2. The electrolyte composition according to claim 1, wherein each of R.sup.1, R.sup.2, and R.sup.3 is substituted by one or more S(O).sub.2F groups.

3. The electrolyte composition according to claim 1, wherein the C.sub.1-C.sub.20 hydrocarbon group is selected independently at each occurrence from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.3-C.sub.6 cycloalkyl, C.sub.2-C.sub.20 alkenyl, C.sub.2-C.sub.20 alkynyl, C.sub.5-C.sub.7, aryl, and C.sub.6-C.sub.20 aralkyl.

4. The electrolyte composition according to claim 1, wherein the C.sub.1-C.sub.20 hydrocarbon group is selected independently at each occurrence from the group consisting of C.sub.1-C.sub.12 alkyl.

5. The electrolyte composition according to claim 1, wherein at least one of R.sup.1, R.sup.2, and R.sup.3 is (CH.sub.2).sub.nS(O).sub.2F, wherein n is independently at each occurrence an integer from 1 to 12 and one or more hydrogen of the (CH.sub.2).sub.n chain may be replaced by F, CN, OS(O).sub.2F and/or S(O).sub.2F and wherein one or more CH.sub.2 groups of the (CH.sub.2).sub.n chain which are not directly connected to the N-atom or the S(O).sub.2F group may be replaced by —O—, —C(O)O—, —OC(O)—, and/or —OS(O).sub.2—.

6. The electrolyte composition according to claim 1, wherein the compound of formula (I) is a compound of formula (II) ##STR00015## wherein n is independently at each occurrence 1, 2, 3, 4, 5 or 6.

7. The electrolyte composition according to claim 1, wherein the compound of formula (I) is ##STR00016##

8. The electrolyte composition according to claim 1, wherein the electrolyte composition comprises 0.01 to 10 wt.-% of the compound of formula (I) based on the total weight of the electrolyte composition.

9. The electrolyte composition according to claim 1, wherein the electrolyte composition is non-aqueous.

10. The electrolyte composition according to claim 1, wherein the aprotic organic solvent (i) is selected from the group consisting of fluorinated and non-fluorinated cyclic and acyclic organic carbonates, fluorinated and non-fluorinated ethers and polyethers, fluorinated and non-fluorinated cyclic ethers, fluorinated and non-fluorinated cyclic and acyclic acetals and ketals, fluorinated and non-fluorinated orthocarboxylic acids esters, fluorinated and non-fluorinated cyclic and acyclic esters and diesters of carboxylic acids, fluorinated and non-fluorinated cyclic and acyclic sulfones, fluorinated and non-fluorinated cyclic and acyclic nitriles and dinitriles, fluorinated and non-fluorinated cyclic and acyclic phosphates, and mixtures thereof.

11. The electrolyte composition according to claim 1, wherein the at least one aprotic organic solvent (i) is selected from the group consisting of fluorinated and non-fluorinated ethers and polyethers, fluorinated and non-fluorinated cyclic and acyclic organic carbonates, and mixtures thereof.

12. The electrolyte composition according to claim 1, wherein the at least one conducting salt (ii) is selected from the group consisting of lithium salts.

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

Description

I. PREPARATION OF ADDITIVES

(1) C. 1

(2) To a solution of Ethenesulfonyl fluoride (22.2 g, 200 mmol, 1.0 eq) and Succinimide (20.2 g, 200 mmol, 1.0 eq) in ethanol (EtOH) (800 ml) was added sodium acetate (AcONa) (3.33 g, 40.0 mmol, 0.2 eq) at ice bath temperature, and the mixture was stirred at room temperature for 30 min. The obtained suspension was quenched with water, extracted with ethyl acetate (EtOAc), washed with bine, and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the crude product was purified by silica gel chromatography (hexanes/EtOAc) to give the product as a white solid (35.6 g, 84% yield).

(3) C. 2

(4) To a solution of Ethenesulfonyl fluoride (11.1 g, 100 mmol, 1.0 eq) and 1-Methylhydantoin (11.5 g, 100 mmol, 1.0 eq) in EtOH (400 ml) was added AcONa (1.67 g, 20.0 mmol, 0.2 eq) at ice bath temperature, and the mixture was stirred at room temperature for 15 h. The obtained suspension was quenched with water, extracted with EtOAc, washed with bine, and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the crude product was purified by silica gel chromatography (hexanes/EtOAc) to give the product as a white solid (19.6 g, 86% yield).

(5) II. 1

(6) To a solution of Ethenesulfonyl fluoride (70.8 g, 569 mmol, 3.0 eq) and Cyanuric acid (25.0 g, 189 mmol, 1.0 eq) in EtOH (950 ml) was added AcONa (15.8 g, 190 mmol, 1.0 eq) at ice bath temperature, and the mixture was stirred at room temperature for 15 h. The obtained suspension was filtrated, and washed by water, EtOH and diethyl ether (Et2O). The product was dried over reduced pressure resulting in a white solid (81.6 g, 93% yield).

(7) C. 3

(8) To a solution of Tris(2-hydroxyethyl) Isocyanurate (25.0 g, 93 mmol, 1.0 eq) and Triethylamine (29.5 g, 288 mmol, 3.1 eq) in CH2Cl2 (400 ml) was added Methanesulfonyl Chloride (33.4 g, 288 mmol, 3.1 eq) at ice bath temperature, and the mixture was stirred at room temperature for 15 h. The obtained suspension was filtrated and washed by CH2Cl2. The solid was purified by silica gel chromatography (hexanes/EtOAc) to give the product as a white solid (2.7 g, 6% yield).

(9) The additives are summarized in Table 1.

(10) TABLE-US-00001 TABLE 1 Additives Compound Comparative 1 (C. 1) 2-Succinimido- ethanesulfonyl fluoride 0 Comparative 2 (C. 2) 2-(1′-Methylhydantoyl)- ethanesulfonyl fluoride (II. 1) 3,3′,3″-(2,4,6-trioxo- [1,3,5]triazinane-1,3,5- triyl)-tris-ethanesulfonyl fluoride Comparative 3 (C. 3) 1,3,5-tris(2- methanesulfonylethyl) 1,3,5-triazine-2,4,6-trione

II. ELECTROLYTE COMPOSITIONS

(11) 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 EL base 1. To this EL base 1 formulation 10 wt % FEC was added (EL base 2). To this EL base 2 formulation different amounts of additives were added. The amounts of the additives were calculated to result in electrolyte samples containing 1 mol/L SO.sub.2F groups (for compounds C.1, C.2 and II.1) or OSO.sub.2CH.sub.3 (compound C.3). The exact compositions are summarized in Table 2. In Table 2 concentrations are given as wt.-% based on the total weight of the electrolyte composition.

III. ELECTROCHEMICAL CELLS

(12) III.1 Silicon Suboxide/Graphite Anodes

(13) 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 μm) and dried under ambient temperature. The sample loading for electrodes on Cu foil was fixed to be 5 mg cm.sup.−2.

(14) III.2 Fabrication of the Test Cells

(15) Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a silicon suboxide/graphite composite anode prepared as described above and lithium metal as working and counter 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 anode//separator//Li foil to produce a half coin cell. Thereafter, 0.15 mL of the different nonaqueous electrolyte compositions were introduced into the coin cell.

IV TESTING OF THE CELLS

(16) Cycle Stability of Coin Halfcells Comprising Silicon Suboxide/Graphite Composite Anode

(17) The coin half cells prepared according to III were tested in a voltage range between 1 V to 0.03 V at room temperature. For the initial 2 cycles, the initial lithiation was conducted in the CC-CV mode, i.e., a constant current (CC) of 0.05 C was applied until reaching 0.01 C. After 5 min resting time, oxidative delithiation was carried out at constant current of 0.05 C up to 1 V. For the cycling, the current density increased to 0.5 C. The results are summarized in Table 2. [%] capacity retention after 230 cycles is based on the capacity retention after the second cycle.

(18) TABLE-US-00002 TABLE 2 Cycle stability of coin halfcells comprising silicon suboxide/ graphite anode at room temperature Capacity Cycle EL Additive retention Retention base concen- after 20 after 230 Electrolyte 2 tration cyc [%] cyc [%] Sample Additive [wt.-%] [wt.-%] at 25° C. at 25° C. 1 (comparative) C.1 98.0 2.0 99.7 85 2 (comparative) C.2 97.9 2.1 99.5 56 3 (inventive) II.I 98.5 1.5 99.3 91 4 (comparative) C.3 98.4 1.6 99.3 73 5 (comparative) none 100.0 0 99.6 80