Acrylonitrile derivatives as additive for electrolytes in lithium ion batteries

Abstract

An electrolyte composition (A) containing (i) at least one aprotic organic solvent; (ii) at least one conducting salt; (iii) at least one compound of formula (NC)(A.sup.1X.sup.1)C═C(X.sup.2A.sup.2)(CN) wherein X.sup.1 and X.sup.2 are independently from each other selected from N(R′), P(R.sup.1), O, and S, and A.sup.1 and A.sup.2 are selected from H or organic substituents; and electrochemical cells containing electrolyte composition (A). ##STR00001##

Claims

1. An electrolyte composition (A) comprising: (i) an aprotic organic solvent; (ii) a conducting salt; (iii) a compound of formula (I) ##STR00020## wherein X.sup.1 and X.sup.2 are independently from each other selected from the group consisting of N(R.sup.1), N═C(R.sup.2)—, and P(R.sup.1); R.sup.1 is selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.3 aralkyl, OR.sup.3, C(O)R.sup.3, C(NR.sup.3)R.sup.4, and C(O)OR.sup.3, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3a, OS(O).sub.2R.sup.3a, S(O).sub.2R.sup.3a, OR.sup.3a, C(O)R.sup.3a, C(O)OR.sup.3a, NR.sup.3aR.sup.3b, and NC(O)R.sup.3aR.sup.3b; R.sup.2 is selected from the group consisting of H, CN, F, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, S(O).sub.2OR.sup.3, OS(O).sub.2R.sup.3, S(O).sub.2R.sup.3, OR.sup.3, C(O)R.sup.3, C(NR.sup.3)R.sup.4, C(O)OR.sup.3, NR.sup.3R.sup.4, NC(O)R.sup.3, P(O)R.sup.3R.sup.4, and SiR.sup.3R.sup.4R.sup.5, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3a, OS(O).sub.2R.sup.3a, S(O).sub.2R.sup.3a, OR.sup.3a, C(O)R.sup.3a, C(O)OR.sup.3a, NR.sup.3aR.sup.3b, and NC(O)R.sup.3aR.sup.3b; R.sup.3, R.sup.4, R.sup.5, R.sup.3a, and R.sup.3b are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.7-C.sub.13 aralkyl, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3c, OS(O).sub.2R.sup.3c, S(O).sub.2R.sup.3c, OR.sup.3c, C(O)R.sup.3c, C(O)OR.sup.3c, NR.sup.3cR.sup.3d, and NC(O)R.sup.3cR.sup.3d; R.sup.3c and R.sup.3d are selected independently from each other from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, and C.sub.5-C.sub.7 (hetero)aryl, wherein alkyl, (hetero)cycloalkyl, alkenyl, and (hetero)aryl may be substituted by one or more substituents selected from the group consisting of F and CN; A.sup.1 is selected from the group consisting of C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, OR.sup.6, C(O)R.sup.6, C(NR.sup.6)R.sup.7 and C(O)OR.sup.6, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6a, OS(O).sub.2R.sup.6a, S(O).sub.2R.sup.6a, OR, C(O)OR.sup.6a, NR.sup.6aR.sup.6b, and NC(O)R.sup.6aR.sup.6b; A.sup.2 is selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, OR.sup.6, C(O)R.sup.6, C(NR.sup.6)R.sup.7 and C(O)OR.sup.6, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6, OS(O).sub.2R.sup.6a, S(O).sub.2R.sup.6a, OR.sup.6a, C(O)OR.sup.6a, NR.sup.6aR.sup.6b, and NC(O)R.sup.6aR.sup.6b with the proviso that in case of X.sup.2 is O or S, A.sup.2 is neither H nor OR.sup.6; R.sup.6, R.sup.7, R.sup.6a, and R.sup.6b are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.7-C.sub.13 aralkyl, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.3-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6c, OS(O).sub.2R.sup.6c, S(O).sub.2R.sup.6c, OR.sup.6c, C(O)R.sup.6c, C(O)OR.sup.6c, NR.sup.6cR.sup.6d, and NC(O)R.sup.6cR.sup.6d; R.sup.6c and R.sup.6d are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, and C.sub.5-C.sub.7 (hetero)aryl, wherein alkyl, (hetero)cycloalkyl, alkenyl, and (hetero)aryl may be substituted by one or more substituents selected from the group consisting of F and CN; and (iv) optionally, a further additive.

2. The electrolyte composition (A) according to claim 1 wherein both X.sup.1 and X.sup.2 are independently from each other selected from the group consisting of N(R.sup.1) and P(R.sup.1).

3. The electrolyte composition (A) according to claim 1, wherein the compound of formula (I) is selected from the group consisting of compounds of formula (I) wherein X.sup.1 and X.sup.2 are independently from each other selected from the group consisting of N(R.sup.1) and N═C(R.sup.2).

4. The electrolyte composition (A) according to claim 1, wherein the compound of formula (I) is selected from the group consisting of compounds of formula (I a) wherein X.sup.1 is N(R.sup.1) and X.sup.2 is N═C(R.sup.2), ##STR00021## wherein R.sup.8 is selected from the group consisting of H, C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl, and R.sup.9 is selected from the group consisting of C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl, wherein C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, and OR.sup.6a.

5. The electrolyte composition (A) according to claim 1, wherein the compound of formula (I) is selected from the group consisting of compounds of formula (I b) wherein X.sup.1 and X.sup.2 are N(R.sup.1) ##STR00022## wherein R.sup.8 is selected from the group consisting of H, C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl, and R.sup.9 is selected from the group consisting of C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl, wherein C.sub.5-C.sub.7 (hetero)aryl and C.sub.7-C.sub.13 aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, and OR.sup.6a.

6. The electrolyte composition (A) according to claim 1, wherein the aprotic organic solvent (i) is selected from the group consisting of: (a) a cyclic or a noncyclic organic carbonate, which may be partly halogenated, (b) a di-C.sub.1-C.sub.10-alkylether, which may be partly halogenated, (c) a di-C.sub.1-C.sub.4-alkyl-C.sub.2-C.sub.6-alkylene ether or polyether, which may be partly halogenated, (d) a cyclic ether, which may be partly halogenated, (e) a cyclic or an acyclic acetal or ketal, which may be partly halogenated, (f) an orthocarboxylic acid ester, which may be partly halogenated, (g) a cyclic or a noncyclic ester of a carboxylic acid, which may be partly halogenated, (h) a cyclic or a noncyclic sulfone, which may be partly halogenated, (i) a cyclic or a noncyclic nitrile or dinitrile, which may be partly halogenated, and (j) an ionic liquid, which may be partly halogenated.

7. The electrolyte composition (A) according to claim 1, wherein the electrolyte composition (A) comprises an aprotic organic solvent (i) that is a cyclic organic carbonate and an aprotic organic solvent (i) that is a noncyclic organic carbonate.

8. The electrolyte composition (A) according to claim 1, wherein the conducting salt (ii) is selected from the group consisting of: Li[F.sub.6-xP(C.sub.yF.sub.2y+1).sub.x], wherein x is an integer in the range from 0 to 6 and y is an integer in the range from 1 to 20; Li[B(R.sup.I).sub.4], Li[B(R.sup.I).sub.2(OR.sup.IIO)] and Li[B(OR.sup.IIO).sub.2] wherein each R.sup.I is independently from each other selected from the group consisting of F, Cl, Br, I, C.sub.1-C.sub.4 alkyl, C.sub.2-C.sub.4 alkenyl, and C.sub.2-C.sub.4 alkynyl, wherein alkyl, alkenyl, and alkynyl may be substituted by one or more OR.sup.III, wherein R.sup.III is selected from the group consisting of C.sub.1-C.sub.6 alkyl, C.sub.2-C.sub.6 alkenyl, and C.sub.2-C.sub.6 alkynyl, and (OR.sup.IIO) is a bivalent group derived from a 1,2- or 1,3-diol, a 1,2- or 1,3-dicarboxlic acid or a 1,2- or 1,3-hydroxycarboxylic acid, wherein the bivalent group forms a 5- or 6-membered cycle via both oxygen atoms with the central B-atom; LiClO.sub.4; LiAsF.sub.6; LiCF.sub.3SO.sub.3; Li.sub.2SiF.sub.6; LiSbF.sub.6; LiAlCl.sub.4, lithium tetrafluoro (oxalato) phosphate; lithium oxalate; and a salt of formula Li[Z(C.sub.nF.sub.2n+1SO.sub.2).sub.m], where m and n are defined as follows: m=1 when Z is selected from the group consisting of oxygen and sulfur, m=2 when Z is selected from the group consisting of nitrogen and phosphorus, m=3 when Z is selected from the group consisting of carbon and silicon, and n is an integer in the range from 1 to 20.

9. The electrolyte composition (A) according to claim 1, wherein the electrolyte composition (A) further comprises at least one additive (iv) which is selected from the group consisting of vinylene carbonate and its derivatives, vinyl ethylene carbonate and its derivatives, methyl ethylene carbonate and its derivatives, lithium (bisoxalato) borate, lithium difluoro (oxalato) borate, lithium tetrafluoro (oxalato) phosphate, lithium oxalate, 2-vinyl pyridine, 4-vinyl pyridine, cyclic exo-methylene carbonates, sultones, organic esters of inorganic acids, acyclic and cyclic alkanes having a boiling point at 1 bar of at least 36° C., and aromatic compounds, optionally halogenated cyclic and acyclic sulfonylimides, optionally halogenated cyclic and acyclic phosphate esters, optionally halogenated cyclic and acyclic phosphines, optionally halogenated cyclic and acyclic phosphites, optionally halogenated cyclic and acyclic phosphazenes, optionally halogenated cyclic and acyclic silylamines, optionally halogenated cyclic and acyclic halogenated esters, optionally halogenated cyclic and acyclic amides, optionally halogenated cyclic and acyclic anhydrides, ionic liquids, and optionally halogenated organic heterocycles.

10. The electrolyte composition (A) according to claim 1, wherein the concentration of the compound of formula (I) is 0.001 to 10 wt.-%, based on the total weight of the electrolyte composition (A).

11. An electrochemical cell comprising (A) the electrolyte composition according to claim 1, (B) a cathode comprising a cathode active material, and (C) an anode comprising an anode active material.

12. The electrochemical cell according to claim 11, wherein the electrochemical cell is a secondary lithium ion battery.

13. The electrochemical cell according to claim 11, wherein at least one cathode active material comprises a material capable of occluding and releasing lithium ions selected from the group consisting of lithiated transition metal phosphates and lithium ion intercalating transition metal oxides.

14. The electrochemical cell according to claim 11, wherein the anode active material comprises a lithium ion intercalating material selected from the group consisting of lithium ion intercalating carbonaceous material, lithium ion intercalating oxides of Ti, and lithium ion uptaking silicon.

15. An electrolyte composition (A) comprising: (i) an aprotic organic solvent; (ii) a conducting salt; (iii) a compound of formula (I) ##STR00023## wherein X.sup.1 is selected from N(R.sup.1), P(R.sup.1), oxygen, and sulfur; X.sup.2 is N═C(R.sup.2); R.sup.1 is selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.6-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, OR.sup.3, C(O)R.sup.3, C(NR.sup.3)R.sup.4, and C(O)OR.sup.3, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3a, OS(O).sub.2R.sup.3a, S(O).sub.2R.sup.3a, OR.sup.3a, C(O)R.sup.3a, C(O)OR.sup.3a, NR.sup.3aR.sup.3b, and NC(O)R.sup.3aR.sup.3b; R.sup.2 is selected from the group consisting of H, CN, F, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, S(O).sub.2OR.sup.3, OS(O).sub.2R.sup.3, S(O).sub.2R.sup.3, OR.sup.3, C(O)R.sup.3, C(NR.sup.3)R.sup.4, C(O)OR.sup.3, NR.sup.3R.sup.4, NC(O)R.sup.3, P(O)R.sup.3R.sup.4, and SiR.sup.3R.sup.4R.sup.5, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3a, OS(O).sub.2R.sup.3a, S(O).sub.2R.sup.3a, OR.sup.3a, C(O)R.sup.3a, C(O)OR.sup.3a, NR.sup.3aR.sup.3b, and NC(O)R.sup.3aR.sup.3b; R.sup.3, R.sup.4, R.sup.5, R.sup.3a, and R.sup.3b are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.7-C.sub.13 aralkyl, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.3c, OS(O).sub.2R.sup.3c, S(O).sub.2R.sup.3c, S(O).sub.2R.sup.3c, C(O)R.sup.3c, OR.sup.3c, C(O)OR.sup.3c, NR.sup.3cR.sup.3d, and NC(O)R.sup.3cR.sup.3d; R.sup.3c and R.sup.3d are selected independently from each other from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, and C.sub.5-C.sub.7 (hetero)aryl, wherein alkyl, (hetero)cycloalkyl, alkenyl, and (hetero)aryl may be substituted by one or more substituents selected from the group consisting of F and CN; A.sup.1 is selected from the group consisting of C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, OR.sup.6, C(O)R.sup.6, C(NR.sup.6)R.sup.7 and C(O)OR.sup.6, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6a, OS(O).sub.2R.sup.6a, S(O).sub.2R.sup.6a, OR.sup.6a, C(O)OR.sup.6a, NR.sup.6aR.sup.6b, and NC(O)R.sup.6aR.sup.6b; A.sup.2 is selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.6-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, C.sub.7-C.sub.13 aralkyl, OR.sup.6, C(O)R.sup.6, C(NR.sup.6)R.sup.7 and C(OR.sup.6, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6a, OS(O).sub.2R.sup.6a, S(O).sub.2R.sup.6a, OR.sup.6a, C(O)OR.sup.6a, NR.sup.6aR.sup.6b, and NC(O)R.sup.6aR.sup.6b with the proviso that in case of X.sup.2 is O or S, A.sup.2 is neither H nor OR.sup.6; R.sup.6, R.sup.7, R.sup.6a, and R.sup.6b are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.2-C.sub.10 alkenyl, C.sub.3-C.sub.6 (hetero)cycloalkenyl, C.sub.2-C.sub.6 alkynyl, C.sub.5-C.sub.7 (hetero)aryl, and C.sub.7-C.sub.13 aralkyl, wherein alkyl, (hetero)cycloalkyl, alkenyl, (hetero)cycloalkenyl, alkynyl, (hetero)aryl, and aralkyl may be substituted by one or more substituents selected from the group consisting of F, CN, C.sub.1-C.sub.6 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.1-C.sub.6 alkenyl, C.sub.5-C.sub.7 (hetero)aryl, S(O).sub.2OR.sup.6c, OS(O).sub.2R.sup.6c, S(O).sub.2R.sup.6c, OR.sup.6c, C(O)R.sup.6c, C(O)OR.sup.6c, NR.sup.6cR.sup.6d, and NC(O)R.sup.6cR.sup.6d; R.sup.6c and R.sup.6d are independently from each other selected from the group consisting of H, C.sub.1-C.sub.10 alkyl, C.sub.3-C.sub.6 (hetero)cycloalkyl, C.sub.1-C.sub.6 alkenyl, and C.sub.5-C.sub.7 (hetero)aryl, wherein alkyl, (hetero)cycloalkyl, alkenyl, and (hetero)aryl may be substituted by one or more substituents selected from the group consisting of F and CN; and (iv) optionally, a further additive.

16. The electrolyte composition (A) according to claim 15, wherein the aprotic organic solvent (i) is selected from the group consisting of: (a) a cyclic or a noncyclic organic carbonate, which may be partly halogenated, (b) a di-C.sub.1-C.sub.10-alkylether, which may be partly halogenated, (c) a di-C.sub.1-C.sub.4-alkyl-C.sub.2-C.sub.6-alkylene ether or polyether, which may be partly halogenated, (d) a cyclic ether, which may be partly halogenated, (e) a cyclic or an acyclic acetal or ketal, which may be partly halogenated, (f) an orthocarboxylic acid ester, which may be partly halogenated, (g) a cyclic or a noncyclic ester of a carboxylic acid, which may be partly halogenated, (h) a cyclic or a noncyclic sulfone, which may be partly halogenated, (i) a cyclic or a noncyclic nitrile or dinitrile, which may be partly halogenated, and (j) an ionic liquid, which may be partly halogenated.

17. The electrolyte composition (A) according to claim 15, wherein the electrolyte composition (A) comprises an aprotic organic solvent (i) that is a cyclic organic carbonate and an aprotic organic solvent (i) that is a noncyclic organic carbonate.

18. The electrolyte composition (A) according to claim 15, wherein the conducting salt (ii) is selected from the group consisting of: Li[F.sub.6-xP(C.sub.yF.sub.2y+1).sub.x], wherein x is an integer in the range from 0 to 6 and y is an integer in the range from 1 to 20; Li[B(R.sup.I).sub.4], Li[B(R.sup.I).sub.2(OR.sup.IIO)] and Li[B(OR.sup.IIO).sub.2] wherein each R.sup.I is independently from each other selected from the group consisting of F, Cl, Br, I, C.sub.1-C.sub.4 alkyl, C.sub.2-C.sub.4 alkenyl, and C.sub.2-C.sub.4 alkynyl, wherein alkyl, alkenyl, and alkynyl may be substituted by one or more OR.sup.III, wherein R.sup.III is selected from the group consisting of C.sub.1-C.sub.6 alkyl, C.sub.2-C.sub.6 alkenyl, and C.sub.2-C.sub.6 alkynyl, and (OR.sup.IIO) is a bivalent group derived from a 1,2- or 1,3-diol, a 1,2- or 1,3-dicarboxlic acid or a 1,2- or 1,3-hydroxycarboxylic acid, wherein the bivalent group forms a 5- or 6-membered cycle via both oxygen atoms with the central B-atom; LiClO.sub.4; LiAsF.sub.6; LiCF.sub.3SO.sub.3; Li.sub.2SiF.sub.6; LiSbF.sub.6; LiAlCl.sub.4, lithium tetrafluoro (oxalato) phosphate; lithium oxalate; and a salt of formula Li[Z(C.sub.nF.sub.2n+1SO.sub.2).sub.m], where m and n are defined as follows: m=1 when Z is selected from the group consisting of oxygen and sulfur, m=2 when Z is selected from the group consisting of nitrogen and phosphorus, m=3 when Z is selected from the group consisting of carbon and silicon, and n is an integer in the range from 1 to 20.

19. The electrolyte composition (A) according to claim 15, wherein the electrolyte composition (A) further comprises at least one additive (iv) which is selected from the group consisting of vinylene carbonate and its derivatives, vinyl ethylene carbonate and its derivatives, methyl ethylene carbonate and its derivatives, lithium (bisoxalato) borate, lithium difluoro (oxalato) borate, lithium tetrafluoro (oxalato) phosphate, lithium oxalate, 2-vinyl pyridine, 4-vinyl pyridine, cyclic exo-methylene carbonates, sultones, organic esters of inorganic acids, acyclic and cyclic alkanes having a boiling point at 1 bar of at least 36° C., and aromatic compounds, optionally halogenated cyclic and acyclic sulfonylimides, optionally halogenated cyclic and acyclic phosphate esters, optionally halogenated cyclic and acyclic phosphines, optionally halogenated cyclic and acyclic phosphites, optionally halogenated cyclic and acyclic phosphazenes, optionally halogenated cyclic and acyclic silylamines, optionally halogenated cyclic and acyclic halogenated esters, optionally halogenated cyclic and acyclic amides, optionally halogenated cyclic and acyclic anhydrides, ionic liquids, and optionally halogenated organic heterocycles.

20. An electrochemical cell comprising (A) the electrolyte composition according to claim 15, (B) a cathode comprising a cathode active material, and (C) an anode comprising an anode active material.

Description

1. PREPARATION OF COMPOUNDS

Compound 1: 2-amino-3-(benzylideneamino)but-2-enedinitrile

(1) To 1 L four necked bottle 54.05 g (0.50 mol) diaminomaleonitrile and 500 ml methanol were added under nitrogen atmosphere. The mixture was heated up to reflux temperature and 53.07 g (0.50 mol) benzaldehyde was added drop-wise within 30 minutes. The mixture was stirred at reflux temperature for 24 hours. After cooling down to 10° C. the precipitated solid was filtered off and slurried in 200 ml of n-hexane. After stirring the suspension for 5 hours at room temperature, the brown solid was filtered off giving 70 g (Yield: 71.35%) 2-amino-3-(benzylideneamino)but-2-enedinitrile after drying 12 hours at 40° C.

Compound 2: 2-amino-3-(p-tolylmethyleneamino)but-2-enedinitrile

(2) To 250 ml four necked bottle 5.41 g (0.050 mol) diaminomaleonitrile, 50 ml tetrahydrofuran and catalytic amount of sulfuric acid were added under nitrogen atmosphere. The mixture was heated up to reflux temperature and 6.01 g (0.050 mol) 4-methylbenzaldehyde was added dropwise within 10 minutes. The mixture was stirred at reflux temperature for 10 hours. Following the evaporation of the solvent the yellow residual was twice slurried and washed in 200 ml n-hexane, giving by filtration 9.94 g (Yield: 94.55%) 2-amino-3-(p-tolylmethyleneamino)but-2-enedinitrile after drying 6 hours at 40° C.

Compound 3: 2-amino-3-(2-pyridilmethylenamino)but-2-enedinitrile

(3) To 250 ml four necked bottle 5.41 g (0.050 mol) diaminomaleonitrile and 50 ml methanol were added under nitrogen atmosphere. At room temperature 5.36 g (0.050 mol) pyridine-2-carbaldehyde was added drop-wise within 5 minutes. After stirring at room temperature for 15 minutes the mixture was cooled down to 0° C. and the precipitated solid was filtered off. The solid was suspended in 100 ml of 1:1 mixture of n-hexane and methyl-tertbutylether. After stirring the suspension for 1 hour at room temperature, the light yellow solid was filtered off giving 7.33 g (Yield: 74.33%) 2-amino-3-(2-pyridilmethylenamino)but-2-enedinitrile after drying 6 hours at 40° C.

Compound 4: 2-amino-3-(benzylamino)but-2-enedinitrile

(4) To 500 ml four necked bottle 10.0 g (0.051 mol) 2-amino-3-(benzylideneamino)but-2-enedinitrile, 100 ml methanol and 150 ml tetrahydrofuran were added under nitrogen atmosphere. At room temperature 1.93 g (0.051 mol) sodium borohydride was added portion-wise within 10 minutes. After stirring at room temperature for 15 minutes the mixture was poured on 1 L ice-water and the precipitated solid was filtered off and washed with water. The filtered material was slurried in 200 ml of n-hexane and after 2 hours stirring at room temperature, the light brown solid was filtered off giving 8.01 g (Yield: 80.90%) 2-amino-3-(benzylamino)but-2-enedinitrile after drying 6 hours at 40° C.

Compound 5: 2-amino-3-(p-tolylmethylamino)but-2-enedinitrile

(5) To 500 ml four necked bottle 10.56 g (0.050 mol) 2-amino-3-(p-tolylmethyleneamino)but-2-enedinitrile, 100 ml methanol and 150 ml tetrahydrofurane were added under nitrogen atmosphere. At room temperature 1.89 g (0.050 mol) sodium borohydride was added portion-wise within 10 minutes. After stirring at room temperature for 15 minutes the mixture was poured on 1 L ice-water and the precipitated solid was filtered off and washed with water. The filtered material was slurried in 400 ml of n-hexane and after 4 hours stirring at room temperature, the light brown solid was filtered off giving 9.87 g (Yield: 93.00%) 2-amino-3-(p-tolylmethylamino)but-2-enedinitrile after drying 6 hours at 40° C.

Compound 6: 2-(benzylamino)-3-(benzylideneamino)but-2-enedinitrile

(6) To 250 ml four necked bottle 4.96 g (0.025 mol) 2-amino-3-(benzylamino)but-2-enedinitrile, 50 ml methanol and catalytic amount of sulfuric acid were added under nitrogen atmosphere. The mixture was heated up to reflux temperature and 2.65 g (0.025 mol) benzaldehyde was added drop-wise within 5 minutes. The mixture was stirred at reflux temperature for 24 hours. After cooling down to 0° C. the precipitated solid was filtered off and slurried in 200 ml of n-hexane. After stirring the suspension for 5 hours at room temperature, the light green solid was filtered off giving 6.46 g (Yield: 90.25%) 2-(benzylamino)-3-(benzylideneamino)but-2-enedinitrile after drying 12 hours at 40° C.

Compound 7: 2,3-bis(benzylamino)but-2-enedinitrile

(7) To 500 ml four necked bottle 14.63 g (0.051 mol) 2-(benzylamino)-3-(benzylideneamino)but-2-enedinitrile, 100 ml methanol and 150 ml tetrahydrofurane were added under nitrogen atmosphere. At room temperature 1.93 g (0.051 mol) sodium borohydride was added portion-wise within 10 minutes. After stirring at room temperature for 15 minutes the mixture was poured on 1 L ice-water and the precipitated solid was filtered off and washed with water. The filtered material was slurried in 400 ml of n-hexane and after 5 hours stirring at room temperature, the light brown solid was filtered off giving 12.22 g (Yield: 83.10%) 2,3-bis(benzylamino)but-2-enedinitrile after drying 6 hours at 40° C.

Compound 8: Diaminomaleonitrile

(8) Purchased from Aldrich

(9) Compounds 1 to 9 are summarized in Table 1.

(10) TABLE-US-00001 TABLE 1 Compound Name Structure 1 2-amino-3-(benzylideneamino) but-2-enedinitrile 2 2-amino-3-(p- tolylmethyleneamino) but-2-enedinitrile 3 2-amino-3-(2- pyridilmethylenamino) but-2-enedinitrile 4 2-amino-3-(benzylamino) but-2-enedinitrile 5 2-amino-3-(p- tolylmethylamino) but-2-enedinitrile 6 2-(benzylamino)-3- (benzylideneamino) but-2-enedinitrile 7 2,3-bis(benzylamino) but-2-enedinitrile 8 Diaminomaleonitrile

2. ELECTROCHEMICAL CELLS

(11) Pouch type cells were used to prepare the electrochemical cells. A high voltage spinel (LiNi.sub.0.5Mn.sub.1.5O.sub.4, BASF SE) was used as cathode active material. A slurry composed of carbon black, graphite, binder and HV-spinel in N-ethyl-2-pyrrolidon (NEP) was prepared in a centrifuge. The slurry was spread onto an aluminum foil and the foil was then dried and cut to dimensions. The electrodes were inserted in a glove box under Argon atmosphere and dried at 120° C. in a vacuum oven. The anode was a graphite anode (Enertek, South Korea, Germany), and a glass fiber separator was used (Whatman GF/A).

(12) The basic electrolyte composition (LP57) contained a mixture of ethylene carbonate and ethyl-methyl carbonate (3:7 by weight) as solvent and 12.7 wt.-% of lithium hexafluorophosphate as conducting salt. The respective additive was solved in the basic electrolyte composition. The amount of electrolyte composition used per cell was 105 μl.

(13) The electrochemical testing was done in a Maccor potentiostat Serie 4000 at 25° C. Cycling measurements were carried out up to an upper voltage of 4.8 V and to a lower voltage of 3.3 V. The first cycle was done at a rate of C/10. A current of 1C was defined as 148 mA/g. A cycle is comprised of one charge and one discharge step. The charge was carried out in constant current constant voltage mode (CCCV). In this mode, a constant current is passed through the electrochemical cell until a cell voltage of 4.8 V was reached. The voltage is then held constant at 4.8 V until the residual current falls to one tenth of its original value or if 30 min have elapsed. The discharge is performed in constant current mode. A constant current was applied to the electrochemical cell until a cell potential of 3.3 V was reached. The cycling program used is shown in Table 2. The steps listed under “Cycling” were repeated several times, i.e. after finishing the 50 cycles at 1C, the cycling program was repeated starting with 3 cycles at 1 C, followed by 3 cycles at 2 C etc. The results of the cycling experiments are shown in Table 3.

(14) TABLE-US-00002 TABLE 2 Cycling program Formation Cycling 0.1 C 0.5 C 1 C 2 C 4 C 10 C 1 C Rest (14.8 mA/g) (74 mA/g) (148 mA/g) (296 mA/g) (592 mA/g) (1480 mA/g) (148 mA/g) time 2 h Number 2 10 3 3 3 3 50 of cycles Performed once Performed multiple times

(15) TABLE-US-00003 TABLE 3 Discharge capacity at 1 C 1 C discharge capacity [%] Cycle # 13 50 100 300 Comparative LP57 100.0 87.2 75.2 20.5 example 1 Comparative LP57 + 0.1 wt.-% 97.4 88.9 77.8 22.2 example 2 Acrylonitrile Comparative LP57 + 0.5 wt.-% 105 97.4 83 22.7 example 3 Acrylonitrile Comparative LP57 + 2 wt.-% 90 72.7 50 5.5 example 4 Acrylonitrile Comparative LP57 + 0.5 wt.-% 98.7 91.3 82.9 64.4 example 1 cpd 8 Inventive LP57 + 0.1 wt.-% 99.1 93.2 87.2 71.8 example 2 cpd 4

(16) The discharge capacity of the 13th cycle of the comparative example 1 (LP 57, the basis electrolyte solution without any additive) was taken as basis value for all discharge capacities displayed in Table 3. It can be seen that a small amount of acrylonitrile has a beneficial effect on the discharge capacity, but that this effect is very small after 300 cycles. The addition of diaminomaleonitrile (compound 8), 2-amino-3-(benzylamino)but-2-enedinitrile (compound 4) or 1,4,5,6-Tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile (compound 9) according to the invention results in a pronounced increase of the discharge capacity even after 300 cycles in comparison to the electrolyte composition containing the same amount of acrylonitrile.