Alkylbenzoate derivatives as electrolyte additive for lithium based batteries

1. An electrolyte composition comprising at least one compound of formula (I)

wherein

R 1 represents a C 1 to C 10 alkyl, and

R 2 represents a OC(O)(C 1 to C 10 alkyl),

wherein C 1 to C 10 alkyl may be substituted by one or more F atoms, and

wherein one or more CH 2 -groups of the C 1 to C 10 alkyl which are not bound directly to O may be replaced by O.

2. The electrolyte composition according to claim 1 , wherein

R 1 represents a C 1 to C 6 alkyl, and

R 2 represents a OC(O)(C 1 to C 6 alkyl),

wherein the C 1 to C 6 alkyl may be substituted by one or more F atoms, and

wherein one or more CH 2 -groups of the C 1 to C 6 alkyl which are not bound directly to 0 may be replaced by 0.

3. The electrolyte composition according to claim 1 , wherein the concentration of the at least one compound of formula (I) in the electrolyte composition is in the range of from 0.1 to 20 wt.-%, based on the total weight of the electrolyte composition.

4. The electrolyte composition according to claim 1 , wherein the electrolyte composition contains further comprises at least one further additive.

5. The electrolyte composition according to claim 1 , wherein the electrolyte composition further comprises at least one SEI forming additive and/or at least one additional overcharge protection additive.

6. The electrolyte composition according to claim 1 , wherein the electrolyte composition further comprises at least one SEI forming additive selected from the group consisting of a vinylene carbonate; a vinylene carbonate derivative; a fluorinated ethylene carbonate; a fluorinated ethylene carbonate derivative; propane sultone; a derivative of propane sultone; ethylene sulfite; a derivative of ethylene sulfite; an oxalate comprising compound; a derivative of an oxalate comprising compound; and an

ionic compound comprising a cation of formula (II)

wherein

X is CH 2 or NR′,

R 3 is selected from represents a C 1 to C 6 alkyl,

R 4 is selected from represents a —(CH 2 ) u —SO 3 —(CH 2 ) v —R″,

—SO 3 — is —O—S(O) 2 — or —S(O) 2 —O—,

u is an integer from 1 to 8 and wherein one or more CH 2 groups of the —(CH 2 ) u — alkylene chain which are not directly bound to the N-atom and/or the SO 3 group may be replaced by O and wherein two adjacent CH 2 groups of the (CH 2 )— alkylene chain may be replaced by a C—C double bond,

v is an integer from 1 to 4,

R′ represents a C 1 to C 6 alkyl,

R″ represents a C 1 -C 20 alkyl, C 2 -C 20 alkenyl, C 2 -C 20 alkynyl, C 6 -C 12 aryl, and C 6 -C 24 aralkyl, which may comprise one or more F atoms, and wherein one or more CH 2 groups of alkyl, alkenyl, alkynyl and aralkyl which are not directly bound to the SO 3 group may be replaced by O,

and an anion selected from bis(oxalato) borate, di:fluoro (oxalato) borate, [F z B(C m F 2m+1 ) 4-z ] − , [F y P(C m F 2m+1 ) 6-y ] − , (C m F 2m+1 ) 2 P(O)O] − , [C m F 2m+1 P(O)O 2 ] 2− , [O—C(O)—C m F 2m+1 ] − , [O—S(O) 2 —C m F 2m+1 ] − , [N(C(O)—C m F 2m+1 ) 2 ] − , [N(S(O) 2 —C m F 2m+1 ) 2 ] − , [N(C(O)—C m F 2m+1 )(S(O) 2 —C m F 2m+1 )] − , [N(C(O)—C m F 2m+1 )(C(O)F)] − , [(N(S(O) 2 —C m F 2m+1 )(S(O) 2 F)] − , [N(S(O) 2 F) 2 ] − , [C(C(O)—C m F 2m+1 ) 3 ] − , [C(S(O) 2 —C m F 2m+1 ) 3 ] − ,

wherein m is an integer from 1 to 8, z is an integer from 1 to 4, and y is an integer from 1 to 6.

7. The electrolyte composition according to claim 1 , wherein the electrolyte composition further comprises an additional overcharge protection additive represented by formula (III)

wherein

R 5 is cyclohexyl or C 6 -C 12 aryl, which may be substituted by one or more substituent selected independently from each other from F, Cl, Br, I, C 6 -C 12 aryl, and C 1 -C 6 alkyl, wherein C 6 -C 12 aryl and C 1 -C 6 alkyl may be substituted by one or more substituent

selected independently from each other from F, Cl, Br and I; and

R 6 , R 7 , R 8 , R 9 and R 10 may be same or different and are independently from each other selected from H, F, Cl, Br, I, C 6 -C 12 aryl, and C 1 -C 6 alkyl, wherein C 6 -C 12 aryl and C 1 -C 6 alkyl may be substituted by one or more substituent selected independently from each other from F, Cl, Br and I.

8. The electrolyte composition according to claim 1 , wherein the electrolyte composition further comprises at least one aprotic organic solvent.

9. The electrolyte composition according to claim 1 , wherein the electrolyte composition further comprises at least one aprotic organic solvent selected from the group consisting of a cyclic carbonate; an acyclic carbonate; a di-C 1 -C 10 -alkylether; a di-C 1 -C 4 -alkyl-C 2 -C 6 -alkylene ether; a di-C 1 -C 4 -alkyl-C 2 -C 6 -alkylene polyether; a cyclic ether; a cyclic acetal; an acyclic acetal; a cyclic ketal; an acyclic ketal; an orthocarboxylic acids ester; a cyclic ester of a carboxylic acid; an acyclic ester of a carboxylic acid; a cyclic sulfone; an acyclic sulfone; a cyclic nitrile; an acyclic nitrile; a cyclic dinitrile; and an acyclic dinitrile.

10. A method of making an electrolyte composition according to claim 1 , the method comprising:

adding at least one compound of formula (I)

to a solution comprising a conductive salt and a solvent,

wherein

R 1 represents a C 1 to C 10 alkyl, and

R 2 represents OC(O)(C 1 to C 10 alkyl),

wherein the C 1 to C 10 alkyl may be substituted by one or more F atoms, and

wherein one or more CH 2 -groups of the C 1 to C 10 alkyl which are not bound directly to O may be replaced by O.

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

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

13. A method of forming a passivating layer on an electrode, the method comprising:

decomposing at least one compound of formula (I)

in the presence of the electrode, the electrode being present in the electrochemical cell, wherein

R 1 represents a C 1 to C 10 alkyl, and

R 2 represents a OC(O)(C 1 to C 10 alkyl),

wherein the C 1 to C 10 alkyl may be substituted by one or more F atoms, and

wherein one or more CH 2 -groups of the C 1 to C 10 alkyl which are not bound directly to O may be replaced by O.