Quaternary ammonium salt, electrolyte, electrolyte solution and electrochemical device

1. A quaternary ammonium salt of the formula (1)

wherein R 1 is straight-chain or branched alkyl having 1 to 4 carbon atoms, R 2 is straight-chain or branched alkyl having 1 to 3 carbon atoms, and X − is N(CN) 2 − or SCN − .

2. A quaternary ammonium salt of the formula (2)

wherein X − is N(CN) 2 − or SCN − , and Me is methyl.

3. A composition wherein the composition comprises at least the quaternary ammonium salt of claim 1 and an organic solvent.

4. A composition according to claim 3 wherein the organic solvent is at least one selected from among cyclic carbonic acid esters, chain carbonic acid esters, phosphoric acid esters, cyclic ethers, chain ethers, lactone compounds, chain esters, nitrile compounds, amide compounds and sulfone compounds.

5. A composition according to claim 4 wherein the organic solvent is at least one selected from among ethylene carbonate, propylene carbonate, dimethyl carbonate, ethylmethyl carbonate, dimethoxyethane and acetonitrile.

6. A composition according to claim 4 wherein the organic solvent is at least one selected from among propylene carbonate and acetonitrile.

7. An electrochemical device which includes an electrolytic solution comprising an electrolyte of the formula (3)

wherein R 1 is straight-chain or branched alkyl having 1 to 4 carbon atoms, R 2 is straight-chain or branched alkyl having 1 to 3 carbon atoms, and X − is N(CN) 2 − or SCN − , and an organic solvent, the organic solvent being at least one selected from propylene carbonate and acetonitrile.

8. A process for preparing a quaternary ammonium salt of the formula (1)

wherein R 1 is straight-chain or branched alkyl having 1 to 4 carbon atoms, R 2 is straight-chain or branched alkyl having 1 to 3 carbon atoms, and X − is N(CN) 2 − or SCN − ,

comprising

(a) a step of reacting an alkylpyrrolidine of the formula (5) and a compound of the formula (6) to prepare a quaternary ammonium salt of the formula (1a)

wherein R 1 is straight-chain or branched alkyl having 1 to 4 carbon atoms,

wherein R 2 is straight-chain or branched alkyl having 1 to 3 carbon atoms and Y Cl, Br or I,

wherein R 1 , R 2 and Y are same as defined above, and

(b) a step of reacting the quaternary ammonium salt of the formula (1a) and a compound of the formula (7)

MX  (7)

wherein M is hydrogen, alkali metal atom, alkaline earth metal atom or metal atom, and X − is N(CN) 2 − or SCN − .