Electrochemical device comprising aliphatic mono-nitrile compound

1. A method of forming a cathode, the method comprising:

disposing an electrolyte comprising an aliphatic mono-nitrile compound on a cathode active material;

heat treating the cathode active material at a temperature of greater than or equal to 30° C. to form an aliphatic mono-nitrile compound-cathode active material complex on a surface of the cathode active material; and then

charging a lithium secondary battery including the aliphatic mono-nitrile compound-cathode active material complex to form the cathode, wherein a protective layer of the aliphatic mono-nitrile compound is bonded to the cathode active material by a ligand-metal bond formed between a transition metal of the cathode active material and the aliphatic mono-nitrile compound.

2. The method according to claim 1 , wherein the aliphatic mono-nitrile compound is a compound represented by the following Formula 1:

R—C═N  Formula 1

wherein R is a C1-C15 alkyl group.

3. The method according to claim 1 , wherein the electrolyte further comprises an additive selected from the group consisting of vinylene carbonate, benzyl methyl ether, and tetramethylene glycol dimethyl ether.

4. The method according to claim 3 , wherein the additive is present in the electrolyte in an amount of 0.1 weight percent to 5 weight percent, based on the total weight of the electrolyte.

5. The method according to claim 1 , wherein the electrolyte further comprises at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, gamma-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

6. The method according to claim 1 , wherein the aliphatic mono-nitrile compound is present in the electrolyte in an amount of 0.1 weight percent to 20 weight percent, based on the total weight of the electrolyte.

7. A method of manufacturing an electrochemical device, the method comprising:

disposing an electrolyte comprising an aliphatic mono-nitrile compound on a cathode comprising a cathode active material;

heat treating the cathode at a temperature of greater than or equal to 30° C. to form an aliphatic mono-nitrile compound-cathode active material complex on a surface of the cathode active material;

disposing the cathode, an anode, and an electrolyte comprising a lithium salt and a solvent to form a lithium secondary battery; and then

charging the lithium secondary battery to manufacture the electrochemical device, wherein a protective layer of the aliphatic mono-nitrile compound is bonded to the cathode active material by a ligand-metal bond formed between a transition metal of the cathode active material and the aliphatic mono-nitrile compound.

8. The method according to claim 7 , wherein the aliphatic mono-nitrile compound is a compound represented by the following Formula 1:

R—C═N  Formula 1

wherein R is a C1-C15 alkyl group.

9. The method according to claim 7 , wherein the electrolyte further comprises an additive selected from the group consisting of vinylene carbonate, benzyl methyl ether, and tetramethylene glycol dimethyl ether.

10. The method according to claim 9 , wherein the additive is present in the electrolyte in an amount of 0.1 weight percent to 5 weight percent, based on the total weight of the electrolyte.

11. The method according to claim 7 , wherein the electrolyte further comprises at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, gamma-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

12. The method according to claim 7 , wherein the aliphatic mono-nitrile compound is present in the electrolyte in an amount of 0.1 weight percent to 20 weight percent, based on the total weight of the electrolyte.