Method of producing lithium-ion secondary battery, lithium-ion secondary battery, and method of using zwitterionic compound

A lithium-ion secondary battery comprising at least a positive electrode, a negative electrode, and an electrolyte solution,

• the negative electrode including at least a negative electrode active material and a solid electrolyte interface (SEI) film, the SEI film being formed on a surface of the negative electrode active material, the film containing a lithium compound,
• the electrolyte solution containing at least a solvent, a lithium salt, and a zwitterionic compound, the solvent not containing a salt,
• the zwitterionic compound containing a phosphonium cation and a carboxylate anion in one molecule,
• an amount of the zwitterionic compound in the electrolyte solution is 0.01 to 0.1 mol/L.

A method of using a zwitterionic compound to restore capacity of a lithium-ion secondary battery, comprising:

• identifying a battery as having a deteriorated capacity, wherein the battery having the deteriorated capacity comprises at least a positive electrode, a negative electrode, and an electrolyte solution, the electrolyte solution comprising a solvent and a lithium salt, and the negative electrode including at least a negative electrode active material and a solid electrolyte interface (SEI) film formed on a surface of the negative electrode active material;
• determining a capacity loss of the battery having the deteriorated capacity;
• selecting an amount of a zwitterionic compound to add to the electrolyte solution of the lithium-ion secondary battery having the deteriorated capacity based on the capacity loss;
• preparing the zwitterionic compound;
• and
• restoring capacity of the lithium-ion secondary battery having the deteriorated capacity by adding the zwitterionic compound to the electrolyte solution of the lithium-ion secondary battery having the deteriorated capacity and the SEI film on the surface of the negative electrode active material,
• wherein the zwitterionic compound contains a phosphonium cation and a carboxylate anion in one molecule, and
• the deteriorated capacity represents a capacity being lower than an initial capacity of the lithium-ion secondary battery.