Quaternary ammonium salt and preparation method thereof

The invention provides a preparation method for a quaternary ammonium salt. The preparation method comprises the following steps: a) causing amine to react with dimethyl carbonate in an organic solvent, thereby generating a quaternary ammonium alkaline compound, and b) performing neutralization reaction on the quaternary ammonium alkaline compound and inorganic complexing acid, and purifying a reaction product, thereby obtaining the quaternary ammonium salt. The invention also provides three quaternary ammonium salts, of which the structures are respectively expressed as (VII), (X) and (XI), according to the preparation method. The quaternary ammonium salt prepared according to the method contains no organic halide residual, so that no halogen ion is ionized by an electrolyte solution prepared from electrolyte and the electrochemical property is excellent. A potential window test proves that the quaternary ammonium salt prepared according to the method provided by the invention has a wider potential window scope, a potential window curve is smooth in the potential window scope, no obvious oxidoreduction peak appears, and the quaternary ammonium salt is suitable for the electrolyte solution of a power storage device.