Electrolyte and preparation method thereof and battery

The invention discloses an electrolyte, which comprises carboxylic ester and halogenated methane. The carboxylic ester can be combined with cations of the electrolyte, haloalkane has a small volume, arole of a lubricant can be played, ion migration resistance is reduced, and ionic conductivity of the electrolyte is thus improved. A potassium salt additive can change the solvation condition of thecations inside the electrolyte and an electrode interface film-forming reaction form, a thin and stable SEI film can be formed on the surface of a negative electrod, and the resistance of the ions embedded in the negative electrode can be reduced. An AgPF6 additive can perform reduction on the surface of the negative electrode to form nano-Ag particles, the SEI film charge transfer impedance is reduced, and the ion embedding/de-embedding resistance is reduced. Through combined actions of the carboxylic ester, the halogenated methane, the electrolyte and the additives, the discharge performance and the cycle performanc