Preparation method of electrolyte functional additive and electrolyte prepared by using electrolyte functional additive

The invention discloses a method for preparing an electrolyte functional additive of a high voltage aluminum electrolytic capacitor electrolyte by using branch- containing carboxylic ester. The method comprises the following steps of (1) adding an alkali aqueous solution into a vessel of branch- containing carboxylic ester, and adjusting a PH value to a value of 12 to 14, (2) adding strong acid into the reaction solution obtained in the step (1) and adjusting the PH value to 1 to 2, (3) washing a product obtained in step (2) by using high pure water, drying the product and measuring the ion content until a requirement is satisfied, (4) melting the strong acid obtained in the step (3) into an organic solvent with a high boiling point, introducing ammonia to adjust the PH value to 7 and 8, and obtaining the electrolyte functional additive. The invention also discloses an electrolyte with the above electrolyte functional additive. The electrolyte comprises a solvent, the electrolyte functional additive, long cha