PURPOSE: To reduce battery manufacturing cost by obtaining a simple washing method for a battery material.

CONSTITUTION: This method is used for washing a lithium secondary battery, and immerses and oscillates a solid battery material containing carboxyl group sodium salt in the water solution of lithium hydroxide. Thereafter, the material is further immersed in water and oscillated. As a result, the material can be washed via a simple process and the conventional complex refining method is not required, thereby reducing the production cost of a battery material. In addition, a solid battery material of high purity with a small concentration of ionic impurities can be easily manufactured by refining an inexpensive commercial solid battery material, using the washing method. Consequently, a battery material containing a small amount of ionic impurities can be made of an inexpensive material through a simple washing method.