▎ 摘　　要

NOVELTY - Secondary battery comprises a negative electrode current collector layer, negative electrode active material layer, electrolyte, positive electrode active material layer, and positive electrode current collector layer arranged in sequence. The electrolyte is provided with a separator, the electrolyte includes an electrolyte. The electrolyte includes an electrolyte sodium salt, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is material that allows free insertion and extraction of sodium ions, M is cobalt, nickel, and manganese. USE - Secondary battery. ADVANTAGE - The battery does not contain lithium material, and is not limited by lithium resource. The battery can be developed for growing feet. The production cost of the battery is reduced. The electrochemical performance of the battery is excellent, the service life of the battery is long, the capacity retention rate is high, the capacity is relatively high. The anode and cathode material is simple, easy to obtain, environment-friendly, the production technique of the whole battery is simple and the cost is low. DETAILED DESCRIPTION - Secondary battery comprises a negative electrode current collector layer, negative electrode active material layer, electrolyte, positive electrode active material layer, and positive electrode current collector layer arranged in sequence. The electrolyte is provided with a separator, the electrolyte includes an electrolyte. The electrolyte includes an electrolyte sodium salt, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is a Na2M2(C2O4)3 2H2O material that allows free insertion and extraction of sodium ions, M is cobalt, nickel, and manganese. An INDEPENDENT CLAIM is included for a method for preparing a secondary battery, which involves: (A) uniformly coating the negative electrode active material layer on the surface of the negative electrode current collector layer, and cutting the negative electrode active material layer after drying to obtain the battery negative electrode; (B) cleaning the positive electrode current collector layer, uniformly coating the positive electrode active material layer on the surface of the positive electrode current collector layer, and cutting the positive electrode active material layer after drying to obtain the battery positive electrode; and (C) using the battery negative electrode, the electrolyte, the separator, and the battery positive electrode to assemble to obtain the secondary battery, where the electrolyte includes an electrolyte, the electrolyte includes an electrolyte sodium salt, the positive electrode active material layer includes a positive electrode active material.