High-voltage stability and electrochemical performance of polyacrylic acid–xanthan gum copolymer-reinforced LiCoO2 cathode material

Abstract

High-voltage LiCoO₂ (LCO) cathode materials are in increasing demand in industry, but their stability is greatly affected by serious irreversible phase transitions and interfacial reactions at high voltages. In order to improve these problems faced by LCO cathode materials at high voltages, we improved the stability of LCO at 4.6 V by preparing a PAALi–XG polymer capping layer, which has good toughness as well as electrical conductivity. To be precise, the cladding layer is the product of heat shrinkage polymerization of lithium polyacrylate (PAALi) and xanthan gum (XG), and we found that the cladding layer not only protects the surface of LCO at high voltage, but also improves its ionic and electronic conductivity. According to the electrochemical test results, when the voltage range was 2.75–4.6 V, the modified material possessed a capacity retention of 196.4 mA h g⁻¹ of 82.7% after 200 cycles at a current density of 2C multiplicity for the first turn. It still has a discharge capacity of 183 mA h g⁻¹ at a high current density of 3C. The results indicate that the cladding layer can maintain stability during cycling and prevent side reactions on the surface. The results show that the cladding layer has the ability to isolate the LCO from direct contact with the electrolyte, delay the escape of Co ions, and thus inhibit the generation of irreversible phase transitions, which greatly improves the cycling stability of the LCO.