An Approach and Mechanistic Insights of Coating-Type Binders for 4.6 V-Licoo2 Cathode of Lithium-Ion Battery

Abstract

The application of binder-derived coatings on active materials has shown promising potential in enhancing the structural stability of cathode materials. Nevertheless, the effects of coating properties and thickness on electron/ion transfer at the active material interface remain insufficiently understood. Conventional PVDF binders exhibit weak interfacial physical interactions with active particles, resulting in non-uniform and discontinuous coating layers that fail to adequately protect the interfacial and structural stability of LiCoO2 (LCO) cathode materials under high-voltage conditions. To address this limitation, a series of polyacrylonitrile copolymer binders were developed in this study to precisely control the coating thickness on the LCO surface, thereby systematically investigating the influence of coating thickness on the performance of 4.6 V LCO. When the binder coating thickness was optimized to 2 nm, the resulting layer demonstrated significantly lower resistance to electron and ion transport compared to conventional PVDF binders. This thin and uniform coating markedly improved the structural and interfacial stability of LCO at a high voltage of 4.6 V, leading to enhanced electrochemical stability in both half-cell and full-cell configurations with LCO electrodes. Specifically, at 0.5 C with a cutoff potential of 4.6 V, the capacity retention of LCO utilizing the P(AN8-HFBM2) binder reached 92% after 100 cycles, a substantial improvement over the 74% retention observed with the PVDF binder. This work presents a practical and effective strategy for optimizing the electrochemical performance of LCO cathode materials at high voltages through the implementation of an aqueous binder system.

Keywords: Lithium-ion battery, Coating-type cathode binder, Uniform interface transmission, Lithium cobalt oxide