Controlled interfacial reactions with Co2P nanoparticles onto natural graphite anode for fast-charging lithium-ion batteries

Natural graphite (NG) is widely utilized as a practical anode in commercial lithium-ion batteries (LIBs) thanks to its high theoretical capacity and low operating voltage as well as high reversibility for Li+ storage. Recently, there has been a strong need to further enhance the fast-charging capability and reduce the charging time of NG for use in expanding electric vehicle applications. To enhance the charging performance of NG, various approaches have been explored to make its surface favorable for fast Li+ intercalation. Herein, we propose a surface modification of NG with functional cobalt phosphide (Co2P). Co2P nanoparticles can be introduced onto NG particles via a thermally induced phase transition process. Various structural and electrochemical investigations have provided insights into the crucial functions and reaction mechanisms of Co2P nanoparticles. We demonstrated that electrochemical conversion reactions of Co2P nanoparticles occurred during the first charging process, and the resulting phases induced effective surface stabilization and high-voltage operation during subsequent cycles. In particular, lithium phosphide (LiP and Li3P) formation is mainly responsible for reducing the overpotential for interfacial reactions between NG and the electrolyte, leading to the effective Li plating suppression and an increase in reversibility during cycles. In practice, the full-cell employing the Co2P@NG anode offered a superior cycling performance over 300 cycles and a charging time of 16.1 min (80 % SOC). We expect our findings make a valuable contribution to the advancement of fast-charging LIBs.