Enhanced Electrochemical Performances of Hard Carbon via Nickel‐Metal Catalyzed Surface Conversion Graphitic Crystallites

Abstract The surface of hard carbon is rich in micropores, disordered graphene layers, defects, and various functional groups that can serve as reactive sites. However, these reaction sites are non‐equivalent sites both electronically and geometrically. Consequently, the solid electrolyte interface (SEI) formed on the hard carbon electrode exhibits instability in the organic electrolyte system, resulting in a continuous depletion of LiPF 6 within the electrolyte, thereby compromising its cycling stability. Herein, the formation of stable SEI is induced by modulating the surface structure of hard carbon fibers. The transition metal nickel is utilized to convert the disordered structure on the surface of hard carbon fibers into graphitic crystallites at high temperatures. This also reduces the functional groups, micropores, defects, and disordered graphene layers on the surface of the hard carbon fibers, making the active sites equiv. Meanwhile, the highly active graphene edges are uniformly exposed as nucleation sites on the fibers surface, which induces the formation of a uniform and dense SEI and inhibits the continuous decomposition of LiPF 6 , thus improving the rate performance and cycling stability of the hard carbon.