A chemically activated graphene-encapsulated LiFePO4 composite for high-performance lithium ion batteries

Abstract

A composite of modified graphene and LiFePO₄ has been developed to improve the speed of charging–discharging and the cycling stability of lithium ion batteries using LiFePO₄ as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO₄ to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO₄ composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO₄ composite as a cathode active material. Interestingly, the CA-graphene/LiFePO₄ composite has exhibited better electrochemical properties than the conventional graphene/LiFePO₄ composite as well as bare LiFePO₄, including exceptional speed of charging–discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO₄ particles. Owing to these properties of CA-graphene, LiFePO₄ could demonstrate enhanced and stably long-lasting electrochemical performance.