Self-assembled graphene and LiFePO4 composites with superior high rate capability for lithium ion batteries

Abstract

A graphene encapsulated LiFePO₄ composite has been synthesized by self-assembly of surface modified LiFePO₄ and graphene oxide with peptide bonds, followed by reduction. The graphene forms a continuous conductive coating network connecting the LiFePO₄ nanoparticles to facilitate electron transportation, resulting in excellent high rate capability with 70% capacity retention at 50 C rate. The apparent activation energy of the graphene encapsulated LiFePO₄ composite (9.6 kJ mol⁻¹) is much lower than that of the carbon coated LiFePO₄ (14.6 kJ mol⁻¹). An excellent cycling performance is also demonstrated, in which the capacity loss is less than 8.6% after 950 cycles at 10 C. Therefore, this hybrid material is promising for use as a cathode material for high rate lithium ion batteries.