Synthesis of LiFePO4/carbon/graphene for high-performance Li-ion battery

•LiFePO4 co-modified by carbon coating and graphene was successfully prepared.•The effects of co-modification technology and graphene content were investigated.•LiFePO4/carbon/graphene composites showed superior electrochemical performance.•The initial discharge capacity exceeded the theoretical specific capacity of LiFePO4. LiFePO4/carbon/graphene (LFP/C/G) composites were synthesized through a solvothermal method which used LFP/carbon with 15 % carbon content (LFP/C-15) as a precursor and changed graphene contents. LFP with 5 % graphene content (LFP/G-5) was synthesized by the same method. The effects of co-modification technology and graphene content on LFP/C/G performance were investigated. As the results, LFP/C/G composites showed a significant improvement in electrochemical properties compared to LFP/C-15 and LFP/G-5. This is attributed to the superior electrical conductivity of graphene and the excellent conductive network formed by co-modification of graphene and carbon coating. Especially, when the graphene content of LFP/C/G is 15 %, the developed material provided the greatest initial discharge specific capacity at 186.2 mAh/g at 0.1C which exceeded the theoretical specific capacity of 170 mAh/g for LFP, and the extremely high capacity retention proportion of 95.2 % after 100 cycles at 0.1C. This finding is a promising technique for the improvement of LFP performance by co-modifying with graphene and carbon coating.