In-situ growth of LiFePO4 on graphene through controlling phase transition for high-performance Li-ion battery

Abstract

The incorporation of graphene (G) has been widely employed to ameliorate the inferior intrinsic electronic and ionic conductivities for phosphate-based cathode materials. Herein, we report on the successful synthesis of an in-situ growth of LiFePO4 on graphene, accomplished through a novel multi-step Precipitation-Hydrothermal-Solid state process. The process involves in-situ precipitation on graphene sheets to yield G/FePO4, followed by a wet chemical lithiation process for synthesizing G/LiFePO4OH. Subsequently, the G/LiFePO4 cathode material, featuring a carbon-coated layer, is produced from LiFePO4OH through a tavorite-olivine phase transition process conducted at 600 °C. As compared to the simple mixing technique, in-situ growth has been proven to be highly efficient for achieving thorough integration of LiFePO4 with graphene. The utilization of LiFePO4OH, a newly developed precursor, has demonstrated effective lithiation method and superior phase purity. Utilizing graphene as a two-dimensional carbon network for embedding LFP nanoparticles results in a composite material that exhibits remarkably high-rate performance with 140.0 mAh g−1 at 20C (~92 % of the capacity at 0.2C) and exceptional cycling behavior with a retention rate of ~98 % even after 1000 cycles at 1C. These remarkable findings emphasize the potential of the in-situ growth of LiFePO4 on graphene process for phosphate-based cathode.