LiFePO4/C composite cathode via CuO modified graphene nanosheets with enhanced electrochemical performance

We report a novel and simple method to prepare high rate performance CuO/graphene nanosheets (GNs) modified LiFePO4 cathode composites (CLFP/G/CuO) via co-precipitation followed by hydrothermal method. Incorporation of CuO into graphene nanosheets greatly enhances the electrical conductivity and electrochemical performance of the LFP/graphene (LFP/G) cathodes throughout the cycle process. The electrochemical and structural characteristics of both CuO modified and unmodified materials were comparatively investigated by a variety of test methods including XRD, Raman, TGA, FT-IR, SEM, TEM, CV, EIS and charge/discharge cycling. Even though both the pristine and modified materials display an orthorhombic olivine-type structure, their contributions to the electrochemical performance were quite different. CLFP/G/CuO displays a high initial capacity of 164 mA h g (1) at 0.2 C and 102 mA h g (1) at 20 C, whereas the CLFP/G delivered 151 and 60 mA h g (1), respectively. The modified composite achieved the satisfied effect to enhance the cycle stability under high-rate discharge conditions with capacity retention ratios of 92% when switching back to the initial conditions (0.2 C). The improvement of the electrochemical performance of CLFP/G/CuO is mainly attributed to the formation of three dimensional conductive structures due to the anchored superficial CuO which can effectively avoid the aggregation of GNs and confirm effective electric contact between intrinsically two dimensional GNSs and LFP particles. This could ensure the ion's diffusion and decrease the electrolyte resistance thus providing much more electrochemical accessible surface area of the cathode composite. (C) 2015 Elsevier B. V. All rights reserved.