LiFePO4/activated carbon/graphene composite with capacitive-battery characteristics for superior high-rate lithium-ion storage

By Guan, Yibiao; Shen, Jinran; Wei, Xufang; Zhu, Qizhen; Zheng, Xiaohui; Zhou, Shuqin; Xu, Bin
Published in Electrochimica Acta 2019

Abstract

LiFePO4 is an attractive cathode material for lithium ion battery due to its high capacity of 170 mAh g?1, long cycle life, good safety and low cost, which suffers from the instinct low electron conductivity and poor rate performance. Herein, a composite material consisting of LiFePO4, activated carbon and graphene is synthesized with a facile solvothermal method, which presents excellent high-rate performance with highly-efficiency capacitive-battery characteristics. The obtained LiFePO4/activated carbon/graphene cathode material has hierarchical porous architecture mainly originated from the activated carbon and interconnected conductive networks constructed by the graphene, ensuring both the abundant pathways for Li+ diffusion and the fast electron transfer. Furthermore, the high surface area (367 m2 g?1) provides a double layer capacitive process during charge/discharge process, and also protects the LiFePO4 against the heavy current attack, especially under high current rate. As a result, the capacitive-battery behavior leads to superior rate capability and long cycle life. The LiFePO4/activated carbon/graphene cathode exhibits a remarkable high capacity of 66 mAh g?1 at an extremely high rate of 100 C, and the brilliant cycle stability is confirmed with the capacity retention of 82% after 3000 cycles, promising the high power applications. Furthermore, this study provides a new insight in simple preparation of the capacitive-battery materials by combing the active components and the capacitive components.

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