| In recent years, lithium-ion batteries (LIBs) have been widely studied and have a long-term development. But the performance of LIBs is far from the expected value, especially in the field of electric vehicles, portable electronic devices, flexible wearable electronic devices and so on. That is because the cathode materials have a high price and low specific capacity, and may cause some safety problem; and the anode is mainly composed of carbon materials with limited capacity, which resulting in a large amount in the battery. Improve the capacity of the anode material can greatly improve the performance and reduce the weight and volume of LIBs; In addition, the existing technology can not make the LIBs be good used in the flexible devices. Therefore, developing the high capacity and high rate cathode materials, and the new high-performance anode materials, as well as developing the new battery technology is the development trend of the LIBs in the future.A great quantity of studies shown that constructed 3D graphene (carbon)-based composite has been demonstrated as an efficient way to improve the electrochemical performances of electrode materials. Therefore, exploring effective preparation method to realize the efficient combination of graphene (carbon) network with the cathode and anode materials is the key for the research of the composite in this field. Considering this, in this research, we designed and prepared three types of 3D structure grapnene (carbon)-based composite and realized the in-situ effectively compound between the network and LiFePO4 cathode material and red phosphorus anode material. Further, we explored and studied the synthesis process, physical properties, electrochemical performances and the synergistic effect of the composites.In this paper, we developed a new preparation method of LiFePO4, and obtained the 3D G/LiFePO4 cathode composite by in suit hydrothemical method. The G/LiFePO4 has a high capacity of 160 mAh/g at 0.2 C, good rate performance (115 mAh/g at 10 C) and cycle performance (94.2 % capacity retention after 100 cycles at 1 C). Then we synthesized the 3DG/LFP/G cathode composite in which CVD graphene was used as the supporting framework, the 3DG/LFP/G shows a higher capacity of 164 mAh/g at 0.2 C, better rate performance (124 mAh/g at 10 C) and cycle performance (95.7 % capacity retention after 200 cycles at 1 C). The EIS investigation suggests that both the electronic conductivity and the Li ion diffusion are promoted by the underlined 3D graphene framework. For anode material, we prepared a flexible hollow carbon cloth with good electrochemical performance by carbonization treatment, use this carbon cloth as substrate, we prepared the flexible P/C anode composite and the capacity is 1063 mAh/g at 0.1 C. Then the capacity is reached to 1100 mAh/g after GO coating treatment, and the cycle performance has a 13 % improvement after 200 cycles, which shows a good electrochemical performance.This work not only provides efficient technological approaches for developing new type phosphate cathode materials for power LIBs, but also opens up the high-performance anode material and verify the feasibility of using it as flexible LIBs, which has important practical significance and academic value. |
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