Study On The Preparation And Electrochemical Performance Of Activated Carbon Fiber-based Self-supporting Electrode Materials

It's a trend for the development of lightweight,thin and flexible energy storage devices in the development of portable electronic devices.Lithium-ion batteries are important in energy storage devices for portable devices because of their high energy density and long life.As the important part of lithium-ion batteries,it is critical to develop flexible electrode materials that can adapt to different battery deformations.Carbon fiber-based materials play an important role in the construction of self-supporting electrode materials due to their excellent electrical and mechanical properties.In this dissertation,the coating and electrospinning methods were used to combine the flexible carbon fibers with LiFePO₄ and Li₄Ti₅O₁₂ to prepare active carbon fiber-based LiFePO₄\C?LFP/CF?composite electrode and Li₄Ti₅O₁₂\C?LTO/CF?composite electrode,and they were assembled into gel-state battery,using a variety of advanced characterization methods to detect a series of electrochemical properties.?1?High-loaded LFP/CF and LTO/CF composite electrodes were prepared by a coating loading method using flexible activated carbon fiber cloth as current collector.The obtained composite electrodes could realize higher active material loading and strong redox reaction capability.The initial capacity of LFP/CF composite electrode at 1C is 150.4mAhg^-1.After 425 cycles,the capacity retention rate is 74.7%.At 5C,the initial capacity is 130mAhg^-1,and the capacity retention is61.5%after 370 cycles.For the LTO/CF composite electrode,the first discharge specific capacity was 148.8mAhg^-1 at 1C.At 5C,the capacity retention rate was86.2%after 160 cycles.?2?Through the electrospinning process,we prepared a flexible self-supporting structure LFP/C fiber cathode and LTO/C fiber cathode.Through the exploration,it was found that we could obtain relatively pure phases on the premise of maintaining good morphology under the conditions of 750?¹5h and 800?⁵h respectively.And it could directly be cut into pieces as electrode without adhesive,current collector.For the LFP/C fiber electrode at 750?¹5h,the initial discharge specific capacities were 157.7mAh/g and 120.1mAh/g at 0.1C and 1C respectively,and the electrode efficiency remained at 100%during all cycles.The LTO/C fiber anode at800?⁵h had an initial discharge specific capacity of 137.7mAhg^-1 at 1C and a capacity retention rate of 74.1%after 700 cycles,in addition,it had an initial discharge capacity of 115mAh/g at 5 C,and the capacity retention rate was 75.3%after 100 cycles.?3?The gel-state battery were assembled by the LFP\C and LTO\C fiber electrodes respectively.For the prepared LFP/C gel battery,the discharge specific capacity at 0.05C and 0.1C could reach 110.1mAh/g and 114.3mAh/g respectively,the efficiency was achieved at 100%after 100 cycles at 0.1C.The discharge specific capacity was maintained at 98mAh/g after 450 cycles.The prepared LTO/C gel battery has a specific discharge capacity of 131.2mAh/g and 103.7mAh/g at 0.05 C and 0.1 C respectively,and the capacity can be maintained at 60mAh/g after 600cycles.