Fabrication And Performance Study Of Carbon Fiber-Based Composite Functional Structures For Lithium Batteries

The increasing demand of large-scale green energy storage in various fields has put forward higher requirements for the comprehensive performance of lithium batteries.Lithium-ion batteries(LIBs)and lithium-sulfur batteries(LSBs)are the two most promising branches of lithium battery systems,which have attracted extensive attention in recent years.However,most of the researches focus on the development and improvement of electrode active materials,ignoring the collaborative optimization of functional components inside the batteries.At present,the anode current collector of commercial LIBs is not in close contact with the active material,thereby resulting in low bonding strength.Besides,the shuttle effect of polysulfides in LSBs is serious,also leading to low utilization of active material.Aiming at the problems above,this paper mainly introduces the design of carbon-fiber based porous composite functional structures.A systematic study was carried out on the preparation of three-dimensional(3D)porous anode current collector for LIBs,the fabrication of interlayer as polysulfide barrier for LSBs,and their influence on the electrochemical performance of batteries.Specifically,the main research contents are as follows:(1)Preparation of CuO/Cu/CF composite current collector with 3D porous structureA chopped carbon fiber felt was fabricated to construct a porous matrix by combining wet-papermaking method with heat-pressing technology.Then copper coated carbon fiber felt was prepared by surface metallization process of carbon fibers to improve the electrical conductivity.Finally,CuO/Cu/CF composite current collector with 3D porous structure was obtained by the introduction of electrochemical active CuO surface structures through liquid-phase oxidation treatment.(2)Study on the performance of CuO/Cu/CF current collector in LIBsWith mesocarbon microbead(MCMB)as the active material,the influence of CuO/Cu/CF composite current collector on the performance of LIBs was systematically studied by electrochemical impedance test,cyclic voltammetry test and cycling charge-discharge test.The influence mechanism of the fibrous network structure in the composite current collector coupled with the unique CuO surface morphology on the battery performance was revealed.(3)Fabrication of interlayer as polysulfide barrier based on electrospinning techniqueA functional interlayer(CCNF interlayer)composed of carbon nanofibers and polar nanoparticles as polysulfide barrier was fabricated via electrospinning technology and two-step heat treatment process of pre-oxidation and high-temperature carbonization.Characterization methods of XRD,XPS,SEM and TEM were used for phase composition analysis and microstructure observation of the composite interlayer.(4)Study on the performance of CCNF interlayer in LSBsThe influence of CCNF interlayer on the performance of LSBs was systematically studied by means of electrochemical test.The cooperative optimization mechanism of carbon nanofiber webs and polar nanoparticles in the composite interlayer on the performance of LSBs was revealed through the visualized adsorption test of polysulfide and the electrode morphology characterization after cycling.