Synthesis And Energy Storage Performaces Of Silicon/Carbon Nanofibers

The massive consumption of fossil fuels has given rise to severe energy and environmental problems,as a result,the research of alternative recyclable energy becomes increasingly important.Lithium-ion batteries,a promising series of new-type energy storage devices,has been hindered by commercial graphite anode(possessing a theoretical capacity of 372 m Ah g^-1).In contrast,silicon with a theoretical capacity of nearly 4200 m Ah g^-1,has been considered as the most promising anode material because of its excellent performance and inexpensive costs.The silicon-based anode materials usually suffer volume expansion(?400%)upon the cycling process,destroying the structure of materials,lowering the capacity of cells and affecting cycling stability.So,silicon-based materials are normally coated with materials with high mechanical strength to avoid capacity exacerbation,during which the solution is usually manipulated precisely to get target products.Electrospinning,a convenient,simple and low-cost synthetic method,is normally considered as an alternative for nanomaterials synthesis via solution reaction.Raw materials can be endowed with modified mechanical and electrical properties via electrospinning.Herein,we prepared silicon/carbon nanofibrous composite via electrospinning,in which the carbon nanofibers would confine the silicon particles to accommodate the volume expansion and stabilize the cycling performance.The work and conclusion are mainly as follows:(1)Construction of silicon monoxide/carbon nanofibrous(Si O/CNF)network.Ball-milled commercial silicon monoxide(Si O)powders were utilized for electrospinning Si O/PAN nanofibers,which afterward underwent heat treatment under high temperature to collect Si O/CNF nanofibers.Then the morphology and the energy storage performance of materials were characterized.It can be concluded that the electrospun silicon monoxide nanofibers possess a specific capacity of 516.5 m Ah g^-1,which is 1.47 times of exclusively commercial Si O powders.As a result,the construction of the nanofibrous network enlarges the capacity of the commercial Si O powders via avoiding their local aggregation,which might lead to incomplete utilization of active materials.(2)Construction of silicon/carbon nanofibrous(Si@void/CNF)network.Based on part(1),nano Si powders were used to prepare Si@PMMA/PAN nanofibers,then the as-electrospun nanofibrous network was heated in air at low temperature and under nitrogen atmosphere at high temperature to obtain Si@void/CNF nanofibrous network.The CNF network offers conducting skeleton while the void space generated by PMMA can confine the expansion of Si nanoparticles and function as a fast ion pathway to further strengthen the electrochemical properties.It's shown that the as-prepared Si@void/CNF nanofibrous network possesses a capacity of 913.6 m Ah g^-1 and reserves 72.9%after 100 cycles at a current density of 100 m A g^-1,showing stable performances,which is ascribed to advanced morphology of the anode materials.