Preparation And Electrochemical Performance Research Of SiO_x Based Composites As Anode Materials For Lithium-ion Battery

With the rapid development of electric vehicles,renewable energy storage systems and other fields,lithium ion batteries?LIB?with high energy density,high power density and long cycle life have become very important.In terms of anode materials,Si based materials have attracted extensive attention due to their high theoretical capacity,low lithiation/delithiation potential and abundant reserves.Among them,SiOx material is an amorphous silica-oxygen binary compound with an oxygen content between 0 and 2?0<x?2?and reversible lithium storage capacity.The most common SiO_x in industry is SiO?that is,x=1?,which is called silicon monoxide or silicon oxide in Chinese.At first,SiO_x is mainly used as insulation material,semiconductor material and optical glass coating material.Now,it is widely used in the research and development of Si based anode material for lithium ion battery.The composite material of the lithium ion battery anode material exhibits different electrochemical properties due to the ratio of the material components.In order to explore the optimal ratio of composite materials and synthesize SiO_x@Fe₃O₄@FLG electrode materials with better electrochemical properties,the cycle performance and rate performance of composite materials with different proportions were investigated.By comprehensively comparing of the electrochemical performance date,it is found that the composite material with the mass ratio of FLG,SiO and K₂FeO₄ at 4:4:2 had the best electrochemical properties.In addition,in order to explore the role of Fe₃O₄ in the composite materials,the properties of SiO_x@FLG composites and SiO_x@Fe₃O₄@FLG composites were compared.By comparison,it is found that the anode material containing Fe₃O₄ nanoparticles has more mesopores,which is conducive to promoting the infiltration of electrolyte and the diffusion of lithium ions,so that the corresponding electrode material shows better electrochemical performance.Herein,we have successfully developed an efficient strategy to synthesize high-performance Fe₃O₄-pillared SiO_x wrapped by few-layered graphene microcomposites via a facile two-step ball-milling technique.Such an elaborately designed egg-like SiO_x@Fe₃O₄@FLG possessed fast electron transport path and forceful capability in accommodating volume expansion during charge/discharge,accordingly,delivering improved lithium storage performances,i.e.,reversible capacities of 833.4 mA h g^-1 at 0.5 A g^-1 after 500cycles with initial Coulombic efficiency of 84.9%and 81.8%capacity retention.