Preparation And Electrochemical Properties Of Silicon/Niobium Pentoxide Composite Anode Materials

Silicon anode material with high capacity for lithium storage is expected to replace graphite as a new generation of lithium-ion battery lithium ion anode material.However,serious volume effect of silicon in the process of lithium ion intercalation and de-intercalation leads to the pulverization of the active material and the collapse of the structure,resulting in the capacity fading of the electrode material and the subsequent limitation of the practical application.In order to solve the problems mentioned above,the paper attempts to prepare silicon/niobium oxide composite materials with nano-silicon,niobium chloride and lithium hydroxide as the precursors,so as to provide a new approach to solving the problem.The researches involved in the study are as follows:a.Preparation of silicon/niobium pentoxide composite by combining titration process and heat treatment;b.Study on the effect of preparation parameters on the morphology and electrochemical properties of the composites,and optimization on the experimental process;c.Research on the morphological characteristics of silicon/niobium pentoxide composites and the effect of this structural feature on electrochemical properties;d.Exploration of the mechanism of lithium silicate on the properties of silicon-based materials.Core-shell silicon/niobium pentoxide composite anode material was prepared by using nano-silicon,niobium chloride and lithium hydroxide as raw materials.In the structure,niobium pentoxide is coated on the surface of silicon particles,which avoid the direct contact between silicon and electrolyte.The oxide coating layer reduces side reactions between silicon and electrolytes,and improves effectively the electrochemical cycle stability of the as-prepared materials.The effect of lithium hydroxide on the synthesis of anode materials was systematically studied.The results demonstrate that lithium hydroxide is not only a precipitant that contributes to the formation of niobium pentoxide precursors,but also a precursor that facilitates the formation of lithium silicate between silicon and niobium pentoxide shells.The formation of lithium silicate transition layer can improve the electronic conductivity of silicon-based materials,and compensate for lithium sources to some extent.The specific discharge capacity of the prepared silicon/niobium oxide composite anode material can reach 2803 mAh/g at 200 mA/g constant charge-discharge current density,and the discharge capacity can still be maintained at 1100 mAh/g after 200 cycles,showing a stable electrochemical performance.