SiO₂/C Composite Anodes For Lithium Ion Battery And Their Electrochemical Performance

Silica?SiO₂?has gradually become one of the current hotspots when it is used as the anode material for the lithium ion batteries because of its wide raw material sources,vast reserves and low cost.Besides,the SiO₂ has low plateau potential and high theoretical specific capacity(1965 mA h g^-1).More importantly,it is easy to prepare and environmentally friendliness.However,similar to the transition metal oxide,the SiO₂ also suffers a large volume change?³00%?in the process of discharge/charge,which possibly causes the whole structure damage and collapse of the electrode and finally leads to the rapid capacity fading and large irreversible capacity.Meanwhile,the intrinsic electrical conductivity of SiO₂ is poor and the low electrical conductivity can not only hinder the rapid extraction and insertion but also reduce the transport efficiency of the ions and electrons,resulting in the bad rate capability and cycle performance.To solve the aforementioned problems,the researchers currently mainly fabricate the SiO₂ composites mixed with carbon materials based on the academic ideas of materials design and nano engineering.In this work,we synthesized the carbon modified SiO₂ nanocomposites by the reaction between dopamine hydrochloride and SiO_2,in which the SiO₂ was obtained by a chemical precipitation approach using the H₂SiO₃ as precursor.In addition,the effect of heat treatment temperature on the electrochemical performance of SiO₂/C composites was also studied.The results showed that the specific capacity of SiO₂/C composites increased with the temperature raising.And after the heat treatment at 1100 ^oC,the specific capacity of SiO₂/C composites could keep the level of 660mA h g^-11 at a current density of 0.1 A g^-1 after 200 cycles.Furthermore,the carbon nanotubes?CNTs?modified SiO₂/C composites was manufactured by an in-situ chemical vapor deposition method.The results revealed that the CNTs were uniformly dispersed in the SiO₂/C substrate and formed a three dimensional conductive network,which was beneficial to the enhancement of the conductivity and structure integrity of the SiO₂/C substrate.The specific capacity of the as-prepared composites could maintain the level of 500 mA h g^-11 at a current density of 0.05 A g^-1 after 100 cycles.On the other hand,the evenly dispersed Co particles were introduced on the surface of SiO₂@C composites.The results illustrated that compared with the pristine SiO₂@C,the specific capacity of the SiO₂@C@Co composites increased to 395 mA h g^-11 at a current density of 0.1 A g^-1after 100 cycles.At last,another yolk-shell-like SiO₂@void@C composite was prepared by the corrosion method,making full use of the voids between the SiO₂spheres and carbon layers to provide available space for the volume expansion during the cycling process.The results demonstrated that the electrochemical property of SiO₂@void@C composite was greatly improved in relation to the pristine SiO₂@C,the specific capacity of the SiO₂@void@C composite reached to 293 mA h g^-11 at a current density of 0.1 A g^-1 after 100 cycles.