Study On Preparation And Performance Of Lithium Titanate/SiO_x Composite Anod Material

Energy is one of the most important topics in the 21st century.Rechargeable lithium-ion batteries play a pivotal role in power grid systems,portable electronic devices,electric vehicles,and large-scale energy storage systems.Lithium titanate anode material has excellent lithium-ion insertion and extraction reversibility and almost negligible volume change during discharge;In addition,lithium titanate is mainly produced by a high-temperature solid-phase reaction,with a simple process and easy industrial production,and has been proven to be a promising anode material for lithium-ion batteries.Unfortunately,low theoretical capacity,intrinsic electronic conductivity and lithium-ion diffusion led to poor rate performance and poor volume energy density,which hinders its large-scale application.This article mainly focuses on the specific capacity,rate performance and cycle performance of lithium titanate(Li₄Ti₅O₁₂),which is the anode material of lithium-ion batteries.The influence of binder pitch/SiO,C/SiO_x co-coating and C/TiO₂ double conductive layer on the electrochemical performance of commercial lithium titanate anode materials was systematically discussed.（1）In this paper,a kind of pitch-based carbon/silicon monoxide/lithium titanate（7LTO3SiO/C）composite negative material was prepared by the processes of high-energy ball milling and pitch pyrolysis.The silicon monoxide is uniformly distributed on the framework composed of pitch-based carbon and lithium titanate by high-energy ball milling.The influence of pitch carbon coating and silicon monoxide on the electrochemical performance of anode materials for lithium-ion batteries was studied.The results show that the pitch-based carbon provides higher electrical conductivity and mechanical strength for the 7LTO3SiO/C composite,which is beneficial to slow down the volume expansion of SiO during charge and discharge and generate a stable SEI film.And adding an appropriate amount of SiO to the composite material is beneficial to increase the specific capacity of the composite material.The prepared 7LTO3SiO/C composite material as a negative electrode material for lithium-ion batteries has excellent cycle stability and rate performance,that is,under the discharge rate of 0.5C,1C,2C,5C,7C,and 10 C,the mass specific capacity is 347 m Ah/g,286 m Ah/g,248 m Ah/g,186 m Ah/g,158 m Ah/g,145 m Ah/g.The capacity retention rate is 99.5%at 10 C for 500 cycles,which is higher than lithium titanate.（2）In this paper,a sol-gel method was used to prepare a double conductive layer C-SiO_x-TiO₂ co-coated Li₄Ti₅O₁₂（CS-TiO₂/LTO）anode material.During a heat treatment process,anatase titanium dioxide was formed by the reaction between the lithium titanate surface and SiO₂ layer.The SiO₂ and polydopamine layers underwent a carbothermal process to form a SiO_x layer.The composite material made full use of the advantages of the high-capacity SiO_x coating layer and the double conductive layer combining anatase titanium dioxide with N-doped C.The effect of C-TiO₂ double conductive layer and SiO_x co-coating on the electrochemical performance of lithium titanate anode materials was studied.The as-prepared CS-TiO₂/LTO had a high tap density and electronic conductivity(8.45×10^-4 S cm^-1),as well as a high ionic conductivity(4.62×10^-12 cm²S^-1),which were responsible for its excellent rate capability（221.7 m Ah/g at 20C）and stable long-term cycling performance（0.008%fade per cycle after 1000 cycles at 20C）.