Synthesis And Research Of Lithium-ion Composite Alloy Anode Materials

With the rapid development of artificial intelligence and information technology,the lithium-ion battery is increasingly important.The commercial graphite anode materials can not meet the requirements of high energy density battery because of its low specific capacity,while the tin-based and silicon-based materials have drawn attentions of researchers due to their high specific capacity.However,the tin-based and silicon-based electrode show huge volume change in the process of charging and discharging,which lead to the pulverization of active substances and the formation of unstable SEI.Eventually causing negative influence on the battery capacity and cycle.In this paper,tin and silicon anode materials are selected for intensive investigations.the tin-based and silicon-based anode materials with unique structure are coated with carbon and copper prepared by ball-milling,vapor deposition and other methods.At the same time we use the SEM and XPS to characterize these materials,and their comprehensive properties were preliminarily analyzed and evaluated.The main content is divided into the following four aspects:1. Tin nanowire anode material coated with carbon was prepared by feasible vapor deposition method.It shows excellent high rate performance and cycle stability,a stable capacity of more than 600 m Ah/g was still realized even after 500 cycles at a rate of0.2C.This carbon-coated linear structure can effectively mitigate the huge volume change of tin during the lithiation and delithiation process.As a result,the material shows excellent electrochemical properties.2. On the basis of the previous experiment,the composite material of tin nanowire embedded with sillicon nano particles and further coated with carbon was prepared by ball-milling and following vapor deposition.The material shows excellent performance on cycling and rate performance.Specially,it has a stable capacity of higher than 1500m Ah/g after 300 cycles at a rate of 0.2C.The coated carbon layer can effectively alleviate the ruptures of tin and silicon huge volume change in the charge and discharge process.In addition,the high conductivity of Li~+in Sn shows a beneficial effect on improving the sluggish kinetics of Si-based anode.Therefore,this material has a high capacity and good rate performance.3. Carbon and copper coated silicon nano particles and tin nano particles were prepared then.The obtained silicon composite material shown a capacity of 2400 m Ah/g after 50 cycles at a rate of 0.2C,while the carbon and copper double-coated tin nano anode material retained a capacity of 500 m Ah/g after 100 cycles at a rate of 0.2C.This kind of structure can also alleviate the huge volume change of tin and silicon in the charge-discharge process.4. Graphite,graphene and nano-tin composite anode materials were prepared by vapor reduction and carbon coating method.Graphite and tin composite anode materials can improve the graphite capacity and multiplier performance,especially its multiplier performance can be significantly improved.In the composite anode materials of graphene and nano-tin,graphene can be used as a buffer substance,which helps to keep the electronic conducting path to each tin particle.the capacity of the tin based composite anode material has a stable capacity of higher than 500 m Ah/g after 100 cycles at a rate of 0.2C.