The Research On Preparation And Property Of Silicon Based Anode Composites For High Performance Li-ion Battery

Under the social background of the development of new energy technology,Lithium-ion batteries are widely used in electric vehicles and various electronic devices due to their high energy density and long cycling life.Therefore,as the core part of the lithium-ion battery anode materials has been paid more and more attention by researchers.At present,Silicon material is regarded as one of the most promising anode materials,its highest theoretical specific capacity(4200m Ah/g)much higher than graphite carbon materials(372m Ah/g).but it has huge volume expansion caused poor cycling stability and low coulombic efficiency which hinders its practical application.In order to solve the problem of volume effect,we use composite strategy to overcome it.In this paper,low volume expansion of SiO and ZnO were respectively compounded with Si,the(Si+SiO)composites were prepared by mechanical ball milling process and(Si+SiO+Zn)composites were prepared by in situ solid state reaction of Si+ZnO?SiO+Zn by ball milling process.In order to further alleviate the volume expansion and enhance the electrical conductivity of silicon based anode composites,The composites were prepared by calcining low-cost asphalt at high temperature.The research results were summarized by phase analysis,microstructure and electrochemical performance:1)Preparing the silicon based composites by direct addition SiO.We researched best condition of milling time ? binder ? proportion of active substances and also researched the(Si+SiO)/G composites electrochemical performance with different proportions.The results show that(Si+SiO)ball milling 5h,using SA binder and selecting the ratios of active substances to6:2:2 is the best,exhibits the first discharge capacity of 3025.7m Ah/g and the first charge capacity of 2341.1m Ah/g,the initial coulombic efficiency of 77.4%.The 50th-cycle capacity have 392.3m Ah/g.when adding graphite modification,the optimized proportions is 4:1,the first charge capacity is 2701.9m Ah/g,the initial coulombic efficiency is 83.5% and after 50th-cycle capacity is 1101.1m Ah/g,the electrochemical properties of the silicon-based materials were remarkably improved.2)Using cheap and environmental Si and ZnO powders.the high-energy mechanical ball-milling can realize the in situ solid state reaction of Si and ZnO,and the Si/SiO/Zn composites are synthesized by guarantee the excess of silicon.The composite has further improvement of the electrochemical performance,especially ball-milling 15 h has best performance,exhibits the first charge capacity of 2138.7m Ah/g,the initial coulombic efficiency of 82.9%.the 50th-cycle capacity is 432.6m Ah/g.3)Carbon coating of Si/SiO/Zn composite with 50% asphalt as carbon source and the effect of carbon coating on electrochemical performance was investigated.The composites systhesized by ball milling 15 h have the best performance by carbon coating.the first charging capacity is 1588.9 m Ah/g,the first Coulomb efficiency is 78.8%,and the capacity is 817.6m Ah/g after 50 cycles,this is due to the carbon coating provides stable coating structure,it's can alleviates the volume change during lithium-ion insertion and extraction processes.