Silicon-based Materials And Their Applications In The Lithium Battery Anodes

With the demand of new energy vehicles,communication and portable devices for high capacity and high endurance of lithium battery,the development of lithium battery has reached a bottleneck.At present,for the negative electrode,graphite is widely used as the main carbon material,its theoretical capacity is only 372m Ah g^-1 in the actual application process,it is close to the theoretical capacity and it is difficult to satisfy higher capacity requirements.Therefore,it is very urgent to study the active materials of high specific capacity anode,among which the silicon and lithium metal anode have been the research hotspot because of their high theoretical specific capacity.However,in the process of charging and discharging,the silicon-based anode materials often have large volume changes,which lead to silicon powder,loss of electrical contact,and continuous side reactions.These changes cause poor cycle life of silicon-based materials,and hinder the widespread commercialization of silicon-based batteries.However,the uncontrolled growth of lithium dendrites,large volume expansion,and complex interface reactions lead to the resulting low coulomb efficiency and short life have hindered its practical application and development.In this paper,silicon carbon composite materials are used to modify the two materials respectively,and different structural designs are carried out,which greatly improve the electrochemical performance of silicon carbon composite materials and lithium metal anode.The main research contents include the following two parts:In this study,a low-cost and large-scale production method is proposed for the preparation of high-performance silicon carbon anode,mainly through carbonization binder to improve the interface contact of silicon carbon anode,improve the overall conductivity of silicon carbon anode and the first charge discharge performance of materials.The mechanical stability of the interface of silicon-based materials is strengthened by adding a certain amount of binder and grinding aids into the crushed silicon under sealed conditions,and carbonization is carried out after drying.The three-dimensional conductive channel is constructed by doping CNT,which greatly improves the electrochemical performance of the silicon-carbon negative electrode.This method is relatively simple Have the foundation of industrial production.Secondly,silicon quantum dots were synthesized and dispersed into the gap of layer reduced graphene oxide,and took silicon quantum dots as the nucleation site to successfully prepare lithium metal anode with sandwich structure.Due to the lithium affinity of silicon quantum dots,the unsafe negative/diaphragm interface of lithium growth is guided to the interlayer position,which effectively improves the cycle performance and safety of the sandwich structure lithium metal negative electrode doped with silicon quantum dots.The uniform distribution of silicon quantum dots and layered electrode structure adjust the plating and stripping of lithium,avoid the growth of lithium on the surface and the continuous accumulation of solid electrolyte film.The growth oriented strategy of this sandwich structure provides a new method for the preparation of high energy lithium battery anode.