Study On The Electrochemical Performance Of Carbon/Tin-doped Silicon-based Composites

With the economic and social development and the continuous transformation of its structure,new energy sources have been widely studied and applied.As an important type of energy storage element,Lithium Ion Batteries(LIBs)have undergone considerable development.However,the current low theoretical specific capacity of commercial graphite anode has gradually become a bottleneck for its development.The more attractive silicon anode has a theoretically high specific capacity(4200 mAh g-1),which is 11.3 times that of the current commercial graphite anode,and has a broad prospect for its application in LIBs anodes.However,the shortcomings associated with high performance are also obvious.The violent volume expansion(400%)during the charging and discharging process causes the silicon anode to crack,break or even powder,which causes irreversible damage to the electrode material and greatly shortens the battery's life.The construction of a carbon/tin-doped silicon-based anode from the perspective of structure design can effectively solve the problems faced by the silicon anode during the charge/discharge cycle,thereby improving its electrochemical performance and accelerating the process of commercial application.Firstly,Sn'nb-Si with nanostructure was prepared by the dealloying method and the reduction deposition method.The structure design of nano-tin particles doping nano-branches silicon ensures that the structure of the negative electrode material is stable during the process of lithiation/delithiation,thereby entailing that the active material has a higher reversible specific capacity during the charge/discharge process.The synergistic effect of silicon and tin provides a relatively high lithium ion diffusion rate while ensuring a high specific capacity.After 55 cycles at current density of 100 mA g-1,Sn#nb-Si can still maintain a reversible specific capacity of 1525.9 mAh g-1.Then,a composite(C1Si2@W-A2)composed of wok ash(The flue deposits after biomass fuel is not fully burned,name after Wok-Ash,abbreviated as W-A),carbon nanotubes(CNTs)and commercial Si nanoparticles was designed and synthesized through a simple one-step ball milling method.The nanoporous structure of W-A buffers the volume expansion of Si nanoparticles in the process of lithiation/delithiation;the network of CNTs provides Li+conductive channels and improves the conductivity of the overall electrode.The electrode circulates stably for 100 cycles at a current density of 100 mA g-1,and the reversible specific capacity is 1528.8 mAh g-1.Quantitative kinetic analysis is used to explore the energy storage mechanism of C1Si2@W-A2,and contributions of battery behavior and capacitor behavior are revealed.In addition,this is the first time that W-A has been explored and applied to active materials in LIBs,providing a solution for waste recycling in related fields.