Study On Tin And Silicon Based Anode Materials For Lithium Ion Battery

With the improving demand for the battery life and portability,it has become the focus for researchers to break through the current energy density of lithium ion battery.Among the anode materials,the theoretical specific capacity of tin and silicon are high.The Li alloying potential of silicon and tin is relatively low?below 0.5 V?,which could provide higher operating voltage for the complete-cell.And the potential is slightly higher than that of Li⁺/Li,which means it is difficult to form Li dendrite.However,the weekness of tin and silicon is also obvious.The volume effect of silicon and tin are serious.After repeated charging and discharging,the electrode volume will be expanded and contracted repeatedly,which will result in pulverization and abscission of the active material followed by the rapid reduction of capacity.With the improvement of consumers'requirement for the light of batteries,the negative electrode of lithium-ion battery has become the focus of research.Thin film electrode refers to the electrode that active material is deposited on the current collector directly,which does not need binder and conductive agent.Study for thin film electrode is meaningful for the development of all solid-state batteries and wearable devices.In this paper,tin thin films are prepared by continuous electroless tin deposition based on copper substrate.The changes of morphology,composition and electrochemical properties are studied by varying the plating time and the concentration of the tin salt.The reaction time and the concentration of SnCl₂ in the bath do not change the composition of the films,but affected the weight,morphology and cyclic performance of the coatings.Because of the dense coating,it can not suppress the huge volume effect,so the reduction of the capacity is serious.In this paper,Cu₆Sn₅/Sn thin film electrode is prepared by immersion plating method on the base of copper foil.The morphology,composition,content and electrochemical properties of the electrode are researched by varying the plating time and SnCl₂concentration.When the reaction time is 30 min and SnCl₂ concentration is 6.5 g L^-1,the thin film electrode shows the decent cycling performance.The capacity is 0.84m A·h·cm^-2 and the coulombic efficiency is about 94%after 70 cycles.This is because the electrode can effectively reserve enough space for the volume effect,and the relatively compact accumulation style can prevent the particles from falling from the coppor substrate.In addition,the Cu-Sn electrode is prepared by immersion plating method on the surface of copper foam.Owing to the small pore size of the foam copper,the effective components in the plating solution can not be diffused into the inner part of the foam copper.The capacity of the electrode is 0.71 mA·h·cm^-2after 100 cyclesIn this paper,nickel electroless plating is carried out on the surface of silicon powder with different size.With the prolonging of electroless plating time,the cycling performance of the material is gradually improved.The capacity of nano-silicon/nickel composite material is 391.1 m A·h·g^-1 after 100 cycles.In addition,silicon/tin composite material is studied.The results showed that the Pd activation process is not necessary for the tin deposition on the surface of silicon powder.And the add of CTAB decreases the agglomeration of materials obviously,and the cycling performance is improved.