Preparation And Electrochemical Properties Of Polyaniline-coated Silicon Nanoparticles Anode For Lithium Ion Battery

Lithium-ion Batteries?LIBs?is of critical importance for portable electronics,transportation and large-scale energy storage systems.There is a growing demand for LIBs with high energy and high-power densities,long-term stability,safety and low cost.To achieve these requirements,novel design structures and high-performance electrode materials are needed.Commercial carbon materials are difficult to meet the requirements of high-performance LIBs anode and safety due to low specific capacity and low discharge platform.Silicon?Si?as a LIBs anode material has the advantages of high capacity(⁴200mAh·g^-1),low cost and suitable discharge platform,which is a potential commercial high-performance anode material.However,in the process of cycle,the large volume changes of Si can cause damage to the electrode structure,resulting in poor long-term stability and limited industrial development.In this paper,the electrochemical properties of Si electrodes are improved via coating conductive polymer.Si nanoparticles?NPs?prepared by DC arc-discharge plasma,pretreated by amino acid?ABA?as the surface modification,and further coated by polyaniline?PANi?via in situ polymerization which was introduced PANi into system to form polyaniline-Si nanoparticles composites?PANi-Si NPs?.The structure of PANi-Si NPs was characterized by XRD,TEM,FTIR,DSC and TGA.Results indicated that the use of ABA during the surface modification of Si NPs,introduced aniline?ANi?groups on the surface of Si NPs and turned Si NPs into the main chain of PANi synthesized in the subsequent in situ polymerization.The PANi-Si NPs composites connected by chemical bonds,quality of PANi content in the composite particles was about 62%.The electrochemical performance properties of Si electrodes were improved via coating conductive polymer.About 92.5%of the initial capacity could be maintained after100 cycles at current density of 100 mA·g^-1.In order to verified the influence of PANi content on the electrochemical performance,this paper synthesized various PANi contents:27 wt.%,62 wt.%and 72 wt.%of PANi-Si NPs samples,using XRD,TEM and electrochemical test to represent various contents of PANi structure and the influence of the electrochemical properties of the composites.The experimental results indicated that when the PANi content is too low,the PANi cladding layer was thin and difficult to cover all Si NPs,resulting in poor battery electrochemical stability;when the PANi content was too high,the PANi cladding layer was thick and the particles are filled with ionic insulating PANi.Si NPs cannot contact with the electrolyte which cause the specific capacity to be low;the PANi content was 62wt.%of the sample,Si NPs surface coating thickness was appropriate and the particle had the property amount of PANi as the buffer layer of Si NPs volume change,with the best electrochemical performance.In order to further improve the utilization rate of Si NPs in PANi-Si NPs composite materials,this paper designed the crosslinked 3D PANi nanowire structure?PNW-Si NPs?using glucose as crosslinking agent.The microstructure of PNW-Si NPs was characterized by XRD,SEM,FTIR and TGA.Experimental results indicated that using glucose as crosslinking agent was successfully synthesized the initial design of microstructure,PANi nanowires with a diameter of 20³0 nm and length 200³00 nm,and distribution of Si NPs form a hierarchical structure among 3D PNW,PANi content of 65 wt.%.The stable reversible capacity of PNW-Si NPs is 779.5 mAh·g^-1,100 mA·g^-1.This kind of porous 3D structure could increase the contact area of Si NPs and electrolyte so as to improve the effect of Si NPs utilization in the particle.