Design And Performance Of Silicon Based Anode Materials For Lithium-Ion Batteries

In recent years,with the development of science and technology,the research and innovation of energy storage devices are more and more important.Although lithium ion battery is one of the more developed energy storage components at present,the theoretical capacity of commercial graphite anode of lithium ion battery is only 372 m Ah g-1,which can not meet the needs of the development of lithium ion battery market.The Si anode,because of its extremely high theoretical capacity（4200 m Ah g-1）,is considered an ideal substitute for graphite anode.However,the Si based anode material has a huge volume expansion/contraction（300 %）during the charging and discharging cycle,which leads to the rapid degradation of the electrode performance.In addition,due to the poor conductivity of Si,the practical application of Si is seriously affected.Therefore,in order to solve the inherent problems of huge volume expansion,low conductivity and unstable solid electrolyte interphase（SEI）layers of silicon anodes in lithium-ion batteries,it is generally considered that appropriate Si-C structure hybridization is a promising method.In this paper,we focused on the above problems and conducted a series of studies on Si-C hybrid materials.The research results are as follows:（1）Inspired by the structure of high-rise buildings,this work uses 0D core-shell Si@SiO2,1D pyrolytic bacterial cellulose（PBC）and 2D reduced graphene oxide（RGO）as raw materials.A three-dimensional Si@SiO2/PBC/RGO（SSPBG）electrode with multiple independent "rooms" was developed by vacuum filtration and high-temperature calcination.In this electrode structure,the SiO2 shell coated on the surface of Si nanoparticles serves as the first barrier to maintain the structure stability,effectively buffering the volume expansion of Si nanoparticles and avoiding their rapid powdering.In addition,the "spring-like" PBC and layered RGO sheets act as the supporting skeleton of the entire structure,while counteracting the microstructural strains and accelerating the transfer of electrons and ions.Under the synergistic effect of SiO2,PBC and RGO,the electrochemical performance of the prepared SSPBG electrode was significantly improved.After electrochemical performance tests,the electrode achieved excellent cycle stability of 901 m Ah g-1 after 500 electrochemical cycles at 2A g-1 current density.When matched with the Li Fe PO4 cathode as a full battery,more than 100 stable charge/discharge cycles can be achieved.（2）Inspired by the structure of dragon fruit,using Si nanoparticles as silicon source and neoprene latex as carbon source,the Si@SiO2@C（SSC）composite was prepared by a simple and extensible method using the characteristics of easy precipitation of neoprene latex in ethanol solution.On the one hand,SiO2 generated on the surface of Si nanoparticles during calcination can effectively buffer the volume change of Si.On the other hand,Si@SiO2 nanoparticles are uniformly coated in flexible and conductive carbon derived by neoprene,which promotes the stability of the entire electrode structure and accelerates electron and ion transport across the entire electrode scale.Electrochemical tests show that when the current density is 2 A g-1,the reversible capacity of SSC electrode after 500 cycles is 1042 m Ah g-1.When the current density is 12 A g-1,the SSC electrode has an excellent rate performance of 798 m Ah g-1.When matched with the Li Fe PO4 cathode material,the full battery can achieve good cycling stability and rate performance.In short,we start from different dimensions of materials,through reasonable structural design of the electrode,the prepared silicon carbon anode shows excellent performance,providing a new idea for the structural design of the silicon/carbon anode of lithium-ion battery.