High energy density is an important indicator of the global battery industry,and the current specific capacity of anode materials can no longer meet this demand.Silicon anodes are expected to replace traditional graphite anodes due to their high specific capacity,wide sources,and low lithium intercalation potential.However,during the charging and discharging process of silicon anodes,the intercalation of lithium ions will cause a large amount of volume expansion and lead to structural fragmentation,and even part of the silicon falls off from the current collector and loses its electrical activity,resulting in rapid capacity decay,which has hindered its development so far.Therefore,in view of these disadvantages of silicon,the performance of silicon anode material is improved to make up for the defects in electrochemical performance.In this paper,micro-scale silicon is used as the research object,and porous silicon(PSi)powder is modified with conductive polymer poly(3,4-ethylenedioxythiophene)(PEDOT)to improve the cycling stability of silicon anode.It can further improve the poor conductivity of micro-silicon and the poor cycle performance caused by volume expansion.The main research contents are as follows:(1)The silicon source uses commercialized aluminum-silicon alloys to prepare micron-scale PSi@PEDOT composites by chemical in-situ polymerization of 3,4-ethylenedioxythiophene(EDOT).The PEDOT shell layer of the composite material not only ensures the conductive network in the composite material,but also can effectively prevent the volume expansion of silicon.In addition,the pores inside the porous silicon material of the core layer provide space voids to buffer the volume expansion of silicon.The results show that the PSi@PEDOT composite with a PEDOT content of 22.5%has the best cycling stability,with an initial discharge specific capacity of 1338.62 m Ah g-1 at a galvanostatic current density of500 m A g-1.The capacity retention rate after 200 cycles was 70.3%,while under the same test parameters,the specific capacity of PSi decreased from 1199 mAh g-1 to 215 m Ah g-1 after 100cycles,and after 200 cycles,only 10.7%capacity retention rate.(2)In view of the PSi@PEDOT-2 composite with high specific capacity and good cycle performance in the above research,in order to improve the long-term cycle stability of PSi@PEDOT composite,it can be combined with graphite to buffer the volume change of silicon,silicon and graphite.Efficient dispersion of ions improves structural integrity and electrical contact properties.This simple silicon-graphite composite anode manufacturing process is controllable and economical.In this paper,G-PSi@PEDOT composites were successfully prepared by mechanical ball milling.By exploring different graphite raw materials,different composite methods,and the relationship between the two Influencing factors such as ratio determine its optimal preparation method and ratio,and the composite material not only retains the advantages of both,but also avoids their disadvantages,thus ensuring its good performance on lithium-ion batteries.The test structure shows that the first reversible specific capacity of Gd-PSi@PEDOT-2 composite is 465.51 m Ah g-1 at a current density of 0.5 A g-1,and the capacity retention rate is 75.55%after 1000 charge-discharge tests.(3)After compounding with graphite,although the long-term cycle performance is good,the specific capacity is still relatively low.In order to further improve the energy density of the material,graphene oxide(GO)was coated on PSi@PEDOT-2 composite material by stirring dispersion and freeze-drying methods.Surface preparation of micron-scale PSi@PEDOT/GO composites.The results show that when the content of PSi,PEDOT and GO of the composite electrode material is 65.0%,22.5%and 12.5%,respectively,and the current density is 300 m A g-1,the specific capacity is still 1102.30 m Ah g-1 after 100 cycles,the capacity retention rate is75.8%.In addition,it can still exhibit a specific capacity of 406.87 m Ah g-1 at a current density of 4 A g-1.The PSi@PEDOT/GO-2 composite shows excellent cycling and rate performance,and has good application prospects. |