Preparation And Properties Of Silicon/carbon Composites For Lithium Ion Batteries

In this paper,copper foam as the working electrode,we prepared silicon using electrodeposition.On this basis,the aniline monomer was added for electrochemical polymerization.Successively,a layer of polymer was coated on the electrodeposited silicon.After carbonization,the silicon/carbon composite material was prepared.We used scanning electron microscopy(SEM),transmission electron microscopy(TEM)to investigate morphology and elemental analysis to investigate composition.The electrochemical properties were characterized by galvanostatic charge/discharge and cyclic voltammetry.By controlling the time of constant current electrodeposition,silicon particles with various sizes and different thickness silicon films with various thicknesses were obtained.And we speculated that in the 1 M SiCl4 + 0.3 M TEAC + CH3CN system,the clectrodeposit of silicon using the copper foam as the working electrode uncderwent in four steps:nucleation and local growth;nuclear growth and growth inhibition;film formation;suppressed growth after a certain thickness;saturation.Electrochcmical polymerization of polyaniline on electrodeposited silicon with different deposition time was carriced out.The carbon/carbon composite obtained after carbonization was used as negative electrode of lithium-ion battery to test the electrochemical performance.It was found that the best electrochemical properties were achieved when silicon was deposited with 3 Coulomb and the elecctropolymerization was performed with 0.9 Coulomb.The first discharge capacity was 3401.3 mAh/g,while the first coulomb efficiency was 80.8%,and the capacity remained at 1057.8 mAh/g after 100 cycles.From this,it can be seen that when the deposited clectricity of clectrodeposited silicon was 3 Coulombs and the electropolymcrizcd electricity was 0.9 Coulombs in the samples,the silicon films deposited by electrodeposition provided substantially all of the capacity in the first cycle.Due to the carbon layer protection,the material had good cycle stability.