The Preparation And Perfromance Of Silicon-based Anode Materials For Lithium-ion Batteries

The rapid development of new energy vehicles urgently needs electrode materials with high capacity,long life and good safety for lithium ion battery.Porous silicon and nano-silicon anode materials are prepared.The structure and morphology of the materials are characterized by XRD,SEM and TEM.The electrochemical performance of the materials is also studied by charge discharge,cyclic voltammetry and AC impedance.Porous silicon is synthesized via magnesium reduction method by using diatomite and Mg as the silicon source and Zn as the reductant,respectively.The electrochemical performance of silicon anode materials were prepared at different temperatures were explored.The results show the initial delithiation capacity of silicon anode materials prepared at 600 ? is 1655mAh/g,which is largest at 0.2A/g,and the materials were prepred at 625 ? show best cycle stability performance.Furthermore,the effects of different electrolytes on the silicon anode materials were studied,and the results show that the cycle stability of the electrode material using electrolyte with VC is better than using electrolyte without VC.Nanoscale silicon is synthesized via a simple and effective metathesis reaction,in which SiCl4 serves as the silicon source and Zn as the reductant,respectively,at a mild temperature of 500 ?.This method for producing nanoscale silicon is simple,facile and low-cost.The as-prepared silicon particles are spherical with a diameter of 150-200 nm and the delithiation capacity can attain as high as 1747.7 mAh g-1 at a current density of 0.2 A g-1.Furthermore,Si/C composites are synthesized via a pyrolytic method with sucrose as the precursor and the capacity retention is 82.0%after 50 cycles.That can be mainly attributed to the introduction of carbon.The Si/PANi composite is prepared via in-situ polymerization method.The effects of different concentrations of the raw materials on the electrochemical performance of Si/PANi composites are researched by orthogonal experiment.For the first time the efficiency of lithiation/delithiation and the first lithium lithiation/delithiation capacity,the theoretical optimal concentration of aniline is 0.2 M,phytic acid is 0.07 M,ammonium persulfate is 0.8 M and the amount of nano silicon is 0.27 g.The effects of different ratios of water ethanol system on the performance of Si/PANi composites are researched.For the first charge/discharge efficiency,the first delithiation capacity and the 50 cycle retention rate in ethanol and water volume ratio of 1:5 has the maximum value,and the values are 66.6%?1768.5 mAh/g and 70.9%,respectively.The results show that the electrolyte mainly affects the cycle stability of materials:the delithiation capacity retention of sample 1 and sample 2 using electrolyte 1 are greater than the use of electrolyte 2 after 10,30,50 cycles,and the capacity retentions are 76.6%and 59.5%,63.1%and 7.5%after 50 cycles,respectively.The electrodes A,B,C and D are treated by heat treatment,respectively,and their electrochemical performances are tested.The retention of before and after heat treatment are 67.7%and 99.7%,32.8%and 45.9%,55.1%and 85.5%,74.4%and 57.6%after 65 cycles,respectively.It can be seen that the heat treatment of the polar plate can improve the cycle performance of the battery to a certain extent.