多孔碳包覆氧化硅的制备及电化学性能研究

Preparation and electrochemical properties of silicon oxide coated with porous carbon

二氧化硅(SiO_(2))作为锂离子电池负极材料时理论比容量可达1965 mA·h·g^(-1),其储量丰富、价格低廉,是下一代锂离子电池负极材料的有力竞争者.文中选取多孔碳(Pc)包覆SiO_(2)(Diatomite)复合材料(SiO_(2)@Pc)作为锂离子电池负极材料,研究了不同SiO_(2)@Pc复合比例对电池首次库伦效率及循环性能的影响.与未包覆的SiO_(2)相比(首效29.9%),SiO_(2)@Pc为1∶2时首次库伦效率可以提高到45%,其循环稳定性明显提高,在100圈后容量保持较高的稳定状态.通过XPS和TG等表征分析确定了SiO_(2)@Pc复合物中各组分的化学形态和百分含量,通过电化学阻抗谱及不同扫描速率下的循环伏安曲线拟合,结果表明:Pc与SiO_(2)恰当比例的复合可以提高SiO_(2)@Pc材料中的Li^(+)的扩散能力;有利于推动SiO_(2)作为锂离子电池负极材料的应用,为低成本高比能的锂离子电池负极材料的研究提供了新的思路.

The theoretical specific capacity of silicon dioxide(SiO_(2))can reach 1965 mA·h·g^(-1) when it is used as anode material for lithium ion batteries,in addition to its rich storage and low cost,which make it a promising candidate for the next generation high specific energy lithium ion batteries anode materials.In this paper,the porous carbon coated diatomite composite material(SiO_(2)@Pc)fabricated via the freezing-drying method was used as the anode material for the lithium ion batteries.The effect of different SiO_(2)@Pc composite ratios on the first coulombic efficiency and cycle performance of the batteries were investigated.Compared with uncoated diatomite(First coulombic efficiency 29.9%),the coulombic efficiency of SiO_(2)@Pc can be increased to 45%or even higher,the cycle stability of the batteries is obviously improved,and the volume remains stable after 100 cycles.The chemical composition and content of each substance in SiO_(2)@Pc were characterized by X-ray photoelectronic spectra(XPS)and thermogravimetry(TG).By means of electrochemical impedance spectroscopy(EIS)and cyclic voltampere(CV)curves fitting under different scanning rates,the results show that a certain proportion of carbon improves the diffusion capacity of Li^(+) in SiO_(2)@Pc composite.This study may promote the application of SiO_(2) as the anode materials for lithium ion batteries and provide a new strategy for the further research of the anode materials for lithium ion batteries with low cost and high specific energy.