锂离子电池用“三明治”型Si/Fe/Si薄膜负极材料的制备及其性能

采用磁控溅射法在铜箔集流体上沉积得到了具有“三明治”结构的Si/Fe/Si薄膜. 高分辨率透射电镜(HRTEM)和选区电子衍射(SAED)分析表明, 该薄膜为非晶态. 扫描电镜(SEM)和能量散射X射线能谱(EDXS)结果表明, 该薄膜循环前总厚度为3.2 μm, 循环200 周后体积膨胀率为265%. 在1.5-0.005 V(vs Li+/Li)和0.1 mA·cm-2条件下, 该薄膜电极首次吸锂量为1.85 mAh·cm-2, 70周后放锂量达最大值0.84 mAh·cm-2, 200周后放锂量仍维持在0.55 mAh·cm-2, 为最高放锂量的66%. 惰性材料铁的加入一方面提高了薄膜的导电性和电极的面积比容量, 有效抑制了电压滞后效应; 另一方面有效抑制了活性物质硅的体积膨胀, 保持了薄膜较好的循环充、放电性能.

Preparation and Properties of Sandwich-type Si/Fe/Si Film Anode for Lithium-ion Battery

A sandwich-type Si/Fe/Si film was deposited on Cu foil by magnetron sputtering. High-resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) results indicated that the sputtered film had an amorphous structure. The cross-sectional scanning electron microscope (SEM) images and the energy dispersive X-ray spectrometry (EDXS) spectra showed that the thickness of the filmwas 3.2 μm, and its volume expansion ratio was up to 265% after the prolonged electrochemical lithiation and delithiation cycles. In the potential range 1.5-0.005 V (vs Li+/Li) at the current density of 0.1 mA·cm-2, the film anode exhibited a high initial lithiation capacity around 1.85 mAh·cm-2, and reached the highest reversible delithiation capacity of 0.84 mAh·cm-2 after 70 cycles. After 200 cycles, it still retained a reversible capacity of 0.55 mAh·cm-2, which was 66%of the highest reversible capacity. The introduction of Fe to Si not only improved the conductivity of the film, which partially reduced the voltage hysteresis, but also effectively suppressed the volume expansion, which led to a prolonged cycle life.