多孔锂-硅薄膜锂离子电池负极材料的电沉积制备及其电化学性能(英文)

Electrodeposition and Electrochemical Property of Porous Li-Si Film Anodes for Lithium-Ion Batteries

采用多步恒电流沉积技术,在铜箔上电沉积制备了多孔锂-硅薄膜电极(LSF).用X射线衍射(XRD)和扫描电镜(SEM)测试手段研究了该电极的结构和表面形貌.作为锂离子电池负极材料,电化学测试结果表明锂-硅薄膜电极具有较好的循环稳定性,通过改变电沉积条件,可有效调控该电极的嵌脱锂容量及首次循环效率.譬如,在0.5mo·lL-1四氯化硅+0.7mo·L-1高氯酸锂的碳酸丙烯酯电解液中,首先以-3.82mA·cm-2的恒定电流密度沉积600s,再将电流密度恒定为-1.27mA·cm-2,继续电沉积7200s,制得锂-硅薄膜电极(LSF-3),该电极以12.7μA·cm-2的电流密度预循环2次,其首次循环库仑效率高达97.1%.预循环2次后,电流密度增加到25.5μA·cm-2,此时,锂-硅薄膜电极充电质量比容量和面积比容量分别为1410mAh·g-1及240.6μAh·cm-2;50次循环后充电比容量为179μAh·cm-2(1049mAh·g-1),容量保持率为74.4%.锂-硅薄膜电极中的活性锂组分可补偿首次循环时不可逆容量损失,同时薄膜电极中的多孔结构可缓解电极材料的体积效应并改善其循环性能.

Porous Li-Si thin films（LSFs） were prepared by a multi-step constant current electrodeposition onto Cu foil.The structure and morphology of the electrodeposited films were characterized using X-ray diffraction（XRD） and scanning electron microscopy（SEM）.As anodes for Li-ion batteries,Li-Si films give high cycling stability,adjustable Li-storage capacity and initial coulombic efficiency under different electrodeposition conditions.For instance,LSF-3 was electrodeposited in an electrolyte of 0.5 mol·L-1 SiCl4＋0.7 mol·L-1 LiClO4＋propylene caronate（PC） under certain conditions（i1=-3.82 mA·cm-2,t1=600 s;i2=-1.27 mA·cm-2,t2=7200 s）.LSF-3 showed the first coulombic efficiency of 97.1% at a current density of 12.7 μA·cm-2.After the two initial pre-cycles,it delivered gravimetric and geometric charge capacities of 1410 mAh·g-1 and 240.6 μAh·cm-2 at 25.5 μA·cm-2.After 50 cycles,its charge capacity was 179.0 μAh·cm-2（1049 mAh·g-1）,retaining 74.4% of its initial capacity.The porous structure in LSFs can accommodate a part of the volume change during Li insertion/extraction and this favors the structural stability.