凹凸棒制备Si@C复合材料及其用于锂离子电池负极材料的电化学性能

硅因其超高的理论比容量而被视为最具潜力的下一代锂离子电池(LIBs)负极材料。目前,硅负极材料的高成本和极其苛刻的合成条件严重阻碍了其在LIBs中的使用。以天然凹凸棒为原料,通过水热法提纯和镁热还原反应制备了硅纳米颗粒(MRR Si),并进一步采用化学气相沉积法以乙炔为碳源制备了MRR Si@C复合材料,系统研究了其作为LIBs负极材料的储锂性能。研究结果表明:通过镁热还原制备的硅纳米在0.2 A/g的电流密度下可展现出2362 mAh/g的比容量,首次库伦效率(CE)为71.87%,100次(0.5 A/g)循环充放电测试后比容量为909 mAh/g。相比之下,在MRR Si纳米颗粒表面沉积碳层后制备的MRR Si@C复合材料可展现出2494 mAh/g的放电容量和78.92%的高CE值。循环性能显示,该复合材料在0.5 A/g的电流密度下充/放电100次后的比容量值可达到1324mAh/g。同时,该复合材料还可在5 A/g的大电流密度下依然可展现出高达844 mAh/g的高比容量。该MRR Si@C复合材料显示了优异的倍率性能和良好的应用前景。

Preparation and lithium-storage performance of attapulgite-derived Si@C composite

Silicon is considered as one of the most promising anode materials of next generation lithium-ion battery (LIBs) due to its extremely high theoretic capacity. However, its applications in LIBs are hindered by the high-cost and harsh synthesis conditions of silicon nanomaterials. In this paper, the natural attapulgite was selected as the precursor for the synthesis of silicon nanoparticles (MRR Si) via hydrothermal purification process followed by magnesium reduction process. By adopting chemical vapor deposition, MRR Si@C composite was prepared and its electrochemical performance was evaluated. Results indicate that the synthesized MRR Si can deliver a high discharge capacity of 2 362 mAh/g under a current density of 0.2 A/g with a coulombic efficiency (CE) of 71.87%. After 100 cycles at 0.5 A/g, the MRR Si-based electrode can deliver a capacity of 909 mAh/g. After the deposition of carbon film, the resulted MRR Si@C composite can deliver a high capacity of 2 494 mAh/g with an enhanced CE of 78.92% and a high capacity of 1 324 mAh/g after 100 cycles at 0.5 A/g. More importantly, the MRR Si@C composite can still remain a high capacity of 844 mAh/g at a high current density of 5 A/g, implying a good rate capability and promising applications of MRR Si in LIBs.