Li-ion batteries (LIBs) have demonstrated great promise in electric vehicles and hybrid electric vehicles. However, commercial graphite materials, the current predominant anodes in LIBs, have a low theoretical capacity of only 372 mAh·g^-1, which cannot meet the ever-increasing demand of LIBs for high energy density. Nanoscale Si is considered an ideal form of Si for the fabrication of LIB anodes as Si-C composites. Synthesis of nanoscale Si in a facile, cost-effective way, however, still poses a great challenge. In this work, nanoscale Si was prepared by a controlled magnesiothermic reaction using diatomite as the Si source. It was found that the nanoscale Si prepared under optimized conditions (800°C, 10 h) can deliver a high initial specific capacity (3053 mAh·g^-1 on discharge, 2519 mAh·g^-1 on charge) with a high first coulombic efficiency (82.5%). When using sand-milled diatomite as a precursor, the obtained nanoscale Si exhibited a well-dispersed morphology and had a higher first coulombic efficiency (85.6%). The Si-C (Si: graphite = 1:7 in weight) composite using Si from the sand-milled diatomite demonstrated a high specific capacity (over 700 mAhg”¹ at 100 mAg”¹), good rate capability (587mAh·g^-1 at 500 mA·g^-1), and a long cycle life (480 mAh·g^-1 after 200 cycles at 500 mA·g^-1). This work gives a facile method to synthesize nanoscale Si with both high capacity and high first coulombic efficiency.

锂离子电池（LIB）在电动汽车和混合动力电动汽车中已展现出广阔的前景。然而，作为目前锂离子电池中主要的阳极的商用石墨材料，其理论容量仅为372 mAh·g ^-1，具有较低的理论容量，无法满足锂离子电池对高能量密度的日益增长的需求。纳米级硅被认为是制造LIB阳极作为Si-C复合材料的一种理想形式的Si。然而，以容易的，成本有效的方式合成纳米级Si仍然是巨大的挑战。在这项工作中，使用硅藻土作为硅源，通过受控的磁热反应制备了纳米级的硅。结果表明，在优化条件下（800℃，10 h）制备的纳米级Si可以提供较高的初始比容量（3053 mAh·g ^-1）放电时为2519 mAh·g ^-1（充电时），首次库仑效率很高（82.5％）。当使用砂磨的硅藻土作为前体时，获得的纳米级Si表现出良好分散的形态，并且具有较高的第一库仑效率（85.6％）。所述Si-C（SI：石墨= 1：7重量），使用的Si从砂研磨的硅藻土复合材料表现出高的比容量（超过700 mAhg” ¹在100 MAG” ¹），良好的倍率性能（587mAh·克^{- 1}以500mA·克^-1），以及长的循环寿命（480毫安·克^-1以500mA 200次循环后·克^-1）。这项工作提供了一种简便的方法来合成具有高容量和高第一库仑效率的纳米级硅。