The Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
Nano Lett. 2013;13(11):5740-7. doi: 10.1021/nl4036498. Epub 2013 Oct 30.
It is well-known that one-dimensional nanostructures reduce pulverization of silicon (Si)-based anode materials during Li ion cycling because they allow lateral relaxation. However, even with improved designs, Si nanowire-based structures still exhibit limited cycling stability for extended numbers of cycles, with the specific capacity retention with cycling not showing significant improvements over commercial carbon-based anode materials. We have found that one important reason for the lack of long cycling stability can be the presence of milli- and microscale Si islands which typically form under nanowire arrays during their growth. Stress buildup in these Si island underlayers with cycling results in cracking, and the loss of specific capacity for Si nanowire anodes, due to progressive loss of contact with current collectors. We show that the formation of these parasitic Si islands for Si nanowires grown directly on metal current collectors can be avoided by growth through anodized aluminum oxide templates containing a high density of sub-100 nm nanopores. Using this template approach we demonstrate significantly enhanced cycling stability for Si nanowire-based lithium-ion battery anodes, with retentions of more than ~1000 mA·h/g discharge capacity over 1100 cycles.
众所周知，一维纳米结构可以减少硅（Si）基阳极材料在锂离子循环过程中的粉碎，因为它们允许横向弛豫。然而，即使采用了改进的设计，基于硅纳米线的结构在延长的循环次数下仍然表现出有限的循环稳定性，其循环后的比容量保持率并没有比商业碳基阳极材料有显著提高。我们发现，循环稳定性差的一个重要原因可能是存在毫微米级的 Si 岛，这些 Si 岛通常在纳米线阵列生长过程中形成。在这些 Si 岛底层中，随着循环的进行，应力不断积累，导致纳米线阳极的比容量下降，这是因为与集流器的接触逐渐丧失。我们表明，通过在含有高密度亚 100nm 纳米孔的阳极氧化铝模板中进行生长，可以避免直接在金属集流器上生长的 Si 纳米线形成这些寄生 Si 岛。使用这种模板方法，我们证明了 Si 纳米线锂离子电池阳极的循环稳定性得到了显著提高，在 1100 次循环中，放电容量保持率超过了 1000 mA·h/g。
