Percolation threshold of graphene nanosheets as conductive additives in Li4Ti5O12 anodes of Li-ion batteries.
Percolation threshold of graphene nanosheets as conductive additives in Li4Ti5O12 anodes of Li-ion batteries.
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DOI：
10.1039/c2nr33099g
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发表时间：
2013-02
期刊：
影响因子：
6.7
通讯作者：
Biao Zhang;Yang Yu;Yusi Liu;Z. Huang;Yanzhen He;Jang‐Kyo Kim
中科院分区：
文献类型：
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作者：
Biao Zhang;Yang Yu;Yusi Liu;Z. Huang;Yanzhen He;Jang‐Kyo Kim
石墨烯纳米片（GNS）被认为是锂离子电池电极的潜在导电添加剂，以取代现有的炭黑（CB）。石墨烯具有极高的长径比和优异的导电性，能够以比CB低得多的含量形成广泛的导电网络。本文报道了具有低渗流阈值的GNS对Li(4)Ti(5)O(12) (LTO)阳极电化学性能的有益影响。实验结果表明，直径为46 μm、厚度为4.5 nm的GNSs的逾渗阈值为1.8 wt%。基于粒子间距离概念的预测给出了 GNS 的渗流阈值为 0.54 wt%，这几乎比 CB 粒子的渗流阈值低一个数量级。 GNS 的低渗透性和高电导率解释了为什么仅含有 5 wt% GNS 的 LTO 阳极比含有 15 wt% CB 的 LTO 阳极具有更好的倍率性能。然而，10 wt% 的较高 GNS 含量会导致 GNS 重新堆叠，从而恶化 Li 离子在 GNS 厚度中的扩散。参数研究表明，GNS 的渗流阈值与 GNS 的纵横比成反比。
Graphene nanosheets (GNSs) have been considered as potential conductive additives for electrodes in Li-ion batteries to replace the existing carbon black (CB). Graphene has exceptionally high aspect ratio and excellent electrical conductivity, enabling the formation of extensive conductive networks at a much lower content than CB. This paper reports the beneficial effects of GNSs with a low percolation threshold on electrochemical performance of Li(4)Ti(5)O(12) (LTO) anodes. The experimental results show that the GNSs with a diameter of 46 μm and a thickness of 4.5 nm have a percolation threshold of 1.8 wt%. The prediction based on the interparticle distance concept gives a percolation threshold of 0.54 wt% for GNSs, which is almost an order of magnitude lower than that for CB particles. The substantially low percolation along with a high electrical conductivity of GNSs explains why the LTO anodes containing only 5 wt% GNSs deliver a much better rate capability than those with 15 wt% CB. However, a higher GNS content of 10 wt% results in re-stacking GNSs, deteriorating the diffusion of Li ions through the thickness of GNSs. The parametric study indicates that the percolation threshold of GNSs is inversely proportional to the aspect ratio of GNSs.