Cathode porosity is a missing key parameter to optimize lithium-sulfur battery energy density
Cathode porosity is a missing key parameter to optimize lithium-sulfur battery energy density
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DOI：
10.1038/s41467-019-12542-6
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发表时间：
2019-10-10
影响因子：
16.6
通讯作者：
Cai, Mei
中科院分区：
文献类型：
--
作者：
Kang, Ning;Lin, Yuxiao;Cai, Mei
虽然高硫负载量一直被视为构建现实高能锂硫电池的关键参数，但对阴极孔隙率的关注较少，硫/碳复合阴极的孔隙率比传统锂离子电池电极的孔隙率高得多。对于高能锂硫电池，需要具有低孔隙率的致密电极，以最大限度地减少电解液的摄入量、寄生重量和成本。在这里，我们报告了通过将阴极孔隙率从 70% 降低到 40%，对锂硫电池的放电极化、可逆容量和电池循环寿命产生的深远影响。根据开发的基于机理的分析模型，我们证明硫的利用受到多硫化锂的溶解度的限制，并且从多硫化锂到Li2S的进一步转化受到碳基体的电子可接触表面积的限制。最后，我们预测优化的阴极孔隙率，以在不牺牲硫利用率的情况下最大化电池水平体积能量密度。
While high sulfur loading has been pursued as a key parameter to build realistic high-energy lithium-sulfur batteries, less attention has been paid to the cathode porosity, which is much higher in sulfur/carbon composite cathodes than in traditional lithium-ion battery electrodes. For high-energy lithium-sulfur batteries, a dense electrode with low porosity is desired to minimize electrolyte intake, parasitic weight, and cost. Here we report the profound impact on the discharge polarization, reversible capacity, and cell cycling life of lithium-sulfur batteries by decreasing cathode porosities from 70 to 40%. According to the developed mechanism-based analytical model, we demonstrate that sulfur utilization is limited by the solubility of lithium-polysulfides and further conversion from lithium-polysulfides to Li2S is limited by the electronically accessible surface area of the carbon matrix. Finally, we predict an optimized cathode porosity to maximize the cell level volumetric energy density without sacrificing the sulfur utilization.