清华大学张强团队报道了调节锂盐以抑制电催化剂上的表面凝胶化用于高能量密度锂硫电池。相关研究成果发表在2022年7月6日出版的《美国化学会杂志》。

锂硫电池作为高能量密度储能装置具有巨大的潜力。电催化剂被广泛用于加速阴极硫氧化还原动力学。电催化剂、溶剂和锂盐之间的相互作用显著决定了锂电池的实际性能。

该文中，双（三氟甲烷磺酰基）酰亚胺锂（LiTFSI）是一种常用的锂盐，可加剧MoS₂电催化剂上的表面凝胶化。具体来说，LiTFSI中的三氟甲基磺酰基与MoS₂电催化剂上的Lewis酸性位点相互作用，生成缺电子中心。具有高Lewis酸性的缺电子中心引发1,3-二氧戊环溶剂的阳离子聚合，并生成表面凝胶层，从而降低电催化活性。

为了解决上述问题，引入了路易斯盐基碘化锂（LiI）来阻断LiTFSI和MoS₂之间的相互作用并抑制表面凝胶化。因此，具有MoS₂电催化剂和LiI添加剂的Li–S电池在袋式电池水平上实现了416 W h kg^–1的超高实际能量密度。

该项工作提供了一种有效提高实际工作锂电池的电催化活性的锂盐，并加深了对储能系统中电催化剂、溶剂和盐之间相互作用的基本理解。

附：英文原文

Title: Regulating Lithium Salt to Inhibit Surface Gelation on an Electrocatalyst for High-Energy-Density Lithium–Sulfur Batteries

Author: Xi-Yao Li, Shuai Feng, Chang-Xin Zhao, Qian Cheng, Zi-Xian Chen, Shu-Yu Sun, Xiang Chen, Xue-Qiang Zhang, Bo-Quan Li, Jia-Qi Huang, Qiang Zhang

Issue&Volume: July 6, 2022

Abstract: Lithium–sulfur (Li–S) batteries have great potential as high-energy-density energy storage devices. Electrocatalysts are widely adopted to accelerate the cathodic sulfur redox kinetics. The interactions among the electrocatalysts, solvents, and lithium salts significantly determine the actual performance of working Li–S batteries. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a commonly used lithium salt, is identified to aggravate surface gelation on the MoS2 electrocatalyst. In detail, the trifluoromethanesulfonyl group in LiTFSI interacts with the Lewis acidic sites on the MoS2 electrocatalyst to generate an electron-deficient center. The electron-deficient center with high Lewis acidity triggers cationic polymerization of the 1,3-dioxolane solvent and generates a surface gel layer that reduces the electrocatalytic activity. To address the above issue, Lewis basic salt lithium iodide (LiI) is introduced to block the interaction between LiTFSI and MoS2 and inhibit the surface gelation. Consequently, the Li–S batteries with the MoS2 electrocatalyst and the LiI additive realize an ultrahigh actual energy density of 416 W h kg–1 at the pouch cell level. This work affords an effective lithium salt to boost the electrocatalytic activity in practical working Li–S batteries and deepens the fundamental understanding of the interactions among electrocatalysts, solvents, and salts in energy storage systems.

DOI: 10.1021/jacs.2c04176

Source: https://pubs.acs.org/doi/10.1021/jacs.2c04176