Computational Criteria for Evaluating Polysulfide Cohesion, Solvation, and Stabilization: Approach for Screening Effective Anchoring Substrates

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• 作者：Chenggang ZhouZhuan Ji ; Bo Han ; Qiyang LiQiang Gao ; Kaisheng Xia ; Jinping Wu
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：121
• 期：1
• 页码：308-314
• 全文大小：409K
• ISSN：1932-7455

文摘

Utilizing the functional groups of carbon substrates or third-party additives to adhere lithium polysulfides for suppressing their dissolution has been demonstrated to be capable of improving the sulfur cathode stability of lithium–sulfur batteries. In the present first-principles study, we systematically investigated the competitions between polysulfide self-cohesion, solvation, and its anchoring strengths on substrates. The dissolution probability of polysulfides in ether-based electrolytes is evaluated by a defined solvation potential ΔP_S-C, which confirms that Li₂S₈ is the most soluble species; the competition of Li₂S₈ anchoring strength on different substrates and its solvation energy is described by a stabilizing potential ΔP_S-A, which can be used to verify if a certain substrate can effectively stabilize polysulfides in cathodes. Two properties for a feasible substrate, containing affinitive sites with high electron density for anchoring polysulfides and containing sufficient affinitive sites to provide multiple interactions for enhancing the stabilization, are necessarily proposed. Accordingly, phosphorylated chitosan, among several substrates, is predicted to be a promising third-party substrate to preserve polysulfides in cathodes and prevent them from being dissolved. Our computational scheme may provide a reliable procedure for rapidly screening most appropriate candidates for designing the novel architecture of sulfur cathodes.