Electrolytes enriched by potassium perfluorinated sulfonates for lithium metal batteries  

用于金属锂电池的全氟烷基磺酸钾盐优化电解液

作　　者：Shihan Qi Huaping Wang Jian He Jiandong Liu Chunyu Cui Mingguang Wu Fang Li Yuezhan Feng Jianmin Ma 戚世瀚;王华平;何健;刘建东;崔春雨;武明光;李芳;冯跃战;马建民(School of Physics and Electronics,Hunan University,Changsha 410082,China;Key Laboratory of Materials Processing and Mold(Zhengzhou University),Ministry of Education,Zhengzhou University,Zhengzhou 450002,China)

机构地区：[1]School of Physics and Electronics,Hunan University,Changsha 410082,China [2]Key Laboratory of Materials Processing and Mold(Zhengzhou University),Ministry of Education,Zhengzhou University,Zhengzhou 450002,China

出　　处：《Science Bulletin》2021年第7期685-693,M0004,共10页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China (11675051);the China Postdoctoral Science Foundation (2020M672477);the Key Research and Development Program of Hunan Province,China (2018GK2031)。

摘　　要：Lithium(Li) metal is widely considered as a promising anode for next-generation lithium metal batteries(LMBs) due to its high theoretical capacity and lowest electrochemical potential. However, the uncontrollable formation of Li dendrites has prevented its practical application. Herein, we propose a kind of multifunctional electrolyte additives(potassium perfluorinated sulfonates) from the multi-factor principle for electrolyte additive molecular design(EDMD) view to suppress the Li dendrite growth. The effects of these additives are revealed through experimental results, molecular dynamics simulations and firstprinciples calculations. Firstly, K^(+)can form an electrostatic shield on the surface of Li anode to prevent the growth of Li dendrites. Secondly, potassium perfluorinated sulfonates can improve the activity of electrolytes as co-conductive salts, and lower the electro-potential of Li nucleation. Thirdly, perfluorinated sulfonate anions not only can change the Li^(+)solvation sheath structure to decrease the desolvation energy barrier and increase the ion migration rate, but also can be partly decomposed to form the superior solid electrolyte interphase(SEI). Benefited from the synergistic effects, an outstanding cycle life over250 h at 1 m A cm^(-2) is achieved in symmetric Li||Li cells. In particular, potassium perfluorinated sulfonate additives(e.g., potassium perfluorohexyl sulfonate, denoted as K+PFHS) can also contribute to the formation of high-quality cathode electrolyte interphase(CEI). As a result, Li||LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2) full cells exhibit significantly enhanced cycling stability. This multi-factor principle for EDMD offers a unique insight on understanding the electrochemical behavior of ion-type electrolyte additives on both the Li metal anode and high-voltage cathode.金属锂由于具有高理论容量和低电极电势,被广泛认为是金属锂电池的有潜力负极材料.然而锂枝晶的不可控生长阻碍了金属锂电池的实际应用.本文基于实验、分子动力学模拟和第一性原理计算的结果,从电解液添加剂分子设计的角度出发,提出了一类抑制锂枝晶的生长的多功能电解液添加剂(以全氟烷基磺酸钾为例).首先,钾离子可以在金属锂负极表面形成一层静电屏蔽层,从而阻止锂枝晶的生长.其次,全氟烷基磺酸钾作为一种共导电盐,可以增加电解液的活度.最后,全氟烷基磺酸阴离子不仅可以改变锂离子溶剂化壳层结构,降低锂离子的去溶剂化能垒,从而达到提高离子迁移率的目的.这种阴离子还可以部分分解,以形成更好的固体电解质界面膜.得益于添加剂的协同效应,锂对称电池在1 m A cm^(-2)的电流密度测试条件下,具有超过250 h长的循环寿命.尤其,全氟己基磺酸钾添加剂还有助于在正极表面生成高质量的阴极固态电解质界面膜.基于Li||LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)的金属锂电池展现出了良好的循环稳定性.这种多因素机理提供了一种独特的视角来理解离子型添加剂在金属锂负极和高压正极处的电化学行为.

关 键 词：ELECTROLYTE ADDITIVES Lithium metal batteries Lithium anode protection Potassium perfluorinated sulfonates 

分 类 号：TM912[电气工程—电力电子与电力传动]