Zhou Hongyao, Liu Ping
Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Department of Nanoengineering, University of California San Diego, La Jolla, CA 92093, United States of America.
Nanotechnology. 2021 Dec 23;33(11). doi: 10.1088/1361-6528/ac3fe2.
Protection of lithium metal has been one of the great challenges to realize a long-life, high-energy-density battery. Polymer coatings on lithium metal surface have been proven to be an effective protection method in terms of improved morphology, higher coulombic efficiency, and a longer cycle life. However, there is a variety of design principles of polymer coatings proposed by the research community, and the influence of polymer swelling in liquid electrolytes remains poorly understood. Herein we use crosslinking density and solvent-polymer interaction to quantitatively explain the mechanical property and the ion-transport property of polymer coatings when swollen in liquid electrolytes. Low crosslinking density is beneficial for reducing the rigidity and enhancing the viscosity of the polymer. Ion conductivity increases with the swelling ratio, and activation energy of lithium-ion transport increases in a polar polymer with strong ion-polymer coupling. We propose that polymer coatings must be combined with the emerging electrolytes with unconventional solvent compositions to realize a practical high-performance lithium metal battery. This study can provide design guidelines for polymer coatings through the optimized interactions with upcoming high-performance electrolytes.
锂金属的保护一直是实现长寿命、高能量密度电池的重大挑战之一。锂金属表面的聚合物涂层已被证明是一种有效的保护方法，可改善锂金属的形貌、提高库仑效率并延长循环寿命。然而，研究界提出了多种聚合物涂层的设计原则，而聚合物在液体电解质中的溶胀影响仍知之甚少。在此，我们利用交联密度和溶剂 - 聚合物相互作用来定量解释聚合物涂层在液体电解质中溶胀时的机械性能和离子传输性能。低交联密度有利于降低聚合物的刚性并提高其粘度。离子电导率随溶胀率增加，而在具有强离子 - 聚合物耦合的极性聚合物中，锂离子传输的活化能增加。我们提出，聚合物涂层必须与具有非常规溶剂组成的新型电解质相结合，以实现实用的高性能锂金属电池。本研究可为通过与即将出现的高性能电解质优化相互作用的聚合物涂层提供设计指导。
