The development of solid polymer electrolytes for lithium–metal (Li⁰) batteries (LMBs) with high energy density and high safety has been a long-standing goal that attracted intensive efforts for over four decades. The low cation transport number (t₊) of most polymer electrolytes based on polyether linkages often leads to a steep ion concentration gradient near the electrode surfaces that strongly reduces charge/discharge rate and favors Li⁰ dendrite growth. Although theoretically, the single-ion conducting polymer electrolytes (SIPEs) have the intrinsic potential to overcome this limitation, their very low ionic conductivities limit practical applications, especially under high current densities. Only high-cation transport number polymer electrolytes (HTPEs) with simultaneously high t₊ and high ionic conductivity could provide a solution to enable high-performance solid-state batteries (SSBs). Differing from previous reviews focusing on the design and synthesis of SIPEs chemical structure and morphology or their electrochemical performance, this review focuses on various strategies for improving the t₊ of polymer electrolytes. Meanwhile, the mechanical properties, interaction mechanisms and advantages of such cationic conducting polymers have also been explored. By summarizing the existing experimental results, we identify that the synergistic effect of high t₊ and high ionic conductivity enables the tolerance towards high current density and long-cycling stability in SSBs. This review will help to guide the design of new solid-electrolyte systems towards practical next-generation SSBs.

中文翻译：

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用于可充电锂金属电池的高阳离子传输数聚合物电解质：现状与未来发展方向


为锂金属 （Li⁰） 电池 （LMB） 开发具有高能量密度和高安全性的固体聚合物电解质一直是一个长期的目标，四十多年来一直受到人们的不懈努力。大多数基于聚醚键的聚合物电解质的低阳离子传输数 （t₊） 通常会导致电极表面附近出现陡峭的离子浓度梯度，这会大大降低充电/放电速率并有利于 Li⁰ 枝晶生长。尽管从理论上讲，单离子导电聚合物电解质 （SIPE） 具有克服这一限制的内在潜力，但它们非常低的离子电导率限制了实际应用，尤其是在高电流密度下。只有同时具有高 t₊ 和高离子电导率的高阳离子传输数聚合物电解质 （HTPE） 才能为高性能固态电池 （SSB） 提供解决方案。与以往侧重于 SIPEs 化学结构和形态的设计和合成或其电化学性能的综述不同，本文侧重于提高聚合物电解质 t₊ 的各种策略。同时，还探索了这种阳离子导电聚合物的力学性能、相互作用机制和优势。通过总结现有的实验结果，我们确定高 t₊ 和高离子电导率的协同效应使 SSB 能够容忍高电流密度和长循环稳定性。 本文将有助于指导新的固体电解质系统的设计，以实现实用的下一代 SSB。