Solid polymer electrolyte (SPE) is a promising alternative to existing liquid electrolytes for next-generation solid-state alkali metal batteries for better safety and higher performance. However, the existing SPEs suffer from low ionic conductivity as well as limited chemistries that satisfy practical implementation. Here we report a new class of polyeutectic electrolyte (PEE) for high-performance energy storage applications. The interaction between alkali bis(trifluoromethanesulfonyl)imide (TFSI) salts (LiTFSI, NaTFSI and KTFSI) and N-isopropylacrylamide molecules (polymer precursor) was found to play an important role in both the formation of eutectic electrolyte and the subsequent polymerization process. The as-prepared PEE exhibited high ionic conductivity of 1.3 × 10⁻⁴ S cm⁻¹ at room temperature and wide electrochemical window, enabling high capacity and excellent stability both in symmetrical cells and all-solid-state alkali metal batteries. Meanwhile, when serving as a separator in redox flow batteries, the modified separator displayed enhanced cell Coulombic efficiency (nearly 99.9%) compared with the commercial Celgard separator (ca. 95%). The results in this work showcase the effectiveness and versatility of PEE for high-performance electrical energy storage systems.

中文翻译：

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用于高性能储能系统的基于共晶的稳定有效的电解质

固态聚合物电解质（SPE）是用于下一代固态碱金属电池的现有液态电解质的有希望的替代品，具有更好的安全性和更高的性能。然而，现有的SPEs具有低离子电导率以及满足实际应用的有限化学方法。在这里，我们报告了一种用于高性能储能应用的新型共晶电解质（PEE）。发现碱性双（三氟甲磺酰基）酰亚胺（TFSI）盐（LiTFSI，NaTFSI和KTFSI）与N-异丙基丙烯酰胺分子（聚合物前体）之间的相互作用在共晶电解质的形成和随后的聚合过程中均起着重要作用。制备的PEE表现出1.3×10 ^-4 S cm的高离子电导率室温下^-1且电化学窗口宽，在对称电池和全固态碱金属电池中均具有高容量和出色的稳定性。同时，当用作氧化还原液流电池的隔板时，与市售的Celgard隔板（约95％）相比，改进的隔板显示出更高的电池库仑效率（接近99.9％）。这项工作的结果展示了PEE在高性能电能存储系统中的有效性和多功能性。