Polyimide/aramid nanofiber aerogel-assisted in situ preparation of thermally stabilized polymer electrolytes for all-solid-state lithium-metal batteries

Abstract

Separator-assisted in-situ polymerization, compatible with mature roll-to-roll manufacturing, is promising for all-solid-state lithium metal polymer batteries (ASSLMPBs). However, traditional separators suffer from excessive weight, inactive ionic conduction regions and poor thermal stability. Herein, we present an ultralight (< 0.1 g cm^-3) aerogel membrane, utilizing low-density structures with macro-vertically oriented three-dimensional pores and functional aramid nanofibers (ANFs) to replace conventional separators in the in-situ polymerization. The aerogel with a high porosity of 92.8 % provides excellent electrolyte absorption and thermal dimensional stability. Compared to traditional polypropylene (PP) separators, the framework proportion in solid polymer electrolytes (SPE) is reduced by seven times, minimizing the non-conductive ionic regions. Additionally, the incorporation of ANFs provides the 1800-fold Young's modulus increase for the aerogel-assisted preparation of SPE compared to no framework. Simultaneously, ANFs can effectively restrict the movement of anions through strong hydrogen bonding interactions, promoting the rapid Li⁺ transport and forming the stable solid electrolyte interface (SEI). ASSLMPBs fabricated using this aerogel-assisted in-situ method demonstrate good long-term cycling stability at 30 °C. The ultralight, thermally stable aerogel membrane developed based on this strategy overcomes the high weight, excessive inert regions, and poor thermal stability of traditional separators, and will promote the development of ASSLMPBs.