Ultrathin composite electrolyte with multifunctional skeleton for solid-state lithium metal batteries

Succinonitrile (SN)-based electrolytes have emerged as promising candidates for lithium metal batteries (LMBs) due to their high ionic conductivity and thermal stability. However, the limited mechanical robustness, low reduction resistance, and residual free SN molecules can damage the electrochemical performance of batteries. Herein, an ultrathin (10 μm) yet mechanically robust composite electrolyte is developed by introducing a rigid multifunctional supporting skeleton, fabricated through in situ growth of zeolitic imidazolate framework (ZIF) nanoparticles within a three-dimensional (3D) aramid nanofibers (ANF) network. The rigid supporting skeleton functionalized with ZIF-67 nanoparticles can selectively absorb lithium salt anions to regulate Li + transport. The well-designed composite electrolyte exhibits a high Li + ionic conductivity of 3 × 10 −4  S cm −1 and a Li  +  transference number of 0.83 at room temperature. Meanwhile, the rigid multifunctional skeleton effectively mitigates side reactions between SN and lithium metal through inducing the formation of the LiF-rich solid electrolyte interphase layer. As a result, the composite electrolyte-based Li||Li, Li||LiFePO 4 and Li||LiNi 0.6 Co 0.2 Mn 0.2 O 2 cells show superior electrochemical performance at room temperature. Notably, the Li||LiFePO 4 cells also deliver stable performance at low temperature. This design offers an efficient, scalable fabrication method for ultrathin solid-state electrolyte-based highly stable and safe LMBs.