Starfish‐Inspired Solid‐State Li‐ion Conductive Membrane with Balanced Rigidity and Flexibility for Ultrastable Lithium Metal Batteries

Abstract The performance of solid‐state lithium‐metal batteries (SSLMB) is often constrained by the low ionic conductivity, narrow electrochemical window, and insufficient mechanical strength of polyethylene oxide (PEO)‐based electrolytes. Inspired by the soft‐outside, rigid‐inside structure of starfish, we designed multifunctional “starfish‐type” composite polymer electrolytes (CPEs) using electrospinning technology. These CPEs feature a three‐dimensional rigid skeleton network composed of polyacrylonitrile/metal–organic frameworks/ionic liquids (PAN/MOFs/ILs), creating continuous and efficient Li + transport channels: MOFs impart rigidity, PEO acts as a cushioning outer layer to enhance interfacial compatibility, and ILs reduce interfacial resistance. The resulting CPEs exhibited excellent ionic conductivity (4.37×10 −4 S cm −1 ), a wide electrochemical window (5.34 V), uniform lithium‐ion flux, and a high transference number (0.69). Leveraging these synergistic advantages, the Li/CPEs/Li symmetric cell demonstrated outstanding dendrite suppression for over 1300 hours, and the LiFePO 4 /CPEs/Li cell retained 90.1 % capacity after 2100 cycles at 1.0 C, which is the best performance reported for SSLMB with MOF/PEO. The formation of multi‐component solid‐electrolyte interphase and its role in stabilizing lithium metal cycling were systematically elucidated through theoretical simulations and spectroscopic analysis. This nature‐inspired design provides a promising strategy for the development of stable solid‐state electrolytes with extended lifespans.