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

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 LiFePO₄/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.