Combined Ion‐Expressway and Li ⁺ ‐Transit Lane in Asymmetric Polymer Electrolyte Enables High‐Voltage Solid‐State Lithium‐Metal‐Batteries

ABSTRACT The development of solid‐state lithium‐metal batteries (SLMBs) is severely hampered by conflicting electrolyte needs of the reactive anode and high‐voltage cathode, leading to lithium dendrite growth and poor interfacial stability. Herein, an asymmetric solid polymer electrolyte (SIPE) is proposed, with the cathode‐facing ionogel polymer electrolyte (IPE) constructing a “High‐Speed Ion Path” and the anode‐facing solid polymer electrolyte (SPE) forming a “Li⁺‐Exclusive Channel.” The ionic liquid (IL) in IPE decouples polymer‐Li⁺ interactions, and the in‐situ produced SiO 2 reinforces conduction networks, boosting ionic conductivity to 0.85 mS cm −1 . MOF in the SPE layer utilizes its porous structure and Lewis acidic sites to restrict anions and enable single Li⁺ transport, achieving a high Li⁺ transference number of 0.79 and uniform flux. Consequently, Li||SIPE||Li cells could cycle stably over 2000 h at 0.2 mA cm −2 . Paired with NCM9055, it retains 88.1% capacity after 120 cycles (0.5 C) with a thin cathode electrolyte interphase (CEI, ≈5.5 nm). SIPE also demonstrates wide‐temperature operation (0–80°C) and enables a scalable Li||SIPE||LFP pouch cell with high areal capacity (5.59 mAh cm −2 ) and 95.4% retention after 90 cycles. This asymmetric design synergizes high ionic conductivity and excellent interface stability, offering a promising strategy for high‐energy SLMBs.