Constructing Gradient Soft‐Rigid Structure for Directed and Fast Li‐Ion Transfer Channels in Composite Solid Electrolytes

Abstract Achieving lithium‐ion flux regulation in composite solid electrolytes (CSEs) remains a critical challenge for developing solid‐state Li‐metal batteries suppressing dendrite growth with high‐voltage compatibility. Here, a new concept of Li⁺ transport gradient soft‐rigid structure CSEs is introduced, which comprises a poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) matrix integrated with acetate‐functionalized cellulose nanocrystals (CNC‐PVAc) and ZIF‐8. This structure enables directed and fast Li⁺ conduction through low‐tortuosity channels, significantly inhibiting lithium dendrite nucleation and growth. The electrochemical stability window of PHCF spans up to 4.82 V versus Li⁺/Li. Theoretical simulations reveal a synergistic intrinsic origin of the exceptional performance for this designed Li⁺ transport gradient soft‐rigid structure CSEs. Consequently, the synthesized CSEs demonstrate high ionic conductivity (1.79 × 10 −4 S cm −1 ) and a notably high Li⁺ transference number (t Li⁺ ) of 0.79 at 60 °C. Corresponding all‐solid‐state LiFePO 4 ||Li and NCM811|| Li cells deliver impressive specific capacities of 163.78 (0.1C) and 190.67 mAh g −1 (0.5C) at 60 °C, respectively. This work presents a high‐performance CSEs with intrinsic safety, providing valuable insights for novel design concept of solid‐state batteries (SMBs).