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

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 LiFePO₄||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).