A novel composite solid electrolyte with ultrahigh ion transference number and stability for solid-state sodium metal batteries.

Benefitting from the synergistic effect of the continuous 3D NZSP framework and PEO/PVDF-HFP asymmetric polymer electrolyte layer, the novel composite solid electrolyte for solid-state sodium metal batteries exhibits ultrahigh ion transference number and stability. [Display omitted] • A novel 3D-NZSP solid electrolyte was synthesized via using NaCl as the templatewe. • The 3D-15PNZSPP exhibits an outstanding transference number of 0.82 at temperature of 30 °C. • The Na/3D-15PNZSPP/Na symmetric cell can cycle for 700 h with a small overpotential. • The assembled Na 0.67 Li 0.24 Mn 0.76 O 2 /3D-15PNZSPP/Na batteries demonstrate remarkable cycling stability. The combination of a Na-ion conducting filler and polymer matrix in composite solid electrolyte (CSE) presents a promising and attractive strategy for improving the energy density and safety of the sodium-metal batteries. The agglomeration and precipitation of inorganic ceramic fillers in the polymer matrix present a major challenge leading to the decreased Na ion conductivity property and transference number, increased interfacial resistance, and worsened mechanical properties of CSEs. Herein, we introduce a novel composite solid electrolyte (denoted as 3D-15PNZSPP), comprising a three-dimensional interconnected porous Na 3 Zr 2 Si 2 PO 12 framework integrated with an asymmetric polymer electrolyte layer, which not only offers continuous conductive pathways and high mechanical strength for Na ions transfer, but also enhances the interfacial compatibility and expands the electrochemical stability window. The 3D-15PNZSPP CSE shows a high Na+ conductivity of 7.6 × 10−4 S cm−1 and an outstanding transference number of 0.82 at temperature of 30 °C. These characteristics enable the Na/3D-15PNZSPP/Na symmetric cell to cycle for over 700 h with a small overpotential. More importantly, the assembled all solid-state Na 0.67 Li 0.24 Mn 0.76 O 2 /3D-15PNZSPP/Na batteries demonstrate remarkable cycling stability and high rate capability, indicating a promising and facile strategy for designing ultra-safe and high-performance solid-state sodium metal batteries. [ABSTRACT FROM AUTHOR]