Local Electric-Field Homogenization via Ferroelectric Grain-Boundary Engineering Enables Long-Life, High-Rate...

Achieving dendrite-free and stable interfaces remains a critical challenge for solid-state sodium metal batteries (SSMBs), especially under low-temperature and high-rate conditions. Here, we report a scalable grain boundary engineering strategy by integrating ferroelectric PbTiO₃ (PTO) into Na₃Zr₂Si₂PO₁₂ (NZSP) electrolyte. Ferroelectric polarization induces local electric-field homogenization at grain boundaries, suppressing sodium dendrite nucleation while improving densification and interfacial ion transport. The PTO-NZSP delivers high ionic conductivities of 3.21 mS cm^-1 at 25°C and 0.47 mS cm^-1 at -20°C, along with markedly reduced interfacial resistance. The symmetric Na cells exhibit ultra-stable plating/stripping for 8730 h at 25°C and 747 h at -20°C, with critical current densities up to 1.45 and 0.45 mA cm^-2, respectively. The full Na/PTO-NZSP/Na₃V₂(PO₄)₃ cells achieve 81% capacity retention after 10 000 cycles at 20 C and 25°C, and 97% after 490 cycles at 3 C and -20°C, highlighting the local ferroelectric field regulation as an effective route toward durable, all-climate SSMBs.