Pressureless all‐solid‐state Na/S batteries with self‐supporting Na5YSi4O12 scaffolds

The development of reliable and affordable all‐solid‐state sodium metal batteries (ASS‐SMBs) requires suitable solid‐state electrolytes with cost‐efficient processing and stabilized electrode/electrolyte interfaces. Here, an integrated porous/dense/porous Na5YSi4O12 (NYS) trilayered scaffold is designed and fabricated by tape casting using aqueous slurries. In this template‐based NYS scaffold, the dense layer in the middle serves as a separator and the porous layers on both sides accommodate the active materials with their volume changes during the charge/discharge processes, increasing the contact area and thus enhancing the utilization rate and homogenizing the current distribution. The Na/NYS/Na symmetric cells with the Pb‐coated NYS scaffold exhibit significantly reduced interfacial impedance and superior critical current density of up to 3.0 mA cm−2 against Na metal owing to enhanced wettability. Furthermore, the assembled Na/NYS/S full cells operated without external pressure at room temperature showed a high initial discharge capacity of 970 mAh g−1 and good cycling stability with a capacity of 600 mAh g−1 after 150 cycles (based on the mass of sulfur). This approach paves the way for the realization of economical and practical ASS‐SMBs from the perspective of ceramic manufacturing. The porous/dense/porous trilayered Na5YSi4O12 is used in an all‐solid‐state sodium/sulfur battery as a scaffold for the electrode active materials. The dense middle layer separates both electrodes and prevents sulfur shuttling and sodium dendrite growth. The porous layers on both sides accommodate the active materials and mitigate volume changes, thus increasing the contact area and distributing the local current.