Confined tandem catalytic quasi-solid sulfur reversible conversion for all-solid-state Na–S batteries

Abstract

Controlling the complex, multiphase sulfur/polysulfide redox process is a fundamental pathway to alleviate the cathodic passivation and unlock the high energy potentials of all-solid-state Na–S electrochemistry. Herein, by employing a confined tandem electrocatalytic approach, we successfully tune the polysulfide speciation pathway to enable energetic, low-temperature (80 °C) Na–S systems based on dense Na₃Zr₂Si₂PO₁₂ ceramic membranes. Our design features york–shell structured MnHCF/PPy@MnO₂ coaxial nanotubes endowed with a localized and confined environment. These components synergistically catalyze the conversion of encapsulated sulfur/sulfide, with MnO₂ effectively directing long-chain polysulfide transition and MnHCF nanoclusters catalyzing low-kinetic Na₂S₄ to Na₂S direct and reversible conversion. This facilitates continuous, fully controllable quasi-solid sulfur conversion, significantly enhancing battery performance. Operando investigations show that, without the mediation of these bi-catalytic centers, the electrodeposited Na₂S₂/Na₂S exhibits a much higher activation energy upon recharging, leading to the accumulation of inactive polysulfide species and exacerbated cathodic passivation. Consequently, our approach enables a low N/P ratio all-solid-state Na–S cell with a high reversible capacity of 1111 mA h g_S⁻¹ and an energy output of 880 W h kg_cathode⁻¹.