Ambient-temperature sodium-sulfur (Na-S) batteries are potential attractive alternatives to lithium-ion batteries owing to their high theoretical specific energy of 1,274 Wh kg⁻¹ based on the mass of Na₂S and abundant sulfur resources. However, their practical viability is impeded by sodium polysulfide shuttling. Here, we report an intercalation-conversion hybrid positive electrode material by coupling the intercalation-type catalyst, MoTe₂, with the conversion-type active material, sulfur. In addition, MoTe₂ nanosheets vertically grown on graphene flakes offer abundant active catalytic sites, further boosting the catalytic activity for sulfur redox. When used as a composite positive electrode and assembled in a coin cell with excess Na, a discharge capacity of 1,081 mA h g_s⁻¹ based on the mass of S with a capacity fade rate of 0.05% per cycle over 350 cycles at 0.1 C rate in a voltage range of 0.8 to 2.8 V is realized under a high sulfur loading of 3.5 mg cm⁻² and a lean electrolyte condition with an electrolyte-to-sulfur ratio of 7 μL mg⁻¹. A fundamental understanding of the electrocatalysis of MoTe₂ is further revealed by in-situ synchrotron-based operando X-ray diffraction and ex-situ time-of-flight secondary ion mass spectrometry.

To enable high performance of all solid-state batteries, a catholyte should demonstrate high ionic conductivity, good compressibility and oxidative stability. Here, a LaCl₃-based Na⁺ superionic conductor (Na_1−xZr_xLa_1−xCl₄) with high ionic conductivity of 2.9 × 10⁻⁴S cm⁻¹ (30 °C), good compressibility and high oxidative potential (3.80 V vs. Na₂Sn) is prepared via solid state reaction combining mechanochemical method. X-ray diffraction reveals a hexagonal structure (P6₃/m) of Na_1−xZr_xLa_1−xCl₄, with Na⁺ ions forming a one-dimensional diffusion channel along the c-axis. First-principle calculations combining with X-ray absorption fine structure characterization etc. reveal that the ionic conductivity of Na_1−xZr_xLa_1−xCl₄ is mainly determined by the size of Na⁺-channels and the Na⁺/La³⁺ mixing in the one-dimensional diffusion channels. When applied as a catholyte, the NaCrO₂||Na_0.7Zr_0.3La_0.7Cl₄||Na₃PS₄||Na₂Sn all-solid-state batteries demonstrate an initial capacity of 114 mA h g⁻¹ and 88% retention after 70 cycles at 0.3 C. In addition, a high capacity of 94 mA h g⁻¹ can be maintained at 1 C current density.