S/MWCNt/LLZO composite electrode with e−/S/Li+ conductive network for all-solid -state Lithium–Sulfur batteries

Highlights: • MWCNt was used as the electronic conductor and host for S cathode. • Cubic LLZO powder prepared by solid-phase method was used as the lithium-ion conductor for S cathode. • Superior cell performance for S/MWCNt/LLZO cathode in PEO -based Li–S batteries. Traditional liquid lithium-sulfur batteries have two key problems: poor safety and shuttle effect. These two challenges can be overcome by using solid-state electrolytes. But poor ionic and electronic conductivity due to solid/solid contact between the electrode and the electrolyte for all-solid-state lithium-sulfur batteries (ASSLSBs). Here, we have synthesized Li_6.4Ga_0.2La₃Zr₂O₁₂(LLZO) conductive ceramics with high ionic conductivity. LLZO is used as the lithium-ion conductor and multi-walled carbon nanotubes (MWCNt) are used as the electronic conductor to form S/MWCNt/LLZO by the thermal diffusion method, resulting in an e⁻/S/Li⁺ conductive network. The prepared S/MWCNt/LLZO composite material, composite solid electrolyte, and lithium metal are assembled into ASSLSBs. After 50 cycles, the high capacity of 825mAh·g⁻¹ is maintained with 72.62% capacity retention at 0.2C and 45°C. The higher capacity indicates the success of forming a conductive network that can improve the electrochemical performance of ASSLSBs. At 0.2C, the capacity of the S/MWCNt/LLZO composite cathode remains at 873mAh·g⁻¹ after 60 cycles when the operating temperature is increased to 60°C, indicating good cycle performance.