Elastic NaxMoS2-Carbon-BASE Triple Interface Direct Robust Solid-Solid Interface for All-Solid-State Na-S Batteries

The developments of all-solid-state sodium batteries are severely constrained by poor Na-ion transport across incompatible solid-solid interfaces. We demonstrate here a triple NaxMoS2-carbon-BASE nanojunction interface strategy to address this challenge using the beta ''-Al2O3 solid electrolyte (BASE). Such an interface was constructed by adhering ternary Na electrodes containing 3 wt % MoS2 and 3 wt % carbon on BASE and reducing contact angles of molten Na to similar to 45 degrees. The ternary Na electrodes exhibited twice improved elasticity for flexible deformation and intimate solid contact, whereas NaxMoS2 and carbon synergistically provide durable ionic/electronic diffusion paths, which effectively resist premature interface failure due to loss of contact and improved Na stripping utilization to over 90%. Na metal hosted via triple junctions exhibited much smaller charge-transfer resistance and 200 h of stable cycling. The novel interface architecture enabled 1100 mAh/g cycling of all-solid-state Na-S batteries when using advanced sulfur cathodes with Na-ion conductive PEO10-NaFSI binder and NaxMo6S8 redox catalytic mediator.