High-performance all-solid-state Li2S batteries using an interfacial redox mediator

Abstract

All-solid-state Li–S batteries based on lithium sulfide cathodes have generated much excitement as possible next-generation energy storage candidates because they can offer a high theoretical energy density exceeding that of lithium-ion batteries, and the possibility of “anode-less” cell designs. However, solid-state Li₂S cathode kinetics are hindered by both limited ionic and electronic transport and a high activation barrier on charge. Here we report a Li₂S/LiVS₂ core–shell cathode architecture design, whereby the shell serves as both a charge-carrier transport vehicle and electron transfer mediator for Li₂S during oxidation. With an argyrodite-type solid electrolyte, the solid-state Li₂S cell exhibits very good rate capability up to 3 mA cm⁻² at room temperature, and nearly 80% capacity retention up to 1000 cycles at a moderate current density of 1 mA cm⁻². High active material loading (4 and 6 mg cm⁻²) is demonstrated in this configuration with stable capacity retention. High areal capacity up to 5.3 mA h cm⁻² with a very high active material loading of 10 mg cm⁻² is also reported, albeit with limited cycle life.