Seamless integration of nanoscale crystalline-amorphous MoO3 domains for high-performance lithium-sulfur batteries

Conversion-type Li-S batteries are characterized by multi-step processes such as the adsorption and conversion of lithium polysulfides (LiPS). Significant research has focused on enhancing each step using heterostructured cathodes. Yet, the seamless integration of these steps is less explored, which is crucial for practical Li-S applications with high sulfur loading and lean electrolytes, where LiPS diffusion delays are significant. We introduce a crystalline-amorphous MoO3 (c-a-MoO3) heterostructure as the cathode host, developed at the nanometer scale. This structure is achieved through a novel method that suppresses the thermal phase transition of MoO3 by impregnation with heteroatoms. This heterostructure enhances the overall conversion kinetics by combining the high adsorption capabilities of amorphous MoO3 with the rapid conversion kinetics of crystalline MoO3. The c-a-MoO3 substrate also promotes 3D Li2S growth, improving sulfur utilization. The c-a-MoO3-based Li-S cell demonstrates superior performance, achieving an initial discharge capacity of 1520 mAh/g at 0.05 C and maintaining excellent cycle stability (decay rate of 0.0713 % over 500 cycles at 1 C). Under practical conditions with a sulfur loading of 6 mg/cm², E/S ratio of 3.6, and N/P ratio of 2, the cell delivers an energy density of 330 Wh/kg, significantly surpassing conventional Li-ion batteries and previous results.