Niobium sulfide nanocomposites as cathode materials for all-solid-state lithium batteries with enhanced electrochemical performance

Abstract

All-solid-state lithium batteries coupled with transition metal sulfide cathodes have gained significant attention due to their high energy density and exceptional safety. However, there are still critical challenges impeding their practical application, such as limited capacity delivery, weak ionic reaction kinetics and volume expansion. Herein, an a-NbS₄/20%VGCF@15%Li₇P₃S₁₁ nanocomposite cathode material is employed in all-solid-state batteries. A certain proportion of VGCF is introduced into crystalline NbS₄ in order to mitigate the volume expansion and improve electronic conductivity. At the same time, a-NbS₄/20%VGCF is in situ coated with a Li₇P₃S₁₁ solid electrolyte layer to achieve an intimate interfacial contact. The obtained a-NbS₄/20%VGCF@15%Li₇P₃S₁₁ nanocomposite exhibits a remarkable electronic conductivity (1.0 × 10⁻¹ S cm⁻¹) and ionic conductivity (5.5 × 10⁻⁴ S cm⁻¹), which are improved by five and two orders of magnitude compared to those of NbS₄, respectively. The Li/Li₆PS₅Cl/a-NbS₄/20%VGCF@15%Li₇P₃S₁₁ battery exhibits a high initial discharge capacity of 1043.25 mA h g⁻¹ at 0.1 A g⁻¹. Even at 0.5 A g⁻¹, it could provide a reversible capacity of 403.2 mA h g⁻¹ after 500 cycles. This work provides a promising cathode material for all-solid-state lithium batteries with improved ionic/electronic conductivity, high reversible capacity and superior cycling stability.