Cesium Phosphotungstate Salt Nanospheres Coated on a 3D Graphene Framework for Lithium Ion Batteries

Abstract

Traditional cathode materials for lithium-insertion compounds, such as LiCoO₂, LiMn₂O₄, LiNiO₂, and LiFePO₄, have been highly successful, but they face severe limitations in terms of energy density and production cost associated with their usage. Therefore, the design of next-generation energy storage devices, such as molecular cluster batteries, is an important and hot topic in current research. While polyoxometalates have been developed for battery components for several years, common POMs, including H₃PW₁₂O₄₀, tend to form heteropoly blues that dissolve in the electrolyte during charging and discharging processes. Hence, finding a polyoxometalates that is less soluble in electrolyte and exhibits certain electrical properties is particularly crucial for lithium-ion battery cathodes. Here, we report the synthesis of zero-dimensional Cs₃PW₁₂O₄₀ nanospheres, followed by the successful embedding of Cs₃PW₁₂O₄₀ nanospheres into three-dimensional graphene sponge, constructing a novel hybrid material of three-dimensional graphene@polyoxometalate (rGO@Cs₃PW₁₂O₄₀) as a new cathode material for LIBs. The prepared rGO@Cs₃PW₁₂O₄₀ half-cell hybrid exhibits excellent electrochemical performance, with high specific capacity (approximately 240 mAh g⁻¹ at 50 mA g⁻¹), outstanding rate capability (95 mAh g⁻¹ at 2 A g⁻¹), and exceptional cycling stability (700 cycles at 1 A g⁻¹). This study provides a new perspective on the application of polyoxometalates in lithium-ion batteries.