Sodium decavanadate encapsulated Mn-BTC POM@MOF as high-capacity cathode material for aqueous sodium-ion batteries

Aqueous sodium-ion batteries are the promising candidates for large scale energy storage applications owing to their cost effectiveness and environmental safety. However, the development of a stable cathode material with high capacity is still a challenging task for the commercial viability of aqueous electrolyte-based sodium-ion batteries. This work demonstrates the development of hierarchically nanostructured high-capacity cathode material by encapsulating sodium decavanadate Na₆V₁₀O₂₈ (NaDV) in the scaffold of manganese-based metal-organic framework Mn-BTC (where BTC is 1,3,5-benzenetricarboxylic acid) by an in situ synthesis. The uniform distribution of NaDV in the pores of Mn-BTC enables the multielectron redox properties of NaDV whereas the diverse 3D diffusion channels, high surface area, and flexible architecture of Mn-BTC ensures high intercalation capacity by suppressing the agglomeration and providing faster ionic diffusion kinetics in the NaDV@Mn-BTC nano-hybrid cathode material. The Mn-BTC framework not only ensures the stabilization of NaDV but also enhances sodium storage capacity by the involvement of Mn in the redox process. The NaDV@Mn-BTC cathode material exhibits high reversible capacity of 137 mAh/g at 1 C rate. High capacity of this cathode material suggests that the development of these nano-hybrid materials is a feasible approach to design high energy cathode materials for aqueous batteries.