Heterojunction interfacial promotion of fast and prolonged alkali-ion storage of urchin-like Nb2O5@C nanospheres

Abstract

The heterojunction interface plays a significant role in enhancing the electrochemical properties of electrode materials. Three-dimensional urchin-like Nb₂O₅ nanospheres encapsulated in nitrogen-doped carbon sheaths with the merits of long cycle durability and a high specific capacity were proved to have potential as sodium-/potassium-ion batteries anode materials. Density functional theory calculations were performed and demonstrated that the heterojunction interface between the Nb₂O₅ and carbon layer could serve as an active site for the adsorption of sodium/potassium ions. In sodium-ion storage, Nb₂O₅@C presented impressive electrochemical performance, delivering stable capacities of 255 mA h g⁻¹ at 1 A g⁻¹ over 150 cycles, and 160 mA h g⁻¹ at 10 A g⁻¹ over 1000 cycles. In terms of potassium-ion storage, it delivered a high capacity of 141 mA h g⁻¹ at 0.5 A g⁻¹ over 500 cycles and an ultra-stable capacity of 116 mA h g⁻¹ at 3.5 A g⁻¹ over 1600 cycles. The kinetic analyses revealed that a larger proportion of pseudocapacitive contribution guarantees Nb₂O₅@C achieving excellent electrochemical properties. Notably, the Na-ion full-cell of Nb₂O₅@C//Na₃V₂(PO₄)₃ retained a remarkable specific capacity of 154 mA h g⁻¹ at 5 A g⁻¹, accompanied with a retention of 86% over 1300 cycles.