3d orbital electron tunning and crystal engineering enables high-capacity vanadium oxide for aqueous ammonium ion batteries.

Vanadium pentoxide (V₂O₅) has shown great potential as the electrode for aqueous ammonium ion batteries (AAIBs) owing to its good electrochemical reversibility and high theoretical capacity. However, the electrochemical performance of V₂O₅ is seriously limited by the weak NH₄⁺ adsorption capability and insufficient active sites of vanadium oxide originated from the unsuitable 3d orbital electron state. Herein, the strategy of a 3d orbital electron tunning and crystal engineering is used to increase the ammonium ion storage capacity of V₂O₅ electrode. The experimental results show that the modified 3d orbital state of V⁴⁺ ( t 2 g 1 ) can effectively increase the active sites of V₂O₅. Therefore, the as-prepared N-VO exhibits a high specific capacity of 249.3 mA h g⁻¹ at 1.0 A g⁻¹ and 69.5 mA h g⁻¹ at 10.0 A g⁻¹, superior to other reported anode material for AAIBs. Noticeably, the prepared resultant quasi-solid-state ammonium ion battery can display considerable cycling stability with capacity retention of 87.9% after a long cycle life of 10 000 cycles at 1 A g⁻¹ and impressive mechanical flexibility with no capacity decay after cycling at different bending angles. [ABSTRACT FROM AUTHOR]