Manipulating defects simultaneously boosts the crystal stability and the electrochemical reversibility toward long-life aqueous zinc ion batteries†

Abstract

A great deal of attention has been paid to vanadium-based materials as promising cathode candidates for aqueous zinc ion batteries (AZIBs) due to their excellent theoretical capacity. However, the strong interactions among Zn²⁺, H₂O and vanadium-based cathodes easily trigger the irreversible dissolution and structure collapse of vanadium, especially at low current density. To address these problems, defect engineering of sulfur doping (point defect) and heterojunction formation (interface defect) is reported herein for designing a robust S-VO₂/V₆O₁₃ (SVO) cathode via a one-step sulfurization. SVO could not only restrict the formation of inactive by-products originating from irreversible dissolution, but also boost the reaction reversibility and kinetics of Zn²⁺ and H⁺, simultaneously solving the major questions of capacity degradation. As a result, a series of spectroscopic and theoretical studies verified that SVO-2 possesses a stable crystal structure and manifests excellent Zn²⁺ and H⁺ storage performance at both low and high current densities. Specifically, a high capacity retention rate of 85.8% can be achieved with a specific capacity of 416 mA h g⁻¹ after 500 cycles at 0.5 A g⁻¹. Even at 10 A g⁻¹, the specific capacity reaches 252 mA h g⁻¹ after 3000 cycles. This work highlights a practical strategy for designing long-term electrodes with great reliability for aqueous batteries.