Carbothermal reduction-induced oxygen vacancies in spinel cathodes for high-performance aqueous zinc-ion batteries

Abstract

Advancement of aqueous zinc-ion batteries (AZIBs) for practical application is limited due to the inferior performance of the existing cathode. Herein, we demonstrate rational design and synthesis of an oxygen vacancy-rich low-valent vanadium-based spinel cathode (O_V-ZnV₂O₄) for the fabrication of high-performance AZIBs. ZnV₂O₄ having an urchin-like morphology with nanorods ∼19 nm in diameter is synthesized carbothermally. The carbothermal reduction induces oxygen vacancies and makes ZnV₂O₄ ideal for Zn²⁺ storage. Theoretical studies show the enhancement of electrical conductivity and facile diffusion of charge carriers due to oxygen vacancies. The urchin-like O_V-ZnV₂O₄ delivers a high discharge capacity (599.6 mA h g⁻¹ at 100 mA g⁻¹) and high energy density (371.8 W h kg⁻¹). The device has a decent cycle life of over 2000 cycles at 4000 mA g⁻¹. A series of ex situ characterization studies and operando X-ray characterization reveal that the charge storage mechanism involves the co-intercalation of Zn²⁺/H⁺ onto the cathode.