Breaking the cascade dissolution loop through the self-inhibition mechanism for zinc–vanadium oxide batteries

Abstract

The pre-intercalation of foreign species into zinc–vanadium oxide battery cathodes has been successfully demonstrated to prevent vanadium dissolution owing to the pillar effect strengthening the V–O bond. Here, we challenge this claim and propose a self-inhibition mechanism for cathode dissolution in zinc–vanadium oxide batteries through pre-intercalation of Ca²⁺ to break the cascade dissolution loop of vanadate cathodes. With the help of the state-of-the-art 3D electron microscopic reconstruction technique, the minor yet key intermediate phase of insoluble calcium vanadate (CaV₂O₆·2H₂O) species is identified on the surface of the electrode at the nanometer scale. In the initial dissolution, Ca-VO₂ releases both Ca²⁺ and vanadium ions, while Ca²⁺ acts as a solution inhibitor to co-precipitate vanadium ions as a protective layer to prevent further dissolution of the vanadium oxide cathode. As a result, it exhibits ultrahigh cycling stabilities for over 140 cycles at 0.1 A g⁻¹ and 16 500 cycles at 30 A g⁻¹. Particularly, in high mass loadings of 20 mg cm⁻², the Ca-VO₂ cathode yields a high areal capacity of 8.11 mAh cm⁻² at 0.1 A g⁻¹. As a demonstration of the practical applications, an Ah-level pouch cell delivers an average capacity of 1.15 Ah over 200 cycles at 0.5 A g⁻¹. This work provides new insights into the role of pre-intercalated Ca²⁺ in mitigating vanadium dissolution, paving the way for the development of ultra-stable cathodes in AZIBs.