Cation- deficient Zn_0.3(NH₄)_0.3V₄O₁₀•0.91H₂O for rechargeable aqueous zinc battery with superior low- temperature performance

The development of aqueous zinc batteries (AZBs) has attracted great attention owing to intrinsic safety, environmental friendliness and low cost. Cathode materials with high capacity and long cycle life at both room temperature and low temperature are urgently needed for practical application of AZBs. Herein, we report cation-deficient nonstoichiometric Zn_0.3(NH₄)_0.3V₄O₁₀·0.91H₂O (ZNV) cathode materials for AZBs. The pre-intercalated Zn²⁺ and structural water act as “pillars” to improve the structure stability. The structural water molecules also provide charge shielding for Zn²⁺ insertion/extraction. Both experiments and theoretical simulations demonstrate that the presence of cation vacancies facilitates Zn²⁺ diffusion during cycles. As a result, the ZNV exhibits a high discharge capacity of 461.1 mAh g⁻¹ at 0.1 A g⁻¹, and negligible decay after 2000 cycles at 2 A g⁻¹. Superior cyclability is also achieved at the low temperature (0, -15, and -30 ℃) with more than 90% capacity retentions over 3500 cycles at 2 A g⁻¹. In addition, the reversible Zn²⁺ (de)intercalation reaction mechanism in ZNV is confirmed. Our work may shed a light on the electrode materials designing and development for wide-temperature AZBs.