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A major limitation of vanadium oxides in aqueous Zn/V2O5 ion battery applications is that it suffers from strong Coulombic ion-lattice interactions with divalent Zn2+. Correspondingly, the vanadium oxides endow the...

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The development of high capacity and stable cathodes is the key to the successful commercialization of aqueous zinc-ion batteries. However, significant solvation penalties limit the choice of available positive electrodes. Herein, hydrated intercalation is proposed to promote reversible (de)intercalation within host materials by rationally designing a matching electrode. In contrast to previously reported works, the as-prepared electrode (NHVO@CC) can achieve fast and reversible intercalation of hydrated zinc ions in the interlayer gap, leading to a high capacity of 517 mAh g −1 at 0.1 A g −1 and excellent electrode stability for long-term cycling. Besides, as a consequence of the flexibility of the NHVO@CC electrode, a quasi-solid-state battery was achieved with equally advantageous electrochemical behavior under various bending states. The proposed hydrated cation direct insertion/ extraction sets up an efficient way of developing high-performance positive electrodes for aqueous batteries.

Ternary cathodes account for more than half of the market share for lithium-ion battery cathodes, and recycling draws considerable attention. The traditional extraction process used to separate and recover Co and Ni from spent ternary cathode leachates produces a large amount of saline wastewater; thus, a green method is urgently needed. In this work, we underscore the crucial role played by metal solvation during extraction, and this provides a new perspective for achieving green separation. The extraction mechanism can be described as follows: metal cations M 2+ (M−Ni and Co) generate stable hydrated ions M(H 2 O) 6 2+ upon solvation. However, Ni(H 2 O) 6 2+ and Co(H 2 O) 6 2+ exhibit different activities in reactions with acidic extractants (HA) and form different complexes, NiA 2 •2H 2 O and CoA 2 , respectively.Correspondingly, the coordinated water increases the electron density and steric hindrance of the center metal ions and thus inhibits the subsequent extraction. Therefore, a means of reducing solvation (adding lactic acid) was developed, and this approach exhibited good performance. The separation factor was improved by a factor of 192. These results open a new avenue for high-performance selective extraction of Co, which features a green recovery process and is suitable for future use in industrial production.