Enhanced reversibility of vanadium oxide cathode by diminished surface precipitation in Zn(TFSI)2 aqueous electrolyte

Yttrium-preintercalated layered manganese oxide as a durable cathode for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) are regarded as competitive alternatives for large-scale energy storage on account of cost-effectiveness and inherent safety. In particular, rechargeable Zn-MnO₂ batteries have drawn increasing attention due to high manufacturing readiness level. However, obtaining MnO₂ with high electrochemical activity and high cyclic stability toward Zn²⁺/H⁺ storage still remains challenging. Herein, we reveal that incorporating yttrium ions (Y³⁺) into layered MnO₂ can regulate the electronic structure of the MnO₂ cathode by narrowing its band gap (from 3.25 to 2.50 eV), thus boosting the electrochemical performance in RAZIBs. Taking advantage of this feature, the optimized Y-MnO₂ (YMO) sample exhibits greater capacity (212 vs. 152 mA h g^-1 at 0.5 A g^-1), better rate capability (94 vs. 61 mA h g^-1 at 8 A g^-1), reduced charge-transfer resistance (79 vs. 148 Ω), and promoted mass transfer kinetics (3.13 × 10^-11vs. 2.37 × 10^-11 cm² s^-1) in comparison with Y-free MnO₂ (MO). More importantly, compared to MO, YMO-0.1 exhibits enhanced energy storage capability by nearly 40% (309 vs. 222 W h kg^-1) and stable cycle performance (94 vs. 52 mA h g^-1 after 3000 cycles). In situ Raman microscopy further reveals that the presence of Y³⁺ endows MnO₂ with remarkable electrochemical reversibility during charge/discharge processes. This work highlights the importance of the Y³⁺ preintercalation strategy, which can be further developed to obtain better cathode materials for aqueous batteries.