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-MnO 2 batteries have drawn increasing attention due to high manufacturing readiness level. However, obtaining MnO 2 with high electrochemical activity and high cyclic stability toward Zn 2+ /H + storage still remains challenging. Herein, we reveal that incorporating yttrium ions (Y 3+ ) into layered MnO 2 can regulate the electronic structure of the MnO 2 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-MnO 2 (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 −11 vs. 2.37 × 10 −11 cm 2 s −1 ) in comparison with Y-free MnO 2 (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 Y 3+ endows MnO 2 with remarkable electrochemical reversibility during charge/discharge processes. This work highlights the importance of the Y 3+ preintercalation strategy, which can be further developed to obtain better cathode materials for aqueous batteries. Preintercalated Y 3+ in layered MnO 2 can elaborately regulate the electronic structure, boost electrochemical activity, and render better electrochemical reversibility of MnO 2 , leading to enhanced energy storage in aqueous Zn-ion batteries.