Modulating residual ammonium in MnO2 for high-rate aqueous zinc-ion batteries

Recent development of manganese dioxide-based materials as zinc-ion battery cathode

The development of advanced cathode materials for zinc-ion batteries (ZIBs) is a critical step in building large-scale green energy conversion and storage systems in the future. Manganese dioxide is one of the most well-studied cathode materials for zinc-ion batteries due to its wide range of crystal forms, cost-effectiveness, and well-established synthesis processes. This review describes the recent research progress of manganese dioxide-based ZIBs, and the reaction mechanism, electrochemical performance, and challenges of manganese dioxide-based ZIBs materials are systematically introduced. Optimization strategies for high-performance manganese dioxide-based materials for ZIBs with different crystal forms, nanostructures, morphologies, and compositions are discussed. Finally, the current challenges and future research directions of manganese dioxide-based cathodes in ZIBs are envisaged.

Smart Aqueous Zinc Ion Battery: Operation Principles and Design Strategy

The zinc ion battery (ZIB) as a promising energy storage device has attracted great attention due to its high safety, low cost, high capacity, and the integrated smart functions. Herein, the working principles of smart responses, smart self-charging, smart electrochromic as well as smart integration of the battery are summarized. Thus, this review enables to inspire researchers to design the novel functional battery devices for extending their application prospects. In addition, the critical factors associated with the performance of the smart ZIBs are comprehensively collected and discussed from the viewpoint of the intellectualized design. A profound understanding for correlating the design philosophy in cathode materials and electrolytes with the electrode interface is provided. To address the current challenging issues and the development of smart ZIB systems, a wide variety of emerging strategies regarding the integrated battery system is finally prospected.

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.