Phase-Modified Strongly Coupled δ/ε-MnO₂ Homojunction Cathode for Kinetics-Enhanced Zinc-Ion Batteries

Abstract

Rechargeable Zn-MnO 2 batteries using mild water electrolytes have garnered significant interest owing to their impressive theoretical energy density and eco-friendly characteristics. However, MnO 2 suffers from huge structural changes during the cycles, resulting in very poor stability at high charge−discharge depths. Briefly, the above problems are caused by slow kinetic processes and the dissolution of Mn atoms in the cycles. In this paper, a 2D homojunction electrode material (δ/ε-MnO 2 ) based on δ-MnO 2 and ε-MnO 2 has been prepared by a two-step electrochemical deposition method. According to the DFT calculations, the charge transfer and bonding between interfaces result in the generation of electronic states near the Fermi surface, giving δ/ε-MnO 2 a more continuous distribution of electron states and better conductivity, which is conducive to the rapid insertion/extraction of Zn 2+ and H + . Moreover, the strongly coupled Mn− O−Mn interfacial bond can effectively impede dissolution of Mn atoms and thus maintain the structural integrity of δ/ε-MnO 2 during the cycles. Accordingly, the δ/ε-MnO 2 cathode exhibits high capacity (383 mAh g −1 at 0.1 A g −1 ), superior rate performance (150 mAh g −1 at 5 A g −1 ), and excellent cycling stability over 2000 cycles (91.3% at 3 A g −1 ). Profoundly, this unique homojunction provides a novel paradigm for reasonable selection of different components.

Ice-template-induced highly ionic conductive PVA/PEG-SiO2 gel polymer electrolyte for zinc-ion batteries

“…1,2 In recent years, aqueous zinc ion batteries (AZIBs) have attracted wide attention due to their great potential in grid energy storage systems and wearable electronic products due to their advantages of low cost, high safety and abundant resources. 3–5 Despite the many advantages of ZIBs, practical applications still face many challenges, including: dendrite growth due to inhomogeneous deposition of Zn anodes, oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), electrode material dissolution and the risk of electrolyte leakage. 6,7 Gel polymer electrolyte (GPE) is considered to be the best choice to solve these problems, due to its quasi-solid-state physical state, stable structure and excellent ionic conductivity (relative to all-solid-state electrolyte).…”