In contemporary years, the increasing demand for high-capacity and safe energy storage has spurred wide attentions in zinc batteries featuring either high voltage, high capacity or both. Despite the extensive research progress, achieving high-energy-density zinc batteries is still challenging and requires a synergy of the multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies, and critically analyze the positive effects and potential issues in optimizing the electrochemistry, cathode materials, electrolytes and device architecture. At the end, the challenges and prospects for the further development of high-energy-density zinc batteries are outlined to guide the research towards new-generation batteries for household appliance, low-speed electric vehicles and large-scale energy storage system.

Design Strategies for High-Energy-Density Aqueous Zinc Batteries.

Due to their high safety and low cost, rechargeable aqueous Zn-ion batteries (RAZIBs) have been receiving increased attention and are expected to be the next generation of energy storage systems. However, metal Zn anodes exhibit a limited-service life and inferior reversibility owing to the issues of Zn dendrites and side reactions, which severely hinder the further development of RAZIBs. Researchers have attempted to design high-performance Zn anodes by interfacial engineering, including surface modification and the addition of electrolyte additives, to stabilize Zn anodes. The purpose is to achieve uniform Zn nucleation and flat Zn deposition by regulating the deposition behavior of Zn ions, which effectively improves the cycling stability of the Zn anode. This review comprehensively summarizes the reaction mechanisms of interfacial modification for inhibiting the growth of Zn dendrites and the occurrence of side reactions. In addition, the research progress of interfacial engineering strategies for RAZIBs is summarized and classified. Finally, prospects and suggestions are provided for the design of highly reversible Zn anodes.
Highlights:
1 The interfacial engineering strategies of surface and electrolyte modifications for high-performance Zn metal anodes are reviewed.2 The reaction mechanisms for inhibiting dendrite growth and side reactions in interface engineering are systematically summarized.3 An outlook on future reference directions for new interface strategies to advance this field is provided.

Interfacial Engineering Strategy for High-Performance Zn Metal Anodes.

Aqueous Mn2+/MnO2 based-batteries have attracted enormous attentions in aqueous energy storage fields, owing to their high working voltage and theoretical capacity (616 mAh g-1) brought by the two-electron reaction (Mn2+/Mn4+). However, there are currently several tricky challenges facing Mn2+/MnO2-based batteries of their complicated working mechanisms, existing issues, and optimization strategies. In this review, we aim to provide a mechanistic understanding and an overview of the insufficiency, the optimization, and the future development for Mn2+/MnO2-based batteries. The existing issues and deficiency in Mn2+/MnO2 based-batteries have been systematically analyzed, of which the optimization strategies have also been rationally summarized, and discussed with deep insights. Also, the often-overlooked optimized objects and aspects have been highlighted with unique perspectives. The proposals of testing methods and performance assessment are presented, containing different degradation mechanisms. Based on the above points, this review would provide guidance and contribute to the further development of aqueous Mn2+/MnO2 based-batteries.

Issues and Opportunities Facing Aqueous Mn2+/MnO2-based batteries.

Aqueous zinc-ion batteries (AZIBs) are one of the promising energy storage systems, which consist of electrode materials, electrolyte, and separator. The first two have been significantly received ample development, while the prominent role of the separators in manipulating the stability of the electrode has not attracted sufficient attention. In this work, a separator (UiO-66-GF) modified by Zr-based metal organic framework for robust AZIBs is proposed. UiO-66-GF effectively enhances the transport ability of charge carriers and demonstrates preferential orientation of (002) crystal plane, which is favorable for corrosion resistance and dendrite-free zinc deposition. Consequently, Zn|UiO-66-GF-2.2|Zn cells exhibit highly reversible plating/stripping behavior with long cycle life over 1650 h at 2.0 mA cm-2, and Zn|UiO-66-GF-2.2|MnO2 cells show excellent long-term stability with capacity retention of 85% after 1000 cycles. The reasonable design and application of multifunctional metal organic frameworks modified separators provide useful guidance for constructing durable AZIBs. 

/pdf/metal-organic-frameworks-functionalized-separators-for-2nfyl7ug.pdf

Metal–Organic Frameworks Functionalized Separators for Robust Aqueous Zinc-Ion Batteries

The practical application of Zn‐metal anodes (ZMAs) is mainly impeded by the limited lifespan and low Coulombic efficiency (CE) resulting from the Zn dendrite growth and side reactions. Herein, a 3D multifunctional host consisting of N‐doped carbon fibers embedded with Cu nanoboxes (denoted as Cu NBs@NCFs) is rationally designed and developed for stable ZMAs. The 3D macroporous configuration and hollow structure can lower the local current density and alleviate the large volume change during the repeated cycling processes. Furthermore, zincophilic Cu and in‐situ‐formed Cu–Zn alloy can act as homogeneous nucleation sites to minimize the Zn nucleation overpotential, further guiding uniform and dense Zn deposition. As a result, this Cu NBs@NCFs host exhibits high CE of Zn plating/stripping for 1000 cycles. The Cu NBs@NCFs–Zn electrode shows low voltage hysteresis and prolonged cycling life (450 h) with dendrite‐free behaviors. As a proof‐of‐concept demonstration, a Zn‐ion full cell is fabricated based on this Cu NBs@NCFs–Zn anode, which demonstrates decent rate capability and improved cycling performance.

Nitrogen‐Doped Carbon Fibers Embedded with Zincophilic Cu Nanoboxes for Stable Zn‐Metal Anodes

\n Many optimization strategies have been employed to stabilize zinc anodes of zinc-ion batteries (ZIBs). Although these commonly used strategies can improve anode performance, they simultaneously induce specific issues at the same time. In this study, through the combination of structural design, interface modification, and electrolyte optimization, an ‘all-in-one’ (AIO) electrode was developed. Compared to the three-dimensional (3D) anode in routine liquid electrolytes, the new AIO electrode can greatly suppress gas evolution and the occurrence of side reactions induced by active water molecules, while retaining the merits of a 3D anode. Moreover, the integrated AIO strategy achieves a sufficient electrode/electrolyte interface contact area, so that the electrode can promote electron/ion transfer, and ensure a fast and complete redox reaction. As a result, it achieves excellent shelving-restoring ability (60 h, four times) and 1200 cycles of long-term stability without apparent polarization. When paired with two common cathode materials used in ZIBs (α-MnO2 and NH4V4O10), full batteries with the AIO electrode demonstrate high capacity and good stability. The strategy of the ‘all-in-one’ architectural design is enlightened to solve the issues of zinc anodes in advanced Zn-based batteries.

Hui Liu

Papers

Integrated ‘all-in-one’ strategy to stabilize zinc anodes for high-performance zinc-ion batteries