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The commercialization of rechargeable zinc-air batteries (ZABs) is significantly impeded by their high charging voltage and low energy efficiency. In this work, we apply soluble KI to ZABs as a reaction modifier to change the oxidation pathway in the charging process from oxygen evolution reaction to I–oxidation reaction (IOR), which enjoys lower oxidation potential and faster kinetics. In addition, we surprisingly find that commercial cost-effective XC72R carbon delivers satisfactory bifunctional IOR and oxygen reduction reaction activity. Density functional theory calculation is provided to demonstrate the IOR mechanism by XC72R carbon. Finally, the KI-modified ZABs with XC72R exhibit a low charging voltage of 1.79 V, improved energy efficiency of 65.3% (2.0 V and 60% for conventional ZABs with noble-metal catalysts), and long cycle life of over 120 h at 5 mA cm–2. Further characterizations have illuminated the reason behind the extended battery cycle life as well. This work can significantly facilitate the future use of rechargeable ZABs in energy storage.

Zinc metal has emerged as seeded anode material in the field of high-efficiency aqueous metal-air battery system due to the advantages of abundant reserves, strong reversibility and high capacity. Unfortunately, the conventional zinc electrodes commonly adopt a flat structure, and the dendrite accumulation and corrosion during the cycle process lead to sub-optimal efficiency and performance. Herein, the zinc electrode is designed as a three-dimensional (3D) spiral structure to improve the utilization efficiency of zinc and the quality of the battery. Compared with the zinc plate, the 3D spiral zinc electrode can shorten the movement distance of the particles in space and the operation period in time, increase the specific surface area of the reaction, reduce the resistance of mass and charge transfer, and achieve the effect of optimizing the performance of the battery system. The results show that the aqueous zinc-air battery made of 3D spiral zinc electrode exhibits better charge-discharge characteristics, higher power density and narrower voltage windows. This study demonstrates a zinc anode with simple feasibility properties and a special structure, aiming to provide a new research direction and innovation strategy for the development of high-performance rechargeable zinc-air battery systems.

The high-dense metal-air batteries are difficult to commercialize on a large scale mainly because of sluggish kinetics of air electrode. The catalysts are of crucial importance for the rate of oxygen reduction reaction (ORR), among which Pt-based catalysts for ORR have shortcomings in stability and cost, and the kind of catalysts with adding C and N to transition metals receive more attention. Here we analyze catalytic performance of graphene supported transition metals-N4(M-N4@G) for ORR based on density functional theory (DFT), verifying rationality of such catalysts with five different transition metals (Pt, Fe, Co, Pd and Ni) embedded in the graphene, and demonstrating that Fe-N4@G has better ORR performance than Pt-N4@G. Moreover, a proposed mechanism of ORR (generating free *O and *OH) is explored to optimize ORR by means of transition-state search in the DFT calculation. Additionally, a novel phenomenon is observed that graphene has a strong attraction to hydrogen atoms, which is facilitated to promote hydrogen evolution reaction of graphene supported catalysts.

Zinc is an ideal energy carrier due to its high energy density, low cost and environmental friendliness. However, dendrite growth during plating/stripping hinders the practical application of zinc-based secondary batteries. Although inhibition strategies have been proposed in recent years to eliminate the negative effects of zinc dendrites, the problem of dendrite growth is still unresolved. Therefore, understanding the formation mechanism of zinc dendrites is necessary to guide the inhibition strategies of zinc dendrite growth. The mechanism of zinc dendrite growth is investigated and the related inhibition strategies are summarized in this review. Firstly, the physicochemical properties of zinc, and advantages and disadvantages of zinc electrode are described in detail. Secondly, the nucleation and dendrite growth of zinc are analyzed based on the existing theoretical models of zinc dendrite growth, pointing out the key factors affecting the nucleation and growth behavior of zinc dendrites. Thirdly, the measures to optimize the electric field distribution on the electrode surface are summarized, enhancing the migration of zinc ions and dendrite-free zinc deposition. Lastly, the challenges and the expectations for zinc-based batteries in the future development are presented.

Flexible zinc-air batteries attract more attention due to their high energy density, safety, environmental protection and low cost. However, the traditional aqueous electrolyte has the disadvantages of leakage and water evaporation, which cannot meet application demand of flexible zinc-air batteries. Hydrogels possessing good conductivity and mechanical properties become a candidate as the electrolytes of flexible zinc-air batteries. In this work, advances in aspects of conductivity, mechanical toughness, environmental adaptability and interfacial compatibility of hydrogel electrolytes for flexible zinc-air batteries are investigated. First, the additives to improve conductivity of hydrogel electrolytes are summarized. Second, the measures to enhance the mechanical properties of hydrogels are taken by way of structure optimization and composition modification. Third, the environmental adaptability of hydrogel electrolytes is listed in terms of temperature, humidity and air composition. Fourth, the compatibility of electrolyte-electrode interface is discussed from physical properties of hydrogels. Finally, the prospect for development and application of hydrogels is put forward.