No abstract

The ability to craft high‐efficiency and non‐precious bifunctional oxygen catalysts opens an enticing avenue for the real‐world implementation of metal‐air batteries (MABs). Herein, Co3O4 encapsulated within nitrogen defect‐rich g‐C3N4 (denoted Co3O4@ND‐CN) as a bifunctional oxygen catalyst for MABs is prepared by graphitizing the zeolitic imidazolate framework (ZIF)‐67@ND‐CN. Co3O4@ND‐CN possesses superb bifunctional catalytic performance, which facilitates the construction of high‐performance MABs. Concretely, the rechargeable zinc‐air battery based on Co3O4@ND‐CN shows a superior round‐trip efficiency of ≈60% with long‐term durability (over 340 cycles), exceeding the battery with the state‐of‐the‐art noble metals. The corresponding lithium‐oxygen battery using Co3O4@ND‐CN exhibits an excellent maximum discharge/charge capacity (9838.8/9657.6 mAh g−1), an impressive discharge/charge overpotential (1.14 V/0.18 V), and outstanding cycling stability. Such compelling electrocatalytic processes and device performances of Co3O4@ND‐CN originate from concurrent compositional (i.e., defect‐engineering) and structural (i.e., wrinkled morphology with abundant porosity) elaboration as well as the well‐defined synergy between Co3O4 and ND‐CN, which produce an advantageous surface electronic environment corroborated by theoretical modeling. By extension, a rich diversity of other metal oxides@ND‐CN with adjustable defects, architecture, and enhanced activities may be rationally designed and crafted for both scientific research on catalytic properties and technological development in renewable energy conversion and storage systems.

A major issue with Li‐O2 batteries is their slow oxygen reduction and evolution kinetics, necessitating catalysts with high catalytic activity to improve reaction kinetics and cycle stability. Herein, a nano‐heterostructured catalyst composed of Co3O4 and Fe2O3 (Co3O4/Fe2O3) with a porous rod morphology is achieved through an interfacial engineering strategy by constructing Fe2O3 on the Co3O4 surface, which can function as a high‐performance cathode in order to efficiently encourage the oxygen reduction and evolution while also reduce the battery polarization during charging and discharging. The density functional theory (DFT) calculations show the differences in charge density at the interface of nano‐heterostructures, demonstrating the occurrence of an electron transfer process in the interface region of Co3O4 and Fe2O3, implying a strong electronic coupling transfer, and in turn changing the electronic structure of the Co3O4. This significantly reduces the adsorption energy of LiO2 intermediates, thereby effectively lowering the overpotential. The resultant Li‐O2 battery has larger discharge specific capacity, lower overpotential for the efficient oxygen evolution/reduction, as well as good cycling stability of 280 cycles. This work demonstrates an effective method to fabricate the nano‐heterostrucutred materials with enhanced catalytic efficiency for advanced energy applications.

Aqueous zinc batteries are promising candidates for energy storage and conversion devices in the “post‐lithium” era due to their high energy density, high safety, and low cost. The electrolyte plays an important role in zinc batteries by conducting and separating the positive and negative electrodes. However, the issues of zinc dendrites growth, corrosion, by‐product formation, hydrogen evolution and leakage, and evaporation of the aqueous electrolytes affect the commercialization of the batteries. Moreover, the widely used aqueous electrolytes result in large battery sizes, which are not conducive to the emerging smart devices. The intrinsic properties of gel polymer electrolytes (GPEs) can solve the above problems. In order to promote the wider application of GPEs‐based zinc batteries, in this review, the working principle and the current problems of zinc batteries are first introduced, andthe merits of GPEs compared to aqueous electrolytes are then summarized. Subsequently, a series of challenges and corresponding strategies faced by GPE is discussed, and an outlook for its future development is finally proposed.

The 3d transition-metal nitrogen-carbon nanocomposites (T-N-C, T=Fe, Co, Ni, etc) with highly active M-Nx sites have received much attention in the field of rechargeable zinc-air battery research. However, how to...