Zinc dendrite growth is controlled by electrolyte flow at high current densities, effectively extending the cycle life of rechargeable zinc–air batteries.

With the rapid economic growth and the deepening awareness of sustainable development, the demand for green and efficient energy storage equipment increases. As a promising energy storage and conversion device, zinc-air batteries (ZABs) have the advantages of high theoretical specific energy density, low cost, and environmental friendliness. Nevertheless, the efficiency of ZABs is closely related to the electrocatalytic capacity of the air electrode due to its sluggish kinetics for oxygen reduction and evolution reaction (ORR/OER). Therefore, it is necessary to develop efficient catalysts to promote the reaction rate. Recently, cobalt-based materials have become a research hotspot for oxygen electrocatalysts owing to their rich natural content, high catalytic activity, and stability. In this review, the mechanisms of the OER/ORR reaction process, the catalyst’s performance characterization, and the various combination methods with the current collector are systematically introduced and analyzed. Further, a broad overview of cobalt-based materials used as electrocatalysts for ZABs is presented, including cobalt-based perovskite, cobalt-nitrogen-carbon (Co−N−C) materials, cobalt oxides, cobalt-containing composite oxides, and cobalt sulfides/phosphides. Finally, various strategies for developing efficient electrocatalysts for ZABs are summarized, highlighting the challenges and future perspectives in designing novel catalysts.

Micro-structured surfaces are assuming an ever-increasing role since they define the ultimate performance of many industrial components and products. Micro-channels, in particular, have many potential applications in micro-fluidic devices, micro heat exchangers, and friction control. This paper proposes an innovative vibration-assisted machining method to generate micro-channels on the external surface of a cylinder. This method, referred to as elliptical vibration texturing, was originally developed by the authors to generate dimple patterns. It uses the modulation of the depth-of-cut by tool vibrations to create surface textures. The most promising features of the proposed method are its high efficiency, low cost, and scalability for mass production. It is shown that with proper combinations of the process parameters the created dimples start to overlap and form channels. An analytical model is established to predict channel formation with respect to the overlapping ratios of the dimples. Channel formation criteria and expressions for channel geometries are given along with a channel generation map that relates channel geometry to the process parameters. Experimental results are given to verify the model. A further example of micro-pattern generation is also given to showcase the flexibility of the process.

A study on the effects of controlling and operating parameters for a Proton Exchange Membrane (PEM) fuel cell on the dynamic phenomena during the loading-up process is presented. The effect of the four parameters of load-up amplitudes and rates, operating pressures and current levels on gas supply or even starvation in the flow field is analyzed based accordingly on the transient characteristics of current output and voltage. Experiments are carried out in a single fuel cell with an active area of 285 cm². The results show that increasing the loading-up amplitude can inevitably increase the possibility of gas starvation in channels when a constant flow rate has been set for the cathode; With a higher operating pressure, the dynamic performance will be improved and gas starvations can be relieved. The transient gas supply in the flow channel during two loading-up mode has also been discussed. The experimental results will be helpful for optimizing the control and operation strategies for PEM fuel cells in vehicles.