Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

The rapid advance of mild aqueous zinc-ion batteries (ZIBs) is driving the development of the energy storage system market. But the thorny issues of Zn anodes, mainly including dendrite growth, hydrogen evolution, and corrosion, severely reduce the performance of ZIBs. To commercialize ZIBs, researchers must overcome formidable challenges. Research about mild aqueous ZIBs is still developing. Various technical and scientific obstacles to designing Zn anodes with high stripping efficiency and long cycling life have not been resolved. Moreover, the performance of Zn anodes is a complex scientific issue determined by various parameters, most of which are often ignored, failing to achieve the maximum performance of the cell. This review proposes a comprehensive overview of existing Zn anode issues and the corresponding strategies, frontiers, and development trends to deeply comprehend the essence and inner connection of degradation mechanism and performance. First, the formation mechanism of dendrite growth, hydrogen evolution, corrosion, and their influence on the anode are analyzed. Furthermore, various strategies for constructing stable Zn anodes are summarized and discussed in detail from multiple perspectives. These strategies are mainly divided into interface modification, structural anode, alloying anode, intercalation anode, liquid electrolyte, non-liquid electrolyte, separator design, and other strategies. Finally, research directions and prospects are put forward for Zn anodes. This contribution highlights the latest developments and provides new insights into the advanced Zn anode for future research.

Manipulating Interfacial Stability Via Absorption-Competition Mechanism for Long-Lifespan Zn Anode

The stability of Zn anode in various Zn-based energy storage devices is the key problem to be solved. Herein, aromatic aldehyde additives are selected to modulate the interface reactions between the Zn anode and electrolyte. Through comprehensively considering electrochemical measurements, DFT calculations and FEA simulations, novel mechanisms of one kind of aromatic aldehyde, veratraldehyde in inhibiting Zn dendrite/by-products can be obtained. This additive prefers to absorb on the Zn surface than H2O molecules and Zn2+, while competes with hydrogen evolution reaction and Zn plating/stripping process via redox reactions, thus preventing the decomposition of active H2O near the interface and uncontrollable Zn dendrite growth via a synactic absorption-competition mechanism. As a result, Zn–Zn symmetric cells with the veratraldehyde additive realize an excellent cycling life of 3200 h under 1 mA cm−2/1 mAh cm−2 and over 800 h even under 5 mA cm−2/5 mAh cm−2. Moreover, Zn–Ti and Zn–MnO2 cells with the veratraldehyde additive both obtain elevated performance than that with pure ZnSO4 electrolyte. Finally, two more aromatic aldehyde additives are chosen to prove their universality in stabilizing Zn anodes.

A Study on the Self-Discharge Behavior of Zinc-Air Batteries with CuO Additives

Zn-air batteries have promise as the next generation of batteries. However, their self-discharge behavior due to the hydrogen evolution reaction (HER) and corrosion of the Zn anode reduce their electrochemical performance. Copper (II) oxide (CuO) effectively suppresses the corrosion and HER. In addition, different electrochemical behavior can be obtained with different shape of nano CuO. To improve the performance of Zn-air batteries, in this study we synthesized nano CuO by the hydrothermal synthesis method with different volumes of NaOH solutions. Materials were characterized by XRD, FE-SEM, and EDX analysis. The sphere-like nano CuO (S-CuO) showed a specific discharge capacity of 428.8 mAh/g and 359.42 mAh/g after 1 h and 12 h storage, respectively. It also showed a capacity retention rate of 83.8%. In contrast, the other nano CuO additives showed a lower performance than pure Zn. The corrosion behavior of nano CuO additives was analyzed through Tafel extrapolation. S-CuO showed an Icorr of 0.053 A/cm2, the lowest value among the compared nano CuO materials. The results of our comparative study suggest that the sphere-like nano CuO additive is the most effective for suppressing the self-discharge of Zn-air batteries.