Tailoring the Electrochemical Deposition of Zn by Tuning the Viscosity of the Liquid Electrolyte

Hydrogen bubble evolution and its induced mass transfer on zinc electrodes in alkaline and neutral media

The evolution of hydrogen bubbles plays a critical role in governing the performance of Zn-based batteries by influencing Zn deposition, electrode morphology, and mass transfer dynamics. This work consolidates recent progress in understanding the dual influence of hydrogen bubble evolution on Zn-based batteries, emphasizing its implications for mass transfer and electrochemical performance. While presenting challenges such as inhomogeneous Zn deposition, dendrite formation, and Zn passivation, hydrogen bubble evolution simultaneously facilitates mass transfer through its forced convective disturbance. Advanced experimental techniques, including electrochemical mass spectrometry, X-ray microscopy, and gas chromatography, are employed to investigate the complex interplay between the hydrogen evolution reaction (HER) and Zn deposition. The hydrogen bubbles induced by the HER not only promote local convection to enhance the transport of zincate or Zn ions but also serve as templates for forming porous Zn structures to increase the electrochemically active surface area and accelerate reaction kinetics. Finally, emerging strategies are explored to mitigate the detrimental effects of the HER, while capitalizing on its beneficial properties to optimize Zn electrode performance, with the ultimate goal of improving the efficiency, safety, and longevity of rechargeable Zn-based energy storage devices.

Decoupled tin-silver batteries with long cycle life and power output stability based on dendrite-free tin anode and halide insertion cathode chemistry

Conventional Ag-Zn batteries have historically faced the challenge of poor cycling stability, rooting in issues associated with Ag cathode dissolution and Zn anode dendrites. Herein, we present a pioneering decoupled Sn-Ag cell, which features two chambers separated by a cation-exchange membrane, containing a dendrite-free Sn metal anode immersed in an alkaline anolyte, and an Ag nanowires/carbon nanotube 3D thick-network cathode in a neutral catholyte. Benefiting from the achieved high electroplating/stripping stability of the metallic Sn anode in the alkaline electrolyte and the electrochemical reversibility of the Ag/AgCl cathode redox couple in the neutral electrolyte, the assembled decoupled Sn-Ag cell demonstrates superior cycling stability, retaining 82.4% of its initial capacity even after 4000 cycles (2 mA cm-2), significantly outperforming both the contrastive decoupled Ag-Zn cell (1500 cycles) and conventional alkaline Ag-Zn batteries (<100 cycles). Furthermore, through the integration of the decoupled Sn-Ag battery with solar cells and power management circuits, an intelligent power system of photovoltaic charging and energy storage was designed, demonstrating its practical viability through maintenance-free charging-discharging during day-night cycles. This research not only significantly increases the lifespan of Ag-batteries with an ultra-flat voltage platform but also opens avenues for the decoupled design of a wide variety of aqueous battery systems.

An Ionic Liquid Supramolecular Gel Electrolyte with Unique Wide Operating Temperature Range Properties for Zinc-Ion Batteries

Zinc-ion batteries are promising candidates for large-scale energy storage. The side reactions of the hydrogen evolution reaction (HER) and zinc dendrite growth are major challenges for developing high-performance zinc-ion batteries. In this paper, a supramolecular gel electrolyte (BLO-ILZE) was self-assembled in an ionic liquid (EMIMBF4) with zinc tetrafluoroborate (Zn(BF4)2) on the separator in situ to obtain a gel electrolyte used in zinc-ion batteries. BLO-ILZE is demonstrated to significantly enhance conductivity over a broad temperature range between -70 and 100 °C. Interestingly, through testing and fitting, it is found that the supramolecular gel electrolyte satisfies the liquid state law over a wide temperature range, and even achieves high conductivity (2.12 mS cm-1) at -40 °C. It is equivalent to the conductivity of aqueous zinc-ion batteries (ZnSO4/H2O) at -10 °C, which is 2.33 mS cm-1. Moreover, the supramolecular gel electrolyte can effectively inhibit the HER, thus exhibiting a longer lifetime in Zn/Zn cells for 3470 h at 1 mA cm-2 compared to the aqueous zinc-ion batteries with the Zn(BF4)2 aqueous electrolyte (400 h at 1 mA cm-2). The assembled V2O5/BLO-ILZE/Zn full cells also showed cycling performance, with 5000 cycles at 0.5 mA g-1 at room temperature, a capacity of 98%, and a coulombic efficiency of about 100%.

Advancements in aqueous zinc-iodine batteries: a review

Aqueous zinc-iodine batteries stand out as highly promising energy storage systems owing to the abundance of resources and non-combustible nature of water coupled with their high theoretical capacity. Nevertheless, the development of aqueous zinc-iodine batteries has been impeded by persistent challenges associated with iodine cathodes and Zn anodes. Key obstacles include the shuttle effect of polyiodine and the sluggish kinetics of cathodes, dendrite formation, the hydrogen evolution reaction (HER), and the corrosion and passivation of anodes. Numerous strategies aimed at addressing these issues have been developed, including compositing with carbon materials, using additives, and surface modification. This review provides a recent update on various strategies and perspectives for the development of aqueous zinc-iodine batteries, with a particular emphasis on the regulation of I2 cathodes and Zn anodes, electrolyte formulation, and separator modification. Expanding upon current achievements, future initiatives for the development of aqueous zinc-iodine batteries are proposed, with the aim of advancing their commercial viability.