Renewable sources of energy, like solar and wind power, could promote a decrease in the world’s dependence on fossil fuels. However, power companies first require a safe, economical means to store the energy for eventual use.
Although huge lithium-ion batteries can perform this task, they pose safety issues and are hampered by the drawback of limited availability of lithium. At present, a team of researchers has developed the prototype of an anode-free, zinc-based battery that works using economical, naturally abundant materials. The results of the study have been published in ACS’ Nano Letters.
Scientists have previously explored aqueous zinc-based batteries for grid-scale energy storage due to their high energy density and safety. Moreover, the materials employed to make these batteries are naturally abundant.
But the rechargeable zinc batteries developed to date have necessitated thick zinc metal anodes, which include lots and lots of zinc, thereby increasing the associated cost. Furthermore, the anodes are susceptible to the formation of dendrites, which are crystalline projections of zinc metal that get deposited on the anode when the battery is charged. The dendrites can cause short-circuit of the battery.
Researchers Yunpei Zhu, Yi Cui, and Husam Alshareef were curious whether a zinc anode was indeed required. They drew inspiration from previous analyses of “anode-free” lithium and sodium-metal batteries and decided to develop a battery where a zinc-rich cathode is the only source for zinc plating onto a copper current collector.
The researchers’ battery included a manganese dioxide cathode pre-intercalated with zinc ions, an aqueous zinc trifluoromethanesulfonate as the electrolyte solution, and a copper foil as the current collector. When the battery is charged, zinc metal is plated onto the copper foil, and when it gets discharged, the metal is stripped off, thereby discharging electrons that power the battery.
The copper current collector was coated with a layer of carbon nanodisks to prevent the formation of dendrites. This layer supported the uniform plating of zinc, thus inhibiting dendrites, and enhanced the efficiency of zinc plating and stripping.
The new battery exhibited high efficiency, stability, and energy density. It retained 62.8% of its storage capacity even after 80 charging and discharging cycles. According to the researchers, the anode-free battery design paves a new path for the use of aqueous zinc-based batteries in energy storage systems.
This study was financially supported by King Abdullah University of Science and Technology.
Zhu, Y., et al. (2021) An Anode-Free Zn–MnO2 Battery. Nano Letters. doi.org/10.1021/acs.nanolett.0c04519.