A zinc battery without an anode that could one day store renewable energy

Renewable energy sources, such as wind and solar power, could help reduce global dependence on fossil fuels. But first, power companies need a safe and economical way to store energy for later use. Massive lithium-ion batteries can get the job done, but they suffer from safety concerns and limited lithium availability. Now researchers report in ACS ‘ Nano Letters have produced a prototype anode-less zinc-based battery that uses low-cost and naturally abundant materials.

Zinc-based aqueous batteries have already been explored for grid-scale energy storage due to their safety and high energy density. In addition, the materials used to make them are naturally abundant. However, the rechargeable zinc batteries developed so far have required thick zinc metal anodes, which contain a large excess of zinc which increases the cost. Additionally, the anodes tend to form dendrites – crystalline projections of metallic zinc that deposit on the anode during charging – which can short circuit the battery. Yunpei Zhu, Yi Cui and Husam Alshareef wondered if a zinc anode is really needed. Drawing on previous explorations of “anode-less” lithium and sodium-metal batteries, the researchers decided to manufacture a battery in which a zinc-rich cathode is the only source of zinc coating on a copper current collector.

In their battery, the researchers used a manganese dioxide cathode that they pre-intercalated with zinc ions, an aqueous solution of zinc trifluoromethanesulfonate electrolyte, and a copper foil current collector. During charging, the zinc metal is plated onto the copper foil and during discharging, the metal is removed, releasing electrons which power the battery. To prevent the formation of dendrites, the researchers covered the copper current collector with a layer of carbon nanodisks. This layer promoted uniform zinc plating, thereby preventing dendrites, and increased the efficiency of zinc plating and stripping. The battery showed high efficiency, energy density and stability, retaining 62.8% of its storage capacity after 80 charge and discharge cycles. The anode-less battery design opens up new directions for the use of aqueous zinc-based batteries in energy storage systems, the researchers say.