An anode-free zinc battery that can one day store renewable energy

Renewable energy sources, such as wind and solar, can help reduce the world’s dependence on fossil fuels. But first, power companies need a safe, cost-effective way to store energy for later use. Massive lithium-ion batteries can do the job, but they suffer from safety issues and limited availability of lithium. Now ACS researchers report ‘ Nano Letters made a prototype of an anode-free, zinc-based battery that uses inexpensive, naturally abundant materials.

Zinc-based aqueous batteries were previously investigated for storing energy on the scale because of their safety and high energy density. In addition, the materials used to manufacture it are naturally plentiful. 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. The anodes also tend to form dendrites – crystal projections of zinc metal that settle on the anode during charging – which can short-circuit the battery. Yunpei Zhu, Yi Cui and Husam Alshareef wondered if a zinc anode was really needed. The researchers were inspired by previous investigations into “anode-free” lithium and sodium metal batteries and decided to make a battery in which a zinc-rich cathode is the only source of zinc plating on a copper current collector.

In their battery, the researchers used a manganese dioxide cathode that pre-charged them with zinc ions, an aqueous zinc trifluoromethanesulfonate electrolyte solution and a copper foil current generator. During charging, zinc metal is plated on the copper foil and during discharge, the metal is stripped, releasing electrons that supply power to the battery. To prevent dendrites from forming, the researchers covered the copper current collector with a layer of carbon nanodiscs. This layer promotes uniform zinc plating, which prevents dendrites, and increases the efficiency of zinc plating and stripping. The battery showed high efficiency, energy density and stability and maintained 62.8% of its storage capacity after 80 charging and discharging cycles. The anode-free battery design opens up new directions for the use of aqueous zinc-based batteries in energy storage systems, the researchers say.