Scientists have developed a new electrolyte that raises the efficiency of the zinc metal anode in zinc batteries to nearly 100%, a breakthrough on the way to an alternative to lithium-ion batteries for large-scale energy storage.

The research is part of an ongoing global quest for new battery chemistries able to store renewable solar and wind energy on the electric grid for use when the sun isn’t shining and the wind isn’t blowing.

“The breakthrough represents a significant advancement toward making zinc metal batteries more accessible to consumers,” Xiulei “David” Ji of the OSU College of Science said. “These batteries are essential for the installation of additional solar and wind farms. In addition, they offer a secure and efficient solution for home energy storage, as well as energy storage modules for communities that are vulnerable to natural disasters.”

Every battery has two electrodes – the anode, from which electrons flow out into an external circuit, and the cathode, which acquires electrons from the external circuit – and the electrolyte, the chemical medium that separates the electrodes and allows the flow of ions between them.

Relying on a metal that’s safe and abundant, zinc-based batteries are energy dense and seen as a possible alternative for grid energy storage to widely used lithium-ion batteries, whose production relies on shrinking supplies of rare metals such as cobalt and nickel. Cobalt and nickel are also toxic and can contaminate ecosystems and water sources if they leach out of landfills.

Electrolytes in lithium-ion batteries are commonly dissolved in flammable organic solvents that often decompose at high operation voltages. Other safety concerns include dendrites, which resemble tiny trees growing inside a battery. They can pierce the separator like thistles growing through cracks in a driveway, leading to unwanted and sometimes unsafe chemical reactions.

Coulombic efficiency, or CE, is a measure of how well electrons are transferred in batteries, the ratio of the total charge extracted from the battery to the charge put in the over a full cycle. Lithium-ion batteries can have a CE in excess of 99%.

The new electrolyte developed by Ji and collaborators including scientists at Massachusetts Institute of Technology, Penn State and the University of California, Riverside, enabled a CE of 99.95%.

“Also, it is worth noting that the efficiency we measured is under harsh conditions that do not mask any damage caused by the hydrogen evolution reaction,” Ji added. “The breakthrough reported here heralds the near-future commercialization of the zinc metal batteries for large-scale grid storage.”

OSU’s Kyriakos Stylianou also took part in this research, which was supported by the National Science Foundation and the U.S. Department of Energy.