The availability of sustainable, inexpensive and efficient zinc batteries could aid in the scaling up of renewable energy storage, like wind energy. Credit: Oregon State University
Zinc metal batteries are a promising alternative to lithium-ion (Li-ion) batteries for large-scale energy storage, as zinc is an abundant resource and more environmentally friendly than the metals used in Li-ion batteries. However, the implementation of zinc batteries on a large scale has been limited due to their low efficiency, which is primarily due to chemical reactions between zinc and water in the battery electrolyte. A team of researchers from Oregon State University (OSU), in collaboration with scientists from the University of California Riverside, MIT, Penn State and HP Inc., has designed a new hybrid electrolyte for zinc batteries, which improves their Coulombic efficiency to nearly 100%.
Coulombic efficiency, which is the ratio of the total charge extracted from the battery to the charge put in over a full cycle, is reduced in zinc batteries due to the hydrogen evolution reaction, a reaction between zinc and water that produces hydrogen gas. The newly designed electrolyte prevents these reactions by forming a passivation layer on the surface of the battery anode. The electrolyte chemistry includes the common battery solvent dimethyl carbonate along with extra chloride salts, primarily concentrated zinc chloride (ZnCl2). The hybrid electrolyte is non-flammable, has a low environmental impact and is relatively inexpensive to produce, explained co-corresponding author Xiulei “David” Ji. The electrolyte’s atomic structure was characterized using femtosecond Raman spectroscopy at co-corresponding author Chong Fang’s lab in the Department of Chemistry at OSU.
Experiments showed that battery cells using the new electrolyte had a Coulombic efficiency of 99.95%, similar to that of Li-ion batteries, which typically have an efficiency over 99%. The battery did not show swelling or leaking after 500 deep cycles and exhibited an energy density of 100 Wh kg-1. In addition to shutting down the hydrogen evolution reaction, the passivation layer prevented the growth of dendrites, which are projections of metal that can pierce the electrolyte and cause battery failure. With the possibility to improve the efficiency and lifetime of zinc metal batteries, this development could enable a feasible, sustainable alternative to Li-ion batteries. This research was published in Nature Sustainability.
“This breakthrough represents a significant advancement toward making zinc metal batteries more accessible to consumers,” said Ji. “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.”
The availability of more environmentally friendly and inexpensive energy storage options can also aid in the reduction of fossil-fuel produced electricity by scaling up the storage of renewable energy in power grids.