A new electrolyte has been developed by scientists under the direction of a researcher at Oregon State University. This new electrolyte improves the efficiency of the zinc metal anode in zinc batteries to nearly 100 percent, paving the way for a lithium-ion battery replacement for large-scale energy storage.
The study is part of a worldwide search for new battery chemistry that can store renewable solar and wind energy on the electric grid so that it can be used when the sun isn’t shining or the wind isn’t blowing.
OSU College of Science professor Xiulei “David” Ji, along with HP Inc. and GROTTHUSS Inc., a spinoff company from Oregon State that published their findings in Nature Sustainability.
Ji stated, “The breakthrough represents a significant step toward making zinc-metal batteries more readily available to consumers.” For further wind and solar farms to be constructed, these batteries are absolutely necessary. In addition, they provide energy storage modules for communities that are susceptible to natural disasters and a safe and effective solution for home energy storage.”
“The discovery represents a significant step forward in making zinc metal batteries more accessible to consumers. These batteries are required for the construction of new solar and wind farms. Furthermore, they provide a safe and efficient alternative for home energy storage, as well as energy storage modules for areas at risk of natural disasters.”
Xiulei “David” Ji of the OSU College of Science
Chemical energy is stored in a battery, which then converts it into electrical energy through reactions. Although there are many different kinds of batteries, the majority of them function in the same fundamental way and have the same fundamental components.
The electrolyte is the chemical medium that separates the electrodes and permits the flow of ions between them. Every battery has two electrodes: the anode, from which electrons flow into an external circuit, and the cathode, from which electrons are acquired from the external circuit.
Zinc-based batteries are thought to be a potential alternative for grid energy storage to widely used lithium-ion batteries, whose production is dependent on diminishing supplies of rare metals like cobalt and nickel. Because they rely on a metal that is safe and abundant, zinc-based batteries are energy dense. Nickel and cobalt are toxic as well, and if they leach from landfills, they can contaminate ecosystems and water sources.
Additionally, lithium-ion batteries’ electrolytes are frequently dissolved in organic solvents that are flammable and frequently decompose at high operating voltages. Dendrites, which look like tiny trees growing inside a battery, are another safety concern. They can penetrate the separator in the same way that thistles grow through driveway cracks, causing undesirable and sometimes dangerous chemical reactions.
Ji stated, “One of the leading candidate technologies for large-scale energy storage is zinc metal batteries.” Our brand-new hybrid electrolyte is made with water and a common battery solvent that is not flammable, cheap, or good for the environment. Zinc chloride is the most important and inexpensive chloride salt in the dissolved mixture that makes up the electrolyte.
According to Ji, a zinc battery-powered storage facility’s electricity can only compete with fossil-fuel-generated electricity if the battery has a long cycle life of thousands of cycles. However, the zinc anode’s poor reversibility has limited its cycle life to this point.
Ji explains that zinc cations in the electrolyte acquire electrons during charging and are plated on the anode surface. By dissolving into the electrolyte during discharge, the plated anode gives up electrons to complete the work.
Ji stated, “This zinc plating and dissolution process is frequently terribly irreversible.” Specifically, some plating electrons cannot be recovered during discharge. In a field known as “coulombic efficiency,” this is a problem.
The ratio of the total charge taken out of the battery to the charge put in over the course of a full cycle is known as the coulombic efficiency, or CE, and it is used to determine how effectively electrons are transferred in batteries. The CE of lithium-ion batteries can sometimes exceed 99%.
A CE of 99.95% was possible with the new electrolyte created by Ji and his team, which also included researchers from the Massachusetts Institute of Technology, Penn State, and the University of California, Riverside.
Ji stated, “The primary difficulty with zinc batteries is that zinc reacts with water in the electrolyte to generate hydrogen gas in what is known as a hydrogen evolution reaction.” In addition to having a short cycle life, this parasitic reaction poses a risk to safety.”
The new electrolyte, notwithstanding, limits water’s reactivity and almost shuts down the hydrogen development response by forming a “passivation layer” on the outer layer of the anode. In the 1990s, the initial commercialization of lithium-ion batteries was made possible by a passivation layer of a similar nature.
Ji attributes the discovery of the electrolyte’s atomic structure using femtosecond Raman spectroscopy to his OSU chemistry colleague Chong Fang and the discovery of the passivation mechanism to Alex Greaney at UC Riverside.
Ji continued, “Also, it is worth noting that the efficiency we measured was under severe conditions that do not conceal any damage caused by the hydrogen evolution reaction.” The advanced technology revealed here proclaims the not so distant future commercialization of the zinc metal batteries for enormous scope and framework capacity.”
More information: Heng Jiang et al, Chloride electrolyte enabled practical zinc metal battery with a near-unity Coulombic efficiency, Nature Sustainability (2023). DOI: 10.1038/s41893-023-01092-x
