Post by account_disabled on Feb 24, 2024 22:17:51 GMT -6
Rechargeable aqueous zinc batteries are finding their niche in stationary storage applications where safety, cost, scalability and carbon footprint are most important. However, zinc-ion batteries generally show lower Coulombic (charging) efficiency than state-of-the-art lithium-ion batteries.
Now, researchers at Oregon State University have developed a new electrolyte that increases the charging efficiency of the zinc-based battery to nearly %. The research is part of the ongoing global search for new chemical batteries capable of storing renewable solar and wind energy into the power grid for use when the sun isn't shining and the wind isn't blowing.
“The breakthrough represents a significant step forward in making zinc metal batteries more accessible to consumers,” said Xiulei “David” Ji of the OSU College of Science. “These batteries are essential for the installation of additional solar and wind farms. Additionally, they offer a safe and efficient solution for home energy storage, as well as energy storage modules for communities that are vulnerable to natural disasters.”
Relying on a metal that is safe and abundant, zinc-based batteries are energy dense and are considered a potential alternative for grid energy storage to the widely used lithium-ion batteries, the production of which depends on the reducing 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 from landfills . Additionally, the electrolytes in lithium-ion batteries typically dissolve in flammable orga C Level Executive List nic solvents that often decompose at high operating voltages. Other safety concerns include dendrites, which resemble small trees growing inside a battery.
“Zinc batteries are one of the leading candidate technologies for large-scale energy storage,” Ji said. “Our new hybrid electrolyte uses water and a common battery solvent, which is non-flammable, cost-effective and has a low environmental impact. The electrolyte is made from a dissolved mixture of inexpensive chloride salts, the main one being zinc chloride.”
He further said that the cost of electricity delivered by a storage facility consisting of zinc batteries could only be competitive with electricity produced from fossil fuels if the battery has a long cycle life of thousands of cycles.
However, until now, the life cycle has been limited by the poor reversibility performance of the zinc anode. Zinc cations in the electrolyte gain electrons and deposit on the surface of the anode during charging, while the plated anode gives up electrons for the workload by dissolving in the electrolyte during discharging.
“This process of electroplating and dissolution is often unfortunately irreversible,” Ji said. “That is, some electrons used in the coating cannot be recovered during the discharge. “This is a problem in an area known as Coulombic efficiency.”
The new electrolyte developed by Ji and collaborators, including scientists from the Massachusetts Institute of Technology, Penn State, and the University of California, Riverside, enabled a Coulombic efficiency of %.
“The main challenge with zinc batteries is that the zinc reacts with water in the electrolyte to generate hydrogen gas in what is called a hydrogen evolution reaction,” Ji said . “This parasitic reaction causes a short life cycle and is also a potential safety hazard.”
However, the new electrolyte restricts the reactivity of water and almost shuts down the hydrogen evolution reaction by forming a "passivation layer" on the anode surface.
“Furthermore, 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 progress reported here heralds the near-future commercialization of zinc metal batteries for large-scale grid storage.