25 September, 2025
Lithium-ion (Li-ion) batteries have long dominated the market for portable electronics, electric vehicles, and grid energy storage. A new generation of batteries using aqueous electrolytes offers compelling advantages for large-scale applications, including lower cost, improved safety, and environmental sustainability. However, parasitic chemical reactions continue to limit their cycle life.
To better understand these limitations, researchers at KAUST are developing advanced analytical tools to precisely identify the root causes of chemical degradation in aqueous batteriesarticle. " id="return-reference-1" href="https://discovery.kaust.edu.sa/en/article/26051/the-right-salt-supercharges-battery-lifespan/#reference-1">[1].
“Even in established battery chemistry, there are still mysteries to solve. By applying new investigative tools, we can uncover hidden mechanisms that determine battery performance,” says Yunpei Zhu, the lead author of the study. “Understanding the ‘why’ behind these processes lays the foundation to designing cheaper, safer, and longer-lasting batteries.”
A typical rechargeable battery includes a liquid electrolyte into which positively charged ions of a metal, such as lithium, sodium, or zinc, are dissolved. When the battery is charged, the ions capture electrons from the surface of an electrode — a process called reduction — and the metal is deposited onto the electrode in its solid form. During discharging, the reverse chemical reaction — oxidation — returns the metal back into solvated ions in the electrolyte.
One factor affecting the lifetime of a battery is the shape and texture of the solid metal electrodeposited on the electrode. For example, needle-like structures can grow on the electrode surface. These dendrites reduce the amount of useful metal, short circuit the battery, causing failure, overheating, or a fire, which represents a major safety concern.
Zhu and his KAUST co-workers investigated these parasitic reactions using a combination of advanced nuclear magnetic resonance, electron microscopy, ultrafast electrochemical experiments, and simulations. Taking zinc as a model metal, they tested five different zinc salts in a water-based, or aqueous, electrolyte: zinc sulfate, zinc perchlorate, zinc chloride, zinc triflate, and zinc bis(trifluoromethanesulfonyl)imide. Each salt uses a different type of negatively charged ion, or anion, in the reaction.
Their analysis indicated that low reversibility in batteries arises from the free water molecules in the aqueous electrolyte, but that these could be reduced by the correct choice of anion. “We used our advanced techniques to watch, at the molecular level, how water molecules behave in battery electrolytes,” explains Zhu. “By comparing different salts, we discovered that certain ions can ‘calm’ the motion of water molecules — and this subtle control greatly improves the performance and lifespan of metal anodes in aqueous batteries.”
Read more at KAUST Discovery.