A new solvent-relay strategy to design better electrolytes for lithium-ion batteries
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Lithium-ion batteries (LiBs) are currently the most widely used rechargeable batteries worldwide, powering countless portable electronics, as well as hybrid and electric vehicles. While they are known to have notable advantages over other rechargeable batteries, particularly high energy densities, engineers have been trying to further improve their stability, safety and durability.
Researchers at the Chinese University of Hong Kong recently introduced a promising strategy to design new electrolytes for LiBs. Using this strategy, which was outlined in a paper published in Nature Energy, they developed a new electrolyte that could boost the durability of high-voltage LiBs, while also reducing the risk of overheating and fires.
"The inspiration for this work came from a simple but often overlooked idea," Yi-Chun Lu, senior author of the paper, told Phys.org.
"Most electrolyte studies focus on electrochemical behavior—how ions move and react—but every chemical reaction also involves heat absorption or release, something we all learn in basic chemistry. This made us wonder: what if we studied battery reactions from a thermal perspective instead? After all, heat generation and accumulation are at the heart of many safety issues in batteries."
When the temperature inside a LiB cell significantly increases, the battery can catch fire or even explode. As part of their recent studies, Lu and his colleagues set out to better understand how electrochemical reactions are linked to the generation of heat in batteries, as this could help them to design safer and intrinsically stable batteries.
"The driving force behind our study was to address thermal safety at its chemical roots," explained Lu. "In battery research, optimizing one parameter often comes at the expense of another. It's a bit like balancing on a seesaw: improving one end often tips the other. When we push for higher performance, safety is often compromised, and vice versa. Our idea was to break this long-standing trade-off."
Using two solvents to create safer LiBs
To improve the performance of batteries, energy engineers typically explore chemical reactions between their underlying components at room temperature. In contrast, to increase their safety, they try to prevent components from reacting in undesirable ways at high temperatures.
The key objective of the recent study by Lu and his colleagues was to design an electrolyte that would exhibit different behaviors at different temperatures, retaining its stability at room temperature and yet preventing a battery from catching fire at high temperatures. To achieve this, they mixed two different solvents, substances that dissolve the lithium salts in LiBs to release ions, which have distinct properties.
"As temperature rises, one solvent effectively 'hands off' the lithium ion to the other—much like a relay race—allowing the electrolyte's structure and reactivity to shift with temperature," said Lu. "We infused this solvent-relay electrolyte into commercial dry cells and compared them with cells using commercial carbonate-based electrolytes."
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A new thermally stable electrolyte
Using their proposed strategy, the researchers created a new electrolyte that they then tested in a widely used type of LiB cells, known as pouch cells. Notably, they found that the resulting cells exhibited excellent electrochemical performance and thermal stability.
To further assess the safety of the cells, Lu and his colleagues performed a so-called nail penetration test, which mimics a real-world scenario in which a battery cell might be punctured, potentially prompting an explosion or fire. Remarkably, the temperature of their battery rose by only about 3.5 °C, after it was punctured, while commercial pouch cells exceeded temperatures of 500 °C.
"Our work tackles battery safety from the electrolyte perspective, which we believe holds great practical potential," said Lu.
"The electrolyte we developed can be directly infused into existing commercial dry cells without redesigning the battery structure, making it highly compatible with current manufacturing processes. We demonstrated its performance in nickel-rich ternary (NCM) lithium-ion batteries, which are known for their high energy density but also their tendency toward thermal runaway, leading to fire or explosion."
Paving the way for safe high-energy LiBs
The strategy introduced by these researchers could soon be used to design other promising electrolytes that could further improve the thermal stability and safety of LiBs. This could in turn help to further increase the energy-density of LiBs, extending the battery life of electronics and electric vehicles, without compromising their safety.
"In reality, every component in a battery—the cathode, separator, and anode—plays a crucial role in determining its overall behavior," added Lu.
"By tailoring these components, we aim to achieve comprehensive safety without compromising performance. In addition, we are expanding our approach beyond lithium-ion systems to explore sodium-ion and other emerging chemistries, where the same principles of intrinsic safety can be applied.
"Our long-term goal is to establish a general design framework for safe, high-energy batteries across different energy-storage technologies."
Written for you by our author Ingrid Fadelli, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
More information: Yue Sun et al, Designing safe and long-life lithium-ion batteries via a solvent-relay strategy, Nature Energy (2025). DOI: 10.1038/s41560-025-01888-5.
Journal information: Nature Energy
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