Researchers have developed a safer lithium-ion battery by changing its electrolyte material, preventing fires when pierced or bent. This innovation could lead to mass production in the next few years. The design maintains compatibility with existing battery manufacturing.
Lithium-ion batteries, widely used in smartphones, laptops, and electric cars, typically consist of a graphite electrode, a metal oxide electrode, and an electrolyte made of lithium salt dissolved in a solvent. This liquid electrolyte enables ion flow for charging and discharging. However, puncturing the battery can create a short circuit, rapidly releasing stored chemical energy and causing fires or explosions through a process known as thermal runaway.
Thermal runaway occurs when negatively charged ions, called anions, break their bonds with lithium, generating heat that perpetuates the destructive cycle. To address this, Yue Sun at the Chinese University of Hong Kong and her colleagues introduced a new solvent, lithium bis(fluorosulfonyl)imide. This material bonds with lithium from the existing solvent only at higher temperatures, when thermal runaway begins. Crucially, anion bonds cannot form in this new electrolyte, halting the heat-release cycle.
In tests, a battery pierced with a nail using the new solvent saw its internal temperature rise by just 3.5°C, compared to over 500°C in conventional batteries. The modified batteries also retained 82 percent of their capacity after 4100 hours of use, matching current technology standards.
"The bad boy is the anion, which has a lot of bond energy – and it’s these bonds breaking that causes thermal runaway," says Gary Leeke at the University of Birmingham, UK. "It’s isolating the bad boy from that process. It’s a big leap in terms of battery safety."
Leeke suggests the findings could integrate into next-generation batteries, with mass production possible in three to five years. The research appears in Nature Energy (DOI: 10.1038/s41560-025-01888-5).