A breakthrough battery technology could vastly improve the safety of batteries used for electric vehicles (EVs) and could enhance the stability of energy grids, scientists say.
Researchers made the breakthrough while developing solid-state sodium-ion (Na-ion) batteries, which could one day supplement and replace the lithium-ion (Li-ion) batteries used in many everyday devices today.
Li-ion batteries, the dominant battery technology found in products ranging from the phones in your hand to electric cars, can suffer from a process known as "thermal runaway." This occurs when a battery experiences a short circuit or physical damage, which sparks a self-sustaining chain reaction that greatly increases heat inside the cells.
Commercial Li-ion batteries also typically contain organic liquid electrolytes, which are an essential component for energy density, as well as efficient charging and discharging. These liquid electrolytes are highly flammable and can lead to batteries catching fire or even exploding when damaged.
Na-ion batteries could be a safer alternative because they contain more stable cathode materials and sodium ions have less electrochemical potential than lithium ions, making them less prone to thermal runaway.
The downside is that Na-ion batteries have a relatively low energy density compared to Li-ion batteries, meaning that they last less time between charges. In addition, Na-ion batteries may presently degrade faster, resulting in a lower overall lifespan. Both of these factors have historically held Na-ion batteries back from becoming mainstream.
But as outlined in the new research, scientists produced a solid material containing sulfur and chlorine that assists conductivity in a similar manner to liquid electrolytes while providing far superior stability. The new battery exhibited a Coulombic efficiency of 99.26% after 600 charging cycles at 0.1C (a 10-hour discharge), nearing the 99% or more that lithium batteries achieve.
Challenging lithium dominance
"We replaced the liquid electrolyte in the battery into a solid-state electrolyte — it’s non-flammable," Yang Zhao, professor in the Department of Mechanical and Materials Engineering at Western University, said in a video uploaded to YouTube.
The team also used the Canadian Light Source, Canada's national synchrotron facility, to examine the movement of ions inside their solid electrolyte, which confirmed their results.
"These X-ray tools allow us to see the local chemical environment, ion pathways, and bonding structures in ways that regular lab instruments can’t," Zhao said in a further statement. "They’re absolutely essential for developing solid-state battery materials."
The new battery technology could help lead to the widespread use of Na-ion batteries, particularly for critical workloads currently filled by more volatile Li-ion batteries, the researchers said. Next, they will have to demonstrate their approach provides the right balance between safety and energy density, as well as a manufacturing method that can be scaled to meet the immense demand for batteries seen around the world.
Despite accounting for around 70% of the world’s rechargeable batteries, Li-ion batteries are primarily used in just a handful of critical applications.
For example, recent International Energy Agency (IEA) data found that the energy sector accounts for over 90% of Li-ion demand.
Currently, battery energy storage systems (BESS) at a national level are under increased scrutiny, particularly after repeated fires at California BESS sites, and require the construction of fire suppression systems. Na-ion could help ease these concerns and speed up the deployment of BESS, which stores the intermittent supply of renewable energy to be delivered later on demand.
Because sodium is plentiful compared with lithium, the mass production of Na-ion batteries could greatly reduce the overall cost of the battery supply chain.
Na-ion batteries also come with the added benefit of being easier to recycle than Li-ion batteries, as covered in a 2023 study, because they contain fewer hazardous materials and no heavy metals.
A number of well-known car brands are already working on Na-ion batteries. In April, the world’s largest battery manufacturer, Contemporary Amperex Technology Co., Limited (CATL), announced that it is mass-producing Na-ion batteries using its new "Naxtra" battery platform. The product is expected to be used in cars from 2026. Chinese auto giant BYD is also developing Na-ion batteries for grid-scale storage purposes.
