Researchers from Kyungpook National University, KAIST, and ETRI have developed a nonflammable electrolyte design technology that maintains high energy density while improving fire safety.
The team said on the 21st that it had created a nonflammable electrolyte design technology that achieves both high energy density and fire safety. The joint research involved Professor Oh Jimin’s team in the Department of Smart Mobility Engineering at Kyungpook National University, Professor Seo Donghwa’s team in the Department of Materials Science and Engineering at KAIST, and Dr. Lee Myungju’s team at the Electronics and Telecommunications Research Institute (ETRI).
Lithium-ion batteries offer high energy density, but fire and thermal runaway risks have long been viewed as their weakness. High-nickel cathode batteries for high-performance electric vehicles are especially prone to fire under harsh driving conditions, making safety assurance a crucial challenge.
High-nickel cathodes are materials that store more energy in the same size by increasing the proportion of nickel. They are advantageous for extending EV driving range, but as the nickel content rises, the structure becomes less stable and the fire risk also increases. In other words, the more energy is packed in, the greater the threat to safety.
Thermal runaway is a phenomenon in which the temperature inside a battery rises rapidly and chemical reactions continue in a chain. Because the materials needed for the reaction keep being supplied within the battery, the internal reaction continues even when external flames are suppressed, making extinguishing difficult.
This is why it is difficult to extinguish battery fires with water or fire suppression agents. As long as oxygen is continuously generated inside the battery, external containment alone cannot easily stop the reaction. Beyond simply increasing firefighting equipment, a materials-based solution that prevents oxygen generation itself has been needed.
The research team identified a mechanism that suppresses oxygen generation, the main cause of thermal runaway. The flame-retardant additive they developed, called P2PFS, captures harmful oxygen released from the cathode during charging and converts it into a stable substance. In effect, it removes the material that feeds ignition before a fire can start. Differential scanning calorimetry (DSC) and mass spectrometry (MS) tests also experimentally confirmed that oxygen generation inside the battery was suppressed.
While many existing safety measures have focused on cooling the heat or slowing the spread of flames, this technology is differentiated by its approach of removing the chemical cause of ignition from inside the battery. Rather than reducing damage after an accident, it addresses the problem at the design stage so that the accident itself does not begin.
The team designed a nonflammable electrolyte system with no loss of battery lifespan by optimally mixing P2PFS with fluorinated additives (FEC), which are widely used in conventional electrolytes and are cost-effective.
In combustion tests evaluating ignition delay, the new electrolyte reduced flame duration to less than half of the previous level. It showed a near-nonflammable characteristic, with flames barely catching even when exposed to fire.
Performance verification was conducted under one of the most unstable conditions. The team applied the new electrolyte to a high-nickel cathode (NCM955) lithium battery, which becomes highly unstable in high-temperature and high-voltage environments. Even under severe operating conditions, the electrolyte did not break down and stably protected the cathode surface, maintaining more than 83% of its initial capacity after more than 200 rapid charge-discharge cycles.
The use of FEC is understood to reflect cost considerations. Rather than replacing the entire electrolyte with a new material, the team added the flame-retardant agent to an additive already widely used, reducing the burden of material sourcing and process changes.
In the battery industry, the trade-off between adding flame-retardant components and losing performance has long been cited as a barrier to commercialization. The results of this study are being viewed as a counterexample to that assumption, showing that safety and performance can be achieved at the same time.
The team also applied the technology to a commercial-scale 1Ah pouch cell, achieving successful validation. After more than 750 charge-discharge cycles in a large-capacity battery environment, it retained 85.2% of its initial capacity. Even in a nail penetration test, which simulates piercing a fully charged battery, the maximum temperature was controlled to around 49 degrees Celsius without fire or explosion.
Unlike small coin cells used in laboratories, a 1Ah pouch cell is a specification close to actual products. Because the material-level achievement was reproduced at the cell level, the result is seen as narrowing the gap between a paper technology and a manufacturing technology.
The penetration test is a validation method that artificially creates the worst-case scenario of internal short circuit. Passing this condition in a commercial-spec cell rather than a small laboratory cell supports the technology’s practical applicability.
Because the design is based on low-cost materials already widely used, it can reportedly be applied without major changes to the production process, increasing the likelihood of commercialization.
Professor Oh said the study went beyond developing a flame-retardant additive and “presented a thermodynamic design principle that controls oxygen reactions inside batteries.” He added that it “could be used as a next-generation electrolyte design platform applicable to a wide range of fields requiring high safety, such as electric vehicles, ESS, robots, drones, and future air mobility.”
The remaining step is broader verification. Since the researchers have said they plan to continue testing real-world applicability, whether the same results can be reproduced in mass-production-scale cells and under various temperature and operating conditions will likely determine commercialization.
The research was supported by the National Research Foundation of Korea (NRF) and the Korea Institute for Advancement of Technology (KEIT), and the results were published online in the international journal Small in the field of materials science. The corresponding authors are Professors Oh Jimin and Seo Donghwa, while the first authors are Dr. Lee Myungju and KAIST researcher Shin Wookseon.
From the perspective of consumers and facility operators, the significance of this technology lies in reducing the probability of accidents itself. It is said to be especially useful in environments where fire can cause major damage, such as underground parking lot charging or large-scale ESS operation, because it blocks the cause of ignition at the design stage.
As fire concerns surrounding electric vehicles and ESS have been cited as obstacles to wider adoption, attention is now focused on whether this approach of controlling the cause of ignition during the design stage can change the direction of battery safety standards.