At the end of the 19th century, electric vehicles first emerged and once enjoyed widespread popularity. However, the 20th century saw them fall into decades of obscurity due to breakthroughs in internal combustion engine technology and the widespread availability of petroleum. It wasn't until the early 21st century, driven by the energy crisis and environmental consensus, with the maturation of lithium-ion battery technology as a core opportunity, that the industry experienced a revival. Manufacturers like Tesla pushed the intelligentization and premiumization of electric vehicles, while government subsidies and policies in various countries accelerated their adoption. The global automotive industry is now stepping into a new electrified era.
In China, the development of electric vehicles over the past decade has achieved leapfrog growth. Annual production surged from about 13,000 units in 2012, to over 1 million in 2018, and exceeded 12 million (12.888 million) in 2024, making China the first country in the world where annual new energy vehicle production broke the 10-million-unit mark. This success is attributed to policy support, technological breakthroughs (such as increased battery energy density and the popularization of fast charging), and a well-established supply chain. The market share of new energy vehicles grew from less than 1% to nearly 40%, surpassing traditional internal combustion engine vehicles for many consecutive months, marking China's transition from a large automotive nation to a powerful automotive country.
However, beneath the massive growth in electric vehicle production lurk numerous safety concerns: the issue of electric vehicle fires.
This article will introduce several cases of electric vehicle fires, including their causes. It will provide a detailed analysis of the potential reasons behind electric vehicle battery fires and the future improvement measures for electric vehicle batteries to address the fire risk.
Figure 1 pictures of fires in various car brands
Li (Leading Ideal) Auto: On October 23, 2025, in Shanghai, China, sparks emerged from the undercarriage of a normally driving Li Auto MEGA, after which the vehicle was rapidly engulfed in flames.
Xiaomi Auto: On October 13, 2025, in Chengdu, Sichuan, China, a speeding Xiaomi SU7 lost control and crashed into a green belt, causing the vehicle to catch fire.
NIO: On October 13, 2025, in Dali, Yunnan, China, a NIO ET7 that had not experienced any collision made abnormal noises before the passenger compartment caught fire.
Avatar technology: On October 5, 2025, in Ningde, Fujian, China, a parked Avatar 06 suddenly caught fire, starting from the passenger seat area.
XPeng motors: On January 7, 2025, in Jinan, Shandong, China, a parked XPeng G3 (already discontinued) caught fire in the front compartment in an underground garage, causing a larger blaze.
BYD: On September 14, 2025, in Beijing, China, a BYD Seal 06 driving near an airport emitted a burning smell and smoke from the air vents before catching fire.
AITO: On August 27, 2024, in Ganzhou, Jiangxi, China, a charging and parked AITO M5 unexpectedly caught fire in the front row.
Based on the fire phenomena in the cases above, preliminary inferences can be made about the causes. The fires in the Li Auto and Xiaomi Auto cases were intense and virtually impossible to extinguish, leaving only the vehicle frame. Generally, when lithium-ion batteries catch fire, flames develop quickly and are difficult to put out, so it can be preliminarily judged that these two brands experienced battery fires. For the other brands, the fire origins were in the passenger compartment or front engine compartment. The BYD vehicle exhibited a precursor burning smell, making it highly probable that other items caught fire first, leading to the vehicle fire. Subsequent official reports on the causes largely align with these speculations: the Xiaomi car crashed into a green belt, causing battery failure and fire. The cause for the Li Auto MEGA fire has not been officially announced, but the extremely rapid ignition (within 10 seconds) strongly suggests a battery pack fire.
Currently, conventional electric vehicles use lithium-ion batteries, primarily divided into two major categories: lithium iron phosphate (LFP) batteries and ternary lithium (NCM/NCA) batteries. The root cause of fire for both types is "thermal runaway" of the battery.
When a vehicle is involved in a collision, the impact intrudes into the battery compartment, potentially causing the battery separator to rupture or the casing to deform. This can lead to direct contact between the positive and negative electrodes, causing a short circuit. The short circuit causes the battery's internal temperature to rise sharply. Excessively high temperatures lead to the decomposition of the electrolyte, producing flammable gases. The graphite anode, if exposed to air at high temperatures, could potentially explode. A battery pack contains thousands of individual cells. If one cell enters thermal runaway, it can trigger a chain reaction, causing adjacent cells to also undergo thermal runaway. When the thermal runaway exceeds a critical, uncontrollable threshold, the fire spreads rapidly. In lithium batteries, this thermal runaway is irreversible and spreads very quickly, often occurring after an accident that causes severe deformation.
However, battery fires like the one in the Li Auto MEGA during normal driving are even more dangerous, as the fire can engulf the vehicle without the occupants' awareness, leaving virtually no time to escape. This is a scenario that all manufacturers must ensure does not happen before batteries leave the factory. The Li Auto MEGA battery fire incident reminds us that the safety testing standards for power batteries used in electric vehicles are still far from ensuring true safety.
Since the main cause of battery fires is short circuits or electrolyte leakage under various circumstances, essentially the breakdown of the battery's physical structure—such as current collectors being crushed by external force, internal lithium dendrites piercing the separator, or the casing breaking due to impact leading to electrolyte leakage—the primary improvement methods focus on three areas:
Coating the aluminum foil surface with high-temperature polymers (like PI, PET) or ceramic materials (like alumina) creates a composite foil. The surface becomes smoother with fewer burrs, which can reduce the growth of lithium dendrites. If porous ceramics are used, electrolyte distribution can be improved, avoiding localized high current density that induces dendrite growth. Battery manufacturer tests indicate that improved batteries, after 500 cycles at 1C rate, show about a 40% reduction in lithium dendrite length. The composite PI aluminum foil has higher toughness compared to pure aluminum foil, mitigating external forces during penetration from impacts, effectively preventing internal short circuits caused by current collector rupture. Automaker data shows that batteries using composite aluminum foil experience a 2-3 second delay in voltage drop after nail penetration, and the thermal runaway temperature is reduced by over 50°C. Ceramics also have a higher melting point (exceeding 400°C) and a lower thermal expansion coefficient. Composite foil with ceramic coating can delay thermal diffusion and expansion at high temperatures. Ceramics are also resistant to electrolyte corrosion. Since copper foil reacting with electrolyte can produce gas leading to battery swelling, using a ceramic coating can also reduce battery swelling. Currently, CATL's Qilin Battery and BYD's Blade Battery have adopted composite aluminum foil and are in mass production. To ensure coating uniformity, sputtering coating—a semiconductor process—is required, increasing the process cost by at least 30%.
To prevent electrolyte leakage and combustion, there are two mainstream improvement approaches: developing solid-state electrolytes and developing non-flammable phosphate ester-based electrolytes.
Solid-State Electrolytes: These are ion conductors in solid form, characterized by being non-flammable, non-corrosive, and non-volatile, reducing the risk of battery thermal runaway and offering higher stability. They can withstand higher charging voltages, allow for thinner electrolyte layers, enabling more energy storage in the same volume, or freeing up space for safer module design.
Phosphate Ester-based Non-flammable Electrolytes: Research into using phosphate esters as solvents for non-flammable electrolytes is underway in several countries (US, Japan, South Korea, China) and is in the initial stages of industrialization. These electrolytes are non-flammable and high-voltage resistant. Their cost is 50%-100% higher than traditional carbonate-based electrolytes but significantly lower than solid-state electrolytes. Furthermore, they can use existing battery production equipment.
Placing an aerogel thermal runaway barrier between cells utilizes the material's ultra-low thermal conductivity to block heat transfer paths. Compared to traditional insulating materials like mica (thermal conductivity 0.2-0.6 W/m·K), aerogel has a thermal conductivity of 0.012-0.024 W/m·K. The time for heat to conduct through aerogel is more than three times longer than through mica. Moreover, aerogel only requires a thickness greater than 0.5mm to achieve efficient insulation. Tests show that using aerogel between cells results in only a 60°C temperature increase in adjacent cells after thermal runaway occurs in one cell.
Electric vehicles are becoming increasingly common. Numerous cases remind us that we cannot ignore the risks of electric vehicle battery fires and even explosions. Therefore, we need to pay more attention to battery improvements focused on safety. Continuous research by scientists is essential for advancements in solid-state electrolytes, non-flammable phosphate ester-based electrolytes, ceramic-coated composite aluminum foil, and aerogel thermal barriers. Although these improvements entail certain costs, this expenditure is absolutely necessary compared to the paramount importance of safety.
Thermal Runaway in Electric Vehicle Batteries
The lab focuses on solid-state battery research to overcome traditional lithium batteries' safety and energy density issues, supporting environmental sustainability. It develops innovative solid-state electrolytes, refines electrode materials, and investigates ion transfer and interface stability to revolutionize battery technology.
The electric vehicle battery industry is rapidly developing, focusing on technological innovation, market competition, and sustainability. Research hotspots include solid-state batteries, new types of electrolytes, BMS optimization, and recycling technologies. The environmental adaptability, safety, and economic viability of batteries are key research areas, and the industry is expected to undergo more innovation and transformation.
We specialize in battery preparation technology research, focusing on overcoming existing energy storage challenges by innovating in electrode materials, battery chemistry, and manufacturing processes to improve performance, enhance safety, and reduce costs. Sustainability and recycling technologies for batteries are also emphasized to mitigate environmental impacts and foster the growth of green energy.
