Why Do Electric Vehicles Spontaneously Combust?
2 Answers
Here is an introduction to the causes of spontaneous combustion in electric vehicles: 1. The sharp surface of lithium dendrites: Lithium dendrites have very sharp surfaces that can easily pierce the separator. Piercing the separator can cause an internal short circuit in the battery (both positive and negative electrode materials and electrons can pass through the separator). After a short circuit, the chemical reaction speed inside the battery accelerates, producing more heat. The increased heat raises the internal temperature of the battery, causing materials that normally do not react, such as the electrolyte, to participate in the reaction, thereby generating even more heat. When the heat generated exceeds the designed heat dissipation capacity, it can lead to thermal runaway, ultimately resulting in spontaneous combustion. 2. Battery structure explanation: During the charging process, lithium ions continuously embed into the "slots" in the graphite anode. When fully charged, most of the "slots" in the graphite anode are occupied. If charging continues at this point, lithium ions moving to the anode surface will combine with electrons but find no available "slots" to embed into the anode material. The unembedded lithium can only accumulate on the anode surface, precipitating in the form of crystals. As more accumulates, lithium dendrites form.
I understand that most electric vehicle fires actually stem from battery issues. Thermal runaway inside lithium batteries is the main cause, such as separator damage leading to short circuits between the positive and negative electrodes, which generates instant heat and triggers a chain reaction. In some cases, aging batteries can have internal materials precipitate and form dendrites, which pierce the separator and cause internal short circuits. Collision accidents that crush the battery pack or extreme high temperatures and prolonged exposure to sunlight without timely heat dissipation can exacerbate the situation. High-power fast charging can also lead to localized overheating of battery cells. Manufacturers now use liquid cooling systems and thermal insulation designs to mitigate these risks, but it's best to avoid charging in high-temperature conditions during daily use. If you smell burning or see a dashboard warning, immediately cut off the power and move away from the vehicle.