Why Do Lithium-Ion Batteries Catch Fire?

2026-04-04 | Eric

Lithium-ion batteries have the advantages of high energy density, long cycle life, low self-discharge rate, and no memory effect. However, if the production process is not strictly controlled or they are used improperly, there is a risk of fire or explosion.

So, why do lithium-ion batteries catch fire? Let’s think about what fire is and how it is generated. Some may say fire is just a phenomenon that our eyes can see. That's true, but there is also a violent oxidation reaction happening in places we can't see, commonly called combustion. As the knowledgeable would say, combustion requires a fuel, an oxidizer, and reaching the ignition point. Lithium-ion batteries don’t seem to be flammable, do they?

1. What components inside lithium-ion batteries could trigger a fire?

Be careful! Don’t be deceived by its exterior—it's important to understand its "heart". The widely used lithium batteries are made up of four components: the positive electrode, the negative electrode, the separator, and the electrolyte. The positive electrode consists of aluminum foil combined with active materials (such as lithium iron phosphate, ternary materials, etc.), while the negative electrode is copper foil combined with graphite (a good conductor of heat and electricity). The separator is a high-quality plastic film that helps prevent interference with internal interactions (mainly the migration of Li+), and it has pores to allow these exchanges. And what does it exchange through? You may be wondering, and here’s where the electrolyte comes in. Once the battery is assembled, a liquid electrolyte is injected to allow full contact between the positive electrode, separator, and negative electrode, forming a cohesive system. The electrolyte used today to enhance lithium-ion battery performance is an organic electrolyte, similar to gasoline in a car’s fuel tank—it both delivers energy (by transferring ions) and poses a fire risk. Now you understand why lithium-ion batteries catch fire: inside, there is an organic electrolyte that’s similar to gasoline!

2. What is an organic electrolyte, and why is it so easily flammable?

Literally speaking, it’s like dissolving sugar in hot water to make sugar water—an organic electrolyte is an electrolyte dissolved in an organic solvent. Common organic solvents include EC (ethylene carbonate) and DMC (dimethyl carbonate). Why is it like gasoline? Because these organic solvents (EC, DMC, etc.) are inherently flammable, just like alcohol or gasoline at home. When exposed to high temperatures or flames, they ignite easily. Organic solvents can decompose at high temperatures, producing gases that can trigger a chain reaction. These gases primarily include carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethane (C2H6), ethylene (C2H4), and HF—many of which are highly flammable and toxic. This makes fires much more likely. If the positive electrode uses ternary materials, oxygen (O2) can be released under high temperature and pressure, which is why ternary batteries tend to catch fire and explode more than other material systems. With flammable materials, an oxidizer, and high temperatures from chain reactions, combustion becomes almost inevitable.

3. Since organic electrolytes are highly flammable, can they be replaced with aqueous electrolytes?

Sure, that’s possible, but if you replace them with aqueous electrolytes, lithium-ion batteries won’t perform as well—almost all of their advantages will disappear, including reduced energy density and shorter cycle life. This would be similar to lead-acid or nickel-based batteries. Using lead-acid batteries in portable electronic products feels awkward, and switching to nickel-based batteries means you can’t charge whenever you want. So, replacing organic electrolytes isn't as simple as it seems!

4. Why can't organic electrolytes just be replaced?

The benefits outweigh the drawbacks. First, organic electrolytes are highly compatible with many high-voltage positive materials, enhancing lithium battery performance (with higher energy density and better rate performance). Second, like aqueous electrolytes, organic electrolytes allow for free movement of ions, making it easy for Li+ to travel between the positive and negative electrodes during charging and discharging. Lastly, organic electrolytes are cost-effective. It's not that they can't be replaced, but currently, there are no better alternatives. Researchers are exploring solid-state electrolytes, which don’t behave like oil or water but still function as electrolytes. Solid-state batteries consist of a positive electrode, negative electrode, solid-state electrolyte, and a separator (which may or may not be present). However, solid-state batteries have a major challenge called interfacial impedance—simply put, it's difficult to achieve a perfect fit between solid materials, which affects the movement of Li+ between the electrodes. For now, lithium-ion batteries still prefer organic electrolytes, and under extreme conditions, they may catch fire or explode.

Safety Tip:

To reduce the safety risks of lithium-ion batteries and ensure their safe use, industry authorities have established safety standards for lithium-ion batteries in different fields. These standards specify the electrical and environmental safety requirements that lithium-ion batteries should meet under normal use and foreseeable misuse conditions, as well as the relevant protective functions the battery packs should have to prevent dangerous situations. When purchasing lithium battery products, it is recommended to choose those with good quality control and reliable safety assurance. Products of such quality are less likely to catch fire or explode.

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