How And Why Does An Electric Vehicle Battery Explode? Let's Find Out

In the last four days, four electric scooters have caught fire due to technical errors. Due to the frequency of such mishaps, people might hesitate to buy EVs.

According to news agency Reuters, lithium-ion batteries, whether used in electric vehicles or electronic devices, are prone to catch fire if they have been improperly manufactured or damaged or if the software that operates the battery is not designed properly.

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What are batteries made of?

First of all, let's understand what a battery is made of - cells, and these cells are just like an object which is filled with a particular form of energy. Now, since energy can neither be created or destroyed, however, it can convert its form.

The energy is stored in the form of electricity (movement of ions) in a battery, which race between two oppositely charged electrodes separated by a "separator".

Now, there are types of batteries - lead-acid and lithium-ion batteries. The only difference between the two of them is their energy density. When one ion of li-ion battery transfers from anode to cathode or cathode to anode, it carries almost thrice the energy than the lead-acid battery.

An electric scooter/vehicle has enough capacity (amount of energy stored) so that it can run a complete house with its power for three to four days without any problem. An EV battery contains a lot of energy which is enough to cause damage to the vehicle operator or people nearby.

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How do batteries catch fire?

The first thing to understand is that an explosion or fire doesn't necessarily need a lot of energy. What it takes is the least time frame to release every small amount of energy stored inside.

If a Li-ion battery stores 1kWh of storage capacity, it will be self-sufficient for combustion if all of that 1kWh releases in a matter of seconds. Every battery has an anode, cathode, and a separator in common, So, if an explosion happens, it is because of these three components only. The separator which separates the other two - anode and cathode - lets their ions transfer only, breaks or damage and then, the shortcircuit takes place which leads to an explosion.

With EV batteries, the primary cause of explosion of batteries is their separator. The main purpose of the separator is to keep the material of both anode and cathode away but continue the transfer of ions. However, due to market demand and advancement in technology, the separator has been made thinner and more thinner.

Despite separators lasting for very long, in such situations, even a single problem with the battery can lead to permanent damage. Since the separator is delicate in nature, it malfunctions due to any external pressure or internal chemical imbalance. While charging, batteries expand a little, and when discharged, they compress which further creates pressure on the separator, and it may fail to function properly. If the separator fails the moment the anode and cathode make contact, it leads to a shortcircuit which further leads to an explosion.

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So, basically, the failure of the separator is the main cause of battery failure and explosion. But what causes the damage of the separator in the first place?

How does a battery separator get damaged?

There are two reasons why battery separators get damaged - electrical instability and external shocks which can damage a thin separator.

Electrical instability happens when they battery is charged or discharged more than the rated capacity. With rechargeable batteries, there is are two ratings - undervoltage and overvoltage. However, if the battery exceeds either of the two ratings while charging, the separator gets damaged.

The other reason, external shock, happens when the battery falls from a certain height, stretch or buries. External shocks may not cause potential damage to the battery immediately. However, after a certain time, it will either explode or cause serious damage.

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When will a battery explode?

Internal electrical misbalance is when an electric vehicle goes through deep discharge or overcharging cycles more often. This leads to an explosion.

While overcharging, the battery gets heated up, and the thing separator gets majorly impacted by the heat energy which directly damages the separator and ends in an explosion.

During deep discharging, the anodic and cathodic reactions create crystal-like material around the separator. When the battery is allowed to charge till the same capacity it creates, the more heat is produced inside the battery which damages the separator.

Since the battery separator is highly volatile to external shocks, an electric vehicle accident will surely result in an explosion because it is usually is extremely thin and can¡¯t resist any shocks.

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