Common Reasons for the Explosion of Lithium-Ion Batteries

According to a US report in 2018, more than 25,000 overheating or fire incidents have been reported over a five-year period due to Lithium-Ion battery explosions. This has been a cause of concern among current and future EV owners. So what’s actually happening and why do batteries sometimes explode? Let’s find out in this blog.

A quick google search will provide multiple videos and images of Lithium-ion (Li-ion) batteries causing fires and explosions. Lithium-ion batteries are used everywhere today, primarily in electronics such as laptops, cell phones, cameras, and most importantly, in electric vehicles.

If Li-ion batteries are exposed to the wrong conditions, there is a slight chance of failure. Such a failure can have huge repercussions for large battery systems, therefore more investigations into these consequences are essential to implement better safety measures.

Before addressing the reasons for battery failure and the subsequent safety measures let us have a sneak peek at the Li-ion battery to check if it is intrinsically safe.

EV Battery Safety

A Li-ion battery stores and releases its electrical energy via electrochemical reactions. When electrical energy is drawn or released from the battery, lithium ions move from one electrode to the other. The electrodes are placed inside a liquid called an electrolyte, which facilitates the movement of ions. The electrolytes consist of lithium salt and organic solvents.

These organic solvents are the leading fire hazard in Li-ion batteries. Furthermore, the cathode(positively charged electrode) in the battery contains oxygen, which could be released if the battery is subjected to duress, e.g., internal short, excessive heat, and more.

To counter this, battery manufacturers have incorporated various battery safety measures. Here are some of them

• Pressure releasing vent holes

Batteries are fundamentally pressurized. Hence, they need an outer wall made of metal, which should have a pressure-sensitive vent hole. If the battery becomes very hot from overpressure (pressure buildup at 3,000 kPa), this vent will release the extra pressure and prevent other cells in the battery pack from catching fire.

• Separator which serves as a fuse

Most lithium-ion batteries employ a separator, which boasts good chemical stability, and excellent mechanical properties. It serves as a fuse when the battery heats up. When the battery reaches 130°C, the separator melts which in turn stops the transport of ions. This action immediately shuts down the cell.

• Positive Temperature Coefficient

This is fundamentally a switch that prevents the battery from overheating by protecting it against current surges in Lithium-ion cells, like a miniature circuit breaker. Self-discharge is when batteries lose their stored charge without the completion of a circuit. This occurs due to chemical reactions inside the cell.

How Does the Li-ion Battery Catch Fire?

The reason that makes lithium-ion batteries so useful is what becomes a bane and gives them the capacity to explode quickly. Lithium is really great at storing energy. When it’s released in small amounts, it powers your EV. When the energy is released completely, it goes BOOM!

Most lithium-ion battery fires and explosions occur due to short-circuiting. This happens when the separator fails and the anode and cathode touch. Once this happens, the battery overheats and explodes.

Common Reasons for Battery Failure

The common reasons for battery failure are:

• Manufacturing Defects: The battery is poorly designed. In that case, there isn’t enough space for the electrodes and separator in the battery. When the battery expands, the electrodes could meet and cause a short circuit. Even a well-designed battery can fail if there is a small defect in manufacturing.

• Improper Usage: Keeping the battery very close to a heat source can cause it to catch fire or explode. Opening the battery pack deliberately or accidentally is bound to cause a short circuit and cause an explosion. That’s why disassembly of the battery pack in electric vehicles leads to rendering the warranty null and void.

EV owners are advised to only get the batteries checked and repaired from authorized service centers. Even high-voltage charging of the battery could cause irreparable damage to it.

• Charger Issues: Using chargers that are insulated in a subpar manner can damage the battery. If the charger causes a short circuit or dissipates heat near the battery, it can do enough damage to cause battery failure. Even though lithium-ion batteries have built-in protections to prevent overcharging, using the wrong chargers can damage the battery in the long term.

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