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Why do lithium batteries in electric cars catch fire?

Over the past decade, lithium-ion batteries have become a part of almost every aspect of everyday life. From smartphones, watches and in general all the Consumer electronicsuntil large high-capacity batteries for electric vehicles, this is the most widespread chemistry of how many are available. Although for the development of technology security is always the most important feature to be preservedthe risk of short circuit or thermal runaway and therefore of a fire, inherent to the technology, is always present. These are the reasons why a lithium battery can catch fire.

Lithium-Ion Batteries Present Some Safety Risks if not cared for properly. The operating principle of lithium-ion batteries makes them prone to combustion. Hence the need to implement security measures by manufacturers and to comply with certain precautions by their users.

The inside of a lithium battery

Broadly speaking, lithium-ion batteries work storing energy in chemical form and releasing it in electrical form through a series of electrochemical reactions. To achieve this, its interior consists of a series of components. The cathode is the electrode formed by positively charged particles. The anode It consists of negatively charged particles. Between them is placed a liquid electrolyte solution through which lithium ions flow from anode to cathode. It is this movement of the ions that establishes an electrical current within the battery.

The development and commercialization of lithium batteries, Nobel Prize in Chemistry 2019
One of the main causes of fire inside a lithium-ion battery comes from the separator that isolates the anode and cathode being damaged.

Another important battery component, often left out of the simplest descriptions, is the separator. It is a thin, porous membrane that serves to isolate the anode from the cathode. In this way, the separator allows the movement of ions between the anode and the cathode without the two terminals physically touching each other, which would cause a short circuit.

Specifically, one of the main causes of fire inside a lithium-ion battery comes from that separator that isolates the anode and the cathode is damaged. In the event that this component breaks, a short circuit will be created, as the anode and cathode come into contact. When this occurs, the electrolytic solution, which consists of a series of organic solvents, is susceptible to heating up and eventually catching fire.

As they move between the electrodes, the lithium ions undergo what is known as electrochemical deposition creating dendrites, which are small, rigid tree-like structures that grow as needle-like projections. These formations are responsible for perforating the separator.

Beyond the puncture and breakage, another of the main causes of explosion and fire of a battery is thermal runaway. This is a phenomenon where high external temperatures can cause exothermic reactions within the battery itself, which in turn further increases its temperature. This self-reinforcing cycle leading to overheating could eventually cause an explosion.

CATL starts the construction of its battery factory in Germany
Another major cause of battery explosion and fire is thermal runaway.

the actual risk

Today, with lithium batteries powering virtually every electronic device around us and even those that transport us, safety precautions are a primary objective for its manufacturers. While batteries are largely safe on a small scale, as they are manufactured in larger volumes, the probability of an increase in the number of safety breach incidents increases. The generalization of these batteries also in electric vehicles means that this trend continues to rise.

To ensure a more secure future, there are a series of paths that chemists and engineers can take for the technological development of these batteries. One solution may be to explore new methods to ensure your safety, such as safer loading techniques and packaging and enclosure systems.

Regardless of whether the goal is to achieve batteries with higher energy density, faster charging rates and minimal degradation, manufacturers know that safety must continue to be a priority in the development and manufacturing process.

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