Lithium-ion battery fires

Published: 5th Oct, 2023

Context:

The onset and intensification of lithium-ion battery fires can be traced to multiple causes, including user behavior, such as improper charging or physical damage.

What are Lithium-ion batteries?

A lithium-ion battery is a type of rechargeable battery that uses lithium ions as the primary component in its electrochemical system.
It is widely used in portable electronic devices, electric vehicles, and various energy storage applications.
Basic structure:
- A battery is made up of an anode (a negative electrode), cathode (a positive electrode), separator, electrolyte, and two current collectors (positive and negative).
- The electrodes are typically made of materials that can intercalate lithium ions during charging and discharging cycles.
- Common cathode materials include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and lithium iron phosphate (LiFePO4).
- Graphite is commonly used as the anode material.
Functioning:
- During a discharge cycle, lithium atoms in the anode are ionized and separated from their electrons.
- The lithium ions move from the anode and pass through the electrolyte until they reach the cathode, where they recombine with their electrons and electrically neutralize.
- The lithium ions are small enough to be able to move through a micro-permeable separator between the anode and cathode.
- In part because of lithium’s small size (third only to hydrogen and helium), Li-ion batteries are capable of having a very high voltage and charge storage per unit mass and unit volume.

Advantages of Li-ion batteries

Disadvantages

They have one of the highest energy densities of any battery technology today.
This means they can store a significant amount of energy for their size and weight.
They also exhibit a relatively low self-discharge rate when compared to other rechargeable batteries, allowing them to hold their charge for extended periods.
In addition, Li-ion battery cells can deliver up to 3.6 Volts, 3 times higher than other technologies.
This means that they can deliver large amounts of current for high-power applications.
Li-ion batteries have no memory effect, a detrimental process where repeated partial discharge/charge cycles can cause a battery to ‘remember’ a lower capacity.
These batteries do not contain toxic cadmium, which makes them easier to dispose of than Ni-Cd batteries.

Li-ion batteries have a tendency to overheat, and can be damaged at high voltages.
In some cases, this can lead to thermal runaway and combustion.
This has caused significant problems, notably the grounding of the Boeing 787 fleet after onboard battery fires were reported.
Li-ion batteries require safety mechanisms to limit voltage and internal pressures, which can increase weight and limit performance in some cases.
Li-ion batteries are also subject to aging, meaning that they can lose capacity and frequently fail after a number of years.
Another factor limiting their widespread adoption is their cost, which is around 40% higher than Ni-Cd.

What causes these fires?

As these batteries are the powerhouses that fuel our smartphones and laptops –and has the ability to store heaps of energy in a small space.
When EV batteries do overheat, they’re susceptible to something called “thermal runaway”.
This chemical reaction can be triggered from faults in the battery – whether that’s an internal failure (such as an internal short circuit), or some kind of external damage. In extreme cases, it causes the battery to catch fire or explode.

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Lithium-ion battery fires

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