Lithium ion batteries (LiB): risks and hazardous waste

This article deals with the risks of lithium-ion batteries, especially regarding fire and electrical issues. It is worth noticing that those risks are not always observed during waste management.

The use of Li-ion batteries (LIBs) is more and more common, from small scale in electrical and electronic equipment to larger scale in cars, etc. Although collection and recycling are only the beginning of a long story, there is more and more waste LIBs. The storage of all those waste LIBs before recycling, recovery, or even disposal is risky!

As discussed in Step 1.12, a LIB is made of some fundamental components. A battery is constituted by one or more cells, each one containing an anode and a cathode, a separator, and a liquid electrolyte. Whatever the chemical composition or size, LIBs have high energy density compared to other batteries. This energy density makes LIBs prone to combustion or explosion, especially when damaged. If this happens, a runaway reaction may occur, with an unexpected release of energy quickly producing a lot of heat. This can be sufficient to ignite other materials such as plastics, and this can spread to other cells and start a fire. There are various reasons for a temperature rise and the most common are short-circuit, continuous heating, or mechanical damage.

• Battery short circuit is usually divided into internal short circuit and external short circuit. When lithium is precipitated during the cycle, and lithium dendrites pierce the separator or when the packages are damaged or deformed, the separator is punctured, and the electrodes are in direct contact to cause internal short circuit. For external short circuit, it means anode and cathode are directly contacted or connected by low resistance material.
• Continuous heating will increase temperature inside LIBs. Due to low heat stability, LIBs are prone to fire. Note that the liquid electrolyte is flammable and can combust, leading to fires and even explosions.
• Mechanical damage can destroy the separator or make anode exposed to air. As lithium is a highly flammable metal combined with electrolytes, it is easy to self-ignite.

Thermal runaway is the direct cause of fires, and it can occur not only in waste processing. There have been many reported incidents and accidents involving battery fires during operation and while in storage, mainly due to overcharging.

Perhaps the best known consumer case of LIBs fire is the Samsung Galaxy Note 7 smartphone in summer 2016 [1]. After investigation, it seems that two different faults were responsible for fires. First, in some phones, the positive and the negative electrodes touched each other, causing a short-circuit, leading to thermal runaway and then fire. This was due to the deformation of the negative electrode in a corner. Second, in some other phones it seems that an irregular welding pierced insulating material and the separator between the two electrodes, causing a short circuit. In both cases, a short circuit was responsible for fire. Since then, more and more incidents have been reported, in waste sorting centres [2] and factories [3] worldwide.

The risk of fire because of short-circuits, and thermal runaway mainly because of damage can cause environmental damage as the organic electrolyte can generate flammable gases (that can maintain fire) and highly toxic fluorine gases (HF, POF₃). Even if fire is avoided, the leakage or the swelling of the cell can be an environmental risk to air, fauna, and flora.

Nowadays, governments are becoming more aware of the problems and risks associated with the collection, storage, and treatment of batteries. Some regulations or guidance for good practice are suggested. Deep discharge reduces the risk of thermal runaway, and it is also common to insulate connectors to limit the risks. It is important to raise awareness about good practices for sorting and recycling LIBs in treatment centres.

References

[1] M. Gikas, J. Beilinson, “Samsung investigation reveals new details about Note 7 battery failures”, 2017, January 22, Consumers reports, https://www.consumerreports.org/smartphones/samsunginvestigation-new-details-note7-battery-failures/

[2] J. Mock, “Recycling Plants Are Catching On Fire, And Lithium-Ion Batteries Are To Blame”, 2020, February 28, The Verge, https://www.theverge.com/2020/2/28/21156477/recycling-plants-fire-batteries-rechargeable-smartphone-lithium-ion

[3] H. Sanderson, “Tesla ‘big battery’ fire fuels concerns over lithium risks”, 2021, August 3, Financial Times, https://www.ft.com/content/8c9c3d50-98a3-4cdf-907f-901f8c328b90