Storing lithium cells and batteries carefully is crucial as improper storage of lithium cells can lead to significant safety hazards such as fire and health issues, as well as degrading battery life.

Those working with lithium must bear these hazards in-mind, both during the lifetime of the associated device (e.g. laptop or smartphone), and in device disposal at the end of its useful lifetime.

This article highlights the risks and best practice for the safe storage of lithium cells. It should not be taken as formal advice. If you require formal advice, you should speak with a fire safety specialist, or seek advice from your local fire and rescue service (e.g. https://www.london-fire.gov.uk/safety/lithium-batteries/).

Lithium cells vs batteries

The terms “lithium cell” and “lithium battery” are often used interchangeably but in reality they refer to different things.

A lithium cell is a simple electrical energy storage component containing two electrodes (one positive and one negative) in an electrolyte.

A lithium battery is a collection of multiple lithium cells connected together. Cells in a battery may be connected together in series, in parallel, or both of these.

This article refers to lithium cells but the same best practice applies to handling both individual lithium cells as well as lithium batteries.

Lithium safety risks

The main safety concerns relating to lithium cells are:

• Their ability to start a fire/explosion
• Their high flamability making them an accelerant to a pre-existing fire
• The toxic chemicals they contain that can be harmful to health if leaked

These risks cannot be eliminated but can be mitigated.

Safety risk: Ability to start a fire/explosion

The most common safety concern discussed regarding lithium cells is that they can start a fire. The main causes are the external igniting of the flammable chemicals in lithium cells, and thermal runaway.

Thermal runaway is when a lithium cell enters an uncontrollable self-heating state, leading to a rapid temperature increase. It arises from overcharging, external heating, internal short circuits, physical damage, or manufacturing defects. This type of issue is the most common cause of well publicised mobile phone, e-bike and e-scooter battery fires where they appear to just spontaniously combust.

Overcharging can also cause lithium cells to catch fire/explode. Whilst batteries are charged by applying a slightly higher voltage to them than they hold, either temporarily applying an excessive voltage to a lithium cell/battery, or applying an excessive voltage after the cell/battery has reached its designed maximum capacity can result in excessive heat production, swelling of the cell(s) and potentially an explosion/fire.

Batteries are a collection of lithium cells and generally come with a “battery management system” which seeks to regulate the charge state of the cells in the battery, preventing them from being overcharged as well as cutting off the draw of power from the battery when it is low ,to prevent it being completely depleted. If fitted and functioning correctly, battery management systems should prevent overcharging in lithium cells. Similarly, the correct charger for a device should regulate the voltage provided to the lithium cells appropriately.

Options to minimise these risks may include:

• Keep lithium cells (or devices containing them) away from heat sources where possible. This includes direct sunlight on hot days
• Inspect devices/cells regularly (particularly before charging). Seek a professional repair or dispose of devices/cells that are not in a good condition or have been recalled
• Avoid fast-charging where possible. Slower charging produces less heat, reducing the risk of thermal runaway
• Only use the original charger that came with your device, or an equivalent charger (check voltage and amp rating) from a good quality manufacturer
• If charging cells directly, use a smart charger to avoid overcharging them

Safety risk: Accelerant to a pre-existing fire

As lithium cells contain flammable chemicals, they are a natural accelerant in the event that they are set alight by an existing fire. The pouch form factor is particularly vulnerable with much minimalistic packaging to protect it from its surroundings.

Options to minimise this risk may include:

• Reduce the density of lithium cell storage (consider separation of lithium cells where a high volume exists)
  It should be noted that this may reduce the impact of a fire in the original storage location but it would logically increase the probability of lithium involvement in a fire by spreading them out to more locations.
• Using a fire-proof container to protect lithium cells from the wider environment and vice-versa
  Pre-made fire-proof containers can be expensive so some may consider creating their own such as by packing lithium cells in sand.

Safety risk: Health risks from toxic chemicals

Lithium batteries contain flammable and toxic chemicals that can be harmful if leaked. Exposure to the electrolyte in particular can cause skin irritation, respiratory issues, and other health hazards. Furthermore, flammable gases can be released from the breakdown of lithium cell electrolyte (particularly triggered by overcharging of a cell).

Options to minimise this risk may include:

• Wearing appropriate protective equipment (e.g. gloves) when handling cells that may have leaked
• Inspecting cells thoroughly before using, handling, or charging them
• Ensuring good ventilation in areas where cells are used or stored

Storing lithium cells

With lithium cells in virtually all mobile electronics, it is common for them to suffer long periods of storage as our electronics choices change, and devices are relegated to a drawer or cupboard. Even when in-storage, it’s important to consider your lithium cells. In-particular, you should:

1. Seek a cool, dry environment: Store batteries in a cool (15-25°C / 59-77°F), dry place and away from heat sources such as direct sunlight. High temperatures can cause batteries to degrade faster, while humidity can lead to corrosion.
2. Consider fire-resistant containers: Use fire-resistant containers or storage boxes designed for lithium batteries to reduce the risk of fire spreading in case of a battery failure.
3. Avoid metal objects: Ensure batteries are not in contact with metal objects to prevent short-circuiting. Store them in their original packaging or in individual plastic cases where possible.
4. Pre-charge to a stable voltage: Store batteries at approximately 40-60% of their charge capacity. Storing them fully charged or completely discharged can reduce their lifespan.
5. Protect from physical damage: Keep batteries away from sharp objects and ensure they are not subject to any physical damage or stress.
6. Perform regular checks: Regularly check (every 3-6 months) lithium cells for signs of damage, swelling, or leakage, as well as checking their charge level and environment conditions. Lithium cells will degrade over time, even when not inuse. It may be sensible to consider disposal of lithium cells that have not been used or maintained in 3+ years.

Conclusion

Lithium cells have become an essential part of our electronics lifestyle, but careful storage, charging and monitoring is essential to mitigate the fire and safety risks associated with their use.

Whilst mitigations are a critical safety step, the risks of lithium use and storage cannot be eliminated. Those storing large quantities of devices containing lithium cells (such as laptops), or lithium cells themselves, should consider the elevated risk of lithium in their fire preparedness plans.