Lithium-ion batteries: canned heat

Use, handling, storage and charging of lithium-ion batteries is an everyday occurrence. Socotec considers how this can be managed safely.

Lithium-ion batteries are in regular use to power the many devices and vehicles that we use as part of our modern daily lives. Fortunately, fire-related incidents involving these batteries are infrequent, but there are significant fire-related hazards associated with these battery cells. The combination of flammable electrolyte and significant stored energy can lead to a fire or explosion due to a single failure (see What you should know).

The main safety concern with lithium-ion batteries is where a battery cell creates more heat than it can effectively dissipate, leading to a rapid uncontrolled release of heat energy known as ‘thermal runaway’. This can result in a fire or explosion, and may occur as a result of manufacturing defects, mechanical damage, exposure to external heating or overcharging/over discharging.

Thermal runaway can lead to the venting of a range of gases from the battery casings, such as hydrogen (extremely flammable), carbon monoxide (toxic, asphyxiant and flammable) and hydrogen fluoride gas (acutely toxic and corrosive).

When a battery cell ruptures or vents due to thermal runaway, immediate ignition of the emitted gases may occur. Alternatively, the gases may accumulate unignited, with the potential for a very rapid combustion (deflagration) or explosion when an external ignition source is encountered.

Fire safety legislation in the UK requires the Responsible Person to reduce the risk of fire and the risk of the spread of fire on the premises. The Responsible Person must also take such general fire precautions as will ensure the safety of employees/residents and take such general fire precautions as may reasonably be required to ensure that the premises are safe.

The Regulatory Reform (Fire Safety) Order 2005 applies to virtually all premises in England and Wales including workplaces and the common parts of all multi-occupied residential buildings.

The Regulatory Reform (Fire Safety) Order (and similar legislation in Scotland) requires the Responsible Person to make a suitable and sufficient assessment of the risks to which people are exposed to identify the general fire precautions they need to take.

What you should know

Lithium-ion batteries are formed of four main components:

1. The capacity of the battery is determined by the cathode – it’s the source of the lithium ions

2. The ions are stored in the anode, which enables the electric current to flow through an external circuit when the battery is charged

3. The separator is the physical barrier that keeps the cathode and anode apart; and

4. The electrolyte acts as a conduit of lithium ions between the cathode and anode.

Before a battery can be installed, the factory must charge and test the unit to identify any faults.
It can become faulty when mishandled, overcharged, short-circuited or heated up.
This could lead to issues such as the battery walls expanding or splintering, which can allow some of the internal compounds to leak out.
Electrolytes are made up of organic compounds, such as salts and solvents. When contained inside a battery unit, the electrolyte doesn’t pose an immediate risk.
If they spill from a battery – because of an accident or if they’re handled improperly – they can react with air and water to produce hydrofluoric acid, which can cause corrosive burns to skin and underlying bone.

For more on safety, visit b.link/Hughes_showers

Ensuring your building is compliant

Fire safety management controls will need to be scaled appropriately for the level of hazard. Undertaking a suitable and sufficient fire risk assessment in compliance with the Regulatory Reform (Fire Safety) Order is the first step. The fire risk assessment should be undertaken by a suitably competent person and should cover handling, storage, use and charging of lithium-ion batteries. For a fire risk assessment to be considered ‘suitable and sufficient’ in accordance with the Regulatory Reform (Fire Safety) Order it must consider all significant risks of fire.

A fire risk assessment is a careful look at the premises, the way in which they are used and the people who use them from a fire safety perspective. It is about understanding the potential risks, then making recommendations to ensure that fire safety precautions are adequate to keep people safe. Typical recommendations for a workplace may relate to:

• only using equipment that is supplied by reputable manufacturers or suppliers and only charging batteries with a suitable original equipment manufacturer or compatible charger designed to safely charge the specific battery cells or battery packs in use
• frequent inspections of batteries for signs of damage

• ensuring that battery handling areas are dry, cool, well-ventilated and free from high levels of humidity

• ensuring that battery handling areas are free from flammable or combustible materials or sharp objects, and that batteries are not left in contact with conductive material
• ensuring that batteries are removed from chargers after charging is complete and that batteries are not left on charge in unoccupied locations

• ensuring that staff are fully trained on the emergency procedures and the specific instructions for dealing with damaged or faulty batteries. Staff should be aware of their limitations in relation to dealing with fires involving lithium-ion batteries

• keeping batteries not in use in appropriate enclosures such as proprietary metal battery storage cabinets or fireproof safety bags

• provision and maintenance of a suitable smoke detection system that provides adequate warning to other occupants of the building (ideally combining smoke and carbon monoxide detection)

• limiting the size of storage areas and ensuring they are dedicated to lithium-ion battery storage only

• consideration for the provision of sprinklers to an appropriate sprinkler system design. (The packaging arrangements of lithium-ion batteries is considered to be a key element in the success or failure of a sprinkler protection system. Fire control may be achieved when sprinklers wet and cool cardboard packaging, such that chain thermal runaway reactions are prevented and fire spread contained); and

• consideration for the provision of a fixed extinguishing agent flooding system.

For residential premises, there isn’t the ability to check battery storage and use practices so a campaign of awareness among residents is needed. Where lithium-ion batteries are found to be used, stored or charged in the premises, a professional fire risk assessment will make appropriate recommendations in relation to the risk.

For more, visit socotec.co.uk

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