UK P&I Club and TT Club teamed up with scientific consultants, Brookes Bell, and issued a whitepaper highlighting the continuing safety threat created by the transportation of lithium-ion batteries.
ccording to the report, the increased demand for ‘green power’ for a wide range of portable devices such as mobile phones, mobility aids and recreation, manufacturing and power storage, through to larger products, such as electric vehicles will undoubtedly result in the production and transport of these batteries rising exponentially in the coming years.
The whitepaper outlines many of the numerous challenges facing the transport industry and raises awareness of the potentially catastrophic situation that can be caused by battery failure, thus in part correcting the widely held perception in the maritime community that risks in the supply chain of such products are relatively small.
The consequences of battery failure and the resultant thermal runaway must be clearly understood and the correct procedures for handling them adhered to throughout their lifespan
said Loss Prevention Director of the UK P&I Club, Stuart Edmonston.
Hazards associated with Li-ion batteries
#1 Mechanical abuse: External local damage to the Li-ion batteries such as impact, indentation, or punctures etc.
Upon damage to the casing, air can enter the battery and react with the active components and electrolyte. These reactions will generate heat.
Mechanical damage which deforms the casing could lead to severe internal component damage or breakage. Breakages in the current collector and separator can allow the electrodes to come into contact, resulting in a short circuit.
#2 Electrical abuse: Overcharging or over-discharging the battery. Usually, batteries are charged to a voltage which corresponds to a specified state of charge. Undesirable electrochemical reactions can take place due to overcharging or over-discharging the battery.
Overcharging or over-discharging can occur due to manufacturing faults or damage to battery cells and ineffective monitoring of the voltage by the battery management system (BMS) in the device. The consequences of overcharging and over-discharging are similar.
Overcharging batteries results in electrolyte decomposition on the cathode surface, which increases the battery temperature. During overcharging, excessive Li-ion migration from the cathode causes the cathode to become unstable.
In oxygen-containing cathodes, this can result in the release of oxygen. The oxygen reacts in heat generating side reactions; the increase in gases and side reactions can lead to battery rupture.
The excess Li ions deposit on the anode forming lithium dendrites. Dendrite growth can reach the stage where they pierce the separator, resulting in short circuit, which can have catastrophic repercussions.
In over-discharge, the Li ions move in the reverse direction where Li ions are continuously released from the anode. This process can reach the stage where the copper current collector is oxidised and releases copper ions. These copper ions can deposit on the cathode surface, eventually leading to short circuit.
#3 Thermal abuse: Subjecting batteries to extreme temperatures. Extreme temperature can refer to external temperature or where the local temperature (inside the battery itself) is too high.
There may also be localised high temperatures within the battery itself due to poor design or manufacture. Theoretically, battery cycling should not cause safety accidents as the heat generated during normal use should not be enough to cause sharp increase in temperature.
However, the electrode heat release rate is often higher than the cooling rate. There is some heat dissipation by radiation, however some heat is likely to remain within the battery. If heat continues to accumulate rather than dissipate, this can lead to heat generating side reactions taking place.
The temperature at which these reactions occur depends on the Li-ion battery composition. Thermal stress or shock can result in a build-up of pressure, which may eventually lead to an explosion.
There has been a suggestion that 60°C is the critical temperature, above which Li-ion batteries are prone to fail. Whilst the temperature for battery failure is battery chemistry dependent, this temperature can act as a helpful reference.
When shipping Li ion batteries, one should consider the route and likely climatic conditions. Temperatures inside a dry van shipping container can reach a factor of 2 over the ambient temperature. In the summer months through the Middle East, this could see temperatures inside a shipping container reach 80°C.
Fire risks and emergency response
Lithium-ion battery fires are very difficult to extinguish. Associated problems with firefighting include the following:
- They are generally within sealed units and their location in a piece of equipment or vehicle can prove very difficult to access and penetrate with a fire-extinguishing medium.
- Larger quantities of water are required to extinguish lithium battery fires. For example, for an electric car you can expect to need around 136,000L of water over four hours instead of 10,000-17,000L over 30 minutes for a combustion engine car.
- Li-ion battery fires have a sustained flame and are difficult to supress because the batteries are self–supporting.
- Re-ignition can occur a considerable time after the fire has been extinguished.
- More resources will likely be required to bring an incident under control and to a conclusion.
- Toxic vapours are flammable, with some lighter and some heavier than air in different proportions. The vapours will therefore not all rise and act like smoke.
Another risk that is sometimes forgotten or even ignored, is the potential for electrocution from the batteries if they are part of a bigger unit. As highlighted above, significant quantities of flowing water will likely to be required to extinguish a major vehicle fire.
One major manufacturer actively advises against submerging the vehicle in water (particularly in a steel container) due to concerns over the electric shock hazards associated with the size of the batteries contained.
Prevention, risk assessment, knowledge and understanding while not sufficient, is a valuable target in areas of the globe where equipment is limited or non-existent.
Basic prevention should include:
- Monitoring when and where such devices and batteries are charged, ensuring that they are on hard surfaces and ideally not charged overnight and left unattended.
- Preferably charging items associated with hobbies or mobility outside of accommodation or workplace, for example mobility scooters, bicycles and scooters. Priority is to consider and ensure an incident doesn’t affect the ability to exit and escape any spaces should an battery failure incident occur.
- Avoiding storing or charging at very low or very high temperatures. Always allow for ventilation in hot environments and do not leave in direct sunlight.
- Avoiding leaving on a continuous charge when a device is not in use.
- Never covering batteries, chargers or charging devices whilst they are plugged in and charging.
- Protecting batteries from being mechanically damaged as far as possible.
- Preferably sourcing branded, genuine battery replacement from reputable suppliers, if required. Copies or generic chargers, charging cables and batteries may look the part but may not have the appropriate safety mechanisms built in.