Behind the convenience of Li-ion batteries lies a potentially hazardous science. SafeQuip delves into the construction of Li-ion batteries, the phenomenon of thermal runaway, and potential hazards associated with these power sources.
Understanding Li-ion battery construction
At their core, Li-ion batteries consist of three essential components:
1. Anode: This is the negative electrode, typically made of a carbon-based material that stores lithium ions when the battery is charged.
2. Cathode: The positive electrode, often composed of lithium cobalt oxide or other lithium-based compounds, is responsible for receiving and releasing Li-ions during charging and discharging.
3. Electrolyte: This is like the battery’s bloodstream. It is a liquid or gel that helps lithium ions move around between the cathode and anode. It’s important to note here that this liquid or gel is flammable.
These three elements are sandwiched together and housed within a protective casing. The casing serves as a barrier to contain the potentially volatile materials inside the battery.
Thermal runaway
Thermal runaway in Li-ion batteries is a dangerous situation where the battery gets extremely hot, leading to the rapid release of heat and gases, which can result in fires or explosions. Several factors can trigger thermal runaway, including:
• Overcharging: Charging a Li-ion battery beyond its recommended voltage limits can cause the electrolyte to break down, leading to overheating.
• Physical damage: Punctures, crushing, or mechanical stress can compromise the battery’s structure, allowing internal components to come into contact and generate heat.
• High temperatures: Exposure to excessive heat, such as leaving a device in a hot car, can accelerate the onset of thermal runaway.
• Manufacturing defects: Faulty manufacturing processes or substandard materials can weaken the battery’s internal components, increasing the risk of thermal runaway.
Potential hazards from Li-ion batteries
Potential hazards associated with Li-ion batteries include:
• Fire: When a Li-ion battery undergoes thermal runaway, it can generate enough heat to ignite the internal materials or surrounding objects. This can lead to a fire, posing a significant safety risk.
• Explosion: In extreme cases, the buildup of pressure from the gases produced during thermal runaway can rupture the battery casing, resulting in an explosion. While such incidents are rare, they can cause severe injuries or property damage.
• Toxic gas emission: Li-ion batteries may emit toxic gases, such as hydrogen fluoride and phosphorus pentafluoride, when they overheat or explode. Inhalation of these gases can be harmful to human health.
Mitigating the risks
There are a few practical steps one can take to help stay safe:
• Use genuine batteries: Always use genuine, manufacturer-recommended batteries and chargers for devices. Counterfeit or substandard products are more likely to pose risks.
• Avoid extreme temperatures: Keep devices and batteries away from extreme temperatures, both hot and cold. Avoid leaving them in direct sunlight or inside a hot vehicle.
• Inspect for damage: Regularly inspect devices and batteries for any signs of physical damage, such as swelling, punctures, or leaks. If any issues are noticed, the battery or device must be replaced.
• Charge safely: Charge devices on non-flammable surfaces, away from combustible materials. Do not leave them unattended while charging, especially overnight.
• Store properly: If Li-ion batteries are needed to be stored for an extended period, keep them in a cool, dry place with a partial charge (around 50%). Avoid storing them fully charged or fully depleted.
• Dispose of old batteries: Old Li-ion batteries, that are no longer in use, should be recycled properly.
• Invest in a Lith-Ex fire extinguisher: Lith-Ex fire extinguishers contain AVD, a naturally occurring agent specifically designed for Li-ion battery fires. AVD is made from the naturally occurring mineral, vermiculite, combined with water. It is a very effective agent that cools, encapsulates, prevents propagation, and extinguishes Li-ion battery fires.
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