Are Lithium-Ion Batteries Safe?

As an advanced energy storage technology, rechargeable batteries have emerged as the preferred option for various applications. They offer several advantages, including safety, reliability, affordability, and versatility. Among the rechargeable batteries, lithium-ion batteries have witnessed significant advancements and are now extensively utilized in renewable energy systems, electric vehicles, and home energy storage solutions. This popularity can be attributed to their exceptional characteristics such as high energy density, elevated output voltage, prolonged lifespan, and minimal self-discharge.

However, as the production and usage of lithium-ion batteries have increased, there has been a rise in fire and explosion incidents associated with them. These incidents have been observed not only in domestic settings but also globally. When a lithium-ion battery pack ignites, it poses challenges for firefighting efforts and can potentially lead to further catastrophic events.

What are the classifications of lithium-ion batteries?

Lithium-ion batteries are widely used and can be categorized based on their positive electrode materials, including lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate. Lithium iron phosphate batteries are commonly employed in energy storage stations, while nickel-cobalt-manganese ternary lithium batteries and lithium iron phosphate batteries are commonly used in power batteries.

The structure of a lithium-ion battery mainly consists of a positive electrode, a negative electrode, a separator, and electrolyte. It is important to note that materials such as the separator and electrolyte are flammable or combustible and can be thermally decomposed, producing flammable gases. This characteristic makes lithium-ion batteries prone to thermal runaway under certain conditions.

With the increasing popularity of electric vehicles, there is a growing demand for extended driving range and faster charging capabilities. To meet these demands, there have been enhancements in the active material content and activity within batteries, resulting in continuous improvements in energy density. However, these advancements also heighten the risk of fire incidents in lithium-ion batteries, as higher energy density implies a greater potential for energy release.

Why do lithium-ion batteries catch fire?

The main cause of lithium-ion battery fires is thermal runaway, which triggers a rapid rise in battery temperature and can ultimately result in fires and explosions. The main reasons for thermal runaway include mechanical abuse, electrical abuse, inherent defects, and high-temperature environments.

Mechanical abuse refers to external forces exerted on the battery during its use and storage, such as compression, collision, or puncture. These forces can cause the battery to deform and damage its separator, resulting in internal short circuits and subsequent fire hazards.

Electrical abuse indicates improper use of the battery, including overcharging, overdischarging, and short circuits. Overcharging refers to exceeding the battery’s rated voltage or charging for an extended period, which increases internal resistance and generates a significant amount of heat. Overdischarging involves using the battery to a low voltage or discharging it completely, which can cause dissolution of the negative electrode copper foil, damage the battery’s structure and performance. Short circuits result in high-current discharge, generating intense heat and posing a safety hazard.

Inherent defects mainly comprise burrs, impurities, process defects, and inconsistencies. Burrs and metal particles can pierce the separator, leading to internal short circuits. Process defects or issues with the battery management system can result in inconsistencies between battery cells, causing individual cells to be overcharged, undergo self-discharge, accelerate aging and performance degradation, ultimately leading to thermal runaway.

Furthermore, high-temperature environments exacerbate the risk of thermal runaway. When the battery is exposed to external heat sources or generates excessive heat internally due to cooling system failure, a high-temperature environment is formed. High temperatures accelerate battery aging, resulting in performance degradation and increased heat generation, forming a vicious cycle that can ultimately lead to thermal runaway. Excessively high temperatures can also cause the decomposition of battery separator materials, leading to internal short circuits and further increasing the risk of thermal runaway.

How to choose lithium-ion batteries

1. Choose products from reputable manufacturers when purchasing lithium-ion batteries and related products. Use chargers that are compatible with the battery’s voltage and current.
2. Follow the provided instructions carefully when charging lithium-ion batteries and related products. Adhere to recommended charging times to prevent overcharging.
3. Handle and store lithium-ion batteries and related products mindfully to minimize exposure to strong external forces such as impacts or compression.
4. Avoid using and storing lithium-ion batteries in high-temperature environments or extreme conditions that could compromise their performance and safety.
5. Refrain from attempting to dismantle or disassemble batteries on your own, as this can be hazardous. Seek professional assistance if necessary.
6. Do not make unauthorized modifications to the electrical circuits of electric bicycles or replace batteries with higher capacities. These actions can lead to overload, short circuits, and other hazards.

How to extinguish a lithium-ion battery fire?

1. Prioritize personal safety: Wear appropriate personal protective equipment and respiratory protection.
2. Disconnect the power source: Before attempting to extinguish the fire, ensure the battery power is disconnected to prevent electrical hazards.
3. Maintain a safe distance: During firefighting, keep a minimum distance of 5 meters unless there is a need to rescue individuals trapped in the vehicle.
4. Firefighting direction: Choose a direction against the wind to suppress the fire, minimizing the risk of inhaling toxic smoke.
5. Avoid cutting and disassembling: Prohibit any cutting or disassembling of the vehicle’s structure and electrical components to avoid electric shock or exacerbating the thermal runaway of the battery.
6. Control the fire: Focus on controlling the fire and continuously reduce the temperature of the battery pack to minimize the risk of explosions.
7. Monitor temperature: Continuously monitor the battery temperature to prevent heat spreading and reignition. Place the vehicle wreckage outdoors and maintain a safe distance from the surroundings until the battery power is fully discharged. Ensure that professionals handle the vehicle wreckage within 24 hours.