As batteries become more prevalent in our daily lives, we are propelled towards a future that depends on their reliability. One technology that stands out is lithium-ion batteries because of their energy density, high voltage, and long lifespan. They are used in various applications, such as smartphones, electric vehicles (EVs), and renewable energy storage systems. Lithium-ion batteries provide an excellent source of energy, but they also pose some risks, one of which is thermal runaway. Thermal runaway is a critical temperature rise that can lead to irreversible and potentially explosive consequences, making battery safety an essential factor in their continued success.
The Dangers of Thermal Runaway
Thermal runaway occurs when a lithium-ion cell’s temperature increases uncontrollably, leading to further heating and a chain reaction that can cause a fire or explosion. It must be avoided to ensure the safety of consumers and devices that use lithium-ion batteries. Although thermal runaway can occur in any type of event that causes heat, there are specific causes that make it more likely to occur. Common reasons for thermal runaway include:
- Internal Short Circuit Detection
- Manufacturing Defects
- Overcharging the cell
- Rapid charging/discharging cycles
- Toxic Decomposition Reactions
- External physical abuse or extreme temperatures during mishandling
Thermal runaway prevention is an essential aspect of battery safety that must be continuously updated and refined. Let’s explore further how to prevent thermal runaway from occurring in lithium-ion batteries.
To prevent thermal runaway, manufacturers need to focus on designing the battery cell, pack, and the overall application, taking into account potential risks, and ensuring that measures are in place to reduce those risks. The following measures can be taken to ensure safer battery handling:
Battery Cell Design
The design of the lithium-ion cell is an excellent place to start. Cell chemistry, size, and the thickness of the anode and cathode layers can all affect a cell’s ability to manage heat. A battery cell’s positive and negative poles should be arranged, so there is an adequate amount of space between each other. When a battery cell is designed with safety in mind, it can reduce the risk of thermal runaway.
Thermal management refers to the way a battery cell is kept at the right temperature. Overheating can cause thermal runaway, so it is crucial to implement effective heat management. Ventilation, heat sinks, and cooling accessories can help with heat transfer and reduce the risks of thermal runaway.
Battery Management Systems (BMS)
A battery management system (BMS) is a vital component of any lithium-ion battery, providing monitoring and charge control to the cells in the battery. BMS monitors the individual battery cell voltage, current and temperature, ensuring that they remain within their safety limits. It also provides cell-to-cell balance and prevents overcharging and undercharging of the individual cell to prevent excessive currents in the pack, which is another risk for thermal runaway.
The structural design of the battery pack is crucial if thermal management is to be achieved. Ventilation is important in helping heat transfer from the battery cells, and a venting system can help relieve pressure if it starts to build up in the battery pack. Combined with active and passive thermal management, the structural design of the battery pack can help reduce the risk of thermal runaway and improve battery safety.
The Role of Active and Passive Thermal Management Systems
Battery thermal runaway detection and prevention systems are grouped into active and passive thermal management operations.
Active Thermal Management
Active thermal management employs technology such as liquid or air cooling, which continuously circulates and cools the battery packs to maintain temperature stability. Active thermal management solutions require energy to operate and may slow a vehicle to avoid excessive temperature issues.
Passive Thermal Management
Passive thermal management, on the other hand, employs approaches such as phase-change materials, which store and dissipate heat when lithium-ion cells become too hot. Similarly, passive schemes include natural air cooling as well as special insulators.
Gas sensors work alongside thermal management, detecting gases that indicate a problem in the battery pack before it becomes a more significant issue. For example, gas sensors can detect increased levels of hydrogen in the battery pack, which is a byproduct of overcharging, leading to an explosive risk. Infrared cameras can identify an overheated cell of the battery pack.
A promising recent development that could revolutionize battery technology is solid-state batteries. Solid-state batteries don’t use flammable liquid, increasing their thermal stability and safety. The applications of this technology are promising, especially for hybrid electric vehicles, where safety and battery pack durability are critical.
In conclusion, the continued effort to reduce the risk of thermal runaway and further improve the safety of lithium-ion batteries in electric vehicles and other applications is a collective responsibility for manufacturers and users alike. By implementing preventive measures and using thermal management solutions, such as active and passive cooling technologies and gas sensors, we can reduce the risk of thermal runaway and contribute to a safer and more sustainable future, powered one cell at a time.