The safety performance of power batteries is influenced by a wide range of factors that span the entire lifecycle, from material selection to end-of-life disposal. These factors are complex and multifaceted, involving aspects such as cell material properties, manufacturing processes, BMS (Battery Management System) design, and battery integration. Manufacturing errors and abuse conditions are inevitable in real-world scenarios, making thermal runaway prevention a critical aspect of battery design. This paper reviews the key factors influencing lithium-ion battery safety, aiming to provide a solid foundation for their application in high-energy and high-power systems.
Lithium-ion batteries have become the dominant energy storage technology due to their high energy density, long cycle life, and ability to deliver high power output. They are widely used in portable electronics and are now gaining traction in electric vehicles and large-scale energy storage systems, supported by growing government policies and market demand. Despite their widespread use, safety incidents remain a concern. Notable cases include fires in Boeing 737 and 787 aircraft batteries, as well as incidents involving BYD and Tesla Model S vehicles. These events highlight that safety remains a major barrier to the adoption of lithium-ion batteries in high-energy applications. Thermal runaway, which can lead to fire or explosion, is not only a primary cause of these issues but also limits the performance and reliability of the battery.
Consumer confidence is heavily affected by potential safety risks, even though BMS is expected to monitor and predict failures. However, the complexity of thermal runaway makes it difficult to ensure full safety throughout the battery's lifecycle. Therefore, continuous research into the causes of safety issues is essential for developing safer and more reliable lithium-ion batteries.
Material selection plays a crucial role in determining the intrinsic safety of a battery. The positive electrode material, such as LiFePO4, offers good thermal stability but at the cost of lower energy density. On the other hand, ternary materials like NMC offer higher energy density but face significant safety challenges. Similarly, the choice of negative electrode materials, such as LTO or Ti0.9Nb0.1Nb2O7, affects fast charging capabilities and overall safety. Electrolytes and separators also contribute significantly to battery safety, with flammable liquid electrolytes posing a risk if not properly managed.
Manufacturing processes, including electrode preparation, cell assembly, and SEI film formation, are vital in ensuring consistent quality and safety. Any deviation during these steps can lead to internal short circuits, increased resistance, or reduced performance. Battery integration, particularly through BMS and stack design, further enhances safety by managing thermal behavior, preventing chain reactions, and improving system-level reliability.
Abuse conditions, such as overcharging, overheating, and mechanical damage, can trigger thermal runaway. Even with optimal design and manufacturing, real-world usage often exposes batteries to unpredictable stresses. Therefore, proactive thermal management strategies—such as cooling systems, safety valves, and insulation layers—are essential to mitigate risks.
In conclusion, the safety of lithium-ion batteries is a multifaceted challenge that requires attention at every stage of the battery lifecycle. From material selection to system integration, each step must be carefully designed to minimize risks. As the demand for high-energy and high-power applications continues to grow, ongoing research and innovation will be key to achieving safer, more efficient battery technologies.
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