Thermal runaway of lithium batteries is indeed an inevitable phenomenon, mainly due to the highly reactive chemical properties of lithium metal, which makes the processing, storage, and use of lithium metal highly environmentally demanding.
1. Reasons for thermal runaway of lithium batteries
1.1 Internal short circuit: When a short circuit occurs between the positive and negative poles inside the battery, a large amount of heat is generated, causing the battery temperature to rise rapidly and leading to uncontrolled heat generation. Short circuits may be caused by defects in the battery manufacturing process, membrane rupture caused by battery aging, or dendrite growth penetrating the membrane.
1.2 Overcharging: When a battery is overcharged, the internal electrolyte will undergo a decomposition reaction, producing a large amount of gas and heat, leading to a rapid increase in battery temperature and causing thermal runaway. Overcharging may be caused by charger malfunction, battery management system (BMS) failure, or improper user operation.
1.3 External damage: When the battery is damaged by impact, compression, or puncture, the electrolyte inside will leak out and react chemically with oxygen in the air, producing a large amount of heat and gas, leading to a rapid increase in battery temperature and causing thermal runaway.
1.4 Battery aging: As the battery is used for a longer period of time, the internal electrolyte will gradually decompose and age, resulting in a decrease in battery capacity, an increase in internal resistance, and a deterioration in heat dissipation performance, which may ultimately lead to thermal runaway of the battery.
1.5 High temperature environment: Long term operation of lithium batteries in high temperature environments may cause the internal temperature of the battery to continue to rise, leading to uncontrolled heating.
2. Countermeasures for thermal runaway of lithium batteries
2.1 Improve battery manufacturing accuracy: Strictly control the quality of electrode plates and separators in the production process. High precision cutting equipment is used to ensure that the polarizer is free of burrs, and advanced quality inspection methods are used to ensure the integrity and uniformity of the diaphragm.
2.2 Optimize material selection and ratio: Choose stable positive and negative electrode materials and electrolytes. For positive electrode materials, while meeting the energy density requirements, priority should be given to material systems with good thermal stability. At the same time, select negative electrode materials that can form a stable SEI film, and adjust the electrolyte composition reasonably, adding some thermally stable additives to suppress the decomposition of the electrolyte.
2.3 Strengthen quality control of battery assembly: Establish strict assembly processes and standards, ensure accurate assembly of components such as electrodes and separators through automated assembly equipment, and conduct strict sealing tests on the assembled batteries.
2.4 Correct charging and discharging methods: Use a charger that meets the battery specifications to avoid overcharging and overdischarging. For lithium battery equipment, reasonable charging and discharging cut-off voltages should be set, and intelligent charging algorithms should be embedded in the device software or charging equipment to dynamically adjust the charging current and voltage according to the battery's state.
2.5 Control the temperature of the usage environment: Try to avoid using and storing batteries in high temperature environments. If the battery is applied to equipment in high-temperature environments, effective heat dissipation devices such as heat sinks, fans, etc. need to be installed.
2.6 Regular inspection and maintenance: For lithium battery equipment that is used for a long time, the battery should be inspected regularly, including visual inspection (for bulges, leaks, etc.) and performance testing (for indicators such as capacity and internal resistance).
3. National and industry response strategies for thermal runaway of lithium batteries
3.1 Improve defense standards: The National Fire and Rescue Bureau and other relevant departments have proposed to improve building fire prevention standards, transform fire prevention and control concepts, and reduce the harm caused by thermal runaway of lithium batteries.
3.2 Strengthen technological breakthroughs: Encourage host manufacturers and related enterprises to strengthen technological research and development, improve production processes, and enhance the safety performance of key materials such as electrolytes and membranes.
3.3 Promote new battery technologies: Solid state batteries and other new battery technologies have higher energy density and more stable performance, becoming a research hotspot for new energy vehicles. Although the manufacturing process of solid-state batteries is complex and costly, with the continuous advancement of technology and cost reduction, it is expected to replace liquid batteries in the future and reduce the risk of thermal runaway.
4. The development path of lithium battery safety technology is still long
With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, portable electronic devices, and other fields, their safety issues have also received increasing attention.
4.1 Research and innovation of battery materials:
At present, lithium-ion batteries mainly rely on positive electrode materials such as lithium cobalt oxide and lithium nickel manganese cobalt oxide, as well as graphite or silicon-based negative electrode materials. These materials may pose safety hazards such as thermal runaway and short circuits during the charging and discharging process.
Therefore, researching safer and more stable battery materials is an important direction for lithium battery safety technology. For example, solid-state batteries have attracted much attention due to their higher energy density and better safety.
4.2 Optimization of Battery Management System (BMS):
BMS is one of the core components of lithium-ion battery packs, responsible for monitoring the voltage, current, temperature and other parameters of the battery pack, and controlling charging and discharging based on these parameters.
By optimizing the BMS algorithm and hardware design, the safety of the battery pack can be improved. For example, by monitoring the health status of the battery pack in real-time, potential safety issues can be alerted and addressed in a timely manner.
4.3 Progress in battery thermal management technology:
Lithium ion batteries generate heat during operation, and if the heat is not dissipated in a timely manner, it can cause the battery temperature to rise, leading to safety issues.
Therefore, researching more efficient battery thermal management technology is also an important direction for lithium battery safety technology. For example, adopting liquid cooling, air cooling and other heat dissipation methods, as well as developing more efficient integrated solutions for thermal management systems.
4.4 Improvement of battery manufacturing and testing technology:
The manufacturing process of lithium-ion batteries has a significant impact on their safety. For example, defects and impurities inside the battery may cause safety issues.
Therefore, improving the quality control and testing technology in the battery manufacturing process is also an important part of lithium battery safety technology. By adopting more advanced manufacturing equipment and testing methods, defects and impurities inside the battery can be reduced, and the safety of the battery can be improved.
4.5 Formulation and improvement of regulations and standards:
With the widespread application of lithium-ion batteries, relevant regulations and standards are constantly being improved. These regulations and standards provide clear requirements and regulations for the safety of lithium-ion batteries.
Therefore, strengthening the formulation and improvement of regulations and standards is also an important direction for the development of lithium battery safety technology. By formulating stricter regulations and standards, the continuous progress and improvement of lithium battery safety technology can be promoted.