How can to Prevent New Energy Vehicle Batteries from Spontaneous Combustion?
Regarding car spontaneous combustion, the main causes of gasoline car spontaneous combustion are circuit aging, short circuits, and fuel leakage, while the spontaneous combustion of new energy vehicles is mostly related to the power battery.
Lithium-ion battery
The lithium-ion battery is a secondary battery that relies on the movement of lithium ions between the positive and negative electrodes to work. During the charge and discharge process, Li+ is embedded and de-embedded between the two electrodes.
When charging, Li+ is de-embedded from the positive electrode and embedded into the negative electrode through the electrolyte. The negative electrode is in a lithium-rich state. The positive electrode loses electrons and undergoes an oxidation reaction, while the negative electrode gains electrons and undergoes a reduction reaction. When discharging, Li+ is de-embedded from the negative electrode and embedded into the positive electrode through the electrolyte. The positive electrode is in a lithium-rich state. The redox reactions of the positive and negative electrodes are opposite to those during charging.
The following points should be noted during the discharge of lithium-ion batteries:
- The discharge current should not be too large
Excessive current will cause internal heating of the battery, which may cause permanent damage.
- Do not over-discharge
After the battery has discharged all the electricity stored inside and the voltage reaches a certain value, continuing to discharge will cause over-discharge. Generally speaking, over-discharging will significantly reduce the battery capacity and even cause the battery to be scrapped.
Factors Influencing the Charging and Discharging of Individual Cells
The end of a power battery’s service life in electric vehicles is indicated when the battery’s capacity diminishes to 80% of its initial performance. During repeated charging and discharging cycles, side reactions within lithium-ion batteries persist, leading to a deterioration in the properties of the battery materials. From the perspective of real-world usage conditions, several key factors affect the lifespan of single power cells, including the cut-off voltage for charging and discharging, the rate of charge and discharge, ambient temperature during use, and storage conditions.
When the power battery is charged and discharged at different rates, it has the following characteristics:
- The battery works stably between the discharge cut-off voltage and the charge cut-off voltage. In this range, the battery voltage has a good correspondence with the stored electricity.
- The amount of electricity that the battery can discharge is related to the discharge rate. The greater the discharge rate, the less electricity can be discharged.
- As the discharge rate increases, the discharge capacity and energy decrease.
Consistency of Single Cells
Batteries of the same specification should have the same capacity, internal resistance, charge and discharge performance, and aging process. A car’s battery pack contains more than a hundred single cells connected in series. If the consistency of the single cells is too different, overcharging or over-discharging will occur. At this time, the temperature of the battery is extremely high, and the probability of spontaneous combustion and thermal runaway is very high.
How to Prevent Thermal Runaway?
There are multiple causes of thermal runaway. For thermal runaway of lithium-ion batteries, the current mainstream solutions in China are mainly external protection and internal improvement. Internal improvement refers to the improvement of the battery itself. External protection is more complicated, mainly referring to the upgrade and improvement of the system.
Battery Cell Composition
Take prismatic batteries as an example: battery packs are usually composed of multiple square battery cells, which are used to store and release a large amount of electrical energy. Since the power battery pack stores a large amount of energy, once an abnormal situation occurs (such as overcharging, over-discharging, high temperature, etc.), it may cause gas generation and pressure increase in the battery pack and even cause fire or explosion in severe cases.
In order to ensure the safety of the battery pack, each power battery is usually equipped with an battery safety vent. The ev battery safety vent is a safety device that can control the internal pressure of the battery and release overpressure or abnormal pressure in time to reduce the risk of explosion or fire.
Working Principle of Prismatic Lithium Batteries
The main explosion principle of the prismatic lithium battery safety vents is based on the principle of thermal expansion characteristics and pressure difference. When the gas pressure inside the battery exceeds the safety value set by the safety vent, the valve will explode and discharge part of the gas through the valve, thereby reducing the pressure of the gas inside the battery and maintaining the safe working state of the battery.
The following requirements need to be met during the lithium battery safety vents process
- First, fast response speed, that is, the ability to blow open the valve in time before the gas pressure inside the battery reaches a dangerous value;
- Second, reliable working performance, that is, the ability to work normally under different environmental conditions and not be affected by external factors;
- Third, long-lasting service life, to ensure long-term and stable operation and avoid frequent replacement. Only in this way can the battery safety be guaranteed.
Hejustamping-China’s Leading Prismatic Lithium Battery Safety Vents Manufacturer
Dongguan Heju Precision Electronic Technology Co., Ltd. specializes in the production of lithium battery safety vents for new energy vehicles and is one of the pioneering companies in China in this field. The company offers a wide variety of models and comprehensive specifications, ensuring that the pressure difference for each unit remains within 0.02MPa, with a CPK greater than 2.0. Heju collaborates with customers on new product development and has successfully passed the three major certification systems: ISO9001, ISO14001, and IATF16949. It consistently delivers high-quality services to prominent domestic battery manufacturers such as Xinwangda, Zhongxinhang, Guoxuan High-tech, Haichen Energy Storage, Tafel, and Ruipu Lanjun, boasting a daily production capacity of tens of millions to meet your production requirements.