Detailed reason for the combustion of dynamic lithium batteries and thermal out-of control prevention measures

2022/04/08

  Author :Iflowpower – Portable Power Station Supplier

Fire, explosion is a more common thermal out-of-control hazard performance in the power lithium battery system, which is also more serious, not only causes property damage and environmental damage, or even cause personal injury or life risk. The possible causes of thermal out-of control cause the power lithium battery system combustion or explosion include: 1, power lithium battery (battery cell) is thermally out of control, ignition electrolyte and other combustible substances; 2, power lithium battery system The local connection resistance is too large in the high-voltage circuit, and there is a large current flowing to the temperature rise to the temperature rise to the fire point temperature, the flammable substance inside the power lithium battery system; 3. Burning outside the dynamic lithium battery system, resulting in power lithium battery system The internal temperature continues to rise, reaching the temperature of the fire point, igniting internal flammable substances.

Analysis of the use of electric vehicles, the first case has a high probability, the risk factor is also high, and the electrical discharge side reactance of the battery leads to thermal out of control is an important reason for the combustion or explosion of the power lithium battery system. The inside of the lithium-ion battery has: 1, the decomposition of the ESI film, the temperature range is 90 ~ 120 ° C; 2, the reaction of the negative electrode and the electrolyte, the temperature reaches 120 ° C; 3, the electrolyte decomposition, the temperature is approximately 200 The reaction of ℃; 4, the reaction of the positive electrode and the electrolyte, accompanying the positive electrode to analyze oxygen, the temperature ranges from 180 to 500 ° C; 5, the reaction of the negative electrode and the binder, about 240 degrees. The root cause of the electrical cell heat loss (combustion, explosion) is that the heat excited side reactive inside the battery cell leads to heat accumulation, the rate of the electrical cells is less than the heat accumulation rate, the temperature continues to rise, directly reaches the fire point temperature, causing combustion and explode.

The heat inside the battery core follows the energy conservation: QP = QA + QA formula Qp is the heat of various negative reactions inside the cell, QE is the heat exchanged in the battery and the environment, that is, heat dissipation, QA is telecommunications self-absorption Thermal and thermal accumulation. If the QEQP QA is a negative value or zero, the internal temperature of the battery will not rise, and the thermal out of control will not occur; if QE
); blocking the positive feedback process of the exothermic side reaction, such as in the Pack module in adopting the bonding fuse Process, or add PTC material between the positive and negative electrode material and the current collector; reduce the heat of the heat-free side reaction, such as the lithium iron phosphate positive material, change the organic solvent component of the electrolyte, etc., improve the temperature of the fire point, such as Add a flame retardant material in the electrolyte, a ceramic diaphragm, etc. The above, the summary of thermal out-of control mechanism and prevention measures have been practiced in the system's full battery design, manufacturing, but there is different chemical properties for different materials systems in the actual, and there are different systems, and different systems.

Design will also cause system-level dangers and solutions to differently, and the effect is very different. The most effective, the most widely used prevention measures are thermal out-of-control monitoring and warning technology. Yantai has created the emergence of new energy lithium-ion battery thermal out-control model technology, opened up the thermal out-control monitoring and automatic fire extinguishing technology of automatic fire extinguishing technology, and creating the rise and development of battery box dedicated automatic fire extinguishing equipment industry.

Lithium-ion battery thermal out of control model is divided into portrait, horizontal and vertical three-dimensional. The vertical direction of the multi-sensor is redundant, that is, multiple fittings, simulates different materials, different environments, and duration algorithms for the history data of the sensor, excluding noise Interference, effectively solve the drain, false positives, early warning lag problems of the threshold method monitoring; vertical use of different methods such as puncture, blunt needle ingress, simulate different types of capacity power lithium battery thermal out-of control process. Through three-dimensional fusion, use mathematical means based on a large number of experiments and true operation data, inactive the intrinsic relationship between various variables caused by heat failure, adoption of neurological principles, forming an extremely early, highly reliable, self-running lithium battery Thermal out of control model, realizing early warning and intelligent control of the battery in hidden dangers.

A large number of early warning examples occurred in the actual train proof proved the effectiveness and advancement of this model, making it a core technology of current battery box thermal out-of-control warning and automatic fire fighting. Early Warning Example No. 2017.

Collect data analysis, other box battery gas content and change rate, 3 battery box gas content and change rate are significantly higher. It is determined that the battery hazard gas exceeds the standard, which may result in battery leakage. After the bus company, car enterprise, battery company work together, unpacking, confirming the battery leakage.

Replace the battery and no longer alarm. Early Warning Example 2 March, 2017 In February 17, the alarm disappeared after the box. This time is the third warning.

Coordinating alarm system, battery company, car enterprise association judgment. Up-demulting, confirming that it is damaged for a single cell safety valve, and the electrolyte leaks. Early Warning Example San March 2017, a pure electric bus No.

7, a bus company, 2-level warning, driver, timely reporting company, and stop running. Data analysis determines that the battery hazard gas exceeds the standard, which may result in battery leakage. After the car company, the battery company works together, unpacking, confirming the battery leakage.

After replacing the battery, no longer alarm. Early Warning Examples On March 20, 2017, a pure electric bus No. 3 box, a pure electric bus No.

3 box, a driver, and stopped operation. Data analysis determines that the battery hazard gas exceeds the standard, which may result in battery leakage. After the unpacking examination, it confirmed that the two batches were unknown.

Based on the thermal out-control model of lithium ion battery, Yantai created a special automatic fire extinguishing device system for new energy development and production, and now has been widely used in Yutong, Zhongtong, Changjiang Automobile, SAIC, and more than 30 hosts, etc. CATL, China Aviation Lithium Electric, Haixi, Prad, etc. In addition to large-scale installation on new energy commercial vehicles, it is also widely used in new energy passengers, new energy airport special vehicles, energy storage power stations / power-saving stations, logistics vehicles and other needs scenes.

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