CN114927781A - Battery thermal runaway comprehensive early warning method and system based on end face pressure detection - Google Patents

Abstract

The invention relates to a comprehensive early warning method and system for battery thermal runaway based on end-face pressure detection. The method includes the following steps: 1) Collecting the battery end-face pressure, and if the battery end-face pressure rises above a set threshold, it is determined that the battery is in the early stage of thermal runaway In the state of self-generating heat, go to step 2); 2) After cooling the battery for a set time, go to step 3); 3) Combine the end face pressure, battery surface temperature and voltage to comprehensively judge whether the battery is in a thermal runaway state, and carry out Warning. Compared with the prior art, the invention can comprehensively determine the thermal runaway of the battery earlier and accurately, realize the safety warning of the battery system, and provide enough precious time for fire fighting and personnel escape.

Description

Comprehensive early warning method and system for battery thermal runaway based on end-face pressure detection

technical field

The invention relates to the field of lithium ion battery safety early warning and protection, in particular to a lithium ion battery thermal runaway comprehensive early warning method and system based on end face pressure detection.

Background technique

The energy crisis caused by the massive consumption of traditional fossil fuels and the dual pressures of air pollution have prompted electrification to gradually become the mainstream direction of automobile development. Lithium-ion power batteries are used as the main power source for electric vehicles due to their advantages of high energy density and long cycle life.

However, the application of lithium-ion battery power system is easily limited by factors such as environment and working conditions. Extreme working environments such as low temperature and fast charging will lead to a series of problems such as aging and thermal runaway. Explosion, these problems have a significant impact on the performance, service life and even safety of lithium-ion power battery packs/batteries. Therefore, a mechanism study on the use process of lithium-ion power batteries in various working environments and working conditions is carried out. The macro-control and management of lithium-ion power batteries play a very important guiding role.

At present, the internal mechanism research, detection and early warning methods of lithium-ion batteries under various working and failure states are relatively simple, and most of them are external physical measurements, such as current, voltage and temperature measurements. However, the actual thermal runaway failure mechanism of lithium-ion power batteries is extremely Complex, the incentives can be divided into mechanical abuse, electrical abuse, thermal abuse and internal defects and other factors, the external physical measurement alone has a large error and hysteresis, so the existing thermal runaway early warning technology cannot be used for escape, treatment, fire fighting and fire fighting. Providing enough time often leads to more serious consequences.

Therefore, with the continuous improvement of capacity requirements, the energy density, power density and capacity of lithium-ion power batteries continue to rise. This trend poses a major challenge to the safety of lithium-ion battery systems operating under extreme conditions. Detection and early warning methods that fit the actual internal reaction principle will become an inevitable choice for the substantial improvement of the safety of lithium-ion battery systems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a comprehensive early warning method and system for battery thermal runaway based on end face pressure detection in order to overcome the above-mentioned defects of the prior art.

The object of the present invention can be realized through the following technical solutions:

A comprehensive early warning method for battery thermal runaway based on end-face pressure detection, comprising the following steps:

1) Collect the pressure on the end face of the battery, if the pressure on the end face of the battery rises above the set threshold, it is determined that the battery is in a state of self-generating heat in the early stage of thermal runaway, and go to step 2);

2) After cooling the battery and continuing for a set time, proceed to step 3);

3) Combine the end face pressure, battery surface temperature and voltage to comprehensively judge whether the battery is in a thermal runaway state, and give an early warning.

In the step 2), combined with the battery thermal management system and the air conditioning system, early joint forced cooling is performed to achieve the maximum temperature rise suppression effect, so as to restore the battery to a normal use state.

The described early joint forced cooling is specifically:

Increase the flow of liquid-cooled coolant to the battery and increase the cooling power of the air conditioning system in the vehicle or in the energy storage power station.

In the step 2), the set time is 10s.

In the described step 3), when any phenomenon occurs in the end face pressure growth rate exceeding the set threshold, the battery surface temperature growth rate exceeding the set threshold and the voltage drop rate exceeding the set threshold, then it is judged that the battery is in a thermal runaway state. At this time, the battery thermal management system cannot block the thermal runaway of the battery, notify the driver or the staff of the energy storage power station to evacuate quickly and call the fire department, and turn on the fire extinguishing device of the battery system, otherwise the battery will continue to work in the current state.

In the step 1), the state of self-generated heat in the early stage of thermal runaway is specifically the state between the start of self-generating heat of the battery and the triggering of thermal runaway.

The battery end face pressure and battery surface temperature data are based on the test data of the battery cells selected by the battery system before leaving the factory, and consider the heat generation of the battery during the charging and discharging process under normal operating conditions and the respiration effect. Deformation and pressure changes, correct the set end face pressure threshold and battery surface temperature growth rate threshold to achieve accurate judgment.

A comprehensive early warning system for battery thermal runaway includes a pressure sensor for collecting battery end face pressure and a processor connected with the pressure sensor to realize early self-generated heat state and thermal runaway state judgment of battery thermal runaway.

The layout of the pressure sensor is as follows:

In the battery system, a plurality of battery cells connected in series are formed into modules by the clamps at both ends, which are bundled with bolts with pre-tightening force or by steel belts. A pressure sensor is installed to accurately measure the end face pressure increase caused by the self-generated thermal expansion of the lithium-ion battery and the internal reaction gas bulge.

Considering that the temperature during the thermal runaway of the battery is too high, in order to prevent the failure of the pressure sensor, high-temperature insulation protection is performed on the outside of the pressure sensor to realize real-time dynamic monitoring.

Compared with the prior art, the present invention has the following advantages:

1. When the ambient temperature of the battery reaches the self-generated heat reaction temperature, the active materials such as electrode materials, electrolytes and additives inside the battery react and release heat, and a certain amount of gas begins to be generated during this process, but thermal runaway has not yet been triggered. The pressure detection determines whether the battery is in the early self-generating stage of thermal runaway, and measures such as cooling are taken in time to prevent the temperature from rising continuously to the trigger temperature of thermal runaway. The invention can realize the early warning of thermal runaway of the lithium ion battery. The response of the means is earlier, and more time for escape and processing can be obtained.

2. The present invention fully considers the thermal runaway reaction mechanism of the lithium ion battery, and corrects the influence of the battery charge and discharge heat generation and temperature rise and the "breathing effect" of the charge and discharge process on detection and judgment.

3. The comprehensive early warning method and system proposed by the present invention only needs to add a pressure sensor on the basis of the existing battery system, which has the advantages of convenient installation, maintenance and low cost.

4. Based on the characteristics of fast response and high sensitivity of the pressure sensor, the present invention realizes the real-time monitoring of the state of each battery cell of the lithium ion battery pack.

5. The sensing and detection technology used in the present invention does not require external power supply, does not generate heat, and has no noise, and can simultaneously meet the requirements of commercial vehicles on the noise, energy consumption and safety of the battery management system.

Sixth, the present invention can realize the supplement and correction to the existing lithium ion battery thermal runaway and thermal runaway spreading mechanical mechanism, and provide theoretical support for the design of lithium ion battery and the management and protection of battery system.

Description of drawings

FIG. 1 is a flow chart of a method for detection and early warning according to the present invention.

Figure 2 is a schematic structural diagram of a comprehensive early warning system for battery thermal runaway.

FIG. 3 is a schematic diagram of a thermal runaway internal temperature-voltage curve of a lithium-ion battery.

FIG. 4 is a schematic diagram of a thermal runaway end-face pressure curve of a lithium-ion battery.

Description of marks in the figure:

1. Pressure sensor, 2. Lithium-ion battery, 3. Battery module fixture.

Detailed ways

In order to make those skilled in the art better understand the solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example

As shown in FIG. 1 , the present invention provides a comprehensive early warning method for battery thermal runaway based on end-face pressure detection. The method includes the following steps:

Step 1: Based on the abnormal rise signal of the end face pressure, it is determined to be the state of early self-generating heat of thermal runaway;

Step 2: Increase the flow of liquid cooling coolant in the battery system and the cooling power of the air conditioning system in the vehicle or in the energy storage power station;

Step 3: Wait for the battery system to cool down for 10s to perform the fourth step judgment;

Step 4: If the end face pressure or battery surface temperature still increases sharply or the voltage drops sharply, notify the driver or the staff of the energy storage power station to evacuate quickly and call the fire department to turn on the battery system fire extinguishing device; if the end face pressure and battery surface temperature If there is no continuous sharp increase and no voltage dip, go to step 5;

Step 5: Continue the current working state.

In the second step, the present invention can restore the battery cells to a normal use state by timely and efficient cooling and suppressing the continuous temperature rise at the stage between the self-generated heat of the lithium ion battery and the triggering of thermal runaway, and can use Increase the combined forced cooling of the battery thermal management system and the vehicle air conditioning system to achieve the greatest suppression effect.

In the fourth step, if the combined forced cooling method is used for maximum power cooling for ten seconds and the battery temperature cannot continue to rise, it is determined that the existing thermal management system of the vehicle or the energy storage power station cannot block the thermal runaway of the system.

The judgment basis needs to comprehensively consider the phenomenon of surface temperature rise, end face pressure rise or battery terminal voltage drop in the process of thermal runaway, so as to achieve a comprehensive and accurate judgment.

If any one of the three monitoring quantities of end face pressure, temperature and voltage is abnormal, the thermal runaway comprehensive early warning system will turn on the fire extinguishing part and notify the driver and staff to evacuate to ensure no casualties, and at the same time, it can achieve early contact with the fire department. Contact to reduce economic losses as much as possible; if there is no abnormality in the three indicators, the current working state can be continued.

As shown in Figure 2, the present invention also provides a comprehensive early warning system for battery thermal runaway based on end face pressure detection, specifically:

The battery cells in the battery system are composed of two end splints and two side plates with pre-tightening force through bolts to form modules, or are bundled with steel strips to form modules, and a pressure sensor is set along the direction of battery cell arrangement to accurately measure The end-face pressure increase caused by the self-generated thermal expansion of the lithium-ion battery and the internal reaction gas bulge.

When the ambient temperature of the battery reaches the self-generated heat reaction temperature, the active materials such as electrode materials, electrolytes and additives inside the battery react and release heat, and a certain amount of gas begins to be generated in this process, but thermal runaway has not yet been triggered. The thermal runaway proposed in the present invention is comprehensive The early warning system can take measures such as cooling in time to prevent the temperature from rising continuously to the trigger temperature of thermal runaway by detecting the pressure increase of the battery end face in the early self-generating stage of thermal runaway.

In addition, the thermal runaway comprehensive early warning system proposed by the present invention detects the change in the pressure on the end face of the battery based on the test data of the selected battery cells in the battery system before leaving the factory, and fully considers the heat generation of the battery during the charging and discharging process under normal operating conditions and the charging and discharging process. The deformation caused by the "breathing effect" is supplemented and corrected by the above-mentioned complex variables to the end face pressure in the detection and early warning process to achieve accurate judgment.

Considering the force and heat transfer during the expansion process along the arrangement direction of the battery cells, arranging the pressure sensor between the edge of the battery pack and the clamp or steel belt can realize the thermal runaway state of any battery cell during the dynamic working condition of the battery module. accurate inspection and judgment.

In this example, considering that the temperature during the thermal runaway of the lithium battery is too high, in order to prevent the failure of the pressure sensor, the present invention provides high temperature insulation protection for the outside of the pressure sensor (in this example, mica sheets are used for insulation), so as to realize monitoring and early warning in the real-time dynamic process .

It should be explained that, as shown in FIG. 4 , the pressure on the end face of the lithium-ion battery in this embodiment is divided into the following three stages during the thermal runaway process:

Stage 1: The stage of pressure increase caused by temperature increase and slight reaction gas production;

Stage 2: The pressure relaxation stage when the lithium-ion battery bulges and squeezes out the clamp;

Stage 3: The pressure surge stage caused by the violent reaction of thermal runaway.

The present invention can accurately detect the thermal runaway of the lithium ion battery system in real time, which is of great significance to the mechanism research, model construction and safety improvement design of lithium ion batteries for vehicles and energy storage power stations. The early warning judgment based on the end face pressure adopted by the invention is about 500-900s ahead of the current scientific research and practical technology methods of temperature swell and voltage sag, which can obtain enough escape and fire protection for the early warning and treatment of thermal runaway. Fire extinguishing time, greatly reduce property damage, and eliminate casualties.

The above description is only a specific implementation method of the present invention, and does not limit the present invention. Anything within the spirit and principle of the present invention is included in the protection scope of the present invention.

Claims (10)

1. a comprehensive early warning method for battery thermal runaway based on end face pressure detection, is characterized in that, comprises the following steps: 1) Collect the pressure on the end face of the battery, if the pressure on the end face of the battery rises above the set threshold, it is determined that the battery is in a state of self-generating heat in the early stage of thermal runaway, and go to step 2); 2) After cooling the battery and continuing for a set time, proceed to step 3); 3) Combine the end face pressure, battery surface temperature and voltage to comprehensively judge whether the battery is in a thermal runaway state, and give an early warning. 2. A kind of comprehensive early warning method for battery thermal runaway based on end-face pressure detection according to claim 1, characterized in that, in the step 2), combined with the battery thermal management system and the air-conditioning system to jointly carry out early joint forced cooling, To achieve the maximum temperature rise suppression effect, to restore the battery to a normal use state. 3. A kind of comprehensive early warning method for battery thermal runaway based on end face pressure detection according to claim 2, is characterized in that, described early joint forced cooling is specifically: Increase the flow of liquid-cooled coolant to the battery and increase the cooling power of the air conditioning system in the vehicle or in the energy storage power station. 4 . The comprehensive early warning method for battery thermal runaway based on end-face pressure detection according to claim 1 , wherein, in the step 2), the set time is 10s. 5 . 5. a kind of battery thermal runaway comprehensive early warning method based on end face pressure detection according to claim 1, is characterized in that, in described step 3), when the end face pressure growth rate exceeds the set threshold value, the battery surface temperature increases When the battery rate exceeds the set threshold and the voltage drop rate exceeds the set threshold, it is judged that the battery is in a thermal runaway state. At this time, the battery thermal management system cannot block the battery thermal runaway and notify the driver or the staff of the energy storage power station. Evacuate quickly and call the fire department, and turn on the battery system fire extinguishing device, otherwise the battery will continue to work in its current state. 6. A kind of comprehensive early warning method for battery thermal runaway based on end-face pressure detection according to claim 1, characterized in that, in the step 1), the early self-generated heat state of thermal runaway is specifically that the battery starts to self-generate heat to states between thermal runaway triggers. 7. A comprehensive early warning method for battery thermal runaway based on end-face pressure detection according to claim 5, wherein the battery end-face pressure and the battery surface temperature data are based on the battery cells selected by the battery system before detection. The test data before leaving the factory takes into account the heat production of the battery during the charging and discharging process under normal operating conditions and the deformation and pressure changes caused by the breathing effect. Make accurate judgments. 8. A battery thermal runaway comprehensive early warning system for realizing the comprehensive early warning method for battery thermal runaway according to any one of claims 1 to 7, wherein the system comprises a pressure sensor for collecting the pressure on the battery end face and a The pressure sensor is connected to the processor for realizing the early self-generated heat state of the battery thermal runaway and the judgment of the thermal runaway state. 9. The comprehensive early warning system for battery thermal runaway according to claim 8, wherein the arrangement of the pressure sensor is as follows: In the battery system, a plurality of battery cells connected in series are formed into modules by the clamps at both ends, which are bundled with bolts with pre-tightening force or by steel belts. A pressure sensor is installed to accurately measure the end face pressure increase caused by the self-generated thermal expansion of the lithium-ion battery and the internal reaction gas bulge. 10. A comprehensive early warning system for battery thermal runaway according to claim 9, characterized in that, considering that the temperature of the battery thermal runaway process is too high, in order to prevent the failure of the pressure sensor, the outside of the pressure sensor is subjected to high temperature insulation protection to realize real-time dynamic monitor.

Images