Lithium battery thermal runaway early warning device and method based on MEMS thermoelectric actuator

Abstract

The invention discloses a lithium battery thermal runaway early warning device and method based on an MEMS thermoelectric actuator. The device comprises the MEMS thermoelectric actuator, a laser range finder and a controller. The MEMS thermoelectric actuator is connected with the positive electrode and the negative electrode of the lithium battery, and the MEMS thermoelectric actuator deforms after heating; the laser range finder is used for collecting a deformation signal of the MEMS thermoelectric actuator and transmitting the deformation signal to the controller; and the controller judges the current state of the lithium battery according to the received deformation signal, and sends a thermal runaway early warning signal when the voltage fluctuation of the lithium battery exceeds a set threshold value. According to the invention, the thermoelectric effect is utilized, and the accurate displacement control and monitoring capability of the MEMS thermoelectric actuator is combined, so that the early warning of the thermal runaway of the lithium battery is realized, the safety of the lithium ion battery is obviously improved, the occurrence of thermal runaway events is reduced, and more efficient battery management is realized, and the personnel safety and the equipment integrity are protected.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal runaway warning for lithium-ion batteries, and in particular relates to a thermal runaway warning device and method for lithium-ion batteries based on a MEMS thermoelectric actuator. Background Art

[0002] Thermal runaway is the most serious safety issue of lithium-ion batteries, which may cause the battery to overheat, burn or even explode. At present, the most widely used method of monitoring battery thermal runaway is to determine whether thermal runaway has occurred by monitoring the battery temperature. However, due to the delayed influence of the heat diffusion process, the response speed of the temperature sensor has a lag, and it is difficult to immediately reflect the real-time status of the battery cell. Abnormalities can often only be detected in the late stage of thermal runaway, and early warning cannot be achieved. Therefore, it is particularly important to develop technologies that can detect and warn of thermal runaway early. Summary of the invention

[0003] The purpose of the present invention is to provide a lithium battery thermal runaway warning device and method based on MEMS thermoelectric actuator, so as to solve the technical problem that the thermal runaway warning method in the prior art has a lag, is difficult to immediately reflect the real-time status of the battery cell, and often can only detect abnormalities in the late stage of thermal runaway, making it impossible to achieve early warning.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] Lithium battery thermal runaway warning device based on MEMS thermoelectric actuator, including

[0006] The MEMS thermoelectric actuator is connected to the positive and negative electrodes of the lithium battery. The MEMS thermoelectric actuator will deform after heating;

[0007] Laser rangefinder, used to collect deformation signals of MEMS thermoelectric actuators and transmit them to the controller;

[0008] The controller determines the current state of the lithium battery based on the received deformation signal, and sends out a thermal runaway warning signal when the lithium battery voltage fluctuation exceeds a set threshold.

[0009] Micro-electromechanical systems have shown great potential in the field of sensors due to their miniaturization, integration and intelligence. Among them, MEMS thermoelectric actuators have the characteristics of simple structure, strong execution force, and the ability to output linear displacement. The present invention utilizes the thermoelectric effect and combines the precise displacement control and monitoring capabilities of MEMS thermoelectric actuators to achieve early warning of thermal runaway of lithium batteries, significantly improve the safety of lithium-ion batteries, reduce the occurrence of thermal runaway events, achieve more efficient battery management, and protect personnel safety and equipment integrity.

[0010] Further optimized, the MEMS thermoelectric actuator includes a first hot arm, a second hot arm, a cold arm and a plurality of protrusions, and the second hot arm is located between the first hot arm and the cold arm. The first hot arm, the second hot arm and the cold arm are connected as a whole at one end, and anchor points are respectively set at the other ends. The MEMS thermoelectric actuator is fixedly connected to the base through the three anchor points, and the plurality of protrusions are in contact with the upper surface of the base to ensure that the MEMS thermoelectric actuator remains horizontal.

[0011] The first hot arm is electrically connected to the positive electrode of the lithium battery through a corresponding anchor point connecting wire, and the second hot arm is electrically connected to the negative electrode of the lithium battery through a corresponding anchor point connecting wire.

[0012] Further optimization, the controller includes a data processing module, a judgment module and an early warning module; wherein the data processing module converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery; the judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; before the lithium battery opens the valve, when its voltage fluctuation exceeds the set threshold, the early warning module sends a thermal runaway early warning signal.

[0013] The lithium battery thermal runaway early warning method, based on the above-mentioned lithium battery thermal runaway early warning device, comprises the following steps:

[0014] Step S1: connect the MEMS thermoelectric actuator to the positive and negative electrodes of the lithium battery to be monitored through wires, connect the laser rangefinder to the controller, and align the ray emitting end and receiving end of the laser rangefinder with the side of the cold arm of the MEMS thermoelectric actuator;

[0015] Step S2: After voltage is applied to the MEMS thermoelectric actuator, Joule heat is generated on the first hot arm and the second hot arm, causing deformation. Compared with the cold arm, the hot arm expands more, causing the MEMS thermoelectric actuator to bend toward one side of the cold arm, generating a micro-motion signal; the laser rangefinder measures the distance between it and the MEMS thermoelectric actuator in real time and sends it to the controller.

[0016] Step S3: The data processing module of the controller converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery; the judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; before the lithium battery opens the valve, when its voltage fluctuation exceeds the set threshold, the warning module sends a thermal runaway warning signal.

[0017] Further optimization, in step S3, the data processing module converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery, specifically:

[0018] When voltage V is applied to the MEMS thermoelectric actuator, the MEMS thermoelectric actuator generates heat ΔQ:

[0019] ΔQ=I2 RΔt (1)

[0020] (1)In the formula, R is the resistance of the MEMS thermoelectric actuator, and I is the current flowing through the MEMS thermoelectric actuator;

[0021] And I=V / R, substituting into it, we get:

[0022]

[0023] The heat ΔQ generated on the MEMS thermoelectric actuator will cause its temperature to rise, that is:

[0024] ΔQ=mcΔT (3)

[0025] (3)In the formula, ΔT is the temperature change value of the MEMS thermoelectric actuator, c is the specific heat capacity of the MEMS thermoelectric actuator, and m is the mass of the MEMS thermoelectric actuator;

[0026] Combining equations (2) and (3), we get:

[0027]

[0028] The temperature change ΔT of the MEMS thermoelectric actuator will cause it to expand thermally. The displacement ΔL of the linear expansion is calculated by the linear expansion coefficient α and the original length L, that is:

[0029] ΔL=αLΔT (5) Combining equations (4) and (5), we get:

[0030]

[0031] That is, according to the distance change ΔL between the laser rangefinder and the MEMS thermoelectric actuator, the lithium battery voltage V is obtained:

[0032]

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The lithium battery thermal runaway warning device based on MEMS thermoelectric actuator described in the present invention can sensitively monitor the voltage information changes in the early stage of lithium battery thermal runaway, realize early warning of lithium ion thermal runaway fire, and improve the timeliness and effectiveness of lithium battery fire warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of a lithium battery thermal runaway warning device based on MEMS thermoelectric actuator;

[0036] Figure 2 It is a structural schematic diagram of a MEMS thermoelectric actuator;

[0037] Figure 3 This is the deformation simulation cloud diagram of the MEMS thermoelectric actuator;

[0038] Figure 4 This is a flow chart of the thermal runaway warning method for lithium batteries;

[0039] Figure 5 This is a simulation diagram of the simulation results of lithium battery voltage-MEMS thermoelectric actuator deformation-time. Specific embodiments

[0040] The specific implementation method of the utility model is given below, and the technical solution of the utility model is clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the utility model, not all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0041] Embodiment 1:

[0042] like Figure 1 As shown, the lithium battery thermal runaway warning device based on MEMS thermoelectric actuator includes

[0043] The MEMS thermoelectric actuator 2 is connected to the positive and negative electrodes of the lithium battery 1, and the MEMS thermoelectric actuator 2 is deformed after heating;

[0044] The laser rangefinder 3 is used to collect the deformation signal of the MEMS thermoelectric actuator 2 and transmit it to the controller 4;

[0045] The controller 4 determines the current state of the lithium battery according to the received deformation signal, and sends out a thermal runaway warning signal when the voltage fluctuation of the lithium battery exceeds a set threshold.

[0046] In this embodiment, if Figure 2 As shown, the MEMS thermoelectric actuator 2 includes a first hot arm 21, a second hot arm 22, a cold arm 23 and three bumps 24, and the second hot arm 22 is located between the first hot arm 21 and the cold arm 23. The first hot arm 21 is the longest, the second hot arm 22 is the longest, and the cold arm 23 is the shortest.

[0047] The first hot arm 21, the second hot arm 21 and the cold arm 23 are connected as a whole at one end, and are respectively provided with anchor points at the other ends, which are denoted as the first anchor point, the second anchor point 26 and the third anchor point 27. The MEMS thermoelectric actuator 2 is fixedly connected to the base 5 through the three anchor points, and the multiple protrusions 24 are all in contact with the upper surface of the base to ensure that the MEMS thermoelectric actuator remains horizontal.

[0048] The first hot arm 21 is electrically connected to the positive electrode of the lithium battery 1 through a connecting wire at the first anchor point 25 , and the second hot arm 22 is electrically connected to the negative electrode of the lithium battery 1 through a connecting wire at the second anchor point.

[0049] In this embodiment, the controller 4 includes a data processing module, a judgment module and an early warning module; wherein the data processing module converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery; the judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; before the lithium battery opens the valve, when its voltage fluctuation exceeds the set threshold, the early warning module sends a thermal runaway early warning signal.

[0050] The MEMS thermoelectric actuator is a highly sensitive micro-power MEMS sensing device. When voltage is applied to the thermoelectric actuator, the first hot arm 21 and the second hot arm 22 will generate Joule heat, thereby deforming. Compared with the cold arm 23, the hot arm expands more, causing the actuator to bend and generate micro-motion signals. Therefore, the voltage changes during the battery operation process can be monitored in real time, and the changes in lithium battery voltage can be accurately captured. It can issue a thermal runaway warning in advance, prevent battery thermal runaway and perform fault detection in advance before a serious battery failure event occurs, and achieve early perception and early intervention, with extremely low power consumption.

[0051] like Figure 3 As shown in FIG. 1 , the simulation result cloud diagram of the MEMS thermoelectric actuator provided in this embodiment. When a voltage is applied to the thermoelectric actuator, it deforms, such as Figure 3 The solid line portion shown in the figure represents the initial state, and the cloud diagram results represent the deformation result after applying a certain voltage.

[0052] Embodiment 2:

[0053] like Figure 4 As shown, the lithium battery thermal runaway warning method, based on the above-mentioned lithium battery thermal runaway warning device, includes the following steps:

[0054] Step S1: connect the MEMS thermoelectric actuator to the positive and negative electrodes of the lithium battery to be monitored through wires, connect the laser rangefinder to the controller, and align the ray emitting end and receiving end of the laser rangefinder with the side of the cold arm of the MEMS thermoelectric actuator.

[0055] Step S2: After voltage is applied to the MEMS thermoelectric actuator, Joule heat is generated on the first hot arm and the second hot arm, causing deformation. Compared with the cold arm, the hot arm expands more, causing the MEMS thermoelectric actuator to bend toward one side of the cold arm, generating a micro-motion signal; the laser rangefinder measures the distance between it and the MEMS thermoelectric actuator cold arm in real time and sends it to the controller.

[0056] Step S3: The data processing module of the controller converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery; the judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; before the lithium battery opens the valve, when its voltage fluctuation exceeds the set threshold, the warning module sends a thermal runaway warning signal.

[0057] In step S3, the data processing module converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery, specifically:

[0058] When voltage V is applied to the MEMS thermoelectric actuator, the MEMS thermoelectric actuator generates heat ΔQ:

[0059] ΔQ=I 2 RΔt (1)

[0060] (1)In the formula, R is the resistance of the MEMS thermoelectric actuator, and I is the current flowing through the MEMS thermoelectric actuator;

[0061] And I=V / R, substituting into it, we get:

[0062]

[0063] The heat ΔQ generated on the MEMS thermoelectric actuator will cause its temperature to rise, that is:

[0064] ΔQ=mcΔT (3)

[0065] (3)In the formula, ΔT is the temperature change value of the MEMS thermoelectric actuator, c is the specific heat capacity of the MEMS thermoelectric actuator, and m is the mass of the MEMS thermoelectric actuator;

[0066] Combining equations (2) and (3), we get:

[0067]

[0068] The temperature change ΔT of the MEMS thermoelectric actuator will cause it to expand thermally. The displacement ΔL of the linear expansion is calculated by the linear expansion coefficient α and the original length L, that is:

[0069] ΔL=αLΔT (5)

[0070] Combining equations (4) and (5), we get:

[0071]

[0072] That is, according to the distance change ΔL between the MEMS thermoelectric actuator and the first thermal arm measured by the laser rangefinder, the lithium battery voltage V is obtained:

[0073]

[0074] In the above formula, R, m, c, α and L are all known parameters.

[0075] In this embodiment, the controller 4 obtains a simulation result diagram of the lithium battery voltage-MEMS thermoelectric actuator deformation-time according to the signal analysis collected in real time by the laser rangefinder 3, as shown in FIG. Figure 5 As shown. Wherein, voltage is the experimental data of the open circuit voltage during the thermal runaway of lithium battery. The real-time open circuit voltage of lithium battery can be obtained by the displacement change ΔL of MEMS thermoelectric actuator and formula (7). Figure 5 It can be seen that the displacement of the MEMS thermal actuator changes with the change of voltage. From the experimental data of voltage, it can be seen that the battery will open the valve before thermal runaway occurs, and the time interval between valve opening and thermal runaway reaches 530s. From the local enlarged image, it can be seen that before 3500 seconds, when the voltage boost rate decreased by 48.7% (±10%), it was determined to be a normal fluctuation of the lithium battery voltage. Before the battery opened the valve, the voltage had changed abnormally at 3500 seconds. At this time, when the voltage boost rate decreased by 283.3%, it was determined to be a precursor to thermal runaway of the lithium battery. The controller will make a quick judgment and send out an early warning signal. The time interval between the early warning moment and the thermal runaway reached 3818s, which is enough to make relevant plans to deal with thermal runaway.

[0076] The thermal runaway warning device in the prior art that uses temperature as a warning signal cannot capture this tiny signal due to the delayed effect of heat diffusion. The thermal runaway warning system based on MEMS thermoelectric actuator described in the present invention can accurately monitor tiny fluctuations in voltage, thereby achieving early warning of thermal runaway.

[0077] The above-mentioned embodiments only express the implementation methods of the present application, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these modifications and improvements all belong to the protection scope of the present application.

Claims

1. A lithium battery thermal runaway warning device based on MEMS thermoelectric actuator, characterized in that: include The MEMS thermoelectric actuator is connected to the positive and negative electrodes of the lithium battery. The MEMS thermoelectric actuator will deform after heating; Laser rangefinder, used to collect deformation signals of MEMS thermoelectric actuators and transmit them to the controller; The controller determines the current state of the lithium battery based on the received deformation signal, and sends out a thermal runaway warning signal when the lithium battery voltage fluctuation exceeds a set threshold.

2. The lithium battery thermal runaway warning device based on MEMS thermoelectric actuator according to claim 1 is characterized in that: The MEMS thermoelectric actuator comprises a first hot arm, a second hot arm, a cold arm and a plurality of bumps, wherein the second hot arm is located between the first hot arm and the cold arm; The first hot arm, the second hot arm and the cold arm are connected as a whole at one end and are respectively provided with anchor points at the other ends. The MEMS thermoelectric actuator is fixedly connected to the base through the three anchor points, and the multiple protrusions are in contact with the upper surface of the base to ensure that the MEMS thermoelectric actuator remains horizontal. The first hot arm is electrically connected to the positive electrode of the lithium battery through a corresponding anchor point connecting wire, and the second hot arm is electrically connected to the negative electrode of the lithium battery through a corresponding anchor point connecting wire.

3. The lithium battery thermal runaway warning device based on MEMS thermoelectric actuator according to claim 2 is characterized in that: The controller includes a data processing module, a judgment module and an early warning module; Among them, the data processing module converts the deformation signal of the MEMS thermoelectric actuator into the real-time voltage signal of the lithium battery; The judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; Before the lithium battery opens its valve, when its voltage fluctuation exceeds the set threshold, the warning module sends a thermal runaway warning signal.

4. A lithium battery thermal runaway early warning method, characterized in that: The lithium battery thermal runaway warning device according to claim 3 comprises the following steps: Step S1: Connect the MEMS thermoelectric actuator to the positive and negative electrodes of the lithium battery to be monitored through wires, connect the laser rangefinder to the controller, and align the ray emitting end and receiving end of the laser rangefinder with the side of the MEMS thermoelectric actuator; Step S2: After the voltage is applied to the MEMS thermoelectric actuator, Joule heat is generated on the first thermal arm and the second thermal arm, thereby causing deformation and generating a micro-motion signal; the laser rangefinder measures the distance between it and the MEMS thermoelectric actuator in real time and sends it to the controller; Step S3: The data processing module of the controller converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery; the judgment module compares the real-time voltage signal with the reference voltage to determine the current working state of the lithium battery; before the lithium battery opens the valve, when its voltage fluctuation exceeds the set threshold, the warning module sends a thermal runaway warning signal.

5. The lithium battery thermal runaway early warning method according to claim 4, characterized in that: In step S3, the data processing module converts the deformation signal of the MEMS thermoelectric actuator into a real-time voltage signal of the lithium battery, specifically: When voltage V is applied to the MEMS thermoelectric actuator, the MEMS thermoelectric actuator generates heat ΔQ: ΔQ=I 2 RΔt (1) (1)In the formula, R is the resistance of the MEMS thermoelectric actuator, and I is the current flowing through the MEMS thermoelectric actuator; And I=V / R, substituting into it, we get: The heat ΔQ generated on the MEMS thermoelectric actuator will cause its temperature to rise, that is: ΔQ=mcΔT (3) (3)In the formula, ΔT is the temperature change value of the MEMS thermoelectric actuator, c is the specific heat capacity of the MEMS thermoelectric actuator, and m is the mass of the MEMS thermoelectric actuator; Combining equations (2) and (3), we get: The temperature change ΔT of the MEMS thermoelectric actuator will cause it to expand thermally. The displacement ΔL of the linear expansion is calculated by the linear expansion coefficient α and the original length L, that is: ΔL=αLΔT (5) Combining equations (4) and (5), we get: That is, according to the distance change ΔL between the laser rangefinder and the MEMS thermoelectric actuator, the lithium battery voltage V is obtained:

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