Device and method for early warning, prevention and control of thermal runaway of battery pack

Abstract

The invention provides a device and method for early warning, prevention and control of thermal runaway of a battery pack, and belongs to the technical field of safety protection of the battery pack, the device comprises at least two batteries which are stacked and fixedly arranged along the thickness direction, the positive electrodes of the at least two batteries are electrically connected in sequence, and the negative electrode pages of the at least two batteries are electrically connected in sequence; the equivalent resistor is arranged between the at least two batteries, and the two ends of the equivalent resistor are electrically connected with the positive electrodes and the negative electrodes of the different batteries through wires respectively; the plurality of thermocouples are arranged on the end face, far away from the equivalent resistor, of the uppermost battery and used for measuring the temperatures of different positions of the surfaces of the batteries; the charging and discharging device is electrically connected with the positive electrodes or the negative electrodes of the at least two batteries and is used for carrying out constant-current charging or constant-current discharging on the at least two batteries according to a fixed multiplying power; wherein the equivalent resistor is combined with at least two batteries and is used for simulating the batteries which are subjected to internal short circuit before thermal runaway. And judging whether thermal runaway exists or not by comparing the DTV curve of the battery to be detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-volatile memory, and in particular to a device and method for battery pack thermal runaway early warning prevention and control. BACKGROUND

[0002] In the era of pursuing green and efficient energy utilization, new energy equipment such as electric vehicles relying on battery packs for energy supply has already entered the lives of the public, and the market share is showing a rapid growth trend. With the wide application of new energy equipment such as electric vehicles, the safety of battery packs as the core energy supply components has attracted much attention. During the actual operation of the battery pack, it faces many challenges from unstable factors. On the one hand, if the charging link is not properly controlled, overcharging is likely to occur, and excessive electrical energy flows into the battery, breaking the original chemical balance; during discharging, it may also fall into over-discharging dilemma, and excessive consumption of electrical quantity damages the internal structure of the battery. On the other hand, line aging, insulation layer damage, etc. may cause short circuit failure, and the instantaneous large current impact will cause the internal temperature of the battery to rise sharply. In addition, when the new energy equipment works continuously in a high-temperature environment, the heat accumulates and is difficult to dissipate, and the chemical reaction rate inside the battery is out of control. Even if the external environment is suitable, the internal material aging and electrode corrosion of the battery after long-term use also occur from time to time.

[0003] These complex and diverse adverse factors may all cause thermal runaway. Once thermal runaway occurs, not only will the battery pack heat up rapidly, but the internal temperature of the battery pack will soar to an extremely high point in a short time, and a large amount of heat accumulation will make the battery shell unable to bear the load, and even melt and deform, which may catch fire at any time. If the fire is not timely contained, in scenarios such as electric vehicle driving and energy storage power station operation, the life safety of surrounding personnel will be severely threatened, and the surrounding environment will be polluted by smoke, fire, and possibly leaked toxic electrolyte.

[0004] Therefore, the present application proposes a device and method for battery pack thermal runaway early warning prevention and control, which can reliably monitor the working state of the battery pack and timely issue a warning when the battery pack is abnormal, especially when there is an internal short circuit, to avoid serious accidents, which is very necessary. SUMMARY

[0005] Therefore, the present application proposes a device and method for battery pack thermal runaway early warning prevention and control, which can reliably monitor the working state of the battery pack and timely issue a warning when the battery pack is abnormal, especially when there is an internal short circuit, to avoid serious accidents, which is very necessary.

[0006] In one aspect, the present application provides a device for battery pack thermal runaway early warning prevention and control, comprising: At least two batteries are stacked and fixed along the thickness direction, and the positive poles of the at least two batteries are sequentially electrically connected, and the negative poles of the at least two batteries are sequentially electrically connected; An equivalent resistance is arranged between the at least two batteries, and the two ends of the equivalent resistance are respectively electrically connected to the positive poles and the negative poles of different batteries through wires; A plurality of thermocouples are arranged on the end face of the uppermost battery away from the equivalent resistance, and are used to measure the temperatures at different positions on the surface of the battery; A charging and discharging device is respectively electrically connected to the positive poles or the negative poles of the at least two batteries, and is used to perform constant-current charging or constant-current discharging on the at least two batteries at a fixed rate; The equivalent resistance is combined with the at least two batteries to simulate a battery that has an internal short circuit before thermal runaway.

[0007] On the basis of the above technical scheme, preferably, the plurality of thermocouples are arranged at positions (L / 10, W / 2), (L / 2, W / 2) and (9L / 10, W / 2) on the end face of the battery, wherein L is the length of the battery, and W is the width of the battery.

[0008] On the basis of the above technical scheme, preferably, the current size of the charging and discharging device for constant-current charging or constant-current discharging is 1C.

[0009] On the basis of the above technical scheme, preferably, the at least two batteries are lithium iron phosphate batteries or ternary lithium batteries.

[0010] Preferably, the equivalent resistance is a metal film resistance or a power electric heating resistance wire.

[0011] On the basis of the above technical scheme, preferably, the device further comprises a thermostat, and the at least two batteries, the equivalent resistance and the plurality of thermocouples are arranged in the thermostat.

[0012] On the basis of the above technical scheme, preferably, the equivalent resistance is provided with a starting switch, and the action time of the starting switch is consistent with the action time of the charging and discharging device.

[0013] On the basis of the above technical scheme, preferably, the device further comprises a thermostat, and the at least two batteries, the equivalent resistance and the plurality of thermocouples are arranged in the thermostat. S1: aligning the device for battery pack thermal runaway early warning and prevention described above; S2: arranging the at least two batteries, the equivalent resistance and the plurality of thermocouples in the thermostat, keeping the temperature constant at 25℃; using the charging and discharging device to perform charging and discharging experiments on the at least two batteries, and the size of the charging current or the discharging current is 1C; S3: Record the temperature at different locations on the battery surface collected by several thermocouples, as well as the battery terminal voltage, to obtain the voltage-temperature relationship under constant current charging or constant current discharging conditions. Solve the first derivative to obtain the V-dT / dV curve of the terminal voltage-temperature change, which is used to describe the temperature rise of the battery under unit voltage. Record and save the V-dT / dV curve of the terminal voltage-temperature change of the battery under different aging conditions as reference data. S4: Several thermocouples are also configured on the battery under test to obtain the terminal voltage and surface temperature of the battery under test under constant current charging or constant current discharging conditions, and convert them into the corresponding terminal voltage-temperature change of the battery under test as measured data. S5: By comparing the measured data with the benchmark data, determine whether the battery under test shows signs of thermal runaway.

[0014] Preferably, step S4 includes the following: S41: Select a discharge rate of 1C and discharge the battery to be tested to SOC1 beforehand; assume that the ambient temperature remains constant. S42: Using a charging rate of 1C, charge the battery under test to SOC2, obtain the SOC change ΔSOC = SOC2 - SOC1 at the current ambient temperature Tbatt, and the charging capacity C corresponding to the charging start-end time period Δt. charge = (I×△t) / 3600, where I is the charging current I=1C, and the measured maximum capacity of the battery under test at the current ambient temperature is C. t =C charge / △SOC, converted to the maximum capacity under constant temperature chamber conditions, is C. normal =C t ×exp[(Ea / R) ×(1 / Tbatt+273.15)-1 / (Tc+273.15) ×I n（Tbatt）-1 ], n(Tbatt) is the temperature-dependent Peukert constant; the health state of the battery under test at the corresponding temperature Tc in the constant temperature chamber is SOH = (C normal / SOCrated)×100%, where SOCrated is the rated capacity of the battery under test at the corresponding temperature Tc in the constant temperature chamber; Obtain the State of Health (SOH) of the battery under test at the corresponding temperature Tc in the constant temperature chamber. During the charging process at a charging rate of 1C, record the V-dT / dV curve of the terminal voltage-temperature change of the battery under test as the measured data.

[0015] Further preferably, step S5 involves finding the benchmark data of the V-dT / dV curve of the terminal voltage-temperature change of the battery with the closest aging degree in the benchmark data and comparing it with the measured data: when the peak value of the measured data is within 10% of the peak value of the benchmark data, it is considered that the battery under test does not have thermal runaway; when the peak value of the measured data exceeds 10% of the peak value of the benchmark data, and as the number of charging cycles increases, the peak value of the measured data curve shifts to the left relative to the peak value of the benchmark data, it is considered that the battery under test has thermal runaway, and an alarm message will be issued.

[0016] The present invention provides a device and method for early warning and prevention of thermal runaway in battery packs, which has the following advantages compared with the prior art: 1. This invention uses an equivalent resistance to perform a substitution experiment to simulate a battery that has an internal short circuit before thermal runaway, obtains the temperature of the thermocouple on the battery surface to calculate its DTV curve, and compares the peak value changes of the battery under test with those of a normal battery. This allows for timely detection and early warning of early thermal runaway in the battery under test, thereby improving vehicle safety performance. 2. By configuring an external equivalent resistor and setting a thermocouple on the battery surface, the short circuit situation in the early and middle stages inside the battery can be simulated, thus eliminating the need to use conventional methods such as puncture and squeezing that damage the structure of the battery under test. 3. A baseline curve for obtaining normal batteries under different aging levels was defined, and a temperature-rate compensation model was constructed. This ensures that even under different ambient temperatures and usage rates, the measured data can be converted to standard conditions for comparison, greatly improving the practicality and robustness of the solution;

[0017] 4. Clear rules for judging curve peaks are given, which can accurately quantify and evaluate the thermal runaway of batteries. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a device and method for early warning and prevention of thermal runaway in a battery pack according to the present invention. Figure 2 This is a structural diagram of the device and method for early warning and prevention of thermal runaway in battery packs according to the present invention. Figure 3This is a schematic diagram of the DTV curves of a normal battery and an internally short-circuited battery, representing a device and method for early warning and prevention of thermal runaway in a battery pack according to the present invention.

[0020] Reference numerals in the attached diagram: 1. Thermocouple; 2. Wire; 3. Equivalent resistance; 4. Switch; 5. Battery. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Existing technologies lack reliable means to monitor the operating status of battery packs and provide timely warnings in case of battery pack malfunctions, especially internal short circuits. Therefore, such as... Figure 2 As shown, the present invention provides a device for early warning and prevention of thermal runaway in battery packs, comprising:

[0023] At least two batteries 5 are stacked and fixedly arranged along the thickness direction, and the positive terminals of the at least two batteries 5 are sequentially electrically connected, and the negative terminals of the at least two batteries are sequentially electrically connected; the batteries here are batteries in normal condition.

[0024] Equivalent resistance 3 is set between at least two batteries, and the two ends of the equivalent resistance are electrically connected to the positive and negative terminals of different batteries respectively through wires 2. Several thermocouples 1 are set on the end face of the uppermost battery that is away from the equivalent resistance, and are used to measure the temperature at different locations on the surface of the battery. A charging and discharging device, electrically connected to the positive or negative terminals of at least two batteries respectively, is used to perform constant current charging or constant current discharging on at least two batteries at a fixed rate; It also includes a constant temperature chamber, in which at least two batteries 5, equivalent resistors 3, several thermocouples 1, wires 2 and switches 4 are installed.

[0025] The equivalent resistor, combined with at least two batteries, simulates an internal short circuit before thermal runaway, i.e., it simulates an internal short circuit through an external short circuit. The equivalent resistor 3 is also equipped with a start switch 4, and the operating time of the start switch 4 is consistent with the operating time of the charging and discharging device. Since there is no need to puncture or squeeze the battery, simply changing the resistance value of the equivalent resistor can simulate short circuit conditions at different stages.

[0026] like Figure 2As shown, to obtain temperature detection signals at different locations on the battery, several thermocouples are positioned at (L / 10, W / 2), (L / 2, W / 2), and (9L / 10, W / 2) positions on the battery end face, where L is the length of the battery and W is the width of the battery. The positions in parentheses represent planar coordinates, with the length direction of the battery as the x-axis and the width direction of the battery as the y-axis.

[0027] In a preferred embodiment, the constant current charging or discharging current of the charging and discharging device is 1C. At least two batteries are lithium iron phosphate batteries or ternary lithium batteries. The equivalent resistance is a metal film resistor or a power heating wire. Depending on the needs, the equivalent resistance can be set to different values, such as 0Ω, 50Ω, 75Ω, or 100Ω, to simulate batteries with different internal short-circuit states; it can also be arbitrarily set as needed.

[0028] To improve the reliability of experimental data, the temperature inside the incubator was maintained at 25℃±1℃.

[0029] like Figure 1 As shown, on the other hand, the present invention also provides a method for early warning and prevention of thermal runaway in battery packs, comprising the following steps: S1: As Figure 2 As shown, the above-mentioned device for early warning and prevention of thermal runaway in battery packs is registered.

[0030] S2: Place at least two batteries, an equivalent resistor, and several thermocouples in a constant temperature chamber and keep the temperature constant at 25°C; use a charge-discharge device to conduct a charge-discharge experiment on at least two batteries, with the charging current or discharging current being 1C.

[0031] S3: Record the temperatures at different locations on the battery surface collected by several thermocouples, as well as the battery's terminal voltage, to obtain the voltage-temperature relationship under constant current charging or discharging conditions. Solve the first derivative to obtain the V-dT / dV curve of the terminal voltage-temperature change, which is used to describe the temperature rise of the battery under unit voltage. Record and save the V-dT / dV curves of the terminal voltage-temperature change of the battery under different aging levels as reference data. This is an early warning method based on differential thermal voltage-current characteristic (DTV) curves.

[0032] like Figure 3As shown, the horizontal axis of the V-dT / dV curve represents voltage, and the vertical axis represents the rate of change of temperature with respect to voltage. The differential thermal voltage-current transformer (DTV) curve is obtained by solving the first derivative of the terminal voltage-temperature VT under constant current charging or discharging conditions, resulting in the V-dT / dV curve representing the terminal voltage-temperature change. DTVB is typically solved using a fixed voltage range to avoid errors introduced by fitting the VT curve. A fixed voltage range ΔV is used instead of dV, where ΔT represents the temperature change within that range. When the fixed voltage range ΔV approaches 0, dV / dT ≈ ΔV / ΔT. Figure 3 The DTV_0 shown indicates the experimental result of a battery without an internal short circuit, i.e., an equivalent resistance of 0, while DTV_75 indicates the experimental result of a battery with an equivalent resistance of 75Ω and an internal short circuit. Obtaining benchmark data lays the foundation for subsequent data comparison with batteries to be tested.

[0033] S4: Several thermocouples are also configured on the battery under test to obtain the terminal voltage and surface temperature of the battery under test under constant current charging or constant current discharging conditions, and convert them into the corresponding calculated terminal voltage-temperature change of the battery under test as measured data.

[0034] Step S4 includes the following: S41: Select a discharge rate of 1C and discharge the battery to be tested to SOC1 beforehand; assume that the ambient temperature remains constant. S42: Using a charging rate of 1C, charge the battery under test to SOC2, obtain the SOC change ΔSOC = SOC2 - SOC1 at the current ambient temperature Tbatt, and the charging capacity C corresponding to the charging start-end time period Δt. charge = (I×△t) / 3600, where I is the charging current I=1C, and the measured maximum capacity of the battery under test at the current ambient temperature is C. t =C charge / △SOC, converted to the maximum capacity under constant temperature chamber conditions, is C. normal =C t ×exp[(Ea / R) ×(1 / Tbatt+273.15)-1 / (Tc+273.15) ×I n（Tbatt）-1 ], n(Tbatt) is the temperature-dependent Peukert constant; the health state of the battery under test at the corresponding temperature Tc in the constant temperature chamber is SOH = (C normal / SOCrated)×100%, where SOCrated is the rated capacity of the battery under test at the corresponding temperature Tc in the constant temperature chamber; Obtain the State of Health (SOH) of the battery under test at the corresponding temperature Tc in the constant temperature chamber. During the charging process at a charging rate of 1C, record the V-dT / dV curve of the terminal voltage-temperature change of the battery under test as the measured data.

[0035] The reason for the above conversion is that the operating conditions of the battery under test are not necessarily under constant temperature chamber conditions. Therefore, the capacity measured under actual operating conditions needs to be converted to the internal temperature conditions of the constant temperature chamber and then converted into the corresponding state of health (SOH) to improve the reliability and accuracy of subsequent peak comparison.

[0036] S5: By comparing the measured data with the benchmark data, determine whether the battery under test shows signs of thermal runaway.

[0037] Step S5 involves finding the battery with the closest aging level among the reference data and comparing the benchmark data with the measured data for the V-dT / dV curve of the terminal voltage-temperature change. When the peak value of the measured data is within 10% of the peak value of the benchmark data, the battery under test is considered to be free from thermal runaway. When the peak value of the measured data exceeds 10% of the peak value of the benchmark data, and the peak value of the measured data curve shifts to the left relative to the peak value of the benchmark data as the number of charging cycles increases, the battery under test is considered to be free from thermal runaway, and an alarm message will be issued.

[0038] At higher temperatures in externally short-circuited batteries, the kinetics of redox reactions within the battery are significantly accelerated, and the ion migration rate is markedly enhanced, effectively reducing the kinetic resistance to lithium-ion insertion / extraction. This synergistic effect directly leads to a significant increase in the Joule heat generation rate within the battery, enabling the battery to achieve the same rate of change of state of charge at lower voltages. Therefore, the peak value of DTV is higher, and the peak value of the dT / dV curve of the externally short-circuited battery shifts to lower voltage values. The increase in temperature affects the reaction rate constant. The increase in A, where A is the frequency factor, R is the ideal gas constant, T is the thermodynamic temperature, and Ea is the activation energy, along with the decrease in ion migration resistance and other reactions, reduces the internal resistance of the battery, increases the current flowing through the battery, and further increases the Joule heat generation rate of the battery.

[0039] Furthermore, by leveraging the characteristics of the DTV curve, a threshold-based method can be used for early warning and prevention of thermal runaway. The content of the threshold judgment is as described above.

[0040] Compared to existing technologies, the present invention can amplify the slight temperature changes of the battery during the early and middle stages of a short circuit, forming the difference between the highest and lowest peaks, thereby achieving diagnosis. At the same time, only the surface temperature of the battery needs to be collected, without the need for internal temperature changes.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for early warning and prevention of thermal runaway in battery packs, characterized in that, include: At least two batteries are stacked and fixedly arranged along the thickness direction, and the positive electrodes of the at least two batteries are sequentially electrically connected, and the negative electrodes of the at least two batteries are sequentially electrically connected. Equivalent resistance is set between at least two batteries, and the two ends of the equivalent resistance are electrically connected to the positive and negative terminals of different batteries respectively through wires. Several thermocouples are placed on the end face of the uppermost battery that is furthest from the equivalent resistance, and are used to measure the temperature at different locations on the surface of the battery. A charging and discharging device, electrically connected to the positive or negative terminals of at least two batteries respectively, is used to perform constant current charging or constant current discharging on at least two batteries at a fixed rate; The equivalent resistance is combined with at least two cells to simulate a cell that has an internal short circuit before thermal runaway.

2. The device for early warning and prevention of thermal runaway in battery packs according to claim 1, characterized in that, The thermocouples are positioned at (L / 10, W / 2), (L / 2, W / 2), and (9L / 10, W / 2) positions on the battery end face, where L is the length of the battery and W is the width of the battery.

3. The device for early warning and prevention of thermal runaway in battery packs according to claim 1, characterized in that, The constant current for charging or discharging in the charging / discharging device is 1C.

4. The device for early warning and prevention of thermal runaway in battery packs according to claim 1, characterized in that, The at least two batteries are either lithium iron phosphate batteries or ternary lithium batteries.

5. The device for early warning and prevention of thermal runaway in a battery pack according to claim 4, characterized in that, The equivalent resistance is a metal film resistor or a power heating wire.

6. The device for early warning and prevention of thermal runaway in a battery pack according to claim 1, characterized in that, It also includes a constant temperature chamber, in which at least two batteries, an equivalent resistor, and several thermocouples are placed.

7. The device for early warning and prevention of thermal runaway in a battery pack according to claim 1, characterized in that, The equivalent resistance is equipped with a start switch, and the operating time of the start switch is consistent with the operating time of the charging and discharging device.

8. A method for early warning and prevention of thermal runaway in battery packs, characterized in that, Includes the following steps: S1: Registered with the device for early warning and prevention of thermal runaway of battery pack as described in any one of claims 1-7; S2: Place at least two batteries, an equivalent resistor, and several thermocouples in a constant temperature chamber and keep the temperature constant at 25°C; use a charging and discharging device to conduct a charging and discharging experiment on at least two batteries, with the charging current or discharging current being 1C. S3: Record the temperature at different locations on the battery surface collected by several thermocouples, as well as the battery terminal voltage, to obtain the voltage-temperature relationship under constant current charging or constant current discharging conditions. Solve the first derivative to obtain the V-dT / dV curve of the terminal voltage-temperature change, which is used to describe the temperature rise of the battery under unit voltage. Record and save the V-dT / dV curve of the terminal voltage-temperature change of the battery under different aging conditions as reference data. S4: Several thermocouples are also configured on the battery under test to obtain the terminal voltage and surface temperature of the battery under test under constant current charging or constant current discharging conditions, and convert them into the corresponding terminal voltage-temperature change of the battery under test as measured data. S5: By comparing the measured data with the benchmark data, determine whether the battery under test shows signs of thermal runaway.

9. A method for early warning and prevention of thermal runaway in a battery pack according to claim 8, characterized in that, Step S4 includes the following: S41: Select a discharge rate of 1C and discharge the battery to be tested to SOC1 beforehand; assume that the ambient temperature remains constant. S42: Using a charging rate of 1C, charge the battery under test to SOC2, obtain the SOC change ΔSOC = SOC2 - SOC1 at the current ambient temperature Tbatt, and the charging capacity C corresponding to the charging start-end time period Δt. charge = (I×△t) / 3600, where I is the charging current I=1C, and the measured maximum capacity of the battery under test at the current ambient temperature is C. t =C charge / △SOC, converted to the maximum capacity under constant temperature chamber conditions, is C. normal =C t ×exp[(Ea / R) ×(1 / Tbatt+273.15)-1 / (Tc+273.15) ×I n（Tbatt）-1 ], n(Tbatt) is the temperature-dependent Peukert constant; the health state of the battery under test at the corresponding temperature Tc in the constant temperature chamber is SOH = (C normal / SOCrated)×100%, where SOCrated is the rated capacity of the battery under test at the corresponding temperature Tc in the constant temperature chamber; Obtain the State of Health (SOH) of the battery under test at the corresponding temperature Tc in the constant temperature chamber. During the charging process at a charging rate of 1C, record the V-dT / dV curve of the terminal voltage-temperature change of the battery under test as the measured data.

10. A method for early warning and prevention of thermal runaway in a battery pack according to claim 9, characterized in that, Step S5 involves finding the battery with the closest aging level among the reference data and comparing the benchmark data with the measured data for the V-dT / dV curve of the terminal voltage-temperature change. When the peak value of the measured data is within 10% of the peak value of the benchmark data, the battery under test is considered to be free from thermal runaway. When the peak value of the measured data exceeds 10% of the peak value of the benchmark data, and the peak value of the measured data curve shifts to the left relative to the peak value of the benchmark data as the number of charging cycles increases, the battery under test is considered to be free from thermal runaway, and an alarm message will be issued.

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