Battery thermal runaway heat estimation device and method

Abstract

The application discloses a battery thermal runaway heat estimation device and method, heat in high-temperature gaseous state is fully exchanged into liquid medium by heat exchange, the proportion of heat absorbed by inert gas above a sealed tank is reduced, and the accuracy of heat calculation of the liquid medium is improved. The instruments and equipment used in the application are common articles, the device has small development risk and low cost, and the device structure is simple, and operation and maintenance are facilitated. The application can accurately measure the temperature rise of the liquid medium with specific heat capacity, and the thermal runaway heat of the battery is calculated from the side, so that the estimation accuracy is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery energy storage, and particularly relates to a device and method for estimating heat generated by battery thermal runaway. BACKGROUND

[0002] In recent years, many battery energy storage fire accidents have occurred at home and abroad, mainly due to thermal runaway reactions of lithium ion batteries, causing fires and explosions. In order to prevent thermal runaway of lithium ion batteries, the operating state of the battery needs to be strictly managed. Since thermal runaway of the battery is a process in which the balance between heat accumulation and dissipation is broken, causing the temperature of the battery to rise, therefore, the thermal management of the battery is very critical.

[0003] The traditional battery thermal management is to design the heat dissipation capacity of the air cooling system and liquid cooling system based on the heat generated by the battery under normal operating conditions, so that the heat generated during the normal charging and discharging process of the battery can be quickly removed, and the battery can always be kept within the specified operating temperature range. However, from the actual application of current energy storage projects, this is far from enough. Conventional heat dissipation methods cannot quickly and effectively divert heat away before the battery thermal runaway, and cannot quickly and effectively suppress the temperature rise of the battery. Therefore, on the one hand, the thermal management capability of the battery needs to be strengthened, and on the other hand, a new cooling technology that can have a rapid cooling effect needs to be developed. However, regardless of which one, first of all, the heat generated by the battery thermal runaway needs to be accurately estimated, and based on this, the cooling power, heat dissipation structure, etc. can be designed accordingly.

[0004] Currently, there are many ways to estimate the heat generated by battery thermal runaway. The most common one is to use an accelerating adiabatic calorimeter to estimate the heat generated by battery thermal runaway in an adiabatic environment. However, this calculation method has a problem that the specific heat capacity of the battery is approximately the specific heat capacity of the battery at normal temperature and steady state, which is quite different from the specific heat capacity of the battery at high temperature state during thermal runaway. The accuracy is poor, and this method needs to use an accelerating adiabatic calorimeter, which has a high cost.

[0005] Patent CN202111260324 (a method and device for measuring lithium battery thermal runaway heat release in real time), which places a sample lithium battery in a protective cage of a combustion bomb, and heats the sample lithium battery at a set heating power; according to the temperature rise and mass change of the sample lithium battery, the change of the internal gas pressure value of the combustion bomb, etc., the heat release of the sample lithium battery is finally calculated. This method considers comprehensively, but the deficiency is that it does not give the value of the specific heat capacity of the battery at constant pressure, which is necessary for calculation. As mentioned above, the specific heat capacity of the battery at constant pressure at normal temperature is quite different from that at high temperature state during thermal runaway, and the specific heat capacity at high temperature state during thermal runaway is difficult to measure accurately.

[0006] CN201910113056 (A method for calculating heat generation of lithium ion battery thermal runaway), this patent is also to calculate the heat generation of battery thermal runaway, by heating the battery to thermal runaway, measuring the temperature change of the battery surface to calculate the heating power and heat dissipation coefficient, then establishing the thermal abuse model of the battery, and calculating the heat of the battery thermal runaway through the model. The same as CN202111260324 is that both need to determine the specific heat capacity of the battery, so this patent also has the same problem as patent CN202111260324.

[0007] CN201811025249 (A method for calculating energy of lithium ion battery thermal runaway), this patent is to establish a battery pack heat transfer and energy transfer calculation model through a heat balance equation. This patent technology needs to use the average specific heat capacity of battery thermal runaway, and also has the problem of the above-mentioned patent CN202111260324.

[0008] In summary, the existing technologies all use the specific heat capacity of the battery at room temperature stable stage instead of the specific heat capacity of the battery at high temperature stage of thermal runaway, which deviates from the actual situation. SUMMARY

[0009] To overcome the problems in the prior art, the purpose of the present application is to provide a battery thermal runaway heat estimation method and device, which can accurately calculate the heat generated by battery thermal runaway.

[0010] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0011] A battery thermal runaway heat estimation device, comprising a sealed tank, a conduit is arranged at the top of the tank, a heat insulation cavity is arranged in the tank, a liquid medium for placing a battery and a capillary tube is arranged in the heat insulation cavity, a pipeline is arranged at the pressure relief valve on the surface of the shell of the battery, the outlet of the pipeline is divided into two paths, one path is connected with the conduit, and the other path is connected with the capillary tube arranged in the liquid medium.

[0012] Further, a pressure gauge and a second thermometer are arranged above the heat insulation cavity.

[0013] Further, a first thermometer and a stirring rod extending into the liquid medium are arranged in the tank.

[0014] Further, a filter is arranged in the liquid medium, and the pipeline is connected with the capillary tube through the filter.

[0015] Further, the top of the filter is located outside the liquid medium, and the top is provided with a pipeline connected with the capillary tube, and the space above the liquid medium is filled with inert gas.

[0016] Further, the mass of the liquid medium is calculated by the following formula:

[0017] m 液体 ≥K*C 电池 / (c 液体 *(T 沸点 -T 常温 )),

[0018] wherein,

[0019] m 液体 is the mass of the liquid medium;

[0020] K is a conversion coefficient;

[0021] C 电池 is the capacity of the battery;

[0022] c 液体 is the specific heat capacity of the liquid medium;

[0023] T 沸点 is the boiling point of the liquid medium;

[0024] T 常温 is the ambient temperature where the liquid medium is located.

[0025] Further, the liquid level of the liquid medium is 5 / 6-6 / 7 of the height of the battery shell.

[0026] A battery thermal runaway heat estimation method based on the device as described above, comprising the following steps:

[0027] Collecting the temperature rise of the liquid medium when the battery is in thermal runaway, and calculating the heat generated by the battery thermal runaway according to the specific heat capacity of the liquid medium and the mass of the liquid medium by the following formula:

[0028] Q 电池 =m 液体 *c 液体 *△T 液体

[0029] wherein, Q 电池 is the heat generated by the battery thermal runaway;

[0030] c 液体 is the specific heat capacity of the liquid medium;

[0031] △T 液体 is the temperature rise of the liquid medium;

[0032] m 液体 is the mass of the liquid medium.

[0033] Further, the liquid medium is a liquid with a thermal conductivity greater than 0.1 W / mK, a specific heat capacity greater than 0.5 kJ / kg*K, and a thermal decomposition temperature greater than 100℃.

[0034] Further, the liquid medium is silicone oil, carbon tetrachloride, N-methyl pyrrolidone or perfluoropolyether.

[0035] Compared with the prior art, the present application has the beneficial effects of:

[0036] In the present application, the calculation method of the battery thermal runaway heat is converted from the temperature rise of the battery shell and the specific heat capacity of the battery to the temperature rise and specific heat capacity of the liquid medium in contact with the battery shell, which replaces the high-temperature specific heat capacity of the battery thermal runaway that is difficult to accurately measure with the stable and measurable specific heat capacity of the liquid medium, and the error is smaller in calculation principle. The present application utilizes heat exchange to fully exchange the heat in the high-temperature gaseous state to the liquid medium, thereby improving the accuracy of the calculated heat of the liquid medium. The instruments and equipment used in the present application are common items, and the device development risk is low and the cost is low. The device structure is simple, easy to operate and maintain.

[0037] Further, the mass of the liquid medium in the tank is sufficient, so that after the liquid medium absorbs the heat of the battery thermal runaway, the temperature rises, and the liquid medium cannot reach the boiling point during the temperature rising process, so that the evaporation of the liquid is avoided, and the amount of the liquid medium is always a fixed value.

[0038] Further, the liquid level of the liquid medium cannot exceed the height of the battery pressure relief valve, and considering that the battery thermal runaway will expand the shell, the height of the liquid medium is 5 / 6-6 / 7 of the height of the battery shell.

[0039] Further, the liquid medium is filled with inert gas above, which reduces the proportion of heat absorption of the inert gas above the sealed tank, and improves the accuracy of heat measurement.

[0040] Further, the filter can fully filter the solid particles in the gas discharged from the conduit, avoid clogging the capillary tube, and also enable the gaseous electrolyte, droplets of electrolyte, etc. in the discharged gas to enter the liquid medium.

[0041] In the present application, the heat generated by the battery thermal runaway is transferred to the liquid medium, and then the specific heat capacity of the liquid medium is stable, and the change is small even under pressure change. Moreover, since it is a sealed environment and the boiling point of the liquid medium is high, it will not evaporate and the mass will not be lost, so the heat generated by the battery thermal runaway is calculated according to the temperature rise of the liquid medium. The present application calculates the battery thermal runaway heat by measuring the temperature rise of the liquid medium with accurate specific heat capacity, thereby improving the accuracy of the estimation.

[0042] Further, in addition to calculating the heat, the present application can calculate the amount of gas generated by the battery thermal runaway through the temperature and pressure of the inert gas above the tank. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The structure diagram of the battery thermal runaway heat estimation device.

[0044] Figure 2 The structure diagram of the capillary, wherein (a) is U-shaped, (b) is circular, and (c) is square.

[0045] In the figure, 1 is a tank body, 2 is a heat insulation cavity, 3 is a stirring rod, 4 is a liquid medium, 5 is a battery, 6 is a filter, 7 is a capillary, 8 is a first thermometer, 9 is a second thermometer, 10 is a pressure gauge, 11 is a conduit, and 12 is an inert gas. DETAILED DESCRIPTION

[0046] The application will be described in detail below with reference to the accompanying drawings.

[0047] The heat of battery thermal runaway comes from chemical and electrochemical reactions inside the battery, which is manifested as rapid temperature rise of the battery shell, and the heat of the battery is transferred from the surrounding space, the copper bar connected to the battery, and other objects in contact with the battery through convection, radiation, and conduction. The maximum temperature of battery thermal runaway is within 1000℃, and the efficiency of heat radiation and heat conduction is low in an air medium, but if a medium with good thermal conductivity is used, the heat conduction efficiency will be significantly improved, which is why liquid cooling systems are increasingly widely used. Based on the above considerations, the application proposes to place the tested battery in a liquid medium with good thermal conductivity and stable physical and chemical properties, and to calculate the heat absorbed by the liquid medium from the battery thermal runaway through the temperature rise amplitude of the liquid medium, thereby indirectly estimating the heat of battery thermal runaway. The measuring device of the application can economically and conveniently estimate the heat generated by battery thermal runaway, providing a direction for safety testing and evaluation of lithium ion energy storage batteries.

[0048] Referring to Figure 1 The battery thermal runaway heat estimation device of the application comprises a tank body 1, a heat insulation cavity 2 is arranged in the tank body 1, and the heat insulation cavity 2 serves to isolate the liquid medium from the heat exchange with the outside. A pressure gauge 10 and a second thermometer 9 are arranged above the heat insulation cavity 2, and a conduit 11 is arranged at the top of the tank body 1; a liquid medium 4 is arranged in the heat insulation cavity 2, a battery 5 is arranged in the liquid medium 4, a stirring rod 3 and a first thermometer 8 are arranged in the tank body 1 and extend into the liquid medium 4. In the application, the stirring rod 3 serves to fully stir the liquid medium, so that the temperature of the liquid medium is quickly and uniformly distributed, and the temperature non-uniformity is reduced.

[0049] A pipeline is arranged at the pressure relief valve on the surface of the shell of the battery 5, the outlet of the pipeline is divided into two paths, one path is connected to the conduit 11, and the other path is connected to a filter 6 (closed filter bottle) in the liquid medium 4, the top of the filter 6 is located outside the liquid medium 4, and a pipeline is arranged at the top and connected to a capillary 7 arranged in the liquid medium 4.

[0050] The application provides a battery thermal runaway heat estimation device, which is characterized in that a sealed tank 1 is arranged, a liquid medium 4 with good thermal conductivity and stable physical and chemical properties is arranged below the sealed tank 1, and inert gas 12 (such as helium, nitrogen and argon) is filled in the sealed tank 1.

[0051] The battery 5 is arranged in the liquid medium 4, when the battery is in thermal runaway, the heat generated by the thermal runaway is conducted to the liquid medium 4 through the heat transfer effect on the surface of the battery shell, and the heat absorbed by the liquid medium 4 from the surface of the battery shell can be calculated by measuring the specific heat capacity of the liquid medium 4 and the temperature rise of the liquid medium 4; meanwhile, a high-temperature-resistant and corrosion-resistant pipeline is led out from the pressure relief valve on the surface of the battery shell and connected to the closed filter bottle in the liquid medium 4, so that the gas-liquid substances generated by the thermal runaway are immersed in the liquid medium 4, through the processing, on the one hand, the residues, liquid electrolyte and the like in the battery enter the liquid medium 4, so that the heat of the residues, liquid electrolyte and the like enters the liquid medium, on the other hand, the filtered gas is again passed through the pipeline and the liquid medium 4 to transfer heat, and finally the gas incompatible with the liquid medium 4 is discharged and floated to the top of the tank 1, the gas amount generated by the battery thermal runaway is calculated by detecting the pressure gauge 10 and the second thermometer 11 at the top of the tank 1.

[0052] Through the above operation, the heat generated by the battery thermal runaway is divided into two parts, one part is transferred through the battery shell and enters the liquid medium 4, and the other part is the gas-liquid mixture with heat discharged through the pressure relief valve, which enters the liquid medium 4 through heat exchange when flowing through the pipeline and the capillary pipeline, and finally is discharged into the inert gas medium enriched in the tank 1. In this way, the battery thermal runaway heat absorbed by the liquid can be calculated by the temperature rise of the liquid. In addition, for the inert gas at the top of the tank 1, the amount of gas discharged by the battery thermal runaway can be calculated according to the gas state equation.

[0053] The sealed tank 1 in the application plays a sealing role, which seals the heat and the gas generated by the thermal runaway reaction.

[0054] The conventional calculation formula of the heat generated by the battery thermal runaway is as follows:

[0055] Q 电池 =m 电池 *c 电池 *△T 电池

[0056] In the formula, Q 电池 is the battery heat, and the unit is J;

[0057] m 电池 is the mass of the battery, in kg;

[0058] c 电池 is the specific heat capacity of the battery at room temperature, in kJ / kg*K;

[0059] △T 电池 is the temperature rise of the battery, in K (or ℃).

[0060] Since c 电池 is generally taken from the value measured at room temperature, not the value in the rapid rising stage of the battery thermal runaway temperature (which is actually impossible to measure), so the heat of the battery thermal runaway calculated by this method is not accurate.

[0061] The present application calculates the heat generated by the battery thermal runaway, which is first transferred to the liquid medium, and then due to the stable properties of the liquid medium, the value of the specific heat capacity is very stable, even if the change is very small under pressure change, and due to the sealed environment, the boiling point of the liquid medium is high, so it will not evaporate and the mass will not be lost. Therefore, the magnitude of the temperature rise of the liquid medium can be indirectly calculated by the following formula.

[0062] Q 电池 =Q 液体 =m 液体 *c 液体 *△T 液体

[0063] In the formula, Q 液体 is the heat of the battery absorbed by the liquid medium;

[0064] c 液体 is the specific heat capacity of the liquid medium;

[0065] △T 液体 is the temperature rise of the liquid medium;

[0066] m 液体 is the mass of the liquid medium.

[0067] As can be seen, since the Cp of the liquid medium is a stable value, the accuracy of the calculation mainly depends on the accuracy of m 液体 , △T 液体 , and the characteristics of the liquid such as high boiling point, stable physical properties, sealed test environment, etc. ensure that the value of m 液体 does not change, and the value of △T 液体 mainly depends on the heat exchange between the battery and the liquid medium, the heat exchange between the battery thermal runaway gas and the liquid medium through the capillary, and the rapid flow of the liquid caused by the stirring of the stirring rod, which can make the liquid temperature uniform and the measured value of the temperature rise more accurate. Therefore, the heat of the battery thermal runaway calculated by this method is more accurate.

[0068] m 电池 *c 电池 *△T 电池 =m 液体 *c 液体 *△T 液体 , the specific heat capacity of the battery in the thermal runaway state can be calculated:

[0069] c 电池 =m 液体 *c 液体 *△T 液体 / (m 电池 *△T 电池 )

[0070] From the formula, the specific heat capacity of the battery in the thermal runaway state is a variable related to the mass of the battery (as the battery is in thermal runaway, the pressure relief valve is opened to spray gas, and the mass of the battery is continuously decreasing) and the temperature rise, rather than a constant value.

[0071] The present application calculates the heat of battery thermal runaway by replacing the temperature rise of the battery shell with the temperature rise of the liquid medium; the lower half of the tank body 1 is a liquid medium, and the upper half is a gas medium. The liquid medium in the present application is a liquid with a thermal conductivity greater than 0.1 W / mK, a specific heat capacity greater than 0.5 kJ / kg*K, stable physicochemical properties (thermal decomposition temperature greater than 100℃), and non-flammable, such as silicone oil, carbon tetrachloride, N-methyl pyrrolidone, perfluorinated solvents such as perfluoropolyether, fluorocarbon solvents, hydrocarbon and organic silicon solvents.

[0072] The mass of the liquid medium 4 in the tank body 1 should be greater than or equal to the amount calculated by the following formula:

[0073] m 液体 ≥K*C 电池 / (c 液体 *(T 沸点 -T 常温 )),

[0074] wherein,

[0075] m 液体 is the mass of the liquid medium, in kg.

[0076] K is a conversion coefficient, with a value of 10 kJ / Ah;

[0077] C 电池 is the capacity of the battery, in Ah;

[0078] c 液体 is the specific heat capacity of the liquid medium, in kJ / kg*K;

[0079] T 沸点This refers to the boiling point of the liquid medium, expressed in Kelvin (K).

[0080] T 常温 The ambient temperature of the liquid medium is expressed in Kelvin (K).

[0081] This formula means that the mass of the liquid medium in the tank should be large enough so that after the liquid medium absorbs the heat from the thermal runaway of the battery, it will never reach the boiling point of the liquid medium as the temperature rises. This avoids the evaporation of the liquid and ensures that the amount of liquid medium remains constant.

[0082] In this invention, the liquid level of liquid medium 4 should be about 5 / 6 to 6 / 7 of the battery casing height, and should not exceed the height of the battery pressure relief valve. Considering that the casing will expand due to battery thermal runaway and the liquid level will rise, 5 / 6 to 6 / 7 is appropriate.

[0083] In this invention, the conduit should be directly and tightly connected to the pressure relief valve on the surface of the battery so that all the gas inside the battery enters the conduit; there should be a filter screen between the conduit and the pressure relief valve to prevent large pieces of debris from entering the conduit and clogging it.

[0084] The present invention includes a filter 6, which can effectively filter solid dust particles in the gas discharged from the conduit, preventing blockage of the capillary tube. The filter 6 also allows gaseous electrolyte and electrolyte droplets in the discharged gas to enter the liquid medium.

[0085] In this invention, a capillary tube 7 is provided, allowing the heat of the gas to be absorbed by the liquid medium 4 through heat exchange. The capillary tube diameter is within 4 mm, and the capillary tube 7 is supported by a metal with good thermal conductivity (thermal conductivity greater than 80 W / mK), such as copper, aluminum, silver, gold, iron, or nickel. The capillary tube 7 is distributed below the surface of the liquid medium 4, allowing the high-temperature gas inside the capillary tube 7 to complete heat exchange with the liquid medium 4. The shape of the capillary tube 7 can be U-shaped, circular, square, etc. Figure 2 As shown in (a), (b) and (c).

Claims

1. A battery thermal runaway heat estimation device, characterized in that, The device includes a sealed tank (1), an insulation chamber (2) is provided inside the tank (1), a liquid medium (4) for placing the battery (5) and the capillary tube (7) is provided inside the insulation chamber (2), and a conduit (11) is provided at the pressure relief valve on the surface of the battery (5); the conduit (11) is directly and tightly connected to the pressure relief valve on the surface of the battery (5), so that all the gas inside the battery (5) can enter the conduit (11); It also includes a filter (6) disposed in the liquid medium (4); the top of the filter (6) is located outside the liquid medium (4), and a pipe connected to the capillary (7) is disposed on the top; the conduit (11) is connected to the capillary (7) via the filter (6).

2. The battery thermal runaway heat estimation device according to claim 1, characterized in that, A pressure gauge (10) and a second thermometer (9) are installed above the insulation cavity (2).

3. The battery thermal runaway heat estimation device according to claim 1, characterized in that, The tank (1) is equipped with a first thermometer (8) and a stirring rod (3) that extends into the liquid medium (4).

4. The battery thermal runaway heat estimation device according to claim 1, characterized in that, An inert gas is filled above the liquid medium (4).

5. The battery thermal runaway heat estimation device according to claim 1, characterized in that, The mass of the liquid medium (4) is calculated by the following formula: m 液体 ≥K*C 电池 / (c 液体 *(T 沸点 -T 常温 )), in, m 液体 The mass of the liquid medium; K is the conversion factor; C 电池 This refers to the battery's capacity. c 液体 Specific heat capacity of the liquid medium; T 沸点 The boiling point of the liquid medium; T 常温 The ambient temperature of the liquid medium.

6. The battery thermal runaway heat estimation device according to claim 1, characterized in that, The liquid level of the liquid medium (4) is 5 / 6 to 6 / 7 of the height of the battery casing.

7. A method for estimating battery thermal runaway heat based on the device according to any one of claims 1-6, characterized in that, Includes the following steps: The temperature rise of the liquid medium during battery thermal runaway is collected. Based on the specific heat capacity and mass of the liquid medium, the heat generated by battery thermal runaway is calculated using the following formula. Q 电池 =m 液体 *c 液体 *△T 液体 In the formula, Q 电池 The heat generated by battery thermal runaway; c 液体 Specific heat capacity of the liquid medium; △T 液体 This refers to the temperature rise of the liquid medium. m 液体 The mass of the liquid medium.

8. A method for estimating battery thermal runaway heat according to claim 7, characterized in that, The liquid medium is a liquid with a thermal conductivity greater than 0.1 W / mK, a specific heat capacity greater than 0.5 kJ / kg*K, and a thermal decomposition temperature greater than 100℃.

9. A method for estimating battery thermal runaway heat according to claim 8, characterized in that, The liquid medium is silicone oil, carbon tetrachloride, N-methylpyrrolidone, or perfluoropolyether.

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