Battery pack thermal management device and thermal management method

Abstract

The present application relates to the technical field of thermal management, in particular to a battery pack thermal management device and a thermal management method. The battery pack thermal management device comprises a box body, the box body has an inner cavity capable of accommodating an electric core and a heat exchange medium; the heat exchange medium is configured to be capable of converting between a gas phase state and a liquid phase state; the electric core is at least partially immersed in the liquid phase heat exchange medium; the air pressure of the inner cavity is lower than the ambient atmospheric pressure; at least part of the heat exchange medium is configured to be capable of evaporating into steam in the inner cavity, the steam moves rapidly to a lower temperature place under the driving of a pressure difference and condenses to release heat, so as to realize the cooling of the electric core; and a heat exchange mechanism connected with the inner cavity of the box body; the heat exchange mechanism is configured to be capable of cooling the liquid phase heat exchange medium. In this way, the isothermal can be realized by using the phase change heat exchange mode, the thermal runaway can be suppressed, and the spread of the thermal runaway can be prevented; the liquid phase heat exchange medium is used for external heat exchange, and the cold and hot demand can be met in a simple and reliable way.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal management, in particular to a battery pack thermal management device and a thermal management method. BACKGROUND

[0002] Lithium ion batteries have low self-discharge, no memory effect, high energy density and other characteristics, but the performance of lithium ion batteries is greatly affected by temperature. Overly high or low temperature and excessive temperature difference will have an important impact on the charge-discharge performance, cycle performance and consistency performance of lithium ion batteries. Under abnormal conditions such as internal short circuit, if the temperature cannot be lowered in time, the battery will have thermal runaway, and then serious consequences will occur.

[0003] In the use of electric vehicles and electrochemical energy storage, the battery system is generally composed of multiple single batteries (hereinafter referred to as battery cells) in series or parallel connection. The inconsistency of temperature will increase the difference in performance between different single batteries, thereby affecting the performance output of the entire battery system. In fast charging state, more heat is generated, and if the heat is not dissipated in time, it is easy to induce thermal runaway. In addition, the battery system also needs to meet the heating demand in low temperature environment. Preventing thermal runaway of battery cells and stopping the spread of thermal runaway are also key functions that thermal management needs to have. Therefore, a comprehensive thermal management technology plays a crucial role in battery performance and operation safety. Thermal management needs to achieve the following goals at several levels:

[0004] 1. Cooling or heating to allow each battery cell in the battery pack to work at a suitable and consistent temperature;

[0005] 2. Removing the heat of an abnormally heated battery cell in time to inhibit the development of thermal runaway;

[0006] 3. Inhibiting the spread of thermal runaway;

[0007] 4. High cost performance and practicality.

[0008] The existing battery pack thermal management methods mainly include air cooling and liquid cooling. Air cooling has large volume and poor performance, and has been less applied. The current mainstream technology is liquid cooling. Liquid cooling mainly includes indirect cooling by liquid cooling plate and immersion direct cooling. The indirect cooling by liquid cooling plate is the main method currently used, but it has problems such as insufficient heat exchange coefficient, large temperature difference before and after the liquid cooling plate, inability to effectively inhibit thermal runaway, and complex structure, which makes it difficult to fully meet the actual needs of thermal management. The immersion direct cooling method has a larger heat exchange coefficient and heat exchange area than the indirect cooling by liquid cooling plate because the heat exchange medium directly contacts the battery cell, and the heat exchange performance is significantly improved. The immersion direct cooling method is divided into single-phase convection heat exchange and gas-liquid two-phase boiling heat exchange.

[0009] Single-phase convection heat transfer relies on the flow of heat transfer medium to exchange heat, and the principle is similar to that of the liquid cooling plate. Although the heat transfer coefficient is greatly improved, there is still a large temperature difference between the front and back. When the number of battery cells is large, it is difficult to ensure uniform flow of the heat transfer medium, and there may even be dead angles, further amplifying the temperature difference problem. When thermal runaway occurs, the ability to remove the heat of the abnormally heated battery cell is similar to that of the liquid flow plate, and it is difficult to suppress the development of thermal runaway. However, after thermal runaway, the heat transfer medium in direct contact with the battery cell will evaporate and absorb heat, so the liquid cooling plate is improved in preventing the spread of thermal runaway.

[0010] The heat transfer performance of gas-liquid two-phase boiling is much higher than that of single-phase convection heat transfer. The battery cell with a higher temperature will cause the surrounding heat transfer medium to evaporate into steam. The steam quickly moves to a lower temperature under the driving of the pressure difference and condenses to release heat. Therefore, the vapor pressure and temperature in the same container tend to be consistent, the temperature of the battery cell is uniform, and the suppression ability of thermal runaway is strong, and the performance is quite excellent. However, the working pressure of the phase change heat transfer mode is generally high, and there is not enough space to install a condenser inside the battery pack. The condenser is easy to leak in the external heat transfer medium, and the structure is complex and unreliable, which is not convenient for heating the battery in a low-temperature state. These problems limit the application of two-phase heat transfer technology.

[0011] It can be seen that the prior art has obvious deficiencies and cannot fully meet the actual needs. SUMMARY

[0012] The purposes of the present application include, for example, providing a battery pack thermal management device and a thermal management method, which can realize uniform temperature by using a phase change heat transfer mode, suppress thermal runaway, and prevent the spread of thermal runaway. The liquid phase heat transfer medium is used for external heat exchange, and a simple and reliable method is used to meet the cold and hot needs.

[0013] Embodiments of the present application can be implemented as follows:

[0014] In a first aspect, the present application provides a battery pack thermal management device, comprising:

[0015] a box body having an inner cavity capable of accommodating battery cells and heat transfer medium; the heat transfer medium is configured to be capable of converting between gas phase and liquid phase; the inner cavity includes an immersion area storing the heat transfer medium in liquid phase, and a non-immersion area above the immersion liquid level of the heat transfer medium in liquid phase in the inner cavity; the non-immersion area is configured to be capable of containing the heat transfer medium in gas phase; the battery cells are at least partially immersed in the liquid phase heat transfer medium; the gas pressure of the inner cavity is lower than the ambient atmospheric pressure, and the boiling point of the heat transfer medium under the gas pressure of the inner cavity is lower than or equal to the target working temperature of the battery cells;

[0016] and a heat exchange mechanism connected with the inner cavity of the box body; the heat exchange mechanism is configured to be capable of cooling the heat transfer medium in liquid phase.

[0017] In an optional embodiment, the battery cell is semi-submerged in the box.

[0018] In an optional embodiment, the top of the box is provided with a through hole corresponding to the number of battery cells; the battery cell passes through the through hole, the bottom of the battery cell is located in the inner cavity, and the top of the battery cell is located outside the box.

[0019] In an optional embodiment, a sealing member is further included, which is arranged between the through hole and the outer wall of the battery cell to seal the gap between the battery cell and the through hole.

[0020] In an optional embodiment, the heat exchange mechanism includes a heat exchange unit and a circulating pump; the box is provided with a liquid inlet and a liquid outlet;

[0021] The liquid inlet and the liquid outlet can be connected with the heat exchange medium in the liquid phase in the inner cavity; the liquid inlet is connected with the liquid outlet through a connecting pipeline, and the heat exchange unit and the circulating pump are arranged on the connecting pipeline.

[0022] In an optional embodiment, a vacuum pump is further included, and the box is provided with an air outlet, and the vacuum pump is connected with the air outlet.

[0023] In an optional embodiment, an injection port is further included, which is arranged on the box, and the injection port can be used to add the heat exchange medium.

[0024] In a second aspect, the present application provides a heat management method, which is based on the battery pack heat management device in any of the foregoing embodiments; the heat management method at least includes the following steps:

[0025] The battery cell is arranged in the inner cavity of the box;

[0026] Before use, the box is vacuumized to a pressure in the inner cavity reaching a preset vacuum degree;

[0027] The heat exchange medium is injected into the box to reach a preset liquid level;

[0028] The heat exchange mechanism is operated according to a preset mode to ensure the smooth operation of the battery pack.

[0029] In an optional embodiment, when the inner cavity is detected to leak, the inner cavity is vacuumized to keep the inner cavity at a preset vacuum degree.

[0030] In an optional embodiment, the inner cavity is determined to leak by detecting the change of the inner pressure of the inner cavity;

[0031] detecting the temperature T of the inner cavity under the current working condition, and detecting the pressure P of the inner cavity under the current working condition; the heat exchange medium corresponds to a determined theoretical equilibrium pressure P0 at the temperature T;

[0032] If P-P0≥the preset difference value is detected, it is determined that the inner cavity has a leakage; if P-P0<the preset difference value is detected, it is determined that the inner cavity has no leakage.

[0033] The beneficial effects of the embodiment of the application include, for example:

[0034] The battery pack thermal management device of the scheme includes a box body and a heat exchange mechanism. The condition for the phase change of the heat exchange medium is created in a way of maintaining negative pressure of the inner cavity, so as to obtain good temperature equalization effect. Meanwhile, the problem of insufficient space for condensation and heat dissipation and the need for heating are solved by adopting the way of heat exchange with the liquid phase heat exchange medium. The scheme breaks through the inherent mode of phase change condensation, and realizes good temperature equalization in a simple and practical way, suppresses and prevents the spread of thermal runaway. The scheme also meets the needs of cooling and heating. Meanwhile, the formation and maintenance of negative pressure solve the hidden danger of leakage of the heat exchange medium to the outside, and the existence of leakage can be found in time through the detection of temperature and pressure. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0036] Figure 1 A working principle diagram of the battery pack thermal management device of the embodiment of the application;

[0037] Figure 2 A structural schematic diagram of the battery pack thermal management device of the embodiment of the application;

[0038] Figure 3 A structural schematic diagram of the battery pack thermal management device of another embodiment of the application.

[0039] Figure legend: 100-box body; 100a-inner cavity; 101-exhaust port; 102-liquid inlet; 103-liquid outlet; 104-liquid injection port; 110-panel; 111-through hole; 120-non-immersed area; 123-immersed liquid level; 130-immersed area; 201-circulating pump; 202-heat exchange unit; 301-vacuum pump; 401-exhaust valve; 402-liquid injection valve; 410-first pipeline; 420-second pipeline; 430-third pipeline; 500-cell; 600-sealing element. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work under the premise that the scope of the present application.

[0042] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0043] In the description of the present application, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is used, only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0044] In addition, if the terms "first", "second" and the like appear, they are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0045] It should be noted that the features in the embodiments of the present application can be combined with each other without conflict.

[0046] Embodiment one

[0047] Please refer to Figure 1 The present embodiment provides a battery pack thermal management device, comprising:

[0048] The box 100 has an inner cavity 100a capable of containing the battery cell 500 and the heat exchange medium; the heat exchange medium is configured to be capable of converting between gas phase and liquid phase; the inner cavity 100a includes an immersion area 130 storing the liquid phase heat exchange medium, and a non-immersion area 120 above the immersion liquid surface 123 of the liquid phase heat exchange medium in the inner cavity 100a; the non-immersion area 120 is configured to be capable of containing the gas phase heat exchange medium; the battery cell 500 is at least partially immersed in the liquid phase heat exchange medium; the air pressure in the inner cavity 100a is lower than the ambient atmospheric pressure; at least part of the heat exchange medium is configured to be capable of evaporating into steam in the inner cavity 100a, and the steam moves rapidly to a lower temperature under the driving of the pressure difference and condenses to release heat, so as to realize the cooling of the battery cell 500 in the inner cavity 100a.

[0049] The heat exchange mechanism is connected with the inner cavity 100a of the box 100; the heat exchange mechanism is configured to be capable of cooling the liquid phase heat exchange medium.

[0050] It should be noted that the target working temperature of the battery cell 500 actually refers to the target environment temperature provided for the working of the battery cell 500, that is, the gas-liquid two-phase equilibrium temperature in the inner cavity 100a. In the present scheme, the air pressure in the inner cavity 100a is lower than the ambient atmospheric pressure, and the boiling point of the heat exchange medium under the pressure in the inner cavity 100a is lower than or equal to the target working temperature of the battery cell 500. In use, the heat exchange medium in the box 100 of the battery pack thermal management device is capable of converting between gas phase and liquid phase. Because the air pressure in the inner cavity 100a is lower than the ambient atmospheric pressure, the inner cavity 100a can make the boiling point of the heat exchange medium in the inner cavity 100a lower than the target working temperature of the battery cell 500 and follow the actual temperature change in the inner cavity 100a, so that the heat exchange medium remains in the liquid phase when the actual temperature of the battery cell 500 is lower than or equal to the equilibrium temperature corresponding to the air pressure in the inner cavity 100a, and part of the heat exchange medium is converted from the liquid phase to the gas phase when the actual temperature of the battery cell 500 is higher than the equilibrium temperature corresponding to the air pressure in the inner cavity 100a. In use, the phase change heat exchange mode is adopted to realize temperature equalization and suppress thermal runaway and prevent the spread of thermal runaway. The liquid phase heat exchange medium is exchanged with the outside by the heat exchange mechanism, which meets the cold and hot demand in a simple and reliable way. In this way, the advantages of the two modes are obtained, and the shortcomings of the two modes are avoided, so that the various demands of thermal management are fully met.

[0051] Further, compared with the gas-liquid two-phase boiling heat exchange scheme of the prior art, the main difference of the present scheme is that the inner cavity 100a forms a negative pressure, and a steam condenser is not required in the inner cavity 100a. At the same time, the heat exchange mechanism of the single-phase convection heat exchange scheme in the prior art is retained.

[0052] It should be noted that the purpose of keeping the inner cavity 100a at negative pressure to achieve gas-liquid two-phase dynamic balance is mainly to achieve the temperature equalization effect, and the phase change of the heat exchange medium is not directly used for exchanging and transferring heat with the environment outside the box 100; meanwhile, in the process of phase change of the gas-liquid two-phase boiling mode, the evaporation and condensation processes of the heat exchange medium all occur inside the box 100, and the main object of the phase change heat exchange is the heat exchange medium in different regions and the different battery cells 500, rather than the environment outside the box 100.

[0053] The single-phase convection heat exchange mode composed of the box 100, the liquid heat exchange medium and the heat exchange mechanism uses the liquid heat exchange medium to exchange heat with the outside to achieve single-phase liquid cooling, and meets the cooling and heating requirements in a simple and reliable manner.

[0054] As can be seen from the figure, the inner cavity 100a includes an immersion area 130 in which the liquid heat exchange medium is stored, and a non-immersion area 120 above the immersion liquid surface 123 of the liquid heat exchange medium in the inner cavity 100a. The bottom of the battery cell 500 is arranged in the immersion area 130.

[0055] The inner cavity 100a specifically analyzes the working principle and characteristics of the battery pack thermal management device of the embodiment, as follows:

[0056] 1. Excellent temperature equalization capability, capable of cooling and heating.

[0057] The saturation vapor pressure is directly related to the temperature. When the temperature rises, the saturation vapor pressure increases, and the evaporation surface that has been in a saturated state becomes unsaturated due to the temperature rise, and evaporation reappears; when the temperature decreases, the saturation vapor pressure decreases, and excess liquid phase condenses.

[0058] When part of the battery cells 500 generate heat to cause the surface temperature of the part of the battery cells 500 to be higher than the temperature corresponding to the equilibrium pressure in the box 100, the liquid heat exchange medium on the surface of the part of the battery cells 500 will boil, i.e., part of the heat exchange medium on the surface of the part of the battery cells 500 absorbs heat to evaporate into vapor.

[0059] The vapor moves upward, part of the vapor is condensed back to the liquid phase by the adjacent heat exchange medium with lower temperature, and part of the vapor floats out of the liquid surface into the non-immersion area 120. The vapor entering the non-immersion space moves rapidly to the area with lower temperature under the driving of the vapor pressure, and is condensed back to the liquid phase by releasing heat after contacting the heat exchange medium or other objects (which can be the liquid heat exchange medium, the surface of other battery cells 500, or the inner wall of the box 100) with lower temperature. In the process of evaporation and condensation, the heat generated locally is quickly and uniformly dispersed to the part of the heat exchange medium close to the liquid surface, and the temperature of the heat exchange medium and the surface of all the battery cells 500 tends to be consistent with the convection heat exchange of the heat exchange medium.

[0060] Similarly, when the battery cell 500 needs to be heated, the heated heat exchange medium will flash when it is delivered into the box 100 through the heat exchange mechanism, and the steam will quickly deliver heat everywhere, thereby achieving the synchronous heating of a large number of battery cells 500.

[0061] 2. Can inhibit thermal runaway and reduce loss.

[0062] When a battery cell 500 is in the initial stage of thermal runaway with rapid temperature rise, intense boiling will occur on its surface, which can quickly transfer the heat generated by the battery cell 500 under a small temperature difference, so that the temperature of the battery cell 500 no longer continues to rise, avoiding more severe thermal runaway.

[0063] 3. Can prevent the spread of thermal runaway and ensure safety.

[0064] Even if uncontrollable thermal runaway occurs, due to the isolation of the liquid phase heat exchange medium, heat is difficult to be concentrated and transferred to adjacent battery cells 500, but is shared by the entire battery pack, so the temperature will not rise sharply in a short time, thereby preventing the spread of thermal runaway.

[0065] 4. Can prevent leakage.

[0066] Since the box 100 is under negative pressure and the sealing member 600 is locked under atmospheric pressure, there is no need to worry about external leakage. That is, the inner cavity 100a maintains negative pressure, which can lower the boiling point of the heat exchange medium on the one hand, and can avoid the leakage of the heat exchange medium from the box 100 (the pressure of the ambient atmosphere is greater than the pressure of the leaked heat exchange medium).

[0067] 5. Low cost.

[0068] Since the inner cavity 100a maintains a vacuum environment, as long as the battery cell 500 shell is well insulated, a cheap ethylene glycol aqueous solution can be used, and an expensive fluorinated liquid is not necessary. Using a conventional liquid phase heat exchange method, the structure is simple and reliable.

[0069] In an optional embodiment, the heat exchange medium is a fluorinated liquid or an ethylene glycol aqueous solution.

[0070] Please continue to refer to Figure 1 and Figure 2In an optional embodiment, the battery pack has a plurality of battery cells 500, each of which is semi-submerged in the box 100. Further, the top of the box 100 has a panel 110 sealing the inner cavity 100a, and the panel 110 is provided with through holes 111 corresponding to the number of battery cells 500; the battery cells 500 pass through the through holes 111, and the bottom of the battery cells 500 is located in the inner cavity 100a, and the top of the battery cells 500 is located outside the box 100. Specifically, the top of the battery cells 500 outside the box 100 is provided with a first pole and a second pole, the bottom of the battery cells 500 is located in the immersion zone 130 of the inner cavity 100a, the middle and upper part of the battery cells 500 is located in the non-immersion zone 120, and the top of the battery cells 500 is located outside the box 100. The battery cells 500 are in sealed connection with the through holes 111.

[0071] In the present embodiment, the top of the box 100 is provided with nine through holes 111, and each of the through holes 111 is inserted into one battery cell 500 to the immersion zone 130 of the inner cavity 100a. Optionally, the battery pack thermal management device further comprises a sealing member 600 arranged between the through hole 111 and the outer wall of the battery cell 500 to seal the gap between the battery cell 500 and the through hole 111. In this way, the heat exchange medium can exchange energy in the box 100 to achieve thermal management, and leakage is avoided.

[0072] In an optional embodiment, the heat exchange mechanism comprises a heat exchange unit 202 and a circulating pump 201; the box 100 is provided with a liquid inlet 102 and a liquid outlet 103; the liquid inlet 102 and the liquid outlet 103 can be connected with the liquid-phase heat exchange medium in the inner cavity 100a; the liquid inlet 102 is connected with the liquid outlet 103 through a connecting pipeline, and the heat exchange unit 202 and the circulating pump 201 are arranged on the connecting pipeline. The heat exchange unit 202 can cool the liquid-phase heat exchange medium or heat the liquid-phase heat exchange medium to input into the box 100, so as to ensure that the battery cells 500 can work in a preset temperature range.

[0073] In an optional embodiment, the battery pack thermal management device further comprises a vacuum pump 301, and the box 100 is provided with a gas extraction port 101, and the vacuum pump 301 is connected with the gas extraction port 101. The purpose of the vacuum pump 301 is to keep the inner cavity 100a in negative pressure, which can reduce the boiling point of the heat exchange medium, and can also avoid the leakage of the heat exchange medium from the box 100 (the pressure of the environment atmospheric pressure is greater than the pressure of the heat exchange medium leaked out).

[0074] It should be noted that in other embodiments of the present application, the battery pack thermal management device can not include a vacuum pump 301, but a gas extraction device is connected before the heat exchange medium is injected into the box 100, so as to ensure that the gas pressure in the inner cavity 100a of the box 100 is lower than the environmental atmospheric pressure.

[0075] In an optional embodiment, the box 100 further comprises a liquid injection port 104, which is arranged on the box 100 and can be used to inject the heat exchange medium.

[0076] When the battery pack thermal management device is in use:

[0077] The heat generating part of the battery cell 500 is immersed in the heat exchange medium in the sealed box 100 through the through hole 111 on the panel 110 of the box 100, and the sealing between the through hole 111 and the battery cell 500 is realized by the sealing element 600. The heat exchange medium with a boiling point higher than the highest working temperature under normal pressure is used, for example, if the highest working temperature of the battery is 50℃, the boiling point of the heat exchange medium used should be higher than 50℃, and the heat exchange medium meeting this condition includes but is not limited to fluorinated liquid, ethylene glycol aqueous solution, etc.

[0078] The box 100 is vacuumized and maintained at negative pressure, which ensures that the heat exchange medium can boil at the target working temperature, for example, if the target working temperature is 30℃ and the heat exchange medium is pure water, the equilibrium pressure in the box is equal to the saturated vapor pressure of water at 30℃, which is about 4.2kPa, that is, the pressure in the cavity 100a is about -97kPa relative to the ambient atmospheric pressure; The vacuum degree before injecting the heat exchange medium should be higher than -97kPa (meaning lower air pressure, such as -98kPa).

[0079] When the actual temperature is higher than the upper limit of the target working temperature, the heat exchange medium is extracted, cooled and circulated back into the box;

[0080] When the actual temperature is lower than the lower limit of the target working temperature, the heat exchange medium is extracted, heated and circulated back into the box.

[0081] Example two

[0082] Please refer to Figure 3 , as an optional embodiment, which is basically the same as the foregoing example one, the difference is that in this embodiment, only the liquid inlet 102 and the liquid outlet 103 are arranged on the box 100; The box 100 is not provided with the air extraction port 101 and the liquid injection port 104, but the air extraction valve 401 is used to replace the air extraction port 101 and the liquid injection valve 402 is used to replace the liquid injection port 104 on the newly designed pipeline.

[0083] Specifically, the battery pack thermal management device further comprises a first pipe 410, a second pipe 420 and a third pipe 430. The inlet 102 and the heat exchange unit 202 are connected by the first pipe 410. One end of the second pipe 420 is connected to the first pipe 410, and the other end of the second pipe 420 extends away from the first pipe 410; from close to the first pipe 410 to away from the first pipe 410, the air extraction valve 401 and the vacuum pump 301 are arranged on the second pipe 420 in sequence. The third pipe 430 is connected to the second pipe 420, and the end of the third pipe 430 is located on the side of the second pipe 420 close to the first pipe 410. The liquid injection valve 402 is arranged on the third pipe 430.

[0084] By operating the air extraction valve 401 and the vacuum pump 301, the vacuum extraction function can be more flexibly adjusted. By operating the liquid injection valve 402, the liquid injection operation can be flexibly realized. Compared with the foregoing embodiments, such a setting mode can further simplify the setting of components related to the box 100, thereby facilitating subsequent maintenance and maintenance.

[0085] Embodiment three

[0086] In a second aspect, the present application provides a thermal management method, which is based on the battery pack thermal management device of any one of the foregoing embodiments; the thermal management method at least comprises the following steps:

[0087] The battery cell 500 is arranged in the inner cavity 100a of the box 100;

[0088] Before use, the box 100 is vacuumed to a pressure of the inner cavity 100a reaching a preset vacuum degree;

[0089] The heat exchange medium is injected into the box 100 to reach a preset liquid level;

[0090] The heat exchange mechanism is operated according to a preset mode to ensure smooth operation of the battery pack.

[0091] Specifically, when the system is well sealed, only vacuum extraction is needed before adding the heat exchange medium, and vacuum extraction is not needed during use. Instead, 1, the air extraction port 101 is opened for vacuum extraction, and the air extraction port 101 is closed after reaching the target vacuum degree; 2, the liquid injection port 104 is opened to suck in the heat exchange medium by vacuum, and the liquid injection port 104 is closed after reaching the target liquid level; 3, the heat exchange mechanism is started, and the battery pack is put into operation.

[0092] In an optional embodiment, when the inner cavity 100a is detected to be leaking, the inner cavity 100a is vacuumed to maintain a preset vacuum degree. In order to ensure performance and prevent possible leakage, vacuum extraction may be needed during operation.

[0093] Further, the change of the internal pressure of the inner cavity 100a is detected to determine whether the inner cavity 100a leaks. The temperature T of the inner cavity 100a under the current working condition is detected, and the pressure P of the inner cavity 100a under the current working condition is detected. Because the heat exchange medium corresponds to a certain saturated vapor pressure P0 at the temperature T; for example, if the water temperature T is 30 DEG C, the corresponding saturated vapor pressure P0 is about 4.2 kPa.

[0094] It should be noted that the saturated vapor pressure is related to the temperature. The vacuum pump 301 can be started or stopped by detecting the pressure and temperature in the box 100. If P-P0≥ the preset difference is detected, it is determined that the inner cavity 100a has a leakage or an initial vacuum degree is not enough; if P-P0< the preset difference is detected, it is determined that the inner cavity 100a has no leakage. For example, when the detection result is P-P0> 2 kPa, it indicates that there is air leakage, and the vacuum pump 301 needs to be started to exhaust the air mixed in the steam until the difference between P and P0 meets the requirement (for example, P-P0< 1 kPa), which indicates that there is no leakage.

[0095] In summary, the battery pack thermal management device and the thermal management method provided by the embodiment of the present application have at least the following advantages:

[0096] 1. Excellent temperature equalization capability, which can balance cooling and heating;

[0097] 2. Can inhibit thermal runaway and reduce loss:

[0098] 3. Can inhibit the spread of thermal runaway and ensure safety:

[0099] 4. Can prevent leakage and has low cost.

[0100] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A battery pack thermal management device, characterized by, The battery pack thermal management device comprises: a box (100) having an inner cavity (100a) capable of containing an electric core (500) and a heat exchange medium; the heat exchange medium is configured to be capable of converting between a gas phase state and a liquid phase state; the inner cavity (100a) comprises an immersion area (130) storing the heat exchange medium in a liquid phase, and a non-immersion area (120) above the immersion liquid level (123) of the heat exchange medium in the liquid phase in the inner cavity (100a); the non-immersion area (120) is configured to be capable of containing the heat exchange medium in a gas phase; the electric core (500) is at least partially immersed in the liquid phase heat exchange medium; the air pressure in the inner cavity (100a) is lower than the ambient atmospheric pressure; at least part of the heat exchange medium is configured to be capable of evaporating into steam in the inner cavity (100a), and the steam moves rapidly to a low temperature under the driving of a pressure difference and condenses to release heat, so as to achieve cooling of the electric core (500); and a heat exchange mechanism connected with the inner cavity (100a) of the box (100); the heat exchange mechanism is configured to cool the heat exchange medium in a liquid phase. The boiling point of the heat exchange medium in the inner cavity (100a) under pressure is lower than or equal to the target working temperature of the electric core (500); the target working temperature of the electric core (500) is the target environment temperature provided for the working of the electric core (500), that is, the air-liquid two-phase equilibrium temperature of the inner cavity (100a); in use, the heat exchange medium in the box (100) of the battery pack thermal management device can convert between a gas phase state and a liquid phase state; because the air pressure in the inner cavity (100a) is lower than the ambient atmospheric pressure, the inner cavity (100a) can make the boiling point of the heat exchange medium in the inner cavity (100a) lower than the target working temperature of the electric core (500) and follow the actual temperature change in the inner cavity (100a), so that the heat exchange medium remains in a liquid phase when the actual temperature of the electric core (500) is lower than or equal to the equilibrium temperature corresponding to the air pressure in the inner cavity (100a), and part of the heat exchange medium changes from a liquid phase to a gas phase when the actual temperature of the electric core (500) is higher than the equilibrium temperature corresponding to the air pressure in the inner cavity (100a). The heat exchange mechanism comprises a heat exchange unit (202) and a circulating pump (201); the box (100) has a liquid inlet (102) and a liquid outlet (103); the liquid inlet (102) and the liquid outlet (103) can be connected with the heat exchange medium in a liquid phase in the inner cavity (100a); the liquid inlet (102) is connected with the liquid outlet (103) through a connecting pipeline, and the heat exchange unit (202) and the circulating pump (201) are arranged on the connecting pipeline.

2. The battery pack thermal management device according to claim 1, wherein: the electric core (500) is arranged in the box (100) in a semi-immersed manner.

3. The battery pack thermal management device according to claim 2, wherein: the top of the box (100) is provided with through holes (111) corresponding in number to the electric cores (500). The electric core (500) passes through the through hole (111), the bottom of the electric core (500) is located in the inner cavity (100a), and the top of the electric core (500) is located outside the box (100).

4. The battery pack thermal management device according to claim 3, characterized in that: Further comprising a sealing member (600) arranged between the through hole (111) and the outer wall of the electric core (500) to seal the gap between the electric core (500) and the through hole (111).

5. The battery pack thermal management device according to claim 1, characterized in that: Further comprising a vacuum pump (301), and the box (100) is provided with an air outlet (101), and the vacuum pump (301) is connected with the air outlet (101).

6. The battery pack thermal management device according to claim 1, characterized in that: Further comprising a liquid injection port (104) arranged on the box (100), and the liquid injection port (104) can be used for filling the heat exchange medium.

7. A thermal management method, characterized in that: The thermal management method is based on the battery pack thermal management device according to any one of claims 1-6; and the thermal management method at least comprises the following steps: arranging the electric core (500) in the inner cavity (100a) of the box (100); before use, the box (100) is vacuumized to a pressure of the inner cavity (100a) reaching a preset vacuum degree; injecting the heat exchange medium into the box (100) to reach a preset liquid level; controlling the heat exchange mechanism to work in a preset mode to ensure the smooth operation of the battery pack.

8. The thermal management method according to claim 7, characterized in that: when the inner cavity (100a) is detected to be leaked, the inner cavity (100a) is vacuumized to keep the inner cavity (100a) at a preset vacuum degree.

9. The thermal management method according to claim 8, characterized in that: the inner cavity (100a) is detected to be leaked by detecting the change of the inner pressure of the inner cavity (100a); detecting the temperature T of the inner cavity (100a) under the current working condition and detecting the pressure P of the inner cavity (100a) under the current working condition; the heat exchange medium corresponds to a certain theoretical equilibrium pressure P0 at the temperature T; if P-P0≥a preset difference value is detected, it is determined that the inner cavity (100a) is leaked; if P-P0

Images