A battery heat equalization method based on a flexible heat-conducting vapor chamber

Abstract

The present invention relates to a battery heat equalization method based on a flexible heat-conducting vapor chamber, belonging to the technical field of battery thermal management. The present invention uses a flexible heat-conducting vapor chamber for battery heat dissipation. When the battery pack or a single battery cell is in a high-temperature state, heat is transferred to the flexible vapor chamber through the heat-conducting silica gel sheet of the flexible heat-conducting vapor chamber to form an evaporation zone. The coolant in the vacuum fluid chamber of the evaporation zone is heated and vaporized in an environment of low vacuum degree, and the volume expands rapidly to form a gas-phase medium that quickly fills the entire vacuum fluid chamber. The coolant absorbs heat during the gasification process to achieve heat dissipation of the battery pack or a single battery cell in a high-temperature state; when the gas-phase medium contacts a battery cell or a cooling plate whose temperature is lower than the gasification temperature of the coolant, it liquefies into a coolant. The heat released during the liquefaction process is transferred to the battery cell or the cooling plate whose temperature is lower than the gasification temperature of the coolant, and the coolant returns to the evaporation heat source under the drive of the spatial gradient concentration difference.

Description

Technical Field

[0001] The invention relates to a battery heat equalization method based on a flexible heat-conducting heat-equalizing plate, belonging to the technical field of battery thermal management. Background Art

[0002] Battery thermal management is a key factor in determining the performance, safety, life and cost of battery use. The performance and reliability of a battery system depends on the weakest battery unit, i.e., the cell, and the safety of the system depends on the most unstable cell. For a battery pack, assuming that the temperature of most cells is 20°C, and cell B is only 10°C due to slow heating, then the entire battery pack must accommodate cell B, and the discharge current is forced to drop from 140A to 100A, a one-third drop in performance. Differences in operating temperature are the main cause of secondary inconsistencies in battery packs, which may lead to performance degradation and safety risks.

[0003] The main methods of power battery heat dissipation are: air cooling, liquid cooling, phase change material cooling and heat pipe cooling. Air cooling is the simplest method. It only requires air to flow through the battery surface to take away the heat generated by the power battery to achieve the purpose of heat dissipation of the power battery pack. However, this method is less effective and it is difficult to achieve a high battery thermal uniformity. Liquid cooling system refers to a cooling system in which the refrigerant directly or indirectly contacts the power battery, and then takes away the heat generated in the battery pack through the circulation of liquid fluid to achieve the heat dissipation effect. Liquid cooling systems often require more complex and rigorous structural designs to prevent the leakage of liquid refrigerant and to ensure the uniformity between battery cells in the battery pack. This also makes the entire cooling system very bulky, which not only increases the weight of the vehicle, but also makes the maintenance and maintenance of the liquid cooling system relatively difficult due to the complexity of the structure and high sealing, and the maintenance cost also increases accordingly. The phase change material cooling system uses phase change material as a heat transfer medium, and uses the characteristics of phase change material that can store and release energy when phase change occurs to achieve the effect of low-temperature heating and high-temperature heat dissipation of power batteries, but the thermal conductivity of phase change material is relatively low. Compared with the traditional forced convection cooling system, the heat pipe cooling system has higher thermal conductivity and good sealing without safety hazards such as leakage. However, due to its shortcomings such as small contact area with the battery, large mass and volume, the heat pipe structure cannot be well matched with the battery and will also increase the volume of the entire battery system. Summary of the invention

[0004] In view of the problems of excessive temperature or uneven temperature distribution in the battery thermal management system, the present invention proposes a battery heat equalization method based on a flexible heat-conducting vapor chamber, that is, by using the flexible vapor chamber to shorten the axial dimension, reducing the resistance loss of the working fluid flow and the axial thermal resistance; increasing the radial dimension, significantly increasing the area of the evaporation surface and the condensation surface, having a small diffusion thermal resistance and a high heat equalization property; improving the heat dissipation ability of the vapor chamber, solving the problem of non-uniform heat in a limited space under high heat flux, reducing the temperature difference between single cells, increasing the reliability of the cooled electronic components, and thus improving the heat dissipation reliability of the battery pack.

[0005] A battery heat equalization method based on a flexible heat-conducting vapor chamber uses a flexible heat-conducting vapor chamber for battery heat dissipation. The flexible heat-conducting vapor chamber includes a flexible vapor chamber and heat-conducting silica gel sheets coated on both side surfaces of the flexible vapor chamber. A vacuum fluid chamber is formed inside the flexible vapor chamber, and a coolant is filled in the fluid chamber.

[0006] The specific steps of the battery heat dissipation method are as follows:

[0007] The battery cell arrays in the battery pack are arranged vertically. The battery pack is placed on the liquid cooling plate, so that the battery cells in the battery pack are arranged in arrays both horizontally and vertically along the liquid cooling plate. Then, the flexible heat-conducting vapor chamber is vertically inserted between the battery cells of the battery pack. The bottom end of the flexible heat-conducting vapor chamber is attached to the liquid cooling plate. Among them, multiple layers of flexible heat-conducting vapor chambers are arranged at intervals horizontally along the liquid cooling plate. The flexible heat-conducting vapor chamber is in an "S" shape longitudinally along the liquid cooling plate. The heat-conducting silica gel sheets on both sides of the flexible heat-conducting vapor chamber are respectively attached to the side walls of the adjacent battery cells in the horizontal direction along the liquid cooling plate.

[0008] When the battery pack or a single battery cell is in a high-temperature state, the heat is transferred to the flexible vapor chamber through the heat-conducting silica gel sheet of the flexible heat-conducting vapor chamber to form an evaporation zone. The coolant in the vacuum fluid chamber of the evaporation zone is vaporized by heat in an environment of low vacuum degree, and the volume expands rapidly to form a gas medium that quickly fills the entire vacuum fluid chamber. The coolant absorbs heat during the gasification process to realize the heat dissipation of the battery pack or a single battery cell in a high-temperature state. When the gas medium contacts the battery cell or the cooling plate whose temperature is lower than the gasification temperature of the coolant, it liquefies into a coolant. The heat released during the liquefaction process is transferred to the battery cell or the cooling plate whose temperature is lower than the gasification temperature of the coolant, and the coolant returns to the evaporation heat source under the drive of the spatial gradient concentration difference.

[0009] The flexible vapor chamber includes a first flexible outer plate, a first copper mesh, a support member, a second copper mesh, and a second flexible outer plate arranged in sequence. The structures of the first flexible outer plate and the second flexible outer plate are the same, and the structures of the first copper mesh and the second copper mesh are the same.

[0010] The two side surfaces of the first flexible outer plate are surface A and surface B respectively. Surface A of the first flexible outer plate is attached to the thermal conductive silica gel sheet. The surface B of the first flexible outer plate is evenly and fixedly provided with a liquid absorption micro-column array I. The liquid absorption micro-columns of the liquid absorption micro-column array I are perpendicular to the first flexible outer plate.

[0011] The two side surfaces of the second flexible outer plate are surface C and surface D respectively. The surface C of the second flexible outer plate is evenly and fixedly provided with a liquid absorption micro-column array II. The liquid absorption micro-columns of the liquid absorption micro-column array II are perpendicular to the second flexible outer plate. The surface D of the second flexible outer plate is attached to the thermal conductive silica gel sheet.

[0012] The two sides of the first copper mesh are respectively attached to the liquid absorption micro-column array I and the support member. The two sides of the second copper mesh are respectively attached to the liquid absorption micro-column array II and the support member. The liquid absorption micro-column array I, the first copper mesh, the support member, the second copper mesh and the liquid absorption micro-column array II form a vacuum fluid cavity.

[0013] Preferably, the liquid absorption micro-column array I has the same structure as the liquid absorption micro-column array II. The height of the liquid absorption micro-columns in the liquid absorption micro-column array I is 60% - 80% of the thickness of the first flexible outer plate. The thickness of the first copper mesh is 60% - 80% of the thickness of the first flexible outer plate. The thickness of the support member is 2.0 - 2.2 times the height of the liquid absorption micro-columns in the liquid absorption micro-column array I.

[0014] Preferably, the liquid absorption micro-columns of the liquid absorption micro-column array I are of hexagonal prism structure. The diameter of the liquid absorption micro-columns is 100 - 200 μm. The spacing between adjacent liquid absorption micro-columns is 300 - 400 μm. The height of the liquid absorption micro-columns is 200 - 400 μm. The liquid absorption micro-column array I and the liquid absorption micro-column array II have a very high capillary pressure.

[0015] The first flexible outer plate and the liquid absorption micro-column array I are of an integrally formed structure. The second flexible outer plate and the liquid absorption micro-column array II are of an integrally formed structure. Preferably, the materials of the first flexible outer plate and the second flexible outer plate are red copper, so that the flexible heat-conducting heat spreader can withstand bending according to the shape of the cylindrical battery cell within the flexible range.

[0016] Both the first copper mesh and the second copper mesh are treated with super-hydrophilic treatment. The aperture of the first copper mesh is 200 - 400 mesh. The first copper mesh treated with super-hydrophilic treatment cooperates with the liquid absorption micro-column array I. The second copper mesh treated with super-hydrophilic treatment and the liquid absorption micro-column array II cooperate to form a composite liquid absorption member, which can provide a powerful capillary pumping pressure. The composite liquid absorption member also provides an effective evaporation and condensation surface.

[0017] The support member is a nylon wire mesh. The support member forms the steam cavity of the vacuum fluid cavity. The nylon wire mesh has good flexibility and hydrophobicity. Steam is easily condensed into liquid droplets on its surface and then directly drips into the liquid absorption core, shortening the return water route.

[0018] The heat-conducting silicone sheet can play a role in heat conduction and insulation, and the liquid cooling plate can accelerate the condensation and liquefaction of the gas-phase medium.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The present invention utilizes the huge latent heat generated during the gas-liquid phase change of thin-film evaporation and steam condensation in the flexible heat-conducting heat sink to achieve rapid heat dissipation of the battery cell or battery pack;

[0021] (2) The coolant of the flexible heat-conducting heat sink of the present invention is less affected by gravity, and there is no need for a power source or any moving components. It is a completely sealed passive device, which can avoid potential safety hazards;

[0022] (3) The flexible heat sink of the present invention uses a composite liquid-absorbing component composed of a micro-column array and a copper mesh treated with super-hydrophilic treatment, ensuring higher capillary pressure and permeability;

[0023] (4) The flexible heat sink of the present invention uses a coarse-pore nylon wire mesh as the steam chamber of the heat sink, preventing the flexible heat sink from being squeezed and deformed, and providing more return paths for the liquid. Description of the Drawings

[0024] Figure 1 It is an assembly diagram of the flexible heat-conducting heat sink, the liquid cooling plate and the battery pack;

[0025] Figure 2 It is an arrangement diagram of the flexible heat-conducting heat sink between battery cells;

[0026] Figure 3 It is a cross-sectional view of the flexible heat sink;

[0027] Figure 4 It is an arrangement diagram of the liquid-absorbing micro-column array I;

[0028] Figure 5 It is a schematic diagram of the working principle of the flexible heat sink;

[0029] In the figure, 1-battery cell, 2-heat-conducting silicone sheet, 3-flexible heat sink, 4-liquid cooling plate, 5-first flexible outer plate, 6-liquid-absorbing micro-column array I, 7-first copper mesh, 8-supporting member, 9-second copper mesh, 10-liquid-absorbing micro-column array II, 11-second flexible outer plate. Embodiments

[0030] The following further describes the present invention in detail in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the described content.

[0031] Example 1: A battery heat equalization method based on a flexible heat-conducting heat sink (see Figure 1 , 2As shown in FIGS. 4 and 5), a flexible heat-conducting vapor chamber is used for battery heat dissipation. The flexible heat-conducting vapor chamber includes a flexible vapor chamber 3 and heat-conducting silica gel sheets 2 coated on both side surfaces of the flexible vapor chamber. A vacuum fluid chamber is formed in the flexible vapor chamber, and a coolant is filled in the fluid chamber;

[0032] The specific steps of the battery heat dissipation method are as follows:

[0033] The battery cells 1 in the battery pack are arranged vertically in an array. The battery pack is placed on the liquid cooling plate 4, so that the battery cells 1 in the battery pack are arranged in an array both horizontally and vertically along the liquid cooling plate 3. Then, the flexible heat-conducting vapor chamber is vertically inserted between the battery cells of the battery pack. The bottom end of the flexible heat-conducting vapor chamber is attached to the liquid cooling plate 3. Among them, multiple layers of flexible heat-conducting vapor chambers are arranged at intervals along the horizontal direction of the liquid cooling plate, and the flexible heat-conducting vapor chamber is in an "S" shape along the vertical direction of the liquid cooling plate. The heat-conducting silica gel sheets on both sides of the flexible heat-conducting vapor chamber are respectively attached to the side walls of the adjacent battery cells along the horizontal direction of the liquid cooling plate;

[0034] When the battery pack or a single battery cell is in a high-temperature state, the heat is transferred to the flexible vapor chamber through the heat-conducting silica gel sheet of the flexible heat-conducting vapor chamber to form an evaporation zone. The coolant in the vacuum fluid chamber of the evaporation zone is heated and vaporized in an environment with a low vacuum degree, and the volume expands rapidly to form a gas-phase medium that quickly fills the entire vacuum fluid chamber. The coolant absorbs heat during the gasification process to realize the heat dissipation of the high-temperature battery pack or single battery cell; when the gas-phase medium contacts the battery cell or the cooling plate with a temperature lower than the gasification temperature of the coolant, it liquefies into a coolant. The heat released during the liquefaction process is transferred to the battery cell or the cooling plate with a temperature lower than the gasification temperature of the coolant, and the coolant returns to the evaporation heat source under the promotion of the spatial gradient concentration difference; this process will be carried out repeatedly in the cavity of the flexible vapor chamber.

[0035] Embodiment 2: The flexible vapor chamber of this embodiment includes a first flexible outer plate 5, a first copper mesh 7, a support member 8, a second copper mesh 9, and a second flexible outer plate 11 arranged in sequence. The structures of the first flexible outer plate 5 and the second flexible outer plate 11 are the same, and the structures of the first copper mesh 8 and the second copper mesh 9 are the same;

[0036] The two side surfaces of the first flexible outer plate 5 are respectively an A surface and a B surface. The A surface of the first flexible outer plate 5 is attached to the heat-conducting silica gel sheet, and a liquid-absorbing micro-column array I 6 is uniformly fixed on the B surface of the first flexible outer plate 5. The liquid-absorbing micro-columns of the liquid-absorbing micro-column array I 6 are perpendicular to the first flexible outer plate 5;

[0037] The two side surfaces of the second flexible outer plate 11 are respectively a C surface and a D surface. A liquid-absorbing micro-column array II 10 is uniformly fixed on the C surface of the second flexible outer plate 11. The liquid-absorbing micro-columns of the liquid-absorbing micro-column array II 10 are perpendicular to the second flexible outer plate 11, and the D surface of the second flexible outer plate 11 is attached to the heat-conducting silica gel sheet;

[0038] On both sides of the first copper mesh, it is respectively attached to the liquid-absorbing micro-column array I and the support member, and on both sides of the second copper mesh, it is respectively attached to the liquid-absorbing micro-column array II and the support member; the liquid-absorbing micro-column array I, the first copper mesh, the support member, the second copper mesh, and the liquid-absorbing micro-column array II form a vacuum fluid chamber.

[0039] Embodiment 3: The flexible heat pipe of this embodiment is basically the same in structure as that of Embodiment 2, the difference being that: the liquid-absorbing micro-column array I and the liquid-absorbing micro-column array II have the same structure. The height of the liquid-absorbing micro-columns in the liquid-absorbing micro-column array I is 60% - 80% of the thickness of the first flexible outer plate, the thickness of the first copper mesh is 60% - 80% of the thickness of the first flexible outer plate, and the thickness of the support member is 2.0 - 2.2 times the height of the liquid-absorbing micro-columns in the liquid-absorbing micro-column array I;

[0040] The liquid-absorbing micro-columns of the liquid-absorbing micro-column array I are of hexagonal prism structure, the diameter of the liquid-absorbing micro-columns is 100 - 200 μm, the spacing between adjacent liquid-absorbing micro-columns is 300 - 400 μm, and the height of the liquid-absorbing micro-columns is 200 - 400 μm; the liquid-absorbing micro-column array I and the liquid-absorbing micro-column array II have a very high capillary pressure;

[0041] The first flexible outer plate and the liquid-absorbing micro-column array I are of an integrally formed structure, and the second flexible outer plate and the liquid-absorbing micro-column array II are of an integrally formed structure; the materials of the first flexible outer plate and the second flexible outer plate are red copper, enabling the flexible heat-conducting heat pipe to withstand bending according to the shape of the cylindrical battery cell within the flexible range;

[0042] Both the first copper mesh and the second copper mesh are treated with super-hydrophilic treatment, and the pore size of the first copper mesh is 200 - 400 mesh; the first copper mesh treated with super-hydrophilic treatment cooperates with the liquid-absorbing micro-column array I, and the second copper mesh treated with super-hydrophilic treatment and the liquid-absorbing micro-column array II cooperate to form a composite liquid-absorbing member, which can provide a powerful capillary pumping pressure, and this composite liquid-absorbing member also provides an effective evaporation and condensation surface.

[0043] The support member is a nylon wire mesh, and the support member forms the steam chamber of the vacuum fluid chamber; the nylon wire mesh has good flexibility and hydrophobicity, and steam is easily condensed into liquid droplets on its surface and then directly drips into the liquid-absorbing core, shortening the return water route.

[0044] The heat-conducting silica gel sheet can play a role in heat conduction and insulation, and the liquid cooling plate can accelerate the condensation and liquefaction of the gas-phase medium.

[0045] The flexible heat pipe of the present invention has the advantages of large contact area with the battery cell, high thermal conductivity, good temperature uniformity, and reversible heat flow direction, etc., to reduce the temperature difference between single cells, and improve the temperature uniformity and reliability of the power battery pack.

[0046] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A battery heat equalization method based on a flexible heat-conducting vapor chamber, characterized in that, The battery is cooled by using a flexible heat-conducting vapor chamber. The flexible heat-conducting vapor chamber includes a flexible vapor chamber and heat-conducting silica gel sheets coated on both side surfaces of the flexible vapor chamber. A vacuum fluid chamber is formed in the flexible vapor chamber, and a coolant is filled in the fluid chamber. The specific steps of the battery cooling method are as follows: The battery cells in the battery pack are arranged vertically in an array. The battery pack is placed on the liquid cooling plate, so that the battery cells in the battery pack are arranged in an array both transversely and longitudinally along the liquid cooling plate. Then, the flexible heat-conducting vapor chamber is vertically inserted between the battery cells of the battery pack. The bottom end of the flexible heat-conducting vapor chamber is attached to the liquid cooling plate. Among them, multiple layers of flexible heat-conducting vapor chambers are arranged at intervals transversely along the liquid cooling plate. The flexible heat-conducting vapor chamber is in an "S" shape longitudinally along the liquid cooling plate. The heat-conducting silica gel sheets on both sides of the flexible heat-conducting vapor chamber are respectively attached to the side walls of adjacent battery cells in the transverse direction along the liquid cooling plate. The flexible vapor chamber includes a first flexible outer plate, a first copper mesh, a support member, a second copper mesh, and a second flexible outer plate arranged in sequence. The structures of the first flexible outer plate and the second flexible outer plate are the same. The structures of the first copper mesh and the second copper mesh are the same. The two side surfaces of the first flexible outer plate are respectively an A surface and a B surface. The A surface of the first flexible outer plate is attached to the heat-conducting silica gel sheet. The B surface of the first flexible outer plate is uniformly fixed with a liquid-absorbing micro-column array I. The liquid-absorbing micro-columns of the liquid-absorbing micro-column array I are perpendicular to the first flexible outer plate. The two side surfaces of the second flexible outer plate are respectively a C surface and a D surface. The C surface of the second flexible outer plate is uniformly fixed with a liquid-absorbing micro-column array II. The liquid-absorbing micro-columns of the liquid-absorbing micro-column array II are perpendicular to the second flexible outer plate. The D surface of the second flexible outer plate is attached to the heat-conducting silica gel sheet. The two sides of the first copper mesh are respectively attached to the liquid-absorbing micro-column array I and the support member. The two sides of the second copper mesh are respectively attached to the liquid-absorbing micro-column array II and the support member. The liquid-absorbing micro-column array I, the first copper mesh, the support member, the second copper mesh, and the liquid-absorbing micro-column array II form a vacuum fluid chamber. When the battery pack or a single battery cell is in a high-temperature state, the heat is transferred to the flexible vapor chamber through the heat-conducting silica gel sheet of the flexible heat-conducting vapor chamber to form an evaporation zone. The coolant in the vacuum fluid chamber of the evaporation zone is heated and vaporized in an environment with a low vacuum degree, and the volume rapidly expands to form a gas-phase medium that quickly fills the entire vacuum fluid chamber. The coolant absorbs heat during the gasification process to cool the battery pack or a single battery cell in the high-temperature state. When the gas-phase medium contacts a battery cell or a cooling plate with a temperature lower than the gasification temperature of the coolant, it liquefies into a coolant. The heat released during the liquefaction process is transferred to the battery cell or the cooling plate with a temperature lower than the gasification temperature of the coolant, and the coolant returns to the evaporation heat source under the drive of the spatial gradient concentration difference.

2. The battery heat equalization method based on a flexible heat-conducting vapor chamber according to claim 1, wherein: The liquid-absorbing micro-column array I and the liquid-absorbing micro-column array II have the same structure. The height of the liquid-absorbing micro-columns in the liquid-absorbing micro-column array I is 60-80% of the thickness of the first flexible outer plate. The thickness of the first copper mesh is 60-80% of the thickness of the first flexible outer plate. The thickness of the support member is 2.0-2.2 times the height of the liquid-absorbing micro-columns in the liquid-absorbing micro-column array I.

3. The battery heat equalization method based on a flexible heat conducting vapor chamber according to claim 2, characterized in that: The liquid-absorbing microcolumns of the liquid-absorbing microcolumn array I are hexagonal prism structures, the diameter of the liquid-absorbing microcolumns is 100 - 200 μm, the spacing between adjacent liquid-absorbing microcolumns is 300 - 400 μm, and the height of the liquid-absorbing microcolumns is 200 - 400 μm.

4. The battery heat equalization method based on a flexible heat pipe according to claim 1, wherein: The first flexible outer plate and the liquid-absorbing microcolumn array I are integrally formed structures, and the second flexible outer plate and the liquid-absorbing microcolumn array II are integrally formed structures.

5. The battery heat equalization method based on a flexible heat conducting vapor chamber according to claim 1, wherein: Both the first copper mesh and the second copper mesh are treated with super-hydrophilic treatment, and the pore size of the first copper mesh is 200 - 400 mesh.

6. The battery heat equalization method based on a flexible heat pipe according to claim 1, characterized in that: The support member is a nylon wire mesh.

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