Battery module, battery pack, and electric system

Abstract

Provided in the present application is an electric system. The electric system comprises a battery pack, and the battery pack comprises a battery module. The battery module comprises a battery cell and a heat absorption layer, wherein the heat absorption layer comprises a water-containing layer, and the heat absorption layer is arranged on at least part of the surface of the battery cell. The water-containing layer comprises a matrix and water, wherein the matrix is a hydrophilic polymer material, and the water in the water-containing layer can be heated to be separated from the matrix. The battery cell and the water-containing layer meet the following condition: equation (a).

Description

Battery pack, battery package and power system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 30, 2023, with application number 202311431396.0 and application name “A battery pack, battery package and power system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of battery technology, and specifically relates to a battery pack, a battery package and a power system. Background Art

[0003] New energy vehicles are gradually entering the mass market. However, as their penetration rate increases, thermal safety issues are becoming increasingly prominent. During a collision or when the battery pack is rapidly charging, a short circuit may occur within a single cell (cell) in the battery pack. This can trigger a violent chemical reaction within the cell, generating a large amount of heat and leading to thermal runaway. If the heat generated at the thermal runaway location cannot be dissipated promptly, this can accelerate thermal runaway, compromising safety.

[0004] Existing technology places aerogel sheets between battery cells, using the low thermal conductivity of aerogel to delay the transfer of heat from runaway cells to other cells, thereby preventing heat diffusion in the battery pack.

[0005] The existing technical feature is that aerogel itself is only a thermal insulation material that can only delay but not prevent the transfer of heat. Specifically, aerogel only delays the heat transfer at the surface where the runaway cell is fitted. However, when a certain position of the battery loses control and the heat generated by the battery rises sharply, the runaway cell will still be transferred to other cells through other components (such as trays and cold plates), which cannot solve the problem of the sharp rise in heat from the root. In addition, in order to achieve better results by using aerogel to prevent heat diffusion, the thickness of the aerogel is usually increased, which further compresses the space in the battery pack, resulting in a decrease in the number of cells that can be installed and a decrease in the volume energy density of the entire pack.

[0006] Summary of the Invention

[0007] In response to the problems of existing battery thermal runaway protection structures affecting volume energy density and insufficient thermal diffusion protection effect, the present application provides a battery pack, an electric vehicle, and an energy storage system.

[0008] The technical solutions adopted by this application to solve the above technical problems are as follows:

[0009] The present application provides a battery pack including a battery cell and a heat absorption layer, wherein the heat absorption layer includes an aquifer, the heat absorption layer being disposed on at least a portion of the surface of the battery cell, the aquifer including a matrix and water, the matrix being a hydrophilic polymer material, and the water in the aquifer being capable of being separated from the matrix by heat;

[0010] The battery core and the aquifer meet the following conditions:

[0011] Where D is the thickness of the aquifer in meters;

[0012] Q c is the capacity of the battery cell, in kJ;

[0013] c p is the specific heat capacity of the battery cell, in kJ kg -1 K -1 ;

[0014] m is the mass of the battery cell, in kg;

[0015] S is the contact area between the battery cell and the heat absorption layer, in m 2 ;

[0016] ρ is the density of the aquifer, in kg m -3 ;

[0017] r is the mass percentage of water in the aquifer.

[0018] Optionally, the thickness D of the aquifer is 0.00025 to 0.001 m.

[0019] Optionally, the capacity Q of the battery cell c It is 576~3456kJ.

[0020] Optionally, the specific heat capacity c of the battery cell p 0.8~1.2kJ kg -1 K -1 .

[0021] Optionally, the mass m of the battery core is 1 to 5 kg.

[0022] Optionally, the contact area S between the battery core and the heat absorption layer is 0.02 to 0.5 m 2 .

[0023] Optionally, the density ρ of the aquifer is 900-1200 kg m -3 .

[0024] Optionally, the mass percentage r of water in the aquifer is 80% to 99%.

[0025] Optionally, the heat absorption layer further includes a packaging film, and the water-containing layer is encapsulated in the packaging film.

[0026] Optionally, the heat absorption layer further includes a first temperature averaging plate and a second temperature averaging plate, the aquifer is sandwiched between the first temperature averaging plate and the second temperature averaging plate, and an edge area of ​​the aquifer is connected to the external space.

[0027] Optionally, a first cavity is formed inside the first temperature vapor chamber, and the first cavity is filled with a phase-change medium, and / or a second cavity is formed inside the second temperature vapor chamber, and the second cavity is filled with a phase-change medium.

[0028] Optionally, the inner wall of the first cavity is provided with first capillary structures that are interconnected, and / or the inner wall of the second cavity is provided with second capillary structures that are interconnected.

[0029] Optionally, the thickness of the first temperature averaging plate and the second temperature averaging plate are each independently 0.2 to 0.5 mm.

[0030] Optionally, there are multiple battery cells, the multiple battery cells are arranged side by side, a single heat absorption layer is provided between two adjacent battery cells, and the heat absorption layer and one of the adjacent battery cells meet the following conditions:

[0031] Optionally, the heat absorption layer is arranged on the surface of the battery core with the largest area.

[0032] Optionally, the area of ​​the heat absorption layer is smaller than or equal to the area of ​​the largest surface of the battery cell.

[0033] Optionally, the water-containing layer is a hydrogel layer.

[0034] The present application also provides a battery pack, comprising the battery pack described above.

[0035] The present application also provides an electricity system, comprising the battery pack or the battery package as described above.

[0036] According to the battery pack provided by the present application, a heat absorption layer is provided on the surface of the battery cell, and an aquifer is provided in the heat absorption layer, and the heat absorption layer is used to isolate the battery cell from other components susceptible to thermal runaway (such as other battery cells or electronic control equipment, etc.); when thermal runaway occurs in the battery cell, the aquifer absorbs the heat generated by the battery cell. When the temperature of the aquifer reaches the vaporization temperature of water, the stored water evaporates rapidly due to the heat and takes away a large amount of heat, effectively reducing the total heat transferred from the runaway battery cell to adjacent components and improving the protection effect against thermal runaway of the battery cell; on the other hand, the applicant found through a large number of experiments that the capacity Q of the battery cell can be increased by 10%. c Specific heat capacity cp , mass m, the contact area S between the battery cell and the heat absorption layer, the density ρ of the aquifer, the mass percentage r of water in the aquifer, and the thickness D of the aquifer, and satisfy the condition When the battery pack is heated, the volume energy density of the battery pack is increased while the protection effect against thermal runaway of the battery cell is ensured, so that the battery pack can have both high volume energy density and good safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic structural diagram of a battery pack provided by the present application;

[0038] FIG2 is an enlarged schematic diagram of point A in FIG1 ;

[0039] FIG3 is a schematic structural diagram of the heat absorption layer provided in this application.

[0040] The reference numerals in the drawings of the specification are as follows:

[0041] 1. Battery cell; 2. Heat absorption layer; 21. First temperature distribution plate; 22. Second temperature distribution plate; 23. Aquifer. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0043] In the description of the present application, unless otherwise specified, “plurality” means two or more.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, or electrical connections; direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0045] The present embodiment provides a battery pack, including a battery cell 1 and a heat absorption layer 2. The heat absorption layer 2 includes an aquifer 23. The heat absorption layer 2 is disposed on at least a portion of the surface of the battery cell 1. The aquifer 23 includes a matrix and water. The matrix is ​​a hydrophilic polymer material. The water in the aquifer can be vaporized by heat and separated from the aquifer 23.

[0046] The battery cell 1 and the aquifer 23 meet the following conditions:

[0047] Where D is the thickness of the aquifer 23 in meters;

[0048] Q c is the capacity of cell 1, in kJ;

[0049] c p is the specific heat capacity of cell 1, in kJ kg -1 K -1 ;

[0050] m is the mass of cell 1, in kg;

[0051] S is the contact area between the battery cell 1 and the heat absorption layer 2, in m 2 ;

[0052] ρ is the density of the aquifer 23, in kg m -3 ;

[0053] r is the mass percentage of water in the aquifer 23.

[0054] The heat absorption layer 2 is used to isolate the battery cell 1 from other components susceptible to thermal runaway (such as other battery cells 1 or electronic control equipment, etc.); when the battery cell 1 experiences thermal runaway, the aquifer 23 absorbs the heat generated by the battery cell 1. When the temperature of the aquifer 23 reaches the vaporization temperature of water, the stored water evaporates rapidly due to the heat and takes away a large amount of heat, effectively reducing the total heat transferred from the runaway battery cell 1 to adjacent components and improving the protection effect against thermal runaway of the battery cell 1. On the other hand, the applicant has found through a large number of experiments that the capacity Q of the battery cell 1 can be increased by 10%. c Specific heat capacity c p , mass m, the contact area S between the battery cell 1 and the heat absorption layer 2, the density ρ of the aquifer 23, the mass percentage r of water in the aquifer 23, and the thickness D of the aquifer 23, and satisfy the condition When the battery pack is obtained, the volume occupied by the aquifer 23 is reduced while ensuring the protection effect against thermal runaway of the battery cell 1, and the volume energy density of the battery pack is increased, so that the battery pack can have both higher volume energy density and better safety.

[0055] In the above embodiment, a heat absorption layer 2 may be provided on both sides of a battery cell 1 , respectively, wherein the battery cell and the heat absorption layer 2 on one side thereof should satisfy the restricted conditions in the above embodiment.

[0056] The above parameters can be measured by referring to the following contents. Specifically:

[0057] Thickness D of the aquifer 23: The thickness D of the aquifer can be measured optically, using the interference of light. Alternatively, the thickness of the aquifer can be measured directly using a measuring device such as a vernier caliper.

[0058] Contact area S between battery cell 1 and heat absorption layer 2: The contact area S between the battery cell and the heat absorption layer is the actual contact area between the heat absorption material and the battery cell. This is the contact area between the heat absorption layer and the adjacent battery cell. It can also be considered the contact area between the aquifer and the adjacent battery cell. Generally, the contact area S between the battery cell and the heat absorption layer is equal to the surface area of ​​the battery cell in contact with the heat absorption layer.

[0059] Specific heat capacity Cp of battery cell 1: The test method for the specific heat capacity of the battery cell is as follows:

[0060] The differential scanning calorimetry (DSC) test method was used.

[0061] Specifically, the specific steps of DSC (differential scanning calorimetry) testing the specific heat capacity of a sample are as follows:

[0062] 1. Sample preparation: Prepare the sample. The sample mass should be smaller than the measurement range of the thermal analyzer calorimeter.

[0063] 2. Sample filling: Fill the DSC sample container with sample powder and ensure that the sample container has the same heat capacity as the reference container used in the experiment.

[0064] 3. Sample closure: Seal the sample container, usually using an aluminum or stainless steel round lid.

[0065] 4. Experimental parameter setting: Set the experimental parameters as needed, including scanning rate, heating rate, cooling rate and temperature range. (Specific experimental parameters are determined according to actual conditions and are not limited in this application)

[0066] 5. Experimental operation: Start the DSC instrument to conduct the experiment and heat or cool the sample according to the set parameters.

[0067] 6. Data acquisition: The heat exchange between the sample and the reference container is recorded by the DSC instrument to obtain the heat flow curve.

[0068] 7. Data analysis: Based on the obtained heat flow curve, use specialized software to analyze and process the curve.

[0069] 8. Specific heat capacity calculation: Based on parameters such as sample mass, scan rate and peak area, use the corresponding formula to calculate the specific heat capacity of the sample.

[0070] Density ρ of the aquifer 23: The density of the aquifer is usually measured with a densitometer. The specific method is as follows:

[0071] Density method: This method determines the density of a substance by measuring its mass within a fixed volume. Place the sample in the densitometer, wait a few seconds for the sample to stabilize, and then read the value displayed on the densitometer.

[0072] The mass percentage of water in an aquifer: TGA (thermogravimetric analysis) can detect the thermal properties, degradation, and water loss of a material by monitoring changes in sample mass, thereby inferring the water content of the material. The following is a method for testing the water content of an aquifer based on TGA:

[0073] 1. Sample preparation: Prepare a sample of the aqueous material and record the initial mass of the sample.

[0074] 2. Sample placement: Place the water-containing material sample evenly on the sample table and try to maintain the uniformity of the sample.

[0075] 3. Set the temperature range: Set the temperature range in the TGA instrument and allow the sample to heat up according to the set temperature.

[0076] 4. Monitor mass changes: During the thermal decomposition of the sample, the TGA instrument will continuously record the change curve of the sample mass. When the water in the sample begins to evaporate, the total mass of the sample will change.

[0077] 5. Calculate water content: By analyzing and calculating the thermal analysis curve, we can get the water content information, which is the mass percentage of water in the aquifer.

[0078] TGA test parameters:

[0079] Atmosphere: Ar, rate: 50.0 mL / min, heating rate: 10°C / min, temperature range for calculating water content: 20-150°C.

[0080] In one embodiment of the present application, the matrix in the aquifer is a hydrophilic polymer material, such as starch, cellulose, polyethylene glycol, sodium alginate, hydrogel, or sodium polyacrylate. Due to the presence of a cross-linked network structure and a large number of hydrophilic groups, hydrophilic polymer materials can absorb and retain a large amount of water (up to 99% water). While retaining a large amount of water, the polymer network structure can also maintain its integrity well, avoiding problems such as liquid flow. These characteristics give hydrophilic polymer materials such as hydrogels great potential in utilizing the cooling capacity of water.

[0081] In some embodiments, the thickness D of the aquifer 23 is 0.00025-0.001 m.

[0082] In specific embodiments, the thickness D of the aquifer 23 may be 0.00025m, 0.0003m, 0.00035m, 0.00038m, 0.0004m, 0.00045m, 0.0005m, 0.00055m, 0.0006m, 0.00065m, 0.0007m, 0.00075m, 0.00078m, 0.0008m, 0.00085m, 0.0009m, 0.00095m or 0.001m.

[0083] The thickness D of the aquifer 23 affects the protection effect of the aquifer 23 against thermal runaway of the battery cell 1 . When the thickness D of the aquifer 23 is within the above range, it is beneficial to improve the protection effect against thermal runaway of the battery cell 1 while reducing the impact on the battery energy density.

[0084] In some embodiments, the capacity Q of the battery cell 1 is c It is 576~3456kJ.

[0085] In a specific embodiment, the capacity Q of the battery cell 1 is c It can be 576kJ, 580kJ, 600kJ, 610kJ, 650kJ, 680kJ, 700kJ, 780kJ, 800kJ, 810kJ, 850kJ, 880kJ, 900kJ, 910kJ, 950kJ, 980kJ, 1000kJ, 1050kJ, 1080kJ, 1110kJ, 1150kJ, 1180kJ kJ, 2450kJ, 2650kJ, 2870kJ, 2980kJ, 3150kJ, 3200kJ, 3350kJ or 3456kJ.

[0086] In the description of this application, the term "capacity Q of the battery cell 1" c " is obtained by converting the energy of the battery cell 1 from electrical energy units to thermal units. Specifically, when the energy of the battery cell 1 is 1Wh, it is converted to the capacity Q of the battery cell 1. c is 1kJ.

[0087] The capacity Q of the battery cell 1 c Related to the energy stored in the battery cell 1, as the capacity Q of the battery cell 1 increases c As the capacity of the battery cell 1 increases, the energy released by the battery cell 1 also gradually increases, but the capacity Q of the battery cell 1 is too high.c This also means that once thermal runaway occurs, it releases more heat. When the capacity of cell 1 is Q c When it is within the above range, it has higher output power and thermal runaway is relatively controllable.

[0088] In some embodiments, the specific heat capacity c of the battery cell 1 is p 0.8~1.2kJ kg -1 K -1 .

[0089] In a specific embodiment, the specific heat capacity c of the battery cell 1 is p can be 0.8kJ kg -1 K -1 , 0.81kJ kg -1 K -1 , 0.85kJ kg -1 K -1 , 0.88kJ kg -1 K -1 , 0.9kJ kg -1 K -1 , 0.91kJ kg -1 K -1 , 0.95kJ kg -1 K -1 , 0.98kJ kg -1 K -1 , 1kJ kg -1 K -1 , 1.05kJ kg -1 K -1 , 1.08kJ kg -1 K -1 , 1.11kJ kg -1 K -1 , 1.15kJ kg -1 K -1 , 1.18kJ kg -1 K -1 or 1.2 kJ kg -1 K -1 .

[0090] In some embodiments, the mass m of the battery core 1 is 1-5 kg.

[0091] In a specific embodiment, the mass m of the battery cell 1 can be 1.0 kg, 1.2 kg, 1.4 kg, 1.7 kg, 1.9 kg, 2.1 kg, 2.2 kg, 2.4 kg, 2.7 kg, 2.9 kg, 3.1 kg, 3.3 kg, 3.5 kg, 3.9 kg, 4.1 kg, 4.3 kg, 4.6 kg, 4.9 kg or 5.0 kg.

[0092] The specific heat capacity c of the battery cell 1 p The mass m of the battery cell 1 determines the heat capacity of the battery cell 1 itself during thermal runaway. When the specific heat capacity c of the battery cell 1 p When the mass m of the battery cell 1 is within the above range, the obtained battery cell 1 has a higher heat capacity.

[0093] In some embodiments, the contact area S between the battery core 1 and the heat absorption layer 2 is 0.02 to 0.5 m 2 .

[0094] In a specific embodiment, the contact area S between the battery core 1 and the heat absorption layer 2 can be 0.02m 2 , 0.05m 2 , 0.08m 2 , 0.1m 2 , 0.12m 2 , 0.15m 2 , 0.18m 2 , 0.2m 2 , 0.22m 2 , 0.25m 2 , 0.28m 2 , 0.3m 2 , 0.32m 2 , 0.35m 2 , 0.38m 2 , 0.4m 2 , 0.42m 2 , 0.45m 2 , 0.48m 2 or 0.5m 2 .

[0095] The contact area S between the battery core 1 and the heat absorption layer 2 affects the heat conduction rate of the battery core 1 to the aquifer 23. As the contact area S between the battery core 1 and the heat absorption layer 2 increases, the heat exchange efficiency between the battery core 1 and the aquifer 23 is improved, so that the aquifer 23 can quickly absorb the heat generated by the battery core 1.

[0096] In some embodiments, the density ρ of the aquifer 23 is 900-1200 kg m -3 .

[0097] In a specific embodiment, the density ρ of the aquifer 23 can be 900 kg m -3 910kg m -3 , 950kg m -3 , 980kg m -3 , 1000kg m -3 、1050kg m -3 、1080kg m -3 1110kg m -3 1150kg m -3 、1180kg m -3 or 1200kg m -3 .

[0098] In some embodiments, the mass percentage r of water in the aquifer 23 is 80% to 99%.

[0099] In a specific embodiment, the mass percentage r of water in the aquifer 23 can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

[0100] The water in the aquifer 23 plays a role in vaporization and heat absorption when the battery cell 1 experiences thermal runaway. The density ρ of the aquifer 23 and the mass percentage r of water in the aquifer 23 affect the amount of heat absorbed by vaporization of the aquifer 23 per unit mass. When the density ρ of the aquifer 23 and the mass percentage r of water in the aquifer 23 are within the above range, it is beneficial to ensure that there is sufficient water for heat absorption by the battery cell 1.

[0101] In some embodiments, the heat absorption layer 2 further includes a packaging film, and the water-containing layer 23 is encapsulated in the packaging film.

[0102] The packaging film is used to shape the aquifer 23 and prevent the evaporation of water in the aquifer 23 in a non-thermal runaway state.

[0103] In the above embodiment, the contact area between the battery cell and the heat absorption layer is the contact area between the packaging film and the adjacent battery cell.

[0104] In some embodiments, the heat absorption layer 2 further includes a first temperature averaging plate 21 and a second temperature averaging plate 22, the water-containing layer 23 is clamped between the first temperature averaging plate 21 and the second temperature averaging plate 22, and the edge area of ​​the water-containing layer 23 is connected to the external space (i.e., the space inside the battery pack), which is conducive to the rapid discharge of water in the water-containing layer 23 into the external space when it vaporizes, thereby achieving a rapid heat dissipation effect.

[0105] The first temperature averaging plate 21 and the second temperature averaging plate 22 have high thermal conductivity. By using the first temperature averaging plate 21, the aquifer 23 and the second temperature averaging plate 22 to form a sandwich structure, the utilization rate of the aquifer 23 can be effectively improved compared to directly using the aquifer 23 as a heat absorption material. In the initial stage of thermal runaway occurring in a local position of the battery cell 1, the heat can be quickly transferred to the entire surface of the battery cell 1, so that the sensible heat and latent heat of the aquifer 23 in each part can be effectively utilized.

[0106] In some embodiments, the first temperature vapor chamber 21 and the second temperature vapor chamber 22 are selected from metal materials or other heat-conducting materials, and other heat-conducting materials include carbon materials.

[0107] In some embodiments, the first temperature vapor chamber 21 and the second temperature vapor chamber 22 are made of metal materials, including one or more of aluminum and its alloys, copper and its alloys, iron and its alloys, and nickel and its alloys.

[0108] In a preferred embodiment, the first temperature averaging plate 21 and the second temperature averaging plate 22 are selected from copper and its alloys. Copper and its alloys have high thermal conductivity and good processing performance.

[0109] In some embodiments, a first cavity is formed inside the first temperature vapor chamber 21 , and a second cavity is formed inside the second temperature vapor chamber 22 . Both the first cavity and the second cavity are filled with a phase-change medium.

[0110] The first temperature averaging plate 21 and / or the second temperature averaging plate 22 are in direct contact with the adjacent battery cells 1. When the first temperature averaging plate 21 or the second temperature averaging plate 22 is locally heated, the phase change medium at the locally heated position will evaporate and diffuse to the unheated position in the form of gas, and condense and release heat at the unheated position, ensuring rapid diffusion of heat, thereby allowing the aquifer 23 to be heated evenly and quickly.

[0111] At the same time, when the battery cell 1 is operating normally, the first temperature equalizing plate 21 and / or the second temperature equalizing plate 22 can be used to reduce the temperature difference on the surface of the battery cell 1, and the sensible heat of the aquifer 23 can be used to absorb part of the heat, thereby improving the heat dissipation efficiency of the battery cell 1 and ensuring the stable operation of the battery cell 1.

[0112] In some embodiments, the inner wall of the first cavity is provided with a first capillary structure that is interconnected, and the inner wall of the second cavity is provided with a second capillary structure that is interconnected.

[0113] The first capillary structure and the second capillary structure are structures that can produce capillary phenomena, including porous structures and / or groove structures. By arranging the first capillary structure on the inner wall of the first cavity and the second capillary structure on the inner wall of the second cavity, it is beneficial to promote the uniform distribution of the liquid phase change medium inside the first cavity and the second cavity. When the phase change medium in the first cavity and the second cavity condenses at an unheated position, the first capillary structure and the second capillary structure are used to continuously attract the liquid phase change medium to the local heated position of the first temperature averaging plate 21 or the second temperature averaging plate 22 through the capillary phenomenon, thereby forming a heat absorption-heat release cycle and improving the thermal conductivity efficiency.

[0114] In some embodiments, the thickness of the first temperature evaporating plate 21 and the second temperature evaporating plate 22 is 0.2-0.5 mm.

[0115] In some embodiments, there are multiple battery cells 1, and the multiple battery cells 1 are arranged side by side. A single heat absorption layer 2 is provided between two adjacent battery cells 1, and the heat absorption layer 2 and any adjacent battery cell 1 meet the following conditions:

[0116] In some embodiments, the heat absorption layer 2 is arranged on the surface of the battery cell 1 with the largest area, thereby ensuring that the heat absorption layer can better absorb the heat generated by the battery cell and improve the safety of the battery pack.

[0117] Furthermore, the area of ​​the heat absorption layer is smaller than or equal to the area of ​​the largest surface of the battery cell.

[0118] Furthermore, the area of ​​the heat absorption layer 2 is consistent with the largest surface area of ​​the battery core 1, which is beneficial to improving the heat conduction efficiency between the heat absorption layer 2 and the battery core 1.

[0119] In some embodiments, in the heat absorption layer 2 , the number of the aquifer 23 is a single layer or multiple layers. When the aquifer 23 is multiple layers, the thickness D of the aquifer 23 refers to the total thickness of the multiple aquifers 23 .

[0120] In some embodiments, the water-containing layer 23 is a hydrogel layer.

[0121] Specifically, hydrogel is a type of polymer with a three-dimensional network structure. It can absorb a large amount of water and swell in water, and after swelling, it can continue to maintain its original structure without being dissolved. By setting the water-containing layer 23 as a hydrogel layer, it is beneficial to maintain a higher content of water between the battery cells 1, while ensuring that the water-containing layer 23 can maintain its shape in the normal working state of the battery, thereby avoiding the loss of water in the water-containing layer 23.

[0122] In some embodiments, the hydrophilic polymer material includes one or more of collagen, gelatin, hyaluronic acid, chitosan, polyacrylic acid and its derivatives, polyvinyl alcohol, polyethylene oxide, and polyacrylamide. In this embodiment, the above hydrophilic polymer material is mixed with water to form the water-containing layer.

[0123] In some embodiments, the battery cell 1 is a lithium iron phosphate battery or a ternary battery.

[0124] In some embodiments, the shape of the battery cell 1 is not particularly limited. For example, the battery cell 1 may be in a rectangular shape or other regular or irregular shape.

[0125] Another embodiment of the present application provides a battery pack, comprising the battery pack described above. The battery pack comprises a sealing cover and a tray that cooperates with the sealing cover to form a receiving cavity, and the battery pack is placed in the receiving cavity.

[0126] Another embodiment of the present application provides an electric power system, including the battery pack or battery package described above, wherein the electric power system can be a vehicle or an energy storage system.

[0127] The present application is further described below through examples.

[0128] Table 1

[0129] Example 1

[0130] This embodiment is used to illustrate the battery pack disclosed in this application.

[0131] Using capacity Q c The lithium iron phosphate battery with a specific heat capacity of 934.27kJ is used as the battery cell, with a mass m of 1.52kg and a specific heat capacity c p About 1010J kg -1 K -1 The contact area between the cell and the heat absorption layer is the area of ​​the cell surface that the heat absorption layer contacts, S is 0.05552m 2 Five battery cells are arranged side by side at intervals, and a heat absorption layer is provided between two adjacent battery cells. The heat absorption layer includes a water-containing layer, which is selected from a hydrogel layer. The mass percentage r of water in the water-containing layer is 85%, the thickness D of the water-containing layer is 0.25 mm, and the density ρ of the water-containing layer is 1000 kg m -3 .

[0132] Examples 2 to 24

[0133] Examples 2 to 24 are used to illustrate the battery pack disclosed in this application, which include most of the features of Example 1, except that:

[0134] The battery packs provided in Examples 2 to 24 use the cell capacities Q shown in Table 1 for Examples 2 to 24. c Specific heat capacity c p , mass m, contact area S between the battery cell and the heat absorption layer, density ρ of the aquifer, mass percentage r of water in the aquifer and thickness D of the aquifer.

[0135] Comparative Examples 1 to 5

[0136] Comparative Examples 1 to 5 are used to compare and illustrate the battery pack disclosed in this application, which include most of the features of Example 1, except that:

[0137] The battery packs provided in Comparative Examples 1 to 5 use the battery cells with the capacities Q shown in Comparative Examples 1 to 5 in Table 1. c Specific heat capacity c p , mass m, contact area S between the battery cell and the heat absorption layer, density ρ of the aquifer, mass percentage r of water in the aquifer and thickness D of the aquifer.

[0138] Performance Testing

[0139] The battery pack prepared above was subjected to the following performance tests:

[0140] 1. Volume energy density test

[0141] The battery pack was subjected to charge and discharge tests to obtain the battery capacity of the battery pack. The volumes of the battery cells and aquifers were measured and calculated, and the volume energy density and volume energy density decrease rate of a single battery cell were obtained using the following formula:

[0142] Volume energy density of a single battery cell = capacity of a single battery cell / volume of a single battery cell;

[0143] Volumetric energy density of a single new battery cell = capacity of a single battery cell / (volume of a single battery cell + volume of aquifer);

[0144] Volume energy density decrease rate = volume energy density of a single battery cell - volume energy density of a single new battery cell.

[0145] Regarding the measurement methods for battery cell volume and aquifer volume: For a single battery cell or aquifer, the battery cell volume can be determined by measuring the length, width, and height of the battery cell; the aquifer volume can be determined by measuring the length, width, and height of the aquifer. Alternatively, measurements can be made using the water displacement method. This application does not impose any further restrictions on this requirement.

[0146] Battery capacity test method:

[0147] 1) At room temperature, charge with a low current to the cut-off voltage and leave for 1 hour;

[0148] 2) Discharge at a constant current of 1 / 3C to the cut-off voltage and leave for 1 hour;

[0149] 3) Repeat steps 1-2 twice. Record the second discharge capacity as the battery capacity.

[0150] Generally, the low current is between 1 / 5 C and 1 / 2 C. In this embodiment, a lithium iron phosphate battery is used, so the cut-off voltage is 3.75V.

[0151] 2. Battery thermal runaway safety test

[0152] Perform a needle penetration test on a battery cell in the battery pack to test whether heat diffusion occurs after the needle penetration triggers thermal runaway in a battery cell (this is based on whether the adjacent battery cell has thermal runaway. Generally, it takes 15 minutes to 30 minutes after the needle penetration battery cell has thermal runaway to determine whether the adjacent battery cell has thermal runaway). At the same time, monitor the maximum temperature of the battery cell where thermal runaway is triggered by the needle penetration.

[0153] Among them, the battery thermal runaway safety test conditions in the needle penetration test are as follows:

[0154] Battery cell SOC: 100%;

[0155] Temperature: room temperature 25℃;

[0156] Needle material: steel needle, diameter 5mm±0.2mm, cone angle 45±3;

[0157] Needle puncture speed: 1mm / s;

[0158] Puncture location: middle side of the top of the battery cell.

[0159] Determine thermal runaway conditions:

[0160] a). The trigger object generates a voltage drop, and the drop value exceeds 25% of the initial voltage;

[0161] b). The temperature at the monitoring point reaches the maximum operating temperature specified by the manufacturer;

[0162] c). The temperature rise rate dT / dt at the monitoring point is ≥1℃ / s and lasts for more than 3s.

[0163] When a) and c) occur simultaneously or b) and c) occur simultaneously, thermal runaway is determined to have occurred.

[0164] Among them, the maximum temperature refers to the highest value among all thermocouple measuring points on the punctured battery cell, usually near the puncture point.

[0165] The test results are entered in Table 2.

[0166] Table 2

[0167] From the test results of Examples 1 to 12 and Comparative Examples 1 to 4, it can be seen that the heat-absorbing layer with a water-containing layer is used as a barrier between adjacent cells in the battery pack, and the capacity Q of the cell is c Specific heat capacity c p , mass m, contact area S between the battery core and the heat absorption layer, density ρ of the aquifer, mass percentage r of water in the aquifer, and thickness D of the aquifer satisfy the conditions When the battery pack is adjusted to the capacity Q, it can achieve both high volume energy density and good thermal runaway prevention. c Specific heat capacity c p , mass m, contact area S between the battery cell and the heat absorption layer, density ρ of the aquifer, mass percentage r of water in the aquifer, and thickness D of the aquifer are all kept in a relatively balanced state, which is conducive to ensuring that when thermal runaway occurs in the battery cell, the aquifer can absorb sufficient heat to suppress the conduction of the thermal runaway phenomenon of the single battery cell to the adjacent battery cells, thereby ensuring that the battery pack has good safety performance. At the same time, the volume occupied by the aquifer in the battery pack is reduced as much as possible, thereby reducing the rate of decrease in the volume energy density of the battery pack.

[0168] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A battery pack, characterized in that: include: Battery cell (1); and A heat absorption layer (2), the heat absorption layer (2) comprising an aquifer (23), the heat absorption layer (2) being arranged on at least a portion of the surface of the battery core (1), the aquifer (23) comprising a matrix and water, the matrix being a hydrophilic polymer material, and the water in the aquifer (23) being able to separate from the matrix by heat; The battery core (1) and the aquifer (23) satisfy the following conditions: in, D is the thickness of the aquifer (23), in m; Q c is the capacity of the battery cell (1), in kJ; c p is the specific heat capacity of the battery cell (1), in kJ kg -1 K -1 ; m is the mass of the battery cell (1), in kg; S is the contact area between the battery cell (1) and the heat absorption layer (2), in m 2 ; ρ is the density of the aquifer (23), in kg m -3 ; r is the mass percentage of water in the aquifer (23).

2. The battery pack according to claim 1, characterized in that: The thickness D of the aquifer (23) is 0.00025-0.001 m.

3. The battery pack according to claim 1 or 2, characterized in that: The capacity Q of the battery cell (1) c It is 576~3456kJ.

4. The battery pack according to any one of claims 1 to 3, characterized in that: The specific heat capacity c of the battery cell (1) p 0.8~1.2kJ kg -1 K -1 .

5. The battery pack according to any one of claims 1 to 4, characterized in that: The mass m of the battery core (1) is 1 to 5 kg.

6. The battery pack according to any one of claims 1 to 5, characterized in that: The contact area S between the battery core (1) and the heat absorption layer (2) is 0.02 to 0.5 m 2 .

7. The battery pack according to any one of claims 1 to 6, characterized in that: The density ρ of the aquifer (23) is 900-1200 kg m -3 .

8. The battery pack according to any one of claims 1 to 7, characterized in that: The mass percentage r of water in the aquifer (23) is 80% to 99%.

9. The battery pack according to any one of claims 1 to 8, characterized in that: The heat absorption layer (2) further comprises a packaging film, and the water-containing layer (23) is packaged in the packaging film.

10. The battery pack according to any one of claims 1 to 9, characterized in that: The heat absorption layer (2) further comprises a first temperature averaging plate (21) and a second temperature averaging plate (22); the water-containing layer (23) is sandwiched between the first temperature averaging plate (21) and the second temperature averaging plate (22); and an edge region of the water-containing layer (23) is connected to an external space.

11. The battery pack according to claim 10, characterized in that: A first cavity is formed inside the first temperature equalizing plate (21), and the first cavity is filled with a phase-change working medium, and / or a second cavity is formed inside the second temperature equalizing plate (22), and the second cavity is filled with a phase-change working medium.

12. The battery pack according to claim 11, characterized in that: The inner wall of the first cavity is provided with first capillary structures that are interconnected, and / or the inner wall of the second cavity is provided with second capillary structures that are interconnected.

13. The battery pack according to claim 10, characterized in that: The thickness of the first temperature balancing plate (21) and the second temperature balancing plate (22) are independently 0.2 to 0.5 mm.

14. The battery pack according to any one of claims 1 to 13, characterized in that: The number of the battery cells (1) is multiple, the multiple battery cells (1) are arranged side by side, a single heat absorption layer (2) is arranged between two adjacent battery cells (1), and the heat absorption layer (2) and one of the adjacent battery cells (1) satisfy the following conditions:

15. The battery pack according to any one of claims 1 to 14, characterized in that: The heat absorption layer (2) is arranged on the surface of the battery core (1) with the largest area.

16. The battery pack according to claim 15, characterized in that: The area of ​​the heat absorption layer (2) is less than or equal to the area of ​​the largest surface of the battery core (1).

17. The battery pack according to any one of claims 1 to 16, characterized in that: The water-containing layer (23) is a hydrogel layer.

18. A battery pack, characterized in that: A battery pack comprising the battery pack as claimed in any one of claims 1 to 17.

19. An electricity system, characterized in that: A battery pack comprising the battery pack according to any one of claims 1 to 17 or a battery pack according to claim 18.

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