Battery assembly and power utilization system

Abstract

The invention relates to the technical field of heat absorption materials, and discloses a battery assembly and a power utilization system. The battery assembly comprises a plurality of battery cells, a heat absorption unit is arranged between every two adjacent battery cells, each heat absorption unit comprises a heat absorption material and at least one layer of framework, each framework is provided with a plurality of holes penetrating in the thickness direction of the framework, and the holes are filled with the heat absorption materials. The battery assembly meets the following condition # imgabs0 #. According to the battery assembly provided by the invention, the heat absorption unit can be ensured to keep the form in the thermal runaway of the battery core, so that the battery assembly is ensured to have relatively good safety.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a battery assembly and an electrical power consumption system. Background Art

[0002] At present, new energy is being continuously popularized. For example, more and more batteries are used in new energy vehicles, energy storage power stations, etc., and their safety issues have attracted more and more attention from all aspects. Due to thermal abuse, mechanical abuse, etc. of the battery, potential safety hazards will be brought to the battery, and even thermal runaway of the battery cells may be triggered. When thermal runaway occurs in the battery cells in the battery pack, a large amount of heat is generated inside, resulting in a rapid increase in the temperature of the battery cells and transfer to adjacent battery cells. If effective isolation means are not taken, the temperature of adjacent battery cells will also rapidly increase and thermal diffusion will occur. Summary of the Invention

[0003] The purpose of the present invention is to provide a battery assembly and an electrical power consumption system. The present invention proposes a parametric design method for a framework based on Young's modulus. By specifying the gap and pressure between battery cells, the selection range of parameters related to the thickness of the framework is determined, so that while the battery assembly meets the functional requirements, it has good safety.

[0004] To achieve the above purpose, on the one hand, the present invention provides a battery assembly. The battery assembly includes a plurality of battery cells, and a heat absorption unit is arranged between two adjacent battery cells. The heat absorption unit includes a heat absorption material and at least one layer of framework. The framework has a plurality of holes penetrating in the thickness direction of the framework, and the heat absorption material fills the holes. The battery assembly satisfies the following conditions:

[0005]

[0006] where x is the thickness of the heat absorption unit, in mm;

[0007] d is the gap between two adjacent battery cells, in mm;

[0008] a is the ratio of the area of the positive projection of the framework on the surface of the heat absorption unit in contact with the battery cell to the area of the surface of the heat absorption unit in contact with the battery cell;

[0009] E1 is the Young's modulus of the framework, in GPa;

[0010] S is the area of the surface of the heat absorption unit in contact with the battery cell, in mm 2 ;

[0011] F1 is the pressure borne by the framework, in N;

[0012] x1 is the thickness of one layer of framework, in mm;

[0013] n is the number of layers of the framework, where n≥1 and n is an integer.

[0014] Preferably, the energy Q of the battery cell is between 576 kJ and 3456 kJ.

[0015] Preferably, the volume V of the heat-absorbing material is between 20000 mm 3 - 300000 mm 3 wherein, the volume V of the heat-absorbing material satisfies: V = (x - a * n * x1)·S.

[0016] Preferably, the thickness x of the heat-absorbing unit is 0.5 - 5 mm.

[0017] Preferably, the gap d between two adjacent battery cells is 0.3 - 3 mm.

[0018] Preferably, the ratio a of the area of the orthographic projection of the framework on the surface where the heat-absorbing unit contacts the battery cell to the surface area of the contact surface between the heat-absorbing unit and the battery cell is 10 - 50%.

[0019] Preferably, the Young's modulus E1 of the framework is 0.0001 - 100 GPa.

[0020] Preferably, the surface area S of the contact surface between the heat-absorbing unit and the battery cell is 5000 - 300000 mm 2 .

[0021] Preferably, the pressure F1 borne by the framework is 5000 - 60000 N.

[0022] Preferably, the pressure F1 borne by the framework satisfies the following formula:

[0023]

[0024] wherein, F is the total pressure borne by the contact surface between the heat-absorbing unit and the battery cell, with the unit of N;

[0025] E2 is the Young's modulus of the heat-absorbing material, with the unit of GPa;

[0026] a is the ratio of the area of the orthographic projection of the framework on the surface where the heat-absorbing unit contacts the battery cell to the surface area of the contact surface between the heat-absorbing unit and the battery cell.

[0027] Preferably, the thickness x1 of one layer of the framework is 0.025 - 2 mm.

[0028] Preferably, the number of layers n of the framework is 1 - 10.

[0029] Preferably, the thickness x of the heat-absorbing unit is greater than or equal to the product of the thickness x1 of one layer of the framework and the number of layers n of the framework.

[0030] Preferably, the total thickness of the skeleton accounts for 1-100% of the thickness of the heat absorption unit, preferably 10-80%.

[0031] Preferably, the heat absorption unit further includes a packaging film for encapsulating the skeleton and the heat absorption material.

[0032] Preferably, the holes are uniformly arranged along the thickness direction of the skeleton.

[0033] Preferably, the ratio of the area of the surface of the heat absorption unit in contact with the battery cell to the surface area of the battery cell in contact with the heat absorption unit is greater than or equal to 0.8 and less than or equal to 1.

[0034] Preferably, the battery assembly includes at least two battery cell groups, each battery cell group includes N battery cells arranged in a row, and a heat absorption unit is arranged between two adjacent battery cell groups, wherein the thickness x of the heat absorption unit satisfies the following relationship: (0.5N ± b) mm ≤ x ≤ (5N ± b) mm; where b is a preset correction factor with the unit of mm.

[0035] Preferably, the phase change temperature of the heat absorption material is between 50°C and 200°C.

[0036] Preferably, the phase change temperature of the heat absorption material is between 70°C and 160°C.

[0037] Preferably, the heat absorption material is a hydrogel.

[0038] Preferably, a plurality of the holes are uniformly arranged along the extending direction of the skeleton.

[0039] The second aspect of the present invention provides an electrical system, including the battery assembly described above.

[0040] According to the technical solution of the present invention, by making the value in the battery assembly satisfy greater than or equal to 10 and less than or equal to 1000, it can ensure that the deformation amount of the heat absorption unit is within a certain range, and further ensure that the heat absorption unit will not be damaged or the material will not overflow due to the extrusion of the battery during thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the battery assembly;

[0042] Figure 2 is a schematic diagram of the heat absorption unit including a hexagonal skeleton;

[0043] Figure 3 is a schematic surface diagram of the hexagonal skeleton;

[0044] Figure 4 It is a schematic diagram of the surface of a square framework;

[0045] Figure 5 It is a schematic diagram of a double-layer square framework;

[0046] Figure 6 It is a schematic diagram of a heat absorption unit containing a single-layer framework;

[0047] Figure 7 It is a schematic diagram of a heat absorption unit containing a multi-layer framework;

[0048] Figure 8 It is a test device for thermal runaway pressure test.

[0049] Description of the reference numerals

[0050] 1. Heat absorption unit; 2. Battery cell; 11. Framework; 12. Heat absorption material; 3. Pressure sensor; 4. Heat insulation board; 5. Fixture baffle; 6. Needle punching point. Specific embodiments

[0051] The following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0052] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating relative importance or implicitly indicating the quantity of the indicated technical features. Thus, unless otherwise specified, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; the meaning of "a plurality" is two or more. The term "comprising" and any deformation thereof means non-exclusive inclusion, and there may be or be added one or more other features, integers, steps, operations, units, components and / or their combinations.

[0053] In addition, the terms indicating the orientation or positional relationship such as "upper", "lower", "inner", "outer", etc. are described based on the orientation or relative positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, rather than indicating that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0054] Furthermore, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0055] As Figure 1-7 shown, the battery assembly of the present invention includes a plurality of battery cells, and at least one surface of each battery cell is provided with a heat absorption unit. The heat absorption unit includes a framework and a heat absorption material. The framework includes a plurality of holes penetrating the framework in the thickness direction of the framework, and the heat absorption material fills the holes. The framework is a single-layer or multi-layer structure.

[0056] In the present invention, the battery assembly satisfies the following conditions:

[0057]

[0058] where x is the thickness of the heat absorption unit, in mm;

[0059] d is the given battery cell gap, in mm;

[0060] a is the ratio of the area of the positive projection of the framework on the surface where the heat absorption unit contacts the battery cell to the area of the surface where the heat absorption unit contacts the battery cell;

[0061] E1 is the Young's modulus of the framework, in GPa;

[0062] S is the area of the surface where the heat absorption unit contacts the battery cell, in mm 2 ;

[0063] F1 is the pressure borne by the framework, in N;

[0064] x1 is the thickness of one layer of the framework, in mm;

[0065] n is the number of layers of the framework, n≥1 and n is an integer.

[0066] When the heat absorption unit satisfies the above parameter conditions, the battery assembly has good safety. Specifically, in the safety test of the battery assembly, after a thermal runaway occurs in one battery cell triggered by a needle prick, no thermal diffusion phenomenon will occur. When the value is less than 10, the framework is prone to large deformation due to too small Young's modulus. Once the battery cell gets out of control, the expansion force will increase sharply, the heat absorption material will break through the encapsulation and leak, and the absorbed heat will decrease, thus being unable to inhibit thermal diffusion; when the value is greater than 1000, the Young's modulus of the framework is extremely large and hardly deforms. Since a certain gap needs to be compressed during design, this compressed gap is provided by the heat absorption material. When the battery cell is charged and discharged cyclically, the heat absorption unit is repeatedly squeezed, and the heat absorption material is continuously squeezed and then overflows the gap between the battery cells, reducing the heat of the heat absorption unit, thus being unable to inhibit thermal diffusion.

[0067] In a more preferred embodiment, the heat absorption unit satisfies the following conditions.

[0068]

[0069] In the above more preferred embodiment, the battery assembly has further improved safety.

[0070] In the battery assembly of the present invention, preferably, the thickness x of the heat absorption unit is 0.5 - 5 mm, more preferably 0.5 - 2 mm. When the thickness of the heat absorption unit is within the above preferred range, not only can the good safety of the battery assembly be ensured, but also the battery assembly has an appropriate energy density. In the present invention, the thickness of the heat absorption unit can be measured by a vernier caliper, a laser rangefinder, etc. And in the present invention, the thickness of the heat absorption unit is the thickness measured after the heat absorption unit is separated from the battery assembly.

[0071] In the battery assembly of the present invention, the cell spacing is determined according to the assembly gap and the overall package space utilization rate of the battery pack. Preferably, the cell gap d is 0.3 - 3 mm. The cell gap can be directly measured as the distance between the opposite surfaces of two adjacent cells, and a heat absorption unit is provided between the opposite surfaces of the two adjacent cells. Generally, the cell gap is measured as the distance between the opposite surfaces of two adjacent cells when the SOC of the cells is 25% in the static state.

[0072] In the battery assembly of the present invention, preferably, the ratio a of the area of the projection of the framework on the surface where the heat absorption unit contacts the cell to the area of the surface where the heat absorption unit contacts the cell is 10 - 50%. When the area ratio of the framework on the surface of the heat absorption unit is within the above preferred range, the heat absorption unit can not only provide sufficient support to ensure that the heat absorption material is not extruded, but also ensure the heat absorption amount of the heat absorption material, so that the battery assembly has good safety. Among them, when determining a, it is only based on the area of the projection of the framework entity structure on the surface where the heat absorption unit contacts the cell, that is, the area of the holes is not counted as the area of the projection on the surface where the heat absorption unit contacts the cell. Further, when the projection of the heat absorption unit on the surface of the cell in contact with the heat absorption unit is within the surface of the cell, the area of the projection of the heat absorption unit on the surface where the heat absorption unit contacts the cell is equal to the surface area of the framework facing the heat absorption unit side, and the area of the surface where the heat absorption unit contacts the cell is the surface area of the heat absorption unit facing the cell side.

[0073] In the battery assembly of the present invention, preferably, the Young's modulus E1 of the skeleton is 0.0001 - 100 GPa. When the Young's modulus of the skeleton is within the above preferred range, the skeleton can provide sufficient support for the heat-absorbing material to ensure that the heat-absorbing material is not extruded, so that the battery assembly has better safety. Among them, the Young's modulus E1 of the skeleton can be determined according to the skeleton material.

[0074] In the battery assembly of the present invention, preferably, the surface area S of the heat-absorbing unit in contact with the battery cell is 5000 - 300000 mm 2 . When the heat-absorbing area on the surface of the heat-absorbing unit is within the above preferred range, it can ensure that the heat-absorbing unit can provide sufficient heat-absorbing capacity, thereby inhibiting battery thermal diffusion. Generally, the heat-absorbing area of the heat-absorbing unit is the area of the surface where the heat-absorbing unit is in contact with the battery cell, or can also be the area of one of the battery cell surfaces in contact with the heat-absorbing unit.

[0075] In the battery assembly of the present invention, the pressure F1 borne by the skeleton is generally given according to the actual situation. If it is too small, the heat-absorbing unit and the battery cell cannot be constrained and fixed. If it is too large, it will damage the battery cell. Preferably, the pressure F1 borne by the skeleton is 5000 - 60000 N.

[0076] Further preferably, the pressure F1 borne by the skeleton satisfies the following formula:

[0077]

[0078] Among them, F is the total pressure borne by the surface of the heat-absorbing unit in contact with the battery cell, and the unit is N;

[0079] E2 is the Young's modulus of the heat-absorbing material, and the unit is GPa;

[0080] a is the ratio of the area of the orthographic projection of the skeleton on the surface of the heat-absorbing unit in contact with the battery cell to the area of the surface of the heat-absorbing unit in contact with the battery cell.

[0081] Among them, the total pressure F borne by the surface of the heat-absorbing unit is calculated through the following steps:

[0082] The top view of the test device is as Figure 8 shown,

[0083] 1. Take a battery cell and charge it to a fully charged state using the standard charging process;

[0084] 2. Place the battery cell in the test fixture as Figure 8 shown. The large surface of the battery cell is insulated and constrained well with the heat-absorbing unit and the heat-insulating plate; among them, the heat-insulating plate can be a silica cover plate.

[0085] 3. Align the pressure sensor with the center of the large surface of the battery cell and the positive and negative sides of the large surface. After assembling the entire fixture, maintain the stability of the entire device (that is, there should be no shaking or parts falling off).

[0086] 4. Trigger thermal runaway of the battery cell and detect the stress feedback from the pressure sensor;

[0087] 5. The force conditions obtained by the three pressure sensors are summed up to obtain the total pressure on the surface of the heat absorption unit.

[0088] Furthermore, in the above test method, in addition to setting three pressure sensors at the above positions, multiple pressure sensors may also be set to determine the total pressure F on the surface of the heat absorption unit based on the sum of the pressures fed back by the multiple pressure sensors.

[0089] In addition, in the above test method, a surface pressure sensor can also be used, that is, a whole test film, which is attached to the large surface of the battery cell (the large surface of the battery cell corresponds to the surface of the insulation board) to output the total pressure F borne by the surface of the heat absorption unit.

[0090] In addition, in the above test method, the pressure sensor can be reset to zero after being set between the fixture baffle and the heat insulation board. Alternatively, the pressure sensor can be set between the fixture baffle and the heat insulation board to obtain the pressure value, and the total pressure on the surface of the heat absorption unit in contact with the battery cell during thermal runaway is determined based on the difference between the pressure value determined after the battery cell thermal runaway and the aforementioned pressure value.

[0091] In addition, for the above step 3, in order to further improve the test accuracy, the test device can simulate the stress condition of the battery cells in the battery pack, that is, the above test device can be tightened by the pressure rod bolt to control the battery stress to be consistent with that in the battery pack (controlled between 0 and 10 KN, preferably between 1 and 6 KN).

[0092] Among them, the thermal runaway of the battery cell can be triggered by the following two methods:

[0093] 1. Puncture the battery cell to trigger thermal runaway, where the puncture location is the middle of the battery cell. Figure 8 The acupuncture point position 6; in addition, the acupuncture position can be the positive electrode position and / or the negative electrode position corresponding to the battery cell.

[0094] 2. In Figure 8 On the basis of the device shown, a heating plate is arranged on the corresponding positive electrode, negative electrode or middle position on the large surface of the battery cell, and the impedance of the heating plate is generally around 45-50Ω; and the heating plate is heated to induce thermal runaway of the battery cell.

[0095] In the battery assembly according to the present invention, preferably, the thickness x1 of one layer of the skeleton is 0.025 - 2 mm. When the thickness of one layer of the skeleton is within the above preferred range, the skeleton can not only provide sufficient support for the heat-absorbing material, but also ensure that the heat-absorbing material in the heat-absorbing unit can provide sufficient heat-absorbing capacity.

[0096] In the battery assembly according to the present invention, the number of layers n of the skeleton increases as the thickness of the heat-absorbing material increases. However, if the number of layers is too large, the production difficulty will increase and it is difficult for the material to meet the design requirements. Preferably, the number of layers n of the skeleton is 1 - 10. Specifically, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. When the number of layers of the skeleton is within the above preferred range, the skeleton can not only provide sufficient support for the heat-absorbing material, but also ensure that the heat-absorbing unit can provide sufficient heat-absorbing capacity, thereby inhibiting battery thermal diffusion.

[0097] In an embodiment of the present application, the thickness x of the heat-absorbing unit is greater than or equal to the product of the thickness x1 of one layer of the skeleton and the number of layers n of the skeleton. When the thickness of the heat-absorbing unit and the total thickness of the skeleton meet the above range, while ensuring the supporting role of the skeleton, the volume of the heat-absorbing material can be further increased to ensure that there is no problem of thermal diffusion in the battery assembly and to ensure the safety of the battery assembly.

[0098] In an embodiment of the present application, the holes are uniformly arranged along the thickness direction of the skeleton. Specifically, by uniformly arranging the holes along the thickness direction of the skeleton, it is convenient for the processing and manufacturing of the skeleton, and the force on the skeleton can be further made uniform, improving the mechanical properties of the skeleton. The so-called uniform arrangement means that, along the thickness direction of the skeleton, the cross-sections of the holes are the same, or the orthographic projections of the holes on the plane perpendicular to the thickness direction of the skeleton completely coincide.

[0099] In addition, in an embodiment of the present application, as Figure 3 shown in Figure 4 figures, a plurality of the holes are uniformly arranged along the extending direction of the skeleton. Specifically, the above-mentioned uniform arrangement means that the distance between adjacent two holes is set to be the same, so as to ensure that on the surface of the heat-absorbing unit in contact with the battery cell, the heat-absorbing material is uniform at different positions, and further ensure the heat absorption uniformity of the heat-absorbing unit. Further, there are two mutually perpendicular directions for the extending direction of the skeleton. The holes are uniformly arranged along the extending direction of the skeleton to be equally spaced along at least one direction for a plurality of holes respectively. This direction is perpendicular to the thickness direction of the skeleton, and these two directions are also perpendicular to each other.

[0100] In an embodiment of the present application, the ratio of the area of the surface of the heat absorption unit in contact with the battery cell to the surface area of the battery cell in contact with the heat absorption unit is greater than or equal to 0.8 and less than or equal to 1. By setting the ratio of the contact area between the heat absorption unit and the surface of the adjacent battery cells, it is ensured that the heat absorption unit fully contacts the surface of the battery cell, so as to ensure the heat absorption effect of the heat absorption unit.

[0101] In an embodiment of the present application, the battery assembly includes at least two battery cell groups, each battery cell group includes N battery cells arranged in a row, and a heat absorption unit is provided between two adjacent battery cell groups. The thickness x of the heat absorption unit satisfies the following relationship: (0.5N ± b) mm ≤ x ≤ (5N ± b) mm; where b is a preset correction factor, and the unit is mm. Specifically, as the number of battery cells in the battery cell group increases, the thickness of the heat absorption unit is increased to ensure that the heat absorption unit can sufficiently absorb the heat that can be released during thermal runaway in the battery cell group, so as to ensure the safety of the battery assembly. Wherein, b is a preset correction factor, which can be determined according to the design requirements of the battery assembly. Usually, the values of b are selected as 0.1, 0.5, 1, etc. Generally, the value of b will increase as the battery capacity increases to ensure the heat absorption capacity of the heat absorption unit.

[0102] In an embodiment of the present application, since the heat absorption material absorbs heat through phase change, for a heat absorption material with a phase change temperature between 50°C and 200°C, when it is applied to the battery assembly, there will be problems such as overflow or breakage of the phase change material due to the large expansion force generated during battery thermal runaway, and then it cannot absorb the heat generated by the thermally out-of-control battery cell, resulting in heat diffusion in the battery assembly. Therefore, by making the battery assembly meet To ensure the heat absorption effect of the heat absorption unit.

[0103] In addition, when the phase change temperature of the phase change material is within this range, it can also effectively absorb the heat generated by the battery cells in the battery assembly during charging and discharging, so as to cool down the battery cells and ensure the normal use of the battery cells.

[0104] Furthermore, in order to ensure that the heat absorption material can prevent heat diffusion in the battery assembly, the phase change temperature of the heat absorption material is required to be between 70°C and 160°C. Specifically, when the phase change temperature of the heat absorption material is within this temperature range, on the one hand, it can ensure that the heat absorption material does not undergo phase change during normal battery operation, so as to ensure the amount of the heat absorption material during thermal runaway of the battery cell. On the other hand, it also ensures that the heat absorption material can fully undergo phase change after a thermally out-of-control battery cell appears in the battery assembly, so as to fully absorb the heat generated by the battery cell.

[0105] In an embodiment of the present application, the heat-absorbing material is a composite material containing a liquid phase change medium. The heat-absorbing effect is achieved by means of the phase change of the liquid phase change medium. Among them, the liquid phase change medium includes at least one of liquids such as water, ethanol, and ethylene glycol. In some embodiments of the present application, the heat-absorbing material may be a hydrogel, hydrated salt, or a composite thereof that retains water. The phase change temperature can be adjusted by controlling the water content in the heat-absorbing material. Among them, the composite may be a composite of a hydrogel or hydrated salt and other materials (such as a flame retardant). Taking the hydrogel as an example, a polymer material with a network structure can be used as the matrix of the hydrogel, and water is used as the liquid phase change medium. In some other embodiments of the present application, the heat-absorbing material 212 may be a material that retains liquids such as ethanol and ethylene glycol.

[0106] In the battery assembly of the present invention, the skeleton 11 includes a plurality of holes penetrating the skeleton in the thickness direction of the skeleton, and the heat-absorbing material 12 fills the holes. The shape of the holes on the skeleton 11 is not particularly limited and can be various conventional regular geometric shapes or irregular shapes. For example, it can be a square, hexagon, or circle, etc. In some embodiments, as Figure 2 and 3 shown, the shape of the holes on the skeleton 11 is a hexagon (preferably a regular hexagon). In some other embodiments, as Figure 4 and 5 shown, the shape of the holes on the skeleton 11 is a square.

[0107] In the battery assembly of the present invention, the skeleton 11 is a single-layer or multi-layer structure. When the skeleton 11 is a single-layer structure, as Figure 6 shown, while the heat-absorbing material 12 fills the holes of the skeleton, it completely covers the upper surface and the lower surface of the skeleton. When the skeleton 11 is a multi-layer structure, as Figure 7 shown, the heat-absorbing material 12 is filled between any two adjacent layers of the skeleton, and the upper surface of the uppermost layer of the skeleton and the lower surface of the lowermost layer of the skeleton are also covered with the heat-absorbing material.

[0108] In the battery assembly of the present invention, the material forming the skeleton 11 preferably has the property of being resistant to high temperatures above 400 °C. In some embodiments, the material forming the skeleton 11 is polyester, polypropylene (PP), or a metal (such as aluminum).

[0109] In the battery assembly of the present invention, the heat-absorbing material 12 can be a heat-absorbing material commonly used in the battery field. In some embodiments, the heat-absorbing material 12 is a hydrogel material.

[0110] In the battery assembly of the present invention, preferably, the total thickness of the skeleton accounts for 1-100% of the thickness of the heat absorbing unit, and more preferably 10-80%. When the percentage of the total thickness of the skeleton to the thickness of the heat absorbing unit is within the above range, it can ensure that the heat absorbing unit can provide sufficient heat absorption capacity, thereby suppressing battery heat diffusion.

[0111] In the battery assembly of the present invention, the heat absorption unit may further include a packaging film for packaging the skeleton and the heat absorption material.

[0112] In the battery assembly of the present invention, preferably, one heat absorption unit 1 (such as Figure 1 According to this preferred embodiment, the battery assembly has good safety while meeting the heat absorption requirement. Specifically, in the safety test of the battery assembly, obvious heat diffusion phenomenon will occur after a battery cell is punctured and thermal runaway occurs.

[0113] In the embodiment of the present invention, when the energy Q of the battery cell is generally between 576 kJ and 3456 kJ, the volume V of the heat absorbing material should be 20000 mm 3 -300000mm 3 In order to ensure that there is enough heat-absorbing material to absorb the heat released by the battery cell and to ensure that the volume energy density reduction rate of the battery assembly is within a certain range, so as to improve the integration level and energy density of the battery assembly. Among them, the volume of the heat-absorbing material V = (xa*n*x1)·S.

[0114] The present invention also provides an electric power system, including the battery assembly described above. The electric power system may be, for example, a vehicle or an energy storage system. Since the electric power system is equipped with the battery assembly described in the present invention, the battery assembly in the electric power system meets the heat absorption requirements and has good safety.

[0115] The heat absorption unit and the power system of the present invention are further described below by way of examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0116] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0117] Examples 1-31 and Comparative Examples 1-7

[0118] Configuration Figure 1The battery assembly shown includes a plurality of battery cells 2 and heat absorption units 1. One heat absorption unit 1 is arranged every two battery cells 2. Among them, the heat absorption unit 1 includes a skeleton 11 and a heat absorption material 12. The heat absorption material is a hydrogel. The skeleton is a single-layer or multi-layer structure. Each layer of the skeleton includes a plurality of holes penetrating the skeleton along the thickness direction of the skeleton. The hydrogel fills the holes, and the skeleton and the heat absorption material are encapsulated in an encapsulation film (aluminum-plastic film). In each battery pack example, the thickness x of the heat absorption unit, the cell gap d, the area ratio a of the skeleton on the surface of the heat absorption unit, the Young's modulus E1 of the skeleton, the heat absorption area S on the surface of the heat absorption unit, the pressure F1 borne by the skeleton, the thickness x1 of one layer of the skeleton, and the number of layers n of the skeleton are shown in Table 1 below.

[0119] Table 1

[0120]

[0121]

[0122] Test Example 1: Compression Test

[0123] The battery cells and heat absorption units configured in Examples 1-31 and Comparative Examples 1-7 were subjected to a compression test. Specifically: 1. Place the battery assembly formed above into a compression device, where the compression device is a tensile testing machine;

[0124] 2. Use the compression device to apply a compression force to one of the battery cells. The force changes from 0 to the value of F1 recorded in Table 1. The tensile testing machine will generate the compression amount x corresponding to the pressure F1 in real time and give the compression deformation amount of the skeleton.

[0125] 3. Obtain the compression deformation rate of the skeleton and record it in Table 2.

[0126] 4. Observe the state of the heat absorption unit and record it in the compression test results in Table 2.

[0127] Test Example 2: Heat Diffusion Test

[0128] The battery packs configured in Examples 1-31 and Comparative Examples 1-7 were subjected to a needle puncture test to test whether heat diffusion occurs after a needle puncture triggers a thermal runaway in one battery cell (judged by whether the adjacent battery cells have thermal runaway), and at the same time monitor the highest temperature of the battery cell where the needle puncture triggers the thermal runaway.

[0129] The test conditions are as follows:

[0130] (1) The state of charge (SOC) of the battery is 100%, that is, fully charged;

[0131] (2) The sample temperature is 45°C ± 2°C;

[0132] (3) Use a 5-mm flat steel needle and insert it into the battery cell at a speed of 1 mm / s until it stops when the battery cell undergoes thermal runaway. When the voltage of the battery cell drops to 75%, it is determined that thermal runaway has occurred.

[0133] (4) Continuously observe until the temperature of the battery cell is less than 100 °C after the experiment.

[0134] (5) Determine whether the battery cells adjacent to the battery cell have undergone thermal runaway. When the voltage of the adjacent battery cell drops to 75%, it is determined that thermal runaway has occurred, i.e., thermal diffusion has occurred.

[0135] The test results are shown in Table 2 below.

[0136] In addition, Test Example 2 can also be tested according to Figure 8 the device shown. When applied to this test device, the battery cells inside can be added in the form of a battery module. Conduct a thermal runaway test on the battery module.

[0137] Test Example 3

[0138] Volume energy density test:

[0139] Perform charge and discharge tests on the obtained battery pack to obtain the battery capacity of the battery pack. Measure and calculate the volumes of the battery cell and the heat absorption unit. The volume energy density and volume energy density decrease rate of a single battery cell are obtained through the following formulas:

[0140] Volume energy density of a single battery cell = Capacity of a single battery cell / Volume of a single battery cell;

[0141] Volume energy density of a single new battery cell = Capacity of a single battery cell / (Volume of a single battery cell + Volume of the heat absorption unit);

[0142] Volume energy density decrease rate = Volume energy density of a single battery cell - Volume energy density of a single new battery cell.

[0143] Among them, the measurement methods for the volume of the battery cell and the heat absorption unit: For a single battery cell or heat absorption unit, the volume of the battery cell can be obtained by measuring the length, width, and height of the battery cell, and the volume of the heat absorption unit can be obtained by measuring the length, width, and height of the heat absorption unit.

[0144] Battery capacity test method:

[0145] 1) At room temperature, charge at a small current (e.g., 1 / 3C) until the cut-off voltage, and let it stand for 1 h;

[0146] 2) Discharge at a constant current of 1 / 3C until the cut-off voltage, and let it stand for 1 h;

[0147] 3) Repeat steps 1 - 2 a total of 2 times, and record the second discharge capacity as the battery capacity.

[0148] In this test example, a lithium iron phosphate battery is used, and the cut-off voltage is 3.75V.

[0149] The results are shown in Table 2 below.

[0150] Table 2

[0151]

[0152]

[0153] From the results in Table 2, it can be seen that according to Examples 1 - 31, the heat absorption unit configured within the parameter range according to the present invention has good mechanical properties. Specifically, in the compression test of the battery module, the heat absorption unit is intact. In Comparative Examples 1 - 7, when the value of the heat absorption unit in the battery module is less than 10 or greater than 1000, in the compression test of the battery module, the heat absorption unit has problems such as package breakage (the aluminum-plastic film of the heat absorption unit is damaged, and the material overflows or leaks from the damaged part) or material overflow (the material is extruded out of the gap between the battery cores due to the expansion of the battery core), and thus the heat absorption unit cannot achieve its heat absorption effect. Based on Examples 3, 4, and 13, when the battery energy is within 537 KJ - 3456 KJ, when the volume of the heat absorption unit is less than 20000 mm 3 , thermal diffusion occurs in the battery. The specific reason is that the amount of the heat absorption material in the heat absorption unit is less and cannot meet the heat release of the battery, resulting in thermal runaway of adjacent battery cores. And based on Examples 21 and 27, when the battery energy is within 537 KJ - 3456 KJ, when the volume of the heat absorption unit is greater than 300000 mm 3 , thermal diffusion does not occur in adjacent battery cores, but the volume energy density decline rate of the battery module is greater than 30%, and the volume energy density of the battery module is too low. Therefore, when the battery energy is within 537 KJ - 3456 KJ, when the volume of the heat absorption unit is greater than 20000 mm 3 and less than 300000 mm 3 , it can ensure that the heat absorption unit has enough volume to absorb the heat generated by the thermally out-of-control battery core, and also ensure that the volume energy density decline rate of the battery module remains at a certain level (i.e., below 30%) to maintain the volume energy density of the battery module. Moreover, when the thickness of the heat absorption unit in the battery module is adjusted within the preferred range (such as 0.1 - 10 mm), it can not only ensure good safety of the battery module, but also the volume energy density decline rate is significantly lower.

[0154] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A battery assembly, characterized in that: The battery assembly includes a plurality of battery cells, a heat absorption unit is arranged between two adjacent battery cells, the heat absorption unit includes a heat absorption material and at least one layer of skeleton, the skeleton has a plurality of holes penetrating along the thickness direction of the skeleton, the heat absorption material fills the holes, and the battery assembly meets the following conditions: Wherein, x is the thickness of the heat absorption unit, in mm; d is the gap between two adjacent cells, in mm; a is the ratio of the area of ​​the orthographic projection of the skeleton on the surface where the heat absorption unit contacts the battery core to the surface area where the heat absorption unit contacts the battery core; E1 is the Young's modulus of the skeleton, in GPa; S is the surface area of ​​the heat absorption unit in contact with the battery core, in mm 2 ; F1 is the pressure on the frame, in N; x1 is the thickness of a layer of skeleton, in mm; n is the number of layers of the skeleton, n≥1 and n is an integer.

2. The battery assembly according to claim 1, characterized in that: The energy Q of the battery cell is between 576kJ and 3456kJ.

3. The battery assembly according to claim 2, characterized in that: The volume V of the heat absorbing material is 20000mm 3 -300000mm 3 between, Wherein, the volume V of the heat absorbing material satisfies: V=(xa*n*x1)·S.

4. The battery assembly according to claim 1, characterized in that: The thickness x of the heat absorption unit is 0.5-5 mm.

5. The battery assembly according to claim 1, characterized in that: The gap d between two adjacent battery cells is 0.3-3 mm.

6. The battery assembly according to claim 1, characterized in that: The ratio a of the area of ​​the orthographic projection of the skeleton on the surface of the heat absorption unit in contact with the battery core to the surface area of ​​the heat absorption unit in contact with the battery core is 10-50%.

7. The battery assembly according to claim 1, characterized in that: The Young's modulus E1 of the skeleton is 0.0001-100 GPa.

8. The battery assembly according to claim 1, characterized in that: The surface area S of the heat absorption unit in contact with the battery core is 5000-300000mm 2 .

9. The battery assembly according to claim 1, characterized in that: The pressure F1 borne by the frame is 5000-60000N.

10. The battery assembly according to claim 1 or 8, characterized in that: The pressure F1 borne by the skeleton satisfies the following formula: Wherein, F is the total pressure on the surface of the heat absorption unit in contact with the battery core, in N; E2 is the Young’s modulus of the endothermic material, in GPa; a is the ratio of the area of ​​the orthographic projection of the skeleton on the surface where the heat absorption unit contacts the battery core to the surface area where the heat absorption unit contacts the battery core.

11. The battery assembly according to claim 1, characterized in that: The thickness x1 of a layer of skeleton is 0.025-2mm.

12. The battery assembly according to claim 1, characterized in that: The number of layers n of the skeleton is 1-10.

13. The battery assembly according to claim 1, characterized in that: The thickness x of the heat absorption unit is greater than or equal to the product of the thickness x1 of the first skeleton layer and the number n of the skeleton layers.

14. The battery assembly according to claim 1, characterized in that: The total thickness of the skeleton accounts for 1-100% of the thickness of the heat absorption unit, preferably 10-80%.

15. The battery assembly according to claim 1, characterized in that: The heat absorption unit further includes a packaging film for packaging the skeleton and the heat absorption material.

16. The battery assembly according to claim 1, characterized in that: The holes are evenly arranged along the thickness direction of the frame.

17. The battery assembly according to claim 1, characterized in that: The ratio of the area of ​​the surface of the heat absorption unit in contact with the battery core to the surface area of ​​the battery core in contact with the heat absorption unit is greater than or equal to 0.8 and less than or equal to 1.

18. The battery assembly according to claim 1, characterized in that: The battery assembly includes at least two battery cell groups, each battery cell group includes N arranged battery cells, and a heat absorption unit is arranged between two adjacent battery cell groups, wherein a thickness x of the heat absorption unit satisfies the following relationship: (0.5N±b)mm≤x≤(5N±b)mm; wherein b is a preset correction factor, and the unit is mm.

19. The battery assembly according to claim 1, characterized in that: The phase transition temperature of the heat absorbing material is between 50°C and 200°C.

20. The battery assembly according to claim 19, characterized in that The phase transition temperature of the endothermic material is between 70°C and 160°C.

21. The battery assembly according to any one of claims 1 to 20, characterized in that: The heat absorbing material is a hydrogel.

22. According to any one of claims 1-20, the plurality of holes are evenly arranged along the extension direction of the skeleton.

23. An electricity system, characterized in that: A battery assembly comprising any one of claims 1-22.

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