Battery assembly and electrical system

Abstract

An electrical system, provided with a battery assembly. The battery assembly comprises a plurality of battery cells (2); a heat absorption unit (1) is arranged between every two adjacent battery cells (2); and each heat absorption unit (1) comprises a heat absorption material (12) and at least one framework (11), the framework (11) being provided with a plurality of holes (13) penetrating in the thickness direction of the framework (11), and the heat absorption material (12) filling the holes (13). The battery assembly meets formula (I).

Description

Battery components and power systems

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202410128727.1, filed on January 29, 2024, entitled “Battery Assembly and Power System,” the entire contents of which are incorporated herein for all purposes; and

[0003] This application also claims priority to Chinese patent application No. 202311871144.X, filed on December 29, 2023, entitled “Battery Assembly and Power Consumption System,” the entire contents of which are incorporated herein for all purposes. Technical Field

[0004] The present application relates to the field of battery technology, and in particular to a battery assembly and a power system. Background Art

[0005] Thermal and mechanical abuse of batteries can pose safety risks and even cause thermal runaway. In related technologies, when a battery cell in a battery pack experiences thermal runaway, a large amount of heat is generated internally, causing the cell temperature to rise rapidly and spread to adjacent cells. Without effective isolation measures, the temperature of adjacent cells will also rise rapidly, causing heat diffusion. Summary of the Invention

[0006] The purpose of the present invention is to provide a battery assembly and power consumption system. The present invention proposes a parametric design method for the skeleton based on Young's modulus. By giving the battery cell gap and pressure, the selection range of parameters related to the skeleton thickness is determined, so that the battery assembly meets the functional requirements while having better safety.

[0007] To achieve the above objectives, the present invention provides a battery assembly, comprising a plurality of battery cells, wherein a heat absorption unit is disposed between two adjacent battery cells, wherein the heat absorption unit comprises a heat absorbing material and at least one layer of a skeleton, wherein the skeleton has a plurality of holes extending through the skeleton along its thickness, wherein the heat absorbing material fills the holes, and wherein the battery assembly satisfies the following conditions:

[0008] Wherein, x is the thickness of the heat absorbing unit, in mm;

[0009] d is the gap between two adjacent cells, in mm;

[0010] a is the ratio 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;

[0011] E1 is the Young's modulus of the skeleton, in GPa;

[0012] S is the surface area of ​​the heat absorption unit in contact with the battery core, in mm 2 ;

[0013] F1 is the pressure on the skeleton, in N;

[0014] x1 is the thickness of one layer of skeleton, in mm;

[0015] n is the number of layers of the skeleton, n≥1 and n is an integer.

[0016] Preferably, the energy Q of the battery cell is between 576kJ and 3456kJ.

[0017] Preferably, 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.

[0018] Preferably, the thickness x of the heat absorption unit is 0.5-5 mm.

[0019] Preferably, the gap d between two adjacent battery cells is 0.3-3 mm.

[0020] Preferably, a ratio a of an area of ​​an orthographic projection of the skeleton on a surface where the heat absorption unit contacts the battery core to an area of ​​a surface where the heat absorption unit contacts the battery core is 10-50%.

[0021] Preferably, the Young's modulus E1 of the skeleton is 0.0001-100 GPa.

[0022] Preferably, the surface area S of the heat absorption unit in contact with the battery core is 5000-300000 mm 2 .

[0023] Preferably, the pressure F1 borne by the skeleton is 5000-60000N.

[0024] Preferably, the pressure F1 borne by the skeleton satisfies the following formula:

[0025] Wherein, F is the total pressure on the surface of the heat absorption unit in contact with the battery core, in N;

[0026] E2 is the Young's modulus of the heat-absorbing material, in GPa;

[0027] a is the ratio 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.

[0028] Preferably, the thickness x1 of one layer of skeleton is 0.025-2 mm.

[0029] Preferably, the number of layers n of the skeleton is 1-10.

[0030] Preferably, the thickness x of the heat absorption unit is greater than or equal to the product of the thickness x1 of the skeleton layer and the number n of the skeleton layers.

[0031] Preferably, the total thickness of the skeleton accounts for 1-100% of the thickness of the heat absorption unit, preferably 10-80%.

[0032] Preferably, the heat absorption unit further comprises a packaging film for packaging the skeleton and the heat absorption material.

[0033] Preferably, the holes are evenly arranged along the thickness direction of the skeleton.

[0034] Preferably, the ratio of the area of ​​the surface of the heat absorption unit in contact with the battery core to the area of ​​the surface 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.

[0035] Preferably, the battery assembly includes at least two battery cell groups, the battery cell group includes N arranged battery cells, and the 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; wherein b is a preset correction factor, the unit is mm.

[0036] Preferably, the phase transition temperature of the heat absorbing material is between 50°C and 200°C.

[0037] Preferably, the phase transition temperature of the endothermic material is between 70°C and 160°C.

[0038] Preferably, the heat absorbing material is a hydrogel.

[0039] Preferably, the plurality of holes are evenly arranged along the extension direction of the skeleton.

[0040] A second aspect of the present invention provides an electricity system comprising the battery assembly described above.

[0041] According to the technical solution of the present invention, by making the battery assembly meet A value greater than or equal to 10 and less than or equal to 1000 can ensure that the deformation of the heat absorption unit is within a certain range, thereby ensuring that the heat absorption unit will not be damaged or material overflow due to the squeezing of the battery during thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a schematic structural diagram of a battery assembly;

[0043] FIG2 is a schematic diagram of a heat absorbing unit comprising a hexagonal framework;

[0044] FIG3 is a schematic diagram of the surface of a hexagonal skeleton;

[0045] FIG4 is a schematic diagram of the surface of a square skeleton;

[0046] Figure 5 is a schematic diagram of a double-layer square skeleton;

[0047] FIG6 is a schematic diagram of a heat absorbing unit comprising a single-layer skeleton;

[0048] FIG7 is a schematic diagram of a heat absorption unit comprising a multi-layer skeleton;

[0049] Figure 8 shows the thermal runaway pressure test device.

[0050] Description of Reference Numerals

[0051] 1. Heat absorption unit; 2. Battery cell; 11. Frame; 12. Heat absorption material; 13. Holes; 14. Packaging film; 3. Pressure sensor; 4. Heat shield; 5. Fixture baffle; 6. Puncture point. DETAILED DESCRIPTION

[0052] The following describes 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 used to illustrate and explain the present invention and are not intended to limit the present invention.

[0053] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate relative importance or implicitly specify the quantity of the technical features indicated. Therefore, unless otherwise specified, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features; "plurality" means two or more. The term "comprising" and any variations thereof are intended to be non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0054] In addition, terms such as "upper", "lower", "inside", and "outside" indicating orientation or positional relationships are described based on the orientation or relative positional relationships shown in the accompanying drawings. They are only simplified descriptions for the convenience of describing this application, and do not indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0055] Furthermore, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, and may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0056] As shown in Figures 1-7, the battery assembly described in the present invention includes a plurality of battery cells 2, and a heat absorption unit 1 is configured on at least one surface of the battery cell 2. The heat absorption unit 1 includes a skeleton 11 and a heat absorption material 12. The skeleton 11 includes a plurality of holes 13 that penetrate the skeleton 11 along the thickness direction of the skeleton 11. The heat absorption material 12 fills the holes 13, and the skeleton 11 is a single-layer or multi-layer structure.

[0057] In the present invention, the battery assembly meets the following conditions:

[0058] Wherein, x is the thickness of the heat absorption unit 1, in mm;

[0059] d is the given gap between cells 2, in mm;

[0060] a is the ratio of the area of ​​the orthographic projection of the skeleton 11 on the surface where the heat absorption unit 1 contacts the battery core 2 to the surface area where the heat absorption unit 1 contacts the battery core 2;

[0061] E1 is the Young's modulus of the skeleton 11, in GPa;

[0062] S is the surface area of ​​the heat absorption unit 1 in contact with the battery core 2, in mm 2 ;

[0063] F1 is the pressure on the frame 11, in N;

[0064] x1 is the thickness of one layer of skeleton 11, in mm;

[0065] n is the number of layers of the skeleton 11, n≥1 and n is an integer.

[0066] When the heat absorption unit 1 meets the above parameter conditions, the battery assembly has good safety. Specifically, in the safety test of the battery assembly, no heat diffusion phenomenon will occur after the thermal runaway of a battery cell 2 is triggered by needle puncture. When the value is less than 10, the skeleton 11 is prone to large deformation due to the small Young's modulus. Once the battery cell 2 loses control, the expansion force will increase sharply, the heat absorbing material 12 will break the package and leak, and the absorbed heat will decrease, thus failing to suppress heat diffusion. When the battery assembly When the value is greater than 1000, the Young's modulus of the skeleton 11 is extremely large and almost no deformation occurs. Since a certain gap needs to be compressed during the design, the compressed gap is provided by the heat-absorbing material 12. When the battery cell 2 is cyclically charged and discharged, the heat-absorbing unit 1 is repeatedly squeezed, and the heat-absorbing material 12 is continuously squeezed, and then overflows the gap between the battery cells 2, reducing the heat of the heat-absorbing unit 1, and thus failing to suppress heat diffusion.

[0067] In a more preferred embodiment, the heat absorption unit 1 satisfies the following conditions.

[0068] In the above preferred embodiment, the battery assembly has further improved safety.

[0069] In the battery assembly of the present invention, the thickness x of the heat absorbing unit 1 is preferably 0.5-5 mm, more preferably 0.5-2 mm. When the thickness of the heat absorbing unit 1 is within this preferred range, the battery assembly can be ensured to have good safety and an appropriate energy density. In the present invention, the thickness of the heat absorbing unit 1 can be measured using a vernier caliper, laser rangefinder, or the like. Furthermore, in the present invention, the thickness of the heat absorbing unit 1 is measured after the heat absorbing unit 1 is removed from the battery assembly.

[0070] In the battery assembly described in the present invention, the spacing between the battery cells 2 is determined based on the assembly gap and the overall space utilization of the battery pack. In a preferred embodiment, the spacing d between the battery cells 2 is 0.3-3 mm. The spacing between the battery cells 2 is directly measured between the opposing surfaces of two adjacent battery cells 2, between which a heat absorption unit 1 is provided. Generally, the spacing between the battery cells 2 is measured when the SOC of the battery cells 2 is 25% in a static state.

[0071] In the battery assembly of the present invention, preferably, the ratio (a) of the area of ​​the orthographic projection of the skeleton 11 on the surface of the heat absorbing unit 1 in contact with the battery cell 2 to the area of ​​the surface of the heat absorbing unit 1 in contact with the battery cell 2 is 10-50%. When the area ratio of the skeleton 11 on the surface of the heat absorbing unit 1 is within this preferred range, the heat absorbing unit 1 not only provides sufficient support to prevent the heat absorbing material 12 from being squeezed out, but also ensures that the heat absorbing material 12 absorbs heat, thereby ensuring the safety of the battery assembly. When determining a, only the area of ​​the orthographic projection of the skeleton 11's physical structure on the surface of the heat absorbing unit 1 in contact with the battery cell 2 is considered. That is, the area of ​​the holes 13 is not included in the orthographic projection of the surface of the heat absorbing unit 1 in contact with the battery cell 2. Furthermore, when the projection of the heat absorbing unit 1 on the surface of the battery cell 2 in contact with the heat absorbing unit 1 is within the surface of the battery cell 2, the area of ​​the orthographic projection of the heat absorbing unit 1 on the surface in contact with the battery cell 2 is equal to the surface area of ​​the skeleton 11 facing the heat absorbing unit 1, and the surface area of ​​the heat absorbing unit 1 in contact with the battery cell 2 is the surface area of ​​the heat absorbing unit 1 facing the battery cell 2.

[0072] In the battery assembly of the present invention, the Young's modulus E1 of the skeleton 11 is preferably between 0.0001 and 100 GPa. When the Young's modulus of the skeleton 11 is within this preferred range, the skeleton 11 can provide sufficient support for the endothermic material 12, preventing it from being squeezed out, thereby ensuring good safety of the battery assembly. The Young's modulus E1 of the skeleton 11 can be determined based on the material of the skeleton 11.

[0073] In the battery assembly of the present invention, preferably, the surface area S of the heat absorption unit 1 in contact with the battery core 2 is 5000-300000 mm 2 When the heat absorption area of ​​the heat absorption unit 1 is within the above-mentioned preferred range, it can ensure that the heat absorption unit 1 can provide sufficient heat absorption capacity, thereby suppressing battery heat diffusion. Generally, the heat absorption area of ​​the heat absorption unit 1 is the area of ​​the surface of the heat absorption unit 1 that is in contact with the battery cell 2, or it can be the area of ​​the surface of one of the battery cells 2 that is in contact with the heat absorption unit 1.

[0074] In the battery assembly of the present invention, the pressure F1 borne by the frame 11 is generally determined based on actual conditions. If it is too small, the heat absorbing unit 1 and the battery cell 2 cannot be restrained and fixed, while if it is too large, the battery cell 2 may be damaged. Preferably, the pressure F1 borne by the frame 11 is 5000-60000N.

[0075] Further preferably, the pressure F1 borne by the skeleton 11 satisfies the following formula:

[0076] Wherein, F is the total pressure on the surface of the heat absorption unit 1 in contact with the battery core 2, in N;

[0077] E2 is the Young's modulus of the heat absorbing material 12, in GPa;

[0078] a is the ratio of the area of ​​the orthographic projection of the skeleton 11 on the surface where the heat absorption unit 1 contacts the battery core 2 to the surface area where the heat absorption unit 1 contacts the battery core 2 .

[0079] The total pressure F on the surface of the heat absorbing unit 1 is calculated by the following steps:

[0080] The top view of the test device is shown in Figure 8.

[0081] 1. Take a battery cell 2 and charge it to full power using the standard charging process.

[0082] 2. Place the battery cell 2 in the test fixture shown in FIG8 . The large surface of the battery cell 2 is insulated and restrained by the heat absorbing unit 1 and the heat insulation board 4 . The heat insulation board 4 can be a silicate cover board.

[0083] 3. Align the pressure sensor 3 with the center of the large surface of the battery cell 2 and the positive and negative sides of the large surface. After assembling the entire fixture, maintain the stability of the entire device (i.e., there will be no shaking or parts falling).

[0084] 4. Trigger thermal runaway of the battery cell 2 and detect the force feedback from the pressure sensor 3;

[0085] 5. The force conditions obtained by the three pressure sensors 3 are summed up to obtain the total pressure on the surface of the heat absorption unit 1.

[0086] In addition, in the above test method, in addition to setting three pressure sensors 3 at the above positions, multiple pressure sensors 3 can also be set to determine the total pressure F on the surface of the heat absorption unit 1 based on the sum of the pressures fed back by the multiple pressure sensors 3.

[0087] In addition, in the above test method, a surface pressure sensor 3, that is, a whole test film, can also be used. The film is attached to the large surface of the battery cell 2 (the large surface of the battery cell 2 corresponds to the surface of the insulation board 4) to output the total pressure F borne by the surface of the heat absorption unit 1.

[0088] Furthermore, in the aforementioned testing method, the pressure sensor 3 can be reset to zero after being placed between the fixture baffle 5 and the thermal insulation board 4. Alternatively, the pressure sensor 3 can be placed between the fixture baffle 5 and the thermal insulation board 4 to obtain a pressure value. The difference between the pressure value determined after the thermal runaway of the battery cell 2 and the aforementioned pressure value can be used to determine the total pressure on the contact surface of the heat absorbing unit 1 and the battery cell 2 during the thermal runaway of the battery cell 2.

[0089] In addition, for the above step 3, in order to further improve the test accuracy, the test device can simulate the stress conditions of the battery cell 2 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).

[0090] The thermal runaway of the battery cell 2 can be triggered by the following two methods:

[0091] 1. Puncture the battery cell 2 to trigger thermal runaway, wherein the puncture position is the middle of the battery cell 2, such as the puncture point 6 shown in FIG8; in addition, the puncture position may be the corresponding positive electrode and / or negative electrode of the battery cell 2.

[0092] 2. Based on the device shown in FIG8 , a heating plate is provided on the corresponding positive electrode, negative electrode or middle position of the large surface of the battery cell 2. 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 2.

[0093] In the battery assembly of the present invention, preferably, the thickness x1 of the skeleton layer 11 is 0.025-2 mm. When the thickness of the skeleton layer 11 is within the above preferred range, the skeleton 11 not only provides sufficient support for the heat-absorbing material 12, but also ensures that the heat-absorbing material 12 in the heat-absorbing unit 1 can provide sufficient heat absorption capacity.

[0094] In the battery assembly of the present invention, the number of layers n of the skeleton 11 increases with the thickness of the heat-absorbing material 12. However, too many layers can increase production difficulties and make it difficult for the material to meet design requirements. Preferably, the number of layers n of the skeleton 11 is 1-10, specifically, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. When the number of layers of the skeleton 11 is within this preferred range, the skeleton 11 not only provides sufficient support for the heat-absorbing material 12, but also ensures that the heat-absorbing unit 1 can provide sufficient heat absorption capacity, thereby suppressing thermal diffusion in the battery.

[0095] In one embodiment of the present application, the thickness x of the heat absorbing unit 1 is greater than or equal to the product of the thickness x1 of the first layer of the skeleton 11 and the number n of the skeleton 11 layers. When the thickness of the heat absorbing unit 1 and the total thickness of the skeleton 11 fall within the above range, the volume of the heat absorbing material 12 can be further increased while ensuring the support function of the skeleton 11, thereby preventing heat diffusion issues in the battery assembly and ensuring the safety of the battery assembly.

[0096] In one embodiment of the present application, the holes 13 are uniformly arranged along the thickness of the skeleton 11. Specifically, by uniformly arranging the holes 13 along the thickness of the skeleton 11, the processing and manufacturing of the skeleton 11 are facilitated, and the force applied to the skeleton 11 is further uniformed, thereby improving the mechanical properties of the skeleton 11. The uniform arrangement means that the cross-sections of the holes 13 are the same along the thickness of the skeleton 11, or that the orthographic projections of the holes 13 on a plane perpendicular to the thickness of the skeleton 11 completely overlap.

[0097] In addition, in one embodiment of the present application, as shown in Figures 3 and 4, the plurality of holes 13 are uniformly arranged along the extension direction of the skeleton 11. Specifically, the uniform arrangement refers to the spacing between two adjacent holes 13 being the same, to ensure that the heat absorbing material 12 is uniform at different locations on the surface of the heat absorbing unit 1 in contact with the battery cell 2, thereby ensuring the uniformity of heat absorption of the heat absorbing unit 1. Furthermore, the extension direction of the skeleton 11 has two mutually perpendicular directions, and the holes 13 are uniformly arranged along the extension direction of the skeleton 11, with multiple holes 13 being equally spaced along at least one direction. These directions are all perpendicular to the thickness direction of the skeleton 11, and these directions are also perpendicular to each other.

[0098] In one embodiment of the present application, the ratio of the area of ​​the surface of the heat absorbing unit 1 in contact with the battery cell 2 to the surface area of ​​the battery cell 2 in contact with the heat absorbing unit 1 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 absorbing unit 1 and the surface of the adjacent battery cell 2, it is ensured that the heat absorbing unit 1 fully contacts the surface of the battery cell 2, thereby ensuring the heat absorption effect of the heat absorbing unit 1.

[0099] In one embodiment of the present application, the battery assembly includes at least two groups of battery cells 2, each group including N arranged battery cells 2. A heat absorption unit 1 is provided between two adjacent groups of battery cells 2, wherein the thickness x of the heat absorption unit 1 satisfies the following relationship: (0.5N±b)mm≤x≤(5N±b)mm; wherein b is a preset correction factor, expressed in mm. Specifically, as the number of battery cells 2 in the group 2 increases, the thickness of the heat absorption unit 1 is increased to ensure that the heat absorption unit 1 can adequately absorb the heat released by the group 2 during thermal runaway, thereby ensuring the safety of the battery assembly. wherein b is a preset correction factor, which can be determined based on the design requirements of the battery assembly. Typically, the value of b is selected from 0.1, 0.5, 1, etc. Generally, the value of b increases with the increase of battery capacity to ensure the heat absorption capacity of the heat absorption unit 1.

[0100] In one embodiment of the present application, since the heat absorbing material 12 absorbs heat through phase change, when the heat absorbing material 12 with a phase change temperature between 50°C and 200°C is used in a battery assembly, there will be problems such as the expansion force generated during thermal runaway of the battery being large, which may cause the phase change material to overflow or be damaged, and thus the heat generated by the thermal runaway battery cell 2 cannot be absorbed, 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 1.

[0101] 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 2 in the battery assembly during charging and discharging, so as to cool the battery cells 2 and ensure the normal use of the battery cells 2.

[0102] Furthermore, to ensure that the endothermic material 12 can prevent heat diffusion within the battery assembly, the phase transition temperature of the endothermic material 12 is required to be between 70°C and 160°C. Specifically, within this temperature range, the endothermic material 12 is prevented from undergoing a phase transition during normal battery operation, thereby ensuring the amount of endothermic material 12 present in the event of thermal runaway in the battery cell 2. Furthermore, it ensures that the endothermic material 12 undergoes a phase transition after a thermal runaway cell 2 is detected in the battery assembly, thereby fully absorbing the heat generated by the cell 2.

[0103] In one embodiment of the present application, the heat-absorbing material 12 is a composite material that retains a liquid phase change medium. The heat absorption 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, ethylene glycol, etc. In some embodiments of the present application, the heat-absorbing material 12 can be a hydrogel, a hydrated salt, or a composite thereof that retains water. The phase change temperature of the heat-absorbing material 12 can be adjusted by regulating the water content in the heat-absorbing material 12. Among them, the composite can be a composite of a hydrogel or a hydrated salt with other materials (such as a flame retardant), etc. Taking hydrogel as an example, a polymer material with a network structure can be used as the matrix of the hydrogel, and water can be used as the liquid phase change medium. In some other embodiments of the present application, the heat-absorbing material 12212 can be a material that retains liquids such as ethanol and ethylene glycol.

[0104] In the battery assembly described in the present invention, the skeleton 11 includes a plurality of holes 13 that penetrate the skeleton 11 along the thickness direction of the skeleton 11, and the heat-absorbing material 12 fills the holes 13. The shape of the holes 13 on the skeleton 11 is not particularly limited, and can be various conventional regular geometric shapes or irregular shapes, for example, square, hexagonal or circular lights. In some embodiments, as shown in Figures 2 and 3, the shape of the holes 13 on the skeleton 11 is a hexagon (preferably a regular hexagon). In other embodiments, as shown in Figures 4 and 5, the shape of the holes 13 on the skeleton 11 is a square.

[0105] In the battery assembly of the present invention, the skeleton 11 has a single-layer or multi-layer structure. When the skeleton 11 has a single-layer structure, as shown in FIG6 , the heat-absorbing material 12 fills the holes 13 of the skeleton 11 while completely covering the upper and lower surfaces of the skeleton 11. When the skeleton 11 has a multi-layer structure, as shown in FIG7 , the space between any two adjacent skeleton layers 11 is filled with heat-absorbing material 12, and the upper surface of the uppermost skeleton layer 11 and the lower surface of the lowermost skeleton layer 11 are also covered with heat-absorbing material 12.

[0106] In the battery assembly of the present invention, the material forming the skeleton 11 preferably has the ability to withstand high temperatures above 400° C. In some embodiments, the material forming the skeleton 11 is polyester, polypropylene (PP), or metal (such as aluminum).

[0107] In the battery assembly of the present invention, the heat absorbing material 12 can be a heat absorbing material 12 conventionally used in the battery field. In some embodiments, the heat absorbing material 12 is a hydrogel material.

[0108] In the battery assembly of the present invention, the total thickness of the skeleton 11 preferably accounts for 1-100%, and more preferably 10-80%, of the thickness of the heat absorbing unit 1. When the total thickness of the skeleton 11 accounts for a percentage of the thickness of the heat absorbing unit 1 within this range, the heat absorbing unit 1 can provide sufficient heat absorption capacity, thereby suppressing heat diffusion from the battery.

[0109] In the battery assembly of the present invention, the heat absorption unit 1 may further include a packaging film 14 for packaging the skeleton 11 and the heat absorption material 12 .

[0110] In the battery assembly of the present invention, preferably, one heat absorption unit 1 is arranged every two battery cells 2 (as shown in FIG1 ). According to this preferred embodiment, the battery assembly not only meets the heat absorption requirements but also has good safety. Specifically, during the safety testing of the battery assembly, after a needle prick triggers thermal runaway in a battery cell 2, significant heat diffusion will be observed.

[0111] In the embodiment of the present invention, when the energy Q of the battery cell 2 is generally between 576kJ and 3456kJ, the volume V of the heat absorbing material 12 should be 20000mm 3 -300000mm 3 The heat absorbing material 12 is placed between the battery cells 2 to ensure sufficient heat absorption material 12 to absorb the heat released by the battery cells 2 and to ensure that the volume energy density reduction rate of the battery assembly is within a certain range, thereby improving the integration level and energy density of the battery assembly. The volume of the heat absorbing material 12, V, is (xa*n*x1)·S.

[0112] The present invention also provides an electrical system comprising the aforementioned battery assembly. The electrical system may be, for example, a vehicle or an energy storage system. Because the electrical system is equipped with the battery assembly described herein, the battery assembly in the electrical system meets heat absorption requirements while also providing excellent safety.

[0113] The following examples further illustrate the heat absorption unit 1 and the power system of the present invention. The examples are implemented based on the technical solution of the present invention and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0114] 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.

[0115] Examples 1-31 and Comparative Examples 1-7

[0116] The battery assembly shown in Figure 1 includes a plurality of battery cells 2 and a heat absorption unit 1, with one heat absorption unit 1 positioned every two battery cells 2. The heat absorption unit 1 comprises a frame 11 and a heat absorption material 12, wherein the heat absorption material 12 is a hydrogel. The frame 11 is a single-layer or multi-layer structure, and each layer of the frame 11 includes a plurality of holes 13 extending through the thickness of the frame 11. The holes 13 are filled with hydrogel. The frame 11 and the heat absorption material 12 are encapsulated in an encapsulation film 14 (aluminum-plastic film). The thickness x of the heat absorption unit 1, the gap d between the battery cells 2, the area ratio a of the frame 11 on the surface of the heat absorption unit 1, the Young's modulus E1 of the frame 11, the heat absorption area S on the surface of the heat absorption unit 1, the pressure F1 on the frame 11, the thickness x1 of a layer of the frame 11, and the number n of the frames 11 in various battery pack examples are shown in Table 1 below.

[0117] Table 1

[0118] Test Example 1: Compression Test

[0119] Compression tests were performed on the battery cells 2 and the heat absorption unit 1 configured in Examples 1-31 and Comparative Examples 1-7. Specifically: 1. The battery assembly constructed as described above was placed in a compression device, wherein the compression device was a tensile testing machine;

[0120] 2. Use the compression device to apply a compressive force to one of the battery cells 2. The force changes from 0 to the value of F1 recorded in Table 1. The tensile tester will generate the compression amount x corresponding to the pressure F1 in real time, giving the compression deformation of the skeleton 11.

[0121] 3. Obtain the compression deformation rate of the skeleton 11 and record it in Table 2.

[0122] 4. Observe the status of the heat absorbing unit 1 and record it in the compression test results in Table 2.

[0123] Test Example 2: Thermal Diffusion Test

[0124] A needle penetration test was performed on the battery packs configured in Examples 1-31 and Comparative Examples 1-7 to test whether heat diffusion occurs after the needle penetration triggers thermal runaway in a battery cell 2 (based on whether the adjacent battery cell 2 experiences thermal runaway). At the same time, the maximum temperature of the battery cell 2 where thermal runaway is triggered by the needle penetration was monitored.

[0125] The test conditions are as follows:

[0126] (1) The battery state of charge (SOC) is 100%, i.e. fully charged;

[0127] (2) The sample temperature is 45°C ± 2°C;

[0128] (3) Using a 5 mm straight steel needle at a speed of 1 mm / s, puncture the battery cell 2 until the battery cell 2 experiences thermal runaway and then stops puncturing. When the voltage of the battery cell 2 drops to 75%, it is determined to be thermal runaway.

[0129] (4) After the experiment, continue to observe until the temperature of cell 2 is less than 100°C;

[0130] (5) Determine whether the battery cell 2 adjacent to the battery cell 2 has thermal runaway. When the voltage of the adjacent battery cell 2 drops to 75%, it is determined that thermal runaway has occurred, that is, heat diffusion has occurred.

[0131] The test results are shown in Table 2 below.

[0132] In addition, Test Example 2 can also be tested according to the apparatus shown in FIG8 , and when applied to the test apparatus, the internal battery cell 2 can be added in the form of a battery assembly. A thermal runaway test is performed on the battery assembly.

[0133] Test Example 3

[0134] Volume energy density test:

[0135] The obtained battery pack is subjected to charge and discharge tests to obtain the battery capacity of the battery pack. The volumes of the battery cell 2 and the heat absorption unit 1 are measured and calculated. The volume energy density and volume energy density decrease rate of a single battery cell 2 are obtained using the following formula:

[0136] Volume energy density of a single battery cell 2 = capacity of a single battery cell 2 / volume of a single battery cell 2;

[0137] Volume energy density of a single new battery cell 2 = capacity of a single battery cell 2 / (volume of a single battery cell 2 + volume of the heat absorption unit 1);

[0138] Volume energy density decrease rate = volume energy density of a single battery cell 2 - volume energy density of a single new battery cell 2.

[0139] Among them, the measurement method of the volume of the battery cell 2 and the volume of the heat absorption unit 1 is: for a single battery cell 2 or heat absorption unit 1, the volume of the battery cell 2 can be obtained by testing the length, width and height of the battery cell 2, and the volume of the heat absorption unit 1 can be obtained by measuring the length, width and height of the heat absorption unit 1.

[0140] Battery capacity test method:

[0141] 1) At room temperature, charge the battery at a low current (e.g. 1 / 3C) to the cut-off voltage and leave it for 1 hour.

[0142] 2) Discharge at a constant current of 1 / 3C to the cut-off voltage and leave for 1 hour;

[0143] 3) Repeat steps 1-2 twice in total and record the second discharge capacity as the battery capacity.

[0144] In this test example, a lithium iron phosphate battery is used, and the cut-off voltage is 3.75V.

[0145] The results are shown in Table 2 below.

[0146] Table 2

[0147] From the results in Table 2, it can be seen that according to Examples 1-31, the heat absorbing unit 1 configured according to the parameter range of the present invention has good mechanical properties. Specifically, in the compression test of the battery assembly, the heat absorbing unit 1 is intact. In Comparative Examples 1-7, when the heat absorbing unit 1 in the battery assembly When the value is less than 10 or greater than 1000, during the compression test of the battery assembly, the heat absorption unit 1 may experience packaging damage (the aluminum-plastic film of the heat absorption unit 1 is damaged, and the material overflows or leaks from the damaged area) or material overflow (the material is squeezed out of the gap between the battery cells 2 due to the expansion of the battery cells 2), and the heat absorption unit 1 may not be able to achieve its heat absorption effect. Based on Examples 3, 4, and 13, it can be seen that when the battery energy is within 537KJ-3456KJ, when the volume of the heat absorption unit 1 is less than 20000mm 3 When the battery is heated, thermal diffusion occurs. The specific reason is that the amount of heat absorbing material 12 in the heat absorbing unit 1 is too small to meet the heat release of the battery, resulting in thermal runaway of the adjacent battery cell 2. Based on Examples 21 and 27, it can be seen that when the battery energy is within 537KJ-3456KJ, when the volume of the heat absorbing unit 1 is greater than 300000mm 3 When the adjacent battery cells 2 do not undergo heat diffusion, the volume energy density of the battery assembly decreases by more than 30%, and the volume energy density of the battery assembly is too low. Therefore, when the battery energy is within 537KJ-3456KJ, when the volume of the heat absorption unit 1 is greater than 20000mm 3 And less than 300000mm 3 When the heat absorption unit 1 has sufficient volume to absorb the heat generated by the thermally runaway battery cell 2, the volumetric energy density of the battery assembly is maintained at a certain level (i.e., below 30%) to maintain the volumetric energy density of the battery assembly. Furthermore, when the thickness of the heat absorption unit 1 in the battery assembly is adjusted within a preferred range (e.g., 0.1-10 mm), the battery assembly not only ensures good safety, but also significantly reduces the volumetric energy density.

[0148] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A battery assembly, characterized in that, The battery assembly includes: a plurality of battery cells (2); and a heat absorption unit (1), the heat absorption unit (1) being disposed between two adjacent battery cells (2), and the heat absorption unit (1) includes: a heat absorption material (12); and at least one layer of a framework (11), the framework (11) having a plurality of holes (13) penetrating in the thickness direction of the framework (11), and the heat absorption material (12) filling the holes (13); The battery assembly satisfies the following conditions: wherein, x is the thickness of the heat absorption unit (1), in mm; d is the gap between two adjacent battery cells (2), in mm; a is the ratio of the area of the orthographic projection of the framework (11) on the surface of the heat absorption unit (1) in contact with the battery cell (2) to the surface area of the heat absorption unit (1) in contact with the battery cell (2); E1 is the Young's modulus of the framework (11), in GPa; S is the surface area of the heat absorption unit (1) in contact with the battery cell (2), with the unit of mm 2 ; F1 is the pressure borne by the framework (11), in N; x1 is the thickness of one layer of the framework (11), in mm; n is the number of layers of the framework (11), n≥1 and n is an integer.

2. The battery assembly according to claim 1, wherein, The energy Q of the battery cell (2) is between 576 kJ and 3456 kJ.

3. The battery assembly according to claim 1 or 2, characterized in that, The volume V of the heat-absorbing material (12) is between 20000 mm 3 and 300000 mm 3 . Wherein, the volume V of the heat absorption material (12) satisfies: V = (x - a * n * x1)·S.

4. The battery assembly according to any one of claims 1 to 3, characterized in that, The thickness x of the heat absorption unit (1) is 0.5 - 5 mm.

5. The battery assembly according to any one of claims 1 to 4, characterized in that, The gap d between two adjacent battery cells (2) is 0.3 - 3 mm.

6. The battery assembly according to any one of claims 1 to 5, characterized in that, The ratio a of the area of the orthographic projection of the framework (11) on the surface of the heat absorption unit (1) in contact with the battery cell (2) to the surface area of the heat absorption unit (1) in contact with the battery cell (2) is 10 - 50%.

7. The battery assembly according to any one of claims 1 to 6, characterized in that, The Young's modulus E1 of the framework (11) is 0.0001 - 100 GPa.

8. The battery assembly according to any one of claims 1 to 7, characterized in that, The surface area S of the heat absorption unit (1) in contact with the battery cell (2) is 5000 - 300000 mm 2 .

9. The battery assembly according to any one of claims 1 to 8, characterized in that, The pressure F1 borne by the framework (11) is 5000 - 60000 N.

10. The battery assembly according to any one of claims 1 to 9, characterized in that, The pressure F1 borne by the skeleton (11) satisfies the following formula: Wherein, F is the total pressure borne by the surface of the heat absorption unit (1) in contact with the battery cell (2), in N; E2 is the Young's modulus of the heat absorption material (12), in GPa; a is the ratio of the area of the orthographic projection of the framework (11) on the surface of the heat absorption unit (1) in contact with the battery cell (2) to the surface area of the heat absorption unit (1) in contact with the battery cell (2).

11. The battery assembly according to any one of claims 1 to 10, characterized in that, The thickness x1 of one layer of the framework (11) is 0.025 - 2 mm.

12. The battery assembly according to any one of claims 1 to 11, characterized in that, The number of layers n of the framework (11) is 1 - 10.

13. The battery assembly according to any one of claims 1 to 12, characterized in that, The thickness x of the heat absorption unit (1) is greater than or equal to the product of the thickness x1 of one layer of the framework (11) and the number of layers n of the framework (11).

14. The battery assembly according to any one of claims 1 to 13, characterized in that, The total thickness of the framework (11) accounts for 1 - 100% of the thickness of the heat absorption unit (1), preferably 10 - 80%.

15. The battery assembly according to any one of claims 1 to 14, characterized in that, The heat absorption unit (1) further includes a packaging film (14) for packaging the framework (11) and the heat absorption material (12).

16. The battery assembly according to any one of claims 1 to 15, characterized in that, The holes (13) are uniformly arranged in the thickness direction of the framework (11).

17. The battery assembly according to any one of claims 1 to 16, characterized in that, The ratio of the area of the surface of the heat absorption unit (1) in contact with the battery cell (2) to the surface area of the battery cell (2) in contact with the heat absorption unit (1) is greater than or equal to 0.8 and less than or equal to 1.

18. The battery assembly according to any one of claims 1 to 17, characterized in that, The battery assembly includes at least two battery cell groups, each battery cell group includes N battery cells (2) arranged in a row, and a heat absorption unit (1) is arranged between two adjacent battery cell groups, wherein the thickness x of the heat absorption unit (1) satisfies the following relationship: (0.5N ± b) mm ≤ x ≤ (5N ± b) mm; where b is a preset correction factor with the unit of mm.

19. The battery assembly according to any one of claims 1 to 18, characterized in that, The phase change temperature of the heat absorption material (12) is between 50°C and 200°C.

20. The battery assembly according to claim 19, wherein The phase change temperature of the heat absorption material (12) is between 70°C and 160°C.

21. The battery assembly according to any one of claims 1-20, characterized in that, The heat absorption material (12) is a hydrogel.

22. The battery assembly according to any one of claims 1-21, wherein a plurality of the holes (13) are uniformly arranged along the extending direction of the framework (11).

23. An electrical power system, characterized in that, Including the battery assembly according to any one of claims 1-22.

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