Battery assembly and device

Abstract

The invention provides a battery assembly and device. The battery assembly comprises Q battery units which are arranged in sequence, a heat absorption part is arranged between any adjacent battery units, each battery unit comprises N single batteries which are arranged in sequence, Q is larger than or equal to 2, N is larger than or equal to 1, the quality of the heat absorption parts is controlled to meet the relational expression defined by the invention, and it can be guaranteed that the heat absorption parts can fully restrain heat diffusion of the thermal runaway battery; and the space utilization rate of the battery assembly is not obviously reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery assembly and device. Background Art

[0002] Continuous overcharging, collisions, or punctures can easily cause internal short circuits in single cells, leading to thermal runaway and potentially affecting adjacent cells. To suppress the spread of heat during thermal runaway in single cells, the industry typically places a flame retardant (such as aerogel) on the surface of the cell's casing. However, aerogel can only slow the transfer of heat and cannot effectively absorb the large amount of heat released within the battery, making it difficult to effectively block the thermal diffusion of batteries experiencing thermal runaway. Therefore, it is necessary to develop a technical solution that can effectively block the thermal diffusion of single cells experiencing thermal runaway. Summary of the Invention

[0003] In view of this, the present application provides a battery assembly and device to solve the problem that abnormal heat generation of single cells in existing battery assemblies cannot be effectively suppressed and diffused.

[0004] Specifically, a first aspect of the present application provides a battery assembly comprising Q sequentially arranged battery cells, a heat sink disposed between any two adjacent battery cells, each battery cell comprising N sequentially arranged single batteries, Q ≥ 2, N ≥ 1; wherein the heat sink comprises a main heat sink material, wherein the main heat sink material comprises a heat absorbing material; wherein a battery cell adjacent to the heat sink satisfies the following relationship with the heat sink:

[0005] (0.6×T 平衡 -28) / [H p +c abs ×(T p -T en )]≤m≤(3×T 平衡 -140) / [H p +c abs ×(T p -T en )];

[0006] Among them, T 平衡 represents the temperature of the N cells in the battery unit when the temperature drop reaches the equilibrium state during the thermal runaway process, in °C; T en is the ambient temperature of the heat absorbing element, in °C; m is the mass of the heat absorbing main material, in kg; H p 、c abs 、T p are the phase change latent heat, specific heat capacity, and phase change temperature of the heat-absorbing material, with units of kJ / kg, kJ / (kg·K), and °C, respectively.

[0007] In this battery assembly, a heat sink is disposed between adjacent battery cells. The mass of the main heat-absorbing material in the heat sink is designed based on its heat absorption characteristics and the amount of heat transferred to the heat sink from a battery cell experiencing thermal runaway in a battery cell adjacent to the heat sink. Controlling the mass of the main heat-absorbing material in the heat sink to satisfy the aforementioned relationship effectively ensures that the heat generated by a battery cell experiencing thermal runaway in the battery cell is fully absorbed by the heat sink, effectively suppressing heat diffusion to adjacent battery cells, thereby ensuring the safety of the entire battery assembly. At the same time, this ensures high effective space utilization within the battery assembly and prevents the heat sink from occupying an excessively large volume.

[0008] In a second aspect, the present application provides a device comprising the battery assembly described in the first aspect of the present application, wherein the device comprises an electrical device or an energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A A schematic diagram of an exemplary structure of a battery assembly provided in an embodiment of the present application is shown.

[0010] Figure 1B Another exemplary structural schematic diagram of the battery assembly provided in an embodiment of the present application is respectively shown.

[0011] Figure 2 A schematic structural diagram of a single battery with a heat absorber provided on the surface provided in an embodiment of the present application.

[0012] Figure 3 A schematic structural diagram of the heat absorbing element provided in an embodiment of the present application.

[0013] Figure 4 for Figure 3 A structural diagram of the main heat-absorbing material. DETAILED DESCRIPTION

[0014] The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0015] The present application embodiment provides a battery assembly. Please refer to Figure 1A and Figure 1B The battery assembly 1000 provided in the embodiment of the present application includes Q battery cells 100 arranged in sequence, each battery cell 100 includes N single batteries 10 arranged in sequence, Q ≥ 2, N ≥ 1; wherein a heat absorption member 200 is provided between any two adjacent battery cells 100. Figure 1A In the example, Q=5 and N=1 are used. Figure 1B In the example, Q=3 and N=2 are used.

[0016] The heat absorbing member 200 includes a heat absorbing main material ( Figure 1A 、 Figure 1B(not shown), the main heat-absorbing material includes a heat-absorbing material; wherein the battery cell adjacent to the heat-absorbing element and the heat-absorbing element satisfy the following relationship:

[0017] (0.6×T 平衡 -28) / [H p +c abs ×(T p -T en )]≤m≤(3×T 平衡 -140) / [H p +c abs ×(T p -T en )];

[0018] Among them, T 平衡 represents the temperature of the N single cells 10 in the battery unit 100 when the temperature drop reaches the equilibrium state during the thermal runaway process, in °C; T en is the ambient temperature of the single battery 10 where thermal runaway occurs, in °C; m is the mass of the main heat-absorbing material, in kg; H p 、c abs 、T p are the phase change latent heat, specific heat capacity, and phase change temperature of the endothermic material, with units of kJ / kg, kJ / (kg·K), and °C, respectively.

[0019] In the above relationship, [H p +c abs ×(T p -T en )] can reflect the heat absorption capacity of the heat absorbing material per unit mass, and its product with m represents the total heat that the heat absorbing material can absorb. Considering that the heat transferred from the battery cell that experiences thermal runaway to the side of the heat absorbing element through the battery cell will be affected by the test environment and test conditions, the inventors found through a large number of experiments that (0.6×T 平衡 -28) can reflect the minimum heat value transferred from the N single cells 10 in a battery unit 100 adjacent to the heat sink 200 through the side of the battery unit 100 facing the heat sink 200 (i.e., the side of a single cell 10 in the battery unit 100 adjacent to the heat sink 200 facing the heat sink 200, recorded as the first surface 10a) during the thermal runaway process, where (3×T 平衡 -140) can reflect the maximum heat value transferred through the first surface 10a by the N single cells 10 in the battery unit 100 in thermal runaway; these are the findings of the inventors of this application through a large number of experimental studies. In this way, there is no need to test the heat generation of each single cell 10 during thermal runaway. Therefore, (0.6×T 平衡 -28) / [H p +cabs ×(T p -T en )] can reflect the minimum mass of the required heat absorbing material in kg, (3×T 平衡 -140) / [H p +c abs ×(T p -T en )] can reflect the maximum mass of the required heat-absorbing material in kg.

[0020] In the present application, the actual mass m of the main heat-absorbing material in kg is controlled to be greater than or equal to the aforementioned minimum mass value, which can effectively ensure that the heat generated by the N single cells 10 in a battery unit 100 adjacent to the heat-absorbing element 200 during thermal runaway can be effectively absorbed, and a chain reaction of thermal runaway that affects adjacent battery cells 100 will not be triggered, thereby ensuring better safety of the battery assembly 1000. In the present application, the actual mass m of the main heat-absorbing material in kg is controlled to be less than or equal to the aforementioned maximum mass value, which can reduce the volume of the heat-absorbing element 200 in the battery assembly 1000, thereby allowing a larger number of single cells 10 to be included in a battery assembly 1000 of a certain volume, resulting in higher space utilization and greater output power of the battery assembly 1000.

[0021] Furthermore, the equations satisfied by the heat sink 200 are universal and can be applied to the manufacture of heat sinks for various battery systems, models, and shapes. For example, the battery cells may include, but are not limited to, lithium batteries, sodium batteries, potassium batteries, and zinc batteries. The battery cells 10 may be square, hexagonal, or other shaped.

[0022] In the embodiments of the present application, provided the mass of the main heat-absorbing material satisfies the aforementioned relationship defined herein, the thickness of a single heat-absorbing element 200 in the battery assembly 1000 is determined to be a ratio of no more than 20% to the thickness of the adjacent battery cell (i.e., the sum of the thicknesses of the individual batteries 10 contained in that battery cell). This allows the battery assembly 1000 to contain a greater number of individual batteries 10, resulting in improved space utilization and a higher power output. In some embodiments, this thickness ratio is less than 19%, or less than 16%, or even less than 13%.

[0023] The above relationship (0.6×T 平衡 -28) / [H p +c abs ×(T p -T en )]≤m≤(3×T 平衡 -140) / [H p +c abs ×(T p -Ten )], the parameters are calculated without taking into account the unit. For example, "c abs is the specific heat capacity of the heat absorbing material, the unit is kJ / (kg·K)” means, c abs It is the value of the heat absorbing material in kJ / (kg·K).

[0024] In this application, (0.6×T 平衡 -28) / [H p +c abs ×(T p -T en )] is called the lower limit of the mass m of the heat absorbing main material in kg, and (3×T 平衡 -140) / [H p +c abs ×(T p -T en )] is called the upper limit of the mass m of the main heat-absorbing material in kg. It can be understood that in this application, the mass m of the main heat-absorbing material in g satisfies: (600×T 平衡 -28000) / [H p +c abs ×(T p -T en )]≤m≤(3000×T 平衡 -140000) / [H p +c abs ×(T p -T en )].

[0025] In this application, a sign that a single cell 10 has experienced "thermal runaway" may be that the voltage of the single cell 10 drops to zero and its explosion-proof valve opens. In some embodiments, the thermal runaway process refers to the process in which the temperature of the single cell 10 rapidly rises from room temperature and then decreases until it returns to room temperature when the single cell 10 experiences thermal runaway.

[0026] In this application, after the heat absorbing material of the heat absorbing element 200 is determined, the specific heat capacity c of the heat absorbing material is abs is the intrinsic parameter of the heat-absorbing material, which can be obtained by looking up the textbook. For example, when the heat-absorbing material is a hydrogel, c abs The phase transition temperature of the heat-absorbing material is 4.2 kJ / (kg·K). p , latent heat of phase change H p It can be obtained by Differential Scanning Calorimetry (DSC) testing. Specifically, a preset mass m1 of heat absorbing material can be taken out from the heat absorbing element 200, and the temperature T at which the preset mass of heat absorbing material undergoes phase change during the temperature rise process can be recorded. p, test its phase change process, greater than T p The total heat H released below a predetermined temperature (such as 300 ° C) can be obtained according to H / m1. The heat released by the unit mass of the endothermic material during phase change can be obtained, that is, the phase change latent heat H of the endothermic material can be obtained. p In addition, the DSC test solution has a dedicated test device, such as a differential scanning calorimeter (DSC). The mass m of the main heat-absorbing material can be obtained by first separating it from the heat-absorbing element 200 and weighing it.

[0027] The above T 平衡 It can be measured under adiabatic conditions. Specifically, Q battery cells are arranged along a first direction. When the battery unit 100 includes a single battery 10, the single battery has two side surfaces opposite to each other along the first direction. Both of these side surfaces are recorded as surfaces 10a' (essentially also the above-mentioned first surface 10a). Take out a battery cell (i.e., a single battery) from the above-mentioned battery assembly, and evenly arrange n thermocouples (n ≥ 2) on the two surfaces 10a' of the single battery. Then, place the single battery 10 in an insulated container (for example, made of an insulating material with good thermal insulation properties) with almost no heat exchange with the surrounding environment. The explosion-proof valve of the single battery 10 can be used as a spray valve in the event of thermal runaway. The single cell 10 is punctured or heated to induce thermal runaway. The temperature of the single cell 10 first rises rapidly and then slowly decreases. When the temperature drop rate of the last temperature measuring point among the 2n temperature measuring points with thermocouples arranged on the two surfaces 10a' reaches 1±0.05°C / min, the temperature drop of the single cell 10 is considered to have reached equilibrium. The temperatures of the 2n temperature measuring points at this time are obtained and their average value is taken to obtain T 平衡 .

[0028] In some embodiments, the single cell 10 is a square cell, the first direction is parallel to the thickness direction of the single cell, and the surface 10a' can be the large side of the single cell 10. The large side of the single cell 10 is the side with the largest area in the square shell. Figure 1A As shown, battery assembly 1000 includes five sequentially arranged battery cells 100, each containing one single battery cell 10. The middle single battery cell 10 can be removed, and the aforementioned thermocouples can be arranged on both large surfaces of the single battery cell 10. In other embodiments, the single battery cell 10 is a prismatic battery, and the first direction can also be parallel to the length or width of the single battery cell 10. Of course, it is understood that the single battery cell 10 can also be a cylindrical battery, and the battery cells can be arranged along the radial direction of the cylindrical battery. In this case, the aforementioned thermocouples can be arranged on the circumferential surface of the cylindrical battery.

[0029] When the battery unit 100 includes N single cells 10 (N ≥ 2), the N single cells 10 are arranged sequentially along a first direction. Of the two single cells 10 located at both ends in the first direction, one is designated as the first cell and the other is designated as the Nth cell. The first cell and the Nth cell each have two side surfaces disposed opposite each other in the first direction, wherein the side surface of the first cell facing away from the Nth cell and the side surface of the Nth cell facing away from the first cell are both designated as surfaces 10a" (essentially, the first surfaces 10a of the first cell and the Nth cell). A battery cell is removed from the above-mentioned battery assembly, and n thermocouples (n ≥ 2) are uniformly arranged on the surfaces 10a" of the first cell and the Nth cell of the battery cell, respectively. The N single cells 10 in the battery cell are then placed in an insulated container with virtually no heat exchange with the surrounding environment. The explosion-proof valve of each single cell 10 can serve as a spray valve in the event of thermal runaway. The N single cells 10 are needled or heated to induce thermal runaway. The temperatures of the N single cells 10 first rise rapidly and then slowly fall. When the temperature drop rate of the last temperature measuring point among the 2n temperature measuring points with thermocouples arranged on the two surfaces 10a" reaches 1±0.05°C / min, it is considered that the temperature drop of the N single cells in the battery unit has reached a balanced state. The temperatures of the 2n temperature measuring points at this time are obtained and their average value is taken to obtain T 平衡 .

[0030] In some embodiments, the single cell 10 is a square cell, and the first direction is parallel to the thickness direction of the single cell 10. The two surfaces 10a" can be the large surfaces of the first cell and the Nth cell, respectively. The large surfaces of the first cell and the Nth cell are the largest side surfaces of the square shells of the two single cells. For example Figure 1B As shown, the battery assembly 1000 includes 3 battery cells 100, each battery cell includes 2 single cells. The middle battery cell 100 can be removed, and the above-mentioned thermocouples are set on the left large surface of the single cell on the left and the right large surface of the single cell on the right.

[0031] In other embodiments, the single cell 10 is a square cell, and the first direction may be parallel to the length or width of the single cell 10. It is understood that the single cell 10 may also be a cylindrical cell, and the first direction may be parallel to the radial direction of the cylindrical cell. In this case, the thermocouples may be arranged on the arc surfaces of the first cell and the Nth cell facing away from each other. For example, n may be 3, 4, 6, 8, 9, 10, 12, 15, 16, 18, 20, etc. The time it takes for the temperature drop of the single cell to reach equilibrium (calculated from the initiation of thermal runaway) may be 2000s, 3000s, or 4000s, etc.

[0032] The above T enis the ambient temperature of the heat absorbing element 200. Generally, T en It can be 20°C, 30°C, 35°C, or 40°C, etc. It should be noted that the ambient temperature of the heat-absorbing material and the heat-absorbing element (or battery assembly, battery cell) is essentially the same. Therefore, for testing convenience, the ambient temperature of the heat-absorbing element is used to reflect the ambient temperature of the heat-absorbing material.

[0033] In some embodiments of the present application, the positive electrode of the single cell 10 may include one or more of a layered oxide positive electrode material and a lithium iron manganese phosphate material. The safety of layered oxide positive electrode materials is relatively poor, and it is particularly suitable to use the above formula of the present application to calculate the mass of the heat absorber provided between the single cells whose positive electrodes use layered oxide positive electrode materials, so as to better ensure that the abnormal heat generation of the single cell can be effectively absorbed by the heat absorber. Taking lithium batteries as an example, their layered oxide positive electrode materials refer to lithium oxides containing at least one non-lithium metal element, and it is more common to contain two or more non-lithium metal elements. In addition, according to the type of non-lithium metal elements, the layered oxide positive electrode material can be divided into monovalent oxide positive electrode materials, binary oxide positive electrode materials, ternary oxide positive electrode materials, multi-element oxide positive electrode materials, etc. Exemplarily, the layered oxide positive electrode materials commonly used in lithium batteries include but are not limited to lithium nickel cobalt manganese oxide (such as LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NFM811), LiNi 0.5 Co 0.3 Mn 0.2 O2 (abbreviated as NCM532)), lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, etc.

[0034] In some embodiments, the Q battery cells and the N single cells are arranged sequentially along a first direction, with each battery cell containing the same number of single cells. For prismatic cells 10, in the battery assembly 1000 of the present application, the Q battery cells 100 can be arranged sequentially along the first direction, with a heat sink 200 disposed between adjacent battery cells 100. The first direction is parallel to the thickness of the heat sink 200 or the thickness of the single cells 10. The heat sink 200 is specifically disposed on a side of the battery cell 100 that is perpendicular to the first direction. For a battery unit comprising N (N ≥ 2) single cells, these N battery cells are also arranged sequentially along the first direction. In the overall battery assembly 1000, the multiple single cells 10 are also arranged along the first direction. Of course, it is understood that in other embodiments, the arrangement directions of the Q battery cells and the N single cells may differ. For example, the Q battery cells may be arranged along the length or width of the single cells, while the N single cells are arranged along the thickness of the single cells.

[0035] In some embodiments of the present application, if the single battery 10 is denoted as A and the heat absorbing element 200 is denoted as B, if each battery unit 100 includes N=1 single battery cells, and any two adjacent battery units 100 are separated by the heat absorbing element 200, then along the first direction, the arrangement of the single battery cells 10 and the heat absorbing element 200 can be ABAB...A (e.g. Figure 1A , or ABAB...AB, etc. In this case, any two adjacent cells 10 in the battery assembly 1000 are separated by a heat sink 200. The heat sink 200 is positioned between the first surfaces 10a of any two adjacent cells 10. In other words, the cells 10 and the heat sink 200 are arranged alternately along the first direction. The placement of a heat sink 200 between any two adjacent cells 10 ensures superior safety performance for any battery assembly 1000. This is particularly suitable for battery assemblies 1000 composed of cells 10 with inherently poor safety performance, such as battery systems employing a ternary positive electrode material.

[0036] Similarly, in some other embodiments of the present application, if the single battery 10 is denoted as A and the heat sink 200 is denoted as B, if each battery unit 100 includes N=2 single batteries 10, and any two adjacent battery units 100 are separated by the heat sink 200, then along the first direction, the arrangement of the single battery 10 and the heat sink 200 can be AAB-AAB...AA (such as Figure 1B In this case, among the multiple single cells 10 of the battery assembly 1000, a heat absorbing member 200 is provided between some adjacent two single cells 10, while a heat absorbing member 200 is not provided between other adjacent two single cells 10. Figure 1B In the first direction indicated by the arrow, no heat sink is provided between the first and second cells, between the third and fourth cells, and between the fifth and sixth cells. This situation is particularly suitable for battery assemblies composed of cells with relatively high inherent safety performance, such as batteries using phosphate materials as the positive electrode material.

[0037] It should be noted that the number N of single cells included in each battery unit can be equal or different. Figure 1A and Figure 1B The examples are all based on the assumption that N is equal. The following is an example of the case where N is not equal: in the battery assembly 1000, the arrangement of the single cells and the heat sink can be AB-AAB-AAAB-AB, etc. When the battery cells on both sides of the heat sink contain different numbers of single cells, the battery cell with the largest number of single cells and the heat sink meet the following conditions: (0.6×T 平衡 -28) / [H p +cabs ×(T p -T en )]≤m≤(3×T 平衡 -140) / [H p +c abs ×(T p -T en )] is enough.

[0038] In some embodiments of the present application, the single cell 10 is a square cell having a square shell. The first surface 10a can be the large surface of the square shell, that is, the side with the largest area in the square shell of the single cell 10. Figure 2 , Figure 2 A schematic structural diagram of a single battery with a heat absorber provided on the surface provided in an embodiment of the present application.

[0039] Figure 2 The single battery 10 is a square battery, and the single battery 10 includes a square shell, and a heat absorbing member 200 is provided on the large surface of the shell. Figure 2 In the figure, a' and b' are the length and height of the first surface of the housing where the heat sink 200 is located, respectively. c' is the dimension of the housing perpendicular to the surface on which the heat sink 200 is located. c' can also be referred to as the width of the housing of the battery cell 10. The plane formed by the length a' and height b' of the housing is the major surface of the housing, while the plane formed by the height b' and width c' of the housing is the minor surface of the housing. Generally, a' ≥ b' > c'.

[0040] The housing of the above-mentioned single battery can be a housing well known to those skilled in the art. In some embodiments, the housing can be a metal housing, such as an aluminum housing or a steel housing. Of course, in other embodiments, the housing can also be an aluminum-plastic film. The housing can accommodate the battery cell assembly ( Figure 2 (not shown in the figure). In addition, the single cell 10 also has a positive electrode column 101 and a negative electrode column 102 exposed on the top of the shell. Of course, the positive electrode column and the negative electrode column can also be arranged at opposite ends of the single cell, such as at both ends in the length direction of the single cell. Among them, the battery cell assembly generally includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and the adjacent positive electrode sheets and negative electrode sheets can be separated by a diaphragm or a semi-solid / all-solid electrolyte material. Accordingly, the single cell 10 can be a liquid battery, or a fully solid-state battery or a semi-solid-state battery. Among them, the positive electrode column 101 of the single cell 10 can be electrically connected to the positive electrode sheet, and the negative electrode column 102 can be electrically connected to the negative electrode sheet, and these two columns can be used as electrode lead-out terminals when the single cell 10 is charged and discharged.

[0041] In the present application, the heat absorbing member 200 may be in the form of a sheet, the thickness of which is less than its transverse dimension. In this case, the heat absorbing member may also be referred to as a "heat absorbing sheet". The thickness direction of the heat absorbing member 200 is perpendicular to the first surface 10a of the single cell 10. The sheet-shaped heat absorbing member has a smaller thickness, which is beneficial for the battery assembly containing a plurality of the above-mentioned single cells 10 to have a greater space utilization rate. The cross-sectional shape of the heat absorbing member 200 may be a regular rectangle, pentagon, hexagon, or other irregular shapes. In some embodiments, the cross-sectional shape of the heat absorbing member 200 is a rectangle (such as Figure 2 ), consistent with the shape of the shell. Figure 2 In the embodiment, the thickness c of the heat sink 200 is much smaller than its length a and smaller than its width b. The thickness c of the heat sink 200 is also much smaller than the width c' of the battery cell 10 casing. Furthermore, the length a of the heat sink 200 can be less than, equal to, or greater than the length a' of the casing, and the width b of the heat sink 200 can be less than, equal to, or greater than the height b' of the casing. Figure 2 The example in the figure is "less than".

[0042] In one embodiment of the present application, the side of a battery cell 10 adjacent to the heat sink 200 that faces the heat sink 200 is designated as a first surface 10a. The ratio of the area of ​​the heat sink 200 contacting the battery cell's first surface 10a (e.g., S1) to the area of ​​the first surface 10a (e.g., S2) is greater than or equal to 0.8 and less than or equal to 1, i.e., S1 / S2 is within the range of 0.8-1. Setting the ratio of the contact area between the heat sink 200 and the battery cell's first surface 10a within this range ensures that the heat sink 200 fully contacts the first surface 10a, thereby ensuring a good heat absorption effect of the heat sink 200. Preferably, the area of ​​the heat sink 200 contacting the first surface 10a is equal to the area of ​​the first surface 10a, so that the heat sink 200 fully absorbs heat transferred from the first surface of the battery cell adjacent to the heat sink.

[0043] In one embodiment of the present application, the side of a single battery cell 10 adjacent to the heat sink 200 that faces the heat sink 200 is designated as the first surface 10a. The distance between the geometric center of the surface of the heat sink 200 in contact with the first surface 10a (denoted as point E) and the geometric center of the first surface 10a (denoted as point F) is less than or equal to 1 mm and greater than or equal to 0. In other words, the distance between points E and F is within a range from greater than or equal to 0 to less than or equal to 1 mm. This ensures that the heat sink 200 does not deviate too far from the first surface 10a, thereby enhancing the heat absorption efficiency of the heat sink.

[0044] In the implementation mode of this application, see Figure 3The heat sink 200 may include a main heat sink material 21 and an encapsulating film 22. The encapsulating film 22 defines a cavity 221 within which the main heat sink material 21 is disposed. The encapsulating film 22 provides enhanced protection for the main heat sink material 21, preventing leakage or loss of the active ingredients within the main heat sink material 21. The encapsulating film 22 may be selected from one or more materials such as PP (polypropylene), PET (polyethylene terephthalate), PI (polyimide), TPU (thermoplastic polyurethane), and aluminum-plastic film. These materials offer a degree of flexibility, allowing the encapsulating film 22 to adhere tightly to the surface of the main heat sink material 21, providing effective protection. In some embodiments, the encapsulating film 22 may be rectangular, with two or four sides heat-sealed. Furthermore, the thickness of the encapsulating film 22 may be tailored to meet specific requirements. In one embodiment, the encapsulating film 22 can be very lightweight, with the weight of the main heat sink material 21 comparable to that of the heat sink 200. The mass of the main heat-absorbing material 21 can be considered as the mass of the heat sink 200. In another embodiment, the mass of the packaging film 22 may approach or exceed the mass of the main heat-absorbing material. In this case, only the mass of the main heat-absorbing material is calculated. Furthermore, when the mass of the packaging film 22 is less than 10% of the mass of the main heat-absorbing material, for ease of measurement, the mass of the heat sink can be considered as the mass of the main heat-absorbing material.

[0045] In some embodiments of this application, see Figure 4 The heat absorbing main material 21 includes a frame 210 and a heat absorbing material 212. The frame 210 has a plurality of holes 211 that pass through the frame along the thickness direction of the frame. The heat absorbing material 212 is filled in the holes 211. In this case, the heat absorbing material 212 is the effective component of the heat absorbing main material 21 to play the role of heat absorption. p Specifically, the H of the heat absorbing material 212 p The skeleton 210 supports and shapes the heat absorbing material 212 and can be made of a mesh polymer material.

[0046] In the present application, the heat-absorbing material 212 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 212 can be a hydrogel that retains water, a hydrated salt that retains water, or a complex thereof. The phase change temperature of the heat-absorbing material 212 can be regulated by regulating the water content in the heat-absorbing material 212. 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 212 can be a material that retains liquids such as ethanol and ethylene glycol.

[0047] In this embodiment of the present application, the phase transition temperature of the heat-absorbing material 212 can be within the range of 85°C to 180°C. The thermal runaway onset temperature of the battery cell 10 is typically within this temperature range, and the phase transition temperature of the heat-absorbing material is controlled to be within this range. This allows the heat-absorbing material to rapidly absorb heat at the onset of thermal runaway in the battery cell 10, thereby removing heat and inhibiting thermal diffusion. Specifically, the phase transition temperature can be 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, etc.

[0048] In the embodiment of the present application, the phase change latent heat H of the heat absorbing material 212 p It can be above 500kJ / kg. This can ensure that the heat absorption capacity of the heat absorbing material is high and better suppress the heat generation and diffusion of the thermal runaway single cell. In some embodiments of the present application, the phase change latent heat H of the heat absorbing material 212 is p In this case, the heat absorbing material 212 has a high heat absorbing capacity and is easy to obtain. p It can be 500 kJ / kg, 600 kJ / kg, 800 kJ / kg, 900 kJ / kg, 1000 kJ / kg, 1200 kJ / kg, 1500 kJ / kg, 1600 kJ / kg, 1800 kJ / kg, 2000 kJ / kg, 2100 kJ / kg, etc.

[0049] In some other embodiments of the present application, the main heat-absorbing material 21 does not include a skeleton and can be solely the aforementioned heat-absorbing material. The aforementioned heat-absorbing material can be directly encapsulated in the encapsulation film 22. For example, the main heat-absorbing material can be the aforementioned hydrogel, hydrated salt, or a composite thereof.

[0050] In one embodiment of the present application, whether the main heat-absorbing material includes the skeleton 210 and the heat-absorbing material 212, or the main heat-absorbing material 21 only includes the heat-absorbing material 212, the main heat-absorbing material is located in the packaging film 22 to achieve sealing and avoid phase change of the heat-absorbing material and reduce the quality of the heat-absorbing material, so as to ensure the heat absorption effect of the heat-absorbing material.

[0051] In the embodiments of the present application, the battery assembly 1000 may be a battery module or a battery pack. Within the battery assembly 1000, multiple battery cells 10 may be connected in series, in parallel, or in a combination thereof to form a battery pack. Multiple battery cells 10 may also be encapsulated within a common housing frame, providing external communication via a unified boundary.

[0052] The present application also provides a device comprising the battery assembly of the present application, wherein the device may include an electrical device or an energy storage system.

[0053] Exemplary electrical devices include, but are not limited to, vehicles (such as ships and cars), consumer electronics (such as mobile phones, tablet computers, and smart wristbands). Exemplary vehicles include pure electric vehicles, hybrid electric vehicles, extended-range electric vehicles, electric buses, and electric trucks. Energy storage systems include site energy backup systems and smart photovoltaic energy storage power stations.

[0054] The technical solution of the present application is further described below with reference to a number of specific embodiments.

[0055] Example 1

[0056] Arrange 5 single cells in sequence along the thickness direction of the single cells, and place a heat absorbing element between the large surfaces of any two adjacent single cells facing each other to obtain a battery assembly. The ambient temperature T of the heat absorbing element is tested. en , recorded in Table 1. In this battery assembly, the arrangement of the single battery (denoted as A) and the heat absorber (denoted as B) is ABABABABA, or (AB)4A. That is, the battery assembly of Example 1 includes 5 battery cells, each of which includes a square single lithium battery cell, as shown in Table 1, and its shell size is: 160mm×90mm×30mm (that is, length a' is 160mm, height b' is 90mm, and width c' is 30mm). The positive electrode material of this single battery is the ternary material NCM811; the mass of the single battery (that is, the battery cell) is 0.95kg.

[0057] The preparation method of the heat absorbing element includes: selecting a gel polymer material and mixing it with water and coating it on a PET substrate, and forming a specific heat capacity c after solidification. abs The hydrogel with a heat absorption capacity of 4.2 kJ / (kg·K) was peeled off from the PET matrix and cut into corresponding sizes to obtain a hydrogel with a mass of m kg (i.e., the main heat-absorbing material was the hydrogel). The main heat-absorbing material was heat-sealed on all sides with aluminum plastic film (thickness of 0.085 mm) to obtain a sheet-like heat-absorbing member (which can be called a "heat-absorbing sheet"). The phase change latent heat H of the heat-absorbing material in the heat-absorbing sheet was measured by DSC method. p 1400kJ / kg, phase transition temperature T p It is 108℃.

[0058] Get T 平衡 Another single cell is selected (the number of the other selected single cells is equal to the number of single cells included in the battery unit in this embodiment), and its T 平衡 , the selected single cell is the same as the single cell in the above battery assembly. In this way, the T 平衡 Compared with the T of the single cell in this embodiment平衡 Same. 平衡 The test method is the same as described above. Specifically, nine thermocouples are evenly arranged on the two large surfaces of the selected single cell to collect temperature. The single cell is then placed in an insulated container with almost no heat exchange with the surrounding environment, and an opening is opened at the explosion-proof valve of the single cell to serve as a spray valve. The single cell is punctured to induce thermal runaway. After thermal runaway, the temperature of the single cell first rises rapidly and then slowly decreases. When the temperature drop rate of the last temperature measurement point among the 18 thermocouples arranged on the single cell reaches 1±0.05℃ / min, the temperature drop of the single cell is considered to have reached equilibrium. The temperatures of the 18 temperature measurement points at this time are obtained, and their average value is taken to obtain T 平衡 , and its specific values ​​are shown in Table 1.

[0059] According to the above relationship provided in the previous part of this application, the upper and lower limits of the mass of the heat-absorbing main material can be calculated, and the results are shown in Table 1. After comparison, it is found that the actual mass m of the heat-absorbing main material in Example 1 is between the upper and lower limits.

[0060] In addition, the thickness of a single heat-absorbing sheet in the battery assembly was measured, and the ratio of the thickness to the thickness of the battery unit (ie, the sum of the width (thickness) of all the single batteries contained therein) was summarized in Table 1.

[0061] The battery assembly was also subjected to a needle penetration test, which specifically includes the following steps: at room temperature, after each single battery is fully charged, a steel needle with a diameter of 3 mm is used to penetrate the middle position of the single battery in the middle battery unit (i.e., the battery in the third battery unit, i.e., the third single battery among the five single batteries arranged in sequence) at a speed of 0.5 mm / s until the battery experiences thermal runaway, and then the test is stopped. The test is continuously observed until the temperature of the battery experiencing thermal runaway is less than 100°C. After the experiment is completed, it is recorded whether the adjacent battery experiences thermal runaway (the thermal runaway standard is voltage reduction or opening of the explosion-proof valve), that is, whether heat diffusion occurs.

[0062] According to the method described in Example 1, battery assemblies of other examples and comparative examples were prepared, and their main characteristics are listed in Table 1, Table 2 and Table 3.

[0063] Among them, in Examples 7-8, the phase change latent heat of the endothermic material is different from that in other examples, which can be achieved by regulating the water content in the endothermic material in Example 1.

[0064] In the battery assemblies of Examples 4, 11, 12, and Comparative Examples 4 and 5, the arrangement of the single cells (denoted as A) and the heat sink (denoted as B) is AABAABAABAABAA, or (AAB)4AA. In other words, such a battery assembly includes five battery cells, each of which includes two prismatic single lithium cells.

[0065] Obtain T in Example 4 平衡 When , two more single cells are selected (i.e., the number of the additionally selected single cells is equal to the number of single cells in the battery unit of this embodiment), which are the same as the single cells in the battery unit of this embodiment. In this way, the T of the two selected single cells is 平衡 The T of the single battery in the battery unit of this embodiment 平衡 The same. Among them, T 平衡 The test method is the same as mentioned above, specifically, the two selected single cells are arranged in sequence along the thickness direction and 9 thermocouples are evenly arranged on the large surfaces facing each other for temperature collection. The two single cells are then placed in an insulated container with almost no heat exchange with the surrounding environment. The explosion-proof valve of each single cell is opened to serve as a spray valve. The two single cells are punctured with a needle to induce thermal runaway. After the thermal runaway is triggered, the temperature of the two single cells first rises rapidly and then slowly decreases. When the temperature drop rate of the last of the 18 temperature measuring points arranged on the two single cells reaches 1±0.05℃ / min, it is considered that the temperature drop of the two single cells has reached a balanced state. The temperatures of the 18 temperature measuring points at this time are obtained, and their average value is taken to obtain T 平衡 , whose specific values ​​are shown in Table 1. T of Examples 11-12 and Comparative Examples 4-5 平衡 The acquisition method is the same as above and will not be repeated here. The specific values ​​are shown in Table 2 and Table 3.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070]

[0071] Table 3

[0072]

[0073] It can be seen from the above tables that in the battery assembly of the embodiment of the present application, when the mass of the heat absorption sheet arranged between adjacent battery cells meets the relationship required by the present application, the heat absorption sheet can effectively suppress the heat diffusion of the single battery cell in thermal runaway to the adjacent battery cell. At the same time, the thickness of the heat absorption sheet and the adjacent battery cells is relatively low, not exceeding 20%, thereby making the total thickness of all the heat absorption sheets in the entire battery assembly low and the effective space utilization rate of the battery assembly high.

[0074] A comparison of Comparative Examples 1-2 with Example 1 reveals that the mass of the heat sink in Comparative Example 2 is less than the lower limit of the aforementioned relationship, failing to suppress heat diffusion from the battery pack experiencing thermal runaway. The actual mass of the heat sink in Comparative Example 1 is greater than the upper limit of the aforementioned relationship. Although heat diffusion from the battery pack experiencing thermal runaway is prevented, the thickness ratio between the heat sink and adjacent battery cells is significant, impacting the space utilization efficiency of the battery pack. A similar phenomenon is observed in a comparison of Comparative Examples 4-5 with Example 4. Furthermore, a comparison of Comparative Example 3 with Example 2 exhibits similar phenomena as the comparison between Comparative Example 2 and Example 1.

[0075] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the scope of the present application, and all such modifications and improvements fall within the scope of protection of the present application.

Claims

1. A battery assembly, characterized in that: The invention comprises Q sequentially arranged battery cells, a heat absorbing element is provided between any two adjacent battery cells, each battery cell comprises N sequentially arranged single batteries, Q ≥ 2, N ≥ 1; wherein the heat absorbing element comprises a heat absorbing main material, and the heat absorbing main material comprises a heat absorbing material; wherein a battery cell adjacent to the heat absorbing element and the heat absorbing element satisfy the following relationship: (0.6×T 平衡 -28) / [H p +c abs ×(T p -T en )]≤m≤(3×T 平衡 -140) / [H p +c abs ×(T p -T en )]; Among them, T 平衡 represents the temperature of the N single batteries in the battery unit when the temperature drop reaches the equilibrium state during the thermal runaway process, in degrees Celsius; T en is the ambient temperature of the heat absorbing element, in °C; m is the mass of the main heat-absorbing material, in kg; H p 、c abs 、T p are the phase change latent heat, specific heat capacity, and phase change temperature of the endothermic material, with units of kJ / kg, kJ / (kg·K), and °C, respectively.

2. The battery assembly according to claim 1, wherein The positive electrode of the single cell includes one or more of a layered oxide positive electrode material and a lithium manganese iron phosphate material.

3. The battery assembly according to claim 1 or 2, wherein: The H p Greater than or equal to 500kJ / kg.

4. The battery assembly according to any one of claims 1 to 3, wherein: The H p In the range of 500-2200kJ / kg.

5. The battery assembly according to any one of claims 1 to 4, wherein: A side of a single battery cell adjacent to the heat absorption element facing the heat absorption element is recorded as a first surface, and a ratio of a surface area of ​​the heat absorption element in contact with the first surface to an area of ​​the first surface is greater than or equal to 0.8 and less than or equal to 1.

6. The battery assembly according to any one of claims 1 to 5, wherein: A side of a single battery cell adjacent to the heat absorber facing the heat absorber is recorded as a first surface, and a distance between a geometric center of a surface of the heat absorber in contact with the first surface and a geometric center of the first surface is less than or equal to 1 mm and greater than or equal to 0.

7. The battery assembly according to any one of claims 1 to 6, wherein: The heat absorbing component further comprises a packaging film, wherein a receiving cavity is formed inside the packaging film, and the main heat absorbing material is arranged in the receiving cavity.

8. The battery assembly according to any one of claims 1 to 7, wherein: The heat-absorbing main material includes a skeleton and the heat-absorbing material. The skeleton has a plurality of holes penetrating the skeleton along the thickness direction of the skeleton, and the heat-absorbing material is filled in the holes.

9. The battery assembly according to any one of claims 1 to 7, wherein: The main heat-absorbing material is the heat-absorbing material.

10. The battery assembly according to any one of claims 1 to 9, wherein: The phase transition temperature T of the heat absorbing material p In the range of 80℃-180℃.

11. The battery assembly according to any one of claims 1 to 10, wherein: The heat absorbing material is a hydrogel, a hydrated salt or a complex thereof.

12. The battery assembly according to any one of claims 1 to 11, wherein: The Q battery units and the N single batteries are arranged in sequence along a first direction, and each battery unit includes the same number of single batteries.

13. The battery assembly according to any one of claims 1 to 12, wherein: The single battery is a square battery, and the heat absorption member is arranged on a side surface of the battery unit that is perpendicular to the thickness direction of the single battery.

14. A device, characterized in that The battery assembly comprises a battery assembly as described in any one of claims 1 to 13, wherein the device comprises an electrical device or an energy storage system.

Images