Battery cell assembly, battery pack and electric equipment

Abstract

The invention discloses a battery cell assembly, a battery pack and electric equipment, the battery cell assembly comprises a plurality of electrically connected battery cells, the plurality of battery cells comprise at least one sodium ion battery cell and at least one lithium ion battery cell, and the ratio of the total number of the sodium ion battery cells to the total number of the lithium ion battery cells is not greater than 1. Therefore, by mixing the lithium ion battery cells and the sodium ion battery cells into a group, battery cell assembly explosion caused by serial thermal runaway of the lithium ion battery cells can be prevented, the thermal safety of the battery cell assembly is improved, and the ratio of the total number of the sodium ion battery cells to the total number of the lithium ion battery cells is set to be smaller than or equal to 1, so that the battery cell assembly is more stable. The energy density of the battery cell assembly and the low-temperature energy efficiency of the whole pack can be ensured, and the practicability of the battery cell assembly is improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and in particular to a battery cell assembly, a battery pack, and an electrical device. Background Technology

[0002] Automotive batteries are typically either lithium iron phosphate (LFP) batteries or sodium-ion batteries. LFP batteries offer good cycle stability and low cost, but suffer from poor low-temperature performance and rapid thermal propagation after thermal runaway. Sodium-ion batteries, on the other hand, have high low-temperature capacity retention and good safety, but lower capacity. Regardless of the type of battery used, both will result in certain defects in the vehicle, leaving room for improvement. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a battery cell assembly that can prevent the battery cell assembly from exploding due to cascading thermal runaway, and can ensure the energy density and overall low-temperature energy efficiency of the battery cell assembly, thereby improving the practicality of the battery cell assembly.

[0004] According to an embodiment of the present invention, a battery cell assembly includes: a plurality of electrically connected battery cells, wherein the plurality of battery cells includes at least one sodium-ion battery cell and at least one lithium-ion battery cell, and the ratio of the total number of sodium-ion battery cells to the total number of lithium-ion battery cells is not greater than 1.

[0005] According to the embodiments of the present invention, by mixing lithium-ion cells and sodium-ion cells into a group, the cell assembly explosion caused by the cascading thermal runaway of lithium-ion cells can be prevented, thereby improving the thermal safety of the cell assembly. Furthermore, by setting the ratio of the total number of sodium-ion cells to the total number of lithium-ion cells to be less than or equal to 1, the energy density and overall low-temperature energy efficiency of the cell assembly can be guaranteed, thereby improving the practicality of the cell assembly.

[0006] According to some embodiments of the present invention, in a battery cell assembly, the plurality of battery cells are stacked, and in the stacking direction, at least one sodium-ion battery cell is provided every first preset number of lithium-ion battery cells, wherein the first preset number is less than or equal to 6.

[0007] According to some embodiments of the present invention, in the stacking direction, the first and last cells are sodium-ion cells.

[0008] According to some embodiments of the present invention, the ratio of the capacity of a single sodium-ion cell to that of a single lithium-ion cell is S, which satisfies: 1 ≤ S ≤ 1.2.

[0009] According to some embodiments of the present invention, a mating gap is provided between adjacent battery cells in the battery cell assembly.

[0010] According to some embodiments of the present invention, in the stacking direction, the width of the mating gap is W, which satisfies: 0 < W < 1 mm.

[0011] According to some embodiments of the present invention, in a cell assembly, the mating gap is filled with an aerogel layer, the aerogel layer being used to completely separate adjacent cells.

[0012] According to some embodiments of the present invention, in the stacking direction, the thickness of the sodium-ion battery cell is H1, the thickness of the lithium-ion battery cell is H2, and the width of the mating gap is W, satisfying: H1=n*H2+(n-1)W, where n is an integer greater than or equal to 2.

[0013] According to some embodiments of the present invention, each of the battery cells is in the shape of a cuboid, and the thickness direction of the battery cell is the stacking direction.

[0014] According to some embodiments of the present invention, the battery cell assembly has a cover plate at each end along its length, and one of the cover plates has an explosion-proof valve and an external terminal. The external terminal and the explosion-proof valve are spaced apart along the width direction of the battery cell, and the width direction of the battery cell is vertical.

[0015] According to some embodiments of the present invention, the external terminal includes a positive terminal and a negative terminal, one of the cover plates is provided with the negative terminal and the other cover plate is provided with the positive terminal, and the explosion-proof valve is located on the same cover plate as one of the positive terminal and the negative terminal.

[0016] According to some embodiments of the present invention, in the battery cell assembly, the explosion-proof valve and the negative terminal are located on the same cover plate.

[0017] The present invention also proposes a battery pack.

[0018] A battery pack according to an embodiment of the present invention includes: a battery tray and a cell assembly according to any of the above embodiments, wherein the battery tray has a receiving cavity and the cell assembly is installed in the receiving cavity.

[0019] According to the battery pack of the present invention, the cell assembly has high thermal safety, which improves the overall thermal safety of the battery pack. In addition, the cell assembly has good energy density and low-temperature energy efficiency of the whole pack, which improves the practicality of the cell assembly and enhances the overall performance of the battery pack.

[0020] According to some embodiments of the present invention, the battery pack is provided with multiple sets of battery cell assemblies, which are arranged in the receiving cavity along a first direction and / or a second direction. Multiple battery cells in each set of battery cell assemblies are connected in series, and the first direction and the second direction intersect.

[0021] According to some embodiments of the present invention, in a battery pack, multiple cells of the same cell assembly are stacked, and in the stacking direction, the cell in any cell assembly that is closest to the adjacent cell assembly is the sodium-ion cell.

[0022] According to some embodiments of the present invention, the battery pack has a partition beam inside the battery tray, the partition beam extending along the first direction or the second direction, the partition beam being used to divide the receiving cavity into a plurality of sub-chambers, each of the sub-chambers having at least one set of the battery cell assembly.

[0023] According to some embodiments of the present invention, in a battery pack, multiple cells of the same cell assembly are stacked, and in the stacking direction, the cell in any cell assembly that is closest to the separator beam is the sodium-ion cell.

[0024] The present invention also proposes an electrical device.

[0025] The electrical device according to embodiments of the present invention includes a battery pack according to any of the above embodiments.

[0026] According to the embodiments of the present invention, the battery cell assembly has high thermal safety, which improves the overall thermal safety of the battery pack. In addition, the battery cell assembly has good energy density and low-temperature energy efficiency of the whole pack, which improves the practicality of the battery cell assembly, enhances the overall performance of the battery pack, and improves the product competitiveness of the electrical equipment.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1 This is a schematic diagram of a battery pack according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of a battery cell according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a battery pack according to another embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of a battery pack according to another embodiment of the present invention.

[0033] Figure label:

[0034] Battery pack 100; First direction F1; Second direction F2;

[0035] Battery tray 1; receiving cavity 11; sub-chamber 111; partition beam 12;

[0036] Battery cell assembly 2; battery cell 21; sodium-ion battery cell 211; lithium-ion battery cell 212; external terminal 213; negative terminal 2131; positive terminal 2132; explosion-proof valve 214; mating clearance 22. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Hereinafter, with reference to the accompanying drawings, a cell assembly 2 according to an embodiment of the present invention will be described.

[0041] like Figures 1-4As shown, the battery cell assembly 2 according to an embodiment of the present invention includes: a plurality of battery cells 21 electrically connected, the plurality of battery cells 21 including at least one sodium-ion battery cell 211 and at least one lithium-ion battery cell 212, wherein the ratio of the total number of sodium-ion battery cells 211 to the total number of lithium-ion battery cells 212 is not greater than 1.

[0042] First, such as Figure 1 As shown, the battery cell assembly 2 includes multiple electrically connected battery cells 21, each including at least one sodium-ion battery cell 211 and at least one lithium-ion battery cell 212, with the sodium-ion battery cells 211 and lithium-ion battery cells 212 arranged alternately. It should be noted that the lithium-ion battery cell 212 can be a lithium iron phosphate battery cell; the sodium-ion battery cell 211 is a polyanionic electrolyte (such as sodium iron phosphate pyrophosphate) or a Prussian blue electrolyte, and the electrolyte of the sodium-ion battery cell 211 is a highly flame-retardant electrolyte.

[0043] The ratio of the total number of sodium-ion cells 211 to the total number of lithium-ion cells 212 can be set to be less than or equal to 1, that is, the total number of sodium-ion cells 211 is less than or equal to the total number of lithium-ion cells 212.

[0044] It is understandable that by setting sodium-ion cells 211 in the cell assembly 2, the sodium-ion cells 211 can be used to block heat diffusion, which can prevent the cell assembly 2 from exploding due to the cascading thermal runaway of lithium-ion cells 212, thereby improving the thermal safety of the cell assembly 2. Furthermore, by setting the ratio of the total number of sodium-ion cells 211 to the total number of lithium-ion cells 212 to be less than or equal to 1, the energy density and overall low-temperature energy efficiency of the cell assembly 2 can be guaranteed.

[0045] According to the embodiments of the present invention, the battery cell assembly 2, by mixing lithium-ion battery cells 212 and sodium-ion battery cells 211 into a group, can prevent the battery cell assembly 2 from exploding due to the cascading thermal runaway of lithium-ion battery cells 212, thereby improving the thermal safety of the battery cell assembly 2. Furthermore, by setting the ratio of the total number of sodium-ion battery cells 211 to the total number of lithium-ion battery cells 212 to be less than or equal to 1, the energy density and overall low-temperature energy efficiency of the battery cell assembly 2 can be guaranteed, thereby improving the practicality of the battery cell assembly 2.

[0046] In some embodiments of the present invention, a plurality of battery cells 21 are stacked, and in the stacking direction, at least one sodium-ion battery cell 211 is provided every first preset number of lithium-ion battery cells 212, wherein the first preset number is less than or equal to 6.

[0047] For example, refer to Figure 1As shown, multiple battery cells 21 are stacked, including several sodium-ion battery cells 211 and several lithium-ion battery cells 212. In the stacking direction, at least one sodium-ion battery cell 211 is provided every first preset number of lithium-ion battery cells 212, and the first preset number is less than or equal to 6. For example, the first preset quantity can be set to 2, and the multiple battery cells 21 can be arranged in the order of lithium-ion battery cell 212, lithium-ion battery cell 212, sodium-ion battery cell 211, or in the order of lithium-ion battery cell 212, lithium-ion battery cell 212, sodium-ion battery cell 211, sodium-ion battery cell 211; the first preset quantity can be set to 3, and the multiple battery cells 21 can be arranged in the order of lithium-ion battery cell 212, lithium-ion battery cell 212, lithium-ion battery cell 212, sodium-ion battery cell 211, or in the order of lithium-ion battery cell 212, lithium-ion battery cell 212, lithium-ion battery cell 212, sodium-ion battery cell 211, sodium-ion battery cell 211.

[0048] It is understandable that the sodium-ion battery cell 211 can block heat diffusion. When the number of continuously stacked lithium-ion battery cells 212 is the first preset number, the temperature of lithium-ion thermal runaway is relatively low. Due to the barrier of the sodium-ion battery cell 211, the lithium-ion battery cell 212 located on the other side of the sodium-ion battery cell 211 is not prone to thermal runaway, which can prevent the battery cell assembly 2 from exploding due to chain thermal runaway and improve the thermal safety of the battery cell assembly 2.

[0049] In some embodiments of the present invention, such as Figure 1 As shown, in the stacking direction, the first and last cells 21 are sodium-ion cells 211. This reduces the impact of low-temperature environments on the cell assembly 2, improving the overall low-temperature energy efficiency of the battery pack. Furthermore, when there are multiple cell assemblies 2, if some cell assemblies 2 experience thermal runaway, the sodium-ion cell 211 located on the outermost side of the stacking direction can prevent heat from spreading to adjacent cell assemblies 2, thus helping to prevent the battery pack 100 from exploding and improving the thermal safety of the battery pack 100.

[0050] In some embodiments of the present invention, the ratio S of the capacity of a single sodium-ion battery cell 211 to the capacity of a single lithium-ion battery cell 212 satisfies: 1 ≤ S ≤ 1.2. That is, the ratio S of the capacity of a single sodium-ion battery cell 211 to the capacity of a single lithium-ion battery cell 212 can be set to be greater than or equal to 1 and less than or equal to 1.2, such as 1, 1.05, 1.1, 1.15, 1.2, etc. It should be noted that the units of the capacity of the sodium-ion battery cell 211 and the capacity of a single lithium-ion battery cell 212 are Ah. This prevents over-discharge or over-charge of the sodium-ion battery cell 211, which helps extend the service life of the sodium-ion battery cell 211 and improves the reliability of the battery cell assembly 2.

[0051] Preferably, the capacity of a single sodium-ion cell 211 and a single lithium-ion cell 212 can be set to be the same. This makes it easier to match lithium-ion cells 212 and sodium-ion cells 211, reduces the design difficulty of the battery pack 100, and allows the power of each cell 21 to be fully utilized, thereby improving the energy utilization rate of the cell assembly 2.

[0052] In some embodiments of the present invention, such as Figure 1 As shown, a mating gap 22 can be provided between adjacent battery cells 21. Therefore, when the battery cell 21 expands during charging and discharging, the mating gap 22 can absorb the expansion of the battery cell 21, so as to avoid excessive compression between adjacent battery cells 21 and improve the thermal safety of the battery cell assembly 2.

[0053] In some embodiments of the present invention, such as Figure 1 As shown, in the stacking direction, the width of the mating gap 22 can be set to W, satisfying: 0 < W < 1 mm. For example, the width W of the mating gap 22 in the stacking direction can be 0.1 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1 mm, etc. This allows the mating gap 22 to effectively absorb the expansion of the cell 21, and avoids the mating gap 22 being too wide, improving space utilization, increasing the energy density of the cell assembly 2, and enhancing the design rationality of the cell assembly 2.

[0054] In some embodiments of the present invention, the mating gap 22 is filled with an aerogel layer, which completely separates adjacent cells 21. Thus, when a cell 21 experiences thermal runaway, the aerogel can effectively delay heat diffusion. This improves the thermal safety of the cell assembly 2.

[0055] In some embodiments of the present invention, such as Figure 1 As shown, in the stacking direction, the thickness of sodium-ion cell 211 is H1, the thickness of lithium-ion cell 212 is H2, and the width of the mating gap 22 is W, satisfying: H1=n*H2+(n-1)W, where n is an integer greater than or equal to 2.

[0056] In other words, in the stacking direction, the thickness of the sodium-ion battery cell 211 can be set as H1, the thickness of the lithium-ion battery cell 212 as H2, and the width of the mating gap 22 as W, satisfying: H1 = n*H2 + (n-1)*W, where n is an integer greater than or equal to 2, such as 2, 3, 4, etc. For example, n can be set to 2, and the thickness H1 of the lithium-ion battery cell 212 is twice the thickness of the lithium-ion battery cell 212 plus the width W of the mating gap 22; or, n can be set to 3, and the thickness H1 of the lithium-ion battery cell 212 is three times the thickness of the lithium-ion battery cell 212 plus twice the width W of the mating gap 22.

[0057] The above settings make it easier to control the overall size of the cell assembly 2 in the stacking direction, which helps to reduce the design difficulty of the battery pack 100.

[0058] In some embodiments of the present invention, such as Figure 2 As shown, each battery cell 21 can be configured to be a cuboid in shape, with the thickness direction of the battery cell 21 (refer to...) Figure 2 The front-to-back direction shown is the stacking direction. This allows the overall structure of the battery cell assembly 2 to more closely resemble a square, making it easier to arrange and improving the practicality of the battery cell assembly 2.

[0059] In some embodiments of the present invention, such as Figure 1 As shown, the battery cell 21 can be installed along its length (reference). Figure 2 The battery cell 21 has cover plates at both ends (shown in the left-right direction). One of the cover plates has an explosion-proof valve 214 and an external terminal 213. The external terminal 213 and the explosion-proof valve 214 are spaced apart along the width direction of the battery cell 21, which is vertical (see reference). Figure 2 (The up and down directions are shown).

[0060] The above-mentioned design allows for flexible design of the dimensions of the battery cell assembly 2 in the chassis height direction, enabling a lower overall height of the battery pack 100 and a higher overall chassis, thus reducing the risk of bottom cutting and improving the practicality of the battery pack 100. When the battery cell 21 experiences thermal runaway and the explosion-proof valve 214 opens, the high-temperature fumes emitted from the explosion-proof valve 214 will be ejected outward from the end of the battery cell 21 along its length. The high-temperature fumes will not directly contact the connecting pieces and sampling harness, reducing the risk of electrical connection failure. Furthermore, the electrolyte overflowing from the explosion-proof valve 214 will not remain at the end of the battery cell 21, making it less likely to connect the two external terminals 213, thereby improving the thermal safety of the battery pack 100.

[0061] In some embodiments of the present invention, such as Figure 2 As shown, the external terminal 213 includes a positive terminal 2132 and a negative terminal 2131. One cover plate has the negative terminal 2131, and the other cover plate has the positive terminal 2132. The explosion-proof valve 214 is located on the same cover plate as one of the positive terminal 2132 and the negative terminal 2131. Therefore, the positive terminal 2132 and the negative terminal 2131 can be respectively located at both ends of the battery cell 21 along its length. When the battery cell 21 experiences thermal runaway and electrolyte leakage, the positive terminal 2132 and the negative terminal 2131 can be effectively prevented from conducting, thus improving the safety of the battery cell assembly 2.

[0062] In some embodiments of the present invention, such as Figure 2As shown, the explosion-proof valve 214 and the negative terminal 2131 can be located on the same cover plate. This optimizes the exhaust path, improves the exhaust efficiency of the battery cell 21 during thermal runaway, enhances the safety of the battery cell 21, and improves the design rationality of the battery cell 21.

[0063] The present invention also proposes a battery pack 100.

[0064] like Figure 1 As shown, the battery pack 100 according to an embodiment of the present invention includes: a battery tray 1 and a cell assembly 2 according to any of the above embodiments. The battery tray 1 is provided with a receiving cavity 11, and the cell assembly 2 is installed in the receiving cavity 11.

[0065] According to the battery pack 100 of the present invention, the cell assembly 2 has high thermal safety, which improves the overall thermal safety of the battery pack 100. In addition, the cell assembly 2 has good energy density and low-temperature energy efficiency of the whole pack, which improves the practicality of the cell assembly 2 and enhances the overall performance of the battery pack 100.

[0066] In some embodiments of the present invention, such as Figures 1-4 As shown, the battery cell assembly 2 consists of multiple groups, which are arranged in the receiving cavity 11 along the first direction F1 and / or the second direction F2. Multiple battery cells 21 in each group of battery cell assembly 2 are connected in series, and the first direction F1 and the second direction F2 intersect.

[0067] For example, such as Figure 1 As shown, multiple sets of battery cell assemblies 2 can be arranged sequentially along the first direction F1 in the receiving cavity 11, and multiple battery cells 21 of each set of battery cell assemblies 2 can be stacked along the first direction F1; or, multiple sets of battery cell assemblies 2 can be arranged sequentially along the second direction F2 in the receiving cavity 11, and multiple battery cells 21 of each set of battery cell assemblies 2 can be stacked along the second direction F2; or, multiple sets of battery cell assemblies 2 can be arranged sequentially along the first direction F1 and the second direction F2 in the receiving cavity 11, and multiple battery cells 21 of each set of battery cell assemblies 2 can be stacked along the first direction F1; or, multiple sets of battery cell assemblies 2 can be arranged sequentially along the first direction F1 and the second direction F2 in the receiving cavity 11, with multiple battery cells 21 of one set of adjacent battery cell assemblies 2 stacked along the first direction F1, and multiple battery cells 21 of the other set stacked along the second direction F2.

[0068] It is understandable that by setting multiple battery cell assemblies 2, the size of a single battery cell assembly 2 can be reduced, which helps to reduce the assembly difficulty of the battery cell assembly 2. Furthermore, by setting multiple battery cells 21 in each battery cell assembly 2 to be connected in series, the voltage matching problem caused by the voltage inconsistency of different types of battery cells 21 can be avoided, thereby improving the design rationality of the battery pack 100.

[0069] In some embodiments of the present invention, such as Figure 3 As shown, multiple cells 21 of the same cell assembly 2 are stacked. In the stacking direction, the cell 21 that is closest to the adjacent cell assembly 2 in any cell assembly 2 is a sodium-ion cell 211. Therefore, when a single cell assembly 2 experiences thermal runaway, the sodium-ion cell 211 can prevent the thermal runaway from spreading to adjacent cell assemblies 2, which helps to prevent a chain reaction from multiple sets of cell assemblies 2 and improves the thermal safety of the battery pack 100.

[0070] In some embodiments of the present invention, such as Figure 3 As shown, the battery tray 1 is provided with a partition beam 12, which extends along a first direction F1 or a second direction F2. The partition beam 12 is used to divide the receiving cavity 11 into a plurality of sub-cavities 111, and each sub-cavity 111 is provided with at least one set of battery cell assembly 2.

[0071] For example, two partition beams 12 can be provided in the battery tray 1. The two partition beams 12 are arranged at intervals along a first direction F1 and extend along a second direction F2. The two partition beams 12 are used to divide the receiving cavity 11 into three sub-chambers 111 along the first direction F1. Each sub-chamber 111 contains a set of battery cell assemblies 2; or, as Figure 3 As shown, two partition beams 12 can be provided in the battery tray 1. One partition beam 12 extends along the first direction F1, and the other partition beam 12 extends along the second direction F2. The partition beam 12 extending along the first direction F1 and the partition beam 12 extending along the second direction F2 intersect. The partition beam 12 is used to divide the receiving cavity 11 into four sub-cavities 111 along the first direction F1 and the second direction F2. Each sub-cavity 111 contains a set of battery cell assemblies 2. Alternatively, two partition beams 12 can be provided in the battery tray 1. One partition beam 12 extends along the first direction F1, and the other partition beam 12 extends along the second direction F2. The partition beam 12 extending along the first direction F1 and the partition beam 12 extending along the second direction F2 intersect. The partition beam 12 is used to divide the receiving cavity 11 into four sub-cavities 111 along the first direction F1 and the second direction F2. Each sub-cavity 111 contains two sets of battery cell assemblies 2. The two sets of battery cell assemblies 2 located in the same sub-cavity 111 are arranged along the first direction F1.

[0072] With the above settings, the partition beam 12 can be used to limit multiple battery cell components 2 to avoid multiple sets of battery cell components 2 squeezing each other, thereby improving the installation stability of the battery cell components 2. In the event of thermal runaway of the battery cell components 2, the partition beam 12 can also be used to delay the thermal diffusion of the battery cell components 2, thereby improving the reliability of the battery pack 100.

[0073] In some embodiments of the present invention, multiple cells 21 of the same cell assembly 2 are stacked. In the stacking direction, the cell 21 in any cell assembly 2 that is closest to the separator beam 12 is a sodium-ion cell 211. Thus, when a single cell assembly 2 experiences thermal runaway, the sodium-ion cell 211 can prevent the thermal runaway from spreading to the separator beam 12, preventing heat transfer to other cell assemblies 2 and thus avoiding a chain reaction, thereby improving the thermal safety of the battery pack 100.

[0074] In some embodiments of the present invention, a slot matching the bottom surface of the battery cell assembly 2 may be provided at the bottom of each sub-chamber 111. The battery cell assembly 2 is installed in the slot and is limited by the partition beam 12, so that the partition beam 12 is used to fix the battery cell assembly 2 and can also provide lateral support for the battery cell assembly 2. As a result, the structural stability of the battery pack 100 can be improved.

[0075] The present invention also proposes an electrical device.

[0076] The electrical device according to embodiments of the present invention includes a battery pack 100 according to any of the above embodiments. It should be noted that the electrical device can be any of the following: a hybrid vehicle, a pure electric vehicle, or a drone.

[0077] According to the embodiments of the present invention, the battery cell assembly 2 has high thermal safety, which improves the overall thermal safety of the battery pack 100. In addition, the battery cell assembly 2 has good energy density and low-temperature energy efficiency of the whole pack, which improves the practicality of the battery cell assembly 2, enhances the overall performance of the battery pack 100, and improves the product competitiveness of the electrical equipment.

[0078] The specific experimental data are as follows:

[0079] This comparative example uses a lithium iron phosphate battery cell (i.e., lithium-ion battery cell 212) as an example. The battery cell 21 has a blade structure and the dimensions of the battery cell 21 are 580mm*120mm*13.5mm. The external terminal 213 is led out from the 120mm*13.5mm cross section, and the positive terminal 2132 and the negative terminal 2131 are on opposite sides.

[0080] The assembly steps for cell assembly 2 are as follows:

[0081] 1. The cell 21 is wrapped with a 0.1mm thick PET insulating film, which does not cover the position of the external terminal 213;

[0082] 2. Apply a 2mm thick layer of structural adhesive to the inner surface of battery tray 1;

[0083] 3. After the coating is applied, the narrow side (580mm*13.5mm) below the battery cell 21 is placed in contact with the inner surface of the battery tray 1;

[0084] 4. Repeat step 3 to stack the cells 21 one by one into the battery tray 1. The positive terminal 2132 and negative terminal 2131 of adjacent cells 21 are placed in opposite directions, and a 1mm air gap is reserved between adjacent cells 21.

[0085] 5. Apply a 2mm thick thermally conductive structural adhesive to the narrow surface of the upper part of cell 21, and attach a 0.6mm thick liquid cooling plate on top of the thermally conductive structural adhesive.

[0086] 6. Using aluminum connecting pieces, the positive terminal 2132 and negative terminal 2131 of adjacent cells 21 are sequentially welded together in series to form cell assembly 2. Connecting pieces are also welded between cell assemblies 2 in series.

[0087] 7. Install the distribution box (BDU) at the front end of battery tray 1;

[0088] 8. Install the sampling board on the outside of the connecting piece and connect the temperature and voltage sampling harness;

[0089] 9. In step 6, aluminum busbars and copper busbars are led out from the positive and negative sides of the battery cell assembly 2, respectively, and connected to the distribution box;

[0090] 10. Attach the 2mm thick PCM sealing cover to the battery tray 1, and fix the edges with sealant and bolts to form the battery pack 100.

[0091] Example 1

[0092] Compared with the comparative example, the difference is that the cells in Example 1 are all sodium iron phosphate pyrophosphate cells (i.e., sodium ion cells 211). The size of the sodium iron phosphate pyrophosphate cells is 580mm*120*25.2mm, and the capacity is the same as that of lithium iron phosphate cells.

[0093] Example 2

[0094] Example 2 is a battery cell assembly 2 composed of lithium iron phosphate cells and sodium iron phosphate pyrophosphate cells. The sodium iron phosphate pyrophosphate cells are 580mm*120*25.2mm in size and have the same capacity as the lithium iron phosphate cells. The difference from the comparative example is that in the battery cell assembly 2 of Example 2, one sodium iron phosphate pyrophosphate cell is placed every other lithium iron phosphate cell; at the same time, the edge cells 21 of the edge battery cell assembly 2 are set as sodium iron phosphate cells 21.

[0095] Example 3

[0096] In Example 3, a battery cell assembly 2 is formed by combining lithium iron phosphate cells and sodium iron phosphate pyrophosphate cells. The sodium iron phosphate pyrophosphate cells are 580mm*120*25.2mm in size and have the same capacity as the lithium iron phosphate cells. The difference from the comparative example is that in the battery cell assembly 2 of Example 3, a sodium iron phosphate pyrophosphate cell is placed every two lithium iron phosphate cells. At the same time, the edge cells 21 of the edge battery cell assembly 2 are set as sodium iron phosphate cells 21.

[0097] Example 4

[0098] Example 4 is a battery cell assembly 2 composed of lithium iron phosphate cells and sodium iron phosphate pyrophosphate cells. The sodium iron phosphate pyrophosphate cells are 580mm*120*25.2mm in size and have the same capacity as the lithium iron phosphate cells. The difference from the comparative example is that in the battery cell assembly 2 of Example 4, one sodium iron phosphate pyrophosphate cell is placed every 5 lithium iron phosphate cells. At the same time, the edge cells 21 of the edge battery cell assembly 2 are set as sodium iron phosphate pyrophosphate cells 21.

[0099] Example 5

[0100] Example 5 is a battery cell assembly 2 composed of lithium iron phosphate cells and sodium iron phosphate pyrophosphate cells. The sodium iron phosphate pyrophosphate cells are 580mm*120*25.2mm in size and have the same capacity as the lithium iron phosphate cells. The difference from the comparative example is that in the battery cell assembly 2 of Example 5, one sodium iron phosphate pyrophosphate cell is placed every 6 lithium iron phosphate cells. At the same time, the edge cells 21 of the edge battery cell assembly 2 are set as sodium iron phosphate cells 21.

[0101] Example 6

[0102] Example 6 is a battery cell assembly 2 composed of lithium iron phosphate cells and sodium iron phosphate pyrophosphate cells. The sodium iron phosphate pyrophosphate cells are 580mm*120*25.2mm in size and have the same capacity as the lithium iron phosphate cells. The difference from the comparative example is that in the battery cell assembly 2 of Example 6, one sodium iron phosphate pyrophosphate cell is placed every 7 lithium iron phosphate cells. At the same time, the edge cells 21 of the edge battery cell assembly 2 are set as sodium iron phosphate cells 21.

[0103] (1) Thermal runaway experiment as follows:

[0104] A heating film is attached to the second cell 21 of the cell assembly 2 along the stacking direction. The heating film is located on the side of the cell facing the first cell 21. The heating film has an area of ​​90mm*90mm and a power of 800W. The heating film is used to heat the cell 21 to 400℃ and keep it at that temperature until the cell 21 thermally runs away. Temperature sensors are arranged on the large surface of each cell 21 away from the heating film, and temperature sensors are also arranged in the center of the heating film.

[0105] Experimental results show that, in the comparative example, all cell components 2 in battery pack 100 experienced thermal runaway. The highest temperature of battery pack 100 reached 690.1℃, the heat generated by thermal runaway was 127530kJ, the maximum internal and external pressure difference of battery pack 100 was 54kPa, and battery pack 100 opened its valve 7 minutes and 30 seconds after the onset of thermal runaway, resulting in an explosion. The safety level was HL7.

[0106] In Example 1, only cell 21 was thermally runaway was triggered. The highest temperature of battery pack 100 reached 176°C, the heat generated by thermal runaway was 1131 kJ, the maximum internal and external pressure difference of battery pack 100 was 0.5 kPa, battery pack 100 did not open the valve, battery pack 100 did not explode, and the safety level was HL2.

[0107] In Example 2, only the thermal runaway of cell 21 was triggered. The highest temperature of the lithium-ion cell 212, which is separated from the thermal runaway cell 21 by the sodium-ion cell 211, was 80°C. The heat generated by the thermal runaway was 3694 kJ. The maximum internal and external pressure difference of the battery pack 100 was 1.5 kPa. The battery pack 100 did not open its valve and did not explode. The safety level was HL2.

[0108] In Example 3, only the thermal runaway of cell 21 was triggered. The highest temperature of the lithium-ion cell 212, which is separated from the thermal runaway cell 21 by the sodium-ion cell 211, was 83.4°C. The heat generated by the thermal runaway was 5144 kJ. The maximum internal and external pressure difference of the battery pack 100 was 2.4 kPa. The battery pack 100 did not open its valve and did not explode. The safety level was HL2.

[0109] In Example 4, only the thermal runaway of cell 21 was triggered. The highest temperature of the lithium-ion cell 212, which is separated from the thermal runaway cell 21 by the sodium-ion cell 211, was 93°C. The heat generated by the thermal runaway was 9491 kJ. The maximum internal and external pressure difference of the battery pack 100 was 4 kPa. The battery pack 100 did not open its valve and did not explode. The safety level was HL2.

[0110] In Example 5, only the thermal runaway of cell 21 was triggered. The highest temperature of the lithium-ion cell 212, which is separated from the thermal runaway cell 21 by the sodium-ion cell 211, was 99.5°C. The heat generated by the thermal runaway was 10941 kJ. The maximum internal and external pressure difference of the battery pack 100 was 4.3 kPa. The battery pack 100 did not open its valve and did not explode. The safety level was HL2.

[0111] In other words, when the ratio of lithium-ion cells 212 to sodium-ion cells 211 does not exceed 6:1 (the charge ratio does not exceed 6:1), the uniformly distributed sodium-ion cells 211 can effectively block heat diffusion between cells 21 within the package. Simultaneously, the heat generated during thermal runaway decreases from 127530 kJ to 10941 kJ, a reduction of 91%.

[0112] In Example 6, all the cell components 2 in the battery pack 100 experienced thermal runaway. The highest temperature of the battery pack 100 reached 688°C, the heat generated by thermal runaway was 124592 kJ, the maximum internal and external pressure difference of the battery pack 100 was 52 kPa, the valve of the battery pack 100 opened 28 minutes after the start of thermal runaway, and the battery pack 100 exploded. The safety level was HL7.

[0113] In other words, when the ratio of lithium-ion cells 212 to sodium-ion cells 211 exceeds 6:1 (the ratio of their charge exceeds 6:1), sodium-ion cells 211 cannot completely block the heat spread process, but they can still effectively delay the heat spread time and improve safety.

[0114] Understandably, sodium-ion cell 211 releases less heat per unit mass and per unit volume during thermal runaway than lithium-ion cell 212, and its maximum temperature during thermal runaway is also significantly lower than that of lithium-ion cell 212. Its heat spread rate is also lower than that of lithium-ion cell 212. At the same time, because sodium-ion cell 211 has a lower valve opening pressure, it can open the valve earlier to spray substances, which can slow down or block the spread of heat diffusion, reduce the heat generation, maximum temperature, and maximum internal pressure during thermal runaway, and reduce the risk of thermal runaway of battery pack 100.

[0115] (2) Low temperature test as follows:

[0116] Battery cell assembly 2 was charged at 25℃ using a constant current rate of 1 / 3 (1 / 3C) to the charging cutoff voltage, rested for 30 minutes, and then discharged at a constant current rate of 1 / 3C to the discharging cutoff voltage. It was then rested at 25℃ for 2 hours, and the discharge energy was recorded. Next, it was charged again at 25℃ using a constant current rate of 1 / 3C to the charging cutoff voltage, rested for 30 minutes, and then placed in a -30℃ environment for 6 hours. It was then discharged again using a constant current rate of 1 / 3C to the discharging cutoff voltage, and the discharge capacity was recorded. The -30℃ discharge energy retention rate (-30℃ discharge energy / 25℃ charging energy) was measured.

[0117] Compared to the comparative example, the discharge energy retention rate of the cell assembly 2 in Examples 1, 2, 3, 4, 5, and 6 at -30℃ increased from 39.8% to 76.4%, 58.1%, 52%, 50.1%, 48.2%, and 46.8%, respectively. This indicates that compared to the cell assembly 2 composed of pure lithium-ion cells 212, the lithium-sodium hybrid cell assembly 2 has a better low-temperature endurance retention rate and is more adaptable to low-temperature environments. This is because when the battery pack 100 discharges in a low-temperature environment, the cell 21 in the middle position accumulates heat due to self-generation, resulting in a higher actual operating temperature than the cell 21 at the edges. At this time, the discharge capacity of the battery pack 100 is determined by the cell 21 at the edges. When the edge cell 21 is replaced by a sodium-ion cell 211 instead of a lithium-ion cell 212, the discharge capacity retention rate of the entire battery pack 100 will be improved because the low-temperature capacity retention rate of the sodium-ion cell 211 is significantly higher than that of the lithium-ion cell 212. Meanwhile, as the lithium-sodium ratio further increases, the rate of decrease in low-temperature discharge energy retention slows down.

[0118] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A battery cell assembly (2), characterized in that, include: A plurality of electrically connected cells (21), wherein the plurality of cells (21) includes at least one sodium-ion cell (211) and at least one lithium-ion cell (212), wherein the ratio of the total number of sodium-ion cells (211) to the total number of lithium-ion cells (212) is not greater than 1.

2. The cell assembly (2) according to claim 1, characterized in that, The plurality of cells (21) are stacked, and in the stacking direction, at least one sodium-ion cell (211) is provided every first preset number of lithium-ion cells (212), wherein the first preset number is less than or equal to 6.

3. The cell assembly (2) according to claim 2, characterized in that, In the stacking direction, the first and last cells (21) are sodium-ion cells (211).

4. The cell assembly (2) according to claim 1, characterized in that, The ratio of the capacity of a single sodium-ion cell (211) to the capacity of a single lithium-ion cell (212) is S, which satisfies: 1≤S≤1.

2.

5. The cell assembly (2) according to claim 2, characterized in that, A mating gap (22) is provided between adjacent battery cells (21).

6. The cell assembly (2) according to claim 5, characterized in that, In the stacking direction, the width of the mating gap (22) is W, which satisfies: 0 < W < 1 mm.

7. The cell assembly (2) according to claim 5, characterized in that, The mating gap (22) is filled with an aerogel layer, which is used to completely separate adjacent cells (21).

8. The cell assembly (2) according to claim 5, characterized in that, In the stacking direction, the thickness of the sodium-ion battery cell (211) is H1, the thickness of the lithium-ion battery cell (212) is H2, and the width of the mating gap (22) is W, satisfying: H1=n*H2+(n-1)*W, where n is an integer greater than or equal to 2.

9. The cell assembly (2) according to claim 2, characterized in that, Each of the battery cells (21) is in the shape of a cuboid, and the thickness direction of the battery cell (21) is the stacking direction.

10. The cell assembly (2) according to claim 9, characterized in that, The battery cell (21) has cover plates at both ends along its length. One of the cover plates has an explosion-proof valve (214) and an external terminal (213). The external terminal (213) and the explosion-proof valve (214) are spaced apart along the width direction of the battery cell (21), which is vertical.

11. The cell assembly (2) according to claim 10, characterized in that, The external terminal (213) includes a positive terminal (2132) and a negative terminal (2131), one of the cover plates is provided with the negative terminal (2131), and the other cover plate is provided with the positive terminal (2132). The explosion-proof valve (214) is located on the same cover plate as one of the positive terminal (2132) and the negative terminal (2131).

12. The cell assembly (2) according to claim 11, characterized in that, The explosion-proof valve (214) and the negative terminal (2131) are located on the same cover plate.

13. A battery pack (100), characterized in that, include: The battery tray (1) and the cell assembly (2) according to any one of claims 1-12, wherein the battery tray (1) is provided with a receiving cavity (11) and the cell assembly (2) is installed in the receiving cavity (11).

14. The battery pack (100) according to claim 13, characterized in that, The battery cell assembly (2) is in multiple groups, and the multiple groups of battery cell assemblies (2) are arranged in the receiving cavity (11) along a first direction (F1) and / or a second direction (F2). Multiple battery cells (21) in each group of battery cell assemblies (2) are connected in series, and the first direction (F1) and the second direction (F2) intersect.

15. The battery pack (100) according to claim 14, characterized in that, Multiple cells (21) of the same cell assembly (2) are stacked. In the stacking direction, the cell (21) that is closest to the adjacent cell assembly (2) in any cell assembly (2) is the sodium-ion cell (211).

16. The battery pack (100) according to claim 14, characterized in that, The battery tray (1) is provided with a partition beam (12) extending along the first direction (F1) or the second direction (F2). The partition beam (12) is used to divide the receiving cavity (11) into a plurality of sub-chambers (111), and each sub-chamber (111) is provided with at least one set of the battery cell assembly (2).

17. The battery pack (100) according to claim 16, characterized in that, Multiple cells (21) of the same cell assembly (2) are stacked. In the stacking direction, the cell (21) of any cell assembly (2) that is closest to the separator beam (12) is the sodium ion cell (211).

18. An electrical appliance, characterized in that, Includes the battery pack (100) according to any one of claims 13-17.

Images