Battery pack and electrical apparatus

Abstract

The present disclosure relates to the technical field of batteries. Provided are a battery pack and an electrical apparatus. The battery pack comprises a case body and a battery unit provided in the case body; the battery unit comprises a first battery and a second battery, the first battery and the second battery being stacked in a first direction; the first battery comprises a first electrode assembly having a first negative electrode sheet, the first negative electrode sheet comprising a first negative electrode current collector, and a deposition layer being formed on at least one surface of the first negative electrode current collector after the first battery is charged; the second battery comprises a second electrode assembly having a second negative electrode sheet, the second negative electrode sheet comprising a second negative electrode current collector and a second negative electrode active material layer, and the second negative electrode active material layer being adhered to at least one surface of the second negative electrode current collector. Because of the characteristic that the first battery exhibits less expansion variation than the second battery, the amount of expansion of the battery unit in the first direction is reduced, thereby reducing the probability of the case body being deformed.

Description

Battery pack and power-consuming device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on the Chinese patent application with application number 202410347135.9, application date March 25, 2024, and invention name “A battery pack and electrical device”, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into the present disclosure as a reference. Technical Field

[0003] The present disclosure relates to the field of battery technology, and in particular to a battery pack and an electrical device. Background Art

[0004] Batteries are increasingly being used in everyday life and production. For example, new energy vehicles equipped with batteries are already widely used, and batteries can be used to fully or partially power these vehicles. Furthermore, batteries are increasingly being used in areas such as energy storage.

[0005] In the related art, at least two batteries are placed in a box to form a battery pack. Since the batteries expand during the charging and discharging process, the box may be easily deformed.

[0006] Summary of the Invention

[0007] In view of this, the embodiments of the present disclosure hope to provide a battery pack and an electrical device that can reduce the probability of deformation of the box.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the embodiment of the present disclosure is implemented as follows:

[0009] A first aspect of an embodiment of the present disclosure provides a battery pack, comprising a box body and a battery unit disposed in the box body, wherein the battery unit comprises a first battery and a second battery, wherein the first battery and the second battery are stacked along a first direction;

[0010] The first battery includes a first electrode assembly having a first negative electrode sheet, the first negative electrode sheet including a first negative electrode collector, wherein a deposition layer is formed on at least one surface of the first negative electrode collector after the first battery is charged;

[0011] The second battery includes a second electrode assembly having a second negative electrode sheet. The second negative electrode sheet includes a second negative electrode collector and a second negative electrode active material layer. The second negative electrode active material layer is attached to at least one surface of the second negative electrode collector.

[0012] The battery pack provided by the embodiments of the present disclosure, on the one hand, has substantially no active material on the surface of the first negative electrode sheet before the first charge and discharge, compared to the second battery, thereby improving safety during the battery production and assembly process. On the other hand, the battery cells include first and second batteries of different types, wherein the energy density of the first battery is higher than that of the second battery, while the cycle stability of the second battery is higher than that of the first battery. Compared to battery cells that use only first batteries or only second batteries, the first and second batteries are mixed and stacked along a first direction, thereby retaining the relatively high energy density of the first battery and the relatively good cycle stability of the second battery, thereby ensuring the energy density of the battery pack while also taking into account the cycle stability of the battery pack. On the other hand, since the first battery and the second battery are of different types, that is, the chemical systems of the first battery and the second battery are different, under the condition of the same gram capacity, the absolute change in the volume of the first battery is smaller than the absolute change in the volume of the second battery, and the deposited layer formed after charging and discharging is soft and has a certain shaping effect and self-adjustment ability. The first battery and the second battery in the battery cell are stacked along the first direction. The first battery and the second battery have different frequencies when expansion occurs. By utilizing the characteristic that the expansion change of the first battery is smaller than that of the second battery, the expansion amount of the battery cell in the first direction is reduced, the squeezing of the battery cell on the box body is reduced or even eliminated, and the probability of deformation of the box body is reduced, thereby improving the service life of the battery pack.

[0013] In some embodiments, at least one end of the battery unit along the first direction is a first battery.

[0014] In this embodiment, since the absolute change in the volume of the first battery is smaller than the absolute change in the volume of the second battery, the first battery is arranged at the end of the battery unit to reduce the squeezing of the end plate of the box along the first direction, thereby reducing the force on the end of the box along the first direction, avoiding fatigue damage to the end plate of the box to a certain extent, and solving the problem of cracks at the weld of the box causing the end plate to fly out in extreme cases.

[0015] In some embodiments, in the battery unit, all the second batteries are sequentially arranged along the first direction to form a battery pack, and at least one first battery is respectively arranged at both ends of the battery pack along the first direction.

[0016] In this embodiment, the force on the area of ​​the box body away from the end plate along the first direction is relatively small and is far away from the connection between the end plate and the side plate. Therefore, all second batteries are clamped between the first batteries spaced apart along the first direction. All second batteries are arranged as close as possible to the area of ​​the box body away from the end plate along the first direction. This can improve the cycle stability of the battery pack while reducing the risk of deformation of the box body due to force.

[0017] In some embodiments, in the battery unit, the second batteries and the first batteries are alternately arranged along the first direction.

[0018] In this embodiment, the first batteries and the second batteries are relatively evenly distributed in the first direction, further avoiding stress concentration caused by the proximity of the two second batteries.

[0019] In some embodiments, in the battery unit, at least one battery located at the center along the first direction is a first battery.

[0020] In this embodiment, stress concentration at the center of the battery cell along the first direction is avoided.

[0021] In some embodiments, the first battery includes a first housing and a compression member, the first electrode assembly and the compression member are both located in the first housing, and the compression member is provided on at least one side of the first electrode assembly in the first direction.

[0022] In this embodiment, on the one hand, the compression member not only restrains the first electrode assembly, reducing or even eliminating the probability of the first electrode assembly swaying within the first housing, but also prevents the compression member from detaching from the first battery during use, reducing the risk of the compression member shifting or misaligning. On the other hand, the compression member can, to a certain extent, limit the deformation of the first electrode assembly when the first battery is charging, improve the uniformity of the force distribution on the first electrode assembly, reduce the risk of wrinkles on the first negative electrode sheet of the first electrode assembly, and extend the life of the first electrode assembly, thereby extending the life of the first battery. During the use of the first battery, that is, during the cycle, if the first electrode assembly expands, the compression member is squeezed by the first electrode assembly and compressively deformed, providing space for the expansion of the first electrode assembly, reducing the force between the first housing and the first electrode assembly, and improving the cycle performance of the first electrode assembly.

[0023] In some embodiments, a compression member is provided at the center of the first housing along the first direction.

[0024] In this embodiment, the compression member is disposed at the center of the first housing along the first direction, which can effectively reduce the force applied to the center of the first housing.

[0025] In some embodiments, an equal number of first electrode assemblies are respectively disposed on both sides of the central compression member along the first direction.

[0026] In this embodiment, the compression member located at the center can be more evenly stressed, thereby avoiding uneven stress at the center of the first housing causing wrinkles in the first electrode assembly and deteriorating the performance of the first battery.

[0027] In some embodiments, at least two compression members are spaced apart along the first direction, and a first electrode assembly is disposed between two adjacent compression members.

[0028] In this embodiment, on the one hand, the multiple first electrode assemblies can improve energy density. The relatively even distribution of the multiple compression members and the multiple first electrode assemblies within the first housing can evenly distribute the forces acting on the first housing, avoid stress concentration, and more effectively alleviate the forces acting on the first housing and improve compression uniformity. On the other hand, a first electrode assembly is disposed between two adjacent compression members, so that the two sidewalls of the first housing along the first direction contact the compression members rather than the first electrode assemblies, thereby reducing the forces acting between the two sidewalls of the first housing along the first direction and the first electrode assemblies, and reducing the forces acting on the ends of the first housing along the first direction.

[0029] In some embodiments, in the first battery, the sum of the total compression of all compression members and the total interlayer spacing of all first electrode assemblies is not less than the total expansion of all deposited layers, wherein the compression of a single compression member is the product of the initial thickness of the compression member and the compression rate, and the total expansion of the deposited layer is the product of the total thickness of all deposited layers and the rebound coefficient of the deposited layer.

[0030] In this embodiment, sufficient space can be provided for the deposition layer, and the first housing of the first battery is unlikely to expand.

[0031] In some embodiments, the material of the compression element includes at least one of polyethylene, polymethacrylate, polyethylene terephthalate, and polytetrafluoroethylene.

[0032] In this embodiment, the above-mentioned material has stable performance and relatively low cost.

[0033] In some embodiments, the battery pack includes a buffer member located in the box, and the buffer member is provided on at least one side of the second battery along the first direction.

[0034] In this embodiment, since the expansion force of the second battery is greater than that of the first battery, a buffer is provided on at least one side of the second battery. The elastic deformation of the buffer absorbs the expansion force, so that the battery unit as a whole exhibits the characteristic of less expansion or no expansion.

[0035] In some embodiments, the second battery is a lithium-ion battery.

[0036] In this embodiment, the lithium-ion battery has the advantages of long service life, good low-temperature discharge performance, and strong charge retention capability.

[0037] In some embodiments, the material of the deposited layer includes one of lithium metal, sodium metal, potassium metal, zinc metal, and manganese metal.

[0038] In this embodiment, the deposition layer adopts the above-mentioned metal material, which has a higher energy storage density.

[0039] A second aspect of an embodiment of the present disclosure provides an electrical device comprising any one of the above-mentioned battery packs for providing electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic structural diagram of a first type of battery unit in one embodiment of the present disclosure;

[0041] FIG2 is a schematic structural diagram of a second battery unit in an embodiment of the present disclosure;

[0042] FIG3 is a schematic structural diagram of a third battery unit in an embodiment of the present disclosure;

[0043] FIG4 is a schematic structural diagram of a fourth battery unit in an embodiment of the present disclosure;

[0044] FIG5 is a schematic structural diagram of a fifth battery unit in an embodiment of the present disclosure;

[0045] FIG6 is a schematic structural diagram of a vehicle in an embodiment of the present disclosure.

[0046] DESCRIPTION OF REFERENCE NUMERALS Battery unit 1 ; Battery 11 ; First battery 11 a ; Second battery 11 b ; Battery pack 11 bb ; Buffer 2 ; Vehicle 1000 ; Battery pack 100 ; Controller 200 ; Motor 300 . DETAILED DESCRIPTION

[0047] The following embodiments of the technical solution of the present disclosure are described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present disclosure and are therefore only examples and are not intended to limit the scope of protection of the present disclosure.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this disclosure.

[0049] In the description of the embodiments of the present disclosure, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0050] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0051] It should be noted that, in the present disclosure, at least two includes two and more, and a plurality includes two and more.

[0052] In the related art, all batteries in the box are of the same type. For example, all batteries in the box are lithium-ion batteries. All batteries breathe at basically the same frequency, and the expansion force changes of the batteries are also consistent. In particular, they are affected by the expansion characteristics of the active material on the negative electrode sheet of the battery. As the SOC (State of Charge) changes, the battery is prone to sudden changes in expansion force and stress concentration. Taking lithium-ion batteries as an example, the active material used in the negative electrode sheet of the battery in the related art is graphite. Graphite is affected by its own expansion characteristic curve, resulting in obvious accelerated expansion changes (increased slope) in the low / high SOC sections, that is, sudden changes in expansion force and stress concentration in a short period of time. This problem may lead to the inability to release battery stress concentration, and the internal electrode assembly may be over-pressured due to the large expansion force, causing the positive and / or negative electrode sheets to deteriorate in dynamics, resulting in lithium deposition in the middle and performance degradation. In severe cases, it may lead to fatigue damage to the end plate of the box. In extreme cases, the weld of the box may crack, causing the end plate to fly out.

[0053] 1 to 6 , an embodiment of the present disclosure provides a battery pack 100 . The battery pack 100 includes a box and a battery cell 1 disposed in the box.

[0054] The box can protect the battery unit 1 and prevent liquid or other foreign matter from affecting the charging and discharging of the battery 11. For example, the box can be a sealed box, which has more reliable dust and water resistance, so it can be used in scenes with more severe, humid, or even submerged environments.

[0055] Referring to Figures 1 to 5 , a battery unit 1 includes a first battery 11a and a second battery 11b, which are stacked along a first direction. The first battery 11a and the second battery 11b are each a type of battery 11. Referring to Figures 1 to 5 , a battery unit 1 includes at least two batteries 11 stacked along a first direction, at least one of which is the first battery 11a, and at least one of which is the second battery 11b.

[0056] For example, in one embodiment, the battery unit 1 includes two batteries 11, one of which may be a first battery 11a and the other a second battery 11b. In another embodiment, the battery unit 1 includes three batteries 11, one of which may be a first battery 11a and the other two may be second batteries 11b. In yet another embodiment, the battery unit 1 includes three batteries 11, two of which may be first batteries 11a and the other may be second batteries 11b.

[0057] At least two batteries 11 in the battery unit 1 are stacked along the first direction, which means that the major surface of each battery 11 intersects the first direction and the major surfaces of each battery 11 are substantially parallel. For example, the major surfaces of each battery 11 in the battery unit 1 are perpendicular to the first direction.

[0058] The first battery 11a includes a first electrode assembly having a first negative electrode sheet, which includes a first negative electrode current collector. After charging the first battery 11a, a deposited layer forms on at least one surface of the first negative electrode current collector. The first electrode assembly serves as the energy storage structure of the first battery 11a. Exemplarily, before the first charge or discharge, the first negative electrode current collector is substantially free of the deposited layer. The first battery 11a is generally referred to as a negative electrode-free battery.

[0059] Exemplarily, the first negative electrode current collector has two opposing surfaces along its thickness direction. After charging, the deposited layer is formed on either or both of the two opposing surfaces of the first negative electrode current collector. In one embodiment, the deposited layer forms one surface of the first negative electrode current collector. In another embodiment, the deposited layer forms both surfaces of the first negative electrode current collector.

[0060] For example, during charging of the first battery 11a, the first active ions of the first battery 11a combine with electrons on the surface of the first negative electrode current collector, depositing to form a deposition layer. Because the first negative electrode sheet is free of negative active material before charging, the mass of the first negative electrode sheet is reduced, thereby increasing the energy density of the first battery 11a.

[0061] The second battery 11b includes a second electrode assembly having a second negative electrode sheet. The second negative electrode sheet includes a second negative electrode current collector and a second negative electrode active material layer. The second negative electrode active material layer is attached to at least one surface of the second negative electrode current collector. The second electrode assembly is the energy storage structure of the second battery 11b.

[0062] Illustratively, the second negative electrode current collector has two opposing surfaces along its thickness direction, and the second negative electrode active material layer is disposed on either or both of the two opposing surfaces of the second negative electrode current collector. In one embodiment, the second negative electrode active material layer is attached to one surface of the second negative electrode current collector. In another embodiment, the second negative electrode active material layer is attached to both surfaces of the second negative electrode current collector.

[0063] The battery pack 100 provided in the embodiment of the present disclosure, on the one hand, has substantially no active material on the surface of the first negative electrode sheet before the first charge and discharge, compared to the second battery 11b, thereby improving the safety of the battery 11 during production and assembly. On the other hand, the battery cell 1 includes different types of first and second batteries 11a, 11b. The energy density of the first battery 11a is higher than that of the second battery 11b, while the cycle stability of the second battery 11b is higher than that of the first battery 11a. Compared to battery cells 1 that utilize only first batteries 11a or only second batteries 11b, a mixture of first and second batteries 11a and 11b stacked along a first direction can retain the relatively high energy density of the first battery 11a and the relatively good cycle stability of the second battery 11b, thereby ensuring the energy density of the battery pack 100 while also taking into account the cycle stability of the battery pack 100. On the other hand, since the first battery 11a and the second battery 11b are of different types, that is, the chemical systems of the first battery 11a and the second battery 11b are different, under the condition of the same gram capacity, the absolute change in the volume of the first battery 11a is smaller than the absolute change in the volume of the second battery 11b, and the deposited layer formed after charging and discharging is soft and has a certain shaping effect and self-adjustment ability. The first battery 11a and the second battery 11b in the battery unit 1 are stacked along the first direction. The first battery 11a and the second battery 11b have different frequencies when expansion occurs. By utilizing the characteristic that the expansion change of the first battery 11a is smaller than that of the second battery 11b, the expansion amount of the battery unit 1 in the first direction is reduced, the squeezing of the box by the battery unit 1 is reduced or even eliminated, and the probability of deformation of the box is reduced, thereby improving the service life of the battery pack 100.

[0064] The battery 11 may be a secondary battery, that is, both the first battery 11a and the second battery 11b may be secondary batteries. A secondary battery is a battery that can be recharged to activate the active material after discharge and continue to be used.

[0065] For example, at least two batteries 11 in the battery pack 100 may be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to the at least two batteries 11 being connected both in series and in parallel. At least two batteries 11 may be directly connected in series, in parallel, or in a hybrid configuration. Alternatively, at least two batteries 11 may be first connected in series, in parallel, or in a hybrid configuration to form a battery module 11, and then at least two battery modules 11 may be connected in series, in parallel, or in a hybrid configuration to form a complete battery module.

[0066] The battery pack 100 may further include other structures. For example, the battery pack 100 may further include a busbar component for achieving electrical connection between at least two batteries 11 .

[0067] In some embodiments, the box includes a box lid, two end panels, two side panels, and a bottom panel. The two end panels are spaced apart along a first direction, and the two side panels are spaced apart along a second direction. The two end panels and the two side panels are connected to define a hollow structure that is open in both top and bottom directions. The box lid closes the top opening of the hollow structure, and the bottom panel closes the bottom opening of the hollow structure to form a closed cavity. The first direction, the second direction, and the top and bottom directions may be perpendicular to each other. In other words, the box has a hexahedral structure, for example, a rectangular parallelepiped.

[0068] In some embodiments, the first battery 11a includes one first electrode assembly. In other embodiments, the first battery 11a includes at least two first electrode assemblies, and the at least two first electrode assemblies are stacked along the first direction.

[0069] In one embodiment, the first battery 11a includes a first housing and a first electrolyte, wherein the first electrolyte and the first electrode assembly are both located within the first housing. The first electrode assembly includes a first positive electrode sheet and a first separator, wherein the first separator is disposed between the first positive electrode sheet and the first negative electrode sheet. The first positive electrode sheet includes a first positive electrode current collector and a first positive electrode active material layer, wherein the first positive electrode active material layer is attached to at least one surface of the first positive electrode current collector. The first active ions in the first electrolyte migrate between the first positive electrode active material layer and the deposition layer to achieve charge and discharge. The first separator is disposed between the first positive electrode sheet and the first negative electrode sheet to prevent short circuits while allowing the first active ions to pass through.

[0070] In one embodiment, the first electrode sheet is provided with a first positive electrode tab, and the first negative electrode sheet is provided with a first negative electrode tab. The first positive electrode tab and the first negative electrode tab can lead current out of the first electrode assembly.

[0071] In some embodiments, the first electrode assembly is a wound structure. Exemplarily, the first positive electrode sheet, the first negative electrode sheet, and the first separator are wound into a wound structure.

[0072] In some embodiments, the first electrode assembly is a laminate structure.

[0073] Exemplarily, there are at least two first positive electrode sheets, first negative electrode sheets and first separators, multiple first positive electrode sheets and multiple first negative electrode sheets are alternately stacked, and a first separator is arranged between adjacent first positive electrode sheets and first negative electrode sheets to form a laminate structure.

[0074] Illustratively, a plurality of first positive electrode sheets may be provided, and the first negative electrode sheet is folded to form a plurality of stacked folded segments, with a first positive electrode sheet being sandwiched between adjacent folded segments to form a laminated structure.

[0075] Illustratively, the first positive electrode sheet and the first negative electrode sheet are both folded to form a plurality of stacked folded segments, which are alternately nested with each other to form a laminate structure.

[0076] In some embodiments, the second battery 11b includes one second electrode assembly. In other embodiments, the second battery 11b includes at least two second electrode assemblies, and the at least two second electrode assemblies are stacked along the first direction.

[0077] In one embodiment, the second battery 11b includes a second outer shell and a second electrolyte, wherein the second electrolyte and the second electrode assembly are both located within the second outer shell. The second electrode assembly includes a second positive electrode sheet and a second separator, wherein the second separator is disposed between the second positive electrode sheet and the second negative electrode sheet. The second positive electrode sheet includes a second positive electrode current collector and a second positive electrode active material layer, wherein the second positive electrode active material layer is attached to at least one surface of the second positive electrode current collector. The second active ions in the second electrolyte migrate between the second positive electrode active material layer and the second negative electrode active material layer to achieve charge and discharge. The second separator is disposed between the second positive electrode sheet and the second negative electrode sheet to prevent short circuits while allowing the second active ions to pass through.

[0078] In one embodiment, the second electrode sheet is provided with a second positive electrode tab, and the second negative electrode sheet is provided with a second negative electrode tab. The second positive electrode tab and the second negative electrode tab can lead current out of the second electrode assembly.

[0079] In some embodiments, the second electrode assembly is a wound structure. Exemplarily, the second positive electrode sheet, the second negative electrode sheet, and the second separator are wound into a wound structure.

[0080] In some embodiments, the second electrode assembly is a laminate structure.

[0081] Exemplarily, there are at least two second positive electrode sheets, second negative electrode sheets, and second separators, multiple second positive electrode sheets and multiple second negative electrode sheets are alternately stacked, and a second separator is set between adjacent second positive electrode sheets and second negative electrode sheets to form a laminate structure.

[0082] Illustratively, a plurality of second positive electrode sheets may be provided, and the second negative electrode sheet may be folded to form a plurality of stacked folded segments, with a second positive electrode sheet being sandwiched between adjacent folded segments to form a laminate structure.

[0083] Illustratively, the second positive electrode sheet and the second negative electrode sheet are both folded to form a plurality of stacked folded segments, which are alternately nested with each other to form a laminate structure.

[0084] The first housing is a hollow structure, and a cavity is formed inside the first housing for accommodating the first electrode assembly and the first electrolyte. The first housing can be in various shapes, such as a rectangular parallelepiped.

[0085] The second housing is a hollow structure, and a space is formed inside the second housing for accommodating the second electrode assembly and the second electrolyte. The second housing can be in various shapes, such as a rectangular parallelepiped.

[0086] In some embodiments, the first shell may be a hard structure. For example, the first shell may be made of hard materials such as aluminum and / or steel.

[0087] In some embodiments, the second housing may be a hard structure. For example, the first housing may be made of a hard material such as aluminum and / or steel.

[0088] In some embodiments, both the first and second positive electrode current collectors can be metal foil or composite current collectors. Metal foil can be made of aluminum, silver-treated aluminum, or stainless steel. The composite current collector can include a polymer base layer and a metal layer. The metal layer can be made of aluminum, an aluminum alloy, or nickel. The polymer base layer can be made of polypropylene, polyethylene terephthalate, or polyethylene.

[0089] It should be noted that the first positive electrode current collector and the second positive electrode current collector may be made of the same material or different materials.

[0090] In some embodiments, both the first and second negative electrode current collectors can be metal foil or composite current collectors. The metal foil can be made of copper, nickel, or the like. The composite current collector can include a polymer substrate and a metal layer. The metal layer can be made of copper, nickel, or the like. The polymer substrate can be made of polypropylene, polyethylene terephthalate, or polyethylene, or the like.

[0091] It should be noted that the first negative electrode current collector and the second negative electrode current collector may be made of the same material or different materials.

[0092] In one embodiment, the first isolation member may be made of polypropylene or polyethylene.

[0093] In one embodiment, the second isolation member may be made of polypropylene or polyethylene.

[0094] In one embodiment, the second battery 11b is a lithium-ion battery. That is, the second battery 11b is charged and discharged through the migration of lithium ions. In other words, the second active ions are lithium ions. Lithium-ion batteries have advantages such as long service life, good low-temperature discharge performance (for example, they can still operate normally at an ambient temperature of -20°C), and strong charge retention.

[0095] In one embodiment, the second negative electrode active material layer may be made of carbon or silicon. For example, the second negative electrode active material layer may be made of graphite.

[0096] In one embodiment, the material of the second positive electrode active material layer may be lithium cobalt oxide, lithium-containing phosphate, lithium manganese oxide, etc. The lithium-containing phosphate may include but is not limited to lithium iron phosphate, a composite material of lithium iron phosphate and carbon, or lithium manganese phosphate, etc.

[0097] The deposited layer can be a metal deposited layer. In one embodiment, the deposited layer comprises a material selected from the group consisting of lithium metal, sodium metal, potassium metal, zinc metal, and manganese metal. Using the aforementioned metal materials in the deposited layer provides a higher energy storage density.

[0098] Referring to Figures 1 to 5 , in one embodiment, the battery pack 100 includes a buffer member 2 positioned within the housing. The buffer member 2 is disposed on at least one side of the second battery cell 11b along a first direction. Because the second battery cell 11b experiences a greater expansion force than the first battery cell 11a, the buffer member 2 is disposed on at least one side of the second battery cell 11b. The elastic deformation of the buffer member 2 absorbs the expansion force, resulting in minimal or no expansion of the battery cell 1 as a whole.

[0099] The buffer member 2 is capable of elastic deformation and can be made of a flexible material. Exemplarily, the material of the buffer member 2 includes at least one of polyethylene, polymethacrylate, polyethylene terephthalate, and polytetrafluoroethylene. These materials have stable performance, are relatively low in cost, and can effectively absorb the expansion force of the second battery 11b.

[0100] In one embodiment, the buffer member 2 may be a flat plate structure. The flat plate structure of the buffer member 2 is easy to shape and can improve the uniformity of the force distribution of the second battery 11b.

[0101] Mechanical simulation of a battery pack in related art revealed that the end of the box along the first direction in which multiple batteries are stacked is subjected to more severe force.

[0102] In one embodiment, referring to Figures 1 to 5, at least one of at least one end of the battery cell 1 along the first direction is a first battery 11a. For example, at least one battery 11 at one end of the battery cell 1 along the first direction is a first battery 11a. For another example, at least one battery 11 at both ends of the battery cell 1 along the first direction is a first battery 11a. Since the absolute value change in the volume of the first battery 11a is smaller than the absolute value change in the volume of the second battery 11b, by arranging the first battery 11a at the end of the battery cell 1, the squeezing of the end plate of the box along the first direction is reduced, thereby reducing the force on the end of the box along the first direction, avoiding fatigue damage to the end plate of the box to a certain extent, and solving the problem of cracking at the weld of the box causing the end plate to fly out in extreme cases.

[0103] In one embodiment, referring to Figures 2, 4 and 5, one battery 11 at both ends of the battery unit 1 along the first direction is a first battery 11a. In other words, there is one first battery 11a at each end of the battery unit 1 along the first direction.

[0104] In one embodiment, referring to Figure 1 , the two batteries 11 at the two ends of the battery unit 1 along the first direction are first batteries 11a. That is, there are two first batteries 11a at each end of the battery unit 1 along the first direction. It is understood that three or even more first batteries 11a may be provided at each end of the battery unit 1 along the first direction. This further reduces stress concentration in the area surrounding the end plates of the box.

[0105] In one embodiment, referring to Figures 1 and 2, in the battery cell 1, all second batteries 11b are sequentially arranged along the first direction to form a battery pack 11bb, and at least one first battery 11a is respectively provided at both ends of the battery pack 11bb along the first direction. That is, in the battery cell 1, all second batteries 11b are sandwiched between the first batteries 11a spaced apart along the first direction. The area of ​​the case away from the end plates along the first direction is less stressed and away from the connection between the end plates and the side plates. Therefore, all second batteries 11b are sandwiched between the first batteries 11a spaced apart along the first direction. By arranging all second batteries 11b as far as possible in the area of ​​the case away from the end plates along the first direction, the cycle stability of the battery pack 100 can be improved while reducing the risk of deformation of the case under stress.

[0106] In one embodiment, referring to Figure 3 , in the battery cell 1, the second cells 11b and the first cells 11a are arranged alternately along the first direction. That is, one second cell 11b is provided between two adjacent first cells 11a in the first direction. This design ensures a relatively even distribution of the first and second cells 11a, 11b, along the first direction, further reducing stress concentration caused by the proximity of two second cells 11b.

[0107] In one embodiment, in the battery cell 1, the second cells 11b and the first cells 11a are arranged alternately along the first direction, with both ends of the battery cell 1 along the first direction being first cells 11a. That is, the first and last cells in the first direction are both first cells 11a, while the remaining first cells 11a and second cells 11b between the first and last two first cells 11a are arranged alternately. This design avoids stress concentration caused by the proximity of the two second cells 11b and reduces stress on the end plates.

[0108] 4 and 5 , in one embodiment, at least one of the battery cells 1 at the center along the first direction is a first battery cell 11 a . This design avoids stress concentration at the center of the battery cell 1 along the first direction.

[0109] It should be noted that the center of the battery unit 1 along the first direction refers to the center point of the projection pattern of the battery unit 1 along the first direction with the plane perpendicular to the top and bottom directions as the projection plane.

[0110] In one embodiment, referring to FIG4 , in a battery cell 1, the four batteries 11 at the center along a first direction are first batteries 11a, and the batteries 11 at both ends of the battery cell 1 along the first direction are also first batteries 11a. In other words, both the beginning and the end of the battery cell 1 along the first direction are first batteries 11a. This prevents stress concentration at the center of the battery cell 1 along the first direction and reduces excessive expansion forces at the ends of the first direction.

[0111] In one embodiment, referring to FIG5 , in a battery cell 1, the battery cell 11 at the center along a first direction is a first battery cell 11a, and the battery cells 11 at both ends of the battery cell 1 along the first direction are both first batteries 11a. In other words, both the beginning and the end of the battery cell 1 along the first direction are first batteries 11a. This prevents stress concentration at the center of the battery cell 1 along the first direction and reduces excessive expansion forces at the ends of the first direction.

[0112] In one embodiment, the first battery 11a includes a first housing and a compression member. The first electrode assembly and the compression member are both located within the first housing. The compression member is disposed on at least one side of the first electrode assembly in the first direction. That is, at least a portion of the compression member overlaps with the first electrode assembly in the first direction. For example, the compression member may be disposed on one side of the first electrode assembly in the first direction. In another example, the compression member may be disposed on both sides of the first electrode assembly in the first direction.

[0113] The expansion of the first battery 11a is mainly the expansion of the first electrode assembly during the charging process. The compression member can undergo elastic deformation and can be compressed when squeezed by the first electrode assembly to provide space for the expansion of the first electrode assembly.

[0114] In this embodiment, on the one hand, the compression member can not only restrain the first electrode assembly, reducing or even eliminating the probability of the first electrode assembly shaking within the first housing, but also prevent the compression member from detaching from the first battery 11a during use, reducing the risk of the compression member shifting and misaligning. On the other hand, the compression member can, to a certain extent, limit the deformation of the first electrode assembly when the first battery 11a is charging, improve the uniformity of the force distribution of the first electrode assembly, reduce the risk of wrinkles on the first negative electrode sheet of the first electrode assembly, and extend the life of the first electrode assembly, thereby extending the life of the first battery 11a. During the use of the first battery 11a, that is, during the cycle, if the first electrode assembly expands, the compression member is squeezed by the first electrode assembly and compressively deformed to provide space for the expansion of the first electrode assembly, reduce the force between the first housing and the first electrode assembly, and improve the cycle performance of the first electrode assembly.

[0115] A mechanical simulation analysis was performed on the battery housing in the related art, and it was found that the housing in the related art is subjected to greater forces at the ends and the center along the first direction.

[0116] In response to the situation in the related art where the center of the housing along the first direction is subjected to greater force, in one embodiment, a compression member is provided at the center of the first housing along the first direction. The compression member is provided at the center of the first housing along the first direction, which can effectively reduce the force applied to the center of the first housing.

[0117] It should be noted that the center of the first housing along the first direction refers to the center point of the projection pattern of the first housing along the first direction, with the plane perpendicular to the top and bottom directions as the projection plane. A compression member is provided at the center of the first housing along the first direction means that the center point of the projection pattern of the first housing along the first direction is located within the projection pattern of the compression member.

[0118] In one embodiment, an equal number of first electrode assemblies are disposed on either side of the central compression member along the first direction. In other words, an even number of first electrode assemblies are evenly distributed on either side of the central compression member along the first direction. This design allows for more uniform force distribution on the central compression member, preventing uneven force distribution at the center of the first housing, which could cause wrinkles in the first electrode assembly and deteriorate the performance of the first battery 11a.

[0119] For example, in one embodiment, there are two first electrode assemblies and one compression member, one compression member is located at the center of the first housing along the first direction, and one first electrode assembly is provided on each side of the compression member along the first direction. It is understood that in other embodiments, two or more first electrode assemblies may be provided on either side of the centrally located compression member.

[0120] In one embodiment, at least two compression members are spaced apart along the first direction, and a first electrode assembly is provided between two adjacent compression members. In this way, each first electrode assembly is provided with a compression member on both sides along the first direction. On the one hand, multiple first electrode assemblies can improve energy density, and multiple compression members and multiple first electrode assemblies are relatively evenly distributed within the first shell, which can balance the force on the first shell and avoid stress concentration, and can more effectively alleviate the force inside the first shell and the compression uniformity. On the other hand, a first electrode assembly is provided between two adjacent compression members, so that the two side walls of the first shell along the first direction contact the compression member instead of the first electrode assembly, so as to reduce the force between the two side walls of the first shell along the first direction and the first electrode assembly, and reduce the force on the end of the first shell along the first direction.

[0121] For example, in one embodiment, there are two first electrode assemblies and three compression members. The three compression members are spaced apart along the first direction, with one first electrode assembly positioned between two adjacent compression members. The middle compression member is located at the center of the first housing along the first direction. In other words, the three compression members sandwich the two first electrode assemblies, with the middle compression member located at the center of the first housing along the first direction. This effectively avoids the problem of greater forces at the ends and center of the first housing along the first direction, ensuring a balanced force distribution across the first housing.

[0122] In some embodiments, the thickness of each compression member is equal.

[0123] In some embodiments, at least two compression members have unequal thicknesses. For example, there are three compression members, two of which have equal thicknesses and unequal thicknesses to another compression member. For example, the compression member located at the center of the first housing along the first direction has a thickness of 2 mm, while the other two compression members each have a thickness of 1 mm.

[0124] In one embodiment, in the first battery 11a, the sum of the total compression of all compression elements and the total interlayer spacing of all first electrode assemblies is no less than the total expansion of all deposited layers. The compression of a single compression element is the product of its initial thickness and its compression ratio, while the total expansion of the deposited layers is the product of the total thickness of all deposited layers and their coefficient of rebound. This design provides ample space for the deposited layers, ensuring that the first housing of the first battery 11a is virtually non-expanding.

[0125] It should be noted that the initial thickness of the compressed part refers to the thickness of the compressed part in the uncompressed state. The compression ratio is the rate of change of the compressed part when it is squeezed by the corresponding surface at 100% SOC.

[0126] It is understood that the total compression of all compression components is the sum of the compression of all compression components in a single first cell 11a. The total interlayer spacing of all first electrode assemblies is the sum of all interlayer spacings in a single first cell 11a. The total expansion of all deposited layers is the sum of the expansion of all deposited layers in a single first cell 11a.

[0127] In this embodiment, the total compression of all compression members is Q, the total interlayer spacing of all first electrode assemblies is W, the total expansion of all deposited layers is E, the thickness of a single deposited layer is H, the number of deposited layers is m, the rebound coefficient of the deposited layer is K, the initial thickness of a single compression member is L, and the compression rate is Y%.

[0128] Therefore, in the first cell 11a, the sum of the total compression of all compression members and the total interlayer spacing of all first electrode assemblies is not less than the total expansion of all deposited layers, which can be expressed as follows:

[0129] Q+W≥E;

[0130] Wherein, Q=L1*Y1%+L2*Y2%…+Lj*Yj%, Lj represents the initial thickness of the j-th compressed part, and Yj% represents the compression ratio of the j-th compressed part;

[0131] Where, E = K*H*m;

[0132] If the interlayer spacing h of all first electrode assemblies is equal, and the number of interlayer spacings of all first electrode assemblies is n, then W=h*n.

[0133] It should be noted that the interlayer spacing of the first electrode assembly refers to the spacing between the various material layers of the first electrode assembly. For example, if the first electrode assembly includes a first positive electrode sheet, a first separator, and a second negative electrode sheet, and the first positive electrode sheet, the first separator, and the second negative electrode sheet are stacked or wound in multiple layers to form the first electrode assembly, then the interlayer spacing of the first electrode assembly is the spacing between the aforementioned layers.

[0134] The coefficient of rebound K is the ratio of the elastic deformation degree of the material after a slow impact to the elastic deformation degree before the impact. For example, at -50°C (Celsius) to 55°C, the coefficient of rebound K of the metal deposit layer can be 0.8 to 1.45.

[0135] The thickness H of a single deposited layer is the theoretical thickness. For example, the test method for the thickness H of a single deposited layer can be: after determining what metal the deposited layer is, the theoretical volume specific capacity R corresponding to the metal can be found, and the first positive electrode is assembled with a half-cell of the metal, and a 0.1C charge-discharge test cycle is performed by applying a voltage curve to obtain a 1cm 2 (square centimeters) The charge capacity S corresponding to the single-sided area of ​​the first positive electrode sheet, then the thickness of a single deposited layer H = S / R. Taking the deposited layer as an example, the theoretical volumetric capacity R corresponding to sodium metal is 1131 mAh / cm 3 (milliampere-hours per cubic centimeter), the first positive electrode is assembled with a sodium metal half-cell, and the 0.1C charge-discharge test cycle is performed by applying a voltage curve to obtain 1cm 2 The charge capacity of the first positive electrode sheet on a single surface area is S = 2.597 mAh / cm 2 (milliampere*hours per square centimeter), the thickness of a single deposited layer is H=S / R*10 (10 is used for unit conversion), H=0.023 mm (millimeter).

[0136] The number of deposited layers, m, is the total number of deposited layers across all first negative electrode sheets in a single first battery 11a. For example, if a single first battery 11a has one first negative electrode sheet, and one surface of the first negative electrode current collector has a deposited layer, then m = 1; if both surfaces of the first negative electrode current collector have deposited layers, then m = 2. For example, if a single first battery 11a has two first negative electrode sheets, and one surface of the first negative electrode current collector has a deposited layer, then m = 2; if both surfaces of the first negative electrode current collector have deposited layers, then m = 4.

[0137] The compression member is capable of elastically deforming under the action of the first electrode assembly. In some embodiments, the compression member is made of at least one of polyethylene, polymethacrylate, polyethylene terephthalate, and polytetrafluoroethylene. These materials have stable performance and relatively low cost.

[0138] In one embodiment, the compression member may be a flat plate structure, which is easy to shape and can improve the uniformity of force distribution on the first electrode assembly when the first electrode assembly expands.

[0139] In some embodiments, the battery pack 100 includes one battery cell 1 .

[0140] In some embodiments, the battery pack 100 includes at least two battery cells 1; the at least two battery cells 1 may be stacked in a top-to-bottom direction. Alternatively, the at least two battery cells 1 may be laid out in a second direction. Alternatively, multiple battery cells 1 may be laid out in a layer in the second direction, with multiple layers of battery cells 1 stacked in a top-to-bottom direction.

[0141] Referring to FIG. 6 , an embodiment of the present disclosure provides an electrical device including a battery pack 100 according to any one of the embodiments of the present disclosure for providing electrical energy.

[0142] Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery-powered vehicles, electric cars, ships, or spacecraft. Electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, while spacecraft may include airplanes, rockets, space shuttles, and spacecraft.

[0143] In the following embodiments, for the convenience of description, a vehicle is used as an example of an electrical device according to an embodiment of the present disclosure.

[0144] Figure 6 is a schematic structural diagram of a vehicle provided in some embodiments of the present disclosure. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. As shown in Figure 6, a battery pack 100 is provided inside the vehicle. The battery pack 100 may be provided at the bottom of the vehicle or at the front or rear of the vehicle. The battery pack 100 may be used to power the vehicle. For example, the battery pack 100 may serve as an operating power source for the vehicle. The vehicle may further include a controller 200 and a motor 300. The controller 200 is used to control the battery pack 100 to power the motor 300, for example, for starting, navigating and operating power requirements of the vehicle during driving.

[0145] In some embodiments of the present disclosure, the battery pack 100 can serve not only as the operating power source of the vehicle, but also as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0146] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present disclosure. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way.

Claims

1. A battery pack, comprising a housing and a battery unit disposed within the housing, wherein the battery unit comprises a first battery and a second battery, wherein the first battery and the second battery are stacked along a first direction; The first battery includes a first electrode assembly having a first negative electrode sheet, wherein the first negative electrode sheet includes a first negative electrode collector, wherein: After the first battery is charged, a deposition layer is formed on at least one surface of the first negative electrode current collector; The second battery includes a second electrode assembly having a second negative electrode sheet. The second negative electrode sheet includes a second negative electrode collector and a second negative electrode active material layer. The second negative electrode active material layer is attached to at least one surface of the second negative electrode collector.

2. The battery pack according to claim 1, wherein: At least one end of the battery unit along the first direction is the first battery.

3. The battery pack according to claim 1, wherein: In the battery unit, all the second batteries are sequentially arranged along a first direction to form a battery pack, and at least one of the first batteries is respectively arranged at both ends of the battery pack along the first direction.

4. The battery pack according to claim 1, wherein: In the battery unit, the second batteries and the first batteries are alternately arranged along a first direction.

5. The battery pack according to claim 1, wherein: Among the battery cells, at least one at the center along the first direction is the first battery.

6. The battery pack according to any one of claims 1 to 5, wherein: The first battery includes a first housing and a compression member. The first electrode assembly and the compression member are both located in the first housing. The compression member is provided on at least one side of the first electrode assembly in a first direction.

7. The battery pack according to claim 6, wherein: A compression member is provided at the center of the first housing along the first direction.

8. The battery pack according to claim 7, wherein: An equal number of first electrode assemblies are respectively provided on both sides of the compression member located at the center along the first direction.

9. The battery pack according to claim 6, wherein: At least two compression members are spaced apart along the first direction, and one first electrode assembly is disposed between two adjacent compression members.

10. The battery pack according to claim 6, wherein: In the first battery, the sum of the total compression of all the compression members and the total interlayer spacing of all the first electrode assemblies is not less than the total expansion of all the deposited layers, wherein the compression of a single compression member is the product of the initial thickness of the compression member and the compression rate, and the total expansion of the deposited layer is the product of the total thickness of all the deposited layers and the rebound coefficient of the deposited layer.

11. The battery pack according to claim 6, wherein: The material of the compression member includes at least one of polyethylene, polymethacrylate, polyethylene terephthalate and polytetrafluoroethylene.

12. The battery pack according to any one of claims 1 to 11, wherein: The battery pack includes a buffer member located in the box body, and the buffer member is provided on at least one side of the second battery along the first direction.

13. The battery pack according to claim 12, wherein: The material of the buffer member includes at least one of polyethylene, polymethacrylate, polyethylene terephthalate and polytetrafluoroethylene.

14. The battery pack according to claim 12, wherein: The buffer component is in a flat plate structure.

15. The battery pack according to any one of claims 1 to 14, wherein: The second battery is a lithium-ion battery.

16. The battery pack according to any one of claims 1 to 15, wherein: The material of the deposition layer includes one of lithium metal, sodium metal, potassium metal, zinc metal and manganese metal.

17. An electrical device comprising the battery pack according to any one of claims 1 to 16 for providing electrical energy.

Images