Pole piece, electrode assembly, battery cell, and battery

Abstract

The application provides an electrode tab, an electrode assembly, a battery monomer and a battery, which can effectively improve the performance of the battery. The electrode tab (20) comprises: an active material layer (31); and a current collector (32), wherein the active material layer (31) is arranged on the surface of the current collector (32), and the current collector (32) comprises a support layer (321), and the tensile strength P of the support layer (321) is between 450 MPa and 1500 MPa.

Description

[0001] This application is a divisional application of the invention application with the application date of September 19, 2022, the Chinese application number of 202211137881.2, and the invention name of "pole piece, electrode assembly, battery cell and battery". TECHNICAL FIELD

[0002] The application relates to the technical field of batteries, in particular to a pole piece, an electrode assembly, a battery cell and a battery. BACKGROUND

[0003] Energy saving and emission reduction is the key to the sustainable development of the automobile industry. In this case, electric vehicles have become an important part of the sustainable development of the automobile industry due to their energy-saving and environmentally friendly advantages. For electric vehicles, battery technology is an important factor in their development.

[0004] In the development of battery technology, the performance of the battery is a problem that cannot be ignored. The performance of the battery not only affects the development and application of battery-related products, but also affects the acceptance of electric vehicles by consumers. Therefore, how to improve the performance of the battery is a problem that needs to be solved. SUMMARY

[0005] The application provides a pole piece, an electrode assembly, a battery cell and a battery, which can effectively improve the performance of the battery.

[0006] In a first aspect, a pole piece is provided, comprising: an active material layer; a current collector, the active material layer being arranged on the surface of the current collector, the current collector comprising a support layer, wherein the tensile strength P of the support layer is between 450 MPa and 1500 MPa.

[0007] In the application, the support layer with a tensile strength of 450 MPa-1500 Mpa is arranged in the current collector, the tensile strength of the pole piece is improved, the tensile ductility of the current collector or the pole piece is avoided in the case of expansion of the active material layer, and the problems of deformation, delamination and fracture are avoided, thereby effectively improving the performance of the battery including the pole piece.

[0008] In some possible implementation manners, the material of the support layer comprises at least one of a nickel foil, a stainless steel foil and an alloy foil.

[0009] Since the tensile strength of the nickel foil, the stainless steel foil and the alloy foil can reach 1000 MPa or even higher, the technical solution sets the material of the support layer to include at least one of the nickel foil, the stainless steel foil and the alloy foil, which can effectively ensure the tensile strength of the support layer and even the pole piece.

[0010] In some possible implementation manners, the thickness d1 of the support layer is between 4 μm and 15 μm.

[0011] The thickness of the support layer is set to be between 4 and 15 microns, that is, the thickness of the support layer is set to be relatively large, so that the high tensile strength of the support layer can be ensured.

[0012] In some possible implementation manners, the tensile strength P of the support layer (321) and the volume capacity C of the active material layer (31) satisfy: C≤P*d1 / 3, wherein d1 is the thickness of the support layer (321).

[0013] In some possible implementation manners, further comprising: a transition layer, arranged between the support layer and the active material layer, the volume resistivity of the transition layer is smaller than the volume resistivity of the support layer at the same temperature.

[0014] The technical solution can effectively improve the conductivity of the pole piece by arranging the transition layer with smaller volume resistivity between the support layer and the active material layer.

[0015] In some possible implementation manners, the volume resistivity of the support layer is greater than or equal to 4*10 -8 Ω·m, and the volume resistivity of the transition layer is less than 4*10 -8 Ω·m at a temperature of 23°C. In this way, the conductivity of the pole piece can be further improved.

[0016] In some possible implementation manners, the transition layer is obtained by evaporating a copper layer or an aluminum layer on the surface of the support layer.

[0017] The technical solution is that the transition layer is obtained by evaporating a copper layer or an aluminum layer on the surface of the support layer. On the one hand, since the conductivity of copper and aluminum is relatively high, the conductivity of the pole piece can be further improved. On the other hand, compared with other processes, the thickness of the transition layer obtained by the evaporation process is relatively small, so that the volume and weight of the pole piece and even the battery can be reduced. On the other hand, since the cost of aluminum is relatively small and the density is relatively low, not only the production cost of the pole piece and the battery is reduced, but also the energy density of the battery is improved.

[0018] In some possible implementation manners, the transition layer is obtained by coating a conductive coating on the surface of the support layer.

[0019] The technical solution is that the transition layer is obtained by coating a conductive coating on the surface of the support layer, since the conductivity of the conductive carbon layer is relatively high, the conductivity of the pole piece can be further improved.

[0020] In some possible implementation manners, the thickness of the transition layer is less than the thickness d1 of the support layer.

[0021] The thickness of the transition layer is set to be less than the thickness of the support layer, so that the thickness and volume of the pole piece can be reduced, and the thickness and volume of the battery can be reduced.

[0022] In some possible implementation manners, a ratio between the thickness d1 of the support layer and the thickness of the transition layer is greater than or equal to 2.

[0023] In some possible implementation manners, the thickness of the transition layer is between 0.05 μm and 5 μm.

[0024] Since the thickness of the transition layer can directly affect the energy density of the battery, the thickness of the transition layer is set to be between 0.05 μm and 5 μm, that is, the thickness of the transition layer is small, and the energy density of the battery can be improved.

[0025] In some possible implementation manners, the thickness of the transition layer is 1 μm.

[0026] The thickness of the transition layer is set to be 1 μm, and a balance between the energy density of the battery and the process level of manufacturing the battery can be achieved.

[0027] In some possible implementation manners, the active material layer is a negative electrode active material layer, and a material of the negative electrode active material layer includes at least one of the following materials: silicon, a silicon alloy, silicon oxide, silicon carbon, lithium metal, and a metal oxide, wherein the metal oxide can be alloyed with lithium.

[0028] When the material of the negative electrode active material layer includes the above-mentioned materials, the pole piece has high specific capacity, and the energy density of the battery can be effectively improved.

[0029] In some possible implementation manners, the volume capacity C of the active material layer is between 600 mAh·mm -3 -3000 mAh·mm -3 .

[0030] In a second aspect, an electrode assembly is provided, including: a plurality of the pole pieces in the first aspect or each implementation manner thereof.

[0031] In a third aspect, a battery monomer is provided, including: a shell having a containing cavity with an opening; the electrode assembly in the second aspect is contained in the containing cavity; and a top cover assembly covering the opening to enclose the electrode assembly in the shell.

[0032] In a fourth aspect, a battery is provided, including: a plurality of the battery monomers in the third aspect; and a box body for containing the plurality of battery monomers.

[0033] In a fifth aspect, a power-using device is provided, comprising the battery of the fourth aspect, wherein the battery is configured to provide power for the power-using device. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0035] Figure 1 is a schematic diagram of a vehicle according to an embodiment of the present application.

[0036] Figure 2 is a structural schematic diagram of a battery according to an embodiment of the present application.

[0037] Figure 3 is an exploded view of a battery cell according to an embodiment of the present application.

[0038] Figure 4 is a schematic diagram of a pole piece according to an embodiment of the present application.

[0039] Figure 5 is a schematic diagram of another pole piece according to an embodiment of the present application.

[0040] In the drawings, the drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0041] The embodiments of the present application will be further described in detail below with reference to the drawings and embodiments. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, i.e., the present application is not limited to the described embodiments.

[0042] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like are only for the purpose of facilitating the description of the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third", etc. are only for the purpose of description and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error.

[0043] The positional words appearing in the following description are the directions shown in the drawings, and are not intended to limit the specific structure of the present application. In the description of the present application, it should be further explained that, unless otherwise explicitly defined and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the art to which the present application belongs; the terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application; the terms "including" and "having" in the specification and claims of the present application and their any variants are intended to cover non-exclusive inclusion. The terms "first", "second" and the like in the specification and claims of the present application are used to distinguish different objects, and are not intended to describe a specific order or primary and secondary relationship.

[0045] In the present application, the phrase "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments.

[0046] The technical solutions described in the embodiments of the present application are applicable to various devices using batteries, for example, mobile phones, portable devices, notebook computers, electric vehicles, electric toys, electric tools, electric vehicles, ships and spacecraft, etc., for example, spacecraft includes airplanes, rockets, space shuttles and spaceships, etc.

[0047] It should be understood that the technical solutions described in the embodiments of the present application are not only limited to the above described devices, but also applicable to all devices using batteries, but for the sake of simplicity of description, the following embodiments are described taking electric vehicles as an example.

[0048] For example, as Figure 1The diagram shown is a structural schematic of a vehicle 1 according to one embodiment of this application. Vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 40, a controller 30, and a battery 10 can be installed inside vehicle 1. The controller 30 controls the battery 10 to supply power to the motor 40. For example, the battery 10 can be installed at the bottom, front, or rear of vehicle 1. The battery 10 can be used to power vehicle 1; for example, it can serve as the operating power source for the vehicle 1's electrical system, such as for the power requirements of starting, navigation, and operation. In another embodiment of this application, the battery 10 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0049] The battery 10 mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery 10 mentioned in this application may include a battery module or a battery pack. The battery 10 generally includes a housing for encapsulating one or more battery cells. The housing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0050] To meet different power demands, battery 10 may include multiple battery cells, which can be connected in series, parallel, or a combination of both. Battery 10 can also be called a battery pack. Optionally, multiple battery cells can first be connected in series, parallel, or a combination of both to form a battery module, and then multiple battery modules can be connected in series, parallel, or a combination of both to form battery 10. That is, multiple battery cells can be directly assembled into battery 10, or they can first be assembled into battery modules, and then the battery modules can be assembled into battery 10.

[0051] For example, such as Figure 2 The diagram shown is a structural schematic of a battery 10 according to an embodiment of this application. The battery 10 may include multiple battery cells 20. The battery 10 may also include a housing (or cover), the interior of which is a hollow structure, and the multiple battery cells 10 are housed within the housing. Figure 2As shown, the box can include two parts, here referred to as a first part 111 and a second part 112, which are buckled together. The shapes of the first part 111 and the second part 112 can be determined according to the shape of the combination of the plurality of battery monomers 20, and the first part 111 and the second part 112 can each have an opening. For example, the first part 111 and the second part 112 can each be a hollow cuboid and each have only one face as an opening face, the opening of the first part 111 and the opening of the second part 112 are oppositely arranged, and the first part 111 and the second part 112 are buckled together to form a box with a closed cavity. Among them, the box can include a bottom plate 112a, a side plate 112b and a beam. The plurality of battery monomers 20 are combined in parallel or in series or in a hybrid combination and placed in the box formed after the buckling of the first part 111 and the second part 112.

[0052] Alternatively, the battery 10 can also include other structures, which will not be described one by one here. For example, the battery 10 can also include a current collection component for realizing the electrical connection between the plurality of battery monomers 20, such as parallel connection or series connection or hybrid connection. Specifically, the current collection component can realize the electrical connection between the battery monomers 20 by connecting the electrode terminals of the battery monomers 20. Further, the current collection component can be fixed to the electrode terminals of the battery monomers 20 by welding. The electrical energy of the plurality of battery monomers 20 can be further led out through the box by a conductive mechanism. Alternatively, the conductive mechanism can also belong to the current collection component.

[0053] According to different power requirements, the number of battery monomers 20 can be set to any value. The plurality of battery monomers 20 can be connected in series, in parallel or in a hybrid manner to achieve a larger capacity or power. Since the number of battery monomers 20 included in each battery 10 can be large, in order to facilitate installation, the battery monomers 20 can be arranged in groups, and each group of battery monomers 20 forms a battery module. The number of battery monomers 20 included in the battery module is not limited and can be set according to requirements.

[0054] In the embodiments of the present application, the battery monomer 20 can include a lithium ion secondary battery, a lithium ion primary battery, a lithium-sulfur battery, a sodium lithium ion battery, a sodium ion battery or a magnesium ion battery, etc. The embodiments of the present application are not limited thereto. The battery monomer 20 can be in the shape of a cylinder, a flat body, a cuboid or other shapes, etc. The embodiments of the present application are also not limited thereto. The battery monomer 20 is generally divided into three types according to the packaging method: cylindrical battery monomers, square battery monomers and soft package battery monomers, and the embodiments of the present application are also not limited thereto.

[0055] As Figure 3The diagram shown is a structural schematic of a battery cell 20 according to an embodiment of this application. The battery cell 20 includes one or more electrode assemblies 22, a housing 211, and a cover plate 212. The housing 211 and the cover plate 212 form an outer shell or battery box 21. The walls of the housing 211 and the cover plate 212 are both referred to as the walls of the battery cell 20. The shape of the housing 211 depends on the shape of the assembled one or more electrode assemblies 22. For example, the housing 211 can be a hollow cuboid, cube, or cylinder, and one side of the housing 211 has an opening so that one or more electrode assemblies 22 can be placed inside the housing 211. For example, when the housing 211 is a hollow cuboid or cube, one plane of the housing 211 is an open surface, that is, this plane does not have a wall, allowing the inside and outside of the housing 211 to communicate. When the housing 211 can be a hollow cylinder, the end face of the housing 211 is an open surface, that is, this end face does not have a wall, allowing the inside and outside of the housing 211 to communicate. The cover plate 212 covers the opening and is connected to the housing 211 to form a closed cavity for housing the electrode assembly 22. The housing 211 is filled with an electrolyte, such as an electrolyte solution.

[0056] The battery cell 20 may also include two electrode terminals 214, which can be disposed on a cover plate 212. The cover plate 212 is typically flat, and the two electrode terminals 214 are fixed to the flat surface of the cover plate 212. The two electrode terminals 214 are a positive electrode terminal 214a and a negative electrode terminal 214b, respectively. Each electrode terminal 214 is provided with a corresponding connecting member 23, or a current collector 23, which is located between the cover plate 212 and the electrode assembly 22, and is used to electrically connect the electrode assembly 22 and the electrode terminal 214.

[0057] like Figure 3 As shown, each electrode assembly 22 has a first tab 221a and a second tab 222a. The first tab 221a and the second tab 222a have opposite polarities. For example, when the first tab 221a is a positive tab, the second tab 222a is a negative tab. The first tab 221a of one or more electrode assemblies 22 is connected to an electrode terminal via a connecting member 23, and the second tab 212a of one or more electrode assemblies 22 is connected to another electrode terminal via another connecting member 23. For example, the positive electrode terminal 214a is connected to the positive tab via a connecting member 23, and the negative electrode terminal 214b is connected to the negative tab via another connecting member 23.

[0058] In this battery cell 20, depending on actual usage requirements, the electrode assembly 22 can be configured as a single unit or multiple units, such as... Figure 3 As shown, the battery cell 20 contains four independent electrode assemblies 22.

[0059] The battery cell 20 can also be provided with a pressure relief mechanism 213. The pressure relief mechanism 213 is used to actuate to release the internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a threshold value.

[0060] The pressure relief mechanism 213 can be various possible pressure relief structures, and the embodiments of the present application are not limited thereto. For example, the pressure relief mechanism 213 can be a temperature-sensitive pressure relief mechanism configured to be able to melt when the internal temperature of the battery cell 20 provided with the pressure relief mechanism 213 reaches a threshold value; and / or, the pressure relief mechanism 213 can be a pressure-sensitive pressure relief mechanism configured to be able to rupture when the internal air pressure of the battery cell 20 provided with the pressure relief mechanism 213 reaches a threshold value.

[0061] The electrode assembly 22 is composed of a positive electrode tab, a negative electrode tab, and a separator. The material of the separator can be polypropylene (PP) or polyethylene (PE), etc. The battery cell 20 mainly relies on the movement of metal ions between the positive electrode tab and the negative electrode tab to work. The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector, the current collector without the positive electrode active material layer protrudes from the current collector with the positive electrode active material layer, and the current collector without the positive electrode active material layer serves as the positive electrode tab. The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode current collector, the current collector without the negative electrode active material layer protrudes from the current collector with the negative electrode active material layer, and the current collector without the negative electrode active material layer serves as the negative electrode tab. In order to ensure that no fusing occurs when passing a large current, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together. In addition, the electrode assembly can be a winding type structure or a stacking type structure, and the embodiments of the present application are not limited thereto.

[0062] At present, the energy density of lithium ion batteries using graphite as the negative electrode active material layer material has approached the theoretical limit and it is difficult to further improve. Selecting high-theoretical-capacity negative electrode materials such as silicon, lithium metal, etc. to replace graphite negative electrodes is an effective way to realize high-energy-density batteries. However, such materials have large expansion, which can cause stretching and extension of the current collector or tab, and further cause deformation, delamination, and fracture, etc.

[0063] To solve the above problems, the application provides an electrode sheet, which comprises a current collector, and the current collector comprises a support layer, and the tensile strength of the support layer is 450-1500 MPa. By arranging the support layer with a tensile strength of 450-1500 MPa in the current collector, the tensile strength of the electrode sheet is improved, and the tensile ductility of the current collector or the electrode sheet is avoided in the case of expansion of the active material layer, and the problems of deformation, delamination and fracture are avoided, so that the performance of the battery comprising the electrode sheet can be effectively improved.

[0064] As shown in Figure 4 Fig. 1 is a schematic diagram of an electrode sheet 30 according to an embodiment of the application. The electrode sheet 30 comprises an active material layer 31 and a current collector 32. The active material layer 31 is arranged on the surface of the current collector 32, and the current collector 32 comprises a support layer 321, and the tensile strength P of the support layer 321 is 450-1500 MPa.

[0065] For example, the tensile strength P of the support layer 321 can be 600-1000 MPa, for example, 800 MPa.

[0066] The active material layer 31 can be arranged on one side of the current collector 32, or on both sides of the current collector 32.

[0067] Optionally, the material of the support layer 321 can comprise at least one of a nickel foil, a stainless steel foil and an alloy foil. The stainless steel foil can be, for example, chromium (Cr) or iron (Fe), and the alloy foil can be, for example, a nickel-iron alloy foil.

[0068] Since the tensile strength of the nickel foil, the stainless steel foil and the alloy foil can reach 1000 MPa or even higher, the technical solution of arranging the material of the support layer 321 to comprise at least one of the nickel foil, the stainless steel foil and the alloy foil can effectively ensure the tensile strength of the support layer 321 and even the electrode sheet 30.

[0069] Since the support layer 321 has high tensile strength, if the support layer 321 is too thin, it may not be able to support the tensile strength P of the support layer 321. Therefore, the thickness of the support layer 321 is arranged to be larger in the application.

[0070] In some embodiments, the thickness d1 of the support layer 321 can be 4-15 μm. For example, the thickness d1 of the support layer 321 can be 8 μm, 10 μm or 12 μm, etc.

[0071] The technical solution of arranging the thickness d1 of the support layer 321 to be 4-15 μm, i.e. arranging the thickness d1 of the support layer 321 to be larger, can ensure the high tensile strength of the support layer 321.

[0072] The thickness d1 of the support layer 321 can directly affect the energy density of the battery. In order to improve the energy density of the battery, the thickness d1 of the support layer 321 is preferably as small as possible. However, in this case, on the one hand, the current manufacturing process of the battery may not meet the requirement, and on the other hand, the tensile strength P of the support layer 321 may be affected.

[0073] Therefore, considering various aspects, the thickness d1 of the support layer 321 in the embodiment of the present application can be 6 μm.

[0074] The technical solution sets the thickness d1 of the support layer 321 to 6 μm. On the one hand, the energy density of the battery and the process capability can be balanced, and on the other hand, the tensile strength P of the support layer 321 is not affected.

[0075] Optionally, the volume resistivity of the support layer 321 is not specifically limited in the embodiment of the present application. For example, the volume resistivity of the support layer 321 can be greater than or equal to 4*10-8Ω·m at a temperature of 23℃.

[0076] It should be noted that the temperature 23℃ in the embodiment of the present application is not an absolute 23℃, and 23℃ around, such as 23±2℃, also belongs to the scope of the embodiment of the present application.

[0077] Further, the volume resistivity of the support layer 321 can be greater than or equal to 4*10-8Ω·m at a temperature of 23℃ and a relative humidity of less than or equal to 65%rh. -8 Ω·m.

[0078] Optionally, in the embodiment of the present application, the active material layer 31 can be a positive active material layer. At this time, the current collector 32 is a positive current collector, and the electrode sheet 30 is a positive electrode sheet.

[0079] Alternatively, the active material layer 31 can be a negative active material layer. At this time, the current collector 32 can be a negative current collector, and the electrode sheet 30 is a negative electrode sheet.

[0080] In the case where the active material layer 31 is a negative active material layer, the material of the negative active material layer can include at least one of the following materials: silicon, silicon alloy, silicon oxide, carbon silicon, lithium metal, and metal oxide, wherein the metal oxide can be alloyed with lithium.

[0081] For example, the material of the negative active material layer can include a mixture of graphite and carbon silicon, or a mixture of graphite and lithium metal.

[0082] When the material of the negative active material layer includes the above-mentioned materials, the electrode sheet 30 can have a high specific capacity, thereby effectively improving the energy density of the battery.

[0083] In some embodiments, when the material of the negative active material layer includes the material described above, the volumetric capacity C of the negative active material layer is higher. Optionally, the volumetric capacity C of the active material layer 31 can be between 600 mAh·mm -3 -3000 mAh·mm -3 .

[0084] For example, the volumetric capacity C of the active material layer 31 can be 800 mAh·mm -3 or 1000 mAh·mm -3 or 1500 mAh·mm -3 or 2000 mAh·mm -3 .

[0085] It is found through experiments that the tensile strength P of the support layer 321 can be positively correlated with the volumetric capacity C of the active material layer 31. That is, the greater the tensile strength P of the support layer 321, the greater the volumetric capacity C of the active material layer 31.

[0086] In some embodiments, the tensile strength P of the support layer 321 and the volumetric capacity C of the active material layer 31 can satisfy the following relationship:

[0087] C≤P*d1 / 3

[0088] In addition to the current collector 32 and the active material layer 31, as Figure 5 shown, in the embodiments of the present application, the pole piece 30 can also include a transition layer 33. The transition layer 33 is arranged between the support layer 321 and the active material layer 31, and the volumetric resistivity of the transition layer 33 is smaller than that of the support layer 321 at the same temperature.

[0089] This technical solution can effectively improve the conductivity of the pole piece 30 by arranging the transition layer 33 with a smaller volumetric resistivity between the support layer 321 and the active material layer 31.

[0090] Optionally, the transition layer 33 can belong to the current collector 32, that is, the current collector 32 can include the transition layer 33.

[0091] Optionally, the transition layer 33 can also not belong to the current collector 32.

[0092] Optionally, referring again to Figure 5 , the two sides of the support layer 321 can be provided with the transition layer 33, and the two sides of the plurality of transition layers 33 can also be provided with the active material layer 31.

[0093] Since the transition layer 33 mainly plays a role in improving the conductivity, the volumetric resistivity of the transition layer 33 should be as small as possible.

[0094] Optionally, the volume resistivity of the transition layer 33 can be less than 4*10-8Ω·m. In this way, the conductivity of the pole piece 30 can be further improved.

[0095] For example, at a temperature of 23℃, the volume resistivity of the transition layer 33 can be less than 4*10 -8 Ω·m. Further, at a temperature of 23℃ and a relative humidity of less than 65%rh, the volume resistivity of the transition layer 33 can be less than 4*10 -8 Ω·m.

[0096] In the case where the material of the support layer 321 includes a nickel foil and a stainless steel foil, the conductivity of the nickel foil and the stainless steel foil is relatively low. For example, the volume resistivity of the nickel foil is generally between 8*10 -8 Ω·m and 20*10 -8 Ω·m. If the current collector 32 is a negative current collector, the conductivity of the nickel foil and the stainless steel foil is lower than that of the copper foil. If the current collector 32 is a positive current collector, the conductivity of the nickel foil and the stainless steel foil is lower than that of the aluminum foil. In addition, if the current collector 32 is a positive current collector, the nickel foil and the stainless steel foil can have a problem of oxidation corrosion at a high potential.

[0097] To solve the above problem, in the embodiments of the present application, the transition layer 33 can be a conductive metal layer. In this way, the poor conductivity of the pole piece 30 in the case where the support layer 321 includes a material with relatively low conductivity (such as a nickel foil and a stainless steel foil) can be improved.

[0098] As an example, a copper layer or an aluminum layer can be evaporated on the surface of the support layer 321 to obtain the transition layer 33. That is, the transition layer 33 is obtained by evaporating a copper layer or an aluminum layer on the surface of the support layer 321.

[0099] In this technical solution, the transition layer 33 is obtained by evaporating a copper layer or an aluminum layer on the surface of the support layer 321. On the one hand, since the conductivity of copper and aluminum is relatively high, the conductivity of the pole piece 30 can be further improved. On the other hand, compared with other processes, the thickness of the transition layer 33 obtained by the evaporation process is relatively small, so that the volume and weight of the pole piece 30 and even the battery can be reduced. On the other hand, since the cost of aluminum is relatively low and the density is relatively low, not only the production cost of the pole piece 30 and the battery is reduced, but also the energy density of the battery is improved.

[0100] As another example, a conductive carbon layer can be coated on the surface of the support layer 321 to obtain the transition layer 33. That is, the transition layer 33 is obtained by coating a conductive coating layer on the surface of the support layer 321.

[0101] Optionally, the conductive carbon layer can be, but is not limited to, conductive carbon black or graphene.

[0102] The conductivity of the conductive carbon layer is high, and thus the transition layer 33 is obtained by coating a conductive coating on the surface of the support layer 321, so that the conductivity of the pole piece 30 can be further improved.

[0103] In some embodiments, the thickness of the transition layer 33 can be less than the thickness d1 of the support layer 321.

[0104] The thickness of the transition layer 33 is set to be less than the thickness d1 of the support layer 321, so that the thickness and volume of the pole piece 30 can be reduced, and thus the thickness and volume of the battery can be reduced.

[0105] Optionally, the ratio between the thickness d1 of the support layer 321 and the thickness of the transition layer 33 can be greater than or equal to 2. For example, the ratio can be 3 or 4, etc.

[0106] The thickness of the transition layer 33 can directly affect the energy density of the battery. In order to improve the energy density of the battery, the thickness of the transition layer 33 should be as small as possible. Therefore, the thickness of the transition layer 33 can be between 0.05 μm and 5 μm. For example, the thickness of the transition layer 33 can be 2 μm or 4 μm.

[0107] However, if the thickness of the transition layer 33 is set too small, the current manufacturing process of the battery may not meet the requirements of the thickness of the transition layer 33.

[0108] Therefore, considering the energy density of the battery and the manufacturing process of the battery, the thickness of the transition layer 33 in the embodiments of the present application can be 1 μm.

[0109] The thickness of the transition layer 33 is set to 1 μm, so that a balance can be achieved between the energy density of the battery and the manufacturing process of the battery.

[0110] Table 1 shows several possible embodiments of the pole piece 30 in the case of including the transition layer 22. It should be understood that Table 1 is only an example, and the embodiments of the present application are not limited thereto.

[0111] Table 1

[0112] Example P C R1 R2 d1 d2 1 600 500 4*10 -8 ]]> 6*10 -9 ]]> 4.5 0.07 2 600 650 5.5*10 -8 ]]> 7.5*10 -9 ]]> 6 1 3 600 880 7.5*10 -8 ]]> 9*10 -9 ]]> 6.5 1.5 4 750 880 9*10 -8 ]] 1*10 -8 ]]> 8.3 2 5 900 950 9*10 -8 ]]> 1.5*10 -8 ]]> 9 2.5 6 1050 1100 9*10 -8 ]]> 2*10 -8 ]]> 10.5 3.2 7 1050 1200 1*10 -7 ]]> 2.5*10 -8 ]]> 10.5 3.2 8 1200 1300 1.8*10 -7 ]]> 2.5*10 -8 ]]> 12 4 9 1280 1500 2.5*10 -7 ]]> 2.8*10 -8 ]]> 12 4.3 10 1350 1600 4*10 -7 ]]> 3.3*10 -8 ]]> 12 4.5 11 1400 1800 5*10 -7 ]]> 3.5*10 -8 ]]> 13.5 4.8 12 1500 2500 6.5*10 -7 ]]> 3.8*10 -8 ]]> 14 4.8

[0113] P in Table 1 is the tensile strength, and the unit is MPa. C is the volume capacity, and the unit is mAh·mm -3 R1 is the volume resistivity of the support layer, R2 is the volume resistivity of the transition layer, and the unit is Ω·m. d1 and d2 are the thicknesses of the support layer and the transition layer, respectively, and the unit is μm.

[0114] In order to further verify the performance of the pole piece 30 of the embodiment of the application, the pole piece 30 of the embodiment of the application is compared with other pole pieces, as shown in Table 2. The pole piece in Comparative Example 1 does not include a transition layer.

[0115] Table 2

[0116]

[0117] The unit of the energy density is Wh / Kg.

[0118] As can be seen from Table 2, the tensile strength of the support layer of the pole piece in Comparative Example 1 is small, so that the pole piece is broken when the battery is fully charged. The tensile strength of the support layer of the pole piece in Comparative Example 2 and the pole piece 30 of the embodiment of the application is large, so that the pole piece is not broken when the battery is fully charged. For Comparative Example 2 and the embodiment of the application, the volume resistivity of the transition layer of the embodiment of the application is smaller than that of Comparative Example 2, and the other parameters are the same, so that the energy density of the embodiment of the application is greater than that of Comparative Example 2.

[0119] Therefore, it can be concluded that the performance of the pole piece 30 of the embodiment of the application is better than that of other pole pieces in various aspects.

[0120] A test method of the tensile strength P and the volume resistivity of the embodiment of the application will be introduced below. It should be understood that the test method of the tensile strength and the volume resistivity of the embodiment of the application is not limited thereto.

[0121] The test method of the tensile strength can be specifically as follows: a current collector sample with a size of 20mm*20mm is taken, the sample is fixed to the test fixture of a high-iron tensile testing machine, and the standard distance between the two fixtures of the tensile testing machine is set to 50mm and the stretching speed is 5mm / min. The force borne by the sample during stretching is divided by the original cross-sectional area of the sample to obtain the tensile strength, and the tensile strength and displacement curve are recorded. During the stretching process of the sample, the material enters the strengthening stage after the yield stage, and the tensile strength suddenly drops with the stretching strength, and the sample is broken at this time, and the tensile strength at this time is the tensile strength of the sample.

[0122] The test method of the volume resistivity can be specifically as follows: the volume resistivity R = p*d, wherein p is the square resistance of the sample, and the unit is Ω; d is the thickness of the sample in m. First, the square resistance p of the sample is tested, and then p and d are multiplied to obtain the volume resistivity.

[0123] The application embodiment can test the sheet resistance p of the sample by the four-probe method. For example, an RTS-9 double electric four-probe tester can be used, and the test environment is: normal temperature 23±2°C, 0.1 MPa, and relative humidity ≤65%. During the test, the sample is cleaned, then placed horizontally on the test table, and the four probes are placed down to make the probes in good contact with the sample surface. Then, the current range of the sample is calibrated in the automatic test mode, the sheet resistance is measured under the appropriate current range, and 8 to 10 data points of the same sample are collected as data measurement accuracy and error analysis. Finally, the average value of the 8 to 10 data is taken as the sheet resistance of the sample.

[0124] The above describes the pole piece 30 of the application embodiment, and a possible preparation method of the pole piece 30 will be described below. The pole piece prepared by the preparation method includes a support layer, a transition layer, and an active material layer. The support layer, the transition layer, and the active material layer can be the support layer 321, the transition layer 33, and the active material layer 31 in the above, and the active material layer 31 is a negative electrode active material layer.

[0125] First, the transition layer 33 can be arranged on the surface of the support layer 321. As described above, the multi-plating layer can be formed on the surface of the support layer 321 by two ways.

[0126] Way one: evaporation method.

[0127] Specifically, the support layer 321 after surface cleaning treatment is placed in a vacuum plating chamber, and the high-purity metal wire in the metal evaporation chamber is melted and evaporated at a high temperature of 1300°C to 2000°C, for example, 1500°C. The evaporated metal is cooled in the cooling system in the vacuum plating chamber for 1 hour, and finally deposited on the support layer 321, so that the transition layer 33 can be formed on the surface of the support layer 321.

[0128] Way two: coating method.

[0129] Specifically, the conductive material and the binder are dispersed in the solvent to form a uniform conductive slurry. The solvent can be N-methylpyrrolidone (NMP) or deionized water. Then, the conductive slurry is coated on the surface of the support layer 321 by at least one of the coating methods of roller coating, extrusion coating, doctor blade coating, and gravure coating, and is subjected to a drying process, so that the transition layer 33 can be formed on the surface of the support layer 321.

[0130] After forming the transition layer 33 on the surface of the support layer 321, the active material layer 31 is prepared on the side of the transition layer 33. The active material layer 31 can be prepared according to conventional methods in the art. For example, first, the negative electrode active material and the conductive agent, binder and thickening agent are dispersed in a solvent to form a uniform negative electrode slurry. The solvent can be NMP or deionized water. Then, the negative electrode slurry is coated on the surface of the transition layer 33, and after drying and other processes, the active material layer 31 is obtained.

[0131] It should be noted that during the preparation of the electrode sheet 30, by reasonably controlling the process conditions of vapor deposition, such as deposition temperature, deposition rate, atmosphere conditions in the deposition chamber, or reasonably controlling the process conditions of coating the coating layer, such as slurry viscosity, solid content, drying rate, etc., the transition layer 33 and the support layer 321 can have high bonding force, which is beneficial to improve the mechanical stability, working stability and service life of the electrode sheet 30.

[0132] The embodiments of the present application also provide an electrode assembly, which can include the electrode sheet 30 in the foregoing embodiments and an electrolyte.

[0133] Specifically, if the electrode sheet 30 in the foregoing embodiments is a negative electrode sheet, the electrode assembly further includes a positive electrode sheet in addition to the electrode sheet 30 and the electrolyte. If the electrode sheet 30 in the foregoing embodiments is a positive electrode sheet, the electrode assembly further includes a negative electrode sheet in addition to the electrode sheet 30 and the electrolyte.

[0134] Optionally, the electrode assembly can be an electrode assembly 22 in Figure 3 .

[0135] The embodiments of the present application also provide a battery monomer, which can include a shell, an electrode assembly in the foregoing embodiments, and a top cover assembly. The shell has a containing chamber with an opening, the electrode assembly is contained in the containing chamber, and the top cover assembly covers the opening to enclose the electrode assembly in the shell.

[0136] Optionally, the battery monomer can be a battery monomer 20 in Figure 2 and Figure 3 , the shell can be a shell 211 in Figure 3 , and the top cover assembly can include a cover plate 212, an electrode terminal 214, a connecting member 23, etc. in Figure 3 .

[0137] The embodiments of the present application also provide a battery, which can include the battery monomer in the foregoing embodiments. In some embodiments, the battery can further include a box body, a current collecting component and other structures, which will not be described here.

[0138] The application further provides a power-using device, which can comprise the battery in the foregoing embodiments, and the battery is used to provide electric energy for the power-using device.

[0139] In some embodiments, the power-using device can be Figure 1 a vehicle 1, a ship or a spacecraft in the foregoing embodiments.

[0140] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A pole piece (30) characterized by, The active material layer (31) is provided on a surface of the current collector (32), the current collector (32) comprises a support layer (321), wherein the tensile strength P of the support layer (321) is between 450 MPa and 1500 MPa. The transition layer (33) is provided between the support layer (321) and the active material layer (31), and the volume resistivity of the transition layer (33) is less than that of the support layer (321) at the same temperature. The material of the support layer (321) comprises at least one of a nickel foil, a stainless steel foil and an alloy foil. The thickness d1 of the support layer (321) is between 4 μm and 15 μm. The volume resistivity of the support layer (321) is greater than or equal to 4*10 -8 Ω.m at a temperature of 23°C, and the volume resistivity of the transition layer (33) is less than 4*10 -8 Ω.m at a temperature of 23°C.

2. The pole piece (30) of claim 1, characterized in that The transition layer (33) is obtained by evaporating a copper layer or an aluminum layer on a surface of the support layer (321).

3. The pole piece (30) of claim 1, characterized in that The transition layer (33) is obtained by applying a conductive coating on a surface of the support layer (321).

4. The pole piece (30) of claim 1, characterized in that The volume capacity C of the active material layer (31) is 500 mAh mm -3 or between 600 mAh mm -3 - 3000 mAh mm -3 .

5. The pole piece (30) of claim 1, characterized in that The thickness of the transition layer (33) is less than the thickness d1 of the support layer (321).

6. The pole piece (30) of claim 1, characterized in that The ratio between the thickness d1 of the support layer (321) and the thickness of the transition layer (33) is greater than or equal to 2.

7. The pole piece (30) of claim 1, characterized in that The thickness of the transition layer (33) is between 0.05 μm and 5 μm.

8. The pole piece (30) of claim 7, characterized in that The thickness of the transition layer (33) is 1 μm.

9. The pole piece (30) of claim 1, characterized in that The active material layer (31) is a negative electrode active material layer, and the material of the negative electrode active material layer comprises at least one of the following materials:

10. The pole piece (30) of claim 9, characterized in that silicon, a silicon alloy, silicon oxide, silicon carbon, lithium metal, a metal oxide, wherein the metal oxide can be alloyed with lithium.

11. The pole piece (30) according to any one of claims 1 to 10, characterized in that The electrode piece (30) according to any one of claims 1 to 11. The electrode assembly according to claim 12 is accommodated in the accommodation cavity.

12. An electrode assembly, characterized by, The top cover assembly covers the opening to enclose the electrode assembly in the shell. The plurality of battery monomers according to claim 13.

13. A battery cell, characterized by The box is used for accommodating the plurality of battery monomers. The battery according to claim 14 is used to provide electric energy for the electric device. ​ ​ 14. A battery, characterized by ​ ​ ​ 15. An electrical device, comprising: ​ ​

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