CN115832193A

CN115832193A - Pole piece, electrode assembly, battery cell and battery

Info

Publication number: CN115832193A
Application number: CN202211137881.2A
Authority: CN
Inventors: 吴李力
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-09-19
Filing date: 2022-09-19
Publication date: 2023-03-21

Abstract

The embodiment of the application provides a pole piece, an electrode assembly, a battery monomer and a battery, which can effectively improve the performance of the battery. The pole piece (20) comprises: an active material layer (31); 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 supporting layer (321), wherein the tensile strength P of the supporting layer (321) is 450-1500 MPa.

Description

Pole piece, electrode assembly, battery monomer and battery

Technical Field

The application relates to the technical field of batteries, in particular to a pole piece, an electrode assembly, a battery monomer and a battery.

Background

Energy conservation and emission reduction are the key points of sustainable development of the automobile industry. Under such circumstances, electric vehicles are an important component of sustainable development of the automobile industry due to their energy saving and environmental protection advantages. In the case of electric vehicles, battery technology is an important factor in the development thereof.

In the development of battery technology, the performance of batteries is a non-negligible problem. The performance of batteries affects not only the development and application of battery-related products, but also consumer acceptance of electric vehicles. Therefore, how to improve the performance of the battery is an urgent problem to be solved.

Disclosure of Invention

The embodiment of the application provides a pole piece, an electrode assembly, a battery monomer and a battery, which can effectively improve the performance of the battery.

In a first aspect, a pole piece is provided, including: an active material layer; the active material layer is arranged on the surface of the current collector, and the current collector comprises a supporting layer, wherein the tensile strength P of the supporting layer is 450-1500 MPa.

According to the embodiment of the application, the support layer with the tensile strength of 450MPa-1500MPa is arranged in the current collector, so that the tensile strength of the pole piece is improved, the problems of deformation, stripping and fracture caused by tensile extension of the current collector or the pole piece under the condition that the active material layer is expanded are avoided, and the performance of a battery comprising the pole piece can be effectively improved.

In some possible implementations, the material of the support layer includes at least one of a nickel foil, a stainless steel foil, and an alloy foil.

Because the tensile strength of the nickel foil, the stainless steel foil and the alloy foil can reach 1000MPa or even higher, the technical scheme sets the material of the supporting layer to at least one of the nickel foil, the stainless steel foil and the alloy foil, and can effectively ensure the tensile strength of the supporting layer and even the pole piece.

In some possible implementations, the thickness d of the support layer ₁ Between 4 μm and 15 μm.

According to the technical scheme, the thickness of the supporting layer is set between 4-15 mu m, namely the thickness of the supporting layer is set to be larger, so that the high tensile strength of the supporting layer can be ensured.

In some possible implementations, the tensile strength P of the support layer (321) and the volume capacity C of the active material layer (31) satisfy: c is less than or equal to P x d ₁ /3 of whichIn d ₁ Is the thickness of the support layer (321).

In some possible implementations, the method further includes: and the transition layer is arranged between the support layer and the active material layer, and the volume resistivity of the transition layer is smaller than that of the support layer at the same temperature.

According to the technical scheme, the transition layer with smaller volume resistivity is arranged between the supporting layer and the active material layer, so that the conductivity of the pole piece can be effectively improved.

In some possible implementations, the volume resistivity of the support layer is greater than or equal to 4 x 10 at a temperature of 23 ℃ ^-8 Ω · m, the volume resistivity of the transition layer being less than 4 x 10 ^-8 Omega.m. Therefore, the conductivity of the pole piece can be further improved.

In some possible implementations, the transition layer is formed by evaporating a copper layer or an aluminum layer on the surface of the support layer.

According to the technical scheme, the transition layer is obtained by evaporating a copper layer or an aluminum layer on the surface of the supporting layer, on one hand, the conductivity of the pole piece can be further improved due to the fact that the conductivity of copper and aluminum is high; on the other hand, compared with other processes, the thickness of the transition layer obtained by the evaporation process is smaller, so that the volume and the weight of the pole piece and even the battery can be reduced; on the other hand, the cost of the aluminum is lower, and the density is lower, so that the production cost of the pole piece and the battery is reduced, and the energy density of the battery is improved.

In some possible implementations, the transition layer is obtained by applying a conductive coating on the surface of the support layer.

According to the technical scheme, the electric conductivity of the conductive carbon layer is higher, so that the transition layer is obtained by coating the conductive coating on the surface of the supporting layer, and the electric conductivity of the pole piece can be further improved.

In some possible implementations, the thickness of the transition layer is less than the thickness d of the support layer ₁ 。

This technical scheme is less than the thickness of supporting layer with the thickness setting ground of transition layer, so, can reduce the thickness and the volume of pole piece, and then reduced the thickness and the volume of battery.

In some possible implementations, the thickness d of the support layer ₁ And the ratio to the thickness of the transition layer is greater than or equal to 2.

In some possible implementations, the transition layer has a thickness between 0.05 μm and 5 μm.

Because the thickness of the transition layer can directly influence the energy density of the battery, the technical scheme sets the thickness of the transition layer between 0.05 μm and 5 μm, namely the thickness of the transition layer is smaller, and the energy density of the battery can be improved.

In some possible implementations, the transition layer has a thickness of 1 μm.

According to the technical scheme, the thickness of the transition layer is set to be 1 mu m, so that balance can be achieved between the energy density of the battery and the process level of manufacturing the battery.

In some possible implementations, the active material layer is an anode active material layer, and a material of the anode active material layer includes at least one of the following materials: silicon, silicon alloys, silicon oxides, silicon carbon, lithium metal, metal oxides, wherein the metal oxides can be alloyed with lithium.

According to the technical scheme, when the material of the negative electrode active material layer comprises the material, the pole piece has high specific capacity, and the energy density of the battery can be effectively improved.

In some possible implementations, the active material layer has a volume capacity C of 600mAh mm ^-3 -3000mAh·mm ^-3 In the meantime.

In a second aspect, there is provided an electrode assembly comprising: a plurality of pole pieces according to the first aspect or the implementations thereof.

In a third aspect, a battery cell is provided, including: a housing having a receiving chamber with an opening; the electrode assembly of the second aspect described above, which is housed in the housing chamber; a cap assembly covering the opening to enclose the electrode assembly in the case.

In a fourth aspect, there is provided a battery comprising: a plurality of battery cells according to the third aspect; a case for accommodating the plurality of battery cells.

In a fifth aspect, there is provided an electrical device, comprising: the battery of the fourth aspect, wherein the battery is used for providing electric energy for the electric device.

Drawings

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 described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for a person skilled in the art to obtain other drawings based on the drawings without any creative effort.

FIG. 1 is a schematic illustration of a vehicle according to one embodiment of the present application.

Fig. 2 is a schematic structural diagram of a battery according to an embodiment of the present application.

Fig. 3 is an exploded view of a battery cell according to one embodiment of the present application.

Fig. 4 is a schematic diagram of a pole piece provided in an embodiment of the present application.

Fig. 5 is a schematic diagram of another pole piece provided in an embodiment of the present application.

In the drawings, the drawings are not necessarily to scale.

Detailed Description

Embodiments of the present application will be described in further detail below with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the application and are not intended to limit the scope of the application, i.e., the application is not limited to the described embodiments.

In the description of the present application, it is to be noted that, unless otherwise specified, "a plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," and the like, indicate an orientation or positional relationship that is merely for convenience in describing the application and to simplify the description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the application. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. "vertical" is not strictly vertical, but is within the tolerance of the error. "parallel" is not strictly parallel but is within the tolerance of the error.

The following description is given with the directional terms as they are used in the drawings and not intended to limit the specific structure of the present application. In the description of the present application, it is also to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the present application can be understood as appropriate by one of ordinary skill in the art.

Unless defined otherwise, 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 application belongs; the terminology used in the description of the application in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "including" and "having," and any variations thereof in the description and claims of this application and the description of the figures above, are intended to cover non-exclusive inclusions. The terms "first," "second," and the like in the description and claims of this application or in the above-described drawings are used for distinguishing between different elements and not for describing a particular sequential or chronological order.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

The technical scheme described in the embodiment of the application is applicable to various devices using batteries, such as mobile phones, portable devices, notebook computers, battery cars, electric toys, electric tools, electric vehicles, ships, spacecrafts and the like, and the spacecrafts comprise airplanes, rockets, space shuttles, spacecrafts and the like.

It should be understood that the technical solutions described in the embodiments of the present application are not limited to be applied to the above-described devices, but may also be applied to all devices using batteries, and for brevity of description, the following embodiments are all described by taking an electric vehicle as an example.

For example, as shown in fig. 1, which is a schematic structural diagram of a vehicle 1 according to an embodiment of the present disclosure, the vehicle 1 may be a fuel-oil vehicle, a gas-fired vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid electric vehicle, or an extended range vehicle. The vehicle 1 may be provided with a motor 40, a controller 30 and a battery 10, the controller 30 being configured to control the battery 10 to supply power to the motor 40. For example, the battery 10 may be provided at the bottom or the head or tail of the vehicle 1. The battery 10 may be used for power supply of the vehicle 1, for example, the battery 10 may be used as an operation power source of the vehicle 1 for a circuit system of the vehicle 1, for example, for power demand for operation in starting, navigation, and running of the vehicle 1. In another embodiment of the present application, the battery 10 may be used not only as an operation power source of the vehicle 1 but also as a driving power source of the vehicle 1 instead of or in part of fuel or natural gas to provide driving power to the vehicle 1.

Reference to the battery 10 in embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery 10 referred to in the present application may include a battery module or a battery pack, etc. Battery 10 generally includes a case for enclosing one or more battery cells. The box can avoid liquid or other foreign matters to influence the charging or discharging of battery monomer.

In order to meet different power requirements, the battery 10 may include a plurality of battery cells, wherein the plurality of battery cells may be connected in series or in parallel or in series-parallel, and the series-parallel refers to a mixture of series connection and parallel connection. Battery 10 may also be referred to as a battery pack. Alternatively, a plurality of battery cells may be connected in series or in parallel or in series-parallel to form a battery module, and a plurality of battery modules may be connected in series or in parallel or in series-parallel to form the battery 10. That is, a plurality of battery cells may directly constitute the battery 10, or a battery module may be first formed and then the battery 10 may be formed.

For example, as shown in fig. 2, the battery 10 may include a plurality of battery cells 20 for a structural schematic diagram of the battery 10 according to an embodiment of the present disclosure. The battery 10 may further include a case (or called a cover), the inside of the case is a hollow structure, and the plurality of battery cells 10 are accommodated in the case. As shown in fig. 2, the case may comprise two parts, herein referred to as a first part 111 and a second part 112, respectively, the first part 111 and the second part 112 snap together. The shape of the first and

second portions

111 and 112 may be determined according to the shape of a combination of a plurality of battery cells 20, and the first and

second portions

111 and 112 may each have one opening. For example, each of the first portion 111 and the second portion 112 may be a hollow rectangular parallelepiped and only one surface of each may be an opening surface, the opening of the first portion 111 and the opening of the second portion 112 are oppositely disposed, and the first portion 111 and the second portion 112 are fastened to each other to form a box body having a closed chamber. Wherein the case may include a bottom plate 112a, side plates 112b, and beams. The plurality of battery cells 20 are connected in parallel or in series-parallel combination and then placed in a box formed by buckling the first part 111 and the second part 112.

Optionally, the battery 10 may also include other structures, which are not described in detail herein. For example, the battery 10 may further include a bus member for electrically connecting the plurality of battery cells 20, such as in parallel or in series-parallel. Specifically, the bus member may achieve electrical connection between the battery cells 20 by connecting electrode terminals of the battery cells 20. Further, the bus bar member may be fixed to the electrode terminals of the battery cells 20 by welding. The electric energy of the plurality of battery cells 20 can be further led out through the box body by the conductive mechanism. Alternatively, the conductive means may also belong to the bus bar member.

The number of the battery cells 20 may be set to any number according to different power requirements. A plurality of battery cells 20 may be connected in series, parallel, or series-parallel to achieve greater capacity or power. Since the number of the battery cells 20 included in each battery 10 may be large, the battery cells 20 may be arranged in groups for convenience of installation, each group of the battery cells 20 constituting a battery module. The number of the battery cells 20 included in the battery module is not limited and may be set as required.

In the embodiment of the present application, the battery cell 20 may include a lithium ion secondary battery, a lithium ion primary battery, a lithium sulfur battery, a sodium lithium ion battery, a sodium ion battery, a magnesium ion battery, or the like, which is not limited in the embodiment of the present application. The battery cell 20 may be a cylinder, a flat body, a rectangular parallelepiped, or other shapes, which is not limited in the embodiment of the present application. The battery cells 20 are generally divided into three types in an encapsulated manner: the cylindrical battery monomer, the square battery monomer and the soft package battery monomer are not limited in the embodiment of the application.

As shown in fig. 3, which is a schematic structural diagram of a battery cell 20 according to an embodiment of the present disclosure, the battery cell 20 includes one or more electrode assemblies 22, a case 211, and a cover plate 212. The housing 211 and cover 212 form a housing or battery compartment 21. The wall of the housing 211 and the cover plate 212 are referred to as the wall of the battery cell 20. The case 211 is determined according to the shape of one or more electrode assemblies 22 after being combined, for example, the case 211 may be a hollow rectangular parallelepiped or a square or a cylinder, and one of the faces of the case 211 has an opening so that one or more electrode assemblies 22 can be placed in the case 211. For example, when the housing 211 is a hollow rectangular parallelepiped or square, one of the planes of the housing 211 is an open plane, i.e., the plane has no wall body so that the housing 211 communicates inside and outside. When the housing 211 may be a hollow cylinder, the end surface of the housing 211 is an open surface, i.e., the end surface has no wall body so that the housing 211 is communicated with the inside and the outside. The cap plate 212 covers the opening and is connected with the case 211 to form a closed cavity in which the electrode assembly 22 is placed. The case 211 is filled with an electrolyte, such as an electrolytic solution.

The battery cell 20 may further include two electrode terminals 214, and the two electrode terminals 214 may be disposed on the cap plate 212. The cap plate 212 is generally in the shape of a flat plate, and two electrode terminals 214 are fixed to the flat plate surface of the cap plate 212, the two electrode terminals 214 being a positive electrode terminal 214a and a negative electrode terminal 214b, respectively. One connecting member 23, which may also be referred to as a current collecting member 23, is disposed at each of the electrode terminals 214, between the cap plate 212 and the electrode assembly 22, for electrically connecting the electrode assembly 22 and the electrode terminals 214.

As shown in fig. 3, 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 tabs 221a of the one or more electrode assemblies 22 are connected to one electrode terminal through one connecting member 23, and the second tabs 212a of the one or more electrode assemblies 22 are connected to the other electrode terminal through the other connecting member 23. For example, the positive electrode terminal 214a is connected to a positive electrode tab through one connecting member 23, and the negative electrode terminal 214b is connected to a negative electrode tab through the other connecting member 23.

In the battery cell 20, the electrode assembly 22 may be provided singly or in plurality according to actual use requirements, and as shown in fig. 3, 4 independent electrode assemblies 22 are provided in the battery cell 20.

The battery cell 20 may further include a pressure relief mechanism 213. The pressure relief mechanism 213 is activated to relieve the internal pressure or temperature of the battery cell 20 when the internal pressure or temperature reaches a threshold value.

The pressure relief mechanism 213 may be any of various possible pressure relief structures, which are not limited in the embodiments of the present application. For example, the pressure relief mechanism 213 may 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, pressure relief mechanism 213 may be a pressure sensitive pressure relief mechanism configured to rupture when the internal air pressure of battery cell 20 in which pressure relief mechanism 213 is disposed reaches a threshold value.

The electrode assembly 22 is composed of a positive electrode tab, a negative electrode tab, and a separator. The material of the isolation film may be polypropylene (PP) or Polyethylene (PE). The battery cell 20 operates by primarily relying on metal ions to move between the positive and negative pole pieces. The positive pole piece includes anodal mass flow body and anodal active substance layer, and anodal active substance layer coats in anodal mass flow body's surface, and the mass flow body protrusion on the anodal active substance layer of uncoated positive active substance layer is in the mass flow body of coating anodal active substance layer, and the mass flow body on the anodal active substance layer of uncoated positive is as anodal utmost point ear. The negative pole piece includes negative current collector and negative active material layer, and the negative active material layer coats in the surface of negative current collector, and the mass flow body protrusion in the mass flow body of coating the negative active material layer of uncoated negative active material layer, the mass flow body of uncoated negative active material layer is as negative pole utmost point ear. In order to ensure that the fuse is not fused when a large current is passed, the number of the positive electrode tabs is multiple and the positive electrode tabs are stacked together, and the number of the negative electrode tabs is multiple and the negative electrode tabs are stacked together. In addition, the electrode assembly may have a winding structure or a lamination structure, and the embodiment of the present application is not limited thereto.

At present, the energy density of a lithium ion battery taking graphite as a material of a negative electrode active material layer is close to the theoretical limit and is difficult to further promote. The selection of high theoretical capacity negative electrode materials, such as silicon, lithium metal and other materials, to replace graphite negative electrodes is an effective way to realize high energy density batteries. However, the expansion of such materials is large, which causes the stretching and extension of the current collector or the pole piece, and further causes the problems of deformation, demoulding, fracture and the like.

In order to solve the above problem, an embodiment of the present application provides a pole piece, where the pole piece includes a current collector, the current collector includes a support layer, and a tensile strength of the support layer is 450MPa to 1500MPa. The support layer with the tensile strength of 450-1500 Mpa is arranged in the current collector, so that the tensile strength of the pole piece is improved, the problems of deformation, stripping and fracture caused by tensile extension of the current collector or the pole piece under the condition that the active material layer expands are solved, and the performance of a battery comprising the pole piece can be effectively improved.

Fig. 4 is a schematic diagram of a pole piece 30 according to an embodiment of the present disclosure. The pole piece 30 includes an active material layer 31 and a current collector 32. Wherein, the active material layer 31 is disposed on the surface of the current collector 32, the current collector 32 comprises a support layer 321, and the tensile strength P of the support layer 321 is between 450MPa and 1500MPa.

Illustratively, the tensile strength P of the support layer 321 may be between 600MPa and 1000MPa, such as 800MPa.

The active material layer 31 may be provided on one surface of the current collector 32, or may be provided on both surfaces of the current collector 32.

Alternatively, the material of the support layer 321 may include at least one of a nickel foil, a stainless steel foil, and an alloy foil. The stainless steel foil may be, for example, chromium (Cr) or iron (Fe), and the alloy foil may be, for example, a nickel-iron alloy foil.

Because the tensile strength of the nickel foil, the stainless steel foil and the alloy foil can reach 1000MPa or even higher, in the technical scheme, the material of the support layer 321 is set to include at least one of the nickel foil, the stainless steel foil and the alloy foil, so that the tensile strength of the support layer 321 and even the pole piece 30 can be effectively ensured.

Since the support layer 321 has high tensile strength, if the support layer 321 is thin, the tensile strength P of the support layer 321 may not be supported. Therefore, the thickness of the support layer 321 is set to be larger in the embodiment of the present application.

In some embodiments, the thickness d of the support layer 321 ₁ And may be between 4 μm and 15 μm. For example, the thickness d of the support layer 321 ₁ May be 8 μm, 10 μm, 12 μm, or the like.

In this embodiment, the thickness d of the supporting layer 321 is adjusted ₁ Is set between 4 μm and 15 μm, i.e., the thickness d of the support layer 321 ₁ The arrangement is large, so that high tensile strength of the support layer 321 can be ensured.

Thickness d of the support layer 321 ₁ The energy density of the battery can be directly influenced, and in order to increase the energy density of the battery, the thickness d of the support layer 321 is set ₁ The smaller the arrangement, the better, but then, on the one hand, the current state of the art for manufacturing batteries may not meet this requirement, and on the other handOn the one hand, the tensile strength P of the support layer 321 may be affected.

Therefore, for all reasons, the thickness d of the support layer 321 of the embodiment of the present application ₁ May be 6 μm.

In this embodiment, the thickness d of the supporting layer 321 is adjusted ₁ The setting at 6 μm, on the one hand, enables a balance to be achieved between the energy density and the process capability of the cell, and, on the other hand, does not have an influence on the tensile strength P of the support layer 321.

Optionally, the volume resistivity of the support layer 321 is not particularly limited in this embodiment. For example, the volume resistivity of the support layer 321 may be greater than or equal to 4 × 10-8 Ω · m at a temperature of 23 ℃.

It should be noted that the temperature of 23 ℃ in the embodiment of the present application is not absolutely 23 ℃, and the temperature around 23 ℃, for example 23 ± 2 ℃, is within the scope of the embodiment of the present application.

Further, the volume resistivity of the support layer 321 may be greater than or equal to 4 x 10% in the case where the temperature is 23 ℃ and the relative humidity is less than or equal to 65% rh ^-8 Ω·m。

Alternatively, in the present embodiment, the active material layer 31 may be a positive electrode active material layer. In this case, the current collector 32 is a positive current collector, and the electrode sheet 30 is a positive electrode sheet.

Alternatively, the active material layer 31 may be an anode active material layer. In this case, the current collector 32 may be a negative electrode current collector, and the electrode sheet 30 may be a negative electrode sheet.

In the case where the active material layer 31 is an anode active material layer, the material of the anode active material layer may include at least one of the following materials: silicon, silicon alloys, silicon oxides, carbon silicon, lithium metal, metal oxides, wherein the metal oxides can be alloyed with lithium.

For example, the material of the anode active material layer may include a mixture of graphite and carbon silicon, or a mixture of graphite and lithium metal.

When the material of the negative electrode active material layer includes the above-described material, the electrode sheet 30 can have a high specific capacity, and thus the energy density of the battery can be effectively improved.

In some embodiments, when the material of the anode active material layer includes the above-described material, the volume capacity C of the anode active material layer is higher. Alternatively, the volume capacity C of active material layer 31 may be 600mAh mm ^-3 -3000mAh·mm ^-3 In the meantime.

For example, the volume capacity C of active material layer 31 may be 800mAh mm ^-3 Or 1000 mAh.mm ^-3 Or 1500 mAh.mm ^-3 Or 2000 mAh.mm ^-3 。

It is found through experiments that the tensile strength P of the support layer 321 may be in a positive correlation with the volume capacity C of the active material layer 31. That is, the larger the tensile strength P of the support layer 321, the larger the volume capacity C of the active material layer 31.

In some embodiments, the tensile strength P of the support layer 321 and the volume capacity C of the active material layer 31 may satisfy the following relationship:

C≤P*d1/3

in addition to current collector 32 and active material layer 31, as shown in fig. 5, in the present embodiment, pole piece 30 may further include transition layer 33. Wherein the transition layer 33 is disposed between the support layer 321 and the active material layer 31, and the volume resistivity of the transition layer 33 is smaller than that of the support layer 321 at the same temperature.

According to the technical scheme, the transition layer 33 with small volume resistivity is arranged between the support layer 321 and the active material layer 31, so that the conductivity of the pole piece 30 can be effectively improved.

Optionally, the transition layer 33 may belong to the current collector 32, i.e. the current collector 32 may comprise the transition layer 33.

Alternatively, the transition layer 33 may not belong to the current collector 32.

Alternatively, referring again to fig. 5, both sides of the support layer 321 may be provided with the transition layer 33, and both sides of the multi-plating layer 33 may also be provided with the active material layer 31.

Since the transition layer 33 mainly serves to improve the electrical conductivity, the volume resistivity of the transition layer 33 should be as small as possible.

Alternatively, the volume resistivity of the transition layer 33 may be less than 4 x 10-8 Ω · m. Thus, the conductivity of the pole piece 30 can be further improved.

For example, the volume resistivity of the transition layer 33 may be less than 4 x 10 at a temperature of 23 ℃ ^-8 Omega.m. Further, the volume resistivity of the transition layer 33 may be less than 4 x 10% with a temperature of 23 ℃ and a relative humidity of less than 65% rh ^-8 Ω·m。

In the case where the material of the support layer 321 includes nickel foil and stainless steel foil, the conductivity of the nickel foil and the stainless steel foil is low, and for example, the volume resistivity of the nickel foil is generally 8 × 10 ^-8 Ω·m～20*10 ^-8 Omega.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 nickel and stainless steel foils have lower electrical conductivity than the aluminum foil. In addition, if the current collector 32 is a positive current collector, nickel foil and stainless steel foil may have a problem of oxidation corrosion at high potential.

In order to solve the above problem, in the embodiment of the present application, the transition layer 33 may be a conductive metal layer. In this way, the problem of poor conductivity of the pole piece 30 in the case where the support layer 321 includes a material having low conductivity (e.g., nickel foil and stainless steel foil) can be improved.

As an example, a copper layer or an aluminum layer may be vapor-deposited on the surface of the support layer 321 to obtain the transition layer 33. That is, the transition layer 33 is formed by vapor-depositing a copper layer or an aluminum layer on the surface of the support layer 321.

According to the technical scheme, the transition layer 33 is obtained by evaporating a copper layer or an aluminum layer on the surface of the support layer 321, on one hand, the conductivity of copper and aluminum is high, so that 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 smaller, so that the volume and the weight of the pole piece 30 and even the battery can be reduced; on the other hand, because the cost of aluminum is lower and the density is lower, the production cost of the pole piece 30 and the battery is reduced, and the energy density of the battery is improved.

As another example, a conductive carbon layer may be applied on the surface of the support layer 321 to obtain the transition layer 33. That is, the transition layer 33 is obtained by applying a conductive coating on the surface of the support layer 321.

Alternatively, the conductive carbon layer may be, but is not limited to, conductive carbon black or graphene.

In the technical scheme, because the conductive carbon layer has higher conductivity, the transition layer 33 is obtained by coating a conductive coating on the surface of the support layer 321, and the conductivity of the pole piece 30 can be further improved.

In some embodiments, the thickness of the transition layer 33 may be less than the thickness d of the support layer 321 ₁ 。

In this embodiment, the thickness of the transition layer 33 is set to be smaller than the thickness d of the support layer 321 ₁ Thus, the thickness and volume of the pole piece 30 can be reduced, and the thickness and volume of the battery are reduced.

Optionally, the thickness d of the support layer 321 ₁ The ratio to the thickness of the transition layer 33 may be greater than or equal to 2. E.g. equal to 3 or 4, etc.

Since the thickness of the transition layer 33 may directly affect the energy density of the battery, in order to increase the energy density of the battery, it is better to set the thickness of the transition layer 33 to be smaller. Thus, the thickness of the transition layer 33 may be between 0.05 μm and 5 μm. Illustratively, the thickness of the transition layer 33 may be 2 μm or 4 μm.

However, if the thickness of the transition layer 33 is set too small, it is likely that the current state of the art for manufacturing batteries cannot meet the requirements for the thickness of the transition layer 33.

Therefore, the thickness of the transition layer 33 of the embodiment of the present application may be 1 μm in consideration of the energy density of the battery and the level of the process of manufacturing the battery.

In this embodiment, the thickness of the transition layer 33 is set to 1 μm, which can balance the energy density of the battery and the level of the process for manufacturing the battery.

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.

TABLE 1

Examples	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

P in Table 1 is tensile strength in MPa. C is volume capacity, unit mAh.mm ^-3 . R1 is the volume resistivity of the support layer, and R2 is the volume resistivity of the transition layer, and has a unit of omega m. d1 and d2 are the thicknesses of the support layer and the transition layer, respectively, in μm.

In order to further verify the performance of the pole piece 30 in the embodiment of the present application, the pole piece 30 in the embodiment of the present application is compared with other pole pieces, which is specifically shown in table 2. Wherein the pole piece of comparative example 1 does not include a transition layer.

TABLE 2

Wherein the unit of the energy density is Wh/Kg.

As can be seen from table 2, since the tensile strength of the support layer of the pole piece of comparative example 1 was small, the pole piece was broken when the battery was fully charged. The tensile strength of the support layer of the pole piece 30 of comparative example 2 and the examples of the present application was large, and therefore, the pole piece was not broken when the battery was fully charged. For comparative example 2 and the examples of the present application, the volume resistivity of the transition layer of the examples of the present application is smaller than that of comparative example 2, the remaining parameters are the same, and the energy density of the examples of the present application is larger than that of comparative example 2.

Therefore, it can be concluded that the performance of the pole piece 30 of the embodiment of the present application is better than that of other pole pieces in all aspects.

A method for measuring the tensile strength P and the volume resistivity of the examples of the present application will be described. It should be understood that the test methods for tensile strength and volume resistivity of the examples of the present application are not limited thereto.

The test method of the tensile strength can be specifically as follows: a current collector sample cut to be 20mm-20mm is taken and fixed on a test clamp of a high-speed rail tensile machine, the standard distance between the two clamps of the tensile machine is set to be 50mm, and the tensile speed is set to be 5mm/min. The force to which the sample is subjected 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. In the stretching process of the sample, the material enters a strengthening stage after passing through a yield stage, the tensile strength of the sample is correspondingly stretched and broken along with the sudden reduction of the tensile strength, and the tensile strength at the moment is the tensile strength of the sample.

The volume resistivity test method specifically comprises the following steps: volume resistivity R = ρ · d, where ρ is the sheet resistance of the sample in Ω; d is the thickness of the sample in m. The square resistance rho of the sample is firstly tested, and then the rho is multiplied by the d to obtain the volume resistivity.

In the embodiment of the present application, a four-probe method may be used to test the sheet resistance ρ of the sample, and the method may be, for example: RTS-9 type double-electric-test four-probe tester is used, and the test environment is as follows: normal temperature 23 plus or minus 2 deg.c, 0.1MPa and relative humidity not higher than 65%. During testing, the surface of the sample is cleaned, then the sample is horizontally placed on a test bench, and the four probes are put down to make the probes well contact with the surface of the sample. And then adjusting the current range of the calibration sample in the automatic test mode, measuring the square resistance under the proper current range, and collecting 8 to 10 data points of the same sample as data measurement accuracy and error analysis. Finally, the average of 8 to 10 data obtained was used as the sheet resistance of the sample.

The electrode sheet 30 of the embodiment of the present application is introduced above, and a possible method for manufacturing the electrode sheet 30 will be described below. The pole piece prepared by the preparation method comprises a supporting layer, a transition layer and an active substance layer. The support layer, the transition layer, and the active material layer may be the support layer 321, the transition layer 33, and the active material layer 31 described above, respectively, and the active material layer 31 is a negative electrode active material layer.

First, a transition layer 33 may be disposed on a surface of the support layer 321. As described above, the multi-plating layer may be formed on the surface of the support layer 321 in two ways.

The first method is as follows: vapor deposition method.

Specifically, the support layer 321 subjected to the surface cleaning treatment is placed in a vacuum plating chamber, a high-purity metal wire in a metal evaporation chamber is melted and evaporated at a high temperature of 1300 ℃ to 2000 ℃, for example, 1500 ℃, the evaporated metal is cooled for 1 hour by a cooling system in the vacuum plating chamber, 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.

The second method comprises the following steps: coating method.

Specifically, a conductive material and a binder are dispersed in a solvent to form a uniform conductive paste. Wherein the solvent can be N-Methylpyrrolidone (NMP) or deionized water. Then, the conductive paste is applied to the surface of the support layer 321 by at least one of roll coating, extrusion coating, blade coating, and gravure coating, and then dried, thereby forming the transition layer 33 on the surface of the support layer 321.

After forming the transition layer 33 on the surface of the support layer 321, the active material layer 31 is prepared on the transition layer 33 side. Among them, the active material layer 31 may be prepared according to a conventional method in the art. For example, first, a negative electrode active material, a conductive agent, a binder, and a thickener are dispersed in a solvent to form a uniform negative electrode slurry. The solvent may be NMP or deionized water, and then the active material layer 31 is obtained by coating the negative electrode slurry on the surface of the transition layer 33 and drying the coating.

It should be noted that, in the process of preparing the pole piece 30, by reasonably regulating and controlling the vapor deposition process conditions, such as deposition temperature, deposition rate, atmosphere conditions of a deposition chamber, and the like, or by reasonably regulating and controlling the coating process conditions, such as slurry viscosity, solid content, drying rate, and the like, a higher bonding force can be provided between the transition layer 33 and the support layer 321, which is beneficial to improving the mechanical stability, the working stability, and the service life of the pole piece 30.

The embodiment of the present application also provides an electrode assembly, which may include the electrode sheet 30 and the electrolyte in the foregoing embodiments.

Specifically, if the electrode sheet 30 in each of the foregoing embodiments is a negative electrode sheet, the electrode assembly includes a positive electrode sheet in addition to the electrode sheet 30 and the electrolyte. If the electrode sheet 30 in each of the foregoing embodiments is a positive electrode sheet, the electrode assembly includes a negative electrode sheet in addition to the electrode sheet 30 and the electrolyte.

Alternatively, the electrode assembly may be the electrode assembly 22 of fig. 3.

The embodiment of the application also provides a battery cell, and the battery cell can comprise a shell, the electrode assembly in the embodiment and a top cover assembly. Wherein the case has an accommodation chamber having an opening, the electrode assembly being accommodated in the accommodation chamber, and the cap assembly covering the opening to enclose the electrode assembly in the case.

Alternatively, the battery cell may be the battery cell 20 of fig. 2 and 3, the case may be the case 211 of fig. 3, and the cap assembly may include the cap plate 212 of fig. 3, the electrode terminal 214, the connection member 23, and the like.

The embodiment of the application also provides a battery, and the battery can comprise the battery cell in each embodiment. In some embodiments, the battery may further include other structures such as a box body and a bus member, which are not described herein.

The embodiment of the present application further provides an electric device, which may include the battery in the foregoing embodiments, where the battery is used to provide electric energy to the electric device.

In some embodiments, the powered device may be the vehicle 1, the watercraft, or the spacecraft of fig. 1.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may be modified or some technical features may be equivalently replaced, but the modifications or the replacements do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A pole piece (30), comprising:

an active material layer (31);

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 supporting layer (321), wherein the tensile strength P of the supporting layer (321) is 450-1500 MPa.

2. The pole piece (30) of claim 1, wherein the material of the support layer (321) comprises at least one of a nickel foil, a stainless steel foil, and an alloy foil.

3. The pole piece (30) according to claim 1 or 2, characterized in that the thickness d of the support layer (321) ₁ Between 4 μm and 15 μm.

4. The pole piece (30) according to any one of claims 1 to 3, characterized in that the tensile strength P of the support layer (321) and the volume capacity C of the active substance layer (31) satisfy:

C≤P*d ₁ /3

wherein d is ₁ Is the thickness of the support layer (321).

5. The pole piece of any one of claims 1 to 4, further comprising:

a transition layer (33) disposed between the support layer (321) and the active material layer (31), the transition layer (33) having a volume resistivity smaller than that of the support layer (321) at the same temperature.

6. Pole piece (30) according to claim 5, characterized in that the volume resistivity of the support layer (321) is greater than or equal to 4 x 10 at a temperature of 23 ℃ ^-8 Ω · m, saidThe volume resistivity of the transition layer (33) is less than 4 x 10 ^-8 Ω·m。

7. The pole piece (30) according to claim 5 or 6, characterized in that the transition layer (33) is obtained by evaporation of a copper or aluminum layer on the surface of the support layer (321).

8. The pole piece (30) according to claim 5 or 6, characterized in that the transition layer (33) is obtained by applying a conductive coating on the surface of the support layer (321).

9. The pole piece (30) according to any one of claims 5 to 8, characterized in that the thickness of the transition layer (33) is smaller than the thickness d of the support layer (321) ₁ 。

10. The pole piece (30) of claim 9, wherein the thickness d of the support layer (321) ₁ The ratio to the thickness of the transition layer (33) is greater than or equal to 2.

11. The pole piece (30) according to any one of claims 5 to 10, characterized in that the thickness of the transition layer (33) is between 0.05 μ ι η -5 μ ι η.

12. The pole piece (30) according to claim 11, characterized in that the thickness of the transition layer (33) is 1 μ ι η.

13. The pole piece (30) according to any one of claims 1 to 12, wherein the active material layer (31) is a negative active material layer, the material of the negative active material layer comprising at least one of the following materials:

silicon, silicon alloys, silicon oxides, silicon carbon, lithium metal, metal oxides, wherein the metal oxides can be alloyed with lithium.

14. The pole piece (30) of claim 13, wherein the activity isThe volume capacity C of the material layer (31) is 600mAh mm ^-3 -3000mAh·mm ^-3 In the meantime.

15. An electrode assembly, comprising:

the pole piece (30) of any one of claims 1 to 14.

16. A battery cell, comprising:

a housing having a receiving chamber with an opening;

the electrode assembly according to claim 15, which is accommodated in the accommodation chamber;

a cap assembly covering the opening to enclose the electrode assembly in the case.

17. A battery, comprising:

a plurality of battery cells according to claim 16;

a case for accommodating the plurality of battery cells.

18. An electric device, comprising: the battery of claim 17, wherein the battery is configured to provide electrical energy to the powered device.