Electrode sheet, battery cell, and electrical device

Abstract

An electrode sheet, a battery cell, and an electrical device. The electrode sheet comprises a current collector (300), two active substance layers, and two transition layers. The current collector (300) comprises a support layer (10), and a first conductive layer (11) and a second conductive layer (12) that are arranged on the two sides of the support layer (10) in a first direction. One active substance layer (102) is arranged on the side of the first conductive layer (11) away from the support layer (10), and the other active substance layer (102) is arranged on the side of the second conductive layer (12) away from the support layer. One transition layer (22) is arranged between at least a part of the first conductive layer (11) and the corresponding active substance layer (102) and protrudes out of the active substance layer (102) in a second direction, and the other transition layer (22) is arranged between at least a part of the second conductive layer (12) and the corresponding active substance layer (102) and protrudes out of the active substance layer (102) in the second direction. Each active substance layer (102) comprises active substance particles, and the average particle size of the active substance particles ranges from 5 μm to 20 μm. Each transition layer comprises solid particles, and the average particle size of the solid particles ranges from 500 nm to 1500 nm. The electrode sheet can improve the structural strength.

Description

Electrodes, batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 8, 2024, with application number 202410027254.6 and titled "Electrode, Battery Cell and Electrical Equipment". Technical Field

[0002] The present application relates to the field of energy storage technology, and in particular to a pole piece, a battery cell and an electrical device. Background Art

[0003] Existing composite current collectors have a three-layer sandwich structure, with a central polymer layer and outer metal layers. The metal layer is used to coat the active material layer and is compacted through cold pressing to form the electrode. Active material particles with a large average particle size in the active material layer can easily cause compression damage to the metal layer, affecting the structural strength of the electrode. Summary of the Invention

[0004] In view of the above situation, the present application provides a pole piece that can improve structural strength.

[0005] Embodiments of the present application provide a pole piece comprising a current collector, two active material layers, and two transition layers. The current collector comprises a support layer, and a first conductive layer and a second conductive layer disposed on either side of the support layer in a first direction, the first direction being the thickness direction of the current collector. One active material layer is disposed on a side of the first conductive layer facing away from the support layer, and the other active material layer is disposed on a side of the second conductive layer facing away from the support layer. One transition layer is disposed between at least a portion of the first conductive layer and the corresponding active material layer, and the other transition layer is disposed between at least a portion of the second conductive layer and the corresponding active material layer. The active material layer comprises active material particles having an average particle size of 5 μm to 20 μm. The transition layer comprises solid particles comprising at least one of aluminum oxide, silicon oxide, silicon carbide, tin oxide, indium oxide, titanium dioxide, cobalt oxide, chromium trioxide, boehmite, amorphous carbon, lithium phosphorus oxynitride, and titanium diboride. The average particle size of the solid particles is 500 nm to 1500 nm.

[0006] In the above-mentioned pole piece, the solid particles are less likely to expand when in contact with the electrolyte than the active material particles, so that the transition layer can buffer the deformation caused by the expansion of the corresponding active material layer. By limiting the average particle size of the active material particles to 5μm to 20μm, the cycle performance, energy density and lithium precipitation performance of the pole piece can be improved. By limiting the average particle size of the solid particles to 500nm to 1500nm, the production cost can be controlled and the interface resistance can be reduced. In addition, the average particle size of the solid particles is smaller than the average particle size of the active material particles, which is conducive to the solid particles playing a buffering role between the active material particles and the current collector, reducing the risk of active material particles with larger average particle size directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the pole piece.

[0007] In some embodiments of the present application, along the second direction, the transition layer protrudes beyond the edge of the peripheral side of the corresponding active material layer, and the second direction is perpendicular to the first direction.

[0008] In the above scheme, one of the transition layers is arranged between at least a portion of the first conductive layer and the corresponding active material layer and protrudes out of the edge of the corresponding active material layer along the second direction, and the other transition layer is arranged between at least a portion of the second conductive layer and the corresponding active material layer and protrudes out of the edge of the corresponding active material layer along the second direction, so that the edge of the transition layer corresponding to the active material layer is relieved of the shear force exerted on the corresponding position of the current collector during the cold pressing process, thereby reducing the risk of damage to the current collector due to excessive shear force and improving the structural strength of the electrode.

[0009] In some embodiments of the present application, the average particle size of the active material particles is 5 to 15 μm, and the average particle size of the solid particles is 500 nm to 1500 nm, so as to further improve the cycle performance, energy density and lithium plating performance of the electrode, so as to further control the production cost and reduce the interface resistance. In addition, it is further beneficial for the solid particles to play a buffering role between the active material particles and the current collector, reducing the risk of active material particles with larger average particle size directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the electrode.

[0010] In some embodiments of the present application, the average particle size of the active material particles is 10 μm to 15 μm to further improve the cycle performance, energy density, and lithium plating performance of the electrode. The average particle size of the solid particles is 800 nm to 1000 nm to further control production costs and reduce interface resistance. In addition, the solid particles are further conducive to playing a buffering role between the active material particles and the current collector, reducing the risk of active material particles with larger average particle size directly contacting the current collector and causing compression damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the electrode.

[0011] In some embodiments of the present application, the compacted density of the active material layer is 3 g / cm 3 Up to 4.5g / cm 3 ; The compacted density of the transition layer is 1.6g / cm 3 Up to 3g / cm 3 . The active material layer and the corresponding transition layer are cold pressed simultaneously. The difference in the materials in the active material layer and the transition layer makes the compaction density of the active material layer different from the compaction density of the transition layer. During the cold pressing process, the compaction density of the active material layer is mainly considered. When the compaction density of the active material layer is too small (less than 3g / cm3), it is easy to cause the energy density of the electrode to be too low; when the compaction density of the active material layer is too large (greater than 4.5g / cm3), it is easy to cause the current collector to be damaged by excessive shear force, affecting the structural strength of the electrode, and it is also easy to cause the channel for ion transmission to be reduced, affecting the cycle performance of the electrode. By limiting the compaction density of the active material layer to 3g / cm3 to 4.5g / cm3, the energy density and cycle performance of the electrode can be improved, and the risk of damage caused by excessive shear force on the current collector can be reduced.

[0012] In some embodiments of the present application, the compacted density of the active material layer is 4.1 g / cm 3 Up to 4.3g / cm 3 ; The compacted density of the transition layer is 2.2g / cm 3 Up to 2.4g / cm 3 , in order to further improve the energy density and cycle performance of the electrode, and reduce the risk of damage to the current collector caused by excessive shear force.

[0013] In some embodiments of the present application, the transition layer includes a connecting portion and an extension portion that are interconnected. Along the first direction, the projection of the connecting portion overlaps with the projection of the corresponding active material layer, which is beneficial to reducing the risk of active material particles directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the electrode. The projection of the extension portion is arranged around the circumference of the projection of the corresponding active material layer, and the projection of the extension portion is also located within the projection of the current collector, so that the edge of the transition layer corresponding to the active material layer can relieve the shear force on the corresponding position of the current collector during the cold pressing process, thereby reducing the risk of damage to the current collector due to excessive shear force, thereby improving the structural strength and conductive performance of the electrode.

[0014] In some embodiments of the present application, the connecting portion is provided with a through hole that passes through the connecting portion along a first direction, the active material layer passes through the through hole and is connected to the corresponding first conductive layer or the second conductive layer, and along the first direction, the projection of the through hole is located within the projection range of the corresponding active material layer. The shear force applied to the current collector by the edge of the active material layer during the cold pressing process is greater than the shear force received by other parts of the current collector. By providing the through hole, the transition layer is adapted to the part of the current collector that is received by the greater shear force, so as to reduce the risk of the active material particles at the edge of the active material layer directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, and alleviate the shear force received by the corresponding position of the current collector during the cold pressing process, thereby reducing the risk of damage to the current collector due to excessive shear force.

[0015] In some embodiments of the present application, along the first direction, the projected overlapping area of ​​the connecting portion and the corresponding active material layer includes an inner periphery and an outer periphery, and the outer periphery is arranged around the circumference of the inner periphery, and the spacing L5 between the inner periphery and the outer periphery satisfies: 0<L5≤1mm. Since the edge stress of the active material layer is large, arranging a transition layer at the edge position is beneficial to playing a buffering role between the edge of the active material layer and the current collector, and is beneficial to increasing the volume of the part where the active material layer passes through the through hole, and thus is beneficial to increasing the volume of the thicker part of the active material layer, thereby improving the energy density of the electrode.

[0016] In some embodiments of the present application, 0<L5≤0.5mm, which is beneficial to further increase the volume of the portion where the active material layer passes through the through hole, and further beneficial to increase the volume of the portion with larger thickness in the active material layer, thereby improving the energy density of the electrode.

[0017] In some embodiments of the present application, the current collector includes two first end faces arranged opposite to each other along the second direction, the active material layer includes two second end faces arranged opposite to each other along the second direction, and the transition layer includes two third end faces arranged opposite to each other along the second direction. Along the second direction, among the first end face, the second end face, and the third end face located on one side of the active material layer, the current collector between the first end face and the third end face forms a hollow foil area for connecting to the electrode terminal, and the transition layer between the second end face and the third end face is a partial extension. The distance L1 between the first end face and the third end face satisfies: 0.2mm≤L1≤1.8mm to limit the area of ​​the hollow foil area. When L1 is too small (less than 0.2mm), the area of ​​the hollow foil area connected to the electrode terminal is easily small, resulting in the risk of weak connection strength; when L1 is too large (greater than 1.8mm), the hollow foil area will occupy a large space in the second direction X, resulting in space waste and affecting the energy density of the electrode. By limiting the range of 0.2mm≤L1≤1.8mm, the connection strength between the hollow foil area and the electrode terminal is improved, and the space wasted in the second direction caused by the hollow foil area is reduced, which is conducive to improving the energy density of the electrode sheet. The distance L2 between the second end face and the third end face satisfies the requirement of 0<L2≤1.5mm, which facilitates visual inspection of whether the transition layer protrudes beyond the edge of the corresponding active material layer in the second direction, and reduces the space wasted caused by the large space occupied by the extension in the second direction.

[0018] In some embodiments of the present application, 0.4 mm ≤ L1 ≤ 0.6 mm is used to further improve the connection strength between the hollow foil area and the electrode terminal and reduce the space wasted in the second direction caused by the hollow foil area, which is beneficial for improving the energy density of the electrode sheet. 0.2 mm ≤ L2 ≤ 0.5 mm is used to further facilitate visual inspection of whether the transition layer protrudes beyond the edge of the corresponding active material layer in the second direction and reduce the space wasted caused by the large space occupied by the extension in the second direction.

[0019] In some embodiments of the present application, the current collector includes two fourth end faces arranged opposite each other along a third direction, the active material layer includes two fifth end faces arranged opposite each other along the third direction, and the transition layer includes two sixth end faces arranged opposite each other along the third direction. The first direction, the second direction, and the third direction are mutually perpendicular. Along the third direction, among the fourth, fifth, and sixth end faces located on the other side of the active material layer, the current collector between the fourth and sixth end faces forms a hollow foil area for connecting to the electrode terminal, and the transition layer between the fifth and sixth end faces constitutes a partial extension. The spacing L3 between the fourth and sixth end faces satisfies the following condition: 0.2 mm ≤ L3 ≤ 1.8 mm, thereby limiting the area of ​​the hollow foil area. When L3 is too small (less than 0.2 mm), the area of ​​the hollow foil area connecting to the electrode terminal is reduced, resulting in a risk of weak connection strength. When L3 is too large (greater than 1.8 mm), the hollow foil area occupies a large space in the second direction X, resulting in wasted space and affecting the energy density of the electrode sheet. By limiting the range of 0.2mm≤L3≤1.8mm, the connection strength between the hollow foil area and the electrode terminal is improved, and the space wasted in the third direction caused by the hollow foil area is reduced, which is conducive to improving the energy density of the electrode sheet. The distance L4 between the fifth end face and the sixth end face satisfies the requirement of 0<L4≤1.5mm. This facilitates visual inspection of whether the transition layer protrudes beyond the edge of the corresponding active material layer in the third direction, and reduces the space wasted caused by the large space occupied by the extension in the third direction.

[0020] In some embodiments of the present application, 0.4mm≤L3≤0.6mm further enhances the connection strength between the hollow foil area and the electrode terminal and reduces the space wasted in the third direction by the hollow foil area, thereby improving the energy density of the electrode. 0.2mm≤L4≤0.5mm further facilitates visual inspection of whether the transition layer protrudes beyond the edge of the corresponding active material layer in the third direction and reduces the space wasted caused by the large space occupied by the extension in the third direction.

[0021] In some embodiments of the present application, along the first direction, the thickness H1 of the current collector satisfies the following conditions: 4 μm ≤ H1 ≤ 16 μm, so as to meet the structural strength requirements of the current collector and reduce the space waste generated by the current collector, which is beneficial to improving the energy density of the electrode. The thickness H2 of the transition layer satisfies the following conditions: 0.5 μm ≤ H2 ≤ 3 μm, so as to improve the buffering performance and bonding strength of the transition layer and reduce the space waste generated by the transition layer, which is beneficial to improving the energy density of the electrode. The thickness H3 of the active material layer satisfies the following conditions: 60 μm ≤ H3 ≤ 160 μm, so as to control the internal resistance of the electrode and reduce the space waste generated by the active material layer, which is beneficial to improving the energy density of the electrode.

[0022] In some embodiments of the present application, 7μm ≤ H1 ≤ 9μm is used to further meet the structural strength requirements of the current collector and reduce the space waste generated by the current collector, which is beneficial to improving the energy density of the electrode. 1μm ≤ H2 ≤ 1.5μm is used to further improve the buffering performance and bonding strength of the transition layer and reduce the space waste generated by the transition layer, which is beneficial to improving the energy density of the electrode. 90μm ≤ H3 ≤ 110μm is used to further control the internal resistance of the electrode and reduce the space waste generated by the active material layer, which is beneficial to improving the energy density of the electrode.

[0023] In some embodiments of the present application, the resistance R of the transition layer satisfies: 1mohm≤R≤20mohm, so as to improve the conductivity of the transition layer.

[0024] An embodiment of the present application further provides a battery cell, which includes an electrode assembly, and the electrode assembly includes any one of the electrode sheets in the above embodiments.

[0025] An embodiment of the present application further provides an electrical device, comprising any one of the pole pieces in the above embodiments or any one of the battery cells in the above embodiments.

[0026] In the above-mentioned electrode sheet, battery cell and electrical equipment, one of the transition layers is arranged between at least a portion of the first conductive layer and the corresponding active material layer and protrudes along the second direction from the edge of the corresponding active material layer, and the other transition layer is arranged between at least a portion of the second conductive layer and the corresponding active material layer and protrudes along the second direction from the edge of the corresponding active material layer. This allows the portion of the transition layer corresponding to the edge of the active material layer to relieve the shear force applied to the corresponding position of the current collector during the cold pressing process, thereby reducing the risk of damage to the current collector due to excessive shear force and improving the structural strength of the electrode sheet. The average particle size of the active material particles is limited to 5μm to 20μm to improve the cycle performance, energy density and lithium precipitation performance of the electrode sheet. Compared with the active material particles, the solid particles are less likely to expand when in contact with the electrolyte, so that the transition layer can buffer the deformation caused by the expansion of the corresponding active material layer. The average particle size of the solid particles is limited to 500nm to 1500nm to control production costs and reduce interface resistance. Moreover, the average particle size of the solid particles is smaller than the average particle size of the active material particles, which is beneficial for the solid particles to act as a buffer between the active material particles and the current collector, reducing the risk of active material particles with larger average particle size directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic plan view of a pole piece in one embodiment of the present application.

[0028] FIG. 2 is a cross-sectional view of FIG. 1 along section line AA.

[0029] FIG3 is a plan view of a pole piece in another embodiment of the present application.

[0030] FIG. 4 is a cross-sectional view taken along section line BB of FIG. 3 .

[0031] FIG5 is a schematic diagram showing an arc-shaped projection of the hole wall of the through hole of the pole piece in one embodiment of the present application.

[0032] FIG6 is a schematic diagram showing a wavy projection of the hole wall of the through hole of the pole piece in one embodiment of the present application.

[0033] FIG7 is a schematic diagram showing a sawtooth-shaped projection of the hole wall of the through hole of the pole piece in one embodiment of the present application.

[0034] FIG8 is a schematic diagram of the structure of a battery cell in one embodiment of the present application.

[0035] FIG9 is a schematic structural diagram of an electrical device in an embodiment of the present application.

[0036] Explanation of the main component symbols: Pole pieces 100a, 100b, Battery cell 200, Electrical device 300, Current collector 10, Support layer 11, First conductive layer 12, Second conductive layer 13, First end surface 101, Fourth end surface 102, Active material layer 20, Second end surface 21, Fifth end surface 22, Transition layer 30, Connecting portion 31, Through hole 311, Extension portion 32, Third end surface 301, Sixth end surface 302, Projected overlapping area 40, Inner periphery 41, Outer periphery 42, Electrode assembly 201, First pole piece 202, Second pole piece 203, Separator 204, Tab 205, First direction Z, Second direction X, Third directionY

[0037] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0039] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centrally located element. When an element is considered to be "set" on another element, it can be directly set on the other element or there may be a centrally located element. When a value is considered to be "equal" to another value, it means that the two values ​​are equal within a set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if the values ​​are unequal, they are still judged to be approximately equal. When a value is considered to have a "1:1" ratio with another value, it means that the two values ​​are equal within a set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if the values ​​are unequal, they are still judged to be equal in ratio.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] It should be understood that, considering the factors of actual processing tolerance, the term "perpendicular" in the technical solution of this application is used to describe the ideal state between two components. In the actual production or use state, there may be a state that is approximately perpendicular between the two components. For example, in combination with the numerical description, perpendicularity can refer to the angle between two straight lines being between 90°±10°, perpendicularity can also refer to the dihedral angle between two planes being between 90°±10°, and perpendicularity can also refer to the angle between a straight line and a plane being between 90°±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic point of view, the components can be considered as "straight lines" or "planes" if the overall extension direction is a straight line or a plane.

[0042] Herein, the term "average particle size" refers to the particle size at which the volume accumulation reaches 50% from the small particle size side in the volume-based particle distribution of the material as measured by a laser particle size analyzer, and may also be referred to as "D50".

[0043] One embodiment of the present application provides a pole piece comprising a current collector, two active material layers, and two transition layers. The current collector comprises a support layer, and a first conductive layer and a second conductive layer disposed on either side of the support layer in a first direction, the first direction being the thickness direction of the current collector. One active material layer is disposed on a side of the first conductive layer facing away from the support layer, and the other active material layer is disposed on a side of the second conductive layer facing away from the support layer. One transition layer is disposed between at least a portion of the first conductive layer and the corresponding active material layer and protrudes beyond the peripheral edge of the corresponding active material layer in a second direction. The other transition layer is disposed between at least a portion of the second conductive layer and the corresponding active material layer and protrudes beyond the peripheral edge of the corresponding active material layer in a second direction perpendicular to the first direction. The active material layer comprises active material particles having an average particle size of 5 μm to 20 μm; the transition layer comprises solid particles comprising at least one of aluminum oxide, silicon oxide, silicon carbide, tin oxide, indium oxide, titanium dioxide, cobalt oxide, chromium trioxide, boehmite, amorphous carbon, lithium phosphorus oxynitride, and titanium diboride. The average particle size of the solid particles is 500 nm to 1500 nm.

[0044] In the above-mentioned electrode, one transition layer is disposed between at least a portion of the first conductive layer and the corresponding active material layer and protrudes along the second direction from the edge of the corresponding active material layer, and the other transition layer is disposed between at least a portion of the second conductive layer and the corresponding active material layer and protrudes along the second direction from the edge of the corresponding active material layer. This allows the portion of the transition layer corresponding to the edge of the active material layer to relieve the shear force applied to the corresponding portion of the current collector during the cold pressing process, thereby reducing the risk of damage to the current collector due to excessive shear force and improving the structural strength of the electrode. Compared to active material particles, solid particles are less likely to expand when in contact with the electrolyte, allowing the transition layer to buffer deformation caused by expansion of the corresponding active material layer. By limiting the average particle size of the active material particles to 5μm to 20μm, the cycling performance, energy density, and lithium deposition performance of the electrode are improved. By limiting the average particle size of the solid particles to 500nm to 1500nm, production costs are controlled and interface resistance is reduced. Moreover, the average particle size of the solid particles is smaller than the average particle size of the active material particles, which is beneficial for the solid particles to act as a buffer between the active material particles and the current collector, reducing the risk of active material particles with larger average particle size directly contacting the current collector and causing extrusion damage to the first conductive layer or the second conductive layer, thereby improving the structural strength of the electrode.

[0045] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0046] Example 1

[0047] Referring to Figures 1 and 2 , one embodiment of the present application provides an electrode sheet 100a. Electrode sheet 100a is used to form a battery cell for use in a secondary battery. A secondary battery is a battery that can be recharged after discharge to activate the active material for continued use. Electrode sheet 100a can optionally be a positive electrode sheet or a negative electrode sheet.

[0048] The electrode sheet 100a includes a current collector 10, two active material layers 20, and two transition layers 30. The current collector 10 is a composite current collector used to collect current. Specifically, the current collector 10 includes a support layer 11, and a first conductive layer 12 and a second conductive layer 13 disposed on either side of the support layer 11 in a first direction Z. The first direction Z is the thickness direction of the current collector 10.

[0049] The support layer 11 is made of a polymer insulating material with high structural strength, low density and mass, which can reduce the thickness and weight of the current collector 10. The first conductive layer 12 and the second conductive layer 13 are made of a metal material. Compared with traditional metal current collectors, the first conductive layer 12 and the second conductive layer 13 arranged on both sides of the support layer 11 are thinner. This helps to reduce the generation of metal burrs when the current collector 10 is mechanically damaged by external impact, thereby reducing the risk of short circuits.

[0050] Optionally, the polymer insulating material includes one or more of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyetherketone (PEK), and polyphenylene sulfide (PPS).

[0051] Optionally, the metal material includes one or more of aluminum, copper, nickel, silver, gold, and iron.

[0052] Referring to Figures 1 and 2 , one active material layer 20 is disposed on the side of the first conductive layer 12 facing away from the support layer 11, and the other active material layer 20 is disposed on the side of the second conductive layer 13 facing away from the support layer 11. The two active material layers 20 are used to generate current and collect the current onto the current collector 10. Specifically, the active material layer 20 is applied to one side of the first conductive layer 12 or one side of the second conductive layer 13 by extrusion coating, transfer coating, spray coating, or other methods.

[0053] Optionally, when viewed along the first direction Z, the two active material layers 20 are continuously arranged in both the length direction and the width direction of the electrode piece 100 a.

[0054] One transition layer 30 is disposed between at least a portion of the first conductive layer 12 and the corresponding active material layer 20 and protrudes beyond the edge of the corresponding active material layer 20 along the second direction X. The other transition layer 30 is disposed between at least a portion of the second conductive layer 13 and the corresponding active material layer 20 and protrudes beyond the edge of the corresponding active material layer 20 along the second direction X. The active material layer 20 corresponding to the first conductive layer 12 refers to the active material layer 20 located on the side of the first conductive layer 12 facing away from the support layer 11, and the active material layer 20 corresponding to the second conductive layer 13 refers to the active material layer 20 located on the side of the second conductive layer 13 facing away from the support layer 11. The current generated by the active material layer 20 is collected by the corresponding transition layer 30 onto the current collector 10. The portion of the transition layer 30 corresponding to the edge of the active material layer 20 is used to alleviate shear forces applied to the corresponding portion of the current collector 10 during the cold pressing process, thereby reducing the risk of damage to the current collector 10 due to excessive shear forces and improving the structural strength and conductive performance of the electrode 100a. The first direction Z is perpendicular to the second direction X. Optionally, the second direction X is the width direction of the current collector 10 .

[0055] The active material layer 20 includes active material particles, and the average particle size of the active material particles is 5μm to 20μm. When the average particle size of the active material particles is too small (less than 5μm), it is easy to cause difficulty in dispersing the slurry, affecting the cycle performance of the electrode 100a. When the average particle size of the active material particles is too large (greater than 20μm), it is easy to cause the solid-phase diffusion resistance of the active ions to increase, the polarization to increase, and affect the energy density and lithium precipitation performance of the electrode 100a. By limiting the average particle size of the active material particles to 5μm to 20μm, the cycle performance, energy density and lithium precipitation performance of the electrode 100a can be improved.

[0056] Optionally, the average particle size of the active material particles can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, and any other value in the range of 5μm to 20μm.

[0057] Furthermore, the average particle size of the active material particles is 10 μm to 15 μm, so as to further improve the cycle performance, energy density and lithium deposition performance of the electrode 100 a.

[0058] The transition layer 30 includes solid particles. Specifically, the transition layer 30 is a layered structure formed by a slurry composed of solid particles on the first conductive layer 12 and the second conductive layer 13. The layered structure has lithium ion conductivity. The solid particles are solid electrolytes that do not contain positive electrode active material particles and negative electrode active material particles. Exemplarily, the solid electrolyte is an oxide solid electrolyte or a sulfide solid electrolyte. It is understood that the materials constituting the transition layer 30 may include, in addition to the solid electrolyte, but are not limited to conductive additives, sintering additives, and binders to improve the structural strength of the transition layer 30. Compared with active material particles, solid particles are less likely to expand when in contact with the electrolyte, so that the transition layer 30 can buffer the deformation caused by the expansion of the corresponding active material layer 20, thereby reducing the risk of separation of the active material layer 20 from the current collector 10.

[0059] Optionally, the solid particles include at least one of aluminum oxide, silicon oxide, silicon carbide, tin oxide, indium oxide, titanium dioxide, cobalt oxide, chromium oxide, boehmite, amorphous carbon, lithium phosphorus oxynitride, and titanium diboride.

[0060] The average particle size of the solid particles is 500nm to 1500nm. When the average particle size of the solid particles is too small (less than 500nm), the production cost will increase. When the average particle size of the solid particles is too large (greater than 1500nm), it is easy to affect the conductive contact between the active material layer 20 and the current collector 10, resulting in a larger interface resistance. By limiting the average particle size of the solid particles to 500nm to 1500nm, the production cost can be controlled and the interface resistance can be reduced. In addition, the average particle size of the solid particles is smaller than the average particle size of the active material particles, which is conducive to the solid particles playing a buffering role between the active material particles and the current collector 10, reducing the risk of active material particles with a larger average particle size directly contacting the current collector 10 and causing extrusion damage to the first conductive layer 12 or the second conductive layer 13, and improving the structural strength of the pole piece 100.

[0061] Optionally, the average particle size of the solid particles can be 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, and any other value within the range of 500 nm to 1500 nm.

[0062] Furthermore, the average particle size of the solid particles is 800nm ​​to 1000nm, so as to further control production costs and reduce interface resistance. In addition, it is further beneficial for the solid particles to play a buffering role between the active material particles and the current collector 10, reducing the risk of active material particles with a larger average particle size directly contacting the current collector 10 and causing extrusion damage to the first conductive layer 12 or the second conductive layer 13, thereby improving the structural strength of the electrode 100a.

[0063] In the aforementioned electrode 100a, one transition layer 30 is disposed between at least a portion of the first conductive layer 12 and the corresponding active material layer 20 and protrudes beyond the edge of the corresponding active material layer 20 along the second direction X. Another transition layer 30 is disposed between at least a portion of the second conductive layer 13 and the corresponding active material layer 20 and protrudes beyond the edge of the corresponding active material layer 20 along the second direction X. This allows the portion of the transition layer 30 corresponding to the edge of the active material layer 20 to mitigate shear forces applied to the corresponding portion of the current collector 10 during the cold pressing process, thereby reducing the risk of damage to the current collector 10 due to excessive shear forces and improving the structural strength and conductivity of the electrode 100a. Compared to active material particles, solid particles are less likely to expand when in contact with the electrolyte, allowing the transition layer 30 to buffer deformation caused by expansion of the corresponding active material layer 20. By limiting the average particle size of the active material particles to 5μm to 20μm, the cycling performance, energy density, and lithium deposition performance of the electrode 100a are improved. By limiting the average particle size of the solid particles to 500nm to 1500nm, production costs are controlled and interfacial resistance is reduced. Furthermore, the average particle size of the solid particles is smaller than that of the active material particles, which helps the solid particles act as a buffer between the active material particles and the current collector 10. This reduces the risk of active material particles with larger average particle sizes directly contacting the current collector 10 and causing compression damage to the first conductive layer 12 or the second conductive layer 13, thereby improving the structural strength of the electrode 100a.

[0064] Please refer to FIG. 1 and FIG. 2 . In some embodiments, the compaction density of the active material layer 20 is 3 g / cm 3 Up to 4.5g / cm 3 The compacted density of the transition layer 30 is 1.6 g / cm 3 Up to 3g / cm 3 . It should be noted that the active material layer 20 and the corresponding transition layer 30 are simultaneously subjected to cold pressing. The difference in the materials of the active material layer 20 and the transition layer 30 makes the compaction density of the active material layer 20 and the compaction density of the transition layer 30 different, and the compaction density of the active material layer 20 and the compaction density of the transition layer 30 are roughly positively correlated. In the process of cold pressing, the compaction density of the active material layer 20 is mainly considered. When the compaction density of the active material layer 20 is too small (less than 3g / cm3), it is easy to cause the energy density of the electrode 100a to be too low; when the compaction density of the active material layer 20 is too large (greater than 4.5g / cm3), it is easy to cause the current collector 10 to be damaged by excessive shear force, affecting the structural strength of the electrode 100a, and it is also easy to cause the channel for ion transmission to be reduced, affecting the cycle performance of the electrode 100a.

[0065] By limiting the compaction density of the active material layer 20 to 3 g / cm 3 to 4.5 g / cm 3 , the energy density and cycle performance of the electrode 100 a are improved, and the risk of damage to the current collector 10 due to excessive shear force is reduced.

[0066] Furthermore, the compacted density of the active material layer 20 is 4.1 g / cm 3 Up to 4.3g / cm 3 The compacted density of the transition layer 30 is 2.2 g / cm 3 Up to 2.4g / cm 3 , in order to further improve the energy density and cycle performance of the electrode 100a, and reduce the risk of damage caused by excessive shear force on the current collector 10.

[0067] Optionally, the compaction density of the active material layer 20 may be 3 g / cm 3 , 3.1g / cm 3 、3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.6g / cm 3 、3.7g / cm 3 、3.8g / cm 3 、3.9g / cm 3 , 4g / cm 3 , 4.1g / cm 3 , 4.2g / cm 3 , 4.3g / cm 3 , 4.4g / cm 3 , 4.5g / cm 3 , and 3g / cm 3 Up to 4.5g / cm 3 Any other value in the range.

[0068] Optionally, the compacted density of the transition layer 30 may be 2.2 g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , and 2.2g / cm 3 Up to 2.4g / cm 3 Any other value in the range.

[0069] In some embodiments, the resistance R of the transition layer 30 satisfies: 1 mohm≤R≤20 mohm, so as to improve the conductivity of the transition layer 30 .

[0070] Alternatively, R may be 1mohm, 2mohm, 3mohm, 4mohm, 5mohm, 6mohm, 7mohm, 8mohm, 9mohm, 10mohm, 01mohm, 12mohm, 13mohm, 14mohm, 15mohm, 16mohm, 17mohm, 18mohm, 19mohm, 20mohm, and any other value within the range of 1mohm≤R≤20mohm.

[0071] Referring to Figures 1 and 2 , in some embodiments, the transition layer 30 includes a connecting portion 31 and an extension portion 32 that are interconnected. Along the first direction Z, the projection of the connecting portion 31 overlaps with the projection of the corresponding active material layer 20, which helps reduce the risk of active material particles directly contacting the current collector 10 and causing compression damage to the first conductive layer 12 or the second conductive layer 13, thereby improving the structural strength of the electrode 100a. The projection of the extension portion 32 is disposed around the projection of the corresponding active material layer 20 and is also located within the projection of the current collector 10. This allows the edge of the transition layer 30 corresponding to the active material layer 20 to relieve the shear force applied to the corresponding portion of the current collector 10 during the cold pressing process, thereby reducing the risk of damage to the current collector 10 due to excessive shear force, thereby improving the structural strength and conductive performance of the electrode 100a.

[0072] Referring to Figures 1 and 2 , in some embodiments, the current collector 10 includes two first end surfaces 101 disposed opposite each other along a second direction X, the active material layer 20 includes two second end surfaces 21 disposed opposite each other along the second direction X, and the transition layer 30 includes two third end surfaces 301 disposed opposite each other along the second direction X. Along the second direction X, among the first end surface 101, the second end surface 21, and the third end surface 301 located on one side of the active material layer 20, the current collector 10 between the first end surface 101 and the third end surface 301 forms a hollow foil region for connecting to an electrode terminal, and the transition layer 30 between the second end surface 21 and the third end surface 301 forms a partially extended portion 32. The electrode terminal may be, but is not limited to, a tab.

[0073] The distance L1 between the first end face 101 and the third end face 301 satisfies: 0.2mm≤L1≤1.8mm, so as to limit the area of ​​the empty foil area. When L1 is too small (less than 0.2mm), the area of ​​the connection between the empty foil area and the electrode terminal is likely to be small, resulting in the risk of weak connection strength; when L1 is too large (greater than 1.8mm), the empty foil area will occupy a large space in the second direction X, resulting in space waste and affecting the energy density of the electrode 100a. By limiting 0.2mm≤L1≤1.8mm, the connection strength between the empty foil area and the electrode terminal is improved, and the space waste generated by the empty foil area in the second direction X is reduced, which is conducive to improving the energy density of the electrode 100a. It can be understood that the method of connecting the empty foil area to the electrode terminal can be, but is not limited to, welding to form a weld mark.

[0074] The distance L2 between the second end face 21 and the third end face 301 satisfies: 0<L2≤1.5mm, so as to facilitate visual detection of whether the transition layer 30 protrudes from the edge of the corresponding active material layer 20 along the second direction X, and reduce the space waste caused by the large space occupied by the extension portion 32 in the second direction X.

[0075] Optionally, L1 can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, and any other value in the range of 0.2mm≤L1≤1.8mm.

[0076] Optionally, L2 can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, and any other value in the range of 0<L2≤1.5mm.

[0077] Furthermore, 0.4 mm ≤ L1 ≤ 0.6 mm, so as to further improve the connection strength between the empty foil area and the electrode terminal and reduce the space waste generated by the empty foil area in the second direction X, which is beneficial to improving the energy density of the electrode 100 a.

[0078] Furthermore, 0.2 mm ≤ L2 ≤ 0.5 mm, so as to further facilitate visual detection of whether the transition layer 30 protrudes from the edge of the corresponding active material layer 20 along the second direction X, and reduce the space waste caused by the large space occupied by the extension portion 32 in the second direction X.

[0079] Referring to Figures 1 and 2 , in some embodiments, the current collector 10 includes two fourth end surfaces 102 disposed opposite each other along a third direction Y, the active material layer 20 includes two fifth end surfaces 22 disposed opposite each other along the third direction Y, and the transition layer 30 includes two sixth end surfaces 302 disposed opposite each other along the third direction Y. The first direction Z, the second direction X, and the third direction Y are mutually perpendicular. Optionally, the third direction Y is the length direction of the current collector 10.

[0080] Along the third direction Y, among the fourth end face 102, the fifth end face 22, and the sixth end face 302 located on the other side of the active material layer 20, the current collector 10 between the fourth end face 102 and the sixth end face 302 forms a hollow foil area for connecting to the electrode terminal, and the transition layer 30 between the fifth end face 22 and the sixth end face 302 is a partial extension portion 32. The electrode terminal can be, but is not limited to, a tab.

[0081] The distance L3 between the fourth end face 102 and the sixth end face 302 satisfies the following conditions: 0.2mm≤L3≤1.8mm, thereby limiting the area of ​​the empty foil area. When L3 is too small (less than 0.2mm), the area of ​​the connection between the empty foil area and the electrode terminal is small, resulting in a risk of weak connection strength. When L3 is too large (greater than 1.8mm), the empty foil area occupies a large space in the third direction Y, resulting in space waste and affecting the energy density of the electrode piece 100a. By limiting 0.2mm≤L3≤1.8mm, the connection strength between the empty foil area and the electrode terminal is improved, and the space waste caused by the empty foil area in the third direction Y is reduced, which is conducive to improving the energy density of the electrode piece 100a.

[0082] The distance L4 between the fifth end face 22 and the sixth end face 302 satisfies: 0<L4≤1.5mm, so as to facilitate visual detection of whether the transition layer 30 protrudes from the edge of the corresponding active material layer 20 along the third direction Y, and reduce the space waste caused by the large space occupied by the extension portion 32 in the third direction Y.

[0083] Optionally, L3 can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, and any other value in the range of 0.2mm≤L3≤1.8mm.

[0084] Optionally, L4 can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, and any other value in the range of 0<L4≤1.5mm.

[0085] Furthermore, 0.4 mm ≤ L3 ≤ 0.6 mm, so as to further improve the connection strength between the empty foil area and the electrode terminal and reduce the space waste caused by the empty foil area, which is beneficial to improving the energy density of the electrode 100 a.

[0086] Furthermore, 0.2 mm ≤ L4 ≤ 0.5 mm, so as to further facilitate visual detection of whether the transition layer 30 protrudes from the edge of the corresponding active material layer 20 along the third direction Y, and reduce the space waste caused by the large space occupied by the extension portion 32 in the second direction X.

[0087] It can be understood that the first end face 101, the second end face 21, the third end face 301, the fourth end face 102, the fifth end face 22 and the sixth end face 302 can respectively be one of a planar structure, a curved surface structure and an irregular structure, wherein the shortest distance between the two end faces is used as the distance limiting the above range.

[0088] It is understandable that, in other embodiments, the edge of the active material layer 20 further has a thinned region, and the second end face 21 or the fifth end face 22 is located at the end of the corresponding thinned region.

[0089] Referring to Figures 1 and 2 , in some embodiments, the two transition layers 30 on either side of the current collector 10 along the first direction Z have equal widths in the second direction X. The projections of the two transition layers 30 are staggered in the second direction X, and each transition layer 30 includes a staggered region that does not overlap with the other transition layer 30. The two staggered regions are spaced apart in the second direction X, and have equal widths in the second direction X of less than or equal to 0.3 mm to meet processing tolerance requirements.

[0090] Optionally, the width of each misaligned area in the second direction X is 0, 0.1 mm, 0.2 mm, 0.3 mm, or any other value within a range of less than 0.3 mm.

[0091] Please refer to Figure 1 and Figure 2 together. In some embodiments, along the first direction Z, the thickness H1 of the current collector 10 satisfies: 4μm≤H1≤20μm, so as to meet the structural strength requirements of the current collector 10 and reduce the space waste generated by the current collector 10, which is conducive to improving the energy density of the electrode 100a.

[0092] Alternatively, H1 may be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, and any other value within the range of 4 μm to 20 μm.

[0093] Furthermore, 7m≤H1≤9m, so as to further meet the structural strength requirement of the current collector 10 and reduce the space waste caused by the large space occupied by the current collector 10, which is beneficial to improving the energy density of the electrode 100a.

[0094] In some embodiments, along the first direction Z, the thickness H2 of the transition layer 30 satisfies the following: 0.5 μm ≤ H2 ≤ 3 μm. When H2 is too small (less than 0.5 μm), the buffering performance and adhesive strength of the transition layer 30 are likely to be affected. When H2 is too large (greater than 3 μm), the transition layer 30 may occupy a large space, resulting in wasted space and affecting the energy density of the pole piece 100a. By limiting the range of 0.5 μm ≤ H2 ≤ 3 μm, the buffering performance and adhesive strength of the transition layer 30 are improved, and the wasted space generated by the transition layer 30 is reduced, which helps to increase the energy density of the pole piece 100a.

[0095] Optionally, H2 can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, and any other value in the range of 0.5μm≤H2≤3μm.

[0096] Furthermore, 1 μm≤H2≤1.5 μm, so as to further improve the buffering performance and bonding strength of the transition layer 30 and reduce the space waste generated by the transition layer 30, which is beneficial to improving the energy density of the pole piece 100 a.

[0097] In some embodiments, along the first direction Z, the thickness H3 of the active material layer 20 satisfies the following: 60 μm ≤ H3 ≤ 160 μm. When H3 is too small (less than 60 μm), the energy density of the electrode 100 a may be too low. When H3 is too large (greater than 160 μm), the internal resistance of the electrode 100 a may be increased and the space occupied by the active material layer 20 may be large, resulting in wasted space. By limiting the range of 60 μm ≤ H3 ≤ 160 μm, the internal resistance of the electrode 100 a is controlled and the wasted space generated by the active material layer 20 is reduced, which helps to improve the energy density of the electrode 100 a.

[0098] Alternatively, H3 may be 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, and any other value in the range of 60μm to 160μm.

[0099] Furthermore, 90 μm≤H3≤110 μm can further control the internal resistance of the electrode 100 a and reduce the active material layer 20 or the space waste generated by the active material layer 20 , which is beneficial to improving the energy density of the electrode 100 a.

[0100] In some embodiments, the coating weight of the active material layer 20 is 100 mg / 1540.25 mm 2 Up to 400mg / 1540.25mm 2 When the coating weight is too small (less than 100mg / 1540.25mm 2 ), which may easily lead to too low energy density of the electrode 100a; when the coating weight is too large (greater than 400mg / 1540.25mm 2 ), which may easily lead to waste of ingredients. In severe cases, it may also cause excessive capacity, resulting in dendrite precipitation, piercing the diaphragm and short circuit, affecting the safety of the battery cell where the electrode 100a is located. By limiting the coating weight of the active material layer 20 to 100mg / 1540.25mm 2 Up to 400mg / 1540.25mm 2 , which can improve the energy density of the electrode 100a, reduce material waste and improve the safety of the battery cell where the electrode 100a is located.

[0101] Optionally, the coating weight of the active material layer 20 may be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, or any other value within the range of 100 to 400, and the corresponding coating weight is in mg / 1540.25 mm 2 .

[0102] Example 2

[0103] Please refer to Figures 3 and 4 together. One embodiment of the present application also provides a pole piece 100b. The difference between the pole piece 100b and the pole piece 100a is that: the connecting portion 31 is provided with a through hole 311 that passes through the connecting portion 31 along the first direction Z, the active material layer 20 passes through the through hole 311 and is connected to the corresponding first conductive layer 12 or the second conductive layer 13. The shear force applied by the edge of the active material layer 20 to the current collector 10 during the cold pressing process is greater than the shear force exerted on other parts of the current collector 10. By providing the through hole 311, the transition layer 30 is adapted to the part of the current collector 10 that is subjected to greater shear force, so as to reduce the risk of active material particles at the edge of the active material layer 20 directly contacting the current collector 10 and causing extrusion damage to the first conductive layer 12 or the second conductive layer 13, and alleviate the shear force exerted on the corresponding position of the current collector 10 during the cold pressing process, thereby reducing the risk of damage to the current collector 10 due to excessive shear force, thereby improving the structural strength and conductive performance of the pole piece 100b. Furthermore, the thickness of the active material layer 20 at the portion passing through the through hole 311 is relatively large, which is beneficial for improving the energy density of the electrode 100 b.

[0104] In some embodiments, along the first direction Z, the projection of the through hole 311 is located within the projection range of the corresponding active material layer 20, and the projection overlapping area 40 of the connecting portion 31 and the corresponding active material layer 20 includes an inner periphery 41 and an outer periphery 42, the inner periphery 41 is the projection of the edge of the hole wall of the through hole 311, and the outer periphery 42 is the projection of the end face of the corresponding active material layer 20, and the outer periphery 42 is arranged around the circumference of the inner periphery 41, and the spacing L5 between the inner periphery 41 and the outer periphery 42 satisfies: 0<L5≤1mm. Since the edge stress of the active material layer 20 is large, arranging a transition layer at the edge position is beneficial to playing a buffering role between the edge of the active material layer 20 and the current collector 10, and is beneficial to increasing the volume of the part where the active material layer 20 passes through the through hole 311, thereby helping to increase the volume of the thicker part of the active material layer 20 and improve the energy density of the electrode 100b.

[0105] Optionally, L5 may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, or any other value within the range of 0<L5≤1 mm.

[0106] Furthermore, 0<L5≤0.5mm is beneficial to further increase the volume of the portion where the active material layer 20 passes through the through hole 311, thereby facilitating an increase in the volume of the portion with a larger thickness in the active material layer 20 and improving the energy density of the electrode 100b.

[0107] In some embodiments, along the first direction Z, the projection shape of the through hole 311 is rectangular, so that the transition layer 30 can form the through hole 311 during the coating process.

[0108] Referring to Figures 5, 6 and 7, it can be understood that in other embodiments, the projection of the hole wall of the through hole 311 is arc-shaped, wavy, serrated, etc., so as to increase the connection area between the hole wall of the through hole 311 and the corresponding active material layer 20, thereby increasing the connection strength between the transition layer 30 and the corresponding active material layer 20.

[0109] It should be noted that, except for the above differences, the parameters of the pole piece 100b and the pole piece 100a are substantially the same, and reference may be made to the description of the pole piece 100a above.

[0110] Please refer to FIG. 8 . An embodiment of the present application further provides a battery cell 200 , including an electrode assembly 201 . The electrode assembly 201 includes the electrode piece 100 a ( 100 b ) in any of the above embodiments.

[0111] In some embodiments, the electrode assembly 201 includes a first electrode plate 202, a separator 204, and a second electrode plate 203 stacked in sequence along a first direction Z. The first electrode plate 202 has a positive polarity, and the second electrode plate 203 has a negative polarity. At least one of the first electrode plate 202 and the second electrode plate 203 is the electrode plate 100a (100b).

[0112] In some embodiments, the first electrode piece 202 is the electrode piece 100a (100b), and the battery cell 200 further includes a plurality of electrode tabs 205, one end of each electrode tab 205 is connected to the empty foil area of ​​the first electrode piece 202, and the other end of each electrode tab 205 extends outward.

[0113] It is understood that in other embodiments, the electrode assembly 201 includes a first electrode 202, a separator 204, and a second electrode 203 that are wound in sequence. The first electrode 202 has a positive polarity, and the second electrode 203 has a negative polarity. Among them, at least one of the first electrode 202 and the second electrode 203 is the electrode 100a (100b).

[0114] Referring to FIG9 , one embodiment of the present application further provides an electric device 300, comprising the electrode 100a (100b) or the battery cell 200 of any of the above embodiments. The electric device 300 may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, or an electric tool.

[0115] In summary, in the above-mentioned electrode 100a (100b), battery cell 200 and electrical device 300, one of the transition layers 30 is arranged between at least a portion of the first conductive layer 12 and the corresponding active material layer 20 and protrudes from the edge of the peripheral side of the corresponding active material layer 20 along the second direction X, and the other transition layer 30 is arranged between at least a portion of the second conductive layer 13 and the corresponding active material layer 20 and protrudes from the edge of the peripheral side of the corresponding active material layer 20 along the second direction X, so that the portion of the transition layer 30 corresponding to the edge of the active material layer 20 is relieved of the shear force on the corresponding position of the current collector 10 during the cold pressing process, thereby reducing the risk of damage to the current collector 10 due to excessive shear force, and improving the structural strength and conductive performance of the electrode 100a (100b). By limiting the average particle size of the active material particles to 5μm to 20μm, the cycle performance, energy density and lithium precipitation performance of the electrode 100a (100b) are improved. Compared to active material particles, solid particles are less likely to expand when in contact with the electrolyte, allowing the transition layer 30 to buffer deformation caused by the expansion of the corresponding active material layer 20. By limiting the average particle size of the solid particles to 500nm to 1500nm, production costs can be controlled and interfacial resistance can be reduced. Furthermore, the average particle size of the solid particles is smaller than the average particle size of the active material particles, which helps the solid particles act as a buffer between the active material particles and the current collector 10, reducing the risk of active material particles with larger average particle sizes directly contacting the current collector 10 and causing compression damage to the first conductive layer 12 or the second conductive layer 13, thereby improving the structural strength of the electrode 100a (100b).

[0116] Hereinafter, the present application will be specifically described based on Examples through Tables 1 to 3, but the present application is not limited to these Examples.

[0117] Among them, the tensile strength of the tab is used as a parameter for comparison. It should be noted that one end of the tab is connected to the empty foil area of ​​the pole piece 100a (100b), and the other end extends outward. The edge portion of the pole piece 100a (100b) (the portion of the edge of the current collector 10 corresponding to the active material layer 20) has a weaker tensile strength than other portions of the pole piece 100a (100b). During the stretching process of the tab, the edge portion of the pole piece 100a (100b) is prone to break and separate first. Therefore, the tensile strength of the tab can reflect the structural strength of the pole piece 100a (100b). The higher the tensile strength of the tab, the higher the structural strength of the pole piece 100a (100b), and the lower the tensile strength of the tab, the lower the structural strength of the pole piece 100a (100b).

[0118] The tensile strength of the tabs of each embodiment and comparative example was measured by the following method. The pole piece 100a (100b) was cut into strips of 20 mm x 10 cm, with the pole piece and tab at either end. The strips were fixed at both ends by a tensile testing machine and stretched at a constant rate of 50 mm / min. The maximum tensile stress at the edge of the pole piece 100a (100b) when it broke was recorded. The ratio of the maximum tensile stress to the cross-sectional area at the break was the tensile strength of the tab.

[0119] The energy density of the batteries of the embodiments and comparative examples was measured in the following manner: at 25°C, the battery was charged to 3.9V at a constant current of 0.5C, and then charged to 0.05C at a constant voltage, and the thickness, width, and length of the battery made of the electrode 100a (100b) were measured. At 25°C, the battery was charged to 4.45V at a constant current of 0.5C, and then charged to 0.025C at a constant voltage, and left for 5 minutes, and discharged to 3.0V at a constant current of 0.1C, and the discharge energy of the battery was recorded. Energy density (Wh / L) = discharge energy (Wh) / (battery thickness (mm) × battery width (mm) × battery length (mm) × 10 -6 ).

[0120] The test standard is: the tab tensile strength is greater than or equal to 26N / mm 2 To pass, greater than or equal to 28N / mm 2 Energy density greater than or equal to 700Wh / L is considered passing, and greater than or equal to 720Wh / L is considered excellent.

[0121] Example 1

[0122] Referring to Figure 2 , the transition layer 30 includes a connecting portion 31 and an extending portion 32 that are interconnected. Along the first direction Z, the projection of the connecting portion 31 overlaps with the projection of the corresponding active material layer 20, while the projection of the extending portion 32 surrounds and surrounds the projection of the corresponding active material layer 20 and is also located within the projection of the current collector 10. L1 = 1.8 mm; L2 = 0.2 mm; L3 = 0.2 mm; L4 = 0.2 mm; H1 = 8 μm; H2 = 2 μm; H3 = 60 μm; the compacted density of the active material layer 20 is 3 g / cm³; the compacted density of the transition layer 30 is 1.6 g / cm³; the average particle size of the active material particles is 5 μm; the average particle size of the solid particles is 500 nm; and the solid particles include aluminum oxide, tin oxide, silicon oxide, boehmite, and calcium carbonate.

[0123] Example 2

[0124] The process was the same as in Example 1 except that the average particle size of the active material particles was 10 μm.

[0125] Example 3

[0126] The process was the same as in Example 1 except that the average particle size of the active material particles was 15 μm.

[0127] Example 4

[0128] The process was the same as in Example 1 except that the average particle size of the active material particles was 20 μm.

[0129] Comparative Example 1

[0130] The process was the same as in Example 1 except that the average particle size of the active material particles was 2 μm.

[0131] Comparative Example 2

[0132] The process was the same as in Example 1 except that the average particle size of the active material particles was 30 μm.

[0133] Example 5

[0134] Except that the average particle size of the solid particles is 800 nm, the rest is the same as Example 1.

[0135] Example 6

[0136] Except that the average particle size of the solid particles is 1000 nm, the rest is the same as Example 1.

[0137] Example 7

[0138] Except that the average particle size of the solid particles is 1500 nm, the rest is the same as Example 1.

[0139] Comparative Example 3

[0140] The process was the same as in Example 1 except that the average particle size of the active material particles was 200 nm.

[0141] Comparative Example 4

[0142] The process was the same as in Example 1 except that the average particle size of the active material particles was 2000 nm.

[0143] Example 8

[0144] 4 , except that the connection portion 31 is provided with a through hole 311 penetrating the connection portion 31 along the first direction Z, the active material layer 20 passes through the through hole 311 and connects to the corresponding first conductive layer 12 or second conductive layer 13 , and L5 is 0.2 mm, the rest is the same as in Example 1.

[0145] Example 9

[0146] Except that L5 is 0.5 mm, the rest is the same as Example 8.

[0147] Example 9

[0148] Except that L5 is 1 mm, the rest is the same as Example 8.

[0149] Example 10

[0150] Except that L5 is 1.5 mm, the rest is the same as Example 8.

[0151] Comparative Example 5 is the same as Example 1 except that the transition layer 30 is made of active material particles.

[0152] Table 1

[0153] From Table 1 we can see that:

[0154] It can be seen from Examples 1-4 and Comparative Examples 1-2 that by limiting the average particle size of the active material particles to 5 μm to 20 μm, the battery energy density (above 700Wh / L) and the structural strength of the electrode (26N / mm 2 above) meet the standards.

[0155] It can be seen from Examples 1, 5-7 and Comparative Examples 3-4 that by limiting the average particle size of the solid particles to 500 nm to 1500 nm, the battery energy density and the structural strength of the pole piece can be achieved.

[0156] As can be seen from Examples 1, 8-11, by providing the through hole 311 and limiting 0 < L5 ≤ 1 mm, the battery energy density and the structural strength of the electrode can be achieved. As can be seen from Example 1 and Comparative Example 5, by providing the transition layer 30, the battery energy density and the structural strength of the electrode can be achieved.

[0157] In Examples 12-16, except for the parameters mentioned in Table 2, all other parameters are the same as those in Example 1.

[0158] Table 2

[0159] As can be seen from Table 2 and Examples 1 and 12-16, by limiting the compaction density of the active material layer 20 to 3 g / cm3 to 4.5 g / cm3 and the compaction density of the transition layer 30 to 1.6 g / cm3 to 3 g / cm3, the battery energy density and the structural strength of the electrode can be achieved.

[0160] In Examples 17-40, except for the parameters mentioned in Table 3, all other parameters are the same as those in Example 1.

[0161] Table 3

[0162] It can be seen from Table 3 and Examples 1 and 17-21 that by limiting 0.2 mm ≤ L1 ≤ 1.8 mm, the battery energy density and the structural strength of the electrode can be achieved.

[0163] It can be seen from Examples 1 and 22-25 that by limiting 0<L2≤1.5mm, the battery energy density and the structural strength of the electrode can meet the standards.

[0164] It can be seen from Examples 1 and 26-30 that by limiting 4μm≤H1≤20μm, the battery energy density and the structural strength of the electrode can meet the standards.

[0165] It can be seen from Examples 1 and 31-35 that by limiting 0.5 μm ≤ H2 ≤ 3 μm, the battery energy density and the structural strength of the electrode can meet the standards.

[0166] It can be seen from Examples 1 and 36-40 that by limiting 60 μm ≤ H3 ≤ 160 μm, the battery energy density and the structural strength of the electrode can meet the standards.

[0167] It should be noted that the test results obtained using L3 as the test parameter are similar to those obtained using L1 as the test parameter. Therefore, the test results obtained using L3 as the test parameter can refer to Examples 1, 17-21; the test results obtained using L4 as the test parameter are similar to those obtained using L2 as the test parameter. Therefore, the test results obtained using L4 as the test parameter can refer to Examples 1, 22-25. In addition, those skilled in the art may make other changes within the spirit of this application. Of course, these changes made in accordance with the spirit of this application should be included in the scope disclosed in this application.

Claims

1. A pole piece, characterized in that, The electrode includes: A current collector, which includes a support layer, and a first conductive layer and a second conductive layer disposed on both sides of the support layer in a first direction, where the first direction is the thickness direction of the current collector; Two active material layers, one of the active material layers is disposed on a side of the first conductive layer away from the support layer, and the other active material layer is disposed on a side of the second conductive layer away from the support layer; Two transition layers, one of the transition layers is disposed between at least a part of the first conductive layer and the corresponding active material layer, and the other transition layer is disposed between at least a part of the second conductive layer and the corresponding active material layer; The active material layer includes active material particles, and the average particle size of the active material particles is 5 μm to 20 μm; The transition layer includes solid particles, and the solid particles include at least one of aluminum oxide, silicon oxide, silicon carbide, tin oxide, indium oxide, titanium dioxide, cobalt oxide, chromium sesquioxide, boehmite, amorphous carbon, lithium phosphorus oxynitride, and titanium diboride; the average particle size of the solid particles is 500 nm to 1500 nm.

2. The electrode sheet according to claim 1, characterized in that Along a second direction, the transition layer protrudes from an edge of a periphery of the corresponding active material layer, and the second direction is perpendicular to the first direction.

3. The pole piece according to claim 2, characterized in that, The average particle size of the active material particles is 5 to 15 μm; the average particle size of the solid particles is 500 nm to 1000 nm.

4. The pole piece according to claim 3, characterized in that, The average particle size of the active material particles is 10 μm to 15 μm; the average particle size of the solid particles is 800 nm to 1000 nm.

5. The electrode sheet according to claim 1, wherein, The compaction density of the active material layer is 3 g / cm 3 to 4.5 g / cm 3 ; the compaction density of the transition layer is 1.6 g / cm 3 to 3 g / cm 3 .

6. The pole piece according to claim 5, characterized in that, The compacted density of the active material layer is 4.1 g / cm 3 to 4.3 g / cm 3 ; the compacted density of the transition layer is 2.2 g / cm 3 to 2.4 g / cm 3 .

7. The pole piece according to any one of claims 1, 4, and 6, characterized in that, The transition layer includes a connecting portion and an extending portion that are connected to each other. Along the first direction, a projection of the connecting portion coincides with a projection of the corresponding active material layer, and a projection of the extending portion is disposed around a periphery of the projection of the corresponding active material layer, and the projection of the extending portion is also located within a projection of the current collector.

8. The pole piece according to claim 7, characterized in that, The connecting portion is provided with a through hole that penetrates the connecting portion in the first direction, and the active material layer passes through the through hole and is connected to the corresponding first conductive layer or second conductive layer. Along the first direction, a projection of the through hole is located within a projection range of the corresponding active material layer.

9. The pole piece according to claim 8, wherein, Along the first direction, an overlapping region between a projection of the connecting portion and the corresponding active material layer includes an inner periphery and an outer periphery, the outer periphery is disposed around a periphery of the inner periphery, and a distance L5 between the inner periphery and the outer periphery satisfies: 0 < L5 ≤ 1 mm.

10. The pole piece according to claim 9, characterized in that, 0 < L5 ≤ 0.5 mm.

11. The electrode tab according to claim 2, wherein, The current collector includes two first end faces disposed opposite to each other in the second direction, the active material layer includes two second end faces disposed opposite to each other in the second direction, and the transition layer includes two third end faces disposed opposite to each other in the second direction; Along the second direction, among the first end face, the second end face, and the third end face located on one side of the active material layer, a distance L1 between the first end face and the third end face satisfies: 0.2 mm ≤ L1 ≤ 1.8 mm; a distance L2 between the second end face and the third end face satisfies: 0 < L2 ≤ 1.5 mm.

12. The electrode sheet according to claim 11, wherein 0.4 mm ≤ L1 ≤ 0.6 mm; 0.2 mm ≤ L2 ≤ 0.5 mm.

13. The pole piece according to claim 11, wherein, The current collector includes two fourth end faces oppositely arranged along a third direction, the active material layer includes two fifth end faces oppositely arranged along the third direction, the transition layer includes two sixth end faces oppositely arranged along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other; Along the third direction, among the fourth end face, the fifth end face and the sixth end face located on the other side of the active material layer, the distance L3 between the fourth end face and the sixth end face satisfies: 0.2 mm ≤ L3 ≤ 1.8 mm; the distance L4 between the fifth end face and the sixth end face satisfies: 0 < L4 ≤ 1.5 mm.

14. The pole piece according to claim 12, wherein, 0.4 mm ≤ L3 ≤ 0.6 mm; 0.2 mm ≤ L4 ≤ 0.5 mm.

15. The pole piece according to claim 1, characterized in that, Along the first direction, the thickness H1 of the current collector satisfies: 4 μm ≤ H1 ≤ 16 μm; the thickness H2 of the transition layer satisfies: 0.5 μm ≤ H2 ≤ 3 μm; the thickness H3 of the active material layer satisfies: 60 μm ≤ H3 ≤ 160 μm.

16. The electrode tab according to claim 15, characterized in that, 7 μm ≤ H1 ≤ 9 μm; 1 μm ≤ H2 ≤ 1.5 μm; 90 μm ≤ H3 ≤ 110 μm.

17. The pole piece according to any one of claims 1, 4, 12, and 16, characterized in that, The resistance R of the transition layer satisfies: 1 mohm ≤ R ≤ 20 mohm.

18. A battery cell, characterized in that, Comprising an electrode assembly, the electrode assembly comprising a pole piece as described in any one of claims 1 to 17.

19. An electrical device, characterized in that, Comprising a pole piece as described in any one of claims 1 to 17 or an electric core as described in claim 18.

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