Secondary battery and electronic device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-30
- Publication Date
- 2026-08-13
Smart Images
Figure CN2024085107_13082026_PF_FP_ABST
Abstract
Description
Secondary batteries and electronic devices Technical Field
[0001] This application relates to the field of battery technology, and more particularly to a secondary battery and electronic device. Background Technology
[0002] Rechargeable batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, and long cycle life. With technological advancements, the requirements for the energy density of rechargeable batteries are becoming increasingly stringent. The most direct and effective method for improving battery energy density in current technology mainly involves increasing the areal density of the electrode film. However, while increasing areal density improves the battery's energy density, it also leads to a deterioration in the battery's kinetic performance, resulting in lithium plating and affecting cycle performance.
[0003] Summary of the Invention
[0004] One objective of this application is to provide a secondary battery and electronic device that can improve cycle performance while increasing energy density.
[0005] The first aspect of this application provides a secondary battery, including an electrode assembly. The electrode assembly includes an anode electrode, which includes a current collector and an active layer disposed on at least one surface of the current collector. The areal density of the active layer is 90 mg / 1540.25 mm². 2 ~180mg / 1540.25mm 2 The active layer has multiple strip-shaped grooves.
[0006] The secondary battery of this application has an active layer areal density of 90 mg / 1540.25 mm². 2 ~180mg / 1540.25mm 2 This allows the active layer to have a suitable thickness, enabling the secondary battery to achieve a high energy density. Furthermore, multiple strip-shaped grooves are formed on the active layer, reserving space for electrolyte transport, improving electrolyte transport capacity, mitigating lithium plating issues caused by insufficient kinetics, and enhancing cycle performance.
[0007] According to some embodiments of this application, the spacing between two adjacent strip-shaped grooves is 100 μm to 2000 μm. When the spacing is less than 100 μm, the spacing is too small, making it difficult to process and reducing the bonding area between the electrode and the separator, thus reducing the adhesion force and causing electrode-separator delamination. When the spacing is greater than 2000 μm, the spacing is too large, limiting the improvement effect on electrolyte transport capacity and the effect on improving cycle performance.
[0008] According to some embodiments of this application, the spacing between two adjacent strip grooves is 300μm to 1000μm, which has a better effect on improving the energy transfer of the electrolyte and significantly improves the cycle performance.
[0009] According to some embodiments of this application, the spacing between two adjacent strip grooves is 500μm to 800μm, which improves the energy transfer effect of the electrolyte and significantly enhances the cycle performance.
[0010] According to some embodiments of this application, the thickness of the active layer is D1, the depth of the strip-shaped groove is D2, and 3% ≤ D2 / D1 ≤ 70%. When D2 / D1 < 3%, D2 is too small, and the improvement effect on cycle performance is limited; when D2 / D1 > 70%, D2 is too large, resulting in excessive etching, which may damage the current collector and may cause lithium plating at the strip-shaped groove, thus having a limited effect on improving cycle performance. Further, 8% ≤ D2 / D1 ≤ 70%.
[0011] According to some embodiments of this application, 15% ≤ D2 / D1 ≤ 40% is more conducive to improving cycle performance.
[0012] According to some embodiments of this application, the secondary battery also includes tabs, current collectors include a first edge and a second edge opposite to each other in a first direction, the tabs extend an electrode assembly through the first edge in a first direction, and strip-shaped grooves are arranged perpendicularly, parallelly or obliquely relative to the first edge.
[0013] According to some embodiments of this application, the current collector includes a third edge and a fourth edge opposite to each other in a second direction perpendicular to the first direction, and a plurality of strip-shaped grooves are arranged from the third edge to the fourth edge.
[0014] According to some embodiments of this application, the strip groove includes a first end located on one side of the first edge in the first direction, and the active layer includes a first region corresponding to the tab in the first direction. The distance between the first end of the strip groove in the first region and the first edge is 0 to 3 mm, thereby reducing the risk of etching the tab when forming the strip groove during the etching process.
[0015] According to some embodiments of this application, the secondary battery has a notch, and the electrode assembly has a stacked structure. The electrode assembly includes a first end face, a first side face, a second side face, a third side face, and a second end face connected in sequence. The first end face and the second end face are arranged opposite each other in a first direction. The first side face, the second side face, and the third side face are located on the same side of the electrode assembly in a second direction perpendicular to the first direction. The first side face and the second side face form a notch, and the coating surface density of the active layer is greater than or equal to 130 mg / 1540.25 mm². 2 .
[0016] According to some embodiments of this application, the secondary battery is L-shaped.
[0017] According to some embodiments of this application, in the second direction, the length of the electrode assembly is L1; in the first direction, the width of the electrode assembly is L2, 1.0≤L1 / L2≤3.0.
[0018] According to some embodiments of this application, 1.25 ≤ L1 / L2 ≤ 3.0.
[0019] According to some embodiments of this application, the compaction density of the active layer is greater than 1.72 g / cm³. 3 .
[0020] According to some embodiments of this application, the electrode assembly further includes a diaphragm and a cathode electrode, the diaphragm being disposed between the anode electrode and the cathode electrode, and the peel strength between the diaphragm and the anode electrode being 5 to 15 N / m.
[0021] A second aspect of this application provides an electronic device comprising any of the aforementioned secondary batteries. Attached Figure Description
[0022] Figure 1 is a schematic diagram of a secondary battery provided in one embodiment of this application, viewed along a third direction.
[0023] Figure 2 is a schematic diagram of the electrode assembly provided in one embodiment of this application as viewed along a first direction.
[0024] Figure 3 is a schematic diagram of the anode sheet provided in one embodiment of this application viewed along a third direction.
[0025] Figure 4 is a cross-sectional schematic diagram of the anode sheet provided in one embodiment of this application.
[0026] Figure 5 is a schematic diagram of the anode sheet provided in another embodiment of this application, viewed along a third direction.
[0027] Figure 6 is a schematic diagram of the anode sheet provided in another embodiment of this application, viewed along a third direction.
[0028] Figure 7 is a cross-sectional schematic diagram of the diaphragm provided in one embodiment of this application.
[0029] Explanation of main component symbols
[0030] Secondary battery 100
[0031] Casing 10
[0032] Electrode assembly 20
[0033] Electrode terminal 30
[0034] Cathode tab 31
[0035] Anode tab 32
[0036] Notch 101, 210
[0037] First end wall 11
[0038] First sidewall 12
[0039] Second sidewall 13
[0040] Third side wall 14
[0041] Second end wall 15
[0042] Fourth sidewall 16
[0043] Cathode electrode 21
[0044] Anode plate 22
[0045] Diaphragm 23
[0046] Cathode current collector 211
[0047] Cathode active layer 212
[0048] Current collector 221
[0049] Active layer 222
[0050] First end face 201
[0051] First side view 202
[0052] Second side 203
[0053] Third side 204
[0054] Second end face 205
[0055] Fourth side 206
[0056] First edge 221a
[0057] Second edge 221b
[0058] Strip-shaped groove 22a
[0059] Area 1, 220
[0060] Third edge 221c
[0061] Fourth Edge 221d
[0062] First end 22a1
[0063] Second end 22a2
[0064] Porous base membrane 231
[0065] Adhesive layer 232
[0066] First direction X
[0067] Second direction Y
[0068] Third direction Z
[0069] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation
[0070] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.
[0071] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to thereby convey this application thoroughly and in detail to those skilled in the art.
[0072] Additionally, for brevity and clarity, the dimensions or thicknesses of various components and layers may be enlarged in the accompanying drawings. Throughout the text, the same numerical values refer to the same elements. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more of the associated enumerated items. Furthermore, it should be understood that when element A is referred to as "connecting" element B, or when element A is referred to as "attached" to element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.
[0073] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".
[0074] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.
[0075] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, the first element, component, region, layer, or portion discussed below may be referred to as the second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.
[0076] Referring to Figure 1, one embodiment of this application provides a secondary battery 100, including a housing 10, an electrode assembly 20, an electrolyte, and electrode terminals 30. The electrode assembly 20 and the electrolyte are housed within the housing 10. The electrode terminals 30 are connected to the electrode assembly 20 and extend from one side of the housing 10 along a first direction X to connect to external components. In this application, the first direction X refers to the longitudinal direction of the secondary battery 100. In this embodiment, there are two electrode terminals 30, namely a cathode terminal and an anode terminal, and the two electrode terminals 30 are located on the same side of the secondary battery 100.
[0077] The secondary battery 100 can have a regular shape, such as a rectangle or a circle, or an irregular shape, such as a T-shape or an L-shape. In this embodiment, the secondary battery 100 is L-shaped. The secondary battery 100 has a notch 101. The notch 101 is used to accommodate external components to improve space utilization.
[0078] The housing 10 is generally L-shaped and includes a first end wall 11, a first side wall 12, a second side wall 13, a third side wall 14, a second end wall 15, and a fourth side wall 16 connected end to end. Electrode terminals 30 extend from the housing 10 through the first end wall 11 along a first direction X. The second end wall 15 and the first end wall 11 are disposed opposite each other in the first direction. The first side wall 12, the second side wall 13, and the third side wall 14 are located on the same side of the housing 10 in a second direction Y perpendicular to the first direction X, and the fourth side wall 16 and the third side wall 14 are disposed opposite each other in the second direction Y. The first side wall 12 and the second side wall 13 form a recess 101. The housing 10 can be a packaging bag sealed with an encapsulating film (such as aluminum-plastic film or steel-plastic film), or it can be a metal housing; this application does not limit this.
[0079] The electrode assembly 20 is generally L-shaped, comprising a first end face 201, a first side face 202, a second side face 203, a third side face 204, a second end face 205, and a fourth side face 206 connected end to end. The secondary battery 100 also includes a cathode tab 31 (see Figure 2) and an anode tab 32 (see Figure 2). The cathode terminal is connected to the electrode assembly 20 via the cathode tab 31, and the anode terminal is connected to the electrode assembly 20 via the anode tab 32. The cathode tab 31 and anode tab 32 extend from the electrode assembly 20 along a first direction X through the first end face 201. The second end face 205 is disposed opposite to the first end face 201 in the first direction. The first side face 202, the second side face 203, and the third side face 204 are located on the same side of the housing 10 in a second direction Y perpendicular to the first direction X, and the fourth side face 206 is disposed opposite to the third side face 204 in the second direction Y. The first side face 202 and the second side face 203 form a recess 210. The shape of the notch 210 is basically the same as that of the notch 101, and the notch 210 is arranged around the notch 101. When the secondary battery 100 is L-shaped, the electrolyte tends to accumulate in the area around the fourth side 206 of the electrode assembly 20, causing an increase in local impedance, which makes lithium plating more likely to occur on the side where the fourth side 206 of the electrode assembly 20 is located.
[0080] In the second direction Y, the distance between the third side surface 204 and the fourth side surface 206 is L1. In the first direction X, the distance between the first end face 201 and the second end face 205 is L2. In some embodiments, 1.0 ≤ L1 / L2 ≤ 3.0. Preferably, 1.25 ≤ L1 / L2 ≤ 3.0.
[0081] Referring to Figures 1 and 2, the electrode assembly 20 includes a cathode electrode 21, an anode electrode 22, and a separator 23 disposed between the cathode electrode 21 and the anode electrode 22. The cathode electrode 21, the separator 23, and the anode electrode 22 are stacked sequentially along the third direction Z to form a stacked structure. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. In other embodiments, the cathode electrode 21, the separator 23, and the anode electrode 22 are stacked along the third direction Z and then wound to form a wound structure.
[0082] The cathode electrode 21 includes a cathode current collector 211 and a cathode active layer 212 disposed on at least one surface of the cathode current collector 211. The cathode current collector 211 includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof. A cathode tab 31 is connected to the cathode current collector 211 and a corresponding electrode terminal 30. The cathode tab 31 may extend outward from one end of the cathode current collector 211, or the cathode tab 31 may be welded to the cathode current collector 211 and extend beyond the electrode assembly 20. The cathode active layer 212 includes a cathode active material, which may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and combinations thereof.
[0083] In some embodiments, the cathode active layer 212 further includes a binder, and optionally a conductive agent. The binder can improve the bonding between the active material particles and the bonding between the active material and the current collector. The binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, etc. The conductive agent can improve the conductivity of the electrode. The conductive agent includes, but is not limited to, graphite, carbon black, acetylene black, metal powder, etc.
[0084] The anode electrode 22 includes a current collector 221 and an active layer 222 disposed on at least one surface of the current collector 221. The current collector 221 comprises at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof. An anode tab 32 is connected to the current collector 221 and a corresponding electrode terminal 30. The anode tab 32 may extend outward from one end of the current collector 221, or the anode tab 32 may be welded to the current collector 221 and extend beyond the electrode assembly 20. The active layer 222 comprises an anode active material, which includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxides, silicon-carbon composites, lithium titanate, and metals capable of forming alloys with lithium.
[0085] In some embodiments, the active layer 222 further includes a binder, and optionally a conductive agent. The binder can improve the bonding between the active material particles and the bonding between the active material and the current collector. The binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, etc. The conductive agent can improve the conductivity of the electrode. The conductive agent includes, but is not limited to, graphite, carbon black, acetylene black, metal powder, etc.
[0086] In some embodiments, the areal density of the active layer 222 is 90 mg / 1540.25 mm. 2 ~180mg / 1540.25mm 2Areal density is the mass of the active layer per unit area on one side of the current collector. When the areal density of the active layer 222 is within the above-mentioned range, it is beneficial for the secondary battery 100 to obtain a high energy density. When the areal density is less than 90 mg / 1540.25 mm², ... 2 When the thickness of the active layer on one side of the current collector is too small, it is limited by the particle size of the active material, resulting in problems such as processing scratches and cold pressing windows; when the surface density is greater than 180mg / 1540.25mm... 2 If the active layer on one side of the current collector is too thick, lithium-ion transport becomes difficult, resulting in poor kinetics and failing to meet the requirements of a secondary battery. High areal density leads to poor wettability of the anode electrode 22, preventing the electrolyte from fully wetting the anode active material, affecting kinetic performance, and easily causing lithium plating problems.
[0087] In some embodiments, the areal density of the active layer 222 is 130 mg / 1540.25 mm². 2 ~180mg / 1540.25mm 2 When the secondary battery 100 is L-shaped, and the areal density of the active layer 222 is within the above-mentioned range, lithium plating is more likely to occur on the side where the fourth side 206 of the electrode assembly 20 is located.
[0088] In some embodiments, the compaction density of the active layer 222 is greater than 1.72 g / cm³. 3 Compaction density is the ratio of the areal density to the thickness of the active layer per unit area on one side of the current collector. When the compaction density of the active layer 222 is within the above range, it is beneficial to obtain a high energy density. High compaction density will lead to deterioration of kinetic performance and make lithium plating problems more likely.
[0089] Referring to Figure 3, the current collector 221 includes a first edge 221a and a second edge 221b opposite each other in a first direction X, and a third edge 221c and a fourth edge 221d opposite each other in a second direction Y. An anode tab 32 extends from the first edge 221a along the first direction X as an electrode assembly. The second direction Y is perpendicular to the first direction X. The active layer 222 is provided with a plurality of strip-shaped grooves 22a. The plurality of strip-shaped grooves 22a are arranged from the third edge 221c to the fourth edge 221d. In other words, the plurality of strip-shaped grooves 22a are distributed throughout the current collector 221. In other embodiments, the plurality of strip-shaped grooves 22a are distributed in a portion of the current collector 221, for example, only in the edge region of the current collector 221. The strip-shaped grooves 22a reserve space for electrolyte transport, improving electrolyte transport capacity, mitigating lithium plating problems, and thus improving cycle performance. The strip-shaped grooves 22a are formed by removing a portion of the active layer 222. Any known technique can be used to remove part of the active layer 222, such as laser etching process to remove part of the active layer 222 to form strip grooves 22a.
[0090] Referring to Figure 3, the strip groove 22a includes a first end 22a1 located on one side of the first edge 221a and a second end 22a2 located on one side of the second edge 221b in the first direction X. The active layer 222 includes a first region 220 corresponding to the anode tab 32 in the first direction X. The first region 220 forms a first projection pattern along the third direction Z on the plane where the current collector 221 is located, and the anode tab 32 forms a second projection pattern along the third direction Z on the plane where the current collector 221 is located; along the first direction X, the two opposite sides of the first projection pattern and the two opposite sides of the second projection pattern in the second direction Y are respectively aligned. In the first direction X, the minimum distance between the first end 22a1 of the strip groove 22a in the first region 220 and the first edge 221a is 0-3 mm. In this way, the risk of etching the anode tab 32 during the etching process to form the strip groove 22a can be reduced. In addition, the strip-shaped groove 22a tends to penetrate the active layer 222 located at the edge of the first edge 221a, so that the electrolyte can quickly enter the strip-shaped groove 22a, which is beneficial to improving the transport performance of the electrolyte.
[0091] In some embodiments, the minimum distance between the first end 22a1 and the first edge 221a of each strip groove 22a is 0 to 3 mm, and the minimum distance between the second end 22a2 and the second edge 221b of each strip groove 22a is 0 to 3 mm. This makes each strip groove 22a tend to penetrate the active layer 222 in the first direction X, which is beneficial to improving the transport performance of the electrolyte.
[0092] Please refer to Figure 3. Multiple strip-shaped grooves 22a are arranged parallel to each other. Viewed along the third direction Z, the distance between two adjacent strip-shaped grooves 22a is D3. In this application, the distance D3 between two adjacent strip-shaped grooves 22a refers to the distance between the geometric center lines of the two adjacent strip-shaped grooves. In some embodiments, 100μm≤D3≤2000μm. When D3<100μm, D3 is too small, which is difficult to achieve due to limitations in processing equipment (such as lasers) and low production efficiency; furthermore, a small D3 reduces the bonding area between the electrode and the separator, decreasing the bonding force and causing electrode-separator delamination problems. When D3>2000μm, with a fixed electrode area, the number of strip-shaped grooves is small, resulting in limited improvement in electrolyte transport capacity, limited improvement in lithium plating, and limited improvement in cycle performance. Preferably, 300μm≤D3≤1000μm provides better improvement in electrolyte energy transport, is more conducive to improving lithium plating, and significantly improves cycle performance. Furthermore, 500μm≤D3≤800μm has a better effect on improving the energy transfer of the electrolyte and significantly improves the cycle performance.
[0093] Referring to Figure 4, in the third direction Z, the depth of the strip groove 22a is D2, and the thickness of the active layer 222 is D1. In this application, the depth of the strip groove 22a refers to the distance between the deepest point of the strip groove 22a and the surface of the active layer 222. In some embodiments, 3% ≤ D2 / D1 ≤ 70%. When D2 / D1 < 3%, D2 is too small, and during the etching process to form the strip groove 22a, incomplete etching may occur, affecting the electrolyte transport performance; moreover, a small D2 has limited effect on improving kinetics. When D2 / D1 > 70%, D2 is too large, resulting in over-etching, which may damage the current collector 221 and may also cause the anode capacity to be less than the cathode capacity, leading to lithium plating problems at the location of the strip groove 22a. Preferably, 8% ≤ D2 / D1 ≤ 70%. More preferably, 15% ≤ D2 / D1 ≤ 40% is more conducive to improving cycle performance. It should be noted that in this application, under the condition that the energy density remains constant, that is, under the condition that the mass loss of the active layer removed by forming the strip groove is fixed, the conditions that the thickness D1 of the active layer, the depth D2 of the strip groove, and the distance D3 between two adjacent strip grooves must satisfy are as follows.
[0094] Referring to Figure 3, the strip-shaped groove 22a is arranged perpendicularly to the first edge 221a. Referring to Figure 5, in another embodiment, the strip-shaped groove 22a is arranged parallel to the first edge 221a. Referring to Figure 6, in another embodiment, the strip-shaped groove 22a is arranged obliquely to the first edge 221a, and the included angle θ between the strip-shaped groove 22a and the first edge 221a satisfies 0° < θ < 90°. Preferably, θ = 45°, which further improves the lithium plating effect.
[0095] Referring to Figure 7, in some embodiments, the separator 23 includes a porous base membrane 231 and an adhesive layer 232 stacked together. The adhesive layer 232 is disposed on the surface of the porous base membrane 231 facing the anode electrode and is bonded to its active layer. The adhesive layer 232 bonds the anode electrode, reducing the risk of misalignment between the separator 23 and the anode electrode. The adhesive layer 232 may also be disposed on the surface of the porous base membrane 231 facing the cathode electrode and bonded to the cathode active layer to reduce the risk of misalignment between the separator 23 and the cathode electrode. In other embodiments, the separator 23 includes an adhesive, and the separator 23 is bonded to both the anode and cathode electrodes.
[0096] In some embodiments, the porous base membrane 231 comprises at least one of polyethylene terephthalate, polyethylene, polypropylene, phenolic resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, or polyurethane. In some embodiments, the adhesive layer 232 comprises at least one of polymethyl methacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer, or polyimide.
[0097] In some embodiments, the peel strength between the diaphragm 23 and the anode plate is 5 to 15 N / m.
[0098] One embodiment of this application also provides an electronic device including any of the rechargeable batteries described above. The electronic device of this application may be, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.
[0099] The performance of the secondary battery provided in this application will be described below through specific embodiments and comparative examples.
[0100] Example 1
[0101] Preparation of the cathode electrode: Cathode active material (lithium cobalt oxide), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) are dissolved in an N-methylpyrrolidone solution at a weight ratio of 97.5:1:1.5 to form a cathode slurry with a solid content of 75%. Aluminum foil is used as the current collector, and the cathode slurry is coated onto the surface of the current collector to obtain the cathode active layer. Subsequently, the anode electrode is obtained through cold pressing and cutting.
[0102] Preparation of the anode electrode: Anode active material (graphite), conductive agent (conductive carbon black), thickener (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) are mixed in a mass ratio of 97.5:1:0.5:1. Deionized water is then added as a solvent, and the mixture is stirred until homogeneous, resulting in an anode slurry with a solid content of 50 wt%. Copper foil is used as the current collector, and the anode slurry is coated onto the surface of the current collector to obtain the anode active layer. Subsequently, the anode electrode is obtained through cold pressing and cutting. Multiple strip-shaped grooves are etched into the anode active layer using laser etching. These grooves are distributed throughout the anode active layer and are parallel to the first edge of the current collector. The structure of the anode electrode is shown in Figure 3.
[0103] Preparation of the diaphragm: Polyethylene membrane was selected as the porous base membrane, and an adhesive layer was formed by coating the surface of the porous base membrane. The peel strength between the diaphragm and the electrode was 10 N / m.
[0104] Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propylene propionate (PP), and vinylene carbonate (VC) were mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 and the organic solvent were mixed in a weight ratio of 8:92 to obtain the electrolyte.
[0105] Lithium-ion battery fabrication: The cathode electrode, separator, and anode electrode are stacked sequentially, with the separator positioned between the cathode and anode electrodes, to obtain the electrode assembly. The electrode assembly is then placed in an aluminum-plastic film packaging bag and heat-pressed under preset pressure. After electrolyte injection and formation, a lithium-ion battery is obtained. The electrode assembly is 86 mm long and 43 mm wide, with a single-sided anode active layer areal density of 130 mg / 1540.25 mm². 2 The thickness of the single-sided anode active layer is 60 μm.
[0106] Example 2-15
[0107] The difference from Example 1 lies in that at least one of the following is different: the areal density of the anode active layer, the distance D3 between two adjacent strip grooves, the depth D2 of the strip grooves, and the ratio D2 / D1 of the thickness D1 of the anode active layer. In each embodiment, the mass loss of the active layer removed by forming the strip grooves is fixed at 1.5 wt%. Specific parameters are shown in Table 1.
[0108] Comparative Examples 1-4
[0109] The difference from Example 1 is that multiple strip-shaped grooves are not etched on the anode active layer. Optionally, the areal density of the anode active layer may be different.
[0110] The test methods for each parameter of this application are described below.
[0111] (1) Anodic active layer areal density test:
[0112] Take the anode sheet and punch it into a piece with an area of 1540.25 mm². 2 Take a small round piece, then weigh it using an electronic balance and record the weight as W1; scrape off the anodic active layer and only measure the weight of the round substrate, record it as W2; the areal density of the single-sided anodic active coating = (W1-W2) / 2.
[0113] (2) Testing of the depth D2 of the groove and the distance D3 between two adjacent grooves:
[0114] The cross-section of the anode plate was scanned using a CT scanner to measure the depth of the grooves and the distance between two adjacent grooves.
[0115] (3) Cyclic capacity retention test:
[0116] When the areal density of the anolyte active layer is 90 mg / 1540.25 mm 2 When charging, the following charging process is used:
[0117] (1) Constant current from 4.8C to 4.25V;
[0118] (2) Constant current from 3.9C to 4.25V;
[0119] (3) Constant current at 3.1C to 4.35V;
[0120] (4) 2C constant current to 4.48V;
[0121] (5) 1.6C constant current to 4.55V, constant voltage to 0.425C.
[0122] When the areal density of the anolyte active layer is 130 mg / 1540.25 mm 2 When charging, the following charging process is used:
[0123] (1) Constant current at 2.5C to 4.25V, constant voltage at 2C;
[0124] (2) Constant current at 2.0C to 4.35V, constant voltage at 1.5C;
[0125] (3) Constant current at 1.5C to 4.45V, constant voltage at 1.2C;
[0126] (4) Constant current at 0.8C to 4.5V, constant voltage at 0.025C.
[0127] When the areal density of the anolyte active layer is 150–180 mg / 1540.25 mm 2 When charging, the following charging process is used:
[0128] (1) Constant current at 1.65C to 4.10V, constant voltage at 1.55C to cutoff;
[0129] (2) Constant current at 1.55C to 4.20V, constant voltage at 1.4C to cutoff;
[0130] (3) Constant current at 1.4C to 4.24V, constant voltage at 1.1C to cutoff;
[0131] (4) Constant current at 1.1C to 4.27V, constant voltage at 0.7C to cutoff;
[0132] (5) Maintain constant current at 0.7C to 4.30V, and constant voltage at 0.4C to cut off;
[0133] (6) Maintain a constant current of 0.4C to 4.5V, and a constant voltage to C / 40 cutoff.
[0134] The above charge-discharge process constitutes one cycle. Record the discharge capacity after the first cycle as the initial discharge capacity. Repeat the above charge-discharge process 1000 times, and record the discharge capacity after 1000 cycles as the final discharge capacity. Capacity retention rate = (Final discharge capacity / Initial discharge capacity) × 100%.
[0135] Peel strength test:
[0136] According to GB / T2792-2014 "Test Method for Peel Strength of Adhesive Tapes", the peel strength between the separator and the anode was tested using a high-speed rail tensile testing machine. The test procedure is as follows: The secondary battery was discharged to 0V, and then the secondary battery was disassembled. The separator and the anode plate bonded to it were removed as a whole, and the electrolyte on the surface was wiped off with lint-free paper. Then, it was cut into strips of 5mm × 5mm. Along the length of the sample, the side of the sample with the anode plate was adhered to a steel plate with double-sided adhesive (Nitto 5000NS). The steel plate was fixed in the corresponding position of the high-speed rail tensile testing machine. The other end of the sample with the separator not adhered to the anode plate was lifted, and the sample was placed in the clamp and clamped. The angle between the lifted part of the sample and the steel plate in space was 180°. The clamp pulled the sample at a speed of 1 ± 0.2 mm / s. The average peel strength of the stable area was finally measured and recorded as the peel strength of the separator, denoted as 'a', with the unit being N / m. Table 1 lists the parameters and evaluation results of various embodiments and comparative examples.
[0137] Table 1
[0138] Comparing Examples 1-15 and Comparative Examples 1-4, it can be seen that when the areal density of the active layer is 90 mg / 1540.25 mm², 2 ~180mg / 1540.25mm 2In this case, setting multiple strip-shaped grooves on the active layer can significantly improve the cycle capacity retention rate. This is because the strip-shaped grooves reserve space for electrolyte transport, enhancing the electrolyte transport capacity, mitigating lithium plating problems caused by insufficient kinetics, and improving cycle performance.
[0139] Comparing Examples 1-12, it is evident that when 3% ≤ D2 / D1 ≤ 70% and / or 100μm ≤ D3 ≤ 2000μm, a higher cycle capacity retention rate is achieved, significantly improving cycle performance. In Example 12, D2 / D1 > 70% and D3 > 2000μm, although cycle performance is improved compared to the case without the strip grooves, the excessive etching depth of the strip grooves leads to lithium plating within them, resulting in the worst improvement in cycle performance. In Examples 3-11, when 8% ≤ D2 / D1 ≤ 70%, the cycle capacity retention rate reaches over 70%. In Examples 4-9, satisfying 8% ≤ D2 / D1 ≤ 70% and / or 300μm ≤ D3 ≤ 1000μm, the cycle capacity retention rate reaches over 82%. In Examples 5-7, when 500μm ≤ D3 ≤ 800μm, the cycle capacity retention rate reaches over 90%.
[0140] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with the claims of this application are still within the scope of this application.
Claims
1. A secondary battery, comprising an electrode assembly, the electrode assembly including an anode electrode, the anode electrode including a current collector and an active layer disposed on at least one surface of the current collector, characterized in that, The areal density of the active layer is 90 mg / 1540.25 mm. 2 ~180mg / 1540.25mm 2 The active layer is provided with multiple strip-shaped grooves.
2. The secondary battery as described in claim 1, characterized in that, The spacing between two adjacent strip-shaped grooves is 100μm to 2000μm.
3. The secondary battery as described in claim 2, characterized in that, The spacing between two adjacent strip-shaped grooves is 300μm to 1000μm.
4. The secondary battery as described in claim 3, characterized in that, The spacing between two adjacent strip-shaped grooves is 500μm to 800μm.
5. The secondary battery according to any one of claims 1-4, characterized in that, The thickness of the active layer is D1, and the depth of the strip groove is D2, where 3% ≤ D2 / D1 ≤ 70%.
6. The secondary battery as described in claim 5, characterized in that, 8% ≤ D2 / D1 ≤ 70%.
7. The secondary battery as described in claim 6, characterized in that, 15% ≤ D2 / D1 ≤ 40%.
8. The secondary battery as described in claim 1, characterized in that, The secondary battery also includes tabs, and the current collector includes a first edge and a second edge opposite to each other in a first direction. The tabs extend from the first edge along the first direction into the electrode assembly, and the strip-shaped grooves are arranged perpendicularly, parallelly, or obliquely relative to the first edge.
9. The secondary battery as described in claim 8, characterized in that, The current collector includes a third edge and a fourth edge opposite each other in a second direction perpendicular to the first direction, and the plurality of strip-shaped grooves are arranged from the third edge to the fourth edge.
10. The secondary battery as described in claim 8, characterized in that, The strip-shaped groove includes a first end located on one side of the first edge in the first direction, and the active layer includes a first region corresponding to the tab in the first direction. The distance between the first end of the strip-shaped groove located in the first region and the first edge is 0-3 mm.
11. The secondary battery as described in claim 1, characterized in that, The secondary battery has a notch, and the electrode assembly has a stacked structure. The electrode assembly includes a first end face, a first side face, a second side face, a third side face, and a second end face connected in sequence. The first end face and the second end face are arranged opposite each other in a first direction. The first side face, the second side face, and the third side face are located on the same side of the electrode assembly in a second direction perpendicular to the first direction. The first side face and the second side face surround the notch. The coating surface density of the active layer is greater than or equal to 130 mg / 1540.25 mm². 2 .
12. The secondary battery as described in claim 11, characterized in that, The secondary battery is L-shaped.
13. The secondary battery as described in claim 12, characterized in that, In the second direction, the length of the electrode assembly is L1; in the first direction, the width of the electrode assembly is L2, 1.0≤L1 / L2≤3.
0.
14. The secondary battery as described in claim 12, characterized in that, 1.25≤L1 / L2≤3.
0.
15. The secondary battery as described in claim 1, characterized in that, The compaction density of the active layer is greater than 1.72 g / cm³. 3 .
16. The secondary battery as described in claim 1, characterized in that, The electrode assembly further includes a diaphragm and a cathode electrode. The diaphragm is disposed between the anode electrode and the cathode electrode, and the peel strength between the diaphragm and the anode electrode is 5 to 15 N / m.
17. An electronic device, wherein, Includes the secondary battery as described in any one of claims 1-16.