Pole piece, preparation method thereof, battery cell, battery and electric device

Abstract

The application discloses a pole piece, a preparation method thereof, a battery cell, a battery and a power utilization device. The pole piece comprises a foil, a first active layer and a second active layer. The first active layer is arranged on the foil in a laminated mode, and the first active layer comprises a first active structure and a second active structure connected with each other. The second active layer is arranged on the first active layer in a laminated mode, and the second active layer comprises a third active structure and a fourth active structure connected with each other, the third active structure is laminated on the first active structure, and the fourth active structure is laminated on the second active structure. The particle diameter D 50 of the main material of the first active structure is less than the particle diameter D 50 of the main material of the second active structure; or the particle diameter D 50 of the main material of the fourth active structure is less than the particle diameter D 50 of the main material of the third active structure. The pole piece disclosed by the application reduces the tortuosity of a thick electrode, increases the infiltration of electrolyte and the diffusion channel of ions in the longitudinal direction, and optimizes the dynamic performance of a battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to an electrode sheet and its preparation method, a battery cell, a battery, and an electrical device. Background Technology

[0002] The energy density and power density of power batteries are mutually restrictive and both are crucial. Continuously improving the areal density of the electrode sheets is aimed at obtaining higher energy density.

[0003] Increasing electrode compaction is a common method to improve the volumetric energy density of batteries. The pore structure of the electrode is crucial for electrolyte wetting and lithium-ion transport in the liquid phase. However, thick electrodes often result in longer lithium-ion transport paths with high tortuosity, increasing battery impedance and negatively impacting battery kinetic performance. Summary of the Invention

[0004] The purpose of this invention is to provide an electrode sheet and its preparation method, a battery cell, a battery, and an electrical device, thereby solving the problem of high tortuosity in thick electrode structures.

[0005] To achieve the objectives of this invention, the following technical solution is provided:

[0006] In a first aspect, the present invention provides an electrode sheet, comprising:

[0007] Foil material; a first active layer, stacked on the foil material, the first active layer comprising a first active structure and a second active structure connected together; a second active layer, stacked on the first active layer, the second active layer comprising a third active structure and a fourth active structure connected together, the third active structure being stacked on the first active structure, and the fourth active structure being stacked on the second active structure; the particle size D of the main material of the first active structure. 50 The particle size D of the main material smaller than that of the second active structure 50 ; or the particle size D of the main material of the fourth active structure. 50 The particle size D of the main material smaller than that of the third active structure 50 .

[0008] In one embodiment, the particle size D of the main material of the first active structure 50 The particle size D of the main material smaller than that of the second active structure 50 ; and the particle size D of the main material of the fourth active structure 50 The particle size D of the main material smaller than that of the third active structure 50 .

[0009] In one embodiment, the first active structure has a first main material, the particle size D of which is... 50Let D1 be a particle size distribution, satisfying: 0.3μm ≤ D1 ≤ 0.6μm. The second active structure has a second main material, and the particle size D of the second main material is... 50 The particle size is D2, satisfying: 0.9μm≤D2≤1.3μm; the third active structure has a third main material, and the particle size D of the third main material is... 50 The fourth active structure has a fourth main material with a particle size D of 0.9 μm ≤ D3 ≤ 1.3 μm, satisfying the condition 0.9 μm ≤ D3 ≤ 1.3 μm. 50 For D4, the following condition must be met: 0.3μm≤D4≤0.6μm.

[0010] In one embodiment, the first active structure has a first conductive agent, the specific surface area of ​​which is A1, satisfying: 80m² 2 / g≤A1≤110m 2 / g, the second active structure has a second conductive agent, the specific surface area of ​​the second conductive agent is A2, satisfying: 80m 2 / g≤A2≤110m 2 / g; The third active structure has a third conductive agent, the specific surface area of ​​which is A3, satisfying: 30m 2 / g≤A3≤60m 2 / g, the fourth active structure has a fourth conductive agent, the specific surface area of ​​the fourth conductive agent is A4, satisfying: 30m 2 / g≤A4≤60m 2 / g.

[0011] In one embodiment, the first active structure further comprises a first binder, wherein the mass ratio of the first main material, the first binder, and the first conductive agent is 100:(2.0-2.5):(0.6-1.2); the second active structure further comprises a second binder, wherein the mass ratio of the second main material, the second binder, and the second conductive agent is 100:(2.0-2.5):(0.6-1.2); the third active structure further comprises a third binder, wherein the mass ratio of the third main material, the third binder, and the third conductive agent is 100:(2.0-2.5):(0.2-0.6); and the fourth active structure further comprises a fourth binder, wherein the mass ratio of the fourth main material, the fourth binder, and the fourth conductive agent is 100:(2.0-2.5):(0.2-0.6).

[0012] In one embodiment, the oil absorption value B of the first conductive agent, the second conductive agent, the third conductive agent, and the fourth conductive agent satisfies: 240ml / 100g≤B≤320ml / 100g.

[0013] In one embodiment, the first active layer includes a plurality of first active structures and a plurality of second active structures, with the plurality of first active structures and the plurality of second active structures alternately arranged; the second active layer includes a plurality of third active structures and a plurality of fourth active structures, with the plurality of third active structures and the plurality of fourth active structures alternately arranged.

[0014] Secondly, the present invention provides a method for preparing an electrode sheet, comprising the following steps:

[0015] Foil materials are available;

[0016] A first active structure and a third active structure are stacked on the foil, and a second active structure and a fourth active structure are stacked on the foil on the same side of the first active structure and the third active structure.

[0017] The first active structure and the second active structure are connected to form a first active layer, and the third active structure and the fourth active structure are connected to form a second active layer. The particle size D of the main material of the first active structure is... 50 The particle size D of the main material smaller than that of the second active structure 50 ; or the particle size D of the main material of the fourth active structure. 50 The particle size D of the main material smaller than that of the third active structure 50 .

[0018] In one embodiment, a first active structure and a third active structure are stacked on the foil, and a second active structure and a fourth active structure are stacked on the same side of the first active structure and the third active structure, comprising:

[0019] Provide a first coating die and a second coating die;

[0020] A slurry is provided, the slurry comprising a first slurry, a second slurry, a third slurry, and a fourth slurry;

[0021] The first coating die coats the foil with the first slurry and the third slurry to form the first active structure and the third active structure, and the second coating die coats the foil with the second slurry and the fourth slurry to form the second active structure and the fourth active structure.

[0022] Thirdly, the present invention provides a battery cell comprising a separator and the electrode sheet described in the first aspect, wherein the separator and the electrode sheet are stacked.

[0023] Fourthly, the present invention provides a battery comprising a casing and a cell as described in the third aspect, the cell being housed within the casing.

[0024] Fifthly, the present invention provides an electrical device, including an electrical appliance and the battery described in the fourth aspect, wherein the battery supplies power to the electrical appliance.

[0025] The electrode provided by the present invention has a first active layer and a second active layer stacked together, and the particle size D of the main material of the first active structure in the first active layer is... 50 The particle size D of the main material smaller than that of the second active structure 50 ; or the particle size D of the main material of the fourth active structure in the second active layer. 50 The particle size D of the main material smaller than that of the third active structure 50 The active material layer is configured with regions of different particle sizes, so that the interface between large and small particles directly forms through holes during the rolling process. This enables the control of the pore size in the vertical direction, reduces the tortuosity of the thick electrode, increases the wetting of the electrolyte and the longitudinal diffusion channels of ions, and optimizes the battery dynamics performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a cross-sectional view of an electrode sheet in one embodiment;

[0028] Figure 2 This is a flowchart of a method for preparing an electrode according to one embodiment;

[0029] Figure 3 This is a flowchart of one step in the preparation method of an electrode according to one embodiment.

[0030] Explanation of reference numerals in the attached figures:

[0031] 10-First active layer, 11-First active structure, 12-Second active structure, 20-Second active layer, 21-Third active structure, 22-Fourth active structure. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0034] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0035] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] refer to Figure 1 The present invention provides an electrode sheet comprising a foil, a first active layer 10, and a second active layer 20.

[0037] A first active layer 10 is stacked on the foil, and the first active layer 10 includes a first active structure 11 and a second active structure 12 connected together. A second active layer 20 is stacked on the first active layer 10, and the second active layer 20 includes a third active structure 21 and a fourth active structure 22 connected together, with the third active structure 21 stacked on the first active structure 11 and the fourth active structure 22 stacked on the second active structure 12; the particle size D of the main material of the first active structure 11 is... 50 The particle size D of the main material is smaller than that of the second active structure 12. 50 ; or the particle size D of the main material of the fourth active structure 22 50 The particle size D of the main material smaller than that of the third active structure 21 50 .

[0038] When the electrode is a positive electrode, the foil material may include, but is not limited to, any one of aluminum foil, composite aluminum foil, or carbon-coated aluminum foil; when the electrode is a negative electrode, the foil material may include, but is not limited to, any one of copper foil, composite copper foil, or carbon-coated copper foil.

[0039] This electrode has a first active layer 10 and a second active layer 20 stacked together, and the particle size D of the main material of the first active structure 11 in the first active layer 10 is... 50 The particle size D of the main material is smaller than that of the second active structure 12. 50 ; or the particle size D of the main material of the fourth active structure 22 in the second active layer 20 50 The particle size D of the main material smaller than that of the third active structure 21 50This involves configuring the active material layer into regions with different particle sizes, allowing the interface between large and small particles to directly form through-holes during the rolling process. This enables control over the pore size in the vertical direction, reduces the tortuosity of thick electrodes, increases electrolyte wetting and ion diffusion channels in the vertical direction, without increasing energy consumption, and optimizes battery kinetic performance. Specifically, the particle size D of the main material... 50 This refers to the average particle size of the active materials in the first active layer 10 and the second active layer 20. The particle size D of the main material... 50 The particle size can be directly measured using a particle size analyzer for testing powder materials; alternatively, it can be obtained by measuring the particle size of the main material in the corresponding area of ​​an SEM image and then using statistical methods to calculate the average particle size.

[0040] In one embodiment, the particle size D of the main material of the first active structure 11 is... 50 The particle size D of the main material is smaller than that of the second active structure 12. 50 Furthermore, the particle size D of the main material of the fourth active structure 22 50 The particle size D of the main material smaller than that of the third active structure 21 50 This allows the interface between large and small particles in the double-layer structure to directly form through holes during the rolling process, enabling the control of the pore size in the vertical direction. This further reduces the tortuosity of the thick electrode, increases the wetting of the electrolyte and the longitudinal diffusion channels of ions, without causing more energy consumption, and optimizes the battery dynamic performance.

[0041] In one embodiment, the first active structure 11 and the third active structure 21 have equal lengths in a first direction; and / or the second active structure 12 and the fourth active structure 22 have equal lengths in the first direction X. The first direction X is perpendicular to the coating direction and parallel to the foil surface. This structural design facilitates the further extension of the through-holes formed during the rolling process based on the interface between large and small particles in each layer of the double-layer structure. This reduces the tortuosity of the thick electrode, increases electrolyte wetting and longitudinal ion diffusion channels, without increasing energy consumption, and optimizes battery kinetic performance.

[0042] In one embodiment, the first active structure 11 has a first main material, the particle size D of which is... 50 For D1, satisfying: 0.3μm≤D1≤0.6μm, the second active structure 12 has a second main material, and the particle size D of the second main material is... 50 For D2, satisfying: 0.9μm≤D2≤1.3μm; the third active structure 21 has a third main material, and the particle size D of the third main material is... 50 The particle size is D3, satisfying: 0.9μm≤D3≤1.3μm. The fourth active structure 22 has a fourth main material, and the particle size D of the fourth main material is... 50 For D4, the following condition must be met: 0.3μm≤D4≤0.6μm.

[0043] The particle size D of the first main material 50 D1 can be 0.3μm, 0.4μm, 0.5μm, 0.6μm, etc., without any restrictions.

[0044] The particle size D of the second main material 50 D2 can be 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, etc., without any restrictions.

[0045] The particle size D of the third main material 50 D3 can be 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, etc., without any restrictions.

[0046] The particle size D of the fourth main material 50 D4 can be 0.3μm, 0.4μm, 0.5μm, 0.6μm, etc., without restriction.

[0047] By controlling the particle size of the main material, micron-sized through pores can be directly formed at the interface between large and small particles when the electrode is rolled, without affecting the solid-phase lithium-ion conduction of the main material itself, while increasing the liquid-phase lithium-ion transport and electrolyte wetting, without bringing more energy consumption.

[0048] In one embodiment, the first main material and the fourth main material are the same, and the second main material and the third main material are the same, which can ensure the consistency of the areal density and compaction of the electrode sheet.

[0049] In one embodiment, the first active structure 11 has a first conductive agent, the specific surface area of ​​which is A1, satisfying: 80m² 2 / g≤A1≤110m 2 / g, the second active structure 12 has a second conductive agent, the specific surface area of ​​the second conductive agent is A2, which satisfies: 80m 2 / g≤A2≤110m 2 / g; The third active structure 21 has a third conductive agent, the specific surface area of ​​which is A3, satisfying: 30m 2 / g≤A3≤60m 2 / g, the fourth active structure 22 has a fourth conductive agent, and the specific surface area of ​​the fourth conductive agent is A4, which satisfies: 30m 2 / g≤A4≤60m 2 / g.

[0050] A1 can be 85m 2 / g≤A1≤105m 2 / g、90m 2 / g≤A1≤100m 2 / g, etc., specifically 80m 2 / g、85m 2 / g、90m 2 / g, 100m 2 / g, 105m 2 / g、110m 2 / g, etc., are not restricted.

[0051] A2 can be 85m 2 / g≤A2≤105m 2 / g、90m 2 / g≤A2≤100m 2 / g, etc., specifically 80m 2 / g、85m 2 / g、90m 2 / g, 100m 2 / g, 105m 2 / g、110m 2 / g, etc., are not restricted.

[0052] A3 can be 35m 2 / g≤A3≤55m 2 / g、40m 2 / g≤A3≤50m 2 / g, etc., specifically 30m 2 / g、35m 2 / g、40m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g, etc., are not restricted.

[0053] A4 can be 35m 2 / g≤A4≤55m 2 / g、40m 2 / g≤A4≤50m 2 / g, etc., specifically 30m 2 / g、35m 2 / g、40m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g, etc., are not restricted.

[0054] The upper layer selects conductive agents with low specific surface area (i.e., the third and fourth conductive agents) to reduce the diffusion barrier of lithium ions in the liquid phase, while the lower layer selects conductive agents with high specific surface area (i.e., the first and second conductive agents) to increase electron transport between particles.

[0055] In one embodiment, the first active structure 11 further comprises a first binder, and the mass ratio of the first main material, the first binder, and the first conductive agent is 100:(2.0-2.5):(0.6-1.2); the second active structure 12 further comprises a second binder, and the mass ratio of the second main material, the second binder, and the second conductive agent is 100:(2.0-2.5):(0.6-1.2); the third active structure 21 further comprises a third binder, and the mass ratio of the third main material, the third binder, and the third conductive agent is 100:(2.0-2.5):(0.2-0.6); the fourth active structure 22 further comprises a fourth binder, and the mass ratio of the fourth main material, the fourth binder, and the fourth conductive agent is 100:(2.0-2.5):(0.2-0.6).

[0056] The mass ratio of the first main material, the first adhesive, and the first conductive agent can be 100:2.0:0.6, 100:2.2:1.0, 100:2.5:1.2, etc., without limitation.

[0057] The mass ratio of the second main material, the second adhesive, and the second conductive agent can be 100:2.0:0.6, 100:2.2:1.0, 100:2.5:1.2, etc., without restriction.

[0058] The mass ratio of the third main material, the third adhesive, and the third conductive agent can be 100:2.0:0.2, 100:2.2:0.4, 100:2.5:0.6, etc., without restriction.

[0059] The mass ratio of the fourth main material, the fourth adhesive, and the fourth conductive agent can be 100:2.0:0.2, 100:2.2:0.4, 100:2.5:0.6, etc., without restriction.

[0060] The mass ratio of the third and fourth conductive agents to the first and second conductive agents can be 1:2.5.

[0061] The types of adhesives include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, without limitation.

[0062] The first active structure 11 and the second active structure 12, located closer to the foil, have a higher content of conductive agent, which helps to enhance the current-collecting ability of the current collector. The third active structure 21 and the fourth active structure 22, located closer to the separator, have a lower content of conductive agent, which helps to reduce tortuosity and promote lithium-ion transport. Designing the conductive agent content according to the conductivity requirement gradient not only helps to improve kinetic performance but also reduces the amount of conductive agent used, further increasing energy density.

[0063] In one embodiment, the oil absorption value B of the first conductive agent, the second conductive agent, the third conductive agent and the fourth conductive agent satisfies: 240ml / 100g≤B≤320ml / 100g.

[0064] B can be 250ml / 100g≤B≤310ml / 100g, 260ml / 100g≤B≤300ml / 100g, 270ml / 100g≤B≤290ml / 100g, etc., specifically 240ml / 100g, 250ml / 100g, 260ml / 100g, 270ml / 100g, 290ml / 100g, 300ml / 100g, 310ml / 100g, 320ml / 100g, etc., without restriction.

[0065] The specific surface area of ​​the conductive agent was tested according to the national standard GB / T 19587; the oil absorption value of the conductive agent was tested using a specific surface area tester according to the national standard GB / T 19587.

[0066] High oil absorption conductive agents can increase the saturation capacity of the electrode, similar to providing a miniature lithium storage tank. The high oil absorption conductive agent forms a local microscopic lithium ion concentration field between particles, which promotes the liquid phase transport of lithium ions under the concentration gradient.

[0067] In one embodiment, the first active layer 10 includes a plurality of first active structures 11 and a plurality of second active structures 12, which are alternately arranged. The second active layer includes a plurality of third active structures 21 and a plurality of fourth active structures 22, which are alternately arranged.

[0068] The alternating arrangement of multiple active structures forms micron-sized pores at the interface between large and small particles during rolling, which helps reduce the tortuosity of the electrode, increases electrolyte wetting and longitudinal ion diffusion channels, and optimizes battery dynamics performance.

[0069] refer to Figure 2 and Figure 3 This invention provides a method for preparing an electrode, comprising the following steps:

[0070] Step S10: Provide foil;

[0071] Step S20: A first active structure 11 and a third active structure 21 are stacked on the foil, and a second active structure 12 and a fourth active structure 22 are stacked on the foil on the same side as the first active structure 11 and the third active structure 21.

[0072] The first active structure 11 and the second active structure 12 are connected to form the first active layer 10, and the third active structure 21 and the fourth active structure 22 are connected to form the second active layer 20. The particle size D of the main material of the first active structure 11 is... 50 The particle size D of the main material is smaller than that of the second active structure 12. 50 ; or the particle size D of the main material of the fourth active structure 22 50 The particle size D of the main material smaller than that of the third active structure 21 50 .

[0073] The particle size D of the main material of two adjacent active structures on the same active material layer 50 The particle size D of the main material of two adjacent active structures stacked on different active material layers is different. 50 different.

[0074] This electrode has a first active layer 10 and a second active layer 20 stacked together. The particle size D of the main material of the first active structure 11 is... 50 The particle size D of the main material is smaller than that of the second active structure 12. 50 ; or the particle size D of the main material of the fourth active structure 22 50 The particle size D of the main material smaller than that of the third active structure 21 50 The active material layer is configured with regions of different particle sizes, so that the interface between large and small particles directly forms through holes during the rolling process. This enables the control of the pore size in the vertical direction, reduces the tortuosity of the thick electrode, increases the wetting of the electrolyte and the longitudinal diffusion channels of ions, and optimizes the battery dynamics performance.

[0075] In one embodiment, step S20 includes steps S21, S22, and S23, including:

[0076] Step S21: Provide a first coating die and a second coating die;

[0077] Step S22: Provide slurry, which includes a first slurry, a second slurry, a third slurry, and a fourth slurry;

[0078] In step S23, the first coating die coats the foil with a first slurry and a third slurry to form a first active structure 11 and a third active structure 21, and the second coating die coats the foil with a second slurry and a fourth slurry to form a second active structure 12 and a fourth active structure 22.

[0079] The first slurry includes a first main material, a first conductive agent, and a first binder; the second slurry includes a second main material, a second conductive agent, and a second binder; the third slurry includes a third main material, a third conductive agent, and a third binder; and the fourth slurry includes a fourth main material, a fourth conductive agent, and a fourth binder.

[0080] When the electrode is a positive electrode, the main material is the positive electrode material, which can be a phosphate positive electrode active material or a ternary positive electrode active material. In specific embodiments, it includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium fluorinated vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. This application does not specifically limit these materials; appropriate materials can be selected according to actual application requirements.

[0081] When the electrode is a negative electrode, the main material is a negative electrode material, which can be a carbon-based negative electrode material or a non-carbon-based negative electrode material. Carbon-based negative electrode materials include at least one of graphite materials and non-graphite materials; among which, graphite materials include at least one of natural graphite or artificial graphite; non-graphite materials include at least one of hard carbon materials or soft carbon materials; non-carbon-based negative electrode materials can be titanium-based materials, tin-based materials, silicon-based materials, nitrides, etc.

[0082] The conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 (carbon 60), and carbon nanotubes; the type of binder has been described in the foregoing embodiments. This application does not specifically limit these materials, and appropriate materials can be selected according to actual application requirements.

[0083] In one embodiment, a plurality of first coating dies and a plurality of second coating dies are alternately arranged.

[0084] The first coating die generates the first active structure 11 and the third active structure 21, and the second coating die generates the second active structure 12 and the third active structure 21. After baking and rolling, straight holes are formed at the interface between large and small particles, which realizes the control of the pore size in the vertical direction, reduces the tortuosity of the thick electrode, increases the wetting of the electrolyte and the longitudinal diffusion channel of ions, and optimizes the battery dynamic performance.

[0085] The present invention provides a battery cell, including a separator and an electrode sheet according to any of the foregoing embodiments, wherein the separator and the electrode sheet are stacked.

[0086] The separator can be any type of woven membrane, nonwoven membrane (non-woven fabric), microporous membrane, composite membrane, rolled membrane, etc., without limitation. Furthermore, the separator is in contact with the third active structure 21 and the fourth active structure 22. The conductive agent in the third active structure 21 and the fourth active structure 22 has a smaller specific surface area and a lower conductive agent content, which helps to reduce the liquid phase mass transfer resistance and promote lithium-ion transport.

[0087] The present invention provides a battery comprising a casing and a cell according to any of the foregoing embodiments, wherein the cell is housed within the casing.

[0088] The battery can be a prismatic battery, a cylindrical battery, or other types such as a prismatic battery, without any restrictions.

[0089] The outer shell is made of a material with high structural strength, specifically metal, high-strength plastic, ceramic, etc. Metal materials include aluminum, aluminum alloys, magnesium alloys, iron, and iron alloys. The outer shell includes a base plate and side plates. The outer shell can be a one-piece structure, meaning the base plate and side plates are manufactured using a single molding process, such as stamping or casting, without limitation. Alternatively, the outer shell can be a separate structure, with the side plates and base plate connected and fixed by welding, bonding, snap-fitting, screwing, etc. The wall thickness of the outer shell can be approximately uniform throughout; that is, the side plates can have a roughly uniform thickness, and the base plate and side plates can also have roughly the same thickness.

[0090] The particle size D of the main material of the first active structure 11 and the fourth active structure 22 on the electrode of this battery is... 50 The particle size D of the main material is smaller than that of the second active structure 12 and the third active structure 21. 50 This allows for the direct formation of through-holes at the interface between large and small particles during the rolling process, enabling control of the pore size in the vertical direction, reducing the tortuosity of thick electrodes, increasing electrolyte wetting and longitudinal ion diffusion channels, without increasing energy consumption, and optimizing battery dynamics performance.

[0091] The present invention also provides an electrical device, including an electrical appliance and a battery as described in any of the foregoing embodiments, wherein the battery supplies power to the electrical appliance. The electrical device may be a television, washing machine, automobile, etc., and is not limited thereto.

[0092] The technical solution of this application will be described in detail below through specific embodiments.

[0093] Example 1

[0094] This embodiment provides a positive electrode sheet, which includes a foil, a first active structure, a second active structure, a third active structure, and a fourth active structure. The foil is aluminum foil, and the oil absorption value B of the conductive agent is 300 ml / 100 g.

[0095] The particle size D of the first main material in the first active structure 50 Given D1 = 0.4 μm, the mass ratio of the first main material to the first binder to the first conductive agent is 100:2.2:1, and the specific surface area A1 of the first conductive agent is 90 m². 2 / g;

[0096] The particle size D of the second main material in the second active structure 50 With D2 = 0.9 μm, the mass ratio of the second main material: second binder: second conductive agent is 100:2.2:1, and the specific surface area A2 of the second conductive agent is 90 m². 2 / g;

[0097] The particle size D of the third main material in the third active structure 50With a diameter D3 of 0.9 μm, the mass ratio of the third main material, the third binder, and the third conductive agent is 100:2.2:0.4; the specific surface area A3 of the third conductive agent is 30 m². 2 / g;

[0098] The particle size D of the fourth main material in the fourth active structure 50 With D4 = 0.4 μm, the mass ratio of the fourth main material: the fourth binder: the fourth conductive agent is 100:2.2:0.4, and the specific surface area A4 of the fourth conductive agent is 30 m². 2 / g.

[0099] 1) Ingredient preparation: Prepare a first slurry for forming the first active structure, a second slurry for forming the second active structure, a third slurry for forming the third active structure, and a fourth slurry for forming the fourth active structure. Each slurry contains an active material, a conductive agent, a binder, and a solvent. The active material is ferric phosphate particles, the conductive agent is carbon black, and the binder is selected from polytetrafluoroethylene. The particle size of the active material, the oil absorption value and specific surface area of ​​the conductive agent, and the proportions of the active material, conductive agent, and binder in each slurry are consistent with the corresponding active structure on the electrode.

[0100] 2) Coating and layering: A first coating die is used to coat the aluminum foil surface with a first slurry and a third slurry to form a first active structure and a third active structure. A second coating die is used to coat the aluminum foil with a second slurry and a fourth slurry to form a second active structure and a fourth active structure. The positive electrode sheet is then prepared by baking and rolling.

[0101] Example 2

[0102] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0103] The particle size D of the second main material in the second active structure 50 The particle size D of the third main material in the third active structure is D2 = 1.1 μm. 50 The value is D3 = 1.1 μm.

[0104] Example 3

[0105] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0106] The particle size D of the second main material in the second active structure 50 The particle size D of the third main material in the third active structure is D2 = 1.3 μm. 50 The value is D3 = 1.3 μm.

[0107] Example 4

[0108] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0109] The particle size D of the second main material in the second active structure 50 The particle size D of the third main material in the third active structure is D2 = 1.1 μm. 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; the specific surface area A4 of the fourth conductive agent is 50m². 2 / g.

[0110] Example 5

[0111] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0112] The particle size D of the second main material in the second active structure 50 The particle size D of the third main material in the third active structure is D2 = 1.1 μm. 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 60 m². 2 / g; The specific surface area A4 of the fourth conductive agent is 60m². 2 / g.

[0113] Example 6

[0114] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0115] The mass ratio of the first main material, the first adhesive, and the first conductive agent is 100:2.2:0.7; the mass ratio of the second main material, the second adhesive, and the second conductive agent is 100:2.2:0.7; the mass ratio of the third main material, the third adhesive, and the third conductive agent is 100:2.2:0.7; and the mass ratio of the fourth main material, the fourth adhesive, and the fourth conductive agent is 100:2.2:0.7.

[0116] Example 7

[0117] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0118] The particle size D of the first main material in the first active structure 50 The particle size D of the second main material in the second active structure is D1 = 0.3 μm. 50 The particle size D of the third main material in the third active structure is D2 = 1.1 μm. 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 With D4 = 0.3 μm, the specific surface area A4 of the fourth conductive agent is 50 m². 2 / g.

[0119] Example 8

[0120] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0121] The particle size D of the first main material in the first active structure 50 The particle size D of the second main material in the second active structure is D1 = 0.6 μm. 50 The particle size D of the third main material in the third active structure is D2 = 1.1 μm. 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 The specific surface area A4 of the fourth conductive agent is 50 m², with D4 = 0.6 μm. 2 / g.

[0122] Example 9

[0123] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0124] The particle size D of the first main material in the first active structure 50 With D1 = 0.6 μm, the specific surface area A1 of the first conductive agent is 80 m². 2 / g; Particle size D of the second main material in the second active structure 50 The surface area of ​​the second conductive agent is D2 = 1.1 μm, and the specific surface area A2 is 80 m². 2 / g; Particle size D of the third main material in the third active structure 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 The specific surface area A4 of the fourth conductive agent is 50 m², with D4 = 0.6 μm. 2 / g.

[0125] Example 10

[0126] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0127] The particle size D of the first main material in the first active structure 50 With D1 = 0.6 μm, the specific surface area A1 of the first conductive agent is 110 m². 2 / g; Particle size D of the second main material in the second active structure 50 With D2 = 1.1 μm, the specific surface area A2 of the second conductive agent is 110 m². 2 / g; Particle size D of the third main material in the third active structure 50The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 The specific surface area A4 of the fourth conductive agent is 50 m², with D4 = 0.6 μm. 2 / g.

[0128] Example 11

[0129] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0130] The oil absorption value (B) of the conductive agent is 260 ml / 100 g. The particle size (D) of the first main material in the first active structure is... 50 With D1 = 0.6 μm, the specific surface area A1 of the first conductive agent is 110 m². 2 / g; Particle size D of the second main material in the second active structure 50 With D2 = 1.1 μm, the specific surface area A2 of the second conductive agent is 110 m². 2 / g; Particle size D of the third main material in the third active structure 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 The specific surface area A4 of the fourth conductive agent is 50 m², with D4 = 0.6 μm. 2 / g.

[0131] Example 12

[0132] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0133] The oil absorption value (B) of the conductive agent is 350 ml / 100 g. The particle size (D) of the first main material in the first active structure is... 50 With D1 = 0.6 μm, the specific surface area A1 of the first conductive agent is 110 m². 2 / g; Particle size D of the second main material in the second active structure 50 With D2 = 1.1 μm, the specific surface area A2 of the second conductive agent is 110 m². 2 / g; Particle size D of the third main material in the third active structure 50 The surface area of ​​the third conductive agent is D3 = 1.1 μm, and the specific surface area A3 is 50 m². 2 / g; Particle size D of the fourth main material in the fourth active structure 50 The specific surface area A4 of the fourth conductive agent is 50 m², with D4 = 0.6 μm. 2 / g.

[0134] Example 13

[0135] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0136] The first active structure is the same as the third active structure, and the particle size D of the first main material is the same as that of the third main material. 50 All have D1 = 0.4 μm.

[0137] The second and fourth active structures are different, and the particle size D of the second main material is different. 50 The particle size D of the fourth main material is D2 = 0.9 μm. 50 The value is D4 = 0.4 μm.

[0138] Comparative Example 1

[0139] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0140] The first active structure is the same as the second active structure, and the particle size D of the first main material is the same. 50 D1 = 0.4 μm;

[0141] The third active structure is the same as the fourth active structure, and the particle size D of the third main material is... 50 The value is D3 = 1.1 μm.

[0142] Comparative Example 2

[0143] This embodiment provides a positive electrode sheet, which is basically the same as that in Embodiment 1, except that:

[0144] The first, second, third, and fourth active structures are identical, and the particle size D of the main material is the same. 50 The thickness is 0.9 μm, the mass ratio of main material: binder: conductive agent is 100:2.2:0.4, and the specific surface area A1 of the conductive agent is 30 m². 2 / g.

[0145] In Examples 1-13 and Comparative Examples 1-2, the conductive agent was carbon black, the binder was polytetrafluoroethylene, the main material was lithium iron phosphate, and the first and second active layers were disposed on aluminum foil. The positive electrode sheet was assembled with the corresponding negative electrode sheet and separator to form a battery.

[0146] The relevant information of the active structures provided in Examples 1-13 and Comparative Examples 1-2 above is shown in Table 1 below.

[0147] Table 1

[0148]

[0149] The electrochemical performance of each battery assembled in the above examples and comparative examples was tested under the following conditions: DC internal resistance at 50% SOC and liquid phase diffusion impedance.

[0150] 50% SOC DC internal resistance test: At room temperature (25±5℃), the battery is discharged at 1 / 3C constant current to 2.0V, charged at 1 / 3C constant current to 50% SOC, and left to stand for 30 minutes; discharged at 1.5C constant current for 30 seconds, and the DC internal resistance at 50% SOC is measured.

[0151] Liquid phase diffusion impedance testing: The above-mentioned positive electrode sheets were assembled into an electrode core; the electrode core was placed in an outer packaging shell, baked, and injected with electrolyte. After encapsulation and impregnation processes, a liquid phase diffusion impedance battery was obtained. Liquid phase diffusion impedance testing was performed using an electrochemical workstation within a frequency range of 300,000 Hz to 0.05 Hz. The electrode liquid and negative electrode sheets were standard materials used in this field.

[0152] The test results are shown in Table 2 below.

[0153] Table 2

[0154] 50% SOC DCIR(Ω) Liquid phase diffusion resistance (Ω) 2C / 0.2C discharge ratio Example 1 0.787 0.464 0.87 Example 2 0.747 0.391 0.91 Example 3 0.802 0.389 0.88 Example 4 0.671 0.341 0.94 Example 5 0.877 0.402 0.89 Example 6 0.912 0.478 0.85 Example 7 0.786 0.488 0.89 Example 8 0.815 0.475 0.84 Example 9 0.823 0.493 0.82 Example 10 0.888 0.509 0.8 Example 11 0.851 0.513 0.73 Example 12 0.874 0.479 0.75 Example 13 1.017 0.527 0.70 Comparative Example 1 1.266 0.563 0.66 Comparative Example 2 1.493 0.603 0.63

[0155] Comparing Examples 4-5 in Tables 1 and 2, when the specific surface area of ​​the conductive agents in the third and fourth active structures increases, and all other conditions remain the same, the battery impedance increases and the rate discharge retention rate decreases.

[0156] Comparing Examples 1 and 6 in Tables 1 and 2, the mass of the first and second conductive agents in Example 6 is the same as the mass of the third and fourth conductive agents. The impedance of the battery in Example 6 is increased, and the rate discharge retention rate is increased.

[0157] Comparing Examples 7-8 in Tables 1 and 2, when the particle size of the first and fourth main materials increases while all other conditions remain the same, the rate discharge retention rate decreases.

[0158] Comparing Examples 8-10 in Tables 1 and 2, when the specific surface area of ​​the first and second conductive agents increases, and all other conditions remain the same, the battery impedance first decreases and then increases, while the rate discharge retention first increases and then decreases.

[0159] Comparing Examples 10-12 in Tables 1 and 2, when the oil absorption value of the conductive agent increases while other conditions remain the same, the liquid phase diffusion resistance of the battery decreases.

[0160] Comparing Examples 1 and 13 in Tables 1 and 2, the first and third main materials of Example 13 have the same particle size, while the first and third main materials of Example 1 have different particle sizes. The rate discharge retention rate of the battery in Example 13 is less than that of the battery in Example 1, and the impedance of the battery in Example 13 is greater than that of the battery in Example 1.

[0161] When comparing Examples 1-13 and Comparative Examples 1-2 in Tables 1 and 2, the impedance of the batteries in Examples 1-13 is less than that of the batteries in Comparative Examples 1-3, and the rate discharge retention rate of the batteries in Examples 1-13 is greater than that of the batteries in Comparative Examples 1-2.

[0162] In summary, a first active layer and a second active layer are stacked on the foil, and the particle size D of the main material of the first active structure in the first active layer is... 50 The particle size D of the main material smaller than that of the second active structure 50 ; or the particle size D of the main material of the fourth active structure in the second active layer. 50 The particle size D of the main material smaller than that of the third active structure 50 The active material layer is configured with regions of different particle sizes, so that the interface between large and small particles directly forms through holes during the rolling process. This enables the control of the pore size in the vertical direction, reduces the tortuosity of the thick electrode, increases the wetting of the electrolyte and the longitudinal diffusion channels of ions, and optimizes the battery dynamics performance.

[0163] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0164] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An electrode sheet, characterized in that, include: Foil; A first active layer is stacked on the foil, and the first active layer includes a first active structure and a second active structure connected to each other. A second active layer is stacked on the first active layer. The second active layer includes a third active structure and a fourth active structure connected to each other. The third active structure is stacked on the first active structure, and the fourth active structure is stacked on the second active structure. The particle size D of the main material of the first active structure 50 The particle size D of the main material smaller than that of the second active structure 50 ; and the particle size D of the main material of the fourth active structure 50 The particle size D of the main material smaller than that of the third active structure 50 ; The first active structure has a first main material with a particle size D50 of D1, satisfying: 0.3μm≤D1≤0.6μm; the second active structure has a second main material with a particle size D50 of D2, satisfying: 0.9μm≤D2≤1.3μm; the third active structure has a third main material with a particle size D50 of D3, satisfying: 0.9μm≤D3≤1.3μm; and the fourth active structure has a fourth main material with a particle size D50 of D4, satisfying: 0.3μm≤D4≤0.6μm.

2. The electrode sheet according to claim 1, characterized in that, The first active structure has a first conductive agent, and the specific surface area of ​​the first conductive agent is A1, which satisfies: 80m² 2 / g≤A1≤110m 2 / g, the second active structure has a second conductive agent, the specific surface area of ​​the second conductive agent is A2, satisfying: 80m 2 / g≤A2≤110m 2 / g; The third active structure has a third conductive agent, the specific surface area of ​​which is A3, satisfying: 30m 2 / g≤A3≤60m 2 / g, the fourth active structure has a fourth conductive agent, the specific surface area of ​​the fourth conductive agent is A4, satisfying: 30m 2 / g≤A4≤60m 2 / g.

3. The electrode sheet according to claim 2, characterized in that, The first active structure further comprises a first binder, wherein the mass ratio of the first main material, the first binder, and the first conductive agent is 100:(2.0-2.5):(0.6-1.2); the second active structure further comprises a second binder, wherein the mass ratio of the second main material, the second binder, and the second conductive agent is 100:(2.0-2.5):(0.6-1.2); the third active structure further comprises a third binder, wherein the mass ratio of the third main material, the third binder, and the third conductive agent is 100:(2.0-2.5):(0.2-0.6); and the fourth active structure further comprises a fourth binder, wherein the mass ratio of the fourth main material, the fourth binder, and the fourth conductive agent is 100:(2.0-2.5):(0.2-0.6).

4. The electrode sheet according to claim 2, characterized in that, The oil absorption value B of the first conductive agent, the second conductive agent, the third conductive agent and the fourth conductive agent satisfies: 240ml / 100g≤B≤320ml / 100g.

5. The electrode sheet according to claim 1, characterized in that, The first active layer includes a plurality of first active structures and a plurality of second active structures, which are alternately arranged. The second active layer includes a plurality of third active structures and a plurality of fourth active structures, which are alternately arranged.

6. A method for preparing an electrode sheet, characterized in that, Includes the following steps: Foil materials are provided; A first active structure and a third active structure are stacked on the foil, and a second active structure and a fourth active structure are stacked on the foil on the same side of the first active structure and the third active structure. The first active structure and the second active structure are connected to form a first active layer, and the third active structure and the fourth active structure are connected to form a second active layer. The particle size D50 of the main material of the first active structure is smaller than the particle size D50 of the main material of the second active structure; and the particle size D50 of the main material of the fourth active structure is smaller than the particle size D50 of the main material of the third active structure. The first active structure has a first main material with a particle size D50 of D1, satisfying: 0.3μm≤D1≤0.6μm; the second active structure has a second main material with a particle size D50 of D2, satisfying: 0.9μm≤D2≤1.3μm; the third active structure has a third main material with a particle size D50 of D3, satisfying: 0.9μm≤D3≤1.3μm; and the fourth active structure has a fourth main material with a particle size D50 of D4, satisfying: 0.3μm≤D4≤0.6μm.

7. The method for preparing the electrode according to claim 6, characterized in that, A first active structure and a third active structure are stacked on the foil, and a second active structure and a fourth active structure are stacked on the foil on the same side of the first active structure and the third active structure, including: Provide a first coating die and a second coating die; A slurry is provided, the slurry comprising a first slurry, a second slurry, a third slurry, and a fourth slurry; The first coating die coats the foil with the first slurry and the third slurry to form the first active structure and the third active structure, and the second coating die coats the foil with the second slurry and the fourth slurry to form the second active structure and the fourth active structure.

8. A battery cell, characterized in that, The electrode comprises a diaphragm and an electrode sheet prepared by the method described in any one of claims 1-5 or as described in claim 6 or 7, wherein the diaphragm and the electrode sheet are stacked together.

9. A battery, characterized in that, It includes a housing and a battery cell as described in claim 8, wherein the battery cell is housed within the housing.

10. An electrical appliance, characterized in that, It includes an electrical device and a battery as described in claim 9, wherein the battery supplies power to the electrical device.

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