Pole piece, battery and electric equipment

Abstract

The invention provides a pole piece, a battery and electric equipment, the pole piece comprises a current collector and an active substance layer, the active substance layer comprises a first active substance layer and a second active substance layer, the first active substance layer is connected between the current collector and the second active substance layer, the first active substance layer comprises a first active material and a first adhesive, and the second active substance layer comprises a second active material and a second adhesive. The second active material layer comprises a second active material and a second adhesive; the thickness h1 of the first active material layer, the average particle size D1 of the first active material, the addition amount B1 of the first adhesive, the peel strength f1 between the first active material layer and the current collector, the thickness h2 of the second active material layer, the average particle size D2 of the second active material, and the addition amount B2 of the second adhesive are equal to one another; and the peeling strength f2 between the second active material layer and the first active material layer meets the condition that f1 is greater than f2, and # imgabs0 #. The pole piece provided by the embodiment of the invention simultaneously improves the capacity and the safety of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece, a battery, and an electrical device. Background Art

[0002] In related technologies, lithium-ion batteries may include electrodes and separators. The positive electrode, separator and negative electrode are stacked in sequence to form a laminated battery cell, or stacked and wound in sequence to form a wound battery cell. When the volume energy density of the battery increases, the probability of safety problems also increases.

[0003] When a battery short circuit occurs, there are several possible scenarios: 1. The positive electrode foil contacts the negative electrode foil; 2. The positive electrode active material contacts the negative electrode active material; 3. The positive electrode active material contacts the negative electrode foil; 4. The positive electrode foil contacts the negative electrode active material. Contact between the positive electrode foil and the negative electrode active material can lead to more severe thermal runaway.

[0004] Therefore, how to avoid contact between the foil of the positive electrode sheet and the active material of the negative electrode sheet is an urgent problem to be solved. Summary of the Invention

[0005] Based on this, the present application provides an electrode, a battery, and an electrical device. The electrode reduces the probability of battery short circuit by setting a first active material layer with higher peel strength, thereby improving the safety and capacity of the battery.

[0006] In a first aspect, the present application provides a pole piece, comprising a current collector and an active material layer, wherein the active material layer is connected to at least one side of the current collector, the active material layer comprises a first active material layer and a second active material layer, the first active material layer is connected between the current collector and the second active material layer, the first active material layer comprises a first active material and a first adhesive, and the second active material layer comprises a second active material and a second adhesive;

[0007] The thickness h1 of the first active material layer, the average particle size D1 of the first active material, the amount of the first binder added B1, the peel strength f1 between the first active material layer and the current collector, the thickness h2 of the second active material layer, the average particle size D2 of the second active material, the amount of the second binder added B2, and the peel strength f2 between the second active material layer and the first active material layer satisfy the following conditions:

[0008] f1>f2, and

[0009] In one possible implementation, the peel strength f1 between the first active material layer and the current collector, and the peel strength f2 between the second active material layer and the first active material layer, satisfy:

[0010] 50gf / 20mm≤f1≤400gf / 20mm, and / or, 10gf / 20mm≤f2≤30gf / 20mm.

[0011] In a possible implementation, the added amount B1 of the first adhesive and the added amount B2 of the second adhesive satisfy: 2%≤B1≤10%, and / or, 0.5%≤B2≤1%.

[0012] In a possible implementation, the thickness h1 of the first active material layer and the thickness h2 of the second active material layer satisfy: 0.04≤h1 / h2≤1;

[0013] In a possible implementation, the thickness h1 of the first active material layer and the thickness h2 of the second active material layer further satisfy:

[0014] 2μm≤h1≤35μm, and / or, 35μm≤h2≤50μm.

[0015] In a possible implementation, the thickness of the active material layer satisfies: 40 μm ≤ h1 + h2 ≤ 50 μm.

[0016] In a possible implementation, the average particle size D1 of the first active material and the average particle size D2 of the second active material satisfy: D1 < D2.

[0017] In a possible implementation, the average particle size D1 of the first active material and the average particle size D2 of the second active material further satisfy:

[0018] 1μm≤D1≤8μm, and / or, 8μm≤D2≤20μm.

[0019] In a possible implementation, active material layers are provided on both surfaces of the current collector.

[0020] In a second aspect, the present application provides a battery comprising a diaphragm and the electrode provided in the first aspect, wherein the electrode and the diaphragm are stacked.

[0021] In a third aspect, the present application provides an electrical device, comprising an electrical device and the battery of the second aspect described above, wherein the battery is used to supply power to the electrical device.

[0022] In the electrode provided in the embodiment of the present application, the active material layer includes a first active material layer and a second active material layer, and the peel strength f1 between the first active material layer and the current collector is greater than the peel strength f2 between the second active material layer and the first active material layer. In this way, when the battery encounters mechanical damage such as acupuncture, the first active material layer can still remain covered on the current collector under high temperature and high stress environment, thereby maintaining the structural stability of the electrode, thereby avoiding contact between the current collector of the positive electrode sheet and the active material of the negative electrode sheet and causing a battery short circuit, and the thickness h1 of the first active material layer, the average particle size D1 of the first active material, the addition amount B1 of the first adhesive, the peel strength f1 between the first active material layer and the current collector, the thickness h2 of the second active material layer, the average particle size D2 of the second active material, the addition amount B2 of the second adhesive, and the peel strength f2 between the second active material layer and the first active material layer meet the following conditions: Thus, the electrode sheet achieves a balance between capacity and safety. Thus, the electrode sheet provided by the embodiment of the present application improves both the capacity and safety of the battery.

[0023] In addition to the technical problems solved by the embodiments of the present application described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions, other technical problems that can be solved by the electrodes, batteries, and electrical equipment provided by the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A schematic diagram of the structure of the electrode provided in an embodiment of the present application;

[0026] Figure 2 This is a schematic diagram of the disassembly of a pole piece after a needle penetration test in the related art;

[0027] Figure 3 Schematic diagram of the disassembly of the electrode provided in an embodiment of the present application after the needle penetration test.

[0028] Description of reference numerals:

[0029] 100 - current collector; 200 - active material layer; 210 - first active material layer; 220 - second active material layer. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present application, and should not be understood as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of the present application are described in detail below in conjunction with the drawings.

[0031] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a fixed connection, an indirect connection via an intermediate medium, internal communication between two components, or an interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0032] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are orientations or positional relationships based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0033] The terms "first," "second," and "third" (if any) in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in orders other than those illustrated or described herein.

[0034] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or display that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or display.

[0035] When a battery short circuit occurs, there are several possible scenarios: 1. The positive electrode foil contacts the negative electrode foil; 2. The positive electrode active material contacts the negative electrode active material; 3. The positive electrode active material contacts the negative electrode foil; 4. The positive electrode foil contacts the negative electrode active material. Contact between the positive electrode foil and the negative electrode active material can lead to more severe thermal runaway.

[0036] Therefore, how to avoid contact between the foil of the positive electrode sheet and the active material of the negative electrode sheet, thereby reducing the probability of thermal runaway of the battery due to short circuit, is an urgent problem that needs to be solved.

[0037] In view of the above problems, the embodiments of the present application provide a pole piece, a battery, and an electrical device, wherein the pole piece is provided with a first active material layer with high peel strength, and the thickness h1 of the first active material layer, the average particle size D1 of the first active material, the addition amount B1 of the first adhesive, the peel strength f1 between the first active material layer and the current collector, the thickness h2 of the second active material layer, the average particle size D2 of the second active material, the addition amount B2 of the second adhesive, and the peel strength f2 between the second active material layer and the first active material layer meet the following conditions: In this way, when the battery is subjected to mechanical damage such as needle puncture, the current collector of the positive electrode sheet will not be exposed, thereby preventing the current collector of the positive electrode sheet from contacting the active material of the negative electrode sheet, thereby improving the safety of the battery and increasing the battery capacity.

[0038] The specific implementation of the electrode, battery and electrical equipment provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0039] The present application provides an electrical device, including a battery and an electrical device, wherein the battery is used to supply power to the electrical device.

[0040] For example, the electrical equipment may be a vehicle, the electrical device may be an electric motor, and the battery may provide electrical energy to the electric motor, thereby driving the vehicle to travel.

[0041] It should be understood that the vehicle can be a new energy vehicle (New Energy Vehicle), such as a pure electric vehicle (Pure Electric Vehicle / Battery Electric Vehicle; abbreviated as: PEV / BEV), a range extended electric vehicle (Range Extended Electric Vehicle; abbreviated as: REEV), a hybrid electric vehicle (Hybrid Electric Vehicle; abbreviated as: HEV), or a fuel cell electric vehicle), and the vehicle can also be any vehicle with a battery pack.

[0042] For another example, the power-consuming device may be an electronic device, the power-consuming device may be a motherboard, the battery may power the motherboard, and the electronic device may be a mobile device such as a mobile phone or a tablet.

[0043] Based on the above embodiment, the present application also provides a battery comprising a separator and electrode sheets, which are stacked. Furthermore, the battery may include a housing, wherein the electrode sheets may include a positive electrode sheet and a negative electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a battery cell, which may be encapsulated within the housing together with an electrolyte.

[0044] Reference Figure 1 As shown, based on the above embodiments, the embodiments of the present application further provide a pole piece, which includes a current collector 100 and an active material layer 200, the active material layer 200 is connected to at least one side of the current collector 100, the active material layer 200 includes a first active material layer 210 and a second active material layer 220, the first active material layer 210 is connected between the current collector 100 and the second active material layer 220, the first active material layer 210 includes a first active material and a first adhesive, and the second active material layer 220 includes a second active material and a second adhesive.

[0045] The thickness h1 of the first active material layer 210, the average particle size D1 of the first active material, the amount B1 of the first binder added, the peel strength f1 between the first active material layer 210 and the current collector 100, the thickness h2 of the second active material layer 220, the average particle size D2 of the second active material, the amount B2 of the second binder added, and the peel strength f2 between the second active material layer 220 and the first active material layer 210 satisfy the following conditions:

[0046] f1>f2, and

[0047] In related technologies, to test battery safety, a needle penetration test can be performed on the battery. This artificially creates an internal short circuit in the battery, thereby simulating the battery's thermal runaway process. During the needle penetration test, the positive electrode current collector 100 should be prevented from contacting the negative electrode active material to prevent the battery from short-circuiting.

[0048] For ease of explanation and understanding, the embodiments of the present application are illustrated by taking a positive electrode sheet as an example. The positive electrode sheet includes a current collector 100 and an active material layer 200. The active material layer 200 may include two layers, namely a first active material layer 210 and a second active material layer 220. The first active material layer 210 is connected between the current collector 100 and the second active material layer 220, and the peel strength f1 between the first active material layer 210 and the current collector 100 is greater than the peel strength f2 between the second active material layer 220 and the first active material layer 210.

[0049] In this way, when the battery is subjected to a needle penetration test, due to the large peel strength f1 between the first active material layer 210 and the current collector 100, the first active material layer 210 can still cover the current collector 100, and the two maintain an effective connection to avoid exposure of the current collector 100, thereby avoiding contact between the current collector 100 of the positive electrode sheet and the active material of the negative electrode sheet, thereby reducing the probability of battery short circuit and improving battery safety.

[0050] In the related art, a protective layer is provided on the current collector 100, thereby preventing the current collector 100 of the positive electrode sheet from contacting the active material of the negative electrode sheet through the protective layer. However, the protective layer is formed by a high-resistance inactive material such as an inorganic non-metal, which will seriously reduce the capacity of the electrode sheet. In this embodiment, no other inactive materials are introduced into the electrode sheet. By providing a first active material layer 210 with a higher peel strength, the current collector 100 of the positive electrode sheet and the active material of the negative electrode sheet are prevented from contacting, and the capacity of the electrode sheet can be effectively maintained, thereby improving the safety and capacity of the battery at the same time.

[0051] For example, the peel strength f1 between the first active material layer 210 and the current collector 100 can be increased by increasing the amount of the first adhesive added B1 in the first active material layer 210. However, the first adhesive is a poor conductor. When the amount of the first adhesive added B1 is increased, the capacity of the positive electrode sheet will be affected. Taking this into account, the average particle size D1 of the first active material can be reduced, thereby reducing the thickness h1 of the first active material layer 210, so that the positive electrode sheet has a thinner first active material layer 210 to reduce the capacity loss of the first active material layer 210.

[0052] The added amount B2 of the second adhesive of the second active material layer 220 can be low, the average particle size D2 of the second active material can be larger, and the thickness h2 of the second active material layer 220 can be larger. In this way, the capacity of the second active material layer 220 is larger, which can increase the capacity of the positive electrode sheet, thereby improving the battery capacity while improving the battery safety.

[0053] Based on the above considerations, in order to achieve a balance between safety and capacity of the positive electrode sheet, the thickness h1 of the first active material layer 210, the average particle size D1 of the first active material, the amount of the first binder added B1, the peel strength f1 between the first active material layer 210 and the current collector 100, the thickness h2 of the second active material layer 220, the average particle size D2 of the second active material, the amount of the second binder added B2, and the peel strength f2 between the second active material layer 220 and the first active material layer 210 can meet the following requirements:

[0054] The above formula comprehensively balances the relationship between the thickness h1 of the first active material layer 210, the average particle size D1 of the first active material, the added amount B1 of the first adhesive, the peel strength f1 between the first active material layer 210 and the current collector 100, the thickness h2 of the second active material layer 220, the average particle size D2 of the second active material, the added amount B2 of the second adhesive, and the peel strength f2 between the second active material layer 220 and the first active material layer 210.

[0055] If the thickness h1 of the first active material layer 210, the average particle size D1 of the first active material, the amount of the first binder added B1, the peel strength f1 between the first active material layer 210 and the current collector 100, the thickness h2 of the second active material layer 220, the average particle size D2 of the second active material, the amount of the second binder added B2, and the peel strength f2 between the second active material layer 220 and the first active material layer 210 are calculated by the above formula and the result is between 0 and 0.2, it means that the first active material layer 210 and the second active material layer 220 are close to each other. In the material layer 220, the added amount B1 of the first adhesive is relatively high, the average particle size D1 of the first active material is relatively small, and the thickness h1 of the first active material layer 210 is relatively small, so that the first active layer and the current collector 100 have a higher bonding strength, thereby improving the safety of the electrode. The added amount B2 of the second adhesive is relatively low, the average particle size D2 of the second active material is relatively large, and the thickness h2 of the second active material layer 220 is relatively large, thereby enabling the second active material layer 220 to have a higher capacity, thereby simultaneously improving the safety and capacity of the battery.

[0056] The current collector 100 of the positive electrode sheet may be aluminum foil, nickel foil or stainless steel foil, which is not limited in the embodiment of the present application.

[0057] In the electrode provided in the embodiment of the present application, the active material layer 200 includes a first active material layer 210 and a second active material layer 220. The peel strength f1 between the first active material layer 210 and the current collector 100 is greater than the peel strength f2 between the second active material layer 220 and the first active material layer 210. In this way, when the battery encounters mechanical damage such as needle puncture, the first active material layer 210 can still remain covered on the current collector 100 under high temperature and high stress environment, thereby maintaining the structural stability of the electrode, thereby preventing the current collector 100 of the positive electrode sheet from contacting the active material of the negative electrode sheet and causing a battery short circuit. In addition, the thickness h1 of the first active material layer 210, the average particle size D1 of the first active material, the addition amount B1 of the first adhesive, the peel strength f1 between the first active material layer 210 and the current collector 100, the thickness h2 of the second active material layer 220, the average particle size D2 of the second active material, the addition amount B2 of the second adhesive, and the peel strength f2 between the second active material layer 220 and the first active material layer 210 meet the following conditions: Thus, the electrode sheet achieves a balance between capacity and safety. Thus, the electrode sheet provided by the embodiment of the present application improves both the capacity and safety of the battery.

[0058] In one possible implementation, the peel strength f1 between the first active material layer 210 and the current collector 100 and the peel strength f2 between the second active material layer 220 and the first active material layer 210 satisfy the following conditions: 50 gf / 20 mm ≤ f1 ≤ 400 gf / 20 mm, and / or 10 gf / 20 mm ≤ f2 ≤ 30 gf / 20 mm.

[0059] It should be noted that the test method for peel strength is well known to those skilled in the art. The tape is bonded to the electrode to be tested, and then the tape is pulled in a direction 90° perpendicular to the electrode. The strength required to peel the second active material layer 220 from the first active material layer 210 is the peel strength f2 between the second active material layer 220 and the first active material layer 210, and the strength required to peel the first active material layer 210 from the current collector 100 is the peel strength f1 between the first active material layer 210 and the current collector 100.

[0060] It is understandable that the greater the amount of adhesive added, the greater the peel strength, but this also results in a loss of capacity. The electrode of the embodiment of the present application requires a comprehensive consideration of safety and capacity. Therefore, in the specific configuration, 50gf / 20mm≤f1≤400gf / 20mm is sufficient to ensure the peel strength f1 between the first active material layer 210 and the current collector 100, thereby effectively preventing the current collector 100 from being exposed when the electrode is punctured, thereby preventing a short circuit in the battery and improving battery safety. 10gf / 20mm≤f2≤30gf / 20mm can effectively control the amount of the second adhesive added B2, thereby increasing the capacity of the second active material layer 220.

[0061] In one possible implementation, the amount of the first adhesive added, B1, and the amount of the second adhesive added, B2, satisfy the following conditions: 2% ≤ B1 ≤ 10%, and / or 0.5% ≤ B2 ≤ 1%. This arrangement effectively increases the amount of the first adhesive added, B1, to be greater than the amount of the second adhesive added, B2. This in turn increases the peel strength f1 between the first active material layer 210 and the current collector 100 to be greater than the peel strength f2 between the second active material layer 220 and the first active material layer 210.

[0062] Among them, the addition amount B1 of the first adhesive and the addition amount B2 of the second adhesive can be obtained by analyzing the element content of the electrode. For example, the first adhesive and the second adhesive are both made of polyvinylidene fluoride, which is a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and other compounds. It is a non-polar chain polymer with a molecular weight generally greater than 300,000. The main mechanism of action of polyvinylidene fluoride is van der Waals force, which forms hydrogen bonds between the F atoms on the long chain and other component particles in the electrode. The action of hydrogen bonds makes the various component particles string together, generating intermolecular forces to play a bonding role. Therefore, the mass ratio of the F element in polyvinylidene fluoride can be obtained by elemental analysis, and then the addition amount of polyvinylidene fluoride can be obtained.

[0063] For example, the amount B1 of the first adhesive added can be any one of 2%, 3%, 4%, 8%, and 10%, or within any range of two values. And / or the amount B2 of the second adhesive added can be any one of 0.5%, 0.6%, 0.7%, 0.8%, and 1%, or within any range of two values.

[0064] In some embodiments, the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 satisfy the following: 0.04≤h1 / h2≤1.

[0065] It should be understood that since the added amount B1 of the first adhesive of the first active material layer 210 is higher than the added amount B2 of the second adhesive of the second active material layer 220, the peel strength f1 between the first active material layer 210 and the current collector 100 is greater than the peel strength f2 between the second active material layer 220 and the first active material layer 210. However, in order to increase the capacity of the electrode, the thickness h1 of the first active material layer 210 should be less than or equal to the thickness h2 of the second active material layer 220, and the first active material layer 210 needs to have a certain thickness to fully cover the current collector 100 and enhance the peel strength f1 between the first active material layer 210 and the current collector 100. Therefore, in this embodiment, the ratio h1 / h2 of the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 can be between 0.04 and 1.

[0066] For example, the ratio h1 / h2 of the thickness h1 of the first active material layer 210 to the thickness h2 of the second active material layer 220 may be any one of 0.04, 0.2, 0.5, 0.8, and 1, or be within any two value ranges.

[0067] In a possible implementation, the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 further satisfy: 2 μm ≤ h1 ≤ 35 μm, and / or 35 μm ≤ h2 ≤ 50 μm.

[0068] With such an arrangement, the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 can satisfy: 0.04≤h1 / h2≤1, and the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 can also be controlled within an appropriate range, thereby improving the safety, capacity and electrical performance of the electrode.

[0069] For example, the thickness h1 of the first active material layer 210 can be any one of 2 μm, 4 μm, 6 μm, 10 μm, and 35 μm, or can be within any two numerical ranges, and / or the thickness h2 of the second active material layer 220 can be any one of 35 μm, 38 μm, 40 μm, 42 μm, and 50 μm, or can be within any two numerical ranges.

[0070] It should be noted that the electrode of this embodiment can be formed by a double-layer coating method to form the first active material layer 210 and the second active material layer 220 respectively. That is, the coating, drying and compaction steps are first performed on the current collector 100 to form the first active material layer 210, and then the coating, drying and compaction steps are performed on the first active material layer 210 to form the second active material layer 220. The advantage of this method is that the electrode with the first active material layer 210 and the second active material layer 220 can use existing coating equipment, which has high compatibility and can reduce the production cost of the electrode.

[0071] In a possible implementation, the thickness of the active material layer 200 satisfies: 40 μm ≤ h1 + h2 ≤ 50 μm.

[0072] That is to say, the sum of the thicknesses of the first active material layer 210 and the second active material layer 220 can be between 40 μm and 50 μm. This is because for the positive electrode sheet, lithium ions need to move a certain distance to be deintercalated into the electrolyte. If the thickness of the active material layer 200 is large, the difficulty of lithium ion deintercalation increases, which is not conducive to improving the electrical performance of the positive electrode sheet. If the thickness of the active material layer 200 is small, it is not conducive to improving the capacity of the positive electrode sheet. Based on these two points, the thickness of the active material layer 200 can be set to 40 μm to 50 μm, thereby improving the electrical performance and capacity of the positive electrode sheet.

[0073] For example, the thickness of the active material layer 200 may be any one value or any two value ranges among 40 μm, 42 μm, 45 μm, 46 μm, and 50 μm.

[0074] In some embodiments, the average particle size D1 of the first active material and the average particle size D2 of the second active material satisfy: D1 < D2.

[0075] In this way, when more first adhesive is added to the first active material layer 210 to increase the peel strength f1 between the first active material layer 210 and the current collector 100, the average particle size D1 of the first active material can be smaller, which is conducive to forming a thinner first active material layer 210, and the second active material layer 220 can be thicker to increase the capacity of the electrode. Therefore, the average particle size D2 of the second active material can be larger.

[0076] It should be noted that when the first active material includes at least two active materials with different components, the average particle size D1 of the first active material should be understood as the average particle size of the active materials with at least two different components; when the first active material includes only one active material with one component, the average particle size D1 of the first active material should be understood as the average particle size of the active material with that component.

[0077] In a possible implementation, the average particle size D1 of the first active material and the average particle size D2 of the second active material further satisfy the following conditions: 1 μm≤D1≤8 μm, 8 μm≤D2≤20 μm.

[0078] It is understood that using a first active material with a particle size of 1 μm to 8 μm helps control the thickness h1 of the first active material layer 210 to between 2 μm and 35 μm, thereby making the first active material layer 210 thinner and thereby increasing the capacity of the electrode. Furthermore, the smaller average particle size D1 of the first active material increases the specific surface area of the first active material layer 210 and improves the diffusion rate of lithium ions, thereby improving the electrochemical performance of the first active material layer 210.

[0079] For example, the average particle size D1 of the first active material may be any one of 1 μm, 2 μm, 5 μm, 6 μm, and 8 μm, or be within any two numerical ranges. The average particle size D2 of the second active material may be any one of 8 μm, 10 μm, 15 μm, 18 μm, and 20 μm, or be within any two numerical ranges.

[0080] In a possible implementation, the first adhesive includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate.

[0081] The second adhesive includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate.

[0082] In some embodiments, the first active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, a ternary material, and a sulfide material.

[0083] The second active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, a ternary material, and a sulfide material.

[0084] That is, this embodiment does not limit the material composition of the first active material layer 210 and the second active material layer 220. For example, the first and second adhesives may both be polyvinylidene fluoride, or the first adhesive may be polyvinylidene fluoride and the second adhesive may be one or more of styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate. The first and second active materials may both be lithium cobalt oxide, or the first active material may be lithium cobalt oxide and the second active material may be a ternary material.

[0085] The preparation and testing processes of the battery provided in this embodiment are described in detail below.

[0086] Example 1

[0087] 1. Preparation of the first active material layer 210: A coating slurry of the first active material layer 210 is obtained by mixing the first active material, the first conductive agent, and the first binder in a mass ratio of 94:5:1. The coating slurry is applied to the current collector 100 using a specially designed gravure roller with adjacent grooves of varying depths. The coating thickness is about 8 μm. After drying, the positive electrode sheet to be coated for secondary coating is obtained.

[0088] The first active material may be lithium cobalt oxide with a particle size of 6 μm, the first conductive agent may be carbon black, and the first binder may be polyvinylidene fluoride.

[0089] 2. Prepare the second active material layer 220: The coating slurry of the second active material layer 220 obtained by mixing the second active material, the second conductive agent, and the second binder in a mass ratio of 98:1:1 is applied by an extrusion coater on the electrode to be coated for the second time obtained in the previous step, with a thickness of about 40 μm, so that the ratio h1 / h2 of the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 is 0.2. After drying and pressing, the positive electrode sheet is obtained.

[0090] The second active material may be lithium cobalt oxide with a particle size of 12 μm, the second conductive agent may be carbon black, and the second binder may be polyvinylidene fluoride.

[0091] 3. Preparation of negative electrode sheet: A negative electrode slurry obtained by mixing the third active material, the third conductive agent, and the third binder in a mass ratio of 90:5:5 is coated on a copper foil, dried to a thickness of about 35-50 μm, and compacted by a roller press to obtain a negative electrode sheet. The negative electrode sheet is washed with an organic solvent and dried to obtain a lithium-supplemented negative electrode sheet.

[0092] The third active material may be graphite, the third conductive agent may be carbon black, and the third binder may be a mixture of styrene-butadiene rubber and carboxymethyl cellulose.

[0093] 4. The positive electrode sheet, separator and negative electrode sheet are stacked in sequence to form a battery cell, which is placed in a battery shell and injected with electrolyte. The shell is then sealed to produce a finished battery.

[0094] Example 2

[0095] The difference between this embodiment and the first embodiment is that the ratio h1 / h2 of the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 is 0.1.

[0096] Example 3

[0097] The difference between this embodiment and the first embodiment is that the ratio h1 / h2 of the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 is 0.4.

[0098] Example 4

[0099] The difference between this embodiment and the first embodiment is that the ratio h1 / h2 of the thickness h1 of the first active material layer 210 and the thickness h2 of the second active material layer 220 is 0.8.

[0100] Example 5

[0101] The difference between this embodiment and the first embodiment is that the added amount B1 of the first adhesive is 3%.

[0102] Example 6

[0103] The difference between this embodiment and the first embodiment is that the added amount B1 of the first adhesive is 7%.

[0104] Example 7

[0105] The difference between this embodiment and the first embodiment is that the average particle size D1 of the first active material is 3 μm.

[0106] Example 8

[0107] The difference between this embodiment and the first embodiment is that the average particle size D1 of the first active material is 9 μm.

[0108] Comparative Example

[0109] The difference between this embodiment and the first embodiment is that in the step of preparing the electrode sheet, the positive electrode sheet is a primary structure, and only the second active material layer 220 is provided.

[0110] It should be noted that the preparation method of the battery provided in this embodiment is well known to those skilled in the art. The negative electrode sheet, separator, and positive electrode sheet are sequentially formed into a battery cell by winding or laminating methods known in the art. The battery cell is then placed in a battery casing and sealed to obtain a battery. The sealing method and the amount of electrolyte used are well known to those skilled in the art.

[0111] The amount of solvent added is well known to those skilled in the art and can be flexibly adjusted based on the viscosity and operability requirements of the slurry to be prepared. The prepared slurry is then applied to the current collector 100, dried, pressed, and then cut into sheets. The drying temperature can be 120°C and the drying time can be 5 hours. The solvent can be various solvents known in the art, such as N-methylpyrrolidone, dimethylformamide, diethylformamide, dimethyl sulfoxide, tetrahydrofuran, water, and alcohols.

[0112] Table 1

[0113] Serial number D1 / μm D2 / μm h1 / μm h2 / μm B1 B2 f1(gf / 20mm) f2(gf / 20mm) t Example 1 6 12 8 40 5％ 1％ 256 24 0.0052 Example 2 6 12 4 40 5％ 1％ 221 25 0.0122 Example 3 6 12 16 40 5％ 1％ 262 24 0.0025 Example 4 6 12 32 4 5％ 1％ 271 26 0.0012 Example 5 6 12 8 40 3％ 1％ 164 23 0.0043 Example 6 6 12 8 40 7％ 1％ 305 25 0.0064 Example 7 3 12 8 40 5％ 1％ 173 24 0.0121 Example 8 9 12 8 40 5％ 1％ 296 23 0.0022 Comparative Example / 12 / 40 / 1％ / 18 /

[0114] in, It can be seen from this that the added amount B1 of the first adhesive is higher than the added amount B2 of the second adhesive, which can make the peel strength f1 between the first active material layer 210 and the current collector 100 greater than the peel strength f2 between the second active material layer 220 and the first active material layer 210, and t in Examples 1 to 8 is all between 0 and 2.

[0115] The batteries of Examples 1 to 8 and the comparative example were tested for energy density, needle penetration rate, and cycle life. The cycle life test method was as follows: at a constant temperature of 25°C, charge the battery at 0.5C to a full charge of 4.5V, then discharge it at 0.5C to 3V, repeating this cycle 800 times. The needle penetration test method was as follows: charge the battery at a constant current of 0.7C to a full charge, then align a needle with a diameter of 3mm and a length of 100mm at the geometric center of the battery and penetrate the battery at a speed of 150±5mm / s, repeating this puncture five times.

[0116] The following is a table summarizing the test results.

[0117] Table 2

[0118]

[0119]

[0120] It can be seen from this that for the positive electrode sheet with the first active material layer 210, the battery's needle puncture pass rate is higher, while for the positive electrode sheet without the first active material layer 210, the battery's needle puncture pass rate is lower. For the positive electrode sheet with a thinner first active material layer 210, the battery's energy density and capacity retention rate are both higher, while for the positive electrode sheet with a thicker first active material layer 210, the battery's energy density and capacity retention rate are relatively low.

[0121] For details, please refer to Figure 2 and Figure 3 As shown, Figure 2 The figure shows the disassembly diagram of the electrode after the needle penetration test in the related art. Figure 3 A schematic diagram of the disassembly of the electrode provided in an embodiment of the present application after a needle penetration test is shown. The electrode in the related art has a large exposed foil area after the needle penetration test, while the electrode provided in an embodiment of the present application has a relatively intact structure after the needle penetration test, and the current collector 100 is basically not exposed.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A pole piece, characterized in that: include: current collector(100); An active material layer (200), the active material layer (200) being connected to at least one side of the current collector (100), the active material layer (200) comprising a first active material layer (210) and a second active material layer (220), the first active material layer (210) being connected between the current collector (100) and the second active material layer (220), the first active material layer (210) comprising a first active material and a first adhesive, and the second active material layer (220) comprising a second active material and a second adhesive; The thickness h1 of the first active material layer (210), the average particle size D1 of the first active material, the amount of the first binder added B1, the peel strength f1 between the first active material layer (210) and the current collector (100), the thickness h2 of the second active material layer (220), the average particle size D2 of the second active material, the amount of the second binder added B2, and the peel strength f2 between the second active material layer (220) and the first active material layer (210) satisfy the following conditions: f1>f2, and 2. The pole piece according to claim 1, characterized in that: The peel strength f1 between the first active material layer (210) and the current collector (100), and the peel strength f2 between the second active material layer (220) and the first active material layer (210) satisfy: 50gf / 20mm≤f1≤400gf / 20mm, and / or, 10gf / 20mm≤f2≤30gf / 20mm.

3. The pole piece according to claim 1 or 2, characterized in that: The addition amount B1 of the first adhesive and the addition amount B2 of the second adhesive satisfy: 2%≤B1≤10%, and / or, 0.5%≤B2≤1%.

4. The pole piece according to claim 1 or 2, characterized in that: The thickness h1 of the first active material layer (210) and the thickness h2 of the second active material layer (220) satisfy: 0.04≤h1 / h2≤1.

5. The pole piece according to claim 4, characterized in that: The thickness h1 of the first active material layer (210) and the thickness h2 of the second active material layer (220) also satisfy: 2μm≤h1≤35μm, and / or, 35μm≤h2≤50μm.

6. The pole piece according to claim 5, characterized in that: The thickness of the active material layer (200) satisfies: 40 μm≤h1+h2≤50 μm.

7. The pole piece according to claim 1 or 2, characterized in that: The average particle size D1 of the first active material and the average particle size D2 of the second active material satisfy the following: D1<D2.

8. The pole piece according to claim 7, characterized in that: The average particle size D1 of the first active material and the average particle size D2 of the second active material further satisfy: 1μm≤D1≤8μm, and / or, 8μm≤D2≤20μm.

9. The pole piece according to claim 1 or 2, characterized in that: The active material layer is provided on both surfaces of the current collector.

10. A battery, characterized in that: It comprises a diaphragm and a pole piece according to any one of claims 1 to 9, wherein the pole piece and the diaphragm are stacked.

11. An electrical device, characterized in that: The invention comprises an electric device and the battery according to claim 10, wherein the battery is used to supply power to the electric device.

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