WO2023173331A1

WO2023173331A1 - Electrochemical apparatus and electronic apparatus

Info

Publication number: WO2023173331A1
Application number: PCT/CN2022/081239
Authority: WO
Inventors: 蔡阳声; 汪颖
Original assignee: 东莞新能安科技有限公司
Priority date: 2022-03-16
Filing date: 2022-03-16
Publication date: 2023-09-21
Also published as: CN116134675A

Abstract

Disclosed in the present application are an electrochemical apparatus and an electronic apparatus. The electrochemical apparatus comprises a wound-type electrode assembly, wherein the electrode assembly comprises an anode plate, a cathode plate, a first separator and a second separator, and the electrode assembly comprises a bending portion. The first separator comprises a first substrate layer, which comprises a first separation portion, wherein the side of the first separation portion that is close to the bending center of the bending portion faces the anode plate, and the side of the first separation portion that is away from the bending center faces the cathode plate. The second separator comprises a second substrate layer, which comprises a second separation portion, wherein the side of the second separation portion that is close to the bending center faces the cathode plate, and the side of the second separation portion that is away from the bending center faces the anode plate. The porosity P₁ of the first separation portion and the porosity P₂ of the second separation portion satisfy 10% ≤ P₁ - P₂ ≤ 25%. When 10% ≤ P₁ - P ₂ ≤ 25%, the material cost of a second separation portion can be reduced, and a first separator is also enabled to have better ion permeability, thereby reducing lithium precipitation phenomena.

Description

Electrochemical devices and electronic devices

Technical field

Embodiments of the present application relate to the field of electrochemistry, and in particular, to an electrochemical device and an electronic device.

Background technique

An electrochemical device, such as a secondary battery, is a device that converts external energy into electrical energy and stores it internally to power external electrical equipment (such as portable electronic devices, etc.) when needed. At present, electrochemical devices are widely used in electrical equipment such as drones, mobile phones, tablets, and laptops. Existing electrochemical devices are prone to lithium deposition after multiple charges and discharges. After lithium is deposited in the electrochemical device, its capacity will decline. In order to reduce the occurrence of lithium precipitation, the material cost of the battery will generally increase.

Contents of the invention

Embodiments of the present application provide an electrochemical device and an electronic device, which can improve the lithium deposition problem of the electrochemical device and balance the cost of the electrochemical device.

In order to solve the above technical problems, one technical solution adopted by this application is to provide an electrochemical device. The electrochemical device includes a rolled electrode assembly. The electrode assembly includes a stacked anode electrode piece, a cathode electrode piece, and a first isolation device. membrane and a second isolation membrane, and the electrode assembly includes a bend. The first isolation film includes a first base material layer, the first base material layer includes a first isolation part located at the bending part, and a side of the first isolation part close to the bending center of the bending part faces In the anode pole piece, the side of the first isolation part away from the bending center faces the cathode pole piece. The second isolation film includes a second base material layer, the second base material layer includes a second isolation part located at the bending part, and a side of the second isolation part close to the bending center faces the cathode. pole piece, the side of the second isolation part away from the bending center faces the anode pole piece. The porosity P ₁ of the first isolation part and the porosity P ₂ of the second isolation part satisfy 10% ≤ _{P 1} -P ₂ ≤ 25%.

In some embodiments, 40%≤P ₁ ≤65%, 30%≤P ₂ ≤55%. In some embodiments, the porosity P ₃ of the first substrate layer satisfies 40% ≤ P ₃ ≤ 65%. The porosity P ₄ of the second base material layer satisfies 30% ≤ P ₄ ≤ 55%. 10%≤P ₃ -P ₄ ≤25%.

In some embodiments, the air permeability value S ₁ of the first isolation part and the air permeability value S ₂ of the second isolation part satisfy 10% ≤ _{S 1} -S ₂ ≤ 50. In some embodiments, 70≤S ₁ ≤160, 70≤S ₂ ≤160.

In some embodiments, the resistance R ₁ of the first isolation part and the resistance R ₂ of the second isolation part satisfy 0.1Ω≤R ₂ -R ₁ ≤0.5Ω. In some embodiments, 0.4Ω≤R ₁ ≤1.1Ω, 0.4Ω≤R ₂ ≤1.1Ω.

In some embodiments, at least one of a first adhesive layer or a first ceramic layer is disposed on the first substrate layer. In some embodiments, at least one of a second adhesive layer or a second ceramic layer is disposed on the second substrate layer. In some embodiments, the first adhesive layer and the first ceramic layer are not provided on the first substrate layer; at least one of the second adhesive layer or the second ceramic layer is provided on the second substrate layer.

In some embodiments, CB ranges from 1.06 to 1.2.

A second aspect of the present application also provides an electronic device, which includes any one of the above electrochemical devices.

In the electrochemical device provided by the embodiment of the present application, the applicant considered that the side of the first isolation part close to the bending center of the bending part faces the anode pole piece, and the side away from the bending center faces the cathode pole piece, so it faces the first The capacity of the cathode active material in the separator is greater than the capacity of the anode active material facing the first separator, and the first separator needs to have relatively high ion permeability. The side of the second isolation part close to the bending center faces the cathode pole piece, and the side away from the bending center faces the anode pole piece. Therefore, the capacity of the cathode active material facing the second isolation part is less than that of the anode active material facing the second isolation part. Capacity, the second isolation part can have weaker ion permeability than the first isolation part, and can achieve a better effect of mitigating lithium precipitation. In view of this, the porosity P ₁ of the first isolation part is set to be greater than the porosity P ₂ of the second isolation part, and 10%≤P ₁ -P ₂ ≤25%. This solution can make the first isolation part have higher ion permeability to reduce the risk of lithium precipitation on the anode plate facing the first isolation part, and the second isolation part can maintain better improvement in the anode electrode facing the second isolation part. It has lower cost when it comes to lithium exfoliation problem. And in this application, the porosity P ₁ of the first isolation part and the porosity P ₂ of the second isolation part satisfy.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. Those of ordinary skill in the art can also obtain other drawings based on the drawings.

Figure 1 is a partial schematic view of an electrode assembly provided by an embodiment of the present application, viewed in a direction parallel to the winding axis; Figure 1 is a part of the winding structure of the electrode assembly, and there may be other winding inner and outer rings. continuation part;

Figure 2 is a schematic side view of an electrode assembly according to an embodiment of the application viewed in a direction parallel to the winding axis;

Figure 3 is a schematic side view of the first isolation film according to an embodiment of the application, viewed in a direction perpendicular to its own thickness;

Figure 4 is a schematic side view of the second isolation film according to an embodiment of the application when viewed in a direction perpendicular to its own thickness.

Figure 5 is an exploded schematic diagram of an electrochemical device provided by an embodiment of the present application;

FIG. 6 is a schematic diagram of an electronic device provided by an embodiment of the present application.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is referred to as being "secured" to another element, it can be directly on the other element, or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element, or there may be one or more intervening elements present therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the technical field belonging to this application. The terms used in the description of this application are only for the purpose of describing specific embodiments and are not used to limit this application. As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

An electrochemical device (such as a lithium-ion battery, a sodium-ion battery, etc.) includes an electrode assembly. The electrode assembly includes a stacked anode plate, a first isolation film, a cathode plate, and a second isolation film. The anode plate includes an anode current collector and anode active material layers disposed on both sides of the anode current collector. The cathode plate includes a cathode current collector and cathode active material layers disposed on both sides of the cathode current collector. When the electrochemical device is charged, the lithium ions from the cathode plate are deintercalated and then pass through the isolation film (which can be the first isolation film or the second isolation film) and embed in the anode plate. However, when some abnormal situations occur: such as insufficient space for lithium insertion in the anode, too much resistance to lithium ion insertion into the anode, lithium ions being deintercalated from the cathode too quickly but unable to be embedded in the anode in the same amount, etc., the lithium ions that cannot be embedded in the anode can only be Electrons are obtained on the surface of the anode, thereby forming silvery white metallic lithium element, which is lithium precipitation. Lithium precipitation not only reduces the performance of the electrochemical device and greatly shortens the cycle life, but also limits the fast charging capacity of the electrochemical device and may pose safety risks.

In view of this, referring to FIGS. 1-5 , the present application discloses an electrochemical device. The electrochemical device may be a battery 10 , specifically a secondary battery such as a lithium-ion battery or a sodium-ion battery. The battery 10 includes a rolled electrode assembly 100 and a battery case 300 . The electrode assembly 100 includes an anode electrode piece 110 , a cathode electrode piece 120 , a first isolation film 140 and a second isolation film 130 arranged in a stack. The anode plate includes an anode current collector and anode active material layers disposed on both sides of the anode current collector. The cathode plate includes a cathode current collector and cathode active material layers disposed on both sides of the cathode current collector. The electrochemical device also includes a first tab 210 and a second tab 220 . The first tab 210 is electrically connected to the anode tab 110 , and the second tab 220 is electrically connected to the cathode tab 120 . The battery case 300 defines a receiving cavity 310, and the electrode assembly 100 is received in the receiving cavity 310 of the battery case 300.

The specific stacking method of the anode plate 110 , the cathode plate 120 , the first isolation film 140 and the second isolation film 130 depends on specific requirements. In one embodiment, the four elements are stacked in the order of the anode pole piece 110, the second isolation film 130, the cathode pole piece 120, and the first isolation film 140 and then rolled, and the winding center is located at the first isolation film 140 away from the cathode electrode. one side of the plate 120 such that the anode plate 110 is located outside the cathode plate 120 . In one embodiment, the four elements are stacked in the order of cathode pole piece 120, first isolation film 140, anode pole piece 110, and second isolation film 130 and then rolled, and the winding center is located at the second isolation film 130 away from the anode pole. one side of the plate 110 such that the cathode plate 120 is located outside the anode plate 110 . Referring to FIG. 1 , in this application, the structure in which the anode pole piece 110 is located outside the cathode pole piece 120 is taken as an example for description.

The first isolation film 140 includes a first base material layer 141. The first isolation film 140 may also include a first adhesive layer or a first ceramic layer. The first adhesive layer facilitates the bonding of the first isolation film 140 to the cathode pole piece or the anode pole piece, and the first ceramic layer facilitates improving the structural strength, thermal performance and safety of the first isolation membrane 140 . In one embodiment, the first isolation film 140 is not provided with the first adhesive layer or the first ceramic layer, that is, it is a bare film. In one embodiment, the first isolation film 140 includes a first base material layer 141 and a first adhesive layer, and the first adhesive layer is bonded to one side of the first base material layer 141 . In one embodiment, the first isolation film 140 includes a first base material layer 141 and a first adhesive layer, and first adhesive layers are respectively provided on both sides of the first base material layer 141 . In one embodiment, the first isolation film 140 includes a first base material layer 141, a first adhesive layer and a first ceramic layer. A first adhesive layer is provided on one side of the first base material layer 141. The first adhesive layer A first ceramic layer is provided on a side of the layer facing away from the first base material layer 141 . In one embodiment, the first isolation film 140 includes a first base material layer 141, a first adhesive layer and a first ceramic layer. The first adhesive layer is provided on one side of the first base material layer 141. The other side of layer 141 is provided with a first ceramic layer. Referring to Figure 3, in one embodiment, the first isolation film 140 includes a first base material layer 141, two first adhesive layers (respectively the first adhesive layer 142a and the first adhesive layer 142b) and two The first ceramic layer (respectively the first ceramic layer 143a and the first ceramic layer 143b), the first adhesive layer 142a is provided on one side of the first base material layer 141, the first adhesive layer 142a is away from the first base material layer 141 The first ceramic layer 143a is provided on one side of the first base material layer 141, the first adhesive layer 142b is provided on the other side of the first base material layer 141, and the first ceramic layer 143b is provided on the side of the first adhesive layer 142b away from the first base material layer 141. .

The second isolation film 130 includes a second base material layer 131. The second isolation film 130 may also include a second adhesive layer or a second ceramic layer. The second adhesive layer facilitates the bonding of the second isolation film 130 to the cathode pole piece or the anode pole piece, and the second ceramic layer facilitates improving the structural strength, thermal performance and safety of the second isolation membrane 130 . In one embodiment, the second isolation film 130 includes a second base material layer 131 and a second adhesive layer, and the second adhesive layer is bonded to one side of the second base material layer 131 . In one embodiment, the second isolation film 130 includes a second base material layer 131 and a second adhesive layer, and second adhesive layers are respectively provided on both sides of the second base material layer 131 . In one embodiment, the second isolation film 130 includes a second base material layer 131, a second adhesive layer and a second ceramic layer. A second adhesive layer is provided on one side of the second base material layer 131. The second adhesive layer A second ceramic layer is provided on a side of the layer facing away from the second base material layer 131 . In one embodiment, the second isolation film 130 includes a second base material layer 131, a second adhesive layer and a second ceramic layer. The second adhesive layer is provided on one side of the second base material layer 131. The other side of layer 131 is provided with a second ceramic layer. Referring to Figure 4, in one embodiment, the second isolation film 130 includes a second base material layer 131, two second adhesive layers (respectively the second adhesive layer 132a and the second adhesive layer 132b) and two The second ceramic layer (respectively the second ceramic layer 133a and the second ceramic layer 133b), the second adhesive layer 132a is provided on one side of the second base material layer 131, and the second adhesive layer 132a is away from the second base material layer 131 The second ceramic layer 133a is provided on one side of the second base material layer 131, the second adhesive layer 132b is provided on the other side of the second base material layer 131, and the second ceramic layer 133b is provided on the side of the second adhesive layer 132b away from the second base material layer 131. .

Referring to FIG. 1 , the rolled electrode assembly 100 includes two opposite bending parts (bending part 160 a and bending part 160 b respectively). The following takes one of the bent portions 160a as an example. The bending portion 160a has a bending center 150, and the bending radius of the bending portion 160a becomes larger as it is farther away from the bending center 150. The bent portion 160a is composed of a bent portion of the anode pole piece 110, a bent portion of the cathode pole piece 120, a bent portion of the first base material layer, and a bent portion of the second base material layer. Each of the four components may have multiple portions located at the curved portion 160a. The specific number of portions of the four components located at the curved portion 160a depends on the number of winding turns of the electrode assembly 100.

The first base material layer 141 includes a first isolation portion 1411 located at the bending portion 160a. The side of the first isolation portion 1411 close to the bending center 150 of the bending portion 160a faces the anode pole piece 110. The first isolation portion 1411 is away from the bending center 150. One side faces the cathode plate 120 . Since the anode pole pieces 110 on both sides of the first isolation portion 1411 are closer to the bending center 150 of the bending portion 160a than the cathode pole pieces 120, the anode active material facing the first isolation portion 1411 (located on the anode pole piece 110 The capacity of the active material) is less than the capacity of the cathode active material facing the first isolation part 1411 (the active material located on the cathode plate 120), and there is a risk of lithium precipitation during use. The first base material layer 141 may have one first isolation part 1411 or multiple first isolation parts 1411. The number of first isolation portions 1411 included in the first base material layer 141 depends on the number of winding turns of the electrode assembly 100 .

The second base material layer 131 includes a second isolation portion 1311 located at the bending portion 160a. The side of the second isolation portion 1311 close to the bending center 150 faces the cathode pole piece 120, and the side of the second isolation portion 1311 away from the bending center 150 faces the anode. Pole piece 110. Since the anode pole pieces 110 on both sides of the second isolation part 1311 are further away from the bending center 150 of the bending part 160a than the cathode pole piece 120, the anode active material facing the first isolation part 1411 (located on the anode pole piece 110 The capacity of the active material) is greater than the capacity of the cathode active material (the active material located on the cathode plate 120) facing the first isolation part 1411. Lithium precipitation is unlikely to occur at this location, so the requirements for the ion permeability of the second isolation portion 1311 can be lower. The second base material layer 131 may have one second isolation part 1311 or multiple second isolation parts 1311. The number of second isolation portions 1311 included in the second base material layer 131 depends on the number of winding turns of the electrode assembly 100 .

The inventor of the present application considered that the cost of an isolation film with large porosity is higher, so in some embodiments, the porosity P ₁ of the first isolation part 1411 is set to be greater than the porosity P ₂ of the second isolation part 1311 . This solution can make the first isolation part 1411 have higher ion permeability, and the second isolation part 1311 have lower material cost. And in this application, the porosity P ₁ of the first isolation part 1411 and the porosity P ₂ of the second isolation part 1311 satisfy 10% ≤ _{P 1} -P ₂ ≤ 25%. Illustratively, P ₁ -P ₂ may be 10%, 15%, 20% or 25%, etc. When 10%≤P ₁ -P ₂ ≤25%, the material cost of the second isolation part 1311 can be further reduced, and the first isolation part 1411 can also have better ion permeability, thereby reducing the lithium deposition phenomenon. of production. Compared with the battery 10 with higher porosity of the first isolation part 1411 and the higher porosity of the second isolation part 1311, the battery 10 in this application has a lower cost. Compared with the battery 10 in which the porosity of the first isolation part 1411 and the second isolation part 1311 are both lower, the battery 10 in this application can have a smaller risk of lithium precipitation and a longer service life.

The specific positions of the bent portions are defined as follows: Referring to FIG. 2 , the electrode assembly 100 has a flat portion 170 and two bent portions (

bent portions

160 a and 160 b respectively) located at both ends of the flat portion 170 . Along the winding circumferential direction of the electrode assembly 100, the inner end of the first isolation film 140 has the nearest two bending parts, and the two bending parts form two bending center lines (respectively the bending center line 20a and the bending center line 20a). Folding center line 20b), two dividing planes (respectively divided plane 30a and dividing plane 30b) divide the electrode assembly 100 into three parts. The flat part 170 is located in the middle of the two dividing planes, and the flat part 170 is located on both sides. bend. Each boundary plane passes through one of the bending center lines and is perpendicular to the flat portion 170 .

The specific location of the bend is defined as follows: "Porosity" refers to the percentage of the pore volume in the material to the total volume of the material in its natural state. For example, the porosity of the first isolation part 1411 refers to the ratio of the total volume of the pores on the first isolation part 1411 to the total volume of the first isolation part 1411 as a whole.

In some embodiments, 40%≤P ₁ ≤65%, 30%≤P ₂ ≤55%. Specifically, P ₁ can be 40%, 45%, 50%, 55%, 60% or 65%, etc., and P ₂ can be 30%, 35%, 40%, 45%, 50% or 55%, etc. In the above solution, when 30%≤P ₁ ≤65% and 30%≤P ₂ ≤65%, the ion permeability of the first isolation part 1411 can be further improved and the cost of the second isolation part 1311 can be reduced.

When the first base material layer 141 has a plurality of first isolation parts 1411 and the second base material layer 131 has a plurality of second isolation parts 1311, the porosity of only one of the first isolation parts 1411 may be different from that of one of the second isolation parts. The above-mentioned relationship exists between the porosity of the portion 1311, and the above-mentioned relationship may also exist between the porosity of all the first isolation portions 1411 and the porosity of all the second isolation portions 1311.

The first base material layer 141 may have only the porosity at all first isolation portions 1411 satisfy the foregoing parameter requirements, or the entire porosity of the first base material layer 141 may meet the foregoing parameter requirements. In one embodiment, the porosity P ₃ of the first base material layer 141 satisfies 40% ≤ P ₃ ≤ 65%. Illustratively, _P3 may be 40%, 45%, 50%, 55%, 60% or 65%, etc. The porosity P ₄ of the second base material layer 131 satisfies 30% ≤ P ₄ ≤ 55%. Illustratively, P ₄ may be 30%, 35%, 40%, 45%, 50% or 55%, etc. 10%≤P ₃ -P ₄ ≤25%, for example, P ₃ -P ₄ can be 10%, 15%, 20% or 25%, etc. The overall porosity of the first base material layer 141 and the overall porosity of the second base material layer 131 meet the above parameter requirements, which can further reduce the material cost of the second base material layer 131 and improve the ion permeability of the first isolation membrane 140 . Over sex.

In some embodiments, the air permeability value S ₁ of the first isolation part 1411 and the air permeability value S ₂ of the second isolation part 1311 satisfy 10s ≤ _{S 1} -S ₂ ≤ 50s. For example, S ₁ -S ₂ can be 10s, 20s, 30s, 40s or 50s, etc. In this solution, the dynamic performance of the first isolation part 1411 can be further improved, and the material cost of the second isolation part 1311 can be reduced.

In some embodiments, 70s≤S ₁ ≤160s, 70s≤S ₂ ≤160s. For example, S ₁ may be 70s, 90s, 110s, 130s or 160s, etc., and S ₂ may be 70s, 90s, 110s, 130s or 160s, etc. The overall porosity of the first base material layer and the overall porosity of the second base material layer 131 meet the above parameter requirements, which can further reduce the material cost of the second base material layer 131 and improve the dynamics of the first base material layer 141 performance.

In some embodiments, along the direction from the surface close to the bending center 150 to the surface away from the bending center 150, the resistance R ₁ of the first substrate layer and the resistance R ₂ of the second substrate layer 131 satisfy 0.1Ω≤R ₂ - R ₁ ≤0.5Ω. For example, R ₂ -R ₁ may be 0.1Ω, 0.2Ω, 0.3Ω, 0.4Ω or 0.5Ω, etc. In this solution, the material cost of the second base material layer 131 can be further reduced, and the dynamic performance of the first base material layer 141 can be improved.

In some embodiments, 0.4Ω≤R ₁ ≤1.1Ω, 0.4Ω≤R ₂ ≤1.1Ω. For example, R ₁ may be 0.4Ω, 0.6Ω, 0.8Ω, 1.0Ω, or 1.1Ω, etc., and R ₂ may be 0.4Ω, 0.6Ω, 0.8Ω, 1.0Ω, or 1.1Ω, etc. In the above solution, the material cost of the second base material layer can be further reduced, and the dynamic performance of the first base material layer 141 can be improved.

In some embodiments, the ion transmission rate of the first isolation part 1411 is higher than the ion transmission rate of the second isolation part 1311 . Specifically, the material of the first isolation part 1411 can be made different from the material of the second isolation part 1311 so that the ion transmittance of the first isolation part 1411 is higher than that of the second isolation part 1311; The microstructural composition of the isolation part 1411 is different from the microstructural composition of the second isolation part 1311, so that the lithium ion transmittance of the first isolation part 1411 is higher than the lithium ion transmittance of the second isolation part 1311. The specific method to make the ion transmission rate of the first isolation part 1411 higher than the ion transmission rate of the second isolation part 1311 depends on actual requirements. In this solution, the dynamic performance of the second isolation part 1311 can be further improved.

In this application, the preparation process of the first base material layer 141 and the second base material layer 131 is a process well known to those skilled in the art. The prepared first base material layer 141 and the first base material layer 141 can be adjusted by adjusting the parameters in the preparation process. The characteristics of the micropores of the second base material layer 131, such as structure, pore size, etc., and the thickness of the isolation film base material, can further adjust the porosity, air permeability value, resistance, etc. of the first base material layer 141 and the second base material layer 131. .

In some embodiments, the material of the first substrate layer 141 or the second substrate layer 131 is selected from a polymer film, a multi-layer polymer film, or a non-woven fabric composed of at least one of the following polymers: polyethylene, polyethylene Acrylic, polyterephthalate, polyethylene formate, polyphenylene phthalamide, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide , polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinyl naphthalene .

The materials of the first adhesive layer 142a and the second adhesive layer 132a are each independently selected from at least one of the following: a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of vinylidene fluoride-trichlorethylene, polyethylene Acrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate Cellulose acetate propionate, cyanoethyl pullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethylcellulose, carboxymethyl Sodium fiber, lithium carboxymethylcellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, styrene-butadiene copolymer, and polyvinylidene fluoride.

The material of the first ceramic layer 143a or the second ceramic layer 143b is selected from at least one of the following: silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, carbide Silicon, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, lithium lanthanum titanate.

Referring to Figure 6, a second aspect of the present application also provides an electronic device 1. The electronic device 1 includes any of the above electrochemical devices. The electronic device 1 of the present application is not particularly limited and may be any electronic device 1 known in the prior art. For example, the electronic device 1 includes, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copy machine, a portable printer, a stereo headset, a video recorder, an LCD TV, a portable Cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting equipment, toys, games Machines, watches, power tools, flashlights, cameras, large household batteries10 and lithium-ion capacitors, etc.

The method of preparing the electrochemical device of the present application is not particularly limited, and any method known in the art can be used.

Comparative example 1

(1) Preparation of cathode plate: Prepare the cathode active material, binder and solvent into a slurry and stir evenly. The slurry is evenly coated on the cathode current collector and dried to obtain a single-sided coated cathode plate. Repeat the above steps on the other surface of the cathode current collector to obtain a double-sided coated cathode plate. Then, it is cold pressed, cut and ready for use. Among them, the cathode plate material: 95.3% lithium iron phosphate + 3.7% PVDF + 1.0% SP.

(2) Preparation of anode plates: Prepare the anode active material, binder, conductive agent and solvent into a slurry, and stir evenly. The slurry is evenly coated on the anode current collector and dried to obtain a single-sided coated anode pole piece. Repeat the above steps on the other surface of the anode current collector to obtain a double-sided coated anode plate. Then, it is cold pressed, cut and ready for use. Among them, the anode plate material is: 95% artificial graphite + 3% CMC + 2% SBR. The CB (CellBalance, the ratio of negative electrode capacity to positive electrode capacity under the same area) value of the anode electrode piece and the cathode electrode piece is 1.08.

(3) Preparation of isolation film: The first isolation film and the second isolation film are single-layer films made of polyethylene material, in which the first base material layer has a porosity of 50%, an air permeability value of 100s, and a resistance of 0.5Ω. The second base material layer has a porosity of 50%, an air permeability value of 100s, and a resistance of 0.5Ω.

(4) Preparation of electrolyte: Mix lithium salt and non-aqueous solvent and stir evenly to obtain electrolyte. Electrolyte material: 1 mol lithium salt + 40% diethyl carbonate (DEC) + 30% ethyl carbonate (EC) + 30% ethyl methyl carbonate (EMC).

(5) Preparation of electrode assembly: The structure of the electrode assembly is a rolled structure, in which the cathode pole piece, the first isolation film, the anode pole piece, and the second isolation film are stacked in sequence and rolled to form an electrode with a winding structure. Components; each electrode component contains an anode tab and a cathode tab; repeat the above steps to obtain multiple electrode components.

(6) Packaging injection and liquidization: Put the electrode assembly into the case, inject the electrolyte, and seal after hot pressing, formation, and degassing.

The terms used in this application are generally terms commonly used by those skilled in the art. If there is any inconsistency with the commonly used terms, the terms in this application shall prevail. In this application, unless otherwise stated, "%" and "parts" are based on weight.

Test Methods:

Porosity test method

1. Disassemble the discharged lithium-ion battery to be tested, then take out the isolation film, and process the isolation film to obtain the isolation film substrate sample.

2. Stack the diaphragms into 6 stacks, flatten them, press them tightly, and remove the air in the diaphragms. Cut the stacked diaphragm according to the cutting plate, measure the cut sample, and obtain the area S of the sample.

3. Measure the thickness of the sample, the number of measurements is 10 or 20 times, and the average value is calculated as B.

4. Use an electronic balance to measure the weight of the diaphragm. The number of measurements is 3 and the average value M is obtained.

5. Calculate by the following formula: porosity p=[(density of separator raw material×S×B-M)/(density of separator raw material×S×B)]×100%.

Breathability value test method

Disassemble the discharged lithium-ion battery to be tested, take out the isolation film, and process the isolation film to obtain an isolation film substrate sample. In an environment where the temperature is 25°C and the humidity is less than 80%, the test sample is made into a size of 4cm × 4cm, and the air permeability value is obtained directly by measuring with the Gurley test (100mL) method using an Air-permeability-tester. The unit is seconds (s), which represents the time required for 100mL of air to pass through the isolation membrane with an area of 4cm×4cm.

Resistance test method

Disassemble the discharged lithium-ion battery to be tested, take out the isolation film, and process the isolation film to obtain an isolation film substrate sample. The bulk resistance of the sample was measured using an electrochemical workstation using the AC impedance method (EIS). The specific method is: use a ring punching machine to cut the sample into a disc with a diameter of 19mm, place it between two stainless steel sheets, and follow the steps of positive electrode shell, stainless steel sheet, separator (the separator needs to be soaked with electrolyte), stainless steel sheet, The negative electrode shell is assembled in sequence and packaged into a CR2032 battery for AC impedance testing. The test frequency range is set to 0.1~106Hz, and the amplitude is set to 5mV.

Lithium-ion battery CB test

Take a fully discharged lithium-ion battery, disassemble the positive and negative electrodes respectively, clean and dry them, and use a 14mm diameter die to punch out 5 complete electrode pieces on the flat single-sided areas of the positive and negative electrodes. Use lithium pieces. Make counter electrodes and assemble them into button cells for testing. Test according to the gram capacity test method, measure the capacity of the positive electrode, recorded as C1, C2, C3, C4, C5, and calculate the average capacity C of the positive electrode punched pole pieces; similarly, measure the capacity of the negative electrode, recorded as A1, A2, A3, A4, and A5, calculate the average capacity A of the negative electrode punched pole pieces. The calculation formula for CB of this lithium-ion battery is CB=A/C.

Comparative example 2

The second base material layer has a porosity of 40%, an air permeability value of 160s, and a resistance of 0.9Ω. Others are the same as Comparative Example 1.

Comparative example 3

The first base material layer has a porosity of 40%, an air permeability value of 160s, and a resistance of 0.9Ω. Others are the same as Comparative Example 1.

Comparative example 4

The first base material layer has a porosity of 60%, an air permeability value of 80s, and a resistance of 0.4Ω. Others are the same as Comparative Example 1.

Example 1

The second base material layer has a porosity of 60%, an air permeability value of 80s, and a resistance of 0.4Ω. Others are the same as Comparative Example 1.

Example 2

The porosity of the second base material layer is 30%, the air permeability value is 180s, and the resistance is 1.1Ω. Others are the same as Example 1.

Example 3

The first base material layer has a porosity of 30%, an air permeability value of 80s, and a resistance of 1.1Ω. Others are the same as Comparative Example 1.

Example 4

The first base material layer has a porosity of 65%, an air permeability value of 70s, and a resistance of 0.35Ω. Others are the same as Example 3.

Example 5

CB is 1.06. Others are the same as Example 1.

Example 6

The second base material layer has a porosity of 40%, an air permeability value of 160s, and a resistance of 0.9Ω. Others are the same as Comparative Example 2.

Example 7

The first base material layer has a porosity of 60%, an air permeability value of 80s, and a resistance of 0.4Ω. CB is 1.06, and the others are the same as Comparative Example 3.

Example 8

The anode CB is 1.04, and the others are the same as in Example 6.

Example 9

The anode CB is 1.02, and the others are the same as in Example 8.

Example 10

The anode CB is 1.1, and the others are the same as in Example 9.

Example 11

The first base material layer has a porosity of 40%, an air permeability value of 160s, and a resistance of 0.9Ω. CB is 1.1, and the others are the same as Example 2.

Example 12

Anode CB is 1.2. Others are the same as Comparative Example 2.

The specific parameters and evaluation results of each example and comparative example are shown in Table 1:

Table 1

Referring to Comparative Example 1 and Example 2, the first isolation membrane parameters of both are the same. The porosity of the second isolation membrane of Example 2 is smaller than the porosity of the second isolation membrane of Comparative Example 1. In the test results, Comparative Example 1 and The non-lithium elution capability of Example 2 is the same, but the cost of the isolation membrane of Example 2 is reduced by 10%. Therefore, making the second isolation film smaller than the first isolation film can reduce the risk of lithium precipitation and at the same time reduce the cost of the isolation film.

See Comparative Example 4 and Comparative Example 1. The parameters of the second isolation membranes of the two are the same. The porosity of Comparative Example 4 is higher than the porosity of Comparative Example 1. According to the test results, Comparative Example 4 has a better ability to prevent lithium precipitation. Therefore, increasing the porosity of the first isolation film can improve the battery's ability to prevent lithium precipitation.

Referring to Example 6 and Comparative Example 1, the parameters of the first isolation film in both are the same. The resistance of Example 6 is higher than that of Comparative Example 1. In the test results, the cost of the isolation film is reduced by 10%, so the first isolation film has the same parameters. The resistance of the second isolation film becomes higher, which can reduce the cost of the isolation film.

Comparing Examples 6 to 12, it can be seen that when CB is in the range of 1.06 to 1.2, the overall performance of the battery is further improved.

It should be noted that the preferred embodiments of the present application are given in the description and drawings of this application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not used as additional limitations on the content of the present application, and are provided for the purpose of making the disclosure of the present application more thorough and comprehensive. Moreover, the above technical features can be continuously combined with each other to form various embodiments not listed above, which are all deemed to be within the scope of the description of this application; further, for those of ordinary skill in the art, they can be improved or transformed according to the above description. , and all these improvements and transformations should fall within the protection scope of the claims appended to this application.

Claims

An electrochemical device, characterized in that it includes a rolled electrode assembly, the electrode assembly includes an anode electrode piece, a cathode electrode piece, a first isolation film and a second isolation film arranged in a stack, the anode electrode piece includes an anode current collector and anode active material layers disposed on both sides of the anode current collector; the cathode pole piece includes a cathode current collector and cathode active material layers disposed on both sides of the cathode current collector; the electrode assembly includes a curved department;

The first isolation film includes a first base material layer, the first base material layer includes a first isolation part located at the bending part, and a side of the first isolation part close to the bending center of the bending part faces In the anode pole piece, the side of the first isolation part away from the bending center faces the cathode pole piece;

The second isolation film includes a second base material layer, the second base material layer includes a second isolation part located at the bending part, and a side of the second isolation part close to the bending center faces the cathode. pole piece, the side of the second isolation part away from the bending center faces the anode pole piece;

The porosity P 1 of the first isolation part and the porosity P 2 of the second isolation part satisfy 10% ≤ P 1 -P 2 ≤ 25%.
The electrochemical device according to claim 1, characterized in that

40%≤P 1 ≤65%; and/or

30% ≤P2≤55 %.
The electrochemical device according to claim 1, characterized in that

The porosity P 3 of the first base material layer satisfies 40% ≤ P 3 ≤ 65%;

The porosity P 4 of the second base material layer satisfies 30% ≤ P 4 ≤ 55%;

10%≤P 3 -P 4 ≤25%.
The electrochemical device according to claim 1, characterized in that

The air permeability value S 1 of the first isolation part and the air permeability value S 2 of the second isolation part satisfy 10s ≤ S 1 -S 2 ≤ 50s.
The electrochemical device according to claim 4, characterized in that

70s≤S 1 ≤160s, 70s≤S 2 ≤160s.
The electrochemical device according to claim 1, characterized in that

The resistance R 1 of the first isolation part and the resistance R 2 of the second isolation part satisfy 0.1Ω≤R 2 -R 1 ≤0.5Ω.
The electrochemical device according to claim 6, characterized in that

0.4Ω≤R 1 ≤1.1Ω, 0.4Ω≤R 2 ≤1.1Ω.
The electrochemical device according to claim 1, characterized in that

At least one of a first adhesive layer or a first ceramic layer is provided on the first base material layer; and/or

At least one of a second adhesive layer or a second ceramic layer is provided on the second base material layer.
The electrochemical device according to claim 1, characterized in that:

A first adhesive layer and a first ceramic layer are not provided on the first base material layer; at least one of a second adhesive layer or a second ceramic layer is provided on the second base material layer.
The electrochemical device of claim 1, wherein CB ranges from 1.06 to 1.2.
An electronic device, characterized by comprising the electrochemical device according to any one of claims 1-10.