CN116134675A - Electrochemical devices and electronic devices - Google Patents

Abstract

The application discloses an electrochemical device and an electronic device. The electrochemical device includes a wound electrode assembly. The electrode assembly includes an anode sheet, a cathode sheet, a first separator and a second separator, and the electrode assembly includes a curved portion. . The first separator includes a first base material layer, the first base material layer includes a first isolation part, the side of the first isolation part close to the bending center of the bending part faces the anode electrode piece, and the side of the first isolation part away from the bending center to the cathode plate. The second isolation film includes a second base material layer, the second base material layer includes a second isolation part, the side of the second isolation part near the bending center faces the cathode electrode piece, and the side of the second isolation part facing away from the bending center faces the anode electrode piece. The porosity _P1 of the first isolation part and the porosity _P2 of the second isolation part satisfy 10% _≤P1 - _P2≤25 %. When 10%≦P ₁ -P ₂ ≦25%, the material cost of the second isolation part can be reduced, and at the same time, the first isolation part can have better ion permeability, thereby reducing the occurrence of lithium precipitation.

Description

Electrochemical devices and electronic devices

technical field

The embodiments of the present application relate to the field of electrochemistry, and in particular, relate 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 inside, so as to supply power to external electrical devices (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 notebook computers. Existing electrochemical devices are prone to lithium deposition after repeated charging and discharging, and the capacity of the electrochemical device will decay after lithium deposition. In order to reduce the phenomenon of lithium precipitation, the material cost of the battery will generally increase.

Contents of the invention

The embodiments of the present application provide an electrochemical device and an electronic device, which can improve the problem of lithium analysis in the electrochemical device and balance the cost of the electrochemical device.

In order to solve the above technical problems, a technical solution adopted by the present application is to provide an electrochemical device, the electrochemical device includes a wound electrode assembly, and the electrode assembly includes a stacked anode sheet, a cathode sheet, a first separator The membrane and the second separator, the electrode assembly include a bent portion. The first isolation film includes a first base material layer, the first base material layer includes a first isolation portion located at the bending portion, and a side of the first isolation portion close to the bending center of the bending portion faces As for the anode sheet, the side of the first isolation part facing away from the bending center faces the cathode sheet. The second isolation film includes a second base material layer, the second base material layer includes a second isolation portion located at the curved portion, and a side of the second isolation portion close to the bending center faces the cathode The pole piece, the side of the second isolation part facing away from the bending center faces the anode pole piece. The porosity _P1 of the first isolation part and the porosity _P2 of the second isolation part satisfy 10% _≤P1 - _P2≤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 insulation part and the air permeability value S ₂ of the second insulation 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 portion and the resistance R ₂ of the second isolation portion 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 disposed on the first substrate layer; at least one of the second adhesive layer or the second ceramic layer is disposed on the second substrate layer.

In some embodiments, the CB ranges from 1.06 to 1.2.

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

In the electrochemical device provided in the embodiment of the present application, the applicant considers that the side of the first isolation part close to the bending center of the bending part faces the anode electrode piece, and the side away from the bending center faces the cathode electrode piece, so the side facing 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 relatively high ion permeability. The side of the second separator near the bending center faces the cathode pole piece, and the side away from the bending center faces the anode pole piece, so the capacity of the cathode active material facing the second separator is less than that of the anode active material facing the second separator Capacity, the ion permeability of the second isolation part may be weaker than that of the first isolation part, and a better effect of slow desorption of lithium can be achieved. In view of this, it is set that the porosity P ₁ of the first isolation portion is greater than the porosity P ₂ of the second isolation portion, and 10%≤P ₁ −P ₂ ≤25%. This solution can make the first separator have higher ion permeability to reduce the risk of lithium segregation on the anode electrode facing the first separator, and the second separator can maintain a better improvement in the anode electrode facing the second separator. It has a lower cost when exfoliating lithium problems. And in the present application, the porosity _P1 of the first isolation part and the porosity _P2 of the second isolation part satisfy.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings that need to be used in the embodiments of the present application. Obviously, the accompanying drawings described below are only some embodiments of the present application. Those skilled in the art can also obtain other drawings according to the accompanying drawings.

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

Fig. 2 is a schematic side view of an electrode assembly provided by an embodiment of the application viewed along a direction parallel to the winding axis;

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

Figure 4 is a schematic side view of the second isolation film provided by an embodiment of the application, viewed along a direction perpendicular to its own thickness

Fig. 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 the 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 said to be "fixed" to another element, it may be directly on the other element, or there may be one or more intervening elements therebetween. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions are used in this specification for the purpose of description only.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the technical field of this application. The terms used in the description of the present application are only for the purpose of describing specific embodiments, and are not used to limit the present application. The term "and/or" used in this specification 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, and the electrode assembly includes an anode sheet, a first separator, a cathode sheet and a second separator arranged in a stacked manner. The anode pole piece includes an anode current collector and an anode active material layer disposed on both sides of the anode current collector, and the cathode pole piece includes a cathode current collector and a cathode active material layer disposed on both sides of the cathode current collector. When the electrochemical device is charged, the lithium ions of the cathode pole piece are deintercalated and inserted into the anode pole piece through the isolation membrane (which may be the first isolation membrane or the second isolation membrane). However, when some abnormal conditions occur: such as insufficient space for lithium intercalation in the anode, too much resistance to intercalation of lithium ions in the anode, excessive lithium ion deintercalation from the cathode but unable to intercalate in the same amount in the anode, etc., the lithium ions that cannot be intercalated in the anode can only Electrons are obtained on the surface of the anode, thereby forming a silver-white metal lithium element, which is lithium precipitation. Lithium analysis not only degrades 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 a safety risk.

In view of this, referring to FIGS. 1-5 , the present application discloses an electrochemical device, which 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 wound electrode assembly 100 and a battery case 300 . The electrode assembly 100 includes an anode pole piece 110 , a cathode pole piece 120 , a first separator 140 and a second separator 130 arranged in layers. The anode pole piece includes an anode current collector and an anode active material layer disposed on both sides of the anode current collector, and the cathode pole piece includes a cathode current collector and a cathode active material layer disposed on both sides of the cathode current collector. The electrochemical device further 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 an accommodating cavity 310 , and the electrode assembly 100 is accommodated in the accommodating cavity 310 in the battery case 300 .

The specific lamination method of the anode electrode piece 110 , the cathode electrode piece 120 , the first separator 140 and the second separator 130 depends on specific requirements. In one embodiment, the four are stacked and wound in the order of the anode pole piece 110, the second separator 130, the cathode pole piece 120, and the first separator 140, and the winding center is located at the first separator 140 away from the cathode pole. One side of the sheet 120 such that the anode sheet 110 is located on the outside compared to the cathode sheet 120 . In one embodiment, the four are stacked and wound in the order of the cathode pole piece 120, the first separator 140, the anode pole piece 110, and the second separator 130, and the winding center is located at the second separator 130 away from the anode. One side of the sheet 110 such that the cathode sheet 120 is located on the outside compared to the anode sheet 110 . Referring to FIG. 1 , in the present application, the structure in which the anode electrode sheet 110 is located outside the cathode electrode sheet 120 is taken as an example for description.

The first isolation film 140 includes a first substrate layer 141 , and the first isolation film 140 may further include a first adhesive layer or a first ceramic layer. The first adhesive layer facilitates the bonding of the first separator 140 to the cathode electrode piece or the anode electrode piece, and the first ceramic layer is beneficial to improve the structural strength, thermal performance and safety of the first separator 140 . In one embodiment, the first isolation film 140 is not provided with the first bonding layer or the first ceramic layer, that is, it is a bare film. In one embodiment, the first isolation film 140 includes a first substrate layer 141 and a first adhesive layer, and the first adhesive layer is bonded to one side of the first substrate layer 141 . In one embodiment, the first isolation film 140 includes a first base material layer 141 and a first adhesive layer, and both sides of the first base material layer 141 are respectively provided with first adhesive layers. In one embodiment, the first isolation film 140 includes a first substrate layer 141, a first adhesive layer, and a first ceramic layer, a first adhesive layer is provided on one side of the first substrate layer 141, and the first adhesive layer A first ceramic layer is provided on the side facing away from the first substrate 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. One side of the first base material layer 141 is provided with a first adhesive layer, and the first base material The other side of layer 141 is provided with a first ceramic layer. Referring to FIG. 3, in one embodiment, the first isolation film 140 includes a first substrate layer 141, two first adhesive layers (respectively a first adhesive layer 142a and a 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 arranged on one side of the first substrate layer 141, and the first adhesive layer 142a faces away from the first substrate layer 141 One side of the first substrate layer 141 is provided with a first ceramic layer 143a, the other side of the first substrate layer 141 is provided with a first adhesive layer 142b, and the side of the first adhesive layer 142b away from the first substrate layer 141 is provided with a first ceramic layer 143b .

The second isolation film 130 includes a second substrate layer 131 , and the second isolation film 130 may further include a second adhesive layer or a second ceramic layer. The second adhesive layer facilitates the bonding of the second separator 130 to the cathode electrode piece or the anode electrode piece, and the second ceramic layer is beneficial to improve the structural strength, thermal performance and safety of the second separator 130 . In one embodiment, the second isolation film 130 includes a second substrate layer 131 and a second adhesive layer, and the second adhesive layer is bonded to one side of the second substrate layer 131 . 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 respectively disposed 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, and the second adhesive layer A second ceramic layer is provided on the side facing away from the second substrate 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, and the second base material The other side of layer 131 is provided with a second ceramic layer. Referring to FIG. 4, in one embodiment, the second isolation film 130 includes a second substrate 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), one side of the second base material layer 131 is provided with a second adhesive layer 132a, and the second adhesive layer 132a is away from the second base material layer 131 One side of the second substrate layer 131 is provided with a second ceramic layer 133a, the other side of the second substrate layer 131 is provided with a second adhesive layer 132b, and the side of the second adhesive layer 132b away from the second substrate layer 131 is provided with a second ceramic layer 133b .

Referring to FIG. 1 , the wound electrode assembly 100 includes two opposite bent portions (curved portion 160 a and bent portion 160 b , respectively). One of the curved portions 160a is used as an example for illustration below. The bending portion 160 a has a bending center 150 , and the farther the bending portion 160 a is from the bending center 150 , the larger the bending radius is. The bent portion 160a is composed of the bent portion of the anode tab 110 , the bent portion of the cathode tab 120 , the bent portion of the first base material layer and the bent portion of the second base material layer. There may be multiple parts of the four located at the bent portion 160 a , and how many of the four are located at the bent portion 160 a depends on the number of winding turns of the electrode assembly 100 .

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

The second substrate 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 sheet 120, and the side of the second isolation portion 1311 facing away from the bending center 150 faces the anode Pole piece 110. Since the anode pole piece 110 on both sides of the second separator 1311 is farther away from the bending center 150 of the curved portion 160a than the cathode pole piece 120, the anode active material facing the first separator 1411 (positioned 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 on the cathode sheet 120 ) facing the first separator 1411 . Lithium precipitation is not easy to occur at this position, so the requirement on the ion permeability of the second isolation part 1311 can be lower. The second base material layer 131 may have one second isolation portion 1311 , or may have a plurality of second isolation portions 1311 . The number of the second isolation portions 1311 of the second base material layer 131 depends on the number of winding turns of the electrode assembly 100 .

The inventors of the present application consider that the cost of an isolation film with large porosity is higher, so in some embodiments, the porosity P ₁ of the first isolation portion 1411 is set to be greater than the porosity P ₂ of the second isolation portion 1311 . This solution can make the first isolation part 1411 have higher ion permeability, and the second isolation part 1311 has 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% _≤P1 - _P2≤25 %. Exemplarily, P ₁ -P ₂ may be 10%, 15%, 20% or 25% and so on. When 10% _≤P1 - _P2≤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 phenomenon of lithium precipitation generation. Compared with the battery 10 in which the porosity of the first isolation part 1411 and the porosity of the second isolation part 1311 are both higher, the battery 10 in the present application has a lower cost. Compared with the battery 10 in which the porosity of the first isolation part 1411 and the porosity of the second isolation part 1311 are both lower, the battery 10 in the present application has less risk of lithium precipitation and has a longer service life.

The specific position of the curved portion is defined as follows: Referring to FIG. 2 , the electrode assembly 100 has a flat portion 170 and two curved portions (curved portion 160 a and curved portion 160 b ) 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 separator 140 has two closest bending positions, and the two bending positions form two bending centerlines (respectively, the bending centerline 20a and the bending centerline 20a). center line 20b), two boundary planes (respectively boundary plane 30a and boundary plane 30b) divide the electrode assembly 100 into three parts, the flat part 170 located in the middle of the two boundary planes, and the two sides located on both sides bending part. Wherein, each boundary plane passes through one of the bending centerlines and is perpendicular to the flat portion 170 .

The specific position of the bent portion is defined as follows: "porosity" refers to the percentage of the volume of pores in the material to the total volume of the material in a natural state. For example, the porosity of the first isolation part 1411 refers to the ratio of the total volume of 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% and so on. 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 while reducing the cost of the second isolation part 1311 .

When the first substrate layer 141 has a plurality of first isolation parts 1411 and the second substrate 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 among the porosities of the parts 1311 , and the above-mentioned relationship may exist between the porosities of all the first partition parts 1411 and the porosities of all the second partition parts 1311 .

The porosity of the first base material layer 141 may only meet the requirements of the aforementioned parameters at all positions of the first isolation portion 1411 , and the overall porosity of the first base material layer 141 may also meet the requirements of the aforementioned parameters. In one embodiment, the porosity P ₃ of the first base material layer 141 satisfies 40%≦ _{P 3} ≦65%. Exemplarily, _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%. Exemplarily, P ₄ may be 30%, 35%, 40%, 45%, 50% or 55%, etc. 10%≤P ₃ -P ₄ ≤25%, for example, P ₃ -P ₄ may be 10%, 15%, 20% or 25%. 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. Transsexual.

In some embodiments, the air permeability value S ₁ of the first isolation portion 1411 and the air permeability value S ₂ of the second isolation portion 1311 satisfy 10s≦ _{S 1} −S ₂ ≦50s. Exemplarily, S ₁ -S ₂ may 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. Exemplarily, 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 substrate layer and the overall porosity of the second substrate layer 131 meet the above parameter requirements, which can further reduce the material cost of the second substrate layer 131 and improve the dynamics of the first substrate layer 141 performance.

In some embodiments, 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. Exemplarily, 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. Exemplarily, 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 different from the material of the second isolation part 1311 so that the ion transmission rate of the first isolation part 1411 is higher than the ion transmission rate of the second isolation part 1311; The microstructure composition of the isolation part 1411 is different from that 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 way 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, and the prepared first base material layer 141 and the second base material layer 131 can be adjusted by adjusting parameters in the preparation process. The characteristics of the micropores of the second substrate layer 131, such as structure, pore diameter, etc., and the thickness of the isolation film substrate, etc., can further adjust the porosity, gas permeability, resistance, etc. of the first substrate layer 141 and the second substrate 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 multilayer polymer film, or a non-woven fabric composed of at least one of the following polymers: polyethylene, polyester Acrylic, polyethylene terephthalate, polyethylene glycol formate, polyphenylene phthalamide, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide , polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cycloolefin copolymer, polyphenylene sulfide, and polyethylene 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: copolymers of vinylidene fluoride-hexafluoropropylene, copolymers of vinylidene fluoride-trichloroethylene, poly Acrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, butyrate acetate cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, carboxymethyl Sodium cellulose, 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 oxide, 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 FIG. 6 , the second aspect of the present application also provides an electronic device 1 , which includes any one of the electrochemical devices described above. The electronic device 1 of the present application is not particularly limited, and it 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 cellular phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headphone, a video recorder, an LCD TV, a portable portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting appliances, toys, games Machines, clocks, electric tools, flashlights, cameras, large household storage batteries 10 and lithium ion capacitors, etc.

The method for 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 the cathode electrode sheet: the cathode active material, the binder and the solvent are formulated into a slurry and stirred evenly. The slurry is evenly coated on the cathode current collector and dried to obtain a single-sided coated cathode sheet. The above steps were repeated on the other surface of the cathode current collector to obtain a double-sided coated cathode sheet. Then, it is used after cold pressing and cutting. Among them, cathode plate material: 95.3% lithium iron phosphate + 3.7% PVDF + 1.0% SP.

(2) Preparation of the anode electrode sheet: 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 sheet. The above steps were repeated on the other surface of the anode current collector to obtain a double-sided coated anode sheet. Then, it is used after cold pressing and cutting. Among them, anode sheet material: 95% artificial graphite + 3% CMC + 2% SBR. The CB (Cell Balance, the ratio of negative electrode capacity to positive electrode capacity under the same area) value of the anode pole piece and the cathode pole 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, wherein the porosity of the first substrate layer is 50%, the air permeability value is 100s, and the resistance is 0.5Ω. The second substrate layer has a porosity of 50%, an air permeability of 100s, and a resistance of 0.5Ω.

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

(5) Preparation of the electrode assembly: the structure of the electrode assembly is a winding structure, wherein the electrodes of the winding structure can be formed by stacking the cathode sheet, the first separator, the anode sheet, and the second separator in sequence and winding them. Assemblies; each electrode assembly includes an anode tab and a cathode tab; repeating the above steps can obtain multiple electrode assemblies.

(6) Encapsulation, liquid injection and formation: put the electrode assembly into the casing, inject the electrolyte, and seal it after hot pressing, formation and degassing.

The terms used in this application are generally commonly used terms by those skilled in the art. If they are inconsistent with commonly used terms, the terms in this application shall prevail. In this application, unless otherwise specified, "%" and "part" are based on weight.

Test Methods:

Porosity test method

1. Disassemble the lithium-ion battery to be tested after discharge, then take out the separator, and process the separator to obtain a sample of the separator substrate.

2. Stack the diaphragms into 6 stacks, flatten them, press them tightly, and get rid of the air in the diaphragms. Cut the stacked diaphragm according to the cutting template, 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. Measure the weight of the diaphragm with an electronic balance, and the number of measurements is 3 times to obtain the average value M.

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

Air permeability test method

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

Resistance Test Method

The discharged lithium-ion battery to be tested is disassembled, and then the separator is taken out, and the separator is processed to obtain a separator substrate sample. The bulk resistance of the samples was measured by the electrochemical workstation using the alternating current 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 positive electrode shell, stainless steel sheet, diaphragm (the diaphragm needs to be infiltrated with electrolyte), stainless steel sheet, The assembly sequence of the negative electrode casing was packaged into a CR2032 battery, and the AC impedance test was performed. 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 each of the positive and negative electrodes, wash and dry them, and use a die with a diameter of 14mm to punch out 5 complete pole pieces on the flat single-sided areas of the positive and negative electrodes respectively. Make counter electrodes and assemble them into button cells for testing. Test with reference to the gram capacity test method, measure the capacity of the positive electrode, and record it as C1, C2, C3, C4, C5, and calculate the average capacity C of the positive electrode blanking plate; similarly, measure the capacity of the negative electrode, record it as A1, A2, A3, A4, A5, the average capacity A of the negative electrode blanking plate is calculated, and the calculation formula of the lithium ion battery CB is CB=A/C.

Comparative example 2

The porosity of the second substrate layer is 40%, the gas permeability is 160s, and the resistance is 0.9Ω. Others are the same as Comparative Example 1.

Comparative example 3

The porosity of the first substrate layer is 40%, the air permeability is 160s, and the resistance is 0.9Ω. Others are the same as Comparative Example 1.

Comparative example 4

The porosity of the first substrate layer is 60%, the air permeability is 80s, and the resistance is 0.4Ω. Others are the same as Comparative Example 1.

Example 1

The porosity of the second substrate layer is 60%, the air permeability is 80s, and the resistance is 0.4Ω. Others are the same as Comparative Example 1.

Example 2

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

Example 3

The porosity of the first substrate layer is 30%, the air permeability is 80s, and the resistance is 1.1Ω. Others are the same as Comparative Example 1.

Example 4

The porosity of the first substrate layer is 65%, the air permeability is 70s, and the resistance is 0.35Ω. Others are identical with embodiment 3.

Example 5

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

Example 6

The porosity of the second substrate layer is 40%, the gas permeability is 160s, and the resistance is 0.9Ω. Others are the same as Comparative Example 2.

Example 7

The porosity of the first substrate layer is 60%, the air permeability is 80s, and the resistance is 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 porosity of the first substrate layer is 40%, the air permeability is 160s, and the resistance is 0.9Ω. CB is 1.1, and others are identical with embodiment 2.

Example 12

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

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

Table 1

Referring to Comparative Example 1 and Example 2, the parameters of the first isolation membrane of the two are the same, and the porosity of the second isolation membrane of Example 2 is smaller than that of the second isolation membrane of Comparative Example 1. In the test results, Comparative Example 1 and Example 2 has the same ability to not separate lithium, but the cost of the separator in Example 2 is reduced by 10%. Therefore, making the second isolation film smaller than the first isolation film can reduce the cost of the isolation film while reducing the risk of lithium deposition.

Refer to Comparative Example 4 and Comparative Example 1. The parameters of the second separator are the same. The porosity of Comparative Example 4 is higher than that of Comparative Example 1. According to the test results, Comparative Example 4 has a better ability to not separate lithium. Therefore, increasing the porosity of the first isolation film can improve the ability of the battery not to decompose lithium.

Referring to Example 6 and Comparative Example 1, the parameters of the first isolation film of the two are the same, and 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 second Second, the resistance of the isolation film becomes higher, and the cost of the isolation film can be reduced.

Comparing Examples 6 to 12 shows that when the 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 application are given in the description of the application and the accompanying drawings, but the application can be implemented in many different forms, and are not limited to the embodiments described in the description. These embodiments are not intended as additional limitations on the content of this application, and the purpose of providing these embodiments is to make the understanding of the disclosure of this application more thorough and comprehensive. Moreover, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as the scope of the description of the present application; furthermore, those of ordinary skill in the art can improve or transform according to the above description , and all these improvements and transformations should belong to the scope of protection of the appended claims of this application.

Claims (11)

1. An electrochemical device, characterized in that it includes a wound electrode assembly, the electrode assembly includes an anode pole piece, a cathode pole piece, a first separator and a second separator arranged in a stacked arrangement, the anode pole The sheet includes an anode current collector and an anode active material layer disposed on both sides of the anode current collector, the cathode sheet includes a cathode current collector and a cathode active material layer disposed on both sides of the cathode current collector, and the electrode assembly including bends; The first isolation film includes a first base material layer, the first base material layer includes a first isolation portion located at the bending portion, and a side of the first isolation portion close to the bending center of the bending portion faces For the anode sheet, the side of the first separator facing away from the bending center faces the cathode sheet; The second isolation film includes a second base material layer, the second base material layer includes a second isolation portion located at the curved portion, and a side of the second isolation portion close to the bending center faces the cathode a pole piece, the side of the second separator facing away from the bending center faces the anode pole piece; The porosity _P1 of the first isolation part and the porosity _P2 of the second isolation part satisfy 10% _≤P1 - _P2≤25 %. 2. The electrochemical device according to claim 1, characterized in that, 40% ≤ P ₁ ≤ 65%; and/or 30% _≤P2≤55 %. 3. The electrochemical device according to claim 1, wherein The porosity _P3 of the first substrate layer satisfies 40% _≤P3≤65 %; The porosity _P4 of the second substrate layer satisfies 30% _≤P4≤55 %; 10% ≤ P ₃ -P ₄ ≤ 25%. 4. The electrochemical device according to claim 1, wherein 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≤S1 - _S2≤50s . 5. The electrochemical device according to claim 4, characterized in that, _{70s≤S1≤160s} , _{70s≤S2≤160s} . 6. The electrochemical device according to claim 1, wherein The resistance R ₁ of the first isolation portion and the resistance R ₂ of the second isolation portion satisfy 0.1Ω≦R ₂ −R ₁ ≦0.5Ω. 7. The electrochemical device according to claim 6, wherein 0.4Ω≤R ₁ ≤1.1Ω, 0.4Ω≤R ₂ ≤1.1Ω. 8. The electrochemical device according to claim 1, wherein At least one of a first adhesive layer or a first ceramic layer is disposed on the first substrate layer; and/or At least one of a second adhesive layer or a second ceramic layer is disposed on the second substrate layer. 9. The electrochemical device according to claim 1, wherein 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. 10. The electrochemical device of claim 1, wherein CB is in the range of 1.06 to 1.2. 11. An electronic device, comprising the electrochemical device according to any one of claims 1-10.

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