CN116848651A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
CN116848651A
CN116848651A CN202280010323.1A CN202280010323A CN116848651A CN 116848651 A CN116848651 A CN 116848651A CN 202280010323 A CN202280010323 A CN 202280010323A CN 116848651 A CN116848651 A CN 116848651A
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electrochemical device
functional layer
area
current collector
electrolyte
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王星永
韩冬冬
刘晓欠
王可飞
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The electrochemical device comprises an electrode pole piece, wherein the electrode pole piece comprises a current collector, the current collector comprises a first area and a second area, an active material layer is arranged on the first area, a functional layer is arranged on the second area, the electrochemical device is tested by a nondestructive ultrasonic intelligent diagnosis system, ultrasonic waves are emitted to the electrochemical device along the thickness direction of the electrochemical device, a signal feedback distribution diagram of the electrochemical device on the ultrasonic waves is obtained, and the area ratio of an area with the signal intensity being greater than or equal to 1333mV is 30-95% based on the area of the electrode pole piece in the signal feedback distribution diagram. The electrochemical device of the present application has high liquid retention and a flat appearance. An electronic device including the electrochemical device is also provided.

Description

Electrochemical device and electronic device
Technical Field
The present application relates to the field of batteries, and more particularly, to an electrochemical device and an electronic device.
Background
Secondary batteries such as lithium ion batteries are widely used in the fields of portable electronic products, electric vehicles, energy storage and the like because of the advantages of high energy density, good cycle performance, environmental protection, safety, no memory effect and the like. However, with the development of technology, the requirements of battery energy density and cycle life are also increasing. On the one hand, the electrolyte plays an important role in the cycle life of the lithium ion battery, and in order to ensure the long cycle life of the battery, a surplus electrolyte needs to be injected into the battery to compensate for the consumption of the electrolyte in the cycle process. However, on the other hand, the surplus electrolyte tends to be unevenly released inside the packaging bag (e.g., aluminum plastic film), which causes irregularities on the surface of the battery, and further causes poor appearance of the battery and loss of energy density.
Disclosure of Invention
In view of the above-mentioned problems of the prior art, the present application provides an electrochemical device and an electronic device including the same, which allow the electrochemical device to have a flat appearance while maintaining a high amount of liquid retention, thereby reducing the loss of energy density while improving the cycle life of the electrochemical device.
In a first aspect, the present application provides an electrochemical device, including an electrode sheet, where the electrode sheet includes a current collector, the current collector includes a first region and a second region, an active material layer is disposed on the first region, and a functional layer is disposed on the second region, where, according to a nondestructive ultrasonic intelligent diagnosis system test, ultrasonic waves with a frequency of 50MHZ are emitted to the electrochemical device along a thickness direction of the electrochemical device, so as to obtain a signal feedback distribution diagram of the electrochemical device on the ultrasonic waves, and an area ratio of a region with a signal intensity greater than or equal to 1333mV is 30% to 95% based on an area of the electrode sheet in the signal feedback distribution diagram.
The ultrasonic wave is a mechanical wave which needs to be transmitted by means of a medium, when electrolyte is not soaked between electrode materials, the ultrasonic wave can be transmitted only by means of direct contact among electrode material particles, the ultrasonic wave is reflected and refracted in a large quantity due to irregular particles, the signal intensity is seriously attenuated, and when the electrolyte can completely soak the electrode materials, a good transmission way is provided for the ultrasonic wave by the liquid environment, and a considerable part of the ultrasonic wave is not interfered by the particles, so that the signal intensity is ensured. Therefore, in the nondestructive ultrasonic intelligent diagnosis system test, the signal feedback intensity and the duty ratio of the electrochemical device to the ultrasonic wave are all the more, the infiltration and the distribution condition of the electrolyte in the electrochemical device can be well represented, and the higher the area duty ratio of the high signal intensity is, the more sufficient and the more uniform the electrolyte is distributed in the electrochemical device.
According to some embodiments of the application, the area ratio of the region having a signal strength greater than or equal to 1333mV is 50% to 95%. At this time, the electrolyte is more fully infiltrated in the electrochemical device, and the liquid retention amount of the electrochemical device is correspondingly further improved, so that the cycle life of the electrochemical device is prolonged.
According to some embodiments of the application, the area ratio of the area with signal intensity less than or equal to 1000 is less than or equal to 10% based on the area of the electrode pad in the signal feedback profile. At this time, the area inside the electrochemical device which is not sufficiently wetted by the electrolyte is less, thereby improving the cycle life of the electrochemical device.
According to some embodiments of the application, the functional layer is capable of absorbing an electrolyte. The inventor of the present application has found that by coating a functional layer capable of absorbing an electrolyte on a current collector region of a pole piece, which is not coated with an active material layer, it is possible to improve the liquid retention amount of an electrochemical device, and at the same time, to prevent the surface roughness of the electrochemical device due to uneven free of the surplus electrolyte inside a packaging bag (e.g., an aluminum plastic film), thereby improving the external flatness of the electrochemical device and reducing the energy density loss thereof. In some embodiments, the functional layer has a swelling degree of 200% to 800%. The swelling degree of the functional layer is in the above range, on the one hand, more electrolyte can be absorbed, thereby improving the liquid retention amount of the electrochemical device and the cycle life of the electrochemical device; on the other hand, it is possible to reduce excessive swelling of the functional layer, thereby improving the energy density of the electrochemical device. In some embodiments, the functional layer has a swelling degree of 300% to 600%.
According to some embodiments of the application, the functional layer is at 2700cm using a Fourier infrared test -1 To 3100cm -1 、1600cm -1 To 1800cm -1 Or 1100cm -1 To 1200cm -1 Has an absorption peak in at least one range of the above. In this case, the functional layer has a hydrocarbon group, an ester group, or the like, and can provide good swelling properties, thereby improving the liquid retention amount of the electrochemical device.
According to some embodiments of the application, the functional layer comprises a polymer.
According to some embodiments of the application, the mass percentage of the polymer is greater than or equal to 50% based on the mass of the functional layer. The mass percentage of the polymer in the functional layer is within the above range, so that the swelling degree of the functional layer can be improved, the liquid retention amount of the electrochemical device can be further improved, and the cycle life of the electrochemical device can be prolonged.
According to some embodiments of the application, the polymer comprises a polymer formed from at least one of an acrylic monomer, a styrenic monomer.
According to some embodiments of the application, the functional layer has a thickness of 1 μm to 20 μm. At this time, the functional layer can have a high electrolyte retention rate, thereby improving the external appearance of the electrochemical device and increasing the energy density of the electrochemical device.
According to some embodiments of the application, the electrolyte retention of the functional layer is 60% to 120%. At this time, the functional layer has higher electrolyte retention rate, which is beneficial to improving the later-period circulation stability of the electrochemical device.
According to some embodiments of the application, the adhesion between the functional layer and the current collector is 100N/m to 600N/m. At this time, the functional layer is not easily detached after absorbing the electrolyte, and can stably store the surplus electrolyte, thereby improving the cycle stability of the electrochemical device.
According to some embodiments of the application, the flatness of the electrochemical device is 0 to 0.5mm.
In a second aspect, the present application provides an electronic device comprising the electrochemical device of the first aspect.
According to the application, the functional layer capable of absorbing electrolyte is coated on the current collector area of the electrode plate, which is not coated with the active material layer, so that the liquid retention amount of the electrochemical device is improved, and meanwhile, uneven surface of the electrochemical device caused by uneven free electrolyte in a packaging bag (such as an aluminum plastic film) is prevented, and further, the appearance flatness of the electrochemical device is improved, and the energy density loss of the electrochemical device is reduced.
Drawings
FIG. 1 is a schematic view of an electrode tab in an electrochemical device according to some embodiments of the application, wherein 1-current collector; 2-an active material layer; 3-functional layer.
FIG. 2 is a graph showing the signal feedback distribution of the electrochemical devices of comparative example 2 and examples 1 to 8 to ultrasonic waves, the left graph of comparative example 2, and the right graph of examples 1 to 8, when tested using a non-destructive ultrasonic intelligent diagnostic system.
Detailed Description
The application is further described below in conjunction with the detailed description. It should be understood that the detailed description is intended by way of illustration only and is not intended to limit the scope of the application.
1. Electrochemical device
The application provides an electrochemical device, which comprises an electrode pole piece, wherein the electrode pole piece comprises a current collector, the current collector comprises a first area and a second area, an active material layer is arranged on the first area, and a functional layer is arranged on the second area, wherein the nondestructive ultrasonic intelligent diagnosis system is adopted to test, ultrasonic waves with the frequency of 50MHz are transmitted to the electrochemical device along the thickness direction of the electrochemical device, a signal feedback distribution diagram of the electrochemical device on the ultrasonic waves is obtained, and the area ratio of the area with the signal intensity larger than or equal to 1333mV is 30-95% based on the area of the electrode pole piece in the signal feedback distribution diagram.
The ultrasonic wave is a mechanical wave which needs to be transmitted by means of a medium, when electrolyte is not soaked between electrode materials, the ultrasonic wave can be transmitted only by means of direct contact among electrode material particles, the ultrasonic wave is reflected and refracted in a large quantity due to irregular particles, the signal intensity is seriously attenuated, and when the electrolyte can completely soak the electrode materials, a good transmission way is provided for the ultrasonic wave by the liquid environment, and a considerable part of the ultrasonic wave is not interfered by the particles, so that the signal intensity is ensured. Therefore, in the nondestructive ultrasonic intelligent diagnosis system test, the signal feedback intensity and the duty ratio of the electrochemical device to the ultrasonic wave are all the more, the infiltration and the distribution condition of the electrolyte in the electrochemical device can be well represented, and the higher the area duty ratio of the high signal intensity is, the more sufficient and the more uniform the electrolyte is distributed in the electrochemical device.
According to some embodiments of the application, the area ratio of the region having a signal strength greater than or equal to 1333mV is 35%, 38%, 40%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, 67%, 70%, 73%, 75%, 77%, 80%, 83%, 85%, 87%, 90%, 92%, 94% or a range consisting of any two of these values. In some embodiments, the area ratio of the region having a signal strength greater than or equal to 1333mV is 50% to 95%. At this time, the electrolyte is more fully infiltrated in the electrochemical device, and the liquid retention amount of the electrochemical device is further improved, so that the cycle life of the electrochemical device is prolonged.
The "second region" in the present application may refer to a blank region on which the active material layer is not disposed on the current collector.
According to some embodiments of the application, the area ratio of the area with signal intensity less than or equal to 1000 is less than or equal to 10% based on the area of the electrode pad in the signal feedback profile. At this time, the area inside the electrochemical device which is not sufficiently wetted by the electrolyte is less, thereby improving the cycle life of the electrochemical device. In some embodiments, the area ratio of the region having a number strength of less than or equal to 1000 is 5%, 6%, 7%, 8%, 9% or a range of any two of these values.
According to some embodiments of the application, the functional layer is capable of absorbing an electrolyte. The inventor of the present application has found that by coating a functional layer capable of absorbing an electrolyte on a current collector region of a pole piece, which is not coated with an active material layer, it is possible to improve the liquid retention amount of an electrochemical device, and at the same time, to prevent the surface roughness of the electrochemical device due to uneven free of the surplus electrolyte inside a packaging bag (e.g., an aluminum plastic film), thereby improving the external flatness of the electrochemical device and reducing the energy density loss thereof.
According to some embodiments of the application, the functional layer has a swelling degree of 200% to 800%. In some embodiments, the functional layer has a swelling degree of 220%, 250%, 270%, 320%, 350%, 370%, 390%, 400%, 420%, 450%, 470%, 500%, 520%, 540%, 570%, 600%, 620%, 650%, 670%, 700%, 720%, 750%, 770%, or a range of any two of these values. The swelling degree of the functional layer is in the above range, on the one hand, more electrolyte can be absorbed, thereby improving the liquid retention amount of the electrochemical device and the cycle life of the electrochemical device; on the other hand, it is possible to reduce excessive swelling of the functional layer, thereby improving the energy density of the electrochemical device. In some embodiments, the functional layer has a swelling degree of 300% to 600%.
According to some embodiments of the application, the functional layer is at 2700cm using a Fourier infrared test -1 To 3100cm -1 、1600cm -1 To 1800cm -1 Or 1100cm -1 To 1200cm -1 Has an absorption peak in at least one range of the above.
In the application, in the Fourier infrared test spectrogram, at 2700cm -1 To 3100cm -1 、1600cm -1 To 1800cm -1 And 1100cm -1 To 1200cm -1 Absorption peaks in the range represent vibrations of hydrocarbon groups, ester groups, and the like. The functional layer contains hydrocarbon groups and ester groups, so that good swelling property can be provided, more electrolyte can be absorbed by the high swelling property, and the liquid retention rate is improved.
According to some embodiments of the application, the functional layer comprises a polymer.
According to some embodiments of the application, the mass percentage of the polymer is greater than or equal to 50% based on the mass of the functional layer. In some embodiments, the mass percent of the polymer is 50%, 60%, 70%, 80%, 90%, 100% or a range of any two of these values based on the mass of the functional layer. The mass percentage of the polymer in the functional layer is within the above range, so that the swelling degree of the functional layer can be improved, the liquid retention amount of the electrochemical device can be further improved, and the cycle life of the electrochemical device can be prolonged.
According to some embodiments of the application, the polymer comprises a polymer formed from at least one of an acrylic monomer, a styrenic monomer.
In some embodiments, the acrylic monomer comprises at least one of the compounds of formula I,
wherein R is 1 Selected from hydrogen or C 1 -C 10 Alkyl, halogen substituted C 1 -C 10 An alkyl group. According to some embodiments of the application, R 1 Selected from C 1 -C 6 Alkyl, halogen substituted C 1 -C 6 An alkyl group. In some embodiments of the application, R 1 Selected from methyl, ethyl, fluoroethyl, propyl, fluoropropyl, butyl, fluorobutyl, pentyl or fluoropentyl.
In some embodiments, the acrylic monomer includes at least one of acrylic acid, methacrylic acid, ethacrylic acid.
In some embodiments, the acrylate monomer comprises at least one of the compounds of formula II,
wherein R is 2 Selected from hydrogen, C 1 -C 10 Alkyl-or halogen-substituted C 1 -C 10 An alkyl group; r is R 3 Selected from C 1 -C 10 Alkyl, halogen substitutedC 1 -C 10 An alkyl group. According to some embodiments of the application, R 2 Selected from hydrogen, C 1 -C 6 Alkyl-or halogen-substituted C 1 -C 6 An alkyl group; r is R 3 Selected from C 1 -C 6 Alkyl, halogen substituted C 1 -C 6 An alkyl group. In some embodiments of the application, R 2 Selected from hydrogen, methyl, ethyl or propyl; r is R 3 Selected from methyl, ethyl, fluoroethyl, propyl, fluoropropyl, butyl, fluorobutyl, pentyl or fluoropentyl.
In some embodiments, the acrylic monomer includes at least one of methyl acrylate, methyl methacrylate, methyl ethacrylate, ethyl acrylate, ethyl methacrylate, ethyl ethacrylate, propyl acrylate, propyl methacrylate, propyl ethacrylate, butyl acrylate, butyl methacrylate, butyl ethacrylate, pentyl methacrylate, or pentyl acrylate.
According to some embodiments of the application, the styrenic monomer comprises at least one of the compounds of formula III,
wherein n is an integer from 1 to 5, such as 2, 3 or 4; each R 4 The same or different are independently selected from hydrogen, C 1 -C 10 Alkyl-or halogen-substituted C 1 -C 10 An alkyl group; r is R 5 And R is 6 The same or different are independently selected from hydrogen, C 1 -C 10 Alkyl-or halogen-substituted C 1 -C 10 An alkyl group. According to some embodiments of the application, R 4 Selected from hydrogen, C 1 -C 6 Alkyl-or halogen-substituted C 1 -C 6 An alkyl group; r is R 5 And R is 6 The same or different, independently selected C 1 -C 16 Alkyl-or halogen-substituted C 1 -C 6 An alkyl group. In some embodiments of the application, R 4 、R 5 And R is 6 Independently selected from hydrogen, methyl, ethylOr propyl.
In some embodiments, the styrenic monomer comprises at least one of styrene, methyl styrene, 2-methyl styrene, 2, 4-dimethyl styrene.
According to some embodiments of the application, the functional layer-forming raw material comprises at least one of a pure acrylic emulsion, a styrene acrylic emulsion, or an acrylate emulsion. In some embodiments, the starting material for the functional layer comprises at least one of a pure acrylic emulsion, a styrene acrylic emulsion, or an acrylate emulsion.
According to some embodiments of the application, the starting materials for the functional layer include pure acrylic emulsion, styrene acrylic emulsion, and acrylate emulsion. In some embodiments, the mass content of the pure acrylic emulsion is 40% to 95%, the mass content of the styrene acrylic emulsion is 5% to 50%, and the mass content of the acrylate emulsion is 1% to 15% based on the total mass of the pure acrylic emulsion, the styrene acrylic emulsion, and the acrylate emulsion.
According to some embodiments of the application, the starting materials for the functional layer include pure acrylic emulsion and acrylate emulsion. In some embodiments, the mass content of the pure acrylic emulsion is from 70% to 95% and the mass content of the acrylate emulsion is from 5% to 30% based on the total mass of the pure acrylic emulsion and the acrylate emulsion.
According to some embodiments of the application, the starting materials for the functional layer include pure acrylic emulsion and styrene acrylic emulsion. In some embodiments, the mass content of the pure acrylic emulsion is 70% to 95% and the mass content of the styrene acrylic emulsion is 5% to 30% based on the total mass of the pure acrylic emulsion and the styrene acrylic emulsion.
According to some embodiments of the application, the starting materials for the functional layer include styrene-acrylic emulsion and acrylate emulsion. In some embodiments, the mass content of the styrene-acrylic emulsion is 70% to 95% and the mass content of the acrylate emulsion is 5% to 30% based on the total mass of the styrene-acrylic emulsion and the acrylate emulsion.
According to some embodiments of the application, the functional layer has a thickness of 1 μm to 20 μm. At this time, the functional layer can have a high electrolyte retention rate, thereby improving the external appearance of the electrochemical device and increasing the energy density of the electrochemical device. In some embodiments, the functional layer has a thickness of 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 18 μm, 19 μm, or a range of any two of these values. In some embodiments, the functional layer has a thickness of 5 μm to 15 μm.
According to some embodiments of the application, the electrolyte retention of the functional layer is 60% to 120%. In some embodiments, the functional layer has an electrolyte retention of 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or a range of any two of these values. At this time, the functional layer has higher electrolyte retention rate, which is beneficial to improving the later-period circulation stability of the electrochemical device.
According to some embodiments of the application, the adhesion between the functional layer and the current collector is 100N/m to 600N/m. At this time, the functional layer is not easily detached after absorbing the electrolyte, and can stably store the surplus electrolyte, thereby improving the cycle stability of the electrochemical device.
According to some embodiments of the application, the flatness of the electrochemical device is 0 to 0.5mm.
According to some embodiments of the application, the active material layer is a positive electrode active material layer and/or a negative electrode active material layer.
According to some embodiments of the present application, the positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent. In some embodiments, the positive electrode active material may include at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, or lithium nickel manganate. In some embodiments, the binder may include various binder polymers, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified styrene-butadiene rubber, or polyurethane. In some embodiments, any conductive material may be used as the conductive agent as long as it does not cause a chemical change. Examples of the conductive agent include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and the like; metal-based materials such as metal powders or metal fibers including copper, nickel, aluminum, silver, and the like; conductive polymers such as polyphenylene derivatives and the like; or mixtures thereof.
According to some embodiments of the application, the negative electrode active material layer includes a negative electrode active material and a binder, and optionally a conductive agent. In some embodiments, the anode active material may include a material that reversibly intercalates/deintercalates lithium ions, lithium metal alloy, or transition metal oxide. In some embodiments, the negative electrode active material includes at least one of a carbon material including at least one of graphite, hard carbon, or a silicon material including at least one of silicon, a silicon oxygen compound, a silicon carbon compound, or a silicon alloy. In some embodiments, the binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamideimide, polyvinylidene fluoride, polytetrafluoroethylene, aqueous acrylic resin, polyvinyl formal, or styrene-acrylic copolymer resin. In some embodiments, any conductive material may be used as the conductive material as long as it does not cause chemical changes. In some embodiments, the conductive material comprises at least one of conductive carbon black, acetylene black, carbon nanotubes, ketjen black, or graphene.
According to some embodiments of the application, the current collector is a positive current collector and/or a negative current collector. In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, or the like) on a polymer substrate. In some embodiments, the negative electrode current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.
The electrochemical device of the present application further includes a separator, and the material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application. For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
The surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer includes inorganic particles and a binder, the inorganic particles being at least one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is at least one selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The polymer layer contains a polymer, and the material of the polymer is at least one selected from polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
The electrochemical device of the present application further includes an electrolyte. The electrolyte that can be used in the present application may be an electrolyte known in the art.
In some embodiments, the electrolyte includes an organic solvent, a lithium salt, and optional additives. The organic solvent of the electrolyte according to the present application may be any organic solvent known in the art as a solvent of the electrolyte. Electrolysis used in the electrolyte according to the applicationThe electrolyte is not limited and may be any electrolyte known in the art. The additive of the electrolyte according to the present application may be any additive known in the art as an electrolyte additive. In some embodiments, the organic solvent includes, but is not limited to: ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate. In some embodiments, the organic solvent comprises an ether-type solvent, for example, comprising at least one of 1, 3-Dioxapentacyclic (DOL) and ethylene glycol dimethyl ether (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, lithium salts include, but are not limited to: lithium hexafluorophosphate (LiPF) 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorophosphate (LiPO) 2 F 2 ) Lithium bis (trifluoromethanesulfonyl) imide LiN (CF) 3 SO 2 ) 2 (LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO) 2 F) 2 ) (LiLSI), lithium bisoxalato borate LiB (C) 2 O 4 ) 2 (LiBOB) or lithium difluorooxalato borate LiBF 2 (C 2 O 4 )(LiDFOB)。
In some embodiments, the electrochemical device of the present application includes, but is not limited to: primary or secondary batteries of all kinds. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the secondary battery includes a lithium secondary battery, a sodium ion battery, and the like; lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.
2. Electronic device
The present application further provides an electronic device comprising an electrochemical device according to the first aspect of the application.
The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini-compact discs, transceivers, electronic notepads, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, gaming machines, watches, power tools, flashlights, cameras, home-use large storage batteries, lithium ion capacitors, and the like.
In the following examples and comparative examples, reagents, materials and instruments used, unless otherwise specified, were commercially available.
Examples and comparative examples
Preparing functional layer slurry: the binders (specific compositions are shown in table 1 and table 2) and the solvents were mixed uniformly to prepare a slurry, which was controlled: viscosity of 200-3000 mPa.s and solid content of 35% -50%. Wherein deionized water is selected as the solvent in the embodiment; n-methylpyrrolidone was used as the solvent in comparative example 1.
Preparing a positive electrode plate: and coating the prepared functional layer slurry on the winding end region of the aluminum foil of the positive current collector, and drying the solvent to obtain the pole piece coated with the functional layer. And coating positive electrode active material slurry on the area without the functional layer, and drying and rolling to obtain the positive electrode plate. Wherein the positive electrode active material slurry is: mixing lithium cobaltate, conductive carbon and polyvinylidene fluoride according to a mass ratio of 96:2:2, and adding N-methyl pyrrolidone (NMP) to prepare slurry.
Preparing a negative electrode plate: and coating the anode active material slurry on the surface of an anode current collector copper foil, and drying and rolling to obtain the anode piece. Wherein, the negative electrode active material slurry is: graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed according to the mass ratio of 98:1:1, and deionized water is added to prepare slurry.
Preparation of a lithium ion battery: sequentially stacking the positive electrode plate, the isolating film (PE porous polymer film) and the negative electrode plate, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, and then winding to obtain an electrode assembly; placing the electrode assembly in an outer packaging aluminum plastic film, and injecting electrolyte(the solvent is EC and DMC in a volume ratio of 1:1, based on the mass of the electrolyte, liPF) 6 The mass concentration of the solution is 12.5 percent), and the preparation of the lithium ion battery is completed through the procedures of vacuum packaging, standing, formation, shaping and the like.
Test method
1. Ultrasonic detection
And using nondestructive ultrasonic intelligent diagnosis equipment (model: UBSC-LD), transmitting ultrasonic waves to the lithium ion battery along the thickness direction of the lithium ion battery, wherein the frequency is 50MHz, and the voltage range of an output interface is selected to be 0-4 v, so as to obtain a signal feedback distribution diagram of the ultrasonic waves at all positions of the battery. And calculating the total area of the electrode plate test in the signal feedback distribution diagram to be S by using integration software, wherein the area of the area with the signal intensity of more than or equal to 1333mV is S1, and the ratio of the area with the signal intensity of more than or equal to 1333mV is: S1/S×100%.
2. Cohesive force
The binding force between the functional layer and the current collector is tested by adopting a high-speed rail tension machine and a 90-degree angle method, namely: making a part of pole piece coated with a functional layer in the lithium ion battery into a strip shape, and adhering a part of the pole piece to a steel plate through double-sided adhesive tape from one end of the pole piece along the length direction; and then fixing the steel plate at the corresponding position of the high-speed rail tensile machine, pulling up the pole piece which is not adhered to the steel plate, putting the pole piece into a chuck through a connector or directly clamping, and starting to test by the high-speed rail tensile machine when the tension of the clamping opening is more than 0kgf and less than 0.02kgf, wherein the average value of the tension in the stable region is finally measured and recorded as the adhesion force between the functional layer and the current collector.
3. Electrolyte retention rate
a) And (3) removing the pole piece coated with the functional layer from the lithium ion battery in the environment of (25+/-3) DEG C. If the other side of the current collector coated with the functional layer is provided with other coatings, the other side needs to be removed by a physical or chemical method, but the functional layer cannot be damaged. Then cutting the current collector coated with the functional layer by a cutting machine;
b) Respectively weighing the current collectors (including current collectors) which are cut and coated with the functional layers by using an electronic day for at least 3 times, and respectively marking the current collectors as m1; m2; m3 … …, the average value m is obtained;
c) Putting the weighed current collector (comprising the current collector) coated with the functional layer into an oven at 85 ℃, baking for 30-60 min to ensure that the electrolyte in the functional layer is completely baked, and then weighing the dried current collector coated with the functional layer for at least 3 times respectively, wherein the weight of the current collector is respectively recorded as M1; m2; m3 … …, taking an average value M;
d) Removing the functional layer by a physical or chemical method, but not damaging the corresponding current collector, weighing the weight of the corresponding current collector for at least 3 times, and respectively marking as G1; g2; g3 … …, taking the average G;
e) The electrolyte retention rate of the functional layer is recorded as follows: r= (M-M)/(M-G) ×100%.
4. Swelling degree
a) And (3) preparation of an adhesive film: and (3) removing the pole piece coated with the functional layer from the lithium ion battery in the environment of (25+/-3) DEG C. If the other side of the current collector coated with the functional layer is provided with other coatings, the other side needs to be removed by a physical or chemical method, but the functional layer cannot be damaged. Then cutting the current collector coated with the functional layer by a cutting machine, putting into dimethyl carbonate DMC to soak and remove electrolyte dissolved in the functional layer, taking out and drying the current collector, putting into water to dissolve the functional layer to form a solution, pouring the solution into a glue film preparation mould, and lifting and removing if bubbles exist; placing the die in a 60 ℃ oven for 12 hours, and observing the appearance and hardness of the adhesive film after baking; if not completely drying, continuing baking until drying;
b) Cutting the prepared adhesive film into small strips by scissors;
c) Weighing the small strips of the adhesive film, and recording the initial weight a; placing into a small bottle, adding electrolyte (EC and DMC with volume ratio of solvent being 1:1, based on electrolyte mass, liPF 6 12.5% by mass) exceeds 2-3 cm of the adhesive film, sealing the vial, and placing the vial into a vacuum drying furnace at 85 ℃ for 6 hours;
d) Testing the swelling degree of the adhesive film: taking out the adhesive film, wiping the adhesive film with dust-free paper, and recording the weight b of the adhesive film at the moment.
Swelling degree= (b-a)/a×100%. And 3 parallel samples are made, and the swelling degree of the functional layer is obtained by carrying out arithmetic average on the obtained swelling degree.
5. Thickness of functional layer
a) And (3) removing the pole piece coated with the functional layer from the lithium ion battery in the environment of (25+/-3) DEG C. If the other side of the current collector coated with the functional layer is provided with other coatings, the other side needs to be removed by a physical or chemical method, but the functional layer cannot be damaged;
b) Putting the pole piece (comprising the current collector) coated with the functional layer into an oven at 85 ℃, baking for 30 to 60 minutes, ensuring that electrolyte in the functional layer is completely baked, measuring the thickness of at least 10 different points of the pole piece (comprising the current collector) coated with the functional layer after baking by using a ten-thousandth ruler, and recording the thickness average value of all the test points as T1;
c) Removing the functional layer by a physical or chemical method, but not damaging the corresponding current collector, measuring the thickness of at least 10 different points of the current collector coated with the functional layer by using a ten-thousandth ruler, and recording the thickness average value of all the test points as T0;
d) The thickness of the functional layer is as follows: (T1-T0).
6. Flatness of
And testing the flatness of the lithium ion battery by adopting a laser scanning method. Specifically, the whole contour of the lithium ion battery is scanned by utilizing optical equipment to manufacture a 3D model, then the difference value between the whole thickness value and the thickness value of the section is calculated and is recorded as P, and if P is less than or equal to 0.5mm, the flatness OK of the lithium ion battery meets the requirements; if P is more than 0.5mm, the flatness NG is not satisfactory.
Test results
TABLE 1
Note that: the percentage content of each component in the raw material composition of the functional layer is mass fraction content.
As can be seen from the data in Table 1, the composition and swelling degree of the functional layer affect the electrolyte retention rate and thus the area ratio of 1333mV or more. With the increase of the swelling degree of the functional layer, the electrolyte retention rate is increased, and the area ratio of more than or equal to 1333mV is also increased. The area with the area more than or equal to 1333mV has a large proportion, so that the electrolyte is fully soaked in the lithium ion battery and distributed uniformly, and the lithium ion battery can have higher liquid retention rate and good flatness, thereby prolonging the cycle life of the lithium ion battery and reducing the loss of energy density.
In addition, as can be seen from the comparative example, the functional layer directly affects the electrolyte retention rate and the area ratio of more than or equal to 1333mV, the swelling degree of the nonfunctional layer or the functional layer is low, the electrolyte retention rate is low, and the flatness of the lithium ion battery is poor.
TABLE 2
Note that: the percentage content of each component in the composition of the functional layer is mass fraction content.
As can be seen from the data in Table 2, the thickness of the functional layer affects electrolyte retention and the area ratio of 1333mV or more. Within a certain range, as the thickness increases, the electrolyte retention rate and the area ratio of more than or equal to 1333mV also increase.
Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application, and that changes, substitutions and alterations may be made therein without departing from the spirit, principles and scope of the application.

Claims (10)

1. An electrochemical device comprises an electrode plate, wherein the electrode plate comprises a current collector, the current collector comprises a first area and a second area, an active material layer is arranged on the first area, a functional layer is arranged on the second area,
and the nondestructive ultrasonic intelligent diagnosis system is adopted for testing, ultrasonic waves with the frequency of 50MHz are transmitted to the electrochemical device along the thickness direction of the electrochemical device, a signal feedback distribution diagram of the electrochemical device on the ultrasonic waves is obtained, and the area ratio of the area with the signal intensity of more than or equal to 1333mV is 30-95% based on the area of the electrode plate in the signal feedback distribution diagram.
2. The electrochemical device of claim 1, wherein the area ratio of the region having the signal strength greater than or equal to 1333mV is 50% to 95%.
3. The electrochemical device of claim 1, wherein an area ratio of the area where the signal intensity is less than or equal to 1000 is 5% to 10% based on the area of the electrode pad in the signal feedback profile.
4. The electrochemical device according to claim 1, wherein the functional layer has a swelling degree of 200% to 800%.
5. The electrochemical device according to claim 1, wherein the functional layer has a swelling degree of 300% to 600%.
6. The electrochemical device of claim 1, wherein the functional layer is at 2700cm using fourier infrared testing -1 To 3100cm -1 、1600cm -1 To 1800cm -1 Or 1100cm -1 To 1200cm -1 Has an absorption peak in at least one range of the above.
7. The electrochemical device of claim 1, wherein the functional layer comprises a polymer that satisfies at least one of the following conditions (1) to (2):
(1) The mass percent of the polymer is greater than or equal to 50% based on the mass of the functional layer;
(2) The polymer includes a polymer formed from at least one of an acrylic monomer, and a styrene monomer.
8. The electrochemical device according to claim 1, wherein the functional layer has a thickness of 1 μm to 20 μm.
9. The electrochemical device according to claim 1, wherein the electrochemical device satisfies at least one of the following conditions (a) to (c):
(a) The electrolyte retention rate of the functional layer is 60 to 120 percent;
(b) The binding force between the functional layer and the current collector is 100N/m to 600N/m;
(c) The flatness of the electrochemical device is 0 to 0.5mm.
10. An electronic device comprising the electrochemical device of any one of claims 1 to 9.
CN202280010323.1A 2022-03-31 2022-03-31 Electrochemical device and electronic device Pending CN116848651A (en)

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