WO2023184366A1 - Electrochemical device and electronic device - Google Patents

Abstract

Provided is an electrochemical device, comprising an electrode sheet. The electrode sheet comprises a current collector; the current collector comprises a first region and a second region; an active material layer is provided on the first region; and a functional layer is provided on the second region. A non-destructive ultrasonic intelligent diagnosis system is used for testing. Ultrasonic waves are transmitted to the electrochemical device in a thickness direction of the electrochemical device, and a signal feedback distribution map of the electrochemical device for the ultrasonic waves is obtained. On the basis of the area of the electrode sheet in the signal feedback distribution map, the area proportion of a region having a signal strength of greater than or equal to 1333 mV is 30% to 95%. The electrochemical device of the present application has a high liquid retention amount and a flat appearance. Also provided is an electronic device comprising the electrochemical device.

Description

Electrochemical devices and electronic devices Technical field

The present application relates to the field of batteries, and specifically to an electrochemical device and an electronic device.

Background technique

Secondary batteries such as lithium-ion batteries are widely used in portable electronic products, electric vehicles, energy storage and other fields due to their high energy density, good cycle performance, environmental protection, safety and no memory effect. However, with the development of technology, people have higher and higher requirements for battery energy density and cycle life. On the one hand, electrolyte plays an important role in the cycle life of lithium-ion batteries. In order to ensure the long cycle life of the battery, excess electrolyte needs to be injected inside the battery to make up for the consumption of electrolyte during the cycle. But on the other hand, the excess electrolyte is easily dissociated unevenly inside the packaging bag (such as aluminum-plastic film), causing the battery surface to be uneven, which in turn leads to poor battery appearance and loss of energy density.

Contents of the invention

In view of the above problems existing in the prior art, the present application provides an electrochemical device and an electronic device including the electrochemical device, so that the electrochemical device has a smooth appearance while maintaining a high liquid retention capacity, thereby improving the cycle of the electrochemical device. life while reducing the loss of energy density.

In a first aspect, the present application provides an electrochemical device, which includes an electrode piece, the electrode piece 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 the current collector includes a first region and a second region. There is a functional layer on the second area. Among them, the non-destructive ultrasonic intelligent diagnosis system is used for testing. Ultrasonic waves with a frequency of 50MHZ are emitted to the electrochemical device along the thickness direction of the electrochemical device to obtain the signal feedback distribution map of the ultrasonic wave from the electrochemical device. Based on the area of the electrode pole in the signal feedback distribution diagram, the area of the area where the signal intensity is greater than or equal to 1333mV accounts for 30% to 95%.

Ultrasonic waves are mechanical waves that rely on media to propagate. When there is no electrolyte infiltration between electrode materials, ultrasonic waves can only propagate by relying on direct contact between electrode material particles. Irregular particles cause a large amount of reflection and refraction of ultrasonic waves. The signal intensity is severely attenuated, and when the electrolyte can completely infiltrate the electrode material, the liquid environment provides a good propagation path for ultrasonic waves, and a considerable part of the ultrasonic waves will not be interfered by particles, thus ensuring the signal strength. Therefore, during the test of the non-destructive ultrasonic intelligent diagnosis system, the intensity and proportion of the ultrasonic signal feedback from various parts of the electrochemical device can well characterize the infiltration and distribution of the electrolyte inside the electrochemical device. The higher the proportion of areas with high signal intensity, the more High, the electrolyte is more fully infiltrated and distributed inside the electrochemical device.

According to some embodiments of the present application, the area ratio of the area where the signal intensity is greater than or equal to 1333mV is 50% to 95%. At this time, the electrolyte is more fully infiltrated inside the electrochemical device, and the liquid retention capacity of the electrochemical device is further increased accordingly, thereby increasing the cycle life of the electrochemical device.

According to some embodiments of the present application, based on the area of the electrode pole piece in the signal feedback distribution diagram, the area proportion of the area where the signal intensity is less than or equal to 1000 is less than or equal to 10%. At this time, there are fewer areas inside the electrochemical device that are not fully infiltrated by the electrolyte, thereby increasing the cycle life of the electrochemical device.

According to some embodiments of the present application, the functional layer is capable of absorbing electrolyte. The inventor of the present application has discovered through research that by coating a functional layer capable of absorbing electrolyte on the current collector area of the pole piece that is not coated with an active material layer, it is possible to increase the liquid retention capacity of the electrochemical device and at the same time prevent the excess electrolyte from being Uneven dissociation inside the packaging bag (such as aluminum-plastic film) causes the surface of the electrochemical device to be uneven, thereby improving the smoothness of the appearance of the electrochemical device and reducing its energy density loss. In some embodiments, the functional layer has a swelling degree of 200% to 800%. The swelling degree of the functional layer is within the above range. On the one hand, it can absorb more electrolyte, thereby increasing the liquid retention capacity of the electrochemical device and improving the cycle life of the electrochemical device; on the other hand, it can reduce excessive swelling of the functional layer. , thereby increasing the energy density of electrochemical devices. In some embodiments, the functional layer has a swelling degree of 300% to 600%.

According to some embodiments of the present application, using Fourier transform infrared testing, the functional layer has an absorption peak in at least one range from 2700cm ^-1 to 3100cm ^-1 , 1600cm ^-1 to 1800cm ^-1 or 1100cm ^-1 to 1200cm ^-1 . At this time, the functional layer has groups such as hydrocarbon groups and ester groups, which can provide good swelling properties and thereby increase the liquid retention capacity of the electrochemical device.

According to some embodiments of the present application, the functional layer includes a polymer.

According to some embodiments of the present application, based on the mass of the functional layer, the mass percentage of the polymer is greater than or equal to 50%. When the mass percentage of the polymer in the functional layer is within the above range, the swelling degree of the functional layer can be increased, thereby increasing the liquid retention capacity of the electrochemical device and improving the cycle life of the electrochemical device.

According to some embodiments of the present application, the polymer includes a polymer formed from at least one of acrylic monomers, acrylate monomers, and styrenic monomers.

According to some embodiments of the present application, the thickness of the functional layer is 1 μm to 20 μm. At this time, the functional layer can have a higher electrolyte retention rate, thereby improving the appearance of the electrochemical device and increasing the energy density of the electrochemical device.

According to some embodiments of the present application, the electrolyte retention rate of the functional layer is 60% to 120%. At this time, the functional layer has a higher electrolyte retention rate, which is beneficial to improving the cycle stability of the electrochemical device in the later period.

According to some embodiments of the present application, the bonding force between the functional layer and the current collector is 100 N/m to 600 N/m. At this time, the functional layer is not easy to fall off after absorbing the electrolyte, and can stably store excess electrolyte, thereby improving the cycle stability of the electrochemical device.

According to some embodiments of the present application, the flatness of the electrochemical device is 0 to 0.5 mm.

In a second aspect, the present application provides an electronic device including the electrochemical device of the first aspect.

By coating a functional layer capable of absorbing electrolyte on the current collector area of the pole piece that is not coated with an active material layer, this application can improve the liquid retention capacity of the electrochemical device while preventing excess electrolyte from unevenly dissociating in the packaging. The inside of the bag (such as aluminum-plastic film) causes the surface of the electrochemical device to be uneven, thereby improving the smoothness of the appearance of the electrochemical device and reducing its energy density loss.

Description of drawings

Figure 1 is a schematic diagram of an electrode plate in an electrochemical device according to some embodiments of the present application, where 1—current collector; 2—active material layer; 3—functional layer.

Figure 2 is a distribution diagram of the ultrasonic signal feedback distribution of the electrochemical devices of Comparative Example 2 and Embodiments 1-8 when tested using a non-destructive ultrasonic intelligent diagnosis system. The left picture is Comparative Example 2 and the right picture is Embodiments 1-8.

Detailed ways

The present application will be further elaborated below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

1. Electrochemical device

The present application provides an electrochemical device, which includes an electrode piece. The electrode piece includes a current collector. The current collector includes a first region and a second region. An active material layer is provided on the first region, and an active material layer is provided on the second region. There is a functional layer. Among them, a non-destructive ultrasonic intelligent diagnostic system is used to test. Ultrasonic waves with a frequency of 50MHZ are emitted to the electrochemical device along the thickness direction of the electrochemical device. The signal feedback distribution map of the ultrasonic wave from the electrochemical device is obtained. Based on the signal feedback distribution The area of the electrode plate in the figure, the area proportion of the area where the signal intensity is greater than or equal to 1333mV is 30% to 95%.

Ultrasonic waves are mechanical waves that rely on media to propagate. When there is no electrolyte infiltration between electrode materials, ultrasonic waves can only propagate by relying on direct contact between electrode material particles. Irregular particles cause a large amount of reflection and refraction of ultrasonic waves. The signal intensity is severely attenuated, and when the electrolyte can completely infiltrate the electrode material, the liquid environment provides a good propagation path for ultrasonic waves, and a considerable part of the ultrasonic waves will not be interfered by particles, thus ensuring the signal strength. Therefore, during the test of the non-destructive ultrasonic intelligent diagnosis system, the intensity and proportion of the ultrasonic signal feedback from various parts of the electrochemical device can well characterize the infiltration and distribution of the electrolyte inside the electrochemical device. The higher the proportion of areas with high signal intensity, the more High, the electrolyte is more fully infiltrated and distributed inside the electrochemical device.

According to some embodiments of the present application, the area proportion of the area where the signal intensity is 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 any two of these values range. In some embodiments, the area proportion of the area where the signal intensity is greater than or equal to 1333 mV is 50% to 95%. At this time, the electrolyte is more fully infiltrated inside the electrochemical device, and the liquid retention capacity of the electrochemical device is further increased, thereby increasing the cycle life of the electrochemical device.

The “second area” in this application may refer to a blank area on the current collector where no active material layer is provided.

According to some embodiments of the present application, based on the area of the electrode pole piece in the signal feedback distribution diagram, the area proportion of the area where the signal intensity is less than or equal to 1000 is less than or equal to 10%. At this time, there are fewer areas inside the electrochemical device that are not fully infiltrated by the electrolyte, thereby increasing the cycle life of the electrochemical device. In some embodiments, the area proportion of the area with signal intensity less than or equal to 1000 is 5%, 6%, 7%, 8%, 9%, or a range consisting of any two of these values.

According to some embodiments of the present application, the functional layer is capable of absorbing electrolyte. The inventor of the present application has discovered through research that by coating a functional layer capable of absorbing electrolyte on the current collector area of the pole piece that is not coated with an active material layer, it is possible to increase the liquid retention capacity of the electrochemical device and at the same time prevent the excess electrolyte from being Uneven dissociation inside the packaging bag (such as aluminum-plastic film) causes the surface of the electrochemical device to be uneven, thereby improving the smoothness of the appearance of the electrochemical device and reducing its energy density loss.

According to some embodiments of the present application, the swelling degree of the functional layer ranges from 200% to 800%. In some embodiments, the swelling degree of the functional layer is 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 consisting of any two of these values. The swelling degree of the functional layer is within the above range. On the one hand, it can absorb more electrolyte, thereby increasing the liquid retention capacity of the electrochemical device and improving the cycle life of the electrochemical device; on the other hand, it can reduce excessive swelling of the functional layer. , thereby increasing the energy density of electrochemical devices. In some embodiments, the functional layer has a swelling degree of 300% to 600%.

According to some embodiments of the present application, using Fourier transform infrared testing, the functional layer has an absorption peak in at least one range from 2700cm ^-1 to 3100cm ^-1 , 1600cm ^-1 to 1800cm ^-1 or 1100cm ^-1 to 1200cm ^-1 .

In this application, in the Fourier transform infrared test spectrum, the absorption peaks in the range of 2700cm ^-1 to 3100cm ^-1 , 1600cm ^-1 to 1800cm ^-1 and 1100cm ^-1 to 1200cm ^-1 represent the vibration of hydrocarbon groups, ester groups, etc. . The functional layer contains hydrocarbon groups and ester groups, which can provide good swelling properties. High swelling properties can absorb more electrolyte and improve the liquid retention rate.

According to some embodiments of the present application, the functional layer includes a polymer.

According to some embodiments of the present application, based on the mass of the functional layer, the mass percentage of the polymer is greater than or equal to 50%. In some embodiments, based on the mass of the functional layer, the mass percentage of the polymer is in a range of 50%, 60%, 70%, 80%, 90%, 100%, or any two of these values. When the mass percentage of the polymer in the functional layer is within the above range, the swelling degree of the functional layer can be increased, thereby increasing the liquid retention capacity of the electrochemical device and improving the cycle life of the electrochemical device.

According to some embodiments of the present application, the polymer includes a polymer formed from at least one of acrylic monomers, acrylate monomers, and styrenic monomers.

In some embodiments, the acrylic monomer includes at least one of the compounds represented by Formula I,

Wherein, R ₁ is selected from hydrogen or C ₁ -C ₁₀ alkyl, or halogen-substituted C ₁ -C ₁₀ alkyl. According to some embodiments of the present application, R ₁ is selected from C ₁ -C ₆ alkyl, halogen-substituted C ₁ -C ₆ alkyl. In some embodiments of the present application, _R1 is selected from methyl, ethyl, fluorine-containing ethyl, propyl, fluorine-containing propyl, butyl, fluorine-containing butyl, pentyl or fluorine-containing pentyl.

In some embodiments, the acrylic monomer includes at least one of acrylic acid, methacrylic acid, and ethacrylic acid.

In some embodiments, the acrylate monomer includes at least one of the compounds represented by Formula II,

Among them, R ₂ is selected from hydrogen, C ₁ -C ₁₀ alkyl or halogen-substituted C ₁ -C ₁₀ alkyl; R ₃ is selected from C ₁ -C ₁₀ alkyl, halogen-substituted C ₁ -C ₁₀ alkyl. According to some embodiments of the present application, R ₂ is selected from hydrogen, C ₁ -C ₆ alkyl or halogen substituted C ₁ -C ₆ alkyl; R ₃ is selected from C ₁ -C ₆ alkyl, halogen substituted C ₁ -C ₆ alkyl. In some embodiments of the present application, R ₂ is selected from hydrogen, methyl, ethyl or propyl; R ₃ is selected from methyl, ethyl, fluoroethyl, propyl, fluoropropyl, butyl, Fluorine-containing butyl, pentyl or fluorine-containing pentyl.

In some embodiments, acrylate monomers include methyl acrylate, methyl methacrylate, ethyl methyl acrylate, ethyl acrylate, ethyl methacrylate, ethyl ethyl acrylate, propyl acrylate, methyl At least one of propyl acrylate, propyl ethylacrylate, butyl acrylate, butyl methacrylate, butyl ethylacrylate, amyl methacrylate or amyl acrylate.

According to some embodiments of the present application, the styrenic monomer includes at least one of the compounds represented by Formula III,

Wherein, n is an integer from 1 to 5, such as 2, 3 or 4; each R ₄ is the same or different and is independently selected from hydrogen, C ₁ -C ₁₀ alkyl or halogen-substituted C ₁ -C ₁₀ alkyl; R ₅ and R ₆ are the same or different and are independently selected from hydrogen, C ₁ -C ₁₀ alkyl, or halogen-substituted C ₁ -C ₁₀ alkyl. According to some embodiments of the application, R ₄ is selected from hydrogen, C ₁ -C ₆ alkyl or halogen-substituted C ₁ -C ₆ alkyl; R ₅ and R ₆ are the same or different, and are independently selected from C ₁ -C ₁₆ Alkyl or halogen substituted C ₁ -C ₆ alkyl. In some embodiments of the present application, R ₄ , R ₅ and R ₆ are independently selected from hydrogen, methyl, ethyl or propyl.

In some embodiments, the styrenic monomer includes at least one of styrene, methylstyrene, 2-methylstyrene, and 2,4-dimethylstyrene.

According to some embodiments of the present application, the raw material forming the functional layer includes at least one of pure acrylic emulsion, styrene acrylic emulsion or acrylic ester emulsion. In some embodiments, the raw material of the functional layer includes at least one of pure acrylic emulsion, styrene acrylic emulsion or acrylic emulsion.

According to some embodiments of the present application, the raw materials of the functional layer include pure acrylic emulsion, styrene acrylic emulsion and acrylic emulsion. In some embodiments, based on the total mass of pure acrylic emulsion, styrene acrylic emulsion and acrylate emulsion, the mass content of pure acrylic emulsion is 40% to 95%, the mass content of styrene acrylic emulsion is 5% to 50%, and the acrylate emulsion The mass content of the emulsion is 1% to 15%.

According to some embodiments of the present application, the raw materials of the functional layer include pure acrylic emulsion and acrylic ester emulsion. In some embodiments, based on the total mass of the pure acrylic emulsion and the acrylic ester emulsion, the mass content of the pure acrylic emulsion is 70% to 95%, and the mass content of the acrylic ester emulsion is 5% to 30%.

According to some embodiments of the present application, the raw materials of the functional layer include pure acrylic emulsion and styrene acrylic emulsion. In some embodiments, based on the total mass of the pure acrylic emulsion and the styrene-acrylic emulsion, 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%.

According to some embodiments of the present application, the raw materials of the functional layer include styrene acrylic emulsion and acrylate emulsion. In some embodiments, based on the total mass of the styrene-acrylic emulsion and the acrylic emulsion, the mass content of the styrene-acrylic emulsion is 70% to 95%, and the mass content of the acrylic emulsion is 5% to 30%.

According to some embodiments of the present application, the thickness of the functional layer is 1 μm to 20 μm. At this time, the functional layer can have a higher electrolyte retention rate, thereby improving the appearance of the electrochemical device and increasing the energy density of the electrochemical device. In some embodiments, the thickness of the functional layer is a range 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 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 present application, the electrolyte retention rate of the functional layer is 60% to 120%. In some embodiments, the functional layer has an electrolyte retention rate of 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, or any of these values. A range consisting of any two. At this time, the functional layer has a higher electrolyte retention rate, which is beneficial to improving the cycle stability of the electrochemical device in the later period.

According to some embodiments of the present application, the bonding force between the functional layer and the current collector is 100 N/m to 600 N/m. At this time, the functional layer is not easy to fall off after absorbing the electrolyte, and can stably store excess electrolyte, thereby improving the cycle stability of the electrochemical device.

According to some embodiments of the present application, the flatness of the electrochemical device is 0 to 0.5 mm.

According to some embodiments of the present application, the active material layer is a positive active material layer and/or a negative active material layer.

According to some embodiments of the present application, the positive active material layer includes a positive active material, a binder, and a conductive agent. In some embodiments, the positive active material may include at least one of lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, or lithium nickel manganate. In some embodiments, the binder may include various binder polymers, such as polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethylcellulose, lithium carboxymethylcellulose, modified At least one of polyvinylidene fluoride, modified styrene-butadiene rubber or polyurethane. In some embodiments, any conductive material can be used as the conductive agent as long as it does not cause chemical changes. Examples of conductive agents include: carbon-based materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.; metal-based materials, such as metal powder or metal fibers including copper, nickel, aluminum, silver, etc. ; Conductive polymers, such as polyphenylene derivatives, etc.; or mixtures thereof.

According to some embodiments of the present application, the negative active material layer includes a negative active material and a binder, and optionally a conductive agent. In some embodiments, the negative active material may include a material that reversibly intercalates/deintercalates lithium ions, lithium metal, lithium metal alloy, or transition metal oxide. In some embodiments, the negative active material includes at least one of carbon material or silicon material, the carbon material includes at least one of graphite and hard carbon, and the silicon material includes silicon, silicon oxy compound, silicon carbon compound or silicon alloy. of at least one. In some embodiments, the binder includes styrene-butadiene rubber, polyacrylic acid, polyacrylate, polyimide, polyamideimide, polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, water-based acrylic resin , at least one of polyvinyl formal or styrene-acrylic acid copolymer resin. In some embodiments, any conductive material can be used as the conductive material as long as it does not cause chemical changes. In some embodiments, the conductive material includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, or graphene.

According to some embodiments of the present application, the current collector is a positive current collector and/or a negative current collector. In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) 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 conductive metal, or a combination thereof.

The electrochemical device of the present application also includes an isolation membrane. The material and shape of the isolation membrane used in the electrochemical device of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the isolation membrane includes polymers or inorganic substances formed of materials that are stable to the electrolyte of the present application. For example, the isolation film may include a base material layer and a surface treatment layer. The base material layer is a non-woven fabric, film or composite film with a porous structure. The base material layer is made of at least one material selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, polypropylene porous membrane, polyethylene porous membrane, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite membrane can be used.

A surface treatment layer is provided on at least one surface of the base layer. 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 layer.

The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, At least one of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy , at least one of polymethylmethacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

The polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride, At least one of poly(vinylidene fluoride-hexafluoropropylene).

The electrochemical device of the present application also includes an electrolyte. Electrolytes useful in this application may be electrolytes 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 solution according to the present application may be any organic solvent known in the prior art that can be used as a solvent for the electrolyte solution. The electrolyte used in the electrolyte solution according to the present application is not limited, and it can be any electrolyte known in the prior art. The additives of the electrolyte according to the present application may be any additives known in the art that can be used as electrolyte additives. In some embodiments, organic solvents include, but are not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) ), propylene carbonate or ethyl propionate. In some embodiments, the organic solvent includes an ether solvent, such as at least one of 1,3-dioxane (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 bistrifluoromethanesulfonimide LiN (CF ₃ SO ₂ ) ₂ (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO ₂ F) ₂ )(LiFSI), lithium bisoxalatoborate LiB(C ₂ O ₄ ) ₂ (LiBOB) or Lithium difluorooxalate borate LiBF ₂ (C ₂ O ₄ ) (LiDFOB).

In some embodiments, electrochemical devices of the present application include, but are not limited to: all kinds of primary or secondary batteries. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, secondary batteries include lithium secondary batteries, sodium ion batteries, etc.; lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium secondary batteries. Ion polymer secondary battery.

2. Electronic devices

The present application further provides an electronic device, which includes the electrochemical device described in the first aspect of the present application.

The electronic equipment or device of the present application is not particularly limited. In some embodiments, electronic devices of the present application include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, and stereo headsets. , VCR, LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle , lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

Examples and Comparative Examples

Functional layer slurry preparation: Mix the binder (see Table 1 and Table 2 for specific composition) and solvent evenly to make a slurry. The slurry needs to be controlled: viscosity 200-3000mPa·s, solid content 35%-50% . Among them, deionized water was used as the solvent in the examples; N-methylpyrrolidone was used as the solvent in Comparative Example 1.

Preparation of the positive electrode sheet: Coat the functional layer slurry prepared above on the winding end area of the positive electrode current collector aluminum foil, and dry the solvent to obtain the electrode sheet coated with the functional layer. The positive electrode active material slurry is coated on the area not coated with the functional layer, and then dried and rolled to obtain the positive electrode sheet. Among them, the positive active material slurry is a slurry made by mixing lithium cobalt oxide, conductive carbon, and polyvinylidene fluoride in a mass ratio of 96:2:2, and adding N-methylpyrrolidone (NMP).

Preparation of the negative electrode sheet: The negative electrode active material slurry is coated on the surface of the negative electrode current collector copper foil, and then dried and rolled to obtain the negative electrode sheet. Among them, the negative active material slurry is: a slurry made by mixing graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose in a mass ratio of 98:1:1, and adding deionized water.

Preparation of lithium-ion battery: Stack the positive electrode sheet, isolation film (PE porous polymer film), and negative electrode sheet in order so that the isolation film acts as an isolation between the positive electrode sheet and the negative electrode sheet, and then roll it up. Wind the electrode assembly to obtain the electrode assembly; place the electrode assembly in the outer packaging aluminum plastic film, inject the electrolyte (the solvent is EC and DMC with a volume ratio of 1:1, based on the mass of the electrolyte, the mass concentration of LiPF ₆ is a solution of 12.5% ), after vacuum packaging, standing, formation, shaping and other processes, the preparation of lithium-ion batteries is completed.

Test Methods

1. Ultrasonic testing

Use non-destructive ultrasonic intelligent diagnostic equipment (model: UBSC-LD) to emit ultrasonic waves to the lithium-ion battery along the thickness direction of the lithium-ion battery with a frequency of 50MHZ. Select the voltage range of the output interface from 0 to 4v to obtain the response to ultrasonic waves everywhere in the battery. Signal feedback distribution diagram. Use the integration software to calculate that the total area of the electrode pole test in the signal feedback distribution diagram is S, and the area of the area with signal strength ≥1333mV is S1. Then the proportion of the area with signal strength ≥1333mV is: S1/S×100%.

2. Adhesion

Use a high-speed rail tensile machine and the 90° angle method to test the bonding force between the functional layer and the current collector. That is, make some of the pole pieces coated with the functional layer in the lithium ion battery into strips, and move the pole pieces from one end of the pole piece along the length direction. Part of the piece is adhered to the steel plate through double-sided tape; then fix the steel plate at the corresponding position of the high-speed rail tensile machine, pull up the pole pieces that are not adhered to the steel plate, and place the pole pieces into the chuck through connectors or directly. Tightly, when the clamp tension is greater than 0kgf and less than 0.02kgf, you can start testing with a high-speed rail tensile machine. The average tensile force in the finally measured stable area is recorded as the bonding force between the functional layer and the current collector.

3. Electrolyte retention rate

a) Remove the pole piece coated with the functional layer from the lithium ion battery in an environment of (25±3)℃. If there is other coating on the other side of the current collector coated with the functional layer, it needs to be removed by physical or chemical methods, but the functional layer cannot be damaged. Then use a cutting machine to cut the current collector coated with the functional layer;

b) Use an electronic balance to weigh the above-cut current collectors coated with functional layers (including current collectors) at least 3 times, respectively, recorded as m1; m2; m3..., and obtain the average value m;

c) Put the weighed current collector (including current collector) coated with the functional layer into an 85°C oven for 30 to 60 minutes to ensure that the electrolyte inside the functional layer is completely dried, and then weigh the dried coatings again. The current collector with the functional layer is weighed at least 3 times, recorded as M1; M2; M3..., and the average value M is obtained;

d) Remove the functional layer using physical or chemical methods, but do not damage the corresponding current collector. Weigh the corresponding current collector at least three times, recorded as G1; G2; G3... respectively, and obtain the average value G;

e) The electrolyte retention rate of the functional layer is recorded as: R=(m-M)/(M-G)×100%.

4. Swelling degree

a) Glue film preparation: Remove the pole piece coated with the functional layer from the lithium ion battery in an environment of (25±3)°C. If there is other coating on the other side of the current collector coated with the functional layer, it needs to be removed by physical or chemical methods, but the functional layer cannot be damaged. Then use a cutting machine to cut the current collector coated with the functional layer, soak it in dimethyl carbonate DMC to remove the electrolyte dissolved in the functional layer, take it out and dry it, and then put it into water to dissolve the functional layer Form a solution and pour this solution into the film preparation mold. If there are bubbles, lift them up and remove them. Place the mold in a 60°C oven for 12 hours. After baking, observe the appearance and hardness of the film. If it is not completely dry, continue baking. , until dry;

b) Cut the prepared adhesive film into small strips with scissors;

c) Weigh the film strip and record the initial weight a; put it into a vial and add electrolyte (the solvent is EC and DMC with a volume ratio of 1:1. Based on the mass of the electrolyte, the mass concentration of LiPF ₆ is 12.5 % solution), exceeding the film by 2 to 3cm, seal the vial, and place it in a vacuum drying oven at a temperature of 85°C for 6 hours;

d) Test the swelling degree of the adhesive film: Take out the adhesive film, wipe it clean with dust-free paper, and record the weight b of the adhesive film at this time.

Swelling degree=(b-a)/a×100%. Make three parallel samples and average the obtained swelling degrees to obtain the swelling degree of the functional layer.

5. Thickness of functional layer

a) Remove the pole piece coated with the functional layer from the lithium ion battery in an environment of (25±3)℃. If there is other coating on the other side of the current collector coated with the functional layer, it needs to be removed by physical or chemical methods, but the functional layer cannot be damaged;

b) Put the above-mentioned pole piece (including current collector) coated with the functional layer into an 85°C oven for 30 to 60 minutes to ensure that the electrolyte inside the functional layer is completely dried. Use a multimeter to measure the pole piece coated with the functional layer after drying. The thickness of the sheet (including current collector) at at least 10 different points is recorded as the average thickness of all test points as T1;

c) Remove the functional layer using physical or chemical methods, but do not damage the corresponding current collector. Use a micrometer to measure the thickness of at least 10 different points of the current collector coated with the functional layer, and record the average thickness of all test points as T0;

d) The thickness of the functional layer is: (T1-T0).

6. Flatness

Laser scanning method is used to test the flatness of lithium-ion batteries. Specifically, optical equipment is used to scan the entire contour of the lithium-ion battery and make a 3D model, and then the difference between the overall thickness value and the cross-section thickness value is calculated, recorded as P. If P ≤ 0.5mm, then the lithium The flatness of the ion battery is OK and meets the requirements; if P>0.5mm, the flatness is NG and does not meet the requirements.

Test Results

Table 1

Note: The percentage content of each component in the raw material composition of the functional layer is the mass fraction content.

It can be seen from the data in Table 1 that the composition and swelling degree of the functional layer will affect its electrolyte retention rate, which will in turn affect the proportion of the area ≥1333mV. As the swelling degree of the functional layer increases, the electrolyte retention rate increases, and the proportion of the area ≥1333mV also increases. The large proportion of the ≥1333mV area indicates that the electrolyte is more fully infiltrated and distributed inside the lithium-ion battery. The lithium-ion battery can have a higher liquid retention rate and good flatness, thereby improving the cycle life of the lithium-ion battery and Reduce energy density losses.

In addition, it can also be seen from the comparative example that the functional layer directly affects the electrolyte retention rate and the proportion of the ≥1333mV area. The swelling degree of the non-functional layer or the functional layer is low, the electrolyte retention rate is low, and the flatness of the lithium-ion battery Difference.

Table 2

Note: The percentage content of each component in the composition of the functional layer is the mass fraction content.

It can be seen from the data in Table 2 that the thickness of the functional layer affects the electrolyte retention rate and the proportion of the area ≥1333mV. Within a certain range, as the thickness increases, the electrolyte retention rate and the proportion of the area ≥1333mV also increase.

Although illustrative embodiments have been shown and described, those skilled in the art will understand that the above-described embodiments are not to be construed as limitations of the present application, and that changes may be made in the embodiments without departing from the spirit, principles and scope of the present application. , substitutions and modifications.

Claims (10)

An electrochemical device includes an electrode pole piece, the electrode pole piece includes a current collector, the current collector includes a first region and a second region, an active material layer is provided on the first region, and the second region There is a functional layer on the Among them, a non-destructive ultrasonic intelligent diagnostic system is used to test, and an ultrasonic wave with a frequency of 50MHZ is emitted to the electrochemical device along the thickness direction of the electrochemical device to obtain the signal feedback distribution diagram of the ultrasonic wave from the electrochemical device. Based on the As for the area of the electrode plate in the signal feedback distribution diagram, the area of the area where the signal intensity is greater than or equal to 1333mV accounts for 30% to 95%. The electrochemical device according to claim 1, wherein the area ratio of the region where the signal intensity is greater than or equal to 1333 mV is 50% to 95%. The electrochemical device according to claim 1, wherein based on the area of the electrode pole piece in the signal feedback distribution diagram, the area proportion of the area where the signal intensity is less than or equal to 1000 is 5% to 10%. The electrochemical device according to claim 1, wherein the swelling degree of the functional layer is 200% to 800%. The electrochemical device according to claim 1, wherein the swelling degree of the functional layer is 300% to 600%. The electrochemical device according to claim 1, wherein, using Fourier transform infrared testing, the functional layer is between 2700cm ^-1 and 3100cm ^-1 , 1600cm ^-1 and 1800cm ^-1 or 1100cm ^-1 and 1200cm ^-1 There is an absorption peak in at least one range. The electrochemical device according to claim 1, wherein the functional layer includes a polymer and satisfies at least one of the following conditions (1) to (2): (1) Based on the mass of the functional layer, the mass percentage of the polymer is greater than or equal to 50%; (2) The polymer includes a polymer formed from at least one of acrylic monomers, acrylate monomers, and styrene monomers. The electrochemical device according to claim 1, wherein the functional layer has a thickness of 1 μm to 20 μm. 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%; (b) The bonding force between the functional layer and the current collector is 100N/m to 600N/m; (c) The electrochemical device has a flatness of 0 to 0.5 mm. An electronic device including the electrochemical device according to any one of claims 1 to 9.

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