CN113097432A - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
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- CN113097432A CN113097432A CN202110342108.9A CN202110342108A CN113097432A CN 113097432 A CN113097432 A CN 113097432A CN 202110342108 A CN202110342108 A CN 202110342108A CN 113097432 A CN113097432 A CN 113097432A
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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
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
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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
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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
- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The present application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive pole piece, a negative pole piece and an isolating membrane positioned between the positive pole piece and the negative pole piece. The positive pole piece or the negative pole piece comprises a current collector, a first layer, a second layer and an active material layer. The first layer is located between the current collector and the second layer, and the second layer is located between the first layer and the active material layer. The average pore size of the first layer is smaller than the average pore size of the second layer. The embodiment of this application is through setting up two coatings between current collector and active material layer to the average pore diameter that makes the first layer is less than the average pore diameter on second floor, has increased the area of contact of current collector with the active material layer, and then improves pole piece adhesion, shortens charge transfer distance, reduces the pole piece internal resistance.
Description
Technical Field
The present application relates to the field of electronic technology, and more particularly, to electrochemical devices and electronic devices.
Background
With the wide application of electrochemical devices (e.g., lithium ion batteries) in various electronic products, users have made higher and higher requirements for energy density, rate capability and cycle performance of electrochemical devices. Generally, in order to increase the energy density of an electrochemical device, the coating amount per unit area of the active material layer may be increased. However, increasing the amount of coating per unit area of the active material layer poses a challenge to the adhesion and resistance of the pole piece.
Therefore, further improvements in adhesion and resistance properties of the pole piece are desired.
Disclosure of Invention
An embodiment of the present application provides an electrochemical device including an electrode assembly including a positive electrode tab, a negative electrode tab, and a separator between the positive electrode tab and the negative electrode tab. The positive pole piece or the negative pole piece comprises a current collector, a first layer, a second layer and an active material layer. The first layer is located between the current collector and the second layer, and the second layer is located between the first layer and the active material layer. The average pore size of the first layer is smaller than the average pore size of the second layer.
In some embodiments, the first layer has an average pore size of 0.01 μm to 0.1 μm and the second layer has an average pore size of 0.1 μm to 50 μm. In some embodiments, the first layer has an average thickness of 0.1 μm to 10 μm and the second layer has an average thickness of 0.1 μm to 10 μm. In some embodiments, the first layer includes a first conductive agent and a first binder, and the second layer includes a second conductive agent and a second binder. In some embodiments, the first conductive agent and the second conductive agent each independently comprise at least one of carbon black, carbon nanotubes, conductive graphite, acetylene black, ketjen black, or graphene. In some embodiments, the first binder and the second binder each independently comprise at least one of an acrylic resin, styrene butadiene rubber, polyacrylic, sodium carboxymethyl cellulose, or sodium alginate. In some embodiments, the mass ratio of the first conductive agent to the first binder is 1 (0.1 to 1). In some embodiments, the mass ratio of the second conductive agent to the second binder is 1 (0.1 to 1). In some embodiments, the adhesion between the active material layer and the second layer is 10 to 50N/m.
Embodiments of the present application also provide an electronic device including the above electrochemical device.
The embodiment of this application is through setting up two coatings between current collector and active material layer to the average pore diameter that makes the first layer is less than the average pore diameter on second floor, has increased the area of contact of current collector with the active material layer, and then improves pole piece adhesion, shortens charge transfer distance, reduces the pole piece internal resistance.
Drawings
Fig. 1 illustrates a cross-sectional view of a pole piece of some embodiments of the present application taken through a plane defined by a thickness direction and a width direction.
Detailed Description
The following examples are presented to enable those skilled in the art to more fully understand the present application and are not intended to limit the present application in any way.
Some embodiments of the present application provide an electrochemical device including an electrode assembly including a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab. In some embodiments, as shown in fig. 1, the positive or negative electrode tab includes a current collector 101, a first layer 102, a second layer 103, and an active material layer 104, the first layer 102 being located between the current collector 101 and the second layer 103, the second layer 103 being located between the first layer 102 and the active material layer 104. For the sake of simplicity, the following description will be made by taking the positive electrode tab as an example, and it should be understood that the negative electrode tab may have a corresponding structure. It should be understood that the first layer 102, the second layer 103, and the active material layer 104 may be located on one side of the current collector 101 or may be both located on both sides of the current collector 101.
In some embodiments, the active material layer 104 includes an active material, for example, a positive electrode active material. In some embodiments, the average pore size of first layer 102 is less than the average pore size of second layer 103. Since the first layer 102 is closer to the current collector 101 than the second layer 103, it is advantageous to enhance the contact of the current collector 101 with the first layer 102 when the average pore size of the first layer 102 is smaller than the average pore size of the second layer 103. In addition, the combination of the first layer 102 and the second layer 103 with different pore diameters increases the contact area among the active material layer 104, the second layer 103, the first layer 102 and the current collector 101, and the increase of the contact area can improve the adhesive force of the pole piece, shorten the electron transfer path and reduce the resistance of the pole piece.
In some embodiments, the first layer 102 has an average pore size of 0.01 μm to 0.1 μm and the second layer 103 has an average pore size of 0.1 μm to 50 μm. The average pore size of the second layer 103 is similar to the particle size of the active material to facilitate matching contact of the active material with the second layer 103. In addition, the first layer 102 has an average pore size of 0.01 μm to 0.1 μm, which is smaller than the average pore size of the second layer 103, and is advantageous for enhancing the contact of the current collector 101 with the first layer 102. If the average pore size of the first layer 102 is too large, it is not favorable for the improvement of the adhesion of the first layer 102 to the current collector 101. If the average pore diameter of the second layer 103 is too large, it is not advantageous to increase the energy density of the electrochemical device.
In some embodiments, the average pore size of the first layer 102 and the second layer 103 can be tested using the following method: and testing the section of the coating after section polishing treatment by adopting a scanning electron microscope, randomly selecting 100 holes in the coating, removing 25 holes with the largest hole diameter and 25 holes with the smallest hole diameter, and calculating the mean hole diameter of the remaining 50 holes to obtain the mean hole diameter of the coating. Of course, this is merely exemplary, and other suitable mean pore size testing methods may also be employed.
In some embodiments, the first layer 102 has an average thickness of 0.1 μm to 10 μm and the second layer 103 has an average thickness of 0.1 μm to 10 μm. If the thickness of the first layer 102 and/or the second layer 103 is too small, the adhesion of the pole piece is not improved. If the thickness of the first layer 102 and/or the second layer 103 is too large, it is not advantageous to increase the energy density of the electrochemical device. In some embodiments, the first layer 102 has an average thickness of 0.1 μm to 5 μm and the second layer 103 has an average thickness of 0.1 μm to 5 μm. In some embodiments, the first layer 102 has an average thickness of 0.1 μm to 3 μm and the second layer 103 has an average thickness of 0.1 μm to 3 μm.
In some embodiments, the average thickness of the first layer 102 and the second layer 103 may be tested using the following method: the cross section of the coating after cross section polishing treatment is tested by adopting a scanning electron microscope, a straight line vertical to the plane of a current collector is made, the vertical line intersects with the upper edge and the lower edge of the coating at two points, the distance between the two points is measured to be the thickness of the coating, 100 thickness values of the coating are randomly selected according to the method, 25 thickness values with the largest numerical value and 25 thickness values with the smallest numerical value are removed, and the average value of the remaining 50 thickness values is calculated to be the average thickness of the coating. Of course, this is merely exemplary, and other suitable average thickness test methods may also be employed.
In some embodiments, first layer 102 includes a first conductive agent and a first binder, and second layer 103 includes a second conductive agent and a second binder. By using a conductive agent and an adhesive force, the first layer 102 and the second layer 103 formed by such a combination are more compatible with or active material layer 104, and the adhesive force between the second layer 103 and the active material layer 104 and between the current collector 101 and the first layer 102 can be improved. In addition, the existence of the conductive agent can also reduce the electron transfer resistance, thereby reducing the resistance of the pole piece.
In some embodiments, the first conductive agent and the second conductive agent each independently comprise at least one of carbon black, carbon nanotubes, conductive graphite, acetylene black, ketjen black, or graphene. In some embodiments, the first binder and the second binder each independently comprise at least one of an acrylic resin, styrene butadiene rubber, polyacrylic, sodium carboxymethyl cellulose, or sodium alginate. In some embodiments, the mass ratio of the first conductive agent to the first binder is 1 (0.1 to 1). In some embodiments, the mass ratio of the second conductive agent to the second binder is 1 (0.1 to 1). By adopting such a mass ratio, while the adhesion force among the current collector 101, the first layer 102, the second layer 103, and the active material layer 104 is ensured, it contributes to a reduction in the electron transfer resistance of the first layer 102 and the second layer 103, and further, a reduction in the pole piece resistance. If the mass content of the first conductive agent is too small, the conductivity of the first layer 102 is adversely affected, and the resistance of the pole piece is adversely decreased. If the mass content of the first conductive agent is too large, an excessive amount of the first conductive agent may adversely affect exertion of the adhesive property of the first layer 102 because the adhesive property of the first conductive agent itself is slightly weak. Likewise, if the mass content of the second conductive agent is too small, the conductivity of the second layer 103 is adversely affected, and thus the reduction in the resistance of the pole piece is adversely affected. If the mass content of the second conductive agent is too large, an excessive amount of the second conductive agent may adversely affect the exertion of the adhesive property of the second layer 103 since the adhesive property of the second conductive agent itself is slightly weak.
In some embodiments, the adhesion between the active material layer 104 and the second layer 103 is 10N/m to 50N/m. By achieving such adhesion, the overall adhesion of the pole piece is improved. Generally, the bond between the active material layer 104 and the second layer 103 in the pole piece is weak, so the average bond between the active material layer 104 and the second layer 103 can be considered as the overall bond of the pole piece. In some embodiments, the adhesion between the active material layer 104 and the second layer 103 may be tested by: adhering the double-sided adhesive to any one surface of a pole piece with the size of 15 x 60mm to be tested, and compacting by using a compression roller to ensure that the compression roller is completely attached to the pole piece; the other side of the double-sided adhesive tape is adhered to the surface of a stainless steel plate, a tensile machine is adopted for testing, one end of the stainless steel is fixed on a clamp below the tensile machine, one end of a sample is reversely bent, the bending angle is 90 degrees, the bent tail end of the sample is fixed on a clamp above the tensile machine, the angle of the sample is adjusted, one end and the other end of the sample are ensured to be in vertical positions, then the sample is stretched at the speed of 50mm/min until the sample is completely stripped from the stainless steel plate, the displacement and the acting force in the process are recorded, and the force when the stress is balanced is the bonding force of a; the 10 samples were randomly tested and the average value of the adhesion was taken as the adhesion. Of course, this is merely exemplary, and other suitable adhesion testing methods may also be employed.
In some embodiments, the average resistance of the pole pieces is 0.5Ohm to 5 Ohm. Thus, good electrical performance of the electrochemical device can be obtained. In some embodiments, the average resistance of the pole piece can be tested by: the method comprises the steps of adopting a two-probe resistance tester to test, adjusting the pressure between the two probes to 0.4t, placing a pole piece to be tested in the middle of the probes, operating the tester, recording the internal resistance value shown by the resistance tester after 5 seconds, testing 20 different points according to the method, and calculating the average value of the recorded 20 internal resistances, namely the average resistance of the pole piece. Of course, this is merely exemplary, and other suitable resistance testing methods may also be employed.
In some embodiments, the internal resistance (IMP) of the battery may be 1mOhm to 10 mOhm. Thus, good electrical performance of the electrochemical device can be obtained. In some embodiments, the IMP of a battery may be tested by: and testing by adopting a manual OCV/IMP voltage and internal resistance testing machine, placing the battery to be tested at the material loading position of the testing machine, operating the instrument, recording IMP values shown by the internal resistance testing instrument after 5 seconds, testing 20 different batteries according to the method, and calculating the average value of the recorded internal resistances of the 20 batteries, namely the IMP of the battery corresponding to the pole piece. Of course, this is merely exemplary, and other suitable internal resistance testing methods may also be employed.
In some embodiments, the first layer 102 and the second layer 103 may be formed by an electrospinning method. By using the electrospinning method, the pore size and thickness of the first layer 102 and the second layer 103 can be better controlled.
In some embodiments, when the positive electrode tab includes the above structure, the active material layer 104 is a positive electrode active material layer, and includes a positive electrode active material. In some embodiments, the positive active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel cobalt manganese, a lithium rich manganese based material, or lithium nickel cobalt aluminate. In some embodiments, the positive electrode active material layer may further include a conductive agent. In some embodiments, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, ketjen black, flake graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the positive electrode active material layer may further include a binder, and the binder in the positive electrode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene. In some embodiments, the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer may be (80 to 99): (0.1 to 10): (0.1 to 10). In some embodiments, the thickness of the positive electrode active material layer may be 10 μm to 500 μm. It should be understood that the above description is merely an example, and any other suitable material, thickness, and mass ratio may be employed for the positive active material layer of the positive electrode tab.
In some embodiments, the current collector of the positive electrode sheet may be an Al foil, but of course, other current collectors commonly used in the art may also be used. In some embodiments, the thickness of the current collector of the positive electrode tab may be 1 μm to 200 μm. In some embodiments, the positive active material layer may be coated only on a partial area of the current collector of the positive electrode tab.
In some embodiments, when the negative electrode tab includes the above structure, the active material layer 104 is a negative electrode active material layer. In some embodiments, the negative active material layer includes a negative active material, which may include at least one of graphite, hard carbon, silicon, silica, or silicone. In some embodiments, a conductive agent and a binder may also be included in the negative active material layer. In some embodiments, the conductive agent in the negative active material layer may include at least one of conductive carbon black, ketjen black, flake graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the binder in the negative active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinyl pyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene. In some embodiments, the mass ratio of the anode active material, the conductive agent, and the binder in the anode active material layer may be (80 to 98): (0.1 to 10): (0.1 to 10). It will be appreciated that the above description is merely exemplary and that any other suitable materials and mass ratios may be employed. In some embodiments, the current collector of the negative electrode sheet may employ at least one of a copper foil, a nickel foil, or a carbon-based current collector.
In some embodiments, the separator comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high density polyethylene, low density polyethylene, or ultra high molecular weight polyethylene. Particularly polyethylene and polypropylene, which have a good effect on preventing short circuits and can improve the stability of the battery through a shutdown effect. In some embodiments, the thickness of the isolation film is in the range of about 5 μm to 50 μm.
In some embodiments, the surface of the separator may further include a porous layer disposed on at least one surface of the substrate of the separator, the porous layer including inorganic particles selected from alumina (Al) and a binder2O3) Silicon oxide (SiO)2) Magnesium oxide (MgO), titanium oxide (TiO)2) Hafnium oxide (HfO)2) Tin oxide (SnO)2) Cerium oxide (CeO)2) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO)2) Yttrium oxide (Y)2O3) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the separator film have a diameter in the range of about 0.01 μm to 1 μm. The binder of the porous layer is at least one selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The porous layer on the surface of the isolating membrane can improve the heat resistance, the oxidation resistance and the electrolyte infiltration performance of the isolating membrane and enhance the adhesion between the isolating membrane and the pole piece.
In some embodiments of the present application, the electrode assembly of the electrochemical device is a wound electrode assembly, a stacked electrode assembly, or a folded electrode assembly. In some embodiments, the positive electrode plate and/or the negative electrode plate of the electrochemical device may be a multilayer structure formed by winding or stacking, or may be a single-layer structure formed by stacking a single-layer positive electrode plate, a single-layer separator, and a single-layer negative electrode plate.
In some embodiments, the electrochemical device comprises a lithium ion battery, but the application is not so limited. In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution including a lithium salt and a non-aqueous solvent. The lithium salt is selected from LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6One or more of LiBOB or lithium difluoroborate. For example, LiPF is selected as lithium salt6Because it has high ionic conductivity and can improve cycle characteristics.
The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvent, or a combination thereof.
The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluoro carbonate compound, or a combination thereof.
Examples of the chain carbonate compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Methyl Ethyl Carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC), Vinyl Ethylene Carbonate (VEC), or a combination thereof. Examples of the fluoro carbonate compound are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1,2, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
Examples of carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ -butyrolactone, decalactone, valerolactone, mevalonic lactone, caprolactone, methyl formate, or combinations thereof.
Examples of the ether compound are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
Examples of other organic solvents are dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
In some embodiments of the present application, taking a lithium ion battery as an example, a positive electrode plate, a separator, and a negative electrode plate are sequentially wound or stacked to form an electrode member, and then the electrode member is placed in, for example, an aluminum plastic film for packaging, and an electrolyte is injected into the electrode member for formation and packaging, so as to form the lithium ion battery. And then, performing performance test on the prepared lithium ion battery.
Those skilled in the art will appreciate that the above-described methods of making electrochemical devices (e.g., lithium ion batteries) are merely examples. Other methods commonly used in the art may be employed without departing from the disclosure herein.
Embodiments of the present application also provide an electronic device including the electrochemical device described above. The electronic device of the embodiment of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, a lithium ion capacitor, and the like.
In the following, some specific examples and comparative examples are listed to better illustrate the present application, wherein a lithium ion battery is taken as an example. For the sake of simplicity, the following only exemplifies that the positive electrode tab includes the first layer and the second layer.
Example 1
Preparing a positive pole piece: the method comprises the following steps of (1) adopting an aluminum foil as a current collector of a positive pole piece, and uniformly coating conductive coating slurry on the surface of the aluminum foil, specifically: mixing acetylene black, graphene and acrylic resin in a ratio of 1: 0.05: 0.8, and uniformly stirring to obtain conductive coating slurry; filling the conductive coating slurry into an electrostatic spinning machine, adjusting the voltage of the electrostatic spinning machine to be 10kV, the pushing speed of the slurry to be 0.5mL/h, and the distance between an electrostatic spinning nozzle and a current collector to be 15 cm; and spraying the conductive coating slurry on a current collector, and baking at 110 ℃ for 10min to obtain the current collector with the first layer, wherein the current collector has an average pore diameter of 0.01 mu m and a thickness of 0.1 mu m. Then adjusting the voltage of an electrostatic spinning machine to be 8kV, the pushing speed of the slurry to be 2mL/h, and the distance between an electrostatic spinning nozzle and a current collector to be 15cm, and carrying out secondary spraying; and baking the current collector subjected to the secondary spraying for 10min at the temperature of 110 ℃ to obtain a second layer of current collector with the average pore diameter of 0.5 mu m and the thickness of 0.5 mu m.
Lithium iron phosphate as a positive electrode active material, conductive carbon black as a conductive agent and polyacrylic acid as a binder in a weight ratio of 98.2: 0.5: and dissolving the mixture in N-methyl pyrrolidone (NMP) solution according to the proportion of 1.3 to form anode slurry, coating the anode slurry on the second layer with the thickness of 200 mu m, baking for 10min at the temperature of 110 ℃, and performing cold pressing and cutting to obtain the anode piece.
Preparing a negative pole piece: graphite, sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber serving as a binder are mixed according to the weight ratio of 97.8: 1.3: the ratio of 0.9 is dissolved in deionized water to form negative electrode slurry. And (3) adopting copper foil with the thickness of 10 mu m as a current collector of the negative pole piece, coating the negative pole slurry on the current collector of the negative pole piece, drying and cutting to obtain the negative pole piece.
Preparing an isolating membrane: the separator substrate was Polyethylene (PE) 8 μm thick, and both sides of the separator substrate were coated with ceramic layers of alumina 2 μm each, and finally both sides coated with ceramic layers were coated with ceramic layers 2.5mg/cm each2And (3) drying the binder polyvinylidene fluoride (PVDF).
Preparing an electrolyte: under the environment that the water content is less than 10ppm, LiPF6Adding non-aqueous organic solvent (ethylene carbonate (EC): Propylene Carbonate (PC): 50, heavy)Quantitative ratio), LiPF6The concentration of (A) is 1.15mol/L, and the electrolyte is obtained after uniform mixing.
Preparing a lithium ion battery: and sequentially stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and winding to obtain the electrode assembly. And (3) placing the electrode assembly in an outer packaging aluminum-plastic film, dehydrating at 80 ℃, injecting the electrolyte, packaging, and performing technological processes such as formation, degassing, edge cutting and the like to obtain the lithium ion battery.
The examples and comparative examples were carried out by changing the parameters in addition to the procedure of example 1, and the specific changed parameters are shown in the following table.
Table 1 shows the respective parameters and evaluation results of examples 1 to 12 and comparative examples 1 to 3. In examples 2 to 12 and comparative examples 1 to 3, the average pore diameter of the first layer was different from that of example 1, and the average pore diameter of the second layer in examples 4 to 7, 9 to 12 and comparative examples 1 to 2 was different from that of example 1, and other parameters were the same as those of example 1. In comparative example 3, the second layer was not formed in the positive electrode sheet, and the thickness of the first layer was 0.05 μm.
TABLE 1
Where "/" indicates the absence of this layer.
As can be seen from comparing examples 1 to 3 and comparative example 3, by forming two layers between the current collector and the active material layer, the average resistance of the pole piece was significantly reduced, the adhesion of the pole piece was significantly increased, and the internal resistance IMP of the electrochemical device was not greatly changed, relative to one layer in comparative example 3.
As can be seen by comparing examples 1 to 3 with comparative example 1, when the average pore size of the first layer is smaller than the average pore size of the second layer, the average resistance of the pole piece decreases, and the average adhesion of the pole piece increases, there is a certain decrease in the internal resistance of the electrochemical device.
As can be seen from comparing examples 1 to 3, 8 to 10, and 12, as the average pore diameter of the first layer increases, the average resistance of the electrode sheet decreases first and then increases, the average cohesive force of the electrode sheet increases first and then decreases, and the internal resistance of the electrochemical device tends to increase to some extent. In addition, the average pore size of the first layer should not be too small, otherwise the adhesion of the pole piece is significantly reduced. In addition, if the average pore size of the first layer is too large, the average resistance of the pole piece and the internal resistance of the electrochemical device may increase.
As can be seen from comparing examples 4 to 7, 11 and comparative example 2, as the average pore diameter of the second layer increases, the average resistance of the electrode sheet tends to increase, the adhesive force of the electrode sheet increases first and then decreases, and the internal resistance of the electrochemical device tends to increase. Therefore, the average pore size of the second layer should not be too large. If the average pore size of the second layer is too large, the average resistance of the pole piece and the internal resistance of the electrochemical device increase, and the adhesion of the pole piece decreases. In addition, if the average pore size of the second layer is too small, the adhesion of the pole piece is significantly reduced.
Table 2 shows the respective parameters and evaluation results of examples 13 to 31. In examples 13 to 31, the average pore diameter of the first layer was 0.05. mu.m, and the average pore diameter of the second layer was 9 μm. In examples 13 to 31, the parameters are as in example 1 except that the thicknesses of the first layer and the second layer, the composition and content of the conductive agent, and the composition and content of the binder are different from those of example 1.
TABLE 2
As can be seen from comparing examples 13 to 16, the average resistance of the electrode sheet tends to increase with the increase in the thickness of the first layer, the adhesion of the electrode sheet increases first and then decreases, and the internal resistance IMP of the electrochemical device increases.
As can be seen from comparative examples 17 to 19, as the thickness of the second layer increases, the average resistance of the electrode sheet tends to increase, the adhesion of the electrode sheet increases and then decreases, and the internal resistance IMP of the electrochemical device increases.
It can be seen from comparative examples 20 to 24 that the use of different conductive agents and binders in the first layer improves the average resistance of the pole piece, the adhesion of the pole piece and the internal resistance IMP of the electrochemical device.
As can be seen from comparative examples 25 to 27, as the mass ratio of the conductive agent to the binder in the first layer decreases, the average resistance of the electrode sheet tends to increase, the adhesion of the electrode sheet tends to increase, and the internal resistance IMP of the electrochemical device increases after decreasing.
It can be seen from comparative examples 28 to 29 that the use of different conductive agents and binders in the second layer all improved the average resistance of the pole piece, the adhesion of the pole piece and the internal resistance IMP of the electrochemical device.
As can be seen from comparing examples 28 and 30 to 31, as the mass ratio of the conductive agent to the binder in the second layer decreases, the average resistance of the electrode sheet tends to increase, the adhesion of the electrode sheet tends to increase, and the internal resistance IMP of the electrochemical device increases after decreasing.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the disclosure herein is not limited to the particular combination of features described above, but also encompasses other combinations of features described above or equivalents thereof. For example, the above features and the technical features having similar functions disclosed in the present application are mutually replaced to form the technical solution.
Claims (10)
1. An electrochemical device, comprising:
a positive electrode plate;
a negative pole piece;
the isolating film is positioned between the positive pole piece and the negative pole piece;
the positive pole piece or the negative pole piece comprises a current collector, a first layer, a second layer and an active material layer, wherein the first layer is positioned between the current collector and the second layer, the second layer is positioned between the first layer and the active material layer, and the average pore diameter of the first layer is smaller than that of the second layer.
2. The electrochemical device according to claim 1, wherein the first layer has an average pore size of 0.01 to 0.1 μm, and the second layer has an average pore size of 0.1 to 50 μm.
3. The electrochemical device of claim 1, wherein the first layer has an average thickness of 0.1 to 10 μ ι η and the second layer has an average thickness of 0.1 to 10 μ ι η.
4. The electrochemical device of claim 1, wherein the first layer comprises a first conductive agent and a first binder, and the second layer comprises a second conductive agent and a second binder.
5. The electrochemical device according to claim 4, wherein the first conductive agent and the second conductive agent each independently comprise at least one of carbon black, carbon nanotubes, conductive graphite, acetylene black, Ketjen black, or graphene.
6. The electrochemical device of claim 4, wherein the first binder and the second binder each independently comprise at least one of an acrylic resin, styrene-butadiene rubber, polyacrylic, sodium carboxymethyl cellulose, or sodium alginate.
7. The electrochemical device according to claim 4, wherein a mass ratio of the first conductive agent to the first binder is 1 (0.1 to 1).
8. The electrochemical device according to claim 4, wherein a mass ratio of the second conductive agent to the second binder is 1 (0.1 to 1).
9. The electrochemical device according to claim 1, wherein an adhesive force between the active material layer and the second layer is 10N/m to 50N/m.
10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.
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| CN113097432B (en) | 2022-06-24 |
| WO2022206128A1 (en) | 2022-10-06 |
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