CN116314608A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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CN116314608A
CN116314608A CN202310303762.8A CN202310303762A CN116314608A CN 116314608 A CN116314608 A CN 116314608A CN 202310303762 A CN202310303762 A CN 202310303762A CN 116314608 A CN116314608 A CN 116314608A
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silicon
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扶强
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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
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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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Abstract

Embodiments of the present application provide electrochemical devices and electronic devices. The electrochemical device comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector, a first layer and a second layer, and the negative electrode current collector is positioned between the first layer and the second layer. The first layer includes a first negative electrode active material, the second layer includes a second negative electrode active material, the first negative electrode active material includes graphite, and the second negative electrode active material includes graphite and a silicon-based material. The ratio of the impedance of the first layer to the impedance of the second layer is 0.7 to 0.9, and the negative electrode tab of the present application can improve the capacity retention rate of the electrochemical device without substantially losing the energy density of the electrochemical device.

Description

Electrochemical device and electronic device
Technical Field
The present application relates to the field of electrochemical energy storage, in particular to electrochemical devices and electronic devices.
Background
With the development of electrochemical energy storage technology, there is an increasing demand for energy density and cycle performance of electrochemical devices (e.g., lithium ion batteries). The silicon-based material is used as the anode active material, so that the energy density of the electrochemical device can be greatly improved, but the silicon-based material is accompanied by volume expansion and contraction of more than 300% in the lithium ion deintercalation process, so that the problems of capacity attenuation and the like are caused. Thus, further improvements in this regard are desired.
Disclosure of Invention
The application provides an electrochemical device, and electrochemical device includes the negative pole piece, and the negative pole piece includes negative pole current collector, first layer and second floor, and negative pole current collector is located between first layer and the second floor. The first layer includes a first negative electrode active material, the second layer includes a second negative electrode active material, the first negative electrode active material includes graphite, and the second negative electrode active material includes graphite and a silicon-based material. The ratio of the impedance of the first layer to the impedance of the second layer is 0.7 to 0.9.
In some embodiments, the ratio of the capacity of the first layer to the capacity of the second layer is 0.6 to 1. In some embodiments, the ratio of the capacity of the first layer to the capacity of the second layer is 0.7 to 1. In some embodiments, the mass percent of silicon-based material in the second layer is 6% to 40%. In some embodiments, the mass percent of silicon-based material in the second layer is 12% to 20%. In some embodiments, the second layer further comprises a binder, the binder in the second layer being 1.4% to 5% by mass. In some embodiments, the second layer further comprises carbon nanotubes, the mass percent of the carbon nanotubes in the second layer being 0.3% to 0.7%. In some embodiments, the second layer further comprises sodium carboxymethyl cellulose, the mass percent of sodium carboxymethyl cellulose in the second layer being 0.3% to 0.7%. In some embodiments, the silicon-based material includes at least one of silicon, a silicon-carbon material, or a silicon oxygen material.
The embodiment of the application also provides an electronic device comprising the electrochemical device.
According to the electrochemical device, the first negative electrode active material in the first layer of the negative electrode pole piece comprises graphite, the second negative electrode active material in the second layer comprises graphite and a silicon-based material, the ratio of the impedance of the first layer to the impedance of the second layer is 0.7-0.9, the multiplying power of the second negative electrode active layer in the charging and discharging process is smaller, and the capacity retention rate of the electrochemical device can be improved under the condition that the energy density of the electrochemical device is not basically lost.
Drawings
Fig. 1 illustrates a cross-sectional view of a negative electrode tab along a width direction according to some embodiments.
Detailed Description
The following examples will allow those skilled in the art to more fully understand the present application, but are not intended to limit the present application in any way.
Some embodiments of the present application provide an electrochemical device that includes a negative electrode tab. Fig. 1 illustrates a cross-sectional view of a negative electrode tab along a width direction according to some embodiments. In some embodiments, as shown in fig. 1, the negative electrode tab includes a negative electrode current collector 110, a first layer 111, and a second layer 112, the negative electrode current collector 110 being located between the first layer 111 and the second layer 112. In some embodiments, the first layer 111 includes a first negative electrode active material including graphite and substantially no silicon-based material. It is understood that the first anode active material may be considered to include substantially no silicon-based material when the mass percentage of the silicon-based material in the first anode active material is 0.2% or less. By completely separating the silicon-based material from the graphite in the first layer 111, a reduction in void voids between the graphite in the first layer 111 during cycling is achieved, thereby reducing the overall expansion of the negative electrode sheet.
In some embodiments, the second layer 112 includes a second negative active material including graphite and a silicon-based material. Therefore, the present application concentrates the silicon-based material on one side of the negative electrode current collector 110. Typically, the mass percent of silicon-based material of the layers on both sides of the negative current collector is the same. In the present application, the silicon-based material on one side is replaced with graphite of equal capacity, and the graphite on the other side is replaced with silicon-based material of equal capacity.
In some embodiments, the ratio of the impedance of the first layer 111 to the impedance of the second layer 112 is 0.7 to 0.9. In some embodiments, the resistance of the first layer 111 and the resistance of the second layer 112 may be adjusted by the Si content, the conductive agent content, the binder type, the coating formulation, the coating quality, the compaction density of the respective coatings. Since the impedance of the first layer 111 is smaller than that of the second layer 112, the first layer 111 can be allowed to have a larger charge-discharge rate, and the second layer 112 can have a smaller charge-discharge rate, so that the capacity fade rate of the negative electrode sheet can be slowed down and the capacity retention rate of the electrochemical device can be improved by reducing the charge-discharge rate of the second layer 112 containing the silicon-based material without changing the overall charge-discharge rate of the electrochemical device.
In some embodiments, the ratio of the capacity of the first layer 111 to the capacity of the second layer 112 is 0.6 to 1. In some embodiments, the capacity of the first layer 111 may be adjusted by the coating quality, and the capacity in the second layer 112 may be adjusted by the coating quality and/or Si content. By making the ratio of the capacity of the first layer 111 to the capacity of the second layer 112 be 0.6 to 1, it is possible to achieve an improvement in the capacity retention rate of the electrochemical device.
In some embodiments, the ratio of the capacity of the first layer 111 to the capacity of the second layer 112 is 0.7 to 1. When the ratio of the capacity of the first layer 111 to the capacity of the second layer 112 is 0.7 to 1, the improvement effect of the capacity retention rate of the electrochemical device is more remarkable.
In some embodiments, the mass percent of silicon-based material in second layer 112 is 6% to 40%, or the mass percent of silicon in second layer 112 is 4% to 20%. In some embodiments, since only silicon in the silicon-based material exerts its capacity, the mass percent of silicon in the second layer 112 is small when the mass percent of silicon in the second layer is less than 6%, and the energy density benefit of the electrochemical device is significantly reduced; when the mass percentage of the silicon-based material in the second layer 112 is greater than 40%, the mass percentage of silicon is greater, and the cyclic expansion of the second layer 112 increases. In some embodiments, the mass percentage of silicon-based material in the second layer 112 is 12% to 20%. When the mass percentage of the silicon-based material in the second layer 112 is 12% to 20%, or the mass percentage of the silicon in the second layer 112 is 4% to 10%, the effect of improving the capacity retention rate of the electrochemical device is more remarkable.
In some embodiments, the silicon-based material includes at least one of silicon, a silicon oxygen material, a silicon carbon material, or a silicon oxygen carbon material. In some embodiments, the negative electrode current collector 110 may employ at least one of a copper foil, a nickel foil, or a carbon-based current collector. The first layer 111 and the second layer 112 may each include a conductive agent, a binder, and a thickener (e.g., sodium carboxymethyl cellulose). In some embodiments, the conductive agent in the first layer 111 and the second layer 112 may include at least one of conductive carbon black, ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the binder in the first layer 111 and the second layer 112 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 first negative electrode active material in the first layer is 97% to 98% by mass. In some embodiments, the second anode active material in the second layer is 93.6% to 98% by mass. In some embodiments, the mass ratio of the first anode active material, the thickener, and the binder in the first layer 111 may be (97 to 98): (0.2 to 0.6): (1.8 to 2.4). In some embodiments, the mass ratio of the second anode active material, the conductive agent, the binder, and the thickener in the second layer 112 may be (93.6 to 98): (0.3 to 0.7): (1.4 to 5): (0.3 to 0.7). In some embodiments, the second layer 112 further includes a binder, the binder in the second layer 112 being 1.4% to 5% by mass. In some embodiments, the second layer 112 further includes carbon nanotubes, and the mass percent of carbon nanotubes in the second layer 112 is 0.3% to 0.7%. In some embodiments, the second layer 112 further comprises sodium carboxymethyl cellulose, the mass percent of sodium carboxymethyl cellulose in the second layer 112 being 0.3% to 0.7%.
In some embodiments, the electrochemical device further comprises a positive electrode tab and a separator, the positive electrode tab and the negative electrode tab being separated by the separator disposed therebetween.
In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer on one or both sides of the positive electrode current collector. In some embodiments, the positive current collector may be aluminum foil, although other positive current collectors commonly used in the art may be used. In some embodiments, the thickness of the positive electrode current collector may be 1 μm to 50 μm.
In some embodiments, the positive electrode active material layer may include a positive electrode active material, a conductive agent, and a binder. In some embodiments, the positive electrode active material may include at least one of lithium cobaltate, lithium iron phosphate, lithium aluminate, lithium manganate, or lithium nickel cobalt manganate. In some embodiments, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, platelet graphite, graphene, or carbon nanotubes. In some embodiments, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. 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 is (80-99): (0.1-10): (0.1-10), but this is merely an example, and any other suitable mass ratio may be employed.
In some embodiments, the barrier film 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. In particular 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 release film is in the range of about 3 μm to 20 μm.
In some embodiments, the surface of the separator may further include a porous layer disposed on at least one surface of the separator, the porous layer includingInorganic particles selected from alumina (Al 2 O 3 ) 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 ) Yttria (Y) 2 O 3 ) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the pores of the barrier 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, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The porous layer on the surface of the isolating film can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolating film, and enhance the cohesiveness between the isolating film and the pole piece.
In some embodiments, the electrochemical device includes a lithium ion battery, but the application is not limited thereto. In some embodiments, the electrochemical device further comprises an electrolyte comprising at least one of fluoroether, fluoroethylene carbonate, or ether nitrile. In some embodiments, the electrolyte further includes a lithium salt including lithium bis (fluorosulfonyl) imide and lithium hexafluorophosphate, the concentration of the lithium salt is 1mol/L to 2mol/L, and the mass ratio of the lithium bis (fluorosulfonyl) imide to the lithium hexafluorophosphate is 0.06 to 5. In some embodiments, the electrolyte may also include a non-aqueous solvent. The nonaqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC) or combinations thereof. Examples of the fluorocarbonate compound are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 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, trifluoromethyl ethylene 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, gamma-butyrolactone, decalactone, valerolactone, mevalonic acid lactone, caprolactone, methyl formate, or combinations thereof.
Examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, or combinations thereof.
Examples of other organic solvents are dimethyl sulfoxide, 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 phosphoric acid esters or combinations thereof.
Embodiments of the present application also provide an electronic device including the above electrochemical device. 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 telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-compact disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power assisted bicycle, a bicycle, an unmanned aerial vehicle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash, a camera, a household large battery, a lithium ion capacitor, and the like.
The following examples and comparative examples are set forth to better illustrate the present application, with lithium ion batteries being used as an example.
Comparative example 1
Preparing a negative electrode plate: artificial graphite as a cathode active material, polyvinylidene fluoride as a binder and sodium carboxymethyl cellulose according to the weight ratio of 97.5:2.1: a ratio of 0.44 was dissolved in deionized water to form a first slurry. The first slurry was coated on one side of a negative electrode current collector using a copper foil of 6 μm thickness, the coating weight being 0.086mg/mm 2 A first layer is formed. Artificial graphite as a cathode active material, si, polyacrylic acid as a binder, carbon nano tubes and sodium carboxymethyl cellulose according to the weight ratio of 59.7:36:3.5:0.4: a ratio of 0.4 was dissolved in deionized water to form a second slurry. The second slurry was coated on the other side of the negative electrode current collector with a coating weight of 0.035.5mg/mm 2 A second layer is formed. And drying, cold pressing and cutting to obtain the negative electrode plate.
Preparing a positive electrode plate: the positive electrode active material lithium cobaltate, a conductive agent and a binder polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of 97.6:1.1:1.3 in an N-methylpyrrolidone (NMP) solution to form a positive electrode slurry. An aluminum foil 8 μm thick was used as a positive electrode current collector, and positive electrode slurry was coated on both sides of the positive electrode current collector, with a coating thickness of 50 μm. And drying, cold pressing and cutting to obtain the positive pole piece.
Preparation of a separation film: the base material of the isolating film is Polyethylene (PE) with the thickness of 8 mu m, two sides of the base material of the isolating film are respectively coated with 2 mu m alumina ceramic layers, and finally two sides coated with the ceramic layers are respectively coated with 2.5mg of adhesive polyvinylidene fluoride (PVDF) and dried.
Preparation of electrolyte: lithium hexafluorophosphate and a nonaqueous organic solvent (ethylene carbonate (EC): propylene Carbonate (PC): polypropylene (PP): diethyl carbonate (DEC) =1:1:1:1, mass percent) were formulated into an electrolyte having a lithium salt concentration of 1.15mol/L under an environment with a water content of less than 10 ppm.
Preparation of a lithium ion battery: sequentially stacking the positive pole piece, the isolating film and the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece to play a role of isolation, and winding to obtain the electrode assembly. And placing the electrode assembly in an outer packaging aluminum plastic film, dehydrating at 80 ℃, injecting the electrolyte, packaging, and carrying out the technological processes of formation, degassing, shaping and the like to obtain the lithium ion battery.
Comparative example 2 and examples 1 to 11 differ in the preparation of the negative electrode sheet, specifically the parameters of the first and second layers, as detailed in tables 1 and 2.
In addition, in the present application, the following method was used to measure the corresponding parameters, and the effective area of the single-layered laminated battery used in the present application was 49.5×42mm 2 。
1) Discharging the battery to 3.0V, disassembling to obtain a positive electrode plate and a negative electrode plate, soaking dimethyl carbonate (DMC) solution for 15min, and drying for later use;
2) The glove box is dried in inert gas environment, a single-layer laminated battery is manufactured by taking the positive pole piece, the negative pole piece punching piece and the positive and negative pole matching in the 1), sealing and filling a liquid, carrying out pressure clamp to keep interface contact, carrying out constant-current charging to a charging cut-off voltage, then carrying out constant-voltage charging until the battery reaches a full charge state, carrying out cut-off current of 0.02C, carrying out direct current discharging to 3.0V to obtain the capacity of the single-layer laminated battery, calculating to obtain the unit area capacity of the negative pole piece (the unit area capacity of the negative pole piece=the capacity of the single-layer laminated battery/the effective area of the single-side laminated battery), calculating to obtain the capacity of the negative pole piece according to the active coating area of the negative pole piece, and repeating the method to obtain the capacity of the other side;
3) Rs+rct (Rs refers to ohmic impedance, rct refers to electrochemical transfer impedance) can be obtained by testing the single-layer laminated battery in the 2) by using an alternating current impedance method, and the absolute value of rs+rct may be different due to the influence of other conditions such as the area of the manufactured single-layer laminated battery and the manufacturing process, but the ratio of rs+rct at two sides of the electrode can be used as the basis of shunting at two sides of the electrode.
4) Capacity retention rate after 500 weeks of cycle = capacity after 500 weeks of cycle/fresh battery capacity, capacity test conditions were constant current charging to 4.5V at 25 ℃, then constant voltage charging to 0.02C, then direct current discharging to 3.0V at 0.2C as one cycle for 500 cycles in total.
5) Constant-current charging the lithium ion battery to 4.45V at a multiplying power of 0.2C, and then constant-voltage charging to 0.02C to finish full charge of the lithium ion battery; and then constant-current discharge is carried out by using a multiplying power of 0.2C until the voltage is reduced to 3.0V, the total capacity discharged in the discharge process is recorded as C and a voltage platform U, the actual thickness, length and width of the lithium ion battery are measured, and the actual volume V of the lithium ion battery is calculated, and the energy density=C×U/V.
Tables 1 and 2 show the respective parameters and evaluation results of examples 1 to 11 and comparative examples 1 to 4.
TABLE 1
Figure BDA0004146273300000081
TABLE 2
Figure BDA0004146273300000082
Figure BDA0004146273300000091
As is apparent from the comparison of examples 1 to 3 and comparative examples 1 to 2, when the ratio of the impedance of the first layer to the impedance of the second layer is 0.7 to 0.9, the energy density loss of the lithium ion battery is small, and the improvement effect of the capacity retention rate of the lithium ion battery is remarkable. In addition, as the silicon mass content of the second layer decreases, the capacity retention rate of the lithium ion battery tends to increase first and then decrease.
As is clear from comparative examples 4 to 6, as the content of the conductive agent in the second layer increases, the impedance of the second layer tends to decrease, and the capacity retention rate of the lithium ion battery tends to decrease.
As is clear from the comparison of examples 7 to 11, as the ratio of the capacity of the first layer and the capacity of the second layer increases, the energy density of the lithium ion battery tends to decrease, and the capacity retention rate of the lithium ion battery tends to increase first and then decrease.
The foregoing description is only of the preferred embodiments of the present application and is presented as a description of the principles of the technology being utilized. It should be understood by those skilled in the art that the scope of the disclosure in this application is not limited to the specific combination of the above technical features, but also covers other technical features formed by any combination of the above technical features or their equivalents. Such as the technical proposal formed by the mutual replacement of the above-mentioned characteristics and the technical characteristics with similar functions disclosed in the application.

Claims (12)

1. An electrochemical device, comprising:
the negative electrode plate comprises a negative electrode current collector, a first layer and a second layer, wherein the negative electrode current collector is positioned between the first layer and the second layer;
wherein the first layer includes a first anode active material, the second layer includes a second anode active material, the first anode active material includes graphite, the second anode active material includes graphite and a silicon-based material, and a ratio of an impedance of the first layer to an impedance of the second layer is 0.7 to 0.9.
2. The electrochemical device according to claim 1, wherein a ratio of a capacity of the first layer to a capacity of the second layer is 0.6 to 1.
3. The electrochemical device according to claim 1, wherein a ratio of a capacity of the first layer to a capacity of the second layer is 0.7 to 1.
4. The electrochemical device of claim 1, wherein the mass percentage of the silicon-based material in the second layer is 6% to 40%.
5. The electrochemical device of claim 1, wherein the mass percent of the silicon-based material in the second layer is 12% to 20%.
6. The electrochemical device according to claim 4, wherein the mass percentage of silicon in the second layer is 4% to 20%.
7. The electrochemical device according to claim 5, wherein the mass percentage of silicon in the second layer is 4% to 10%.
8. The electrochemical device of claim 4, wherein the second layer further comprises a binder, the mass percentage of the binder in the second layer being 1.4% to 5%.
9. The electrochemical device of claim 4, wherein the second layer further comprises carbon nanotubes, the mass percent of the carbon nanotubes in the second layer being 0.3% to 0.7%.
10. The electrochemical device of claim 4, wherein the second layer further comprises sodium carboxymethyl cellulose, the sodium carboxymethyl cellulose in the second layer being 0.3 to 0.7 mass%.
11. The electrochemical device of claim 1, wherein the silicon-based material comprises at least one of silicon, a silicon-carbon material, or a silicon oxygen material.
12. An electronic device comprising the electrochemical device according to any one of claims 1 to 11.
CN202310303762.8A 2023-03-27 2023-03-27 Electrochemical device and electronic device Pending CN116314608A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116504923A (en) * 2023-06-28 2023-07-28 宁德新能源科技有限公司 Electrochemical device, electronic device and preparation method of negative electrode plate

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116504923A (en) * 2023-06-28 2023-07-28 宁德新能源科技有限公司 Electrochemical device, electronic device and preparation method of negative electrode plate
CN116504923B (en) * 2023-06-28 2023-09-19 宁德新能源科技有限公司 Electrochemical device, electronic device and preparation method of negative electrode plate

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