CN114497557A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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CN114497557A
CN114497557A CN202111599163.2A CN202111599163A CN114497557A CN 114497557 A CN114497557 A CN 114497557A CN 202111599163 A CN202111599163 A CN 202111599163A CN 114497557 A CN114497557 A CN 114497557A
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active material
nanoparticles
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陶威
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Dongguan 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
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Abstract

Embodiments of the present application provide an electrochemical device and an electronic device. The electrochemical device comprises a negative pole piece, wherein the negative pole piece comprises a negative active material layer, the negative active material layer comprises a negative active material and nanoparticles, and the nanoparticles comprise at least one of Sn, Ag, Au, Pt or Ni. The negative active material layer comprises the nano particles, so that more small pores can be formed in the negative active material layer, and the infiltration speed of the electrolyte in the negative pole piece is obviously improved.

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, the requirements for energy density and cycle performance of electrochemical devices (e.g., lithium ion batteries) are increasing. In order to increase the energy density of the electrochemical device, the compaction density and the coating weight of the negative electrode sheet are generally increased, which easily causes poor electrolyte infiltration. Therefore, improving the electrolyte wetting becomes an important aspect for improving the energy density and cycle performance of the electrochemical device.
Disclosure of Invention
The application provides an electrochemical device, electrochemical device includes negative pole piece, and negative pole piece includes negative pole active material layer, and negative pole active material layer includes negative pole active material and nanoparticle, and the nanoparticle includes at least one in Sn, Ag, Au, Pt or Ni.
In some embodiments, the nanoparticles are distributed throughout the anode active material layer. In some casesIn an embodiment, the negative electrode sheet further includes a negative electrode current collector, the negative active material layer includes a first layer and a second layer, the first layer is disposed between the negative electrode current collector and the second layer, the negative active material includes a first negative active material and a second negative active material, the first layer includes the first negative active material, and the second layer includes the second negative active material and nanoparticles. In some embodiments, the nanoparticles comprise surface-modified nanoparticles. In some embodiments, the surface-modified nanoparticle comprises XaN and X comprise at least one of Sn, Ag, Au, Pt or Ni, N comprises at least one of Cl, F, O, I or S, and a is more than or equal to 1 and less than or equal to 4. In some embodiments, the surface-modified nanoparticle comprises a core portion comprising X and a coating layer disposed on a surface of the core portion, the coating layer comprising XaN, X comprises at least one of Sn, Ag, Au, Pt or Ni, N comprises at least one of Cl, F, O, I or S, and a is more than or equal to 1 and less than or equal to 4. In some embodiments, the nanoparticles have an average particle size of 2nm to 100 nm. In some embodiments, the mass content of the nanoparticles in the negative electrode active material layer is 0.1% to 1%. In some embodiments, the mass content of nanoparticles in the second layer is 0.1% to 1%. In some embodiments, the negative active material comprises at least one of hard carbon, soft carbon, mesocarbon microbeads, silicon carbon, silicon oxygen, or phosphorus. In some embodiments, the electrochemical device further includes an electrolyte, and the contact angle of the negative active material layer with the electrolyte is 15 ° to 30 °.
Embodiments of the present application also provide an electronic device including the electrochemical device described above.
According to the cathode electrode, the cathode active material layer comprises the nano particles, wherein the nano particles comprise at least one of Sn, Ag, Au, Pt or Ni, so that more small pores can be formed in the cathode active material layer, and the infiltration speed of electrolyte in the cathode pole piece is obviously improved.
Drawings
Fig. 1 illustrates a schematic view of an anode active material layer according to some embodiments of the present application.
Fig. 2 illustrates a schematic structural view of a negative pole piece according to some embodiments of the present application.
Fig. 3 illustrates a schematic view of an anode active material layer according to some embodiments of the present application.
Fig. 4 illustrates a schematic of contact angle measurement of an electrolyte on a negative pole piece according to some embodiments of the present application.
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.
The infiltration of the electrolyte on the negative pole piece relates to solid, liquid and gas three-phase contact. The infiltration of the electrolyte is different from lithium ion diffusion, and the infiltration of the electrolyte is that various components such as solvent molecules, additives, lithium ions and the like in the electrolyte are transmitted into the negative pole piece through the pores on the negative pole piece and are mainly related to the pore structure and affinity of the negative pole piece; the diffusion speed of lithium ions is related to the tortuosity and porosity of pores, and only the length of a path for the lithium ions to diffuse from the surface of the negative pole piece to the inside of the negative pole piece is related. When the electrolyte is injected into the lithium ion battery, the electrolyte is firstly discharged out of the air in the shell, then the electrolyte can be attached to the surfaces of the positive pole piece and the negative pole piece, and some electrolyte can enter the space between the positive pole piece, the isolating membrane and the negative pole piece through the isolating membrane of the lithium ion battery. The phenomenon that the negative pole piece is soaked by the electrolyte and the negative pole piece is reversely soaked by the electrolyte in the isolating membrane can occur along with the time, when the standing time is long to a certain degree, the soaking of the negative pole piece is in a balanced state under the action of surface tension, the concept of a contact angle can be introduced in the process, the smaller the contact angle is, the higher the corresponding soaking speed is, and the soaking efficiency of the electrolyte is higher.
Some embodiments of the present application provide an electrochemical device comprising a negative electrode tab comprising a negative active material layer. In some embodiments, as shown in fig. 1, the negative active material layer 10 includes a negative active material 101 and nanoparticles 102, the nanoparticles 102 including at least one of Sn, Ag, Au, Pt, or Ni.
By introducing the nanoparticles 102 into the negative active material layer 10, more small pores can be formed in the negative active material layer 10, so that the infiltration speed of the electrolyte inside the negative pole piece is obviously improved. In some embodiments, the negative active material 101 includes at least one of hard carbon, soft carbon, mesocarbon microbeads, silicon carbon, silicon oxygen, or phosphorus.
In some embodiments, as shown in fig. 1, the nanoparticles 102 are not distributed only on the surface of the anode active material layer 10, but are distributed (typically, uniformly distributed) throughout the anode active material layer 10. In some embodiments, the negative active material 101, the nanoparticles 102, and other materials in the negative active material layer 10 are uniformly mixed. By distributing the nanoparticles 102 throughout the negative active material layer 10, more small pores can be formed in the entire negative active material layer 10, so that the infiltration speed of the electrolyte inside the negative electrode plate is obviously improved, and the surface infiltration of the electrolyte on the negative active material layer 10 is facilitated.
In some embodiments, as shown in fig. 2, the negative electrode tab further includes a negative electrode collector 9, and the negative active material layer 10 includes a first layer 11 and a second layer 12, the first layer 11 being disposed between the negative electrode collector 9 and the second layer 12. It should be understood that although fig. 2 shows that the first layer 11 and the second layer 12 are located only on one side of the negative electrode collector 9, this is merely exemplary, and the first layer 11 and/or the second layer 12 may also be present on the other side of the negative electrode collector 9. In some embodiments, the negative current collector 9 may employ at least one of a copper foil, a nickel foil, or a carbon-based current collector. In some embodiments, the thickness of the negative electrode current collector 9 may be 5 μm to 20 μm, but this is merely exemplary, and other suitable thicknesses may also be employed.
In some embodiments, the negative electrode active material includes a first negative electrode active material 1011 and a second negative electrode active material 1012, the first layer 11 includes the first negative electrode active material 1011, and the second layer 12 includes the second negative electrode active material 1012 and the nanoparticles 102. In some embodiments, the first negative active material 1011 and the second negative active material 1012 may each independently include at least one of hard carbon, soft carbon, mesocarbon microbeads, silicon carbon, silicon oxygen, or phosphorus. In some embodiments, the nanoparticles 102 are distributed throughout the second layer 12. By introducing the nanoparticles 102 in the second layer 12, which is closer to the electrolyte than the first layer 11, the impregnation of the electrolyte in the negative electrode sheet is also facilitated.
In some embodiments, the nanoparticles 102 have an average particle size of 2nm to 100 nm. By adopting the nano particles with smaller particle size, more small pores can be formed in the negative active material layer, and the infiltration speed of the electrolyte in the negative pole piece is further improved. In some embodiments, the nanoparticles 102 have an average particle size of 2nm to 50 nm. If the average particle diameter of the nanoparticles 102 is too large, small pores are less constructed in the anode active material layer; if the average particle size of the nanoparticles 102 is too small, the pores formed are too small to facilitate the electrolyte to infiltrate into the negative active material layer.
In some embodiments, the mass content of the nanoparticles 102 in the anode active material layer 10 is 0.1% to 1%. In some embodiments, the mass content of nanoparticles 102 in second layer 12 is 0.1% to 1%. If the mass content of the nanoparticles 102 is too small, the effect of improving the wetting of the electrolyte is relatively limited; if the mass content of the nanoparticles 102 is too large, it is not advantageous to increase the energy density of the electrochemical device since the nanoparticles cannot function as a negative active material. When the nanoparticles are not added to the negative electrode active material layer, the contact angle of the negative electrode active material layer with the electrolyte is about 30 ° to 40 °. When the nanoparticles are added to the negative electrode active material layer in an amount of 0.1 to 1% by mass, the contact angle of the negative electrode active material layer with the electrolyte decreases to 15 ° to 30 °.
In some embodiments, the nanoparticles 102 comprise surface-modified nanoparticles. The negative active material (such as graphite, hard carbon, silicon and the like) generally has certain repellency to oily substances, and the surface of the nano particles is coated with a layer of groups through surface modification treatment on the nano particles, and the groups are oleophilic and have stronger wettability to the electrolyte, so that the electrolyte can be further improvedAnd (5) infiltrating. When the surface-modified nanoparticles are added to the negative active material layer in an amount of 0.1 to 1% by mass, the contact angle of the negative active material layer with the electrolyte decreases to 5 ° to 15 °. In some embodiments, the surface of the nanoparticles may be modified by chemical treatment, e.g., oxidation, e.g., Ag is oxidized to AgO, i.e., an O group may be attached to the surface of Ag. In some embodiments, the surface-modified nanoparticles comprise XaN, X comprises at least one of Sn, Ag, Au, Pt or Ni, N comprises at least one of Cl, F, O, I or S, and a is more than or equal to 1 and less than or equal to 4.
In some embodiments, the nanoparticles having surfaces modified with inorganic ions comprise a core portion and a coating layer disposed on the surface of the core portion, the core portion comprising X, the coating layer comprising XaN, X comprising at least one of Sn, Ag, Au, Pt, or Ni, N comprising at least one of Cl, F, O, I, or S, 1 ≦ a ≦ 4. In some embodiments, the surface-modified nanoparticle comprises a core-shell structure, the core portion being the core and the coating being the shell. In some embodiments, the core-shell structure may be formed by surface modification or surface coating, for example, a layer of AgO may be coated on the surface of Ag particles, resulting in AgO-coated Ag particles; AgO-coated Ag particles can also be obtained by surface oxidation of Ag particles. As shown in fig. 2 or 3, the surface-modified nanoparticles 102 are present in the anode active material layer 10 or the second layer 12.
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 negative active material, the conductive agent, and the binder in the negative active material layer may be (78 to 98.5): (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 electrochemical device includes an electrode assembly that may include a negative pole piece, a positive pole piece, and a separator disposed between the positive and negative pole pieces.
In some embodiments, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer. In some embodiments, the positive electrode current collector may be an aluminum foil, but other positive electrode current collectors commonly used in the art may also be used. In some embodiments, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector. 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 be coated only on a partial area of the positive electrode collector.
In some embodiments, the positive electrode active material layer may further include a positive electrode active material, a conductive agent, and a binder. In some embodiments, the conductive agent of the positive electrode sheet may include at least one of conductive carbon black, flake graphite, graphene, or carbon nanotubes. In some embodiments, the binder in the positive electrode sheet may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, a polyamide, polyacrylonitrile, a polyacrylate, a polyacrylic acid, a polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, a polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. In some embodiments, the positive active material includes, but is not limited to, at least one of lithium cobaltate, lithium nickelate, lithium nickel manganate, lithium nickel cobaltate, lithium iron phosphate, lithium nickel cobalt aluminate, or lithium nickel cobalt manganate. 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 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 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 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, the electrochemical device comprises a lithium ion battery, but the application is not so limited. In some embodiments, the electrochemical device further comprises an electrolyte comprising at least one of fluoroether, fluoroether 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 1 to 2mol/L, and the mass ratio of lithium bis (fluorosulfonyl) imide to lithium hexafluorophosphate is 0.06 to 5. In some embodiments, the electrolyte may further include a non-aqueous solvent. 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, gamma-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.
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, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notebook, 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 drone, 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.
Comparative example 1
Preparing a negative pole piece: the current collector adopts copper foil with the thickness of 8 mu m, the negative active material adopts artificial graphite, and the binder adopts styrene butadiene rubber and sodium carboxymethyl cellulose. Mixing a negative electrode active material, styrene butadiene rubber and sodium carboxymethylcellulose in a mass percentage of 96: 2: 2, dispersing the mixture in deionized water to form slurry, uniformly stirring the slurry, coating the slurry on a copper foil, drying the slurry to form a negative active material layer, wherein the thickness of the negative active material layer is 80 mu m, and performing cold pressing and stripping to obtain the negative pole piece.
Preparing a positive pole piece: mixing nickel cobalt lithium manganate, conductive carbon black and a binder polyvinylidene fluoride (PVDF) according to the mass percentage of 94.8: 2.8: and 2.4, fully stirring and uniformly mixing the mixture in an N-methylpyrrolidone solvent system, and coating the mixture on an aluminum foil with the thickness of 10 mu m to obtain a positive active material layer, wherein the thickness of the positive active material layer is 120 mu m. And drying and cold pressing to obtain the positive pole piece.
Preparing an isolating membrane: and stirring the polyacrylate to form uniform slurry, coating the slurry on the two side surfaces of the porous base material (polyethylene), and drying to form the isolating membrane.
Preparing an electrolyte: under the environment that the water content is less than 10ppm, lithium hexafluorophosphate and a nonaqueous organic solvent (ethylene carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC), Propyl Propionate (PP), Vinylene Carbonate (VC), wherein the mass percentage ratio of lithium hexafluorophosphate to the Vinylene Carbonate (VC) is 8: 92 was formulated to form an electrolyte having a lithium salt concentration of 1 mol/L.
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 105 ℃, injecting the electrolyte, packaging, and carrying out technological processes of formation, degassing, shaping and the like to obtain the lithium ion battery.
In other examples and comparative examples, the preparation of the positive electrode sheet, the separator, the electrolyte and the lithium ion battery were all substantially the same as in example 1, and only the preparation of the negative electrode sheet was somewhat different, with the differences in the parameters shown in the corresponding tables.
In addition, in the present application, the following method is employed to measure the corresponding parameters.
(1) Contact angle test: at 25 ℃, a small drop of electrolyte is titrated on the negative pole piece by a contact angle tester, and the contact angle theta of the liquid drop contacting the surface of the negative pole is captured by an LED light source and a CCD camera, as shown in FIG. 4.
(2) Liquid retention coefficient test: liquid retention coefficient is equal to liquid retention amount/battery capacity
The amount of liquid may be equal to the amount of electrolyte injected into the battery, or the amount of electrolyte extracted from the battery. The capacity of the battery is that the battery is fully charged at 25 ℃, and the specific steps are as follows, charging is carried out at 0.5 ℃ to the rated voltage of 4.48V, then charging is carried out at constant voltage until the current is reduced to 0.02C, standing is carried out for 20min, then discharging is carried out at 0.2C, discharging is carried out to 3V, and the discharging capacity is recorded.
(3) And (3) testing the cycle performance:
the lithium ion battery is placed in a thermostat with the temperature of 25 +/-2 ℃ for standing for 2 hours, and is charged to 4.48V at the rate of 1C, and then is charged to 0.05C at the constant voltage of 4.48V. And then, discharging to 3.0V at a rate of 1C to perform a cycle performance test, and taking the ratio of the capacity of the lithium ion battery after 500 cycles to the initial capacity as a parameter for evaluating the cycle performance of the lithium ion battery.
Comparative example 1 and examples 1 to 5
In example 1, in the negative active material layer, nanoparticles Ag were further included, and the mass ratio of the negative active material artificial graphite, styrene-butadiene rubber, sodium carboxymethyl cellulose, and Ag was 95: 2: 2: 1, otherwise the same as in comparative example 1. Examples 2 to 5 differ from example 1 only in the material of the nanoparticles used.
TABLE 1
Nanoparticles Particle size of nanoparticles Surface contact angle Cycle performance Liquid retention coefficient (g/Ah)
Comparative example 1 Is free of 35° 71.30％ 1.50
Example 1 Ag 15nm 20° 80.30％ 1.60
Example 2 Sn 15nm 30° 75.30％ 1.51
Example 3 Au 15nm 28° 77.40％ 1.52
Example 4 Pt 15nm 25° 78.30％ 1.52
Example 5 Ni 15nm 28° 77.10％ 1.52
It can be seen from comparing examples 1 to 5 and table 1 that by adding nanoparticles to the negative electrode active material layer, the surface contact angle between the electrolyte and the negative electrode sheet can be reduced, the cycle performance of the lithium ion battery can be improved, and the liquid retention coefficient of the lithium ion battery can be improved. In addition, the nanoparticles are added into the negative active material layer, the roughness of the surface of the negative pole piece can be improved by the nanoparticles, the surface tension of the electrolyte on the surface of the negative pole piece is reduced to a certain degree, and different metals have different lithium-philic characteristics and are different in infiltration of the electrolyte, so that the expressed contact angles are different, wherein the lithium-philic characteristics of Ag and Pt are better, so that the expressed contact angles are smaller, and the electrolyte is easier to infiltrate.
Examples 6 to 16
Examples 6 to 16 differ from example 1 only in that the nanoparticles used are surface chemically modified nanoparticles and/or differ in particle size.
TABLE 2
Figure BDA0003432456850000091
Figure BDA0003432456850000101
It can be seen from comparing examples 6 to 9 and example 1 that the affinity between the nanoparticles and the electrolyte can be enhanced by modifying the surface of the nanoparticles, thereby improving the wetting of the electrolyte, and the activity of the nanoparticles can be reduced after the surface modification of the nanoparticles, thereby improving the stability of the metal nanoparticles and reducing the side reaction, wherein Ag is used2The most compatible of O and AgF, the best effect of improving the wettability of the electrolyte and excellent circulating level.
As can be seen from comparing examples 10 to 16, the particle size of the modified nanoparticles also has an effect on the contact angle of the electrolyte on the negative electrode plate, wherein the smaller the particle size and the wider the distribution, the better the wetting effect on the electrolyte, but as the particle size becomes smaller, the activity of the nanoparticles also increases, so that the particle size too small also affects the degree of side reaction, resulting in the degradation of cycle performance. Therefore, small-particle size nanoparticles have an improving effect on electrolyte impregnation, but small-particle size nanoparticles also cause an increase in side reactions, and it is necessary to balance the influence of both on the cycle performance of the lithium ion battery.
Example 17
The negative active material layer of example 17 had a two-layer structure of an upper layer and a lower layer, the lower layer being closer to the negative current collector than the upper layer, the lower layer having the negative active material layer composition of comparative example 1, the upper layer having the negative active material layer composition of example 8, and the ratio of the thickness of the upper layer to the thickness of the lower layer being 1: 4.
TABLE 3
Nanoparticles Particle size of nanoparticles Surface contact angle Cycle performance Liquid retention coefficient (g/Ah)
Example 8 Ag2O-modified Ag 15nm 16° 82.20％ 1.65
Example 17 Ag2O-modified Ag 15nm 16° 83.20％ 1.66
By utilizing the double-layer coating technology, the upper layer accounts for 20 percent, the lower layer accounts for 80 percent, and the modified metal nano particles are added into the upper layer, so that the electrolyte infiltration can be effectively improved. Because the electrolyte must be infiltrated from the upper layer to the lower layer, the upper layer is the bottleneck of infiltration, the infiltration effect of the upper layer is improved, the electrolyte infiltration of the negative pole piece can be effectively improved, and the cycle performance of the lithium ion battery is improved; in addition, compared with a single-layer design, the double-layer design of the negative electrode active material layer reduces the using amount of the nano particles, and reduces side reactions, so that the cycle performance is further obviously improved. In addition, the use amount of the nano particles can be reduced, and the cost is saved.
Examples 18 to 23
Examples 18 to 23 differ from example 8 only in the content of each component of the anode active material layer employed.
TABLE 4
Figure BDA0003432456850000111
It can be seen from comparing example 8 with examples 18 to 23 that the content of the modified nanoparticles is directly related to the effect of improving the electrolyte wetting, and the higher the content of the nanoparticles is, the smaller the corresponding contact angle is, however, when the content of the modified nanoparticles is higher than 2%, the cycle performance of the lithium ion battery is obviously deteriorated, because the too high content of the modified metal nanoparticles causes a certain side reaction, which further affects the decay of the cycle performance.
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 features having similar functions disclosed in the present application are mutually replaced to form the technical solution.

Claims (10)

1. An electrochemical device, comprising:
the negative electrode plate comprises a negative active material layer, the negative active material layer comprises a negative active material and nanoparticles, and the nanoparticles comprise at least one of Sn, Ag, Au, Pt or Ni.
2. The electrochemical device of claim 1, wherein the negative electrode tab further comprises a negative electrode current collector, the negative active material layer comprises a first layer and a second layer, the first layer is disposed between the negative current collector and the second layer, the negative active material comprises a first negative active material and a second negative active material, the first layer comprises the first negative active material, the second layer comprises the second negative active material and the nanoparticles.
3. The electrochemical device of claim 1 or 2, wherein the nanoparticles comprise surface-modified nanoparticles comprising XaN, X comprises at least one of Sn, Ag, Au, Pt or Ni, N comprises at least one of Cl, F, O, I or S, and a is more than or equal to 1 and less than or equal to 4.
4. The electrochemical device of claim 1 or 2, wherein the nanoparticles comprise surface-modified nanoparticles comprising a core portion comprising X and a coating layer on a surface of the core portion comprising XaN, X comprises at least one of Sn, Ag, Au, Pt or Ni, N comprises at least one of Cl, F, O, I or S, and a is more than or equal to 1 and less than or equal to 4.
5. The electrochemical device according to claim 1 or 2, wherein the average particle diameter of the nanoparticles is 2nm to 100 nm.
6. The electrochemical device according to claim 1, wherein the mass content of the nanoparticles in the negative electrode active material layer is 0.1% to 1%.
7. The electrochemical device according to claim 2, wherein the mass content of the nanoparticles in the second layer is 0.1% to 1%.
8. The electrochemical device of claim 1, wherein the negative active material comprises at least one of hard carbon, soft carbon, mesocarbon microbeads, silicon carbon, silicon oxygen, or phosphorus.
9. The electrochemical device according to claim 1, further comprising an electrolyte, a contact angle of the negative electrode active material layer with the electrolyte is 15 ° to 30 °.
10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.
CN202111599163.2A 2021-12-24 2021-12-24 Electrochemical device and electronic device Pending CN114497557A (en)

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