WO2024113237A1 - 电极及其制备方法、电池和用电装置 - Google Patents

电极及其制备方法、电池和用电装置 Download PDF

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WO2024113237A1
WO2024113237A1 PCT/CN2022/135503 CN2022135503W WO2024113237A1 WO 2024113237 A1 WO2024113237 A1 WO 2024113237A1 CN 2022135503 W CN2022135503 W CN 2022135503W WO 2024113237 A1 WO2024113237 A1 WO 2024113237A1
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active layer
electrode
current collector
porosity
pore
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PCT/CN2022/135503
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English (en)
French (fr)
Inventor
郑蔚
武宝珍
王育文
游兴艳
白文龙
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宁德时代新能源科技股份有限公司
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Priority to CN202280013357.6A priority Critical patent/CN117461155A/zh
Priority to PCT/CN2022/135503 priority patent/WO2024113237A1/zh
Publication of WO2024113237A1 publication Critical patent/WO2024113237A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of 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
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of 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
    • 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

Definitions

  • the present application relates to the field of battery technology, and in particular to an electrode and a preparation method thereof, a battery and an electrical device.
  • the embodiments of the present application provide an electrode and a method for preparing the electrode, a battery and an electrical device to solve the technical problem of poor liquid phase transport capacity of the electrode.
  • an embodiment of the present application provides an electrode.
  • the electrode of the embodiment of the present application includes a current collector and an active layer combined with the current collector, the active layer includes a first active layer and a second active layer, the first active layer is combined with the current collector, the second active layer is combined on the surface of the first active layer away from the current collector, and the porosity of the second active layer is greater than the porosity of the first active layer.
  • the electrode of the embodiment of the present application effectively increases the contact area between the active layer and the electrolyte through the second active layer contained therein, and effectively enriches the lithium ion migration channel and transmission space, increases the lithium ion transmission rate, and improves the kinetic performance of lithium ion migration, thereby significantly improving the liquid phase transport capacity of the electrode of the embodiment of the present application, thereby improving the fast charging capability of the electrode of the embodiment of the present application; and the presence of the first active layer, which works together with the second active layer, endows the electrode of the embodiment of the present application with a high energy density, high structural stability, excellent cycle performance, and can effectively avoid polarization and lithium plating, thereby improving the safety of the battery.
  • the porosity of the second active layer is more than 30% higher than the porosity of the first active layer.
  • the porosity of the second active layer is 40% to 95% higher than the porosity of the first active layer.
  • Controlling the porosity difference between the two active layers within this range can reduce the migration path of lithium ions in the active layer contained in the electrode of the embodiment of the present application and increase the lithium ion transmission space, thereby further increasing the liquid phase transport capacity of the active layer and improving the fast charging capability.
  • the average porosity of the second active layer is 25% to 55%.
  • the diameter of the pores in the second active layer is 5-20 ⁇ m.
  • the porosity of the first active layer can be indirectly controlled, and the synergistic effect between the two active layers can be improved, thereby further increasing the liquid phase transport capacity of the active layer 20 and improving the fast charging capability.
  • the porosity of the second active layer increases in a gradient along the surface direction away from the current collector.
  • the porosity of the second active layer By controlling the porosity of the second active layer to be distributed in a gradient in this direction, the migration rate and transmission space of lithium ions into the active layer can be further increased.
  • the total thickness of the first active layer and the second active layer is not less than 40 ⁇ m.
  • the second active layer has a thickness of 10-60 ⁇ m.
  • This thickness range can effectively increase the energy density of the active layer, and has rich porosity, which can control the effective migration path of lithium ions into the active layer.
  • the particle size Dv50 of the active material contained in the first active layer is greater than the particle size Dv50 of the active material contained in the second active layer.
  • the active material contained in the second active layer includes a first active material and a second active material, and the particle size Dv50 of the first active material is greater than 30% different from the particle size Dv50 of the second active material.
  • the first active layer and/or the second active layer comprises the following components in percentage by weight:
  • the ratio of the first active layer to the second active layer within this range enables the active layer to have high energy density and low internal resistance.
  • the electrode is a positive electrode, and the active material contained in the active layer is a positive electrode active material; or the electrode is a negative electrode, and the active material contained in the active layer is a negative electrode active material.
  • the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof.
  • the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate.
  • the binder includes at least one of polyvinylidene fluoride, styrene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan.
  • the conductive agent includes at least one of acetylene black, superconducting carbon, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the dispersant includes sodium carboxymethyl cellulose.
  • the electrode active materials, binders, conductive agents and dispersants can act synergistically to improve the layer structure and electronic conductivity of the active layer.
  • the electrode is a negative electrode
  • the active material contained in the second active layer includes amorphous carbon
  • the present invention provides a method for preparing an electrode.
  • the method for preparing an electrode in the present invention comprises the following steps:
  • the surface electrode active layer of the electrode active layer facing away from the current collector is subjected to pore formation treatment to form a porous structure in the surface electrode active layer, so that the porosity of the surface electrode active layer is greater than the porosity of the inner electrode active layer close to the current collector.
  • the preparation method of the present application performs pore-forming treatment on the surface electrode active layer of the electrode active layer so that the surface electrode active layer forms a porous structure with abundant pores. And its porosity is higher than the porosity of the inner electrode active layer close to the current collector and not subjected to pore-forming treatment, thereby giving the prepared electrode the electrode characteristics of the above text application embodiment, such as having a large contact area with the electrolyte, having a high liquid phase transport capacity and fast charging capacity, and the prepared electrode has a high energy density, structural stability, and excellent cycle performance.
  • the electrode preparation method of the embodiment of the present application can ensure that the prepared electrode structure and electrochemical performance are stable, and the efficiency is high, saving production costs.
  • the material of the surface electrode active layer contains a pore former, and the pore former is dispersed in the surface electrode active layer so that the pore former forms pores during the pore forming process, thereby forming a porous structure in the surface electrode active layer.
  • the content of the pore former in the surface electrode active layer is 8wt% to 20wt% of the solid content of the active layer slurry forming the surface electrode active layer.
  • the thickness of the surface electrode active layer is 10 to 60 ⁇ m.
  • the pore-forming agent includes at least one of ammonium bicarbonate, ammonium carbonate, ammonium chloride, polymethyl methacrylate, starch, and polyvinyl pyrrolidone. These pore-forming agents have thermal decomposition characteristics, and thus, can be decomposed by appropriate heat treatment.
  • the pore forming treatment is to heat treat the surface electrode active layer to decompose the pore forming agent.
  • the heat treatment can decompose the pore forming agent in the surface electrode active layer, thereby forming a porous structure in situ in the surface electrode active layer.
  • the heat treatment temperature is 70° C. to 150° C. At this temperature, the pore former can be effectively decomposed, leaving a porous structure with abundant pores in the surface electrode active layer.
  • the method for forming an electrode active layer on a current collector comprises the following steps:
  • the second electrode slurry containing the pore-forming agent forms a wet film on the surface of the inner electrode active layer away from the current collector, and after drying and rolling, forms the surface electrode active layer combined with the inner electrode active layer.
  • the distribution of the pore former can be effectively controlled, and ultimately the distribution depth, structure and uniformity of the porous structure in the active layer can be controlled.
  • the second electrode slurry is a plurality of portions, in which the content of the pore former increases in a gradient, and the plurality of portions of the second electrode slurry are sequentially treated on the surface of the inner electrode active layer in the order of the content of the pore former from low to high to form the wet film.
  • the second electrode slurry is set with a gradient content of the pore former, so that the content of the pore former changes in a gradient in the formed surface electrode active layer.
  • the present application provides a battery.
  • the battery of the present application includes a positive electrode and a negative electrode, wherein the positive electrode is an electrode of the above-mentioned embodiment of the application or an electrode prepared by the electrode preparation method of the above-mentioned embodiment of the application, and the active material contained in the active layer of the electrode is a positive electrode material; and/or
  • the negative electrode is the electrode of the above-mentioned application embodiment or an electrode prepared by the electrode preparation method of the above-mentioned application embodiment, and the active material contained in the active layer of the electrode is a negative electrode material.
  • the battery of the embodiment of the present application contains the electrode of the embodiment of the above text application. Therefore, the battery of the embodiment of the present application has good cycle performance, can be fast charged, has strong fast charging capability, and at the same time improves the safety performance of the battery.
  • the present application provides an electric device.
  • the electric device of the present application includes a battery of the present application, and the battery is used to provide electric energy.
  • the electric device of the embodiment of the present application contains the battery of the embodiment of the above-mentioned application, so the electric device has a long battery life, can be quickly charged, and is highly safe.
  • Figure 1 is an electron microscope image of the current electrode active layer by ion beam cross section polishing (CP);
  • FIG2 is a schematic diagram of the structure of an electrode having an active layer on one side according to an embodiment of the present application
  • FIG3 is a schematic diagram of the structure of an electrode with active layers on both sides according to an embodiment of the present application
  • FIG3A is a schematic diagram of the structure of a pore structure
  • FIG3B is a schematic diagram of the structure of another pore structure
  • FIG4 is a schematic diagram of a process for preparing an electrode according to an embodiment of the present application.
  • FIG5 is a schematic structural diagram of an implementation of a battery cell according to an embodiment of the present application.
  • FIG6 is an exploded schematic diagram of the battery cell shown in FIG5 ;
  • FIG7 is a schematic structural diagram of an implementation scheme of a battery module according to an embodiment of the present application.
  • FIG8 is a schematic structural diagram of an implementation scheme of a battery pack according to an embodiment of the present application.
  • FIG9 is a schematic diagram of the exploded structure of the battery pack shown in FIG8 ;
  • FIG. 10 is a schematic diagram of an embodiment of an electrical device including a battery according to an embodiment of the present application as a power source.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • the active layer in the embodiment of the present application refers to the active layer contained in the electrode, which at least contains the structure of the electrode active material and is combined with the current collector.
  • Porosity refers to the percentage (%) of the total pore volume in the active layer to the total volume of the active layer.
  • Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations
  • electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields.
  • the market demand is also constantly expanding, and at the same time, the requirements for battery cycle performance, fast charging capability, high power and other performance are becoming higher and higher.
  • the surface pore structure deteriorates, resulting in poor liquid phase transport capacity, such as hindering the rate of lithium ion migration into the active layer, including hindering the transport of lithium ions diffused from the positive electrode to the inside of the negative electrode, resulting in further deterioration of the lithium salt concentration gradient in the thickness direction of the negative electrode, thereby deteriorating the kinetics of lithium ion migration, and also resulting in poor fast charging capacity, so it needs to be improved.
  • the transmission of lithium ions in the battery electrolyte in the active layer contained in the current electrode has become the shortest link in the entire kinetic process with the lowest efficiency.
  • the thickness or compaction density of the active layer is large, that is, it has a longer transmission path or a smaller transmission space (low porosity), which makes this problem more prominent.
  • due to the low transmission rate a large lithium ion concentration gradient will be formed, which makes lithium deposition more likely to occur on the negative electrode diaphragm side, increasing the risk of short circuit in the battery.
  • the active layer contained in the thick electrode is subjected to micro-pore processing, such as laser or mechanical pore processing.
  • micro-pore processing such as laser or mechanical pore processing.
  • the inventors have found that whether it is laser drilling or mechanical drilling, the hole is a vertical or nearly vertical channel distributed along the thickness direction of the electrode sheet. Although it has a certain improvement on the migration of lithium ions into the active layer, the effect is not obvious; and its industrialization process is complicated, which greatly increases the process cost; at the same time, laser drilling or mechanical drilling may destroy the layer structure of the active layer and the structure of the active particles contained therein, resulting in the active layer falling off, performance deterioration, and poor cycle performance.
  • a powdered thermal decomposition additive is additionally added to the electrode slurry, the prepared electrode slurry is coated on the current collector to obtain a lithium ion battery wet electrode sheet, and the lithium ion battery wet electrode sheet is heated and dried to prepare a lithium ion battery electrode sheet with a vertical pore structure.
  • the electrode structure formed is such as the electrode formed by the laser or laser drilling mentioned above, which does not significantly improve the migration of lithium ions into the active layer, and the pores are formed in the area close to the current collector, resulting in a decrease in the electrode energy density.
  • the inventor further discovered that by improving the structure of the active layer, specifically improving the porosity distribution of the active layer, the liquid phase transport capacity of the active layer contained in the electrode can be significantly improved, and the fast charging capability can be improved. Therefore, the following electrode and preparation method are proposed to significantly improve the effect of the electrode on the migration of lithium ions into the active layer, ensure the high energy density and cycle performance of the electrode, and improve the fast charging capability.
  • the embodiment of the present application provides an electrode.
  • the electrode of the embodiment of the present application includes a current collector 10 and an active layer 20 combined with the current collector; wherein the active layer 20 includes a first active layer 21 and a second active layer 22, the first active layer 21 is combined with the current collector 10, the second active layer 22 is combined on the surface of the first active layer 21 away from the current collector 10, and the porosity of the second active layer 22 is greater than the porosity of the first active layer 21.
  • the first active layer 21 and the second active layer 22 together constitute the active layer 20 contained in the electrode of the embodiment of the present application.
  • the active layer 20 can be combined on one surface of the current collector 10, as shown in Figure 2, and of course, the active layer 20 can also be combined on two opposite surfaces of the current collector 10, as shown in Figure 3.
  • the porosity of the second active layer 22 contained in the electrode of the embodiment of the present application is greater than the porosity of the first active layer 21, and the second active layer 22 is arranged on the outer surface of the active layer 20 contained in the electrode, so that the presence of the second active layer 22 and its combination position effectively increase the contact area between the active layer 20 and the electrolyte, and effectively enrich the lithium ion migration channel and transmission space, increase the lithium ion transmission rate, and improve the kinetic performance of lithium ion migration, thereby significantly improving the liquid phase transport capacity of the electrode of the embodiment of the present application, thereby improving the fast charging capacity of the electrode of the embodiment of the present application; and the porosity of the first active layer 21 is lower than that of the above-mentioned second active layer 22, so it has a high compaction density.
  • the first active layer 21 and the second active layer 22 work together to give the electrode of the embodiment of the present application a high energy density, high structural stability, excellent cycle performance, and can effectively avoid polarization and lithium precipitation, thereby improving the safety of the battery. Furthermore, the first active layer 21 is directly combined with the current collector 10 and disposed inside the electrode. Therefore, the first active layer 21 with relatively low porosity does not affect the liquid phase transport capability and fast charging capability of the electrode.
  • the porosity of the second active layer 22 is higher than the porosity of the first active layer 21 by more than 30%, and can be further higher by 40% to 95%.
  • the porosity difference can be controlled to be higher by 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc., which are typical but non-limiting porosity differences.
  • the migration path of lithium ions in the active layer 20 contained in the electrode of the embodiment of the present application can be reduced and the lithium ion transmission space can be increased, thereby further increasing the liquid phase transport capacity of the active layer 20 and improving the fast charging capability.
  • the average porosity of the second active layer 22 is 25% to 55%. In the exemplary examples, the porosity may be 25%, 30%, 35%, 40%, 45%, 50%, 55%, and other typical but non-limiting porosities.
  • the diameter of the pores contained in the second active layer 22 may be 5 to 20 ⁇ m, and may further be 10 to 15 ⁇ m. In the exemplary examples, the pore diameters may be 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 17 ⁇ m, 20 ⁇ m, and other typical but non-limiting pore diameters.
  • the porosity of the second active layer 22 may be indirectly controlled, and the synergistic effect between the two active layers may be improved, thereby further increasing the liquid phase transport capacity of the active layer 20 and improving the fast charging capacity.
  • the porosity contained in the second active layer 22 increases in a gradient along the surface direction away from the current collector 10. That is, in the direction from the surface of the second active layer 22 in contact with the first active layer 21 to the surface direction away from the first active layer 21, the porosity gradient of the second active layer 22 increases, that is, the pores become more and more abundant or the pore diameter gradually increases.
  • the porosity of the second active layer 22 By controlling the porosity of the second active layer 22 to be distributed in a gradient in this direction, the contact and wetting area between the electrolyte and the active layer 20 can be further increased, and the migration rate and transmission space of lithium ions into the active layer 20 can be increased, thereby further improving the liquid phase transport capacity of the active layer 20, and further improving the fast charging capacity.
  • the thickness of the second active layer 22 may be 10-60 ⁇ m, further 10-40 ⁇ m, and further 15-25 ⁇ m, and in the exemplary embodiment, the thickness may be 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, etc.
  • Typical but non-limiting thicknesses. This thickness range can control the effective migration path of lithium ions to the inside of the active layer 22, and improve the energy density of the electrode in the embodiment of the present application in combination with the first active layer 21.
  • the material contained in the second active layer 22 in the above embodiments must contain electrode active materials.
  • it can also contain conductive agents and binders to ensure that the second active layer 22 has high cycle performance and low internal resistance on the basis of high porosity.
  • the pore structure in the second active layer 22 may be a rich three-dimensional pore structure as shown in FIG. 3A , or may be a pore structure with openings facing away from the first active layer 21 as shown in FIG. 3B .
  • the particle size Dv50 of the active material contained in the second active layer 22 in the above embodiments is smaller than the particle size Dv50 of the active material contained in the first active layer 21.
  • the particle size Dv50 of the active material contained in the second active layer 22 is more than 30% smaller than the particle size Dv50 of the active material contained in the first active layer 21.
  • the second active layer 22 may include the following components in percentage by weight:
  • the active material contained in the second active layer 22 is a positive electrode active material; in the exemplary embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)
  • the active material contained in the second active layer 22 is a negative electrode active material.
  • the negative electrode active material may include at least one of carbon, silicon-based materials, tin-based materials and lithium titanate.
  • carbon may include at least one of natural graphite, artificial graphite, soft carbon and hard carbon
  • silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy materials
  • tin-based materials may include tin-based materials may include at least one selected from elemental tin, tin oxide and tin alloy materials.
  • These negative electrode materials have high electronic and ionic conductivity, and the second active layer 22 formed with components such as conductive agents and binders has a stable layer structure, and the porous structure contained is stable.
  • the binder contained in the second active layer 22 is at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin; when the electrode of the present application embodiment is a negative electrode, the binder contained in the second active layer 22 may include at least one of styrene rubber (SBR) (such as styrene-butadiene rubber), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chito
  • SBR styrene rubber
  • PAA polyacrylic
  • the conductive agent contained in the second active layer 22 includes at least one of acetylene black, superconducting carbon, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. These conductive agents can be evenly dispersed, and on the basis of giving the second active layer 22 high electronic conductivity, they can play a synergistic role with components such as active materials and binders, thereby improving the stability of the layer structure of the second active layer 22 and the porous structure contained therein.
  • the dispersant contained in the second active layer 22 may be, but is not limited to, sodium carboxymethyl cellulose (CMC). These dispersants can effectively improve the uniformity of the dispersion of the materials contained in the second active layer 22, thereby improving the mechanical uniformity of the layer structure of the second active layer 22 and the porous structure contained therein, and can improve the distribution uniformity of the pores contained in the porous structure.
  • CMC sodium carboxymethyl cellulose
  • the combination between the first active layer 21 and the second active layer 22 contained in the active layer 20 may be an in-situ combination formed by film formation directly on the surface of the first active layer 21.
  • the interface between the first active layer 21 and the second active layer 22 may be a transition layer formed by the materials of the respective layers, and the structures of the two layers are realized through the transition layer.
  • other structural forms may also be adopted.
  • the porosity of the first active layer 21 contained in the active layer 20 is lower than that of the second active layer 22, such as lower than 30% or more of the second active layer 22, and further lower than 40% to 95%.
  • This porosity range can further improve the relatively high compaction density of the first active layer 21, improve the high energy density of the active layer 20, and enhance the bonding strength between the first active layer 21 and the current collector 10, thereby improving the mechanical properties of the active layer 20.
  • the total thickness of the first active layer 21 and the second active layer 22 is controlled to be not less than 40 ⁇ m. Controlling the thickness of the first active layer 21 can effectively increase the energy density of the active layer 20, and in combination with the thickness of the second active layer 22, increase the energy density of the electrode of the embodiment of the present application, without affecting the liquid phase transport capacity and fast charging capacity of the active layer 20.
  • the material contained in the first active layer 21 in the above embodiments must contain electrode active materials. Of course, it can also contain conductive agents and binders to ensure that the first active layer 21 has a high compaction density, high cycle performance and low internal resistance.
  • the particle size Dv50 of the active material contained in the first active layer 21 in the above embodiments is greater than the particle size Dv50 of the active material contained in the second active layer 22.
  • the particle size Dv50 of the active material contained in the first active layer 21 is greater than the particle size Dv50 of the active material contained in the second active layer 22 by more than 30%.
  • the particle size of the active material contained in the first active layer 21 is controlled to be greater than the particle size of the active material contained in the second active layer 22, and the compaction density of the first active layer 21 is increased, thereby improving the energy density of the electrode.
  • the component type or content of the first active layer 21 may be the same as or different from the component type or content of the second active layer 22.
  • the first active layer 21 may include the following components in percentage by mass:
  • the first active layer 21 in this ratio range and the second active layer 22 thereof together can further improve the energy density and cycle performance of the electrode in the embodiment of the present application and reduce the internal resistance of the electrode.
  • the active material contained in the first active layer 21 is a positive electrode active material; in the exemplary embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NC
  • the positive electrode active materials have high capacity, and the first active layer 21 formed with components such as conductive agents and binders has a stable structure and high compaction density. At this time, the positive electrode material contained in the first active layer 21 can be the same as the positive electrode active material contained in the second active layer 22, or different.
  • the active material contained in the first active layer 21 is a negative electrode active material.
  • the negative electrode active material includes at least one of carbon, silicon-based materials, tin-based materials and lithium titanate.
  • carbon can include at least one of natural graphite, artificial graphite, soft carbon and hard carbon
  • silicon-based materials can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material
  • tin-based materials can include tin-based materials can include at least one selected from elemental tin, tin oxide and tin alloy material.
  • the negative electrode materials have high electronic and ionic conductivity, and the first active layer 21 formed with conductive agents, binders and other components has a stable layer structure and high compaction density.
  • the negative electrode material contained in the first active layer 21 can be the same as the negative electrode active material contained in the second active layer 22, or it can be different.
  • the capacity of the electrode active material contained in the first active layer 21 is higher than that of the electrode active material contained in the second active layer 22 to increase the energy density of the active layer 20 .
  • the active material contained in the second active layer 22 when the electrode is a negative electrode, includes amorphous carbon. At this time, the active material contained in the first active layer 21 does not contain amorphous carbon, and can be other high-capacity active materials to achieve different active materials and give the electrode a high energy density.
  • the polarity of the electrode active materials contained in the first active layer 21 and the second active layer 22 is the same, that is, when the electrode is a positive electrode, the electrode active materials contained in the first active layer 21 and the second active layer 22 are both positive electrode active materials; when the electrode is a negative electrode, the electrode active materials contained in the first active layer 21 and the second active layer 22 are both negative electrode active materials.
  • the type and content of the active material contained in the first active layer 21 can be the same as or different from the type and content of the active material contained in the second active layer 22.
  • the binder contained in the first active layer 21 includes at least one of polyvinylidene fluoride, styrene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the conductive agent contained in the first active layer 21 includes at least one of acetylene black, superconducting carbon, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. These conductive agents can be evenly dispersed to give the first active layer 21 high electronic conductivity.
  • the conductive agent contained in the first active layer 21 can be the same as the conductive agent contained in the second active layer 22, or different.
  • the dispersant contained in the first active layer 21 includes but is not limited to sodium carboxymethyl cellulose (CMC). These dispersants can effectively improve the uniformity of the dispersion of the materials contained in the second active layer 22, thereby improving the mechanical uniformity of the layer structure of the second active layer 22 and the porous structure contained therein, and can improve the distribution uniformity of the pores contained in the porous structure.
  • CMC carboxymethyl cellulose
  • the current collector 10 contained in the electrodes of the above embodiments can be adjusted according to the polarity of the electrode.
  • the current collector 10 when the electrode of the embodiment of the present application is a positive electrode, the current collector 10 can be a positive electrode current collector, and when the electrode of the embodiment of the present application is a negative electrode, the current collector 10 can be a negative electrode current collector. Its thickness and other properties can be adjusted according to the needs of specific applications.
  • the present invention provides a method for preparing an electrode. As shown in FIG4 , the method for preparing an electrode in the present invention comprises the following steps:
  • S02 performing pore forming treatment on the surface electrode active layer of the electrode active layer facing away from the current collector to form a porous structure in the surface electrode active layer, so that the porosity of the surface electrode active layer is greater than the porosity of the inner electrode active layer close to the current collector.
  • the current collector in step S01 can be the current collector 10 contained in the electrode of the above text application embodiment, and the electrode active layer is the pre-treatment layer of the active layer 20 contained in the electrode of the above text application embodiment.
  • the surface electrode active layer in step S02 refers to the surface part of the electrode active layer in step S01 that is away from the current collector, that is, the electrode active layer in step S01 is divided into two parts according to the direction parallel or approximately parallel to the surface of the current collector, the inner electrode active layer close to the current collector and the surface electrode active layer away from the current collector.
  • a porous structure is formed in the surface electrode active layer of the electrode active layer, so the porosity of the surface electrode active layer must be greater than the porosity of the inner electrode active layer close to the current collector. Similarly, since the porous structure is only formed in the surface electrode active layer, the thickness of the surface electrode active layer is less than the total thickness of the electrode active layer.
  • the surface electrode active layer with a porous structure formed after the pore-forming treatment in step S02 constitutes the second active layer 22 of the active layer 20 contained in the electrode of the above text application embodiment, and the remaining inner electrode active layer that has not been subjected to the pore-forming treatment and is close to the current collector constitutes the first active layer 21 of the active layer 20 contained in the electrode of the above text application embodiment.
  • the preparation method of the present application performs a pore-forming treatment on the surface electrode active layer of the electrode active layer so that the surface electrode active layer forms a porous structure with abundant pores.
  • the inner electrode active layer that has not been pore-formed has no porous structure. Therefore, the porous structure with abundant pores in the surface electrode active layer after the pore-forming treatment has a higher porosity than the inner electrode active layer close to the current collector and not pore-formed.
  • the prepared electrode Since the porosity in the surface layer of the active layer contained in the prepared electrode is higher than the porosity of the active layer close to the current collector, the prepared electrode is endowed with the electrode characteristics of the above text application embodiment, such as having a large contact area with the electrolyte, having a high liquid phase transport capacity and fast charging capacity, and the prepared electrode has a high energy density, structural stability, and excellent cycle performance.
  • the electrode preparation method of the embodiment of the present application can ensure that the prepared electrode structure and electrochemical performance are stable, and the efficiency is high, saving production costs.
  • the electrode active layer formed on the current collector is a pre-treatment layer of the active layer 20 contained in the electrode of the above application embodiment. Therefore, the electrode active layer at least contains an electrode active material.
  • the electrode active layer formed contains the components and contents of the active material, conductive agent, binder and dispersant contained in the first active layer 21 and the second active layer 20 in the above active layer 20.
  • the thickness of the electrode active layer may be the total thickness of the active layer 20, such as the sum of the thickness of the first active layer 21 and the thickness of the second active layer 20, such as the total thickness is not less than 40 ⁇ m.
  • the thickness of the inner electrode active layer may be the thickness of the first active layer 21 included in the active layer 20; the thickness of the surface electrode active layer may be the thickness of the second active layer 22 included in the active layer 20, such as 10 to 60 ⁇ m.
  • the surface electrode active layer subjected to pore forming treatment in step S02 contains a pore forming agent.
  • the pore forming agent is dispersed in the surface electrode active layer so that it forms pores during the pore forming treatment in step S02, thereby forming a porous structure in the surface electrode active layer.
  • the content of the pore-forming agent in the surface electrode active layer can be 8wt% to 20wt% of the solid content of the active layer slurry forming the surface electrode active layer.
  • the morphology and porosity of the porous structure formed by the pore-forming treatment can be adjusted and controlled. If controlled within the aforementioned range, the mechanical stability of the active layer formed after the pore-forming treatment can be improved, and the pores of the porous structure are evenly distributed and abundant, and its porosity is relatively improved.
  • the pore former includes at least one of ammonium bicarbonate, ammonium carbonate, ammonium chloride, polymethyl methacrylate, starch, and polyvinyl pyrrolidone.
  • These pore formers have thermal decomposition characteristics, so they can be decomposed by appropriate heat treatment, thereby forming a rich porous structure without destroying the mechanical properties and structure of the surface electrode active layer.
  • the slurry formed by the mixing of these pore formers and active materials has good dispersibility and high slurry stability, and can avoid the formation of gel. If these pore formers are mixed with silicon-based materials, the dispersibility and stability of the slurry can be improved, the formation of gel can be avoided, and the film-forming property of the slurry can be improved.
  • the method of forming an electrode active layer on a current collector in step S01 comprises the following steps:
  • the first electrode slurry in step S011 may contain the components contained in the first active layer 21 in the active layer 20 contained in the electrode of the above text application embodiment, and prepare the electrode slurry with a solvent. Of course, it can also be an electrode slurry containing other components. Compared with the second electrode slurry in step S012, it does not contain a pore-forming agent component to ensure that the inner electrode active layer maintains a low porosity and high density during the pore-forming treatment in the above step S02.
  • the thickness of the inner electrode active layer can be controlled and adjusted according to the thickness of the first active layer 21 in the active layer 20 contained in the electrode of the above text application embodiment.
  • the method of forming the inner electrode active layer on the current collector by the first electrode slurry can be carried out according to the method of forming a film on the current collector by the existing electrode slurry.
  • the second electrode slurry in step S012 may contain the components contained in the second active layer 22 in the active layer 20 contained in the electrode of the above text application, and the electrode slurry is prepared with a solvent. Of course, it can also be an electrode slurry containing other components. Compared with the first electrode slurry in step S011, it contains a pore-forming agent component to ensure that it can form a porous structure in the surface electrode active layer during the pore-forming treatment in the above step S02. The thickness of the surface electrode active layer can be controlled and adjusted according to the thickness of the second active layer 22 in the active layer 20 contained in the electrode of the above text application embodiment. The method of forming the surface electrode active layer on the inner electrode active layer with the second electrode slurry can be carried out according to the method of forming a film on the current collector using the existing electrode slurry.
  • the second electrode slurry may be formed on the surface of the inner electrode active layer directly when the inner electrode active layer is wet, or may be formed on the surface of the inner electrode active layer after the inner electrode active layer is preliminarily dried.
  • the second electrode slurry can be configured into several portions, and the content of the pore former in each portion can be controlled to be different, such as increasing in a gradient.
  • the film forming process can be carried out in the order of the content of the pore former from low to high.
  • the content of the pore former increases in a gradient from the inner electrode active layer to the outer electrode active layer.
  • a porous structure can be formed in the surface electrode active layer, and the porosity of the porous structure increases in a gradient from the inner electrode active layer to the outer electrode active layer.
  • the drying process in step S012 is mainly to dry the wet film, but it should be ensured that the pore-forming agent is not destroyed. Therefore, the drying process can be carried out at a temperature lower than the thermal decomposition temperature of the pore-forming agent mentioned above. For example, the drying process is carried out at a temperature lower than the temperature of 70°C to 150°C for the heat treatment used below. In the exemplary embodiment, the drying process temperature can be 60 to 90°C.
  • the roller pressing process in step S012 is used to improve the compaction density and corresponding mechanical properties of the electrode active layer consisting of the inner electrode active layer and the surface electrode active layer formed on the current collector.
  • the purpose of performing pore forming treatment on the surface electrode active layer is to form a porous structure in the surface electrode active layer with a relatively large porosity, such as forming a porosity higher than the porosity of the inner electrode active layer.
  • the surface electrode active layer forms the second active layer 22 in the active layer 20 contained in the electrode of the above text application embodiment, and the inner electrode active layer constitutes the first active layer 21 in the active layer 20 contained in the electrode of the above text application embodiment.
  • the electrode active layer including the inner electrode active layer and the surface electrode active layer is formed first, which can ensure the stability of the porous structure formed by the pore forming treatment in step S02.
  • the electrode active layer is first formed on the surface of the current collector according to the method of the electrode active layer, such as including a drying treatment and a roller pressing treatment.
  • the electrode active layer is first formed, and then the heat treatment is performed to decompose the pore-forming agent to form a porous structure, thereby ensuring the stability of the porous structure and effectively avoiding the undesirable phenomenon of overpressure on the surface of the active layer caused by the pore-forming treatment followed by the roller pressing treatment, which leads to deterioration of the porosity.
  • the pore former is at least one of ammonium bicarbonate, ammonium carbonate, ammonium chloride, polymethyl methacrylate, starch, and polyvinyl pyrrolidone in step S01 above
  • the pore forming treatment is to heat treat the surface electrode active layer to decompose the pore former. Since the pore former decomposes in the surface electrode active layer, a porous structure is formed in situ in the surface electrode active layer, forming a porosity higher than that of the inner electrode active layer.
  • the temperature of the above-mentioned heat treatment can be 70°C to 150°C, and can further be 100°C to 150°C.
  • the above-mentioned pore former can be effectively decomposed, leaving a porous structure with abundant pores in the surface electrode active layer, and improving the mechanical properties of the active layer formed by the heat treatment.
  • the temperature of the heat treatment can be controlled according to the decomposition temperature characteristics of the specific pore former.
  • the heating rate of the heat treatment can also be controlled to ensure that the surface electrode active layer has a rich pore expansion structure and high mechanical properties, so as to reduce the adverse effects on the surface electrode active layer during the heat treatment process, that is, the decomposition process of the pore former, such as the reduction of mechanical properties.
  • the embodiment of the present application provides a battery.
  • the battery of the embodiment of the present application includes a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode can be an electrode of the embodiment of the present application, such as when the positive electrode is an electrode of the embodiment of the present application, the electrode is a positive electrode, and the active layer 20 contained therein is a positive electrode active layer.
  • the negative electrode is an electrode of the embodiment of the present application, the electrode is a negative electrode, and the active layer 20 contained therein is a negative electrode active layer.
  • the battery of the embodiment of the present application contains the electrode of the embodiment of the above text application, the battery of the embodiment of the present application has good cycle performance, can be fast charged, has strong fast charging capability, and at the same time improves the safety performance of the battery.
  • the battery of the present application can be a secondary battery.
  • the battery of the present application when the battery of the present application is a secondary battery, it includes a positive electrode, a separator and a negative electrode. That is, at least one of the positive and negative electrodes contained in the secondary battery can be an electrode of the present application embodiment.
  • the battery of the embodiment of the present application may include any one of a battery cell, a battery module, and a battery pack.
  • the battery cell refers to a battery housing and a battery cell encapsulated in the battery housing.
  • the shape of the battery cell is not particularly limited, and it can be cylindrical, square, or any other shape.
  • FIG5 is a battery cell 30 of a square structure as an example.
  • the outer packaging of the battery cell 30 may include a shell 31 and a cover plate 33.
  • the shell 31 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 31 has an opening connected to the receiving cavity, and the cover plate 33 is used to cover the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film may form an electrode assembly 32 through a winding process and/or a lamination process.
  • the electrode assembly 32 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 32.
  • the number of electrode assemblies 32 contained in the battery cell 30 may be one or more, which can be adjusted according to actual needs.
  • the positive electrode, the separator, the negative electrode and the electrolyte can be assembled to form the battery cell 30.
  • the positive electrode, the separator and the negative electrode can be formed into the electrode assembly 32 through a winding process or a lamination process, and the electrode assembly 32 is placed in an outer package, dried and then injected with electrolyte, and then vacuum packaged, left to stand, formed, shaped and other processes are performed to obtain the battery cell 30.
  • the battery cells 30 according to the present application can be assembled into a battery module.
  • the battery module can contain multiple battery cells 30, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG7 is a schematic diagram of a battery module 40 as an example.
  • a plurality of battery cells 30 may be arranged in sequence along the length direction of the battery module 40. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 30 may be fixed by fasteners.
  • the battery module 40 may further include a housing having an accommodation space, and the plurality of battery cells 30 may be accommodated in the accommodation space.
  • the battery modules 40 described above may also be assembled into a battery pack, and the number of battery modules 40 contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • the battery pack 50 may include a battery box and a plurality of battery modules 40 disposed in the battery box.
  • the battery box includes an upper box body 51 and a lower box body 52, wherein the upper box body 51 is used to cover the lower box body 52 and form a closed space for accommodating the battery modules 40.
  • the plurality of battery modules 40 may be arranged in the battery box in any manner.
  • the embodiments of the present application further provide an electrical device, which includes a battery according to the above embodiments of the present application, such as one or more of a secondary battery, a battery module, or a battery pack.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a secondary battery, a battery module, or a battery pack according to its usage requirements.
  • Fig. 10 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • This embodiment provides a negative electrode sheet, including a copper foil current collector, a first active layer bonded to the copper foil current collector, and a second active layer bonded to the surface of the first active layer away from the copper foil current collector.
  • the second active layer has a porous structure, and its porosity and thickness parameters of the second active layer are shown in Table 1 below.
  • first negative electrode slurry artificial graphite, anode active material, artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water according to a weight ratio of 48:48:1:2:1 to prepare the first negative electrode slurry;
  • Preparation of the second negative electrode slurry According to the preparation method of the first negative electrode slurry, the negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in the solvent deionized water according to the proportion, and the pore-forming agent ammonium bicarbonate is added to prepare the second negative electrode slurry, and the ammonium bicarbonate is controlled to account for 12% of the solid content of the negative electrode slurry.
  • SBR binder styrene butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • the first negative electrode slurry in step S1 is applied to a copper foil current collector to form an inner electrode active layer; then, the second negative electrode slurry is applied to the outer surface of the inner electrode active layer to form a wet film, which is then dried at 70° C. and then cold pressed to form a composite electrode active layer of an inner electrode active layer (first active layer) and an outer electrode active layer laminated and bonded with the inner electrode active layer on the current collector;
  • the negative electrode semi-finished product prepared in step S2 is heated up to 100° C., so that the ammonium bicarbonate pore-forming agent contained in the outer electrode active layer is gradually decomposed and forms a porous structure in the outer electrode active layer. At this time, the outer electrode active layer forms a second active layer with a porous structure.
  • Embodiment A2 to Embodiment A14 respectively provide a negative electrode plate, and the structure of each negative electrode plate is the same as that of Embodiment A1, except that the porosity and thickness of the second active layer contained in each negative electrode plate are different.
  • the porosity and thickness parameters of the second active layer contained in the negative electrode plate in each embodiment are respectively shown in Table 1 below.
  • the preparation methods of the negative electrode sheets in Examples A2 to A14 are also prepared by referring to the preparation method of the negative electrode sheet in Example A1, except that the type and content of the pore former contained in the second negative electrode slurry are controlled differently.
  • the comparative example provides a negative electrode sheet, comprising a copper foil current collector and an active layer bonded to the copper foil current collector, wherein the material type and content of the active layer are the same as those of the first active layer in Example A1.
  • the preparation method of the negative electrode plate of this comparative example comprises the following steps:
  • step S2 of Example A1 The film forming treatment is carried out according to step S2 of Example A1, except that in step S2 of this comparative example, the second negative electrode slurry in step S2 of Example A1 is replaced by the first negative electrode slurry, that is, in this step S2, only the first negative electrode slurry without a pore-forming agent is used for film forming treatment, and then after drying at 70°C, a cold pressing treatment is carried out to obtain a negative electrode substrate.
  • the comparative example provides a negative electrode plate, comprising a copper foil current collector and an active layer bonded to the copper foil current collector.
  • the type and content of the material contained in the active layer are the same as the type and content of the material contained in the active layer in comparative example A1.
  • the difference is that the porosity of the active layer contained in the negative electrode plate of this comparative example is controlled to be 1% on average, that is, there is no porosity difference in the active layer contained in the negative electrode plate of this comparative example.
  • Embodiments B1 to B14 and Comparative Examples B1 to B2 respectively provide a secondary battery, each of which includes a battery cell formed by a positive electrode sheet, a separator and a negative electrode sheet, and also includes an electrolyte.
  • the positive electrode sheet is prepared according to the following method:
  • the positive electrode active material lithium nickel cobalt manganese oxide (NCM523, i.e., LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed in a weight ratio of 96:2:2, and then N-methylpyrrolidone (NMP) is added as a solvent, and stirred under the action of a vacuum stirrer until the system is uniform to obtain a positive electrode slurry with a solid content of 75wt%; the positive electrode slurry is uniformly coated on an aluminum foil with a thickness of 13 ⁇ m at a coating density of 13.7mg/cm 2 ; and then dried, cold pressed, and cut to obtain the positive electrode sheet of the embodiment;
  • NMP N-methylpyrrolidone
  • Negative electrode sheet the negative electrode sheet provided in the above Examples A1 to A14 and Comparative Examples A1 to A2 respectively;
  • Electrolyte In an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), organic solvents ethylene carbonate (EC)/ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3/7, 12.5 wt % (based on the weight of the ethylene carbonate/ethyl methyl carbonate solvent) of LiPF 6 was added and dissolved in the organic solvent, and stirred uniformly to obtain an electrolyte;
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • Secondary battery assembly stack the positive electrode sheet/separator/negative electrode sheet in the order of stacking to form a battery cell, place the bare battery cell in an outer package, inject the above-mentioned electrolyte and seal it to obtain secondary batteries respectively; wherein, the secondary battery in Example B1 contains the negative electrode sheet provided in Example A1 above, the secondary battery in Example B2 contains the negative electrode sheet provided in Example A2 above, and so on, the secondary battery in Comparative Example B1 contains the negative electrode sheet provided in Comparative Example A1 above.
  • the 25°C fast charging cycle life/cycle number test method at 25°C, the secondary battery is charged at a rate of 0.5C and discharged at a rate of 1C, and a continuous cycle test is performed in the range of 3% to 97% state of charge (SOC) until the capacity of the secondary battery is less than 80% of the initial capacity, and the number of cycles is recorded as the cycle performance.
  • SOC state of charge
  • the second active layer contained in the electrode of the embodiment of the present application is set to a porous structure, and its porosity is controlled and adjusted, which can effectively enrich the lithium ion migration channel and transmission space, increase the lithium ion transmission rate, and improve the kinetic performance of lithium ion migration, thereby effectively improving the cycle performance.
  • the low porosity of the first active layer is retained, thereby effectively improving the high compaction density of the electrode active layer and improving the capacity of the electrode.
  • Comparing Examples A1 to A12 with Examples A13 and A14, controlling the porosity ratio between the second active layer and the first active layer contained in the electrode will also have a certain effect on the cycle performance of the electrode, such as too low (Example A13) or too high (Example A14) will affect the cycle performance of the electrode.
  • the electrodes provided in the embodiments of the present application are significantly higher than the cycle performance of the electrodes in Comparative Example A1.
  • the cycle performance and fast charging performance of the secondary battery containing the electrode in Comparative Example A2 are improved compared to the secondary battery containing the electrode in Comparative Example A1, the improvement is not obvious, and further measured that its energy density is lower than that of the secondary battery containing the electrode in Comparative Example A1.

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Abstract

一种电极及其制备方法、电池和用电装置。电池包括电极，电极包括集流体（10）和与集流体（10）结合的活性层（20），活性层（20）包括第一活性层（21）和第二活性层（22），第一活性层（21）与集流体（10）结合，第二活性层（22）结合在第一活性层（21）的背离集流体（10）的表面上，且第二活性层（22）的孔隙率大于第一活性层（21）的孔隙率。该电极的能量密度高，结构稳定，循环性能优异。

Description

电极及其制备方法、电池和用电装置 技术领域
本申请涉及电池技术领域，具体涉及一种电极及其制备方法、电池和用电装置。
背景技术
节能减排是汽车产业可持续发展的关键，电动车辆由于其节能环保的优势成为汽车产业可持续发展的重要组成部分。对于电动车辆而言，电池技术又是关乎其发展的一项重要因素。
而且随着电池应用的越来越普及，市场对电池的相关性能如循环性能等要求越来越高，而且随着电动新能源车的市场占有率逐步的提高，当前对续航的要求逐步提高的同时，对充电速率的要求也越来越高。但是当前电极由于其所含活性层结构导致其液相输运能力和快充能力差。
发明内容
鉴于上述问题，本申请实施例提供一种电极及其制备方法、电池和用电装置，以解决电极液相输运能力差的技术问题。
第一方面，本申请实施例供了一种电极。本申请实施例电极包括集流体和与集流体结合的活性层，所述活性层包括第一活性层与第二活性层，所述第一活性层与所述集流体结合，所述第二活性层结合在第一活性层的背离所述集流体的表面上，且所述第二活性层的孔隙率大于所述第一活性层的孔隙率。
本申请实施例电极通过所含的第二活性层有效增大了活性层与电解液接触的面积，而且有效丰富了锂离子迁移通道和传输空间，增大了锂离子传输速率，提高锂离子迁移的动力学性能，从而显著提高本申请实施例电极的液相输运能力，从而提高了本申请实施例电极的快充能力；而第一活性层的存在，其与第二活性层共同作用，赋予本申请实施例电极高的能量密度，且结构稳定性高，循环性能优异，而且能够有效避免发生极化现象和析锂，提高电池的安全性。
一些实施例中，所述第二活性层的孔隙率比所述第一活性层的孔隙率高出30％以上。
一些实施例中，所述第二活性层的孔隙率比所述第一活性层的孔隙率高出40％～95％。
控制两活性层之间的孔隙率差在该范围，能够降低锂离子在本申请实施例电极所含活性层中的迁移路径和增大锂离子传输空间，从而进一步增大活性层的液相输运能 力，并提高快充能力。
一些实施例中，所述第二活性层的孔隙率的平均值为25％～55％。
一些实施例中，所述第二活性层所含孔隙的直径为5～20μm。
通过对第二活性层的孔隙率和孔隙直径在该范围，可以间接控制第一活性层的孔隙率，提高两活性层之间的增效作用，从而进一步增大活性层20的液相输运能力，并提高快充能力。
一些实施例中，在所述第二活性层中，沿背离所述集流体的表面方向，所述第二活性层所含孔隙率呈梯度增大。通过控制第二活性层的孔隙率呈该方向的梯度分布，能够进一步提高锂离子向活性层内部迁移速率和传输空间。
一些实施例中，所述第一活性层与第二活性层总厚度不小于40μm。
一些实施例中，所述第二活性层的厚度为10～60μm。
该厚度范围能够有效提活性层的能量密度，并具有丰富的孔隙率，能够控制锂离子有效向活性层的内部迁移路径。
一些实施例中，所述第一活性层所含活性材料的粒径Dv50大于所述第二活性层所含活性材料的粒径Dv50。
一些实施例中，所述第二活性层所含的活性材料包括第一活性材料和第二活性材料，且所述第一活性材料的粒径Dv50比所述第二活性材料的粒径Dv50相差30％以上。
通过将第二活性层与第一活性层所含活性材料粒径大小控制，使得第一活性层和第二活性层之间起到增效作用，提高电极的能量密度。
一些实施例中，所述第一活性层和/或所述第二活性层包括如下质量百分比含量的组分：
Figure PCTCN2022135503-appb-000001
该比例范围的第一活性层和第二活性层使得活性层的能量密度高、内阻小。
一些实施例中，所述电极为正极，所述活性层所含的活性材料为正极活性材料；或所述电极为负极，所述活性层所含的活性材料为负极活性材料。
示范例中，所述正极活性材料包括镍钴锰酸锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的至少一种。
示范例中，所述负极活性材料包括人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的至少一种。
示范例中，所述粘结剂包括聚偏氟乙烯、苯橡胶、聚丙烯酸、聚丙烯酸钠、聚丙烯酰胺、聚乙烯醇、海藻酸钠、聚甲基丙烯酸、羧甲基壳聚糖中的至少一种。
示范例中，所述导电剂包括乙炔黑、超导碳、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的至少一种。
示范例中，所述分散剂包括羧甲基纤维素钠。
该些电极活性材料、粘结剂、导电剂和分散剂能够增效作用，提高活性层的层结构和电子导率。
一些实施例中，所述电极为负极，且所述第二活性层所含活性材料包括无定型碳。
第二方面，本申请实施例提供了一种电极的制备方法。本申请实施例电极制备方法包括如下步骤：
在集流体上形成电极活性层；
对所述电极活性层的背离集流体的表层电极活性层进行造孔处理，在所述表层电极活性层中形成多孔结构，使得所述表层电极活性层的孔隙率大于靠近所述集流体的内层电极活性层的孔隙率。
本申请制备方法通过对电极活性层的表层电极活性层进行造孔处理，以使得表层电极活性层形成多孔结构，具有丰富的孔隙。且其孔隙率高于靠近集流体且未被造孔处理的内层电极活性层的孔隙率，从而赋予制备的电极具有如上文本申请实施例电极特性，如具有与电解液大的接触面积，具有高的液相输运能力和快充能力，而且制备的电极能量密度高，结构稳定性，循环性能优异。另外，本申请实施例电极制备方法能够保证制备的电极结构和电化学性能稳定，而且效率高，节约生产成本。
一些实施例中，所述表层电极活性层的材料含有造孔剂。通过在表层电极活性层中分散造孔剂，以使得其在造孔处理过程中造孔，以在表层电极活性层形成多孔结构。
一些实施例中，所述造孔剂在所述表层电极活性层中的含量为的所述造孔剂占形成所述表层电极活性层的活性层浆料固含量的8wt％～20wt％。通过控制造孔剂在表层电极活性层中的含量，从而能够调节和控制在造孔处理形成多孔结构的形态和孔隙率大小。
一些实施例中，所述表层电极活性层的厚度为10～60μm。
一些实施例中，所述造孔剂包括碳酸氢铵、碳酸铵、氯化铵、聚甲基丙烯酸甲酯、淀粉、聚乙烯吡咯烷酮中的至少一种。该些造孔剂具有热分解特性，因此，可以通过适当的热处理使得其分解。
一些实施例中，所述造孔处理是对所述表层电极活性层进行热处理，使所述造孔剂分解。采用热处理能够使得该造孔剂在表层电极活性层中分解，从而在表层电极活性层中原位形成多孔结构。
一些实施例中，所述热处理的温度为70℃～150℃。该温度下能够有效使得上述的造孔剂分解，在表层电极活性层中留下具有丰富孔的多孔结构。
一些实施例中，所述在集流体上形成电极活性层的方法包括如下步骤：
将第一电极浆料在集流体上形成内层电极活性层；
将含有所述造孔剂的第二电极浆料在所述内层电极活性层的背离所述集流体的表面形成湿膜，经干燥处理和辊压处理后，形成与所述内层电极活性层结合的所述表层电极活性层。
采用分别形成不同活性层，能够有效控制造孔剂的分布，最终控制多孔结构在活性层中的分布深度、结构和均匀性。
一些实施例中，所述第二电极浆料为若干份，在所述若干份中，所述造孔剂的含量呈梯度增加，若干份的所述第二电极浆料是按照所述造孔剂的含量由低到高的先后顺序依次在所述内层电极活性层的表面成膜处理，形成所述湿膜。将第二电极浆料设置造孔剂梯度含量，从而使得在形成的表层电极活性层中，造孔剂含量呈梯度变化。
第三方面，本申请实施例提供了一种电池。本申请实施例电池包括正极和负极，所述正极为上文本申请实施例电极或由上文本申请实施例电极制备方法制备的电极，且所述电极的活性层所含的活性材料为正极材料；和/或
所述负极为上文本申请实施例电极或由上文本申请实施例电极制备方法制备的电极，且所述电极的活性层所含的活性材料为负极材料。
本申请实施例电池含有上文本申请实施例电极，因此，本申请实施例电池循环性能好，可快充，其快充能力强，同时提高了电池的安全性能。
第三方面，本申请实施例提供了一种用电装置。本申请实施例用电装置包括本申请实施例电池，所述电池用于提供电能。
这样，本申请实施例用电装置含上文本申请实施例电池，因此，该用电装置续航能力强，可快充，且安全性高。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1为当前电极活性层的离子束剖面研磨(Cross section polisher,CP)电镜图；
图2为本申请实施例电极单面含有活性层的结构示意图；
图3为本申请实施例电极双面含有活性层的结构示意图；其中，图3中A图为一种孔隙结构的结构示意图，B图为另一种孔隙结构的结构示意图；
图4为本申请实施例电极制备方法流程示意图；
图5为本申请实施例电池单体的一实施方式的结构示意图；
图6为图5所示电池单体的分解示意图；
图7为本申请实施例电池模块的一实施方式结构示意图；
图8为本申请实施例电池包的一实施方式结构示意图；
图9为图8所示电池包的分解结构示意图；
图10为包含本申请实施例电池作为电源的用电装置的一实施方式的示意图。
具体实施方式中的附图标号如下：
10、集流体；
20、活性层，21、第一活性层，22、第二活性层；
30、电池单体，31、壳体，32、电极组件，33、盖板；
40、电池模块；
50、电池包，51、箱体，52、下箱体。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；也可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请实施例中的具体含义。
活性层在本申请实施例中是指电极所含的活性层，至少含有电极活性材料的结构，其与集流体结合。
孔隙率是指活性层中总孔隙体积占活性层总共体积的百分比(％)。
目前，从市场形势的发展来看，动力电池的应用越加广泛。动力电池不仅被应用于水力、火力、风力和太阳能电站等储能电源系统，而且还被广泛应用于电动自行车、电动摩托车、电动汽车等电动交通工具，以及军事装备和航空航天等多个领域。随着动力电池应用领域的不断扩大，其市场的需求量也在不断地扩增，同时对电池的循环性能和快充能力以及大功率等性能要求也越来越高。
然而当前电极一般将电极浆料在集流体上成膜后辊压形成活性层。发明人在对活性层的微结构研究中发现，由于辊压工艺，使得活性层表面最先与冷压辊接触，所以往往会出现极片表面过压的情况。如图1所示，从极片CP电镜图上可以看到，活性层表层中出现孔隙率恶化的情况。表层孔道结构恶化，从而导致其液相输运能力差，如阻碍了锂离子向活性层内部迁移的速率，包括阻碍从正极扩散过来的锂离子向负极极片内部的输运，导致负极厚度方向的锂盐浓度梯度进一步恶化，从而恶化了电锂离子迁移的动力学性能，同时也导致快充能力差，因此需要重点改善。
尤其在大电流工况下，电池电解液中的锂离子在当前电极所含活性层中传输成了整个动力学过程效率最低的短板环节。特别是对于高负载量电极，其活性层的厚度或压实密度较大，即具有更长的传输路径或更小的传输空间(孔隙率低)，导致此问题更为突出。此外，由于传输速率低会形成较大的锂离子浓度梯度，这使得负极隔膜侧更易发生析锂，增大了电池内短路的风险。
为了改善现有电极活性层存在的上述问题，在一些实施例中，对厚电极所含的活性层进行微造孔处理，如进行激光或机械造孔处理。但是发明人研究发现，无论是激光打孔还是机械打孔，该孔是沿极片厚度方向分布的垂直或近似垂直孔道，其对锂离子向活性层内迁移效果虽然有一定的改善，但是效果不明显；而且其工业化工艺复杂，大大增加工艺成本；同时激光打孔或者机械打孔可能破坏活性层层结构和所含活性颗粒结构，导致活性层掉粉，性能恶化，循环性能差。
另一些实施例中，在电极浆料中额外添加粉末状热分解添加剂，将制备得到的电极浆料涂覆到集流体上得到锂离子电池湿极片，对锂离子电池湿极片进行加热干燥，从而制备得到具有垂直孔道结构的锂离子电池极片。但是发明人研究发现，虽然其电极含有垂直孔道结构，由于其是在活性层厚度方向进行造孔，形成的电极结构如上述的激光或激光打孔形成的电极，其对锂离子向活性层内部迁移的改善不明显，而且在靠近集流体的区域进行造孔，导致电极能量密度降低。
基于发明人对现有电极存在不足的研究，发明人进一步研究发现，通过对活性层进行结构改进，具体的是活性层所含孔隙率分布的改进，能够显著改善电极所含活性层的液相输运能力，并提高快充能力。由此提出了如下电极及其制备方法，以显著改善电极对锂离子向活性层内部迁移的效果，并保证电极高的能量密度和循环性能，同时提高快充能力。
电极
第一方面，本申请实施例提供了一种电极。结合图2和图3，本申请实施例电极包括集流体10和与集流体结合的活性层20；其中，活性层20包括第一活性层21与第二活性层22，第一活性层21与集流体10结合，第二活性层22结合在第一活性层21的背离集流体10的表面上，且第二活性层22的孔隙率大于第一活性层21的孔隙率。
其中，第一活性层21和第二活性层22一起构成了本申请实施例电极所含的活性层20。按照第二活性层22、第一活性层21和集流体10上述的层叠关系，第二活性层22、第一活性层21和集流体10是依次层叠形成三明治结构。另外，该活性层20可以结合在集流体10的一个表面，如图2中所示，当然该活性层20也可以结合在集流体10的相对两表面，如图3中所示。
本申请实施例电极所含的第二活性层22所含的孔隙率大于第一活性层21所含的孔隙率，且将第二活性层22设置在电极所含活性层20的外表层，这样，第二活性层22的存在和其结合位置，有效增大了活性层20与电解液接触的面积，而且有效丰富了锂离子迁移通道和传输空间，增大了锂离子传输速率，提高锂离子迁移的动力学性能，从而显著提高本申请实施例电极的液相输运能力，从而提高了本申请实施例电极的快充能力；而第一活性层21的孔隙率低于上述第二活性层22，因此其具有高的压实密度。因此，第一活性层21与第二活性层22共同作用，赋予本申请实施例电极高的能量密度，且结构稳定性高，循环性能优异，而且能够有效避免发生极化现象和析锂，提高电池的安全性。而且第一活性层21是直接与集流体10结合，设置在电极内部，因此，相对低孔隙率的第一活性层21不影响电极的液相输运能力和快充能力。
一些实施例中，第二活性层22的孔隙率比第一活性层21的孔隙率高出30％以上，进一步可以高出40％～95％，具体可以控制高出30％、35％、40％、45％、50％、55％、60％、65％、70％、75％、80％、85％、90％、95％、等典型但非限制性的孔隙率差异。通过控制第二活性层22与第一活性层21两者孔隙率的差异比例，如控制在该范围，能够降低锂离子在本申请实施例电极所含活性层20中的迁移路径和增大锂离子传输空间，从而进一步增大活性层20的液相输运能力，并提高快充能力。
一些实施例中，第二活性层22的孔隙率的平均值为25％～55％，示范例中，可以是25％、30％、35％、40％、45％、50％、55％等典型但非限制性的孔隙率。另一些实施例中，第二活性层22所含孔隙的直径可以为5～20μm，进一步可以是10～15μm，示范例中，可以是5μm、8μm、10μm、12μm、15μm、17μm、20μm等典型但非限制性的孔隙直径。通过对第二活性层22的孔隙率和孔隙直径在该范围，可以间接控制第二活性层22的孔隙率，提高两活性层之间的增效作用，从而进一步增大活性层20的液相输运能力，并提高快充能力。
一些实施例中，在第二活性层22中，沿背离集流体10的表面方向，第二活性层22所含孔隙率呈梯度增大。也即是在第二活性层22的与第一活性层21接触表面至背离第一活性层21的表面方向，第二活性层22的孔隙率梯度增大，也即是孔隙越来越丰富或孔隙直径逐渐增大。通过控制第二活性层22的孔隙率呈该方向的梯度分布，能够进一步提高电解液与活性层20的接触和浸润面积，提高锂离子向活性层20内部迁移速率和传输空间，从而进一步提高活性层20液相输运能力，并进一步提高快充能力。
一些实施例中，第二活性层22的厚度可以为10～60μm，进一步可以是10～40μm，更进一步可以是15～25μm，示范例中可以是10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、55μm、60μm等典型但非限制性的厚度。该厚度范围，能够控制锂离子有效向活性层22的内部迁移路径，并结合第一活性层21提高本申请实施 例电极的能量密度。
由于第二活性层22依然是活性层结构，因此，上述各实施例中的第二活性层22所含的材料必然是含有电极活性材料。当然进一步还可以含有导电剂和粘结剂，保证第二活性层22在具有高孔隙率的基础上，具有高的循环性能和低内阻。
一些实施例中，第二活性层22中的孔隙结构可以是如图3中的A图所示，为丰富的三维孔隙结构，也可以是如图3中B图所示的，开口背离第一活性层21的孔隙结构。
一些实施例中，上述各实施例中第二活性层22所含活性材料的粒径Dv50小于第一活性层21所含活性材料的粒径Dv50。如实施例中，第二活性层22所含活性材料的粒径Dv50比第一活性层21所含活性材料的粒径Dv50小30％以上。通过将第二活性层22所含活性材料粒径控制小于第一活性层21所含活性材料粒径，使得第一活性层21和第二活性层22之间起到增效作用，提高电极的能量密度，并提高第二活性层22所含丰富孔隙结构。
如一些实施例中，第二活性层22可以包括如下质量百分比含量的组分：
Figure PCTCN2022135503-appb-000002
该比例范围的第二活性层22，其与第一活性层21一起，赋予活性层20的能量密度高、内阻小，能够提高第二活性层22中多孔结构的稳定性，从而能够进一步提高了本申请实施例电极的循环性能，降低了电极内阻。
一些实施例中，当本申请实施例电极为正极时，第二活性层22所含的活性材料为正极活性材料；示范例中，该正极活性材料包括镍钴锰酸锂、锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。该些正极活性材料容量高，而且与导电剂、粘结剂等组分形成第二活性层22层结构稳定，所含的多孔结构稳定。
当本申请实施例电极为负极时，第二活性层22所含的活性材料为负极活性材料。示范例中，负极活性材料可以包括碳、硅基材料、锡基材料和钛酸锂中的至少一种。其中，碳可以包括天然石墨、人造石墨、软炭、硬炭中的至少一种；硅基材料可以包 括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的至少一种；锡基材料可以包括锡基材料可包括选自单质锡、锡氧化物和锡合金材料中的至少一种。该些负极材料电子和离子导率高，而且与导电剂、粘结剂等组分形成第二活性层22层结构稳定，所含的多孔结构稳定。
一些实施例中，当本申请实施例电极为正极时，第二活性层22所含的粘结剂聚偏氟乙烯、聚四氟乙烯、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种；当本申请实施例电极为负极时，第二活性层22所含的粘结剂可以包括苯橡胶(SBR)(如丁苯橡胶)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)和羧甲基壳聚糖(CMCS)中的至少一种。该些粘结剂能够提高第二活性层22层结构和其所含的多孔结构的稳定性。
一些实施例中，第二活性层22所含的导电剂包括乙炔黑、超导碳、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的至少一种。该些导电剂能够均匀分散，在赋予第二活性层22高的电子导率的基础上，能够与活性材料、粘结剂等组分之间起到增效作用，提高第二活性层22的层结构和其所含的多孔结构的稳定性。
一些实施例中，第二活性层22所含的分散剂可以但不限于羧甲基纤维素钠(CMC)。该些分散剂能够有效提高第二活性层22所含材料分散的均匀性，从而提高第二活性层22层结构和其所含的多孔结构的力学均一性，并能够提高多孔结构所含孔隙的分布均匀性。
一些实施例中，活性层20所含的第一活性层21与第二活性层22之间的结合可以是直接在第一活性层21表面成膜构成的原位结合。另外，第一活性层21与第二活性层22界面可以由各自层材料形成的过渡层，通过该过渡层实现两者的结构。当然也可以是采用其他形式的结构方式。
一些实施例中，活性层20所含的第一活性层21的孔隙率低于上述第二活性层22，如低于第二活性层22的30％以上，进一步可以低于40％～95％。该孔隙率范围能够进一步提高第一活性层21具有相对高的压实密度，提高活性层20高的能量密度，并增强第一活性层21与集流体10之间的结合强度，从而提高活性层20的力学性能。
一些实施例中，在上述第二活性层22的厚度基础上，也即是在上述第二活性层22厚度为10～60μm的基础上，控制第一活性层21与第二活性层22总厚度不小于40μm。控制第一活性层21的厚度，能够有效提活性层20的能量密度，并结合第二活性层22的厚度提高本申请实施例电极的能量密度，而且不影响活性层20的液相输运能力和快充能力。
由于第一活性层21是构成活性层20能量密度的主要结构，因此，上述各实施例中的第一活性层21所含的材料必然是含有电极活性材料。当然进一步还可以含有导电剂和粘结剂，保证第一活性层21在具有高压实密度，具有高的循环性能和低内阻。
一些实施例中，如上文第二活性层22中所述的，上述各实施例中第一活性层21所含活性材料的粒径Dv50大于第二活性层22所含活性材料的粒径Dv50。如实施例中，第一活性层21所含活性材料的粒径Dv50比第二活性层22所含活性材料的粒径Dv50大30％以上。将第一活性层21所含活性材料粒径控制大于第二活性层22所含活性材料粒径，增大第一活性层21的压实密度，从而提高电极的能量密度。
如一些实施例中，第一活性层21所含的组分种类或含量可以与第二活性层22所含的组分种类或含量相同也可以不同，如一些实施例中，该第一活性层21可以包括如下质量百分比含量的组分：
Figure PCTCN2022135503-appb-000003
该比例范围的第一活性层21，其第二活性层22一起，能够进一步提高了本申请实施例电极的能量密度和循环性能，降低了电极内阻。
同样，一些实施例中，当本申请实施例电极为正极时，第一活性层21所含的活性材料为正极活性材料；示范例中，该正极活性材料包括镍钴锰酸锂、锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。该些正极活性材料容量高，而且与导电剂、粘结剂等组分形成第一活性层21层结构稳定，压实密度高。此时，第一活性层21所含正极材料可以与第二活性层22所含的正极活性材料相同，也可以不同。
当本申请实施例电极为负极时，第一活性层21所含的活性材料为负极活性材料。示范例中，负极活性材料包括可以碳、硅基材料、锡基材料和钛酸锂中的至少一种。其中，碳可以包括天然石墨、人造石墨、软炭、硬炭中的至少一种；硅基材料可以包括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的至少一种；锡基材料可以包括锡基材料可包括选自单质锡、锡氧化物和锡合金材料中的至少一种。该些负极材料电子和离子导率高，而且与导电剂、粘结剂等组分形成第一活性层21层结构 稳定，压实密度高。此时，第一活性层21所含负极材料可以与第二活性层22所含的负极活性材料相同，也可以不同。
当第一活性层21与第二活性层22所含电极活性材料不同时，理想的是第一活性层21所含电极活性材料的容量高于第二活性层22所含电极活性材料的容量，以提高活性层20的能量密度。
如实施例中，当电极为负极时，第二活性层22所含活性材料包括无定型碳，此时，第一活性层21所含活性材料不含无定型碳，可以是其他高容量的活性材料，以实现两者活性材料不同，并赋予电极高的能量密度。
需要说明的是，第一活性层21和第二活性层22所含的电极活性材料极性是相同的，也即是，当电极为正极时，第一活性层21和第二活性层22所含的电极活性材料均为正极活性材料；当电极为负极时，第一活性层21和第二活性层22所含的电极活性材料均为负极活性材料。另外，第一活性层21所含的活性材料的种类和含量可以与第二活性层22所含的活性材料的种类和含量相同或不同。
一些实施例中，第一活性层21所含的粘结剂包括可以聚偏氟乙烯、苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。该些粘结剂能够提高第一活性层21层结构，第一活性层21所含的粘结剂的种类和含量可以与第二活性层22所含的粘结剂的种类和含量相同或不同。第一活性层21所含粘结剂可以与第二活性层22所含的粘结剂相同，也可以不同。
一些实施例中，第一活性层21所含的导电剂包括乙炔黑、超导碳、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。该些导电剂能够均匀分散，在赋予第一活性层21高的电子导率。第一活性层21所含导电剂可以与第二活性层22所含的导电剂相同，也可以不同。
一些实施例中，第一活性层21所含的分散剂包括可以但不限于羧甲基纤维素钠(CMC)。该些分散剂能够有效提高第二活性层22所含材料分散的均匀性，从而提高第二活性层22层结构和其所含的多孔结构的力学均一性，并能够提高多孔结构所含孔隙的分布均匀性。
上文各实施例电极所含集流体10可以根据电极极性做调整，如当本申请实施例电极为正极时，该集流体10可以是正极集流体，当本申请实施例电极为负极时，该集流体10可以是负极集流体。其厚度等性能可以根据具体的应用的需要进行调整。
电极的制备方法
第二方面，本申请实施例提供了一种电极的制备方法。如图4所示，本申请实施例电极制备方法包括如下步骤：
S01：在集流体上形成电极活性层；
S02：对电极活性层的背离集流体的表层电极活性层进行造孔处理，在表层电极活性层中形成多孔结构，使得表层电极活性层的孔隙率大于靠近集流体的内层电极活性层的孔隙率。
其中，步骤S01中的集流体可以为上文本申请实施例电极所含的集流体10，电极活性层为上文本申请实施例电极所含的活性层20的前处理层。步骤S02中的表层电极活性层是指步骤S01中的电极活性层的背离集流体的表层部分，也即是按照与平行或近似平行集流体表面方向，将步骤S01中的电极活性层分为两部分，靠近集流体的内层电极活性层和背离集流体的表层电极活性层。经步骤S02中的造孔处理后，是在电极活性层的表层电极活性层形成多孔结构，那么必然使得表层电极活性层的孔隙率大于靠近集流体的内层电极活性层的孔隙率。同样，由于仅在表层电极活性层形成多孔结构，那么表层电极活性层的厚度小于电极活性层的总厚度。因此，经步骤S02中造孔处理后形成有多孔结构的表层电极活性层构成了上文本申请实施例电极所含的活性层20的第二活性层22，剩下没有被造孔处理且靠近集流体的内层电极活性层构成上文本申请实施例电极所含的活性层20的第一活性层21。
这样，本申请制备方法通过对电极活性层的表层电极活性层进行造孔处理，以使得表层电极活性层形成多孔结构，具有丰富的孔隙。而没有被造孔处理的内层电极活性层无多孔结构。因此，被造孔处理后的表层电极活性层中具有丰富孔隙的多孔结构，其孔隙率高于靠近集流体且未被造孔处理的内层电极活性层的孔隙率。由于制备的电极所含活性层的表层中孔隙率高于靠近集流体一侧活性层的孔隙率，赋予制备的电极具有如上文本申请实施例电极特性，如具有与电解液大的接触面积，具有高的液相输运能力和快充能力，而且制备的电极能量密度高，结构稳定性，循环性能优异。另外，本申请实施例电极制备方法能够保证制备的电极结构和电化学性能稳定，而且效率高，节约生产成本。
步骤S01：
在集流体上形成的电极活性层是作为上文本申请实施例电极所含的活性层20的前处理层。因此，该电极活性层至少是含有电极活性材料，如一些实施例中，形成的电极活性层含有上文活性层20中的第一活性层21和第二活性层20所含的活性材料、导电剂、粘结剂和分散剂等组分和含量。
另外，形成电极活性层的厚度可以是上文活性层20的总厚度，如可以是第一活性层21的厚度与第二活性层20的厚度之和，如总厚度不小于40μm。示范例中，上述内层电极活性层的厚度可以是上文活性层20所含第一活性层21的厚度；如上述表层电极活性层的厚度可以是上文活性层20所含第二活性层22的厚度，如可以是 10～60μm。
一些实施例中，被步骤S02中进行造孔处理的表层电极活性层中含有造孔剂。通过在表层电极活性层中分散造孔剂，以使得其在步骤S02中的造孔处理过程中造孔，以在表层电极活性层形成多孔结构。
一些实施例中，造孔剂在表层电极活性层中的含量可以为的造孔剂占形成所述表层电极活性层的活性层浆料固含量的8wt％～20wt％。通过控制造孔剂在表层电极活性层中的含量，从而能够调节和控制在造孔处理形成多孔结构的形态和孔隙率大小。如控制在前述的范围，能够提高经造孔处理后形成的活性层力学稳定性，且多孔结构孔隙分布均匀且丰富，其孔隙率相对提高。
在示范例中，该造孔剂包括碳酸氢铵、碳酸铵、氯化铵、聚甲基丙烯酸甲酯、淀粉、聚乙烯吡咯烷酮中的至少一种。该些造孔剂具有热分解特性，因此，可以通过适当的热处理使得其分解，从而在不破坏表层电极活性层力学性能和结构的前提下形成丰富的多孔结构。而且，该些造孔剂与活性材料混合处理形成的浆料分散性好，浆料稳定性高，且可以避免形成凝胶。如该些造孔剂硅基材料混合后，可提高浆料的分散性和稳定性，避免形成凝胶状，提高浆料的成膜性。
一些实施例中，步骤S01中在集流体上形成电极活性层的方法包括如下步骤：
S011：将第一电极浆料在集流体上形成内层电极活性层；
S012：将含有造孔剂的第二电极浆料在内层电极活性层的背离集流体的表面形成湿膜，经干燥处理和辊压处理后，形成与内层电极活性层结合的表层电极活性层。
其中，步骤S011中的第一电极浆料可以含有上文本申请实施例电极所含的活性层20中第一活性层21所含的组分，并与溶剂配制电极浆料。当然还可以是含有其他组分的电极浆料。与步骤S012中的第二电极浆料相比，其不含有造孔剂组分，以保证其在上述步骤S02中造孔处理过程中，保持内层电极活性层低的孔隙率和高的密实度。形成内层电极活性层的厚度可以按照上文本申请实施例电极所含活性层20中的第一活性层21的厚度进行控制和调节。将第一电极浆料在集流体上形成内层电极活性层的方式可以按照现有电极浆料在集流体上成膜的方式进行。
步骤S012中的第二电极浆料是可以含有上文本申请电极所含的活性层20中的第二活性层22所含的组分，并与溶剂配制电极浆料。当然还可以是含有其他组分的电极浆料。与步骤S011中的第一电极浆料相比，其含有造孔剂组分，以保证其在上述步骤S02中造孔处理过程中，能够在表层电极活性层中形成多孔结构。形成表层电极活性层的厚度可以按照上文本申请实施例电极所含活性层20中的第二活性层22的厚度进行控制和调节。将第二电极浆料在内层电极活性层上形成表层电极活性层的方式可以按照现有电极浆料在集流体上成膜的方式进行。
另外，第二电极浆料在内层电极活性层表面成膜可以是在内层电极活性层为湿膜时候直接内层电极活性层表面成膜，也可以待内层电极活性层初步干燥后在初步干燥后的内层电极活性层表面成膜。
一些实施例中，可以将第二电极浆料配置成若干份，并控制造孔剂在每一份中的含量不同，如呈梯度增加。这样，在将若干份第二电极浆料在内层电极活性层表面成膜时，可以按照造孔剂的含量由低到高的先后顺序依次成膜处理。从而使得在形成的表层电极活性层中，由内层电极活性层至外层电极活性层的方向，造孔剂含量呈梯度增加。这样，当在步骤S02的造孔处理时，可以在表层电极活性层形成的多孔结构，且使得多孔结构的孔隙率由内层电极活性层至外层电极活性层的方向呈梯度增加。
步骤S012中的干燥处理主要是为了使得湿膜干燥，但是应该保证造孔剂不被破坏。因此，该干燥处理可以是在低于上文造孔剂热分解温度一下进行干燥处理。如低于下文采用热处理的温度为70℃～150℃的温度进行干燥处理，示范例中，该干燥处理的温度可以是60～90℃。
步骤S012中的辊压处理以提高在集流体上形成的内层电极活性层和表层电极活性层构成的电极活性层的压实密度和相应的力学性能。
步骤S02：
对表层电极活性层进行造孔处理是为了在表层电极活性层中形成多孔结构，具有相对大的孔隙率，如形成比内层电极活性层孔隙率高的孔隙率。经过造孔处理后，表层电极活性层形成上文本申请实施例电极所含的活性层20中的第二活性层22，内层电极活性层构成了上文本申请实施例电极所含的活性层20中的第一活性层21。而且是先形成包括内层电极活性层和表层电极活性层的电极活性层，能够保证在步骤S02中造孔处理形成的多孔结构的稳定性。如能够避免由于先造孔处理后进行辊压处理导致的活性层表面出现过压的情况而导致孔隙率恶化的不良现象。如当表层电极活性层含有造孔剂并采用下文热处理使得造孔剂分解造孔时，先按照电极活性层的方法在集流体表面形成电极活性层，如包括干燥处理和辊压处理，先形成电极活性层，后进行热处理使得造孔剂分解形成多孔结构，从而保证多孔结构稳定性，有效避免了先造孔处理后进行辊压处理导致的活性层表面出现过压的情况而导致孔隙率恶化的不良现象。
一些实施例中，当形成表层电极活性层含有造孔剂，如示范例中，该造孔剂为上文步骤S01中的碳酸氢铵、碳酸铵、氯化铵、聚甲基丙烯酸甲酯、淀粉、聚乙烯吡咯烷酮中的至少一种时，该造孔处理是对表层电极活性层进行热处理，使造孔剂分解。由于该造孔剂在表层电极活性层中分解，从而在表层电极活性层中原位形成多孔结构，形成比内层电极活性层孔隙率高的孔隙率。
实施例中，上述热处理的温度可以是70℃～150℃，进一步可以100℃～150℃。该温度下能够有效使得上述的造孔剂分解，在表层电极活性层中留下具有丰富孔的多孔结构，并提高热处理形成的活性层力学性能。另外，该热处理的温度可以根据具体造孔剂的分解温度特性进行控制。另外，还可以控制热处理的升温速率，从而保证表层电极活性层具有丰富的扩孔结构且力学性能高，以降低热处理过程中也即是造孔剂分解过程中对表层电极活性层造成的如力学性能降低等不利影响。
电池
第三方面，本申请实施例提供了一种电池。本申请实施例电池包括正极和负极，其中，正极、负极中的至少一极片可以上文本申请实施例电极，如当正极为上文本申请实施例电极，该电极为正极，且所含的活性层20为正极活性层。当负极为上文本申请实施例电极，该电极为负极，且所含的活性层20为负极活性层。
这样，由于本申请实施例电池含有上文本申请实施例电极，因此，本申请实施例电池循环性能好，可快充，其快充能力强，同时提高了电池的安全性能。
示范例中，本申请实施例电池可以是二次电池。当本申请实施例电池为二次电池时，其包括正极、隔膜和负极。也即是，二次电池所含的正极、负极中的至少一极片可以上文本申请实施例电极。
实施例中，本申请实施例电池可以包括电池单体、电池模块、电池包中的任一种。
其中，电池单体是指包括电池壳体和封装于该电池壳体内的电芯。电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图5是作为一个示例的方形结构的电池单体30。
在一些实施例中，如图6所示，电池单体30的外包装可包括壳体31和盖板33。壳体31可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体31具有与容纳腔连通的开口，盖板33用于盖设开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺和/或叠片工艺形成电极组件32。电极组件32封装于容纳腔。电解液浸润于电极组件32中。电池单体30所含电极组件32的数量可以为一个或多个，可以根据实际需求来调节。
电池单体30的制备方法是公知的。在一些实施例中，可将正极、隔离膜、负极和电解液组装形成电池单体30。作为示例，可将正极、隔离膜、负极经卷绕工艺或叠片工艺形成电极组件32，将电极组件32置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到电池单体30。
在本申请的一些实施例中，根据本申请的电池单体30可以组装成电池模块，电池模块所含电池单体30的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图7是作为一个示例的电池模块40的示意图。如图7所示，在电池模块40中，多个电池单体30可以是沿电池模块40的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体30进行固定。
可选地，电池模块40还可以包括具有容纳空间的外壳，多个电池单体30容纳于该容纳空间。
在一些实施例中，上述电池模块40还可以组装成电池包，电池包所含电池模块40的数量可以根据电池包的应用和容量进行调节。
图8和图9是作为一个示例的电池包50的示意图。如图8和图9所示，在电池包50中可以包括电池箱和设置于电池箱中的多个电池模块40。电池箱包括上箱体51和下箱体52，上箱体51用于盖设下箱体52，并形成用于容纳电池模块40的封闭空间。多个电池模块40可以按照任意的方式排布于电池箱中。
用电装置
第四方面，本申请实施方式还提供一种用电装置，用电装置包括上文本申请实施例的电池，如可以二次电池、电池模块或电池包中的一种或多种。二次电池、电池模块或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。该用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图10是作为一个示例的用电装置的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
1.电极实施例
实施例A1
本实施例提供了一种负电极极片，包括铜箔集流体和结合在铜箔集流体上的第一活性层和结合在第一活性层的背离铜箔集流体的表面上第二活性层。其中，第二活性 层具有多孔结构，其孔隙率和第二活性层的厚度参数分别如下表1中所示。
本实施例负电极极片的制备方法包括如下步骤：
S1.第一负极浆料和第二负极浆料的配制：
第一负极浆料的配制：负极活性物质人造石墨、负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为48:48:1:2:1溶于溶剂去离子水中，配制第一负极浆料；
第二负极浆料的配制：按照第一负极浆料的配制方法，将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照比例溶于溶剂去离子水中，同时添加造孔剂碳酸氢铵造孔剂配制成第二负极浆料，并控制碳酸氢铵占负极浆料固含量的12％。
S2.在集流体上形成电极活性层：
先将步骤S1中的第一负极浆料在铜箔集流体形成内层电极活性层；再将第二负极浆料在内层电极活性层外表面形成成膜处理形成湿膜，后于70℃干燥处理后，进行冷压处理，在集流体上先后形成内层电极活性层(第一活性层)和与内层电极活性层层叠结合的外层电极活性层的复合电极活性层；
S3.对电极活性层所含的外层电极活性层进行造孔处理：
将步骤S2制备的负极半成品升温速率升温至100℃，使得外层电极活性层所含的碳酸氢铵造孔剂逐渐分解并在外层电极活性层中形成多孔结构，此时外层电极活性层形成具有多孔结构的第二活性层。
实施例A2至实施例A14
实施例A2至实施例A14分别提供了一种负电极极片，各负电极极片的结构均与实施例A1相同，不同在于各负电极极片所含第二活性层的孔隙率和厚度不同，各实施例中负电极极片所含第二活性层的孔隙率和厚度参数分别如下文表1中所示。
实施例A2至实施例A14中各负电极极片的制备方法也参照实施例A1中负电极极片制备方法制备，不同在于控制第二负极浆料所含造孔剂种类和含量的不同。
对比例A1
对比例提供了一种负电极极片，包括铜箔集流体和结合在铜箔集流体上的活性层。其中，该活性层所含材料种类和含量与实施例A1中第一活性层所含材料种类和含量相同。
本对比例负电极极片的制备方法包括如下步骤：
S1.负极浆料的配制：按照实施例A1的步骤S1配制第一负极浆料；
S2.负极浆料的配制：按照实施例A1的步骤S2成膜处理，不同在于在本对比例步骤S2中是将实施例A1的步骤S2中的第二负极浆料替换成第一负极浆料，也即是 本步骤S2中只采用不含造孔剂的第一负极浆料成膜处理，后于70℃干燥处理后，进行冷压处理，得到负极基片。
对比例A2
对比例提供了一种负电极极片，包括铜箔集流体和结合在铜箔集流体上的活性层。其中，该活性层所含材料种类和含量与对比例A1中活性层所含材料种类和含量相同。不同在于，本对比例负电极极片所含活性层的孔隙率平均控制1％，也即是本对比例负电极极片所含活性层中，不存在孔隙率差。
2.二次电池实施例
实施例B1至实施例B14和对比例B1至对比例B2
本实施例B1至实施例B14和对比例B1至对比例B2分别提供一种二次电池，各二次电池包括正极极片、隔膜和负极极片形成的电芯，还包括电解液。
其中，正极极片按照如下方法制备：
将正极活性材料镍钴锰酸锂(NCM523即LiNi 0.5Co 0.2Mn 0.3O 2)、粘结剂聚偏氟乙烯、导电剂乙炔黑按照重量比96：2：2进行混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为75wt％的正极浆料；将正极浆料按照13.7mg/cm 2的涂敷密度均匀涂覆于厚度为13μm的铝箔上；之后经过烘干、冷压、分切，得到实施例的正极极片；
负极极片：分别为上文实施例A1至实施例A14和对比例A1至对比例A2中提供的负极极片；
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5重量％(基于碳酸乙烯酯/碳酸甲乙酯溶剂的重量计)LiPF 6溶解于上述有机溶剂中，搅拌均匀，得到电解液；
隔离膜：使用市售的厚度为20μm、平均孔径为80nm的PP-PE共聚物微孔薄膜。
二次电池组装：按照正极极片/隔膜/负极极片层叠顺序依次层叠形成电芯，并将裸电芯置于外包装中，注入上述电解液并封装，分别得到二次电池；其中，实施例B1中二次电池含有上文实施例A1提供的负极极片，实施例B2中二次电池含有上文实施例A2提供的负极极片，依次类推，对比例B1中二次电池含有上文对比例A1提供的负极极片。
电极和二次电池相关数据测试
对上述各实施例和对比例中电极和二次电池分别进行如下表1中相关项目测试，测试结果如下表1中所示：
其中，25℃快充循环寿命/圈数测试方法：在25℃下，将二次电池分别以0.5C倍 率充电，以1C倍率放电，进行3％～97％电荷状态(SOC)区间的连续循环测试，直至二次电池的容量小于初始容量的80％，记录循环圈数，记为循环性能。
表1中的其他性能按照国标或行标测定。
表1
Figure PCTCN2022135503-appb-000004
由表1可知，将本申请实施例电极所含的第二活性层设置为多孔结构，并将，对其孔隙率进行控制和调节，能够有效提高丰富了锂离子迁移通道和传输空间，增大了锂离子传输速率，提高锂离子迁移的动力学性能，从而有效提高循环性能，同时保留第一活性层低的孔隙率，从而能够有效提高电极活性层的高的压实密度，提高电极的 容量。
对比实施例A1至实施例A10、实施例A13和实施例A14与实施例A11和实施例A12，控制电极所含第二活性层的厚度，也会对电极的循环性能有一定的影响，如过低(实施例A11)或过高(实施例A12)都会影响电极的循环性能；但是本申请实施例提供的电极均明显高于对比例A1中电极的循环性能。
对比实施例A1至实施例A12与实施例A13和实施例A14，控制电极所含第二活性层与第一活性层之间的孔隙率比例，也会对电极的循环性能有一定的影响，如过低(实施例A13)或过高(实施例A14)都会影响电极的循环性能。但是本申请实施例提供的电极均明显高于对比例A1中电极的循环性能。含对比例A2中电极的二次电池的循环性能和快充等性能虽然比含对比例A1中电极的二次电池有所改善，但是改善不明显，而且进一步测得其能量密度则比含对比例A1中电极的二次电池低。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (19)

  1. 一种电极，包括集流体和与所述集流体结合的活性层，其特征在于：所述活性层包括第一活性层与第二活性层，所述第一活性层与所述集流体结合，所述第二活性层结合在所述第一活性层的背离所述集流体的表面上，且所述第二活性层的孔隙率大于所述第一活性层的孔隙率。
  2. 根据权利要求1所述的电极，其特征在于：所述第二活性层的孔隙率比所述第一活性层的孔隙率高出30％以上。
  3. 根据权利要求1或2所述的电极，其特征在于：所述第二活性层的孔隙率比所述第一活性层的孔隙率高出40％～95％；和/或
    所述第二活性层的孔隙率的平均值为25％～55％；和/或
    所述第二活性层所含孔隙的直径为5～20μm。
  4. 根据权利要求1-3任一项所述的电极，其特征在于：在所述第二活性层中，沿背离所述集流体的表面方向，所述第二活性层的孔隙率呈梯度增大。
  5. 根据权利要求1-4任一项所述的电极，其特征在于：所述第一活性层与所述第二活性层总厚度不小于40μm；和/或
    所述第二活性层的厚度为10～60μm；和/或
    所述第一活性层所含活性材料的粒径Dv50大于所述第二活性层所含活性材料的粒径Dv50。
  6. 根据权利要求1-5所述的电极，其特征在于：所述第二活性层所含的活性材料包括第一活性材料和第二活性材料，且所述第一活性材料的粒径Dv50比所述第二活性材料的粒径Dv50相差30％以上。
  7. 根据权利要求1-6任一项所述的电极，其特征在于：所述第一活性层和/或所述第二活性层包括如下质量百分比含量的组分：
    活性材料 80％～97％；
    导电剂   1％～10％；
    粘结剂   1％～5％；
    分散剂   1％～5％。
  8. 根据权利要求7所述的电极，其特征在于：所述电极为正极，所述活性层所含的活性材料为正极活性材料；或
    所述电极为负极，所述活性层所含的活性材料为负极活性材料。
  9. 根据权利要求8所述的电极，其特征在于：所述正极活性材料包括镍钴锰酸锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的至少一种；和/或
    所述负极活性材料包括人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的至少一种；和/或
    所述粘结剂包括聚偏氟乙烯、苯橡胶、聚丙烯酸、聚丙烯酸钠、聚丙烯酰胺、聚乙烯醇、海藻酸钠、聚甲基丙烯酸、羧甲基壳聚糖中的至少一种；和/或
    所述导电剂包括乙炔黑、超导碳、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的至少一种；和/或
    所述分散剂包括羧甲基纤维素钠。
  10. 根据权利要求8或9所述的电极，其特征在于：所述电极为负极，且所述第二活性层所含活性材料包括无定型碳。
  11. 一种电极的制备方法，包括如下步骤：
    在集流体上形成电极活性层；
    对所述电极活性层的背离集流体的表层电极活性层进行造孔处理，在所述表层电极活性层中形成多孔结构，使得所述表层电极活性层的孔隙率大于靠近所述集流体的内层电极活性层的孔隙率。
  12. 根据权利要求11所述的制备方法，其特征在于：所述表层电极活性层的材料含有造孔剂。
  13. 根据权利要求12所述的制备方法，其特征在于：所述造孔剂占形成所述表层电极活性层的活性层浆料固含量的8wt％～20wt％；和/或
    所述表层电极活性层的厚度为10～60μm；和/或
    所述造孔剂包括碳酸氢铵、碳酸铵、氯化铵、聚甲基丙烯酸甲酯、淀粉、聚乙烯吡咯烷酮中的至少一种。
  14. 根据权利要求12或13所述的制备方法，其特征在于：所述造孔处理是对所述表层电极活性层进行热处理，使所述造孔剂分解。
  15. 根据权利要求12-14任一项所述的制备方法，其特征在于：所述热处理的温度为70℃～150℃。
  16. 根据权利要求13-15任一项所述的制备方法，其特征在于：所述在集流体上形成电极活性层的方法包括如下步骤：
    将第一电极浆料在集流体上形成内层电极活性层；
    将含有所述造孔剂的第二电极浆料在所述内层电极活性层的背离所述集流体的表面形成湿膜，经干燥处理和辊压处理后，形成与所述内层电极活性层结合的所述表层电极活性层。
  17. 根据权利要求16所述的制备方法，其特征在于：所述第二电极浆料为若干份，在所述若干份中，所述造孔剂的含量呈梯度增加，若干份的所述第二电极浆料是按照所述造孔剂的含量由低到高的先后顺序依次在所述内层电极活性层的表面成膜处理，形成所述湿膜。
  18. 一种电池，包括正极和负极，其特征在于，所述正极为权利要求1-10任一项所述的电极或由权利要求11-17任一项所述的制备方法制备的电极，且所述电极的活性层所含的活性材料为正极材料；和/或
    所述负极为权利要求1-8任一项所述的电极或由权利要求9-15任一项所述的制备方法制备的电极，且所述电极的活性层所含的活性材料为负极材料。
  19. 一种用电装置，其特征在于，所述用电装置包括如权利要求18所述的电池，所述电池用于提供电能。
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CN114975860A (zh) * 2022-06-28 2022-08-30 重庆冠宇电池有限公司 一种负极片和电池

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