WO2024055188A1 - Feuille d'électrode négative, batterie secondaire et appareil électrique - Google Patents

Feuille d'électrode négative, batterie secondaire et appareil électrique Download PDF

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Publication number
WO2024055188A1
WO2024055188A1 PCT/CN2022/118684 CN2022118684W WO2024055188A1 WO 2024055188 A1 WO2024055188 A1 WO 2024055188A1 CN 2022118684 W CN2022118684 W CN 2022118684W WO 2024055188 A1 WO2024055188 A1 WO 2024055188A1
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active material
material layer
conductive agent
negative electrode
negative
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PCT/CN2022/118684
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English (en)
Chinese (zh)
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吴凯
温浩楠
严青伟
王家政
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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 CN202280005726.7A priority Critical patent/CN118044000A/zh
Priority to PCT/CN2022/118684 priority patent/WO2024055188A1/fr
Publication of WO2024055188A1 publication Critical patent/WO2024055188A1/fr

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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
    • H01M4/13—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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

  • This application belongs to the technical field of secondary batteries, and specifically relates to a negative electrode plate, a secondary battery and an electrical device.
  • Secondary batteries are widely used in various consumer electronics and electric vehicles due to their outstanding characteristics such as light weight, no pollution, and no memory effect. As the demand for power batteries gradually expands, customers' demand for power battery energy density is also getting higher and higher.
  • the technical means used to improve the energy density of batteries often lead to the degradation of other aspects of battery performance, such as the dynamic performance, fast charging performance and cycle performance of the battery, while increasing the energy density.
  • this application provides a negative electrode plate, a secondary battery and a power device, aiming to take into account the energy density of the secondary battery while making the secondary battery have better dynamic performance and fast charging. performance and cycle performance.
  • a negative electrode plate including:
  • a negative active material layer is located on at least one surface of the negative current collector.
  • the negative active material layer includes a first conductive agent and a second conductive agent with different aspect ratios.
  • the conduction factor of the negative active material layer is expressed as is i 0 , then the conduction factor of the negative active material layer satisfies: 0.005 ⁇ i 0 ⁇ 3;
  • the conduction factor i 0 (aspect ratio of the first conductive agent*mass proportion of the first conductive agent in the negative active material layer)/total thickness of the negative active material layer+ (Aspect ratio of the second conductive agent*mass proportion of the second conductive agent in the negative active material layer)/total thickness of the negative active material layer;
  • the conduction factor i 0 ((weight of the first conductive agent in the first negative active material layer + second negative active material layer weight of the first conductive agent in the unit area)/total weight of the active material layer on one side of the negative electrode per unit area*aspect ratio of the first conductive agent+(weight of the second conductive agent in the first negative active material layer+second negative active material layer The weight of the second conductive agent)/the total weight of the active material layer on one side of the negative electrode per unit area*the aspect ratio of the second conductive agent)/the total thickness of the active material layer.
  • this application at least includes the following beneficial effects:
  • the negative electrode piece of the present application is provided with a first conductive agent and a second conductive agent with different aspect ratios, and at the same time, a conduction factor i 0 is introduced, and the conduction factor i 0 is related to the aspect ratio of the conductive agent and the conductive agent.
  • the mass proportion in the negative active material layer is positively correlated and negatively correlated with the thickness of the negative active material layer; by adjusting the aspect ratio of the first conductive agent and its mass proportion in the negative active material layer, the second conductive agent
  • the aspect ratio and its mass proportion in the negative active material layer and the thickness of the negative active material layer make the conduction factor i 0 of the negative active material layer satisfy 0.005 ⁇ i 0 ⁇ 3, even in a thicker negative electrode
  • the electron movement path in the negative active material layer can still be increased in the active material layer, so that as much negative active material as possible can participate in the charge and discharge process. In this way, when the above-mentioned negative electrode plate is applied to a secondary battery, it can improve the dynamic performance, fast charging performance and cycle performance of the secondary battery while taking into account the energy density of the secondary battery.
  • the aspect ratio of the first conductive agent is recorded as a, then the aspect ratio of the first conductive agent satisfies: a ⁇ 1000;
  • the first conductive agent includes one or more of carbon black, superconducting acetylene black, Ketjen black and nanosilver wires.
  • the aspect ratio of the second conductive agent is recorded as b, then the aspect ratio of the second conductive agent satisfies: 1000 ⁇ b ⁇ 10000;
  • the second conductive agent includes one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.
  • the negative active material layer further includes a negative active material, and the negative active material is a carbon-based active material or a mixture of a carbon-based active material and a silicon-based active material.
  • the silicon-based active material includes one or more of silicon, silicon-oxygen materials, and silicon-carbon materials.
  • the negative active material layer is a single layer, and the thickness of the negative active material layer is 46.9-126.6 ⁇ m.
  • the mass proportion of the first conductive agent in the negative active material layer is 0.5 to 5%; the mass proportion of the second conductive agent in the negative active material layer It is 0.005 ⁇ 6%.
  • the mass ratio of the carbon-based active material to the silicon-based active material is (75-100): (0-25).
  • the negative active material layer includes:
  • the first negative active material layer is located on at least one surface of the negative current collector.
  • the conduction factor of the first negative active material layer is denoted as i 1 , then the conduction factor of the first negative active material layer satisfies :0.1 ⁇ i 1 ⁇ 6;
  • the second negative electrode active material layer is located on the surface of the first negative electrode active material layer away from the negative electrode current collector.
  • the conduction factor of the second negative electrode active material layer is denoted as i 2 , then the second negative electrode active material layer
  • the conduction factor of the material layer satisfies: 0 ⁇ i 2 ⁇ 0.75.
  • the mass proportion of the silicon-based material in the first negative active material layer is greater than the mass proportion of the silicon-based material in the second negative active material layer;
  • the mass ratio of the carbon-based material and the silicon-based material in the first negative active material layer is (75-95): (5-25); the carbon-based material and silicon in the second negative active material layer are The mass ratio of the base material is (90 ⁇ 100): (0 ⁇ 10).
  • the mass proportion of the first conductive agent in the first negative active material layer is 0.5-5%; the second conductive agent in the first negative active material layer The mass proportion is 0.05 ⁇ 6%.
  • the mass proportion of the first conductive agent in the second negative active material layer is 0.5 to 5%; the second conductive agent in the second negative active material layer The mass proportion is 0 ⁇ 3%.
  • the sum of the thicknesses of the first negative active material layer and the second negative active material layer is 46.9-126.6 ⁇ m;
  • the thickness ratio of the first negative active material layer and the second negative active material layer is (0.25 ⁇ 0.67):1.
  • the negative electrode sheet has a sheet density of 8.4 mg/cm 2 to 13 mg/cm 2 .
  • a second aspect of the present application provides a secondary battery, which includes the negative electrode plate of the first aspect of the present application.
  • a third aspect of the present application provides an electrical device, which includes the secondary battery of the second aspect of the present application.
  • FIG. 1 is a schematic diagram of an embodiment of a negative electrode sheet.
  • FIG. 2 is a schematic diagram of an embodiment of a negative electrode plate.
  • FIG. 3 is a schematic diagram of an embodiment of a secondary battery.
  • FIG. 4 is an exploded view of FIG. 3 .
  • Figure 5 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • the negative electrode sheet provided by this application includes: a negative electrode current collector; a negative electrode active material layer located on at least one surface of the negative electrode current collector.
  • the negative electrode active material layer includes a first conductive agent and a second conductive agent with different aspect ratios.
  • the negative electrode The conduction factor of the active material layer is recorded as i 0 , then the conduction factor of the negative active material layer satisfies: 0.005 ⁇ i 0 ⁇ 3;
  • the conduction factor i 0 (aspect ratio of the first conductive agent*mass proportion of the first conductive agent in the negative active material layer)/total thickness of the negative active material layer+(th The aspect ratio of the second conductive agent*the mass proportion of the second conductive agent in the negative active material layer)/the total thickness of the negative active material layer;
  • the conduction factor i 0 ((weight of the first conductive agent in the first negative active material layer + the weight of the first conductive agent in the second negative active material layer The weight of a conductive agent) / the total weight of the active material layer on one side of the negative electrode per unit area * the aspect ratio of the first conductive agent + (the weight of the second conductive agent in the first negative active material layer + the second conductive agent in the second negative active material layer The weight of the second conductive agent)/the total weight of the active material layer on one side of the negative electrode per unit area*the aspect ratio of the second conductive agent))/the total thickness of the active material layer.
  • the negative electrode piece of the present application is provided with a first conductive agent and a second conductive agent with different aspect ratios, and at the same time, a conduction factor i 0 is introduced, and the conduction factor i 0 is related to the length of the conductive agent.
  • the diameter ratio is positively correlated with the mass proportion of the conductive agent in the negative active material layer, and negatively correlated with the thickness of the negative active material layer; by adjusting the aspect ratio of the first conductive agent and its mass proportion in the negative active material layer ratio, the aspect ratio of the second conductive agent and its mass proportion in the negative active material layer and the thickness of the negative active material layer, so that the conduction factor i 0 of the negative active material layer satisfies 0.005 ⁇ i 0 ⁇ 3, Even in a thick negative active material layer, the electron movement path in the negative active material layer can still be increased, so that as much negative active material as possible can participate in the charge and discharge process. In this way, when the above-mentioned negative electrode plate is applied to a secondary battery, it can improve the dynamic performance, fast charging performance and cycle performance of the secondary battery while taking into account the energy density of the secondary battery.
  • the greater the aspect ratio of the conductive agent the more elongated and linear its shape will be.
  • its dosage can be appropriately reduced.
  • the smaller the aspect ratio of the conductive agent the shape tends to be short tube or point-like.
  • its dosage can be appropriately increased.
  • the conduction factor is positively correlated with the aspect ratio of the conductive agent and the mass proportion of the conductive agent in the negative active material layer, and is negatively correlated with the thickness of the negative active material layer.
  • the conduction factor (the length of the conductive agent Diameter ratio*the mass proportion of the conductive agent in the negative active material layer)/the total thickness of the negative active material layer ( ⁇ m).
  • the conduction factor i 0 of the negative active material layer (aspect ratio of the first conductive agent * mass proportion of the first conductive agent in the negative active material layer)/ The total thickness of the negative active material layer ( ⁇ m) + (the aspect ratio of the second conductive agent * the mass proportion of the second conductive agent in the negative active material layer) / the total thickness of the negative active material layer ( ⁇ m).
  • the conduction factor i 0 of the negative active material layer is measured using the following method: 1. Before embedding lithium, perform cross-sectional CP characterization of the negative electrode piece and measure the thickness of the negative active material layer; 2. , before embedding lithium, weigh out the weight of the negative electrode piece per unit area and the weight of the negative electrode current collector per unit area, based on the formula: (weight of the negative electrode piece per unit area - weight of the negative electrode current collector per unit area)/2, calculation unit The weight of the active material layer on one side of the negative electrode per area; 3.
  • the conduction factor i 0 of the negative active material layer ((the first conductive agent in the first negative active material layer Weight + weight of the first conductive agent in the second negative electrode active material layer) / total weight of the active material layer on one side of the negative electrode per unit area * aspect ratio of the first conductive agent + ( second conductive agent in the first negative electrode active material layer Weight + weight of the second conductive agent in the second negative active material layer)/total weight of the active material layer on one side of the negative electrode per unit area*aspect ratio of the second conductive agent))/total thickness of the active material layer.
  • the conduction factor i 0 of the total negative active material layer is measured using the following method: 1. Before lithium insertion, the negative electrode piece Perform cross-sectional CP characterization and measure the thickness of the total negative active material layer; 2. Before embedding lithium, weigh the weight of the negative electrode piece per unit area and the weight of the negative electrode current collector per unit area, based on the formula: (negative electrode piece per unit area weight - the weight of the negative electrode current collector per unit area)/2, calculate the total weight of the active material layer on one side of the negative electrode per unit area; 3.
  • the first negative active material layer on the surface of the current collector; 4. Soak the second negative active material layer in pure water, rinse it several times until the binder is washed away, and dry to obtain the silicon in the second negative active material layer.
  • the weight of the agent and the weight of the second conductive agent 5.
  • the first conductive agent and the second conductive agent in the first negative active material layer are respectively Carry out SEM scanning and measure the aspect ratio of the first conductive agent and the second conductive agent in the first negative active material layer; 8. Substitute each measurement value obtained above into the formula: ((The first conductive agent in the first negative active material layer Agent weight + weight of the first conductive agent in the second negative electrode active material layer) / total weight of the active material layer on one side of the negative electrode per unit area * aspect ratio of the first conductive agent + ( second conductive agent in the first negative electrode active material layer Agent weight + weight of the second conductive agent in the second negative active material layer)/total weight of the active material layer on one side of the negative electrode per unit area*aspect ratio of the second conductive agent))/total thickness of the active material layer, calculate the total The conduction factor i 0 of the negative active material layer.
  • the inventor found that when the negative electrode plate of the present application meets the above design conditions and optionally meets one or more of the following conditions, the kinetics of the secondary battery can be further improved. performance, fast charging performance and cycle performance.
  • the aspect ratio of the first conductive agent is recorded as a, then the aspect ratio of the first conductive agent satisfies: a ⁇ 1000; for example, the aspect ratio of the first conductive agent can satisfy 1.01 ⁇ a ⁇ 800, 1.01 ⁇ a ⁇ 200, 100 ⁇ a ⁇ 500 or 200 ⁇ a ⁇ 800, etc.
  • the shape of the first conductive agent tends to be short tube-like or dot-like. Further, the aspect ratio of the first conductive agent satisfies: 1.01 ⁇ a ⁇ 200.
  • the first conductive agent includes one or more of carbon black, superconducting acetylene black, Ketjen black and nanosilver wires.
  • the aspect ratio of the second conductive agent is recorded as b, then the aspect ratio of the second conductive agent satisfies: 1000 ⁇ b ⁇ 10000; for example, the aspect ratio of the second conductive agent can satisfy 1000 ⁇ b ⁇ 5000, 2000 ⁇ b ⁇ 7000 or 5000 ⁇ b ⁇ 10000, etc.
  • the shape of the second conductive agent tends to be elongated and linear.
  • the linear second conductive agent can be attached to the surface of the silicon-based active material. In the case of a silicon-based active material While conducting electrons, it restrains the expansion of silicon-based materials during the lithium insertion process. Further, the aspect ratio of the second conductive agent satisfies: 5000 ⁇ b ⁇ 10000.
  • the second conductive agent includes one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.
  • the negative active material layer further includes a negative active material, and the negative active material is a carbon-based active material or a mixture of a carbon-based active material and a silicon-based active material.
  • the negative active material may be entirely carbon-based active material, or may be partly carbon-based active material and partly silicon-based active material.
  • the negative active material is partly carbon-based active material and partly silicon-based active material.
  • Silicon-based active materials have high capacity but their volume expansion rate is too large during the lithium intercalation process. Although carbon-based active materials have a smaller volume expansion rate during the lithium intercalation process, their capacity is lower than that of silicon-based active materials.
  • the carbon-based active material includes one or more of artificial graphite and natural graphite.
  • the silicon-based active material includes one or more of silicon, silicon-oxygen materials, and silicon-carbon materials.
  • FIG. 1 is a schematic diagram of an embodiment of a negative electrode plate.
  • the negative active material layer is a single layer, and the thickness of the negative active material layer is 46.9-126.6 ⁇ m; for example, it can be 46.9-51.5 ⁇ m, 52.5-75 ⁇ m, 54-68 ⁇ m, or 75 ⁇ m. ⁇ 126.6 ⁇ m etc.
  • Technicians have found through research that when the thickness of the negative active material layer is within the above range, the secondary battery can have excellent dynamic performance, fast charging performance and cycle performance while taking into account the energy density of the secondary battery.
  • the thickness of the above-mentioned negative electrode active material layer is measured using the following method: cross-sectional CP characterization of the negative electrode piece is performed, and the thickness of the negative electrode active material layer is measured.
  • the mass proportion of the first conductive agent in the negative active material layer is 0.5-5%; for example, it can be 0.5-1%, 1-5%, or 2-4%.
  • the mass proportion of the second conductive agent in the negative active material layer is 0.005-6%; for example, it can be 0.005-1.55%, 0.87-3.1%, 0.15-5% or 1-6%.
  • the mass ratio of the carbon-based active material to the silicon-based active material is (75 ⁇ 100): (0 ⁇ 25); for example, it can be (75 ⁇ 85): (15 ⁇ 25) or ( 85 ⁇ 100):(0 ⁇ 15) etc.
  • Embodiments of the present application also provide a method for preparing a negative electrode sheet, including: preparing a negative electrode slurry, and coating the negative electrode slurry on at least one surface of the negative electrode current collector to form a negative electrode active material layer.
  • FIG. 2 is a schematic diagram of an embodiment of a negative electrode plate.
  • the negative active material layer includes: a first negative active material layer located on at least one surface of the negative current collector, and the conduction factor of the first negative active material layer is denoted as i 1 , Then the conduction factor of the first negative active material layer satisfies: 0.1 ⁇ i 1 ⁇ 6; the second negative active material layer is located on the surface of the first negative active material layer away from the negative current collector, and the conduction factor of the second negative active material layer is The pass factor is recorded as i 2 , then the conduction factor of the second negative electrode active material layer satisfies: 0 ⁇ i 2 ⁇ 0.75.
  • the conduction factor i 1 of the first negative electrode active material layer and the conduction factor i 2 of the second negative electrode active material layer independently satisfy the above range, the first negative electrode active material layer and the conduction factor i 2 can also be made.
  • the conduction factor i 0 of the total negative active material layer composed of the second negative active material layer satisfies: 0.005 ⁇ i 0 ⁇ 3.
  • the conduction factor i 1 (aspect ratio of the first conductive agent * mass proportion of the first conductive agent in the first negative electrode active material layer) / total mass of the first negative electrode active material layer Thickness ( ⁇ m) + (aspect ratio of the second conductive agent * mass proportion of the second conductive agent in the first negative active material layer)/total thickness of the first negative active material layer ( ⁇ m).
  • the conduction factor i 1 is measured using the following method: 1. Before lithium embedding, perform cross-sectional CP characterization of the negative electrode piece and measure the thickness of the first negative electrode active material layer; 2. Before lithium embedding, take out the negative electrode piece per unit area Separate the upper and lower layers to obtain the first negative electrode active material layer located on the surface of the negative electrode current collector; 3. Weigh the weight of the negative electrode sheet per unit area after removing the second negative electrode active material layer, and the weight of the negative electrode current collector per unit area, based on Formula: (weight of the negative electrode sheet per unit area after removing the second negative electrode active material layer - weight of the negative electrode current collector per unit area)/2, calculate the weight of the first negative electrode active material layer on one side of the negative electrode per unit area; 4.
  • the current collector and the first negative active material layer located on its surface are soaked in pure water. All the first negative active material layers are washed and mixed in pure water. Filter and rinse multiple times until the binder is washed and dried.
  • the mixture of silicon-based material, carbon-based material, first conductive agent and second conductive agent in the first negative electrode active material layer is obtained by drying; and the mixture is subjected to physical classification treatment to obtain the silicon-based material in the first negative electrode active material layer. weight, the weight of the carbon-based material, the weight of the first conductive agent and the weight of the second conductive agent; 5.
  • the conduction factor i 2 (aspect ratio of the first conductive agent * mass proportion of the first conductive agent in the first negative electrode active material layer) / total mass of the first negative electrode active material layer Thickness ( ⁇ m) + (aspect ratio of the second conductive agent * mass proportion of the second conductive agent in the first negative active material layer)/total thickness of the first negative active material layer ( ⁇ m).
  • the conduction factor i 2 is measured using the following method: 1. Before lithium embedding, perform cross-sectional CP characterization of the negative electrode piece and measure the thickness of the second negative electrode active material layer; 2. Before lithium embedding, take out the negative electrode piece per unit area Separate the upper and lower layers to obtain a single layer of the second negative active material layer, and weigh its weight to obtain the weight of the second negative active material layer on one side of the negative electrode per unit area; 3.
  • the negative electrode per unit area The weight of the second negative electrode active material layer on one side is used to calculate the mass proportion of the first conductive agent in the second negative electrode active material layer; based on the weight of the second conductive agent in the second negative electrode active material layer and the second negative electrode on one side of the negative electrode per unit area According to the weight of the active material layer, calculate the mass proportion of the second conductive agent in the second negative electrode active material layer; 6.
  • the mass proportion of the silicon-based material in the first negative active material layer is greater than the mass proportion of the silicon-based material in the second negative active material layer.
  • the silicon-based material in the first negative active material layer will not produce an excessive expansion effect.
  • the electrochemical performance of the secondary battery is more affected by the second negative active material layer.
  • Providing more carbon-based materials in the second negative active material layer can improve the cycle and storage performance of the secondary battery.
  • the mass proportion of silicon-based materials in the first negative active material layer is relatively large.
  • the conduction factor i 1 of the first negative active material layer is in the above range, the mass proportion of the linear conductive agent in it is relatively large. , which can conduct electrons for the silicon-based active material while reducing the expansion of the silicon-based material during the lithium insertion process; the carbon-based material in the second negative electrode active material layer accounts for a large proportion of the mass, and the conduction of the second negative electrode active material layer
  • the pass factor i 2 is within the above range, the secondary battery can have better electrochemical performance.
  • the mass ratio of the carbon-based material and the silicon-based material in the first negative active material layer is (75 ⁇ 95): (5 ⁇ 25); for example, it can be (75 ⁇ 85): (15 ⁇ 25) or (85 ⁇ 95): (5 ⁇ 15) etc.
  • the mass ratio of the carbon-based material and the silicon-based material in the second negative electrode active material layer is (90 ⁇ 100): (0 ⁇ 10); for example, it can be (90 ⁇ 95): (5 ⁇ 10), (95 ⁇ 100): (0 ⁇ 5) or (90 ⁇ 98): (2 ⁇ 10) etc.
  • the mass proportion of the first conductive agent in the first negative active material layer is 0.5-5%; for example, it can be 0.5-1.2%, 1.5-3%, or 1-5%.
  • the mass proportion of the second conductive agent in the first negative active material layer is 0.05-6%; for example, it can be 0.05-1%, 0.3-2.1%, or 2.1-6%.
  • the mass proportion of the first conductive agent in the second negative electrode active material layer is 0.5-5%; for example, it can be 0.5-1%, 1-4%, or 2-5%.
  • the mass proportion of the second conductive agent in the second negative electrode active material layer is 0 to 3%; for example, it can be 0 to 0.5%, 0.3 to 1%, or 1 to 3%.
  • the sum of the thicknesses of the first negative active material layer and the second negative active material layer is 46.9-126.6 ⁇ m.
  • Technicians have found through research that when the sum of the thicknesses of the first negative electrode active material layer and the second negative electrode active material layer is within the above range, the secondary battery can have excellent kinetics while taking into account the energy density of the secondary battery. performance, fast charging performance and cycle performance.
  • the thickness ratio of the first negative active material layer and the second negative active material layer is (0.25 ⁇ 0.67):1.
  • the thickness of the second negative electrode active material layer is beneficial to form a gradient pore distribution between the second negative electrode active material layer and the first negative electrode active material layer, so that the active ions released from the positive electrode are dispersed in the negative electrode membrane.
  • the liquid phase conduction resistance on the surface of the layer is reduced, which can avoid the accumulation of active ions on the surface of the negative electrode film layer and cause lithium precipitation.
  • the uniform diffusion of active ions in the negative electrode film layer is conducive to reducing polarization and further improving the power of the secondary battery. chemical performance and cycle performance.
  • the ratio of the thickness of the first negative electrode active material layer and the second negative electrode active material layer mentioned above is measured using the following method: before lithium embedding, perform cross-sectional CP characterization of the negative electrode piece, and measure the thickness of the first negative electrode active material layer respectively. thickness and the thickness of the second negative electrode active material layer, and then calculate the ratio of the thickness of the first negative electrode active material layer to the thickness of the second negative electrode active material layer.
  • the negative electrode piece has an area density of 8.4 mg/cm 2 to 13 mg/cm 2 .
  • Technicians have found through research that when the density of the negative electrode piece is within the above range, the energy density and fast charging performance of the negative electrode piece can be further improved.
  • the surface density of the above-mentioned negative electrode piece is measured using the following method: Use a punching die to punch out a 1cm 2 negative electrode piece, and then weigh it to obtain the total weight M0 of the 1cm 2 piece; punch out a 1cm 2 negative electrode Clean the active material layer of the electrode piece with pure water, and then weigh it to obtain the weight M1 of the negative electrode current collector. Then calculate the electrode piece surface density of the negative electrode piece based on the formula (M0-M1)/2.
  • Embodiments of the present application also provide a method for preparing a negative electrode sheet, including the following steps:
  • the negative electrode current collector can use conventional metal foil or composite current collector.
  • the metal foil may be copper foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material layer usually also includes conductive agents, binders and other optional auxiliaries.
  • the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight, based on the total weight of the negative electrode film layer.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • other optional additives may be PTC thermistor materials, etc.
  • the weight ratio of the other additives in the negative electrode film layer is 0 to 15% by weight, based on the total weight of the negative electrode film layer.
  • Secondary batteries refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery includes a positive electrode sheet, the negative electrode sheet provided above in this application, a separator and an electrolyte.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • a positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may use a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for lithium ion batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (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 NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100% by weight, based on the total weight of the positive electrode film layer count.
  • the cathode active material may be a cathode active material known in the art for sodium-ion batteries.
  • the cathode active material may be a cathode active material known in the art for sodium-ion batteries.
  • only one type of positive electrode active material may be used alone, or two or more types may be combined.
  • the positive active material can be selected from sodium iron composite oxide (NaFeO 2 ), sodium cobalt composite oxide (NaCoO 2 ), sodium chromium composite oxide (NaCrO 2 ), sodium manganese composite oxide (NaMnO 2 ), sodium nickel Composite oxide (NaNiO 2 ), sodium nickel titanium composite oxide (NaNi 1/2 Ti 1/2 O 2 ), sodium nickel manganese composite oxide (NaNi 1/2 Mn 1/2 O 2 ), sodium iron manganese composite Oxide (Na 2/3 Fe 1/3 Mn 2/3 O 2 ), sodium nickel cobalt manganese composite oxide (NaNi 1/3 Co 1/3 Mn 1/3 O 2 ), sodium iron phosphate compound (NaFePO 4 ), sodium manganese phosphate compound (NaMn P O 4 ), sodium cobalt phosphate compound (NaCoPO 4 ), Prussian blue materials, polyanionic materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc.,
  • the positive electrode film layer also optionally includes binders, conductive agents and other optional auxiliaries.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the weight ratio of the binder in the positive electrode film layer is 0 to 20% by weight, based on the total weight of the positive electrode film layer.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0 to 20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40 to 80 wt%, and the viscosity at room temperature is adjusted to 5000 to 25000 mPa ⁇ s; the positive electrode slurry is coated on the positive electrode current collector and dried , cold pressing and other processes, the positive electrode piece can be obtained; the unit area density of the positive electrode powder coating is 150 ⁇ 350 mg/m 2 , and the compacted density of the positive electrode piece is 3.0 ⁇ 3.6g/cm 3 , optionally 3.3 ⁇ 3.5 g/cm 3 .
  • the calculation formula of the compacted density is
  • Compaction density coating surface density / (thickness of electrode piece after extrusion - thickness of current collector).
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the thickness of the isolation film is 6-40 ⁇ m, optionally 12-20 ⁇ m.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an electrolyte that serves to conduct ions between a positive electrode and a negative electrode.
  • the electrolyte solution may include electrolyte salts and solvents.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide ( LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • the concentration of the electrolyte salt is usually 0.5 to 5 mol/L.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), carbonic acid Dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), One or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulf
  • additives are also included in the electrolyte.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, and additives that improve the low-temperature performance of the battery. Additives etc.
  • the secondary battery of the present application is a lithium-ion secondary battery.
  • the secondary battery can be prepared according to conventional methods in the art, for example, the positive electrode sheet, the separator film, and the negative electrode sheet are wound (or stacked) in order, so that the separator film is between the positive electrode sheet and the negative electrode sheet for isolation. function to obtain the battery core, place the battery core in the outer package, inject the electrolyte and seal it to obtain a secondary battery.
  • FIG. 3 shows an example of a square-structured secondary battery 4 .
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • the outer package may include a housing 41 and a cover 43 .
  • the housing 41 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 41 has an opening communicating with the accommodation cavity, and the cover plate 43 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 42 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 42 .
  • the number of electrode assemblies 42 contained in the secondary battery 4 can be one or more, and can be adjusted according to requirements.
  • the above-mentioned secondary batteries can also be assembled into a battery pack, and the number of secondary batteries contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • FIG. 5 is a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of secondary batteries 4 provided in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the secondary battery 4 .
  • the plurality of secondary batteries 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery or battery pack.
  • the secondary battery or battery pack may be used as a power source for the device or as an energy storage unit for the device.
  • the device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop, 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, or an electric golf ball). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select secondary batteries or battery packs according to its usage requirements.
  • FIG. 6 shows an electrical device 5 as an example.
  • the electric device 5 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the electrode pieces After drying, the electrode pieces are cold pressed and cut into negative electrode pieces with a length of 735mm and a film width of 93mm.
  • the area density of the electrode pieces is 12 mg/cm. 2
  • the compacted density is 1.6g/cm 3
  • the total thickness of both sides of the pole piece is 158 ⁇ m.
  • the preparation method of the negative electrode piece in Examples 2-8 is basically similar to the preparation method of the negative electrode piece in Example 1.
  • the main difference lies in: the type and/or amount of the first conductive agent used when preparing the negative electrode piece, and the amount of the first conductive agent.
  • At least one of the type and/or amount of the conductive agent, the thickness of the negative active material layer, and the mass ratio of the carbon-based material and the silicon-based material in the negative active material layer is different. See Table 1 for details.
  • the preparation method of the negative electrode piece in Examples 2-8 and the preparation method of the negative electrode piece in Example 1 also include the following differences: the mass ratio of the negative active material, conductive agent and other auxiliaries and the area density of the electrode piece when preparing the negative electrode piece At least one of them is different.
  • Example 2 the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), the thickener sodium carboxymethyl cellulose (CMC), and the viscose
  • the binder styrene-butadiene rubber (SBR) is mixed according to the mass ratio of 95.795:0.005:1:1.2:2; the polar sheet density is 8.18 mg/cm 2 .
  • Example 3 the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), the thickener sodium carboxymethyl cellulose (CMC), and the binder D Styrene rubber (SBR) is mixed according to the mass ratio of 94.75:1.05:1:1.2:2; the polar sheet density is 8.26 mg/cm 2 .
  • Example 4 the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), conductive agent acetylene black (as the first conductive agent), thickener sodium carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) were mixed at a mass ratio of 92.56:3.24:1:1.2:2; the electrode sheet surface density was 8.44 mg/cm 2 .
  • Example 5 the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), nanosilver wires (as the first conductive agent), thickener sodium carboxymethyl cellulose (CMC), and binder butyl styrene
  • SBR The rubber
  • SBR is mixed according to the mass ratio of 94.76:1.04:1:1.2:2; the polar sheet density is 8.44mg/cm 2 .
  • Example 6 the negative active material, single-walled carbon nanotubes (as the second conductive agent), nanosilver wires (as the first conductive agent), thickener sodium carboxymethyl cellulose (CMC), and binder butyl styrene
  • SBR The rubber
  • SBR is mixed according to the mass ratio of 94.88:0.92:1:1.2:2; the polar sheet density is 8.44mg/cm 2 .
  • Example 7 the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), the thickener sodium carboxymethyl cellulose (CMC), and the binder D Styrene rubber (SBR) is mixed according to the mass ratio of 90.3:5.5:1:1.2:2; the polar sheet density is 8.63 mg/cm 2 .
  • Example 8 the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), the thickener sodium carboxymethyl cellulose (CMC), and the binder D Styrene rubber (SBR) is mixed according to the mass ratio of 95.275:0.525:1:1.2:2; the pole sheet density is 8.28 mg/cm 2 .
  • Preparation of the first negative electrode slurry combine the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) , the binder styrene-butadiene rubber (SBR) is mixed according to the mass ratio of 95.745:0.055:1:1.2:2, add the solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • SBR styrene-butadiene rubber
  • Preparation of the second negative electrode slurry combine the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethyl cellulose (CMC) , the binder styrene-butadiene rubber (SBR) is mixed according to the mass ratio of 95.5:0.3:1:1.2:2, add the solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • SBR styrene-butadiene rubber
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 4.22 mg/cm 2 and 6.62 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces were cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece was 10.84mg/cm 2 and the compacted density was 1.6g/cm 3 .
  • the total thickness of both sides of the pole piece was 144 ⁇ m.
  • the preparation method of the negative electrode piece in Examples 10-11 is basically similar to the preparation method of the negative electrode piece in Example 9.
  • the main difference lies in: when preparing the negative electrode piece, the first conductive agent used in the first negative active material layer is The type and/or amount, the type and/or amount of the second conductive agent in the first negative active material layer, the thickness of the first negative active material layer, and the mass ratio of the carbon-based material and the silicon-based material in the first negative active material layer At least one of them is different, see Table 2 for details.
  • the preparation method of the negative electrode sheet in Examples 10-11 and the preparation method of the negative electrode sheet in Example 9 also include the following differences: when preparing the negative electrode sheet, the negative active material, conductive agent and other auxiliary agents in the first negative active material layer At least one of the mass ratio and the polar area density is different.
  • the negative electrode active material single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener carboxymethyl Sodium cellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 94.8:1:1:1.2:2.
  • CMC carboxymethyl Sodium cellulose
  • SBR binder styrene-butadiene rubber
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 3.25 mg/cm 2 and 6.62 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 9.87mg/cm 2
  • the compacted density is 1.6g/cm 3
  • the total thickness of both sides of the pole piece is 133 ⁇ m.
  • the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 94.384:1.416:1:1.2:2.
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 2.79 mg/cm 2 and 6.62 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 9.52mg/cm 2
  • the compacted density is 1.6g/cm 3
  • the total thickness of both sides of the pole piece is 126 ⁇ m.
  • the preparation method of the negative electrode piece in Examples 12-14 is basically similar to the preparation method of the negative electrode piece in Example 10.
  • the main difference lies in: when preparing the negative electrode piece, the amount of the first conductive agent used in the second negative electrode active material layer is The type and/or amount, the type and/or amount of the second conductive agent in the second negative electrode active material layer, the thickness of the second negative electrode active material layer, and the mass ratio of the carbon-based material and the silicon-based material in the second negative electrode active material layer At least one of them is different, see Table 2 for details.
  • the preparation method of the negative electrode sheet in Examples 12-14 and the preparation method of the negative electrode sheet in Example 10 also include the following differences: when preparing the negative electrode sheet, the negative active material, conductive agent and other auxiliary agents in the second negative active material layer At least one of the mass ratio and the polar area density is different.
  • the negative electrode active material conductive agent acetylene black (as the first conductive agent), thickener sodium carboxymethylcellulose (CMC), and binder styrene-butadiene rubber (SBR) Mix according to the mass ratio of 95.8:1:1.2:2.
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 3.25 mg/cm 2 and 7.08 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 10.33mg/cm 2
  • the compacted density is 1.6g/cm 3
  • the total thickness of both sides of the pole piece is 138 ⁇ m.
  • the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 95.5:0.3:1:1.2:2.
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 3.25 mg/cm 2 and 6.1 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 9.35mg/cm 2
  • the compacted density is 1.6g/cm 3
  • the total thickness of both sides of the pole piece is 126 ⁇ m.
  • the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 95.3:0.5:1:1.2:2.
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 3.25 mg/cm 2 and 5.4 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 8.65mg/cm 2 and the compacted density is 1.6g/cm 3 .
  • the total thickness of both sides of the pole piece is 117 ⁇ m.
  • Example 15 The difference between Example 15 and Example 14 is that: the first negative active material layer in Example 14 is the same as the second negative active material layer in Example 15, and the second negative active material layer in Example 14 is the same as that in Example 14.
  • the first negative active material layer in 15 is the same.
  • the preparation of the first negative electrode slurry the negative electrode active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 95.3:0.5:1:1.2:2, add solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • CMC carboxymethylcellulose
  • SBR binder styrene-butadiene rubber
  • Preparation of the second negative electrode slurry combine the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) , the binder styrene-butadiene rubber (SBR) is mixed at a mass ratio of 94.8:1:1:1.2:2, add solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • SBR styrene-butadiene rubber
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 5.4 mg/cm 2 and 3.25 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 8.65mg/cm 2 and the compacted density is 1.6g/cm 3 .
  • the total thickness of both sides of the pole piece is 117 ⁇ m.
  • Preparation of the first negative electrode slurry add the negative active material, multi-walled carbon nanotubes (as the second conductive agent), the conductive agent Ketjen Black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC ) and the binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 94.8:1:1:1.2:2, add solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • CMC carboxymethylcellulose
  • SBR binder styrene-butadiene rubber
  • Preparation of the second negative electrode slurry combine the negative active material, multi-walled carbon nanotubes (as the second conductive agent), the conductive agent carbon black (as the first conductive agent), and the thickener sodium carboxymethylcellulose (CMC) , the binder styrene-butadiene rubber (SBR) is mixed according to the mass ratio of 95.3:0.5:1:1.2:2, add the solvent deionized water, and stir under the action of a vacuum mixer until the system is uniform;
  • SBR styrene-butadiene rubber
  • the first negative electrode slurry and the second negative electrode slurry are evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 8 ⁇ m at 3.25 mg/cm 2 and 5.4 mg/cm 2 in sequence, and dried at 110°C for 20 minutes. After drying, the pole pieces are cold-pressed and cut to obtain negative electrode pole pieces with a length of 735mm and a film width of 93mm.
  • the surface density of the pole piece is 8.65mg/cm 2 and the compacted density is 0.705g/cm 3 .
  • the total thickness of both sides of the pole piece is 253 ⁇ m.
  • Example 17 The difference between Example 17 and Example 2 is that in Example 17, the negative active material, single-walled carbon nanotubes (as the second conductive agent), the conductive agent acetylene black (as the first conductive agent), and the thickener carboxymethyl Sodium cellulose (CMC) and binder styrene-butadiene rubber (SBR) are mixed at a mass ratio of 94.2:1.6:1:1.2:2; the pole sheet density is 6.8 mg/cm 2 .
  • CMC carboxymethyl Sodium cellulose
  • SBR binder styrene-butadiene rubber
  • the preparation method of the negative electrode piece in Comparative Example 1 is basically similar to the preparation method of the negative electrode piece in Example 1. The difference is that only the first conductive agent is included, and the negative active material of the same quality is used instead of the second conductive agent. For details, see Table 1.
  • the preparation method of the negative electrode piece in Comparative Example 2 is basically similar to the preparation method of the negative electrode piece in Example 2. The difference is that only the first conductive agent is included, and the negative active material of the same quality is used instead of the second conductive agent. For details, see Table 1.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 3 and the negative electrode sheet in Example 9 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 4 and the negative electrode sheet in Example 10 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 5 and the negative electrode sheet in Example 11 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 6 and the negative electrode sheet in Example 12 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 7 and the negative electrode sheet in Example 13 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the difference between the preparation method of the negative electrode sheet in Comparative Example 8 and the negative electrode sheet in Example 14 is that: the first negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used instead of the second conductive agent; A negative active material layer only includes the first conductive agent, and the negative active material of the same quality is used to replace the second conductive agent. See Table 2 for details.
  • the thickness of the material layer can adjust the conduction factor of the active material layer. See Table 1 or Table 2 for details.
  • the parameters of the negative electrode plates of Examples 1-8, 17 and Comparative Examples 1-2 are as shown in Table 1 below.
  • the parameters of the negative electrode pieces of Examples 9 to 16 and Comparative Examples 3 to 8 are as shown in Table 2 below.
  • i 0 in Table 1 and Table 2 represents the conduction factor of the negative active material layer when the negative active material layer is a single layer, or the conduction factor of the total negative active material layer when the negative active material layer is two layers; i total Indicates the conduction factor of the total negative active material layer when there are two negative active material layers.
  • i 1 indicates the conduction factor of the first negative active material layer when there are two negative active material layers.
  • i 2 indicates that the negative active material layer is The conduction factor of the second negative active material layer when there are two layers.
  • L 0 represents the thickness of the negative electrode active material layer when the negative electrode active material layer is a single layer
  • L 1 represents the thickness of the first negative electrode active material layer when the negative electrode active material layer is a double layer
  • L 2 represents the thickness of the first negative electrode active material layer when the negative electrode active material layer is a double layer The thickness of the two negative electrode active material layers.
  • r1 represents the aspect ratio of the first conductive agent
  • r2 represents the aspect ratio of the second conductive agent
  • n 01 indicates the mass proportion of the first conductive agent when the negative active material layer is a single layer
  • n 02 indicates the mass proportion of the second conductive agent when the negative active material layer is a single layer
  • n 11 indicates that the negative active material layer is two layers
  • n 12 represents the mass proportion of the second conductive agent in the first negative active material layer when the negative active material layer is two layers
  • n 21 Indicates the mass proportion of the first conductive agent in the second negative electrode active material layer when the negative electrode active material layer is two layers.
  • n 22 indicates the mass proportion of the second conductive agent in the second negative electrode active material layer when the negative electrode active material layer is two layers. The quality ratio in .
  • m 0 represents the mass ratio of the carbon-based active material and the silicon-based active material in the negative active material layer when the negative active material layer is a single layer
  • m 1 represents the carbon-based active material in the first negative active material layer when there are two negative active material layers.
  • m2 represents the mass ratio of the carbon-based active material and the silicon-based active material in the second negative active material layer when the negative active material layer is two layers.
  • SWCNT stands for single-walled carbon nanotube
  • MWCNT stands for multi-walled carbon nanotube
  • NCM 811 lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O 2
  • Super P conductive agent carbon black
  • PVDF binder polyvinylidene fluoride
  • NMP N-Methylpyrrolidone
  • the compacted density of the positive electrode piece is 3.5g/cm 3 and the areal density is 18.04mg/cm 2 .
  • Isolation film Polyethylene film (PE) with a thickness of 12 ⁇ m is used as the isolation film.
  • Preparation of the secondary battery Stack the positive electrode sheet, the isolation film, and the negative electrode sheet in the above embodiments or comparative examples in order, so that the isolation film plays an isolation role between the positive and negative electrode sheets, and then
  • the bare battery core is obtained by winding; the bare battery core is placed in an outer packaging shell, dried and then injected with the electrolyte prepared above. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.
  • Each prepared secondary battery was charged to 3.4V at a rate of 0.02C at 45°C, then charged to 3.75V at a rate of 0.1C.
  • the measured capacity was marked C0, and then charged to 4.25V at a rate of 0.33C at 25°C.
  • V the capacity measured by charging at 4.25V constant voltage to 0.05C is marked as C1
  • the capacity measured by discharging to 2.5V at 0.33C is marked as D0; let it stand for 5 minutes; discharge it with 0.33D0 to 2.5V; let it stand 5 minutes; charge to 4.25V at 0.33D0, charge to 0.05D0 at 4.25V constant voltage; let it stand for 5 minutes; discharge at 0.33D0 for 90 minutes.
  • the battery power is 50% of the full charge, which is called 50 % SOC; record the resting voltage after 30 minutes of rest and mark it as V0; record the voltage V1 after discharging with 4D0 for 30 seconds.
  • 50% SOC discharge DCR (V0-V1)/4D0.
  • Each prepared secondary battery was charged to 3.4V at a rate of 0.02C at 45°C, then charged to 3.75V at a rate of 0.1C.
  • the measured capacity was marked C0, and then charged to 4.25V at a rate of 0.33C at 25°C.
  • V the capacity measured by charging at 4.25V constant voltage to 0.05C is marked as C1
  • the capacity measured by discharging to 2.5V at 0.33C is marked as D0; let it stand for 5 minutes; discharge it with 0.33D0 to 2.5V; let it stand 5 minutes; charge to 4.25V at 0.33D0, charge to 0.05D0 at 4.25V constant voltage; let it stand for 5 minutes; discharge at 0.33D0 for 90 minutes.
  • the battery power is 50% of the full charge, which is called 50 % SOC; record the resting voltage after 30 minutes of rest and mark it as V2; record the voltage V3 after charging with 4D0 for 30 seconds.
  • 50% SOC charging DCR (V3-V2)/4D0.
  • the main difference between Examples 2-4 is that by adjusting the mass proportion of the second conductive agent with a large aspect ratio and the thickness of the negative active material layer, the conduction factor of the negative active material layer is adjusted; from the embodiment It can be seen from the results of 2-4 that by increasing the mass proportion of the second conductive agent with a large aspect ratio, the conduction factor of the negative active material layer can be improved, thereby improving the kinetic performance, fast charging performance and cycle performance of the secondary battery. .
  • Embodiments 14-15 The main difference between Embodiments 14-15 is that the first negative active material layer in Embodiment 14 is the same as the second negative active material layer in Embodiment 15, and the second negative active material layer in Embodiment 14 is the same as that in Embodiment 15.
  • the first negative active material layer in is the same; it can be seen from the results of Example 14 and Example 15 that when the negative active material layer is two layers, the conduction factor of the total negative active material layer satisfies 0.005 ⁇ i 0 ⁇ 3
  • the mass proportion of the silicon-based material in the first negative electrode active material layer is set to be greater than the mass proportion of the silicon-based material in the second negative electrode active material layer, and the thickness of the first negative electrode active material layer is set to be smaller than the second negative electrode active material layer.
  • the thickness of the active material layer while the conduction factor of the first negative active material layer satisfies 0.1 ⁇ i 1 ⁇ 6, and the conduction factor of the second negative active material layer satisfies 0 ⁇ i 2 ⁇ 0.75, can further improve the performance of the secondary battery. Kinetic performance, fast charging performance and cycle performance.
  • Example 1 and Comparative Example 1 From the results of Example 1 and Comparative Example 1, the results of Example 2 and Comparative Example 2, the results of Example 9 and Comparative Example 3, the results of Example 10 and Comparative Example 4, the results of Example 11 and Comparative Example 5 , the results of Example 12 and Comparative Example 6, the results of Example 13 and Comparative Example 7, and the results of Example 14 and Comparative Example 8, it can be seen that when the negative active material layer contains a linear conductive agent with a large aspect ratio , can improve the fast charging performance and cycle capacity retention rate of secondary batteries; and reduce the full charge expansion rate of the negative electrode sheet after 500 cycles, especially when the negative active material layer contains silicon-based active materials, the negative active material layer After adding the linear conductive agent, the volume expansion rate of the negative electrode plate decreased more significantly.
  • the technician analyzed the reason. This may be because the linear conductive agent can adhere to the surface of the silicon-based active material and conduct conduction for the silicon-based active material. The electrons simultaneously bind the expansion of the silicon-based material during the lithium insertion process.

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Abstract

La présente invention concerne une feuille d'électrode négative, une batterie secondaire et un appareil électrique. La feuille d'électrode négative comprend : un collecteur de courant d'électrode négative ; et une couche de matériau actif d'électrode négative située sur au moins une surface du collecteur de courant d'électrode négative, la couche de matériau actif d'électrode négative comprenant un premier agent conducteur et un second agent conducteur ayant différents rapports de forme, un facteur de conduction de la couche de matériau actif d'électrode négative étant désigné i0, et le facteur de conduction de la couche de matériau actif d'électrode négative satisfaisant : 0,005 ≤ i0 ≤ 3.
PCT/CN2022/118684 2022-09-14 2022-09-14 Feuille d'électrode négative, batterie secondaire et appareil électrique WO2024055188A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015053165A (ja) * 2013-09-06 2015-03-19 日立化成株式会社 リチウムイオン二次電池用正極及びリチウムイオン二次電池
CN109980199A (zh) * 2019-03-20 2019-07-05 宁德新能源科技有限公司 负极活性材料及其制备方法及使用该负极活性材料的装置
CN112670445A (zh) * 2020-12-22 2021-04-16 银隆新能源股份有限公司 锂离子电池负极及其制备方法、锂离子电池
WO2021251663A1 (fr) * 2020-06-11 2021-12-16 주식회사 엘지에너지솔루션 Anode et batterie secondaire la comprenant

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015053165A (ja) * 2013-09-06 2015-03-19 日立化成株式会社 リチウムイオン二次電池用正極及びリチウムイオン二次電池
CN109980199A (zh) * 2019-03-20 2019-07-05 宁德新能源科技有限公司 负极活性材料及其制备方法及使用该负极活性材料的装置
WO2021251663A1 (fr) * 2020-06-11 2021-12-16 주식회사 엘지에너지솔루션 Anode et batterie secondaire la comprenant
CN112670445A (zh) * 2020-12-22 2021-04-16 银隆新能源股份有限公司 锂离子电池负极及其制备方法、锂离子电池

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