WO2023082039A1 - 负极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

负极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023082039A1
WO2023082039A1 PCT/CN2021/129506 CN2021129506W WO2023082039A1 WO 2023082039 A1 WO2023082039 A1 WO 2023082039A1 CN 2021129506 W CN2021129506 W CN 2021129506W WO 2023082039 A1 WO2023082039 A1 WO 2023082039A1
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active material
negative electrode
material layer
electrode sheet
battery
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PCT/CN2021/129506
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English (en)
French (fr)
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吕树芹
李晓伟
裴振兴
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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 JP2023501362A priority Critical patent/JP2023552027A/ja
Priority to CN202180088578.5A priority patent/CN116670861A/zh
Priority to PCT/CN2021/129506 priority patent/WO2023082039A1/zh
Priority to KR1020237001017A priority patent/KR20230070442A/ko
Priority to EP21939977.1A priority patent/EP4207361A4/en
Priority to US18/069,989 priority patent/US20230146812A1/en
Publication of WO2023082039A1 publication Critical patent/WO2023082039A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • 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
    • 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
    • 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
    • H01M4/133—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
    • H01M4/139—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 technical field of lithium batteries, in particular to a negative pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • the wide application of lithium-ion batteries has led to higher and higher requirements for the overall performance of batteries. More and more application scenarios require power batteries to have both high energy density and good charge and discharge characteristics.
  • the design of the negative electrode directly affects the performance of the battery, especially the charging-related characteristics of the battery. How to obtain a battery with both energy density and kinetic performance by optimizing the design of the negative electrode sheet is a common challenge in the industry.
  • the purpose of this application is to provide a negative electrode sheet to meet the existing needs.
  • the present application also provides a secondary battery, a battery module, a battery pack and an electrical device using the negative electrode sheet.
  • the inventors of the present application have found that by using two or more layers of active material on the negative electrode, and adjusting the relationship between the layer spacing of each layer of active material and the coating weight, it is possible to obtain a higher energy Density and better charge-discharge kinetic performance of the battery negative electrode.
  • the first aspect of the present application provides a negative electrode sheet, including a negative electrode current collector and an active material layer disposed on at least one surface of the negative electrode current collector, wherein the active material layer includes a first active material layer. a material layer and a second active material layer disposed on the surface of the first active material layer, the first active material layer includes a first active material, the second active material layer includes a second active material, and the active The material layer satisfies: ⁇ CW 2 ⁇ CW 1 , where,
  • d 1 interlayer spacing corresponding to the d002 peak of the first active material, in nm;
  • CW 1 the mass of the first active material layer set on the negative electrode current collector per unit area, the unit is: g/m 2 ;
  • CW 2 the mass of the second active material layer provided on the negative electrode current collector per unit area, the unit is g/m 2 .
  • the application limits the coating weight of the second active material layer.
  • the distance between the active material layers of the second layer of active material is larger, it means that its charging ability is stronger and its capacity is lower.
  • the coating weight is small, a good charging level can be achieved; when the second layer of active material The distance between the active material layers of the first layer is relatively small, and its charging ability becomes weaker, and its capacity is higher.
  • the coating weight of the second active material layer accounts for the coating weight of the entire electrode sheet.
  • the coat-to-weight ratio should be increased.
  • the inventors of the present application have unexpectedly found that, using a double-layer active material layer structure, the active material layer spacing of the first active material layer is small and the capacity is high, so that the pole piece and battery have a relatively high energy density; the second layer
  • the active material layer of the active material layer has a large spacing between the active material layers, which reduces the lithium intercalation resistance on the surface of the negative electrode sheet.
  • a battery negative electrode with an active material layer that satisfies the above relationship has both energy density and good charge-discharge kinetic performance.
  • the active material layer satisfies:
  • the inventor further limited the coating weight and relationship between layers. When this relationship is satisfied, the rate performance and energy density of the negative electrode sheet and the battery can be better improved.
  • Da 50 the volume average particle diameter of the first active material, in ⁇ m
  • Db 50 the volume average particle diameter of the second active material, in ⁇ m.
  • the coating weight of the active material layer is adjusted, so that the pole piece and the battery can take into account the fast charging performance and energy density.
  • volume average particle diameter Da 50 of the first active material and the volume average particle diameter Db 50 of the second active material satisfy
  • the kinetic performance is further improved, and it is beneficial to realize the processing performance when the coating amount of the second layer is low.
  • the range of the interlayer spacing d1 corresponding to the d002 peak of the first active material is 0.335-0.3362 nm
  • the range of the interlayer spacing d2 corresponding to the d002 peak of the second active material is 0.3356 ⁇ 0.38nm.
  • the volume average particle diameter Da50 of the first active material is in the range of 8-20 ⁇ m
  • the volume average particle diameter Db50 of the second active material is in the range of 4-12 ⁇ m.
  • the mass CW 1 of the first active material layer provided on the negative electrode current collector per unit area ranges from 80 to 200 g/m 2
  • the mass CW 1 of the second active material layer provided on the negative electrode current collector per unit area is The mass CW 2 ranges from 10 to 110 g/m 2 .
  • the first active material is natural graphite or artificial graphite material
  • the second active material is artificial graphite material
  • the first active layer and/or the second active layer contains soft carbon or hard carbon.
  • the second aspect of the present application provides a secondary battery, which includes the negative electrode sheet of the first aspect of the present application.
  • a third aspect of the present application provides a battery module, which includes the secondary battery of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack, which includes one of the secondary battery of the second aspect of the present application and the battery module of the third aspect.
  • the fifth aspect of the present application provides an electric device, which includes at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the negative electrode sheet of the present application.
  • FIG. 2 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 3 is an exploded schematic view of an embodiment of the secondary battery of the present application.
  • Fig. 4 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 5 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 6 is an exploded view of FIG. 5 .
  • FIG. 7 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source of the present application.
  • Embodiments of the negative electrode sheet, the secondary battery, the battery module, the battery pack, and the electrical device of the present application are disclosed in detail below in detail with reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known items and repeated descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.
  • ranges disclosed herein are defined in terms of lower and upper limits, and 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 and may be combined arbitrarily, ie 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, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, 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" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • 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 in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, 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) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active material after the battery is discharged and continue to be used.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions such as lithium ions
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte is between the positive pole piece and the negative pole piece, and mainly plays the role of conducting active ions.
  • the design of the negative electrode directly affects the performance of the battery, especially the charging-related characteristics of the battery. How to obtain a battery with both energy density and kinetic performance by optimizing the design of the negative electrode sheet is a common challenge in the industry.
  • the negative electrode sheet of the present application adopts double or multiple active material layers, and regulates the relationship between the layer spacing of each active material layer and the coating weight, which can have both high energy density and good charge and discharge kinetic performance.
  • the negative electrode sheet of the present application includes a negative electrode current collector and an active material layer arranged on at least one surface of the negative electrode current collector, wherein the active material layer includes a first active material layer and an active material layer arranged on the surface of the first active material layer on the second active material layer, the first active material layer includes the first active material, the second active material layer includes the second active material, and the active material layer satisfies: ⁇ CW 2 ⁇ CW 1 , where ,
  • d 1 interlayer spacing corresponding to the d002 peak of the first active material, in nm;
  • CW 1 the mass of the first active material layer set on the negative electrode current collector per unit area, unit: g/m 2 ; if both sides of the negative electrode current collector are provided with the first active material layer and the second active material layer, it should be Bifacial quality of the first active material layer.
  • CW 2 the mass of the second active material layer set on the negative electrode current collector per unit area, unit: g/m 2 ; if both sides of the negative electrode current collector are provided with the first active material layer and the second active material layer, it should be Bifacial quality of the second active material layer.
  • the present application adopts double or multi-layer active material layers on the negative electrode, and regulates the relationship between the layer spacing of each layer of active material layers and the coating weight, so as to obtain a combination of higher energy density and higher energy density.
  • a battery negative electrode with better charge and discharge kinetics More specifically, the inventors of the present application have found that two layers of active material layers are coated on the current collector on the same side of the negative electrode sheet, and the active material layer spacing of the second active material layer is greater than that of the first active material layer.
  • lithium ions migrate from the positive electrode to the negative electrode, due to the large interlayer spacing of the surface material and the low lithium ion intercalation resistance, lithium ions can be quickly embedded in the surface active material to avoid lithium ions in the negative electrode due to excessive charging rate. surface precipitation. Because the larger the distance between the layers of the negative electrode active material, the lower the capacity of the material, and the greater the coating weight of the second layer of active material, the greater the impact on the overall capacity of the negative electrode sheet. In order to take into account both the capacity of the negative electrode sheet and the performance of the charging window, this application requires the coating weight of the second active material layer. When the distance between the active material layers of the second layer of active material is larger, it means that its charging ability is stronger and its capacity is lower.
  • the coating weight when the coating weight is small, a good charging level can be achieved; when the second layer of active material The distance between the active material layers of the first layer is relatively small, and its charging ability becomes weaker, and its capacity is higher. At this time, in order to make the overall electrode sheet have better charging performance, the coating weight of the second active material layer accounts for the coating weight of the entire electrode sheet. The coat-to-weight ratio should be increased.
  • the inventors of the present application have found that using a double-layer active material layer structure, the active material layer spacing of the first active material layer is small and the capacity is high, so that the pole piece and the battery have a relatively high energy density; The active material layer spacing is large, which reduces the lithium intercalation resistance on the surface of the negative electrode sheet.
  • a battery negative electrode with an active material layer that satisfies the above relationship has both energy density and good charge-discharge kinetic performance.
  • the active material layer satisfies:
  • the weight of the second active material layer is adjusted according to the layer spacing and the weight of the first active material layer. On the whole, in order to make the negative electrode sheet have both high energy density and dynamic performance, the coating weight of the second active material layer should satisfy
  • the inventors of the present application have found that the smaller the weight of the active material layer coated on the negative electrode sheet, the larger the layer spacing of the active material, the lower the internal resistance of the electrode sheet and the battery, and the better the charge and discharge performance, but the weight of the active material layer is small and The active material layer spacing is large, and under the same battery capacity, the energy density of the battery decreases due to the increase in the amount of foil and other auxiliary materials and the increase in the amount of materials used.
  • the inventor further limited the coating weight and relationship between layers. When this relationship is satisfied, the rate performance and energy density of the negative electrode sheet and the battery can be better improved.
  • Da 50 the volume average particle diameter of the first active material, in ⁇ m
  • Db 50 the volume average particle diameter of the second active material, in ⁇ m.
  • each active material layer adjusts the coating weight of the active material layer and the active material particle size between each active material layer to meet: and inversely proportional to At the same time, the pole piece and the battery take into account the fast charging performance and energy density.
  • the volume average particle diameter Da 50 of the first active material and the volume average particle diameter Db 50 of the second active material satisfy
  • the relative relationship between the particle sizes of the active materials in the two active material layers is specified to further improve the kinetic performance and facilitate the realization of processing performance when the coating amount of the second layer is low.
  • the interlayer distance d1 corresponding to the d002 peak of the first active material ranges from 0.335 to 0.3362 nm
  • the interlayer distance d2 corresponding to the d002 peak of the second active material ranges from 0.3356 to 0.38 nm. nm.
  • the volume average particle diameter Da50 of the first active material ranges from 8 to 20 ⁇ m
  • the volume average particle diameter Db50 of the second active material ranges from 4 to 12 ⁇ m.
  • the mass CW 1 of the first active material layer set on the negative electrode current collector per unit area ranges from 80 to 200 g/m 2
  • the mass CW 2 of the second active material layer set on the negative electrode current collector per unit area is The range is 10-110g/m 2 .
  • the volume average particle diameter D50 of a material is a well-known meaning in the art, and can be measured by methods and instruments known in the art. For example, it can be determined by using a laser particle size analyzer (such as the British Malvern Mastersizer 2000E) with reference to the GB/T 19077-2016 particle size distribution laser diffraction method.
  • a laser particle size analyzer such as the British Malvern Mastersizer 2000E
  • the negative electrode sheet further includes a conductive agent and a binder, the type and content of which are not specifically limited, and can be selected according to actual needs.
  • the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • Binders may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylamide (PAM), One or more of polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resins
  • acrylic resins for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylamide (PAM), One or more of polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • Other optional additives can be the same or different.
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the active material layer is disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two opposing surfaces in its thickness direction, and the active material layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • FIG. 1 shows a negative electrode current collector and an active material layer on its surface, wherein both surfaces of the negative electrode current collector shown in FIG. 1 have a first active material layer and a second active material layer.
  • the negative electrode sheet 10 of the present application can also have other embodiments.
  • the negative electrode sheet 10 is composed of the negative electrode current collector 11, the first active material layer 121 disposed on one side of the negative electrode current collector, and the first active material layer 121 disposed on the first active material layer.
  • the second active material layer 122 on the material layer 121 is formed.
  • the negative electrode sheet of the present application does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet of the present application may further include a conductive primer layer (for example, composed of a conductive agent and a binder) disposed between the negative electrode current collector and the second negative electrode film layer.
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the first negative electrode film layer.
  • the preparation method of the negative electrode sheet of the present application may include the following steps:
  • the coating amounts of the first active material layer and the second active material layer satisfy CW 1 and CW 2 respectively.
  • the slurry A includes the first active material, one or more of a conductive agent, a binder and a thickener.
  • the slurry B includes a second active material, one or more of a conductive agent, a binder and a thickener.
  • the secondary battery includes a positive electrode sheet
  • the positive electrode sheet generally includes a positive electrode collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector and including a positive electrode active material.
  • the positive electrode current collector has two opposite surfaces in its 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 can be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used for the positive electrode current collector.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode film layer includes a positive electrode active material
  • the positive electrode active material can be a positive electrode active material known in the art for secondary batteries.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, 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 One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium manganese iron phosphate
  • One or more of the composite materials with carbon and their respective modified compounds may be not limited to these materials, and other conventionally known materials that can be used as a secondary battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the modified compounds of the above-mentioned positive electrode active materials may be doping modification, surface coating modification, or both doping and surface coating modification of the positive electrode active material.
  • the positive electrode film layer generally includes a positive electrode active material, optionally a binder, and optionally a conductive agent.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder used for the positive film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoro One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoro
  • fluorine-containing acrylate resin fluorine-containing acrylate resin
  • the conductive agent used in the positive film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the composition or parameters of each positive electrode film layer given in this application all refer to the composition or parameter range of a single film layer of the positive electrode current collector.
  • the positive electrode film layer is arranged on two opposite surfaces of the positive electrode current collector, if the composition or parameters of the positive electrode film layer on any one of the surfaces meet the requirements of this application, it is deemed to fall within the protection scope of this application.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the secondary battery of the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the type of electrolyte salt is not specifically limited, and can be selected according to actual needs.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAs F 6 (lithium hexafluoroarsenate), LiFSI (difluorosulfonyl Lithium imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO 2 F 2 ( One or more of lithium difluorophosphate), LiDFOP (lithium difluorooxalatephosphate) and LiTFOP (lithium tetrafluorooxalatephosphate).
  • the type of solvent is not specifically limited, and can be selected according to actual needs.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate ester (DPC), methyl propyl carbonate (MPC), ethylene propyl 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), butyric acid
  • ethyl ester EB
  • 1,4-butyrolactone GBL
  • sulfolane SF
  • MSM dimethyl sulfone
  • the solvent is a non-aqueous solvent.
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from one or more 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. When the separator is a multilayer composite film, the materials of each layer may be the same or different.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • 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 can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 2 shows a secondary battery 5 with a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to requirements.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • Embodiments of the present application further provide an electric device, the electric device includes at least one of the secondary battery, the battery module, and the battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 7 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the lithium ion batteries comprising the negative electrode sheet of the present application of Examples 1-9 were prepared according to the following method.
  • the first active material of the first active material layer, the conductive agent Super-P, the binder SBR, and the thickener CMC are mixed in a mass ratio of 96:1:2:1, and the deionized After fully stirring and mixing in the water solvent system, the slurry A is obtained;
  • the second active material of the second active material layer, the conductive agent Super-P, the binder SBR, and the thickener CMC are mixed in a mass ratio of 96:1:2:1, and the deionized After fully stirring and mixing in the water solvent system, the slurry B is obtained;
  • the coating amounts of the first active material layer and the second active material layer satisfy CW 1 and CW 2 respectively.
  • NMP solvent N-methylpyrrolidone
  • a polyethylene film was used as a separator.
  • the positive electrode, separator, and negative electrode in order, so that the separator is between the positive electrode and the negative electrode for isolation, and then wind the electrode assembly; place the electrode assembly in the outer packaging After being dried, the electrolyte is injected, and the secondary battery is obtained through processes such as vacuum packaging, standing still, chemical formation, and shaping.
  • the preparation method of the secondary battery of Comparative Examples 1-3 is similar to that of Examples 1-13, the difference lies in the preparation process of the negative electrode sheet, see Table 1 for details.
  • Charging time at 25°C, at 85% SOC, the time used for constant current charging to 85% SOC at the rate of constant current charging to 85% SOC is the charging time described in this application.
  • the present application adopts two or more active material layers on the negative electrode, and regulates the relationship between the layer spacing of each layer of active material layers and the coating weight, so as to obtain a higher energy density and better Battery negative electrode with charge and discharge kinetics.
  • the negative electrode materials prepared by the method of the present invention all satisfy the charging time ⁇ 75min and the 0.3C energy density ⁇ 170Wh/kg.
  • Comparative Examples 1-3 do not conform to the relationship between the layer spacing of each layer of active material layers of the present application and the coating weight, specifically, Comparative Example 1 is compared with Example 1 of the present application, wherein in Comparative Example 1 The second active material uses hard carbon with a larger layer spacing, and its capacity density is much lower than that of Example 1 of the present application. That is to say, the larger the distance between the active material layers of the second active material layer, the stronger the charging capacity, but the lower the capacity, which obviously fails to balance the energy density and charge-discharge kinetic performance.
  • the interlayer spacing relative factor ⁇ is not within the scope of this application (1 ⁇ 1.12), and energy density and charge-discharge kinetic performance cannot be taken into account.
  • Comparative Example 3 is a single-layer coating, which shows that under the premise of the same coating amount, single-layer coating cannot balance the energy density and charge-discharge kinetic performance.
  • the CW 2 /(CW 2 +CW 1 ) of Example 5 exceeds the scope of the present application, resulting in that although the charging and discharging kinetics performance is good, the energy density cannot be taken into account.
  • the example The CW 2 /(CW 2 +CW 1 ) of 4 exceeds the scope of the present application, resulting in that although the energy density is good, the kinetic performance of charge and discharge cannot be balanced.
  • Example 6 Compared with Example 1, Example 6, and Example 7, the Db50/Da50 of Example 8 and Example 9 are outside the scope of this application, and the energy density and charge-discharge kinetic performance cannot be balanced.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

Abstract

本申请公开了一种负极极片、二次电池、电池模块、电池包和用电装置。本申请公开的负极极片包括负极集流体和设置在所述负极集流体至少一个表面的活性物质层，其中，所述活性物质层包括第一活性物质层和设置在所述第一活性物质层表面上的第二活性物质层，所述第一活性物质层包括第一活性材料，所述第二活性物质层包括第二活性材料，所述活性物质层满足：α×CW 2≤CW 1，其中，α：层间距相对因子，(I) 且1≤α≤1.12。使用本申请的负极极片获得的二次电池，电池的倍率性能与能量密度均能得到较好提升。

Description

负极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种负极极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，锂离子电池的应用范围越来越广泛，例如，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。锂离子电池的广泛应用，导致当前对电池的综合性能要求也越来越高，越来越多的应用场景要求动力电池既具备较高的能量密度，又具有良好的充放电特性。负极作为锂离子电池最关键的组成之一，其设计直接影响电池的性能发挥，特别是电池的充电相关特性。如何通过优化负极极片设计，从而得到兼顾能量密度和动力学性能的电池是目前行业内普遍面临的挑战。
发明内容
本申请的目的在于针对现有的需求，提供一种负极极片。本申请还提供了使用该负极极片的二次电池、电池模块、电池包和用电装置。本申请的发明人发现，通过在负极采用双层或多层活性物 质层，并调控各层活性物质层的层间距与涂敷重量的之间的关系，可以获得一种兼具更高的能量密度和更好的充放电动力学性能的电池负极。
为了达到上述目的，本申请的第一方面提供了一种负极极片，包括负极集流体和设置在所述负极集流体至少一个表面的活性物质层，其中，所述活性物质层包括第一活性物质层和设置在所述第一活性物质层表面上的第二活性物质层，所述第一活性物质层包括第一活性材料，所述第二活性物质层包括第二活性材料，所述活性物质层满足：α×CW 2≤CW 1，其中，
α：层间距相对因子，
Figure PCTCN2021129506-appb-000001
且1≤α≤1.12；
d 1：第一活性材料的d002峰对应的层间距，单位为nm；
d 2：第二活性材料的d002峰对应的层间距，单位为nm；
CW 1：单位面积负极集流体上设置的第一活性物质层的质量，单位为：g/m 2；
CW 2：单位面积负极集流体上设置的第二活性物质层的质量，单位为：g/m 2。
由此，通过在负极采用双层或多层活性物质层，并调控各层活性物质层的层间距与涂敷重量的之间的关系，可以获得一种兼具更高的能量密度和更好的充放电动力学性能的电池负极。更具体地，本申请的发明人发现，在负极极片同一侧集流体上涂敷两层活性物质层，第二层活性物质层的活性材料层间距大于第一层活性物 质层的活性材料层间距，锂离子从正极迁移到负极时，因表层的材料层间距大，锂离子嵌入阻抗低，锂离子能够快速嵌入到表层活性材料中，避免因充电速率过大，导致锂离子在负极极片表面析出。因负极活性材料层间距越大，材料的容量越低，第二层活性材料的涂敷重量越大，对负极极片整体的容量发挥影响也越大。为兼顾负极极片容量发挥和充电窗口性能，本申请对第二层活性物质层的涂敷重量进行限定。当第二层活性物质层的活性材料层间距越大时，代表其充电能力越强，容量越低，相应地，涂敷重量较小时，即可达到良好的充电水平；当第二层活性物质层的活性材料层间距相对小时，其充电能力变弱，容量较高，此时，为了使极片整体具有较好的充电性能，第二层活性物质层的涂敷重量占整体极片的涂敷重量比值应提高。本申请的发明人出乎意料地发现，使用双层活性物质层结构，第一层活性物质层的活性材料层间距小，容量高，使极片及电池具有相对高的能量密度；第二层活性物质层的活性材料层间距大，降低负极极片表层嵌锂阻抗，在大倍率充电时，避免锂离子在负极表面沉积，提高电池充电窗口。因此，满足上述关系的活性物质层的电池负极兼具能量密度和良好的充放电动力学性能。
在本申请的任意实施方式中，所述活性物质层满足：
Figure PCTCN2021129506-appb-000002
为兼顾电池能量密度和充电性能，避免一种性能过设计而影响另一种性能不满足，发明人根据实际测试效果，进一步限定了第 一活性物质层和第二活性物质层的涂布重量与层间距的关系。满足该关系时，负极极片及电池的倍率性能与能量密度均能得到较好提升。
在本申请的任意实施方式中，
Figure PCTCN2021129506-appb-000003
与
Figure PCTCN2021129506-appb-000004
成反比，且
Figure PCTCN2021129506-appb-000005
其中，
Da 50：第一活性材料的体积平均粒径，单位为μm；
Db 50：第二活性材料的体积平均粒径，单位为μm。
根据每层活性物质层的层间距及粒径大小，调整活性物质层的涂敷重量，使极片及电池兼顾快充性能及能量密度。
在本申请的任意实施方式中，所述第一活性材料的体积平均粒径Da 50和第二活性材料的体积平均粒径Db 50满足
Figure PCTCN2021129506-appb-000006
通过规定两层活性物质层中活性材料的粒径相对关系，进一步提高动力学性能，并有利于第二层涂敷量低时的加工性能实现。
在本申请的任意实施方式中，所述第一活性材料的d002峰对应的层间距d 1的范围为0.335～0.3362nm，所述第二活性材料的d002峰对应的层间距d 2的范围为0.3356～0.38nm。
在本申请的任意实施方式中，所述第一活性材料的体积平均粒径Da50的范围为8～20μm，所述第二活性材料的体积平均粒径Db50的范围为4～12μm。
在本申请的任意实施方式中，单位面积负极集流体上设置的第一活性物质层的质量CW 1的范围为80～200g/m 2，单位面积负 极集流体上设置的第二活性物质层的质量CW 2的范围为10～110g/m 2。
在本申请的任意实施方式中，所述第一活性材料为天然石墨或人造石墨材料，和/或，所述第二活性材料为人造石墨材料。
在任意实施方式中，所述第一活性层和/或所述第二活性层中包含软碳或硬碳。
本申请第二方面提供一种二次电池，其包括本申请第一方面的负极极片。
本申请第三方面提供一种电池模块，其包括本申请第二方面的二次电池。
本申请第四方面提供一种电池包，其包括本申请第二方面的二次电池、第三方面的电池模块中的一种。
本申请第五方面提供一种用电装置，其包括本申请第二方面的二次电池、第三方面的电池模块、第四方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面 所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的负极极片的一实施方式的示意图。
图2是本申请的二次电池的一实施方式的示意图。
图3是本申请的二次电池的一实施方式的分解示意图。
图4是本申请的电池模块的一实施方式的示意图。
图5是本申请的电池包的一实施方式的示意图。
图6是图5的分解图。
图7是本申请的二次电池用作电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5二次电池
51壳体
52电极组件
53盖板
具体实施方式
以下适当地参照附图详细说明具体公开了本申请的负极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也 可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
二次电池
二次电池又称为充电电池或蓄电池，是指在电池放电后可通充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解质。在二次电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解质在正极极片和负极极片之间，主要起到传导活性离子的作用。
[负极极片]
负极作为锂离子电池最关键的组成之一，其设计直接影响电池的性能发挥，特别是电池的充电相关特性。如何通过优化负极极片设计，从而得到兼顾能量密度和动力学性能的电池是目前行业内普遍面临的挑战。
为了解决上述问题，发明人进行了大量的研究，提供了一种 负极极片。本申请的负极极片采用双层或多层活性物质层，并调控各层活性物质层的层间距与涂敷重量的关系，能够兼具较高的能量密度和良好的充放电动力学性能。
本申请的负极极片包括负极集流体和设置在所述负极集流体至少一个表面的活性物质层，其中，所述活性物质层包括第一活性物质层和设置在所述第一活性物质层表面上的第二活性物质层，所述第一活性物质层包括第一活性材料，所述第二活性物质层包括第二活性材料，所述活性物质层满足：α×CW 2≤CW 1，其中，
α：层间距相对因子，
Figure PCTCN2021129506-appb-000007
且1≤α≤1.12；
d 1：第一活性材料的d002峰对应的层间距，单位为nm；
d 2：第二活性材料的d002峰对应的层间距，单位为nm；
CW 1：单位面积负极集流体上设置的第一活性物质层的质量，单位为：g/m 2；如果负极集流体的两面均设置第一活性物质层和第二活性物质层，则应该为第一活性物质层的双面质量。
CW 2：单位面积负极集流体上设置的第二活性物质层的质量，单位为：g/m 2；如果负极集流体的两面均设置第一活性物质层和第二活性物质层，则应该为第二活性物质层的双面质量。
由此，本申请通过在负极采用双层或多层活性物质层，并调控各层活性物质层的层间距与涂敷重量的之间的关系，可以获得一种兼具更高的能量密度和更好的充放电动力学性能的电池负极。更具体地，本申请的发明人发现，在负极极片同一侧集流体上涂敷两层活性物质层，第二层活性物质层的活性材料层间距大于第一层活性物质层的活性材料层间距，锂离子从正极迁移到负极时，因表层的材料层间距大，锂离子嵌入阻抗低，锂离子能够快速嵌入到表层活性材料中，避免因充电速率过大，导致锂离子在负极极片表面析出。因负极活性材料层间距越大，材料的容量越低，第二层活性材料的涂敷重量越大，对负极极片整体的容量发挥影响也越大。为兼顾负极极片容量发挥和充电窗口性能，本申请对第二层活性物质层的涂敷重量进行要求。当第二层活性物质层的活性材料层间距越大 时，代表其充电能力越强，容量越低，相应地，涂敷重量较小时，即可达到良好的充电水平；当第二层活性物质层的活性材料层间距相对小时，其充电能力变弱，容量较高，此时，为了使极片整体具有较好的充电性能，第二层活性物质层的涂敷重量占整体极片的涂敷重量比值应提高。本申请的发明人发现，使用双层活性物质层结构，第一层活性物质层的活性材料层间距小，容量高，使极片及电池具有相对高的能量密度；第二层活性物质层的活性材料层间距大，降低负极极片表层嵌锂阻抗，在大倍率充电时，避免锂离子在负极表面沉积，提高电池充电窗口。因此，满足上述关系的活性物质层的电池负极兼具能量密度和良好的充放电动力学性能。
在一些实施方式中，所述活性物质层满足：
Figure PCTCN2021129506-appb-000008
第二活性物质层重量根据层间距以及第一活性物质层重量进行调整，整体上，为使负极极片兼具高能量密度与动力学性能，第二活性物质层的涂敷重量应满足
Figure PCTCN2021129506-appb-000009
本申请的发明人发现，负极极片上涂布的活性物质层重量越小，活性材料的层间距越大，极片及电池内阻越低，充放电性能越好，但活性物质层重量小及活性材料层间距大，相同电池容量下，由于箔材等辅材用量增加及材料用量增加，导致电池能量密度降低。为兼顾电池能量密度和充电性能，避免一种性能过设计而影响另一种性能不满足，发明人根据实际测试效果，进一步限定了第一活性物质层和第二活性物质层的涂布重量与层间距的关系。满足该关系时，负极极片及电池的倍率性能与能量密度均能得到较好提升。
在一些实施方式中，
Figure PCTCN2021129506-appb-000010
与
Figure PCTCN2021129506-appb-000011
成反比，且
Figure PCTCN2021129506-appb-000012
其中
Da 50：第一活性材料的体积平均粒径，单位为μm；
Db 50：第二活性材料的体积平均粒径，单位为μm。
根据每层活性物质层的层间距及粒径大小，调整活性物质层 的涂敷重量与各活性物质层之间活性材料粒径满足：
Figure PCTCN2021129506-appb-000013
与
Figure PCTCN2021129506-appb-000014
成反比且
Figure PCTCN2021129506-appb-000015
时，极片及电池兼顾快充性能及能量密度。
在一些实施方式中，所述第一活性材料的体积平均粒径Da 50和第二活性材料的体积平均粒径Db 50满足
Figure PCTCN2021129506-appb-000016
规定两层活性物质层中活性材料的粒径相对关系，进一步提高动力学性能，并有利于第二层涂敷量低时的加工性能实现。
在一些实施方式中，所述第一活性材料的d002峰对应的层间距d 1的范围为0.335～0.3362nm，所述第二活性材料的d002峰对应的层间距d 2的范围为0.3356～0.38nm。
在一些实施方式中，所述第一活性材料的体积平均粒径Da50的范围为8～20μm，所述第二活性材料的体积平均粒径Db50的范围为4～12μm。
在一些实施方式中，单位面积负极集流体上设置的第一活性物质层的质量CW 1的范围为80～200g/m 2，单位面积负极集流体上设置的第二活性物质层的质量CW 2的范围为10～110g/m 2。
在本申请中，材料的体积平均粒径D50为本领域公知的含义，可采用本领域已知的方法和仪器测定。例如，可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)测定。
在一些实施方式中，所述负极极片还包含导电剂以及粘结剂，其种类和含量并不受具体的限制，可根据实际需求进行选择。作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑等)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)及羧甲基壳聚糖(CMCS)中的一种或几种。其它可选助剂 种类可以相同，也可以不同，作为示例，其他可选助剂可包括增稠剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在本申请的负极极片中，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等。
在一些实施方式中，活性物质层设置在负极集流体的至少一个表面上。例如，负极集流体具有在自身厚度方向相对的两个表面，活性物质层设置于负极集流体相对的两个表面的其中任意一者或两者上。
图1示出了负极集流体及其表面的活性物质层，其中图1所示的负极集流体的两个表面均具有第一活性物质层和第二活性物质层。
当然，本申请的负极极片10也可具有其他的实施方式，例如，负极极片10由负极集流体11、设置在负极集流体其中一侧的第一活性物质层121和设置在第一活性物质层121上的第二活性物质层122构成。
另外，本申请的负极极片并不排除除了负极膜层之外的其他附加功能层。例如在一些实施方式中，本申请的负极极片还可以包括设置在负极集流体和第二负极膜层之间的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还包括覆盖在第一负极膜层表面的保护层。
在一些实施方式中，本申请的负极极片的制备方法可包括如下步骤：
1.分别制备包含第一活性材料的浆料A和包含第二活性材料的浆料B；
2.根据第一活性材料的层间距和第二活性材料的层间距，计 算CW 1和CW 2；
3.将浆料A涂覆于集流体上，烘干，得到涂覆了第一活性物质层的极片A；
4.在极片A表面涂覆浆料B，烘干，然后经过冷压、分切得到本申请所述的负极极片；
其中，第一活性物质层和第二活性物质层的涂覆量分别满足CW 1和CW 2。
在一些实施方式中，所述浆料A包含第一活性材料，导电剂、粘结剂和增稠剂中的一种或多种。
在一些实施方式中，所述浆料B包含第二活性材料，导电剂、粘结剂和增稠剂中的一种或多种。
具体的负极制备方法可以参考本申请提供的具体实施例，该处不赘述。
[正极极片]
二次电池包括正极极片，正极极片通常包括正极集流体以及设置于正极集流体至少一个表面上且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置在正极集流体的两个相对表面中的任意一者或两者上。
在本申请的正极极片中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等。
在本申请的正极极片中，正极膜层包括正极活性材料，正极活性材料可采用本领域公知的用于二次电池的正极活性材料。作为示例，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物 的示例可包括但不限于锂钴氧化物、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一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在本申请的正极极片中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
本申请的正极极片中，正极膜层通常包含正极活性材料以及可选地粘结剂和可选地导电剂。正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、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、含氟丙烯酸酯树脂中的一种或几种。作为示例，用于正极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或几种。需要说明的是，本申请所给的各正极膜层的组成或参数均指正极集流体单面膜层的组成或参数范围。当正极膜层设置在正极集流体相对的两个表面上时，其中任意一个表面上的正极膜层的组成或参数满足本申请，即认为落入本申请的保护范围内。
[电解质]
电解质在正极极片和负极极片之间起到传导活性离子的作用。本申请的二次电池对电解质的种类没有具体的限制，可根据需 求进行选择。例如，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐的种类不受具体的限制，可根据实际需求进行选择。作为示例，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiA sF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
在一些实施方式中，溶剂的种类不受具体的限制，可根据实际需求进行选择。作为示例，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1，4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，可选地，溶剂为非水溶剂。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间， 起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可相同或不同。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
本申请对二次电池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2是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51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51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个二次电池5可以是沿电池模块4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二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图5和图6是作为一个示例的电池包1。参照图5和图6，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
本申请的实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池、电池模块、电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述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。
所述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7是作为一个示例的用电装置。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
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂、第一活性材料、第二活性材料都可商购获得或是按照常规方法进行合成获得，以及实施例中使用的仪器均可商购获得。
实施例1-9
按照下述方法制备实施例1-9的包含本申请的负极极片的锂离子电池。
负极极片的制备
1.根据表1，将第一活性物质层的第一活性材料，导电剂Super-P、粘结剂SBR、增稠剂CMC、按质量比96∶1∶2∶1进行混合，在去离子水溶剂体系中充分搅拌混合均匀后，得到浆料A；
2.根据表1，将第二活性物质层的第二活性材料，导电剂Super-P、粘结剂SBR、增稠剂CMC、按质量比96∶1∶2∶1进行混合，在去离子水溶剂体系中充分搅拌混合均匀后，得到浆料B；
3.根据表1，先将浆料A涂覆于Cu箔上，烘干，得到涂覆了第一活性物质层的极片A；
4.根据表1，在极片A表面涂浆料B，烘干，然后经过冷压、分切得到具有双层活性物质层的负极极片；
其中，第一活性物质层和第二活性物质层的涂覆量分别满足CW 1和CW 2。
正极极片的制备
将正极活性材料LiFePO 4、导电剂乙炔黑、粘结剂聚偏氟乙烯(PVDF)按质量比96∶2∶2进行混合，加入溶剂N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系呈均一状，获得正极浆料；将正极浆料均匀涂布在正极集流体铝箔上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到正极极片。
电解液的制备
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1∶1∶1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF 6溶解于上述有机溶剂中，配制成浓度为1mol/L的电解液。
隔离膜的制备
使用聚乙烯膜作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
对比例1-3
对比例1-3的二次电池的制备方法与实施例1-13类似，不同之处在于负极极片的制备过程，详见表1。
测试部分
能量密度：在25℃下，将锂离子电池以1C恒流充电至4.2V，然后以4.2V恒压充电至电流小于0.05C，然后再以0.1C放电到2.8V，得到放电能量Q。称取电池的质量为M，则能量密度＝Q/M。
充电时间：在25℃下，85％SOC时的析锂窗口倍率恒流充电至85％SOC时所用时间，为本申请所述充电时间。
Figure PCTCN2021129506-appb-000017
本申请通过在负极采用双层或多层活性物质层，并调控各层活性物质层的层间距与涂敷重量的之间的关系，可以获得一种兼具更高的能量密度和更好的充放电动力学性能的电池负极。
根据表1，由实施例1-9与对比例1-3的比较可以看出，通过在负极采用双层活性物质层，并调控各层活性物质层的层间距与涂敷重量的之间的关系，得到的二次电池兼具更高的能量密度和更好的充放电动力学性能。简言之，通过本发明的方法制得的负极材料，均满足充电时间≤75min、0.3C能量密度≥170Wh/kg。
对比例1-3不符合本申请的各层活性物质层的层间距与涂敷重量的之间的关系，具体地，对比例1与本申请的实施例1相比较，其中对比例1中的第二活性材料采用了层间距更大的硬碳，其容量密度远低于本申请的实施例1。也就是说，第二层活性物质层的活性材料层间距越大时，其充电能力越强，然而容量越低，显然无法兼顾能量密度和充放电动力学性能。与实施例1相比，对比例2中，层间距相对因子α不在本申请范围(1≤α≤1.12)，也无法兼顾能量密度和充放电动力学性能。与实施例1相比，对比例3为单层涂布，说明在相同涂布量的前提下，单层涂布无法兼顾能量密度和充放电动力学性能。
进一步地，与实施例1-3相比较，实施例5的CW 2/(CW 2+CW 1)超过本申请范围，导致尽管充放电动力学性能良好但却无法兼顾能量密度，相反，实施例4的CW 2/(CW 2+CW 1)超过本申请范围，导致尽管能量密度良好但却无法兼顾充放电动力学性能。
进一步地，与实施例1、实施例6、实施例7相比较，实施例8与实施例9的Db50/Da50在本申请范围外，也无法兼顾能量密度和充放电动力学性能。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (13)

  1. 一种负极极片，包括负极集流体和设置在所述负极集流体至少一个表面的活性物质层，其中，所述活性物质层包括第一活性物质层和设置在所述第一活性物质层表面上的第二活性物质层，所述第一活性物质层包括第一活性材料，所述第二活性物质层包括第二活性材料，所述活性物质层满足：α×CW 2≤CW 1，其中，
    α：层间距相对因子，
    Figure PCTCN2021129506-appb-100001
    且1≤α≤1.12；
    d 1：第一活性材料的d002峰对应的层间距，单位为nm；
    d 2：第二活性材料的d002峰对应的层间距，单位为nm；
    CW 1：单位面积负极集流体上设置的第一活性物质层的质量，单位为：g/m 2；
    CW 2：单位面积负极集流体上设置的第二活性物质层的质量，单位为：g/m 2。
  2. 根据权利要求1所述的负极极片，其中，所述活性物质层满足：
    Figure PCTCN2021129506-appb-100002
  3. 根据权利要求1或2所述的负极极片，其中，
    Figure PCTCN2021129506-appb-100003
    与
    Figure PCTCN2021129506-appb-100004
    成反比，且
    Figure PCTCN2021129506-appb-100005
    其中
    Da50：第一活性材料的体积平均粒径，单位为μm；
    Db50：第二活性材料的体积平均粒径，单位为μm。
  4. 根据权利要求2或3所述的负极极片，其中，所述第一活性材料的体积平均粒径Da 50和第二活性材料的体积平均粒径Db 50满足
    Figure PCTCN2021129506-appb-100006
  5. 根据权利要求2-4中任一项所述的负极极片，其中，
    所述第一活性材料的d002峰对应的层间距d 1的范围为0.335～0.3362nm，所述第二活性材料的d002峰对应的层间距d 2的范围为0.3356～0.38nm。
  6. 根据权利要求2-5中任一项所述的负极极片，其中，所述第一活性材料的体积平均粒径Da 50的范围为8～20μm，所述第二活性材料的体积平均粒径Db 50的范围为4～12μm。
  7. 根据权利要求2-6中任一项所述的负极极片，其中，单位面积负极集流体上设置的第一活性物质层的质量CW 1的范围为80～200g/m 2，单位面积负极集流体上设置的第二活性物质层的质量CW 2的范围为10～110g/m 2。
  8. 根据权利要求1-7中任一项所述的负极极片，其中，
    所述第一活性材料为天然石墨或人造石墨材料，和/或，
    所述第二活性材料为人造石墨材料。
  9. 根据权利要求1-8中任一项所述的负极极片，其中，
    所述第一活性层和/或所述第二活性层中包含软碳或硬碳。
  10. 一种二次电池，其中，所述二次电池包括根据权利要求1-9中任一项所述的负极极片。
  11. 一种电池模块，其中，包括根据权利要求10所述的二次电池。
  12. 一种电池包，其中，包括根据权利要求10所述的二次电池或根据权利要求11所述的电池模块。
  13. 一种用电装置，包括根据权利要求10所述的二次电池、根据权利要求11所述的电池模块、根据权利要求12所述的电池包中的至少一种。
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