CN117438535A - Negative pole piece, secondary battery and electric equipment - Google Patents

Negative pole piece, secondary battery and electric equipment Download PDF

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Publication number
CN117438535A
CN117438535A CN202311297341.5A CN202311297341A CN117438535A CN 117438535 A CN117438535 A CN 117438535A CN 202311297341 A CN202311297341 A CN 202311297341A CN 117438535 A CN117438535 A CN 117438535A
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China
Prior art keywords
active material
negative electrode
material layer
current collector
density
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CN202311297341.5A
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Chinese (zh)
Inventor
田晓霜
王浩
侯永宣
于子龙
吴声本
项海标
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Zhejiang Liwei Energy Technology Co ltd
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Zhejiang Liwei Energy Technology Co ltd
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Priority to CN202311297341.5A priority Critical patent/CN117438535A/en
Publication of CN117438535A publication Critical patent/CN117438535A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention discloses a negative pole piece, a secondary battery and electric equipment, wherein the negative pole piece comprises a current collector and coatings arranged on two sides of the current collector, and the coatings comprise a first active material layer and a second active material layer; the first active material layer is positioned between the second active material layer and the negative electrode current collector; the surface density of the first active material layer is CW1, and the compaction density upper limit window is PD1; the surface density of the second active material layer is CW2, and the compaction density upper limit window is PD2; the compaction density upper limit window PD4 of the negative electrode sheet satisfies the following formula: PD4 is less than or equal to (CW1+CW2)/(CW1/PD 1+CW2/PD 2). By the scheme design of the invention, the charging capacity of the negative electrode plate can be considered, meanwhile, the compaction density of the negative electrode plate is greatly improved, and the energy density advantage of double-layer coating is fully exerted.

Description

Negative pole piece, secondary battery and electric equipment
Technical Field
The invention relates to the technical field of energy storage, in particular to a negative electrode plate, a secondary battery and electric equipment.
Background
With the increasing demand for lithium ion battery cell energy density, a negative plate double-layer coating process is generated. When the lithium ion battery core is charged, the charging capability requirement on the surface layer of the negative electrode active material is larger than that of the bottom layer. The traditional negative plate coating process mainly adopts single-layer coating, and when a high-magnification system is designed, the negative plate active material needs to adopt an active material with high charging capability in order to meet the charging capability of the surface layer of the negative plate. The gram capacity and the compaction density of the active material with high charging capacity are low, so that the energy density of the battery core is greatly limited, and the charging capacity of the active material at the bottom layer is excessive.
However, the current double-layer coated negative electrode plate cannot achieve comprehensive compaction maximization of the double-layer coated negative electrode plate while considering charging capability, and energy density improvement is limited.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the first aspect of the invention provides a negative electrode plate, which can effectively improve the energy density.
The second aspect of the invention also provides a preparation method of the negative electrode plate.
The third aspect of the present invention also provides a secondary battery.
The fourth aspect of the invention also provides electric equipment.
According to the negative electrode plate provided by the embodiment of the first aspect of the invention, the negative electrode plate comprises a current collector and coating layers arranged on two sides of the current collector, and the coating layers comprise a first active material layer and a second active material layer; the first active material layer is positioned between the second active material layer and the negative electrode current collector;
the surface density of the first active material layer is CW1, and the compaction density upper limit window is PD1; the surface density of the second active material layer is CW2, and the compaction density upper limit window is PD2;
the compaction density upper limit window PD4 of the negative electrode plate meets the following formula: PD4 is less than or equal to (CW1+CW2)/(CW1/PD 1+CW2/PD 2).
The negative electrode plate provided by the embodiment of the invention has at least the following beneficial effects:
by the scheme design of the invention, the following formulas are satisfied by limiting the compaction density upper limit window PD4 of the negative electrode plate by combining the surface density ratios of different first active material layers and second active material layers: and PD4 is less than or equal to (CW1+CW2)/(CW1/PD 1+CW2/PD 2), so that the first active material layer is not easily exceeded by the upper compaction window of the first active material layer although the first active material layer is pressed when the negative electrode sheet is rolled. Meanwhile, as the rolling compaction density PD4 of the negative electrode plate is calculated by combining the compaction density upper limit windows of the first active material layer and the second active material layer, the charging capacity of the negative electrode plate can be considered on the premise of considering the compaction windows of the first active material layer and the second active material layer, the compaction density of the negative electrode plate is greatly improved, and the energy density advantage of double-layer coating is fully exerted.
According to some embodiments of the invention, the first active material layer density CW1 is in the range of 50-150 (mg/1540.25 mm) 2 )。
1540.25mm 2 For measuring the area of the disc, representing 1540.25mm, by weight of active material 2 The cathode material weight on the area is 50-150 mg.
According to some embodiments of the invention, the second active material layer density CW2 is in the range of 15-90 (mg/1540.25 mm) 2 )。
According to some embodiments of the invention, PD1 ranges from 1.70 to 1.85g/cm 3 。
According to some embodiments of the invention, PD2 ranges from 1.40 to 1.69g/cm 3 。
According to some embodiments of the invention, the first active material layer includes a first anode active material, a first conductive agent, and a first binder.
According to some embodiments of the invention, the second active material layer includes a second anode active material, a second conductive agent, and a second binder.
According to some embodiments of the invention, the first negative electrode active material comprises at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, a silicon-based material, a silicon oxygen material, or a carbon-silicon composite material.
According to some embodiments of the invention, the second negative active material is at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon-based material, silicon oxygen material, or carbon-silicon composite material.
According to some embodiments of the invention, the starting materials for the first active material layer may include: 70 to 99.9 weight percent of first cathode active material, 0.05 to 15 weight percent of first conductive agent and 0.05 to 15 weight percent of first binder.
According to some embodiments of the invention, the raw materials of the second active material layer may include: 70 to 99.9 weight percent of second cathode active material, 0.05 to 15 weight percent of second conductive agent and 0.05 to 15 weight percent of second binder.
According to some embodiments of the invention, the first conductive agent and the second conductive agent may be the same or different, and are independently selected from at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber.
According to some embodiments of the invention, the first binder and the second binder may be the same or different, and are independently selected from one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), and carboxymethyl chitosan (CMCS).
According to some embodiments of the invention, the current collector may be a metal foil or a composite current collector. As an example of the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As examples, the metallic material may include one or more of copper, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).
According to the preparation method of the negative electrode plate provided by the embodiment of the second aspect of the invention, the preparation method comprises the following steps:
s1, providing first active material slurry, coating the first active material slurry on two sides of a current collector, drying, and rolling for the first time to obtain a first active material layer;
s2, providing second active material slurry, coating the second active material slurry on the basis of the step S1, drying, and rolling for the second time to obtain the negative electrode plate.
According to some embodiments of the invention, the first roll compaction density PD3 is designed to be 93% to 99% PD1 when 1.ltoreq.CW1/CW2.ltoreq.9.
The third aspect of the invention provides a secondary battery comprising the negative electrode tab.
According to some embodiments of the invention, the secondary battery further comprises a positive electrode sheet, a separator, and an electrolyte.
According to some embodiments of the invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposing in the thickness direction thereof, and the positive electrode active material film layer is provided on either or both of the two opposing surfaces of the positive electrode current collector.
The positive electrode active material film layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for a battery cell, which is well known in the art.
For example, when the battery cell is a lithium ion battery cell, a lithium metal battery cell, the positive electrode active material may include one or more of lithium transition metal oxide, olivine structured lithium-containing phosphate, and their respective modified compounds. Examples of lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of olivine structured lithium-containing phosphates may include one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate and carbon composites, and their respective modified compounds. The present application is not limited to these materials, and other conventionally known materials that can be used as the positive electrode active material may be used.
According to some embodiments of the invention, to further increase the energy density of the battery cell, the positive electrode active material may include a material having the general formula Li a Ni b Co c M d O e A f Is a lithium transition metal oxide and modified compounds thereof. A is more than or equal to 0.8 and less than or equal to 1.2,0.5, B is more than or equal to 2 and less than or equal to 1, c is more than 0 and less than or equal to 1, d is more than 0 and less than or equal to 1, e is more than or equal to 1 and less than or equal to 0 and less than or equal to 1, M comprises one or more of Mn, al, zr, zn, cu, cr, mg, fe, V, ti and B, and A comprises one or more of N, F, S and Cl.
According to some embodiments of the invention, the positive electrode active material may include LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333)、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523)、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622)、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)、LiNi 0.85 Co 0.15 Al 0.05 O 2 、LiFePO 4 And LiMnPO 4 One or more of the following.
According to some embodiments of the invention, the positive electrode active material film layer further optionally includes a positive electrode conductive agent. The kind of the positive electrode conductive agent is not particularly limited, and the positive electrode conductive agent includes, as an example, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
According to some embodiments of the invention, the positive electrode active material film layer further optionally includes a positive electrode binder. The kind of the positive electrode binder is not particularly limited in the present application, and the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate-based resin, as an example.
According to some embodiments of the invention, the positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As examples, the metallic material may include one or more of aluminum, aluminum alloys, nickel alloys, titanium alloys, silver, and silver alloys. As an example, the polymeric material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).
According to some embodiments of the invention, the positive electrode active material film layer is formed by coating positive electrode slurry on a positive electrode current collector, drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
According to some embodiments of the present invention, a method of manufacturing a secondary battery is known. In some embodiments, the positive electrode tab, the separator, the negative electrode tab, and the electrolyte may be assembled to form a secondary battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet may be wound and/or laminated to form an electrode assembly, the electrode assembly is placed in an outer package, dried and then injected with an electrolyte, and the electrode assembly is obtained through the steps of packaging, standing, formation, shaping and the like.
According to some embodiments of the present invention, the separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly plays a role in preventing the positive electrode and the negative electrode from being shorted. The type of separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.
According to some embodiments of the invention, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of the layers are the same or different.
According to some embodiments of the invention, the electrolyte acts to conduct active ions between the positive and negative electrode sheets. The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may include at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte solution).
According to some embodiments of the invention, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.
According to some embodiments of the present invention, the kind of electrolyte salt is not particularly limited and may be selected according to actual requirements. For example, the electrolyte salt includes a lithium salt for a lithium ion battery, which includes lithium hexafluorophosphate (LiPF, as an example 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium perchlorate (LiClO) 4 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium bis (fluorosulfonyl) imide (LiLSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium difluorooxalato borate (LiBOB), lithium difluorophosphate (LiPO) 2 F 2 ) One or more of lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP)。
According to some embodiments of the present invention, the kind of the solvent is not particularly limited, and may be selected according to actual requirements. In some embodiments, as examples, the solvent may include one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), 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), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS), and diethylsulfone (ESE).
A third aspect of the present invention provides an electrical device comprising the secondary battery described above.
According to some embodiments of the invention, the powered device may be, but is not limited to, a mobile device (e.g., a cell phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf car, an electric truck, etc.), an electric train, a watercraft, a satellite, an energy storage system, etc.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
fig. 1 is a schematic structural view of a negative electrode sheet prepared in example 1 of the present invention;
wherein 1 is a current collector, 2 and 3 are first active material layers; and 4 and 5 are second active material layers.
Detailed Description
The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described with reference to the embodiments, but the present invention is not limited to these embodiments.
The reagents, methods and apparatus employed in the present invention, unless otherwise specified, are all conventional in the art.
Example 1
Embodiment 1 provides a negative electrode plate, the structural schematic diagram of which is shown in fig. 1, wherein the negative electrode plate comprises a current collector and coating layers arranged on two sides of the current collector, and the coating layers comprise a first active material layer and a second active material layer; the first active material layer is positioned between the second active material layer and the negative electrode current collector; the preparation method comprises the following steps:
s1, slurry composition of a first active material layer is as follows: 96.5wt% of graphite, 1wt% of conductive carbon black and 1.5wt% of styrene-butadiene rubber; the solid content is 40-45 wt%; coating first active material slurry on two sides of a current collector, drying and first rolling to obtain a first active material layer; the compacted density of the first roll was PD3.
S2, the slurry composition of the second active material layer is as follows: 96.5wt% of graphite, 1wt% of conductive carbon black and 1.5wt% of styrene-butadiene rubber; the solid content is 40-45 wt%; and (3) coating the second active material slurry on two sides of the current collector on the basis of the step (S1), drying and rolling for the second time to obtain the negative electrode plate. Other parameters are shown in Table 1.
Preparation of positive electrode plate
The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (abbreviated as NCM 811), a conductive agent Super P and a binder PVDF are fully stirred and mixed in a proper amount of N-methylpyrrolidone (NMP) according to a mass ratio of 96.5:1.5:2, so that uniform anode slurry is formed; and (3) coating the positive electrode slurry on the surface of a positive electrode current collector aluminum foil, and drying and cold pressing to obtain a positive electrode plate.
Diaphragm
And a PP/PE composite isolating film is adopted.
Preparation of electrolyte
Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then mixing the LiPF 6 Uniformly dissolving in the solution to obtain an electrolyte.In the electrolyte, liPF 6 The concentration of (C) was 1mol/L.
Preparation of secondary battery
Sequentially stacking and winding the positive electrode plate, the diaphragm and the negative electrode plate to obtain an electrode assembly; and placing the electrode assembly into an outer package, adding the prepared electrolyte, and obtaining the secondary battery after the procedures of packaging, standing, formation, aging and the like.
Examples 2 to 5
Examples 2-5 provide a series of negative electrode sheets, which were prepared in a similar manner to example 1, with the difference in the parameters of Table 1, specifically Table 1.
TABLE 1
Examples 6 to 8 and comparative examples 1 to 2
Examples 6-8 and comparative examples 1-2 provide a series of negative electrode sheets, which were prepared in a manner similar to example 1, except that the parameters of Table 2 were different, as shown in Table 2.
TABLE 2
Performance testing
The following tests were carried out on the above examples and comparative examples, and the results are shown in table 3:
cell energy density: cell energy density = cell energy/cell size;
lithium is not separated out at normal temperature and directly fills the upper limit window: and (3) full charge and discharge are carried out at normal temperature by adopting a target multiplying power, and the charge and discharge are circulated for 30 times. Then disassembling under the full charge condition, and checking the interface of the pole piece.
Test standard: the surface of the pole piece has no lithium precipitation and no black spots.
TABLE 3 data for examples 1-8 and comparative examples 1-2
As is apparent from the above examples and comparative example 1, when the range of the present invention is not satisfied, the battery cell energy density is high, but it impairs the battery cell performance, resulting in that the normal temperature lithium-free direct charging upper limit window is only 2.5C, and the charging effect is significantly reduced. When PD4 of comparative example 2 is larger than (CW1+CW2)/(CW1/Pd1+CW2/PD 2), the cell performance is deteriorated, resulting in that the normal temperature lithium-free direct charging upper limit window is only 2.3C.
The present invention has been described in detail with reference to the above embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.

Claims (10)

1. The negative electrode plate is characterized by comprising a current collector and coating layers arranged on two sides of the current collector, wherein the coating layers comprise a first active material layer and a second active material layer; the first active material layer is positioned between the second active material layer and the negative electrode current collector;
the surface density of the first active material layer is CW1, and the compaction density upper limit window is PD1; the surface density of the second active material layer is CW2, and the compaction density upper limit window is PD2;
the compaction density upper limit window PD4 of the negative electrode plate meets the following formula: PD4 is less than or equal to (CW1+CW2)/(CW1/PD 1+CW2/PD 2).
2. The negative electrode sheet according to claim 1, wherein the first active material layer density CW1 is in the range of 50 to 150 (mg/1540.25 mm) 2 )。
3. The negative electrode sheet according to claim 1, wherein the second active material layer density CW2 is in the range of 15 to 90 (mg/1540.25 mm) 2 )。
4. The negative electrode sheet according to claim 1, wherein PD1 is in the range of 1.70 to 1.85g/cm 3 。
5. The negative electrode sheet according to claim 1, wherein PD2 is in the range of 1.40 to 1.69g/cm 3 。
6. The negative electrode tab of claim 1, wherein the first active material layer comprises a first negative electrode active material, a first conductive agent, and a first binder;
and/or; the second active material layer includes a second anode active material, a second conductive agent, and a second binder.
7. The method for preparing a negative electrode sheet according to any one of claims 1 to 6, comprising the steps of:
s1, providing first active material slurry, coating the first active material slurry on two sides of a current collector, drying, and rolling for the first time to obtain a first active material layer;
s2, providing second active material slurry, coating the second active material slurry on the basis of the step S1, drying, and rolling for the second time to obtain the negative electrode plate.
8. The method of claim 7, wherein the first rolling compaction density PD3 is set to 93% to 99% PD1 when 1.ltoreq.CW1/CW2.ltoreq.9.
9. A secondary battery comprising the negative electrode tab of any one of claims 1 to 6.
10. An electric device comprising the secondary battery according to claim 9.
CN202311297341.5A 2023-10-08 2023-10-08 Negative pole piece, secondary battery and electric equipment Pending CN117438535A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311297341.5A CN117438535A (en) 2023-10-08 2023-10-08 Negative pole piece, secondary battery and electric equipment

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311297341.5A CN117438535A (en) 2023-10-08 2023-10-08 Negative pole piece, secondary battery and electric equipment

Publications (1)

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