WO2024082931A1 - 正极片、电芯和电池 - Google Patents

正极片、电芯和电池 Download PDF

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WO2024082931A1
WO2024082931A1 PCT/CN2023/121215 CN2023121215W WO2024082931A1 WO 2024082931 A1 WO2024082931 A1 WO 2024082931A1 CN 2023121215 W CN2023121215 W CN 2023121215W WO 2024082931 A1 WO2024082931 A1 WO 2024082931A1
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Prior art keywords
region
insulating layer
positive electrode
electrode sheet
layer
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PCT/CN2023/121215
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English (en)
French (fr)
Inventor
赵君义
贺飞
李素丽
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珠海冠宇电池股份有限公司
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Publication of WO2024082931A1 publication Critical patent/WO2024082931A1/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
    • H01M4/13—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • 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
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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 disclosure relates to the field of battery technology, and in particular to a positive electrode sheet, a battery cell and a battery.
  • lithium-ion batteries With the popularity of lithium-ion batteries, lithium-ion batteries now occupy 50% to 70% of the market.
  • the negative electrode of lithium-ion batteries on the market is wider than the positive electrode, resulting in poor coverage of the positive and negative electrodes during winding or stacking (Figure 7). Therefore, it is necessary to correct the coverage difference between the positive and negative electrodes in time, otherwise the core will appear flat or spiral due to poor coverage of the electrode ( Figure 8).
  • the resulting core will be too high or have insufficient coverage, which will cause the core to be scrapped. Poor coverage of the positive and negative electrodes may lead to sufficient local Li source and insufficient local Li source, resulting in insufficient battery kinetic performance.
  • the present disclosure provides a positive electrode sheet, a battery cell and a battery.
  • the positive and negative electrode sheets in the present application are designed with equal width, which solves the problem of poor positive and negative electrode coverage during battery cell preparation and greatly improves the safety of the battery.
  • the present invention provides a positive electrode sheet, which includes a current collector, an active material layer, a first insulating layer and a second insulating layer;
  • the current collector has a first surface and a second surface disposed opposite to each other; the first surface has a first region, a second region and a third region in sequence along the short side; the second surface has a fourth region, a fifth region and a sixth region in sequence along the short side;
  • the second region and the fifth region are provided with an active material layer
  • the first region, the third region, the fourth region and the sixth region are provided with a first insulating layer
  • a second insulating layer is provided on the active material layer and the first insulating layer.
  • the present invention manufactures the electrode sheets of lithium-ion batteries into equal-width electrode sheets (as shown in FIG. 1 ), adopts a positive and negative electrode sheet design with the same width, and makes the edges of the positive and negative electrode sheets overlap and ensure the coverage of the positive and negative electrode sheets without a diaphragm as traction, so as to facilitate the winding or stacking of the positive and negative electrode sheets.
  • the width of a conventional positive electrode sheet is smaller than that of a negative electrode sheet.
  • the present application widens the current collector and arranges a first insulating layer and a second insulating layer on the long side and surface of the positive electrode sheet, respectively (as shown in FIGS. 2-4 ), wherein a second insulating layer is arranged on top of the active material layer and the first insulating layer, which means that a second insulating layer is arranged on the side of the active material layer and the first insulating layer away from the current collector (as shown in FIG. 3 ).
  • the implementation of the above measures ensures that the proportion of flat and spiral positive and negative electrode sheets is greatly reduced, the yield of the entire winding process can be significantly improved, and the capacity ratio of the positive and negative electrodes is ensured.
  • safety performance it far exceeds all current batteries with diaphragm assemblies, and the battery performance has been significantly improved in both furnace temperature and needle puncture performance tests.
  • the thickness of the first insulating layer is less than or equal to the thickness of the active material layer; the first insulating layer is used to adjust the positive and negative electrode capacity ratio on the one hand, and also has the function of absorbing the electrolyte on the other hand.
  • the width of the first insulating layer is 0.3mm to 0.8mm (for example: 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm); the present disclosure takes into account the difference in the pole pieces of conventional positive and negative electrodes of 1.2 to 1.8mm (this difference is because the capacity of the negative electrode must be larger than the capacity of the positive electrode to ensure that the Li + ions coming out of the positive electrode have a place to be accommodated to avoid the formation of Li dendrites), so a first insulating layer of a certain width (the width is 0.3 to 0.8mm) is provided on the long side of the positive electrode, and the first insulating layer has strong wettability, so that the wettability of the positive electrode sheet can be improved to a certain extent.
  • the width of the first insulating layer is 0.5 mm.
  • the thickness of the second insulating layer is 3 ⁇ m to 20 ⁇ m (for example: 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m);
  • the functions of the second insulating layer include: isolating the positive and negative electrodes, conducting Li ions, and adsorbing the electrolyte.
  • the thickness of the second insulating layer is 5 ⁇ m to 15 ⁇ m.
  • the width of the second insulating layer is greater than the width of the active material layer.
  • the width of the second insulating layer is less than or equal to the width of the current collector.
  • the width of the second insulating layer is equal to the width of the current collector.
  • the thickness of the active material layer is 10 ⁇ m to 100 ⁇ m (for example, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, or 100 ⁇ m).
  • the thickness of the active material layer is 30 ⁇ m to 50 ⁇ m.
  • the first insulating layer is an electrospinning layer or a luminous material layer.
  • the second insulating layer can be made of any material that performs an insulating function.
  • the second insulating layer is an insulating film or an electrospinning layer.
  • the second insulating layer is an electrospinning layer.
  • the insulating film includes organic matter or inorganic matter.
  • the inorganic substance includes at least one of aluminum oxide, silicon oxide, ceramic oxide and barium sulfate.
  • the organic matter includes PVDF or PTFE.
  • the electrospinning layer comprises a skeleton material and an adhesive polymer
  • the mass ratio of the framework material to the adhesive polymer is (1-10):(0.1-1).
  • the mass ratio of the framework material to the adhesive polymer is (1-10):1.
  • the mass ratio of the framework material to the adhesive polymer is 6:1.
  • the luminous material layer includes luminous material, and the luminous material includes at least one of rare earth aluminate and rare earth silicate.
  • the porosity of the electrospun layer is 25% to 90%.
  • the porosity of the electrospun layer is 30% to 90%.
  • the spun layer has a higher porosity, so the spun layer has a good electrolyte adsorption capacity. This structure is conducive to the transmission of Li + , as well as structural stability and heat dissipation, resulting in the excellent performance of this series of lithium-ion batteries at furnace temperature and acupuncture.
  • the framework-type material includes hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ), or includes hydroxyapatite and ceramics.
  • the particle size distribution of the hydroxyapatite particles is: D 10 is 0.02 ⁇ m to 0.06 ⁇ m, D 50 is 0.8 ⁇ m to 1.2 ⁇ m, and D 99 is 2.0 ⁇ m to 3.3 ⁇ m.
  • the ceramic includes but is not limited to at least one of TiO 2 , Al 2 O 3 , MgO, Mg(OH) 2 , AL(OH) 3 , boehmite, and SiO 2 ;
  • the aspect ratio of the ceramic particles is 0.5-5.
  • the ceramics used in the present invention all have a certain aspect ratio, and the aspect ratio is between 0.5 and 5.
  • This type of ceramic has a good specific surface area and can complement the structure of hydroxyapatite.
  • the formed spinning layer has a significant porous structure.
  • the ceramic powder with such an aspect ratio is beneficial to the transmission of Li + , as well as structural stability and heat dissipation.
  • the aspect ratio of the ceramic particles is 3.
  • the present invention adopts framework materials such as nano-scale hydroxyapatite and/or ceramics, and a bonding polymer (adhesive) to prepare a very thin spinning layer (a first insulating layer and a second insulating layer) on both sides of the positive electrode through electrostatic spinning.
  • the diameter of the spinning line is 200nm to 300nm (nano-scale wire mesh structure), which completely covers both sides of the positive electrode sheet, can replace the structure of the conventional diaphragm layer, and play the role of effectively blocking the positive and negative electrode sheets.
  • Thermal abuse testing is to test the heat resistance of the battery by placing it under a certain temperature.
  • the spinning layer (first insulating layer and second insulating layer) on the positive electrode can still maintain a complete structure above 400°C, and skeleton materials such as hydroxyapatite and ceramics have certain flame retardancy and can maintain a certain structure at high temperatures to avoid short circuits inside the battery cell caused by short circuits of the positive and negative electrodes.
  • the battery's safety performance can also be raised to a new level, continuously improving the battery's furnace temperature pass rate and acupuncture pass rate.
  • the framework material comprises hydroxyapatite and ceramic, and the mass ratio of hydroxyapatite to ceramic is (1-100):(1-100).
  • the framework material comprises hydroxyapatite and ceramic, and the mass ratio of hydroxyapatite to ceramic is (1-10):(1-10).
  • the framework-type material comprises hydroxyapatite and ceramic, and the mass ratio of hydroxyapatite to ceramic is (1-5):(1-5).
  • the mass ratio of hydroxyapatite to ceramic is 2:1.
  • the adhesive polymer includes but is not limited to at least one of polyvinylidene fluoride (PVDF), polyvinyl pyrrolidone, vinylidene fluoride-hexafluoropropylene polymer, polyacrylonitrile, sodium carboxymethyl cellulose, sodium polyacrylate, polyacrylic acid, polyacrylate, styrene-butadiene copolymer, butadiene-acrylonitrile polymer, polyvinyl alcohol, polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, and polyacrylic acid-styrene polymer.
  • PVDF polyvinylidene fluoride
  • PVDF polyvinyl pyrrolidone
  • vinylidene fluoride-hexafluoropropylene polymer polyacrylonitrile
  • sodium carboxymethyl cellulose sodium polyacrylate
  • polyacrylic acid polyacrylate
  • styrene-butadiene copolymer butadiene-acrylon
  • the first insulating layer and the second insulating layer are electrospun layers composed of hydroxyapatite, ceramics and PVDF.
  • the electrospun layers are easily infiltrated with the electrolyte and can transport the electrolyte outside the core body to the inside of the electrode, thereby improving the wettability of the electrode to a certain extent.
  • the first insulating layer is a luminous material layer
  • the luminous material layer includes at least one of rare earth aluminate and rare earth silicate.
  • the rare earth aluminate includes at least one of 4Sr0.7Al 2 O 3 :1Eu, SrAl 2 O 4 :Eu 2+ , SrAl 2 O 4 :Eu 2+ ,Dy 3+ , SrAl 2 O 4 :Eu 2+ ,Nd 3+ , SrAl 2 O 4 :Eu 2+ ,Dy 3+ ,Nd 3+ , Sr 4 Al 14 O 2 :Eu 2+ , Sr 4 Al 14 O 2 :Eu 2+ , Dy 3+ , Ca 2 Al 2 O 4 :Eu 2+ ,Dy 3+ ;
  • the rare earth silicate includes at least one of Sr 2 MgSi 2 O 7 :Eu 2+ ,Dy 3+ , Sr 2 MgSi 2 O 7 :Eu 2+ ,Dy 3+ ,Nd 3+ , and Sr 2 ZnSi 2 O 7 :Eu 2+ ,Dy 3+ .
  • the luminous material layer also includes PVDF.
  • the mass ratio of the luminous material to PVDF is (9-19):(1-10).
  • the luminous material disclosed in the present invention can emit a kind of light when irradiated by a specific light source (ultraviolet light, sunlight, fluorescent light, indoor environmental stray light, etc.), and then the target CCD (charge coupled device) can identify the edge of the positive electrode sheet according to the light source (as shown in FIG9 ), so as to facilitate the real-time adjustment of the tape position of the positive electrode sheet.
  • a specific light source ultraviolet light, sunlight, fluorescent light, indoor environmental stray light, etc.
  • the target CCD charge coupled device
  • the positive and negative electrode sheets themselves are in equal width processing. The implementation of the above measures ensures that the positive and negative electrode sheets appear flat, and the proportion of spirals is greatly reduced, and the yield of the entire winding process can be significantly improved.
  • the present disclosure also provides a method for preparing the above-mentioned positive electrode sheet, comprising the following steps:
  • the positive electrode active material layer is arranged in the second region and the fifth region of the current collector;
  • a first insulating layer is disposed on the first region, the third region, the fourth region, and the sixth region of the current collector;
  • the second insulating layer is arranged on both side surfaces of the current collector.
  • the method for preparing the positive electrode sheet includes:
  • the framework material, the adhesive polymer and an appropriate amount of a strong polar organic solvent are mixed to obtain a spinning solution;
  • the spinning solution is used to perform electrostatic spinning on the long sides of the current collector coated with the active material layer (four regions: the first region, the third region, the fourth region and the sixth region) to prepare the first insulating layer; then, electrostatic spinning is performed on the surfaces of both sides of the current collector coated with the active material layer to prepare the second insulating layer.
  • the method for preparing the positive electrode sheet includes:
  • the luminous material is mixed with PVDF and an appropriate amount of a strong polar organic solvent to obtain a luminous solution;
  • the luminous solution is applied to the long sides of the current collector coated with the active material layer (four regions: the first region, the third region, the fourth region and the sixth region) to prepare the first insulating layer; then, electrostatic spinning is performed on the surfaces of both sides of the current collector coated with the active material layer to prepare the second insulating layer.
  • the highly polar organic solvent includes at least one of NMP, DMA, DMF, dioxane, m-cresol and chloroform.
  • the high voltage power supply for electrospinning is 0-50KV, a dual syringe pump is used, the minimum liquid supply is 10 ⁇ L/h, the environment is at room temperature: 25 ⁇ 3°C, and the humidity is ⁇ 10%RH.
  • the present disclosure also provides a battery cell, which is composed of a negative electrode sheet and the positive electrode sheet mentioned above, the negative electrode sheet and the positive electrode sheet have the same width, and the battery cell does not include a separator.
  • the battery cell is a rolled core or a stacked core.
  • the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer; the negative electrode active material layer is arranged on both side surfaces of the negative electrode current collector.
  • the negative electrode current collector is copper foil.
  • the present disclosure also provides a battery, which includes the above-mentioned positive electrode sheet or the above-mentioned battery cell.
  • the present invention has the following beneficial effects:
  • the present invention widens the current collector, and uses electrospinning to spin skeleton materials such as hydroxyapatite and ceramics to the edge of the positive electrode sheet, and then performs double-sided spinning on the positive electrode sheet.
  • the positive and negative electrode sheets maintain the same width to ensure the coverage of the positive and negative electrode sheets, and then the positive and negative electrode sheets are directly bonded for use, so that the battery electrode sheets have direct processability, and the poor coverage of the battery is reduced from about 1.5% to about 0.02%, and the spiral ratio is reduced from about 0.5% to 0;
  • the present invention can safely raise the furnace temperature of the original PE or PP type diaphragm type lithium ion battery from 130°C to above 200°C, and at the same time, the battery's needle puncture pass rate reaches 100%;
  • the present invention utilizes nanoscale skeleton materials such as hydroxyapatite and ceramics, and uses electrospinning technology to spin the skeleton materials onto the edge and surface of the positive electrode sheet to isolate the negative electrode sheet from direct contact.
  • the positive electrode sheet, the negative electrode sheet, and the electrolyte are then assembled into a lithium-ion battery, and the safety performance of the battery is then tested.
  • the following results are finally found: the furnace temperature test safety performance of the battery can safely pass the furnace temperature test of 200°C to 250°C, and the battery for the acupuncture test can achieve 100% pass.
  • the present invention uses an oily slurry to apply long-lasting luminous powder to the edge of the positive electrode sheet, which not only isolates the direct contact of the negative electrode sheet, but also can position the positive electrode sheet.
  • Use UV or other light sources to irradiate for more than 60 seconds in advance, and after standing for about 60 seconds, the coating position will spontaneously emit light, and then the edge of the positive electrode sheet is obtained through CCD reception and processing, and then the edge is overlapped with the negative electrode sheet and wound.
  • This design can greatly reduce the Li ion deposition caused by uneven local current density of the battery, avoid the deposition and growth of Li dendrites, avoid the risk of internal self-discharge caused by puncturing the diaphragm, and ensure that the yield of the core can be stably improved and output.
  • This design can reduce the original poor coverage to 0.005%, and the spiral ratio from about 0.5% to 0.
  • FIG2 is a schematic diagram of two top-view cross-sections of the positive electrode sheet disclosed in the present invention.
  • FIG. 3 is a schematic side cross-sectional view of the positive electrode sheet of the present disclosure; wherein the width of the first insulating layer 13 is W 13 , the thickness of the first insulating layer 13 is T 13 , the width of the second insulating layer 14 is W 14 , and the thickness of the second insulating layer 14 is T 14 ;
  • FIG4 Surface area arrangement of the positive electrode current collector of the present invention (short side view);
  • Figure 5 Schematic diagram of the aspect ratio of ceramics; where R1 is the length of the ceramic particle and R2 is the diameter of the ceramic particle. path;
  • Figure 6 Schematic diagram of electrospinning of hydroxyapatite & ceramic solutions
  • Figure 7 Front view of the positive and negative electrode sheets with poor coverage
  • Figure 7-1 is a front view of a normal winding core
  • Figure 7-2 is a front view of a winding core with poor coverage
  • FIG8 is a schematic diagram of the structure of a core and a defective core disclosed in the present invention, wherein FIG8-1 is a cross-sectional view of a core disclosed in the present invention, FIG8-2 is a cross-sectional view of a defective core with a flat phenomenon, and FIG8-3 is a cross-sectional view of a defective core with a spiral phenomenon;
  • Figure 9 Brief illustration of the coiled structure.
  • the reference numerals are as follows: 1 positive electrode sheet, 11 current collector, 12 active material layer, 13 first insulating layer, 14 second insulating layer; 111 first area, 112 second area, 113 third area, 114 fourth area, 115 fifth area, 116 sixth area; 2 negative electrode sheet; 3 Diaphragms.
  • the present disclosure provides positive electrode sheets, battery cells and batteries. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve them. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all deemed to be included in the present disclosure.
  • the methods and applications of the present disclosure have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present disclosure to implement and apply the technology of the present disclosure.
  • the reagents, instruments and materials used in the present disclosure can be obtained through commercial channels.
  • hydroxyapatite can be a commercially available product, and hydroxyapatite can also be prepared by the following preparation method (hydrothermal method):
  • the main component of the long-lasting luminous powder material product is a mixture of 4Sr0.7Al 2 O 3 :1Eu, Yao Dexing Technology luminous powder CAS number: 12004347, density is 3.6g/cm 3 , and can maintain good stability under -60°C ⁇ 600°C conditions.
  • Hydrothermal method refers to a method of preparing materials in a sealed pressure vessel, using water as a solvent, dissolving and recrystallizing powder. Compared with other powder preparation methods, the powder prepared by the hydrothermal method has the advantages of complete grain development, small particle size, uniform distribution, light particle agglomeration, relatively cheap raw materials, and easy to obtain suitable chemical stoichiometry and crystal form.
  • Battery full charging system constant current and constant voltage charging at a certain rate (0.7C) in a constant temperature room at 25°C. When the voltage reaches the cut-off voltage, it will jump to the constant voltage mode for charging. When the charging is cut off at the cut-off current (generally 0.02C), the charging is considered to be completed, and then the furnace temperature test is carried out.
  • Puncture test Charge and discharge the battery cell at 0.7C/0.7C for 5 cycles, and complete the puncture test within 2 days after the cycle, and puncture the battery after it is fully charged; use a 4mm diameter iron nail to pierce one of the three positions on the left, center and right side of the battery cell, respectively, with a needle speed of 30mm/s, and the nail remains in the battery.
  • the left or right puncture position is 7.5 ⁇ 2.5mm away from the edge; it is required to puncture from the deep pit surface. Observe for 1h or the highest temperature on the surface of the battery cell drops to the peak value of 10°C or below, and stop the experiment. Judgment criteria: no fire, no explosion.
  • Oven temperature test Heat up from room temperature (25°C) to specified temperature (usually 130°C/135°C/140°C/145°C/150°C/155°C/160°C/165°C/170°C/175°C/180°C/185°C/190°C/195°C/200°C/205°C/210°C/215°C/220°C/225°C/230°C/235°C/240°C/245°C/250°C) at 5°C/min for constant temperature stage. Maintain the constant temperature for a certain period of time (usually 10min/30min/60min). After the time is up, open the thermostat to confirm the battery. If there is no fire, explosion or smoking, the battery can pass the oven temperature test.
  • specified temperature usually 130°C/135°C/140°C/145°C/150°C/155°C/160°C/165°C/170°C/175°C/180°C/185°C/190°C/195°C/200°C/205°C/
  • Fluorescence is the light emitted by a substance after absorbing light or other electromagnetic radiation. In most cases, the wavelength of the emitted light is longer than the wavelength of absorption and has lower energy.
  • the positive and negative electrodes are wound according to a certain width. Since they are flat structures obtained by the circular motion of the winding needle with the diaphragm as the traction, the positive electrode sheets are generally narrower than the negative electrode sheets. Due to the limited deviation correction ability or the wavy edge of the incoming material, the positive and negative electrodes appear to be at the same height or exposed on one side of the winding core. When viewed from the top, it can be found that the positive and negative electrodes are on the same horizontal plane. At this time, the winding core is called poorly flush.
  • the positive and negative electrodes are wound according to a certain width. Since they are flat structures obtained by circular motion around the winding needle with the diaphragm as the traction, the positive electrode is generally narrower than the negative electrode. Due to the limited deviation correction ability or the wavy edge of the diaphragm material, the positive and negative electrodes appear to be spirally rising or spirally descending to a certain extent along with the winding needle. This defect is similar to the spiral structure of DNA. The appearance of this structure will cause the winding core to be too high. If it is too high, the cavity design of the aluminum-plastic film will appear, and the encapsulation or Li ion deposition and Li crystallization cannot be completed, and the risk of self-discharge increases.
  • the positive electrode sheet 1 provided in this embodiment includes a current collector 11 , an active material layer 12 , a first insulating layer 13 and a second insulating layer 14 ;
  • the current collector has a first surface and a second surface disposed opposite to each other; the first surface has a first region 111, a second region 112 and a third region 113 in sequence along the short side; the second surface has a fourth region 114, a fifth region 115 and a sixth region 116 in sequence along the short side;
  • the second region 112 and the fifth region 115 are provided with an active material layer 12;
  • the first region 111, the third region 113, the fourth region 114 and the sixth region 116 are provided with a first insulating layer 13;
  • a second insulating layer 14 is provided on the active material layer 12 and the first insulating layer 13;
  • the thickness of the first insulating layer 13 is 10 ⁇ m, the thickness of the active material layer 12 is 30 ⁇ m, the width is 0.5 mm, and the length is equal to the length of the current collector;
  • the width of the second insulating layer 14 is equal to the width of the current collector 11 , the thickness of the second insulating layer 14 is 3 ⁇ m to 20 ⁇ m (see Table 1 for details), and the length of the second insulating layer 14 is equal to the length of the current collector 11 ;
  • the current collector 11 is aluminum foil with a thickness of 9 ⁇ m;
  • the first insulating layer 13 or the second insulating layer 14 is an electrostatic spinning layer, and the porosity of the first insulating layer 13 and the second insulating layer 14 is 80%.
  • the positive electrode active material is LiCoO 2 , accounting for 98.0%;
  • the conductive agent is conductive carbon black, accounting for 1.0%;
  • the binder is polyvinylidene fluoride, accounting for 1.0%;
  • a spinning solution to electrospin on the long side of the current collector coated with an active material to obtain a first spinning layer (ie, a first insulating layer);
  • electrospinning The parameters of electrospinning are as follows: high voltage power supply: 40KV, dual syringe pump setting, liquid supply volume 30000 ⁇ L/h; environment at room temperature: 25 ⁇ 3°C, humidity ⁇ 10%RH.
  • high voltage power supply 40KV
  • dual syringe pump setting liquid supply volume 30000 ⁇ L/h
  • environment at room temperature 25 ⁇ 3°C
  • humidity ⁇ 10%RH The schematic diagram of electrospinning is shown in Figure 6.
  • the negative electrode sheet provided in this embodiment includes a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode current collector is copper foil with a thickness of 5 ⁇ m and a width the same as that of the positive electrode sheet.
  • the negative electrode active material layer is arranged on both sides of the negative electrode current collector.
  • the negative electrode active material slurry is coated on the surfaces of both sides of the negative electrode current collector to obtain a negative electrode sheet; the composition and ratio of the negative electrode active material layer are as follows: the negative electrode active material is mesophase carbon microbeads, accounting for 96.5%; the conductive agent is carbon nanotubes, accounting for 0.9%; the adhesive is SBR, accounting for 1.3%; the dispersant is sodium carboxymethyl cellulose/CMC, accounting for 1.3%.
  • the positive electrode sheet and the negative electrode sheet obtained above are overlapped and wound to obtain a winding core; or the sheets are stacked to obtain a stacked core, and the corresponding coverage defect items of the winding core or the stacked core are recorded ( Figure 7 and Figure 8), and then packaged, injected, formed, double-sealed, sorted, OCV, and a battery is obtained.
  • Example 2 Similar to Example 2, except that: the first insulating layer and the second insulating layer do not contain ceramic powder, and the ratio of hydroxyapatite to PVDF is 6:1.
  • Example 7a is similar to Example 2, except that the ceramic powder in the first insulating layer and the second insulating layer is boehmite.
  • Embodiment 7b is similar to Embodiment 2, except that the ceramic powder in the first insulating layer and the second insulating layer is Al 2 O 3 .
  • Embodiment 7c is similar to Embodiment 2, except that the ceramic powder in the first insulating layer and the second insulating layer is SiO 2 .
  • Example 7d is similar to Example 2, except that the ceramic powder in the first insulating layer and the second insulating layer is MgO.
  • the first insulating layer is a luminous material layer
  • the luminous material layer includes 4Sr0.7Al 2 O 3 :1Eu and PVDF.
  • the preparation method of the positive electrode sheet is as follows:
  • the positive electrode active material slurry is coated on both sides of the current collector to obtain a current collector coated with the active material; the composition and ratio of the positive electrode active material layer are the same as in Example 2;
  • a spinning solution is used to perform electrostatic spinning on both sides of the current collector coated with the active material to obtain a second insulating layer.
  • the width of the second insulating layer 14 is smaller than the width of the current collector 11
  • the thickness of the second insulating layer 14 is 5 ⁇ m (see Table 1 for details)
  • the length of the second insulating layer 14 is equal to the length of the current collector 11
  • the width of the second insulating layer is 0.5mm smaller than the width of the current collector 11.
  • This comparative example is a conventional cell structure with a diaphragm:
  • the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer.
  • the positive electrode current collector is an aluminum foil with a thickness of 9 ⁇ m.
  • the positive electrode active material layer is arranged on both side surfaces of the positive electrode current collector.
  • the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode current collector is a copper foil with a thickness of 5 ⁇ m and a width wider than that of the positive electrode sheet.
  • the negative electrode active material layer is arranged on both sides of the negative electrode current collector.
  • the diaphragm uses a normal PE base film, and the coating structure is 1+7+2+1, where 1 means that both sides have a 1 ⁇ m thick adhesive layer (the adhesive is PVDF adhesive), 2 ⁇ m means a 2 ⁇ m ceramic coating on one side, and the ceramic uses a normal Al2O3 coating, and 7 ⁇ m means that the base film uses a 7 ⁇ m PE base film.
  • the data of the poor coverage items of the batteries prepared in the above embodiments and comparative examples are shown in Table 1.
  • the batteries prepared in the above embodiments and comparative examples were subjected to electrical performance tests, and the test results are shown in Table 2.
  • the present disclosure omits the conventional separator and sets the positive and negative electrode sheets to have the same width setting, which is convenient for winding or stacking the positive and negative electrode sheets.
  • the equal width design of the positive and negative electrode sheets can reduce the poor coverage to less than 0.03%. Based on the poor coverage of 0.02% and 200W cores per day, more than 2,000 battery cells can be saved, and nearly 73W cores can be saved in a year.
  • the furnace temperature test pass rate of the battery cell is significantly improved, the heat resistance of the battery is increased from 130°C to 240°C, and the battery's needle puncture pass rate directly reaches 100%.
  • the second insulating layer of the pole piece when the thickness of the second insulating layer of the pole piece is reduced to below 5 ⁇ m, the self-discharge capacity of the battery is amplified, which is not conducive to the long-term storage and use of the battery; when the thickness of the second insulating layer reaches 20 ⁇ m, the entire thickness of the normal diaphragm is occupied by the second insulating layer, resulting in a significant decrease in the energy density per unit volume of the battery cell. Taking self-discharge and energy density into consideration, the second insulating layer can fully play its role when the thickness is 5-15 ⁇ m, which can not only improve the furnace temperature pass rate of the battery, but also will not significantly reduce the energy density per unit volume of the battery.
  • the first insulating layer is designed with an electrospinning layer or a luminous material layer, both of which can play a role in isolating the direct contact of the negative electrode.
  • the luminous material layer design of Example 8 can also position the electrode, and the edge of the electrode emits light, so that the CCD can completely capture the edge of the electrode, and then the edge of the positive electrode overlaps with the negative electrode and winds it, greatly reducing the coverage and spiral problems of the positive and negative electrode sheets, and can greatly reduce the Li ion deposition caused by the uneven local current density of the battery, avoid the deposition and growth of Li dendrites, and avoid the risk of internal self-discharge caused by puncturing the diaphragm, so that the yield of the core can be stably improved and output; in terms of energy density and self-discharge, the luminous material of Example 8 can be at the same level as the electrospinning material of Examples 1-7.

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Abstract

一种正极片、电芯和电池。正极片包括集流体、活性物质层、第一绝缘层和第二绝缘层；集流体具有相背设置的第一表面和第二表面；第一表面沿短边侧依次具有第一区域、第二区域和第三区域；第二表面沿短边侧依次具有第四区域、第五区域和第六区域；第二区域和第五区域设置有活性物质层；第一区域、第三区域、第四区域和第六区域设置有第一绝缘层；活性物质层和第一绝缘层之上设置有第二绝缘层。正负极片为等宽设计，解决了电芯制备时出现正负极覆盖不良的问题，大大提高了电池的安全性。

Description

正极片、电芯和电池
交叉引用
本申请基于申请号为202211288844.1、申请日为2022年10月20日的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本公开涉及电池技术领域，具体涉及正极片、电芯和电池。
发明背景
目前随着锂离子电池的普及，现在的锂离子电池已经占据市场50％～70％，市场上的锂离子电池的极片均是负极片比正极片偏宽，导致在卷绕或者叠片时出现正负极的覆盖不良(图7)的现象，因此需要及时纠正正负极的覆盖差值，否则会因极片覆盖不良而导致卷芯出现平齐或者螺旋的现象(图8)，如此出来的卷芯将会出现超高、覆盖不足等现象，从而导致卷芯被报废处理。正负极片出现覆盖不良有可能导致局部的Li源充足，局部Li源不足，使得电池动力学性能不足，同时正负极片出现覆盖不良还有可能导致局部Li枝晶的形成，易发生隔膜刺穿，从而导致电池局部短路，电池自放电变大，使得电池的持续放电能力大大削弱，不利于电池的长久使用，此外，电池的自放电过大还会导致电池的静态以及动态压差，从而导致电脑出现配组异常无法开机，长期使用也会导致Li枝晶刺破隔膜的风险明显增大，从而导致电池出现内部短路、电池异常放电的现象，最后还容易引发电池局部热失控，从而导致手机、笔记本出现着火的风险。
发明内容
有鉴于此，本公开提供了正极片、电芯和电池。本申请中的正负极片为等宽设计，解决了电芯制备时出现正负极覆盖不良的问题，大大提高了电池的安全性。
为了实现上述公开的目的，本公开提供以下技术方案：
本公开提供了一种正极片，该正极片包括集流体、活性物质层、第一绝缘层 和第二绝缘层；
集流体具有相背设置的第一表面和第二表面；第一表面沿短边侧依次具有第一区域、第二区域和第三区域；第二表面沿短边侧依次具有第四区域、第五区域和第六区域；
第二区域和第五区域设置有活性物质层；
第一区域、第三区域、第四区域和第六区域设置有第一绝缘层；
活性物质层和第一绝缘层之上设置有第二绝缘层。
本公开为了解决极片出现的覆盖不良等事项，将锂离子电池的极片制作成等宽极片处理(如图1)，采用相同宽度的正负极片设计，在无隔膜作为牵引下，使得正负极片的边缘重合和保证正负极片的覆盖，方便正负极片进行卷绕或者叠片。常规正极片宽度小于负极片宽度，为了达到等宽极片的技术效果，弥补常规正极片的宽度，本申请将集流体做了加宽处理，并在正极片长边侧和表面分别设置了第一绝缘层和第二绝缘层(如图2-4所示)，其中，活性物质层和第一绝缘层之上设置有第二绝缘层，指的是在活性物质层和第一绝缘层背离集流体的一侧设置有第二绝缘层(如图3所示)，以上措施的落实保证正负极片出现平齐、螺旋的比例大大降低，整个卷绕环节的良率能够显著提升，保证了正负极的容量之比，在安全性能方面远远超过目前所有隔膜组件的电池，使得电池性能在炉温和针刺性能测试中均有了明显的提升。
作为优选，第一绝缘层的厚度小于等于活性物质层的厚度；第一绝缘层一方面用于调节正负极容量比，另一方面还具有吸附电解液的作用。
作为优选，第一绝缘层的宽度为0.3mm～0.8mm(例如：0.3mm、0.4mm、0.5mm、0.6mm、0.7mm、0.8mm)；本公开考虑到常规正负极的极片差值在1.2～1.8mm的差值(此差值是因为负极的容量一定要比正极的容量大，才能保证从正极出来的Li+离子都有地方收纳，避免Li枝晶的形成)，所以在正极长边侧设置一定宽度的第一绝缘层(该宽度在0.3～0.8mm)，该第一绝缘层具有强的浸润性，从而使得正极片的浸润性能够得到一定程度的提高。
在本公开提供的具体实施例中，第一绝缘层的宽度为0.5mm。
作为优选，第二绝缘层的厚度为3μm～20μm(例如：3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm)；第二绝缘层的作用包括：隔绝正负极、导通Li离子以及吸附电解液的作用。
优选地，第二绝缘层的厚度为5μm～15μm。
作为优选，第二绝缘层的宽度大于活性物质层的宽度。
作为优选，第二绝缘层的宽度小于等于集流体的宽度。
在本公开提供的具体实施例中，第二绝缘层的宽度等于集流体的宽度。
作为优选，活性物质层的厚度为10μm～100μm(例如：10μm、20μm、30μm、40μm、50μm、60μm、70μm、80μm、90μm、100μm)。
在本公开提供的实施例中，活性物质层的厚度为30μm～50μm。
作为优选，所述第一绝缘层为静电纺丝层或夜光材料层。
在本公开中，第二绝缘层只要是起到绝缘作用的材料即可。作为优选，第二绝缘层为绝缘膜或静电纺丝层。在本发明提供的具体实施例中，第二绝缘层为静电纺丝层。
作为优选，所述绝缘膜包括有机物或无机物。
作为优选，所述无机物包括氧化铝、氧化硅、氧化陶瓷、硫酸钡中的至少一种。
作为优选，所述有机物包括PVDF或PTFE。
作为优选，静电纺丝层包括骨架型材料和粘结性聚合物；
作为优选，骨架型材料与粘结性聚合物的质量比为(1～10)：(0.1～1)。
优选地，骨架型材料与粘结性聚合物的质量比为(1～10)：1。
在本公开提供的具体实施例中，骨架型材料与粘结性聚合物的质量比为6：1。
作为优选，夜光材料层包括夜光材料，夜光材料包括稀土铝酸盐、稀土硅酸盐中的至少一种。
作为优选，静电纺丝层的孔隙率为25％～90％。优选地，静电纺丝层的孔隙率为30％～90％。采用纺丝出来的纺层具有较高的孔隙率，这样纺层的就具有很好的电解液吸附能力。该结构既有利于Li+的传输，也有利于结构稳定和热量的疏散，导致该系列的锂离子电池能够在炉温以及针刺表现优异。
作为优选，骨架型材料包括羟基磷灰石(Ca10(PO4)6(OH)2)，或者包括羟基磷灰石和陶瓷。
作为优选，羟基磷灰石颗粒的粒径分布为：D10为0.02μm～0.06μm，D50为0.8μm～1.2μm，D99为2.0μm～3.3μm。
作为优选，陶瓷包括但不限于TiO2、Al2O3、MgO、Mg(OH)2、AL(OH)3、勃姆石、SiO2中的至少一种；
作为优选，陶瓷的颗粒长径比为0.5～5。
本公开使用的陶瓷均是具有一定规格的长径比，长径比的比值在0.5～5，该类陶瓷具有很好的比表面积，能够和羟基磷灰石在结构互补，形成的纺丝层有明显的孔隙结构，具有如此长径比的陶瓷粉既有利于Li+的传输，也有利于结构稳定和热量的疏散。
在本公开提供的具体实施例中，陶瓷的颗粒长径比为3。
本公开采用纳米级羟基磷灰石和/或陶瓷等骨架型材料，与粘结性聚合物(粘接剂)通过静电纺丝的方式在正极的双面各制备一层十分薄的纺丝层(第一绝缘层和第二绝缘层)，纺丝的线条直径在200nm～300nm(纳米级别的丝网结构)，完全覆盖正极片的双面，可取代常规隔膜层的结构，起到有效阻隔正、负极片的作用。
热滥用测试即是将电池处于一定温度之下，测试电池的耐热受性，正极片上面的纺丝层(第一绝缘层和第二绝缘层)在400℃以上仍能够保持完整的结构，并且羟基磷灰石、陶瓷等骨架型材料均具有一定的阻燃性，能够在高温下保持一定的结构，避免正负极片短接出现电芯内部短路现象。如此一来可以在提高电池卷绕或者叠片覆盖率的同时，还可以将电池的安全性能提高到一个新的档次，持续提高了电池的炉温通过率以及针刺的通过率。
作为优选，骨架型材料包括羟基磷灰石和陶瓷，羟基磷灰石与陶瓷的质量比为(1～100)：(1～100)。
优选地，骨架型材料包括羟基磷灰石和陶瓷，羟基磷灰石与陶瓷的质量比为(1～10)：(1～10)。
更优选地，骨架型材料包括羟基磷灰石和陶瓷，羟基磷灰石与陶瓷的质量比为(1～5)：(1～5)。
在本公开提供的具体实施例中，羟基磷灰石与陶瓷的质量比为2：1。
作为优选，粘结性聚合物包括但不限于聚偏二氟乙烯(PVDF)、聚乙烯吡咯烷酮、偏氟乙烯-六氟丙烯聚合物、聚丙烯腈、羧甲基纤维素钠、聚丙烯酸钠、聚丙烯酸、聚丙烯酸酯、苯乙烯-丁二烯共聚物、丁二烯-丙烯腈聚合物、聚乙烯醇、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚丙烯酸乙酯、聚丙烯酸-苯乙烯聚合物中的至少一种。
在本公开提供的具体实施例中，第一绝缘层和第二绝缘层为羟基磷灰石&陶瓷&PVDF构成的静电纺丝层，该静电纺丝层易与电解液浸润，能够将卷芯本体外部的电解液往极片内部输送，使得极片的浸润性得到一定程度的提高。
作为优选，第一绝缘层为夜光材料层，夜光材料层包括稀土铝酸盐、稀土硅酸盐中的至少一种。稀土铝酸盐包括4Sr0.7Al2O3：1Eu、SrAl2O4：Eu2+、SrAl2O4：Eu2+,Dy3+、SrAl2O4：Eu2+,Nd3+、SrAl2O4：Eu2+,Dy3+,Nd3+、Sr4Al14O2：Eu2+、Sr4Al14O2：Eu2+,Dy3+、Ca2Al2O4：Eu2+,Dy3+中的至少一种；
稀土硅酸盐包括Sr2MgSi2O7：Eu2+,Dy3+、Sr2MgSi2O7：Eu2+,Dy3+,Nd3+、Sr2ZnSi2O7：Eu2+,Dy3+中的至少一种。
作为优选，夜光材料层还包括PVDF。
作为优选，夜光材料与PVDF的质量比为(9～19)：(1～10)。
本公开中的夜光材料经过特定的光源(紫外光、太阳光、日灯光、室内环境杂散光等)照射能够发出一种光，然后目标CCD(电荷耦合器件，charge coupled device)能够根据该光源进行识别正极片的边缘(如图9)，便于实时进行调解正极片的走带位置，又加上正负极片本身是处于等宽处理，以上措施的落实保证正负极片出现平齐、螺旋的比例大大降低，整个卷绕环节的良率能够显著提升。
本公开还提供了上述正极片的制备方法，包括如下步骤：
先将正极活性物质层设置在集流体的第二区域和第五区域；
然后将第一绝缘层设置在集流体的第一区域、第三区域、第四区域和第六区域；
最后将第二绝缘层设置在集流体两侧表面。
在本公开提供的一实施例中，上述正极片的制备方法包括：
将正极活性物质层浆料涂布在集流体两侧表面(两个区域：第二区域和第五区域)，得到涂覆有活性物质层的集流体；
将骨架型材料、粘结性聚合物与适量强极性有机溶剂混合，得到纺丝溶液；
采用纺丝溶液在涂覆有活性物质层的集流体长边侧(四个区域：第一区域、第三区域、第四区域和第六区域)进行静电纺丝，制备第一绝缘层；然后，在涂覆有活性物质层的集流体两侧表面进行静电纺丝，制备第二绝缘层。
在本公开提供的另一实施例中，上述正极片的制备方法包括：
将正极活性物质层浆料涂布在集流体两侧表面(两个区域：第二区域和第五区域)，得到涂覆有活性物质层的集流体；
将夜光材料与PVDF、适量强极性有机溶剂混合，得到夜光溶液；
将夜光溶液涂布在涂覆有活性物质层的集流体长边侧(四个区域：第一区域、第三区域、第四区域和第六区域)，制备第一绝缘层；然后，在涂覆有活性物质层的集流体两侧表面进行静电纺丝，制备第二绝缘层。
作为优选，强极性有机溶剂包括NMP、DMA、DMF、二氧六环、间甲酚、氯仿中的至少一种。
作为优选，静电纺丝的高压电源为0-50KV，采用双注射泵设置，最小供液量为10μL/h，环境处于室温：25±3℃，湿度≤10％RH。
本公开还提供了一种电芯，该电芯由负极片和上述正极片组成，负极片与正极片的宽度相同，该电芯不包括隔膜。
在本公开提供的具体实施例中，电芯为卷芯或叠芯。
作为优选，负极片包括负极集流体和负极活性物质层；负极活性物质层设置于负极集流体两侧表面。
在本公开提供的具体实施例中，负极集流体为铜箔。
本公开还提供了一种电池，电池包括上述正极片，或者上述电芯。
与现有技术相比，本公开具有的有益效果为：
1、针对目前的电芯结构(隔膜/正极/隔膜/负极)覆盖不良问题，本公开对集流体进行了加宽处理，并利用静电纺丝方式将羟基磷灰石&陶瓷等骨架型材料纺丝到正极片的边缘，然后在正极片上再进行双面纺丝，正负极片保持一样的宽幅保证正负极片的覆盖，随后进行正负极片直接贴合使用，使得电池的极片具有直接加工性，将电池的覆盖不良从1.5％左右降低到0.02％左右，螺旋比例从0.5％左右降到0；
2、本公开能够将原PE或者PP型隔膜型锂离子电池的炉温安全从130℃提到200℃以上的水平，同时将电池的针刺的通过率达到100％；
3、本公开利用羟基磷灰石&陶瓷等纳米级骨架型材料，使用静电纺丝技术将骨架型材料纺丝到正极片的边缘以及表面上，起到隔绝负极片的直接接触作用，接着将正极片和负极片、电解液组装成锂离子电池，然后测试电池的安全性能，最终发现如下结果：电池的炉温测试安全性能可以安全通过200℃到250℃的炉温测试，针对于针刺实验的电池能够实现100％的通过。
4、本公开将长效夜光粉利用油性浆料涂布到正极片的边缘位置，不仅起到隔绝负极片的直接接触作用，还可以对正极片进行定位作用。利用UV等光源提前60s以上的时间进行照射，经过大约60s的时间静置，该涂层位置会自发进行发光，然后经过CCD接受与处理得到正极片的边缘，进而与负极片进行边缘重合贴合卷绕。该设计方案能够极大程度降低电池局部电流密度不均导致的Li离子沉积现象，避免Li枝晶的沉积与长大，避免刺破隔膜而出现内部自放电的风险，使得卷芯的良率能够稳定的提升和输出。该设计方案能够将原来的覆盖不良降低到0.005％，螺旋比例从0.5％左右降到0。
附图说明
图1：本公开正极片和负极片等宽的示意图，其中，W1＝W2；
图2：本公开正极片两种俯视剖面示意图；
图3：本公开正极片侧视剖面示意图；其中，第一绝缘层13的宽度为W13，第一绝缘层13的厚度为T13，第二绝缘层14的宽度为W14，第二绝缘层14的厚度为T14；
图4：本公开正极集流体的表面区域设置(短边侧视视角)；
图5：陶瓷的长径比示意图；其中，R1为陶瓷颗粒的长，R2为陶瓷颗粒的直 径；
图6：羟基磷灰石&陶瓷溶液静电纺丝的示意图；
图7：正负极片覆盖不良的正视图；其中，图7-1为正常卷芯正视图，图7-2为覆盖不良卷芯正视图；
图8：本公开卷芯与不良卷芯结构示意图，其中，图8-1为本公开卷芯剖视图，图8-2为出现平齐现象的不良卷芯剖视图，图8-3为出现螺旋现象的不良卷芯剖视图；
图9：卷绕结构的简要说明。
附图标记如下：
1正极片，11集流体，12活性物质层，13第一绝缘层，14第二绝缘层；
111第一区域，112第二区域，113第三区域，114第四区域，115第五区
域，116第六区域；
2负极片；
3隔膜。
具体实施方式
本公开提供了正极片、电芯和电池，本领域技术人员可以借鉴本文内容，适当改进工艺参数实现。特别需要指出的是，所有类似的替换和改动对本领域技术人员来说是显而易见的，它们都被视为包括在本公开。本公开的方法及应用已经通过较佳实施例进行了描述，相关人员明显能在不脱离本公开内容、精神和范围内对本文所述的方法和应用进行改动或适当变更与组合，来实现和应用本公开技术。
本公开中所用试剂、仪器或材料等均可通过商业渠道获得。
本实施例中，羟基磷灰石可为市售产品，羟基磷灰石还可采用以下的制备方法(水热法)制备：
S1：将22g CaCl2的水溶液逐步滴加到600g乙醇和600g油酸的混合溶液中并持续搅拌100min(搅拌频率10Hz)，之后再逐步滴加入70g NaOH水溶液得到油酸钙前驱体。
S2：持续搅拌前驱体100min(搅拌频率10Hz)，之后再逐步滴加入28.8g NaH2PO4水溶液至该前驱体中，并将混合物转移至3L反应釜中，在180℃油浴中反应36h。得到的反应产物分别用去离子水和乙醇离心、洗涤至少三次，干燥得到羟基磷灰石备用。
本实施例中，长效夜光粉材料产品主要成分是混合物：4Sr0.7Al2O3：1Eu，耀德兴科技夜光粉CAS号：12004347，密度在3.6g/cm3，在-60℃～600℃条件下能够保持良好的稳定性。
术语解释：
水热法：是指一种在密封的压力容器中，以水作为溶剂、粉体经溶解和再结晶的制备材料的方法。相对于其他粉体制备方法，水热法制得的粉体具有晶粒发育完整，粒度小，且分布均匀，颗粒团聚较轻，可使用较为便宜的原料，易得到合适的化学计量物和晶形等优点。
电池满充制度：以一定的倍率(0.7C)在25℃恒温房进行恒流恒压充电，电压到截止电压时进行跳转到恒压模式进行充电，到截止电流(一般指0.02C)切断充电视为充电结束，然后进行炉温测试。
针刺测试：将电芯用0.7C/0.7C充放电进行5次循环，并且在循环后2天内完成针刺测试，并且将电池充满电后针刺；使用直径4mm的铁钉分别穿过电芯的左侧、中心及右侧三个位置中的一个位置，针速30mm/s，钉子留在电池内，左边或者右边针刺位置距离边缘7.5±2.5mm；要求从深坑面针刺。观察1h或者电芯表面最高温度下降至峰值10℃及以下，停止实验。判定标准：不起火，不爆炸。
炉温测试：从室温25℃以5℃/min进行升温到指定温度(一般是130℃/135℃/140℃/145℃/150℃/155℃/160℃/165℃/170℃/175℃/180℃/185℃/190℃/195℃/200℃/205℃/210℃/215℃/220℃/225℃/230℃/235℃/240℃/245℃/250℃)进行恒温阶段，恒温保持一定时间(一般是10min/30min/60min)，到时间后打开恒温箱进行电池确认，电池未发生起火、爆炸、冒烟即算电池能够通过炉温测试。
荧光发光原理：紫外光照射到某些原子时，光的能量使得原子核周围的一些电子由原来的轨道跃迁到了能量更高的轨道，即从基态跃迁到第一激发单线态或者第二激发单线态等，第一激发单线态或者第二激发单线态等是不稳定的，所以会恢复基态，当电子由第一激发单线态恢复到基态时，能量会以光的形式释放， 所以产生荧光。荧光是物质吸收光照或者其他电磁辐射后发出的光，大多数情况下，发光波长比吸收波长较长，能量更低。
覆盖不良-平齐：正负极片按照一定宽幅进行卷绕，由于它们是以隔膜作为牵引进行绕卷针进行圆周运动得到的扁平化结构的东西，一般来说正极片都比负极片窄，因纠偏能力有限或者来料波浪边导致卷芯的一侧出现正负极片处于同一个高度或者露出部分一样，从顶部观看就会发现正负极处于同一个水平面时，称此时的卷芯为平齐不良。
覆盖不良-螺旋：正负极片按照一定宽幅进行卷绕，由于它们是以隔膜作为牵引进行绕卷针进行圆周运动得到的扁平化结构的东西，一般来说正极片都比负极片窄，因纠偏能力有限或者隔膜来料波浪边导致牵引的正负极片出现随着卷针出现一定程度螺旋上升或者螺旋下降的不良，此不良类似于DNA一样的螺旋结构，该结构的出现会导致卷芯出现超高的问题，超高就会出现超铝塑膜的腔体设计，不能完成封装或者Li离子沉积、Li结晶的形成，自放电风险加大。
下面结合实施例，进一步阐述本发明：
实施例1-5
1、正极片的结构及制备方法
(1)正极片的结构
如图2-4所示，本实施例提供的正极片1包括集流体11、活性物质层12、第一绝缘层13和第二绝缘层14；
集流体具有相背设置的第一表面和第二表面；第一表面沿短边侧依次具有第一区域111、第二区域112和第三区域113；第二表面沿短边侧依次具有第四区域114、第五区域115和第六区域116；
第二区域112和第五区域115设置有活性物质层12；
第一区域111、第三区域113、第四区域114和第六区域116设置有第一绝缘层13；
活性物质层12和第一绝缘层13之上设置有第二绝缘层14；
第一绝缘层13的厚度为10μm，活性物质层12的厚度为30μm，宽度为0.5mm，长度等于集流体的长度；
第二绝缘层14的宽度等于集流体11的宽度，第二绝缘层14的厚度为3μm～20μm(具体见表1)，第二绝缘层14的长度等于集流体11的长度；
集流体11为铝箔，厚度为9μm；
第一绝缘层13或所述第二绝缘层14为静电纺丝层，第一绝缘层13和所述第二绝缘层14的孔隙率均为80％。
(2)正极片的制备方法
a.将正极活性物质浆料涂覆于集流体两侧表面，得到涂覆有活性物质的集流体；正极活性物质层的组成及配比：正极活性物质为LiCoO2，占比98.0％；导电剂为导电炭黑，占比1.0％；粘结剂为聚偏二氟乙烯，占比1.0％；
b.将羟基磷灰石、陶瓷粉(Al2O3，其颗粒长径比为3，示意图见图5)、PVDF(羟基磷灰石：陶瓷：PVDF＝4:2:1)混合在NMP中，搅拌100min(搅拌频率10Hz)，最终得到纺丝溶液；
c.采用纺丝溶液，在涂覆有活性物质的集流体长边侧进行静电纺丝，得到第一纺丝层(即第一绝缘层)；
然后，在涂覆有活性物质的集流体两侧表面进行静电纺丝，得到第二纺丝层(即第二绝缘层)。
静电纺丝的参数规格：高压电源：40KV，采用双注射泵设置，供液量30000μL/h；环境处于室温：25±3℃，湿度≤10％RH。静电纺丝的示意图见图6。
2、负极片的结构及制备方法
(1)负极片的结构
本实施例提供的负极片包括负极集流体和负极活性物质层，负极集流体为铜箔，厚度为5μm，宽度与上述正极片宽度相同；所述负极活性物质层设置于负极集流体两侧表面。
(2)负极片的制备方法
将负极活性物质浆料涂覆于负极集流体两侧表面，得到负极片；负极活性物质层的组成及配比：负极活性物质为中间相碳微球，占比96.5％；导电剂为碳纳米管，占比0.9％；粘接剂为SBR，占比1.3％；分散剂为羧甲基纤维素钠/CMC，占比1.3％。
3、电池的组装
将上述得到的正极片和负极片进行重合卷绕，得到卷芯；或者叠片，得到叠芯，记录下卷芯或叠芯对应的覆盖不良项(图7和图8)，封装、注液、化成、二封、分选、OCV、得到电池。
电池中的电解液配方为：EC:EMC:DEC＝3:5:2，LiPF6摩尔占比1.2mol/L。 实施例6
与实施例2近似，不同之处在于：第一绝缘层和第二绝缘层中不含陶瓷粉，羟基磷灰石：PVDF＝6:1。
实施例7组
实施例7a与实施例2近似，不同之处在于：第一绝缘层和第二绝缘层中陶瓷粉为勃母石。
实施例7b与实施例2近似，不同之处在于：第一绝缘层和第二绝缘层中陶瓷粉为Al2O3。
实施例7c与实施例2近似，不同之处在于：第一绝缘层和第二绝缘层中陶瓷粉为SiO2。
实施例7d与实施例2近似，不同之处在于：第一绝缘层和第二绝缘层中陶瓷粉为MgO。
实施例8
与实施例2近似，不同之处在于：第一绝缘层为夜光材料层，夜光材料层包括4Sr0.7Al2O3：1Eu、PVDF。
正极片的制备方法如下：
a.将正极活性物质浆料涂覆于集流体两侧表面，得到涂覆有活性物质的集流体；正极活性物质层的组成及配比同实施例2；
b.将夜光材料、PVDF、NMP混合，得到油性浆料(夜光溶液)；各物质质量占比如下：
夜光材料    35％
PVDF        10％
NMP         55％
将羟基磷灰石、陶瓷粉(Al2O3，其颗粒长径比为3，示意图见图5)、PVDF(羟基磷灰石：陶瓷：PVDF＝4:2:1)混合在NMP中，搅拌100min(搅拌频率10Hz)，得到纺丝溶液；
c.通过挤压转移涂布的方式，将夜光溶液涂布在涂覆有活性物质的集流体长 边侧，得到第一绝缘层；
然后，采用纺丝溶液，在涂覆有活性物质的集流体两侧表面进行静电纺丝，得到第二绝缘层。
实施例9
与实施例2相近：不同之处在于：第二绝缘层14的宽度小于集流体11的宽度，第二绝缘层14的厚度为5μm(具体见表1)，第二绝缘层14的长度等于集流体11的长度，第二绝缘层的宽度比集流体11的宽度小0.5mm。
对比例1
本对比例为常规有隔膜的电芯结构：
正极片包括正极集流体和正极活性物质层，正极集流体为铝箔，厚度为9μm；所述正极活性物质层设置于正极集流体两侧表面。
负极片包括负极集流体和负极活性物质层，负极集流体为铜箔，厚度为5μm，宽度比正极片宽；所述负极活性物质层设置于负极集流体两侧表面。
隔膜使用正常PE基膜，涂层结构为1+7+2+1，其中1表示双面均有1μm厚度的胶层(该胶为PVDF胶)，2μm表示单面2μm的陶瓷涂层，陶瓷使用正常的Al2O3涂层，7μm表示基膜选用7μmPE基膜。
将隔膜、正极片、负极片进行组装得到卷芯，记录下对应的覆盖不良项，然后封装，注电解液进行组装电池、继续进行化成、二封、分选、OCV、得到电池。电池性能测试：
上述实施例和对比例制备的电池覆盖不良项数据见表1。对上述实施例和对比例制备的电池进行电性能测试，测试结果见表2。
表1

表2

由上述实验结果可知，本公开省略了常规隔膜，设置正负极片具有相同的宽度设置，方便正负极片进行卷绕或者叠片，通过实验发现正负极片等宽设计可以将覆盖不良降低到0.03％以内。按照覆盖不良0.02％、每天200W个卷芯来算，如此一来就可以节约2000多个电芯，一年基本上可以节约近73W卷芯。
随着第二绝缘层厚度的增加，电芯的炉温测试通过率得到显著提升，电池耐热程度从130℃提升到240℃，电池的针刺通过直接到100％的通过率。
但极片的第二绝缘层厚度降低到5μm以下时，电池的自放电能力放大，不利于电池长期放置使用功能；当第二绝缘层的厚度到20μm的时候，相比于正常隔膜的整体厚度被第二绝缘层占用，导致电芯的单位体积能量密度显著下降。综合考虑自放电以及能量密度的情况下，第二绝缘层的厚度在5～15μm时能够充分发挥其作用，既能够提高电池的炉温通过率，又不会明显降低电池的单位体积的能量密度。
第一绝缘层采用静电纺丝层或夜光材料层设计，均可以起到隔绝负极片的直接接触作用。实施例8的夜光材料层设计还可以对极片进行定位，极片的边缘发出光芒，使得CCD能够完整捕捉到极片的边缘，然后将正极片的边缘与负极片重合卷绕，极大降低正负极片的覆盖问题和螺旋问题，能够极大程度降低电池局部电流密度不均导致的Li离子沉积现象，避免Li枝晶的沉积与长大，避免刺破隔膜而出现内部自放电的风险，使得卷芯的良率能够稳定的提升和输出；在能量密度方面和自放电方面上，实施例8的夜光材料能够和实施例1-7的静电纺丝材料在一致的水平上。
以上所述仅是本公开的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本公开原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本公开的保护范围。

Claims (15)

  1. 一种正极片，其特征在于，包括集流体、活性物质层、第一绝缘层和第二绝缘层；
    所述集流体具有相背设置的第一表面和第二表面；所述第一表面沿短边侧依次具有第一区域、第二区域和第三区域；所述第二表面沿短边侧依次具有第四区域、第五区域和第六区域；
    第二区域和第五区域设置有活性物质层；
    第一区域、第三区域、第四区域和第六区域设置有第一绝缘层；
    活性物质层和第一绝缘层之上设置有第二绝缘层。
  2. 根据权利要求1所述的正极片，其特征在于，所述第一绝缘层的厚度小于等于活性物质层的厚度；
    所述第一绝缘层的宽度为0.3mm～0.8mm。
  3. 根据权利要求1或2所述的正极片，其特征在于，所述第二绝缘层的厚度为3μm～20μm；
    优选地，第二绝缘层的厚度为5μm～15μm。
  4. 根据权利要求1-3任一项所述的正极片，其特征在于，所述第二绝缘层的宽度大于活性物质层的宽度。
  5. 根据权利要求1-4任一项所述的正极片，其特征在于，所述第二绝缘层的宽度小于等于集流体的宽度；
    第二绝缘层的宽度等于集流体的宽度。
  6. 根据权利要求1-5任一项所述的正极片，其特征在于，所述活性物质层的厚度为10μm～100μm；
    活性物质层的厚度为30μm～50μm。
  7. 根据权利要求1-6任一项所述的正极片，其特征在于，所述第一绝缘层为静电纺丝层或夜光材料层；
    所述第二绝缘层为绝缘膜或静电纺丝层。
  8. 根据权利要求7所述的正极片，其特征在于，所述静电纺丝层包括骨架型材料和粘结性聚合物；
    作为优选，所述骨架型材料与所述粘结性聚合物的质量比为(1～10)：(0.1～1)。
  9. 根据权利要求7或8所述的正极片，其特征在于，所述夜光材料层包括夜 光材料，所述夜光材料包括稀土铝酸盐、稀土硅酸盐中的至少一种。
  10. 根据权利要求7-9任一项所述的正极片，其特征在于，所述静电纺丝层，其孔隙率为25％～90％；
    优选地，静电纺丝层的孔隙率为30％～90％。
  11. 根据权利要求8所述的正极片，其特征在于，所述骨架型材料包括羟基磷灰石，或者包括羟基磷灰石和陶瓷；
    所述陶瓷包括TiO2、Al2O3、MgO、AL(OH)3、勃母石、SiO2中的至少一种；
    作为优选，所述陶瓷的颗粒长径比为0.5～5；
    作为优选，所述粘结性聚合物包括聚偏二氟乙烯、聚乙烯吡咯烷酮、偏氟乙烯-六氟丙烯聚合物、聚丙烯腈、羧甲基纤维素钠、聚丙烯酸钠、聚丙烯酸、聚丙烯酸酯、苯乙烯-丁二烯共聚物、丁二烯-丙烯腈聚合物、聚乙烯醇、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚丙烯酸乙酯、聚丙烯酸-苯乙烯聚合物中的至少一种。
  12. 根据权利要求9所述的正极片，其特征在于，所述稀土铝酸盐包括4Sr0.7Al2O3：1Eu、SrAl2O4：Eu2+、SrAl2O4：Eu2+,Dy3+、SrAl2O4：Eu2+,Nd3+、SrAl2O4：Eu2+,Dy3+,Nd3+、Sr4Al14O2：Eu2+、Sr4Al14O2：Eu2+,Dy3+、Ca2Al2O4：Eu2+,Dy3+中的至少一种；
    所述稀土硅酸盐包括Sr2MgSi2O7：Eu2+,Dy3+、Sr2MgSi2O7：Eu2+,Dy3+,Nd3+、Sr2ZnSi2O7：Eu2+,Dy3+中的至少一种。
  13. 权利要求1-12中任一项所述正极片的制备方法，其特征在于，包括如下步骤：
    先将正极活性物质层设置在集流体的第二区域和第五区域；
    然后将第一绝缘层设置在集流体的第一区域、第三区域、第四区域和第六区域；
    最后将第二绝缘层设置在集流体两侧表面。
  14. 一种电芯，其特征在于，所述电芯由负极片和权利要求1-12中任一项所述正极片组成，所述负极片与所述正极片的宽度相同。
  15. 一种电池，其特征在于，所述电池包括权利要求1-12中任一项所述正极片，或者权利要求14所述电芯。
PCT/CN2023/121215 2022-10-20 2023-09-25 正极片、电芯和电池 WO2024082931A1 (zh)

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