WO2024113988A1 - 一种二次电池以及用电设备 - Google Patents

一种二次电池以及用电设备 Download PDF

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Publication number
WO2024113988A1
WO2024113988A1 PCT/CN2023/115491 CN2023115491W WO2024113988A1 WO 2024113988 A1 WO2024113988 A1 WO 2024113988A1 CN 2023115491 W CN2023115491 W CN 2023115491W WO 2024113988 A1 WO2024113988 A1 WO 2024113988A1
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WO
WIPO (PCT)
Prior art keywords
adhesive
negative electrode
secondary battery
particles
positive electrode
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PCT/CN2023/115491
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English (en)
French (fr)
Inventor
林峰
程忠
陈继钦
李艳玲
李朝荣
Original Assignee
欣旺达动力科技股份有限公司
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Publication of WO2024113988A1 publication Critical patent/WO2024113988A1/zh

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Classifications

    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/233—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions
    • H01M50/242—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions adapted for protecting batteries against vibrations, collision impact or swelling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/244—Secondary casings; Racks; Suspension devices; Carrying devices; Holders characterised by their mounting method
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/249—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders specially adapted for aircraft or vehicles, e.g. cars or trains
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/289—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by spacing elements or positioning means within frames, racks or packs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of batteries, and in particular discloses a secondary battery and an electrical device.
  • lithium ions are transferred back and forth between the positive electrode, negative electrode and diaphragm with the electrolyte as the medium, so it is necessary to ensure a good bonding interface between the diaphragm and the electrode.
  • the bonding coating on the surface of the diaphragm forms a bonding effect with the electrode, and the bonding strength has an important impact on the entire life cycle of the lithium-ion battery. Insufficient bonding strength between the diaphragm and the electrode will lead to a poor bonding interface and hindered lithium ion transmission, which has an important impact on the service life of the lithium-ion battery.
  • lithium-ion batteries will continue to be subjected to working vibration and may be subjected to severe impact under extreme conditions of use.
  • the positive and negative electrodes of lithium-ion batteries are prone to misalignment, resulting in contact short circuits between the positive and negative electrodes, causing safety accidents.
  • the diaphragm is a physical isolation barrier between the positive and negative electrodes.
  • the bonding strength between the diaphragm and the electrode has an important influence on the dislocation of the electrodes in the vibration of lithium-ion batteries. Strengthening the bonding strength between the diaphragm and the electrode is conducive to improving the safety performance of lithium-ion batteries under working conditions.
  • the present application provides a secondary battery and an electrical device, aiming to solve the technical problems that the bonding strength between the pole piece and the diaphragm of the existing secondary battery is poor, causing ion transmission obstruction and easy misalignment of the pole piece, resulting in poor electrochemical performance and poor safety performance of the secondary battery.
  • the present application provides a secondary battery, wherein a positive electrode sheet, a separator and a negative electrode sheet are sequentially arranged in the secondary battery;
  • the diaphragm includes a substrate and an adhesive coating disposed on the surface of the substrate, wherein the adhesive coating
  • the layer includes a first adhesive, the average particle size of the primary particles of the first adhesive is 0.02-0.5 ⁇ m, and the average particle size of the secondary particles of the first adhesive is 0.5-10 ⁇ m; the surface roughness of the positive electrode sheet is 0.1-6.5 ⁇ m; the surface roughness of the negative electrode sheet is 0.5-12 ⁇ m.
  • the positive electrode plate includes a positive electrode active material
  • the negative electrode plate includes a negative electrode active material
  • the particles of the positive electrode active material have a Dv50 of 1 to 8 ⁇ m
  • the particles of the negative electrode active material have a Dv50 of 4 to 17 ⁇ m.
  • the ratio of the particles Dv50 of the positive electrode active material to the average particle size of the primary particles of the first adhesive, as well as the ratio of the particles Dv50 of the negative electrode active material to the average particle size of the primary particles of the first adhesive are both ⁇ 10; the ratio of the particles Dv50 of the positive electrode active material to the average particle size of the secondary particles of the first adhesive, as well as the ratio of the particles Dv50 of the negative electrode active material to the average particle size of the secondary particles of the first adhesive are both ⁇ 0.5.
  • the adhesive coating also includes a second adhesive
  • the first adhesive includes at least one of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), copolymer derivatives of vinylidene fluoride, and copolymer derivatives of tetrafluoroethylene
  • the second adhesive includes at least one of polyethylene glycol, polymethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyacrylic acid, polyvinyl acetate, acrylic ester copolymer, styrene-butadiene latex, styrene-acrylic latex, polyvinyl alcohol, and sodium carboxymethyl cellulose.
  • the thickness of the adhesive coating is 0.5-10 ⁇ m, and the surface density of the adhesive coating is 0.2-1.5 g/m 2 .
  • the substrate includes one or more of polyethylene, polypropylene, PET non-woven fabric, PVDF, and polyimide porous membrane.
  • the diaphragm also includes an inorganic material layer, which is arranged between the substrate and the adhesive coating.
  • the inorganic material layer contains an inorganic material, and the inorganic material includes at least one of aluminum oxide, boehmite, silicon dioxide, calcium sulfate, magnesium sulfate and magnesium hydroxide.
  • the first adhesive is embedded in the surface of the positive electrode sheet to a depth of 0.1 to 2 ⁇ m, and is embedded in the surface of the negative electrode sheet to a depth of 0.5 to 5 ⁇ m.
  • the present application also provides an electrical device, which includes the above-mentioned secondary battery, and the secondary battery is used as a power supply for the electrical device.
  • FIG. 1 is a schematic diagram of a partial structure of a secondary battery according to an embodiment.
  • FIG. 2 is a schematic diagram of the structure of the electrode interface and the bonding coating interface according to an embodiment of the present invention.
  • the present application provides a secondary battery, which includes a positive electrode sheet, a separator, and a negative electrode sheet arranged in sequence;
  • the diaphragm includes a substrate and an adhesive coating disposed on the surface of the substrate, the adhesive coating includes a first adhesive, the average particle size of the primary particles of the first adhesive is 0.02 to 0.5 ⁇ m, and the average particle size of the secondary particles of the first adhesive is 0.5 to 10 ⁇ m; the adhesive coating is used to bond the positive electrode sheet and the negative electrode sheet to both sides of the diaphragm;
  • the surface roughness of the positive electrode plate is 0.1-6.5 ⁇ m; the surface roughness of the negative electrode plate is 0.5-12 ⁇ m.
  • the positive electrode sheet and the negative electrode sheet are bonded together by the adhesive coating on the surface of the diaphragm, and the diaphragm plays the role of isolation and bonding.
  • the average particle size of the primary particles of the first adhesive of the diaphragm is 0.02-0.5 ⁇ m, and the average particle size of the secondary particles is 0.5-10 ⁇ m, so that the surface of the adhesive coating of the diaphragm is microscopically uneven, so that the surface has a relatively suitable roughness, and the roughness of the surface of the diaphragm is 0.2-0.9 ⁇ m.
  • the positive electrode sheet and the negative electrode sheet are also set to have a certain roughness of the surface interface (that is, its surface is microscopically uneven).
  • the average particle size of the primary particles of the first adhesive of the present application can be any one of 0.02 ⁇ m, 0.05 ⁇ m, 0.1 ⁇ m, 0.2 ⁇ m, 0.3 ⁇ m, 0.5 ⁇ m, or a range value between any two values.
  • the average particle size of the secondary particles of the first adhesive can be any one of 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, or a range value between any two values.
  • the bonding strength between the electrodes can be improved, and the tightness between the electrode sheet and the diaphragm can be further improved. Therefore, during the charge and discharge cycle of the secondary battery, the transmission rate of lithium ions between the positive electrode sheet and the negative electrode sheet is faster, which reduces the internal resistance of the secondary battery and is beneficial to improving the cycle performance of the secondary battery. Due to the improvement of the bonding strength, the positive electrode sheet and the negative electrode sheet of the secondary battery can be prevented from being misaligned in a strong vibration environment, and the secondary battery can be prevented from short-circuiting, thereby improving the safety performance.
  • the positive electrode sheet contains a positive electrode active material
  • the positive electrode active material can include one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium iron phosphate.
  • the negative electrode sheet contains a negative electrode active material, and the negative electrode active material includes one or more of graphite, graphite/silicon composite material, and lithium titanate.
  • the roughness of the electrode sheet can be controlled by changing the particle size of the active material (positive electrode active material or negative electrode active material), or by controlling the rolling pressure on the electrode sheet during the rolling process of the electrode sheet, or by adjusting the particle size of the active material and the rolling pressure at the same time.
  • the roughness used in this application is the arithmetic mean roughness Sa.
  • the test method for the surface roughness of the pole piece (positive pole piece or negative pole piece) and the diaphragm is: first, the Keyence VHX-7000 is used to perform a 3D scan on the surface of the pole piece (or diaphragm), and the scanning area is 5mm ⁇ 5mm, and then the computer equipment software is calculated, and multiple parallel samples are continuously tested and calculated. The average of multiple parallel sample tests is the pole piece roughness.
  • the test method for the average particle size of the primary particles of the first binder in the bonding coating is: the SEM equipment is used to photograph the bonding coating on the surface of the diaphragm, and the ruler counts the average of multiple primary particles (the longest dimension of a sphere or a sphere approximate to a sphere) as the average particle size of the primary particles.
  • the test method for the average particle size of the secondary particles of the first binder in the bonding coating is: the SEM equipment is used to photograph the surface coating of the diaphragm, and the ruler counts the average of multiple secondary particles (the longest dimension of a sphere or a sphere approximate to a sphere) as the average particle size of the secondary particles.
  • the Dv50 of the particles of the positive active material is 1 to 8 ⁇ m, and the Dv50 of the particles of the negative active material is 4 to 17 ⁇ m.
  • the Dv50 of the positive active material and the negative active material within the above range can cooperate with the average particle size of the primary particles and secondary particles of the first adhesive to enhance the anchoring force and improve the bonding strength.
  • the average particle size ratio of the particles Dv50 of the positive electrode active material to the primary particles of the first adhesive and the The ratio of Dv50 of the particles of the negative active material to the average particle size of the primary particles of the first adhesive is ⁇ 10; the ratio of Dv50 of the particles of the positive active material to the average particle size of the secondary particles of the first adhesive, and the ratio of Dv50 of the particles of the negative active material to the average particle size of the secondary particles of the first adhesive are both ⁇ 0.5.
  • the first adhesive is embedded into the surface of the positive electrode sheet to a depth of 0.1 to 2 ⁇ m, and embedded into the surface of the negative electrode sheet to a depth of 0.5 to 5 ⁇ m.
  • the bonding force between the separator and the positive electrode sheet is 1 to 15 N/m, and the bonding force between the separator and the negative electrode sheet is 0.5 to 6 N/m.
  • the test process for the depth of the first adhesive embedded in the electrode surface is: take out the positive electrode + diaphragm + negative electrode unit from the discharged battery, ensure that the diaphragm and the electrode remain bonded and not loose when sampling, perform argon ion cross-section cutting on the positive electrode + diaphragm + negative electrode unit, perform SEM photography on the cut unit cross-section, use a ruler to record the depth of the adhesive coating embedded in the electrode, collect multiple data points and take the average as the embedding depth value of the first adhesive.
  • the bonding coating further includes a second adhesive
  • the first adhesive includes at least one of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), copolymer derivatives of vinylidene fluoride, and copolymer derivatives of tetrafluoroethylene
  • the second adhesive includes polyethylene glycol, polymethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyacrylic acid, polyvinyl acetate, acrylic acid ester multi-polymer, styrene-butadiene latex, styrene-acrylic latex, polyvinyl alcohol, and sodium carboxymethyl cellulose.
  • the first adhesive and the second adhesive are compounded to form the bonding coating, which further improves the bonding performance of the bonding coating
  • the positive electrode sheet includes a positive electrode binder
  • the negative electrode sheet includes a negative electrode binder
  • the negative electrode binder includes one or more of polyurethane, polymethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyacrylic acid, polyvinyl acetate, acrylic acid copolymer, styrene-butadiene latex, styrene-acrylic latex, polyvinyl alcohol, and sodium carboxymethyl cellulose.
  • the positive electrode binder includes polyvinylidene fluoride or a copolymer derivative of vinylidene fluoride.
  • the separator faces the bonding coating of the positive electrode sheet, and faces the bonding coating of the negative electrode sheet.
  • the first adhesive or the second adhesive composition of the adhesive coating can be the same or different.
  • the adhesive in the adhesive coating can form hydrogen bonds with the positive electrode adhesive and the negative electrode adhesive at the surface interface.
  • the positive electrode adhesive, the negative electrode adhesive and the adhesive in the diaphragm adhesive coating are used in combination, so that hydrogen bonds are formed between the diaphragm and the pole piece due to the interaction of the adhesive, which effectively improves the bonding strength between the pole piece and the diaphragm.
  • the coverage of the bonding coating on the surface of the substrate is 5%-80%, preferably 30%-60%.
  • the thickness of the bonding coating is 0.5-10 ⁇ m, and the surface density of the bonding coating is 0.2-1.5 g/m 2 . The above-mentioned bonding coating thickness and surface density range can obtain a lower battery internal resistance while ensuring bonding performance.
  • the substrate of the present application includes one or more of polyethylene, polypropylene, PET nonwoven fabric, PVDF, and polyimide porous membrane.
  • the substrate composed of the above materials has the advantages of wide sources and good film-forming effect.
  • the diaphragm also includes an inorganic material layer, the inorganic material layer is arranged between the substrate and the bonding coating, and the inorganic material layer includes an inorganic material, and the inorganic material includes at least one of aluminum oxide, boehmite, silicon dioxide, calcium sulfate, magnesium sulfate, and magnesium hydroxide.
  • the thickness of the substrate is 4 to 20 ⁇ m and the porosity of the substrate is 30% to 70%.
  • the present application also provides an electric device, which includes a secondary battery, and the secondary battery is used as a power supply for the electric device.
  • the electric device includes at least an electric car, a mobile phone, a tablet computer, a VR device, and a smart watch.
  • the secondary battery provided by the present application matches the diaphragm and the pole piece, which can improve the bonding strength between the diaphragm and the pole piece, prevent the two from being misaligned due to vibration and causing a battery short circuit, and can also improve the tightness between the diaphragm and the pole piece, reduce the DC internal resistance of the secondary battery, and increase the cycle life.
  • PVDF-HFP (whose average primary particle size is 0.2 ⁇ m, and the average secondary particle size is 4 ⁇ m) and polyethylene glycol in a mass ratio of 1:1 were uniformly mixed to obtain a coating slurry, and the coating slurry was coated on both sides of a PE substrate containing an inorganic material layer with a thickness of 13 ⁇ m (a 9 ⁇ m PE substrate was coated with 2 ⁇ m thick aluminum oxide on both sides) by micro-concave roller coating.
  • the coating surface density was 1.0 g/m 2 and the single-side thickness of the coating was 2 ⁇ m.
  • the positive electrode sheet, negative electrode sheet and separator prepared above are wound to obtain a winding core, and further shaped, welded to the tabs, inserted into a square aluminum shell, baked, injected, packaged, left to stand, and formed to obtain a finished secondary battery.
  • the depth of the binder in the separator embedded in the surface of the positive electrode sheet is 0.1 to 2 ⁇ m, and the depth of the binder embedded in the surface of the negative electrode sheet is 0.5 to 5 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP in step 3 is 0.02 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP in step 3 is 0.1 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP in step 3 is 0.5 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the secondary particles of PVDF-HFP in step 3 is 0.8 ⁇ m.
  • Example 2 The same as Example 1, except that the average secondary particles of PVDF-HFP in step 3 are The particle size is 3 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the secondary particles of PVDF-HFP in step 3 is 8 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the secondary particles of PVDF-HFP in step 3 is 10 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP is 0.15 ⁇ m, the average particle size of the secondary particles is 2.5 ⁇ m, the Dv50 of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is 2 ⁇ m, the Dv50 of graphite is 5 ⁇ m, the surface roughness of the positive electrode sheet is 0.8 ⁇ m, and the surface roughness of the negative electrode sheet is 2.9 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP is 0.08 ⁇ m, the average particle size of the secondary particles is 1 ⁇ m, the Dv50 of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is 1 ⁇ m, the Dv50 of graphite is 4 ⁇ m, the surface roughness of the positive electrode sheet is 0.3 ⁇ m, and the surface roughness of the negative electrode sheet is 3.2 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP is 0.3 ⁇ m, the average particle size of the secondary particles is 6 ⁇ m, the Dv50 of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is 8 ⁇ m, the Dv50 of graphite is 17 ⁇ m, the surface roughness of the positive electrode sheet is 6.5 ⁇ m, and the surface roughness of the negative electrode sheet is 10.2 ⁇ m.
  • Example 2 The same as Example 1, except that the average particle size of the primary particles of PVDF-HFP is 0.18 ⁇ m, the average particle size of the secondary particles is 7 ⁇ m, the Dv50 of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is 5 ⁇ m, the Dv50 of graphite is 14 ⁇ m, the surface roughness of the positive electrode sheet is 4.2 ⁇ m, and the surface roughness of the negative electrode sheet is 8.5 ⁇ m.
  • the method is the same as Example 1, except that the positive electrode sheets with different surface roughness are obtained by adjusting the rolling parameters of the positive electrode sheets.
  • the method is the same as Example 1, except that negative electrode sheets with different surface roughness are obtained by adjusting the rolling parameters of the negative electrode sheet.
  • Example 2 The same as Example 1, except that the total coating thickness of the coating slurry is 0.5 ⁇ m.
  • Example 2 The same as Example 1, except that the total coating thickness of the coating slurry is 3 ⁇ m.
  • Example 2 The same as Example 1, except that the total coating thickness of the coating slurry is 6 ⁇ m.
  • Example 2 The same as Example 1, except that the total coating thickness of the coating slurry is 10 ⁇ m.
  • Example 2 The same as Example 1, except that the total coating density of the coating slurry is 0.2 g/m 2 .
  • Example 2 The same as Example 1, except that the total coating density of the coating slurry is 1.5 g/m 2 .
  • Example 2 The same as Example 1, except that PVdF-HFP is replaced by PTFE (polytetrafluoroethylene).
  • PTFE polytetrafluoroethylene
  • Example 2 The same as Example 1, except that PVdF-HFP is replaced by PVdF (polyvinylidene fluoride).
  • PVdF polyvinylidene fluoride
  • Example 2 The same as Example 1, except that polyethylene glycol is replaced by polyacrylate.
  • Example 2 The same as Example 1, except that polyethylene glycol is replaced by polyacrylic acid.
  • Example 2 Same as Example 1, except that the average particle size of the PVDF-HPF secondary particles is 0.1 ⁇ m, the Dv50 of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is 0.1 ⁇ m, the Dv50 of graphite is 2 ⁇ m, and the positive electrode The surface roughness of the electrode piece is 0.1 ⁇ m, and the surface roughness of the negative electrode piece is 0.8 ⁇ m.
  • the method is the same as Example 1, except that in step 3, there are no secondary particles of PVDF-HFP in the coating slurry (static electricity is introduced to avoid agglomeration of primary particles), and there is no polyethylene glycol.
  • the relevant parameters of the separator, positive electrode sheet and negative electrode sheet prepared in the above examples and comparative examples are recorded in Table 1.
  • the peel strength of the separator and the electrode sheet (positive electrode sheet, negative electrode sheet), as well as the DC resistance and cycle life of the secondary battery are tested, and the relevant data are recorded in Table 2.
  • the test method is as follows: 1) Peel strength test of diaphragm and electrode: After discharging the battery to a cut-off voltage of 3.2V, disassemble the battery to obtain the bonding unit of diaphragm/positive electrode sheet/diaphragm/negative electrode sheet, cut the bonding unit into 50mm width strips, and after the electrolyte on the surface of the bonding unit evaporates, use a universal tensile testing machine to perform a 180° peeling tensile test on the diaphragm and electrode, with a stretching speed of 50mm/min and a stretching stroke of 100mm. The force detected when the positive electrode sheet (negative electrode sheet) is peeled off is the peeling strength, so as to obtain the bonding strength values of the diaphragm and the positive electrode sheet, and the diaphragm and the negative electrode sheet respectively.
  • the present application can improve the bonding strength between the diaphragm and the electrode sheets by setting the particle size of the adhesive particles of the diaphragm bonding coating to match the surface roughness of the positive electrode sheet and the negative electrode sheet, which is beneficial to reducing the DC internal resistance of the battery and improving the cycle life of the battery.
  • the secondary battery and the electrical device provided by the present application are provided with a first adhesive of the separator.
  • the average particle size of the primary particles is 0.02 to 0.5 ⁇ m, and the average particle size of the secondary particles is 0.5 to 10 ⁇ m, so that the surface of the bonding coating of the diaphragm is microscopically uneven and has a high roughness.
  • the positive electrode plate and the negative electrode plate are also set to a surface interface with a certain roughness (that is, their surfaces are microscopically uneven).
  • the first adhesive particles of the diaphragm can be embedded in the electrode plates to form a strong anchoring between the bonding coating and the electrode plates, thereby improving the bonding strength between the bonding coating and the electrode plates, and can further improve the tightness between the electrode plates and the diaphragm. Therefore, during the charge and discharge cycle of the secondary battery, the transmission rate of lithium ions between the positive electrode plate and the negative electrode plate is faster, which reduces the internal resistance of the secondary battery and is beneficial to improving the cycle performance of the secondary battery. Moreover, due to the improvement of the bonding strength, the positive electrode plate and the negative electrode plate of the secondary battery can be prevented from being misaligned in a strong vibration environment, thereby avoiding short circuit of the secondary battery and improving safety performance.

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

一种二次电池以及用电设备。其中二次电池包括依次设置的正极极片、隔膜以及负极极片；隔膜包括基材以及设置在基材表面的粘接涂层，粘接涂层包括第一粘接剂，第一粘接剂的一次颗粒的平均粒径为0.02～0.5μm，第一粘接剂的二次颗粒的平均粒径为0.5～10μm；正极极片的表面粗糙度为0.1～6.5μm；负极极片的表面粗糙度为0.5～12μm。所述隔膜的粘接涂层表面微观上凹凸不平，具有较高的粗糙度，同时正极极片和负极极片也设置成具有一定粗糙度的表界面(即其表面在微观上凹凸不平)，所以在隔膜与极片(正极极片、负极极片)粘接时，隔膜与极片形成强的锚合，提高粘接涂层与极片之间的粘接强度以及紧密性，降低电池内阻，提高循环寿命。

Description

一种二次电池以及用电设备
相关申请交叉引用
本申请要求于2022年11月28日提交的、题目为一种二次电池以及用 电设备的中国专利申请申请号为202211501079.7的优先权，该申请的全部 内容通过引用并入本文。
技术领域
本申请涉及电池领域，特别公开了一种二次电池以及用电设备。
背景技术
目前，二次电池成为新能源行业重点产业之一，其除用于3C数码领域等领域外，在电动汽车行业也得到广泛使用。二次电池的循环寿命和安全性是二次子电池获得认可的重要前提。
二次电池，特别是锂离子电池充放电过程中，锂离子以电解液为介质，在正极、负极和隔膜之间来回传输，需要确保隔膜与电极之间有良好的粘结界面。隔膜表面的粘结涂层与电极之间形成粘结作用，粘结强度对锂离子电池全生命周期有重要影响。隔膜与电极粘结强度不足会导致粘结界面变差，锂离子传输受阻，对锂离子电池使用寿命有重要影响。
另外，锂离子电池在使用过程中，特别是电动汽车用锂离子电池的实际工况使用下，锂离子电池会持续受到工况振动以及极端使用条件下可能受到剧烈冲击作用，锂离子电池正负极容易发生错位，导致正负极之间接触短路，造成安全事故。隔膜作为正极和负极的物理隔离屏障，隔膜与电极之间的粘结强度对锂离子电池振动电极错位有重要影响，增强隔膜与电极之间粘结强度，有利于提升锂离子电池工况使用下的安全性能。
发明内容
本申请提供一种二次电池和用电设备，旨在解决现有二次电池的极片与隔膜之间的粘结强度差，引起离子传输受阻以及极片容易错位，导致二次电池电化学性能差以及安全性能差的技术问题。
鉴于此，本申请提供一种二次电池，该二次电池依次设置的正极极片、隔膜以及负极极片；
所述隔膜包括基材以及设置在所述基材表面的粘接涂层，所述粘接涂 层包括第一粘接剂，所述第一粘接剂的一次颗粒的平均粒径为0.02～0.5μm，所述第一粘接剂的二次颗粒的平均粒径为0.5～10μm；所述正极极片的表面粗糙度为0.1～6.5μm；所述负极极片的表面粗糙度为0.5～12μm。
进一步地，所述正极极片包括正极活性物质，所述负极极片包括负极活性物质，所述正极活性物质的颗粒Dv50为1～8μm，所述负极活性物质的颗粒的Dv50为4～17μm。
进一步地，所述正极活性物质的颗粒Dv50与所述第一粘接剂的一次颗粒的平均粒径的比值，以及所述负极活性物质的颗粒Dv50与所述第一粘接剂的一次颗粒的平均粒径的比值均≥10；所述正极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值，以及所述负极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值均≥0.5。进一步地，所述粘接涂层还包括第二粘接剂，所述第一粘接剂包括聚偏氟乙烯(PVdF)、聚偏氟乙烯-六氟丙烯共聚物(PVdF-HFP)、聚四氟乙烯(PTFE)、偏氟乙烯的共聚衍生物、四氟乙烯的共聚衍生物中的至少一种，所述第二粘接剂包括聚乙二醇、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚甲基丙烯酸乙酯、聚甲基丙烯酸丁酯、聚丙烯酸、聚醋酸乙烯酯、丙烯酸酯类多元共聚物、丁苯乳胶、苯丙乳胶、聚乙烯醇、羧甲基纤维素钠中的至少一种。
进一步地，所述负极极片包括负极粘结剂，所述负极粘接剂含有-COOH、-OH、C＝O、C＝C、-NH2中的至少一种基团。
进一步地，所述粘接涂层的厚度为0.5～10μm，所述粘接涂层的面密度为0.2～1.5g/m2。
进一步地，所述基材包括聚乙烯、聚丙烯、PET无纺布、PVDF、聚酰亚胺多孔膜中的一种或者多种。
进一步地，所述隔膜还包括无机材料层，所述无机材料层设置在所述基材和粘接涂层之间，所述无机材料层含有无机材料，所述无机材料包括氧化铝、勃姆石、二氧化硅、硫酸钙、硫酸镁和氢氧化镁中的至少一种。
进一步地，所述第一粘接剂嵌入所述正极极片表面的深度为0.1～2μm，嵌入所述负极极片表面的深度为0.5～5μm。
本申请还提供一种用电设备，该用电设备包括上述的二次电池，所述二次电池用于作为所述用电设备的供电电源。
附图说明
构成本申请的一部分的说明书附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定，在附图中：
图1为一实施例二次电池局部结构示意图。
图2为一实施例极片界面和粘结涂层界面结构示意图。
具体实施方式
下述实施例中所使用的实验方法如无特殊说明，均为常规方法。
下述实施例中所用的材料、试剂等，如无特殊说明，均可从商业途径得到。
在一实施例中，本申请提供一种二次电池，其包括依次设置的正极极片、隔膜以及负极极片；
所述隔膜包括基材以及设置在所述基材表面的粘接涂层，所述粘接涂层包括第一粘接剂，所述第一粘接剂的一次颗粒的平均粒径为0.02～0.5μm，所述第一粘接剂的二次颗粒的平均粒径为0.5～10μm；所述粘接涂层用于将所述正极极片和所述负极极片粘接在所述隔膜两面；
所述正极极片的表面粗糙度为0.1～6.5μm；所述负极极片的表面粗糙度为0.5～12μm。
在本实施中，正极极片和负极极片通过隔膜表面的粘接涂层粘接在一起，隔膜起到隔离和粘接的作用。隔膜的第一粘接剂的一次颗粒的平均粒径为0.02～0.5μm，二次颗粒的平均粒径为0.5～10μm，使得隔膜的粘接涂层表面微观上凹凸不平，使其表面具有较合适的粗糙度，隔膜表面的粗糙度为0.2～0.9μm，同时正极极片和负极极片也设置成具有一定粗糙度的表界面(即其表面在微观上凹凸不平)。具体地，本申请第一粘接剂的一次颗粒的平均粒径可以是0.02μm、0.05μm、0.1μm、0.2μm、0.3μm、0.5μm中的任意一个数值，也可以是任意两个数值之间的范围值，第一粘接剂的二次颗粒的平均粒径可以是0.5μm、1μm、2μm、5μm、8μm、10μm中的任意一个数值，也可以是任意两个数值之间的范围值。通过以上设置，在隔膜与极片(正极极片、负极极片)粘接时，隔膜的第一粘接剂颗粒能够嵌入到极片中使粘接涂层与极片形成强的锚合，从而提高粘接涂层与极片 之间的粘接强度，且还能够进一步提高极片和隔膜之间的紧密性，因而二次电池在充放电循环过程中，锂离子在正极极片和负极极片之间的传输速率更快，降低了二次电池的内阻，有利于提高二次电池的循环性能，且由于粘接强度的提升，可以避免二次电池在强烈震动的环境下正极极片和负极极片发生错位，避免二次电池短路，提升安全性能。在本实施例中，正极极片包含有正极活性物质，正极活性物质可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸铁锂中的一种或多种。负极极片包含有负极活性物质，负极活性物质包括石墨、石墨/硅复合材料、钛酸锂中的一种或多种。为获得不同粗糙度的极片，可以通过改变活性物质(正极活性物质或负极活性物质)的粒径，或者在极片辊压过程中，控制对极片的辊压压力，也可以同时调整活性材料粒径大小以及辊压压力，来控制极片的粗糙度。
其中，本申请采用的粗糙度为算数平均粗糙度Sa，极片(正极极片或负极极片)和隔膜表面粗糙度的测试方式为：首先采用基恩士VHX-7000对极片(或隔膜)表面进行3D扫描，扫描区域5mm×5mm，然后经过计算机设备软件计算，连续测试并计算出多个平行样取，多个平行样测试的均值即为极片粗糙度。粘结涂层中第一粘结剂的一次颗粒的平均粒径的测试方式为：采用SEM设备拍摄隔膜表面粘结涂层，标尺统计多个一次颗粒(球或近似球的最长尺寸)的均值作为一次颗粒平均粒径。粘结涂层中第一粘结剂的二次颗粒的平均粒径的测试方式为：SEM设备拍摄隔膜表面涂层，标尺统计多个二次颗粒(球或近似球的最长尺寸)的均值作为二次颗粒平均粒径。
为了使粘接涂层的第一粘接剂颗粒能更好地嵌入极片表面的缝隙中，获得更高的锚合力和紧密性，在另一实施例中，所述正极活性物质的颗粒Dv50为1～8μm，所述负极活性物质的颗粒的Dv50为4～17μm。正极活性物质和负极活性物质的Dv50在上述范围内，可以与第一粘接剂的一次颗粒、二次颗粒的平均粒径相互配合，来提升锚合力，提高粘接强度。
为进一步提升锚合力，进一步优化正极活性物质、负极活性物质与第一粘接剂的一次颗粒和二次颗粒的粒径选择，在另一实施例中正极活性物质的颗粒Dv50与所述第一粘接剂的一次颗粒的平均粒径比值，以及所述 负极活性物质的颗粒的Dv50与所述第一粘接剂的一次颗粒的平均粒径比值均≥10；所述正极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值，以及所述负极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值均≥0.5。
在一些实施例中，第一粘接剂嵌入所述正极极片表面的深度为0.1～2μm，嵌入所述负极极片表面的深度为0.5～5μm。且隔膜与所述正极极片的粘结力为1～15N/m，所述隔膜与所述负极极片之间的粘结力为0.5～6N/m。
其中，第一粘结剂嵌入极片表面(正极极片表面或负极极片表面)的深度的测试流程为：从放电态电池中取出正极+隔膜+负极单元，取样时确保隔膜与极片保持粘结不松动，将正极+隔膜+负极单元进行氩离子截面切割，将切割后的单元截面进行SEM拍摄，用标尺记录粘结涂层嵌入极片的深度，采集多个数据点取均值为第一粘结剂嵌入深度值。
在一些实施例中，所述粘接涂层还包括第二粘接剂，所述第一粘接剂包括聚偏氟乙烯(PVdF)、聚偏氟乙烯-六氟丙烯共聚物(PVdF-HFP)、聚四氟乙烯(PTFE)、偏氟乙烯的共聚衍生物、四氟乙烯的共聚衍生物中的至少一种，所述第二粘接剂包括聚乙二醇、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚甲基丙烯酸乙酯、聚甲基丙烯酸丁酯、聚丙烯酸、聚醋酸乙烯酯、丙烯酸酯类多元共聚物、丁苯乳胶、苯丙乳胶、聚乙烯醇、羧甲基纤维素钠中的一种或多种。在本实施例中，第一粘接剂和第二粘接剂复配组成粘接涂层，进一步提高粘接涂层的粘接性能，从而提高粘结涂层与极片的粘接强度。
在一些实施例中，所述正极极片包括正极粘接剂，所述负极极片包括负极粘接剂，其中，负极粘接剂含有-COOH、-OH、C＝O、C＝C、-NH2中的至少一种基团，例如负极粘结剂包括聚氨酯、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚甲基丙烯酸乙酯、聚甲基丙烯酸丁酯、聚丙烯酸、聚醋酸乙烯酯、丙烯酸酯类多元共聚物、丁苯乳胶、苯丙乳胶、聚乙烯醇、羧甲基纤维素钠、中的一种或多种。正极粘接剂包括聚偏氟乙烯或偏氟乙烯的共聚衍生物。
在另一实施例中，隔膜面向正极极片的粘接涂层，和面向负极极片的 粘接涂层的第一粘接剂或第二粘接剂组成可以相同也可以不同，为提高隔膜与极片之间的粘接强度，粘接涂层中的粘接剂与正极粘接剂、负极粘接剂能够在表界面形成氢键。在本实施例中，正极粘接剂、负极粘接剂与隔膜粘接涂层中的粘接剂配合使用，使得隔膜和极片之间由于粘接剂的相互作用，形成氢键，有效地提高了极片与隔膜之间的粘接强度。
基于成本和粘接强度考虑，在一些实施例中，粘接涂层在所述基材表面的覆盖率为5％-80％，优选为30％～60％。在一些实施例中，粘接涂层的厚度为0.5～10μm，所述粘接涂层的面密度为0.2～1.5g/m2。上述粘接涂层厚度和面密度范围可以获得较低电池内阻的同时，还可以确保粘接性能。
在一些实施例中，本申请的基材包括聚乙烯、聚丙烯、PET无纺布、PVDF、聚酰亚胺多孔膜中的一种或者多种。上述材料组成的基材具有来源广泛，成膜效果好的优点。为提高隔膜的热稳定性以及机械强度，在另一实施例中，隔膜还包括无机材料层，无机材料层设置在基材和粘结涂层之间，无机材料层包括无机材料，无机材料包括氧化铝、勃姆石、二氧化硅、硫酸钙、硫酸镁和氢氧化镁中的至少一种。
为了使二次电池充放电循环过程中，锂离子能够快速在隔膜中穿梭，同时降低隔膜内阻，在一些实施例中，基材的厚度为4～20μm，基材的孔隙率为30％～70％。
在另一方面，本申请还提供一种用电设备，该用电设备包含二次电池，二次电池用于作为用电设备的供电电源。用电设备至少包括电动汽车、手机、平板电脑、VR设备、智能手表。
本申请提供的二次电池，将隔膜和极片进行匹配设备，能够提高隔膜和极片之间的粘接强度，防止因震动导致两者错位，引起电池短路，另外还能够提高隔膜和极片之间的紧密型，降低二次电池的直流内阻，提高循环寿命。
为清楚理解本申请技术方案，以下结合具体实施例对本申请作进一步详细描述，这些实施例不能理解为限制本申请所要求保护的范围。
实施例1
1)正极极片的制备：将质量比为96:2:2的LiNi0.6Co0.2Mn0.2O2(Dv50 为4μm)、PVDF、SP混合均匀后，放入NMP溶剂中搅拌均匀，获得正极浆料，将正极浆料涂布在铝箔表面，经过烘干、辊压以及分切后获得表面粗糙度为2.8μm的正极极片。
2)负极极片的制备：将质量比为94:2:1:3的石墨(Dv50为6μm)、羧甲基纤维素钠、聚乙二醇、SP混合均匀后，放入去离子水中搅拌均匀，获得负极浆料，将负极浆料涂布在铜箔表面，经烘干、辊压以及分切后获得表面粗糙度为6μm的负极极片。
3)隔膜的制备：将质量比为1:1的PVDF-HFP(其一次颗粒的平均粒径为0.2μm，二次颗粒的平均粒径为4μm)、聚乙二醇混合均匀得到涂层浆料，采用微凹辊涂的方式将涂层浆料涂覆在厚度为13μm的含有无机材料层的PE基材两面(9μm的PE基材两面各涂覆2μm厚的氧化铝)，涂覆面密度为1.0g/m2，涂覆的单面厚度为2μm。
4)二次电池的制备：将上述制得的正极极片、负极极片、隔膜通过卷绕获取卷芯，进一步通过整形、极耳焊接、入方形铝壳、烘烤、注液、封装、静置、化成获得成品二次电池。其中，隔膜中的粘结剂嵌入正极极片表面的深度为0.1～2μm，嵌入负极极片表面的深度为0.5～5μm。
实施例2
与实施例1相同，不同的是，步骤3中PVDF-HFP的一次颗粒的平均粒径为0.02μm。
实施例3
与实施例1相同，不同的是，步骤3中PVDF-HFP的一次颗粒的平均粒径为0.1μm。
实施例4
与实施例1相同，不同的是，步骤3中PVDF-HFP的一次颗粒的平均粒径为0.5μm。
实施例5
与实施例1相同，不同的是，步骤3中PVDF-HFP的二次颗粒的平均粒径为0.8μm。
实施例6
与实施例1相同，不同的是，步骤3中PVDF-HFP的二次颗粒的平均 粒径为3μm。
实施例7
与实施例1相同，不同的是，步骤3中PVDF-HFP的二次颗粒的平均粒径为8μm。
实施例8
与实施例1相同，不同的是，步骤3中PVDF-HFP的二次颗粒的平均粒径为10μm。
实施例9
与实施例1相同，不同的是，PVDF-HFP的一次颗粒的平均粒径为0.15μm，二次颗粒的平均粒径为2.5μm，LiNi0.6Co0.2Mn0.2O2Dv50为2μm，石墨的Dv50为5μm，正极极片的表面粗糙度为0.8μm，负极极片的表面粗糙度为2.9μm。
实施例10
与实施例1相同，不同的是，PVDF-HFP的一次颗粒的平均粒径为0.08μm，二次颗粒的平均粒径为1μm，LiNi0.6Co0.2Mn0.2O2Dv50为1μm，石墨的Dv50为4μm，正极极片的表面粗糙度为0.3μm，负极极片的表面粗糙度为3.2μm。
实施例11
与实施例1相同，不同的是，PVDF-HFP的一次颗粒的平均粒径为0.3μm，二次颗粒的平均粒径为6μm，LiNi0.6Co0.2Mn0.2O2Dv50为8μm，石墨的Dv50为17μm，正极极片的表面粗糙度为6.5μm，负极极片的表面粗糙度为10.2μm。
实施例12
与实施例1相同，不同的是，PVDF-HFP的一次颗粒的平均粒径为0.18μm，二次颗粒的平均粒径为7μm，LiNi0.6Co0.2Mn0.2O2Dv50为5μm，石墨的Dv50为14μm，正极极片的表面粗糙度为4.2μm，负极极片的表面粗糙度为8.5μm。
实施例13～实施例16
与实施例1相同，不同的是，通过调整对正极极片的辊压参数，得到不同表面粗糙度的正极极片。
实施例17～20
与实施例1相同，不同的是，通过调整对负极极片的辊压参数，得到不同表面粗糙度的负极极片。
实施例21
与实施例1相同，不同的是，涂层浆料的涂覆总厚度0.5μm。
实施例22
与实施例1相同，不同的是，涂层浆料的涂覆总厚度3μm。
实施例23
与实施例1相同，不同的是，涂层浆料的涂覆总厚度6μm。
实施例24
与实施例1相同，不同的是，涂层浆料的涂覆总厚度10μm。
实施例25
与实施例1相同，不同的是，涂层浆料的涂覆总密度为0.2g/m2。
实施例26
与实施例1相同，不同的是，涂层浆料的涂覆总密度为1.5g/m2。
实施例27
与实施例1相同，不同的是，将PVdF-HFP替换为PTFE(聚四氟乙烯)。
实施例28
与实施例1相同，不同的是，将PVdF-HFP替换为PVdF(聚偏二氟乙烯)。
实施例29
与实施例1相同，不同的是，将聚乙二醇替换为聚丙烯酸酯。
实施例30
与实施例1相同，不同的是，将聚乙二醇替换为聚丙烯酸。
实施例31
与实施例1相同，不同的是，在步骤3中，不加入聚乙二醇。
对比例1
与实施例1相同，不同的是PVDF-HPF二次颗粒的平均粒径为0.1μm，LiNi0.6Co0.2Mn0.2O2的Dv50为0.1μm，石墨的Dv50为2μm，正极 极片的表面粗糙度为0.1μm，负极极片的表面粗糙度为0.8μm。
对比例2
与对比例1相同，不同的是，涂层浆料中不含聚乙二醇。
对比例3
与实施例1相同，不同的是步骤3中，涂层浆料中不存在PVDF-HFP的二次颗粒(通过引入静电的方式避免一次颗粒聚团)，且不存在聚乙二醇。
将上述实施例和对比例制备得到的隔膜、正极极片和负极极片的相关参数记录在表1中。并测试隔膜与极片(正极极片、负极极片)的剥离强度，以及二次电池的直流电阻和循环寿命，就相关数据记录在表2中。
测试方法如下：1)隔膜与极片剥离强度测试：将电池放电至截止电压3.2v后，对电池进行拆解，获得隔膜/正极极片/隔膜/负极极片的粘结单元，将粘结单元裁剪成50mm宽度样条，待粘结单元表面电解液挥发后，用万能拉力机对隔膜和电极进行180°剥离拉伸测试，拉伸速度50mm/min，拉伸行程100mm，当正极极片(负极极片)剥离下来时检测到的力即为剥离强度，以此分别获得隔膜与正极极片，以及隔膜与负极极片的粘接强度值。
2)电池DCR测试：在25℃条件下，对电池以1C/1C的充放电倍率分容三次，取三次容量均值为电池的实际容量C0，按电池实际容量C0调节电池到50％SOC状态；以4C的电流放电10s，记录放电前后的电压差值，DCR定义为电池放电前后电压差值与电流的比值即DCR＝ΔU/I。
3)电池循环寿命测试：分别在25℃条件下和45℃条件下，以1C/1C的充放电电流，0～100％SOC将电池循环至容量保持率为80％，记录此时的循环圈。
表1各实施例和对比例制备得到的隔膜、正极极片和负极极片的相关参数

表2各实施例和对比例制备得到的隔膜与极片(正极极片、负极极片)的剥离强度以及二次电池的直流电阻和循环寿命

根据上述表格数据可见，本申请通过设置隔膜粘接涂层的粘接剂颗粒粒径大小与正极极片和负极极片的表面粗糙度相互匹配，能够提高隔膜与极片之间的粘接强度，有利于降低电池直流内阻，提高电池的循环寿命。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。
工业应用
本申请具有如下有益技术效果：
本申请所提供的二次电池以及用电设备，由于隔膜的第一粘接剂的一 次颗粒的平均粒径为0.02～0.5μm，二次颗粒的平均粒径为0.5～10μm，使得隔膜的粘接涂层表面微观上凹凸不平，具有较高的粗糙度，同时正极极片和负极极片也设置成具有一定粗糙度的表界面(即其表面在微观上凹凸不平)，所以在隔膜与极片(正极极片、负极极片)粘接时，隔膜的第一粘接剂颗粒能够嵌入到极片中使粘接涂层与极片形成强的锚合，从而提高粘接涂层与极片之间的粘接强度，且还能够进一步提高极片和隔膜之间的紧密性，因而二次电池在充放电循环过程中，锂离子在正极极片和负极极片之间的传输速率更快，降低二次电池的内阻，有利于提高二次电池的循环性能，且由于粘接强度的提升，可以避免二次电池在强烈震动的环境下正极极片和负极极片发生错位，避免二次电池短路，提升安全性能。

Claims (10)

  1. 一种二次电池，其中，包括依次设置的正极极片、隔膜以及负极极片；
    所述隔膜包括基材以及设置在所述基材表面的粘接涂层，所述粘接涂层包括第一粘接剂，所述第一粘接剂的一次颗粒的平均粒径为0.02～0.5μm，所述第一粘接剂的二次颗粒的平均粒径为0.5～10μm；
    所述正极极片的表面粗糙度为0.1～6.5μm；所述负极极片的表面粗糙度为0.5～12μm。
  2. 根据权利要求1所述的二次电池，其中，所述正极极片包括正极活性物质，所述负极极片包括负极活性物质，所述正极活性物质的颗粒Dv50为1～8μm，所述负极活性物质的颗粒的Dv50为4～17μm。
  3. 根据权利要求2所述的二次电池，其中，所述正极活性物质的颗粒Dv50与所述第一粘接剂的一次颗粒的平均粒径的比值，以及所述负极活性物质的颗粒Dv50与所述第一粘接剂的一次颗粒的平均粒径的比值均≥10；所述正极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值，以及所述负极活性物质的颗粒Dv50与所述第一粘接剂的二次颗粒的平均粒径的比值均≥0.5。
  4. 根据权利要求1所述的二次电池，其中，所述粘接涂层还包括第二粘接剂，所述第一粘接剂包括聚偏氟乙烯、聚偏氟乙烯-六氟丙烯共聚物、聚四氟乙烯、偏氟乙烯的共聚衍生物、四氟乙烯的共聚衍生物中的至少一种，所述第二粘接剂包括聚乙二醇、聚丙烯酸甲酯、聚甲基丙烯酸甲酯、聚甲基丙烯酸乙酯、聚甲基丙烯酸丁酯、聚丙烯酸、聚醋酸乙烯酯、丙烯酸酯类多元共聚物、丁苯乳胶、苯丙乳胶、聚乙烯醇和羧甲基纤维素钠中的至少一种。
  5. 根据权利要求2所述的二次电池，其中，所述负极极片包括负极粘结剂，所述负极粘接剂含有-COOH、-OH、C＝O、C＝C和-NH2中的至少一种基团。
  6. 根据权利要求1所述的二次电池，其中，所述粘接涂层的厚度为0.5～10μm，所述粘接涂层的面密度为0.2～1.5g/m2。
  7. 根据权利要求1～6任一项所述的二次电池，其中，所述基材包括聚乙烯、聚丙烯、PET无纺布、PVDF、聚酰亚胺多孔膜中的一种或者多 种。
  8. 根据权利要求7所述的二次电池，其中，所述隔膜还包括无机材料层，所述无机材料层设置在所述基材和粘接涂层之间，所述无机材料层含有无机材料，所述无机材料包括氧化铝、勃姆石、二氧化硅、硫酸钙、硫酸镁和氢氧化镁中的至少一种。
  9. 根据权利要求1所述的二次电池，其中，所述第一粘接剂嵌入所述正极极片表面的深度为0.1～2μm，嵌入所述负极极片表面的深度为0.5～5μm。
  10. 一种用电设备，其中，包括权利要求1～9任一项所述的二次电池，所述二次电池用于作为所述用电设备的供电电源。
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