WO2022143904A1 - 极片及电池 - Google Patents

极片及电池 Download PDF

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Publication number
WO2022143904A1
WO2022143904A1 PCT/CN2021/143101 CN2021143101W WO2022143904A1 WO 2022143904 A1 WO2022143904 A1 WO 2022143904A1 CN 2021143101 W CN2021143101 W CN 2021143101W WO 2022143904 A1 WO2022143904 A1 WO 2022143904A1
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WO
WIPO (PCT)
Prior art keywords
pole piece
tab
active material
pole
lithium
Prior art date
Application number
PCT/CN2021/143101
Other languages
English (en)
French (fr)
Inventor
张健
孙雷明
张双虎
彭冲
Original Assignee
珠海冠宇电池股份有限公司
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Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Priority to EP21914635.4A priority Critical patent/EP4152436A1/en
Priority to KR1020237002358A priority patent/KR20230029832A/ko
Priority to JP2023500036A priority patent/JP2023533260A/ja
Publication of WO2022143904A1 publication Critical patent/WO2022143904A1/zh
Priority to US18/066,274 priority patent/US20230122728A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • 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
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/40—Alloys based on alkali metals
    • H01M4/405—Alloys based on lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • 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 invention relates to a pole piece and a battery, belonging to the field of batteries.
  • Lithium-ion batteries are the most important type of battery for consumer electronic products such as smartphones and notebook computers. With the upgrading of consumer electronic products such as smartphones, the requirements for energy density, charging speed and safety performance of lithium-ion batteries are getting higher and higher.
  • the conventional structure of the soft-pack lithium-ion battery tab is welded to one end of the pole piece.
  • the lithium-ion battery with this structure has a large internal resistance, which is not conducive to fast charging of the battery. Welding the tab in the middle of the pole piece or near the middle area can Effectively reduce the internal resistance of the battery, which is beneficial to improve the charging speed of the battery.
  • the coating at the preset tab position in the middle of the pole piece is removed, and the tab is welded after exposing the current collector. , and then paste it with adhesive tape for protection.
  • the tape is usually also attached to the exposed current collector around the tab and the functional coating around the tab (that is, the functional coating is close to the tab. area) to cover the tabs and protect the tabs.
  • the conventional pole piece structure there is a height difference between the area of the functional coating near the tab and the current collector.
  • the current collector is completely fitted, which makes the functional coating area close to the electrode ear prone to negative electrolyte, which makes the lithium ion concentration in this area too different from other areas, and there are problems such as easy precipitation of lithium, which reduces the safety and rate of the electrode and battery. performance, etc.
  • the invention provides a pole piece, which can effectively improve the protection of the negative electrode area of the pole ear, avoid problems such as lithium precipitation, and improve the safety and rate performance of the pole piece and the battery.
  • the present invention also provides a battery, which adopts the above-mentioned pole piece and has good performances such as safety and rate capability.
  • a pole piece comprising a current collector and a functional layer disposed on a first surface of the current collector, a pole lug is also provided in the middle of the first surface, and the functional layer on the first surface has a first surface close to the pole lug.
  • the end point of the end of the first gradient area away from the pole lug is c
  • the end point of the end of the first gradient area close to the pole lug is d
  • c and d are the end points of the end of the first gradient area close to the pole lug.
  • the acute included angle between the connecting line of d and the plane parallel to the surface of the pole piece is ⁇ , and ⁇ is 10-80°.
  • the width of the first gradient area is 0.25-3 mm.
  • the functional layer includes an active material layer and a primer layer located between the active material layer and the surface of the current collector, and the active material layer has the first gradient region and the first normal region.
  • the primer layer has a second gradient area close to the tab and a second normal area away from the tab, and the thickness of the second gradient area gradually decreases in a direction close to the tab.
  • the end point of the end of the second gradient area away from the pole lug is e
  • the end point of the end of the second gradient area close to the pole lug is f
  • e the end point of the end of the second gradient area close to the pole lug
  • ⁇ the acute included angle between the line of f and the plane parallel to the surface of the pole piece
  • the minimum distance from the active material layer to the tabs is not greater than the minimum distance from the primer layer to the tabs.
  • the minimum distance from the active material layer to the tab is m
  • the minimum distance from the primer layer to the tab is n, where 0 ⁇ n-m ⁇ 3mm.
  • the minimum distance from the surface of the first gradient region to the first surface of the current collector is greater than the maximum distance from the surface of the primer layer to the first surface of the current collector.
  • Another aspect of the present invention provides a battery including the above-mentioned pole piece.
  • the pole piece provided by the present invention can reduce the height difference between the slope area and the pole lug and the exposed current collector around the pole lug by setting a gradient area (that is, the above-mentioned first gradient area) in the functional layer area close to the pole lug, Make the adhesive tape better bond with the tab, the exposed current collector around the tab, and the slope area, improve the protection effect on the tab area, avoid the enrichment of electrolyte and the resulting lithium precipitation and other problems, and improve the Performances such as rate, safety, stability and service life of pole pieces and batteries.
  • a gradient area that is, the above-mentioned first gradient area
  • FIG. 1 is a schematic cross-sectional view of a first surface of a pole piece according to an embodiment of the present invention
  • FIG. 2 is a schematic cross-sectional view of a first surface of a pole piece according to another embodiment of the present invention.
  • a pole piece is provided, as shown in FIGS. 1-2 , the pole piece includes a current collector 1 and a functional layer disposed on the first surface of the current collector, and a pole lug is also provided in the middle of the first surface 4.
  • the functional layer on the first surface has a first gradient area 31 close to the tab 4 and a first normal area 32 away from the tab. The thickness of the first gradient area 31 gradually decreases along the direction close to the tab 4 .
  • the pole piece provided by the present invention by setting the above-mentioned first gradient area, it is beneficial to make the adhesive tape more closely adhere to the tab, the exposed current collector around the tab, and the slope area around the tab, and improve the coverage of the tab. And protection effect, avoid the enrichment of electrolyte near the pole ear and the resulting lithium precipitation and other problems, thereby improving the rate, safety, stability and service life of the pole piece and battery.
  • the pole piece of the present invention can be provided with a functional layer only on the first surface, or a functional layer can be provided on the second surface opposite to the first surface at the same time (that is, both the positive and negative surfaces of the current collector are provided with functional layers) , can be set as required during specific implementation, wherein, the functional layer on the second surface can be a conventional structure in the field, which is not particularly limited in the present invention, and will not be repeated.
  • a functional layer is also provided on the second surface, the thickness of the second surface functional layer is equal to the thickness of the functional layer in the first normal area of the first surface, and the thickness of the second surface functional layer is the same as that of the first surface.
  • the sum of the thicknesses of the functional layers of the first normal region is 90-120 ⁇ m.
  • the end point of the end of the first gradient area 31 away from the tab 4 is c, and the first gradient area 31 is close to the end of the tab 4 .
  • the end point of one end is d, and the acute included angle between the line connecting c and d and the plane parallel to the surface of the pole piece (hereinafter referred to as the first slope angle) is ⁇ , and ⁇ is 10-80°, such as 10°, 15° , 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or a range of any two of them, such as 20 -80° or 20-70°, etc., which is beneficial to improve the rate and stability of the pole piece.
  • c is the critical point of the thickness change of the functional layer (that is, the intersection of the boundary line between the first normal area 32 and the first gradient area 31 formed in the above projection), and d is the first gradient area 31 (in the form of an arc or slope) The intersection formed in the above projection with the dividing line of the vertical plane of the functional layer parallel to the thickness direction of the functional layer.
  • the width a of the first gradient area 31 can be 0.25-3mm, and further can be 0.5-2.5mm or 0.5-2mm or 0.5-1.5mm, and the width a is the distance from the end of the first gradient area 31 away from the tab to The distance from the end close to the tab in the direction parallel to the plane of the surface of the functional layer, or in other words, the width a is the boundary between the first normal area 32 and the first gradient area 31 to the first gradient area 31 and parallel to the functional layer. The distance of the dividing line of the vertical plane of the functional layer in the layer thickness direction in the direction parallel to the plane of the surface of the functional layer.
  • the functional layer includes an active material layer
  • the coating layer 2 , the active material layer 3 has the above-mentioned first gradient region 31 and the first normal region 32 .
  • the primer layer 2 has a second gradient area 21 close to the tab 4 and a second normal area 22 away from the tab 4 , and the thickness of the second gradient area 21 gradually decreases along the direction close to the tab 4 .
  • the end point of the end of the second gradient area 21 away from the tab 4 is e
  • the end point of the second gradient area 21 close to the end of the tab 4 is f
  • e and f The acute included angle between the connecting line and the plane parallel to the surface of the pole piece is ⁇ (hereinafter referred to as the second slope angle), and ⁇ is 10-80°, such as 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or a range of any two of them.
  • e is the critical point of the thickness change of the primer layer (that is, the intersection of the boundary line between the second normal area 22 and the second gradient area 21 formed in the above projection), and f is the second gradient area 21 (in the form of an arc or an inclined plane). ) and the dividing line of the vertical plane of the primer layer parallel to the thickness direction of the primer layer formed in the above projection.
  • the connecting line of e and c is the same as the thickness direction of the functional layer (ie, in the direction close to the tab, the starting positions of the first gradient area 31 and the second gradient area 32 are the same).
  • the minimum distance from the active material layer 3 to the tabs 4 is not greater than the minimum distance from the primer layer 2 to the tabs 4, which is beneficial for the surface of the entire functional layer to be more homogeneous and smooth, and to improve its performance such as safety and magnification.
  • the minimum distance from the active material layer 3 to the tab 4 is m
  • the minimum distance from the undercoat layer 2 to the tab 4 is n, 0 ⁇ n-m ⁇ 3mm (that is, as shown in FIG. 1, the undercoat layer 2 is close to the tab
  • the distance b from one end of the active material layer 3 to the end of the active material layer 3 close to the tab 4 is 0-3mm), further, 0 ⁇ n-m ⁇ 2.5mm or 0 ⁇ n-m ⁇ 2mm or 0 ⁇ n-m ⁇ 1.5mm or 0 ⁇ n-m ⁇ 1mm, relatively speaking, if n-m is too small ( ⁇ 0), the excess part of the primer layer will affect the smoothness of the surface of the functional layer, and the primer layer usually has a large adhesive force, which is difficult to clean or scrape off, which affects the manufacture of the pole piece. , and n-m is too large (>3mm), which will cause a large part of the active material layer area near the tab to be unprotected by the primer, which is not conduc
  • the minimum distance from the surface of the first gradient area 31 to the first surface of the current collector 1 is greater than the maximum distance from the surface of the primer layer 2 to the first surface of the current collector 1, or in other words, the first surface of the current collector 1
  • the lowest point of the surface of the first gradient area 31 is located above the primer layer 2, that is, when the primer layer is not provided with a second gradient area (that is, the primer layer is entirely composed of the second normal area)
  • the first The minimum distance from the surface of a gradient area 31 to the first surface of the current collector 1 is greater than the thickness of the primer layer 2; when the primer layer has the second gradient area 21 and the second normal area 22, the surface of the first gradient area 31 reaches The minimum distance from the first surface of the current collector 1 is greater than the thickness of the primer layer 2 corresponding to the second normal region 22 .
  • the primer of the present invention may be a conventional safety coating with protective function in the art, for example, may include an inorganic particle coating and/or a polymer coating, and the inorganic particle coating may be a conventional ceramic coating without active materials , it can also be an active material layer containing an active material and a binder content higher than the above-mentioned active material layer, or a mixed coating of the ceramic coating and the active material layer.
  • peeling force peeling force between the primer layer and the current collector, usually the peeling force is greater than 30N/m, which can enhance the adhesion of the functional layer on the current collector and improve the safety and service life of the pole piece. and other characteristics.
  • the peeling force of the above-mentioned primer layer relative to the current collector is greater than the peeling force of the active material layer relative to the current collector.
  • the peeling force of each coating relative to the current collector can be adjusted by adjusting the binder content in the coating layer.
  • the mass content of the binder in the primer layer is more than 3 times that of the binder in the active material layer, which is beneficial for the primer layer to have a higher peeling force relative to the current collector, improve the safety of the pole piece, and also It can take into account the characteristics of improving the energy density of the pole piece.
  • the above-mentioned primer layer is an inorganic particle coating, and its raw materials include inorganic particulate material, a conductive agent and a binder, wherein the mass content of the inorganic particulate material is 55% to 96%, and the viscosity is 55% to 96%.
  • the mass content of the binding agent is 3% to 40%, and the mass content of the conductive agent is 1% to 5%.
  • the inorganic particulate material may be selected from lithium cobalt oxide (LCO), nickel-cobalt-manganese ternary material (NCM), nickel-cobalt-aluminum ternary material (NCA), nickel-cobalt-manganese-aluminum quaternary material (NCMA), lithium iron phosphate (LFP), Lithium Manganese Phosphate (LMP), Lithium Vanadium Phosphate (LVP), Lithium Manganate (LMO), Lithium Rich Manganese Base, Alumina, Boehmite, Magnesium Oxide, Titanium Oxide, Silica, Calcium Oxide, Oxide At least one of manganese, zirconia, yttrium oxide, hafnium oxide, cerium oxide, and thorium oxide.
  • LCO lithium cobalt oxide
  • NCM nickel-cobalt-manganese ternary material
  • NCA nickel-cobalt-aluminum ternary material
  • the above-mentioned active material layer can also be a conventional active material layer in the art.
  • the raw materials of the active material layer include active material, binder and conductive agent, wherein the mass content of the active material is 93% ⁇ 99% %, the mass content of the binder is 0.5% to 2%, and the mass content of the conductive agent is 0.5% to 5%.
  • the above-mentioned pole piece may be a positive pole piece or a negative pole piece.
  • the above-mentioned pole piece is a positive pole piece
  • the above-mentioned functional layer includes the above-mentioned active material layer
  • the raw materials of the active material layer include active material, adhesive agent and conductive agent
  • the active material can be the conventional positive active material in the field such as lithium-containing active material, for example, it can include lithium cobalt oxide, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, iron manganese phosphate
  • the current collector can be a conventional positive current collector in the field such as aluminum foil
  • the above The pole piece is a negative electrode piece
  • the above-mentioned functional layer includes the above-mentioned active material layer
  • the binder and conductive agent in the above-mentioned primer layer and active material layer can be conventional materials in the art, for example, the binder can include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride Amide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, At least one of polyhexafluoropropylene and styrene-butadiene rubber (SBR); the conductive agent may include at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.
  • PVDF polyvinylidene fluoride
  • Amide polyacrylonitrile
  • polyacrylate polyacrylic acid
  • polyacrylate sodium carboxymethyl cellulose (CMC
  • the pole piece of the present invention can be prepared by the gravure coating method and the extrusion coating method in the field of conventional methods.
  • the gravure coating method can be used to first coat the slurry containing the raw material of the primer layer on the surface of the current collector. After drying, the slurry containing the active material layer is coated by extrusion coating method, and then after drying and rolling treatment, scrape off or wash off the coating at the pole ear position, and the exposed surface at the pole ear position
  • the pole pieces are obtained by welding the pole tabs on the current collector; wherein, the coating thickness of each area can be controlled according to the preset first gradient area and the first normal area position, slope angle and other parameters to obtain the pole pieces that meet the requirements.
  • the gravure coating method can be used to coat a primer layer on the current collector.
  • the gravure roller At the ear position, when the primer layer is composed of a second gradient area and a second normal area, the gravure roller is provided with a camber coating position corresponding to the above-mentioned second gradient area to form the above-mentioned second gradient area; of course, when When the undercoat layer does not have the second gradient area (ie, it is entirely composed of the second normal area), a gravure roll without the above-mentioned arc surface coating portion can be used to perform the coating process of the undercoat layer.
  • Another aspect of the present invention provides a battery including the above-mentioned pole piece.
  • the battery of the present invention may include a positive electrode sheet with the above-mentioned structural design (that is, the above-mentioned electrode sheet is a positive electrode sheet), or a negative electrode sheet with the above-mentioned structural design (that is, the above-mentioned electrode sheet is a negative electrode sheet), or may also include the above-mentioned structural design.
  • the positive electrode sheet and the negative electrode sheet with the above-mentioned structural design that is, the above-mentioned electrode sheet includes a positive electrode sheet and a negative electrode sheet).
  • the above-mentioned battery also includes a negative pole piece, which can be a conventional negative pole piece in the art; when the above-mentioned pole piece is a negative pole piece, the above-mentioned battery also includes a positive pole piece, and the positive pole piece can also be this It is a conventional positive electrode sheet in the field, which is not particularly limited in the present invention.
  • the above-mentioned battery also includes a separator between the positive electrode sheet and the negative electrode sheet, the separator is used to separate the positive electrode sheet and the negative electrode sheet, which can be a conventional separator in the art, which is not particularly limited in the present invention.
  • the battery of the present invention may be a lithium-ion battery, which may be of a wound type or a laminated type, preferably a wound type structure.
  • the battery of the present invention can be prepared according to conventional methods in the field.
  • the positive electrode sheet, the separator and the negative electrode sheet can be stacked in sequence, then rolled (or stacked) to form a battery core, and then encapsulated, injected, chemically formed, and divided into volumes.
  • OCV open circuit voltage
  • NMP N-methylpyrrolidone
  • a first blank area with a width of about 10mm is left in the preset tab area (that is, the area is not coated with slurry.
  • the above-mentioned positive electrode active material layer slurry is coated on the positive and negative surfaces of the positive electrode current collector by extrusion coating method, and after drying, part of the coating in the preset tab area is removed, A second blank area with a width of about 8 mm and located in the middle of the above-mentioned first blank area (this area is not coated with slurry) is formed; after rolling treatment, a layered primer layer is formed on the two surfaces of the current collector. and the positive electrode active material layer, welding a tab with a width of about 6 mm in the middle of the second blank area to obtain a positive electrode sheet;
  • the coating thickness of each area of the first surface of the current collector provided with the tabs is controlled, and a primer layer 2 and a first surface of the current collector are formed on the first surface of the current collector.
  • the above-mentioned negative electrode slurry is coated on the positive and negative surfaces of the negative electrode current collector, and after drying and rolling, a negative electrode sheet is obtained.
  • positive electrode sheet and negative electrode sheet are rolled, cut, and produced, they are stacked and placed in the order of positive electrode sheet, separator, and negative electrode sheet, and then rolled to form a bare cell, which is then packaged, injected, chemically formed, and divided into volumes. , OCV and other processes, the lithium-ion battery is made.
  • Example 1 The difference between Example 1 and Example 1 is:
  • Example 1 The difference between Examples 3-6 and Example 1 is that the parameters such as the primer layer, the positive electrode active material layer, the slope angle of the first gradient area/the second gradient area are different, as shown in Table 1, except those shown in Table 1. Except for the difference, the remaining conditions are the same as those in Example 1.
  • Example 1 The difference between this comparative example and Example 1 is that there is no primer layer; the positive electrode active material layer has no first gradient region (ie, it is entirely composed of the first normal region), and other conditions are the same as those of Example 1.
  • the lithium-ion batteries of each embodiment and the comparative example are subjected to charge-discharge test and safety test to evaluate the normal temperature charging window (rate performance) and safety performance of the battery, wherein,
  • Charge and discharge test method Charge the lithium-ion battery at the charging rate of 0.5C, 1C, 1.5C, and 2C under the environment of 25°C ⁇ 3°C. After charging to 4.45V, change it to constant voltage charging, and the cut-off current is 0.05C , after the battery is fully charged, let it stand for 10 minutes, and then discharge at a rate of 0.5C. This is a charge-discharge cycle. After 20 cycles, the battery is fully charged, and then dissect and observe the lithium precipitation in the tab area. For its normal temperature charging window, the normal temperature charging window of the batteries of each embodiment and comparative example is measured as shown in Table 1;

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Abstract

本发明提供一种极片及电池，极片包括集流体和设置于集流体第一表面的功能层，所述第一表面的中间还设有极耳，所述第一表面的功能层具有靠近极耳的第一坡度区和远离极耳的第一正常区，所述第一坡度区的厚度沿靠近极耳的方向逐渐降低。本发明能够提高电池的倍率性和安全性等性能。

Description

极片及电池
本申请要求于2020年12月30日提交中国专利局、申请号为202011628655.5、申请名称为“极片及电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及一种极片及电池，属于电池领域。
背景技术
锂离子电池是智能手机、笔记本电脑等消费电子产品的最主要电池种类，随着智能手机等消费电子产品的升级换代，对锂离子电池的能量密度、充电速度以及安全性能要求越来越高。常规结构的软包锂离子电池极耳焊接在极片的一端，这种结构的锂离子电池内阻较大，不利于电池进行快速充电，将极耳焊接在极片中间或靠近中间的区域可有效降低电池内阻，有利于提高电池的充电速度，通常是在集流体上涂覆功能涂层后，再将极片中间预设极耳位置处的涂层除去，露出集流体后焊接极耳，然后贴上胶纸进行保护，胶纸除需与极耳上表面粘接外，通常也会与极耳周边裸露的集流体以及极耳周边的功能涂层(即功能涂层靠近极耳的区域)粘接，以覆盖极耳，实现对极耳的保护。然而，常规极片结构中，功能涂层靠近极耳的区域与集流体之间存在高度差，该高度差基本与功能涂层的厚度一致，使得胶纸在该区域无法与极耳周边裸露的集流体完全贴合，导致靠近极耳的功能涂层区域容易负极电解液，使得该区域锂离子浓度与其他区域差别过大，存在易析锂等问题，降低极片及电池的安全性和倍率性等性能。
发明内容
本发明提供一种极片，能够有效提高对极耳负极区域的保护，避免析锂等问题，提高极片及电池的安全性和倍率性等性能。
本发明还提供一种电池，采用上述极片，具有良好的安全性和倍率性等性能。
本发明的一方面，提供一种极片，包括集流体和设置于集流体第一表面的功能层，第一表面的中间还设有极耳，第一表面的功能层具有靠近极耳的第一坡度区和远离极耳的第一正常区，第一坡度区的厚度沿靠近极耳的方向逐渐降低。
根据本发明的一实施方式，在极片平行于其厚度方向的投影中，第一坡度区远离极耳的一端的端点为c，第一坡度区靠近极耳的一端的端点为d，c和d的连线与平行于极片表面的平面的锐夹角为α，α为10-80°。
根据本发明的一实施方式，上述第一坡度区的宽度为0.25-3mm。
根据本发明的一实施方式，上述功能层包括活性材料层和位于活性材料层与集流体表面之间的底涂层，上述活性材料层具有上述第一坡度区和第一正常区。
根据本发明的一实施方式，上述底涂层具有靠近极耳的第二坡度区和远离极耳的第二正常区，上述第二坡度区的厚度沿靠近极耳的方向逐渐降低。
根据本发明的一实施方式，在极片平行于其厚度方向的投影中，第二坡度区远离极耳的一端的端点为e，第二坡度区靠近极耳的一端的端点为f，e和f的连线与平行于极片表面的平面的锐夹角为β，β为10-80°。
根据本发明的一实施方式，上述活性材料层至极耳的最小距离不大于上述底涂层至极耳的最小距离。
根据本发明的一实施方式，上述活性材料层至极耳的最小距离为m，上述底涂层至极耳的最小距离为n，0≤n-m≤3mm。
根据本发明的一实施方式，上述第一坡度区的表面至集流体第一表面的最小距离大于底涂层表面至集流体第一表面的最大距离。
本发明的另一方面，提供一种电池，包括上述极片。
本发明的实施，至少具有如下有益效果：
本发明提供的极片，通过在靠近极耳的功能层区域设置坡度区(即上述第一坡度区)，能够降低该坡度区与极耳、极耳周边裸露的集流体之间的高度差，使胶纸与极耳、极耳周边裸露的集流体、坡度区更好的粘接，提高对极耳区域的保护效果，避免电解液的富集以及由此导致的析锂等问题，进而 提高极片及电池的倍率性、安全性、稳定性和使用寿命等性能。
附图说明
图1为本发明一实施方式的极片第一表面的截面示意图；
图2为本发明另一实施方式的极片第一表面的截面示意图；
附图标记说明：1：集流体；2：底涂层；3：活性材料层；4：极耳；21：第二坡度区；22：第二正常区；31：第一坡度区；32：第一正常区；α：第一坡度角；β：第二坡度角；a：第一坡度区的宽度；b：底涂层靠近极耳的一端至活性材料层靠近极耳的一端的距离。
具体实施方式
为使本领域技术人员更好地理解本申请的方案，下面结合附图对本申请作进一步地详细说明。
本发明的一方面，提供一种极片，如图1-图2所示，该极片包括集流体1和设置于集流体第一表面的功能层，第一表面的中间还设有极耳4，第一表面的功能层具有靠近极耳4的第一坡度区31和远离极耳的第一正常区32，第一坡度区31的厚度沿靠近极耳4的方向逐渐降低。
本发明提供的极片，通过设置上述第一坡度区，利于使胶纸与极耳、极耳周边裸露的集流体、极耳周边的坡度区粘接的更为紧密，提高对极耳的覆盖和保护效果，避免极耳附近电解液的富集以及由此导致的析锂等问题，进而提高极片及电池的倍率性、安全性、稳定性和使用寿命等性能。
具体地，本发明的极片可以只在第一表面设置功能层，也可以同时在与第一表面相对的第二表面设置功能层(即集流体的正反两个表面均设置有功能层)，具体实施时可根据需要设置，其中，第二表面的功能层可以是本领域常规结构，本发明对此不做特别限制，不再赘述。
在一具体实施方式中，在第二表面亦设有功能层，第二表面功能层的厚度与第一表面第一正常区的功能层的厚度相等，第二表面功能层的厚度与第一表面的第一正常区的功能层的厚度的总和为90-120μm。
根据本发明的研究，如图1所示，在极片平行于其厚度方向的投影中， 第一坡度区31远离极耳4的一端的端点为c，第一坡度区31靠近极耳4的一端的端点为d，c和d的连线与平行于极片表面的平面的锐夹角(以下简称第一坡度角)为α，α为10-80°，比如可以为10°、15°、20°25°、30°、35°、40°、45°、50°、55°、60°、65°、70°、75°、80°或其中任意两个值组成的范围，例如20-80°或20-70°等，利于提高极片的倍率性和稳定性等性能。其中，c为功能层厚度变化的临界点(即第一正常区32与第一坡度区31的分界线在上述投影中形成的交点)，d为第一坡度区31(呈弧面或斜面)与平行于功能层厚度方向的功能层竖直面的分界线在上述投影中形成的交点。
进一步地，第一坡度区31的宽度a可以为0.25-3mm，进一步可以为0.5-2.5mm或0.5-2mm或0.5-1.5mm，该宽度a即为第一坡度区31远离极耳的一端至其靠近极耳的一端在平行于功能层表面所在平面方向上的距离，或者说，该宽度a是第一正常区32与第一坡度区31的分界线至第一坡度区31与平行于功能层厚度方向的功能层竖直面的分界线在平行于功能层表面所在平面方向上的距离。相对而言，a过小(＜0.25mm)，影响胶纸与包括极耳、极耳周边裸露的集流体、极耳周边的功能层的整体界面的粘接性，对极片的倍率性和安全性等性能改善效果较为有限，而a过大(＞3mm)，会导致功能层的损失较大，影响极片的能量密度及容量等特性。
为进一步提高电池的安全性等性能，在本发明的一实施方式中，如图1和图2所示，功能层包括活性材料层3和位于活性材料层3与集流体1表面之间的底涂层2，活性材料层3具有上述第一坡度区31和第一正常区32。
进一步地，底涂层2具有靠近极耳4的第二坡度区21和远离极耳4的第二正常区22，第二坡度区21的厚度沿靠近极耳4的方向逐渐降低。
具体地，在极片平行于其厚度方向的投影中，第二坡度区21远离极耳4的一端的端点为e，第二坡度区21靠近极耳4的一端的端点为f，e和f的连线与平行于极片表面的平面的锐夹角为β(以下简称第二坡度角)，β为10-80°，比如可以为10°、15°、20°25°、30°、35°、40°、45°、50°、55°、60°、65°、70°、75°、80°或其中任意两个值组成的范围。其中，e为底涂层厚度变化的临界点(即第二正常区22与第二坡度区21的分界线在上述投影中形成的交点)，f为第二坡度区21(呈弧面或斜面)与平行于底涂层厚 度方向的底涂层竖直面的分界线在上述投影中形成的交点。一般优选e与c的连线与功能层的厚度方向相同(即，在靠近极耳的方向上，第一坡度区31和第二坡度区32的起始位置相同)。
一般情况下，活性材料层3至极耳4的最小距离不大于底涂层2至极耳4的最小距离，利于整个功能层表面更为均质平滑，提高其安全性和倍率性等性能。
具体地，活性材料层3至极耳4的最小距离为m，底涂层2至极耳4的最小距离为n，0≤n-m≤3mm(即，如图1所示，底涂层2靠近极耳4的一端至活性材料层3靠近极耳4的一端的距离b为0-3mm)，进一步地，0≤n-m≤2.5mm或0≤n-m≤2mm或0≤n-m≤1.5mm或0≤n-m≤1mm，相对而言，n-m过小(＜0)，底涂层超出部分会影响功能层表面的平整度，且底涂层通常粘结力较大，难以清洗或刮掉，影响极片的制造，而n-m过大(＞3mm)，会导致有较大部分靠近极耳的活性材料层区域未受到底涂层保护，不利于极片的安全性等性能。
经进一步研究，第一坡度区31的表面至集流体1第一表面的最小距离大于底涂层2的表面至集流体1第一表面的最大距离，或者说，以集流体1的第一表面为基准，第一坡度区31表面的最低点位于底涂层2的上方，意即，当底涂层未设置有第二坡度区时(即底涂层全部由第二正常区组成)，第一坡度区31的表面至集流体1第一表面的最小距离大于底涂层2的厚度；当底涂层具有第二坡度区21和第二正常区22时，第一坡度区31的表面至集流体1第一表面的最小距离大于第二正常区22对应的底涂层2的厚度。
本发明的底涂层可以是本领域常规具有保护功能的安全涂层，例如可以包括无机颗粒涂层和/或聚合物涂层，该无机颗粒涂层可以是常规不含有活性材料的陶瓷涂层，也可以是含有活性材料且粘结剂含量比上述活性材料层高的活性材料层，或者是该陶瓷涂层和活性材料层的混合涂层。该底涂层与集流体之间具有较大的剥离力(粘结力)，通常剥离力大于30N/m，可以增强功能层在集流体上的黏附力度，提高极片的安全性和使用寿命等特性。
上述底涂层相对于集流体的剥离力大于活性材料层相对于集流体的剥离力，具体可通过调整涂层中的粘结剂含量实现各涂层相对集流体剥离力的调控，一般情况下，底涂层中粘结剂质量含量是活性材料层中粘结剂质量含量 的3倍以上，利于底涂层具有更高的相对于集流体的剥离力，提高极片的安全性，同时亦能兼顾提高极片的能量密度等特性。
在本发明的一优选实施方式中，上述底涂层为无机颗粒涂层，其原料包括无机颗粒材料、导电剂和粘结剂，其中，无机颗粒材料的质量含量为55％～96％，粘结剂的质量含量为3％～40％，导电剂的质量含量为1％～5％。
具体地，无机颗粒材料可以选自钴酸锂(LCO)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)、镍钴锰铝四元材料(NCMA)、磷酸铁锂(LFP)、磷酸锰锂(LMP)、磷酸钒锂(LVP)、锰酸锂(LMO)、富锂锰基、氧化铝、勃姆石、氧化镁、氧化钛、氧化硅、氧化钙、氧化锰、氧化锆、氧化钇、氧化铪、氧化铈、氧化钍中的至少一种。
上述活性材料层亦可以是本领域常规活性材料层，在一优选实施方式中，该活性材料层的原料包括活性材料、粘结剂和导电剂，其中，活性材料的质量含量为93％～99％，粘结剂的质量含量为0.5％～2％，导电剂的质量含量为0.5％～5％。
具体地，上述极片可以是正极片或者负极片，例如，在一实施方式中，上述极片为正极片，上述功能层包括上述活性材料层，该活性材料层的原料包括活性材料、粘结剂和导电剂，活性材料具体可以是含锂活性材料等本领域常规正极活性材料，例如可以包括钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂中的至少一种，上述集流体可以是铝箔等本领域常规正极集流体；在另一实施方式中，上述极片为负极片，上述功能层包括上述活性材料层，该活性材料层的原料包括活性材料、粘结剂和导电剂，该活性材料具体可以包括石墨、中间相碳微球、软碳、硬碳、硅材料、硅氧材料、硅碳材料、钛酸锂材料等中的至少一种，上述集流体可以是铜箔等本领域常规负极集流体。
上述底涂层和活性材料层中的粘结剂、导电剂可以是本领域常规材料，例如，粘结剂可以包括聚偏氟乙烯(PVDF)、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳(CMC)、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯和丁苯橡胶(SBR)中的至少一种；导电剂可以包括导电炭黑、碳纳米管、导电石墨、石墨烯中的至少一种。
本发明的极片可采用凹版涂布法、挤压涂布法本领域常规方法制备，具体实施时，可以先采用凹版涂布法将含有底涂层原料的浆料涂敷于集流体的表面，经干燥后，再采用挤压涂布法涂覆含有活性材料层的浆料，然后经干燥、辊压处理后，刮掉或清洗掉极耳位的的涂层，在极耳位露出的集流体上焊接极耳，即得到极片；其中，可以根据预设第一坡度区和第一正常区位置、坡度角等参数，控制各区域的涂层厚度，以得到符合要求的极片。以凹版涂布法为例说明，比如可以采用凹版涂布法在集流体上涂布底涂层，凹版涂布过程中所用的凹版辊设有预留极耳槽，以对应形成极片上的极耳位，当底涂层由第二坡度区和第二正常区组成时，凹版辊上设有与上述第二坡度区对应的弧面涂布部位，以形成上述第二坡度区；当然，当底涂层不具有第二坡度区时(即全部由第二正常区组成)，可以采用未设有上述弧面涂覆部位的凹版辊进行底涂层的涂覆过程。
本发明的另一方面，提供一种电池，包括上述极片。
本发明的电池可以包括具有上述结构设计的正极片(即上述极片为正极片)，或者包括具有上述结构设计的负极片(即上述极片为负极片)，或者可以同时包括具有上述结构设计的正极片和具有上述结构设计的负极片(即上述极片包括正极片和负极片)。当上述极片为正极片时，上述电池还包括负极片，该负极片可以是本领域常规负极片；当上述极片为负极片时，上述电池还包括正极片，该正极片亦可以是本领域常规正极片，本发明对此不做特别限制。
上述电池还包括位于正极片和负极片之间的隔膜，该隔膜用于间隔正极片和负极片，其可以是本领域常规隔膜，本发明对此亦不做特别限制。
具体地，本发明的电池可以是锂离子电池，其可以是卷绕式或叠片式，优选卷绕式结构。
本发明的电池可以按照本领域常规方法制得，如可以将正极片、隔膜、负极片依次叠放后，卷绕(或叠片)形成电芯，然后经封装、注液、化成、分容、OCV(开路电压)测试等工序后，制得电池，该些步骤/工序均为本领域常规操作，本发明对此不做特别限制，不再赘述。
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请的实 施例，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
实施例1
(1)正极片的制备
将55wt％LFP、40wt％PVDF、5wt％导电炭黑混合，加入N-甲基吡咯烷酮(NMP)，搅拌均匀后制成底涂层浆料；
将95wt％钴酸锂、2wt％导电炭黑、1wt％碳纳米管、2wt％PVDF混合，加入NMP，搅拌均匀后制成正极活性材料层浆料；
使用凹版涂布工艺将上述底涂层浆料涂覆在正极集流体正反两个表面，其中，在预设极耳区域留有宽度约10mm的第一空白区(即该区域不涂覆浆料)；经干燥后，再采用挤压涂布法将上述正极活性材料层浆料涂敷于正极集流体的正反两个表面，经干燥后，除去预设极耳区域的部分涂层，形成宽度约为8mm且位于上述第一空白区正中间的第二空白区(该区域不涂覆浆料)；经辊压处理后，在集流体的两个表面分别形成层叠设置的底涂层和正极活性材料层，在第二空白区域的正中间焊接宽度约为6mm的极耳，得到正极片；
其中，根据预设第一坡度区的宽度和坡度角等参数，控制集流体设有极耳的第一表面的各区域涂层厚度，在集流体第一表面形成底涂层2和具有第一坡度区31和第一正常区32的正极活性材料层3，并满足第一正常区32对应的正极活性材料层3的厚度为50μm，第一坡度区31的宽度a＝1.5mm，第一坡度角α＝78°；底涂层无第二坡度区(即全部由第二正常区组成)，其厚度为3μm；正极活性材料层至极耳的最小距离m＝1mm，底涂层至极耳的最小距离n＝2mm(即底涂层靠近极耳的一端至正极活性材料层靠近极耳的一端的距离b＝n-m＝1mm)。
(2)负极片的制备
将96wt％人造石墨、1wt％导电炭黑、1.5wt％SBR和1.5wt％CMC混合，加入去离子水，搅拌均匀后制成浆料；
将上述负极浆料涂覆在负极集流体正反两个表面，经干燥、辊压后，得 到负极片。
(3)电池的制备
将上述正极片和负极片经辊压、分切、制片后，按照正极片、隔膜、负极片的顺序层叠放置，然后卷绕形成裸电芯，再经封装、注液、化成、分容、OCV等工序后，制成锂离子电池。
实施例2
实施例与实施例1的区别在于：
将96wt％LFP、3wt％PVDF、1wt％导电炭黑混合，加入NMP，搅拌均匀后制成底涂层浆料(即底涂层原料组成与实施例1不同)；所制成的正极片中，第一坡度区的宽度a＝2.5mm，第一坡度角α＝48°；底涂层具有第二坡度区和第二正常区，第二坡度角β＝30°；在靠近极耳方向上，第二坡度区和第一坡度区的起始位置相同；n＝3mm，n-m＝2mm；其余条件与实施例1相同。
实施例3-6
实施例3-6与实施例1的差别在于底涂层、正极活性材料层、第一坡度区/第二坡度区的坡度角等参数不同，具体如表1所示，除表1示出的差别外，其余条件与实施例1相同。
对比例1
该对比例与实施例1的区别在于：无底涂层；正极活性材料层无第一坡度区(即全部由第一正常区组成)，其余条件与实施例1相同。
对比例2
该对比例与实施例1的区别在于：底涂层靠近极耳的一端与正极活性活性层靠近极耳的一端对齐(即n-m＝0)，且无坡度区(即第一坡度角α＝0°，第二坡度角β＝0°)。
各实施例及对比例电池的性能测试
对各实施例及对比例的锂离子电池进行充放电测试及安全测试，评估电 池的常温充电窗口(倍率性能)与安全性能，其中，
充放电测试方法：在25℃±3℃环境下将锂离子电池分别以0.5C、1C、1.5C、2C的充电倍率进行充电，充电至4.45V后改为恒压充电，截止电流为0.05C，电池充满电后静置10min，然后以0.5C的倍率进行放电，此为一次充放电循环，循环20次后电池充满电，然后解剖观察极耳区的析锂情况，其中最大不析锂倍率为其常温充电窗口，测定各实施例及对比例的电池的常温充电窗口如表1所示；
安全测试方法：在25℃±3℃环境下将锂离子电池以0.5C充电倍率充满电，截止电压4.45V，截止电流0.05C；然后按照如下方法进行针刺测试：将直径3mm的钨钢钉以100mm/s的速度刺穿电池中间位置，然后退出；电池经过该钢刺刺穿过程不起火即为通过。测得各实施例及对比例的电池的满电针刺通过率如表1所示。
表1.各实施例和对比例的条件差异及电池性能测定结果
Figure PCTCN2021143101-appb-000001
*表示满电针刺通过率＝通过的电池数量与测试总电池数量的比值，以实施例2的“19/20”为例说明，其表示共测试20只电池，经过上述钢刺刺穿过程不起火的电池数量为19。
从表1可以看出，正极片上极耳附近区域的功能层存在坡度区，有利于提高电池的充电窗口，使其具有更好的倍率性和安全性等性能，同时在正极活性材料层与集流体间设置底涂层，利于进一步提升电池的安全性。
以上，对本申请的实施方式进行了说明。但是，本申请不限定于上述实施方式。凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (12)

  1. 一种极片，其特征在于，包括集流体和设置于集流体第一表面的功能层，所述第一表面的中间还设有极耳，所述第一表面的功能层具有靠近极耳的第一坡度区和远离极耳的第一正常区，所述第一坡度区的厚度沿靠近极耳的方向逐渐降低。
  2. 根据权利要求1所述的极片，其特征在于，在极片平行于其厚度方向的投影中，第一坡度区远离极耳的一端的端点为c，第一坡度区靠近极耳的一端的端点为d，c和d的连线与平行于极片表面的平面的锐夹角为α，α为10-80°。
  3. 根据权利要求1或2所述的极片，其特征在于，所述第一坡度区的宽度为0.25-3mm。
  4. 根据权利要求1或2所述的极片，其特征在于，所述功能层包括活性材料层和位于活性材料层与集流体表面之间的底涂层，所述活性材料层具有所述第一坡度区和第一正常区。
  5. 根据权利要求4所述的极片，其特征在于，所述底涂层具有靠近极耳的第二坡度区和远离极耳的第二正常区，所述第二坡度区的厚度沿靠近极耳的方向逐渐降低。
  6. 根据权利要求5所述的极片，其特征在于，在极片平行于其厚度方向的投影中，第二坡度区远离极耳的一端的端点为e，第二坡度区靠近极耳的一端的端点为f，e和f的连线与平行于极片表面的平面的锐夹角为β，β为10-80°。
  7. 根据权利要求4所述的极片，其特征在于，所述活性材料层至极耳的最小距离不大于所述底涂层至极耳的最小距离。
  8. 根据权利要求4或7所述的极片，其特征在于，所述活性材料层至极耳的最小距离为m，所述底涂层至极耳的最小距离为n，0≤n-m≤3mm。
  9. 根据权利要求4-7任一项所述的极片，其特征在于，所述第一坡度区的表面至集流体第一表面的最小距离大于底涂层表面至集流体第一表面的最大距离。
  10. 根据权利要求1或4所述的极片，其特征在于，所述极片为正极片，所述功能层包括活性材料层，所述活性材料层的原料包括活性材料、粘结剂和导电剂；所述活性材料包括钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂中 的至少一种。
  11. 根据权利要求1或4所述的极片，其特征在于，所述极片为负极片，所述功能层包括活性材料层，所述活性材料层的原料包括活性材料、粘结剂和导电剂，所述活性材料包括石墨、中间相碳微球、软碳、硬碳、硅材料、硅氧材料、硅碳材料、钛酸锂材料中的至少一种。
  12. 一种电池，其特征在于，包括权利要求1-9任一项所述的极片。
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