CN115548255A - Positive plate and lithium ion battery - Google Patents

Positive plate and lithium ion battery Download PDF

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Publication number
CN115548255A
CN115548255A CN202211303525.3A CN202211303525A CN115548255A CN 115548255 A CN115548255 A CN 115548255A CN 202211303525 A CN202211303525 A CN 202211303525A CN 115548255 A CN115548255 A CN 115548255A
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China
Prior art keywords
layer
positive electrode
coating
current collector
area
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CN202211303525.3A
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Chinese (zh)
Inventor
姚怡鑫
张文轩
邸会芳
宋江涛
方双柱
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Application filed by Zhuhai Cosmx Battery Co Ltd filed Critical Zhuhai Cosmx Battery Co Ltd
Priority to CN202211303525.3A priority Critical patent/CN115548255A/en
Publication of CN115548255A publication Critical patent/CN115548255A/en
Priority to PCT/CN2023/118400 priority patent/WO2024087921A1/en
Pending legal-status Critical Current

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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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

Abstract

The invention provides a positive plate and a lithium ion battery. The positive plate comprises a current collector, wherein the current collector comprises a first area and a second area in the length direction of the current collector; the surface of the current collector in the first area comprises a first coating and a second coating which are sequentially stacked, and the surface of the current collector in the second area comprises a first coating and a positive active material layer which are sequentially stacked; the first coating is a conductive bottom coating, and the second coating is an insulating functional layer; the second coating is disposed on at least a portion of a surface of the first coating in the first region. The invention obviously improves the nail penetration rate and the high-temperature storage performance of the battery during primer continuous coating by specially designing the positive plate.

Description

Positive plate and lithium ion battery
Technical Field
The invention belongs to the field of batteries, and relates to a positive plate and a lithium ion battery.
Background
Since the commercialization of lithium ion batteries, lithium ion batteries have been widely used in the fields of portable electronic products, new energy vehicles, and the like due to their characteristics of excellent electrochemical properties, small self-discharge, rapid charge and discharge, high energy density, and the like. Along with the improvement of the safety requirement of a consumer on the battery, the safe lithium ion battery capable of passing the nail penetration test is produced.
At present, the lithium ion battery of accessible through the drift bolt test can carry out the preliminary treatment to the positive pole current collector, the mode of preliminary treatment is that the priming coat that sets up and have the conductivity between anodal active material layer and the anodal current collector, set up the insulating layer in anodal empty foil region, but certain clearance can be left between priming coat and the insulating layer this moment, because the interstitial site is the low-lying district of pole piece, tend to here gathering during the coating of anodal active material layer, thereby lead to here anodal active material more, can arouse in the cycle process and analyse the lithium problem, in addition, interstitial site does not have primer or insulating layer, there is certain risk of failure when carrying out the drift bolt test to this place.
In order to solve the problem, a primer coating strategy is proposed, wherein the primer coating strategy is that a primer coating is integrally formed during production and covers a positive current collector and a hollow foil area below a positive active material layer, so that the problems of lithium precipitation and safety caused by gaps are avoided, the production process is simplified, and the production efficiency is improved. However, even the primer coating has certain defects, on one hand, because the primer coating is positioned between the positive active material layer and the positive current collector, certain electron and ion transmission capabilities are required, some inorganic materials containing lithium, such as lithium iron phosphate, lithium manganese phosphate, ternary materials and the like, can be used as the primer coating, and the blank foil area after the primer coating also contains the primer coating materials, so that the material or gas production rate is too high during high-temperature storage of the battery, the high-temperature storage performance of the battery core is seriously deteriorated, and meanwhile, on the basis of the requirement of not losing too much energy density, the primer coating is thinner during actual production, so that the blank foil area of the positive electrode lacks enough protection, and the nail penetration test passing rate is obviously reduced.
Therefore, how to improve the high-temperature storage performance of the cathode sheet during the primer continuous coating and improve the nail penetration rate of the battery core is a technical problem to be solved in the field.
Disclosure of Invention
The invention provides a positive plate, which is characterized in that the nail penetration rate and the high-temperature storage performance of a battery during bottom coating are obviously improved by specially designing the positive plate.
The invention also provides a lithium ion battery, which has good nail penetration rate and high-temperature storage performance due to the positive plate.
The invention provides a positive plate, which comprises a current collector, wherein the current collector comprises a first area and a second area in the length direction of the current collector;
the surface of the current collector in the first area comprises a first coating and a second coating which are sequentially stacked, and the surface of the current collector in the second area comprises a first coating and a positive active material layer which are sequentially stacked;
the first coating is a conductive bottom coating, and the second coating is an insulating functional layer;
the second coating is disposed on at least a portion of a surface of the first coating in the first region.
According to the invention, the insulating functional layer is arranged on at least part of the surface of the conductive bottom coating in the non-positive electrode active material layer covering area, so that the nail penetration rate of the battery is obviously improved, and the insulating functional layer can obstruct a contact channel between the conductive bottom coating and electrolyte to a certain extent, thereby obviously improving the problem of high-temperature storage gas generation easily generated by the battery after bottom coating.
The current collector of the present invention may be selected from the positive electrode current collectors commonly used in the art, such as aluminum foil, and the thickness of the selected current collector may be in the range of 4 to 20 μm.
In the present invention, the thicknesses of the conductive undercoat layer in the first region and the conductive undercoat layer in the second region may be equal or different, and the equal thicknesses of the conductive undercoat layer and the conductive undercoat layer are advantageous for continuous arrangement of the conductive undercoat layer, and when the thicknesses of the conductive undercoat layer and the conductive undercoat layer are different, it is preferable that the thickness of the conductive undercoat layer in the first region is greater than the thickness of the conductive undercoat layer in the second region, and the first region is a blank foil region, and the greater the thickness of the conductive undercoat layer is, the more advantageous the protection of the positive electrode plate is.
It can be understood that when the second coating layer is provided on the entire surface of the first coating layer of the first region, it is more advantageous to improve the nail penetration performance and the high-temperature storage performance of the battery.
In a particular embodiment, the second coating layer of the invention is selected from an inorganic filler layer and/or an insulating glue paper layer. The inorganic filler layer can obviously increase the thickness of a protective layer of a non-active material layer covering area, the improvement effect of the battery nail penetration rate is more obvious, the insulating adhesive paper layer has a better isolation effect, the contact channel between the conductive bottom coating and electrolyte can be better isolated, and the high-temperature storage gas production problem of the battery is further better improved.
When the second coating simultaneously comprises the inorganic filler layer and the insulating adhesive paper layer, the inorganic filler layer and the insulating adhesive paper layer can be arranged in parallel, namely, the inorganic filler layer is arranged on part of the surface of the first coating, and the insulating adhesive paper layer is arranged on part of the surface of the first coating; the inorganic filler layer and the insulating gummed paper layer can also be arranged in a stacked mode, the inorganic filler layer can be arranged on the surface of the first coating layer firstly, the insulating gummed paper layer is arranged on the surface of the inorganic filler layer, and the inorganic filler layer can also be arranged on the surface of the first coating layer firstly and the insulating gummed paper layer is arranged on the surface of the insulating gummed paper layer secondly.
The inventor researches and discovers that when the second coating layer simultaneously comprises the inorganic filler layer and the insulating gummed paper layer, the inorganic filler layer and the insulating gummed paper layer are sequentially stacked, namely the inorganic filler layer is firstly arranged on the surface of the first coating layer, and then the insulating gummed paper layer is arranged on the surface of the inorganic filler layer, so that the battery can obtain more excellent nail penetration performance and high-temperature storage performance.
In a specific embodiment, the inorganic filler layer comprises 50 to 99.5 mass percent of inorganic filler and 0.5 to 50 mass percent of binder.
Wherein, in order to ensure that the inorganic filler layer has good insulating property, the powder resistivity of the selected inorganic filler is required to be more than 10 5 Ω cm, and specifically, the inorganic filler may be selected from one or more of alumina, boehmite, magnesia, magnesium hydroxide, titania, tin oxide, calcium hydroxide, nickel oxide, zinc oxide, zirconia, hafnia, silica, ceria, and barium sulfate.
The binder may be selected from binders conventionally used in the art, such as one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polypropylene, polyethylene, polytetrafluoroethylene, polystyrene, modified polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polymethacrylate, polyacrylate.
Furthermore, in order to ensure that the inorganic filler layer has more excellent compactness and improve the nail penetration performance of the positive plate, the D50 particle size of the selected inorganic filler can be controlled to be less than 40 mu m.
In a specific embodiment, the adhesive paper layer comprises adhesive paper, and the adhesive paper comprises a base layer and an adhesive layer arranged on the surface of the base layer. Specifically, the glue layer may be disposed on only one surface of the substrate layer, or may be disposed on both surfaces of the substrate layer.
The material of the matrix layer can be selected from one or more of PET, PI, PVC, PE, PP, PTFE, PC, PO, PA, PS and PU as long as the matrix layer is used for insulation. The glue layer material can be selected from one or more of rubber-based materials, acrylic-based materials or other polymer materials with adhesive property.
For better identification, the color of the adhesive paper of the present invention may be selected from one or more of white, blue, green, red, yellow and orange.
In order to further enhance the insulating property and the nail penetration property of the insulating gummed paper, a ceramic layer can be arranged between the substrate layer and the adhesive layer or on the surface of the substrate layer deviating from the adhesive layer. Wherein the ceramic layer comprises an inorganic filler and a binder. The selection principle of the inorganic filler is consistent with that of the inorganic filler in the inorganic filler layer, and the selectable types of the binding agents are also consistent with those of the binding agents in the inorganic filler layer.
In a specific embodiment, the positive electrode active material layer comprises 70-98.9% of positive electrode material, 0.3-15% of conductive agent and 0.8-15% of binder by mass percentage.
The cathode material of the present invention may be selected from cathode materials commonly used in the art, including but not limited to one or more of lithium cobaltate, nickel cobalt manganese ternary material, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickel cobalt aluminate ternary material, lithium nickelate, lithium vanadate, lithium titanate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium manganese rich-based material.
The conductive agent can also be one or more of conductive carbon black, carbon nanotube, graphene and acetylene black which are conventionally used in the field.
The optional type of binder is consistent with the optional type of inorganic filler and will not be described in detail herein.
The first coating layer of the present invention may be a conductive primer layer conventional in the art, and specifically may include an inorganic material, a binder and a conductive agent. The inorganic material can be one or more of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickelate, lithium vanadate, lithium manganese oxide, lithium titanate, lithium vanadium phosphate, lithium vanadyl phosphate and lithium-rich manganese-based materials. The selection principle of the conductive agent is consistent with that of the conductive agent in the positive active material layer, and the selection principle of the binder is consistent with that of the binder in the inorganic filler layer.
It is understood that in order to provide the positive electrode sheet with good nail penetration performance and good energy density, the thicknesses of the functional layers such as the inorganic filler layer, the insulating adhesive paper layer, the positive electrode active material layer, the conductive primer layer, and the like need to be limited. The ratio of the single-layer thickness of the inorganic filler layer to the thickness of the conductive primer layer in the second region and the ratio of the single-layer thickness of the insulating adhesive paper layer to the thickness of the conductive primer layer in the second region both satisfy (0.05-50): 1.
Specifically, according to the difference of the nail penetration performance and the energy density requirement, the thickness of the inorganic filler layer can be set to be 1-50 μm, the thickness of the insulating adhesive paper layer can be set to be 1-60 μm, the thickness of the positive electrode active material layer can be set to be 20-180 μm, and the thickness of the conductive primer layer is 1-50 μm. Furthermore, in order to ensure the bonding firmness of the insulating adhesive paper layer, the thickness of an adhesive layer in the insulating adhesive paper layer is not less than 1%.
In a specific embodiment, the current collector further comprises a third area, a positive tab is arranged on the surface of the current collector in the third area, and the third area is located in the first area or the second area.
When the third area is located in the first area, the tab is arranged at the empty foil at the end part of the current collector, at the moment, the tab is arranged on any surface of the current collector, and the other surface can be normally provided with a conductive bottom coating.
When the third area is located in the second area, the third area is arranged in the middle of the tab, namely in the length direction of the current collector, the tab is arranged in the middle area of the positive active material layer, at the moment, the tab is arranged on any surface of the current collector, and the third area corresponding to the other surface is a hollow foil area.
In yet another specific embodiment, the current collector further comprises a fourth region contiguous with the second region in a lengthwise direction of the current collector; the fourth area is a hollow foil area, and a positive tab is arranged on the surface of the current collector in the fourth area. The empty foil area means that the surface of the current collector in the area is not provided with any coating, and only the positive electrode tab is welded.
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present invention, and as shown in fig. 1, the positive electrode sheet according to the present invention includes a current collector 02, and in a length direction of the current collector 02, the current collector 02 includes a first region, a second region, and a third region, which are adjacent to each other in sequence, wherein the first region is located at two end positions of the current collector 02, and includes a first end portion 05-1 of the positive electrode sheet and a second end portion 05-2 of the positive electrode sheet. The first end part 05-1 of the positive plate comprises a first end part 05-1-1 area of the positive plate positioned on the upper surface of the current collector and a first end part 05-1-2 area of the positive plate positioned on the lower surface of the current collector, and the second end part 05-2 of the positive plate comprises a second end part 05-2-1 area of the positive plate positioned on the upper surface of the current collector and a second end part 05-2-2 area of the positive plate positioned on the lower surface of the current collector; the second region is located at the middle of the current collector 02, and is the positive electrode active material layer fixing region 05-3. The third region is located in the first region and is a positive tab welding region 05-4.
The surfaces of the current collectors at the first end part 05-1 and the second end part 05-2 of the positive plate comprise a conductive bottom coating layer 04 and an insulating functional layer which are sequentially stacked, wherein the insulating functional layer is selected from an inorganic filler layer 06; the surface of the current collector in the positive electrode active material layer fixing area 05-3 includes a conductive undercoat layer 04 and a positive electrode active material layer 03 stacked in this order; and the positive lug 01 is arranged on the surface of the current collector of the positive lug welding area 05-4. As shown in fig. 1, an insulating functional layer is provided on the surface of the conductive undercoat layer 04 in the area 05-2-1. Furthermore, the battery has higher nail penetration rate and better high-temperature storage performance, and insulating functional layers can be arranged on the surfaces of the conductive base coating layers 04 in the areas 05-2-1, 05-2-2, 05-1-1 and 05-1-2.
In the embodiment shown in fig. 1, the thickness of the conductive primer layer at the first end 05-1 of the positive electrode sheet, the thickness of the conductive primer layer at the second end 05-2 of the positive electrode sheet, and the thickness of the conductive primer layer at the fixing area 05-3 of the positive electrode active material layer may be the same or different, and may be adjusted according to the actual design of the battery cell, and preferably, the thickness of the conductive primer layer at the second end 05-2 of the positive electrode sheet is not less than the thickness of the conductive primer layer at the fixing area 05-3 of the positive electrode active material layer is not less than the thickness of the conductive primer layer at the first end 05-1 of the positive electrode sheet.
Fig. 2 is a schematic structural diagram of a positive plate according to yet another embodiment of the present invention, compared to the positive plate of fig. 1, the positive plate of fig. 2 is in a tab middle-arrangement structure, that is, a positive tab welding area 05-4 is disposed in the second area, a positive tab 01 is disposed on the positive tab welding area 05-4 on the upper surface of the current collector, and a positive tab welding area 05-4 is disposed on the lower surface of the current collector for empty foil. In contrast to the positive electrode tab of fig. 1, the first region of the positive electrode tab of fig. 2 only includes the positive electrode tab second end 05-2. And insulating functional layers are arranged on the surfaces of the conductive base coating layers in the 05-2-1 area and the 05-2-2 area of the second end part of the positive plate, and are selected from the inorganic filler layer 06.
Fig. 3 is a schematic structural diagram of a positive plate according to still another embodiment of the present invention, and as shown in fig. 3, the positive plate of the present invention includes a current collector 02, and in a length direction of the current collector 02, the current collector 02 includes a first region, a second region and a fourth region which are adjacently adjacent in sequence, where the first region is located at a second end 05-2 of the positive plate, and the second end 05-2 of the positive plate includes a region 05-2-1 located at the second end of the positive plate on the upper surface of the current collector and a region 05-2-2 located at the second end of the positive plate on the lower surface of the current collector; the second area is positioned in the middle of the current collector 02 and is a positive electrode active material layer fixing area 05-3; the fourth area is located at the first end 05-1 of the positive plate and is an empty foil area, and the upper surface of the current collector 02 of the fourth area is provided with a positive tab 01. The surface of the current collector at the second end part 05-2 of the positive plate comprises a conductive bottom coating 04 and an insulating function layer which are sequentially stacked, wherein the insulating function layer is selected from an inorganic filler layer 06 and an insulating adhesive paper layer 07 which are sequentially stacked, the inorganic filler layer 06 is arranged on the upper surface and the lower surface of the current collector 02, and the insulating adhesive paper layer 07 is arranged on the surface, away from the current collector 02, of the inorganic filler layer 06; the surface of the current collector in the positive electrode active material layer fixing area 05-3 includes a conductive undercoat layer 04 and a positive electrode active material layer 03, which are stacked in this order.
The preparation method of the positive plate is not particularly limited, and in a specific embodiment, the raw material for forming the first coating layer is uniformly dispersed in a solvent according to a certain proportion to form a first coating slurry, then the first coating slurry is coated on the surface of the current collector by gravure coating or extrusion coating, and the first coating layer can be formed after drying. When the thickness of the conductive base coat in the first area is different from that of the conductive base coat in the second area, different mesh numbers or different engraving depths can be set in different areas on the gravure roller so that different areas can obtain different thicknesses of the conductive base coat, and the thickness of the conductive base coat in different areas can be controlled by setting different feeding amounts on an extruder.
After the setting of the first coat is completed, the preparation of the second coat and the positive electrode active material layer is performed. The preparation of the positive active material layer and the preparation of the second coating are partially sequential and can be carried out simultaneously or step by step.
When the second coating is selected from the inorganic filler layer, the raw materials for forming the inorganic filler layer are mixed in a solvent according to a certain proportion to form inorganic filler layer slurry, then the inorganic filler layer slurry is coated on at least part of the surface of the first coating in the first area in a gravure coating or extrusion coating mode, and the inorganic filler layer is obtained after drying; when the second coating is selected from the insulating adhesive paper layer, the insulating adhesive paper is adhered to at least part of the surface of the first coating in the first area by using an adhesive adhering device.
When the positive active material layer is prepared, raw materials for forming the positive active material layer are mixed in a solvent according to a certain proportion to form positive active material layer slurry, then the slurry is coated on the surface of the first coating layer of the second area, and the positive active material layer can be obtained after drying.
In a second aspect, the invention provides a lithium ion battery, which comprises the positive plate provided by the first aspect of the invention. The lithium ion battery provided by the invention comprises the positive plate, so that the lithium ion battery has excellent nail penetration rate and high-temperature storage performance.
The lithium ion battery provided by the invention comprises a negative plate, a diaphragm and electrolyte besides the positive plate.
The negative electrode sheet can be a negative electrode sheet conventionally used in the art, and the negative active material can be one or more of graphite, graphene, silicon oxygen negative electrode, lithium titanate and lithium negative electrode. The separator and the electrolyte can be made of materials conventional in the art, and are not described in detail herein.
When the lithium ion battery is prepared, the positive plate provided by the first aspect of the present invention may be rolled, cut, and sheeted, and then wound together with the negative plate and the separator to form a roll core, and the lithium ion battery is formed after processes such as packaging, baking, liquid injection, aging, formation, secondary sealing, and sorting, which belong to conventional operations in the field and are not described herein again.
The implementation of the invention has at least the following beneficial effects:
1. according to the positive plate provided by the invention, the insulating functional layer is arranged on at least part of the surface of the conductive bottom coating in the non-positive active material layer covering area, so that the nail penetration rate of the battery is obviously improved, the insulating functional layer can obstruct a contact channel between the conductive bottom coating and electrolyte to a certain extent, and the substance in the conductive bottom coating is prevented from generating side reaction due to the electrolyte, so that the problem of high-temperature storage gas generation easily generated by the battery after bottom coating and continuous coating is obviously solved.
2. The lithium ion battery provided by the invention has excellent nail penetration rate and high-temperature storage performance due to the positive plate.
Drawings
Fig. 1 is a schematic structural view of a positive electrode sheet according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a positive electrode sheet according to yet another embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a positive plate according to still another embodiment of the present invention;
FIG. 4 is a schematic structural view of a positive electrode sheet of comparative example 1;
FIG. 5 is a schematic structural view of a positive electrode sheet of comparative example 2;
FIG. 6 is a schematic structural view of a positive electrode sheet according to example 2;
FIG. 7 is a schematic structural view of a positive electrode sheet according to example 3;
FIG. 8 is a schematic view of the positive electrode sheet of example 4;
FIG. 9 is a schematic view of the positive electrode sheet of example 5;
FIG. 10 is a schematic view of the positive electrode sheet of example 6;
FIG. 11 is a schematic view of the positive electrode sheet of example 8;
FIG. 12 is a schematic view of the positive electrode sheet of example 9;
fig. 13 is a schematic structural view of a positive electrode sheet according to example 11.
Description of the reference numerals:
05-1: a positive plate first end; 05-1-1: the first end part of the positive plate is positioned on the upper surface of the current collector; 05-1-2: the first end part of the positive plate is positioned on the lower surface of the current collector; 05-2: a positive plate second end; 05-2-1: the second end part of the positive plate is positioned on the upper surface of the current collector; 05-2-2: the second end part of the positive plate is positioned on the lower surface of the current collector; 05-3: a positive electrode active material layer fixing region; 05-4: a positive tab welding area; 01: a positive tab; 02-a current collector; 03: a positive electrode active material layer; 04: a conductive undercoat layer; 06: an inorganic filler layer; 07: and an insulating adhesive paper layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Hereinafter, the positive electrode sheet and the lithium ion battery provided by the present invention will be described in further detail by specific examples.
Comparative example 1
Fig. 4 is a schematic structural view of the positive electrode sheet of comparative example 1, and as shown in fig. 4, the positive electrode sheet of this comparative example includes a positive electrode sheet first end portion 05-1, a positive electrode sheet second end portion 05-2, a positive electrode active material layer fixing region 05-3, a positive electrode tab welding region 05-4, a positive electrode tab 01, a current collector 02, a positive electrode active material layer 03, and a conductive undercoat layer 04. The positive electrode tab first end 05-1 includes a 05-1-1 region and a 05-1-2 region, and the positive electrode tab second end 05-2 includes a 05-2-1 region and a 05-2-2 region.
The first end part 05-1 of the positive plate refers to an area which is close to the inside of the winding core and is not covered by the positive active material, the second end part 05-2 of the positive plate refers to an area which is close to the outside of the winding core and is not covered by the positive active material, the fixing area 05-3 of the positive active material layer refers to an area which is covered by the positive active material, and the welding area 05-4 of the positive lug is located at the first end part 05-1 of the positive plate. The positive tab 01 is arranged in the positive tab welding area 05-4 and on the upper surface of the current collector 02, the conductive base coat layer 04 covers the upper and lower surfaces of the current collector 02 (except the positive tab welding area 05-4), and the positive active material layer 03 is arranged on the conductive base coat layer surface of the positive active material layer fixing area 05-3.
The preparation method of the positive plate and the lithium ion battery of the comparative example comprises the following steps:
1) Preparation of positive plate
A. Adding lithium iron phosphate, PVDF and conductive carbon black into NMP, uniformly mixing to obtain conductive primer slurry, uniformly coating the conductive primer slurry on the surface of a current collector 02 aluminum foil of a positive plate first end part 05-1 (except a positive lug welding area 05-4), a positive plate second end part 05-2 and a positive active material layer fixing area 05-3, and drying to form a conductive primer layer 04;
wherein the mass ratio of the lithium iron phosphate to the PVDF to the conductive carbon black in the conductive undercoat 04 is 90; the conductive undercoat layer thickness at the positive electrode sheet first end portion 05-1 was 3 μm, the conductive undercoat layer thickness at the positive electrode sheet second end portion 05-2 was 7 μm, and the conductive undercoat layer thickness at the positive electrode active material layer fixing region 05-3 was 5 μm.
B. Adding lithium cobaltate, PVDF (polyvinylidene fluoride) and conductive carbon black into NMP (N-methyl pyrrolidone) to be uniformly mixed to obtain positive active slurry, coating the positive active slurry on the upper surface of a conductive primer layer of a fixing area 05-3 of a positive active substance layer, and drying to obtain a positive active substance layer 03;
in the positive electrode active material layer 03, the mass ratio of lithium cobaltate, PVDF and conductive carbon black is 96:2, the thickness of the positive electrode active material layer 03 was 85 μm.
C. And welding the positive tab on the surface of the aluminum foil in the positive tab welding area 05-4 in an ultrasonic welding mode to obtain the positive plate.
2) Preparation of negative plate
A. Dispersing graphite, conductive carbon black, styrene-butadiene latex and sodium carboxymethylcellulose in deionized water, uniformly stirring to obtain negative active slurry, coating the negative active slurry on two functional surfaces of a copper foil, and drying to obtain a negative plate containing a negative active layer;
wherein, in the negative active layer, the mass ratio of graphite, conductive carbon black, styrene-butadiene latex and sodium carboxymethyl cellulose is 96.5.
3) Preparation of lithium ion battery
Sequentially stacking the prepared positive plate, the diaphragm and the prepared negative plate, then winding to obtain a winding core, placing the winding core in an aluminum-plastic film which is well punched, injecting electrolyte into an aluminum-plastic film package, and performing vacuum sealing, standing, formation, secondary sealing and other processes to obtain the lithium ion battery;
wherein the electrolyte is lithium salt LiPF 6 A solution prepared from non-aqueous organic solvents of ethylene carbonate, propyl propionate, diethyl carbonate and propylene carbonate; the membrane is a Polyethylene (PE) membrane coated with ceramic and polyvinylidene fluoride.
Comparative example 2
Fig. 5 is a schematic structural diagram of the positive electrode sheet of comparative example 2, and as shown in fig. 5, compared with the positive electrode sheet of comparative example 1, the positive electrode sheet of this comparative example does not have the first end portion 05-1 of the positive electrode sheet, the positive electrode tab welding area 05-4 is located in the middle area of the positive electrode active material layer fixing area 05-3, the positive electrode tab 01 is located in the positive electrode tab welding area 05-4 on the upper surface of the current collector 02, and the positive electrode tab welding area 05-4 on the lower surface of the current collector 02 is an empty foil area.
The preparation method of the positive plate and the lithium ion battery of the comparative example refers to comparative example 1, and is not described herein again.
Example 1
The structure of the positive electrode sheet of the present embodiment is the same as that of fig. 1, and as shown in fig. 1, compared with the positive electrode sheet of the comparative example 1, the positive electrode sheet of the present embodiment is further provided with an inorganic filler layer 06 on the surface of the conductive undercoat layer located in the area 05-2-1 of the second end portion 05-2 of the positive electrode sheet.
The method for preparing the positive plate and the lithium ion battery in the embodiment basically refers to comparative example 1, and is different in that the preparation of the inorganic filler layer is added in the preparation process of the positive plate.
The preparation method of the inorganic filler layer comprises the following steps: adding aluminum oxide and PVDF into NMP, uniformly mixing to obtain inorganic filler layer slurry, coating the inorganic filler layer slurry on the surface of the conductive bottom coating layer in the area 05-2-1 of the second end part 05-2 of the positive plate, and drying to obtain the inorganic filler layer;
wherein the mass ratio of the alumina to the PVDF in the inorganic filler layer is 94.
The remaining steps are identical to those of comparative example 1 and are not described in detail here.
Example 2
Fig. 6 is a schematic structural diagram of the positive electrode sheet of example 2, and as shown in fig. 6, in the positive electrode sheet of this embodiment, compared with the positive electrode sheet of example 1, the inorganic filler layer 06 is coated on the surfaces of the conductive undercoat layers located in the areas 05-2-1 and 05-2-2 of the second end portion 05-2 of the positive electrode sheet, the composition and thickness of the inorganic filler layer 06 are the same as those of example 1, and the preparation methods of the positive electrode sheet and the lithium ion battery refer to example 1, and are not described again here.
Example 3
Fig. 7 is a schematic structural diagram of the positive electrode sheet of example 3, and as shown in fig. 7, in comparison with the positive electrode sheet of example 1, the inorganic filler layer 06 is also coated on the surface of the conductive undercoat layer in the area 05-1-1 and the area 05-1-2 of the first end 05-1 of the positive electrode sheet and on the surface of the conductive undercoat layer in the area 05-2-1 and the area 05-2-2 of the second end 05-2 of the positive electrode sheet, the composition and thickness of the inorganic filler layer 06 are the same as those in example 1, and the method for preparing the positive electrode sheet and the lithium ion battery refers to example 1, and is not described herein again.
Example 4
Fig. 8 is a schematic structural view of the positive electrode sheet of example 4, and as shown in fig. 8, compared with the positive electrode sheet of example 3, the positive electrode sheet of this example further has an insulating adhesive paper layer 07 on the surface of the inorganic filler layer 06 in the region 05-2-1 of the second end portion 05-2 of the positive electrode sheet.
The preparation method of the positive plate and the lithium ion battery in the embodiment basically refers to the embodiment 3, and the difference is that an insulating adhesive paper layer 07 is stuck on the surface of the inorganic filler layer 06 in the 05-2-1 area of the second end part 05-2 of the positive plate, the insulating adhesive paper layer 07 comprises a PET substrate layer and a rubber adhesive layer, the thickness of the substrate layer is 12 μm, the thickness of the rubber adhesive layer is 3 μm, the total thickness of the insulating adhesive paper is 15 μm, and the color is green. The remaining steps are the same as those in embodiment 3, and are not described herein again.
Example 5
Fig. 9 is a schematic structural diagram of the positive electrode sheet of example 5, and as shown in fig. 9, compared with the positive electrode sheet of example 4, the positive electrode sheet of this example is provided with an insulating adhesive paper layer 07 on the surface of the inorganic filler layer located in the regions 05-1-1 and 05-1-2 of the first end 05-1 of the positive electrode sheet and the regions 05-2-1 and 05-2-2 of the second end 05-2 of the positive electrode sheet. The thickness and the composition of the insulating adhesive paper layer are the same as those of the insulating adhesive paper layer in example 4, and the preparation steps of the positive plate and the lithium ion battery refer to example 4, which is not described herein again.
Example 6
Fig. 10 is a schematic structural diagram of the positive electrode sheet of example 6, and as shown in fig. 10, compared with the positive electrode sheet of example 5, the order of arrangement of the inorganic filler layer 06 and the insulating adhesive paper layer 07 is reversed in the positive electrode sheet of this example, the insulating adhesive paper layer 07 is firstly arranged on the surface of the conductive base coat layer arranged in the regions 05-1-1 and 05-1-1 of the first end portion 05-1 of the positive electrode sheet, and the regions 05-2-1 and 05-2-2 of the second end portion 05-2 of the positive electrode sheet, and then the inorganic filler layer 06 is arranged on the surface of the insulating adhesive paper layer 07.
The steps for preparing the positive plate and the lithium ion battery refer to example 5, and are not described in detail herein.
Example 7
The structure of the positive electrode sheet of this example is the same as that of fig. 3, and as shown in fig. 3, compared with the positive electrode sheet of example 5, the area 05-1-1 and the area 05-1-2 of the first end 05-1 of the positive electrode sheet are both provided with empty foils, and the conductive primer layer 04, the inorganic filler layer 06 and the insulating adhesive paper layer 07 are not provided in the areas.
In the preparation of the positive plate, the steps of coating the conductive primer layer 04, the inorganic filler layer 06 and the insulating adhesive paper layer 07 on the 05-1-1 area and the 05-1-2 area of the first end portion 05-1 of the positive plate are omitted, and the rest steps of the preparation of the positive plate and the preparation steps of the lithium ion battery refer to example 5, which is not described herein again.
Example 8
Fig. 11 is a schematic structural view of the positive electrode sheet of example 8, and as shown in fig. 11, compared with the positive electrode sheet of example 7, the inorganic filler layer 06 is not disposed on the surface of the conductive undercoat layer in the area 05-2-2 of the second end portion 05-2 of the positive electrode sheet, and the insulating adhesive paper layer 07 is directly disposed on the surface of the conductive undercoat layer in the area 05-2-2.
The preparation method of the positive plate and the lithium ion battery refers to example 7, and details are not repeated here.
Example 9
Fig. 12 is a schematic structural view of the positive electrode sheet of example 9, and as shown in fig. 12, compared with the positive electrode sheet of example 7, in the area 05-2-1 located at the second end portion 05-2 of the positive electrode sheet, only one half of the surface of the conductive primer layer is provided with the inorganic filler layer 06, and the other half of the surface of the conductive primer layer is directly provided with the insulating adhesive paper layer 07 without the inorganic filler layer 06. Wherein, the half area provided with the inorganic filler layer 06 starts from the middle position of the 05-2-1 area of the second end part 05-2 of the positive plate and ends at the tail end position of the current collector.
The preparation method of the positive plate and the lithium ion battery refers to example 7, and details are not repeated here.
Example 10
The structure of the positive electrode sheet of this example is identical to that of fig. 2, and as shown in fig. 2, the positive electrode sheet of this example is provided with an inorganic filler layer 06 on the surface of the conductive undercoat layer in the area 05-2-1 and the area 05-2-2 of the second end portion 05-2 of the positive electrode sheet, compared to the positive electrode sheet of comparative example 2, and the composition and preparation method of the inorganic filler layer 06 are as in reference example 1.
The remaining preparation steps of the positive plate and the lithium ion battery are the same as those of comparative example 2, and are not described again here.
Example 11
Fig. 13 is a schematic structural view of the positive electrode sheet in example 11, and as shown in fig. 13, in the positive electrode sheet in this embodiment, compared with the positive electrode sheet in example 10, an insulating adhesive paper layer 07 is further disposed on the inorganic filler layer surface in the 05-2-1 region and the 05-2-2 region of the second end portion 05-2 of the positive electrode sheet, the composition and thickness of the insulating adhesive paper layer 07 are the same as those in example 4, and after the inorganic filler layer 06 is prepared, the insulating adhesive paper layer is attached to the surface of the inorganic filler layer 06.
The remaining steps of the positive plate and the lithium ion battery refer to example 10, and are not described herein again.
Test examples
The lithium ion batteries prepared in the above examples and comparative examples were subjected to the following performance tests:
1. nail penetration performance
The test method comprises the following steps: using a 3mm steel nail, piercing the geometric center area of the lithium ion battery at a speed of 30mm/s, and judging the standard: if the battery does not smoke or ignite, the battery is judged to pass, and if the battery does smoke or ignite, the battery is judged to not pass. Each group was tested for 50 cells, and the nail penetration rate% = number of passes/number of tests × 100%.
2. High temperature storage Properties
The test method comprises the following steps: after charging the cell to 100% soc, the cell was placed at an ambient temperature of 70 ℃, the process data was measured once a day, and the voltage, internal resistance, and thickness of the cell were measured, respectively; and judging that the battery core is inflated when the expansion of the battery core thickness is more than 10% compared with the initial thickness. And recording the days used after the battery is stored until the battery core is inflated.
3. Energy density
The test method comprises the following steps: battery energy density = (battery capacity × plateau voltage)/(thickness × height × width).
The results of the above performance tests are shown in table 1:
TABLE 1
Energy density/(Wh/L) Nail penetration test pass rate Days of high temperature storage
Example 1 720 94％ 6
Example 2 718 96％ 7
Example 3 716 100％ 12
Example 4 715 100％ 19
Example 5 711 100％ 40
Example 6 711 100％ 38
Example 7 715 100％ 39
Example 8 716 98％ 38
Example 9 716 94％ 37
Example 10 721 100％ 10
Example 11 719 100％ 42
Comparative example 1 722 56％ 2
Comparative example 2 725 52％ 2
From table 1, it can be seen that:
1. as can be seen from comparison of examples 1 to 6 with comparative example 1, in examples 10 to 11 and comparative example 2, the inorganic filler layer and/or the insulating adhesive paper layer having an insulating function is provided on at least a portion of the surface of the conductive primer layer in the first region, although the energy density of the battery is slightly reduced, the nail penetration test pass rate and the high-temperature storage performance of the battery are significantly improved.
2. As can be seen from comparative examples 1 to 3, the larger the area of the inorganic filler layer covered on the surface of the conductive undercoat layer in the first region, the more excellent the nail penetration test passage rate and the high-temperature storage performance of the battery.
3. It can be seen from comparative examples 3-5 that the high-temperature storage performance of the battery can be further improved by adhering the insulating adhesive paper layer on the surface of the inorganic filler layer.
4. As can be seen from comparison of examples 5 and 6, the inorganic filler layer and the insulating adhesive paper layer sequentially stacked on the surface of the conductive base coat layer in the first region are more excellent in high-temperature storage performance of the battery than the insulating adhesive paper layer and the inorganic filler layer sequentially stacked on the surface of the conductive base coat layer in the first region.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The positive plate is characterized by comprising a current collector, wherein the current collector comprises a first area and a second area in the length direction of the current collector;
the surface of the current collector in the first area comprises a first coating and a second coating which are sequentially stacked, and the surface of the current collector in the second area comprises a first coating and a positive active material layer which are sequentially stacked;
the first coating is a conductive bottom coating, and the second coating is an insulating functional layer;
the second coating is disposed on at least a portion of a surface of the first coating in the first region.
2. The positive electrode sheet according to claim 1, wherein said second coating layer is selected from an inorganic filler layer and/or an insulating adhesive paper layer.
3. The positive electrode sheet according to claim 1 or 2, wherein the second coating layer comprises an inorganic filler layer and an insulating adhesive paper layer, which are sequentially stacked.
4. The positive electrode sheet according to claim 2 or 3, wherein the inorganic filler layer comprises 50 to 99.5 mass% of an inorganic filler and 0.5 to 50 mass% of a binder.
5. The positive electrode sheet according to any one of claims 1 to 4, wherein the positive electrode active material layer comprises 70 to 98.9 mass% of the positive electrode material, 0.3 to 15 mass% of the conductive agent, and 0.8 to 15 mass% of the binder.
6. The positive electrode sheet according to claim 2 or 3, wherein the inorganic filler layer has a thickness of 1 to 50 μm; and/or the presence of a gas in the gas,
the thickness of the insulating adhesive paper layer is 1-60 mu m.
7. The positive electrode sheet according to any one of claims 1 to 6, wherein the thickness of the positive electrode active material layer is 20 to 180 μm; and/or the presence of a gas in the gas,
the thickness of the first coating is 1-50 μm.
8. The positive electrode sheet according to any one of claims 1 to 7, wherein the current collector further comprises a third region, a positive electrode tab is arranged on the surface of the current collector in the third region, and the third region is located in the first region or the second region.
9. The positive electrode sheet according to any one of claims 1 to 7, wherein the current collector further comprises a fourth region adjoining the second region in a longitudinal direction of the current collector; the fourth area is a hollow foil area, and a positive tab is arranged on the surface of the current collector in the fourth area.
10. A lithium ion battery comprising the positive electrode sheet according to any one of claims 1 to 9.
CN202211303525.3A 2022-10-24 2022-10-24 Positive plate and lithium ion battery Pending CN115548255A (en)

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