CN115332727A - Diaphragm, roll up core and battery - Google Patents

Diaphragm, roll up core and battery Download PDF

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Publication number
CN115332727A
CN115332727A CN202211041073.6A CN202211041073A CN115332727A CN 115332727 A CN115332727 A CN 115332727A CN 202211041073 A CN202211041073 A CN 202211041073A CN 115332727 A CN115332727 A CN 115332727A
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diaphragm
area
arc
ceramic layer
region
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CN115332727B (en
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徐寒姣
王烽
李素丽
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Cell Separators (AREA)

Abstract

The invention relates to the technical field of lithium ion batteries, and provides a diaphragm, a winding core and a battery. The diaphragm comprises a base material, wherein the base material is divided into an arc area and a flat area; at least one surface of the circular arc area is provided with a first adhesive layer and/or a first ceramic layer, and at least one surface of the flat area is provided with a second adhesive layer and/or a second ceramic layer; wherein the compression ratio of the arc area is greater than that of the flat area. Set up different functional areas on this diaphragm, make the battery that contains this diaphragm avoid appearing the problem that circular arc district diaphragm takes place the glue film stifled hole in charging process, can not influence lithium ion transmission and be obstructed, and then effectively solve the problem that the lithium was analysed to the black spot.

Description

Diaphragm, roll up core and battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a diaphragm, a winding core containing the diaphragm and a battery containing the diaphragm or the winding core.
Background
Lithium ion batteries are clean energy sources with small volume, light weight and high energy storage ratio, and are widely used in various fields at present. The lithium ion battery comprises a winding type battery cell, the winding type battery cell is an electrode assembly formed by winding a positive plate, a negative plate and a diaphragm after the roller plates through a winding machine, and the positive plate and the negative plate are separated by the diaphragm in the winding process.
In a winding type battery cell, the battery cell can be divided into an unbent flat area and a bent arc area. The electrode plate of the coiled battery cell expands in the charging process, internal stress is generated in the battery cell, the flat area can expand outwards in the thickness direction of the battery cell, and the internal stress is low, and the arc area is stable in structure and difficult to release compared with the flat area, so that the arc area generates larger internal stress when the expansion of the electrode plate is inhibited; due to internal stress extrusion, the diaphragm in the arc area of the battery cell is blocked by a glue layer, so that lithium ion transmission is blocked, and further, black spot lithium precipitation is generated.
Therefore, the development of a battery diaphragm capable of solving the problem of black spot lithium deposition is of great significance.
Disclosure of Invention
The present invention has been made to overcome the above problems occurring in the prior art, and an object of the present invention is to provide a separator, a jelly roll including the separator, and a battery including the separator or the jelly roll. Set up different functional areas (circular arc district and plateau) on this diaphragm, the compression ratio in circular arc district is greater than the compression ratio in plateau district, makes the battery that contains this diaphragm avoid appearing the circular arc district diaphragm in charging process and takes place the problem in glue film shutoff hole, can not influence lithium ion transmission and be obstructed, and then effectively solve the problem that the lithium was analysed to the black spot.
In order to achieve the above object, a first aspect of the present invention provides a separator including a substrate divided into a circular arc region and a flat region; at least one surface of the circular arc area is provided with a first adhesive layer and/or a first ceramic layer, and at least one surface of the flat area is provided with a second adhesive layer and/or a second ceramic layer; wherein the compression ratio of the arc area is greater than that of the flat area. .
The second aspect of the invention provides a winding core, which is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, wherein the first diaphragm and the second diaphragm are diaphragms in the first aspect of the invention; wherein, along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
In a third aspect of the invention, a battery is provided that includes at least one of the separator according to the first aspect of the invention and the jelly roll according to the second aspect of the invention.
The technical scheme adopted by the invention has the following beneficial effects:
the diaphragm provided by the invention is provided with different functional areas (the arc area and the flat area), the compression ratio of the arc area is greater than that of the flat area, so that the problem that the diaphragm of the arc area blocks holes of a glue layer in the charging process of a battery containing the diaphragm is avoided, the transmission resistance of lithium ions is not influenced, and the problem of black spot lithium precipitation is further effectively solved.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
Drawings
FIG. 1 is a schematic view of a roll core structure according to an embodiment of the present invention.
Fig. 2 is a schematic view of a roll core structure according to an embodiment of the present invention.
Fig. 3 shows a schematic view of the structure of the separator of the present invention in the width direction (both ends are not shown).
Description of the reference numerals
101: a circular arc region; 102: a flat region; 103: a positive electrode; 104: and a negative electrode.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are given by way of illustration and explanation only, not limitation.
Unless defined otherwise, all scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The invention provides a diaphragm, which comprises a substrate, wherein the substrate is divided into an arc area and a flat area; at least one surface of the circular arc area is provided with a first adhesive layer and/or a first ceramic layer, and at least one surface of the flat area is provided with a second adhesive layer and/or a second ceramic layer;
wherein the compression ratio of the arc area is greater than that of the flat area.
When diaphragm and pole piece winding form the core structure, the different regions of diaphragm substrate can present two kinds of states: the membrane substrate has a curved state and an unbent state, and correspondingly, the membrane substrate has a curved region and an unbent region. In the present invention, the "arc region" may be a portion of the bending region of the diaphragm substrate including the inflection point of the bending portion, or the "arc region" may be the entire bending region of the diaphragm substrate. The "flat region" may be an entire unbent region and a partially bent region of the separator substrate, and the partially bent region does not include a bending point, or may be an entire unbent region of the separator substrate.
In the invention, under a certain environmental temperature, a certain pressure is applied to the diaphragm for a certain period of time, the thickness of the diaphragm can change, and the "compression ratio" refers to the ratio of the thickness change difference of the diaphragm after compression to the thickness of the diaphragm before compression, namely the compression ratio = (the thickness before compression-the thickness after compression)/the thickness before compression = 100%.
Specifically, in the present invention, the test conditions of the "compression ratio" of the separator include: the diaphragm was continuously compressed at a pressure of 1MPa for 30min at 80 ℃.
The inventor of the invention finds that after screening is carried out by testing the compression ratios of different materials, a first adhesive layer and/or a first ceramic layer is coated on at least one surface of an arc area, and the first adhesive layer and/or the first ceramic layer are made of materials with large compression ratios; and coating a second glue layer and/or a second ceramic layer on at least one surface of the flat area, wherein the second glue layer and/or the second ceramic layer are made of materials with small compression ratio. Therefore, the compression ratio of the arc area is larger than that of the flat area, so that the diaphragm of the arc area has a larger compression ratio, and the internal stress caused by the expansion of the pole piece attached to the arc area can be buffered, so that the phenomenon that the diaphragm glue layer of the arc area is extruded to block the hole is avoided, the transmission of lithium ions is not influenced, and the problem of lithium precipitation due to black spots is effectively solved.
In one example, one surface of the circular arc area is coated with a first adhesive layer, the surface of the same side of the flat area is coated with a second ceramic layer, and the compression ratio of the circular arc area is larger than that of the flat area.
In one example, the two maximum surfaces opposite to the arc area are coated with a first glue layer, the two maximum surfaces opposite to the flat area are coated with a second ceramic layer, and the compression ratio of the arc area is larger than that of the flat area.
In one example, one surface of the circular arc area is coated with a first glue layer, the surface on the same side of the flat area is coated with a second ceramic layer, the surface, far away from the substrate, of the second ceramic layer is coated with a second glue layer, and the compression ratio of the circular arc area is larger than that of the flat area.
In one example, two opposite maximum surfaces of the circular arc area are coated with a first glue layer, two opposite maximum surfaces of the flat area are coated with a second ceramic layer, the surface, far away from the substrate, of the second ceramic layer is coated with a second glue layer, and the compression ratio of the circular arc area is larger than that of the flat area.
In one example, one surface of the circular arc area is coated with a first ceramic layer, and the surface of the first ceramic layer far away from the substrate is coated with a first glue layer; the surface of the same side of the flat area is coated with a second ceramic layer, and the surface of the second ceramic layer, which is far away from the substrate, is coated with a second glue layer; the compression ratio of the arc area is larger than that of the flat area.
In one example, the two largest surfaces opposite to the circular arc area are coated with a first ceramic layer, and the surface of the first ceramic layer far away from the substrate is coated with a first glue layer; two opposite maximum surfaces of the flat area are coated with a second ceramic layer, and the surface of the second ceramic layer, which is far away from the substrate, is coated with a second glue layer; the compression ratio of the arc area is larger than that of the flat area.
In one example, the separator substrate is a porous substrate, and a separator substrate conventionally used in the art may be selected.
Illustratively, the porous substrate is selected from at least one of polyethylene, polypropylene, multi-layer polyethylene polypropylene, polyethylene polypropylene blend, polyimide, polyetherimide, polyamide, meta-aramid, para-aramid, and meta-para-blended aramid.
In order to better solve the problem of lithium deposition from battery black spots, one or more technical characteristics of the battery black spots can be further optimized.
In a preferred embodiment, as shown in fig. 1, the arc region 101 is the entire curved region of the diaphragm substrate, and the flat region 102 is the entire unflexed region of the diaphragm substrate.
In one example, the ratio of the compression ratio of the arc region to the flat region is a, which satisfies: a is more than or equal to 1.5 and less than or equal to 5.
Illustratively, the ratio of the compression ratio of the arc region to the flat region may be 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, and 5.
Preferably, a satisfies: a is more than or equal to 1.8 and less than or equal to 3.
More preferably, a satisfies: a is more than or equal to 2 and less than or equal to 2.5.
In one example, the compression ratio of the arc region is 10-35%.
Illustratively, the compression ratio of the arc region may be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%.
Preferably, the compression ratio of the circular arc area is 20-30%.
In the invention, the compression ratio of the circular arc area refers to compression ratio data tested after the first glue layer and/or the first ceramic layer is coated on the surface of the diaphragm base material of the circular arc area.
In one example, the compression ratio of the flat zone is 2-30%.
Illustratively, the compression ratio of the flat region may be 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%.
Preferably, the compression ratio of the flat zone is 5-15%.
In the invention, the compression ratio of the flat area refers to the compression ratio data tested after the surface of the flat area is coated with the second glue layer and/or the second ceramic layer.
In one example, the thickness of the first glue layer is 0.5 μm to 20 μm, and may be, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm.
Preferably, the thickness of the first glue layer is 1-10 μm.
In one example, the thickness of the second adhesive layer is 0.5 μm to 20 μm, and may be, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm.
Preferably, the thickness of the second glue layer is 1-10 μm.
In one example, the first ceramic layer has a thickness of 0.5 μm to 20 μm, and may be, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm.
Preferably, the thickness of the first ceramic layer is 1 μm to 10 μm.
In one example, the second ceramic layer has a thickness of 0.5 μm to 20 μm, and may be, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm.
Preferably, the thickness of the second ceramic layer is 1 μm to 10 μm.
In one example, the first bondline comprises a first polymer and the second bondline comprises a second polymer.
In one example, the first polymer and the second polymer are each independently selected from at least one of homopolymers or copolymers of olefinic monomers, halo-substituted olefinic monomers, acrylic monomers, and styrenic monomers.
Illustratively, the olefinic monomers include, but are not limited to, butadiene, ethylene, propylene, and acrylonitrile.
Illustratively, the halo-substituted olefinic monomers include, but are not limited to, vinylidene fluoride, hexafluoropropylene, vinylidene fluoride, tetrafluoroethylene, and trichloroethylene.
Illustratively, the acrylic monomers include, but are not limited to, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, ethyl methacrylate, acrylic acid, acrylamide, methacrylic acid.
Illustratively, the styrenic monomers include, but are not limited to, styrene, methyl styrene.
Illustratively, the first polymer and the second polymer are each independently selected from one or more of a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of vinylidene fluoride-trichloroethylene, polystyrene, polyacrylate, polyacrylic acid, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, a copolymer of ethylene-vinyl acetate, polyimide, polyphenylene terephthalamide, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, a copolymer of styrene-butadiene, and polyvinylidene fluoride.
In the present invention, the first polymer and the second polymer may be the same or different.
In one example, the first ceramic layer includes first ceramic particles and a first binder, and the second ceramic layer includes second ceramic particles and a second binder.
In one example, the first ceramic particles are present in an amount of 50 to 99.9wt% and the first binder is present in an amount of 0.1 to 50wt%, based on the total mass of the first ceramic layer.
In one example, the second ceramic particles are present in an amount of 50 to 99.9wt% and the second binder is present in an amount of 0.1 to 50wt%, based on the total mass of the second ceramic layer.
In an example, the first ceramic particles and the second ceramic particles are each independently selected from at least one of a metal oxide, an inorganic metal salt, a metal nitride, and an inorganic ceramic solid state electrolyte.
Illustratively, the metal oxide includes, but is not limited to, aluminum oxide, magnesium oxide, calcium oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, boehmite, and zinc oxide.
Illustratively, the inorganic metal salts include, but are not limited to, barium sulfate, calcium carbonate, and magnesium sulfate.
Illustratively, metal nitrides include, but are not limited to, tungsten nitride, silicon carbide, boron nitride, aluminum nitride, titanium nitride, and magnesium nitride.
Illustratively, the inorganic ceramic solid electrolyte includes, but is not limited to, at least one of NASICON-structured, perovskite-structured, anti-perovskite-structured, thio-LISICON-structured, and garnet-structured solid electrolyte particles.
In one example, the first ceramic particles and the second ceramic particles are each independently selected from one or more of alumina, magnesia, silica, titania, zirconia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, magnesium nitride, tin dioxide, magnesium hydroxide, boehmite, and calcium carbonate.
In the present invention, the first ceramic particles and the second ceramic particles may be the same or different.
In an example, the first binder and the second binder are each independently selected from one or more of a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of vinylidene fluoride-trichloroethylene, polystyrene, polyacrylate, polyacrylic acid, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, a copolymer of ethylene-vinyl acetate, polyimide, polyterephthalamide, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, a copolymer of styrene-butadiene, and polyvinylidene fluoride.
In the present invention, the first binder and the second binder may be the same or different.
The second aspect of the invention provides a winding core, which is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, wherein the first diaphragm and the second diaphragm are diaphragms in the first aspect of the invention; and along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
In the present invention, the first separator and the second separator may be the same or different, and preferably the first separator and the second separator are the same.
As shown in fig. 1 and 3, the winding core has a wound structure formed by sequentially stacking a first separator, a negative electrode sheet 104, a second separator, and a positive electrode sheet 103. The width of the arc zone 101 is the curvature of the wound structure and the width of the flat zone 102 is the non-curvature of the wound structure along the direction of core stretch.
In the present invention, the width direction of the separator is the same as the direction in which the core is stretched.
The inventors of the present invention have found that, in the winding structure of the winding core, the inflection point of the bending region is a portion where the internal stress is the largest, and the black spot lithium deposition is more likely to occur in this portion, and therefore, the effect of suppressing the black spot lithium deposition can be achieved by increasing the compression ratio of the separator at the inflection point of the bending. In order to achieve an effect of more effectively suppressing the black spot lithium deposition, the compression ratio of the diaphragm in the curved region including the inflection point portion of the curve or the compression ratio of the diaphragm in the entire curved region may be increased.
In an example, as shown in fig. 2, the arc region 101 is a portion of a membrane bending region and includes a bending inflection point (e.g., a bending location within a black dashed box), and the flat region 102 is a membrane full unbent region and a partial bending region and does not include a bending inflection point.
In the invention, the inflection point of the bending part is the intersection point of the central line of the winding core and the bending area.
In one example, as shown in fig. 1, the arc region 101 is the entire curved region of the diaphragm substrate, and the flat region 102 is the entire unflexed region of the diaphragm substrate.
In one example, the width L of the arc region is
Figure BDA0003820892230000101
Wherein d is the thickness of the winding core.
In the present invention, the core bending region is configured as a semicircular structure having a core thickness d as a diameter, and the arc length of the semicircle is the maximum width of the arc region, but the actual shape of the arc region is not limited to the standard semicircular shape. For example, the structure of the winding core is actually similar to the curvature formed by winding the multilayer cloth, which is not a standard semicircle.
In an example, the minimum width of the arc region of 0.01mm refers to the minimum width of the inflection point at the bend that includes the bending region of the diaphragm.
In one example, the maximum width of the arc region
Figure BDA0003820892230000102
Which is the arc length of a semicircle with the core thickness d as the diameter.
The structure of the battery except the winding core can be carried out according to the mode in the field, and the effect of inhibiting black spot lithium deposition can be realized.
In a third aspect, the present invention provides a battery comprising at least one of the separator according to the first aspect of the present invention and the jelly roll according to the second aspect of the present invention.
In one example, the battery includes a positive electrode sheet, a negative electrode sheet, a nonaqueous electrolyte solution, and a separator according to the first aspect of the present invention, the separator being disposed between the positive electrode sheet and the negative electrode sheet.
In one example, the battery includes the winding core according to the second aspect of the present invention and a nonaqueous electrolytic solution.
In one example, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer coated on one or both surfaces of the positive electrode collector.
Illustratively, the positive electrode current collector is a substance having conductivity without causing adverse chemical changes in the secondary battery, including, but not limited to, aluminum alloys, nickel alloys, titanium alloys.
The positive electrode active material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode active material is not particularly limited, and any of the positive electrode active materials commonly used in the art may be used, and may be, for example, at least one of lithium cobaltate, lithium manganate, lithium nickelate, and lithium nickel cobalt manganese lithium phosphate.
In one example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector.
The negative electrode current collector is a substance having conductivity without causing adverse chemical changes in the secondary battery, and may be selected from copper, stainless steel, aluminum, nickel, titanium, carbon cloth, or a composite of the materials.
The anode active material layer includes an anode active material, an anode conductive agent, and an anode binder. The negative electrode active material is not particularly limited, and any of the negative electrode active materials commonly used in the art may be used, and for example, may be at least one of graphite, lithium titanate, and silicon-based negative electrodes.
In one example, the positive electrode conductive agent and the negative electrode conductive agent are independently selected from at least one of conductive graphite, ultra-fine graphite, acetylene black, conductive carbon black SP, superconducting carbon black, carbon nanotubes, and conductive carbon fibers.
In one example, the positive and negative electrode binders are independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, polyvinylidene fluoride, and copolymers of vinylidene fluoride-fluorinated olefins.
The nonaqueous electrolytic solution may use any electrolyte commonly used in the art, and is not particularly limited herein.
In the present invention, when terms are distinguished by numbers, for example, "first ceramic layer", "second ceramic layer", etc., the numbers in such expressions are used only for distinguishing purposes and do not indicate a sequential order, and the numerical size of the numbers does not have any limiting effect on the technical solution unless otherwise specified.
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, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The invention is described in detail below with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
In the following examples and comparative examples, in preparing the first ceramic layer, the second ceramic layer and the slurry, other components are dissolved using a solvent, which may be one or more selected from the group consisting of water, N-methyl-2-pyrrolidone, acetone, tetrahydrofuran, chloroform, dichloromethane, dimethylformamide and cyclohexane.
Since the separator needs to be dried after coating the slurry, the solvent may be volatilized after drying, and thus the quality of the final coating does not include the quality of the solvent.
The method of the cell separator compression ratio test in the following examples and comparative examples is illustrated as follows:
(1) Testing and recording the thickness of the diaphragm before it is uncompressed;
(2) Continuously compressing the diaphragm at 80 deg.C under 1Mpa for 30min, and recording the compressed thickness;
(3) Calculating according to a formula: compression ratio = (before compression thickness-after compression thickness)/before compression thickness 100%.
Example 1
1. Preparation of the separator
(1) Preparing first glue line slurry
Mixing a vinylidene fluoride-hexafluoropropylene copolymer (a first polymer) and N-methyl-2-pyrrolidone (a solvent) to obtain a first glue line slurry;
(2) Preparing the second ceramic layer slurry
And mixing the aluminum oxide particles (second ceramic particles), the copolymer of vinylidene fluoride and hexafluoropropylene (second binder) and N-methyl-2-pyrrolidone (solvent) to obtain second ceramic layer slurry. Wherein, the content of the second ceramic particles is 60wt% and the content of the second binder is 40wt% based on the total mass of the second ceramic layer slurry;
(3) Adopting any one of coating processes of gravure coating, dip coating, transfer coating, spraying and the like, performing double-sided coating on the arc area of the diaphragm substrate by using first glue layer slurry, performing double-sided coating on the flat area of the diaphragm substrate by using second ceramic layer slurry, and drying;
wherein, the ratio of the compression ratio of the arc area to the flat area A =2.5;
the width L of the circular arc area is 7.85mm, the thickness of the first adhesive layer is 4 mu m, and the thickness of the second ceramic layer is 4 mu m.
2. Preparation of positive plate
Mixing the positive active material, the positive conductive agent and the positive binder according to a certain proportion, adding N-methyl pyrrolidone, stirring and dispersing to prepare positive slurry. In the positive electrode slurry, the solid component contained 97.2wt% of Lithium Cobaltate (LCO), 1.5wt% of conductive carbon black, and 1.3wt% of polyvinylidene fluoride (PVDF). And then coating the positive slurry on a positive current collector at one time by coating equipment (double-sided coating), drying, slitting and preparing a sheet to obtain the positive pole piece.
3. Preparation of negative plate
Mixing the negative active material, the negative conductive agent, the negative binder and the thickening agent according to a certain proportion, adding deionized water, stirring and dispersing to prepare negative slurry. In the negative electrode slurry, the solid components comprise 96.9% of graphite, 0.5% of conductive carbon black, 1.3% of sodium carboxymethylcellulose (CMC) and 1.3% of Styrene Butadiene Rubber (SBR), and then the negative electrode slurry is coated on a negative electrode current collector (double-sided coating), and the negative electrode pole piece is prepared by drying, slitting and tabletting.
4. Preparation of the Battery
And (3) preparing the positive plate prepared in the step (2), the negative plate prepared in the step (3) and the diaphragm prepared in the step (1) into a winding core (battery core), wherein the total thickness of the battery core is 5mm, preparing the battery core and the aluminum plastic film into a battery, then performing the working procedures of electrolyte injection, aging, formation, sorting and the like, and finally testing the electrochemical performance of the battery.
Example 2
The process is carried out according to example 1, with the difference from example 1 that:
1. preparation of the separator
(1) Preparing first glue line slurry
Mixing a vinylidene fluoride-trichloroethylene copolymer (a first polymer) and dichloromethane (a solvent) to obtain a first glue line slurry;
(2) Preparing the second glue line sizing agent
Mixing polyvinylidene fluoride (second polymer) and dichloromethane (solvent) to obtain second glue line slurry;
(3) Preparing the second ceramic layer slurry
The magnesium oxide particles (second ceramic particles), polyvinylidene fluoride (second binder), and methylene chloride (solvent) were mixed to obtain a second ceramic layer slurry. Wherein, based on the total mass of the second ceramic layer slurry, the content of the second ceramic particles is 70wt%, and the content of the second binder is 30wt%;
(4) Adopting any one of coating processes of gravure coating, dip coating, transfer coating, spraying and the like, carrying out double-sided coating on the arc area of the diaphragm substrate by using first glue layer slurry, carrying out double-sided coating on the flat area of the diaphragm substrate by using second ceramic layer slurry, and coating second glue layer slurry on the surface of the second ceramic layer; drying;
wherein, the ratio of the compression ratio of the arc area to the flat area A =2;
the circular arc district width L is 7.85mm, and the thickness of first glue film is 4 μm, and the total thickness of second ceramic layer and second glue film is 4 μm (the thickness ratio of second ceramic layer and second glue film 3: 1).
Example 3
The process is carried out according to example 1, with the difference from example 1 that:
1. preparation of the separator
(1) Preparing first glue line slurry
Mixing an ethylene-vinyl acetate copolymer (first polymer) and acetone (solvent) to obtain a first glue line slurry;
(2) Preparing first ceramic layer slurry
Silica particles (first ceramic particles), an ethylene-vinyl acetate copolymer (first binder), and acetone (solvent) were mixed to obtain a first ceramic layer slurry. Wherein, based on the total mass of the first ceramic layer slurry, the content of the first ceramic particles is 60wt%, and the content of the first binder is 40wt%;
(3) Preparing the second glue line sizing agent
Mixing polyacrylic acid (second polymer) and acetone to obtain second glue layer slurry;
(4) Preparing the second ceramic layer slurry
And mixing the aluminum nitride particles (second ceramic particles), polyacrylic acid (second binder) and acetone (solvent) to obtain second ceramic layer slurry. Wherein, based on the total mass of the second ceramic layer slurry, the content of the second ceramic particles is 95wt%, and the content of the second binder is 5wt%;
(5) Adopting any one of coating processes of gravure coating, dip coating, transfer coating, spraying and the like, performing double-sided coating on the arc area of the diaphragm substrate by using first ceramic layer slurry, and coating first adhesive layer slurry on the surface of the first ceramic layer; coating the flat area of the diaphragm substrate with a second ceramic layer slurry on two sides, and coating a second adhesive layer slurry on the surface of the second ceramic layer; drying;
wherein, the ratio of the compression ratio of the arc area to the flat area A =2.2;
the circular arc region width L is 7.85mm, the thickness of first ceramic layer and first glue film is 4 μm (the thickness ratio of first ceramic layer and first glue film 1: 2), and the total thickness of second ceramic layer and second glue film is 4 μm (the thickness ratio of second ceramic layer and second glue film 1: 1).
Example 4
The process is carried out according to example 1, with the difference from example 1 that: the first polymer was replaced with polyacrylic acid, wherein the ratio of the compression ratio of the circular arc region to the flat region, a =1.8.
Example 5
The process is carried out according to example 1, with the difference from example 1 that: the content of the second ceramic particles is 70wt% and the content of the second binder is 30wt% based on the total mass of the second ceramic layer slurry; and the ratio A =3 of the compression ratio of the circular arc area to the flat area.
Example 6
The process is carried out according to example 1, with the difference from example 1 that: the width L of the arc zone is 0.1mm, and the inflection point of the bending part of the diaphragm bending zone is included.
Example 7
The process is carried out according to example 1, with the difference from example 1 that: the width L of the arc zone is 5mm, and the inflection point of the bending part of the diaphragm bending area is included.
Comparative example 1
The process is carried out according to example 1, with the difference from example 1 that: the flat area is only coated with a second adhesive layer, and the material and the thickness of the second adhesive layer are the same as those of the first adhesive layer; the ratio of the compression ratio of the arc zone to the flat zone a =1.
Comparative example 2
The process is carried out according to example 1, with the difference from example 1 that: the arc area is only coated with a first ceramic layer, and the first ceramic layer and a second ceramic layer are made of the same material and have the same thickness; the ratio of the compression ratio of the arc area to the flat area A =1.
Comparative example 3
The process is carried out according to example 2, with the difference from example 2 that: polyacrylic acid is used for replacing the first polymer, and the thickness ratio of the second ceramic layer to the second adhesive layer is 2:1, wherein the ratio of the compression ratio of the circular arc area to the flat area a =1.34.
Comparative example 4
The process is carried out according to example 1, with the difference from example 1 that: the second adhesive is polyacrylic acid, the content of the second ceramic particles is 75wt% and the content of the second adhesive is 25wt% based on the total mass of the second ceramic layer slurry, wherein the ratio of the compression ratio of the arc area to the flat area is A =5.5.
Examples of the experiments
(1) Normal temperature cycle test of battery
The lithium ion batteries of the above examples and comparative examples were placed in an environment of 25 ℃ and charged with 3C constant current and constant voltage to 4.45v and 4.45v constant voltage to 0.05C cutoff current; then standing for 15min; discharge to 3V with 1C current. Recording the initial capacity as Q1, recording the capacity of the battery cycling to 600 weeks as Q2, and calculating the capacity retention rate of the battery after normal-temperature cycling according to the following formula: capacity retention ratio (%) = (Q2/Q1) × 100%.
(2) Battery expansion test
Measuring the initial thickness M1 of the electrode plate, measuring the thickness M2 after the electrode plate is cycled to 600 weeks, and calculating the expansion rate of the battery after normal-temperature cycle according to the following formula: battery swelling rate (%) = [ (M2-M1)/M1 ] × 100%.
(3) Battery lithium assay
And (4) disassembling the battery which is circulated for 600 weeks to observe whether a lithium precipitation phenomenon occurs.
TABLE 1
Figure BDA0003820892230000181
According to the results in table 1, compared with the comparative example, the lithium deposition degree at the arc area in the embodiment of the present invention is significantly reduced, and the compression ratio of the arc area to the flat area is higher, i.e., the arc area is less prone to lithium deposition when the compression ratio of the arc area is higher, which indicates that the problem of lithium deposition from the arc black spot caused by the blocking of the hole by the film adhesive layer in the arc area can be effectively solved by increasing the compression ratio of the arc area.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents and the like included within the spirit and scope of the present invention.

Claims (10)

1. A diaphragm, characterized in that the diaphragm comprises a substrate, wherein the substrate is divided into a circular arc area and a flat area; at least one surface of the circular arc area is provided with a first adhesive layer and/or a first ceramic layer, and at least one surface of the flat area is provided with a second adhesive layer and/or a second ceramic layer;
wherein the compression ratio of the arc area is greater than that of the flat area.
2. The diaphragm of claim 1, wherein the ratio of the compression ratio of the arc region to the flat region is a, the a satisfying: a is more than or equal to 1.5 and less than or equal to 5;
preferably, a satisfies: a is more than or equal to 1.8 and less than or equal to 3.
3. The diaphragm of claim 1, wherein the compression ratio of the arc zone is 10-35%;
and/or the compression ratio of the flat zone is 2-30%.
4. The separator of claim 1, wherein the first glue layer and the second glue layer each independently have a thickness of 0.5-20 μ ι η;
and/or the first ceramic layer and the second ceramic layer each independently have a thickness of 0.5 μm to 20 μm.
5. The separator of claim 1, wherein the first glue layer comprises a first polymer and the second glue layer comprises a second polymer;
and/or, the first polymer and the second polymer are each independently selected from at least one of homopolymers or copolymers of olefin monomers, halogen-substituted olefin monomers, acrylic monomers, and styrenic monomers.
6. The separator of claim 1, wherein the first ceramic layer comprises first ceramic particles and a first binder, and the second ceramic layer comprises second ceramic particles and a second binder;
and/or the first ceramic particles and the second ceramic particles are each independently selected from at least one of metal oxides, inorganic metal salts, metal nitrides, and inorganic ceramic solid-state electrolytes.
7. A winding core, characterized in that the winding core is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, wherein the first diaphragm and the second diaphragm are the diaphragms in any one of claims 1 to 6;
wherein, along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
8. The winding core of claim 7, wherein the arc zone is part of a membrane bending region and includes a bending inflection point, and the flat zone is a membrane full unbent region and a partial bending region and does not include a bending inflection point; and the inflection point of the bending part is the intersection point of the central line of the winding core and the bending area.
9. The winding core of claim 7, wherein the arc zone is an overall curved region of the separator and the flat zone is an overall unbent region of the separator;
and/or the width L of the arc area is
Figure FDA0003820892220000021
Wherein d is the thickness of the winding core.
10. A battery, characterized in that the battery comprises at least one of the separator of any one of claims 1-6 and the jelly roll of any one of claims 7-9.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010176901A (en) * 2009-01-27 2010-08-12 Sony Corp Secondary battery
CN103184013A (en) * 2011-12-28 2013-07-03 天津东皋膜技术有限公司 Polyvinyl composite microporous membrane with thermocompression bonding characteristic
CN111725569A (en) * 2020-06-24 2020-09-29 珠海冠宇电池股份有限公司 Roll up core and battery
CN112768784A (en) * 2020-12-14 2021-05-07 东莞新能安科技有限公司 Electrochemical device and electronic device
CN113471630A (en) * 2021-06-30 2021-10-01 宁德新能源科技有限公司 Winding type battery cell and battery
CN216773319U (en) * 2022-01-27 2022-06-17 宁波容百新能源科技股份有限公司 Naked electric core and lithium cell

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010176901A (en) * 2009-01-27 2010-08-12 Sony Corp Secondary battery
CN103184013A (en) * 2011-12-28 2013-07-03 天津东皋膜技术有限公司 Polyvinyl composite microporous membrane with thermocompression bonding characteristic
CN111725569A (en) * 2020-06-24 2020-09-29 珠海冠宇电池股份有限公司 Roll up core and battery
CN112768784A (en) * 2020-12-14 2021-05-07 东莞新能安科技有限公司 Electrochemical device and electronic device
CN113471630A (en) * 2021-06-30 2021-10-01 宁德新能源科技有限公司 Winding type battery cell and battery
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