CN116259707A - Anti-wrinkling winding type positive electrode plate, preparation method thereof and winding core - Google Patents

Anti-wrinkling winding type positive electrode plate, preparation method thereof and winding core Download PDF

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Publication number
CN116259707A
CN116259707A CN202211573949.1A CN202211573949A CN116259707A CN 116259707 A CN116259707 A CN 116259707A CN 202211573949 A CN202211573949 A CN 202211573949A CN 116259707 A CN116259707 A CN 116259707A
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positive electrode
thickness
winding
positive
electrode plate
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刘念
李鹏
徐辉
车丽媛
刘汉祥
苑丁丁
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Hubei Eve Power Co Ltd
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Hubei Eve Power Co Ltd
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Priority to CN202211573949.1A priority Critical patent/CN116259707A/en
Publication of CN116259707A publication Critical patent/CN116259707A/en
Priority to PCT/CN2023/137140 priority patent/WO2024120492A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention discloses a fold-preventing coiled positive electrode plate, a preparation method thereof and a coiled core, wherein the positive electrode plate is covered with positive electrode material layers with different thicknesses on a positive electrode current collector and is provided with concave embossing with different depths in different areas, so that the loss of energy density caused by that the positive electrode material layers are not coated on the positive electrode current collector due to interval coating can be avoided, the thickness of the coiled position of the positive electrode plate is smaller than the thickness of the electrode plate at other positions after the positive electrode plate is coiled, the gap at the coiled position is larger than the gap of a main body surface after the coiling is completed, redundant stress release space can be provided at the coiled position after the electrode plate is heated and expanded, the uniformity of internal stress of the electric core is ensured, and the phenomena of coiled core deformation and electrode plate fold can be well reduced; meanwhile, the effect and the effect of absorbing and dispersing stress of the positive pole piece at the winding position can be obviously improved, so that the anti-wrinkling and circulating performance of the electrode piece are obviously improved, and the large-scale application of the winding positive pole piece is facilitated.

Description

Anti-wrinkling winding type positive electrode plate, preparation method thereof and winding core
Technical Field
The invention relates to the technical field of battery pole pieces, in particular to an anti-wrinkling winding type positive pole piece, a preparation method thereof and a winding core.
Background
Along with the continuous breakthrough of material technology and manufacturing process of secondary batteries such as lithium ion batteries, the secondary batteries are widely applied to various fields, and various convenience is brought to the production and life of people. However, in the mass production and application process of the secondary battery, people find that the existing winding core can cause the problem of wrinkling of the positive electrode plate due to uneven stress distribution in the production and application process, so that the electrical property and service life of the winding core are seriously influenced, and the winding core is taken as an important component part of the secondary battery, which directly influences the electrical property and service life of the secondary battery, and also limits the mass popularization and application of the secondary battery.
Disclosure of Invention
The invention aims at: aiming at the problem that the current positive electrode plate is easy to wrinkle and the electric performance and service life are reduced, the invention provides a wrinkle-preventing winding positive electrode plate, a preparation method and a winding core thereof, and the positive electrode plate is characterized in that the sectional area and thickness of a positive electrode material layer are subjected to targeted design, and embossing depths of different areas are defined in a targeted manner, so that the loss of energy density caused by that the positive electrode material layer is not coated on the upper part of a positive electrode current collector due to interval coating is avoided, the energy density and the circulation times of the positive electrode plate are effectively improved, redundant stress release space can be provided at a winding position, the effect and effect of absorbing and dispersing stress of the positive electrode plate at the winding position are obviously improved, the uniformity of internal stress of a battery core is ensured, the phenomena of winding core deformation and electrode plate wrinkling are reduced, the wrinkle resistance and the circulation performance of the electrode plate are obviously improved, and the large-scale application of the winding positive electrode plate is facilitated.
In order to achieve the above object, the present invention provides a fold-preventing wound positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer covering the positive electrode current collector; the positive electrode material layer is divided into a first coating area and a second coating area; the thickness of the second coating area is smaller than that of the first coating area; the second coating area corresponds to a bending part when the positive electrode sheet is wound; the widths of the first coating area and the second coating area are gradually increased along the winding direction by the winding starting part of the positive electrode sheet; the positive electrode material layer is provided with a concave embossing, the depth of the concave embossing in the first coating area is 5-10% of the thickness of the corresponding pole piece, and the depth of the concave embossing in the second coating area is 5-8% of the thickness of the corresponding pole piece.
According to the anti-wrinkling coiled positive electrode plate, the positive electrode current collector is covered with the positive electrode material layers, so that the loss of energy density caused by that the positive electrode material layers are not coated on the positive electrode current collector due to interval coating is avoided, and the energy density and the cycle times of the positive electrode plate are effectively improved; the positive electrode material layers with different thicknesses are further arranged, so that the thickness of the wound position of the positive electrode sheet is smaller than that of the other positions of the positive electrode sheet after the positive electrode sheet is wound, the gap at the wound position is larger than that of the main body surface after the positive electrode sheet is wound, redundant stress release space can be provided at the wound position after the positive electrode sheet is heated and expanded, the uniformity of internal stress of the battery core is ensured, the flatness of the winding core and the positive electrode sheet is ensured, and the winding core deformation and the pole sheet wrinkling phenomenon are reduced well; meanwhile, the electrode plate is provided with concave embossing with different depths in different areas, so that the effect and effect of absorbing and dispersing stress of the positive electrode plate at the winding position are obviously improved, the anti-wrinkling and circulating performances of the electrode plate are obviously improved, and the large-scale application of the wound positive electrode plate is facilitated.
Preferably, the thickness of the positive electrode plate in the second coating area is 90-95% of that of the positive electrode plate in the first coating area; for example, the positive electrode sheet thickness of the second coating zone is 90%, 91%, 92%, 93%, 94% or 95% of the positive electrode sheet thickness of the first coating zone; the second coating area has an excessively thick positive electrode material layer, the anti-wrinkling effect of the positive electrode plate is poor, the second coating area has an excessively thin positive electrode material layer, the second coating area is easy to break during pressing, and the performance of the positive electrode plate can be influenced; the preferable thickness ratio has good anti-wrinkling effect, and the pole piece is not easy to break during pressing.
Wherein, preferably, the thickness of the positive electrode material layer is 50-300 μm; for example, the positive electrode material layer thickness may be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, or 300 μm; the thickness of the positive electrode material layer is preferable, and the electrical performance of the positive electrode is better.
Preferably, the thickness of the positive electrode current collector is 3-30 μm; for example, the thickness of the positive electrode current collector may be 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm; the thickness of the positive current collector is preferable, and the electrical performance of the positive current collector is better.
Preferably, the positive current collector is aluminum foil; the aluminum foil is used as the positive current collector, and has good electrical property, low cost and wide raw material sources.
Preferably, the thickness of the second coating area gradually increases along the winding direction of the positive electrode sheet; the preferable thickness change has better anti-wrinkling effect and better electrical property of the positive plate.
Wherein, preferably, the concave embossing is spherical, octagonal or dodecagonal; the preferable concave embossing shape is easy to process, more regular in shape, more uniform in stress absorption and release, lower in wrinkling degree of the battery cell, more in cycle times and better in multiplying power performance; most preferably, the concave embossing is a sphere with the diameter of 2-5 mm; too small diameter can cause too large pressure intensity on the pole piece, so that the pole piece is invalid and the performance of the battery cell is affected, and too large diameter can cause the embossing shape to be changed into a non-spherical shape, so that the effect of absorbing and releasing stress is poor, and the effect of improving wrinkles is further affected and the performance of the battery cell is reduced; for example, the diameter of the recessed embossment may be 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, or 5.0 μm.
Furthermore, the invention also provides a preparation method of the anti-wrinkling winding type positive electrode plate, which comprises the following steps:
(1) Coating the positive electrode slurry on two sides of a positive electrode current collector to form a positive electrode coating, so as to obtain a positive electrode sheet semi-finished product;
(2) And carrying out cold pressing and embossing treatment on the semi-finished positive electrode plate to obtain a coiled positive electrode plate finished product.
Preferably, in the step (1), the positive electrode slurry is one of lithium cobaltate, ternary lithium manganate and lithium iron phosphate positive electrode slurry systems; the preferred positive electrode paste has better electrical properties.
Preferably, in the step (1), the coating is performed by using a transfer coater; the preferable coating equipment has good coating effect, high efficiency and adjustable coating thickness.
Preferably, in the step (2), the pressure of the cold pressing treatment is 0.1-0.35 mpa; the preferable cold pressing pressure is moderate in density and better in electrical property of the positive electrode material layer.
Preferably, in the step (2), the embossing treatment is segmented embossing, the embossing pressure of the first coating area is 0.2-0.65 mpa, and the embossing pressure of the second coating area is 0.05-0.55 mpa; the embossing is carried out by adopting different pressures, and the obtained positive electrode plate has better electrical property and mechanical property.
Preferably, in the step (2), during the cold pressing and embossing treatment, a roller with an uneven surface is used for cold pressing, and embossing is formed at the same time of cold pressing; two rollers can be adopted to synchronously carry out, one roller with flat surface carries out cold pressing, and the other roller with uneven surface carries out embossing; cold pressing the polar plate, embossing in the second coating area, and embossing in the first coating area during winding; the specific cold pressing and embossing treatment method is based on the fact that the positive pole piece meeting the design requirement can be formed, and various existing cold pressing and embossing processes can be selected to be combined according to actual conditions.
Wherein, in the step (2), preferably, the cold pressing and embossing treatment are simultaneously carried out; the optimized treatment process has higher production efficiency without affecting the performance of the positive electrode plate, can shorten the production period, and is beneficial to reducing the energy consumption and the production cost.
Furthermore, the invention also provides a winding type winding core capable of preventing wrinkles; the winding core comprises a winding needle, and a positive pole piece, a negative pole piece and a diaphragm which are wound on the winding needle; the diaphragm is arranged between the positive pole piece and the negative pole piece; the positive pole piece is the winding type positive pole piece capable of preventing wrinkles.
Wherein, preferably, the width d of the first coating area on the positive electrode current collector n =d 1 (n-1) + (a+b+c); width L of the very coated region n =L 1 +3.14 x n (a+b+c); wherein d 1 The width of the positive pole piece is the width of the first winding positive pole piece; l (L) 1 =0 to 1mm; n is the number of winding layers; a is the thickness of the positive electrode plate; b is the thickness of the negative electrode plate; c is the thickness of the diaphragm; the preferable width of the coating area can better reduce the stress during winding and better reduce the generation of pole piece wrinkles.
Preferably, the thickness of the positive electrode plate is 10-800 μm; for example, the thickness of the positive electrode sheet may be 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, or 800 μm; more preferably, the thickness of the positive electrode plate is 100-200 μm; the thickness of the pole piece is preferable, and the electrical property and the mechanical property of the winding core are better.
Preferably, the thickness of the negative electrode plate is 10-800 μm; for example, the negative electrode tab may have a thickness of 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, or 800 μm; more preferably, the thickness of the negative electrode plate is 100-200 mu m; the thickness of the pole piece is preferable, and the electrical property and the mechanical property of the winding core are better.
Preferably, the thickness of the diaphragm is 3-50 μm; for example, the thickness of the separator may be 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm; the thickness of the diaphragm is preferable, and the electrical property and mechanical property of the winding core are better.
Wherein, preferably, at least one surface of the diaphragm is provided with a rubberized layer; through the rubberizing layer, can be better with positive pole piece and negative pole piece bonding, the electrical property of rolling up the core is better.
Wherein, preferably, the membrane is a PE/PP base membrane; the preferred diaphragm type has better electrical performance and better winding core performance.
In summary, due to the adoption of the technical scheme, the beneficial effects of the invention are as follows:
1. the positive electrode plate is covered with the positive electrode material layer on the positive electrode current collector, so that the loss of energy density caused by that the positive electrode material layer is not coated on the upper part of the positive electrode current collector due to interval coating is avoided, and the energy density and the cycle times of the positive electrode plate can be effectively improved.
2. The thickness of the positive electrode material layer on the positive electrode plate is different, so that the thickness of the wound part of the electrode plate is smaller than that of the electrode plate at other positions after the electrode plate is wound, and the gap of the wound part of the winding core is larger than that of the main body surface after the electrode plate is wound, so that redundant stress release space can be provided at the wound part after the electrode plate is heated and expanded, the uniformity of internal stress of the battery core is ensured, the flatness of the winding core and the electrode plate is ensured, and the phenomena of winding core deformation and electrode plate wrinkling are reduced better.
3. The concave embossing structure arranged on the positive pole piece can better absorb and disperse stress generated at the winding position of the positive pole piece in the production and use processes, thereby effectively preventing the pole piece from wrinkling and having positive effects on improving the performance and the service life of the pole piece.
4. The embossing structures on the positive electrode plate have different depths in different areas, so that the effect and effect of absorbing and dispersing stress of the positive electrode plate at a winding position are obviously improved, the anti-wrinkling and circulating performances of the electrode plate are obviously improved, and the large-scale application of the winding positive electrode plate is facilitated.
5. The preparation method of the positive electrode plate is simple and reliable, the preparation process can be adjusted according to actual production conditions, the production efficiency is effectively increased, the production cost is saved, and the large-scale production of the positive electrode plate is facilitated.
6. After the coiled core is manufactured into a finished battery core, the problem of wrinkling of the coiled part of the battery core is greatly improved in the circulation process, the circulation performance is also obviously improved, and after the circulation battery core is disassembled, the coiled part is not blackened due to lithium precipitation compared with a normal pole piece, so that the reliability of the battery core is better.
Drawings
FIG. 1 is a schematic front view of the positive electrode sheet in example 1 of the present invention;
FIG. 2 is a schematic cross-sectional view of the positive electrode sheet in example 1 of the present invention;
FIG. 3 is a schematic view showing the structure of a winding core in embodiment 1 of the present invention;
the marks in the figure: 1-a first application zone; 2-a second application zone; 3-concave embossing; 4-positive electrode current collector; 5-a positive electrode material layer; 6-a positive pole piece; 7-a membrane; 8-a negative electrode piece; 9-winding needle.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
The winding type positive pole piece capable of preventing wrinkles is composed of a positive current collector 4 (aluminum foil with the thickness of 10 mu m) and positive material layers 5 (lithium iron phosphate positive electrode) covered on two sides of the positive current collector as shown in fig. 1 and 2; the positive electrode material 5 is divided into 4 first coating areas 1 and 3 second coating areas 2; the thickness of the second coating region 2 is 190 μm (200×95%) (the thickness of the positive electrode material layer 5 is 180 μm), and the thickness of the pole piece of the first coating region 1 is 200 μm (the thickness of the positive electrode material layer 5 is 190 μm); the second coating area 2 corresponds to a bending part when the positive pole sheet is wound; the 1 st first coating zone has a width of 5.0mm (i.e., the width of the winding needle 9 is 5mm, the design size is 5 mm), the 2 nd first coating zone has a width of 5.41mm (5+1×0.2+0.2+0.01), the 3 rd first coating zone has a width of 5.82mm (5+2×0.2+0.01), the 4 th first coating zone has a width of 6.23mm (5+3×0.2+0.2+0.01), the 1 st second coating zone has a width (L 1 =0.5 mm) is 1.756mm (0.5+3.14×1×0.2+0.19+0.01), the width of the 2 nd second coating region3.012mm (0.5+3.14×2 (0.2+0.19+0.01)), the width of the 3 rd second coating zone being 4.268mm (0.5+3.14×3 (0.2+0.19+0.01)); the positive electrode material layer 5 is provided with concave embossments 3 (spherical, 3mm in diameter, and the embossing depth of the second coating area 2 is 11.4 mu m (190 x 6%)) and the embossing depth of the first coating area 2 is 16 mu m (200 x 8%)).
The preparation method comprises the following steps:
(1) Coating lithium iron phosphate positive electrode slurry on two sides of a positive electrode current collector by adopting a transfer coater to form a positive electrode coating, so as to obtain a positive electrode sheet semi-finished product;
(2) Cold pressing (the pressure is 0.35 Mpa) the second coating area by adopting a roller with an uneven surface on the semi-finished product of the positive pole piece, and embossing is formed at the same time of cold pressing; then embossing the first coating area (the pressure is 0.35 MPa) during winding to obtain a winding type positive electrode plate finished product.
The fold-preventing winding type winding core is manufactured by adopting the fold-preventing winding type positive pole piece, and as shown in figure 3, the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (graphite and 200 mu m) and a diaphragm 7 (10 mu m) which are wound on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Example 2
An anti-wrinkling winding type positive electrode plate consists of a positive electrode current collector 4 (aluminum foil with the thickness of 10 mu m) and positive electrode material layers 5 (lithium iron phosphate positive electrode) covered on two sides of the positive electrode current collector; the positive electrode material 5 is divided into 4 first coating areas 1 and 3 second coating areas 2; the thickness of the second coating region 2 is 180 μm (200×90%) (the thickness of the positive electrode material layer 5 is 170 μm), and the thickness of the pole piece of the first coating region 1 is 200 μm (the thickness of the positive electrode material layer 5 is 190 μm); the second coating area 2 corresponds to a bending part when the positive pole sheet is wound; the 1 st first coating zone has a width of 5.0mm (i.e., the width of the winding needle 9 is 5mm, the design size) and the 2 nd first coating zone has a width of 5.41mm (5+1×0.2+0.2+0.01), the 3 rd first coating zone has a width of 5.82mm (5+2×0.2+0.01), the 4 th first coating zone has a width of 6.23mm (5+3×0.2+0.01), the 1 st second coating zone has a width of 5+1×0.2+0.01)Width (L) 1 =0.5 mm) of 1.725mm (0.5+3.14×1×0.2+0.18+0.01), the width of the 2 nd second coating zone is 2.449mm (0.5+3.14×2×0.01), and the width of the 3 rd second coating zone is 4.174mm (0.5+3.14×3×0.18+0.01); the positive electrode material layer 5 is provided with concave embossments 3 (spherical, 3mm in diameter, and 10.8 μm (180×6%) in embossing depth on the second coating area 2), and 16 μm (200×8%) in embossing depth on the first coating area 2).
The preparation method comprises the following steps:
(1) Coating lithium iron phosphate positive electrode slurry on two sides of a positive electrode current collector by adopting a transfer coater to form a positive electrode coating, so as to obtain a positive electrode sheet semi-finished product;
(2) The semi-finished product of the positive electrode plate is rolled in the second coating area by adopting two rollers synchronously, one roller with flat surface is cold-pressed (the pressure is 0.1 Mpa), and the other roller with uneven surface is embossed (0.2 Mpa); then embossing the first coating area (the pressure is 0.2 MPa) during winding to obtain a winding type positive electrode plate finished product.
The fold-preventing winding type winding core is manufactured by adopting the fold-preventing winding type positive pole piece, and comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (graphite and 200 mu m) and a diaphragm 7 (10 mu m) which are wound on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Example 3
An anti-wrinkling winding type positive electrode plate consists of a positive electrode current collector 4 (aluminum foil with the thickness of 10 mu m) and positive electrode material layers 5 (lithium iron phosphate positive electrode) covered on two sides of the positive electrode current collector; the positive electrode material 5 is divided into 4 first coating areas 1 and 3 second coating areas 2; the thickness of the second coating region 2 was 184 μm (200×92%) (the thickness of the positive electrode material layer 5 was 174 μm), and the thickness of the electrode sheet of the first coating region 1 was 200 μm (the thickness of the positive electrode material layer 5 was 190 μm); the second coating area 2 corresponds to a bending part when the positive pole sheet is wound; the width of the 1 st first coating zone is 5.0mm (i.e. the width of the winding needle 9 is 5mm, the design size is 5 mm), the width of the 2 nd first coating zone is 5.41mm (5+1×0.2+0.01)), the width of the 3 rd first coating zone is 5.82mm (5+2×0.2+0.01)), the width of the 4 th first coating zone is 6.23mm (5+3×0.2+0.2+0.01)), the width of the 1 st second coating zone (l1=0.5 mm) is 1.737mm (0.5+3.14×1×0.184+0.01)), the width of the 2 nd first coating zone is 2.974mm (0.5+3.14×2×0.184+0.01)), and the width of the 3 rd second coating zone is 4.211 (0.5+3+0.14×0.184+0.01); the positive electrode material layer 5 is provided with concave embossments 3 (spherical, 3mm in diameter, and the embossing depth of the second coating area 2 is 11.4 mu m (184 x 6%)) and the embossing depth of the first coating area 2 is 16 mu m (200 x 8%)).
The preparation method comprises the following steps:
(1) Coating lithium iron phosphate positive electrode slurry on two sides of a positive electrode current collector by adopting a transfer coater to form a positive electrode coating, so as to obtain a positive electrode sheet semi-finished product;
(2) Cold pressing the positive electrode plate (the pressure is 0.35 Mpa), embossing the positive electrode plate in a second coating area (the pressure is 0.65 Mpa), and embossing the first coating area (the pressure is 0.55 Mpa) during winding to obtain the winding positive electrode plate finished product.
The fold-preventing winding type winding core is manufactured by adopting the fold-preventing winding type positive pole piece, and comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (graphite and 200 mu m) and a diaphragm 7 (10 mu m) which are wound on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Comparative example 1
A wound positive electrode sheet differs from example 1 only in that the second coating zone 2 is a blank layer (i.e., there is no positive electrode material layer), nor is there a depressed embossing.
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Comparative example 2
A wound positive electrode sheet was different from example 1 only in that the positive electrode material layer thickness was exactly the same, i.e., the sheet thickness was 200 μm (positive electrode material layer thickness was 190 μm), and the embossing depth was the same (16 μm).
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Comparative example 3
The wound positive electrode sheet was different from example 1 only in that neither the second coating region 2 nor the first coating region 1 had concave embossing.
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Comparative example 4
A wound positive electrode sheet differs from example 1 only in that the second coating region 2 has no depressed embossing.
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Comparative example 5
A wound positive electrode sheet differs from example 1 only in that the first coating zone 1 has no depressed embossing.
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Blank 1
A wound positive electrode sheet, which is different from example 1 in that: the positive electrode material layers were the same thickness (95 μm) and had no depressed embossing.
The coiled positive pole piece is adopted to manufacture a coiled winding core, and the winding core comprises a winding needle 9, a positive pole piece 6, a negative pole piece 8 (200 mu m) and a diaphragm 7 (10 mu m), wherein the positive pole piece 6, the negative pole piece 8 (200 mu m) and the diaphragm 7 (10 mu m) are coiled on the winding needle 9; the separator 7 is disposed between the positive electrode sheet 6 and the negative electrode sheet 8.
Experimental example 1: experiment of influence of pole piece structure on core winding performance
The test experiments (average of 20 samples per group) for cell wrinkling degree, cycle number (25 ℃, 80% soh) and cell rate performance (3C/1C) were performed on the cores of examples 1-3, comparative examples 1-5 and blank 1, and the test results were as follows:
Figure DEST_PATH_IMAGE002
experimental example 2: embossed shape experiment
The same pole piece and winding core as in example 1 in structure and size were used, except that: the embossing depth is 8% of the thickness of the pole piece; the embossed areas are the same (circles of 3mm diameter); the embossing shapes are different; the cell wrinkling degree, cycle number (25 ℃, 80% soh) and cell rate performance (3C/1C) of the rolled cores (averaged over 20 samples per group) were examined and the results were as follows:
Figure DEST_PATH_IMAGE004
as can be seen from the results of experimental example 2, the shape of the concave embossing has a certain influence on the electrical performance of the winding core, especially has a larger influence on the cycle number, while the embossing shape has a more remarkable influence on the wrinkling degree of the winding core, wherein the anti-wrinkling performance and the cycle number of the winding core are remarkably superior to those of other shapes by adopting the concave embossing of a sphere, an octagon or a dodecagon, and the rate performance of the battery core is also better.
Experimental example 3: embossing depth test
The same pole piece and winding core as in example 1 in structure and size were used, except that: the thickness of the positive electrode sheet is 200 mu m (first coating area), and the thickness of the sheet in the second coating area 2 is 190 mu m; the concave embossing depths are different; the cell wrinkling degree and cycle number (25 ℃, 80% soh) of the core were measured (average of 20 samples per group) and the results were as follows:
Figure DEST_PATH_IMAGE006
as can be seen from the result of experimental example 3, the embossing depth has a significant effect on the wrinkling degree and the cycle number of the winding core, wherein when the embossing depth exceeds 10% of the pole piece, the pole piece overpressure (exceeding the upper compaction limit of the material) performance of the embossing area is obviously reduced; when the embossing depth is lower than 5% of the thickness of the pole piece, the cell folds are improved to a certain extent, but the improvement of the cycle performance is not obvious; when the embossing depth of the normal coating area is 5-10% of the thickness of the pole piece, and when the embossing depth of the very coating area is 5-8% of the thickness of the pole piece, the embossing depth reduces the wrinkling degree of the battery cell and obviously improves the cycle performance.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (11)

1. The anti-wrinkling coiled positive electrode plate is characterized by comprising a positive electrode current collector (4) and a positive electrode material layer (5) covered on the positive electrode current collector; the positive electrode material layer (5) is divided into a first coating area (1) and a second coating area (2), and the thickness of the second coating area (2) is smaller than that of the first coating area (1); the second coating area (2) corresponds to a bending part of the positive pole sheet during winding; the widths of the first coating area (1) and the second coating area (2) are gradually increased along the winding direction at the winding starting position of the positive electrode level sheet; the positive electrode material layer (5) is further provided with concave embossing (3), the depth of the concave embossing (3) in the first coating area (1) is 5-10% of the thickness of the corresponding pole piece, and the depth of the concave embossing (3) in the second coating area (2) is 5-8% of the thickness of the corresponding pole piece.
2. The coiled positive electrode sheet according to claim 1, characterized in that the positive electrode sheet thickness of the second coating zone (2) is 90-95% of the positive electrode sheet thickness of the first coating zone (1).
3. The coiled positive electrode sheet according to claim 1, characterized in that the positive electrode material layer (5) has a thickness of 50-300 μm; and/or the thickness of the positive electrode current collector (4) is 3-30 mu m.
4. The wound positive-electrode sheet according to claim 1, characterized in that the thickness of the second coating zone (2) increases gradually in the positive-electrode sheet winding direction.
5. Wound positive electrode sheet according to any one of claims 1 to 4, characterized in that the concave embossing (3) is of the sphere, octagon or dodecagon type.
6. A method of preparing the wrinkle-resistant rolled positive electrode sheet of any one of claims 1 to 5, comprising the steps of:
(1) Coating the positive electrode slurry on two sides of a positive electrode current collector to form a positive electrode coating, so as to obtain a positive electrode sheet semi-finished product;
(2) And carrying out cold pressing treatment and embossing treatment on the semi-finished positive pole piece to obtain a coiled positive pole piece finished product.
7. The method according to claim 6, wherein in the step (2), the pressure of the cold pressing treatment is 0.1 to 0.35mpa.
8. The method according to claim 6 or 7, wherein in the step (2), the embossing treatment is a segmented embossing, the embossing pressure in the first coating region is 0.2 to 0.65mpa, and the embossing pressure in the second coating region is 0.05 to 0.55mpa.
9. An anti-wrinkling winding type winding core comprises a winding needle (9) and a positive pole piece (6), a negative pole piece (8) and a diaphragm (7) which are wound on the winding needle (9); the diaphragm (7) is arranged between the positive electrode plate (6) and the negative electrode plate (7); the positive electrode plate (6) is characterized by being a fold-preventing coiled positive electrode plate according to any one of claims 1-5.
10. The wrinkle-preventing wound core according to claim 9, characterized in that the width dn = d1+ (n-1) x (a+b+c) of the first coating zone (1) on the positive current collector (4); the width ln=l1+3.14×n (a+b+c) of the very coated region (2); wherein d1 is the width of the positive pole piece wound for the first circle; l1=0 to 1mm; n is the number of winding layers; a is the thickness of the positive electrode plate; b is the thickness of the negative electrode plate; c is the membrane thickness.
11. The wrinkle-preventing winding core according to claim 9 or 10, characterized in that the thickness of the positive pole piece (6) is 10-800 μm; and/or the thickness of the negative electrode plate (8) is 10-800 mu m; and/or the thickness of the diaphragm (7) is 3-50 mu m.
CN202211573949.1A 2022-12-08 2022-12-08 Anti-wrinkling winding type positive electrode plate, preparation method thereof and winding core Pending CN116259707A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024120492A1 (en) * 2022-12-08 2024-06-13 湖北亿纬动力有限公司 Winding-type positive electrode sheet and preparation method therefor, and winding core

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024120492A1 (en) * 2022-12-08 2024-06-13 湖北亿纬动力有限公司 Winding-type positive electrode sheet and preparation method therefor, and winding core

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