CN113745450A - Thick electrode structure of lithium ion battery - Google Patents

Thick electrode structure of lithium ion battery Download PDF

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Publication number
CN113745450A
CN113745450A CN202110886214.3A CN202110886214A CN113745450A CN 113745450 A CN113745450 A CN 113745450A CN 202110886214 A CN202110886214 A CN 202110886214A CN 113745450 A CN113745450 A CN 113745450A
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coating
electrode
current collector
thickness direction
slurry
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陈素娜
马华
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Tianjin EV Energies Co Ltd
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Tianjin EV Energies 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/78—Shapes other than plane or cylindrical, e.g. helical
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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

Abstract

The invention provides a thick electrode structure of a lithium ion battery, which comprises a coating machine die head, wherein a gap between a coating die head lip and a current collector is formed between the coating machine die head and a negative current collector, the coating machine die head is provided with a plurality of coating machine die head cavities, each cavity is not communicated with each other, different components of negative electrode slurry are extruded from a slit of the coating machine die head lip, the different components of negative electrode slurry are wet-coated on the current collector while being formed, non-tab side blank and tab side blank are respectively arranged on two sides of a coating layer of a rolled pole roll, electrode thickness direction grooves are arranged in the electrode thickness direction, groove gaps are arranged among the grooves in the electrode thickness direction, and an electrode thickness direction groove is arranged on the surface of each pole piece. The thick electrode structure of the lithium ion battery is beneficial to the infiltration of electrolyte from the surface of the dressing layer to the direction of the current collector, improves the binding force between the dressing layer and the current collector, the multiplying power and the cycle performance of the thick electrode battery, and reduces the risk of lithium precipitation under high-multiplying-power charging and discharging.

Description

Thick electrode structure of lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion power battery production, and particularly relates to a thick electrode structure of a lithium ion battery.
Background
With the gradual maturity of the technical development of lithium ion batteries, the national policy continuously supports and promotes the technical development of new energy industry, and the new energy automobile industry has higher and higher requirements on high energy density, high power and light weight of lithium ion batteries. At present, the method for improving the energy density of the lithium ion battery is to increase the volume of a cell structure design space from the structural design angle so as to increase the total amount of active substances; secondly, from the electrochemical design angle, the proportion of inactive material components is reduced, and the proportion of active materials in the electrode is improved; and thirdly, from the design angle of a material system, the thickness of the current collector is reduced or the proportion of the active substance to the current collector (copper and aluminum foil) is increased, namely the coating amount of the electrode is increased. However, with the increase of the thickness of the electrode, the stripping force of the pole piece is poor, the pore distribution is uneven, and meanwhile, the difficulty of the electrolyte permeating from the interface of the diaphragm and the dressing layer to the interface of the dressing layer and the current collector is increased, so that the lithium precipitation of the battery at a high-rate negative electrode is easily caused due to the fact that the electrolyte does not completely soak the electrode, and potential safety hazards are generated. In addition, the tortuosity of the pole piece is increased, the ion transmission path is lengthened, the ionic and electronic conductivity is reduced, the DCR is increased, and the multiplying power and the cycle performance are deteriorated. Therefore, how to construct a novel electrode structure of a thick electrode of a lithium ion battery is important, the DCR of the battery is reduced, the risk of lithium precipitation during charging at a high rate is reduced, and the rate and the cycle performance of the battery are improved.
The electrode structure of the existing thick electrode is mostly the electrode structure with single-component slurry, which increases the single-layer coating amount, improves the proportion of active substances of the single-component slurry, or prepares slurry with a porous channel conductive agent such as directional carbon fiber or magnetic hollow carbon fiber and the like, and constructs the single porosity and pore diameter with larger porosity and pore diameter. The electrode structures of the thick electrodes are all single in porosity and pore size, and the electrode structures with low tortuosity, high porosity and high conductivity are constructed by increasing the proportion of active substances or adding a conductive agent with porous channels, such as oriented carbon fibers or magnetic hollow carbon fibers, from the viewpoint of improving the surface density of the electrodes and from the viewpoint of preparing electrode slurry. The design of the electrode with single porosity and pore diameter structure increases the single-layer coating amount, reduces the proportion of active substances, adds the porous channel conductive agent, and has the advantages that the baking temperature of the pole piece is high along with the increase of the thickness of the electrode, the adhesive and the conductive agent float upwards along with the solvent, the stripping force of the pole piece is poor, and the distribution of the conductive agent and pores is uneven; in order to improve the energy density of the battery, the coating amount of the electrode is increased simply from the angle of improving the surface density of the electrode, the thickness of the electrode is increased, the porosity tortuosity of a pole piece is increased, and the infiltration of electrolyte of a thick electrode is more difficult.
Disclosure of Invention
In view of the above, the present invention is directed to a thick electrode structure of a lithium ion battery, so as to implement multi-layer wet coating of multi-component slurry to construct a multi-layer coated thick electrode.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a thick electrode structure of a lithium ion battery comprises a coating machine die head, a negative current collector, a dressing layer, a pole piece, a pole lug and a current collector, a gap between the coating die head lip and the current collector is formed between the coating machine die head and the negative current collector, the coating machine die head is provided with a plurality of coating machine die head cavities, each cavity is not communicated with each other, the negative electrode slurry with different components is extruded from a slit of a die head lip of a coating machine, the negative electrode slurry with different components is formed through a gap between the coating die head lip and a current collector and is simultaneously wet-coated on the current collector, a coating layer of a rolled pole piece is provided with non-pole lug side blank and pole lug side blank on two sides respectively, grooves in the thickness direction of the electrode are arranged along the thickness direction of the electrode, groove gaps are arranged among the grooves in the thickness direction of the electrode, the pole lug is positioned at one end of the pole piece, and the surface of each pole piece is provided with grooves in the thickness direction of the electrode; the current collector is arranged in the middle of the dressing layer.
Furthermore, the multi-component negative electrode slurry utilizes a multi-layer coating mode to construct a multi-stage pore structure with small to large porosity and pores from the current collector to the surface of the dressing layer.
Further, the coating sequence from the current collector to the surface of the dressing layer is conventional slurry with gradually increased particle size.
Further, the particle size ranges are: d50 ═ 13.5 ± 2um to 14.5 ± 2um, and the uppermost layer was a large-particle size slurry of a secondary fluid to which 2 ± 0.5% octanol, an active resin, and a paraffin oil capillary suspension were added.
Further, the particle size range of the large particle size slurry of the secondary fluid is as follows: d50 ═ 14.5 ± 2 um.
Furthermore, the thickness of the single-side coating coated by the sizing agents with different particle sizes is 37-45um, 37-49um, 42-59um and 47-69um, and the single-side surface density is 3.77-5.02mg/cm2, 3.77-5.02mg/cm2, 4.28-6.05mg/cm2 and 4.8-7.08mg/cm 2.
Further, the width range of the gap between the die head lip of the coating machine and the current collector is 100-250 um.
Furthermore, grooves in the thickness direction of the electrode are respectively formed in the coating layers on the two sides of the current collector on the surface of the electrode roll along the thickness direction of the electrode by using a laser generator such as ultrashort pulse or low-temperature ultraviolet light.
Furthermore, the groove depth of the groove in the thickness direction of the electrode is 1/3-2/3 of the thickness of the electrode, and the groove width range is as follows: 35-50 um.
Compared with the prior art, the thick electrode structure of the lithium ion battery has the following advantages:
(1) according to the thick electrode structure of the lithium ion battery, the multi-stage pore structure with the porosity and the pore diameter from the current collector to the surface of the dressing layer from small to large is constructed in a multi-layer coating mode, so that the electrolyte can be infiltrated from the surface of the dressing layer to the current collector, the binding force between the dressing layer and the current collector is improved, the multiplying power and the cycle performance of the thick electrode battery are improved, and the lithium precipitation risk under high-power charging and discharging is reduced.
(2) According to the thick electrode structure of the lithium ion battery, the grooves are respectively constructed in the thickness direction of the coating layers on the two sides of the current collector by using the laser generators such as ultrashort pulse or low-temperature ultraviolet light, so that a permeation channel is provided for the electrolyte infiltration of the thick electrode, the electrochemical impedance spectrum EIS is reduced, the capacity of the battery is favorably exerted, and the lithium precipitation risk of high-rate charge and discharge is reduced; compared with the method for constructing the thick electrode groove by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, the method for constructing the groove by rolling the etching roller reduces the damage to the electrode structure and improves the uniformity of the electrode pore structure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow profile under minimum wet film thickness constraints for multiple layers according to an embodiment of the present invention;
FIG. 2 is a schematic plan view of a laser groove processing of a rolled pole piece according to an embodiment of the present invention;
fig. 3 is a schematic cross-sectional view of a laser groove processing of a rolled pole piece according to an embodiment of the present invention.
Description of reference numerals:
1-a coating machine die head; 2-coating the gap between the lip of the die head and the current collector; 3-a die head cavity of a coating machine I; 4-coating machine die head cavity; 5-third coating machine die head cavity; 6-first negative electrode slurry coating; 7-a second negative electrode slurry coating; 8-a third negative electrode slurry coating; 9-a negative current collector; 10-a dressing layer; 11-leaving white on the non-tab side; 12-leaving white on the side of the tab; 13-cutting the bottom edge of the pole piece; 14-electrode thickness direction trenches; 15-trench gaps; 16-pole piece; 17-a tab; 18-current collector.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
A thick electrode structure of a lithium ion battery is shown in figures 1 to 3 and comprises a coating machine die head 1, a first coating machine die head cavity 3, a second coating machine die head cavity 4, a third coating machine die head cavity 5, a first negative electrode slurry coating 6, a second negative electrode slurry coating 7, a third negative electrode slurry coating 8, a negative electrode current collector (copper foil) 9, a dressing layer 10, a non-tab side margin 11, a tab side margin 12, a pole piece cutting bottom edge 13, a pole piece 16, a tab 17 and a current collector 18, wherein a gap 2 between a coating die head lip and the current collector is formed between the coating machine die head 1 and the negative electrode current collector 9, the coating machine die head 1 is provided with a plurality of coating machine die head cavities, each cavity is not communicated with each other, different-component negative electrode slurry is extruded from the coating machine die head lip slit, and wet coating is carried out on the current collector 18 while different-component negative electrode slurry is formed after passing through the gap 2 between the coating die head lip and the current collector, the two sides of a dressing layer 10 of the rolled pole coil are respectively provided with a non-pole lug side margin 11 and a pole lug side margin 12, grooves 14 in the thickness direction of the pole are arranged along the thickness direction of the pole, a groove gap 15 is arranged between the grooves 14 in the thickness direction of the pole, a pole lug 17 is positioned at one end of a pole piece 16, and the surface of each pole piece 16 is provided with the grooves 14 in the thickness direction of the pole; a current collector 18 is arranged in the middle of the dressing layer 10.
Specifically, the coating machine die head 1 is provided with a plurality of die cavities, namely a first coating machine die head cavity 3, a second coating machine die head cavity 4 and a third coating machine die head cavity 5 …, the plurality of cavities are not communicated with each other, and the negative electrode slurry with different components is extruded from slits of lips of different cavities, so that the negative electrode slurry with different components is simultaneously and wetly coated on the current collector 18; the coating sequence from the current collector 18 to the surface of the dressing layer 10 is that the conventional slurry with gradually increased particle size (the particle size D50 is 13.5 +/-2 um-14.5 +/-2 um), the uppermost layer is large-particle size slurry (the particle size D50 is 14.5 +/-2 um) added with secondary fluid of capillary suspension such as 2 +/-0.5% of octanol, active resin and paraffin oil, and a multistage pore structure with small-to-large surface porosity and pores from the current collector 18 to the dressing layer 10 is constructed by a multilayer coating mode.
The rolled polar roll consists of the width of a dressing layer 10, non-polar-lug-side blank 11 and polar-lug-side blank 12, grooves 14 (namely pore channels for electrolyte permeation) in the electrode thickness direction are formed in the rolled polar roll by utilizing a laser generator such as ultra-short pulse or low-temperature ultraviolet, and the like, groove gaps 15 are formed among the grooves 14 in the electrode thickness direction, and the rolled polar roll with the grooves in the electrode thickness direction is obtained; and cutting the rolled pole piece roll with the grooves in the thickness direction of the electrode, cutting off the bottom edge, and performing die cutting to obtain the formed pole piece 16.
The coating machine die head 1 is provided with a plurality of die cavities, so that the cathode slurry with different components can be simultaneously wet-coated on the current collector, and a multilayer coating thick electrode is constructed; the multi-layer coating mode is utilized to construct a multistage pore structure with porosity and pore diameter from the current collector to the surface of the dressing layer from small to large, so that the electrode density and the binding force between the dressing layer and the current collector are improved, the infiltration of electrolyte from the surface of the dressing layer to the direction of the current collector is facilitated, the multiplying power and the cycle performance of the battery are improved, and the risk of lithium precipitation under high-power charging and discharging is reduced; after rolling, grooves in the thickness direction of the electrode are formed in the pole roll by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, a groove gap is formed between every two grooves, a pore channel for electrolyte permeation is constructed, the tortuosity of a pole piece is reduced, a lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR and EIS electrochemical impedance of the battery is reduced, the capacity of the battery is improved, the improvement of the electrolyte wettability of a thick electrode is facilitated, and the lithium precipitation risk under high-rate charging and discharging is reduced. Compared with a mode of rolling the pole piece by using an etching roller to construct the groove, the method reduces the damage of the electrode pore structure, improves the uniformity of the electrode pore structure and the uniformity of current density distribution, and reduces the risk of lithium precipitation by high-rate charging and discharging.
Gaps 2 (approximately 100-250 um) between die head lips of the coating machine and a current collector are formed between the die head 1 of the coating machine and the current collector (the thickness of copper foil is 8 +/-1 um)9 of the negative electrode, and the negative electrode slurry with different components is extruded from the slits of the die head lips of the coating machine to form wet coatings of the negative electrode slurry with different components;
preferably, the different-component negative electrode slurry is composed of conventional slurry with gradually increased particle size (the particle size D50 is 12.5 ± 2um, 13.5 ± 2um, 14.0 ± 2um, 14.5 ± 2um) and large-particle size slurry (the particle size D50 is 14.5 ± 2um) added with secondary fluid of capillary suspension of 2 ± 0.5% octanol, active resin, paraffin oil, etc., the slurry with different particle size is coated with single-side coating thickness of 37-45um, 37-49um, 42-59um, 47-69um, and single-side surface density of 3.77-5.02mg/cm2, 3.77-5.02mg/cm2, 4.28-6.05mg/cm2, 4.8-7.08mg/cm2, which correspond to the first negative electrode slurry coating 6, the second negative electrode slurry coating 7, and the third negative electrode slurry coating 8 … …, respectively.
As shown in fig. 2 and fig. 3, the rolled pole roll consists of a dressing layer 10 (width of the dressing layer is 284 +/-1.0 mm, thickness of the dressing layer is 364 +/-3 um, and coated double-sided surface density is 36.32 +/-0.4 mg/cm2), a non-pole ear side white space 11 and a pole ear side white space 12; grooves 14 (the groove depth is 1/3-2/3 of the electrode thickness, and the groove width is 35-50um) in the electrode thickness direction are respectively formed in the coating layers 10 on the two sides of the current collector 18 on the surface of the polar roll along the electrode thickness direction by using a laser generator of ultrashort pulse or low-temperature ultraviolet and the like, and a groove gap 15 is formed between the grooves 14 in the electrode thickness direction; the electrode roll is cut firstly, the cut bottom edge 13 of the electrode sheet is cut off, then die cutting is carried out, the electrode sheet 16 (length and width (270 +/-0.3) × (98 +/-0.3) mm) is obtained, the electrode tab 17 is positioned at one end of the electrode sheet 16, and the surface of each electrode sheet 16 after die cutting is ensured to be provided with a groove 14 in the electrode thickness direction, so that the tortuosity of the electrode sheet 14 is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the electrolyte wettability of a thick electrode is improved, the impregnation time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
The method comprises the following specific implementation steps:
with negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector form gap 2 (about 200um) between 1 lip of coating machine die head and the mass collector 9, three kinds of different component negative pole thick liquids are from three cavity: after being extruded by lips of a die head cavity 3 of a first coating machine, a die head cavity 4 of a second coating machine and a die head cavity 5 of a third coating machine, the three-layer wet coating of the negative electrode slurry with different components is realized through a gap 2 between the lips of the die head of the coating machine and a current collector, the wet coating with the third-level porosity and the pore structure is favorable for the infiltration of electrolyte from the surface of a coating layer 10 to the direction of the current collector 18, and the bonding force between the coating layer 10 and the current collector 18 is improved, so that the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under high-multiplying-power charging and discharging is reduced;
the three groups of different-component negative electrode slurry are composed of a first negative electrode slurry coating 6 (single-side coating thickness 49um, single-side coating surface density 5.02mg/cm2) formed by small-particle-size conventional slurry (particle size D50 ═ 13.5um), a second negative electrode slurry coating 7 (single-side coating thickness 59um, single-side coating surface density 6.05mg/cm2) formed by large-particle-size conventional slurry (particle size D50 ═ 14.0um), and a third negative electrode slurry coating 8 (single-side coating thickness 69um, single-side coating surface density 7.08mg/cm2) formed by large-particle-size slurry (particle size D50 ═ 14.5um) added with 2% of secondary fluid of capillary suspension such as octanol, active resin and paraffin oil;
Coating three types of negative electrode slurry with different components on a current collector 18 to obtain a coated electrode roll, wherein a coating layer 10 (the width of the coating layer is 284mm, the thickness of the coating layer is 364um, and the density of the coated double-sided surface is 36.32mg/cm2) and non-tab side white spots 11 and tab side white spots 12 on two sides of the coating layer are coated;
rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 1/2 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction;
the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Example 1
With negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector form gap 2 (about 200um) between 1 lip of coating machine die head and the mass collector 9, three kinds of different component negative pole thick liquids are from three cavity: after being extruded by lips of a die head cavity 3 of a first coating machine, a die head cavity 4 of a second coating machine and a die head cavity 5 of a third coating machine, the three-layer wet coating of the negative electrode slurry with different components is realized through a gap 2 between the lips of the die head of the coating machine and a current collector, the wet coating with the third-level porosity and the pore structure is favorable for the infiltration of electrolyte from the surface of a coating layer 10 to the direction of the current collector 18, and the bonding force between the coating layer 10 and the current collector 18 is improved, so that the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under high-multiplying-power charging and discharging is reduced;
the three groups of different-component negative electrode slurry are composed of a first negative electrode slurry coating 6 (single-side coating thickness 49um, single-side coating surface density 5.02mg/cm2) formed by small-particle-size conventional slurry (particle size D50 ═ 13.5um), a second negative electrode slurry coating 7 (single-side coating thickness 59um, single-side coating surface density 6.05mg/cm2) formed by large-particle-size conventional slurry (particle size D50 ═ 14.5um), and a third negative electrode slurry coating 8 (single-side coating thickness 69um, single-side coating surface density 7.08mg/cm2) formed by large-particle-size slurry (particle size D50 ═ 14.5um) added with 2% of secondary fluid of capillary suspension such as octanol, active resin and paraffin oil;
The particle size of the negative electrode material of the large-particle-size conventional slurry forming the second negative electrode slurry coating 7 is increased from D50-14.0 um to D50-14.5 um, and the particle size of the layer 2 material from the current collector 18 to the surface of the dressing layer 10 is increased, so that the porosity and the pore size of the dressing layer are increased, the electrolyte wettability of a thick electrode is improved, the electrolyte wetting time is shortened, the multiplying power and the cycle performance of the battery are improved, and the lithium precipitation risk under high-multiplying-power charging and discharging is reduced; coating three types of negative electrode slurry with different components on a current collector 18 to obtain a coated electrode roll, wherein a coating layer 10 (the width of the coating layer is 284mm, the thickness of the coating layer is 364um, and the density of the coated double-sided surface is 36.32mg/cm2) and non-tab side white spots 11 and tab side white spots 12 on two sides of the coating layer are coated;
rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 1/2 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction; the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Example 2
With negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector form gap 2 (about 200um) between 1 lip of coating machine die head and the mass collector 9, three kinds of different component negative pole thick liquids are from three cavity: after being extruded by lips of a die head cavity 3 of a first coating machine, a die head cavity 4 of a second coating machine and a die head cavity 5 of a third coating machine, the three-layer wet coating of the negative electrode slurry with different components is realized through a gap 2 between the lips of the die head of the coating machine and a current collector, the wet coating with the third-level porosity and the pore structure is favorable for the infiltration of electrolyte from the surface of a coating layer 10 to the direction of the current collector 18, and the bonding force between the coating layer 10 and the current collector 18 is improved, so that the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under high-multiplying-power charging and discharging is reduced;
the three groups of different-component negative electrode slurry are composed of a first negative electrode slurry coating 6 (single-side coating thickness is 45um, single-side coating surface density is 5.02mg/cm2) formed by small-particle-size conventional slurry (particle size D50 is 12.5um), a second negative electrode slurry coating 7 (single-side coating thickness is 59um, single-side coating surface density is 6.05mg/cm2) formed by large-particle-size conventional slurry (particle size D50 is 14.0um), and a third negative electrode slurry coating 8 (single-side coating thickness is 69um, single-side coating surface density is 7.08mg/cm2) formed by large-particle-size slurry (particle size D50 is 14.5um) added with secondary fluid of capillary suspension such as 2% of octanol, active resin and paraffin oil;
The particle size of the negative electrode material of the small-particle-size conventional slurry forming the first negative electrode slurry coating 6 is reduced from D50-13.5 um to D50-12.5 um, the particle size of the current collector 18 and the dressing layer 10 close to the current collector, namely the material particle size of the first negative electrode slurry coating 6 is reduced, the binding power of the current collector 18 and the dressing layer 10 is improved, and the cycle performance of the battery is improved; coating three types of negative electrode slurry with different components on a current collector 18 to obtain a coated electrode roll, wherein a coating layer 10 (the width of the coating layer is 284mm, the thickness of the coating layer is 360um, and the density of the coated double-sided surface is 36.32mg/cm2) and non-tab side white margins 11 and tab side white margins 12 on two sides of the coating layer are coated;
rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 1/2 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction; the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Example 3
With negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector form gap 2 (about 200um) between 1 lip of coating machine die head and the mass collector 9, three kinds of different component negative pole thick liquids are from three cavity: after being extruded by lips of a die head cavity 3 of a first coating machine, a die head cavity 4 of a second coating machine and a die head cavity 5 of a third coating machine, the three-layer wet coating of the negative electrode slurry with different components is realized through a gap 2 between the lips of the die head of the coating machine and a current collector, the wet coating with the third-level porosity and the pore structure is favorable for the infiltration of electrolyte from the surface of a coating layer 10 to the direction of the current collector 18, and the bonding force between the coating layer 10 and the current collector 18 is improved, so that the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under high-multiplying-power charging and discharging is reduced;
the three groups of different-component negative electrode slurry are composed of a first negative electrode slurry coating 6 (single-side coating thickness 49um, single-side coating surface density 5.02mg/cm2) formed by small-particle-size conventional slurry (particle size D50 ═ 13.5um), a second negative electrode slurry coating 7 (single-side coating thickness 59um, single-side coating surface density 6.05mg/cm2) formed by large-particle-size conventional slurry (particle size D50 ═ 14.0um), and a third negative electrode slurry coating 8 (single-side coating thickness 69um, single-side coating surface density 7.08mg/cm2) formed by large-particle-size slurry (particle size D50 ═ 14.5um) added with 2% of secondary fluid of capillary suspension such as octanol, active resin and paraffin oil;
Coating three types of negative electrode slurry with different components on a current collector 18 to obtain a coated electrode roll, wherein a coating layer 10 (the width of the coating layer is 284mm, the thickness of the coating layer is 364um, and the density of the coated double-sided surface is 36.32mg/cm2) and non-tab side white spots 11 and tab side white spots 12 on two sides of the coating layer are coated;
rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 2/3 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction; the depth of the grooves 14 in the thickness direction of the electrode is increased from 1/2 of the thickness of the electrode to 2/3, the width of the grooves and the gaps of the grooves arranged among the grooves are unchanged, the difficulty of thick electrode electrolyte infiltration is reduced, the electrolyte infiltration is improved, the multiplying power and the cycle performance of the battery are improved, and the risk of lithium precipitation of a negative electrode under high-multiplying-power charging and discharging is reduced; the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Example 4
With negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector form gap 2 (about 200um) between 1 lip of coating machine die head and the mass collector 9, three kinds of different component negative pole thick liquids are from three cavity: after being extruded by lips of a die head cavity 3 of a first coating machine, a die head cavity 4 of a second coating machine and a die head cavity 5 of a third coating machine, the three-layer wet coating of the negative electrode slurry with different components is realized through a gap 2 between the lips of the die head of the coating machine and a current collector, the wet coating with the third-level porosity and the pore structure is favorable for the infiltration of electrolyte from the surface of a coating layer 10 to the direction of the current collector 18, and the bonding force between the coating layer 10 and the current collector 18 is improved, so that the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under high-multiplying-power charging and discharging is reduced; the three groups of different-component negative electrode slurry are composed of a first negative electrode slurry coating 6 (single-side coating thickness 49um, single-side coating surface density 5.02mg/cm2) formed by small-particle-size conventional slurry (particle size D50 ═ 13.5um), a second negative electrode slurry coating 7 (single-side coating thickness 59um, single-side coating surface density 6.05mg/cm2) formed by large-particle-size conventional slurry (particle size D50 ═ 14.0um), and a third negative electrode slurry coating 8 (single-side coating thickness 69um, single-side coating surface density 7.08mg/cm2) formed by large-particle-size slurry (particle size D50 ═ 14.5um) added with 2% of secondary fluid of capillary suspension such as octanol, active resin and paraffin oil;
The addition proportion of the secondary fluid of the capillary suspension such as octanol, active resin, paraffin oil and the like is increased from 2.0% to 2.3%, the formation of larger conductive agent aggregates among active substance particles is promoted, the filling density of the active substance particles is not reduced due to preferred orientation, and pores are enlarged, so that the total porosity of the coating layer is increased, a permeation channel is provided for the infiltration of electrolyte, the electrolyte infiltration of an electrode is improved, the multiplying power and the cycle performance of a battery are improved, and the lithium precipitation risk of high-multiplying-power charging and discharging is reduced; coating three types of negative electrode slurry with different components on a current collector 18 to obtain a coated electrode roll, wherein a coating layer 10 (the width of the coating layer is 284mm, the thickness of the coating layer is 364um, and the density of the coated double-sided surface is 36.32mg/cm2) and non-tab side white spots 11 and tab side white spots 12 on two sides of the coating layer are coated;
rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 1/2 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction; the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Example 5
With negative current collector 9 (copper foil thickness is 8um) upward roll, wear the area, through extrusion coating machine dorsal roll, make 1 lip of coating machine die head and negative current collector 9 between form coating machine die head lip and the current collector gap 2 (about 200um), four kinds of different component negative pole thick liquids are from four cavitys: after being extruded by the lips of the die head cavity 3 of the first coating machine, the die head cavity 4 of the second coating machine and the die head cavity 5 … … of the third coating machine, the four-layer wet coating of the negative electrode slurry with different components is realized through the gap 2 between the lips of the die head of the first coating machine and the current collector, so that a wet coating with four-stage porosity and pore structure from the current collector to the surface of the coating layer is formed, the wetting of electrolyte from the surface of the coating layer 10 to the direction of the current collector 18 is facilitated, the bonding force between the coating layer 10 and the current collector 18 is improved, the multiplying power and the cycle performance of a thick electrode battery are improved, and the risk of lithium precipitation under the high-rate charging and discharging is reduced;
the four different components of the negative electrode slurry are composed of a negative electrode slurry coating 1A (single-sided coating thickness 37um, single-sided surface density 3.77mg/cm2) composed of small-particle-size conventional slurry (particle size D50 ═ 13.5um) and a negative electrode slurry coating 1B (single-sided coating thickness 42um, single-sided surface density 4.28mg/cm2) composed of small-particle-size conventional slurry (particle size D50 ═ 14um) together to form a first negative electrode slurry coating 6, and a second negative electrode slurry coating 7 (single-sided coating thickness 47um, single-sided surface density 4.80mg/cm2) composed of large-particle-size conventional slurry (particle size D50 ═ 14.5um) composed of large-particle-size conventional slurry (particle size D50 ═ 14.5um) composed of secondary fluid added with capillary suspension such as 2% octanol, active resin, paraffin oil and the like to form a third negative electrode slurry coating 8 (single-sided coating thickness 52um, single-sided surface density 5.31mg/cm 2); the pore structure design of the electrode is changed from three-layer slurry wet coating to four-layer slurry wet coating, and the particle size of the active material particles of the cathode slurry of the second layer is larger than that of the active material particles of the cathode slurry of the first layer wet coating, so that the formation of the four-stage porosity and the pore structure is facilitated, a pore channel for multi-stage electrolyte permeation is formed, the wettability of the electrolyte is increased, the lithium precipitation risk of high-rate charge and discharge is reduced, and the rate and the cycle performance of the battery are improved; coating four kinds of negative pole slurry with different components on a current collector 18, and obtaining a coated pole roll by a coating layer (the width of the coating layer is 284mm, the thickness of the coating layer is 364um, and the density of the coated double-sided surface is 36.32mg/cm2)10 and non-pole ear side white margins 11 and pole ear side white margins 12 on two sides of the coating layer;
Rolling the coated pole roll to obtain a rolled pole roll, respectively arranging electrode thickness direction grooves 14 (the groove depth is 1/2 of the electrode thickness and the groove width is 42um) on the dressing layer 10 on two sides of the current collector 18 of the rolled pole roll along the electrode thickness direction by using a laser generator such as ultrashort pulse or low-temperature ultraviolet, and the like, and arranging groove gaps 15 among the electrode thickness direction grooves 14 to obtain the pole roll with the grooves along the electrode thickness direction; the pole roll with the grooves formed in the thickness direction of the electrode is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, the pole piece 16 (the length of the pole piece is 270mm, the width of the pole piece is 98mm) is obtained, the pole lug 17 is located at one end of the pole piece 16, it is guaranteed that the grooves 14 in the thickness direction of the electrode are formed in the surface of each pole piece 16 after die cutting, the tortuosity of the pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR of the battery is reduced, the wettability of electrolyte of the thick electrode is improved, the wetting time after liquid injection is shortened, and the lithium precipitation risk under high-rate charging and discharging is reduced.
Comparative example 1
The comparative example is a thick electrode structure of a lithium ion battery, comprising the following steps:
winding and threading a negative current collector 9 (the thickness of copper foil is 8um), extruding a back roller of the coating machine to form a gap 2 (about 200um) between a die head lip of the coating machine and the current collector between the die head lip of the coating machine and the negative current collector 9 (the thickness of copper foil is 8um), and after single-component negative slurry is extruded from the three cavity lips, realizing wet coating of the single-component negative slurry through the gap 2 between the die head lip of the coating machine and the current collector; the single-component negative electrode slurry is respectively extruded from the cavity of the die head 1 of the coating machine, a single-stage pore structure from the current collector 18 to the surface of the coating layer 10 is formed through the gap 2 between the lip of the die head of the coating machine and the current collector, the electrolyte is difficult to infiltrate from the surface of the coating layer 10 to the direction of the current collector 18, the adhesive force between the coating layer 10 and the current collector 18 is poor, the multiplying power and the cycle performance of the thick electrode battery are reduced, and the risk of lithium precipitation is high under the high-multiplying power charging and discharging; coating the single-component negative electrode slurry on a current collector 18, and obtaining a coated pole coil by a coating layer 10 (the coating width is 284mm, the coating thickness is 364 mu m, and the coating surface density is 36.32mg/cm2) and non-pole-tab side white margins 11 and pole-tab side white margins 12 on two sides of the coating layer; the coated pole roll is firstly cut, the pole piece cutting bottom edge 13 is cut off, then die cutting is carried out, a pole piece 16 (the pole piece length is 270mm, the pole piece width is 98mm) is obtained, a pole lug 17 is located at one end of the pole piece 16, the pole piece tortuosity of a thick electrode is increased, the lithium ion transmission path is long, the electronic conductivity is low, the battery DCR is large, the electrolyte wettability is poor, the impregnation time after liquid injection is long, and the lithium precipitation risk exists in charging and discharging under high magnification.
From the data comparison of the preferred embodiment, the embodiments 1 to 5 and the comparative example 1, the adhesion of the pole piece, the first effect of the battery, the discharge capacity of 0.33C and the DCR, by using the novel electrode structure of the thick electrode of the lithium ion battery provided by the preferred embodiment and the embodiments 1 to 5, the die head 1 of the coating machine is provided with a plurality of die cavities which are not communicated with each other, so that the negative electrode slurry with different components is extruded from the slits of the lips of different cavities, and the multilayer wet coating of the negative electrode slurry with different components is realized; the multi-layer coating mode is utilized to construct a multistage pore structure with porosity and pore diameter from the current collector to the surface of the dressing layer from small to large, so that the wetting of electrolyte from the surface of the dressing layer to the current collector is facilitated, the binding force between the dressing layer and the current collector is improved, the multiplying power and the cycle performance of the battery are improved, and the risk of lithium precipitation under high-power charging and discharging is reduced; compared with the method of constructing the grooves by rolling the pole pieces by using a laser etching roller, the ultrashort pulse laser processing technology is provided with the grooves in the thickness direction of the electrodes, so that the damage to the pore structures of the electrodes is reduced, and the uniformity of the pore structures of the electrodes is improved; the porous channel for electrolyte permeation is constructed, so that the tortuosity of a pole piece is reduced, the lithium ion transmission path is shortened, the electronic conductivity is improved, the DCR and EIS electrochemical impedance of the battery is reduced, the capacity of the battery is improved, the electrolyte wettability of a thick electrode is improved, the wetting time after electrolyte injection is shortened, and the lithium precipitation risk under high-rate charge and discharge is reduced.
The pole piece adhesion, the first effect of the battery, the 0.33C discharge capacity, the DCR and the full-electricity disassembly interface of the soft-package lithium ion batteries of preferred examples, examples 1 to 5 and comparative example 1 were compared, and the specific results are shown in table 1.
Table 1 comparison of negative plate adhesion, porosity and cell electrical performance data
Figure BDA0003194215330000171
As can be seen from the data in table 1, the method of the preferred embodiment and examples 1 to 5 is used to construct a novel electrode structure of a thick electrode of a lithium ion battery, and the adhesion of a negative electrode sheet is respectively improved by 0.08, 0.06, 0.17, 0.11, 0.07 and 0.1N compared with the soft package lithium ion battery constructed by a conventional electrode structure; the porosity of the negative plate is respectively improved by 9.8%, 11.8%, 9.6%, 9.4%, 10.1% and 11.1%; the first effect is respectively improved by 0.2%, 0.5%, 0.3%, 0.8%, 0.4% and 0.4%; the discharge capacity is respectively improved by 0.3, 0.7, 0.4, 0.9, 0.4 and 0.5 Ah; the DCR is reduced by 0.06, 0.07, 0.05, 0.075, 0.07, 0.08 mOmega respectively.
Data helpful to understanding the present solution:
1. principle of extrusion coater:
the slurry is put into a storage tank, the screw pump enables the slurry to have certain pressure, the slurry passes through a filter and a feeding pipe to reach an intercoat valve, the slurry enters a die head through the action of the intercoat valve to be coated, or the slurry flows back to the storage tank through a reflux valve and a reflux pipe when the coating is stopped. When the coating machine is used for coating, the coating valve is opened, the reflux valve is closed, slurry with certain pressure is pushed into the die cavity from the feed inlet, and the slurry is sprayed on the metal base material through a gap of the die lip; when coating is stopped, the reflux valve is opened, the coating valve is closed, slurry stops spraying due to no feeding and no pressure in the die cavity, and the slurry flows back to the storage tank through the reflux valve; when the gap coating operation is carried out, the two actions are repeated, and the opening and closing time of the coating valve and the return valve determines the size of the coating area and the size of the blank area of the pole piece.
2. The electrochemical reaction process of the electrode:
electron flow: the electron conduction of the current collector and the coating interface is larger than the interface contact resistance;
electron transport in solid phase such as active material and conductive agent ═ conductivity
Lithium ion current: lithium ions in the electrolyte in the pores of the coating diffuse, migrate and the like;
diffusion of lithium ions in solid phase: SEI film, inside of active material particle
Interfacial charge exchange: the charge exchange at the interface of the electrolyte/electrode, the electron gain and loss, the lithium removal/insertion of the active substance, and the electrochemical reaction
3. Porosity of the pole piece coating:
porosity is the volume fraction of pores in the electrode coating, and is a relatively macroscopic concept, which can be calculated by the compacted density of the coating, the mass percentages of the components of the coating and the true density of the components of the coating. The porosity is mainly controlled by the rolling process, and the pores are filled with electrolyte and conduct lithium ions.
4. Pore tortuosity of the pole piece coating:
tortuosity: the difference in particle shape, which results in stacked pores, is mostly not straight-through pores, tortuosity is a weight-playing parameter describing the morphology of pores in porous media, physically defined as the ratio of the actual path length of a substance through the porous media to the media distance (thickness). The tortuosity of the pole piece is related to the porosity, the pore diameter and the distribution thereof, and the connectivity of the pores.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (9)

1. A lithium ion battery thick electrode structure is characterized in that: the coating layer of the rolled pole coil is provided with non-pole ear side white and pole ear side white respectively on two sides, electrode thickness direction grooves are arranged along the electrode thickness direction, groove gaps are arranged among the electrode thickness direction grooves, the pole ear is positioned at one end of the pole piece, and the surface of each pole piece is provided with the electrode thickness direction grooves; the current collector is arranged in the middle of the dressing layer.
2. The thick electrode structure of claim 1, wherein: the multi-layer coating method is characterized in that a multi-stage pore structure with small to large porosity and pores from a current collector to the surface of a dressing layer is constructed by using a plurality of negative electrode slurry with different components in a multi-layer coating mode.
3. The thick electrode structure of claim 2, wherein: the coating sequence from the current collector to the surface of the dressing layer is a conventional slurry with gradually increasing particle size.
4. The thick electrode structure of claim 3, wherein: the particle size range is as follows: d50 ═ 13.5 ± 2um to 14.5 ± 2um, and the uppermost layer was a large-particle size slurry of a secondary fluid to which 2 ± 0.5% octanol, an active resin, and a paraffin oil capillary suspension were added.
5. The thick electrode structure of claim 4, wherein: the particle size range of the large-particle size slurry of the secondary fluid is as follows: d50 ═ 14.5 ± 2 um.
6. The thick electrode structure of claim 2, wherein: the thickness of the single-side coating coated by the sizing agent with different particle sizes is 37-45um, 37-49um, 42-59um and 47-69um, and the single-side surface density is 3.77-5.02mg/cm2, 3.77-5.02mg/cm2, 4.28-6.05mg/cm2 and 4.8-7.08mg/cm 2.
7. The thick electrode structure of claim 1, wherein: the width range of the gap between the die head lip of the coating machine and the current collector is 100-250 um.
8. The thick electrode structure of claim 1, wherein: grooves in the thickness direction of the electrode are respectively formed on the surface of the electrode roll along the thickness direction of the electrode on the coating layers on the two sides of the current collector by using a laser generator such as ultrashort pulse or low-temperature ultraviolet light.
9. The thick electrode structure of claim 1, wherein: the groove depth of the groove in the thickness direction of the electrode is 1/3-2/3 of the thickness of the electrode, and the groove width range is as follows: 35-50 um.
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