CN111682162A - Battery pole piece and preparation method thereof - Google Patents

Battery pole piece and preparation method thereof Download PDF

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Publication number
CN111682162A
CN111682162A CN202010448633.4A CN202010448633A CN111682162A CN 111682162 A CN111682162 A CN 111682162A CN 202010448633 A CN202010448633 A CN 202010448633A CN 111682162 A CN111682162 A CN 111682162A
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coating
compaction
pole piece
density
low
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王忠明
崔云
王理
祝媛
刘建华
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Huizhou Yiwei Energy Battery Co ltd
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Huizhou Yiwei Energy Battery Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • 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
    • 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)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to the technical field of batteries, and discloses a battery pole piece and a preparation method thereof, wherein the preparation method comprises the following steps: coating the slurry on a current collector for the first time, drying, and then performing first rolling to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece; and coating the slurry on the high-compaction coating for the second time, drying, and then performing second rolling to form a low-compaction coating on the high-compaction coating, wherein the low-compaction coating and the prepared pole piece jointly form a battery pole piece. The battery pole piece prepared by the method can effectively reduce the internal resistance of the battery, improve the infiltration performance of electrolyte, increase the discharge capacity and improve the coulombic efficiency and the cycle performance while keeping the high energy density of the battery.

Description

Battery pole piece and preparation method thereof
Technical Field
The invention relates to the technical field of batteries, in particular to a battery pole piece and a preparation method thereof.
Background
The lithium ion battery is used as a secondary energy source, has the advantages of high energy density, high working voltage, wide working temperature range, small volume, light weight and the like, and is widely applied to the fields of digital equipment, power automobiles, energy storage and the like. In the application of lithium ion batteries, especially in electric vehicles, the energy density of the batteries is a major factor that restricts the development of lithium ion batteries. At present, researchers have made extensive studies on how to improve the energy density of lithium ion batteries, and the approaches mainly include the following means: 1. selecting battery materials with high performance: high-performance anode and cathode materials, light and thin or porous foils and diaphragms, high-voltage electrolytes, solid electrolytes and the like; 2. increasing the cut-off voltage and voltage window of the battery; 3. modifying the foil and the pole piece; 4. the coating thickness and the compaction density of the pole piece are improved.
Among them, increasing the coating thickness and the compaction density of the positive/negative electrode sheets is the most direct method for increasing the energy density of the battery. Thick electrodes and high compaction may increase the energy density of the cell to some extent. The energy density of the battery can be increased along with the increase of the coating thickness, but the problems of internal resistance increase, insufficient electrolyte infiltration and the like can be caused along with the increase of the coating thickness to a certain degree, so that the electrochemical performances of the battery such as cycle, multiplying power and the like can be reduced; and the lithium ions are difficult to be inserted and removed, the utilization rate of the anode and the cathode is reduced, and lithium precipitation of the cathode is easy to cause safety problems. Similarly, increasing the compaction density reduces contact resistance, thereby increasing conductivity, reducing electrochemical impedance, and within a certain range, reducing the thickness of the pole piece, and increasing the energy density of the battery. And too high compaction density blocks up the transmission channel of ions in the electrolyte, so that the resistance encountered by ion diffusion is increased, and the electrochemical properties such as multiplying power performance and the like of the lithium battery can be influenced.
At present, the traditional coating process is a one-time coating process, and the one-time coating process is adopted, because all the slurry is coated on the current collector at one time, the wet thickness of the slurry is large, and the drying temperature is required to be higher or the drying time is longer. Meanwhile, the rolling compounding of the pole piece in the one-time coating process is increased during rolling, and when high thickness and high compaction density are pursued, the phenomena of roll sticking, pole piece hardening and flexibility deterioration, surface curling unevenness, even fragment and chip breakage and the like easily occur under overhigh rolling pressure, so that the product quality is influenced. In order to solve the above problems, patent 201811287761.4 discloses a method for manufacturing a high-compaction-density pole piece of a lithium ion battery, which converts one-time coating into two-time or multiple-time coating, reduces the thickness of a single-time coating wet coating, reduces drying and rolling loads, can avoid the phenomena of roll sticking, poor hardening and flexibility of the pole piece, uneven surface curling and even fragment and chip breakage, and simultaneously improves compaction density by two-time or multiple-time rolling, and increases the volumetric specific energy of the battery. However, the method still cannot effectively solve the problems of increased internal resistance of the battery, poor electrolyte wetting performance, difficult lithium ion intercalation and deintercalation, reduced discharge capacity, poor cycle stability and the like caused by the high-thickness and high-compaction-density pole piece.
Disclosure of Invention
Aiming at overcoming the defects in the prior art, the invention mainly aims to provide a preparation method of a battery pole piece. The other purpose is to provide a battery pole piece prepared based on the method. The battery pole piece can effectively reduce the internal resistance of the battery, improve the infiltration performance of the electrolyte, increase the discharge capacity and improve the coulombic efficiency and the cycle performance while keeping the high energy density of the battery.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a battery pole piece comprises the following steps:
coating the slurry on a current collector for the first time, drying, and then performing first rolling to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece;
and coating the slurry on the high-compaction coating for the second time, drying, and then performing second rolling to form a low-compaction coating on the high-compaction coating, wherein the low-compaction coating and the prepared pole piece jointly form a battery pole piece.
In one embodiment, the slurry includes a positive/negative electrode active material, a conductive agent, and a binder; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150).
In one embodiment, when the battery pole piece is a negative pole piece, the density of the high-compaction coating is more than or equal to 1.5g/cm3The density of the low-compaction coating is less than or equal to 1.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
In one embodiment, when the battery pole piece is a positive pole piece, the density of the high compaction coating is more than or equal to 3.5g/cm3The density of the low-compaction coating is less than or equal to 3.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
In one embodiment, the thickness of the battery pole piece is 30 to 300 μm.
In one embodiment, when the battery pole piece is a negative pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm.
In one embodiment, when the battery pole piece is a positive pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm.
In one embodiment, the first coating and the second coating are applied in the same or different manners, and are one of extrusion coating, spray coating, and doctor blade coating.
In one embodiment, the first rolling and the second rolling are performed in the same or different manners, and are respectively cold pressing or hot pressing.
A battery pole piece is prepared by any one of the preparation methods.
Compared with the prior art, the invention has at least the following advantages:
the method adopts the methods of fractional coating and fractional rolling to ensure that the thickness and the compaction density of the battery pole piece are more flexible and controllable, wherein the first rolling is high compaction treatment, the second rolling is low compaction treatment, a double-layer structure formed by combining a high compaction coating and a low compaction coating is regulated and controlled, the density of the low compaction coating is lower, the porosity is higher, and the gap between positive/negative active material particles is larger; the high-compaction coating has high density and low porosity, and gaps among positive/negative active material particles are small; the low-compaction coating and the high-compaction coating are combined, so that the high energy density of the battery is maintained, the electrolyte infiltration performance can be improved, the internal resistance of a solid phase and a liquid phase is reduced, the lithium ions are easy to insert and separate, the transfer speed of the lithium ions in the pole piece is improved, the discharge capacity is increased, and the coulomb efficiency and the cycle performance are improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a flowchart illustrating steps of a method for manufacturing a battery electrode tab according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a battery pole piece according to an embodiment of the invention.
Fig. 3 is a graph comparing energy densities of the batteries of example 4, example 5 and comparative example 1 according to the present invention.
FIG. 4 is a graph showing the discharge cycle test of 1C/IC batteries at a temperature of 25 ℃ for the batteries of example 4, example 5 and comparative example 1 according to the present invention.
FIG. 5 is a graph showing discharge cycle test of 3C/0.5C cells at a temperature of 45 ℃ for the cells of example 4, example 5 and comparative example 1 according to the present invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In one embodiment, referring to fig. 1, a method for manufacturing a battery electrode plate includes the following steps:
s110, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150).
The content of the positive/negative electrode active material is related to the energy density of the battery, and the energy density of the battery can be improved by increasing the content of the positive/negative electrode active material within a certain range, but if the content of the positive/negative electrode active material is too high, the conductivity and the bonding performance of the slurry are obviously reduced, and even the positive/negative electrode active material falls off, so the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is preferably (90-98): 0.5-5): 45-150. For another example, the mass ratio of the positive/negative electrode active material, the conductive agent, and the binder is 94:2.5: 100. For another example, the mass ratio of the positive/negative electrode active material, the conductive agent, and the binder is 95:2.7: 98.
In still another embodiment, the positive/negative electrode active material may be a reagent conventionally used in the art, and may include at least one of graphite, Si/C, SiO/C, LiCO, LFP, NCM, NCA, and the like. The positive/negative electrode active material is related to the energy density of the battery, and SiO/C, LiCO, LFP, NCM, and NCA having excellent electrical properties are selected as the material of the positive/negative electrode active material, whereby a battery having a high energy density can be produced. As another example, the positive/negative electrode active material includes SiO/C. As another example, the positive/negative electrode active material includes LiCO.
In still another embodiment, the adhesive may be a reagent conventionally used in the art, and may be at least one of PVDF adhesive, SBR adhesive, PAA adhesive, CMC adhesive, and the like. The binder also relates to the energy density of the battery, and a battery having a high energy density can be produced by selecting an SBR binder, a PAA binder, and a CMC binder having excellent chemical properties as the materials of the binder. As another example, the binder includes an SBR binder. As another example, the adhesive comprises PVDF adhesive.
In still another embodiment, the conductive agent may be an agent conventionally used in the art, and may be at least one of conductive carbon, carbon fiber, carbon tube, and the like. The conductive agent is also related to the energy density of the battery, and conductive carbon, carbon fiber and carbon tube with excellent electrical properties are selected as the material of the conductive agent, so that the battery with high energy density can be prepared.
And S120, coating the slurry on a current collector for the first time, and rolling for the first time after drying to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
S130, coating the slurry on the high-compaction coating for the second time, drying, and then performing second rolling to form a low-compaction coating on the high-compaction coating, wherein the low-compaction coating and the prepared pole piece jointly form a battery pole piece.
On one hand, different from the traditional coating process, the method adopts the methods of multiple coating and multiple rolling, can reduce the thickness of the single-coating wet coating, enables the thickness of the single-coating slurry wet coating to be thinner than that of the single-coating slurry wet coating, reduces the single drying and rolling load, can avoid the phenomena of roller sticking, poor hardening and flexibility of a pole piece, uneven surface curling, broken piece, brittle piece and the like, and simultaneously improves the compaction density and increases the volumetric specific energy of the battery through the multiple rolling.
On the other hand, the method adopts a method of coating and rolling in a grading way to enable the thickness and the compaction density of the battery pole piece to be more flexible and controllable, wherein the first rolling in the step S120 is high compaction treatment, the second rolling in the step S130 is low compaction treatment, a double-layer structure formed by combining a high compaction coating and a low compaction coating is regulated and controlled, the density of the low compaction coating is lower, the porosity is higher, and the clearance between positive/negative active material particles is larger; the high-compaction coating has high density and low porosity, and gaps among positive/negative active material particles are small; the low-compaction coating and the high-compaction coating are combined, so that the high energy density of the battery is maintained, the electrolyte infiltration performance can be improved, the internal resistance of a solid phase and a liquid phase is reduced, the lithium ions are easy to insert and separate, the transfer speed of the lithium ions in the pole piece is improved, the discharge capacity is increased, and the coulomb efficiency and the cycle performance are improved.
Of course, the steps of first coating and first rolling may be repeated a plurality of times to form a multi-layered highly compacted coating according to actual requirements; or the steps of the second coating and the second rolling may be repeated a plurality of times to form a multi-layered low-compaction coating layer; or the steps of the first coating and the first rolling and the steps of the second coating and the second rolling can be alternately repeated for a plurality of times to form a plurality of layers of high-compaction coatings and a plurality of layers of low-compaction coatings, and the high-compaction coatings and the low-compaction coatings are alternately attached.
In one embodiment, when the battery pole piece is a negative pole piece, the density of the high-compaction coating is more than or equal to 1.5g/cm3The density of the low-compaction coating is less than or equal to 1.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3. It should be noted that, as the density of the high-compaction coating of the negative electrode sheet increases, the capacity retention rate of the battery increases and then decreases through a large number of experimental tests, because the compaction densities are different, the slurries have different porosities, and the higher the compaction density is, the tighter the contact between the active material particles is, the poorer and poorer the wettability of the electrode sheet becomes, thereby causing difficulty in the insertion and extraction of lithium ions, and increasing the polarization of the battery. However, as the density is compactedThe reduction can improve the wettability of the pole piece, but the contact between active material particles and between the active material particles and a current collector is poor, so that the electronic conductivity of the negative electrode is reduced, and even the active material particles fall off in the battery cycle process. After a large number of experimental tests, the density of the high-compaction coating is 1.6g/cm3～1.8g/cm3And when the density of the low-compaction coating is 1.2g/cm3～1.4g/cm3And when the lithium ion battery is used, the cycle performance and the rate performance of the lithium ion battery are optimal. The density of the highly densified coating is therefore preferably 1.6g/cm3～1.8g/cm3The density of the low-compaction coating is preferably 1.2g/cm3～1.4g/cm3. More preferably, the high-compaction coating has a density of 1.7g/cm3The density of the low-compaction coating is 1.3g/cm3。
In one embodiment, when the battery pole piece is a positive pole piece, the density of the high-compaction coating is more than or equal to 3.5g/cm3The density of the low-compaction coating is less than or equal to 3.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3. It should be noted that, after a lot of experimental tests, as the density of the high-compaction coating of the positive plate increases, the capacity retention rate of the battery increases and then decreases, and when the density of the high-compaction coating is 3.8g/cm3～4.0g/cm3And when the density of the low-compaction coating is 3.2g/cm3～3.4g/cm3And when the lithium ion battery is used, the cycle performance and the rate performance of the lithium ion battery are optimal. The density of the highly densified coating is therefore preferably 3.8g/cm3～4.0g/cm3The density of the low-compaction coating is preferably 3.2g/cm3～3.4g/cm3. More preferably, the high compaction coating has a density of 3.9g/cm3The density of the low-compaction coating is 3.3g/cm3。
In another embodiment, the thickness of the battery pole piece is 30 μm to 300 μm. The current collector is a foil material, and the thickness of the current collector is generally only 5-15 μm, so the thickness of the battery pole piece is mainly determined by the sum of the thicknesses of the high-compaction coating and the low-compaction coating. A large number of experimental tests prove that when the thickness of the battery pole piece is 30-300 mu m, the energy density and the coulombic efficiency of the battery are high. In another example, the thickness of the battery pole piece is 100 μm. In another example, the thickness of the battery pole piece is 200 μm.
For example, when the battery pole piece is a negative pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm. As another example, the high-compaction coating has a thickness of 120 μm and the low-compaction coating has a thickness of 50 μm. As another example, the high densified coating layer can have a thickness of 100 μm and the low densified coating layer can have a thickness of 30 μm. More preferably, the thickness of the high-compaction coating is 90 to 110 μm and the thickness of the low-compaction coating is 40 to 60 μm.
On one hand, when the slurry coating is too thin, the slurry coating and a current collector cannot be well compacted, the electrical contact is weak, the platform voltage is higher, and the cycle performance of the battery is reduced; when the slurry coating is too thick, the slurry coating is extruded, expansion is easy to occur, electrical contact with a current collector is easy to lose in the circulation process, the platform voltage is increased, and the circulation performance of the battery is reduced. Moreover, with the increase of the thickness of the slurry coating, the coating precision is reduced, so that the thicknesses of different positions of the pole piece are different, the internal resistance of the battery is gradually increased, and the consistency of the battery is gradually reduced. A large number of experimental tests prove that when the thickness of the high-compaction coating is 90-110 mu m and the thickness of the low-compaction coating is 40-60 mu m, the voltage of the pole piece platform is lower and the cycle performance of the battery is the best.
On the other hand, the slurry coating is too thin, the connection between active materials is weak, the internal resistance is low, the first lithium intercalation capacity is high, but lithium intercalation damages the weak connection between the active materials, gaps occur, the internal resistance is increased, the lithium deintercalation capacity is low, the first coulomb efficiency is low, and the gaps continue to become larger along with the circulation, so that the circulation stability is poor. The slurry coating is too thick, resulting in clumping together of active particles. The volume expansion changes greatly, the contact between the active material and the current collector is loosened and even falls off, and the cycle performance is deteriorated. Through a large number of experimental tests, when the thickness of the high-compaction coating is 90-110 μm and the thickness of the low-compaction coating is 40-60 μm, the discharge specific capacity of the battery is the highest, and the cycle performance of the battery is the best.
In summary, because the high-compaction coating has high density and the low-compaction coating has low density, the two coatings have different lithium ion transfer rates and have different influences on electrochemical properties such as energy density and cycle performance of the battery, the high-compaction coating and the low-compaction coating need to be reasonably regulated and controlled in density and thickness, and when the high-compaction coating is 30-200 μm and the low-compaction coating is 10-100 μm, the internal resistance of the battery can be effectively reduced, the electrolyte wettability can be improved, the discharge capacity can be increased, and the coulombic efficiency and the cycle performance can be improved while the high-energy density of the battery is maintained. Particularly, when the thickness of the high compaction coating is 90-110 μm and the thickness of the low compaction coating is 40-60 μm, the discharge specific capacity of the battery is the highest, and the cycle performance of the battery is the best.
Similarly, for example, when the battery pole piece is a positive pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm. As another example, the high-compaction coating has a thickness of 120 μm and the low-compaction coating has a thickness of 50 μm. As another example, the high densified coating layer can have a thickness of 100 μm and the low densified coating layer can have a thickness of 30 μm. More preferably, the thickness of the high-compaction coating is 90 to 110 μm and the thickness of the low-compaction coating is 40 to 60 μm.
In yet another embodiment, the first coating and the second coating are applied in the same or different manners, and are one of extrusion coating, spray coating and doctor blade coating. The coating method is conventional in the art, and the method of the present invention can be realized by adopting conventional methods by those skilled in the art. For another example, the first coating and the second coating are both spraying. For another example, the first coating mode is extrusion coating, and the second coating mode is doctor blade coating. Therefore, the coating effect is better, and the slurry coating is more uniform.
In still another embodiment, the first rolling and the second rolling are performed in the same or different manners, respectively, as cold pressing or hot pressing. The rolling is performed by conventional methods in the art, and the method of the present invention can be implemented by conventional methods by those skilled in the art. For another example, the first rolling and the second rolling are both hot pressing. For another example, the first rolling mode is hot pressing, and the second rolling mode is cold pressing. Thus, the rolling effect is better.
In another embodiment, the drying is a conventional method in the art, and those skilled in the art can implement the method of the present invention by using a conventional method.
Referring to fig. 2, a battery electrode plate is prepared by any one of the above-mentioned preparation methods. For example, the battery pole piece comprises a current collector, a high compaction coating and a low compaction coating, wherein the current collector is a metal current collector. For example, the current collector is a foil. In another example, the current collector is an aluminum foil. In another example, the current collector is a copper foil. The high-compaction coating is coated on one side of the current collector. The low compaction coating is coated on a side of the high compaction coating away from the current collector.
Of course, the high-compaction coat may be provided in multiple layers; or the low compaction coating can be provided in multiple layers; or the high compaction coating and the low compaction coating can be set to be multiple layers, and each high compaction coating and each low compaction coating are attached alternately.
When the battery pole piece is a negative pole piece, the thickness of the high-compaction coating is 30-200 mu m, and the thickness of the low-compaction coating is 10-100 mu m; the density of the high-compaction coating is more than or equal to 1.5g/cm3The density of the low-compaction coating is less than or equal to 1.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
For another example, when the battery pole piece is a positive pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is10-100 μm; the density of the high-compaction coating is more than or equal to 3.5g/cm3The density of the low-compaction coating is less than or equal to 3.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
The high-compaction coating and the low-compaction coating are formed by coating and rolling slurry, and the slurry comprises a positive/negative electrode active material, a conductive agent and a binder; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). For another example, the mass ratio of the positive/negative electrode active material, the conductive agent, and the binder is 94:2.5: 100. For another example, the mass ratio of the positive/negative electrode active material, the conductive agent, and the binder is 95:2.7: 98. As another example, the positive/negative electrode active material includes at least one of graphite, Si/C, SiO/C, LiCO, LFP, NCM, and NCA. In another example, the thickness of the battery pole piece is 30-300 μm.
Compared with the prior art, the invention has at least the following advantages:
the preparation process is simple, the industrial production is easy to realize, and the thickness and the compaction density of the battery pole piece are more flexible and controllable by adopting a method of fractional coating and fractional rolling, wherein the first rolling is high compaction treatment, the second rolling is low compaction treatment, a double-layer structure formed by combining a high compaction coating and a low compaction coating is regulated and controlled, the density of the low compaction coating is lower, the porosity is higher, and the clearance between positive/negative electrode active substance particles is larger; the high-compaction coating has high density and low porosity, and gaps among positive/negative active material particles are small; the low-compaction coating and the high-compaction coating are combined, so that the high energy density of the battery is maintained, the electrolyte infiltration performance can be improved, the internal resistance of a solid phase and a liquid phase is reduced, the lithium ions are easy to insert and separate, the transfer speed of the lithium ions in the pole piece is improved, the discharge capacity is increased, and the coulomb efficiency and the cycle performance are improved.
The battery pole piece of any one of the above embodiments can be applied to a lithium ion battery, but is not limited to the battery industry, and can also be applied to other industries.
The following are specific embodiments
Example 1
S111, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and S121, coating the slurry on a current collector for the first time, drying, and then carrying out cold pressing for the first time to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
S131, coating the slurry on the high-compaction coating layer for the second time, drying, and performing second rolling to form a low-compaction coating layer on the high-compaction coating layer, where the low-compaction coating layer and the prepared pole piece together form the battery pole piece of example 1. Wherein the thickness of the high compaction coating of the negative plate is 30 mu m, and the density of the high compaction coating is 1.5g/cm3. The thickness of the low compaction coating of the negative plate is 10 mu m, and the density of the low compaction coating is 1.4g/cm3. The thickness of the high compaction coating of the positive plate is 30 mu m, and the density of the high compaction coating is 3.5g/cm3. The thickness of the low compaction coating of the positive plate is 10 mu m, and the density of the low compaction coating is 3.4g/cm3。
Example 2
S112, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and S122, coating the slurry on a current collector for the first time, and rolling for the first time after drying to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
And S132, coating the slurry on the high-compaction coating for the second time, drying, and then performing second rolling to form a low-compaction coating on the high-compaction coating, wherein the low-compaction coating and the prepared pole piece jointly form the battery pole piece in the embodiment 2. Wherein the thickness of the high compaction coating of the negative plate is 200 mu m, and the density of the high compaction coating is 1.6g/cm3. The thickness of the low compaction coating of the negative plate is 100 mu m, and the density of the low compaction coating is 1.5g/cm3. The thickness of the high compaction coating of the positive plate is 200 mu m, and the density of the high compaction coating is 3.6g/cm3. The thickness of the low compaction coating of the positive plate is 100 mu m, and the density of the low compaction coating is 3.5g/cm3。
Example 3
S113, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and S123, coating the slurry on a current collector for the first time, and rolling for the first time after drying to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
S133, coating the slurry on the high-compaction coating layer for the second time, drying, and performing second rolling to form a low-compaction coating layer on the high-compaction coating layer, where the low-compaction coating layer and the prepared pole piece together form the battery pole piece of example 3. Wherein the thickness of the high compaction coating of the negative plate is 110 mu m, and the density of the high compaction coating is 1.8g/cm3. The thickness of the low compaction coating of the negative plate is 60 mu m, and the density of the low compaction coating is 1.3g/cm3. The thickness of the high compaction coating of the positive plate is 110 mu m, and the density of the high compaction coating is 3.9g/cm3. The thickness of the low compaction coating of the positive plate is 60 mu m, and the density of the low compaction coating is 3.2g/cm3。
Example 4
S114, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and S124, coating the slurry on a current collector for the first time, and rolling for the first time after drying to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
S134, coating the slurry on the high-compaction coating layer for the second time, drying, and performing second rolling to form a low-compaction coating layer on the high-compaction coating layer, where the low-compaction coating layer and the prepared pole piece together form the battery pole piece of example 4. Wherein the thickness of the high compaction coating of the negative plate is 100 mu m, and the density of the high compaction coating is 1.7g/cm3. The thickness of the low compaction coating of the negative plate is 50 mu m, and the density of the low compaction coating is 1.2g/cm3. The thickness of the high compaction coating of the positive plate is 100 mu m, and the density of the high compaction coating is 4.0g/cm3. The thickness of the low compaction coating of the positive plate is 50 μm, and the density of the low compaction coating is 3.3g/cm3。
Example 5
S115, uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and S125, coating the slurry on a current collector for the first time, and rolling for the first time after drying to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece.
S135, coating the slurry on the high-compaction coating layer for the second time, drying, and performing second rolling to form a low-compaction coating layer on the high-compaction coating layer, where the low-compaction coating layer and the prepared pole piece together form the battery pole piece of example 5. Wherein the thickness of the high compaction coating of the negative plate is 100 mu m, and the density of the high compaction coating is 1.6g/cm3. The thickness of the low compaction coating of the negative plate is 50 mu m, and the density of the low compaction coating is 1.4g/cm3. The thickness of the high compaction coating of the positive plate is 100 mu m, and the density of the high compaction coating is 3.8g/cm3. The thickness of the low compaction coating of the positive plate is 50 μm, and the density of the low compaction coating is 3.4g/cm3。
Comparative example 1
Uniformly mixing the positive/negative electrode active material, the conductive agent and the binder to obtain slurry; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150). Wherein, the slurry proportion of the anode is LCO: CNT: PVDF 97.6: 0.85: 0.7: 0.85, the slurry proportion of the negative electrode is C: SP: CMC: SBR 95: 2: 1.5: 1.5.
and coating the slurry on a current collector, drying and then rolling to form a first compacted coating on the current collector, wherein the first compacted coating and the current collector jointly form a preparation pole piece.
And coating the slurry on the first compacted coating for the second time, drying, and then performing second rolling to form a second compacted coating on the first compacted coating, wherein the second compacted coating and the prepared pole piece jointly form the battery pole piece of the comparative example 1. Wherein the thickness of the first compacted coating of the negative plate is 100 mu m, and the density of the first compacted coating is 1.5g/cm3(ii) a The thickness of the second compacted coating of the negative plate is 50 mu m, and the density of the second compacted coating is 1.5g/cm3. The thickness of the first compacted coating layer of the positive electrode sheet was 100 μm, and the density of the first compacted coating layer was 3.7g/cm3(ii) a The thickness of the second compacted coating layer of the positive electrode sheet was 50 μm, and the density of the second compacted coating layer was 3.7g/cm3。
Experiment: the lithium ion battery with the electric capacity of 0.5Ah is assembled by taking the battery pole pieces of the embodiment 1-the embodiment 5 and the comparative example 1, and the test is as follows: (1) the energy density of the lithium ion battery, (2) the internal resistance change rate of 500-week discharge, (3) the discharge cycle performance of the 1C/IC battery at the temperature of 25 ℃, and (4) the discharge cycle performance of the 1C/IC battery at the temperature of 45 ℃. The test results show that compared with the comparative example 1, the volume energy density of the lithium ion battery provided by the embodiment of the invention is obviously improved; the internal resistance of the lithium ion battery is not increased while the thickness and the density of the pole piece are improved, and after 500 weeks of discharge, the internal resistance increase rate of the lithium ion battery is smaller, the conductivity is better, and the energy cycle is better; the capacity retention rate of the lithium ion battery of the embodiment of the invention is close to that of the comparative example 1 at the temperature of 25 ℃, and the lithium ion battery of the embodiment of the invention is proved to have no poor cycle performance caused by high thickness and high density of the pole piece; the capacity retention rate of the lithium ion battery of the embodiment of the invention is higher than that of the lithium ion battery of the embodiment of the invention in comparison with the comparison example 1 at the temperature of 45 ℃, which proves that the lithium ion battery of the embodiment of the invention has better cycle performance under the condition of high temperature (45 ℃). See table 1 and fig. 3-5 for details. In order to avoid the data in the graph being too dense and difficult to distinguish, only the data of example 4 and example 5 are selected and plotted with the data of comparative example 1, and the results are shown in fig. 3 to fig. 5. The effects of the other embodiments are similar to those of embodiments 4 and 5, and are not described again.
TABLE 1 internal discharge resistance variation of lithium ion battery
Figure BDA0002506866220000131
Figure BDA0002506866220000141
As can be seen from table 1, compared to comparative example 1, while the thickness and density of the electrode sheet are improved, the internal resistance of the lithium ion batteries of examples 1 to 5 of the present invention is not increased, and after 500 weeks of discharge, the internal resistance increase rate of the lithium ion batteries of examples 1 to 5 is smaller, the conductivity is better, and the energy cycle is better. In addition, compared with the embodiments 1 to 2, the embodiments 3 to 5 select the thickness range and the density range of the low-compaction coating layer and the thickness range and the density range of the high-compaction coating layer, so that the internal resistance increase rate of the prepared lithium ion battery is smaller, the conductivity is better, and the energy cycle is better.
Fig. 3 is a graph comparing energy densities of the batteries of example 4, example 5 and comparative example 1 according to the present invention. Wherein DB represents the lithium ion battery of comparative example 1; SY-1 represents the lithium ion battery of example 4; SY-2 represents the lithium ion battery of example 5. As can be seen from fig. 3, the volumetric energy densities of the lithium ion batteries of examples 4 and 5 were significantly improved relative to comparative example 1.
FIG. 4 is a graph showing the discharge cycle test of 1C/IC batteries at a temperature of 25 ℃ for the batteries of example 4, example 5 and comparative example 1 according to the present invention. Wherein KB represents the lithium ion battery of comparative example 1; SY-1 represents the lithium ion battery of example 4; SY-2 represents the lithium ion battery of example 5. As can be seen from fig. 4, the capacity retention rates of the lithium ion batteries of examples 4 and 5 at a temperature of 25 ℃ are close to those of comparative example 1, which proves that the lithium ion batteries prepared by the method of the present invention have no deterioration of cycle performance due to the high thickness and high density of the pole piece.
FIG. 5 is a graph showing discharge cycle test of 3C/0.5C cells at a temperature of 45 ℃ for the cells of example 4, example 5 and comparative example 1 according to the present invention. Wherein KB represents the lithium ion battery of comparative example 1; SY-1 represents the lithium ion battery of example 4; SY-2 represents the lithium ion battery of example 5. As can be seen from fig. 5, the capacity retention rates of the lithium ion batteries of examples 4 and 5 are higher than that of comparative example 1 at a temperature of 45 ℃, which proves that the lithium ion battery prepared by the method of the present invention has better cycle performance at a high temperature (45 ℃).
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. The preparation method of the battery pole piece is characterized by comprising the following steps:
coating the slurry on a current collector for the first time, drying, and then performing first rolling to form a high-compaction coating on the current collector, wherein the high-compaction coating and the current collector jointly form a preparation pole piece;
and coating the slurry on the high-compaction coating for the second time, drying, and then performing second rolling to form a low-compaction coating on the high-compaction coating, wherein the low-compaction coating and the prepared pole piece jointly form a battery pole piece.
2. The method for preparing a battery pole piece according to claim 1, wherein the slurry comprises a positive/negative electrode active material, a conductive agent and a binder; wherein the mass ratio of the positive/negative electrode active material, the conductive agent and the binder is (90-98): (0.5-5): 45-150).
3. The preparation method of the battery pole piece according to claim 1, wherein when the battery pole piece is a negative pole piece, the density of the high-compaction coating is more than or equal to 1.5g/cm3The density of the low-compaction coating is less than or equal to 1.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
4. The preparation method of the battery pole piece according to claim 1, wherein when the battery pole piece is a positive pole piece, the density of the high-compaction coating is more than or equal to 3.5g/cm3The density of the low-compaction coating is less than or equal to 3.5g/cm3And the difference between the density of the high-compaction coating and the density of the low-compaction coating is more than or equal to 0.1g/cm3。
5. The method for preparing the battery pole piece according to claim 1, wherein the thickness of the battery pole piece is 30-300 μm.
6. The preparation method of the battery pole piece according to claim 1, wherein when the battery pole piece is a negative pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm.
7. The method for preparing the battery pole piece according to claim 1, wherein when the battery pole piece is a positive pole piece, the thickness of the high compaction coating is 30-200 μm, and the thickness of the low compaction coating is 10-100 μm.
8. The preparation method of the battery pole piece according to claim 1, wherein the first coating and the second coating are in the same or different modes and are respectively one of extrusion coating, spray coating and doctor blade coating.
9. The preparation method of the battery pole piece according to claim 1, wherein the first rolling and the second rolling are cold pressing or hot pressing respectively in the same or different modes.
10. A battery pole piece is characterized by being prepared by the preparation method of any one of claims 1 to 9.
CN202010448633.4A 2020-05-25 2020-05-25 Battery pole piece and preparation method thereof Pending CN111682162A (en)

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CN114420885A (en) * 2022-01-25 2022-04-29 上海兰钧新能源科技有限公司 Pole piece manufacturing method
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