CN116130808A - Composite pole piece, preparation method thereof and secondary battery - Google Patents

Composite pole piece, preparation method thereof and secondary battery Download PDF

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Publication number
CN116130808A
CN116130808A CN202310092448.XA CN202310092448A CN116130808A CN 116130808 A CN116130808 A CN 116130808A CN 202310092448 A CN202310092448 A CN 202310092448A CN 116130808 A CN116130808 A CN 116130808A
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Prior art keywords
active material
pole piece
temperature
combination
binder
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Inventor
丁丽平
娄豫皖
和祥运
陈海廷
万生辉
王卡
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Ningxia Baofeng Yuneng Technology Co Ltd
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Ningxia Baofeng Yuneng Technology 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/13—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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a composite pole piece, a preparation method thereof and a secondary battery. The composite pole piece comprises a current collector and an active material layer arranged on at least one side of the current collector; at least one side of the active material layer is provided with a functional layer; the functional layer includes a combination of a functional additive, a first binder, and a first lubricant. The composition of the active material layer and the functional layer is regulated, so that the prepared composite pole piece has the advantages of high compaction density and high energy density, good electrolyte wettability, low internal resistance and long service life.

Description

Composite pole piece, preparation method thereof and secondary battery
Technical Field
The invention belongs to the technical field of electrode sheet materials, and particularly relates to a composite electrode sheet, a preparation method thereof and a secondary battery.
Background
The production process of the traditional battery pole piece mainly adopts a wet process, specifically uses water, N-methylpyrrolidine or other substances as solvents, uniformly mixes active substances, conductive agents, binders, thickeners, solvents and other components, then coats the surface of a current collector, and then bakes the coated electrode through a baking device to remove the solvents in the pole piece. The wet process is widely applied to the battery production process due to the simple coating process and high efficiency, but the wet process has the problems of high energy consumption, environmental pollution caused by organic solvents, high recovery cost and poor adhesive property of the pole piece.
Based on the above, the dry electrode process is rapidly developed, and is initially applied to the field of production of supercapacitor electrodes, specifically, after uniformly mixing active carbon, a conductive agent and a binder, performing fibrosis treatment on the mixture, preparing a self-supporting dry film by hot rolling, and finally preparing a pole piece.
Compared with the wet process, the dry electrode process avoids using toxic solvents with high cost in the production process, reduces the energy consumption in the drying process, and can obviously reduce the production cost of the pole piece. However, the dry process has many process problems in the electrode production process, mainly in the following aspects: 1) Because the battery active material has a large specific gravity, active materials, conductive agents and binders are difficult to mix uniformly during mixing, and flexible dry films are difficult to obtain during rolling due to uneven fibrosis in the follow-up process; 2) If the electrode sheet with high compaction density is prepared, the dry film needs to be rolled for multiple times, so that the requirement on equipment is greatly increased; 3) The pole piece produced by the dry electrode process has larger compaction density, and holes left in the baking process are omitted, so that the infiltration performance of the pole piece is poor, long-time liquid injection is needed, and the cycle performance of the battery is not improved; 4) If the binder is not sufficiently fibrillated, local polarization in the electrode is increased, and the amount of the binder used is increased, resulting in an increase in the internal resistance of the electrode.
Therefore, in the art, there is a need to develop an electrode sheet and a process for preparing the same, which not only solve the above problems, but also provide an electrode sheet having good flexibility and electrochemical properties.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a composite pole piece, a preparation method thereof and a secondary battery. The composition of the active material layer and the functional layer is regulated, so that the prepared composite pole piece has the advantages of high compaction density and high energy density, good electrolyte wettability, low internal resistance and long service life.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite pole piece comprising a current collector and an active material layer disposed on at least one side of the current collector;
at least one side of the active material layer is provided with a functional layer;
the functional layer includes a combination of a functional additive, a first binder, and a first lubricant.
According to the invention, the functional layer is arranged on at least one side of the active material layer, and the composition of the functional layer is further regulated, so that the prepared composite pole piece has the advantages of high compaction density and high energy density, good electrolyte wettability, low internal resistance and long service life. In addition, the addition of the functional additive can reduce the irreversible capacity of the pole piece lost in the first circulation process and improve the safety performance of the battery. The addition of the first lubricant is favorable for the sufficient fibrosis of the binder, can reduce the phenomenon of sticking to rollers and improves the film pressing quality of the electrode plate.
Preferably, the functional layer comprises 0.5% to 30% of the first binder, 65% to 99% of the functional additive and 0.5% to 5% of the first lubricant, preferably 3% to 15% of the first binder, 70% to 95% of the functional additive and 0.5% to 3% of the first lubricant.
According to the invention, the pole piece has the advantages of high first charge and discharge efficiency and good electrolyte wettability by regulating and controlling the content of each component in the functional layer.
In the present invention, the content of the first binder is 0.5% to 30%, for example, 0.5%, 1%, 2%, 5%, 10%, 20%, 30%, or the like.
In the present invention, the content of the functional additive is 65% to 99%, and for example, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99% and the like can be used.
In the present invention, the content of the first lubricant is 0.5% to 5%, for example, 0.5%, 1%, 2%, 5%, or the like.
Preferably, the first binder comprises any one or a combination of at least two of polytetrafluoroethylene, linear polyether, polyvinylidene fluoride, polyimide, styrene-butadiene copolymer, polysiloxane and copolymers thereof, ethylene-vinyl acetate copolymer or branched polyether.
In the present invention, the polysiloxane and its copolymer may be, for example, polydimethylsiloxane.
Preferably, the functional additive comprises any one or a combination of at least two of a lithium supplementing additive, a sodium supplementing additive, a flame retardant additive or a conductive agent.
Preferably, the lithium supplementing additive comprises any one or a combination of at least two of a lithium-rich compound, a binary lithium compound, lithium powder or lithium tape.
Preferably, the sodium supplement additive comprises any one or a combination of at least two of sodium-rich compounds, sodium powder or sodium flakes.
Preferably, the flame retardant additive comprises any one or a combination of at least two of silica, alumina, boehmite, aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate.
Preferably, the first lubricant comprises any one or a combination of at least two of high-purity graphite, KS-6 conductive graphite, molybdenum disulfide or boron nitride with purity of more than or equal to 99.99%.
Preferably, the active material layer comprises 60% to 98.5% of active material, 0.5% to 10% of conductive agent, 0.5% to 25% of second binder and 0.5% to 5% of second lubricant, preferably 80% to 98% of active material, 0.5% to 5% of conductive agent, 1% to 10% of second binder and 0.5% to 3% of second lubricant.
In the present invention, the active layer is made to have a high energy density and a high compacted density by controlling the content of each component in the active material layer.
In the present invention, the content of the active material is 60% to 98.5%, for example, 60%, 70%, 80%, 90%, 98.5%, or the like.
In the present invention, the content of the conductive agent is 0.5% to 10%, for example, 0.5%, 1%, 2%, 5%, 10%, or the like.
In the present invention, the content of the second binder is 0.5% to 25%, and for example, may be 0.5%, 1%, 2%, 5%, 10%, 15%, 20%, 25%, or the like.
In the present invention, the content of the second lubricant is 0.5% to 5%, for example, 0.5%, 1%, 2%, 5%, or the like. The second lubricant is added to facilitate sufficient fiberization of the binder, so that the phenomenon of sticking to rollers can be reduced, and the film pressing quality of the electrode plate is improved.
Preferably, the active material includes a positive electrode active material or a negative electrode active material.
In the present invention, the positive electrode active material means a material that can be used as a positive electrode material of a battery, and for example, can be a material having a lithium ion intercalation and deintercalation function such as Li x MeO 2 Wherein Me comprises transition metal elements such as Mn, ni or Co, and x is the stoichiometric number of lithium. Phosphate positive electrode materials such as lithium iron phosphate LiFePO 4 Lithium iron manganese phosphate (LiMn) x Fe 1-x PO 4 ) Etc.; for example, a material having a sodium ion intercalation and deintercalation function such as a layered structure compound Na x MeO 2 Wherein Me comprises transition metal elements such as Mn, fe, ni or Co, and x is the stoichiometric number of sodium. Prussian blue compound A x MA[MB(CN) 6 ]·zH 2 O, wherein A is an alkali metal ion and MA and MB are transition metal ions. AggregationThe structural formula of the anionic compound is Na x M y [(XO m ) n - ] z Wherein M is a variable valence metal ion such as vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu); x is P, S, V or Si.
The negative electrode active material includes at least one of graphite, mesophase carbon microspheres, lithium titanate, soft carbon, or hard carbon.
Preferably, the conductive agent includes any one or a combination of at least two of acetylene black, super-P, carbon nanotubes, carbon fibers, ketjen black, graphite, or graphene.
Preferably, the second binder comprises any one or a combination of at least two of polytetrafluoroethylene, linear polyether, polyvinylidene fluoride, polyimide, styrene-butadiene copolymer, polysiloxane and copolymers thereof, ethylene-vinyl acetate copolymer or branched polyether.
Preferably, the second lubricant comprises any one or a combination of at least two of high-purity graphite, KS-6 conductive graphite, molybdenum disulfide or boron nitride with the purity of more than or equal to 99.99 percent.
In a second aspect, the present invention provides a method of preparing a composite pole piece according to the first aspect, the method comprising the steps of:
respectively and sequentially carrying out heat treatment, jet milling and low-temperature granulation on the active material layer material and the functional layer material; and then carrying out primary hot pressing on the treated active material layer mixture and the functional layer mixture to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector to obtain the composite pole piece.
According to the pole piece preparation method provided by the invention, the high-temperature heat treatment and the low-temperature granulation process are added in the dry electrode preparation process, the viscosity of the adhesive is in a trend of rising and then falling along with the rising of the temperature, the viscosity of the adhesive can be in an optimal state through proper high-temperature heat treatment, the adhesive can be fully fibrillated in the jet milling process, and the defect that the electrode of the battery material is not easy to form a film is overcome.
Preferably, the temperature at which the active material layer material is heat-treated is 40 to 125 ℃, for example, 40 ℃, 60 ℃, 80 ℃, 100 ℃, 120 ℃, 125 ℃, etc. may be used.
Preferably, the temperature of the heat treatment of the functional layer material is 40 to 80 ℃, for example, 40 ℃, 60 ℃, 80 ℃ and the like.
Preferably, the air flow medium used for the air flow crushing comprises at least one of air, argon, nitrogen, hydrogen or hydrogen-argon mixture.
Preferably, the humidity of the air flow medium is less than or equal to 20% RH.
Preferably, the temperature of the low-temperature granulation treatment is 5 to 20 ℃, for example, 5 ℃, 8 ℃, 10 ℃, 20 ℃ and the like can be used.
Preferably, the low-temperature granulation treatment mode comprises stirring granulation or spray granulation.
Preferably, the particle size of the low-temperature granulation treatment is 20 to 60 mesh, for example, 20 mesh, 40 mesh, 60 mesh, etc.
Preferably, the temperature of the primary hot press is 60 to 250 ℃, for example, 60 ℃, 80 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃, and the like.
Preferably, the temperature of the secondary thermocompression bonding is 60 to 250 ℃, for example, 60 ℃, 80 ℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃, or the like.
In a third aspect, the present invention provides a secondary battery comprising an electrode sheet, an electrolyte and a separator, the electrode sheet being the composite sheet according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a composite pole piece, which is characterized in that a functional layer is arranged on at least one side of an active material layer, and the composition of the functional layer is further regulated and controlled, so that the prepared composite pole piece has the advantages of high compaction density and high energy density, good electrolyte wettability, low internal resistance and long service life. In addition, the addition of the functional additive can reduce the irreversible capacity of the pole piece lost in the first circulation process and improve the safety performance of the battery. The addition of the first lubricant is favorable for the sufficient fibrosis of the binder, can reduce the phenomenon of sticking to rollers and improves the film pressing quality of the electrode plate.
According to the pole piece preparation method provided by the invention, the high-temperature heat treatment and the low-temperature granulation process are added in the dry electrode preparation process, the viscosity of the adhesive is in a trend of rising and then falling along with the rising of the temperature, the viscosity of the adhesive can be in an optimal state through proper high-temperature heat treatment, the adhesive can be fully fibrillated in the jet milling process, and the defect that the electrode of the battery material is not easy to form a film is overcome.
Drawings
Fig. 1 is a schematic structural diagram of a composite electrode sheet provided in example 1, wherein 1-aluminum foil, 2-positive electrode active material layer, 3-functional layer;
FIG. 2 is a flow chart of a method for preparing the composite pole piece provided in example 1;
fig. 3 is a picture of a nickel cobalt lithium manganate composite dry film (gray active material nickel cobalt lithium manganate layer, black part is a functional layer) provided in example 1;
fig. 4 is a scanning electron microscope image of a black functional layer of the nickel cobalt lithium manganate composite pole piece provided in embodiment 1;
fig. 5 is a scanning electron microscope image of a gray active material layer of the nickel cobalt lithium manganate composite pole piece provided in example 1.
Detailed Description
The technical scheme of the invention is further described below by combining the attached drawings and the specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides a composite positive plate, as shown in fig. 1, the composite positive plate comprises an aluminum foil current collector and positive electrode active material layers arranged on two sides of the aluminum foil current collector; functional layers are provided on both sides of the positive electrode active material layer.
Wherein the positive electrode active material layer comprises 90% of nickel cobalt lithium manganate ternary material, 2% of conductive carbon black, 5% of polytetrafluoroethylene binder and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%; the functional layer comprises 5% of polytetrafluoroethyleneEthylene binder, 87% lithium supplement additive Li 5 FeO 4 5% of conductive additive Super P and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%.
The embodiment also provides a preparation method of the composite pole piece, as shown in fig. 2, comprising the following steps:
respectively carrying out heat treatment, high-pressure argon jet milling (the humidity of argon is less than or equal to 20% RH) and low-temperature spray granulation treatment at 12 ℃ on the anode active material layer material and the functional layer material in sequence, wherein the temperature of the heat treatment of the anode active material layer material is 80 ℃, the temperature of the heat treatment of the functional layer material is 60 ℃, and the particle size of the low-temperature granulation treatment is 40 meshes; and then carrying out primary hot pressing on the processed anode active material layer mixture and the functional layer mixture at 150 ℃ to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector at 150 ℃ to obtain the composite pole piece shown in figures 3-5.
Example 2
The embodiment provides a composite positive plate, which comprises an aluminum foil current collector and positive electrode active material layers arranged on two sides of the aluminum foil current collector; functional layers are provided on both sides of the positive electrode active material layer.
Wherein the positive electrode active material layer comprises 88% of nickel cobalt lithium manganate ternary material, 2% of conductive carbon black, 8% of polytetrafluoroethylene binder and 2% of high-purity graphite lubricant with purity more than or equal to 99.99%; the functional layer comprises 7% of polytetrafluoroethylene binder and 86% of lithium supplement additive Li 5 FeO 4 5% of conductive additive SP and 2% of high-purity graphite lubricant with purity more than or equal to 99.99%.
The embodiment also provides a preparation method of the composite pole piece, which comprises the following steps:
respectively carrying out heat treatment, high-pressure argon jet milling (the humidity of argon is less than or equal to 20% RH) and low-temperature spray granulation treatment at 12 ℃ on the anode active material layer material and the functional layer material in sequence, wherein the temperature of the heat treatment of the anode active material layer material is 80 ℃, the temperature of the heat treatment of the functional layer material is 60 ℃, and the particle size of the low-temperature granulation treatment is 40 meshes; and then carrying out primary hot pressing on the treated anode active material layer mixture and the functional layer mixture at 150 ℃ to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector at 150 ℃ to obtain the composite pole piece.
Example 3
The embodiment provides a composite positive plate, which comprises an aluminum foil current collector and positive electrode active material layers arranged on two sides of the aluminum foil current collector; functional layers are provided on both sides of the positive electrode active material layer.
Wherein the positive electrode active material layer comprises 87% of nickel cobalt lithium manganate ternary material, 2% of conductive carbon black, 10% of polytetrafluoroethylene binder and 1% of high-purity graphite lubricant with purity more than or equal to 99.99%; the functional layer comprises 10% of polytetrafluoroethylene binder and 84% of lithium supplement additive Li 5 FeO 4 5% of conductive additive Super P and 1% of high-purity graphite lubricant with purity more than or equal to 99.99%.
The embodiment also provides a preparation method of the composite pole piece, which comprises the following steps:
respectively carrying out heat treatment, high-pressure argon jet milling (the humidity of argon is less than or equal to 20% RH) and low-temperature spray granulation treatment at 12 ℃ on the anode active material layer material and the functional layer material in sequence, wherein the temperature of the heat treatment of the anode active material layer material is 80 ℃, the temperature of the heat treatment of the functional layer material is 60 ℃, and the particle size of the low-temperature granulation treatment is 40 meshes; and then carrying out primary hot pressing on the treated anode active material layer mixture and the functional layer mixture at 150 ℃ to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector at 150 ℃ to obtain the composite pole piece.
Example 4
The embodiment provides a composite positive plate, which comprises an aluminum foil current collector and positive electrode active material layers arranged on two sides of the aluminum foil current collector; functional layers are provided on both sides of the positive electrode active material layer.
Wherein the positive electrode active material layer comprises 90% of nickel cobalt lithium manganate ternary material, 2% of conductive carbon black and 5% of polymerTetrafluoroethylene binder and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%; the functional layer comprises 5% of polytetrafluoroethylene binder and 87% of lithium supplement additive Li 5 FeO 4 5% of conductive additive Super P and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%.
The embodiment also provides a preparation method of the composite pole piece, which comprises the following steps:
sequentially carrying out heat treatment, high-pressure argon jet milling (the humidity of argon is less than or equal to 20% RH) and low-temperature spray granulation at 12 ℃ on the anode active material layer material and the functional layer material respectively, wherein the temperature of the heat treatment of the anode active material layer material is 55 ℃, the temperature of the heat treatment of the functional layer material is 45 ℃, and the particle size of the low-temperature granulation is 40 meshes; and then carrying out primary hot pressing on the treated anode active material layer mixture and the functional layer mixture at 150 ℃ to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector at 150 ℃ to obtain the composite pole piece.
Example 5
The embodiment provides a composite positive plate, which comprises an aluminum foil current collector and positive electrode active material layers arranged on two sides of the aluminum foil current collector; functional layers are provided on both sides of the positive electrode active material layer.
Wherein the positive electrode active material layer comprises 90% of nickel cobalt lithium manganate ternary material, 2% of conductive carbon black, 5% of polytetrafluoroethylene binder and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%; the functional layer comprises 5% of polytetrafluoroethylene binder and 87% of lithium supplement additive Li 5 FeO 4 5% of conductive additive Super P and 3% of high-purity graphite lubricant with purity more than or equal to 99.99%.
The embodiment also provides a preparation method of the composite pole piece, which comprises the following steps:
respectively carrying out heat treatment, high-pressure argon jet milling (the humidity of argon is less than or equal to 20% RH) and low-temperature spray granulation treatment at 12 ℃ on the anode active material layer material and the functional layer material in sequence, wherein the temperature of the heat treatment of the anode active material layer material is 80 ℃, the temperature of the heat treatment of the functional layer material is 60 ℃, and the particle size of the low-temperature granulation treatment is 60 meshes; and then carrying out primary hot pressing on the treated anode active material layer mixture and the functional layer mixture at the temperature of 250 ℃ to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector at the temperature of 250 ℃ to obtain the composite pole piece.
Example 6
This example differs from example 1 in that the functional layer contains lithium supplement additive Li 5 FeO 4 The mass percentage of (2%) was 72%, and the conductive additive Super P was 20%, all other than that in example 1.
Example 7
The difference between this example and example 1 is that the lubricant in the functional layer is 3% molybdenum disulfide by mass, and the other is the same as example 1.
Example 8
The difference between this example and example 1 is that the lubricant in the active material layer is 3% boron nitride by mass, and the other is the same as example 1.
Example 9
This example differs from example 1 in that the temperature of the low-temperature granulation treatment during the preparation is 20℃and the other is the same as in example 1.
Example 10
The difference between this example and example 1 is that the wet process is used for preparation, and the specific method is that 90% of nickel cobalt lithium manganate material, 2% of conductive carbon black and 8% of polyvinylidene fluoride are added into a certain proportion of N-methyl pyrrolidone to dissolve and prepare a glue solution, then the conductive agent is added into the glue solution to fully disperse according to a certain stirring speed and stirring time, and finally the active material nickel cobalt lithium manganate material is added and stirred uniformly to prepare the required slurry. And coating the slurry on the current collector according to a certain coating mode and process to prepare the pole piece.
Comparative example 1
This comparative example is different from example 1 in that no functional layer is provided, and the other is the same as example 1.
Comparative example 2
The comparative example differs from example 1 in that no lubricant was added to the functional layer, which included 5% of polytetrafluoroethylene binder, 87% of lithium supplement additive Li 5 FeO 4 8% of conductive additive Super P, the other components are the same as in example 1.
Application examples 1 to 10 and comparative application examples 1 to 2
The lithium ion batteries were prepared from the composite positive electrode sheets provided in examples 1 to 10 and comparative examples 1 to 2, and the preparation methods were as follows:
preparing a negative plate: mixing graphite, a binding agent styrene-butadiene rubber, a thickener sodium carboxymethyl cellulose and conductive carbon black of a conductive agent, and dispersing the mixture in deionized water to obtain negative electrode slurry; the negative electrode slurry contains 95wt% of graphite, 1.5wt% of sodium carboxymethyl cellulose, 1.5wt% of conductive carbon black, and 2wt% of styrene-butadiene rubber as solid components.
Preparation of a lithium ion battery: the positive plate, the negative plate and the diaphragm are prepared into a battery cell through a lamination process, an aluminum plastic film is adopted for packaging, moisture is removed after baking is carried out for 48 hours in a vacuum state, electrolyte is injected, and the battery is formed and separated to obtain the required soft-package lithium ion battery.
Test conditions
The lithium ion batteries provided in application examples 1 to 10 and comparative application examples 1 to 2 were tested and prepared as follows:
(1) Internal resistance test: internal resistance (50 HZ) was measured at 50% SOC using an AC internal resistance tester
(2) And (3) testing the cycle performance: (1) charging the battery to a voltage of 4.15V by constant current 1C charging; (2) then leaving the charged battery to stand for 10min; (3) Then the current of 1C carries out constant current discharge on the battery until the terminal voltage is lower than 3V; (4) resting for 10min, and entering the next cycle.
The test results are shown in table 1:
TABLE 1
Figure BDA0004085725980000121
Figure BDA0004085725980000131
As can be seen from table 1, the composite pole piece provided by the invention has the advantages of good electrolyte wettability, low internal resistance and long service life at the same time of having high compaction density and high energy density by arranging the functional layer on at least one side of the active material layer and further regulating and controlling the composition of the functional layer, so that the battery cell prepared by the embodiment has smaller internal resistance and longer cycle life compared with the comparative example.
Compared with the application example 1, the pole pieces provided in the comparison application examples 1 and 2 cannot achieve the technical effect of the application.
The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to, i.e. does not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.

Claims (10)

1. The composite pole piece is characterized by comprising a current collector and an active material layer arranged on at least one side of the current collector;
at least one side of the active material layer is provided with a functional layer;
the functional layer includes a combination of a functional additive, a first binder, and a first lubricant.
2. A composite pole piece according to claim 1, characterized in that the functional layer comprises 0.5-30% of the first binder, 65-99% of the functional additive and 0.5-5% of the first lubricant, preferably 3-15% of the first binder, 70-95% of the functional additive and 0.5-3% of the first lubricant.
3. The composite pole piece of claim 1 or 2, wherein the first binder comprises any one or a combination of at least two of polytetrafluoroethylene, linear polyether, polyvinylidene fluoride, polyimide, styrene-butadiene copolymer, polysiloxane and copolymers thereof, ethylene-vinyl acetate copolymer, or branched polyether;
preferably, the functional additive comprises any one or a combination of at least two of a lithium supplementing additive, a sodium supplementing additive, a flame retardant additive or a conductive agent;
preferably, the lithium supplementing additive comprises any one or a combination of at least two of a lithium-rich compound, a binary lithium compound, lithium powder or a lithium band;
preferably, the sodium supplement additive comprises any one or a combination of at least two of sodium-rich compounds, sodium powder or sodium flakes;
preferably, the flame retardant additive comprises any one or a combination of at least two of silica, alumina, boehmite, aluminum hydroxide, magnesium hydroxide or ammonium polyphosphate;
preferably, the first lubricant comprises any one or a combination of at least two of high-purity graphite, KS-6 conductive graphite, molybdenum disulfide or boron nitride with purity of more than or equal to 99.99%.
4. A composite pole piece according to any of claims 1-3, characterized in that the active material layer comprises 60-98.5% active material, 0.5-10% conductive agent, 0.5-25% second binder and 0.5-5% second lubricant, preferably 80-98% active material, 0.5-5% conductive agent, 1-10% second binder and 0.5-3% second lubricant;
preferably, the active material includes a positive electrode active material or a negative electrode active material;
preferably, the conductive agent comprises any one or a combination of at least two of acetylene black, super-P, carbon nanotubes, carbon fibers, ketjen black, graphite or graphene;
preferably, the second binder comprises any one or a combination of at least two of polytetrafluoroethylene, linear polyether, polyvinylidene fluoride, polyimide, styrene-butadiene copolymer, polysiloxane and copolymers thereof, ethylene-vinyl acetate copolymer or branched polyether;
preferably, the second lubricant comprises any one or a combination of at least two of high-purity graphite, KS-6 conductive graphite, molybdenum disulfide or boron nitride with the purity of more than or equal to 99.99 percent.
5. A method of preparing a composite pole piece according to any of claims 1-4, characterized in that the method comprises the steps of:
respectively and sequentially carrying out heat treatment, jet milling and low-temperature granulation on the active material layer material and the functional layer material; and then carrying out primary hot pressing on the treated active material layer mixture and the functional layer mixture to obtain a composite dry film, and finally carrying out secondary hot pressing and compounding on the composite dry film and the current collector to obtain the composite pole piece.
6. The method of claim 5, wherein the active material layer material is heat treated at a temperature of 40-125 ℃;
preferably, the temperature of the heat treatment of the functional layer material is 40-80 ℃.
7. The method of claim 5 or 6, wherein the air flow medium used for air flow pulverization comprises at least one of air, argon, nitrogen, hydrogen or hydrogen-argon mixture;
preferably, the humidity of the air flow medium is less than or equal to 20% RH.
8. The method according to any one of claims 5 to 7, wherein the low temperature granulation treatment is at a temperature of 5 to 20 ℃;
preferably, the low-temperature granulation treatment mode comprises stirring granulation or spray granulation;
preferably, the particle size of the low temperature granulation treatment is 20-60 mesh.
9. The method according to any one of claims 5 to 8, wherein the temperature of the primary hot press is 60 to 250 ℃;
preferably, the temperature of the secondary hot press compounding is 60-250 ℃.
10. A secondary battery, characterized in that the secondary battery comprises an electrode sheet, an electrolyte and a separator, the electrode sheet being the composite sheet according to any one of claims 1 to 4.
CN202310092448.XA 2023-02-09 2023-02-09 Composite pole piece, preparation method thereof and secondary battery Pending CN116130808A (en)

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