CN115360330A - Preparation method of positive pole piece, positive pole piece and lithium ion battery - Google Patents

Preparation method of positive pole piece, positive pole piece and lithium ion battery Download PDF

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CN115360330A
CN115360330A CN202210995287.0A CN202210995287A CN115360330A CN 115360330 A CN115360330 A CN 115360330A CN 202210995287 A CN202210995287 A CN 202210995287A CN 115360330 A CN115360330 A CN 115360330A
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positive electrode
preparing
ncm
positive pole
pole piece
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王纯哲
郑传佐
黄全伟
宋炳辉
欧阳任
周湘
文进
邓俊
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Xiangtan University
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Xiangtan University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention discloses a preparation method of a positive pole piece, the positive pole piece and a lithium ion battery, wherein the preparation method comprises the following steps: preparing NCM 811 coated with a fast ion conductor; mixing the NCM 811 coated with the fast ion conductor, the carbon black and the polyvinylidene fluoride according to the mass ratio of 8-9; preparing a positive electrode slurry based on the mixture; coating the positive electrode slurry on a porous current collector to obtain a positive electrode material; and preparing the positive pole piece based on the positive pole material. According to the preparation method of the positive pole piece, the NCM 811 active matter coated by the fast ion conductor is covered on the porous current collector, so that the positive pole piece prepared by the method has high active matter carrying capacity and high energy density, the cycle performance and the energy density are improved, and the electrochemical performance of the battery is improved remarkably.

Description

Preparation method of positive pole piece, positive pole piece and lithium ion battery
Technical Field
The invention relates to the technical field of battery preparation, in particular to a preparation method of a positive pole piece, the positive pole piece and a lithium ion battery.
Background
Nowadays, the development of power batteries is not kept, and ternary positive electrode materials have greater opportunities in positive electrode materials of the power batteries; the high specific capacity of the high-nickel ternary cathode material is just the irreplaceable advantage. Certainly, both opportunities and challenges exist, the ternary positive electrode material has the advantage of high specific capacity, but the cycling stability and the safety of the ternary positive electrode material cannot meet the requirements of the power battery.
The method aims to solve the problem of the ternary cathode material, and can modify the high-nickel cathode material by means of coating, doping and the like. Although the coating modification improves the cycle stability of the NMC811, the long cycle performance of the NMC811 needs to be improved, and the aim of improving the energy density cannot be achieved.
Disclosure of Invention
Objects of the invention
The invention aims to provide a preparation method of a positive pole piece, the positive pole piece and a lithium ion battery to solve the problems.
(II) technical scheme
In order to solve the above problems, a first aspect of the present invention provides a method for preparing a positive electrode sheet, including: preparing NCM 811 coated with a fast ion conductor; mixing the NCM 811 coated with the fast ion conductor, the carbon black and the polyvinylidene fluoride according to the mass ratio of 8-9; preparing a positive electrode slurry based on the mixture; coating the positive electrode slurry on a porous current collector to obtain a positive electrode material; and preparing the positive pole piece based on the positive pole material.
Further, the coating of the positive electrode slurry on a porous current collector to obtain a positive electrode material includes: drying the positive electrode slurry in a vacuum drying oven for 12-15h to obtain a porous current collector coated with a fast ion conductor; the temperature of the vacuum drying oven was: 80-120 ℃.
Further, the preparing of the positive electrode slurry based on the mixture includes: mixing the mixture with methyl pyrrolidone to prepare the positive electrode slurry; the mass part of the methyl pyrrolidone is 15-20 times of that of the polyvinylidene fluoride.
Further, the NCM 811 for preparing the coated fast ion conductor includes: pretreating the NCM 811 powder to obtain a dried NCM 811 powder; dissolving 1 part by mole of the dried NCM 811 powder, 0.01-0.02 part by mole of niobium isopropoxide and 0.01-0.03 part by mole of citric acid in a solvent to obtain a sample solution; and drying the sample liquid to obtain the NCM 811 coated with the fast ion conductor.
Further, the preparing the NCM 811 coated fast ion conductor further comprises: and stirring the sample liquid to obtain the uniformly mixed sample liquid.
Further, stirring is carried out by using a stirrer, and the stirring speed is 200-300r/min.
Further, the drying the sample liquid includes: heating the uniformly mixed sample liquid for 8-12h to obtain sample powder; the heating temperature is 70-90 ℃.
Further, the drying the sample liquid further comprises: sintering the sample powder; the sintering temperature is as follows: 780-830 ℃ for: 12-15h, and the heating rate is 3-5 ℃/min.
Further, the pre-processing comprises: placing NCM 811 powder into vacuum drying oven at 80-120 deg.C for drying for 8-12h.
According to another aspect of the invention, a positive pole piece is provided, which is prepared by adopting the preparation method of any one of the above technical schemes.
According to another aspect of the present invention, there is provided a lithium ion battery, including the positive electrode plate described in any one of the above technical solutions.
(III) advantageous effects
The technical scheme of the invention has the following beneficial technical effects:
according to the preparation method of the positive pole piece, the NCM 811 active matter coated by the fast ion conductor is covered on the porous current collector, so that the positive pole piece prepared by the method has high active matter carrying capacity and high energy density, the double promotion of the cycle performance and the energy density is realized, and the electrochemical performance of the battery is obviously improved.
Drawings
Fig. 1 is an electron microscope scanning image of a prior art positive electrode sheet.
Fig. 2 is a flow chart of a method for manufacturing a positive electrode sheet according to an embodiment of the present invention.
Fig. 3 is an electron microscope scanning image of a positive electrode sheet according to an embodiment of the invention.
Fig. 4 is an element distribution diagram of a positive electrode tab according to an embodiment of the present invention.
FIG. 5 is an electron microscopy scan image of a positive pole piece according to another embodiment of the invention.
Fig. 6 is an element distribution diagram of a positive electrode sheet according to another embodiment of the present invention.
Fig. 7 is an electron microscope scanning image of a positive electrode tab according to yet another embodiment of the invention.
Fig. 8 is an element distribution diagram of a positive electrode tab according to still another embodiment of the present invention.
Fig. 9 is a graph comparing cycle performance of a lithium ion battery according to an embodiment of the invention with a lithium ion battery of the prior art.
Fig. 10 is a graph comparing the rate capability of a lithium ion battery according to an embodiment of the present invention with that of a lithium ion battery of the prior art.
Fig. 11 is a graph of cycle performance of two current collectors at different loadings for a positive electrode sheet according to an embodiment of the present invention.
Fig. 12 is a graph of cycle performance at high active loading for a positive pole piece according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
In the drawings a schematic view of a layer structure according to an embodiment of the invention is shown. The figures are not drawn to scale, with certain details exaggerated and some details possibly omitted for clarity. The shapes of the various regions, layers and the relative sizes and positional relationships therebetween shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, as the actual requirements dictate.
It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not drawn to scale.
EC is an abbreviation of Ethylene carbonate, a chinese translation is Ethylene carbonate, and is a common solvent for lithium ion battery electrolytes.
EMC is an abbreviation of ethyl methyl carbonate, the chinese translation is ethyl methyl carbonate or methyl ethyl carbonate, a common solvent for lithium ion battery electrolytes.
DMC is an abbreviation of Dimethyl carbonate, the chinese translation is Dimethyl carbonate, a common solvent for lithium ion battery electrolytes.
Fig. 1 is an electron microscope scanning image of a prior art positive electrode sheet.
As shown in fig. 1, the particle surface of the positive electrode sheet in the prior art is very smooth, which results in low energy density and poor stability, and the long cycle performance of the positive electrode sheet is still to be improved.
In an embodiment of the present invention, a method for preparing a positive electrode plate is provided, which may include: preparing NCM 811 coated with fast ion conductor; mixing the NCM 811 coated with the fast ion conductor, the carbon black and the polyvinylidene fluoride according to the mass ratio of 8-9; preparing a positive electrode slurry based on the mixture; coating the positive electrode slurry on a porous current collector to obtain a positive electrode material; and preparing the positive pole piece based on the positive pole material.
According to the preparation method of the positive pole piece, the NCM 811 active matter coated by the fast ion conductor is covered on the porous current collector, so that the positive pole piece prepared by the method has high active matter carrying capacity and high energy density, the double improvement of the cycle performance and the energy density is realized, and the electrochemical performance of the battery is obviously improved.
The porous structure of the porous current collector greatly improves the contact problem among particles, a lithium ion transmission channel is constructed, the loading capacity of active substances is improved, the stability of electrochemical performance is ensured, and the ionic conductivity is greatly improved. The cycle performance of the coated anode is obviously improved, and the improvement of energy density and the stability of cycle performance are realized.
Fig. 2 is a flow chart of a method for manufacturing a positive electrode sheet according to an embodiment of the present invention.
As shown in fig. 2, in an embodiment of the present invention, a method for preparing a positive electrode sheet is provided, which at least includes the following steps:
s100, preparing NCM 811 coated with the fast ion conductor.
S200, mixing the NCM 811 coated with the fast ion conductor, the carbon black and the polyvinylidene fluoride according to the mass ratio of 8-9: 0.5-1.
And S300, preparing positive electrode slurry based on the mixture.
And S400, coating the positive electrode slurry on a porous current collector to obtain a positive electrode material.
S500, preparing the positive pole piece based on the positive pole material.
According to the preparation method of the positive pole piece, the NCM 811 active matter coated by the fast ion conductor covers the porous current collector, so that the positive pole piece prepared by the method has high active matter carrying capacity and high energy density, and can help the positive pole to stabilize the electrochemical performance.
In an alternative embodiment, the porous current collector may be a porous aluminum foil current collector.
In an alternative embodiment, the coating may be knife coating.
The active material loading capacity on the porous aluminum foil current collector can be regulated and controlled through the blade coating thickness and the times, the operation is simple and convenient, the 3D porous structure of the porous aluminum foil better solves the problem of particle contact, a lithium ion transmission channel is constructed, the ionic conductivity is improved, and the electrochemical performance is stabilized.
In an alternative embodiment, the NCM 811 coating the fast ion conductor may be a lithium niobate coated NCM 811.
In an alternative embodiment, the coating the positive electrode slurry on a porous current collector to obtain a positive electrode material may include: and drying the positive electrode slurry in a vacuum drying oven for 12-15h to obtain the porous current collector (namely the positive electrode material) coated with the fast ion conductor.
In an alternative embodiment, the temperature of the vacuum drying oven may be: 80-120 ℃.
In an alternative embodiment, the preparing the positive electrode slurry based on the mixture may include: and mixing the mixture with methyl pyrrolidone to prepare the positive electrode slurry.
In an alternative embodiment, the mass part of the methyl pyrrolidone may be 15 to 20 times that of the polyvinylidene fluoride.
In an alternative embodiment, the preparing the NCM 811 coated fast ion conductor may include: pretreating the NCM 811 powder to obtain a dried NCM 811 powder; dissolving 1 part of the dried NCM 811 powder, 0.01-0.02 part of niobium isopropoxide and 0.01-0.03 part of citric acid in a molar ratio in a solvent to obtain a sample solution; and drying the sample solution to obtain the NCM 811 coated with the fast ion conductor.
In a preferred embodiment, the preparing the NCM 811 coated fast ion conductor may include: pretreating the NCM 811 powder to obtain a dried NCM 811 powder; dissolving the dried NCM 811 powder, 0.02 part of niobium isopropoxide and 0.03 part of citric acid in a solvent according to a molar ratio of 1 part to obtain a sample solution; and drying the sample liquid to obtain the NCM 811 coated with the fast ion conductor.
In an alternative embodiment, the solvent may be ethanol.
In an alternative embodiment, the volume of ethanol may be 20-40ml.
In an alternative embodiment, the preparing the NCM 811 coated fast ion conductor may further include: and stirring the sample liquid to obtain the uniformly mixed sample liquid.
In an alternative embodiment, the agitation may be performed using a blender.
In an alternative embodiment, the stirring speed may be 200-300r/min.
In an alternative embodiment, the stirring time may be 12-15 hours.
In an alternative embodiment, the drying the sample liquid may include: heating the uniformly mixed sample liquid for 8-12h to obtain sample powder; the heating temperature is 70-90 ℃.
In an optional embodiment, the drying the sample liquid may further include: and sintering the sample powder.
In an alternative embodiment, the temperature of the sintering may be: 780-830 ℃.
In an alternative embodiment, the sintering time may be: 12-15h.
In an alternative embodiment, the temperature rise rate of the sintering may be 3-5 ℃/min.
In an alternative embodiment, the pre-processing may include: placing NCM 811 powder into vacuum drying oven at 80-120 deg.C for drying for 8-12h.
In another embodiment of the invention, a positive electrode plate is provided, which is prepared by adopting the preparation method of any one of the above technical schemes.
In another embodiment of the present invention, a lithium ion battery is provided, which may include the positive electrode tab according to any one of the above technical solutions.
In another embodiment of the present invention, a method for manufacturing a lithium ion battery is provided, in which the positive electrode plate is cut into a circular electrode plate, and the circular electrode plate and an electrolyte are assembled into a button battery.
In an optional embodiment, the electrolyte is a mixed solution of EC, EMC and DMC.
In an alternative embodiment, the volume ratio of the EC, the EMC, and the DMC in the mixed solution is 1.
FIG. 3 is an electron microscope scan image of a positive electrode sheet according to an embodiment of the invention.
As shown in fig. 3, the positive electrode sheet prepared by the preparation method of the positive electrode sheet of the present invention has a very rough particle surface, a sufficiently high positive electrode active material loading capacity and a high energy density, realizes double promotion of cycle performance and energy density, and significantly improves the electrochemical performance of the battery.
FIG. 4 is an elemental distribution diagram of a positive electrode sheet according to an embodiment of the invention.
As shown in FIG. 4, the transition metals Ni, mn, co and Nb of the positive electrode sheet prepared by the method for preparing the positive electrode sheet are uniformly distributed on the surface of the NMC811 particles, which shows that LiNbO 3 The surface of the NMC811 is uniformly coated.
FIG. 5 is an electron microscopy scan image of a positive pole piece according to another embodiment of the invention.
As shown in fig. 5, a), b) and c) are electron microscope scanning images of the positive electrode sheet at different scales, respectively. It can be seen from the graph (a) that the pore diameter of the PFA (porous current collector) is about 200-300 μm and is formed by connecting aluminum wires with the wall thickness of 20-30 μm, and it can be seen from the graph (c) that a large number of NMC811 particles are uniformly distributed on the aluminum wall of the PFA, the calibration of the PFA-loaded NMC811 particles is visually seen, and the loading capacity of the positive active material is greatly improved.
Fig. 6 is an element distribution diagram of a positive electrode sheet according to another embodiment of the present invention.
As shown in FIG. 6, the transition metal elements Ni, mn and Co are uniformly adhered to the PFA collector, and it is known from the Nb distribution diagram of FIG. (e) that the transition metal elements Ni, mn and Co are coated on the PFA collector via LiNbO 3 Coated NMC811 material.
Fig. 7 is an electron microscope scanning image of a positive electrode tab according to yet another embodiment of the invention.
As shown in fig. 7, a), b) and c) are electron microscope scanning images of the positive electrode sheet at different scales, respectively. It can be seen from the graph (a) that the porous structure of PFA is well maintained after many times of charge and discharge, and the phenomena of aluminum wire breakage and structure collapse do not occur, and LiNbO is known from the graph (b) 3 After cycling of-NMC-811 @ PFA, the NMC811 particles remained uniformly distributed on the PFA, with no appearance of particle shedding, indicating that the PFA structure is very stable.
Fig. 8 is an element distribution diagram of a positive electrode tab according to still another embodiment of the present invention.
As shown in FIG. 8, FIG. 8 shows LiNbO after charge-discharge cycling (electrochemical cycling) 3 Distribution of elements of-NMC811 @ PFA, from the figure(b-e) LiNbO can be seen more intuitively 3 After 100 charging and discharging times, each element is still uniformly distributed on the PFA current collector in the NMC811@ PFA. FIG. e shows the distribution of Nb, liNbO, after a long period of charge and discharge 3 The coating layer does not fall off.
Cutting the dried positive electrode into a circular pole piece with the diameter of 12mm, assembling the circular pole piece with EC/EMC/DMC type electrolyte into a button battery, and carrying out electrochemical performance test under the condition that the charging and discharging of 2.8-4.3V are cut to voltage, wherein the test result is as follows:
fig. 9 is a graph comparing cycle performance of a lithium ion battery according to an embodiment of the invention with a lithium ion battery of the prior art.
As shown in FIG. 9, liNbO was observed at a current density of 0.5C in the range of 2.8 to 4.3V in the charge-discharge voltage 3 The first cycle of the NMC811 positive electrode has a specific capacity of 176mAh/g, the first cycle of the uncoated NMC811 positive electrode has a specific capacity of 178mAh/g, and the difference in the first cycle capacity release is very small; after 150 cycles, the uncoated NMC811 positive electrode capacity is rapidly attenuated, and after 150 cycles, the uncoated NMC811 positive electrode capacity is 110mAh/g, the capacity retention rate is 62.5 percent, and LiNbO 3 The positive electrode capacity of the-NMC 811 is 150mAh/g, and the capacity retention rate is 87%. The analysis shows that the long cycle performance of the NMC811 cathode material coated with the coating is greatly improved.
Fig. 10 is a graph comparing the rate capability of a lithium ion battery according to an embodiment of the present invention with that of a lithium ion battery of the prior art.
As shown in fig. 10, at lower current densities of 0.2C, 0.5C, 1C, 2C, there was no major difference in the capacity released by the uncoated NMC811 positive electrode and the coated NMC811 positive electrode, but when the current density reached 5C, the coated NMC811 positive electrode had begun to exhibit excellent capacity release of 120mAh/g, while the uncoated NMC811 positive electrode capacity release was 110mAh/g. When the current density was further increased to 10C, it can be seen from the figure that the uncoated NMC811 positive electrode could not release capacity, while the coated NMC811 positive electrode still could release capacity close to 70mAh/g, indicating LiNbO 3 The coating layer improves the multiplying power of NMC811And (4) performance.
Fig. 11 is a graph of cycle performance of two current collectors at different loadings for a positive electrode sheet according to an embodiment of the present invention.
As shown in FIG. 11, liNbO was reacted with 3 The coated NMC811 material is coated on PFA and a conventional (AF) current collector, liNbO 3 -NMC811@ AF only 110mAh/g remains in capacity release after 200 cycles and cell failure occurs after 200 cycles, whereas LiNbO 3 -NMC811@ PFA capacity remaining 130mAh/g after 200 cycles, when no battery such as LiNbO is present 3 -NMC811@ AF, and over 600 cycles again the capacity remaining is still at considerable 100 mAh/g. Figure (a) demonstrates that the use of PFA as NMC811 current collector effectively enhances its long cycle performance. In order to further highlight the advantages of PFA as the positive electrode current collector in long cycle performance, the active material loading was increased to 15mg/cm2, the test current density was 0.2C, and the test temperature was not room temperature. The test results are shown in FIG. (b), liNbO 3 -NMC811@ AF head circle release capacity ratio LiNbO 3 the-NMC811 @ PFA is much lower, probably due to LiNbO at high active loading 3 The-nmc811 @ af positive electrode particles were not in complete contact with the electrolyte, resulting in incomplete release of capacity. In the first 200 cycles, the cycle performances of the two cycles are not greatly different, the capacity is kept to be about 155mAh/g, but LiNbO is generated after 200 cycles 3 The specific volume of the-NMC811 @ AF discharge decayed drastically, with LiNbO 3 The situation of-NMC811 @ PFA does not occur after 200 cycles, the PFA shows a slow decay trend, the discharge capacity release is still 165mAh/g after 250 cycles, the capacity retention rate is as high as 82.5 percent and is obviously higher than LiNbO 3 -nmc811@ af. Comparing the electrochemical performance of the two at low active material loadings of 10mg/cm2 and higher loadings of 15mg/cm2, it was found that PFA was used as LiNbO 3 The current collector of the NMC811 anode can obviously improve the long cycle performance and the cycle life of the NMC811 anode.
Fig. 12 is a graph of cycle performance at high active loading for a positive pole piece according to an embodiment of the invention.
As shown in FIG. 12, liNbO was added 3 The loading capacity of an active substance of-NMC811 @ PFA is increased to 42mg/cm2, the battery is firstly subjected to charge-discharge activation under the current density of 0.05C due to the overlarge loading capacity of the active substance, and then a long-cycle performance test is carried out under the current density of 0.1C, the result is shown in the figure, when the loading capacity of the active substance is increased to 42mg/cm2, under the condition of charge-discharge of 0.1C, the first-cycle discharge capacity is 175 mAh/g, the capacity release is not greatly influenced, the loading capacity of the active substance is greatly increased, and on the premise that the first-cycle discharge capacity is not greatly influenced, the capacity release of the battery is still 150mAh/g after 100 cycles, the capacity retention rate is 85%, so that LiNbO is used as a material for improving the capacity of the battery, and the battery capacity retention rate is high 3 the-NMC811 @ PFA can keep better first cycle capacity release and cycle performance under a very high active substance loading capacity (42 mg/cm < 2 >), has very important reference significance for realizing the requirement of a high energy density lithium battery, and provides a very good experimental thought for the subsequent research of a lithium ion battery with high energy density and long cycle life.
The invention combines the porous aluminum foil current collector with the coating anode, the porous structure of the porous aluminum foil current collector greatly improves the contact problem among particles, the loading capacity of active substances is improved, the stability of electrochemical performance is ensured, and the ionic conductivity is greatly improved. The cycle performance of the coated anode is obviously improved, and the energy density is improved and the cycle performance is stable by combining the anode and the coated anode.
On the premise of coating, more active substances are coated on the porous aluminum foil current collector in a blade mode, the problem of interface contact between particles and between electrolyte and the active substances is solved, a lithium ion transmission channel is constructed, and the ionic conductivity is improved. The stable circulation under the condition that the loading of the positive active material is up to 42mg/cm < 2 > is realized, and a solution is provided for realizing the improvement of the energy density.
The invention aims to protect a preparation method of a positive pole piece, the positive pole piece and a lithium ion battery, wherein the preparation method comprises the following steps: preparing NCM 811 coated with a fast ion conductor; mixing the NCM 811, the carbon black and the polyvinylidene fluoride coated with the fast ion conductor according to the mass ratio of 8-9; preparing a positive electrode slurry based on the mixture; coating the positive electrode slurry on a porous current collector to obtain a positive electrode material; and preparing the positive pole piece based on the positive pole material. According to the preparation method of the positive pole piece, the NCM 811 active matter coated by the fast ion conductor is covered on the porous current collector, so that the positive pole piece prepared by the method has high active matter carrying capacity and high energy density, the dual promotion of the cycle performance and the energy density is realized, and the electrochemical performance of the battery is obviously improved.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention shall be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundary of the appended claims, or the equivalents of such scope and boundary.

Claims (11)

1. A preparation method of a positive pole piece is characterized by comprising the following steps:
preparing NCM 811 coated with a fast ion conductor;
mixing the NCM 811 coated with the fast ion conductor, the carbon black and the polyvinylidene fluoride according to the mass ratio of 8-9;
preparing a positive electrode slurry based on the mixture;
coating the positive electrode slurry on a porous current collector to obtain a positive electrode material;
and preparing the positive pole piece based on the positive pole material.
2. The preparation method of the positive pole piece according to claim 1, wherein the step of coating the positive pole slurry on a porous current collector to obtain the positive pole material comprises the following steps:
drying the positive electrode slurry in a vacuum drying oven for 12-15h to obtain a porous current collector coated with a fast ion conductor;
the temperature of the vacuum drying oven was: 80-120 ℃.
3. The method for preparing the positive electrode sheet according to claim 1, wherein the preparing of the positive electrode slurry based on the mixture comprises:
mixing the mixture with methyl pyrrolidone to prepare the positive electrode slurry;
the mass portion of the methyl pyrrolidone is 15-20 times of that of the polyvinylidene fluoride.
4. The method for preparing the positive pole piece according to claim 1, wherein the preparing the fast ion conductor coated NCM 811 comprises:
pretreating the NCM 811 powder to obtain a dried NCM 811 powder;
dissolving 1 part of the dried NCM 811 powder, 0.01-0.02 part of niobium isopropoxide and 0.01-0.03 part of citric acid in a molar ratio in a solvent to obtain a sample solution;
and drying the sample liquid to obtain the NCM 811 coated with the fast ion conductor.
5. The method for preparing the positive electrode plate according to claim 4, wherein the preparing the NCM 811 coated with the fast ion conductor further comprises:
and stirring the sample liquid to obtain the uniformly mixed sample liquid.
6. The method for producing a positive electrode sheet according to claim 5,
and stirring by using a stirrer at the stirring speed of 200-300r/min.
7. The method for preparing the positive electrode sheet according to claim 5, wherein the drying the sample solution comprises:
heating the uniformly mixed sample liquid for 8-12h to obtain sample powder;
the heating temperature is 70-90 ℃.
8. The method for preparing the positive electrode sheet according to claim 7, wherein the step of drying the sample solution further comprises:
sintering the sample powder;
the sintering temperature is as follows: 780-830 ℃ for: 12-15h, and the heating rate is 3-5 ℃/min.
9. The method for preparing the positive electrode plate according to claim 4, wherein the pretreatment comprises:
placing NCM 811 powder into vacuum drying oven at 80-120 deg.C for drying for 8-12h.
10. A positive electrode sheet, characterized by being produced by the production method according to any one of claims 1 to 9.
11. A lithium ion battery comprising the positive electrode sheet according to claim 10.
CN202210995287.0A 2022-08-18 2022-08-18 Preparation method of positive pole piece, positive pole piece and lithium ion battery Pending CN115360330A (en)

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