CN116404113A - Composite positive plate, preparation method thereof and energy storage device comprising composite positive plate - Google Patents

Composite positive plate, preparation method thereof and energy storage device comprising composite positive plate Download PDF

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Publication number
CN116404113A
CN116404113A CN202310681757.0A CN202310681757A CN116404113A CN 116404113 A CN116404113 A CN 116404113A CN 202310681757 A CN202310681757 A CN 202310681757A CN 116404113 A CN116404113 A CN 116404113A
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coating layer
composite positive
positive electrode
electrode sheet
protective layer
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CN116404113B (en
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谢炎崇
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Shenzhen Haichen Energy Storage Control Technology Co ltd
Xiamen Hithium Energy Storage Technology Co Ltd
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Shenzhen Haichen Energy Storage Control Technology Co ltd
Xiamen Hithium Energy Storage 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
    • 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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0411—Methods of deposition of the material by extrusion
    • 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
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application relates to a composite positive plate, a preparation method thereof and an energy storage device comprising the same. The composite positive plate comprises a current collector, a coating layer A, a plurality of inserting parts and a protective layer B. In the composite positive plate, the structural strength of the plate material is enhanced and the electrochemical performance of the energy storage device is improved by a specially designed interface connection mode.

Description

Composite positive plate, preparation method thereof and energy storage device comprising composite positive plate
Technical Field
The application relates to the technical field of energy storage, in particular to a composite positive plate for a lithium battery, a preparation method thereof and an energy storage device comprising the composite positive plate.
Background
Secondary batteries are increasingly pursued in the direction of high energy density as the age progresses. The main positive electrode material used in the current cylindrical secondary battery is lithium iron phosphate, the theoretical gram capacity of the material is only 170mAh/g, and the material belongs to a lower level in the positive electrode material. It is therefore desirable to use some positive electrode material with a high theoretical gram capacity for developing a high energy density secondary battery. The theoretical gram capacity of the lithium-rich manganese-based material can exceed 350mAh/g, and the lithium-rich manganese-based material also has the advantages of high working voltage, high energy density and the like, so the lithium-rich manganese-based material is considered as a lithium ion battery anode material with great application prospect.
The current method for preparing the positive plate from the lithium-rich manganese-based material in scientific research or market comprises the following steps: (1) premixing raw materials: adding the main material into a stirrer for stirring and premixing to obtain a mixture; (2) wetting: stirring and dispersing the mixture and an organic solvent under a vacuum condition; (3) high speed dispersion: under the vacuum condition, adding an organic solvent, and stirring and dispersing at a high speed to obtain mixed slurry; (4) sieving: sieving the mixed slurry prepared in the high-speed dispersion step to remove large particles to obtain positive electrode slurry; (5) coating: and coating the anode slurry on an aluminum foil, and fully drying to form a coating layer to obtain the anode plate.
The lithium-rich manganese-based material still has the defects of first irreversible capacity loss, voltage attenuation, oxygen precipitation, metal manganese element dissolution and the like in the circulating process, so that the structural stability of the material is poor in the circulating process, and the circulating performance of the secondary battery is further deteriorated. At present, the material structure stability is mainly improved through element doping, metal coating and oxide coating, but in order to meet the actual industrial requirements, the lithium-rich manganese-based material still needs to be further improved in the aspects of material stability, secondary battery electrical performance and the like.
Disclosure of Invention
It is an object of the present invention to provide a composite positive electrode sheet for an energy storage device having improved structural strength of the sheet material and an energy storage device made therefrom having improved electrochemical performance.
In one aspect, the present application provides a composite positive plate for an energy storage device, which is characterized in that it includes a current collector, a coating layer a, a plurality of insertion portions, and a protective layer B, wherein:
the coating layer A is arranged on the surface of the current collector and comprises a lithium-rich manganese-based material, and the chemical formula of the coating layer A is xLi 2 MnO 3 ·(1-x)LiMO 2 Wherein 0 is<x<1, M is Ni and/or Mn;
the insertion part and the protective layer B comprise ternary materials with a chemical formula of LiNi a Mn b Co c O 2 Wherein a+b+c=1;
the plurality of insertion parts are inserted into the interface of the coating layer a in a column shape, wherein an angle at which the insertion parts are inserted into the interface of the coating layer a is 45 ° to 90 ° with respect to the surface of the coating layer a; the spacing between the plurality of insertion portions is 50 μm or less; the width of each of the plurality of insertion portions is 10 μm to 18 μm; the depth of the insertion portion inserted into the coating layer a is 15 μm to 30 μm with respect to the surface of the coating layer a;
the protective layer B is provided on the surface of the coating layer a in which the insertion portion is inserted.
In another aspect, the present application provides a method for preparing the composite positive electrode sheet of the present invention, characterized in that the method comprises:
(1) Preparation of coating layer A: coating slurry containing a lithium-rich manganese-based material on the surface of a current collector to form a coating layer A;
(2) Preparation of the insert: inserting the slurry containing the ternary material into the interface of the coating layer A in a needle tube extrusion injection mode;
(3) Preparation of protective layer B: a slurry containing a ternary material is coated on the surface of the coating layer a in which the insertion portion is inserted.
In another aspect, the present application provides an energy storage device characterized in that it comprises the composite positive electrode sheet of the present invention.
The composite positive plate of the invention has a specially designed insertion portion. Therefore, the lithium ion battery prepared from the lithium ion battery has improved structural strength of the pole piece material and improved electrochemical properties of the lithium battery, such as rate discharge capacity and cycle performance.
Drawings
Fig. 1 shows a schematic diagram of a preparation flow of a composite positive electrode sheet of the present invention.
FIG. 2 shows the particle morphology of a positive electrode material used in the present invention, wherein (a) is a lithium-rich manganese-based material; (b) is a ternary material.
Fig. 3 shows the particle and coating distribution of a partial cross section of the composite positive electrode sheet of the present invention.
Detailed Description
The ternary material has the advantages of high discharge voltage, high energy density, long cycle life and the like, has the voltage range well matched with the lithium-rich manganese-based material, and can be used as a protective layer of the lithium-rich manganese-based material to inhibit the defects of the lithium-rich manganese-based material in a coating mode, for example, the corrosion of electrolyte is reduced, so that the dissolution of metal manganese element is reduced, and the stability of the lithium-rich manganese-based material is directly improved. In a typical positive electrode sheet preparation method, a ternary material is coated on a lithium-rich manganese-based material. Because the two materials are only bonded simply and the physical property difference of the lithium-rich manganese-based material and the ternary material is large, the pole piece material can still be peeled off in the later stage of charge-discharge cycle.
Therefore, the invention designs a composite positive plate which comprises an aluminum foil, a coating layer A (lithium-rich manganese-based material), a plurality of insertion parts and a protective layer B (ternary material), and the ternary material is specially distributed in the lithium-rich manganese-based material and on the surface layer by designing a special interface connection mode, so that the effect of enhancing the structural strength of the pole plate material can be achieved, and the electrochemical performance of an energy storage device, especially a lithium ion battery, is improved.
In one aspect, the present application provides a composite positive plate for an energy storage device, which is characterized in that it includes a current collector, a coating layer a, a plurality of insertion portions, and a protective layer B, wherein:
the coating layer A is arranged on the surface of the current collector and comprises a lithium-rich manganese-based material, and the chemical formula of the coating layer A is xLi 2 MnO 3 ·(1-x)LiMO 2 Wherein 0 is<x<1, M is Ni and/or Mn;
the insertion part and the protective layer B comprise ternary materials with a chemical formula of LiNi a Mn b Co c O 2 Wherein a+b+c=1;
the plurality of insertion parts are inserted into the interface of the coating layer a in a column shape, wherein an angle at which the insertion parts are inserted into the interface of the coating layer a is 45 ° to 90 ° with respect to the surface of the coating layer a; the spacing between the plurality of insertion portions is 50 μm or less; the width of each of the plurality of insertion portions is 10 μm to 18 μm; the depth of the insertion portion inserted into the coating layer a is 15 μm to 30 μm with respect to the surface of the coating layer a;
the protective layer B is provided on the surface of the coating layer a in which the insertion portion is inserted.
In a specific embodiment, the current collector is an aluminum foil, which may have a thickness of 10 μm to 20 μm.
In a specific embodiment, the morphology of the particles of the lithium-rich manganese-based material used to prepare coating layer a of the present application is shown in fig. 2 (a).
In a specific embodiment, the thickness of the coating layer a may be 40 μm to 80 μm, for example, about 60 μm.
In a specific embodiment, the morphology of the particles of the ternary material used to prepare the insert and protective layer B of the present application is shown in figure 2 (B).
In a specific embodiment, the spacing between the plurality of the insertion portions is 40 μm or less, preferably 30 μm or less.
In a specific embodiment, the width of each of the plurality of inserts is from 12 μm to 16 μm, preferably about 14 μm.
The plurality of insertion portions are inserted into the interface of the coating layer a in a columnar shape. The cross-section of the column may be circular, oval, square, rectangular or any shape deemed suitable by the person skilled in the art. In this application, when referring to the width of the insertion portion, it is meant for a circular cross-section its diameter, for an oval cross-section its long diameter, for a square cross-section its side length, and for a rectangular cross-section its long side length.
In a specific embodiment, the insert is inserted into the coating layer a to a depth of 20 μm to 30 μm, preferably about 25 μm, with respect to the surface of the coating layer a.
In a specific embodiment, the thickness of the protective layer B is 20 μm to 40 μm, preferably 30 μm to 40 μm, more preferably about 35 μm.
In another aspect, the present application provides a method of preparing the composite positive electrode sheet of the present invention, the method comprising the steps of:
(1) Preparation of coating layer A: coating slurry containing a lithium-rich manganese-based material on the surface of a current collector to form a coating layer A;
(2) Preparation of the insert: inserting the slurry containing the ternary material into the interface of the coating layer A in a needle tube extrusion injection mode;
(3) Preparation of protective layer B: a slurry containing a ternary material is coated on the surface of the coating layer a in which the insertion portion is inserted.
The specific flow of preparing the composite positive plate is shown in figure 1.
In one embodiment, the composite positive electrode sheet of the present invention is prepared as follows:
1. preparation of coating layer A (refer to (a) diagram in FIG. 1)
(1) The weight ratio is 95 percent: 2%:3% weighing corresponding amounts of lithium-rich manganese-based material, conductive carbon black and polyvinylidene fluoride in a stirring tank, and adding a proper amount of N-methyl pyrrolidone (NMP) and stirring for 6 hours to obtain uniform slurry with proper viscosity.
(2) The slurry is uniformly coated on the aluminum foil by an extrusion coating mode to form a coating layer A.
2. Preparation of the insertion portion (refer to (b) view in FIG. 1)
(2) The weight ratio is 95 percent: 2%:3% of a ternary material, conductive carbon black and polyvinylidene fluoride with corresponding amounts are weighed in a stirring tank, and then a proper amount of N-methyl pyrrolidone (NMP) is added to be stirred for 6 hours, so that uniform slurry with proper viscosity is obtained.
(2) The slurry is loaded in a special device such as an injector, and the injection quantity, the injection angle, the movement displacement, the frequency and the like are controlled by a needle tube extrusion injection mode to insert the slurry into the interface of the coating layer A, wherein the injection angle is theta (45-90 degrees) relative to the surface of the coating layer A, the width of an insertion part is D, the interval is L, and the depth is h.
3. Preparation of protective layer B (refer to (c) in FIG. 1)
And (3) rapidly coating the uniform slurry of the ternary material prepared in the step (2) on the coating layer A inserted with the insertion part in an extrusion coating mode, and then sufficiently drying through an oven to form a protective layer B, thereby obtaining the composite positive plate with the coating layer A, the insertion part and the protective layer B.
In another aspect, the present application provides an energy storage device comprising the composite positive electrode sheet of the present invention.
In a specific embodiment, the energy storage device is a lithium ion battery.
In one embodiment, the lithium ion battery of the present invention is prepared as follows:
(1) The weight ratio is 95 percent: 2.5%:2.5 percent of artificial graphite, conductive carbon black and sodium carboxymethylcellulose with corresponding amounts are weighed in a stirring tank, and a proper amount of deionized water is added to stir for 5 hours to obtain uniform slurry with proper viscosity; and coating the slurry on copper foil with the thickness of 10 mu m, putting the copper foil into a vacuum oven, and drying the copper foil at 150 ℃ for 15 hours to obtain the negative plate.
(2) And (3) putting the positive electrode plate and the negative electrode plate into a press machine for pressing, and then adopting a puncher to respectively intercept a positive electrode wafer with phi 15mm and a negative electrode wafer with phi 18 mm.
(3) The positive electrode wafer and the negative electrode wafer are placed in a glove box filled with an argon protective atmosphere for battery assembly, wherein 1mol/L lithium hexafluorophosphate is used for dissolving in the following molar ratio of 1:1 and diethyl carbonate as electrolyte; and assembling the anode wafer, the cathode wafer, the polyethylene diaphragm and other components together, then injecting electrolyte, and finally preparing the lithium ion battery.
The technical scheme of the present invention will be described in detail with reference to specific embodiments.
Preparation of composite positive plate
The following composite positive electrode sheets of examples and comparative examples were prepared using the method shown in fig. 1.
Example 1
1. Preparation of coating layer A
(1) The weight ratio is 95 percent: 2%:3% of corresponding amount of lithium-rich manganese-based material 0.6Li is weighed 2 MnO 3 ·0.4LiMnO 2 And (3) adding conductive carbon black and polyvinylidene fluoride into a stirring tank, and adding a proper amount of N-methyl pyrrolidone (NMP) and stirring for 6 hours to obtain uniform slurry with proper viscosity.
(2) The above slurry was uniformly coated on an aluminum foil by means of extrusion coating to form a coating layer a having a thickness of about 60 μm.
2. Preparation of the insertion portion
(1) The weight ratio is 95 percent: 2%:3% of ternary material LiNi with corresponding weight 0.6 Mn 0.2 Co 0.2 O 2 And (3) adding conductive carbon black and polyvinylidene fluoride into a stirring tank, and adding a proper amount of N-methyl pyrrolidone (NMP) and stirring for 6 hours to obtain uniform slurry with proper viscosity.
(2) The slurry is loaded in a special device, and the slurry is inserted into the interface of the coating layer A by controlling the injection quantity, the injection angle, the movement displacement, the frequency and the like through a needle tube extrusion injection mode, wherein the injection angle is 45 degrees relative to the surface of the coating layer A, the width of the insertion part is about 10 mu m, the interval is about 30 mu m, and the depth is about 15 mu m.
3. Preparation of protective layer B
The uniform slurry of the ternary material prepared in step 2 was rapidly coated on the above-mentioned coating layer a with the insertion portion interposed by means of extrusion coating, and then sufficiently dried by an oven to form a protective layer B having a thickness of about 20 μm.
Thus, a composite positive electrode sheet having a coating layer a, an insertion portion and a protective layer B was obtained, and the distribution of particles and coating layers in the cross section thereof was as shown in fig. 3.
Example 2
The composite positive electrode sheet was produced in the same manner and with the same materials as in example 1, except that the width of the insertion portion was controlled to be 12 μm.
Example 3
The composite positive electrode sheet was produced in the same manner and with the same materials as in example 1, except that the width of the insertion portion was controlled to be 14 μm.
Example 4
The composite positive electrode sheet was produced in the same manner and with the same materials as in example 1, except that the width of the insertion portion was controlled to be 16 μm.
Example 5
The composite positive electrode sheet was produced in the same manner and with the same materials as in example 1, except that the width of the insertion portion was controlled to 18 μm.
Example 6
The composite positive electrode sheet was fabricated by the same method and material as in example 1, but the spacing between the insertion portions was controlled to be 40 μm.
Example 7
A composite positive electrode sheet was fabricated by the same method and material as in example 1, but the pitch between the insertion portions was controlled to be 50 μm.
Example 8
The composite positive electrode sheet was fabricated by the same method and material as in example 1, but the depth of the insertion portion was controlled to 20 μm.
Example 9
The composite positive electrode sheet was fabricated by the same method and material as in example 1, but the depth of the insertion portion was controlled to 25 μm.
Example 10
The composite positive electrode sheet was fabricated by the same method and material as in example 1, but the depth of the insertion portion was controlled to be 30 μm.
Example 11
A composite positive electrode sheet was fabricated by the same method and material as in example 1, but the thickness of the protective layer B was controlled to 25 μm.
Example 12
A composite positive electrode sheet was fabricated by the same method and material as in example 1, but the thickness of the protective layer B was controlled to be 30 μm.
Example 13
A composite positive electrode sheet was fabricated by the same method and material as in example 1, but the thickness of the protective layer B was controlled to be 35 μm.
Example 14
A composite positive electrode sheet was fabricated by the same method and material as in example 1, but the thickness of the protective layer B was controlled to 40 μm.
Comparative example 1
A composite positive electrode sheet including only the coating layer a was prepared using the same method and material as in step 1 of example 1.
Comparative example 2
1. Preparation of coating layer A
A coating layer a was prepared on an aluminum foil using the same method and material as in step 1 of example 1.
2. Preparation of protective layer B
The protective layer B was formed on the coating layer a using the same method and material as in step 3 of example 1. And obtaining the composite positive plate with the coating layer A and the protective layer B.
Manufacturing of lithium ion battery
Using the composite positive electrode sheets prepared in the above examples and comparative examples, lithium ion batteries were fabricated according to the following procedure.
(1) The weight ratio is 95 percent: 2.5%:2.5 percent of artificial graphite, conductive carbon black and sodium carboxymethylcellulose with corresponding amounts are weighed in a stirring tank, and a proper amount of deionized water is added to stir for 5 hours to obtain uniform slurry with proper viscosity; and coating the slurry on copper foil with the thickness of 10 mu m, putting the copper foil into a vacuum oven, and drying the copper foil at 150 ℃ for 15 hours to obtain the negative plate.
(2) And (3) putting the positive electrode plate and the negative electrode plate into a press machine for pressing, and then adopting a puncher to respectively intercept a positive electrode wafer with phi 15mm and a negative electrode wafer with phi 18 mm.
(3) The positive electrode wafer and the negative electrode wafer are placed in a glove box filled with an argon protective atmosphere for battery assembly, wherein 1mol/L lithium hexafluorophosphate is used for dissolving in the following molar ratio of 1:1 and diethyl carbonate as an electrolyte. And assembling the anode wafer, the cathode wafer, the polyethylene diaphragm and other components together, then injecting electrolyte, and finally preparing the lithium ion battery.
Test method
The following test was performed on the composite positive electrode sheet or lithium ion battery fabricated above.
1) Peel force test
The positive electrode sheet of 20mm by 70mm was cut, the coating was stuck and fixed with a 3M double-sided tape, and then 180 DEG peel test was performed by a high-speed rail tensile machine at a strain rate of 10mm/min, and the result was based on the average value of the peel force in the longitudinal direction in N/cm.
2) Rate discharge capacity
The prepared lithium battery was charged to 4.5V at 0.5C rate at 25C, and then discharged to 3V at 0.5C rate, and the 0.5C discharge capacity was recorded. Then, the charge was carried out to 4.5V at a 1C rate, and then the discharge was carried out to 3V at a 1C rate, whereby a 1C discharge capacity was recorded.
3) Cycle performance test
And charging the prepared lithium battery to 4.5V at the rate of 1C at 25 ℃, discharging to 3V at the rate of 1C, and dividing the capacity of the 1 st cycle by the initial capacity to obtain a retention rate value by taking the capacity of the 200 th cycle as the initial capacity.
The results obtained are shown in Table 1 below.
Table 1: electrochemical test results for lithium ion batteries
Figure SMS_1
Data analysis:
as can be seen from comparative examples 1 and 2 in table 1, the single coated positive electrode sheet, although having high structural strength (as evaluated by the magnitude of the peeling force) and capacity performance, has the disadvantage of being very poor in cycle performance due to the presence of the lithium-rich manganese-based material itself.
As can be seen from experimental examples 1 and 2 in Table 1, the composite positive plate provided by the invention is provided with the insertion parts which are specially distributed, so that the structural strength of the plate material can be obviously improved, and the electrochemical performance of the lithium battery can be improved.
As can be seen from examples 1, 2, 3, 4, and 5 in table 1, when the width of the insertion portion is gradually increased (10 to 20 μm), the electrochemical performance of the lithium battery is increased first and then decreased because when the insertion portion is too large, i.e., the ternary material ratio is excessively large, the gram capacity of the positive electrode sheet material is indirectly decreased, and thus the optimal parameter of the width of the insertion portion in the composite positive electrode sheet of the present invention is about 14 μm.
As can be seen from examples 1, 7 and 8 in Table 1, as the spacing of the insertion portions increases gradually (30 to 50 μm), the structural strength of the electrode sheet material becomes poor, and the electrochemical performance of the lithium battery becomes poor, so that the spacing of the insertion portions in the composite positive electrode sheet of the present invention is preferably not more than 30. Mu.m.
As can be seen from examples 6, 7, 8 in table 1, as the depth of the insertion portion gradually increases (15 to 30 μm), the electrochemical performance of the lithium battery increases and then decreases for the same reason as described above, so that the optimum parameter of the depth of the insertion portion in the composite positive electrode sheet of the present invention is about 25 μm.
As can be seen from examples 9, 10, 11, 12 in table 1, when the thickness of the protective layer B is increased from 20 μm to 40 μm, the electrochemical performance of the lithium battery is increased and then decreased, because when the thickness of the protective layer B is too thick, it is difficult for the electrolyte to infiltrate into the inside and the material characteristics cannot be exerted, so the optimal thickness of the protective layer B of the composite positive electrode sheet is about 35 μm.

Claims (13)

1. The composite positive plate for the energy storage device is characterized by comprising a current collector, a coating layer A, a plurality of inserting parts and a protective layer B, wherein:
the coating layer A is arranged on the surface of the current collector and comprises a lithium-rich manganese-based material, and the chemical formula of the coating layer A is xLi 2 MnO 3 ·(1-x)LiMO 2 Wherein 0 is<x<1, M is Ni and/or Mn;
the insertion part and the protective layer B comprise ternary materials with a chemical formula of LiNi a Mn b Co c O 2 Wherein a+b+c=1;
the plurality of insertion parts are inserted into the interface of the coating layer a in a column shape, wherein an angle at which the insertion parts are inserted into the interface of the coating layer a is 45 ° to 90 ° with respect to the surface of the coating layer a; the spacing between the plurality of insertion portions is 50 μm or less; the width of each of the plurality of insertion portions is 10 μm to 18 μm; the depth of the insertion portion inserted into the coating layer a is 15 μm to 30 μm with respect to the surface of the coating layer a;
the protective layer B is provided on the surface of the coating layer a in which the insertion portion is inserted.
2. The composite positive electrode sheet according to claim 1, wherein a pitch between the plurality of insertion portions is 40 μm or less.
3. The composite positive electrode sheet according to claim 1, wherein a pitch between the plurality of insertion portions is 30 μm or less.
4. The composite positive electrode sheet according to claim 1, wherein the width of each of the plurality of insertion portions is 12 μm to 16 μm.
5. The composite positive electrode sheet according to claim 1, wherein the width of each of the plurality of insertion portions is about 14 μm.
6. The composite positive electrode sheet according to claim 1, wherein the depth of the insertion portion into the coating layer a is 20 μm to 30 μm with respect to the surface of the coating layer a.
7. The composite positive electrode sheet according to claim 1, wherein the depth of the insertion portion into the coating layer a is about 25 μm with respect to the surface of the coating layer a.
8. The composite positive electrode sheet according to claim 1, wherein the thickness of the protective layer B is 20 μm to 40 μm.
9. The composite positive electrode sheet according to claim 1, wherein the thickness of the protective layer B is 30 μm to 40 μm.
10. The composite positive electrode sheet according to claim 1, wherein the thickness of the protective layer B is about 35 μm.
11. A method of preparing the composite positive electrode sheet of any one of claims 1 to 10, characterized in that the method comprises the steps of:
(1) Preparation of coating layer A: coating slurry containing a lithium-rich manganese-based material on the surface of a current collector to form a coating layer A;
(2) Preparation of the insert: inserting the slurry containing the ternary material into the interface of the coating layer A in a needle tube extrusion injection mode;
(3) Preparation of protective layer B: a slurry containing a ternary material is coated on the surface of the coating layer a in which the insertion portion is inserted.
12. An energy storage device comprising the composite positive electrode sheet of any one of claims 1 to 10.
13. The energy storage device of claim 12, wherein the energy storage device is a lithium ion battery.
CN202310681757.0A 2023-06-09 2023-06-09 Composite positive plate, preparation method thereof and energy storage device comprising composite positive plate Active CN116404113B (en)

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