CN114975853A - Composite positive pole piece and preparation method and application thereof - Google Patents

Composite positive pole piece and preparation method and application thereof Download PDF

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Publication number
CN114975853A
CN114975853A CN202210526729.7A CN202210526729A CN114975853A CN 114975853 A CN114975853 A CN 114975853A CN 202210526729 A CN202210526729 A CN 202210526729A CN 114975853 A CN114975853 A CN 114975853A
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active layer
positive electrode
lithium
active material
conductive agent
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王坤
成小康
苏威同
田冰冰
李真棠
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Guangdong Carriage Power Technology Co ltd
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Guangdong Carriage Power 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of 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
    • H01M4/62—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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses a composite positive pole piece and a preparation method and application thereof, wherein the composite positive pole piece comprises a current collector, first active layers arranged on the upper surface and the lower surface of the current collector, and a second active layer arranged on the first active layer, wherein the materials of the first active layer and the second active layer respectively comprise positive active substances, a conductive agent, a binder and solid electrolyte; the active materials in the first active layer and the second active layer are different materials, or the material of the first active layer is the same as the material forming the second active layer, but the mass ratio of the positive electrode active material to the conductive agent in the first active layer to the second active layer is different. The battery cell composed of the composite positive pole piece provided by the invention can obtain excellent comprehensive properties such as high energy density, high rate performance, high safety performance, long cycle performance, low cost and the like.

Description

Composite positive pole piece and preparation method and application thereof
Technical Field
The invention relates to the technical field of positive electrode materials, in particular to a composite positive electrode plate and a preparation method and application thereof.
Background
Since the commercial popularization of lithium ion batteries, lithium ion batteries have many advantages such as high energy density, high discharge voltage, long cycle life, no memory effect, environmental protection, low self-discharge, and high stability, and have been widely used as power sources for various consumer electronics products, electric vehicles, energy storage power stations, and the like.
However, with the rapid development of consumer electronics, electric vehicles, energy storage and other industries, people have made higher requirements on lithium ion batteries in terms of energy density, rate capability, safety performance, cycle performance, quick charge performance, high and low temperature performance, stability, cost and the like. In this case, the single-layer structure electrode often fails to satisfy the performance requirements.
Accordingly, there is a need for improvements and developments in the art.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a composite positive pole piece and a preparation method and application thereof, and aims to solve the problem that the conventional lithium ion battery negative pole material is poor in comprehensive electrical property.
The technical scheme of the invention is as follows:
a composite positive pole piece comprises a current collector, first active layers arranged on the upper surface and the lower surface of the current collector, and a second active layer arranged on the first active layer, wherein the material for forming the first active layer comprises a first positive active substance, a first conductive agent, a first binder and a first solid electrolyte, and the material for forming the second active layer comprises a second positive active substance, a second conductive agent, a second binder and a second solid electrolyte; the first positive electrode active material and the second positive electrode active material are different materials, or the material forming the first active layer is the same as the material forming the second active layer, the mass ratio of the first positive electrode active material in the first active layer is different from the mass ratio of the second positive electrode active material in the second active layer, and the mass ratio of the first conductive agent in the first active layer is different from the mass ratio of the second conductive agent in the second active layer.
The composite positive pole piece is characterized in that the first positive active material is one of lithium iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary, nickel-cobalt-aluminum ternary and lithium manganate; the second positive electrode active material is one of lithium iron phosphate, lithium cobaltate, nickel cobalt manganese ternary, nickel cobalt aluminum ternary and lithium manganate.
The composite positive pole piece is characterized in that the first positive active substance is lithium iron phosphate, and the second positive active substance is a nickel-cobalt-manganese ternary material.
The composite positive pole piece is characterized in that the first positive active substance is a nickel-cobalt-manganese ternary material, and the second positive active substance is lithium cobaltate.
The composite positive pole piece is characterized in that the first positive active material is lithium iron phosphate, and the second positive active material is lithium cobaltate.
The composite positive pole piece is characterized in that the material for forming the first active layer comprises, by mass, 80-88% of a first positive active substance, 0.5-5% of a first conductive agent, 0.5-5% of a first binder and 5-20% of a first solid electrolyte; the material forming the second active layer includes, in mass percent, 80 to 88% of a second positive electrode active material, 0.5 to 5% of a second conductive agent, 0.5 to 5% of a second binder, and 5 to 20% of a second solid electrolyte.
The composite positive pole piece is characterized in that the first conductive agent and the second conductive agent are independently selected from one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, ketjen black, conductive graphite and carbon fibers; the first binder and the second binder are independently selected from one or more of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polymethyl methacrylate, polyvinyl chloride, polyethylene imine, poly (phenylene terephthalamide), poly (methoxy polyethylene glycol) methacrylate, poly (2-methoxyethyl glycidyl ether), polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene carbonate, polytrimethylene carbonate and polypropylene carbonate; the first solid electrolyte and the second solid electrolyte are independently selected from one or more of lithium lanthanum zirconium oxygen, lithium lanthanum zirconium tantalum oxygen, lithium lanthanum titanium oxygen, titanium aluminum lithium phosphate, zirconium lithium phosphate, germanium aluminum lithium phosphate, lithium germanium phosphorus sulfur, lithium phosphorus sulfur chloride, lithium phosphorus sulfur bromide and lithium phosphorus sulfur iodide.
A preparation method of a composite positive pole piece comprises the following steps:
mixing a first positive electrode active material, a first conductive agent, a first binder and N-methylpyrrolidone to form a first slurry;
mixing a second positive electrode active material, a second conductive agent, a second binder and N-methylpyrrolidone to form a second slurry;
coating the first slurry on the upper surface and the lower surface of a current collector to form a first active layer;
and coating the second slurry on the surface of the first active layer to form a second active layer, so as to obtain the composite positive pole piece.
The application of the composite positive pole piece is characterized in that the composite positive pole piece is used for preparing an all-solid-state lithium ion battery.
Has the advantages that: the composite positive pole piece provided by the invention is of a double-layer structure and comprises a first active layer and a second active layer, the composite positive pole piece of the double-layer structure can avoid the defects of one active layer, obtain the advantages of the other active layer, even complement each other, obtain the gain effect which is difficult to achieve by single-layer coating, and improve the comprehensive performance of the electrode and the battery.
Drawings
Fig. 1 is a schematic structural diagram of a composite positive electrode sheet according to the present invention.
Detailed Description
The invention provides a composite positive pole piece and a preparation method and application thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and more clear and definite. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a composite positive electrode plate provided in the present invention, and as shown in the figure, the composite positive electrode plate includes a current collector 10, a first active layer 20 disposed on the upper and lower surfaces of the current collector 10, and a second active layer 30 disposed on the first active layer 20, where a material forming the first active layer includes a first positive electrode active material, a first conductive agent, a first binder and a first solid electrolyte, and a material forming the second active layer includes a second positive electrode active material, a second conductive agent, a second binder and a second solid electrolyte; the first positive electrode active material and the second positive electrode active material are different materials, or the material forming the first active layer is the same as the material forming the second active layer, the mass ratio of the first positive electrode active material in the first active layer is different from the mass ratio of the second positive electrode active material in the second active layer, and the mass ratio of the first conductive agent in the first active layer is different from the mass ratio of the second conductive agent in the second active layer.
In the composite positive pole piece provided by the invention, the first positive active substance and the second positive active substance are different materials, which means that the first positive active substance and the second positive active substance are different materials in gram volume, compacted density, rate capability, safety performance, cycle performance or cost, so that the double-layer structure composite positive pole piece composed of different active substance materials can avoid the defects of one active layer, obtain the advantages of the other active layer, achieve the effect of complementing each other, and enable the battery cell composed of the composite positive pole piece to obtain excellent comprehensive performances such as high energy density, high rate capability, high safety performance, long cycle performance, low cost and the like.
In the composite positive electrode plate provided by the invention, the material forming the first active layer is the same as the material forming the second active layer, the mass ratio of the first positive electrode active substance in the first active layer is different from the mass ratio of the second positive electrode active substance in the second active layer, and the mass ratio of the first conductive agent in the first active layer is different from the mass ratio of the second conductive agent in the second active layer. That is to say, the formula proportions of the first active layer and the second active layer in the composite positive pole piece are different, and the composite positive pole piece with a double-layer structure formed under the condition can avoid the defects of one active layer, obtain the advantages of the other active layer and achieve the effect of bringing out the best in each other, so that the battery cell formed by the composite positive pole piece can obtain excellent comprehensive performances such as high energy density, high rate capability, high safety performance, long cycle performance, low cost and the like.
In some embodiments, the first positive electrode active material is one or more of lithium iron phosphate, lithium cobaltate, ternary nickel cobalt manganese, ternary nickel cobalt aluminum, and lithium manganate, but is not limited thereto; the second positive active material is one or more of lithium iron phosphate, lithium cobaltate, ternary nickel-cobalt-manganese, ternary nickel-cobalt-aluminum and lithium manganate, but is not limited thereto.
In some specific embodiments, a composite positive electrode sheet is provided, which includes a current collector, a first active layer disposed on upper and lower surfaces of the current collector, and a second active layer disposed on the first active layer, wherein a material forming the first active layer includes a first positive active material, a first conductive agent, a first binder, and a first solid electrolyte, and a material forming the second active layer includes a second positive active material, a second conductive agent, a second binder, and a second solid electrolyte; the first positive active material is lithium iron phosphate, and the second positive active material is a nickel-cobalt-manganese ternary material. In this embodiment, because the lithium iron phosphate has a higher safety performance, a better cycle performance, and a lower cost compared with the nickel-cobalt-manganese ternary material, and the nickel-cobalt-manganese ternary material has a higher energy density compared with the lithium iron phosphate, when the composite positive electrode plate provided by this embodiment is used for preparing an all-solid-state lithium ion battery, the cycle capacity retention rate of the battery can be effectively improved by 500 cycles, the safety performance of the battery can be improved, and the manufacturing cost can be reduced.
In some specific embodiments, there is also provided a composite positive electrode sheet including a current collector, a first active layer disposed on upper and lower surfaces of the current collector, and a second active layer disposed on the first active layer, wherein a material forming the first active layer includes a first positive active material, a first conductive agent, a first binder, and a first solid electrolyte, and a material forming the second active layer includes a second positive active material, a second conductive agent, a second binder, and a second solid electrolyte; the first positive electrode active substance is a nickel-cobalt-manganese ternary material, and the second positive electrode active substance is lithium cobaltate. In this embodiment, the composite positive electrode sheet has a higher compaction density, so that when the composite positive electrode sheet provided by this embodiment is used for preparing an all-solid-state lithium ion battery, the volume energy density of the battery can be effectively improved.
In some specific embodiments, there is also provided a composite positive electrode sheet including a current collector, a first active layer disposed on upper and lower surfaces of the current collector, and a second active layer disposed on the first active layer, wherein a material forming the first active layer includes a first positive active material, a first conductive agent, a first binder, and a first solid electrolyte, and a material forming the second active layer includes a second positive active material, a second conductive agent, a second binder, and a second solid electrolyte; the first positive electrode active material is lithium iron phosphate, and the second positive electrode active material is lithium cobaltate. In this embodiment, because lithium cobaltate has higher energy density and higher safety, better cycling stability and lower cost than lithium cobaltate, when the composite positive electrode plate provided by this embodiment is used for preparing an all-solid-state lithium ion battery, the retention rate of the cycling capacity of the battery can be effectively improved by 500 cycles, the safety performance of the battery can be improved, and the manufacturing cost can be reduced.
In some embodiments, the material forming the first active layer includes, in mass percent, 80 to 88% of a first positive electrode active material, 0.5 to 5% of a first conductive agent, 0.5 to 5% of a first binder, and 5 to 20% of a first solid electrolyte; the material forming the second active layer includes, in mass percent, 80 to 88% of a second positive electrode active material, 0.5 to 5% of a second conductive agent, 0.5 to 5% of a second binder, and 5 to 20% of a second solid electrolyte.
In some embodiments, the first and second conductive agents are independently selected from one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, ketjen black, conductive graphite, and carbon fibers, but are not limited thereto. In this embodiment, the first conductive agent and the second conductive agent may be the same or different.
In some embodiments, the first and second binders are independently selected from one or more of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polymethyl methacrylate, polyvinyl chloride, polyethylene imine, poly-phenylene terephthalamide, poly-methoxypolyethylene glycol methacrylate, poly-2-methoxyethyl glycidyl ether, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene carbonate, polytrimethylene carbonate, and polypropylene carbonate, but are not limited thereto. In this embodiment, the first adhesive and the second adhesive may be the same or different.
In some embodiments, the first solid state electrolyte and the second solid state electrolyte are independently selected from one or more of lithium lanthanum zirconium oxygen, lithium lanthanum zirconium tantalum oxygen, lithium lanthanum titanium oxygen, lithium titanium aluminum phosphate, lithium zirconium phosphate, lithium germanium aluminum phosphate, lithium germanium phosphorous sulfide, lithium phosphorous sulfide chloride, lithium phosphorous sulfide bromide, and lithium phosphorous sulfide iodide, but are not limited thereto. In the present embodiment, the first solid electrolyte and the second solid electrolyte may be the same or different.
In some embodiments, there is also provided a method for preparing a composite positive electrode sheet, comprising the steps of:
s10, mixing a first positive electrode active material, a first conductive agent, a first binder and N-methyl pyrrolidone to form first slurry;
s20, mixing a second positive electrode active material, a second conductive agent, a second binder and N-methyl pyrrolidone to form a second slurry,
s30, coating the first slurry on the upper surface and the lower surface of a current collector to form a first active layer;
and S40, coating the second slurry on the surface of the first active layer to form a second active layer, and obtaining the composite positive pole piece.
The preparation method of the composite positive pole piece provided by this embodiment is simple and easy to operate, the prepared composite positive pole piece is of a double-layer structure, and includes a first active layer and a second active layer, the composite positive pole piece of the double-layer structure can avoid the disadvantage of one active layer, and obtain the advantage of the other active layer, so as to achieve the effect of bringing out the best in each other, so that the battery cell composed of the composite positive pole piece can obtain excellent comprehensive properties such as high energy density, high rate performance, high safety performance, long cycle performance, low cost and the like.
In this embodiment, the solid content in the first slurry and the second slurry is 30 to 70%, and may be, for example, 40%, 50%, 60%, 70%, or the like.
In some embodiments, the application of the composite positive electrode plate is also provided, wherein the composite positive electrode plate is used for preparing an all-solid-state lithium ion battery. In this embodiment, the all-solid-state lithium ion battery further includes a solid electrolyte and a negative electrode plate, and the solid electrolyte is not limited in this embodiment, and may be any known solid electrolyte that can be used in a lithium ion battery, such as lithium lanthanum zirconium oxygen, lithium lanthanum zirconium tantalum oxygen, lithium lanthanum titanium oxygen, titanium aluminum lithium phosphate, zirconium lithium phosphate, germanium aluminum lithium phosphate, lithium germanium phosphorus sulfur, lithium phosphorus sulfur chloride, lithium phosphorus sulfur bromide, lithium phosphorus sulfur iodide, and the like. In this embodiment, the negative electrode plate active material is not limited, and may be one or a combination of at least two of artificial graphite, silicon carbon material, natural graphite, carbon black, carbon fiber, carbon nanotube, graphene, hard carbon, silicon, tin, and silica. And separating the positive pole piece and the negative pole piece by using a solid electrolyte to form an electrode group, placing the electrode group into a battery case, and sealing the battery case to obtain the all-solid-state lithium ion battery.
The invention is further illustrated by the following specific examples:
example 1
The first active material layer slurry is formed by mixing 87.5% of lithium iron phosphate, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of an aluminum foil to form a first active material layer; the second active material layer slurry is formed by mixing 87.5% of nickel-cobalt-manganese ternary material, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent, and is coated on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 20g/m 2 The coating surface density of the second active material layer is 85g/m 2 。
Example 2
The first active material layer slurry is formed by mixing 87.5% of lithium iron phosphate, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of an aluminum foil to form a first active material layer; the second active material layer slurry is formed by mixing 87.5% of nickel-cobalt-manganese ternary material, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent, and is coated on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 72g/m 2 The second active material layer has a coating surface density of 50g/m 2 。
Example 3
The first active material layer slurry is prepared by mixing 87.5% of nickel-cobalt-manganese ternary material, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent to form slurry, and coating the slurry on the surface of an aluminum foil to form a first active material layer; second activityThe material layer slurry is prepared by mixing 87.0% of nickel-cobalt-manganese ternary material, 1.2% of conductive carbon black, 0.5% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent to form slurry, and coating the slurry on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 50g/m 2 The second active material layer has a coating surface density of 50g/m 2 。
Example 4
The first active material layer slurry is prepared by mixing 87.5% of nickel-cobalt-manganese ternary material, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent to form slurry, and coating the slurry on the surface of an aluminum foil to form a first active material layer; the second active material layer slurry is formed by mixing 86.5% of nickel-cobalt-manganese ternary material, 1.5% of conductive carbon black, 0.7% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 50g/m 2 The second active material layer has a coating surface density of 50g/m 2 。
Example 5
The first active material layer slurry is formed by mixing 87.5% of nickel-cobalt-manganese ternary material, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of an aluminum foil to form a first active material layer; the second active material layer slurry is formed by mixing 87.5% of lithium cobaltate, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 50g/m 2 The second active material layer has a coating surface density of 52g/m 2 。
Example 6
The first active material layer slurry is 87.5 percent of lithium iron phosphate, 0.8 percent of conductive carbon black, 0.4 percent of carbon nano tube, 1.3 percent of polyvinylidene fluoride, 10 percent of lithium aluminum titanium phosphate and N-methyl pyrrolidone solventMixing to form slurry, and coating the slurry on the surface of an aluminum foil to form a first active material layer; the second active material layer slurry is formed by mixing 87.5% of lithium cobaltate, 0.8% of conductive carbon black, 0.4% of carbon nano tube, 1.3% of polyvinylidene fluoride, 10% of lithium aluminum titanium phosphate and an N-methyl pyrrolidone solvent, and is coated on the surface of the first active material layer to form a second active material layer. The first active material layer has a coating surface density of 74g/m 2 The second active material layer has a coating surface density of 50g/m 2 。
Comparative example 1
The active substance slurry is a slurry formed by mixing 87.5 percent of nickel-cobalt-manganese ternary material, 0.8 percent of conductive carbon black, 0.4 percent of carbon nano tube, 1.3 percent of polyvinylidene fluoride, 10 percent of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent, the obtained slurry is coated on the surface of an aluminum foil to form a positive pole piece, and the coating surface density is 100g/m 2 。
Comparative example 2
The active substance slurry is prepared by mixing 87.5 percent of lithium cobaltate, 0.8 percent of conductive carbon black, 0.4 percent of carbon nano tube, 1.3 percent of polyvinylidene fluoride, 10 percent of lithium aluminum titanium phosphate and N-methyl pyrrolidone solvent to form slurry, and the obtained slurry is coated on the surface of an aluminum foil to form a positive pole piece, wherein the coating surface density is 100g/m 2 。
The positive electrode plates of examples 1-2 and comparative example 1 were assembled into an all-solid-state lithium ion battery, and the battery puncture passage rate, the cycle capacity retention rate, and the cost were evaluated, and the results are shown in table 1.
Table 1 results of performance testing
Figure BDA0003644816050000101
As can be seen from the data in Table 1, the double-layer structure composite positive pole piece prepared in the embodiment 1-2 of the invention can improve the safety performance and the cycle performance of the all-solid-state battery and reduce the battery cost.
The positive electrode plates in examples 3 to 4 and comparative example 1 were assembled into an all-solid-state lithium ion battery, and the internal resistance, rate capability, and cycle capacity retention rate of the battery were evaluated, with the results shown in table 2.
Table 2 results of performance testing
Figure BDA0003644816050000111
As can be seen from the data in table 2, the double-layer structure composite positive electrode plate prepared in embodiments 3 to 4 of the present invention can reduce the internal resistance of the all-solid battery, and improve the rate and cycle performance.
The positive electrode sheets in example 5 and comparative example 1 were assembled into an all-solid-state lithium ion battery, and the positive electrode compaction density and the volumetric energy density of the battery were evaluated, with the results shown in table 3.
Table 3 results of performance testing
Figure BDA0003644816050000112
As can be seen from the data in table 3, the double-layer structure composite positive electrode sheet prepared in example 5 of the present invention can improve the positive electrode compaction density and the volume energy density.
The positive electrode plates in example 6 and comparative example 2 were assembled into an all-solid-state lithium ion battery, and the safety performance, cycle capacity retention rate, and cost of the battery were evaluated, with the results shown in table 4.
Table 4 results of performance testing
Figure BDA0003644816050000113
Figure BDA0003644816050000121
As can be seen from the data in table 4, the double-layer structure composite positive electrode plate prepared in embodiment 6 of the present invention can improve the safety performance and cycle performance of the all-solid battery, and reduce the battery cost. .
In summary, the composite positive electrode sheet provided by the present invention has a double-layer structure, and includes the first active layer and the second active layer, the composite positive electrode sheet having the double-layer structure can avoid the disadvantage of one active layer, and obtain the advantage of the other active layer, so as to achieve the effect of bringing out the best in each other, so that the battery cell composed of the composite positive electrode sheet can obtain excellent comprehensive properties such as high energy density, high rate capability, high safety performance, long cycle performance, low cost, etc.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims (9)

1. A composite positive pole piece is characterized by comprising a current collector, first active layers arranged on the upper surface and the lower surface of the current collector, and a second active layer arranged on the first active layer, wherein the material for forming the first active layer comprises a first positive active substance, a first conductive agent, a first binder and a first solid electrolyte, and the material for forming the second active layer comprises a second positive active substance, a second conductive agent, a second binder and a second solid electrolyte; the first positive electrode active material and the second positive electrode active material are different materials, or the material forming the first active layer is the same as the material forming the second active layer, the mass ratio of the first positive electrode active material in the first active layer is different from the mass ratio of the second positive electrode active material in the second active layer, and the mass ratio of the first conductive agent in the first active layer is different from the mass ratio of the second conductive agent in the second active layer.
2. The composite positive electrode sheet according to claim 1, wherein the first positive active material is one of lithium iron phosphate, lithium cobaltate, ternary nickel cobalt manganese, ternary nickel cobalt aluminum, and lithium manganate; the second positive electrode active material is one of lithium iron phosphate, lithium cobaltate, nickel cobalt manganese ternary, nickel cobalt aluminum ternary and lithium manganate.
3. The composite positive electrode plate according to claim 2, wherein the first positive electrode active material is lithium iron phosphate, and the second positive electrode active material is a nickel-cobalt-manganese ternary material.
4. The composite positive electrode sheet according to claim 2, wherein the first positive electrode active material is a nickel-cobalt-manganese ternary material, and the second positive electrode active material is lithium cobaltate.
5. The composite positive electrode sheet according to claim 2, wherein the first positive electrode active material is lithium iron phosphate, and the second positive electrode active material is lithium cobaltate.
6. The composite positive electrode sheet according to claim 1, wherein the material forming the first active layer comprises, in mass percent, 80 to 88% of a first positive active material, 0.5 to 5% of a first conductive agent, 0.5 to 5% of a first binder, and 5 to 20% of a first solid electrolyte; the material forming the second active layer includes, in mass percent, 80 to 88% of a second positive electrode active material, 0.5 to 5% of a second conductive agent, 0.5 to 5% of a second binder, and 5 to 20% of a second solid electrolyte.
7. The composite positive electrode sheet according to any one of claims 1 to 6, wherein the first conductive agent and the second conductive agent are independently selected from one or more of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, ketjen black, conductive graphite and carbon fibers; the first binder and the second binder are independently selected from one or more of polyvinylidene fluoride, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polymethyl methacrylate, polyvinyl chloride, polyethylene imine, poly-phenylene terephthamide, poly-methoxy polyethylene glycol methacrylate, poly-2-methoxyethyl glycidyl ether, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene carbonate, polytrimethylene carbonate and polypropylene carbonate; the first solid electrolyte and the second solid electrolyte are independently selected from one or more of lithium lanthanum zirconium oxygen, lithium lanthanum zirconium tantalum oxygen, lithium lanthanum titanium oxygen, titanium aluminum lithium phosphate, zirconium lithium phosphate, germanium aluminum lithium phosphate, lithium germanium phosphorus sulfur, lithium phosphorus sulfur chloride, lithium phosphorus sulfur bromide and lithium phosphorus sulfur iodide.
8. A preparation method of the composite positive pole piece according to any one of claims 1 to 7, characterized by comprising the following steps:
mixing a first positive electrode active material, a first conductive agent, a first binder and N-methylpyrrolidone to form a first slurry;
mixing a second positive electrode active material, a second conductive agent, a second binder and N-methylpyrrolidone to form a second slurry,
coating the first slurry on the upper surface and the lower surface of a current collector to form a first active layer;
and coating the second slurry on the surface of the first active layer to form a second active layer, so as to obtain the composite positive pole piece.
9. The application of the composite positive pole piece according to any one of claims 1 to 7, wherein the composite positive pole piece is used for preparing an all-solid-state lithium ion battery.
CN202210526729.7A 2022-05-16 2022-05-16 Composite positive pole piece and preparation method and application thereof Pending CN114975853A (en)

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