CN116031410A - Composite positive plate, preparation method and application - Google Patents
Composite positive plate, preparation method and application Download PDFInfo
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- CN116031410A CN116031410A CN202310320225.4A CN202310320225A CN116031410A CN 116031410 A CN116031410 A CN 116031410A CN 202310320225 A CN202310320225 A CN 202310320225A CN 116031410 A CN116031410 A CN 116031410A
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- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 238000000576 coating method Methods 0.000 claims abstract description 229
- 239000011248 coating agent Substances 0.000 claims abstract description 216
- 239000006258 conductive agent Substances 0.000 claims abstract description 60
- 239000007774 positive electrode material Substances 0.000 claims abstract description 59
- 239000000463 material Substances 0.000 claims abstract description 54
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000013543 active substance Substances 0.000 claims abstract description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 18
- 150000002500 ions Chemical class 0.000 claims abstract description 14
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 11
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 9
- 239000006255 coating slurry Substances 0.000 claims description 93
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 76
- 239000011230 binding agent Substances 0.000 claims description 64
- 239000007784 solid electrolyte Substances 0.000 claims description 58
- 238000003756 stirring Methods 0.000 claims description 48
- 239000011247 coating layer Substances 0.000 claims description 47
- 239000002033 PVDF binder Substances 0.000 claims description 45
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 45
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 42
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 42
- 239000002048 multi walled nanotube Substances 0.000 claims description 34
- 238000002156 mixing Methods 0.000 claims description 31
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 28
- 230000007704 transition Effects 0.000 claims description 25
- 239000010439 graphite Substances 0.000 claims description 24
- 229910002804 graphite Inorganic materials 0.000 claims description 24
- 239000003292 glue Substances 0.000 claims description 23
- 239000002270 dispersing agent Substances 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 18
- 239000010410 layer Substances 0.000 claims description 16
- 238000007581 slurry coating method Methods 0.000 claims description 16
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 15
- -1 polytetrafluoroethylene Polymers 0.000 claims description 12
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 10
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 7
- 238000005303 weighing Methods 0.000 claims description 6
- 229920002125 Sokalan® Polymers 0.000 claims description 4
- 229920002401 polyacrylamide Polymers 0.000 claims description 4
- 239000004584 polyacrylic acid Substances 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- 239000002002 slurry Substances 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 2
- 239000006230 acetylene black Substances 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 229920001223 polyethylene glycol Polymers 0.000 claims description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 2
- 239000002109 single walled nanotube Substances 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims 3
- 239000000243 solution Substances 0.000 description 21
- 229910011328 LiNi0.6Co0.2Mn0.2O2 Inorganic materials 0.000 description 20
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 17
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 13
- 229910052782 aluminium Inorganic materials 0.000 description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 12
- 239000011888 foil Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 7
- 239000011244 liquid electrolyte Substances 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 238000002347 injection Methods 0.000 description 3
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- 238000009413 insulation Methods 0.000 description 3
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- 238000012360 testing method Methods 0.000 description 3
- FVXHSJCDRRWIRE-UHFFFAOYSA-H P(=O)([O-])([O-])[O-].[Ge+2].[Al+3].[Li+].P(=O)([O-])([O-])[O-] Chemical compound P(=O)([O-])([O-])[O-].[Ge+2].[Al+3].[Li+].P(=O)([O-])([O-])[O-] FVXHSJCDRRWIRE-UHFFFAOYSA-H 0.000 description 2
- NRJJZXGPUXHHTC-UHFFFAOYSA-N [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] Chemical compound [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] NRJJZXGPUXHHTC-UHFFFAOYSA-N 0.000 description 2
- CVJYOKLQNGVTIS-UHFFFAOYSA-K aluminum;lithium;titanium(4+);phosphate Chemical compound [Li+].[Al+3].[Ti+4].[O-]P([O-])([O-])=O CVJYOKLQNGVTIS-UHFFFAOYSA-K 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
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- 239000003792 electrolyte Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 229910000659 lithium lanthanum titanates (LLT) Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 229910013716 LiNi Inorganic materials 0.000 description 1
- CHZUADMGGDUUEF-UHFFFAOYSA-N [Mn](=O)(=O)([O-])[O-].[Co+2] Chemical compound [Mn](=O)(=O)([O-])[O-].[Co+2] CHZUADMGGDUUEF-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
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Images
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention relates to the field of lithium ion batteries, in particular to a composite positive electrode plate, a preparation method and application thereof, comprising a positive electrode current collector and a composite coating coated on at least one side surface of the positive electrode current collector, wherein the composite coating comprises a first active coating, a second active coating and a functional coating which are sequentially arranged along a direction far away from the positive electrode current collector; the first active coating and the second active coating are respectively and independently ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content in the ternary nickel cobalt lithium manganate materials of the first active coating is higher than that in the ternary nickel cobalt lithium manganate materials of the second active coating; the first conductive agent content in the first active coating is lower than the first conductive agent content in the second active coating. Ensures enough coating quality of the positive electrode active material, maintains good interface contact, reduces interface impedance, and meets the use requirements of high energy density and long cycle life.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a composite positive plate, a preparation method and application.
Background
As an energy storage secondary battery, the lithium ion battery has the advantages of high energy density, good cycle life, high voltage, no memory effect, environmental friendliness and the like, and rapidly becomes a focus of vigorous research in the field of new energy automobiles. With the gradual increase of the marketization degree of the new energy automobile, the automobile performance quality is expected to be higher and higher, so that the endurance mileage (energy density) and the safety of the new energy automobile become the most favorable competitive bright points.
The ternary nickel cobalt lithium manganate (NCM) positive electrode material is a common high-capacity positive electrode material, wherein the larger the nickel element content is, the higher the gram capacity is exerted, and if the use amount of the positive electrode material is further increased, the energy density of a battery can be effectively improved, but the problems of poor electrochemical performance, high safety risk and the like of multiplying power, circulation and the like are accompanied. In addition, due to possible foreign metal foreign matters in the production process of the lithium battery or burr scraps generated in the pole piece die cutting process or improper use of lithium dendrites or battery cells generated in the long-term use process of the lithium battery, the separator can be pierced to cause serious consequences such as short circuit, ignition, explosion and the like of the battery.
CN115472767a discloses a three-layer structure positive electrode plate, and a preparation method and application thereof, wherein the positive electrode plate is composed of a positive electrode current collector, a ternary active material first coating, a lithium iron phosphate second coating and a ceramic third coating, and the electrode plate is applied to a lithium ion battery, so that direct contact of the positive electrode plate and the negative electrode plate after diaphragm breakage can be effectively avoided, the possibility of short circuit is reduced, and the diffusion of lithium ions can be promoted by using a gradient pore structure. However, the adjacent coatings have different solid properties, it is difficult to ensure good interface contact, and there are also problems that the energy density is limited to increase, and the electron conductivity of the positive electrode active material coating far from the current collector is low, which still remains to be further optimized.
Disclosure of Invention
The invention aims to provide a composite positive electrode plate, a preparation method and application thereof, which ensure enough coating quality of positive electrode active substances, solve the problem of low electronic conductivity, maintain good interface contact, reduce interface impedance and meet the use requirements of high energy density and long cycle life; on the other hand, the functional coating plays roles of ion conduction and electronic insulation, and the positive electrode plate and the negative electrode plate are separated when the diaphragm fails.
In order to achieve the above object, the present invention adopts the following technical scheme.
The composite positive electrode plate comprises a positive electrode current collector and a composite coating coated on at least one side surface of the positive electrode current collector, wherein the composite coating comprises a first active coating, a second active coating and a functional coating which are sequentially arranged along a direction far away from the positive electrode current collector; the first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-series, eight-series, seven-series, six-series or five-series ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content in the ternary nickel cobalt lithium manganate material of the first active coating is higher than that in the ternary nickel cobalt lithium manganate material of the second active coating; the first conductive agent content of the first active coating is lower than the first conductive agent content of the second active coating.
Further, the first active coating and the second active coating respectively and independently comprise 95-97wt% of a first positive electrode active material, 1-3wt% of a first conductive agent, 1-2wt% of a first binder and 0.2-1wt% of zirconium dioxide; the active substances with ion conductivity in the first active coating and the second active coating comprise at least one of LATP, LLZO, LATO and LAGP, and the coating thickness of the active substances with ion conductivity is 5-30 nm. LATP is the abbreviation of lithium aluminum titanium phosphate, LLZO is the abbreviation of lithium lanthanum zirconium oxide, LATO is the abbreviation of lithium lanthanum titanate, and LAGP is the abbreviation of lithium aluminum germanium phosphate.
Further, the first conductive agent is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, acetylene black, conductive graphite and graphene; the first binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyacrylamide and polyvinylidene fluoride; the zirconium dioxide is in a powder form, and the particle diameter of the powder zirconium dioxide is 10-100 nm.
Further, the thickness of the first active coating is 60-100 mu m, the thickness of the second active coating is 30-100 mu m, and the thickness of the functional coating is 5-10 mu m.
Further, the functional coating comprises 85-90 wt% of a first solid electrolyte, 6-10 wt% of a second binder and 2-5 wt% of a dispersing agent. Preferably, the solid electrolyte comprises several particle size combinations.
Further, the first solid electrolyte is at least one of LATP, LLZO, LATO and LAGP; the second binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyacrylamide and polyvinylidene fluoride; the dispersing agent is at least one of polyoxyethylene, polyvinylpyrrolidone, polyethylene glycol and polyethylene oxide. LATP is the abbreviation of lithium aluminum titanium phosphate, LLZO is the abbreviation of lithium lanthanum zirconium oxide, LATO is the abbreviation of lithium lanthanum titanate, and LAGP is the abbreviation of lithium aluminum germanium phosphate.
Further, a transition layer is further arranged between the second active coating and the functional coating, and comprises 93-96wt% of mixture, 2-4wt% of second conductive agent and 2-3wt% of third binder according to weight percentage; the mixture comprises, by weight, 30-70wt% of a second positive electrode active material and 30-70wt% of a second solid electrolyte.
Further, the second positive electrode active material in the mixture is the same as the first positive electrode active material in the second active coating layer, and the second solid electrolyte in the mixture is the same as the first solid electrolyte material in the functional coating layer.
The preparation method of the composite positive electrode plate comprises the steps of sequentially coating first active coating slurry, second active coating slurry and functional coating slurry on at least one side surface of a positive electrode current collector to form a composite coating, and obtaining the composite positive electrode plate; the first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-series, eight-series, seven-series, six-series or five-series ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content in the ternary nickel cobalt lithium manganate material of the first active coating is higher than that in the ternary nickel cobalt lithium manganate material of the second active coating; the first conductive agent content of the first active coating is lower than the first conductive agent content of the second active coating.
Further, the preparation of the first active coating slurry is specifically as follows: weighing a first positive electrode active material, a first conductive agent, a first binder, zirconium dioxide and a solvent according to a preset proportion of each component in the first active coating, mixing and stirring the first binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the first conductive agent and the zirconium dioxide to continuously stir until uniformly dispersed first active coating slurry is obtained; the preparation of the second active coating slurry comprises the following steps: weighing a first positive electrode active material, a first conductive agent, a first binder, zirconium dioxide and a solvent according to a preset proportion of each component in the second active coating, mixing and stirring the first binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the first conductive agent and the zirconium dioxide to continuously stir until uniformly dispersed second active coating slurry is obtained; the preparation of the functional coating slurry specifically comprises the following steps: and weighing the first solid electrolyte, the second binder, the dispersing agent and the solvent according to the preset proportion of each component in the functional coating, and mixing and stirring the first solid electrolyte, the second binder, the dispersing agent and the solvent until the uniformly dispersed functional coating slurry is obtained.
Further, after each completion of the slurry coating, drying and rolling treatment are performed, and then the next slurry coating is performed.
Further, after the second active coating slurry is coated, the transition layer slurry is coated first, and then the functional coating slurry is coated; the preparation of the transition layer slurry specifically comprises the following steps: and mixing and stirring the third binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the second conductive agent and the second solid electrolyte, and continuously stirring until the uniformly dispersed transition coating slurry is obtained.
Further, the coating area of the functional coating is the area of the first active coating and the second active coating, wherein the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm.
The composite positive electrode plate or the composite positive electrode plate prepared by the preparation method of the composite positive electrode plate is applied to a lithium ion battery.
The invention has the beneficial effects that:
1. the invention defines that the content of the first conductive agent in the first active coating is lower than that of the first conductive agent in the second active coating, and the design is used for ensuring that the problem of low conductivity caused by far transmission channels of positive active materials in the middle or outer area can be effectively solved when the positive electrode surface density and the thickness of the pole piece are increased. According to the invention, the first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-system, eight-system, seven-system, six-system or five-system ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capability, and the nickel element content in the ternary nickel cobalt lithium manganate material of the first active coating is higher than that in the ternary nickel cobalt lithium manganate material of the second active coating, so that the lithium ion conducting capability can be improved as a whole, a stable interface layer can be formed on the surface of the ternary nickel cobalt lithium manganate material in situ, the corrosion of electrolyte is prevented, the interface impedance is reduced, the performance advantage of the ternary nickel cobalt lithium manganate material can be further exerted to the maximum extent, and the purposes of greatly improving the energy density, excellent multiplying power circulation performance and improving the safety are synchronously realized.
2. The first active coating and the second active coating comprise zirconium dioxide, and the addition of the zirconium dioxide can reduce the generation of hydrofluoric acid and inhibit the dissolution of the ternary nickel cobalt lithium manganate material, so that the circulation stability is improved. And gaps can be filled as much as possible by regulating the particle size of the nano zirconium dioxide, so that different components are in tight contact, the internal resistance of the battery is reduced, and the stability is improved.
3. The transition layer contains the second solid electrolyte and the second positive electrode active material, the second positive electrode active material is the same as the first positive electrode active material in the second active coating, and the second solid electrolyte is the same as the first solid electrolyte material in the functional coating, so that the problem of poor contact of two-phase interfaces caused by different solid properties can be solved, the efficient conduction of lithium ions between the coatings is ensured, the cycle and multiplying power performance of the battery are not influenced, and meanwhile, the capacity of the battery can be improved by utilizing the positive electrode active material to generate a charging and discharging process.
4. The functional coating is a solid electrolyte functional coating, plays roles of ion conduction and electronic insulation, is equivalent to adding a safety protection layer to the positive electrode plate, prevents the positive electrode plate and the negative electrode plate from being in direct contact after the diaphragm is invalid, and reduces the short circuit risk; meanwhile, the first solid electrolyte with various particle size combinations can increase the space utilization rate of the coating as much as possible, reduce the porosity, reduce the liquid electrolyte injection amount, ensure the mechanical strength and the stability of the coating and further improve the safety of the battery. And secondly, the functional coating, namely the solid electrolyte layer, can be applied to a lithium battery instead of an organic liquid electrolyte, so that the safety problems of leakage, flammability, volatilization, poor stability and the like of the liquid electrolyte are directly eliminated. In addition, the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm, and the excessive coating width of the tab side of the functional coating not only reduces metal burrs generated in the die cutting process, but also can avoid direct contact between the positive current collector and the negative electrode plate after the diaphragm is damaged, so that the safety is further improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the description of the embodiments or the prior art will be briefly introduced below, it being obvious that the drawings in the description below are only some examples of the present invention.
Fig. 1 is a schematic structural diagram of a composite positive electrode sheet provided by an embodiment of the invention, wherein 1-positive electrode current collector, 2-first active coating, 3-second active coating, 4-transition coating and 5-functional coating.
Detailed Description
Further advantages and effects of the present invention will become readily apparent to those skilled in the art from the disclosure herein, by referring to the accompanying drawings and the preferred embodiments. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be understood that the preferred embodiments are presented by way of illustration only and not by way of limitation.
It should be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
In a first embodiment, referring to fig. 1, a composite positive electrode sheet includes a positive electrode current collector 1 and composite coatings symmetrically coated on both side surfaces of the positive electrode current collector 1, wherein the composite coatings include a first active coating 2 with a thickness of 80 μm, a second active coating 3 with a thickness of 40 μm, a transition coating 4 with a thickness of 10 μm, and a functional coating 5 with a thickness of 5 μm, which are sequentially arranged in a direction away from the positive electrode current collector. The positive electrode current collector is aluminum foil with the thickness of 12 mu m.
The first active coating layer includes 97wt% of a first positive electrode active material, 1.5wt% of a first conductive agent, 1wt% of a first binder, and 0.5wt% of zirconium dioxide. The first positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.8 Co 0.1 Mn 0.1 O 2 The LATP coating layer has a thickness of 15nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The second active coating layer includes 96wt% of a first positive electrode active material, 2wt% of a first conductive agent, 1.5wt% of a first binder, and 0.5wt% of zirconium dioxide. First positiveThe polar active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer has a thickness of 10nm, the conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The transition coating comprises 95 weight percent of mixture, 3 weight percent of second conductive agent and 2 weight percent of third binder; the mixture includes, in weight percent, 51wt% of the second positive electrode active material and 49wt% of the second solid electrolyte. The second positive electrode active material is LATP coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer had a thickness of 10nm and was the same as the material of the first positive electrode active material in the second active coating layer. The second solid electrolyte is LATP, the material of the second solid electrolyte is the same as that of the first solid electrolyte in the functional coating, the second conductive agent is multi-wall carbon nano tubes, and the third binder is polyvinylidene fluoride.
The functional coating comprises 90wt% of a first solid electrolyte, 6wt% of a second binder and 4wt% of a dispersing agent. The first solid electrolyte is LATP, the second binder is polyvinylidene fluoride, and the dispersing agent is polyethylene oxide.
The content (1.5 wt%) of the first conductive agent in the first active coating is lower than the content (2 wt%) of the first conductive agent in the second active coating, and the design is used for ensuring that the problem of low conductivity caused by the far distance of the positive electrode active material transmission channel in the middle or outer area can be effectively solved when the positive electrode surface density and the thickness of the pole piece are increased.
The first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-system, eight-system, seven-system, six-system or five-system ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) Nickel element content (LiNi) in ternary nickel cobalt lithium manganate material higher than that of second active coating 0.6 Co 0.2 Mn 0.2 O 2 ) Not only can improve the lithium ion conductivityThe stable interface layer can be formed on the surface of the ternary nickel cobalt lithium manganate material in situ, so that the corrosion of electrolyte is prevented, the interface impedance is reduced, the performance advantage of the ternary nickel cobalt lithium manganate material is further brought into full play, and the purposes of greatly improving the energy density, realizing excellent multiplying power cycle performance and improving the safety are synchronously realized.
The first active coating and the second active coating comprise zirconium dioxide, and the addition of the zirconium dioxide can reduce the generation of hydrofluoric acid and inhibit the dissolution of the ternary nickel cobalt lithium manganate material, so that the circulation stability is improved. And gaps can be filled as much as possible by regulating the particle size of the nano zirconium dioxide, so that different components are in tight contact, the internal resistance of the battery is reduced, and the stability is improved.
The transition layer contains the second solid electrolyte and the second positive electrode active material, the second positive electrode active material is the same as the first positive electrode active material in the second active coating, and the second solid electrolyte is the same as the first solid electrolyte material in the functional coating, so that the problem of poor contact of two-phase interfaces caused by different solid properties can be solved, the efficient conduction of lithium ions between the coatings is ensured, the cycle and multiplying power performance of the battery are not influenced, and meanwhile, the capacity of the battery can be improved by utilizing the positive electrode active material to generate a charging and discharging process.
The functional coating is a solid electrolyte functional coating, plays roles of ion conduction and electronic insulation, is equivalent to adding a safety protection layer to the positive electrode plate, prevents the positive electrode plate and the negative electrode plate from being in direct contact after the diaphragm is invalid, and reduces the short circuit risk; meanwhile, the solid electrolyte with various particle size combinations can increase the space utilization rate of the coating as much as possible, reduce the porosity and the liquid electrolyte injection amount, ensure the mechanical strength and the stability of the coating and further improve the safety of the battery. And secondly, the functional coating, namely the solid electrolyte layer, can be applied to a lithium battery instead of an organic liquid electrolyte, so that the safety problems of leakage, flammability, volatilization, poor stability and the like of the liquid electrolyte are directly eliminated.
The preparation method of the composite positive plate comprises the following steps:
1) Matching withPreparing a first active coating slurry: adding 1wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 97wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 1.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring was continued at a suitable rate until a uniformly dispersed first active coating slurry was obtained.
2) Preparing a second active coating slurry: adding 1.5wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 96wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 2wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed second active coating slurry was obtained.
3) Preparing transitional coating slurry, adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 48wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 47wt% LATP, 3wt% multi-walled carbon nanotubes, and stirring was continued at a suitable rate until a uniformly dispersed transitional coating slurry was obtained.
4) Preparing functional coating slurry, and uniformly mixing 90wt% of LATP, 6wt% of polytetrafluoroethylene and 4wt% of polyethylene oxide to obtain the functional coating slurry.
5) And coating the first active coating slurry, the second active coating slurry, the transition coating slurry and the functional coating slurry on the surfaces of two sides of the aluminum foil with the thickness of 12 mu m in sequence according to the set coating thickness, wherein the coating areas of the functional coating comprise the areas of the first active coating and the second active coating, and the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm. And drying and rolling the pole piece in time after each slurry coating, and then carrying out next slurry coating to finally obtain the composite positive pole piece.
In a second embodiment, the composite positive electrode plate comprises a positive electrode current collector and composite coatings symmetrically coated on two side surfaces of the positive electrode current collector, wherein the composite coatings comprise a first active coating with the thickness of 100 μm, a second active coating with the thickness of 80 μm, a transition coating with the thickness of 10 μm and a functional coating with the thickness of 10 μm, which are sequentially arranged along a direction away from the positive electrode current collector.
The positive electrode current collector is aluminum foil with the thickness of 12 mu m.
The first active coating layer includes 96wt% of a first positive electrode active material, 2wt% of a first conductive agent, 1.5wt% of a first binder, and 0.5wt% of zirconium dioxide in weight percent. The first positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.8 Co 0.1 Mn 0.1 O 2 The LATP coating layer has a thickness of 15nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The second active coating layer includes 95wt% of a first positive electrode active material, 2.5wt% of a first conductive agent, 2wt% of a first binder, and 0.5wt% of zirconium dioxide. The positive active material is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer has a thickness of 10nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The transition coating comprises, by weight, 95% of the mixture, 3% of the second conductive agent, and 2% of the third binder. The mixture includes, in weight percent, 51wt% of the second positive electrode active material and 49wt% of the second solid electrolyte. The second positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer had a thickness of 10nm and was the same as the material of the first positive electrode active material in the second active coating layer. The second solid electrolyte is LATP, the material of the second solid electrolyte is the same as that of the first solid electrolyte in the functional coating, the second conductive agent is multi-wall carbon nano tubes, and the third binder is polyvinylidene fluoride.
The functional coating comprises 90wt% of a first solid electrolyte, 6wt% of a second binder and 4wt% of a dispersing agent. The first solid electrolyte is LATP, the second binder is polyvinylidene fluoride, and the dispersing agent is polyethylene oxide.
The preparation method of the composite positive plate comprises the following steps:
1) Preparing a first active coating slurry: adding 1.5wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 96wt% of LATP-coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 2wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed first active coating slurry was obtained.
2) Preparing a second active coating slurry: adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 2.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed second active coating slurry was obtained.
3) Preparing transitional coating slurry, adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 48wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 47wt% LATP, 3wt% multi-walled carbon nanotubes, and stirring was continued at a suitable rate until a uniformly dispersed transitional coating slurry was obtained.
4) Preparing functional coating slurry, and uniformly mixing 90wt% of LATP, 6wt% of polytetrafluoroethylene and 4wt% of polyethylene oxide to obtain the functional coating slurry.
5) And coating the first active coating slurry, the second active coating slurry, the transition coating slurry and the functional coating slurry on the surfaces of two sides of the aluminum foil with the thickness of 12 mu m in sequence according to the set coating thickness, wherein the coating areas of the functional coating comprise the areas of the first active coating and the second active coating, and the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm. And drying and rolling the pole piece in time after each slurry coating, and then carrying out next slurry coating to finally obtain the composite positive pole piece.
In a third embodiment, a composite positive electrode sheet includes a positive electrode current collector and composite coatings symmetrically coated on both side surfaces of the positive electrode current collector, wherein the composite coatings include a first active coating layer with a thickness of 60 μm, a second active coating layer with a thickness of 30 μm, a transition coating layer with a thickness of 20 μm, and a functional coating layer with a thickness of 10 μm, which are sequentially arranged in a direction away from the positive electrode current collector. The positive electrode current collector is aluminum foil with the thickness of 12 mu m.
The first active coating layer includes 95wt% of a first positive electrode active material, 2wt% of a first conductive agent, 2wt% of a first binder, and 1wt% of zirconium dioxide. The first positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.8 Co 0.1 Mn 0.1 O 2 The LATP coating layer has a thickness of 15nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The second active coating layer includes 95wt% of a first positive electrode active material, 3wt% of a first conductive agent, 1wt% of a first binder, and 1wt% of zirconium dioxide. The positive active material is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer has a thickness of 10nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The transition coating comprises 93wt% of the mixture, 4wt% of the second conductive agent and 3wt% of the third binder in percentage by weight. The mixture includes, in weight percent, 51wt% of the second positive electrode active material and 49wt% of the second solid electrolyte. The second positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer had a thickness of 10nm and was the same as the material of the first positive electrode active material in the second active coating layer. The second solid electrolyte is LATP and is coated with functionsThe first solid electrolyte in the layer is the same material, the second conductive agent is multi-wall carbon nano tube, and the third binder is polyvinylidene fluoride.
The functional coating comprises, by weight, 85% of a first solid electrolyte, 10% of a second binder and 5% of a dispersing agent. The first solid electrolyte is LATP, the second binder is polyvinylidene fluoride, and the dispersing agent is polyethylene oxide.
The preparation method of the composite positive plate comprises the following steps:
1) Preparing a first active coating slurry: adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 2wt% of conductive graphite and multiwall carbon nanotubes, 1wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed first active coating slurry was obtained.
2) Preparing a second active coating slurry: adding 1wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 3wt% of conductive graphite and multiwall carbon nanotubes, 1wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed second active coating slurry was obtained.
3) Preparing transitional coating slurry, adding 3wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 47wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 46wt% LATP, 4wt% multi-walled carbon nanotubes, and stirring was continued at a suitable rate until a uniformly dispersed transitional coating slurry was obtained.
4) Preparing functional coating slurry, and uniformly mixing 85wt% of LATP, 10wt% of polytetrafluoroethylene and 5wt% of polyethylene oxide to obtain the functional coating slurry.
5) And coating the first active coating slurry, the second active coating slurry, the transition coating slurry and the functional coating slurry on the surfaces of two sides of the aluminum foil with the thickness of 12 mu m in sequence according to the set coating thickness, wherein the coating areas of the functional coating comprise the areas of the first active coating and the second active coating, and the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm. And drying and rolling the pole piece in time after each slurry coating, and then carrying out next slurry coating to finally obtain the composite positive pole piece.
In a fourth embodiment, a composite positive electrode sheet includes a positive electrode current collector and composite coatings symmetrically coated on both side surfaces of the positive electrode current collector, wherein the composite coatings include a first active coating layer with a thickness of 100 μm, a second active coating layer with a thickness of 100 μm, a transition coating layer with a thickness of 20 μm, and a functional coating layer with a thickness of 10 μm, which are sequentially arranged in a direction away from the positive electrode current collector. The positive electrode current collector is aluminum foil with the thickness of 12 mu m.
The first active coating layer includes 95wt% of a first positive electrode active material, 2wt% of a first conductive agent, 2wt% of a first binder, and 1wt% of zirconium dioxide. The first positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.8 Co 0.1 Mn 0.1 O 2 The LATP coating layer has a thickness of 15nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The second active coating layer includes 95wt% of a first positive electrode active material, 2.5wt% of a first conductive agent, 2wt% of a first binder, and 0.5wt% of zirconium dioxide. The positive active material is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer has a thickness of 10nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The transition coating comprises 96wt% of a mixture, 2wt% of a second conductive agent and 2wt% of a third binder in percentage by weight. The mixture includes 50wt% of the second positive electrode active material and 50wt% of the second solid electrolyte in weight percent. The second positive electrode active material is LATP coated polycrystalline ternary nickelLithium cobalt manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer had a thickness of 10nm and was the same as the material of the first positive electrode active material in the second active coating layer. The second solid electrolyte is LATP, the material of the second solid electrolyte is the same as that of the first solid electrolyte in the functional coating, the second conductive agent is multi-wall carbon nano tubes, and the third binder is polyvinylidene fluoride.
The functional coating comprises 90wt% of a first solid electrolyte, 8wt% of a second binder and 2wt% of a dispersing agent. The first solid electrolyte is LATP, the second binder is polyvinylidene fluoride, and the dispersing agent is polyethylene oxide.
The preparation method of the composite positive plate comprises the following steps:
1) Preparing a first active coating slurry: adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 2wt% of conductive graphite and multiwall carbon nanotubes, 1wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed first active coating slurry was obtained.
2) Preparing a second active coating slurry: adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 2.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed second active coating slurry was obtained.
3) Preparing transitional coating slurry, adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 48wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 48wt% LATP, 2wt% multi-walled carbon nanotubes, and stirring was continued at a suitable rate until a uniformly dispersed transitional coating slurry was obtained.
4) Preparing functional coating slurry, and uniformly mixing 90wt% of LATP, 8wt% of polytetrafluoroethylene and 2wt% of polyethylene oxide to obtain the functional coating slurry.
5) And coating the first active coating slurry, the second active coating slurry, the transition coating slurry and the functional coating slurry on the surfaces of two sides of the aluminum foil with the thickness of 12 mu m in sequence according to the set coating thickness, wherein the coating areas of the functional coating comprise the areas of the first active coating and the second active coating, and the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm. And drying and rolling the pole piece in time after each slurry coating, and then carrying out next slurry coating to finally obtain the composite positive pole piece.
In a fifth embodiment, a composite positive electrode sheet includes a positive electrode current collector and composite coatings symmetrically coated on both side surfaces of the positive electrode current collector, wherein the composite coatings include a first active coating layer with a thickness of 80 μm, a second active coating layer with a thickness of 40 μm, a transition coating layer with a thickness of 10 μm, and a functional coating layer with a thickness of 5 μm, which are sequentially arranged in a direction away from the positive electrode current collector. The positive electrode current collector is aluminum foil with the thickness of 12 mu m.
The first active coating layer includes 95wt% of a first positive electrode active material, 2.5wt% of a first conductive agent, 2wt% of a first binder, and 0.5wt% of zirconium dioxide. The first positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.8 Co 0.1 Mn 0.1 O 2 The LATP coating layer has a thickness of 15nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The second active coating layer includes 95wt% of a first positive electrode active material, 3wt% of a first conductive agent, 1wt% of a first binder, and 1wt% of zirconium dioxide. The positive active material is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer has a thickness of 10nm, the first conductive agent is conductive graphite and multi-walled carbon nanotubes, and the first binder is polyvinylidene fluoride.
The transition coating comprises 95wt percent by weight% of a mixture, 3wt% of a second conductive agent, 2wt% of a third binder. The mixture includes, in weight percent, 51wt% of the second positive electrode active material and 49wt% of the second solid electrolyte. The second positive electrode active substance is LATP coated polycrystalline ternary nickel cobalt lithium manganate material, namely LiNi 0.6 Co 0.2 Mn 0.2 O 2 The LATP coating layer had a thickness of 10nm and was the same as the material of the first positive electrode active material in the second active coating layer. The second solid electrolyte is LATP, the material of the second solid electrolyte is the same as that of the first solid electrolyte in the functional coating, the second conductive agent is multi-wall carbon nano tubes, and the third binder is polyvinylidene fluoride.
The functional coating comprises 87wt% of a first solid electrolyte, 9wt% of a second binder and 4wt% of a dispersing agent. The first solid electrolyte is LATP, the second binder is polyvinylidene fluoride, and the dispersing agent is polyethylene oxide.
The preparation method of the composite positive plate comprises the following steps:
1) Preparing a first active coating slurry: adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 2.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed first active coating slurry was obtained.
2) Preparing a second active coating slurry: adding 1wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 95wt% of LATP coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 3wt% of conductive graphite and multiwall carbon nanotubes, 1wt% of zirconium dioxide, and stirring at a suitable speed was continued until a uniformly dispersed second active coating slurry was obtained.
3) Preparing transitional coating slurry, adding 2wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 48wt% of LATP-coated polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 47wt% LATP, 3wt% multi-walled carbon nanotubes, and stirring was continued at a suitable rate until a uniformly dispersed transitional coating slurry was obtained.
4) Preparing a functional coating slurry, and uniformly mixing 87wt% of LATP, 9wt% of polytetrafluoroethylene and 4wt% of polyethylene oxide to obtain the functional coating slurry.
5) And coating the first active coating slurry, the second active coating slurry, the transition coating slurry and the functional coating slurry on the surfaces of two sides of the aluminum foil with the thickness of 12 mu m in sequence according to the set coating thickness, wherein the coating areas of the functional coating comprise the areas of the first active coating and the second active coating, and the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm. And drying and rolling the pole piece in time after each slurry coating, and then carrying out next slurry coating to finally obtain the composite positive pole piece.
The component contents of examples one to five are summarized in Table 1.
Table 1 contents of components of examples one to five
Comparative example one, a single coated positive electrode sheet, comprised only a current collector and a first active coating layer of 135 μm thickness disposed on both side surfaces of the current collector. The preparation method of the specific single-coating positive electrode plate comprises the following steps:
1) Preparing a first active coating slurry: adding 1wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 97wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 1.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring was continued at a suitable rate until a uniformly dispersed first active coating slurry was obtained.
2) And coating the first active coating slurry on the surface of an aluminum foil with the thickness of 12 mu m according to the set coating thickness, and then drying and rolling the pole piece in time to obtain the single-coating positive pole piece.
The second comparative example is a double-coating positive electrode plate, which comprises a current collector, and a first active coating with the thickness of 125 mu m and a functional coating with the thickness of 10 mu m which are sequentially overlapped on the surface of the current collector from inside to outside. The preparation method of the specific double-coating positive electrode plate comprises the following steps:
1) Preparing a first active coating slurry: adding 1wt% of polyvinylidene fluoride into N-methyl pyrrolidone serving as a solvent, mixing and stirring to form uniform glue solution, and adding 97wt% of LATP coated polycrystalline LiNi 0.8 Co 0.1 Mn 0.1 O 2 1.5wt% of conductive graphite and multiwall carbon nanotubes, 0.5wt% of zirconium dioxide, and stirring was continued at a suitable rate until a uniformly dispersed first active coating slurry was obtained.
2) Preparing functional coating slurry, and uniformly mixing 90wt% of LATP, 6wt% of polytetrafluoroethylene and 4wt% of polyethylene oxide to obtain the functional coating slurry.
3) And coating the first active coating slurry and the functional coating slurry on the surface of an aluminum foil with the thickness of 12 mu m according to the set coating thickness, carrying out timely drying and rolling treatment on the pole piece after each slurry coating, and then carrying out next slurry coating to finally obtain the double-coating positive pole piece.
The composite positive electrode plate prepared in the first embodiment and the second embodiment, the single-coating positive electrode plate prepared in the first comparative embodiment and the double-coating positive electrode plate prepared in the second comparative embodiment are assembled into a battery through manufacturing procedures of sheet making, lamination, packaging, liquid injection and the like, and can pass overcharge, external short circuit and hot box safety test, wherein the hot box test temperature can exceed 130 ℃. The size of the assembled batteries in each example of the present invention was the same as that in the comparative example. The same performance test method is adopted for the batteries in each embodiment of the invention and the comparative example, wherein the overcharge, external short circuit and hot box safety test can be referred to national standard GB38031-2020. The test results are shown in Table 2.
Table 2 test results
As can be seen from table 2, the first and second examples passed the overcharge, external short-circuit, and hot box safety tests, and the normal temperature 1c@500 cycles of the first and second examples were higher in capacity retention than the first and second comparative examples, and the 1c@500 cycles were 500 cycles of the cycle under the condition of 1C charge-discharge magnification.
The above embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention.
Claims (14)
1. The utility model provides a compound positive pole piece, this compound positive pole piece includes positive pole current collector and coats in the compound coating of positive pole current collector at least one side surface, its characterized in that: the composite coating comprises a first active coating, a second active coating and a functional coating which are sequentially arranged along the direction far away from the positive current collector;
the first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-series, eight-series, seven-series, six-series or five-series ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content in the ternary nickel cobalt lithium manganate material of the first active coating is higher than that in the ternary nickel cobalt lithium manganate material of the second active coating;
The first conductive agent content in the first active coating is lower than the first conductive agent content in the second active coating.
2. The composite positive electrode sheet according to claim 1, wherein: the first active coating and the second active coating respectively and independently comprise 95-97wt% of a first positive electrode active material, 1-3wt% of a first conductive agent, 1-2wt% of a first binder and 0.2-1wt% of zirconium dioxide;
the active substances with ion conductivity in the first active coating and the second active coating comprise at least one of LATP, LLZO, LATO and LAGP, and the coating thickness of the active substances with ion conductivity is 5-30 nm.
3. The composite positive electrode sheet according to claim 2, wherein: the first conductive agent is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, acetylene black, conductive graphite and graphene;
the first binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyacrylamide and polyvinylidene fluoride;
the zirconium dioxide is in a powder form, and the particle diameter of the powder zirconium dioxide is 10-100 nm.
4. The composite positive electrode sheet according to claim 1 or 2, characterized in that: the thickness of the first active coating is 60-100 mu m, the thickness of the second active coating is 30-100 mu m, and the thickness of the functional coating is 5-10 mu m.
5. The composite positive electrode sheet according to claim 1 or 2, characterized in that: the functional coating comprises, by weight, 85-90% of a first solid electrolyte, 6-10% of a second binder and 2-5% of a dispersing agent.
6. The composite positive electrode sheet according to claim 5, wherein: the first solid electrolyte is at least one of LATP, LLZO, LATO and LAGP; the second binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyacrylamide and polyvinylidene fluoride; the dispersing agent is at least one of polyoxyethylene, polyvinylpyrrolidone, polyethylene glycol and polyethylene oxide.
7. The composite positive electrode sheet according to claim 1 or 2, characterized in that: a transition layer is further arranged between the second active coating and the functional coating, and comprises 93-96wt% of mixture, 2-4wt% of second conductive agent and 2-3wt% of third binder;
the mixture comprises, by weight, 30-70wt% of a second positive electrode active material and 30-70wt% of a second solid electrolyte.
8. The composite positive electrode sheet according to claim 7, wherein: the second positive electrode active material in the mixture is the same as the first positive electrode active material in the second active coating layer, and the second solid electrolyte in the mixture is the same as the first solid electrolyte material in the functional coating layer.
9. A preparation method of a composite positive plate is characterized by comprising the following steps: sequentially coating first active coating slurry, second active coating slurry and functional coating slurry on at least one side surface of the positive electrode current collector to form a composite coating, thereby obtaining a composite positive electrode plate;
the first active coating and the second active coating are respectively and independently monocrystal or polycrystal nine-series, eight-series, seven-series, six-series or five-series ternary nickel cobalt lithium manganate materials coated by active substances with ion conducting capacity, and the nickel element content in the ternary nickel cobalt lithium manganate material of the first active coating is higher than that in the ternary nickel cobalt lithium manganate material of the second active coating;
the first conductive agent content of the first active coating is lower than the first conductive agent content of the second active coating.
10. The method for preparing the composite positive electrode sheet according to claim 9, wherein the preparation of the first active coating slurry specifically comprises: weighing a first positive electrode active material, a first conductive agent, a first binder, zirconium dioxide and a solvent according to a preset proportion of each component in the first active coating, mixing and stirring the first binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the first conductive agent and the zirconium dioxide to continuously stir until uniformly dispersed first active coating slurry is obtained;
The preparation of the second active coating slurry comprises the following steps: weighing a first positive electrode active material, a first conductive agent, a first binder, zirconium dioxide and a solvent according to a preset proportion of each component in the second active coating, mixing and stirring the first binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the first conductive agent and the zirconium dioxide to continuously stir until uniformly dispersed second active coating slurry is obtained;
the preparation of the functional coating slurry specifically comprises the following steps: and weighing the first solid electrolyte, the second binder, the dispersing agent and the solvent according to the preset proportion of each component in the functional coating, and mixing and stirring the first solid electrolyte, the second binder, the dispersing agent and the solvent until the uniformly dispersed functional coating slurry is obtained.
11. The method for preparing a composite positive electrode sheet according to claim 9 or 10, characterized in that: after each slurry coating, drying and rolling treatment are performed, and then the next slurry coating is performed.
12. The method for preparing a composite positive electrode sheet according to claim 9 or 10, characterized in that: after the second active coating slurry is coated, the transition layer slurry is coated first, and then the functional coating slurry is coated;
The preparation of the transition layer slurry specifically comprises the following steps: and mixing and stirring the third binder and the solvent to form a glue solution, and then adding the first positive electrode active material, the second conductive agent and the second solid electrolyte, and continuously stirring until the uniformly dispersed transition coating slurry is obtained.
13. The method for preparing a composite positive electrode sheet according to claim 9 or 10, characterized in that: the coating area of the functional coating is the area of the first active coating and the second active coating, wherein the width of the functional coating close to the tab side exceeds the width of the first active coating and the second active coating by 0.5-2 mm.
14. Use of a composite positive electrode sheet according to any one of claims 1 to 8 or a composite positive electrode sheet according to any one of claims 9 to 13 in a lithium ion battery.
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