CN116417566A - Positive electrode plate, preparation method thereof and lithium ion battery - Google Patents
Positive electrode plate, preparation method thereof and lithium ion battery Download PDFInfo
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- CN116417566A CN116417566A CN202310551268.3A CN202310551268A CN116417566A CN 116417566 A CN116417566 A CN 116417566A CN 202310551268 A CN202310551268 A CN 202310551268A CN 116417566 A CN116417566 A CN 116417566A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 16
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 238000000576 coating method Methods 0.000 claims abstract description 52
- 239000011248 coating agent Substances 0.000 claims abstract description 45
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 22
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 210000000746 body region Anatomy 0.000 claims abstract description 15
- 239000011230 binding agent Substances 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 12
- VYFOAVADNIHPTR-UHFFFAOYSA-N isatoic anhydride Chemical compound NC1=CC=CC=C1CO VYFOAVADNIHPTR-UHFFFAOYSA-N 0.000 claims abstract description 9
- NEILRVQRJBVMSK-UHFFFAOYSA-N B(O)(O)O.C[SiH](C)C.C[SiH](C)C.C[SiH](C)C Chemical compound B(O)(O)O.C[SiH](C)C.C[SiH](C)C.C[SiH](C)C NEILRVQRJBVMSK-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000002002 slurry Substances 0.000 claims description 22
- 239000007774 positive electrode material Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 12
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 9
- 239000002033 PVDF binder Substances 0.000 claims description 7
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 7
- UBKGOWGNYKVYEF-UHFFFAOYSA-N 6-fluoro-1h-3,1-benzoxazine-2,4-dione Chemical compound N1C(=O)OC(=O)C2=CC(F)=CC=C21 UBKGOWGNYKVYEF-UHFFFAOYSA-N 0.000 claims description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 6
- 239000006258 conductive agent Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 238000005520 cutting process Methods 0.000 claims description 4
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- 239000003960 organic solvent Substances 0.000 claims description 4
- -1 polytetrafluoroethylene Polymers 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 4
- VAAIGNBVENPUEI-UHFFFAOYSA-N 5-fluoro-1h-3,1-benzoxazine-2,4-dione Chemical compound N1C(=O)OC(=O)C2=C1C=CC=C2F VAAIGNBVENPUEI-UHFFFAOYSA-N 0.000 claims description 3
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 3
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- 238000004519 manufacturing process Methods 0.000 claims description 3
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- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 229920005989 resin Polymers 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- 229920005596 polymer binder Polymers 0.000 claims description 2
- 239000002491 polymer binding agent Substances 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 239000011888 foil Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 239000011267 electrode slurry Substances 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
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- 238000001556 precipitation Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- YZYKZHPNRDIPFA-UHFFFAOYSA-N tris(trimethylsilyl) borate Chemical compound C[Si](C)(C)OB(O[Si](C)(C)C)O[Si](C)(C)C YZYKZHPNRDIPFA-UHFFFAOYSA-N 0.000 description 3
- 239000010405 anode material Substances 0.000 description 2
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- 238000011056 performance test Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000004513 sizing Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910011328 LiNi0.6Co0.2Mn0.2O2 Inorganic materials 0.000 description 1
- 229910011624 LiNi0.7Co0.1Mn0.2O2 Inorganic materials 0.000 description 1
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
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- 230000007547 defect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
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- 230000017525 heat dissipation Effects 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
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- 230000007774 longterm Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
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- 238000012546 transfer Methods 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
-
- 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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive pole piece, a preparation method thereof and a lithium ion battery. The positive electrode plate provided by the invention comprises a main body region, a mixing region and a conductive coating region, wherein the mixing region is a mutual-dissolving region formed by a main body region material and a conductive coating region material in a coating process; wherein the conductive coating region comprises the following components in percentage by mass (0.3-0.7): (0.2-0.5): (0.1-0.2) a polymeric binder, isatoic anhydride and tris (trimethylsilane) borate. According to the invention, through the arrangement of the conductive coating area and the mixing area with specific components, the problem of lithium analysis in the battery thinning area is effectively solved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive pole piece, a preparation method thereof and a lithium ion battery.
Background
With the increasing increase of environmental pollution, the new energy industry is receiving more and more attention. The lithium ion power battery is taken as an important component of the electric vehicle, and the service life of the electric vehicle is directly influenced by the performance of the lithium ion power battery, so that the lithium ion power battery is also attracting a great deal of attention. Compared with other shells, the aluminum-shell lithium ion battery has the advantages of light weight, high specific energy, good safety, long service life and the like, and is widely applied. The lithium ion power battery with the aluminum metal shell has the advantages of good heat dissipation performance, high mechanical strength and the like, and is touted by the majority of lithium battery manufacturers.
However, in the existing electrode production process, on the one hand, in the coating process, the fluidity of the electrode slurry leads to lower slurry thickness or coating surface density at the coating edge (skived zone) than in the intermediate material zone (main body zone), resulting in Li in the actual charge and discharge process + The migration path is longer, the migration resistance is increased, and lithium separation in a thinning area and the like are easy to cause; the thickness of the edge of the negative electrode plate is uneven, even after rolling, the flatness of the edge of the electrode plate is difficult to ensure, the uneven electrode plate is easy to cause larger overpotential, lithium is deposited on the surface of the negative electrode material, the phenomenon of lithium precipitation occurs, and the performance of the battery is influenced; the lithium deposition phenomenon continuously occurs, and in severe cases, the separator is penetrated, resulting in an internal short circuit of the battery. On the other hand, due to the fluctuation of the density of the coating surface, the ratio (NP ratio) of the capacity of the cathode pole piece to the capacity of the anode pole piece in the thinning area is easy to be too small, and lithium is easy to be separated from the surface of the cathode in the thinning area in the charging process; therefore, lithium is degraded in a thinning area in a long-term circulation process, large-area lithium precipitation in the battery core is further led, and potential safety hazards are brought in the use process of the battery core. In addition, in the battery reaction, the edge thinning area NP is too small due to the large local current at the edge of the pole piece, so that local overcharge at the edge of the negative pole piece is easy to occur; the partial overcharge easily causes electrolyte decomposition, so that the internal pressure of the battery is increased, the electrolyte is irreversibly lost, and the capacity of the battery is attenuated, even a safety accident is caused.
In order to solve the above problems, the conventional method generally increases the NP ratio of the skived region by increasing the surface density of the anode coating, thereby eliminating the lithium-precipitation risk of the skived region. However, the increased negative electrode material increases the formation of an SEI film and causes an increase in consumption of electrolyte, increases the NP ratio and consumes excessive positive electrode active material and reduces positive electrode gram capacity exertion; furthermore, an excessively large NP ratio tends to cause Li + Excessive loss and deterioration of cycle performance.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defects existing in the production process of the electrode plate in the prior art, so as to provide a positive electrode plate, a preparation method thereof and a lithium ion battery.
Therefore, the invention provides the following technical scheme:
the invention provides a positive electrode plate, which comprises a main body region, a mixing region and a conductive coating region, wherein the mixing region is a mutual-dissolving region formed by a main body region material and a conductive coating region material in a coating process;
wherein the conductive coating region comprises the following components in percentage by mass (0.3-0.7): (0.2-0.5): (0.1-0.2) a polymeric binder, isatoic anhydride and tris (trimethylsilane) borate.
Optionally, the width of the conductive coating region is 3-7mm.
Optionally, the width of the mixing area is 1.0-3.5mm.
Optionally, the thickness of the conductive coating region is 10-50% of the thickness of the main body region;
and/or the thickness of the body region is 25-250 μm.
Optionally, the polymer binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyimide, polyacrylonitrile, polysilicone ether and polyethylene oxide resin;
and/or the isatoic anhydride comprises at least one of 5-fluoroisatoic anhydride and 6-fluoroisatoic anhydride;
and/or the positive electrode active material in the main body area is lithium iron phosphate, ternary lithium battery positive electrode material or multi-element lithium battery positive electrode material.
The invention also provides a preparation method of the positive plate, which comprises the following steps:
s1, preparing main body area slurry;
s2, dissolving a high molecular binder, isatoic anhydride and tris (trimethylsilane) borate in an organic solvent to obtain conductive coating area slurry;
and S3, coating the slurry of the main body area and the slurry of the conductive coating area on a current collector at the same time, drying, rolling and cutting to obtain the positive plate.
Alternatively, the current collector in the present invention is conventional in the art, for example, aluminum foil is typically used as the positive electrode current collector.
Optionally, in step S2, the solid content of the conductive coating area slurry is 20-45%;
and/or the organic solvent is a solvent commonly used in the art, and may be, for example, N-methylpyrrolidone.
Optionally, in step S3, the temperature of the drying is 90-120 ℃.
Optionally, in step S1, the main body area slurry includes: the specific composition of the positive electrode active material, the conductive agent, the binder and the solvent is conventional in the art, and can be adjusted according to the type, model and the like of the battery.
The invention also provides a lithium ion battery, which comprises the positive electrode plate or the positive electrode plate prepared by the preparation method.
The invention covers the high-power thin electrode of a conventional Hybrid Electric Vehicle (HEV) and the high-energy thick electrode scheme of a pure Electric Vehicle (EV) through limiting the thickness of a main body area.
In the present invention, the positive active material in the main body region is a conventional active material in a lithium ion battery, and for example, may be lithium iron phosphate, a ternary lithium battery positive electrode material or a multi-element lithium battery positive electrode material. Typically, but not by way of limitation, the ternary lithium battery positive electrode material comprises Li 2 Ni x Co y Mn z O 2 (0.3.ltoreq.x.ltoreq.0.95; 0.ltoreq.y.ltoreq.0.3; 0.05.ltoreq.z.ltoreq.0.3), the high nickel ternary positive electrode material typically including, but not limited to, liNi 0.9 Co 0.05 Mn 0.05 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.7 Co 0.1 Mn 0.2 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 The mass ratio of the electrode active layer is 80% -95%. The multi-element lithium battery positive electrode material comprises Li 2 Ni x Co y Mn z T n O 2 (0.3.ltoreq.x.ltoreq.0.95; 0.ltoreq.y.ltoreq.0.3; 0.05.ltoreq.z.ltoreq.0.3; 0.ltoreq.n.ltoreq.0.3; T is Al or a transition metal element such as Fe, cr, cu, etc.).
In the present invention, the coating method is well known in the art. Typically, but not limited to, the following steps may be included: and (3) mixing the lithium iron phosphate anode material, the binder and the conductive agent according to the mass ratio of 94.6:3.7:1.7, fully stirring, adding NMP to adjust the viscosity of the slurry, fully stirring and mixing, and finally adding NMP to adjust the viscosity of the slurry to form the anode slurry with the viscosity of 4500-8000 mPas and the solid content of 60% -70%. The positive electrode slurry was uniformly coated on a 6 μm aluminum foil with a double-sided coating weight of about 50mg/cm 2 。
Wherein the binder comprises one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyacrylate, polyimide, polyacrylonitrile, polysilicone ether and polyethylene oxide resin, and the mass ratio of the electrode active layer is 2% -5%.
The conductive agent comprises one or more of Carbon Nanotubes (CNTs), conductive carbon black (SP), ketjen black, acetylene black, 350G, carbon fiber (VGCF), graphite conductive agent (KS, S-O), graphene and the like, and the mass ratio in the electrode active layer is 1.5% -5%.
In the invention, other compositions and preparation methods of the provided lithium ion battery are conventional in the field.
The technical scheme of the invention has the following advantages:
the positive electrode plate provided by the invention comprises a main body region, a mixing region and a conductive coating region, wherein the mixing region is a mutual-dissolving region formed by a main body region material and a conductive coating region material in a coating process; wherein the conductive coating region comprises the following components in percentage by mass (0.3-0.7): (0.2-0.5): (0.1-0.2) a polymeric binder, isatoic anhydride and tris (trimethylsilane) borate. According to the invention, through the arrangement of the conductive coating area and the mixing area with specific components, the problem of lithium analysis in the battery thinning area is effectively solved. Specifically, 1) the positive electrode Li of the skived region is reduced by providing a conductive coating on the skived region + The content of the battery core is increased, the NP ratio of the thinning area of the battery core is improved, and the risk of excessively small NP ratio caused by polarization and coating tolerance of the thinning area is eliminated; 2) By the arrangement, the thinning trend of the edge thickness of the main body area is slowed down, the thickness of the positive electrode edge thinning area is increased, and the distance between the positive electrode edge thinning area and the negative electrode edge thinning area is reduced, so that the thickness of the positive electrode edge thinning area is effectively shortenedLi + A migration path; 3) At the same time, the thinning area Li can be effectively improved + Diffusion coefficient, reduce the possibility of lithium analysis in the thinning area of the cathode, and improve the safety performance of the battery. Compared with the conventional method for improving the NP ratio, the method has the advantages of cost and performance, and particularly, on one hand, the NP ratio of a skived area is improved without increasing the coating amount of the negative electrode, so that the material cost is reduced; on the other hand, the increase of electrolyte consumption caused by the formation of an SEI film of redundant anode materials can be avoided; in addition, the invention realizes the increase of the NP ratio by reducing the positive electrode content of the thinning area, can not reduce the capacity exertion of positive electrode gram, and also avoids Li caused by overlarge NP ratio + Occurrence of excessive loss, deterioration of cycle performance, and the like; in addition, the Li between the positive electrode thinning region and the negative electrode thinning region can be reduced by slowing down the thinning trend of the edge thickness of the main body region + Diffusion distance. The isatoic anhydride in the conductive coating can neutralize the alkalinity of the surface of the positive electrode material particles, can form a film on the positive electrode, and the fluorinated anhydride can generate LiF, so that the conductivity is improved, the internal resistance is reduced, the generation of cracks in the particles of the positive electrode material in the circulation process is inhibited, and the circulation is improved. The tri (trimethylsilane) borate forms a stable and compact CEI film on the positive electrode, inhibits the dissolution of transition metal of the positive electrode material, improves the stability of the positive electrode material, and can improve the charge transfer capacity of the electrode and improve the circulation.
The preparation method of the positive pole piece provided by the invention has the advantages of simple process method and low cost. Wherein, the main body area sizing agent and the conductive coating area sizing agent are coated on the aluminum foil at the same time, so that the thinning trend of the edge thickness of the main body area can be slowed down to reduce Li between the positive pole thinning area and the negative pole thinning area + Diffusion distance and reduced NP ratio of the cell thinning area through mutual dissolution, thereby improving lithium separation of the thinning area.
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 needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic structural view of a positive electrode sheet in embodiment 1 of the present invention;
reference numerals:
1. a body region; 2. a mixing area; 3. and a conductive coating area.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The embodiment provides a positive electrode plate, as shown in fig. 1, which comprises a main body area 1, a mixing area 2 and a conductive coating area 3, wherein the specific composition and the preparation method are as follows:
s1, mixing a lithium iron phosphate positive electrode material, a polyvinylidene fluoride (PVDF) binder and conductive carbon black (SP) according to the mass ratio of 94.6:3.7:1.7, fully stirring, adding NMP to adjust the viscosity of the slurry, fully stirring and mixing, and finally adding NMP to adjust the viscosity of the slurry to form the positive electrode slurry with the viscosity of 4500-8000 mPas and the solid content of 60% -70%. The positive electrode slurry was uniformly coated on a 6 μm aluminum foil with a double-sided coating weight of 50mg/cm 2 。
S2, polyvinylidene fluoride: 5-fluoroisatoic anhydride: tris (trimethylsilyl) borate: n-methylpyrrolidone at 0.3:0.5:0.2:1, revolution 20rpm, rotation 1500rpm,40min stirring, and testing, slurry viscosity 3000cP and solid content 35%.
S3, in the positive electrode coating process, coating the slurry on a 13-mu m carbon-coated aluminum foil by using an extrusion coater, then drying at a high temperature (the drying temperature is between 90 and 120 ℃) a coating oven, and then rolling and cutting to obtain a positive electrode plate with a main body area thickness of 170 mu m, a mixed material area width of 3mm, a conductive coating area width of 7mm and a thickness of 42 mu m.
Example 2
This embodiment provides a positive electrode sheet, which differs from embodiment 1 only in that: a high molecular binder: 5-fluoroisatoic anhydride: tris (trimethylsilyl) borate: the mass ratio of the N-methyl pyrrolidone is 0.6:0.3:0.1:1.
example 3
This embodiment provides a positive electrode sheet, which differs from embodiment 1 only in that: a high molecular binder: 5-fluoroisatoic anhydride: tris (trimethylsilyl) borate: the mass ratio of the N-methyl pyrrolidone is 0.7:0.2:0.1:1.
example 4
This embodiment provides a positive electrode sheet, which differs from embodiment 1 only in that: the 5-fluoroisatoic anhydride is replaced by the 6-fluoroisatoic anhydride with equal mass.
Example 5
This embodiment provides a positive electrode sheet, which differs from embodiment 1 only in that: the thickness of the main body area of the obtained positive electrode plate is 170 mu m, the width of the mixed material area is 1mm, the width of the conductive coating area is 3mm, and the thickness is 17 mu m.
Comparative example 1
This comparative example provides a positive electrode sheet differing from example 1 in that lithium iron phosphate slurry was coated on a 13 μm carbon-coated aluminum foil alone using an extrusion coater without adding Li + An ion conductive coating.
Test case
Assembled battery
The negative electrode adopts deionized water for homogenization, artificial graphite particles, styrene-butadiene rubber, sodium carboxymethyl cellulose and conductive agent SP are adopted, the mass ratio is 96:1.7:1.3:1, the viscosity of the slurry is regulated to 2500-4500 mPa.s, and the solid content is regulated to 55-65%. The prepared slurry was uniformly coated on an 8 μm copper foil with a double-sided coating weight of 25mg/cm 2 Then by dryingRolling, die cutting and punching to obtain the negative electrode plate.
And assembling the prepared positive and negative pole pieces and the diaphragm together through a Z-shaped lamination process, packaging the positive and negative pole pieces and the diaphragm into a soft package battery, baking, injecting liquid, forming, and sealing to prepare the battery cell. Electrolyte is 1M LiPF 6 Dissolved in a mixed solution (volume ratio is 1:1) of ethylene carbonate and methyl ethyl carbonate.
Low temperature charging performance test
The normal temperature is discharged to 2.0V cut-off by using 1C constant current, then the 1C constant current and constant voltage charge is carried out to 3.8V, and 0.05C cut-off is carried out, the initial charge capacity C0 is calculated, the normal temperature is discharged to 2.0V cut-off by using 1C constant current, and then the obtained product is placed in a low temperature test cabinet at the temperature of minus 20 ℃ for 8 hours; at-20 ℃,1C was charged to 3.8V at constant current and constant voltage, charge capacity C1 was recorded, cycle repeated 10 times, charge capacity C2 per cycle was recorded,..c10, percent of charge efficiency (%) =average (c1:c10)/c0×100%.
Cycle performance test
-20 ℃,1/3C charge, 1/3C discharge, repeat cycle 200 turns, cycle retention (%) = c200/c1×100%.
Lithium separation: and disassembling the battery after circulation, and observing whether the edge area of the pole piece is separated from lithium. The specific test results are shown in the following table:
TABLE 1
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. The positive electrode plate is characterized by comprising a main body region, a mixing region and a conductive coating region, wherein the mixing region is a mutual-dissolving region formed by a main body region material and a conductive coating region material in a coating process;
wherein the conductive coating region comprises the following components in percentage by mass (0.3-0.7): (0.2-0.5): (0.1-0.2) a polymeric binder, isatoic anhydride and tris (trimethylsilane) borate.
2. The positive electrode sheet according to claim 1, wherein the width of the conductive coating region is 3-7mm.
3. The positive electrode sheet of claim 1, wherein the blend zone has a width of 1.0-3.5mm.
4. The positive electrode sheet according to claim 1, wherein the thickness of the conductive coating region is 10-50% of the thickness of the main body region;
and/or the thickness of the body region is 25-250 μm.
5. The positive electrode sheet according to any one of claims 1 to 4, wherein the polymer binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylate, polyimide, polyacrylonitrile, polysilicone ether, polyethylene oxide resin;
and/or the isatoic anhydride comprises at least one of 5-fluoroisatoic anhydride and 6-fluoroisatoic anhydride;
and/or the positive electrode active material in the main body area is lithium iron phosphate, ternary lithium battery positive electrode material or multi-element lithium battery positive electrode material.
6. A method for preparing the positive electrode sheet according to any one of claims 1 to 5, comprising the steps of:
s1, preparing main body area slurry;
s2, dissolving a high molecular binder, isatoic anhydride and tris (trimethylsilane) borate in an organic solvent to obtain conductive coating area slurry;
and S3, coating the slurry of the main body area and the slurry of the conductive coating area on a current collector at the same time, drying, rolling and cutting to obtain the positive plate.
7. The method of manufacturing a positive electrode sheet according to claim 6, wherein in step S2, the solid content of the conductive coating area slurry is 20-45%;
and/or the organic solvent comprises N-methyl pyrrolidone.
8. The method according to claim 6, wherein in step S3, the temperature of the drying is 90-120 ℃.
9. The method according to claim 6, wherein in step S1, the main body area slurry includes: positive electrode active material, conductive agent, binder and solvent.
10. A lithium ion battery comprising the positive electrode sheet according to any one of claims 1 to 5 or the positive electrode sheet prepared by the preparation method according to any one of claims 6 to 9.
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