CN115312684B - Positive pole piece and battery - Google Patents
Positive pole piece and battery Download PDFInfo
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- CN115312684B CN115312684B CN202211018533.3A CN202211018533A CN115312684B CN 115312684 B CN115312684 B CN 115312684B CN 202211018533 A CN202211018533 A CN 202211018533A CN 115312684 B CN115312684 B CN 115312684B
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- 239000011230 binding agent Substances 0.000 claims abstract description 42
- 238000005056 compaction Methods 0.000 claims abstract description 35
- 239000006258 conductive agent Substances 0.000 claims abstract description 22
- 239000012528 membrane Substances 0.000 claims abstract description 12
- 239000007774 positive electrode material Substances 0.000 claims description 50
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 239000002033 PVDF binder Substances 0.000 claims description 14
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 14
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 239000011888 foil Substances 0.000 claims description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 229910052744 lithium Inorganic materials 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 229910019142 PO4 Inorganic materials 0.000 claims description 3
- NDPGDHBNXZOBJS-UHFFFAOYSA-N aluminum lithium cobalt(2+) nickel(2+) oxygen(2-) Chemical compound [Li+].[O--].[O--].[O--].[O--].[Al+3].[Co++].[Ni++] NDPGDHBNXZOBJS-UHFFFAOYSA-N 0.000 claims description 3
- 239000006229 carbon black Substances 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 claims description 3
- 229910002102 lithium manganese oxide Inorganic materials 0.000 claims description 3
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 claims description 3
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 claims description 3
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 239000010452 phosphate Substances 0.000 claims description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 11
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 11
- 238000000034 method Methods 0.000 abstract description 10
- 230000008569 process Effects 0.000 abstract description 8
- 239000013543 active substance Substances 0.000 abstract description 6
- 239000011149 active material Substances 0.000 abstract description 2
- 238000000605 extraction Methods 0.000 abstract description 2
- 238000009830 intercalation Methods 0.000 abstract description 2
- 230000002687 intercalation Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 39
- 238000012360 testing method Methods 0.000 description 11
- 239000000853 adhesive Substances 0.000 description 10
- 230000001070 adhesive effect Effects 0.000 description 10
- 239000011267 electrode slurry Substances 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 10
- 239000010439 graphite Substances 0.000 description 10
- 229910002804 graphite Inorganic materials 0.000 description 10
- 239000002245 particle Substances 0.000 description 10
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 description 9
- 238000003825 pressing Methods 0.000 description 8
- 238000000576 coating method Methods 0.000 description 6
- 238000001035 drying Methods 0.000 description 5
- 229910003002 lithium salt Inorganic materials 0.000 description 5
- 159000000002 lithium salts Chemical class 0.000 description 5
- 239000007773 negative electrode material Substances 0.000 description 5
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 4
- 239000002270 dispersing agent Substances 0.000 description 4
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 4
- 239000003960 organic solvent Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- -1 polyethylene Polymers 0.000 description 3
- 239000004743 Polypropylene Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- 238000000926 separation method Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000002003 electrode paste Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 description 1
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- 239000004005 microsphere Substances 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910021384 soft carbon Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
Classifications
-
- 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
-
- 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
- H01M10/04—Construction or manufacture in general
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/043—Processes of manufacture in general involving compressing or compaction
- H01M4/0435—Rolling or calendering
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a positive pole piece and a battery, and relates to the technical field of batteries; the positive pole piece comprises a positive current collector and a positive membrane; the positive electrode membrane is arranged on at least one side surface of the positive electrode current collector and comprises a positive electrode active substance, a conductive agent and a binder; the positive pole piece satisfies the formula: -0.01 < (-0.3788 XPD+1.155). Times.ρ/(12 XBET) < 0.0335. On one hand, the compaction density is controlled, the performance of the lithium ion extraction and intercalation process can be improved on the premise of ensuring the power performance, the single conductive network in the pole piece is perfected, the internal resistance of the pole piece is reduced, and the rebound problem of the pole piece is improved; on the other hand, the density of the binder, the specific surface area of the active material and the compaction density are cooperatively controlled, so that the power performance of the battery can be effectively improved while the rebound of the pole piece is ensured to be small.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a positive pole piece and a battery.
Background
In the process of charging and discharging the battery, the pole piece is easy to rebound, the rebound refers to the phenomenon that the thickness of the pole piece is increased compared with the thickness after rolling, and the service performance and the safety performance of the battery can be directly affected by the fact that the rebound of the pole piece is large. In order to control the rebound of the pole piece in the prior art, the compaction density or the rolling process of the pole piece is usually improved, but the existing scheme for improving the rebound of the pole piece can influence the power performance of the battery, so that the power performance of the battery is reduced, and the service life of the battery is shortened. Thus, the prior art lacks pole pieces that both ensure the power performance of the battery and control bouncing.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a positive electrode plate and a battery which have small rebound and excellent power performance.
Embodiments of the present invention are implemented as follows:
In a first aspect, the present invention provides a positive electrode sheet comprising:
a positive electrode current collector;
the positive electrode diaphragm is arranged on at least one side surface of the positive electrode current collector and comprises a positive electrode active material, a conductive agent and a binder;
the positive pole piece satisfies the formula: -0.01 < (-0.3788 x pd+1.155) xp/(12 x BET) < 0.0335; PD is the compaction density of the positive pole piece, and the unit is g/cm 3; ρ is the density of the binder in g/cm 3; BET is the specific surface area of the positive electrode active material in m 2/g.
In an alternative embodiment, the positive electrode sheet satisfies the formula: -0.0031 < (-0.3788 x pd+1.155) xp/(12 x BET) < 0.021;
preferably, the positive electrode sheet satisfies the formula: 0 < (-0.3788 XPD+1.155) ×ρ/(12×BET) < 0.005.
In an alternative embodiment, the compacted density of the positive electrode sheet satisfies 2.5g/cm 3≤PD≤3.5g/cm3;
Preferably, the compacted density of the positive electrode sheet satisfies 2.85g/cm 3≤PD≤3.05g/cm3.
In an alternative embodiment, the density of the binder satisfies 1.70g/cm 3≤ρ≤1.80g/cm3;
Preferably, the density of the binder satisfies 1.77g/cm 3≤ρ≤1.80g/cm3.
In an alternative embodiment, the specific surface area of the positive electrode active material satisfies 0.8m 2/g≤BET≤5m2/g;
Preferably, the specific surface area of the positive electrode active material satisfies 2.2m 2/g≤BET≤3.6m2/g.
In an alternative embodiment, the porosity of the positive electrode sheet ranges from 20% to 60%;
preferably, the porosity of the positive electrode sheet ranges from 25% to 45%.
In an alternative embodiment, the positive electrode current collector is selected from any one of aluminum foil, carbon coated aluminum foil, and nickel mesh;
And/or the number of the groups of groups,
The positive electrode active material is selected from any one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide and olivine-structured lithium-containing phosphate;
And/or the number of the groups of groups,
The conductive agent is selected from any one of carbon black and carbon nano tubes;
And/or the number of the groups of groups,
The binder is PVDF.
In an alternative embodiment, the positive electrode membrane comprises a mass ratio of (90-97): (1-5): the positive electrode active material, the conductive agent and the binder of (1-5).
In an alternative embodiment, both side surfaces of the positive electrode current collector are provided with positive electrode diaphragms.
In a second aspect, the present invention provides a battery comprising the positive electrode sheet of any one of the preceding embodiments.
The embodiment of the invention has at least the following advantages or beneficial effects:
The embodiment of the invention provides a pole piece, which comprises a positive pole current collector and a positive pole diaphragm; the positive electrode membrane is arranged on at least one side surface of the positive electrode current collector and comprises a positive electrode active substance, a conductive agent and a binder; the positive pole piece satisfies the formula: -0.01 < (-0.3788 x pd+1.155) xp/(12 x BET) < 0.0335; PD is the compaction density of the positive pole piece, and the unit is g/cm 3; ρ is the density of the binder in g/cm 3; BET is the specific surface area of the positive electrode active material in m 2/g.
On one hand, the positive pole piece can improve the performance of the process of removing and embedding lithium ions on the premise of ensuring the power performance by controlling the compaction density so as to perfect a single conductive network in the pole piece and reduce the internal resistance of the pole piece, thereby fully improving the rebound problem of the pole piece; on the other hand, the density of the binder, the specific surface area of the positive electrode active material and the compaction density are cooperatively controlled, so that the power performance and the service life of the battery can be effectively improved while the rebound of the pole piece is further reduced.
The embodiment of the invention provides a battery, which comprises the positive electrode plate. Therefore, the battery also has the advantages of small rebound and excellent power performance.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
The embodiment of the invention provides a positive electrode plate, which comprises: a positive electrode current collector; the positive electrode membrane is arranged on at least one side surface of the positive electrode current collector, and is obtained by coating positive electrode slurry on the positive electrode current collector, drying and cold pressing, wherein the positive electrode slurry comprises a positive electrode active substance, a conductive agent and a binder; wherein, the positive pole piece satisfies the formula: -0.01 < (-0.3788 x pd+1.155) xp/(12 x BET) < 0.0335; PD is the compaction density of the positive pole piece, and the unit is g/cm 3; ρ is the density of the binder in g/cm 3; BET is the specific surface area of the positive electrode active material in m 2/g.
When the positive electrode plate is subjected to preparation operation, positive electrode slurry can be prepared firstly, and positive electrode active substances, conductive agents and binders are mixed according to a certain mass ratio, wherein the mass ratio of the positive electrode active substances, the conductive agents and the binders is (90-97): (1-5): (1-5). Then, NMP was added and stirred with a refiner to form a uniformly mixed stable positive electrode slurry. Next, a positive electrode paste may be applied to at least one side surface of the positive electrode current collector, and dried and cold-pressed to form a positive electrode membrane on the side surface of the positive electrode current collector. And then carrying out cold pressing treatment on the dried positive pole piece under a certain pressure and a roll gap, and adjusting the compaction density of the positive pole piece by adjusting cold pressing parameters. And finally, slitting the cold-pressed positive electrode plate, and then slitting the positive electrode plate to a specified size for later use.
In the formula satisfied by the positive electrode plate, PD is the compaction density of the positive electrode plate, and the unit is g/cm 3. When the lithium ion battery is charged and discharged, lithium ions are extracted and intercalated between the positive electrode material and the negative electrode material, and the extraction and intercalation processes of the lithium ions are closely related to the compaction density of the positive electrode plate. On one hand, as the compaction density of the positive electrode plate is increased, positive electrode active material particles are tightly contacted with each other, an electronic conductive network in the plate is perfect, and the internal resistance is reduced; however, the compaction density is too high, so that the pole piece bounces in the circulation process, the contact chain of the conductive agent and the adhesive with the positive electrode active material breaks, and particles among the positive electrode active materials are mutually stripped, so that the charge transfer resistance is increased, and the rate performance and the circulation performance of the battery are deteriorated. On the other hand, the compaction density of the positive electrode plate is improved, the porosity in the electrode plate is reduced continuously, the liquid retention amount of electrolyte in the electrode plate is reduced continuously, the ionic conductivity of the electrode plate is reduced, the conductive network is deteriorated, and the internal resistance of the battery is increased. Therefore, the proper compaction density is selected, so that the rebound of the positive pole piece can be reduced, and the power performance of the battery can be ensured.
In the formula satisfied by the positive electrode sheet, the BET positive electrode represents the specific surface area of the positive electrode active material. The positive electrode active material with small particle size has larger specific surface area, and larger contact area with electrolyte, so that the diffusion path of lithium ions is shortened, and the deintercalation of lithium ions in the material under high current density is facilitated, therefore, the positive electrode active material with small particle size is beneficial to improving the rate capability of the battery. Meanwhile, as the particle diameter of the positive electrode active material particles increases, the ion transport distance is also reduced, and thus battery power performance can be improved. However, when the particle diameter of the positive electrode active material is too small, the difficulty of dispersing the slurry is increased accordingly, so that the manufacturing cost is increased accordingly. Therefore, the proper specific surface area of the positive electrode active material is selected, so that the lithium ion battery can have excellent power performance and rate capability, the service life of the lithium ion battery can be prolonged, and the manufacturing cost can be controlled.
In the formula satisfied by the positive electrode sheet, ρ is the density of the adhesive in the positive electrode formulation. On the one hand, the higher the density of the binder, the larger the volume of the binder particles, which can increase the conductive contact between the positive electrode active material and the conductive agent, and thus can improve the electron conductivity. That is, increasing the binder density can collect micro-current between the active materials and the conductive carbon to perfect the middle conductive network of the pole piece, reduce internal resistance, and optimize power performance. Particularly, the larger the specific surface area of the pole piece in the rebound process, a good conductive network can be maintained so as to ensure the power performance of the battery. On the other hand, when the density of the binder is too small, it cannot maintain close contact between the positive electrode active material and the conductive agent, so that a perfect conductive network cannot be formed, and the problem of serious rebound of the electrode sheet occurs at the later stage of the cycle, resulting in serious degradation of the battery capacity.
In summary, in the embodiment of the invention, on one hand, by controlling the compaction density, the rebound problem of the pole piece can be improved on the premise of ensuring the power performance, the multiplying power performance and the cycle performance of the battery; on the other hand, the density of the binder, the specific surface area of the positive electrode active material and the compaction density are cooperatively controlled, so that the rebound of the pole piece is further reduced, and meanwhile, the power performance and the service life of the battery are effectively improved.
Alternatively, in the embodiment of the present invention, the positive electrode sheet satisfies the formula: -0.0031 < (-0.3788 x pd+1.155) xp/(12 x BET) < 0.021; preferably, the positive electrode sheet satisfies the formula: 0 < (-0.3788 XPD+1.155) ×ρ/(12×BET) < 0.005. When the parameters of the positive pole piece are controlled within the formula range, the pole piece can rebound less, and the power performance and the service life are better.
Illustratively, in embodiments of the present invention, the compacted density of the positive electrode sheet satisfies 2.5+.PD+.3.5; the compaction density of the positive pole piece meets PD of 2.85-3.05. By selecting the compaction density within this range, the density of the binder and the specific surface area of the positive electrode active material can be better matched so as to satisfy the requirements of the above formula. The contact between the particles of the positive electrode active material is tighter, so that the internal resistance of the pole piece can be reduced, the rebound of the pole piece in the circulating process is reduced, and the rate capability and the circulating performance of the battery are improved.
Illustratively, in embodiments of the present invention, the density of the binder satisfies 1.70+.ρ+.1.80; preferably, the density of the binder satisfies 1.77.ltoreq.ρ.ltoreq.1.80. By selecting the density of the binder within the range, the compaction density of the positive electrode plate and the specific surface area of the positive electrode active material can be better matched, so that the requirements of the formula can be met. The contact area between the positive electrode active material and the electrolyte is increased, the multiplying power performance is better, and the ion transmission distance in the circulation process is reduced, so that the power performance of the battery is improved.
Illustratively, in the embodiment of the present invention, the specific surface area of the positive electrode active material satisfies 0.8. Ltoreq.BET. Ltoreq.5; preferably, the specific surface area of the positive electrode active material satisfies 2.2.ltoreq.BET.ltoreq.3.6. By selecting the specific surface area of the positive electrode active material within the range, the compaction density of the positive electrode plate and the density of the binder can be better matched to meet the requirements of the formula. The micro-current between the active substance and the conductive agent particles is ensured, so that the power performance of the battery is improved, meanwhile, a good conductive network can be maintained, the rebound of the pole piece is reduced, and the power performance of the battery is improved.
Further alternatively, in an embodiment of the present invention, the porosity of the positive electrode sheet ranges from 20% to 60%; preferably, the porosity of the positive electrode sheet ranges from 25% to 45%. The compacted density of the positive electrode plate can influence the porosity of the positive electrode plate to a certain extent. And the control of the porosity can improve the ionic conductivity of the pole piece, influence the conductive network formed by the pole piece, and even change the internal resistance of the battery. Therefore, the control of porosity is performed on the basis of controlling the compaction density, so that the rebound of the pole piece can be further reduced, and the power performance of the battery is ensured.
In the embodiment of the present invention, the types of the positive electrode current collector, the positive electrode active material, the conductive agent, and the binder may be selected according to the need. The positive electrode current collector is illustratively selected from any one of aluminum foil, carbon-coated aluminum foil, and nickel mesh, and may also be selected as a composite current collector doped with a conductive substance. Illustratively, the positive electrode active material is selected from any one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, and olivine structured lithium-containing phosphate. The conductive agent is selected from any one of carbon black and carbon nano tubes, and the binder is PVDF.
It should be further noted that, in order to ensure the usability of the positive electrode sheet, in the embodiment of the present invention, both side surfaces of the positive electrode current collector are provided with positive electrode diaphragms. And the thickness and the like of the positive electrode diaphragms at the two sides are the same.
The embodiment of the invention also provides a battery which can be a square battery or a cylindrical or soft package battery. The battery comprises the positive pole piece, a shell, a negative pole piece, a separation film and electrolyte. The positive electrode plate, the isolating film and the negative electrode plate are sequentially stacked, and the bare cell is formed by winding or lamination. And filling the bare cell into the shell, and then injecting electrolyte to obtain the battery. The positive pole piece has the characteristics of small rebound and excellent power performance, so that the battery also has the advantages.
In the embodiment of the present invention, the negative electrode tab includes a negative electrode current collector and a negative electrode membrane disposed on at least one side surface of the negative electrode current collector, and illustratively, both side surfaces are provided with the negative electrode membrane. The negative electrode membrane is coated on a negative electrode current collector through negative electrode slurry, and is obtained after drying and cold pressing. The negative electrode slurry comprises a negative electrode active material, a conductive agent, a binder and a dispersing agent, wherein the negative electrode active material can be selected from graphite, soft carbon, hard carbon, mesophase carbon microspheres, silicon-based materials and the like, the conductive agent can be selected from SP, the binder can be selected from LA133, the dispersing agent can be selected from CMC, and the negative electrode active material, the conductive agent, the binder and the dispersing agent are mixed according to a certain mass ratio, deionized water is added, and the mixture is stirred by a refiner to be uniformly mixed to obtain the negative electrode slurry.
It should be noted that the isolation film may be selected according to actual requirements. For example, the isolating film can be selected from polyethylene film, polypropylene film, polyvinylidene fluoride film, non-woven fabric and the like; while the separator film may have different coating layers. Such as alumina coatings, boehmite coatings, PVDF coatings, and the like. The electrolyte includes a lithium salt solute and a solvent. The kind of lithium salt and solvent is not particularly limited, and may be selected according to actual requirements. For example, lithium salts may be selected from LiPF 6、LiTFSi、LiBF4, and the like. Illustratively, an embodiment of the present invention may be selected in which Ethylene Carbonate (EC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then a sufficiently dried lithium salt LiPF 6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1.2 mol/L.
The preparation process of the battery and the performance of the prepared battery are described in detail below with reference to specific examples:
Example 1
The embodiment provides a battery, which is prepared by the following method:
S1: preparing a positive electrode plate; mixing an anode active material NCM111, a conductive agent SP and a binder PVDF according to a certain proportion, adding NMP, and stirring by a refiner to obtain uniformly mixed and stable anode slurry; coating positive electrode slurry on two side surfaces of a current collector aluminum foil, and drying and cold pressing; continuing cold pressing and slitting to obtain a positive pole piece;
S2: preparing a negative electrode plate; mixing negative electrode active material graphite, a conductive agent SP, a binder LA133 and a dispersing agent CMC according to a certain mass ratio, adding deionized water, and stirring by a refiner to obtain uniformly mixed and stable negative electrode slurry; coating the negative electrode slurry on two side surfaces of a current collector copper foil, and drying and cold pressing; continuing cold pressing and slitting to obtain a negative electrode plate;
S3: preparing electrolyte; mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolving fully dried lithium salt LiPF 6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1.2 mol/L;
s4: and (3) battery forming: a polypropylene film with the thickness of 16um is used as a separation film; sequentially stacking the positive pole piece, the isolating film and the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece, and then winding the positive pole piece, the isolating film and the negative pole piece to obtain a bare cell; and placing the bare cell in a shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other procedures to obtain the 8Ah lithium ion battery.
In the above preparation process, the preparation parameters of the battery are shown in table 1:
TABLE 1 parameters of example 1
Example 2
The present embodiment provides a battery which is different from embodiment 1 in that each parameter of the battery provided in the present embodiment satisfies table 2.
TABLE 2 example 2 parameters
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 3 |
| Density ρ (g/cm 3) of adhesive | 1.79 |
| Specific surface area BET (m 2/g) of positive electrode active material | 3.6 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.00077 |
| Porosity of positive electrode sheet | 32％ |
Example 3
The present embodiment provides a battery which is different from embodiment 1 in that each parameter of the battery provided in the present embodiment satisfies table 3.
TABLE 3 parameters of example 3
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.95 |
| Density ρ (g/cm 3) of adhesive | 1.78 |
| Specific surface area BET (m 2/g) of positive electrode active material | 3.2 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0017 |
| Porosity of positive electrode sheet | 35％ |
Example 4
The present embodiment provides a battery which is different from embodiment 1 in that each parameter of the battery provided in the present embodiment satisfies table 4.
TABLE 4 parameters of example 4
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.85 |
| Density ρ (g/cm 3) of adhesive | 1.8 |
| Specific surface area BET (m 2/g) of positive electrode active material | 2.2 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0051 |
| Porosity of positive electrode sheet | 38％ |
Example 5
The present embodiment provides a battery which is different from embodiment 1 in that the parameters of the battery provided in the present embodiment satisfy table 5.
TABLE 5 parameters of example 5
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.9 |
| Density ρ (g/cm 3) of adhesive | 1.7 |
| Specific surface area BET (m 2/g) of positive electrode active material | 3 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0026 |
| Porosity of positive electrode sheet | 37％ |
Example 6
The present embodiment provides a battery which is different from embodiment 1 in that each parameter of the battery provided in the present embodiment satisfies table 6.
TABLE 6 parameters of example 6
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.5 |
| Density ρ (g/cm 3) of adhesive | 1.7 |
| Specific surface area BET (m 2/g) of positive electrode active material | 5 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0058 |
| Porosity of positive electrode sheet | 40％ |
Comparative example 1
Comparative example 1 provides a battery which is different from example 1 in that each parameter of the battery provided in comparative example 1 satisfies table 7.
TABLE 7 parameters of comparative example 1
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 5 |
| Density ρ (g/cm 3) of adhesive | 1.7 |
| Specific surface area BET (m 2/g) of positive electrode active material | 5 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | -0.021 |
| Porosity of positive electrode sheet | 20％ |
Comparative example 2
Comparative example 2 provides a battery which is different from example 1 in that each parameter of the battery provided in comparative example 1 satisfies table 8.
TABLE 8 parameters of comparative example 2
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.8 |
| Density ρ (g/cm 3) of adhesive | 1.8 |
| Specific surface area BET (m 2/g) of positive electrode active material | 0.4 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0353 |
| Porosity of positive electrode sheet | 38％ |
Comparative example 3
Comparative example 3 provides a battery which is different from example 1 in that each parameter of the battery provided in comparative example 1 satisfies table 9.
TABLE 9 parameters of comparative example 3
| Mass ratio of NCM111, SP, PVDF | 97:1.4:1.2 |
| Graphite, SP, LA133, CMC mass ratio | 32:0.4:0.5:0.3 |
| Compaction density PD of positive pole piece (g/cm 3) | 2.5 |
| Density ρ (g/cm 3) of adhesive | 2.4 |
| Specific surface area BET (m 2/g) of positive electrode active material | 1.1 |
| (-0.3788×PD+1.155)×ρ/(12×BET) | 0.0378 |
| Porosity of positive electrode sheet | 40％ |
Experimental example 1
The batteries provided in examples 1 to 6 and comparative examples 1 to 3 were subjected to a maximum charge rate test under the following conditions: the batteries prepared in examples 1 to 6 and comparative examples 1 to 3 were fully charged at x C and fully discharged at 1C 10 times at 25C, and then the batteries were fully charged at x C, and then the negative electrode sheet was disassembled, and the lithium precipitation condition on the surface of the negative electrode sheet was observed. If lithium is not separated from the surface of the negative electrode, the charging rate x C is gradually increased by taking 0.1C as a gradient, the test is carried out again until lithium is separated from the surface of the negative electrode, the test is stopped, and the charging rate (x-0.1) C at the moment is the maximum charging rate of the battery, and the test result is shown in table 10.
TABLE 10 multiplying power test results
| Project | Maximum charging rate (C) |
| Example 1 | 3.2C |
| Example 2 | 3.5C |
| Example 3 | 3.8C |
| Example 4 | 3.1C |
| Example 5 | 4.0C |
| Example 6 | 3.1C |
| Comparative example 1 | 3.0C |
| Comparative example 2 | 2.8C |
| Comparative example 3 | 1.4C |
As can be seen from the comparative data of examples 1 to 6 and comparative examples 1 to 3 in Table 10, the positive electrode sheet provided in this example satisfies the requirements of-0.01 < (-0.3788 XPD+1.155). Times.ρ/(12 XPT) < 0.0335, and the rate performance of the battery produced therefrom is more excellent. Meanwhile, it is seen from the mutual comparison between examples 1 to 6 that the positive electrode sheet has superior rate performance when it satisfies the requirement of 0 < (-0.3788 ×pd+1.155) ×ρ/(12×bet) < 0.005. In addition, as can be seen from comparison of the rate data of examples 1 to 6 and comparative example 1, the examples of the present invention can effectively improve the rate performance of the battery by adjusting the compacted density of the positive electrode sheet. As can be seen from the comparison of the multiplying power data of examples 1-6 and comparative example 2, the multiplying power performance of the battery can be effectively improved by adjusting the specific surface area of the positive electrode active material of the positive electrode sheet to meet the formula requirement of the positive electrode sheet. Meanwhile, as can be seen from comparison of multiplying power data of examples 1-6 and comparative example 3, the multiplying power performance of the battery can be effectively improved by adjusting the density of the binder of the positive electrode plate to meet the formula requirement of the positive electrode plate.
Experimental example 2
The batteries provided in examples 1to 6 and comparative examples 1to 3 were subjected to power performance test under the conditions that the lithium ion battery was fully charged with a constant current and a constant voltage at 25℃with a 1C current, and after standing for 5min, the 1C was discharged for 48min, and after standing for 5min, 1045W was discharged to 2.5V, and a discharge current was outputted. The test results are shown in Table 11.
TABLE 11 Power test results
| Project | 1045W DC/s |
| Example 1 | 9.4 |
| Example 2 | 10.1 |
| Example 3 | 10.3 |
| Example 4 | 9.0 |
| Example 5 | 10.8 |
| Example 6 | 8.9 |
| Comparative example 1 | 8.2 |
| Comparative example 2 | 6.8 |
| Comparative example 3 | 5.5 |
As can be seen from the comparative data of examples 1 to 6 and comparative examples 1 to 3 in Table 11, the positive electrode sheet provided in this example satisfies the requirements of-0.01 < (-0.3788 XPD+1.155). Times.ρ/(12 XPT) < 0.0335, and the power performance of the battery produced therefrom is more excellent. Meanwhile, it is seen from the mutual comparison between examples 1 to 6 that the positive electrode sheet has superior power performance when it satisfies the requirement of 0 < (-0.3788 ×pd+1.155) ×ρ/(12×bet) < 0.005. In addition, as can be seen from comparison of the power data of examples 1 to 6 and comparative example 1, the examples of the present invention can effectively improve the power performance of the battery by adjusting the compacted density of the positive electrode tab. As can be seen from the comparison of the power data of examples 1-6 and comparative example 2, the specific surface area of the positive electrode active material of the positive electrode sheet is adjusted in the embodiment of the invention, so that the specific surface area meets the formula requirement of the positive electrode sheet, and the power performance of the battery can be effectively improved. Meanwhile, as can be seen from comparison of the power data of examples 1-6 and comparative example 3, the power performance of the battery can be effectively improved by adjusting the binder density of the positive electrode sheet to meet the formula requirement of the positive electrode sheet.
Experimental example 2
The batteries provided in examples 1 to 6 and comparative examples 1 to 3 were subjected to a test for the positive electrode sheet rebound rate under the following test conditions: and measuring the thickness of the rolled cathode pole piece by using a ten-thousandth ruler, standing for two hours, and measuring the thickness of the pole piece, wherein the calculation formula of the rebound rate is the thickness difference of the positive pole piece before and after the rolling and the thickness of the positive pole piece after the rolling. The test results are shown in Table 12.
TABLE 12 thickness rebound test results
| Project | Thickness rebound rate (%) |
| Example 1 | 5.21％ |
| Example 2 | 5.10％ |
| Example 3 | 3.37％ |
| Example 4 | 5.30％ |
| Example 5 | 2.25％ |
| Example 6 | 5.23％ |
| Comparative example 1 | 6.55％ |
| Comparative example 2 | 8.00％ |
| Comparative example 3 | 7.02％ |
As can be seen from the comparative data of examples 1 to 6 and comparative examples 1 to 3 in Table 12, the positive electrode sheet provided in this example satisfies the requirements of-0.01 < (-0.3788 XPD+1.155). Times.ρ/(12 XBET). Times.0.0335, and the prepared battery sheet has a lower rebound rate and a smaller rebound. Meanwhile, it is seen from the mutual comparison between examples 1 to 6 that the positive electrode sheet has a lower rebound rate than when it satisfies the requirement of 0 < (-0.3788 ×pd+1.155) ×ρ/(12×bet) < 0.005. In addition, as can be seen from the comparison of the data of examples 1-6 and comparative example 1, the examples of the present invention can effectively reduce the rebound rate of the positive electrode sheet by adjusting the compacted density of the positive electrode sheet. As can be seen from the comparison of the data of examples 1-6 with the data of comparative examples 2 and 3, the specific surface area of the positive electrode active material of the positive electrode sheet and the density of the binder of the positive electrode sheet are adjusted, so that the specific surface area of the positive electrode active material of the positive electrode sheet meets the formula requirement of the positive electrode sheet, and the rebound rate of the positive electrode sheet can be effectively reduced.
In summary, the positive electrode plate and the battery provided by the embodiment of the invention can improve the rebound problem of the electrode plate on the premise of ensuring the power performance, the multiplying power performance and the cycle performance of the battery by controlling the compaction density; meanwhile, the density of the binder, the specific surface area of the positive electrode active material and the compaction density are cooperatively controlled, so that the rebound of the pole piece is further reduced, and meanwhile, the power performance and the service life of the battery are effectively improved.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A positive electrode sheet, characterized by comprising:
a positive electrode current collector;
A positive electrode membrane disposed on at least one side surface of the positive electrode current collector, the positive electrode membrane including a positive electrode active material, a conductive agent, and a binder;
The positive pole piece satisfies the formula: 0 < (-0.3788 XPD+1.155) ×ρ/(12×BET) < 0.005; PD is the compaction density of the positive electrode plate, and the unit is g/cm 3; ρ is the density of the binder in g/cm 3; BET is the specific surface area of the positive electrode active material, in m 2/g;
The compaction density of the positive pole piece meets 2.5g/cm 3≤PD≤3.5g/cm3;
The density of the binder satisfies 1.70g/cm 3≤ρ≤1.80g/cm3;
The specific surface area of the positive electrode active material satisfies 0.8m 2/g≤BET≤5m2/g.
2. The positive electrode sheet according to claim 1, wherein:
The compaction density of the positive electrode plate meets 2.85g/cm 3≤PD≤3.05g/cm3.
3. The positive electrode sheet according to claim 1, wherein:
the density of the binder satisfies 1.77g/cm 3≤ρ≤1.80g/cm3.
4. The positive electrode sheet according to claim 1, wherein:
The specific surface area of the positive electrode active material satisfies 2.2m 2/g≤BET≤3.6m2/g.
5. The positive electrode sheet according to claim 1, wherein:
The porosity of the positive electrode plate ranges from 20% to 60%.
6. The positive electrode sheet according to claim 5, wherein:
The porosity of the positive electrode plate ranges from 25% to 45%.
7. The positive electrode sheet according to claim 1, wherein:
the positive current collector is selected from any one of aluminum foil, carbon-coated aluminum foil and nickel screen;
And/or the number of the groups of groups,
The positive electrode active material is selected from any one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide and olivine-structured lithium-containing phosphate;
And/or the number of the groups of groups,
The conductive agent is selected from any one of carbon black and carbon nanotubes;
And/or the number of the groups of groups,
The binder is PVDF.
8. The positive electrode sheet according to claim 1, wherein:
The positive electrode diaphragm comprises the following components in percentage by mass (90-97): (1-5): the positive electrode active material, the conductive agent and the binder of (1-5).
9. The positive electrode sheet according to claim 1, wherein:
The positive electrode membrane is arranged on both side surfaces of the positive electrode current collector.
10. A battery comprising the positive electrode sheet according to any one of claims 1 to 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1830104A (en) * | 2003-07-28 | 2006-09-06 | 昭和电工株式会社 | High density electrode and battery using the electrode |
| CN109494349A (en) * | 2018-10-17 | 2019-03-19 | 宁德时代新能源科技股份有限公司 | Negative pole piece and secondary battery |
| CN113086978A (en) * | 2021-03-30 | 2021-07-09 | 宁德新能源科技有限公司 | Negative electrode material, and electrochemical device and electronic device comprising same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1830104A (en) * | 2003-07-28 | 2006-09-06 | 昭和电工株式会社 | High density electrode and battery using the electrode |
| CN109494349A (en) * | 2018-10-17 | 2019-03-19 | 宁德时代新能源科技股份有限公司 | Negative pole piece and secondary battery |
| CN113086978A (en) * | 2021-03-30 | 2021-07-09 | 宁德新能源科技有限公司 | Negative electrode material, and electrochemical device and electronic device comprising same |
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