CN117525282A - Cathode plate of lithium ion battery and preparation method and application thereof - Google Patents
Cathode plate of lithium ion battery and preparation method and application thereof Download PDFInfo
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- CN117525282A CN117525282A CN202311459444.7A CN202311459444A CN117525282A CN 117525282 A CN117525282 A CN 117525282A CN 202311459444 A CN202311459444 A CN 202311459444A CN 117525282 A CN117525282 A CN 117525282A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 92
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 92
- 238000002360 preparation method Methods 0.000 title abstract description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 31
- 238000009792 diffusion process Methods 0.000 claims abstract description 30
- 239000011149 active material Substances 0.000 claims abstract description 28
- 150000001875 compounds Chemical class 0.000 claims abstract description 19
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 229940126062 Compound A Drugs 0.000 claims abstract description 4
- NLDMNSXOCDLTTB-UHFFFAOYSA-N Heterophylliin A Natural products O1C2COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC2C(OC(=O)C=2C=C(O)C(O)=C(O)C=2)C(O)C1OC(=O)C1=CC(O)=C(O)C(O)=C1 NLDMNSXOCDLTTB-UHFFFAOYSA-N 0.000 claims abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 47
- 229910052799 carbon Inorganic materials 0.000 claims description 28
- 239000011230 binding agent Substances 0.000 claims description 21
- 239000006258 conductive agent Substances 0.000 claims description 16
- 239000003792 electrolyte Substances 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 239000011888 foil Substances 0.000 claims description 5
- 229910012851 LiCoO 2 Inorganic materials 0.000 claims description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 claims description 2
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 claims description 2
- 229910014689 LiMnO Inorganic materials 0.000 claims description 2
- 229910002991 LiNi0.5Co0.2Mn0.3O2 Inorganic materials 0.000 claims description 2
- 229910012888 LiNi0.6Co0.1Mn0.3O2 Inorganic materials 0.000 claims description 2
- 229910011328 LiNi0.6Co0.2Mn0.2O2 Inorganic materials 0.000 claims description 2
- 229910015717 LiNi0.85Co0.15Al0.05O2 Inorganic materials 0.000 claims description 2
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 claims description 2
- 229910013290 LiNiO 2 Inorganic materials 0.000 claims description 2
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 claims description 2
- 230000004888 barrier function Effects 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000010410 layer Substances 0.000 description 78
- 239000002344 surface layer Substances 0.000 description 21
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- 238000000034 method Methods 0.000 description 15
- 230000005540 biological transmission Effects 0.000 description 11
- 239000002041 carbon nanotube Substances 0.000 description 11
- 229910021393 carbon nanotube Inorganic materials 0.000 description 11
- 238000005553 drilling Methods 0.000 description 11
- 239000002033 PVDF binder Substances 0.000 description 10
- 239000006257 cathode slurry Substances 0.000 description 10
- 238000009826 distribution Methods 0.000 description 10
- 239000002002 slurry Substances 0.000 description 10
- 239000006230 acetylene black Substances 0.000 description 9
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 9
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 9
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- 229910021389 graphene Inorganic materials 0.000 description 3
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- 239000000463 material Substances 0.000 description 3
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
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- 239000010405 anode material Substances 0.000 description 1
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to the technical field of batteries, in particular to a lithium ion battery cathode plate, a preparation method and application thereof. Comprises a current collector and active material layers arranged on the surfaces of two sides of the current collector; wherein the active material layer comprises a first layer close to the current collector and a second layer far away from the current collector; the composition of the first layer comprises a lithium-containing compound A, and the diffusion coefficient of lithium ions is D1; the component of the second layer comprises a lithium-containing compound B, and the diffusion coefficient of lithium ions is D2; and D2 > D1; in addition, a plurality of grooves are arranged on the active material layer, and the depth of each groove is 5 mu m to the thickness of the pole piece. The cathode plate has better high-temperature cycle performance.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a lithium ion battery cathode plate, a preparation method and application thereof.
Background
The current high temperature cycling (45 ℃) performance of the cell at high rates can be severely degraded, mainly due to loss of positive electrode active material, thickening of the positive electrode electrolyte interface (CEI) film, increased internal resistance, and dissolution of transition metals. This situation is further exacerbated especially with thick electrodes. The contact sites between the positive electrode particles and the carbon binder region are not uniform, so that the local region is blocked, lithium ion transmission is not uniform, and the reaction in the thick positive electrode is not uniform, thereby causing the degradation of the battery. More importantly, when lithium ions are unevenly transmitted and have lithium ion concentration difference, the crystal structure of the positive electrode material is changed, the probability of cracking particles is high, and the high-temperature cycle performance of the lithium ion battery is greatly reduced.
Disclosure of Invention
The present invention aims to solve the technical problems in the prior art described above. Therefore, the invention provides a lithium ion battery cathode plate, and a preparation method and application thereof.
In a first aspect of the present invention, there is provided a cathode sheet for a lithium ion battery, comprising:
a current collector and active material layers provided on both side surfaces of the current collector;
the active material layer comprises a first layer close to the current collector and a second layer far away from the current collector;
the components of the first layer comprise a lithium-containing compound A, and the diffusion coefficient of lithium ions is D1; the components of the second layer comprise a lithium-containing compound B, and the diffusion coefficient of lithium ions is D2; and D2 > D1;
the active material layer is provided with a plurality of grooves, and the depth of each groove is 5 mu m to the thickness of the pole piece.
According to the invention, the lithium-containing compounds in different areas of the active material layer are regulated to have different lithium ion diffusion coefficients, so that the concentration distribution of lithium ions in the bottom layer area and the surface layer area close to and far away from the current collector is regulated, the concentration distribution difference of lithium ions is reduced, the damage of the crystal structure of the lithium-containing compound is avoided, and meanwhile, the cycle performance of the lithium-containing compound under high-temperature cycle is effectively improved. In the prior art, the main reason why different areas of the active material layer have different lithium ion diffusion coefficients is to adjust the lithium ion transmission efficiency so as to perform high-power discharge, but the problem of high-temperature cycle drop is not solved, and the main reason why the high-temperature cycle drop is ignored is that the cathode structure is damaged. The invention creatively improves the high-temperature cycle performance of the lithium ion battery by regulating and controlling the lithium ion diffusion coefficient of the lithium-containing compound near and far from the bottom layer region and the surface layer region of the current collector.
The grooves are arranged in the cathode region, so that the high-temperature cycle performance can be improved, the main reason is that the lithium ion shuttle tortuosity is reduced, the lithium ion shuttle distance is shortened, lithium ions can reach the bottom layer more quickly, and the lithium ion concentration is more uniform; in addition, the lattice distortion of the lithium-containing compound at high temperature is more serious, and the difference of lithium ion concentration of the lithium-containing compound at the bottom layer and the surface layer can be reduced by arranging the grooves, so that the lattice distortion is reduced. The depth of the cathode groove has positive correlation with the concentration distribution of lithium ions, the depth of the groove is limited to be 5 mu m to the thickness of the pole piece, and the lithium ion battery prepared from the cathode pole piece has better high-temperature cycle performance in the range.
The invention combines the two points of 'arranging grooves' and 'having different lithium ion diffusion coefficients of different active material layers', and can cooperatively improve the high-temperature cycle performance of the lithium ion battery.
In some embodiments of the invention, the first layer has a thickness of 10 to 100 μm and/or the second layer has a thickness of 5 to 100 μm.
In some preferred embodiments of the invention, the first layer has a thickness of 10 to 50 μm and/or the second layer has a thickness of 5 to 50 μm.
In some more preferred embodiments of the invention, the first layer has a thickness of 15 to 30 μm and/or the second layer has a thickness of 5 to 15 μm.
In some embodiments of the invention, the D2 is > 1×10 -11 cm 2 S, D1 is less than or equal to 1 multiplied by 10 -11 cm 2 /s。
In some preferred embodiments of the invention, the D2 is > 4X 10 -11 cm 2 /s, getD1 is less than or equal to 4 multiplied by 10 - 12 cm 2 /s。
In some embodiments of the invention, the spacing between adjacent grooves is 0.1-30 mm; preferably 1 to 4mm.
In some embodiments of the invention, the pole piece thickness is a pole piece single-sided thickness, the pole piece single-sided thickness being 10-200 μm.
Preferably, when the thickness of one side of the pole piece is more than or equal to 40 mu m, the depth of the groove is 20 mu m; and when the thickness of one side of the pole piece is less than 40 mu m, the depth of the groove is half of the thickness of one side of the pole piece.
In some embodiments of the present invention, the content of the lithium-containing compound in the first layer is 90% to 99% by weight.
In some embodiments of the present invention, the content of the lithium-containing compound in the second layer is 90% to 99% by weight.
In some embodiments of the invention, the composition of the active material layer further comprises a conductive agent.
In some embodiments of the invention, the conductive agent is selected from at least one of carbon nanotubes, acetylene black, graphene, and graphite alkyne.
In some embodiments of the invention, the content of the conductive agent in the second layer is greater than the content of the conductive agent in the first layer; further, the content of the conductive agent in the second layer is 1.1 to 2.0 times that in the first layer.
In some embodiments of the present invention, the content of the conductive agent in the first layer is 0.3% to 0.6% by weight.
In some embodiments of the invention, the composition of the active material layer further comprises conductive carbon.
In some embodiments of the invention, the conductive carbon is selected from at least one of carbon nanotubes, graphene;
preferably, the carbon nanotubes are single-walled carbon nanotubes;
preferably, the number of layers of the graphene is less than 20.
In some embodiments of the invention, the content of conductive carbon in the second layer is greater than the content of conductive carbon in the first layer; further, the content of the conductive carbon in the second layer is 1.1 to 2.0 times that in the first layer.
In some embodiments of the invention, the conductive carbon content of the first layer is 0.4% to 0.8% by weight.
In some embodiments of the invention, the composition of the active material layer further comprises a binder.
In some embodiments of the present invention, the binder is selected from at least one of PVA (polyvinyl alcohol), PTFE (polytetrafluoroethylene), CMC (carboxymethyl cellulose), PVDF (polyvinylidene fluoride), SBR (styrene butadiene rubber), polyurethane.
In some embodiments of the invention, the binder content in the second layer is greater than the binder content in the first layer; further, the content of the binder in the second layer is 1.1 to 2.0 times that in the first layer.
In some embodiments of the invention, the binder content in the first layer is 0.8% to 1.6% by weight.
In the invention, the conductive agent, the conductive carbon and the binder belong to a carbon binder region, the region blockage caused by unbalance of the carbon binder region can further aggravate the non-uniformity of lithium ion distribution, the concentration of the surface layer lithium ions far away from one end of the current collector is high, the concentration of the bottom layer lithium ions near one end of the aluminum foil current collector is low, and the concentration difference between the surface layer lithium ions and the bottom layer lithium ions is 5-60 percent according to different blockage conditions. The invention sets the difference of the contents of conductive carbon, conductive agent and binder in different areas, and the carbon content of the surface layer is higher than that of the bottom layer. The method is favorable for improving the electron transmission performance, ensures the structural stability of the surface layer lithium-containing compound at high temperature, ensures the mutual communication of carbon bonding areas, and prevents the cathode pulverization caused by electron blockage. The technology is further matched with the arrangement of grooves and the adjustment of different diffusion coefficients of lithium ions to ensure smooth ion and electron transmission of the surface layer and the bottom layer.
In the invention, the content of the conductive agent, the conductive carbon and the binder in the surface layer is 1.1-2 times that in the bottom layer, and if the content exceeds 2 times, the energy density of the battery cell is lost; if the amount is less than 1.1 times, the effect of improving the high-temperature cycle performance of the lithium ion battery cannot be achieved.
In some embodiments of the invention, the lithium-containing compound is selected from LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiMnPO 4 、LiFePO 4 、LiNi 1/3 Co 1/3 Mn 1/3 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.1 Mn 0.3 O 2 、LiNi 0.85 Co 0.15 Al 0.05 O 2 At least one of them.
In some embodiments of the invention, the current collector is selected from at least one of aluminum foil, carbon paper, aluminum-based current collectors.
According to a second aspect of the invention, a preparation method of the lithium ion battery cathode plate is provided, and the preparation method comprises the step of arranging active material layers comprising the grooves on two sides of the current collector.
In some embodiments of the present invention, the preparation method specifically includes the steps of:
preparing a first slurry comprising a lithium-containing compound A and a second slurry comprising a lithium-containing compound B, coating the first slurry on both side surfaces of a current collector, coating the second slurry on the surface of the formed coating, and providing a coating with grooves.
In the present invention, the grooves may be formed by methods commonly used in the art, including but not limited to: the reserving mode of the groove comprises the steps of coating a sacrificial layer or directly not coating; the groove arrangement mode comprises laser drilling, electric spark drilling, a rolling grinding tool processing technology with pinholes, mechanical drilling or erasing.
The third aspect of the invention provides a lithium ion battery, which comprises a cathode pole piece, an anode pole piece, electrolyte and an isolating film which is arranged between the cathode pole piece and the anode pole piece, wherein the cathode pole piece is the cathode pole piece of the lithium ion battery.
The separator of the present invention may be selected from separators known to those skilled in the art, including but not limited to: polyethylene, polypropylene, polyvinylidene fluoride, and their multilayer composite films.
The electrolyte in the present invention includes an electrolyte salt and an organic solvent, wherein the specific types and compositions of the electrolyte salt and the organic solvent are not particularly limited, and the electrolyte salt and the organic solvent contain a positive electrode film-forming additive, a negative electrode film-forming additive, a cycle-improving additive, and the like.
The beneficial effects are that:
according to the invention, the lithium-containing compounds with different lithium ion diffusion coefficients are used for layered coating, the lithium ion diffusion coefficient of the surface layer lithium-containing compound is higher than that of the bottom layer, and the relative uniformity of the lithium ion concentration of the surface layer and the bottom layer can be ensured. The grooves reduce the tortuosity of lithium ion transmission, accelerate the lithium ion transmission and further ensure the uniformity of the surface layer and the bottom layer lithium ions.
In addition, the invention can further solve the contact problem of the carbon bonding area by improving the content of conductive carbon, conductive agent and binder in the surface layer, ensure the smooth electron transmission of the carbon bonding area, avoid channel blockage, avoid uneven ion transmission and ensure the smooth electron transmission.
The scheme of the invention can be used for solving the problem of high-temperature cycle attenuation of the lithium battery.
Drawings
The invention is further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic diagram of the cathode plate structure of the lithium ion battery (taking lithium cobaltate as an example) of the invention.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
The description as it relates to "first", "second", etc. in the present invention is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values for the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
In the description of the present invention, the terms "comprises" and "comprising," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
In order to improve the cycle performance of the lithium ion battery under high-temperature cycle, the invention starts from improving the uniformity of lithium ions and the smoothness of electron transmission in a carbon bonding area, and provides a cathode plate of the lithium ion battery.
Referring to fig. 1, the cathode sheet of the lithium ion battery of the present invention includes a current collector and active material layers disposed on both side surfaces of the current collector; the active material layer is provided with two layers, including a first layer (i.e., the bottom layer in fig. 1) close to the current collector and a second layer (i.e., the surface layer in fig. 1) far from the current collector; the lithium ion diffusion coefficient of the lithium-containing compound in the second layer is greater than the lithium ion diffusion coefficient of the lithium-containing compound in the first layer; the active material layer is provided with a plurality of grooves through a laser drilling process.
The electrochemical pseudo two-dimensional (P2D) model of the lithium ion battery is built based on the porous electrode theory and the concentrated solution theory. The actual chemical reaction process inside the battery is considered, including a solid phase diffusion process, a liquid phase diffusion process, a migration process, a charge transfer process and a solid-liquid phase potential balancing process. The electrochemical reaction and the surface intercalation and deintercalation lithium process on each electrode are described by using the Butler-Volmer equation, and the diffusion process of lithium ions inside the particles is described by using Fick's second diffusion law. The partial differential equations describing the reaction process and the corresponding boundary condition form a model, so that the charge-discharge curve of the external characteristics of the reaction battery can be obtained in a short calculation time, and meanwhile, the detailed problems of solid-phase concentration distribution and solid-phase potential distribution of anode and cathode materials, liquid-phase concentration distribution and solid-phase potential distribution of electrolyte and the like in the internal reaction process can be obtained.
The invention is found by the above calculation simulation concentration difference: when serious ion blockage occurs, the ion concentration difference between the surface layer and the bottom layer can be 50-80%, the double-layer coating can be reduced to 20-50%, the design of the upper and lower carbon materials can be reduced to 20-40%, and finally the laser drilling process can be matched to reduce the ion concentration difference to 5-15%. The three technical means contributed to the reduction of the lithium ion concentration difference by about 15%, about 10% and about 20%, respectively.
In addition, the mass loss is measured by directly adopting a pole piece comparison weighing method before and after punching. The specific measurement method comprises the following steps: the mass M0 of the copper foil with the length of 10cm multiplied by 10cm, the mass M1 of the pole piece with the material and the mass M2 after laser drilling are respectively weighed. The loss rate of the active material= (M1-M2)/(M1-M0) ×100%, and the loss of the active material was measured to be 0.05% to 20%.
Examples
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.
Example 1
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
lithium cobaltate A1 (lithium ion diffusion coefficient 5×10) -11 cm 2 S), carbon nanotubes, acetylene black, PVDF in a weight ratio of 97.9:0.5:0.4:1.2 mixing, adding NMP solvent, and stirring to prepare cathode slurry.
And uniformly coating the cathode slurry on two sides of an aluminum foil, and drying and compacting to obtain a cathode plate A1. The thickness of one side of the pole piece is controlled to be 50 mu m.
Example 2
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
97.9% lithium cobalt oxide B1 (lithium ion diffusion coefficient 3X 10) -12 cm 2 S), 0.5% of carbon nano tube, 0.4% of acetylene black and 1.2% of PVDF, adding NMP and stirring to prepare cathode slurry B1;
and uniformly coating the cathode slurry on two sides of the aluminum foil, and drying and compacting to obtain a cathode plate which is denoted as B1. The thickness of one side of the control pole piece is (30 μm).
Example 3
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
97.3% of lithium cobalt oxide A1 (lithium ion diffusion coefficient 5X 10) -11 cm 2 S), 0.7% of carbon nano tube, 0.5% of acetylene black and 1.5% of PVDF are mixed, NMP is added, and the mixture is stirred to prepare cathode slurry A2;
97.9% lithium cobalt oxide B1 (lithium ion diffusion coefficient 3X 10) -12 cm 2 S), 0.5% of carbon nano tube, 0.4% of acetylene black and 1.2% of PVDF, adding NMP and stirring to prepare cathode slurry B1;
the slurry A2 is used as a surface layer coating, the slurry B1 is used as a bottom layer coating, the pole pieces A2-B1 are prepared through double-layer coating, the mass ratio of the surface layer to the bottom layer slurry is 3:7, the surface layer thickness is (11 mu m), and the bottom layer thickness is (19 mu m).
Example 4
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
97.0% lithium cobaltate A1 (lithium ion diffusion coefficient 5X 10) -11 cm 2 S), 0.7% of carbon nano tube, 0.7% of acetylene black and 1.6% of PVDF, adding NMP and stirring to prepare cathode slurry A3;
97.9% lithium cobalt oxide B1 (lithium ion diffusion coefficient 3X 10) -12 cm 2 S), 0.5% of carbon nano tube, 0.4% of acetylene black and 1.2% of PVDF, adding NMP and stirring to prepare cathode slurry B1;
the slurry A3 was used as a top layer coating material, B1 was used as a primer coating material, A3-B1 was formed by double coating, the ratio of the top layer to the primer was 3:7, the thickness of the top layer was 9. Mu.m, and the thickness of the primer was 11. Mu.m.
Example 5
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
reference example 1 was made, with the difference that: after being prepared into an A1 cathode pole piece, the A1 cathode pole piece is subjected to laser drilling to obtain a perforated cathode pole piece A1-C1.
The specific steps of laser drilling are as follows: performing a laser cleaning process on the cathode plate after slitting to obtain a laser-perforated electrode plate; the perforation depth was set to 12 μm and the perforation slot pitch was set to 2mm by adjusting to 70 KW.
Example 6
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
reference example 4 was made, with the difference that: in example 6, the A3-B1 pole piece was laser drilled to form an A3-B1-C2 pole piece.
The specific steps of laser drilling are as follows: performing a laser cleaning process on the cathode plate after slitting to obtain a laser-perforated electrode plate; the perforation depth was set to 12 μm and the perforation slot pitch was set to 2mm by adjusting to 70 KW.
Example 7
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
97.9% lithium cobaltate A1 (lithium ion diffusion coefficient 5X 10) -11 cm 2 S), 0.5% of carbon nano tube, 0.4% of acetylene black and 1.2% of PVDF, adding NMP and stirring to prepare cathode slurry A1;
97.0% lithium cobaltate A1 (lithium ion diffusion coefficient 5X 10) -11 cm 2 S), 0.7% of carbon nano tube, 0.7% of acetylene black and 1.6% of PVDF, adding NMP and stirring to prepare cathode slurry A3;
a1 is used as bottom layer slurry, A3 is used as surface layer slurry, A3:A1=3:7, the pole piece A3-A1 is formed, the thickness of the surface layer is 9 mu m, and the thickness of the bottom layer is 11 mu m.
Example 8
The embodiment provides a lithium ion battery cathode plate, which is prepared by the following steps:
reference example 6 was made, with the difference that: and setting the punching depth to be 3 mu m only to obtain the cathode pole piece A3-B1-C3 pole piece.
Application example
And the manufactured composite negative plate and the corresponding positive plate are manufactured into a battery finished product through the following procedures of rolling, slitting, laser cleaning, tab welding, winding, packaging, baking, liquid injection, formation, degassing, secondary sealing and the like.
And (3) rolling: placing the pole piece in two rollers rotating in opposite directions to enable the pole piece to be compressed and deformed, and obtaining the designed thickness of the pole piece;
splitting: cutting the coated large pole piece into a designed width size by a slitting machine;
laser cleaning: carrying out laser cleaning on the corresponding area of the pole piece to clean the tab slot;
welding the electrode lugs: performing laser welding on positive and negative electrode lugs in a groove cleaning area;
winding: combining the cathode and anode plates and the diaphragm into a bare cell;
and (3) packaging: the bare cell is placed in an aluminum plastic film, and top side sealing is carried out;
baking: placing the top-side sealed battery cell into an oven at 80 ℃ for baking, and controlling the moisture content;
and (3) liquid injection: pumping out air after electrolyte is injected into the battery cell and completing sealing;
and (3) formation: charging the battery for the first time to form a stable SEI film;
degassing: an air knife is used for puncturing the air bag, and waste gas generated by formation is discharged;
and (2) sealing: and (3) pumping the electrolyte, and reserving proper electrolyte to prevent the battery cell from expanding.
Test case
And (3) carrying out 45 ℃ cycle test on the finished battery cell for 500 weeks, wherein the test method comprises the following steps: 3.6C CC to 4.27V,2.8C CC to 4.35V,CV to 1.8C,1.8C CC to 4.4V,CV to 1.5C,1.5C CC to 4.5V,CV to 1.2C,1.2C CC to 4.55V,CV to XXC; discharge system: 0.7CDCto 3.0V.
The results are shown in Table 1.
Table 1 results of cell experiments for different cathode sheets
And comparing and analyzing the pole pieces A1 and B1, wherein the pole piece A1 has a rapid lithium ion diffusion coefficient, and has better high-temperature cycle performance and smaller swealling.
The groups A2-B1 and A3-B1 coated by the cathode double layer have better high-temperature cycle performance than the groups A1 and B1 coated by the single layer, because the diffusion coefficients of the upper layer and the lower layer are different in the double layer coating, so that lithium ions are distributed more uniformly, and lithium cobalt oxide crystals are not damaged.
The conductive carbon, the conductive agent and the binder are relatively more, so that the carbon-binder area is more complete, the conductive network is smoother, and the normal transmission of electrons is ensured.
In the embodiment 5, the pole pieces A1-C1 are improved in high-temperature cycle performance after being perforated, the effect is better than that of the double layers A3-B1, and the surface laser perforation improvement effect is most obvious. The cathode punching can solve the problem that lattice distortion of lithium cobalt oxide occurs due to overhigh local lithium ion concentration of the lithium cobalt oxide.
In the embodiment 6, when the pole piece is combined by three technical elements, the A3-B1-C2 pole piece is formed, and the improvement effect is optimal.
Example 7 shows that the strategy of increasing the carbon material content alone gives the worst improvement.
As is evident from a comparison of example 6 and example 8, the improvement effect is limited when the laser drilling depth is less than 5. Mu.m.
Therefore, for the improvement of the concentration distribution of lithium ions, laser drilling, double-layer lithium cobaltate with different lithium ion diffusion coefficients and carbon content distribution can be adopted independently or two technical elements can be selected for matching or three technical elements can be combined for use, so that the high-temperature cycle performance of the lithium ion battery can be improved to a certain extent; wherein, the combination of the three technical elements can improve the high-temperature cycle performance to the greatest extent.
In general, the invention starts from the improved principle that the lattice damage is caused by too much intercalation or deintercalation of lithium ions into or from the surface lithium cobalt oxide lattice by reducing the concentration difference between the surface layer and the bottom layer of the pole piece, and the lithium cobalt oxide lattice has small change, stable structure and stable performance.
While the embodiments of the present invention have been described in detail with reference to the drawings, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of one of ordinary skill in the art. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Claims (10)
1. A lithium ion battery cathode pole piece, comprising:
a current collector and active material layers provided on both side surfaces of the current collector;
the active material layer comprises a first layer close to the current collector and a second layer far away from the current collector;
the components of the first layer comprise a lithium-containing compound A, and the diffusion coefficient of lithium ions is D1; the components of the second layer comprise a lithium-containing compound B, and the diffusion coefficient of lithium ions is D2; and D2 > D1;
the active material layer is provided with a plurality of grooves, and the depth of each groove is 5 mu m to the thickness of the pole piece.
2. The lithium-ion battery cathode pole piece of claim 1, wherein D2 > 1 x 10 -11 cm 2 S, D1 is less than or equal to 1 multiplied by 10 -11 cm 2 /s。
3. The lithium ion battery cathode pole piece of claim 1, wherein the spacing between adjacent grooves is 0.1-30 mm.
4. The lithium ion battery cathode pole piece of claim 1, wherein the pole piece thickness is 10-200 μm.
5. The lithium ion battery cathode sheet according to claim 1, wherein the composition of the active material layer further comprises a conductive agent, the content of the conductive agent in the second layer being greater than the content of the conductive agent in the first layer; and/or the number of the groups of groups,
the composition of the active material layer further comprises conductive carbon, and the content of the conductive carbon in the second layer is greater than that of the conductive carbon in the first layer; and/or the number of the groups of groups,
the composition of the active material layer further includes a binder, and the content of the binder in the second layer is greater than the content of the binder in the first layer.
6. The lithium ion battery cathode sheet according to claim 5, wherein if the composition of the active material layer further includes a conductive agent, the content of the conductive agent in the second layer is 1.1 to 2.0 times that in the first layer; and/or the number of the groups of groups,
if the composition of the active material layer further includes conductive carbon, the content of the conductive carbon in the second layer is 1.1 to 2.0 times that of the conductive carbon in the first layer; and/or the number of the groups of groups,
if the composition of the active material layer further includes a binder, the content of the binder in the second layer is 1.1 to 2.0 times the content of the binder in the first layer.
7. The lithium ion battery cathode pole piece of claim 1, wherein the lithium-containing compound is selected from the group consisting of LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiMnPO 4 、LiFePO 4 、LiNi 1/3 Co 1/3 Mn 1/3 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.1 Mn 0.3 O 2 、LiNi 0.85 Co 0.15 Al 0.05 O 2 At least one of them.
8. The lithium ion battery cathode pole piece of claim 1, wherein the current collector is selected from at least one of aluminum foil, carbon paper, aluminum-based current collector.
9. A method of manufacturing a lithium ion battery cathode sheet according to any one of claims 1 to 8, comprising providing active material layers comprising the grooves on both sides of the current collector.
10. The utility model provides a lithium ion battery, includes negative pole piece, positive pole piece, electrolyte and separates the barrier film between positive and negative pole piece, its characterized in that: the cathode sheet is a lithium ion battery cathode sheet according to any one of claims 1 to 8.
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