CN110504409B - Positive plate capable of improving permeability and lithium ion battery - Google Patents
Positive plate capable of improving permeability and lithium ion battery Download PDFInfo
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- CN110504409B CN110504409B CN201910753416.3A CN201910753416A CN110504409B CN 110504409 B CN110504409 B CN 110504409B CN 201910753416 A CN201910753416 A CN 201910753416A CN 110504409 B CN110504409 B CN 110504409B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/043—Processes of manufacture in general involving compressing or compaction
- H01M4/0435—Rolling or calendering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a positive plate for improving permeability, which comprises a current collector, wherein n active material layers with the same thickness are arranged on two sides of the current collector; wherein n is more than or equal to 1 and less than or equal to 10; the contact angle of the surface of the current collector is theta 0 ，0.50≤COS(θ 0 ) Less than 0.99, and the contact angle of the surface of the active layer is theta n ，θ n ≤30°，θ n Is the contact angle of the surface of the nth active layer; when COS (theta) is more than or equal to 0.50 0 ) At < 0.94, theta 1 ＝θ 0 If n is greater than or equal to 2, theta n ＝θ 1 *0.9 n+1 When COS (theta) is more than or equal to 0.94 0 ) At < 0.99, theta 1 ＝θ 0 If n is not less than 2, theta n ＝θ 1 *0.9 n+1 . The positive plate with the improved permeability has good pole piece wettability, the standing time of a battery cell after the battery is injected with liquid is shortened, the infiltration rate of electrolyte on the positive plate with the improved permeability is improved, the production efficiency and the yield are improved, the interface state of the prepared battery electrode is more uniform, and the interface current density is more uniform in the charging and discharging process.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a positive plate capable of improving permeability and a lithium ion battery.
Background
In recent years, new energy automobiles and 3C consumer products are popularized on a larger scale, and requirements on the performance aspects of high energy density, high-rate charge and discharge, long service life, high safety and the like of lithium ion batteries are higher and higher. The market of power lithium ion batteries has demands for batteries with high energy density, high multiplying power and long service life, and the multiplying power performance, safety and long cycle life of the batteries are considered while the energy density of the batteries is improved, the uniformity of electrolyte distribution in a battery core, particularly the compaction density of a positive plate for improving the permeability is high, the porosity is low, the infiltration rate of the electrolyte is low, the production efficiency of the batteries is limited, even the defects of lithium metal precipitation, poor dynamic performance and the like caused by poor infiltration of the electrolyte can occur, and meanwhile, byproducts can be generated on the surface of a negative electrode to influence the cycle life and safety of the batteries. Therefore, the key to obtain the balance between the high energy density and the high-rate charge-discharge technology and improve the product quality lies in the structural design of the pole piece.
Generally, the actual construction condition of the cell product is that the positive electrode active material layer has high compaction density and low porosity (20-35%), the electrolyte infiltration rate is much slower than that of the negative electrode and the diaphragm, and the liquid absorption rate of the whole cell is determined by the speed. Therefore, the infiltration rate of the electrolyte to the anode is improved to a certain degree, the production efficiency and the yield can be improved, the uniformity of an electrode interface, the dynamic performance, the cycle life and the like of the battery are improved, and the consistency and the yield of the battery product are improved. Generally, the improvement of the energy density of the battery core and the improvement of the charge-discharge rate are a pair of contradictions in the performance of the battery product, and how to balance the relationship among the dynamic performance, the energy density and the cycle life of the battery has been a research hotspot in the industry.
Disclosure of Invention
In view of this, the present invention is directed to provide a positive plate with improved permeability and a lithium ion battery, where the positive plate with improved permeability has the characteristics of good dynamic performance, high energy density, and long cycle life.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
the positive plate comprises a current collector, wherein n active material layers with the same thickness are arranged on two sides of the current collector; wherein n is more than or equal to 2 and less than or equal to 10;
the contact angle between the surface of the current collector and the electrolyte is theta 0 ，0.50≤COS(θ 0 ) Less than 0.99, and the contact angle between the surface of the active material layer and the electrolyte is theta n and theta n ≤30°；
When COS (theta) is more than or equal to 0.50 0 ) At < 0.94, theta 1 ＝θ 0 /2，θ n ＝θ 1 *0.9 n+1 When COS (theta) is more than or equal to 0.94 0 ) At < 0.99, theta 1 ＝θ 0 ，θ n ＝θ 1 *0.9 n+1 。
Furthermore, the active layer is made of a positive electrode main material, a conductive agent and a surfactant,
wherein:
X n ＝A n *D n ，
D n is the weight part of the conductive agent in the nth active layer,
A n is the specific surface area of the conductive agent in the n-th active layer,
W n the amount of the surfactant added in the nth active layer.
Further, the specific surface area A of the conductive agent n ＝20-200m 2 (iv) g; preferably, the specific surface area A of the conductive agent n ＝50-150m 2 /g。
Further, the conductive agent is at least one of SP carbon black, ketjen black, VGCF, a single-walled carbon nanotube, a multi-walled carbon nanotube or graphene; the surfactant is at least one of polyether modified siloxane, macromolecular polyether modified acrylate and organic silicon modified polyacrylate; the positive electrode main material is at least one of NCA, NCM523, NCM622, NCM811 or LFP.
Further, the addition amounts of the positive electrode main material, the conductive agent and the surfactant are 100: (1-3): (0.1-1).
The active layer further comprises a binder. The addition ratio of the main material of the positive electrode, the conductive agent, the surfactant and the binder is 100: (1-3): (0.1-1): (3-4).
Furthermore, n active layers with the same thickness are arranged on two sides of the current collector, and n is more than or equal to 2 and less than or equal to 5; the contact angle of the surface of the current collector is theta 0 ，0.70≤COS(θ 0 )＜0.99。
Further, the sum of the thicknesses of the active layers is t n ，t n =20-50 μm; the porosity of the active layers is the same.
Further, the current collector is a light foil; the surface of the optical foil is coated with a conductive material layer; the conductive material layer is one of carbon material or metal particles.
The preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating n layers, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate for improving permeability.
The preparation method of the lithium ion battery comprises the following steps: and punching, laminating, welding, assembling and injecting, pre-charging, forming, degass, aging and the like on the positive plate, the negative plate, the diaphragm and the electrolyte which are used for improving the permeability to obtain the battery core.
Compared with the prior art, the positive plate and the lithium ion battery with the improved permeability have the following advantages:
(1) According to the positive plate for improving the permeability, the contact angle between the positive active material layer and the current collector and the electrolyte is set, so that the positive plate for improving the permeability obtains good wettability, the standing time of the battery cell after the battery is injected with liquid is shortened, the wetting rate of the electrolyte on the positive plate for improving the permeability is improved, the production efficiency and the yield are improved, the electrode interface state of the prepared battery is more uniform, the interface current density in the charging and discharging process is more uniform, the consistency of the battery cell product is better, the cycle life is long, and the rate capability and the dynamic performance are excellent.
(2) The active material layer of the positive plate for improving the permeability is composed of a plurality of layers of mechanisms, the contact angle of the active material layer is sequentially reduced from inside to outside, the layers have gradient distribution of surface energy, and the adjacent interfaces have step adsorption power on the adsorption of electrolyte, so that the absorption rate of a positive material on the electrolyte is improved, the flow of the electrolyte in the transverse direction close to the interface is promoted, and the liquid absorption rate of the positive plate for improving the permeability is improved. The efficiency and yield of the battery cell liquid injection process are improved, the uniformity among the interfaces of the electrodes is better, the consistency of the battery cell products is improved, and the dynamic performance, the cycle performance and the like are obviously improved.
(3) The positive plate with the improved permeability can better balance the charge-discharge characteristics with large multiplying power in a high-energy-density battery cell product, does not have the interface degradation phenomena such as lithium precipitation and the like caused by poor infiltration of electrolyte, and effectively reduces the polarization phenomenon of the plate.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are all conventional methods unless otherwise specified.
The present invention will be described in detail with reference to examples.
Example 1
The positive plate for improving the permeability comprises a current collector, wherein 2 active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =13 °, contact angle θ of active layer surface 1 ＝13.0°，θ 2 ＝10.5°。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode is mainly made of lithium iron phosphate, the conductive agent is sp, the surfactant is polyether modified siloxane, the binder is PVDF, and according to the formula, the adding proportion of the No. 1 active material layer is 100:3:0.1:4, the addition ratio of the 2 nd active material layer is 100:3:0.2:4.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating n layers, and rolling and baking to obtain the positive electrode plate with improved permeability.
A lithium ion battery comprises the positive plate for improving permeability.
Example 2
The positive plate for improving the permeability comprises a current collector, wherein 3 active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =40 °, contact angle θ of active layer surface 1 ＝20.0°，θ 2 ＝16.2,°，θ 3 ＝14.6。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode comprises a main material NCM523, a conductive agent sp and CNT, a surfactant polyether modified siloxane and a binder PVDF, wherein according to the formula, the addition proportion of the No. 1 active material layer is 100:2:1:0.2:3.5, the addition ratio of the 2 nd active material layer is 100:2.0:1.0:0.4:4, the adding ratio of the No. 3 active material layer is 100:2.5:0.5:0.6:4.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating 3 layers of the positive electrode slurry, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate for improving permeability.
Example 3
The positive plate for improving the permeability comprises a collectorThe two sides of the current collector are provided with 2 active material layers with the same thickness; the contact angle of the surface of the current collector is theta 0 =18 °, contact angle θ of active layer surface 1 ＝18.0°，θ 2 ＝14.6°。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode comprises a main material NCM523, a conductive agent sp and CNT, a surfactant organosilicon modified polyacrylate and a binder PVDF, wherein according to the formula, the addition proportion of the No. 1 active material layer is 100:2:1:0.1:3.5, the adding proportion of the 2 nd active material layer is 100:2.0:2.0:0.4:3.5.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating 2 layers of the positive electrode slurry, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate for improving permeability.
Example 4
The positive plate for improving the permeability comprises a current collector, wherein 3 active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =32 °, contact angle θ of active layer surface 1 ＝16.0°，θ 2 ＝13.0°，θ 3 ＝11.6。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode is prepared from NCM622 as a main material, sp and VGCF as conductive agents, organic silicon modified polyacrylate as a surfactant, PVDF as a binder, and a 1 st active material layer in a proportion of 100:2:1:0.5:3.5, the addition ratio of the 2 nd active material layer is 100:1.5:1.5:0.7:3.5, the adding ratio of the 3 rd active material layer is 100:2:1:0.9:3.5.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating 3 layers of the positive electrode slurry, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate for improving the permeability.
Example 5
The positive plate for improving the permeability comprises a current collector, wherein 4 active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =40 °, contact angle θ of active layer surface 1 ＝20.0°，θ 2 ＝16.2°，θ 3 ＝14.6，θ 4 ＝13.1。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode is prepared from NCM622 as a main material, sp and CNT as conductive agents, polyether modified polyacrylate as a surfactant, PVDF as a binder, and a 1 st active material layer in a proportion of 100:2:1:0.8:3.5, the addition ratio of the 2 nd active material layer is 100:2.0:1.0:0.3:3.5, the addition ratio of the 3 rd active material layer is 100:2.5:0.5:0.5:3.5, the addition ratio of the 4 th active material layer is 100:2.7:0.3:0.7:3.5.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating 4 layers of the positive electrode slurry, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate for improving permeability.
Example 6
The positive plate for improving the permeability comprises a current collector, wherein 5 active layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =56 °, contact angle θ of active layer surface 1 ＝28.0°，θ 2 ＝22.7°，θ 3 ＝20.4，θ 4 ＝18.4，θ 5 ＝16.5。
The active layer consists of a positive electrode main material, a conductive agent and a surfactant,
the positive electrode is mainly composed of NCM622, the conductive agents are sp, VGCF and CNT, the surfactant is polyether modified polyacrylate, the binder is PVDF, the adding proportion of the No. 1 active material layer is 100:2:0.5:0.5:1.0:3.5, the addition ratio of the 2 nd active material layer is 100:1.0:0.3:1.7:0.4:3.5, the adding ratio of the 3 rd active material layer is 100:1.0:0.5:1.5:0.6:3.5, the addition ratio of the 4 th active material layer is 100:1.5:0.5:1.0:0.8:3.5, the adding ratio of the 5 th active material layer is 100:2.0:0.5:0.5:1.0:3.5.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating 5 layers, and rolling and baking to obtain the positive electrode plate with improved permeability.
A lithium ion battery comprises the positive plate for improving the permeability.
Comparative example 1
The positive plate comprises a current collector, wherein active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =32 °, contact angle θ of active layer surface 1 ＝32.0°。
The active layer is composed of a positive main material, a conductive agent and a surfactant, wherein the positive main material is lithium iron phosphate, the conductive agent is sp, the binder is PVDF, and the addition ratio of the PVDF is 100:3:4.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, and rolling and baking to obtain the positive electrode plate with improved permeability.
A lithium ion battery comprises the positive plate.
Comparative example 2
The positive plate comprises a current collector, wherein active material layers with the same thickness are arranged on two sides of the current collector; the contact angle of the surface of the current collector is theta 0 =40 °, contact angle θ of active layer surface 1 ＝40°。
The active layer is composed of a positive electrode main material, a conductive agent and a surfactant, the positive electrode main material is NCM523, the conductive agent is sp and CNT, the binder is PVDF, and the addition ratio of the active layer to the positive electrode main material is 100:2:1:3.5.
the preparation method of the positive plate for improving the permeability comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, and rolling and baking to obtain the positive electrode plate with the improved permeability.
A lithium ion battery comprises the positive plate.
The positive plate with improved permeability and the lithium ion battery obtained in examples 1 to 5 and comparative examples 1 to 2 were tested by the following method:
(1) And (3) testing the interface performance of the electrode: at room temperature, the lithium ion batteries prepared in examples 1-5 and comparative examples 1-2 were fully charged at 4C and fully discharged at 1C, and then fully charged at 4C, and then the negative electrode piece was disassembled and the lithium deposition on the surface of the negative electrode piece was observed. Wherein, the lithium precipitation area of the surface of the negative electrode of less than 5 percent is considered to be slightly lithium precipitation, the lithium precipitation area of the surface of the negative electrode of 5 percent to 30 percent is considered to be moderately lithium precipitation, and the lithium precipitation area of the surface of the negative electrode of more than 30 percent is considered to be severely lithium precipitation.
(2) And (3) testing cycle performance: the lithium ion batteries prepared in examples 1-5 and comparative examples 1-2 were charged at 3C rate and discharged at 1C rate at room temperature, and full charge discharge cycle tests were performed until the capacity of the lithium ion battery was less than 80% of the initial capacity, and the number of cycles was recorded.
(3) Testing the pole piece infiltration performance: at room temperature, 5 μ L of electrolyte was dropped on the surface of each of the negative electrode sheets of the lithium ion batteries prepared in examples 1 to 5 and comparative examples 1 to 2, and the time required for the electrolyte droplets to completely disappear was recorded.
(4) Storage performance: the fully charged cell was stored in an environment of 55 ℃ for 7 days, and the capacity change before and after storage was tested, with the capacity retention after storage = (capacity after storage/capacity before storage) × 100%.
The results are reported in Table 1.
TABLE 1 test results of examples 1-6 and comparative examples 1-2
The embodiment 1-6 changes the contact angle of the gradient distribution of each active material layer to generate the step difference of the surface energy between each layer of the positive electrode, so that the infiltration rate of the electrolyte is accelerated, and the comparison with the comparative example 1-2 shows that the imbibition time of the positive electrode plate with the improved infiltration capacity of the embodiment is obviously shortened, the infiltration rate of the electrolyte to the electrode plate is effectively improved, and the distribution uniformity of the electrolyte in the whole structure of the battery cell is promoted. Therefore, the lithium precipitation condition of the electrode interface is obviously improved, the cycle life is obviously prolonged, and the high-temperature storage capacity retention rate is also improved.
The positive electrode active material layer preferably has 2-5 layers, and the conventional battery core product is similar to the comparative example, and the positive electrode active material layers of the conventional battery core product are all in a 1-layer structure.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (11)
1. The utility model provides an improve positive plate of infiltration ability which characterized in that: the positive plate comprises a current collector, wherein n active material layers with the same thickness are arranged on two sides of the current collector; wherein n is more than or equal to 2 and less than or equal to 10;
the contact angle between the surface of the current collector and the electrolyte is theta 0 ，0.50≤COS(θ 0 ) Less than 0.99, and the contact angle between the surface of the active material layer and the electrolyte is theta n and theta n ≤30°；
When COS (theta) is more than or equal to 0.50 0 ) At < 0.94, theta 1 ＝θ 0 /2，θ n ＝θ 1 *0.9 n+1 When COS (theta) is more than or equal to 0.94 0 ) At < 0.99, theta 1 ＝θ 0 ，θ n ＝θ 1 *0.9 n+1 。
2. The positive electrode sheet for improving permeability according to claim 1, wherein: the active layer is made of a positive electrode main material, a conductive agent and a surfactant,
wherein:
X n ＝A n *D n ，
D n is the weight part of the conductive agent in the nth active layer,
A n is the specific surface area of the conductive agent in the n-th active layer,
W n the amount of the surfactant added in the nth active layer.
3. The positive electrode sheet for enhancing permeability according to claim 2, wherein: the specific surface area A of the conductive agent n ＝20-200m 2 /g。
4. The positive electrode sheet for improving permeability according to claim 3, wherein: the specific surface area A of the conductive agent n ＝50-150m 2 /g。
5. The positive electrode sheet for enhancing permeability according to claim 2, wherein: the conductive agent is at least one of SP carbon black, ketjen black, VGCF, a single-walled carbon nanotube, a multi-walled carbon nanotube or graphene; the surfactant is at least one of polyether modified siloxane, macromolecular polyether modified acrylate and organic silicon modified polyacrylate; the positive main material is at least one of NCA, NCM523, NCM622, NCM811 or LFP.
6. The positive electrode sheet for enhancing permeability according to claim 2, wherein: the addition ratio of the main material of the positive electrode, the conductive agent and the surfactant is 100: (1-3): (0.1-1).
7. The positive electrode sheet for improving permeability according to claim 1, wherein: n active layers with the same thickness are arranged on two sides of the current collector, and n is more than or equal to 2 and less than or equal to 5; the contact angle of the surface of the current collector is theta 0 ，0.70≤COS(θ 0 )＜0.99。
8. The positive electrode sheet for improving permeability according to claim 1, wherein: the sum of the thicknesses of the active layers is t n ，t n =20-50 μm; the porosity of the active layers is the same.
9. The positive electrode sheet for improving permeability according to claim 1, wherein: the current collector is a smooth foil; the surface of the optical foil is coated with a conductive material layer; the conductive material layer is one of carbon material or metal particles.
10. The method for producing a positive electrode sheet having an improved permeability according to claim 1, characterized in that: the method comprises the following steps:
(1) Mixing a conductive agent, a surfactant and a main positive electrode material to prepare positive electrode slurry;
(2) And respectively coating the positive electrode slurry on two sides of a current collector, coating n layers, and rolling and baking to obtain the positive electrode plate with the improved permeability.
11. A lithium ion battery, characterized by: a positive electrode sheet for improving permeability according to any one of claims 1 to 9.
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| JP2000058039A (en) * | 1998-08-06 | 2000-02-25 | Masaru Sugita | Evaluation method for battery constituting material, and battery material selected in the method |
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