CN107437623B - Lithium ion battery positive plate and preparation method thereof - Google Patents

Lithium ion battery positive plate and preparation method thereof Download PDF

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CN107437623B
CN107437623B CN201610364778.XA CN201610364778A CN107437623B CN 107437623 B CN107437623 B CN 107437623B CN 201610364778 A CN201610364778 A CN 201610364778A CN 107437623 B CN107437623 B CN 107437623B
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lithium ion
ion battery
polymer
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CN107437623A (en
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许虎
林玉春
史东洋
金海族
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Contemporary Amperex Technology Co Ltd
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • General Chemical & Material Sciences (AREA)
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Abstract

The invention discloses a lithium ion battery positive plate which comprises a positive current collector and a positive active material layer distributed on the positive current collector, wherein the positive active material layer is provided with polymer conductive convex layers distributed at intervals, and the polymer conductive convex layers contain olefin polymers and conductive agents. According to the invention, the polymer conductive convex layer on the lithium ion battery positive plate can form an interlayer gap, and the support framework is formed between the pole piece and the isolating membrane through the polymer conductive convex layer, so that a buffer gap exists between the pole piece and the isolating membrane, a buffer space is created for the pole piece with concentrated expansion stress in the circulation process, the expansion stress of the pole piece in the circulation process can be effectively released, the distortion and deformation caused by the expansion of the pole piece are reduced, and the safety performance and the cycle life of the lithium ion battery are improved. In addition, the invention also discloses a preparation method of the lithium ion battery positive plate and a lithium ion battery.

Description

Lithium ion battery positive plate and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery positive plate with ideal safety performance and cycle performance and a preparation method thereof.
Background
Currently, lithium ion batteries have been widely used as power batteries. With the increasingly intense market competition, various lithium ion battery companies are constantly exploring and improving the performance and manufacturing process of power lithium ion batteries. The battery core is used as a core component of the lithium ion battery, and two modes of lamination and winding are generally adopted, wherein the winding mode is adopted by most lithium ion battery manufacturing enterprises due to simple process, high assembly efficiency and easy automation.
In the application process of the lithium ion battery, the safety performance and the cycle life are very important. As is well known, conventional wound lithium ion batteries typically compact pole pieces to increase the packing density of the positive electrode of the cell. In the process of charging and discharging, the pole piece of the lithium ion battery can generate volume expansion due to different lithium removal or lithium insertion states of active substances. The expansion of pole piece inevitably leads to the coiling type lithium ion battery electricity core interlaminar to produce the internal stress, if the expansion stress that produces can not obtain effective release, when the circulation reaches certain degree, will lead to the distortion of coiling type electricity core, leads to the short circuit even from this and causes the potential safety hazard. In addition, the pole piece that constantly extrudes makes the later stage of circulation pole piece interlayer clearance lock and leads to the electrolyte infiltration nature to worsen, and the not enough cycle performance that can lead to the later stage of infiltration of electrolyte worsens.
In view of this, it is necessary to provide a lithium ion battery positive plate with ideal safety performance and cycle performance and a preparation method thereof.
Disclosure of Invention
The invention aims to: overcomes the defects of the prior art, and provides a lithium ion battery positive plate with ideal safety performance and cycle performance and a preparation method thereof.
In order to achieve the above object, the present invention provides a positive plate of a lithium ion battery, which includes a positive current collector and a positive active material layer distributed on the positive current collector, wherein the positive active material layer is provided with polymer conductive convex layers distributed at intervals.
As an improvement of the lithium ion battery positive plate, the polymer conductive convex layer contains an olefin polymer and a conductive agent.
As an improvement of the lithium ion battery positive plate of the present invention, the olefin polymer is at least one selected from VDF polymer, HFP polymer, VDF-HFP polymer, polyacrylic acid, polystyrene butadiene copolymer, polyvinyl alcohol, polyalkenyl ester, polyurethane, chlorinated rubber, and epoxy resin, and is preferably VDF polymer, HFP polymer, or VDF-HFP polymer.
As an improvement of the lithium ion battery positive plate, the conductive agent is selected from one or more of acetylene black, activated carbon, carbon black and conductive graphite, and the acetylene black is preferred.
As an improvement of the lithium ion battery positive plate, the weight ratio of the olefin polymer to the conductive agent is 50-95: 50-5.
As an improvement of the lithium ion battery positive plate, the thickness of the polymer conductive convex layer is 5-50 mu m, and the width is 2-8 mm.
As an improvement of the lithium ion battery positive plate, the polymer conductive convex layer is arranged on one side or two sides of the surface of the positive plate.
As an improvement of the lithium ion battery positive plate, the polymer conductive convex layers are distributed in parallel at intervals, and the distance between the polymer conductive convex layers is 5-30 mm.
As an improvement of the lithium ion battery positive plate, the polymer conductive convex layer is parallel to and spaced from the non-winding edge of the lithium ion battery positive plate, or parallel to and spaced from the non-winding edge of the lithium ion battery positive plate at an angle of not more than 50 degrees, preferably not more than 30 degrees
In order to achieve the above object, the present invention provides a method for preparing a positive plate of a lithium ion battery, comprising the following steps:
1) providing a positive current collector;
2) preparing positive electrode slurry, uniformly coating the positive electrode slurry on a positive electrode current collector, drying and then carrying out cold pressing to obtain a positive electrode plate;
3) mixing an olefin polymer and a conductive agent, dissolving the mixture in an organic solvent, and dispersing and stirring to obtain conductive polymer slurry; and
4) coating the conductive polymer slurry on one side or two sides of the positive plate obtained in the step 2) in an interval stripe shape, drying to obtain the positive plate provided with the polymer conductive convex layers distributed at intervals, and performing die cutting and stripping to obtain the lithium ion battery positive plate.
As an improvement of the preparation method of the lithium ion battery positive plate, the organic solvent in the step 3) is one or more selected from N-methyl pyrrolidone, ethyl acetate, diethyl carbonate, dimethyl carbonate and propyl propionate.
As an improvement of the method for preparing the positive plate of the lithium ion battery, in the step 3), the olefin polymer is at least one selected from VDF polymer, HFP polymer, VDF-HFP polymer, polyacrylic acid, polystyrene butadiene copolymer, polyvinyl alcohol, polyalkenoic acid ester, polyurethane, chlorinated rubber and epoxy resin.
As an improvement of the preparation method of the lithium ion battery positive plate, the conductive agent in the step 3) is selected from one or more of acetylene black, activated carbon, carbon black and conductive graphite.
As an improvement of the preparation method of the lithium ion battery positive plate, in the conductive polymer slurry in the step 3), the weight content of the olefin polymer and the conductive agent is 5-95%, and the weight content of the organic solvent is 5-95%.
In addition, the invention also provides a lithium ion battery, which comprises a positive plate, a negative plate, an isolating membrane arranged between the positive plate and the negative plate, and electrolyte, wherein the positive plate is the positive plate of the lithium ion battery.
Compared with the prior art, the lithium ion battery positive plate and the preparation method thereof have the following advantages:
firstly, the polymer conductive convex layer on the positive plate can form an interlayer gap, so that the permeation of electrolyte in the battery cell is increased, the infiltration of the electrolyte in the battery cell is facilitated, the Li + fast migration capability is ensured in the charging and discharging processes, and the cycle life and the storage performance of the battery cell are improved.
Secondly, the polymer conductive convex layer on the positive plate can form an interlayer gap, and a support framework is formed between the pole piece and the isolating membrane through the polymer conductive convex layer, so that a certain buffer gap exists between the pole piece and the isolating membrane, a buffer space is created for the pole piece with concentrated expansion stress in the circulation process, and the expansion stress of the pole piece in the circulation process can be effectively released, so that the distortion and deformation caused by the expansion of the pole piece are obviously reduced, the safety accident caused by the short circuit of the battery is prevented, and the safety performance and the cycle life of the lithium ion battery are improved.
Finally, when the polymer conductive convex layer is formed, the dispersing function of the VDF-HFP polymer in the organic solvent can be well matched with the conductive agent, the conductive agent is uniformly dispersed in the slurry, a good conductive effect is achieved, battery polarization and internal resistance increase caused by the polymer conductive convex layer are reduced or eliminated, and organic solvent pulping adopted by the polymer conductive convex layer can be well similar to and compatible with a positive plate manufactured by the same organic solvent slurry. In addition, because the VDF-HFP polymer has viscosity, other binders do not need to be introduced in the preparation of the conductive bump layer of the polymer, the preparation process can be simplified, and the impedance of the battery can be reduced.
Drawings
The lithium ion battery positive plate and the preparation method thereof of the present invention are described in detail below with reference to the accompanying drawings and examples, wherein:
fig. 1A and 1B are schematic structural diagrams of a positive electrode sheet in a lithium ion battery according to embodiment 2 of the present invention, in which a polymer conductive convex layer is distributed on a single surface of the positive electrode sheet.
Fig. 2A and 2B are schematic structural diagrams of a positive plate in a lithium ion battery according to embodiment 10 of the present invention, wherein polymer conductive convex layers are distributed on two sides of the positive plate.
Fig. 3 is a comparison of cell DCR test performance in lithium ion batteries of examples 1, 4, 8 and comparative example 1 of the present invention.
Fig. 4 is a comparison of the cycle performance and the storage performance of the lithium ion batteries of example 1 and comparative example 1 according to the present invention.
Examples
In order to make the object, technical solution and technical effect of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the examples given in this specification are for the purpose of illustration only and are not intended to limit the invention.
Example 1
Preparing a positive plate: mixing positive electrode active material Li (Ni)1/3Co1/3Mn1/3)O2The conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97: 2: 1, uniformly mixing and adding the mixture into N-methyl-2-pyrrolidone (NMP) serving as a solvent to prepare positive electrode slurry with certain viscosity; and uniformly coating the positive slurry on a positive current collector aluminum foil, drying and then carrying out cold pressing to prepare the positive plate to be provided with the polymer conductive convex layer.
Preparing a positive plate polymer conductive convex layer: mixing VDF-HFP polymer (the weight content of HFP is 5-15%) and acetylene black according to the mass ratio of 2: 1, dissolving the mixture in an organic solvent N-methyl-2-pyrrolidone after mixing, and stirring until the mixture is uniformly dispersed until the mixture is completely dissolved and no suspended matter exists, so as to obtain conductive polymer slurry; coating the conductive polymer slurry on the two sides of the positive plate prepared in the previous step in a parallel and spaced stripe shape, and drying to obtain the positive plate with the hot-pressing meltable polymer conductive convex layer; after drying, the conductive polymer forms polymer conductive convex layers which are distributed in parallel and at intervals on the surface of the positive plate, the thickness of the polymer conductive convex layers is 30 mu m, the width of each convex layer is 3mm, and the distance between every two adjacent convex layers is 6 mm; the angle between the wales and the non-winding side is 0 deg.. And die cutting and slitting the dried positive plate to prepare the lithium ion battery positive plate provided with the polymer conductive convex layer.
Preparing a negative plate: mixing graphite serving as a negative electrode active substance, acetylene black serving as a conductive agent, sodium carboxymethyl cellulose (CMC) serving as a thickening agent and Styrene Butadiene Rubber (SBR) serving as a binder in a mass ratio of 96: 2: 1: 1, uniformly mixing and adding the mixture into solvent water to prepare cathode slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying, and then carrying out cold pressing, die cutting and stripping to prepare the lithium ion battery negative plate.
Preparing an isolating membrane: selecting a polyethylene microporous film as a porous isolating film substrate; mixing inorganic aluminum trioxide powder, polyvinylpyrrolidone and an acetone solvent according to a weight ratio of 3: 1.5: 5.5, uniformly mixing to prepare slurry, coating the slurry on one surface of the base material, drying and splitting to prepare the isolating membrane.
Preparing an electrolyte: lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate was 1: 2: 1) to obtain a desired electrolyte.
Preparing a lithium ion battery: and winding the positive plate, the negative plate and the isolating membrane provided with the polymer conductive convex layer to obtain a battery core, and then carrying out processes such as packaging, liquid injection, formation, exhaust and the like to prepare the lithium ion battery.
Example 2
The lithium ion battery in embodiment 2 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the polymer conductive convex layer is only arranged on one surface of the positive plate, and the structure of the positive plate provided with the polymer conductive convex layer is shown in fig. 1A and 1B.
Example 3
The lithium ion battery in embodiment 3 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the thickness of the polymer conductive convex layer arranged on the positive plate is 50 μm.
Example 4
The lithium ion battery in embodiment 4 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the thickness of the polymer conductive convex layer arranged on the positive plate is 3 μm.
Example 5
The lithium ion battery in embodiment 5 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the spacing between adjacent polymer conductive bump layers was 15 mm.
Example 6
The lithium ion battery in embodiment 6 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the spacing between adjacent polymer conductive bump layers was 30 mm.
Example 7
The lithium ion battery in embodiment 7 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: in the step of preparing the polymer conductive bump, a VDF-HFP polymer (HFP content 5-15% by weight) and acetylene black are mixed in a weight ratio of 3: 1, dissolving the mixture in an organic solvent N-methyl-2-pyrrolidone after mixing, dispersing the mixture at a high speed for 3 hours at the temperature of 45 ℃, and slowly stirring the mixture at a low speed for 1.5 hours until the mixture is completely dissolved and no suspended matters exist, thus obtaining the conductive polymer slurry.
Example 8
The lithium ion battery in embodiment 8 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: in the step of preparing the polymer conductive convex layer, the weight ratio of VDF to acetylene black is 2: 1, dissolving the mixture in an organic solvent N-methyl-2-pyrrolidone, dispersing the mixture at a high speed for 3 hours at 45 ℃, slowly stirring the mixture at a low speed for 1.5 hours until the mixture is completely dissolved and no suspended matters exist, thus obtaining conductive polymer slurry, wherein the width of a convex layer is 5 mm.
Example 9
The lithium ion battery in embodiment 9 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: in the step of preparing the polymer conductive convex layer, the distribution directions of the polymer conductive convex layer are different. In the lithium ion battery of embodiment 1 of the present invention, the polymer conductive convex layer is distributed in parallel with the non-winding edge. In example 9 of the present invention, the polymer conductive convex layer was arranged parallel to the non-winding edge at an angle of 15 °, and the width of the convex layer was 8 mm.
Example 10
The lithium ion battery in embodiment 10 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: in the step of preparing the polymer conductive convex layer, the distribution directions of the polymer conductive convex layer are different. In the lithium ion battery of embodiment 1 of the present invention, the polymer conductive convex layer is distributed in parallel with the non-winding edge. In example 10 of the present invention, the polymer conductive convex layer was distributed in parallel to the non-winding edge at 30 °, and the positive electrode sheet provided with the polymer conductive convex layer had a structure as shown in fig. 2A and 2B, and the width of the convex layer was 8 mm.
Comparative example 1
Preparing a positive plate: mixing positive electrode active material Li (Ni)1/3Co1/3Mn1/3)O2The conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97: 2: 1, uniformly mixing and adding the mixture into N-methyl-2-pyrrolidone (NMP) serving as a solvent to prepare positive electrode slurry with certain viscosity; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying, cold pressing, die cutting and slitting to obtain the positive electrode plate of the lithium ion battery.
Preparing a negative plate: mixing graphite serving as a negative electrode active material, acetylene black serving as a conductive agent, sodium carboxymethyl cellulose (CMC) serving as a thickening agent and Styrene Butadiene Rubber (SBR) serving as a binder in a weight ratio of 96: 2: 1: 1, uniformly mixing and adding the mixture into solvent water to prepare cathode slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying, and then carrying out cold pressing, die cutting and stripping to directly prepare the lithium ion battery negative plate.
Preparing an isolating membrane: selecting a polyethylene microporous film as a porous isolating film substrate; mixing aluminum trioxide powder, polyvinylpyrrolidone and an acetone solvent according to a weight ratio of 3: 1.5: 5.5, uniformly mixing to prepare slurry, coating the slurry on one surface of the base material, drying and splitting to prepare the isolating membrane.
Preparing an electrolyte: lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate was 1: 2: 1) to obtain a desired electrolyte.
Preparing a lithium ion battery: and winding the positive plate, the negative plate and the isolating membrane to obtain a bare cell, and then carrying out processes of packaging, liquid injection, formation, exhaust and the like to obtain the lithium ion battery.
Performance testing
Capacity retention rate: in order to represent the influence of the lithium ion battery positive plate and the comparative lithium ion battery positive plate on the cycle life and the safety performance of the battery cell, the battery cell adopting the lithium ion battery positive plate and the comparative lithium ion battery positive plate is subjected to 60 ℃ and 2C/3C cycle for 800 times respectively, and the capacity retention rate is inspected. In the cycle test, the voltage range was 2.8V to 4.2V, charging was performed at a rate of 2C, and discharging was performed at a rate of 3C, and the cycle capacity retention rate was a ratio of the 3C discharge capacity at the 800 th cycle to the 2 nd 3C discharge capacity.
Infiltration speed: the lithium ion battery positive plate and the lithium ion battery positive plate of the invention have the influence on the electrolyte infiltration speed, the battery cell is taken out after being soaked in the electrolyte for 5 hours, and is placed at 90 ℃ for drying time to represent, and whether the battery cell is dried is judged by judging whether the internal resistance of the battery cell is more than 100 MOmega (if the internal resistance is more than 100 MOmega), and the battery cell is dried.
DCR test: the cells of examples 1, 4, 8 and 1 were tested for DCR and the effect of the thickness of the polymer conductive bump and the composition of the polymer conductive bump on the DCR of the cell was examined.
Cycling performance and storage performance: the cells of example 1 and comparative example 1 were subjected to a 45 ℃ 1C/1C cycle performance test, and in order to ensure the reliability of data, 2 cells were used as a parallel sample test for each example, while a 60 ℃ 100% SOC storage performance test was performed for example 1 and comparative example 1.
Table 1 shows the test results of the examples and the comparative examples, and it can be seen from the test result data of table 1 that:
1. the thickness of the polymer conductive convex layer has obvious influence on the infiltration speed of the electrolyte and is in positive correlation, but the thickness of the polymer conductive convex layer is not too large, and the ion conduction capability is reduced due to too large interlayer gaps in the charging and discharging processes of the battery, so that the cycle performance is influenced.
2. The spacing of the polymer conductive bumps has an effect on the performance of the cell, but is not significant.
3. As can be seen from the comparison between examples 1 and 8, the composition of the polymer conductive bump layer has an effect on the performance of the cell: the improvement effect of the VDF-HFP polymer is better than that of the VDF monomer polymer, which is also shown in the DCR test result shown in FIG. 3, and the DCR of the polymer conductive bump layer of the VDF monomer polymer is higher than that of other groups.
TABLE 1 examination results of examples and comparative examples
Figure BDA0001001972170000091
4. As can be seen from example 7, as the ratio of polymer to conductive agent increases, the average internal resistance of the cell increases.
5. The conductive polymer bump layers used in examples 9 and 10 also provide unexpected improvements, albeit parallel to the non-winding edges at angles of 15 ° and 30 °.
In addition, the positive plate provided with the polymer conductive convex layer with proper thickness can obviously improve the cycle performance of the battery cell while effectively improving the wettability of the electrolyte. As is apparent from fig. 3 and 4, the battery cell of the positive electrode sheet of example 1 provided with the polymer conductive convex layer having the thickness of 30 μm has significantly improved 45 ℃ 1C/1C cycle performance and 60 ℃ 100% SOC storage performance compared to comparative example 1.
It is understood that although the conductive polymer convex layers are shown in the embodiments of the present invention as being distributed in parallel and at intervals, those skilled in the art can also make the conductive polymer convex layers in other forms according to actual needs. For example, according to other embodiments of the present invention, the conductive polymer bump layers may be in a non-parallel discrete distribution. In addition, the space between the parallel and spaced polymer conductive convex layers can be optimized and adjusted according to the requirement. For example, according to a preferred embodiment of the present invention, when winding into a cell, the spacing between the polymer conductive convex layers corresponding to the winding turns can be preferably reduced as required relative to the spacing between the polymer conductive convex layers at other positions on the pole piece.
In combination with the above detailed description of the embodiments of the present invention, it can be seen that, compared with the prior art, the lithium ion battery and the positive plate thereof of the present invention have the following advantages:
firstly, the polymer conductive convex layer on the positive plate can form an interlayer gap, so that the permeation of electrolyte in the battery cell is increased, the infiltration of the electrolyte in the battery cell is facilitated, the Li + fast migration capability is ensured in the charging and discharging processes, and the cycle life and the storage performance of the battery cell are improved.
Secondly, the polymer conductive convex layer on the positive plate can form an interlayer gap, and a support framework is formed between the pole piece and the isolating membrane through the polymer conductive convex layer, so that a certain buffer gap exists between the pole piece and the isolating membrane, a buffer space is created for the pole piece with concentrated expansion stress in the circulation process, and the expansion stress of the pole piece in the circulation process can be effectively released, so that the distortion and deformation caused by the expansion of the pole piece are obviously reduced, the safety accident caused by the short circuit of the battery is prevented, and the safety performance and the cycle life of the lithium ion battery are improved.
Finally, when the polymer conductive convex layer is formed, the dispersing function of the VDF-HFP polymer in the organic solvent can be well matched with the conductive agent, the conductive agent is uniformly dispersed in the slurry, a good conductive effect is achieved, and the increase of battery polarization and internal resistance caused by the polymer conductive convex layer is reduced or eliminated.
The present invention can be modified and adapted appropriately from the above-described embodiments, according to the principles described above. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. The utility model provides a lithium ion battery positive plate, its includes the anodal mass flow body and distributes the anodal active material layer on the anodal mass flow body, its characterized in that: the positive active material layer is provided with polymer conductive convex layers distributed at intervals of 5-30 mm; the polymeric conductive bump layer contains a VDF-HFP polymer and a conductive agent.
2. The positive electrode sheet of the lithium ion battery according to claim 1, characterized in that: the conductive agent is selected from one or more of acetylene black, activated carbon, carbon black and conductive graphite.
3. The positive electrode sheet of the lithium ion battery according to claim 1, characterized in that: the weight ratio of the VDF-HFP polymer to the conductive agent is 50-95: 50-5.
4. The positive electrode sheet of the lithium ion battery according to claim 1, characterized in that: the thickness of the polymer conductive convex layer is 5-50 mu m, and the width of the polymer conductive convex layer is 2-8 mm.
5. The positive electrode sheet of the lithium ion battery according to claim 1, characterized in that: the polymer conductive convex layer is arranged on one side or two sides of the surface of the positive plate.
6. The positive electrode sheet of the lithium ion battery according to claim 1, characterized in that: the polymer conductive convex layers are distributed in parallel and at intervals.
7. The positive electrode sheet of the lithium ion battery according to claim 6, wherein: the polymer conductive convex layer and the non-winding edge of the lithium ion battery positive plate are distributed in parallel and at intervals, or are distributed in parallel and at intervals with an angle of not more than 50 degrees.
8. The positive electrode sheet of the lithium ion battery according to claim 6, wherein: the polymer conductive convex layer and the non-winding edge of the lithium ion battery positive plate are distributed in parallel at intervals at an angle not greater than 30 degrees.
9. A preparation method of a lithium ion battery positive plate is characterized by comprising the following steps:
1) providing a positive current collector;
2) preparing positive electrode slurry, uniformly coating the positive electrode slurry on a positive electrode current collector, drying and then carrying out cold pressing to obtain a positive electrode plate;
3) mixing VDF-HFP polymer and a conductive agent, dissolving the mixture in an organic solvent, and dispersing and stirring the mixture to obtain conductive polymer slurry; and
4) coating the conductive polymer slurry on one side or two sides of the positive plate obtained in the step 2) in a spaced stripe shape, drying to obtain the positive plate provided with the polymer conductive convex layers distributed at intervals of 5-30mm, and performing die cutting and stripping to obtain the lithium ion battery positive plate.
10. The utility model provides a lithium ion battery, its includes positive plate, negative pole piece, separates the barrier film between positive plate and negative pole piece to and electrolyte, its characterized in that: the positive electrode sheet is the positive electrode sheet for a lithium ion battery according to any one of claims 1 to 8.
CN201610364778.XA 2016-05-27 2016-05-27 Lithium ion battery positive plate and preparation method thereof Active CN107437623B (en)

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CN103972471A (en) * 2014-04-19 2014-08-06 东风商用车有限公司 Positive pole piece of high-rate lithium iron phosphate battery and manufacturing method thereof

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CN103972471A (en) * 2014-04-19 2014-08-06 东风商用车有限公司 Positive pole piece of high-rate lithium iron phosphate battery and manufacturing method thereof

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