CN114284642A - Multilayer coating diaphragm and polymer battery prepared from same - Google Patents
Multilayer coating diaphragm and polymer battery prepared from same Download PDFInfo
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- CN114284642A CN114284642A CN202111407755.XA CN202111407755A CN114284642A CN 114284642 A CN114284642 A CN 114284642A CN 202111407755 A CN202111407755 A CN 202111407755A CN 114284642 A CN114284642 A CN 114284642A
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a multilayer coating diaphragm and a polymer battery prepared by the same, wherein the diaphragm comprises a diaphragm base material and a multilayer polymer coating coated on the diaphragm base material; the multi-layer polymeric coating includes a low swell ratio polymeric coating and a high swell ratio polymeric coating; the polymer coating with low swelling ratio is uniformly coated on the surface of the diaphragm base material; the high swelling ratio polymer coating is coated on the low swelling ratio polymer coating at intervals. Compared with the existing diaphragm, in the design of the multilayer coating diaphragm, the low-swelling-rate polymer coating can improve the mechanical strength of the diaphragm and ensure the adhesion between the diaphragm and an electrode; the high swelling rate polymer coating can improve the electrolyte retaining amount in the battery, and the high swelling rate polymer coating can complement each other through different actions of the coatings, so that the infiltration capacity of the gluing diaphragm is greatly improved, the cohesiveness between the electrode and the diaphragm is enhanced, the interface consistency is ensured, and the electrochemical performance and the safety performance of the battery are improved.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a multilayer coating diaphragm and a polymer battery prepared by the same.
Background
With the increasing popularity of electric vehicles year by year, the power battery industry is also rapidly developing, and the demand for batteries with high energy density and safety is increasing. In each part of the battery, the performance of the diaphragm material plays a crucial role in improving the stability and safety of the battery, and the direction of improving the energy density of the battery and optimizing the interface stability and safety of the battery by using the diaphragm with various coating layers on the surface and the thermal compounding process of the diaphragm and the pole piece also becomes a research hotspot of the industry.
CN111755648A is an asymmetric coating layer coated on the separator, which comprises at least one inorganic ion conductor layer coated on one side of the base film, and at least one organic polymer layer coated on the other side of the base film. The inorganic ion conductor functional layer and the organic polymer functional layer which are coated on the two surfaces of the base film asymmetrically achieve the purposes of reducing the interface impedance between the diaphragm and the electrode and improving the characteristics of the diaphragm such as thermal stability, liquid absorption rate, ionic conductivity and the like. CN212230512U is provided with three coating layers on the diaphragm, and the third coating layer is connected with the substrate layer, and the second coating layer is thermal-insulated aerogel layer. Through the overlapping arrangement of the three coating layers, the liquid absorption performance and the liquid retention performance of the diaphragm are both improved. CN107611314A scribbles the first coating and the second coating of adhesive polymer respectively on the both sides of diaphragm, through carrying out different diaphragm coating designs to positive and negative pole, makes lithium ion battery can satisfy the requirement to hardness and dynamics. The CN112952296A diaphragm is composed of a composite base film and a conductive ceramic coating, wherein the composite base film is prepared by mixing polyolefin and first conductive ceramic, and the ionic conductivity is improved by constructing a conductive network. Although the porosity and the liquid absorption of the battery can be improved to a certain extent, the functional coating can slow down the electrolyte infiltration rate of the battery core, influence the consistency and the stability of the interface of the battery core, and also do not improve the safety performance under the conditions of puncture damage such as internal short circuit of acupuncture and the like, and the preparation process is more complicated and the cost is higher, so the invention provides the multilayer coating diaphragm and the polymer battery prepared by the same for solving the problems.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a multilayer coating diaphragm and a polymer battery prepared by the same, wherein the low-swelling-rate polymer coating can improve the mechanical strength of the diaphragm and ensure the adhesion between the diaphragm and an electrode; the high-swelling-rate polymer coating can improve the electrolyte retaining capacity in the battery, the wetting capacity of the gluing diaphragm is greatly improved by mutual complementation under different actions of the coatings, the cohesiveness between the electrode and the diaphragm is enhanced, the interface consistency is ensured, free electrolyte is not contained in the prepared polymer battery, the risks of corrosion and leakage of the liquid electrolyte on the aluminum plastic film are greatly reduced, and the electrochemical performance and the safety performance of the battery are improved. The interval coating enables the whole glue coating amount of the diaphragm to be less than that of the uniform coating design, and the production cost is also reduced.
In order to achieve the above object, a first aspect of the present invention provides a multilayer coated separator including a separator substrate and a multilayer polymer coating layer coated on the separator substrate; the multi-layer polymeric coating includes a low swell ratio polymeric coating and a high swell ratio polymeric coating; the polymer coating with low swelling ratio is uniformly coated on the surface of the diaphragm base material; the high swelling ratio polymer coating is coated on the low swelling ratio polymer coating at intervals.
The second aspect of the invention provides a polymer battery, which comprises a positive electrode, a negative electrode and a diaphragm, wherein the diaphragm is the multilayer coating diaphragm.
A third aspect of the present invention provides a method for producing a polymer battery, comprising:
(1) uniformly coating the slurry of the low-swelling-rate polymer coating on the surface of the diaphragm base material in a gravure coating mode, and coating the slurry of the high-swelling-rate polymer coating on the diaphragm base material at intervals in a striped inclined line shape to obtain a multilayer coating diaphragm;
(2) regularly stacking or winding a certain number of positive and negative pole pieces and the multilayer coating diaphragm together, and packaging the positive and negative pole pieces and the multilayer coating diaphragm into a polymer battery by using an aluminum-plastic film;
(3) after the battery is injected with liquid, the battery is placed into a pressure formation cabinet for heating and pressure formation, and the coating of the multilayer coating diaphragm swells and is firmly combined with the pole piece under the action of pressure;
(4) and after the battery after hot pressing is connected with charge and discharge equipment for capacity grading, degassing and tightening the battery until no free electrolyte exists in the battery core.
The multilayer coating diaphragm designed by the invention and the polymer battery prepared by the same have the advantages that:
1) the liquid retention capacity of the battery is remarkably improved, compared with a conventional polymer coated diaphragm, the wettability can be greatly improved, the wetting rate of the polymer coated diaphragm is equivalent to that of a ceramic diaphragm, a formed gel layer is uniform and stable, the interface stability can be improved, and the cycle performance is excellent;
2) the diaphragm gel layer can be tightly attached to the surface of the electrode during the battery needling short circuit, and certain toughness is kept, so that the contact internal resistance can be effectively improved, the temperature rise is reduced, and the battery safety is improved;
3) the preparation process is simple, and the production cost is reduced;
4) the prepared polymer battery has no free electrolyte inside, so that the risk of the liquid electrolyte corroding the aluminum plastic film and leaking is greatly reduced.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 is a schematic sectional and plan view of a separator.
Fig. 2 is a composite schematic diagram of a soft-package battery separator.
Fig. 3 is a graph showing the cycle at 45 c of the assembled pouch cells of comparative example and examples 1-6 after they were compounded.
Fig. 4 is a disassembled interface diagram of the assembled pouch cells of comparative example and examples 1-6 after standard charging and discharging for 10 circles.
FIG. 5 is a height chart of the liquid surface rising after the separator was fixed by the glass slide clips and immersed in the electrolyte at the same height for 40 seconds in comparative example and examples 1 to 6.
Description of reference numerals:
1-diaphragm substrate, 2-low swelling ratio polymer coating, 3-high swelling ratio polymer coating, 4-front clamp, 5-rear clamp, 6-silica gel pad and 7-battery.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
The invention provides a multilayer coated separator, comprising a separator substrate and a multilayer polymer coating coated on the separator substrate; the multi-layer polymeric coating includes a low swell ratio polymeric coating and a high swell ratio polymeric coating; the polymer coating with low swelling ratio is uniformly coated on the surface of the diaphragm base material; the high swelling ratio polymer coating is coated on the low swelling ratio polymer coating at intervals. The cross-sectional and plan view of the diaphragm is schematically shown in figure 1.
Optionally, the maximum swelling liquid absorption capacity of the high-swelling-rate polymer coating component in the electrolyte is 20-100% of the mass of the high-swelling-rate polymer coating component, and the maximum swelling liquid absorption capacity of the low-swelling-rate polymer coating component in the electrolyte is less than 20%.
Optionally, the separator substrate is at least one of PE, PP, cellulose, PET, PI, non-woven fabric, and electrospun separator.
Optionally, the raw material for forming the polymer coating is polymer binder slurry, or mixed slurry of polymer binder and inorganic material;
the inorganic material is at least one of aluminum oxide, magnesium hydroxide, layered composite oxide, boehmite, silicon dioxide and silicon carbide;
the polymer binder comprises a high swelling ratio polymer binder and a low swelling ratio polymer binder;
the high-swelling-rate polymer binder is preferably at least one of polyvinylidene fluoride and polyacrylonitrile, and the low-swelling-rate polymer binder is preferably at least one of polyethylacrylate, polymethyl methacrylate and ethylene-tetrafluoroethylene copolymer;
the mass fraction of the inorganic material in the mixed slurry is 0-90%, and the mass fraction of the polymer binder is 10-100%.
Optionally, the multi-layer polymeric coating is at least two layers;
the multilayer polymeric coating is coated on one or both sides of the separator substrate.
Optionally, the combined thickness of the low-swell-ratio polymer coating and the high-swell-ratio polymer coating is not more than 6 μm;
the thickness of the low swelling ratio polymer coating is 1-2 mu m;
the thickness of the high swelling ratio polymer coating is 2-4 mu m;
the high swelling polymer coating is preferably applied at striped diagonal intervals, the coating intervals being in the range of 500 μm to 2 mm.
And uniformly coating the slurry of the low-swelling-rate polymer coating on the surface of the diaphragm base material in a gravure coating mode, and coating the slurry of the high-swelling-rate polymer coating on the diaphragm base material to obtain the multilayer coating diaphragm.
According to the invention, the low-swelling-rate polymer coating can improve the mechanical strength of the diaphragm and ensure the adhesion between the diaphragm and the electrode; the high swelling rate polymer coating can improve the electrolyte retaining amount in the battery, and the high swelling rate polymer coating can complement each other through different actions of the coatings, so that the infiltration capacity of the gluing diaphragm is greatly improved, the cohesiveness between the electrode and the diaphragm is enhanced, the interface consistency is ensured, and the electrochemical performance and the safety performance of the battery are improved.
The invention also provides a polymer battery, which comprises a positive electrode, a negative electrode and a diaphragm, wherein the diaphragm is the multilayer coating diaphragm.
The present invention also provides a method for preparing a polymer battery, comprising:
(1) uniformly coating the slurry of the low-swelling-rate polymer coating on the surface of the diaphragm base material in a gravure coating mode, and coating the slurry of the high-swelling-rate polymer coating on the diaphragm base material at intervals to obtain a multilayer coating diaphragm;
(2) regularly stacking or winding a certain number of positive and negative pole pieces and the multilayer coating diaphragm together, and packaging the positive and negative pole pieces and the multilayer coating diaphragm into a polymer battery by using an aluminum-plastic film;
(3) after the battery is injected with liquid, the battery is placed into a pressure formation cabinet for heating and pressure formation, and the coating of the multilayer coating diaphragm swells and is firmly combined with the pole piece under the action of pressure;
(4) and after the battery after hot pressing is connected with charge and discharge equipment for capacity grading, degassing and tightening the battery until no free electrolyte exists in the battery core.
Optionally, the slurry of the high-swelling-ratio polymer coating comprises an inorganic material, a high-swelling-ratio polymer binder and an organic solvent;
the slurry of the low swelling ratio polymer coating comprises an inorganic material, a low swelling ratio polymer binder and an organic solvent;
the organic solvent is preferably NMP; the inorganic material is preferably at least one of aluminum oxide, magnesium hydroxide, layered composite oxide, boehmite, silicon dioxide and silicon carbide.
Optionally, the positive and negative plates are in direct contact with the high swelling ratio polymer coating;
the temperature range for preparing the polymer battery is 60-85 ℃, and the pressure range is 0.1-0.8 MPa;
the polymer battery is at least one of a soft package battery, a cylindrical battery and a square aluminum shell battery, and the soft package battery is preferred. The composite schematic diagram of the soft-package battery separator is shown in figure 2.
According to the invention, the diaphragm gel layer can be tightly attached to the surface of the electrode during the battery needling short circuit, and certain toughness is maintained, so that the contact internal resistance can be effectively improved, the temperature rise is reduced, and the battery safety is improved; the prepared polymer battery has no free electrolyte inside, so that the risk of the liquid electrolyte corroding the aluminum plastic film and leaking is greatly reduced.
The present invention will be described in more detail below by way of examples and comparative examples.
Comparative example
1) Preparing a diaphragm:
a. adopts a diaphragm with a base film of PE and two surfaces both provided with a layer of boehmite coating with the diameter of 2 mu m.
2) Assembling the soft package battery:
b. 30 sheets of the NCM622 ternary positive electrode sheet, 31 artificial graphite negative electrode sheets, and 32 separators were neatly stacked together.
c. And packaging the battery cell by using an aluminum plastic film, and assembling into a 50Ah soft package battery.
d. Injecting electrolyte into the battery, wherein the electrolyte is 1M LiPF6When the solution was dissolved in EC, EMC: 3:7(w/w), the amount of the injected solution was 3.3 g/Ah.
3) Thermal compounding of the diaphragm electrode:
e. the battery is externally connected with an air bag and put into a pressure formation cabinet at the temperature of 30 ℃, and the positive electrode and the negative electrode are respectively connected with charge and discharge equipment. The pressure of the pressure formation cabinet is adjusted to 0.6MPa, and the battery is compressed. And setting a pre-charging program to charge to 3.55V at 0.05C, standing for 1h, charging to 4.35V at 0.1C, standing for 10min, and stopping.
f. And after the pre-charging procedure is stopped, the external air bag is taken down, the pressure of the pressure forming cabinet is relieved, the battery is taken out, and the external liquid pumping pipe pumps out the gas of the battery.
g. Connecting the positive electrode and the negative electrode of the battery with charge-discharge equipment, setting the program to be 0.3C for discharging to 2.75V, 0.3C for charging to 4.35V, standing for 10min, repeating the process for 3 times, and stopping.
h. The battery is taken down from the charging and discharging equipment, the external liquid pumping pipe is connected with the battery, the free electrolyte of the battery is pumped out, and the quality of the battery is recorded.
Example 1
1) Preparing a diaphragm:
a. coating low-swelling polymer coating slurry (magnesium hydroxide: polyethylacrylate: 7:3) and high-swelling polymer coating slurry (PVDF) on one side of a PE diaphragm substrate, wherein the low-swelling polymer coating is uniformly coated, the high-swelling polymer coating is coated on the low-swelling polymer coating at an oblique line interval, the coating interval is 500 mu m, the coating thicknesses of the low-swelling polymer coating and the high-swelling polymer coating are respectively 1 mu m and 2 mu m, and the other side of the diaphragm is treated in the same way to prepare the coated diaphragm.
2) Assembling the soft package battery with the same comparison example;
3) thermal compounding of the diaphragm electrode:
b. the battery is externally connected with an air bag and put into a pressure formation cabinet at the room temperature of 30 ℃, and the positive electrode and the negative electrode are respectively connected with charge and discharge equipment. The pressure of the pressure formation cabinet is adjusted to 0.6MPa, and the battery is compressed. And setting a pre-charging program to charge to 3.55V at 0.05C, standing for 1h, charging to 4.35V at 0.1C, standing for 10min, and stopping.
c. And after the pre-charging procedure is stopped, the external air bag is taken down, the pressure of the pressure forming cabinet is relieved, the battery is taken out, and the external liquid pumping pipe pumps out the gas of the battery.
d. Connecting the positive electrode and the negative electrode of the battery with a charging and discharging device, setting the program to be 0.2C for discharging to 2.75V, 0.2C for charging to 3.9V, standing for 10min, and stopping.
e. Taking the battery off from the charging and discharging equipment, placing the battery in a hot pressing cabinet, and adjusting the temperature of the hot pressing cabinet to 70 ℃, the pressure to 0.06MPa and the hot pressing time to 60 min. And when the battery is cooled, taking down the battery, externally connecting a liquid pumping pipe, pumping out free electrolyte of the battery, and recording the quality of the battery.
Example 2
1) Preparing a diaphragm:
a. coating low-swelling polymer coating slurry (boehmite: ethyl acrylate: 8:2) and high-swelling polymer coating slurry (PVDF) on one side of a PE diaphragm substrate, wherein the low-swelling polymer coating is uniformly coated, the high-swelling polymer coating is coated on the low-swelling polymer coating at intervals in an inclined line shape, the coating interval is 700 mu m, the coating thicknesses of the low-swelling polymer coating and the high-swelling polymer coating are respectively 1 mu m and 2 mu m, and the other side of the diaphragm is treated in the same way to prepare the coated diaphragm.
2) Assembling the soft package battery with the same comparison example;
3) the separator electrode was thermally replicated as in example 1.
Example 3
1) Preparing a diaphragm:
a. coating low-swelling polymer coating slurry (boehmite: ethyl acrylate ═ 6:4) and high-swelling polymer coating slurry (PVDF) on one side of a PE diaphragm substrate, wherein the low-swelling polymer coating is uniformly coated, the high-swelling polymer coating is coated on the low-swelling polymer coating at intervals in an inclined line shape, the coating interval is 1000 mu m, the coating thicknesses of the low-swelling polymer coating and the high-swelling polymer coating are respectively 1 mu m and 2 mu m, and the other side of the diaphragm is treated in the same way to prepare the coated diaphragm.
2) Assembling the soft package battery with the same comparison example;
3) the separator electrode was thermally replicated as in example 1.
Example 4
1) Preparing a diaphragm:
a. coating a PE membrane substrate with low swelling ratio polymer coating slurry (Al)2O3: polyethylacrylate 9:1), and high swelling polymer coating syrup (Al)2O3: PVDF ═ 1:9), in which the low swelling polymer coating was uniformly coated, the high swelling polymer coating was coated diagonally above the low swelling polymer coating at intervals of 1000 μm, the coating thicknesses of the low swelling polymer coating and the high swelling polymer coating were 1 μm and 3 μm, respectively, and the other side of the separator was treated in the same manner, to prepare a coated separator.
2) Assembling the soft package battery with the same comparison example;
3) the separator electrode was thermally replicated as in example 1.
Example 5
1) Preparing a diaphragm:
a. coating low-swelling polymer coating slurry (boehmite: ethyl acrylate: 8:2) and high-swelling polymer coating slurry (PVDF) on one side of a PE diaphragm substrate, wherein the low-swelling polymer coating is uniformly coated, the high-swelling polymer coating is coated on the low-swelling polymer coating at intervals in an inclined line shape, the coating interval is 2000 mu m, the coating thicknesses of the low-swelling polymer coating and the high-swelling polymer coating are respectively 1 mu m and 2 mu m, and the other side of the diaphragm is treated in the same way to prepare the coated diaphragm.
2) Assembling the soft package battery with the same comparison example;
3) the separator electrode was thermally replicated as in example 1.
Example 6
1) Preparing a diaphragm:
a. coating low-swelling-rate polymer coating slurry (magnesium-aluminum layered composite hydroxide: polyethylacrylate: 7:3) and high-swelling-rate polymer coating slurry (PVDF) on one side of a PE diaphragm substrate, wherein the low-swelling-rate polymer coating is uniformly coated, the high-swelling-rate polymer coating is coated on the low-swelling-rate polymer coating at intervals in an inclined line manner, the coating interval is 1000 mu m, the coating thicknesses of the low-swelling-rate polymer coating and the high-swelling-rate polymer coating are respectively 2 mu m and 2 mu m, and the other side of the diaphragm is treated in the same way to prepare the coated diaphragm.
2) Assembling the soft package battery with the same comparison example;
3) the separator electrode was thermally replicated as in example 1.
Fig. 3 is a graph showing the cycle at 45 c of the assembled pouch cells of comparative example and examples 1-6 after they were compounded. As can be seen from the cycle performance in fig. 3, the examples all have higher capacity retention than the comparative examples, and it can be seen that the multilayer coating of the separator can significantly improve the battery performance.
Fig. 4 is a disassembled interface diagram of the assembled pouch cells of comparative example and examples 1-6 after standard charging and discharging for 10 circles. As can be seen from fig. 4, the cell interface consistency of the examples is significantly improved compared to the comparative examples.
FIG. 5 is a height chart of the liquid surface rising after the separator was fixed by the glass slide clips and immersed in the electrolyte at the same height for 40 seconds in comparative example and examples 1 to 6. As can be seen from FIG. 5, the membranes of examples 1-6 had greatly improved liquid absorption and wettability compared to the comparative examples.
Test example 1
The diaphragm samples prepared in comparative examples and examples 1 to 6 were subjected to liquid retention and air permeabilityAnd (6) testing. The method for testing the liquid retention amount comprises the following steps: determination of the Mass m of a Dry cell0Respectively assembling and compounding the prepared diaphragms into soft package battery liquid injection, tightening the battery after standard charging and discharging for 3 circles, and measuring the mass m of the battery core1The battery capacity is m1-m0. Air permeability test method: a sample of the septum was taken to measure the average time required to permeate 100mL of gas. The results are shown in Table 1.
TABLE 1
As can be seen from the data of examples 1 to 3 in Table 1, when the thickness of the coating layer of the separator is unchanged, the coating interval of the high swelling ratio polymer coating layer is increased, the air permeability of the separator is improved to a certain extent, and the liquid retention amount is improved accordingly. However, when the coating interval was increased to the level of example 5, the air permeability was improved, but the liquid retention was decreased, and it was estimated that the porosity was too high and the electrolyte was lost. It can be seen from examples 3, 4 and 6 that the retention can be effectively improved by properly increasing the thickness of the high swelling polymer coating or the low swelling polymer coating at constant coating intervals. And the proportion of the inorganic material and the binder in the coating is all the preferred examples.
Test example 2
The polymer batteries prepared in comparative examples and examples 1 to 6 were subjected to a battery needle test. The test method comprises the following steps: the cell was then monitored for voltage drop and temperature rise at 25 ℃ by penetrating the cell at a depth of 6mm perpendicular to the cell surface at a rate of 0.1mm/s using a stainless steel needle of 1mm diameter and the cell was brought to full charge before testing. The results are shown in Table 2.
TABLE 2
As can be seen from the data of examples 1 to 3 in table 2, as the coating interval of the high-swelling polymer coating increases, the coating amount of the high-swelling polymer coating decreases, the pressure drop of the battery needling increases, and the temperature rise increases, so that the gel layer is supposed to effectively increase the contact resistance, reduce the temperature rise, and slow down the thermal runaway of the battery. As can be seen from examples 3 and 6, the increased thickness of the low swell ratio polymer coating also has some reduction in the needle pressure drop and temperature rise.
Test example 3
The swelling capacity of the polymer coating is tested by placing a certain amount of polymer slurry in a culture dish, drying to form a film with a thickness of about 0.5mm, cutting the film into 2cm × 2cm, and accurately weighing the film with a mass m0Then placing the cut adhesive film and 20mL of electrolyte into a sample tube, heating to 70 ℃ and keeping for 24h, then taking out the swollen adhesive film, wiping off the liquid electrolyte on the surface, and quickly weighing the adhesive film with the mass m1The swelling degree is tau 100% × (m)1-m0)/m0. The results are shown in Table 2.
TABLE 3
As can be seen from the test results of the comparative examples and examples, the polymer batteries using the multi-layer coated separator according to the present invention have improved liquid retention, wettability, interfacial uniformity, and safety.
Compared with the existing diaphragm, in the design of the multilayer coating diaphragm, the low-swelling-rate polymer coating can improve the mechanical strength of the diaphragm and ensure the adhesion between the diaphragm and an electrode; the high swelling rate polymer coating can improve the electrolyte retaining amount in the battery, and the high swelling rate polymer coating can complement each other through different actions of the coatings, so that the infiltration capacity of the gluing diaphragm is greatly improved, the cohesiveness between the electrode and the diaphragm is enhanced, the interface consistency is ensured, and the electrochemical performance and the safety performance of the battery are improved.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A multilayer coated separator comprising a separator substrate and a multilayer polymeric coating coated on the separator substrate;
the multi-layer polymeric coating includes a low swell ratio polymeric coating and a high swell ratio polymeric coating;
the polymer coating with low swelling ratio is uniformly coated on the surface of the diaphragm base material;
the high swelling ratio polymer coating is coated on the low swelling ratio polymer coating at intervals.
2. The multilayer coated separator according to claim 1, wherein the high swelling polymer coating component has a maximum swelling liquid-absorbing capacity of 20 to 100% by mass in the electrolyte, and the low swelling polymer coating component has a maximum swelling liquid-absorbing capacity of 20% or less by mass in the electrolyte.
3. The multilayer coated separator of claim 1, wherein the separator substrate is at least one of PE, PP, cellulose, PET, PI, non-woven fabric, and electrospun separator.
4. The multilayer coated separator according to claim 1, wherein a raw material forming the polymer coating layer is a polymer binder slurry, or a mixed slurry of a polymer binder and an inorganic material;
the inorganic material is preferably at least one of aluminum oxide, magnesium hydroxide, layered composite oxide, boehmite, silicon dioxide and silicon carbide;
the polymer binder comprises a high swelling ratio polymer binder and a low swelling ratio polymer binder;
the high-swelling-rate polymer binder is preferably at least one of polyvinylidene fluoride and polyacrylonitrile, and the low-swelling-rate polymer binder is preferably at least one of polyethylacrylate, polymethyl methacrylate and ethylene-tetrafluoroethylene copolymer;
the mass fraction of the inorganic material in the mixed slurry is 0-90%, and the mass fraction of the polymer binder is 10-100%.
5. The multilayer coated separator of claim 1, wherein the multilayer polymeric coating is at least two layers;
the multilayer polymeric coating is coated on one or both sides of the separator substrate.
6. The multilayer coated separator of claim 1, wherein the combined thickness of the low-swell-ratio polymer coating and the high-swell-ratio polymer coating is no greater than 6 μ ι η;
the thickness of the low swelling ratio polymer coating is 1-2 mu m;
the thickness of the high swelling ratio polymer coating is 2-4 mu m;
the high swelling polymer coating is preferably applied at striped diagonal intervals, the coating intervals being in the range of 500 μm to 2 mm.
7. A polymer battery comprising positive and negative electrodes and a separator, the separator being the multilayer coated separator of any one of claims 1 to 6.
8. The method for preparing the polymer battery according to claim 7, comprising the steps of:
(1) uniformly coating the slurry of the low-swelling-rate polymer coating on the surface of the diaphragm base material in a gravure coating mode, and coating the slurry of the high-swelling-rate polymer coating on the diaphragm base material at intervals to obtain a multilayer coating diaphragm;
(2) regularly stacking or winding a certain number of positive and negative pole pieces and the multilayer coating diaphragm together, and packaging the positive and negative pole pieces and the multilayer coating diaphragm into a polymer battery by using an aluminum-plastic film;
(3) after the battery is injected with liquid, the battery is placed into a pressure formation cabinet for heating and pressure formation, and the coating of the multilayer coating diaphragm swells and is firmly combined with the pole piece under the action of pressure;
(4) and after the battery after hot pressing is connected with charge and discharge equipment for capacity grading, degassing and tightening the battery until no free electrolyte exists in the battery core.
9. The polymer battery produced by multi-layer coating of a separator according to claim 8, wherein the slurry of the high-swelling polymer coating layer comprises an inorganic material, a high-swelling polymer binder, and an organic solvent;
the slurry of the low swelling ratio polymer coating comprises an inorganic material, a low swelling ratio polymer binder and an organic solvent;
the organic solvent is preferably NMP; the inorganic material is preferably at least one of aluminum oxide, magnesium hydroxide, layered composite oxide, boehmite, silicon dioxide and silicon carbide.
10. The polymer battery prepared by the multilayer coating of the diaphragm of claim 8, wherein the positive and negative pole pieces are in direct contact with the high swelling ratio polymer coating;
the temperature range for preparing the polymer battery is 60-85 ℃, and the pressure range is 0.1-0.8 MPa;
the polymer battery is at least one of a soft package battery, a cylindrical battery and a square aluminum shell battery, and the soft package battery is preferred.
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