CN111755648A - Asymmetric coating composite diaphragm and preparation method and application thereof - Google Patents
Asymmetric coating composite diaphragm and preparation method and application thereof Download PDFInfo
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- CN111755648A CN111755648A CN201910237760.7A CN201910237760A CN111755648A CN 111755648 A CN111755648 A CN 111755648A CN 201910237760 A CN201910237760 A CN 201910237760A CN 111755648 A CN111755648 A CN 111755648A
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- H01—ELECTRIC ELEMENTS
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- H01M10/05—Accumulators with non-aqueous electrolyte
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Abstract
The invention discloses an asymmetric coating composite diaphragm and a preparation method and application thereof. The asymmetric coating composite diaphragm comprises a base film and coatings with different components and functions, wherein the coatings are respectively coated on the A surface and the B surface of the base film; the asymmetric coating comprises at least one inorganic functional layer coated on one side of the base film and at least one organic functional layer coated on the other side of the base film; wherein the inorganic functional layer comprises an inorganic ion conductor and the organic functional layer comprises an organic polymer. The invention also provides a preparation method of the asymmetric coating composite diaphragm and application of the asymmetric coating composite diaphragm in a lithium ion battery. The inorganic ion conductor functional layer and the organic polymer functional layer which are coated on the two surfaces of the base film in an asymmetric way are used for realizing the synergistic effect of different functional layers, and 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 are achieved.
Description
Technical Field
The invention relates to the technical field of diaphragms. And more particularly, to an asymmetrically coated composite separator, a method of preparing the same, and applications thereof.
Background
In the lithium ion battery, the diaphragm is one of the key materials of the lithium battery, mainly plays a role in isolating positive and negative electrode materials and conducting lithium ions, and the quality of the performance directly determines the specific energy density, the cycle performance and the safety performance of the lithium ion battery.
At present, the thermal stability of the diaphragm is improved by coating a ceramic layer on a polyolefin diaphragm in the market, for example, by providing a modified alumina ceramic coated diaphragm in CN 206758535U, the thermal stability, moisture absorption and liquid retention of the alumina ceramic coated diaphragm are improved, and the safety performance, rate discharge and safety performance of the lithium battery diaphragm are improved. CN107611326A uses a cyclodextrin compound as an aqueous binder in the aqueous slurry, so that the water absorption of the aqueous ceramic powder coating diaphragm is reduced, and the heat resistance and the high-rate charge-discharge efficiency of the lithium ion battery are improved. And the use of organic solvent is avoided, so that the method is safe and environment-friendly, and the production cost is reduced. In CN109411681A, by introducing inorganic ceramic particles at the positive electrode side and introducing vulcanized polyacrylonitrile at the negative electrode side, the thermal stability of the diaphragm is improved, and the growth of lithium dendrites is effectively inhibited. The prior art is to coat a ceramic coating on the surface of the separator, which can effectively improve the thermal stability of the separator, but also can increase the impedance of the battery, so that the reproducibility of the data of the battery is poor. This is especially true for ternary systems with higher specific energies, which is also a limiting factor for the failure of ternary materials to be applied on a large scale.
Therefore, the invention provides an asymmetric coating composite diaphragm and a preparation method and application thereof, and aims to solve the technical problems.
Disclosure of Invention
A first object of the present invention is to provide an asymmetrically coated composite separator. The asymmetrically coated composite diaphragm can provide a transmission channel for lithium ions in the process of charging and discharging, improves the stability to lithium, and has higher ionic conductivity and lower interface impedance.
The second purpose of the invention is to provide a preparation method of the asymmetric coating composite diaphragm. According to the invention, the inorganic ion conductor coating and the organic polymer coating are respectively coated on the two sides of the diaphragm, so that the asymmetric coating composite diaphragm is successfully prepared.
A third object of the present invention is to provide an application of the asymmetrically coated composite separator.
A fourth object of the present invention is to provide an inorganic paint.
In order to achieve the purpose, the invention adopts the following technical scheme:
an asymmetrically coated composite separator comprising a base film and an asymmetric coating layer coated on the base film; the asymmetric coating comprises at least one inorganic coating coated on the positive side of the base film and at least one organic coating coated on the negative side of the base film; wherein the inorganic coating comprises an inorganic ionic conductor and the organic coating comprises an organic polymer.
Preferably, the raw materials of the inorganic coating comprise the following components in parts by weight:
preferably, the inorganic ion conductor is one or more of lithium aluminum germanium phosphate, lithium aluminum titanium phosphate and lithium lanthanum zirconium oxide.
Preferably, the binder is polyvinylidene fluoride (PVDF).
Preferably, the plasticizer is dibutyl phthalate (DBP).
Preferably, the coupling agent is gamma-glycidoxypropyltrimethoxysilane (KH 560).
Preferably, the wetting dispersant is BYK 111.
Preferably, the wetting agent a is BYK 307.
Preferably, the solvent is an organic solvent; further, the organic solvent is N-methylpyrrolidone (NMP).
Preferably, the raw materials of the organic coating comprise the following components in parts by weight:
preferably, the water-based binder is one or more of BYK-LPC22346 and BM 451B.
Preferably, the dispersing agent is one or more of BYK-LPC22136, BYK-W980 and BYK-W965.
Preferably, the defoaming agent is one or more of BYK-1785, alcohol and triol ether.
Preferably, the wetting agent B is BYK-LPX 20990.
Preferably, the anti-settling agent is LAPONITE RD.
Preferably, the organic polymer is polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene, polymethyl methacrylate, aramid, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer or polyaniline.
Preferably, the thickness of the base film is 5 to 25 μm.
Preferably, the thickness of the inorganic coating is 1-12 μm.
Preferably, the thickness of the organic coating is 1-10 μm.
Preferably, the base film is a polypropylene film, a polyethylene film or a polypropylene-polyethylene-polypropylene combined film.
Preferably, the inorganic ion conductor is in the form of particles, and the particle size of the inorganic ion conductor is 0.2 to 3 μm.
The invention also provides a preparation method of the asymmetric coating composite diaphragm, which comprises the following steps:
1) preparing inorganic coating slurry:
mixing and ball-milling an inorganic ion conductor, a plasticizer, a coupling agent, a wetting dispersant, a wetting agent A and a part of solvent for 3-12 hours according to a ratio to obtain a mixture A;
mixing and stirring the binder and the residual solvent for 3-12 hours to obtain a mixture B;
shearing, stirring and dispersing the mixture A and the mixture B at a high speed for 3-12 h, and filtering by using 100-mesh and 300-mesh filter cloth to obtain inorganic coating slurry;
2) preparing organic coating slurry:
mixing and stirring a dispersing agent, a defoaming agent, a wetting agent B and deionized water to obtain a mixture C;
mixing and stirring the mixture C and the organic polymer for pre-dispersion to obtain slurry A;
ball-milling the slurry A for 3-12 h to obtain slurry B;
mixing and stirring the slurry B and the anti-settling agent for 20-60 min to obtain slurry C;
shearing, stirring and dispersing the slurry C and the water-based binder at a high speed for 0.5-5 h, and filtering with a filter cloth of 100 meshes and 300 meshes to obtain organic coating slurry;
3) uniformly coating inorganic coating slurry on one surface of a base film; uniformly coating the organic coating slurry on the other side of the base film; and drying to obtain the asymmetric coating composite diaphragm.
Preferably, the viscosity of the inorganic coating slurry in the step 1) is 30 to 100 mPas.
Preferably, the viscosity of the organic coating slurry in the step 2) is 10-20 mPa & s.
Preferably, the rotation speed of the ball milling process in the step 1) is 100-400 rpm.
Preferably, the rotation speed of the ball milling process in the step 2) is 100-400 rpm.
Preferably, the coating speed in the step 3) is 0.5-5 m/min, and the drying temperature is 50-70 ℃.
The invention also provides application of the asymmetric coating composite diaphragm in a lithium ion battery.
The invention also provides an inorganic coating, which comprises the following components in parts by weight:
it will be understood by those skilled in the art that the definitions of the inorganic ion conductor, binder, plasticizer, coupling agent, wetting dispersant, wetting agent a and solvent in the inorganic coating are the same as those of the components in the inorganic coating.
In addition, unless otherwise specified, any range recited herein includes any value between the endpoints and any sub-range defined by any value between the endpoints or any value between the endpoints.
The invention has the following beneficial effects:
according to the invention, the inorganic ion conductor coating and the organic polymer coating with synergistic effect are respectively coated on the two sides of the base film, so that the thermal stability of the diaphragm can be improved, the liquid absorption rate and the ionic conductivity of the diaphragm can be improved, and the interface impedance of the diaphragm can be reduced.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
Fig. 1 shows an sem image of the LAGP coating in the asymmetrically coated LAGP-PP-P (VDF-HFP) composite separator prepared in example 1.
Fig. 2 shows a scanning electron micrograph of PVDF-P (VDF-HFP) coating in the asymmetrically coated composite membrane of LAGP-PP-P (VDF-HFP) made in example 1.
Fig. 3 shows the thermal shrinkage profile of the asymmetrically coated LAGP-PP-P (VDF-HFP) composite separator prepared in example 1.
Fig. 4 shows a graph of discharge performance of a lithium ion battery comprising the LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator prepared in example 1.
Fig. 5 shows a graph of rate performance of a lithium ion battery comprising the LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator prepared in example 1.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
The prior battery separator is generally coated with a ceramic layer on the surface to improve the thermal stability of the separator, however, the battery separator coated with the ceramic layer has high battery impedance and low ionic conductivity. Therefore, the invention provides the asymmetrically coated composite diaphragm, and the inorganic ion conductor coating and the organic polymer coating are respectively coated on the two sides of the base film, so that the thermal stability of the diaphragm can be improved, the liquid absorption rate and the ionic conductivity of the diaphragm can be improved, and the interface impedance of the diaphragm can be reduced.
Specifically, the invention provides an asymmetric coating composite diaphragm, which comprises a base film and an asymmetric coating coated on the base film; the asymmetric coating comprises at least one inorganic coating coated on one side of the base film and at least one organic coating coated on the other side of the base film; wherein the inorganic coating comprises an inorganic ionic conductor and the organic coating comprises an organic polymer. The inorganic coating comprising the inorganic ion conductor is an oily system, and the organic coating comprising the organic polymer is an aqueous system, so that the problem that the organic solvent on one side dissolves the coating on the other side in the coating process is solved; in addition, the synergistic effect of the inorganic coating layer including the inorganic ion conductor and the organic coating layer including the organic polymer not only improves the stability of the battery separator to lithium, but also has higher ionic conductivity and lower interfacial resistance.
Further, the raw materials of the inorganic coating comprise the following components in parts by weight:
the inorganic coating is used for improving the thermal stability of the diaphragm, improving the liquid absorption rate of the diaphragm and improving the ionic conductivity of the diaphragm, and in addition, the type and the proportion of the raw materials in the formula of the inorganic coating coated on the surface of the diaphragm are adjusted, so that the obtained asymmetric coating composite diaphragm has higher thermal stability, higher liquid absorption rate, higher ionic conductivity and lower interface impedance; wherein, the inorganic ion conductor is used for conducting lithium ions and improving the thermal stability; the binder is used for effectively adhering the inorganic ion conductor particles, the coating and the base film together; the plasticizer is used for enhancing the flexibility of the diaphragm; the coupling agent is used for improving the interface effect of the organic diaphragm and the inorganic ion conductor; the wetting dispersant exists in the solvent phase in the form of small particles in which the inorganic ionic conductor is stabilized; the wetting agent A enables the inorganic ion conductor particles to rapidly enter a solvent phase; the solvent functions as a dispersion medium.
Further, the inorganic ion conductor is one or more of germanium aluminum lithium phosphate, titanium aluminum lithium phosphate and lithium lanthanum zirconium oxide; the binder is polyvinylidene fluoride (PVDF); the plasticizer is dibutyl phthalate (DBP); the coupling agent is gamma-glycidoxypropyltrimethoxysilane (KH 560); the wetting dispersant is BYK 111; the wetting agent is BYK 307; the solvent is N-methyl pyrrolidone. The invention optimizes the reagent to obtain the composite membrane with better performance.
In a preferred embodiment, the inorganic ion conductor is in the form of particles having a particle size of 0.2 to 3 μm; according to the invention, the particle size of the inorganic ion conductor is controlled within the range, so that the coated diaphragm with a smooth surface, uniform properties and smaller thickness is obtained.
Further, the raw materials of the organic coating comprise the following components in parts by weight:
50-100 parts of deionized water.
The organic coating is used for improving the liquid absorption rate of the diaphragm and reducing the interface impedance generated by contact with a lithium cathode, and the obtained asymmetric battery diaphragm has higher thermal stability, higher liquid absorption rate, higher ionic conductivity and lower interface impedance by adjusting the types and the proportions of raw materials in the formula of the organic coating coated on the surface of the battery diaphragm; wherein, the organic polymer has the functions of improving the liquid absorption rate and reducing the interface impedance; the aqueous binder effectively adheres the organic polymer particles and the coating and the base film; the dispersant causes the organic polymer to be present in the solvent phase in the form of stable small particles; the defoaming agent is used for reducing the surface tension of the organic coating slurry and inhibiting or reducing the generation of foam; wetting agent B causes the organic polymer particles to rapidly enter the aqueous phase; the anti-settling agent is used for preventing organic polymer particles from agglomerating and settling into the bottom of the water phase; deionized water was used for the dispersed phase.
As a preferred embodiment, the aqueous binder is BYK-LPC 22346; the dispersant is BYK-LPC 22136; the defoaming agent is BYK-1785; the wetting agent is BYK-LPX 20990; the anti-settling agent is laponited; the organic polymer is polyvinylidene fluoride, polymethyl methacrylate, aramid fiber, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer or polyaniline. The invention optimizes the reagent to obtain the composite membrane with better performance.
As a preferred embodiment, the thickness of the base film is 5 to 25 μm; the thickness of the inorganic coating is 1-12 mu m; the thickness of the organic coating is 1-10 mu m.
As a preferred embodiment, the base film is a polypropylene film, a polyethylene film, or a polypropylene-polyethylene-polypropylene combined film. The invention optimizes the base film to obtain the asymmetric coating composite diaphragm with better performance.
The invention also provides a preparation method of the asymmetric coating composite diaphragm, which comprises the following steps:
1) preparing inorganic coating slurry:
mixing and ball-milling an inorganic ion conductor, a plasticizer, a coupling agent, a wetting dispersant, a wetting agent A and a part of solvent for 3-12 hours according to a ratio to obtain a mixture A;
mixing and stirring the binder and the residual solvent for 3-12 hours to obtain a mixture B;
shearing, stirring and dispersing the mixture A and the mixture B at a high speed for 3-12 h, and filtering by using 100-mesh and 300-mesh filter cloth to obtain inorganic coating slurry; the inorganic coating slurry prepared by the method has stable performance, and the sedimentation rate is less than 1mm in 24 hours before;
2) preparing organic coating slurry:
mixing and stirring a dispersing agent, a defoaming agent, a wetting agent B and deionized water to obtain a mixture C;
mixing and stirring the mixture C and the organic polymer for pre-dispersion to obtain slurry A;
ball-milling the slurry A for 3-12 h to obtain slurry B;
mixing and stirring the slurry B and the anti-settling agent for 20-60 min to obtain slurry C;
shearing, stirring and dispersing the slurry C and the water-based binder at a high speed for 0.5-5 h, and filtering with a filter cloth of 100 meshes and 300 meshes to obtain organic coating slurry; the organic coating slurry prepared by the method has stable performance, and the sedimentation rate is less than 1mm in 24h before;
3) uniformly coating inorganic coating slurry on one surface of a base film; uniformly coating the organic coating slurry on the other side of the base film; and drying to obtain the asymmetric coating composite diaphragm. It should be understood by those skilled in the art that the amount of the solvent mixed with the inorganic ion conductor, the plasticizer, the coupling agent, the wetting dispersant and the wetting agent a in step 1), and the amount of the solvent mixed with the binder can be adjusted according to actual needs, which is a conventional technical means, and the present invention is not limited thereto.
As a preferred embodiment, the viscosity of the inorganic coating slurry in step 1) is 30 to 100mPa · s.
As a preferred embodiment, the viscosity of the organic coating slurry in the step 2) is 10 to 20mPa · s.
As a preferred embodiment, the rotation speed of the ball milling process in the step 1) is 100-400 rpm.
As a preferred embodiment, the rotation speed of the ball milling process in the step 2) is 100-400 rpm.
As a preferable embodiment, the coating speed in the step 3) is 0.5-5 m/min, and the drying temperature is 50-70 ℃.
According to the invention, the performance of the obtained asymmetric coating composite diaphragm is better by adjusting the operation parameters in the preparation method.
The invention also provides application of the asymmetric coating composite diaphragm in a lithium ion battery.
The invention also provides an inorganic coating, which comprises the following components in parts by weight:
in the present invention, the production method is a conventional method unless otherwise specified, and the raw materials used are commercially available from public places unless otherwise specified.
Example 1
An asymmetric coating composite diaphragm comprises a base film and an asymmetric coating coated on the base film; the asymmetric coating comprises an inorganic coating coated on one side of the base film and an organic coating coated on the other side of the base film; wherein the content of the first and second substances,
the raw materials of the inorganic coating comprise:
the organic coating comprises the following raw materials:
the base film is a polypropylene film (namely a PP film, the model is celgard 2500).
The preparation method of the asymmetric coating composite diaphragm comprises the following steps:
1) preparing inorganic coating slurry:
20g of Li1.5Al0.5Ge1.5(PO4)31g of DBP, 1g of KH560, 3g of BYK111, 1g of BYK307 and 50g of NMP, and performing mixed ball milling for 12 hours to obtain a mixture A;
mixing and stirring 2g of PVDF and 20g of NMP for 5 hours to obtain a mixture B;
shearing, stirring and dispersing the mixture A and the mixture B at a high speed for 5h, and filtering by using a filter cloth with 100-300 meshes to obtain inorganic coating slurry with the viscosity of 50mPas, wherein the sedimentation rate is less than 1mm in the first 24 h;
2) preparing organic coating slurry:
mixing and stirring 4g of BYK-LPC22136, 1g of BYK-LPX20990, 1g of BYK-1785 and 70g of deionized water for 5 hours to obtain a mixture C;
mixing and stirring the mixture C and 20g of PVDF-P (VDF-HFP) for pre-dispersion for 60min to obtain slurry A;
ball-milling the slurry A for 12h to obtain slurry B;
mixing and stirring the slurry B and 1g of LAPONITE RD for 20-60 min to obtain slurry C;
shearing, stirring and dispersing the slurry C and 4g of BYK-LPC22346 at a high speed for 3h, and filtering by using a filter cloth with 100 meshes and 300 meshes to obtain organic coating slurry with the viscosity of 10mPas, wherein the 24h before the sedimentation rate is less than 1 mm;
3) uniformly coating the inorganic coating slurry obtained in the step 1) on one surface of a PP film by using an automatic film coating machine, and drying for 2h at the temperature of 55 ℃;
uniformly coating the organic coating slurry obtained in the step 2) on the other surface of the PP film by using an automatic coating machine, and drying for 3 hours at 50 ℃; the LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator was obtained.
Scanning electron micrographs of the prepared LAGP-PP-P (VDF-HFP) asymmetrically coated composite membrane are shown in fig. 1 and fig. 2, wherein fig. 1 is a scanning electron micrograph of a LAGP coating, and fig. 2 is a scanning electron micrograph of a PVDF-P (VDF-HFP) coating. The PP separator had a thickness of 25 microns before coating and a separator thickness of 30 microns after coating, with a lag inorganic coating thickness of 2 microns and a PVDF-P (VDF-HFP) organic coating thickness of 3 microns. The LAGP-PP-P (VDF-HFP) composite separator coating thickness, pick-up, conductivity, and interfacial resistance data are compared in Table 1, and the heat shrinkage data are compared in FIG. 3, where the curve ● is the heat shrinkage curve of the PP-based film at the pending temperature, and the curve O is the heat shrinkage curve of the LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator at the pending temperature.
The resulting LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator was subjected to charge and discharge performance testing using button cell CR 2032:
using NCM811 as positive electrode and lithium metal as contrast electrode, LAGP-PP-P (VDF-H)FP) asymmetric coating composite diaphragm as diaphragm, 1mol/L LiPF6(volume ratio is Ethylene Carbonate (EC): dimethyl carbonate (DMC): methyl ethyl carbonate (EMC): 1: 1: 1) as electrolyte, and assembled into the cell CR2032 button cell in an argon-protected glove box. And (3) carrying out multiplying power charge and discharge test on the battery on a Land tester, wherein the multiplying power of charge and discharge is 0.2C, and the charge and discharge voltage interval is 3.0-4.2V. The battery adopting LAGP-PP-P (VDF-HFP) to asymmetrically coat the composite diaphragm has the initial discharge capacity of 192mAh/g at 0.2C, the capacity of 185mAh/g after 100 cycles, and the capacity retention rate of 96%.
As shown in fig. 4 and 5, curve ● in fig. 4 is the discharge performance curve of the lithium ion battery using the lag P-PP-P (VDF-HFP) asymmetrically coated composite separator prepared in the present example, and curve o is the discharge performance curve of the lithium ion battery using the alumina organic separator prepared in comparative example 1; in fig. 5, the curve ● is the rate performance curve of the lithium ion battery using the LAGP-PP-P (VDF-HFP) asymmetrically coated composite separator prepared in the present example, and the curve o is the rate performance curve of the lithium ion battery using the alumina organic separator prepared in comparative example 1.
The results show that: compared with the traditional PP diaphragm and the traditional alumina coating diaphragm, the double-sided asymmetric coating composite diaphragm can effectively improve the liquid absorption rate and the thermal stability, obviously improve the ionic conductivity, obviously reduce the interface impedance and has excellent cycle performance and rate capability.
Example 2
An asymmetrically coated composite separator, similar to example 1, except that the base film was a polyethylene film (i.e., PE film) having a thickness of 16 microns, the lag inorganic coating thickness was 5 microns, and the P (VDF-HFP) organic coating thickness was 3 microns; LAGP-PE-P (VDF-HFP) asymmetrically coated composite membranes were obtained, the performance data of which are compared in Table 1.
Example 3
An asymmetrically coated composite separator, as in example 1, except that the lag inorganic ion conductor coating thickness was 12 microns, and the P (VDF-HFP) coating thickness was 5 microns; LAGP-PP-P (VDF-HFP) asymmetrically coated composite membranes were obtained, the performance data of which are compared in Table 1.
Example 4
An asymmetrically coated composite separator, similar to example 1, except that the inorganic ion conductor in the inorganic coating layer is Li1.5Al0.5Ti1.5(PO4)3(LATP) with a thickness of 2 μm of the inorganic coating; the organic polymer in the organic coating is PVDF-HFP, and the thickness of the organic coating is 3 microns; the LATP-PP-P (VDF-HFP) asymmetrically coated composite separator was obtained and the composite separator performance data are compared in Table 1.
Comparative example 1
A separator was obtained as in example 1, except that aluminum oxide was used in place of Li in the inorganic coating layer1.5Al0.5Ge1.5(PO4)3The thickness of the inorganic coating is 2 microns, and the inorganic coating is free of organic coating; the performance data of the prepared aluminum oxide organic diaphragm are compared and shown in the table 1.
Comparative example 2
A separator, similar to example 1, except that the inorganic coating layer was Li1.5Al0.5Ge1.5(PO4)32 μm thick without organic coating; LAGP-PP films were prepared and the performance data are compared in Table 1.
Comparative example 3
A separator, identical to example 1, except that the PP film was uncoated on both sides, the performance data are compared in table 1.
Comparative example 4
A separator, as in comparative example 3, except that a PE film was used instead of a PP film, the performance data are compared in table 1.
Comparative example 5
An asymmetrically coated composite separator, similar to example 1, is different only in that the wetting dispersant is 1 part (i.e. 1g) in the inorganic slurry, and the obtained coated separator has a serious missing coating phenomenon and cannot be used in subsequent experiments.
Comparative example 6
An asymmetrically coated composite separator is similar to example 1, except that wetting agent B is not added into the organic slurry, and the obtained coated separator has uneven surface and serious agglomeration of organic polymer particles, and cannot be used in subsequent experiments.
Comparative example 7
A separator, the same as example 1, except that the organic coating layer was P (VDF-HFP) and 3 μm thick, and no inorganic coating layer; p (VDF-HFP) -PP films were produced, the performance data of which are compared in Table 1.
TABLE 1 Table of performance data for comparison of the separators prepared in examples 1-4 and comparative examples 1-4 with conventional composite separators
As can be seen from table 1, the liquid absorption rate and the ionic conductivity of the double-sided asymmetrically coated composite separator are significantly improved and the interface impedance is reduced compared with a PP separator, a PE separator, a single-sided AL-PP separator, a single-sided LAGP-PP separator, and a single-sided P (VDF-HFP) -PP separator.
Test example
The thermal stability of the asymmetrically coated composite separator was tested by the following steps:
the results are shown in table 2 and show that: compared with a PP diaphragm, a single-side AL-PP diaphragm and a single-side LAGP-PP diaphragm, the thermal stability of the double-side asymmetrically coated composite diaphragm is obviously improved.
TABLE 2 thermal stability of different asymmetrically coated composite membranes
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (10)
1. The asymmetric coating composite diaphragm is characterized by comprising a base film and asymmetric coatings coated on the A surface and the B surface of the base film; the asymmetric coating comprises at least one inorganic coating coated on one side of the base film and at least one organic coating coated on the other side of the base film; wherein the coating material of the inorganic coating layer comprises an inorganic ion conductor, and the coating material of the organic coating layer comprises an organic polymer.
2. The asymmetrically coated composite separator according to claim 1, wherein the raw material of the inorganic coating comprises the following components in parts by weight:
3. the asymmetrically coated composite separator according to claim 1 or 2, wherein the inorganic ion conductor is one or more of lithium aluminum germanium phosphate, lithium aluminum titanium phosphate and lithium lanthanum zirconium oxide.
4. The asymmetrically coated composite separator according to claim 1, wherein the raw materials of the organic coating comprise the following components in parts by weight:
5. the asymmetrically coated composite separator according to claim 1, wherein the thickness of the base film is 5 to 25 μm.
6. The asymmetrically coated composite separator according to claim 1, wherein the inorganic coating layer has a thickness of 1 to 12 μm.
7. The asymmetrically coated composite separator according to claim 1, wherein the organic coating has a thickness of 1 to 10 μm.
8. A method of making an asymmetrically coated composite separator as claimed in any of claims 1 to 7, comprising the steps of:
1) preparing inorganic coating slurry:
mixing and ball-milling an inorganic ion conductor, a plasticizer, a coupling agent, a wetting dispersant, a wetting agent A and a part of solvent for 3-12 hours according to a ratio to obtain a mixture A;
mixing and stirring the binder and the residual solvent for 3-12 hours to obtain a mixture B;
shearing, stirring and dispersing the mixture A and the mixture B at a high speed for 3-12 h, and filtering by using 100-mesh and 300-mesh filter cloth to obtain inorganic coating slurry;
2) preparing organic coating slurry:
mixing and stirring a dispersing agent, a defoaming agent, a wetting agent B and deionized water to obtain a mixture C;
mixing and stirring the mixture C and the organic polymer for pre-dispersion to obtain slurry A;
ball-milling the slurry A for 3-12 h to obtain slurry B;
mixing and stirring the slurry B and the anti-settling agent for 20-60 min to obtain slurry C;
shearing, stirring and dispersing the slurry C and the water-based binder at a high speed for 0.5-5 h, and filtering with a filter cloth of 100 meshes and 300 meshes to obtain organic coating slurry;
3) uniformly coating inorganic coating slurry on one surface of a base film; uniformly coating the organic coating slurry on the other side of the base film; and drying to obtain the asymmetric coating composite diaphragm.
9. Use of an asymmetrically coated composite separator as defined in any of claims 1 to 7 in a lithium ion battery.
10. The inorganic coating is characterized by comprising the following components in parts by weight:
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| CN114188668A (en) * | 2021-12-17 | 2022-03-15 | 蜂巢能源科技股份有限公司 | Coating slurry, preparation method thereof, composite diaphragm and lithium ion battery |
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| CN114188668B (en) * | 2021-12-17 | 2024-02-13 | 蜂巢能源科技股份有限公司 | Coating slurry, preparation method thereof, composite diaphragm and lithium ion battery |
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