CN114649638A - Coated diaphragm and preparation method and application thereof - Google Patents
Coated diaphragm and preparation method and application thereof Download PDFInfo
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- CN114649638A CN114649638A CN202210546423.8A CN202210546423A CN114649638A CN 114649638 A CN114649638 A CN 114649638A CN 202210546423 A CN202210546423 A CN 202210546423A CN 114649638 A CN114649638 A CN 114649638A
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/443—Particulate material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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Abstract
The application discloses a coated diaphragm and a preparation method and application thereof, relating to the technical field of secondary batteries. The coated separator includes: the base film is a porous film; a heat-resistant layer disposed on at least one side surface of the base film; the point-shaped coating is arranged on one side of the heat-resistant layer and comprises an inorganic point-shaped coating and an organic point-shaped coating, the inorganic point-shaped coating is regularly distributed, and the organic point-shaped coating is randomly distributed between and/or on the inorganic point-shaped coatings. The problem that lithium dendrite phenomenon and potential instability are easily generated in the prior art is solved by arranging the regular inorganic point-like coating and the random organic point-like coating.
Description
Technical Field
The application relates to the field of secondary batteries, in particular to a coated diaphragm and a preparation method and application thereof.
Background
The diaphragm is used as four main components of the lithium battery, and plays roles of blocking electrons and allowing lithium ions to pass between a positive electrode and a negative electrode. Because the diaphragm has poor heat resistance and no adhesion effect with a positive electrode and a negative electrode, the surface of the diaphragm is usually coated with one or two inorganic heat-resistant layers such as alumina and boehmite heat-resistant layers in the prior art, and then the heat-resistant layers are coated with one organic adhesion layer such as PVDF (polyvinylidene fluoride) and PMMA (polymethyl methacrylate).
In order to improve the phenomenon, the chinese patent publication No. CN111916627A discloses a lithium ion battery and a diaphragm thereof, wherein an organic coating is coated longitudinally on the diaphragm, the organic coating comprises a strip-shaped coating body and a dot-shaped coating body, and the design can provide a certain space for the expansion of a pole piece in the processes of charging and discharging and circulation. However, the regular design in this technical solution has certain disadvantages: firstly, the lithium ion battery is bonded with a pole piece at equal intervals in the longitudinal direction, so that lithium ions are easily enriched in the longitudinal direction to cause lithium absorption and generate a lithium dendrite phenomenon; secondly, the strip-shaped coating body enables the lithium ion shuttle diaphragm to be easily divided into regions to shuttle, and the potential between the positive electrode and the negative electrode generates regular strength and weakness, so that the potential is unstable.
Disclosure of Invention
The application aims to provide a coating diaphragm and a preparation method and application thereof, and solves the problems that lithium dendrite phenomenon is easy to generate and potential is unstable in the prior art by arranging a regular inorganic point-shaped coating and a random organic point-shaped coating.
In order to achieve the above purpose, the embodiments of the present application adopt the following technical solutions: a coated separator comprising: the base membrane is a porous film; a heat-resistant layer disposed on at least one side surface of the base film; the point coating is arranged on one side of the heat-resistant layer and comprises inorganic point coatings and organic point coatings, the inorganic point coatings are regularly distributed, and the organic point coatings are randomly distributed among and/or on the inorganic point coatings.
In the technical scheme, the inorganic point-shaped coating is coated on the heat-resistant layer, so that the inorganic point-shaped coating cannot be compressed when the diaphragm and the pole piece are bonded and hot-pressed, the original height is kept, and a supporting effect can be achieved; and then, an organic dot coating is sprayed between the inorganic dot coatings by adopting a spraying technology, the organic dot coatings are randomly distributed between or on the inorganic dot coatings, when the diaphragm is bonded with the pole piece for hot pressing, the organic dot coatings are compressed, after the organic dot coatings are compressed to the height of the inorganic dot coatings, the organic dot coatings are not compressed, the height of the organic dot coatings and the height of the inorganic dot coatings are kept, after electrolyte is injected, the organic dot coatings can absorb the electrolyte and swell, at the moment, because a large space is still reserved between the inorganic dot coatings and is enough for the swelling of the organic dot coatings, the bulging phenomenon of the battery can not be caused, the space between the inorganic dot coatings can store the electrolyte, and the liquid storage performance of the battery is improved. Furthermore, the inorganic point coating can solve the phenomenon of regional penetration of lithium ions of the strip-shaped inorganic layer, and avoid the instability of potential voltage caused by the strength of the regularity of potential; the randomly distributed organic point-shaped coating enables the bonding position of the diaphragm and the pole piece to have randomness, and the phenomenon of regional bonding or non-bonding can be avoided, so that the phenomenon that lithium ions are enriched in the bonding position to generate lithium dendrites can be avoided.
Further, according to the embodiment of the present application, wherein the porous film is a polypropylene film, a polyethylene film or a polyethylene/polypropylene composite film.
Further, according to the embodiment of the application, the thickness of the heat-resistant layer is 0.5-3.5 mu m.
Further, according to the embodiment of the present application, the heat-resistant layer and the inorganic dot coating layer include ceramic particles, a stabilizer, glue and a wetting agent.
Further in accordance with an embodiment of the present application, wherein the ceramic particles are one or more of alumina, boehmite, silica, and aluminum hydroxide.
Further, according to the embodiment of the present application, wherein the stabilizer is one or more of gelatin, methyl cellulose, carboxymethyl cellulose, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol.
Further, according to the embodiment of the application, the glue is one or more of acrylic acid, styrene butadiene rubber, polystyrene and polyacrylate.
Further, according to the embodiment of the application, the wetting agent is one or more of sodium dodecyl sulfate, fatty alcohol, ethylene oxide, butyl naphthalene sulfonic acid sodium salt and nonylphenol polyoxyethylene ether.
Further, according to the embodiment of the application, the grain size of the ceramic grains of the heat-resistant layer is 0.5-2 mu m.
Further, according to the embodiment of the application, the grain size of the ceramic grains of the inorganic dot coating is 0.2-1 mu m.
Further, according to the embodiment of the present application, wherein the ceramic particles of the inorganic dot coating are porous ceramic.
Further, according to the embodiment of the application, the thickness of the inorganic dot coating is 0.5-3 mu m.
Further, according to the embodiment of the application, the width of the inorganic dot coating is 200-500 mu m.
Further, according to the embodiment of the application, the distance between the inorganic dot-shaped coatings is 1000-.
Further, according to the embodiment of the application, the coverage rate of the inorganic dot coating is 1-25%.
Further, according to the embodiment of the application, the particle size of the organic dot coating ranges from 50 to 500 mu m.
Further, according to the embodiment of the application, the thickness of the organic dot coating is 3-7 mu m.
Further, according to the embodiment of the application, the coverage rate of the organic dot coating is 5-20%.
Further, according to the embodiment of the present application, wherein the organic dot coating comprises an organic binder and glue.
Further, according to the embodiment of the present application, wherein the organic binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, and polymethyl methacrylate.
Further, according to the embodiment of the application, the glue is one or more of acrylic acid, styrene-butadiene rubber, polystyrene and polyacrylate.
In order to achieve the above object, the embodiments of the present application also disclose a method for preparing a coated separator, comprising the steps of:
preparing heat-resistant layer slurry, inorganic dot coating slurry and organic dot coating slurry;
coating the heat-resistant layer slurry on at least one side surface of the base film, and drying to form a heat-resistant layer;
coating the inorganic dotted coating slurry on the heat-resistant layer by using a dotted micro-concave roller, and drying to form an inorganic dotted coating;
and (3) coating organic point coating slurry on the inorganic point coating by using a spraying technology to form an organic point coating which is randomly distributed.
In order to achieve the purpose, the embodiment of the application also discloses application of the coated separator in a lithium battery.
Compared with the prior art, the method has the following beneficial effects: according to the application, the inorganic point-shaped coating is coated on the heat-resistant layer, so that the inorganic point-shaped coating cannot be compressed when the diaphragm and the pole piece are bonded and hot-pressed, the original height is kept, and a supporting effect can be achieved; and then, an organic dot coating is sprayed between the dot-shaped inorganic layers by adopting a spraying technology, the organic dot-shaped coating is randomly distributed between or on the inorganic dot-shaped coatings, when the diaphragm is bonded with the pole piece for hot pressing, the organic dot-shaped coating is compressed, after the organic dot-shaped coating is compressed to the height of the inorganic dot-shaped coating, the organic dot-shaped coating is not compressed, the height of the organic dot-shaped coating and the height of the inorganic dot-shaped coating are kept, after electrolyte is injected, the organic dot-shaped coating absorbs the electrolyte and swells, at the moment, because a large space is still reserved between the inorganic dot-shaped coatings, the swelling of the organic dot-shaped coating is enough, the battery swelling phenomenon can not be caused, the space between the inorganic dot-shaped coatings can store the electrolyte, and the liquid storage performance of the battery is improved. Furthermore, the inorganic point coating can solve the phenomenon of regional penetration of lithium ions of the strip-shaped inorganic layer, and avoid the instability of potential voltage caused by the strength of the regularity of potential; the randomly distributed organic point-shaped coating enables the bonding position of the diaphragm and the pole piece to have randomness, and the phenomenon of regional bonding or non-bonding can be avoided, so that the phenomenon that lithium ions are enriched in a large amount at the bonding position to generate lithium dendrites can be avoided.
Drawings
FIG. 1 is a schematic diagram of the structure of one of the coated membranes of the present application.
FIG. 2 is a schematic view of a coated separator in accordance with the present application in combination with a pole piece.
FIG. 3 is a perspective view of a coated separator of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clear and fully described, embodiments of the present invention are further described in detail below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of some embodiments of the invention and are not limiting of the invention, and that all other embodiments obtained by those of ordinary skill in the art without the exercise of inventive faculty are within the scope of the invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal", etc. indicate orientations or positional relationships only for the convenience of description and simplification of the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "a," "an," "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
For the purposes of simplicity and explanation, the principles of the embodiments are described by referring mainly to examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that the embodiments may be practiced without these specific details. In some instances, well-known methods and structures have not been described in detail so as not to unnecessarily obscure the embodiments. In addition, all embodiments may be used in combination with each other.
As shown in fig. 1 to 3, the present application discloses a coated separator, which solves the problems of the prior art that a lithium dendrite phenomenon is easily generated and the potential is unstable by providing a regular inorganic dot coating and a random organic dot coating. Specifically, the coated separator includes a base film 1, a heat-resistant layer 2, and a dot coating layer. The base film 1 is a porous film, and specifically, a polypropylene film, a polyethylene film or a polyethylene/polypropylene composite film may be used, without limiting the present application.
The thickness of the heat-resistant layer 2 is 0.5-3.5 mu m, and the heat-resistant layer is arranged on at least one side surface of the base film in a full coating mode to play a heat-resistant role. The heat-resistant layer 2 specifically comprises ceramic particles, a stabilizer, glue and a wetting agent, and the particle size of the ceramic particles is 0.5-2 mu m. Wherein, the ceramic particles are one or more of alumina, boehmite, silica and aluminum hydroxide; the stabilizer is one or more of gelatin, methylcellulose, carboxymethyl cellulose, sodium polyacrylate, polyethylene oxide and polyvinyl alcohol, and the proportion of the stabilizer accounts for 0.05-2wt% of the ceramic particles; the glue is one or more of acrylic acid, styrene-butadiene rubber, polystyrene and polyacrylate, and the proportion accounts for 0.05-8wt% of the ceramic particles; the wetting agent is one or more of sodium dodecyl sulfate, fatty alcohol, ethylene oxide, butyl naphthalene sulfonic acid sodium salt and nonylphenol polyoxyethylene ether, and accounts for 0.05-2wt% of the ceramic particles.
The dot coating comprises an inorganic dot coating 3 and an organic dot coating 4. The inorganic dot-shaped coatings 3 are regularly distributed, and the organic dot-shaped coatings 4 are randomly distributed between and/or on the inorganic dot-shaped coatings 3. In contrast, when the diaphragm is bonded with the pole piece 5 for hot pressing, the inorganic point-shaped coating 3 is not compressed, the original height is kept, and a supporting function can be achieved; and then, a layer of organic dot-shaped coating 4 is sprayed between the inorganic dot-shaped coatings by adopting a spraying technology, the organic dot-shaped coatings 4 are randomly distributed between or on the inorganic dot-shaped coatings 3, when a diaphragm and a pole piece 5 are bonded and hot-pressed, the organic dot-shaped coatings 4 are compressed, after the organic dot-shaped coatings 4 are compressed to the height of the inorganic dot-shaped coatings 3, the organic dot-shaped coatings 4 are not compressed, the height of the organic dot-shaped coatings 3 is kept, after the electrolyte is injected, the organic dot-shaped coatings 4 can absorb the electrolyte to swell, at the moment, because a large space is still reserved between the inorganic dot-shaped coatings 3, the swelling of the organic dot-shaped coatings 4 is enough, the battery swelling phenomenon cannot be caused, the space between the inorganic dot-shaped coatings 3 can store the electrolyte, and the liquid storage performance of the battery is improved.
Furthermore, the inorganic point-like coating 3 can solve the phenomenon of regional penetration of lithium ions of the strip-shaped inorganic layer, and avoid the instability of potential voltage caused by the strength of the regularity of potential; the randomly distributed organic point-shaped coating 4 ensures that the bonding position of the diaphragm and the pole piece 5 has randomness, and can avoid the phenomenon of regional bonding or non-bonding, thereby avoiding the generation of lithium dendrite due to the large enrichment of lithium ions at the bonding position.
Specifically, the inorganic dot coating 3 comprises ceramic particles, a stabilizer, glue and a wetting agent, and except that the particle size range of the ceramic particles is 0.2-1 mu m, the raw materials and the proportion of each component are consistent with those of the heat-resistant layer. In addition, the shape of the inorganic dot-shaped coating 3 is preferably regular square, rectangle or circle, the width is 200-500 mu m, the thickness is 0.5-3 mu m, the distance between the inorganic dot-shaped coatings 3 is 1000-2000 mu m, and the coverage rate is 1-25%, so that the supporting effect of the inorganic dot-shaped coating 3 can be ensured.
Furthermore, the ceramic particles in the inorganic point-shaped coating 3 are preferably porous ceramic particles, the aperture is 30-100 nm, the porosity is 40-65%, and the air permeability of the point-shaped coating is ensured.
The organic dot coating 4 includes an organic binder and glue. Wherein the organic binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer and polymethyl methacrylate. The glue is one or more of acrylic acid, styrene-butadiene rubber, polystyrene and polyacrylate, and accounts for 2-20wt% of the organic binder. The organic dot-shaped coating 4 is formed in a spraying mode, the appearance is similar to a volcanic eruption opening, the particle size range is 50-500 mu m, the thickness is 3-7 mu m, the coverage rate is 5-20%, and the binding force of the organic dot-shaped coating 4 is ensured.
In addition, the application also discloses a preparation method of the coating diaphragm, which comprises the following steps:
preparing heat-resistant layer slurry, inorganic dot coating slurry and organic dot coating slurry, specifically:
preparing the heat-resistant layer slurry comprises the following steps: selecting ceramic particles, adding water, stirring at a high speed of 1500rpm for 1h, then adding a thickening agent, quickly stirring at 1500rpm for 1h, adding glue at a third step, and stirring at 1000rpm for 30 min; finally adding a wetting agent into the mixture, and stirring the mixture for 30min at a low speed of 200rpm to obtain heat-resistant layer slurry;
preparing inorganic dot coating slurry comprises the following steps: selecting ceramic particles with smaller particle size, and preparing heat-resistant layer slurry in the other steps;
preparing organic dot coating slurry comprises the following steps: and (3) completely dispersing water and glue water, then adding an organic adhesive, stirring at a high speed of 1500rpm for 3h, and finally adding water for dilution to obtain the organic dot-shaped coating slurry.
Coating the heat-resistant layer slurry on at least one side surface of the base film, and drying to form a heat-resistant layer, specifically: and (3) fully coating the heat-resistant layer slurry on one side or two sides of the base film by using the twill micro-gravure, drying and rolling.
And (3) coating the inorganic dotted coating slurry on the heat-resistant layer by using a dotted micro-concave roller, and drying to form an inorganic dotted coating.
Using a spraying technology to coat organic point-shaped coating slurry on a point-shaped inorganic ceramic layer to form a randomly distributed point-shaped organic coating, specifically: and spraying the prepared organic dot coating slurry between the inorganic dot coatings randomly by adopting a rotary spraying or airflow spraying mode.
When the coated diaphragm is applied to a lithium battery, the inorganic point-shaped coating cannot be compressed when the diaphragm is bonded with a pole piece and is hot-pressed, the original height is kept, and a supporting effect can be achieved; and then, an organic dot coating is sprayed between the inorganic dot coatings by adopting a spraying technology, the organic dot coatings are randomly distributed between or on the inorganic dot coatings, when the diaphragm is bonded with the pole piece for hot pressing, the organic dot coatings are compressed, after the organic dot coatings are compressed to the height of the inorganic dot coatings, the organic dot coatings are not compressed, the height of the organic dot coatings and the height of the inorganic dot coatings are kept, after electrolyte is injected, the organic dot coatings can absorb the electrolyte and swell, at the moment, because a large space is still reserved between the inorganic dot coatings and is enough for the swelling of the organic dot coatings, the bulging phenomenon of the battery can not be caused, the space between the inorganic dot coatings can store the electrolyte, and the liquid storage performance of the battery is improved. Furthermore, the inorganic point coating can solve the phenomenon of regional penetration of lithium ions of the strip-shaped inorganic layer, and avoid the instability of potential voltage caused by the strength of the regularity of potential; the randomly distributed organic point-shaped coating enables the bonding position of the diaphragm and the pole piece to have randomness, and the phenomenon of regional bonding or non-bonding can be avoided, so that the phenomenon that lithium ions are enriched in a large amount at the bonding position to generate lithium dendrites can be avoided.
Finally, the technical effects of the present application will be further described below by way of examples and comparative examples, but the present application is not limited to these examples.
[ example 1 ]
Preparing slurry: mixing 100 parts of alumina with the particle size of 0.8 mu m and 250 parts of water at 1500rpm, stirring for 1h, adding 10 parts of carboxymethyl cellulose, quickly stirring for 1h at 1500rpm, then adding 15 parts of butadiene styrene rubber, stirring for 30min at 1000rpm, and finally adding 5 parts of sodium dodecyl sulfate, stirring for 30min at low speed of 200rpm to obtain heat-resistant layer slurry; preparing 100 parts of porous alumina with the particle size of 0.4 mu m, the pore diameter of 80nm and the porosity of 55 percent with the refractory layer ceramic slurry to obtain inorganic punctiform coating slurry; mixing 100 parts of water and 10 parts of SBR at 500rpm, stirring for 1h, adding 40 parts of PVDF, stirring for 3h at high speed at 1500rpm, and then adding 100 parts of water for dilution to obtain organic dot coating slurry;
micro-gravure coating: fully coating heat-resistant layer slurry on a diaphragm by using a 100-line-number 50-micron-depth twill roller, drying and rolling, then coating inorganic dot-shaped coating slurry on the heat-resistant layer by using a dot-shaped micro-concave roller, and drying and rolling to obtain an inorganic dot-shaped coating, wherein the inorganic dot-shaped coating is 2 microns high, 220 microns wide, 1200 microns apart from dots, and the coverage rate of the inorganic dot-shaped coating is 3.4%;
spraying an organic dot coating: spraying organic dot-like coating slurry between inorganic dot-like coatings by adopting an air flow spraying technology, wherein the average particle size of sprayed particles is 220 mu m, the thickness is 3.5 mu m, and the gram weight of the sprayed particles is 0.5g/m2The coverage rate is 19 percent, and the average particle size and thickness of the sprayed coating can be controlled by adjusting the airflow rate.
The prepared coated membrane is tested for gas permeability (the time required for 100ml of gas to pass through the membrane with a fixed area), thermal shrinkage (130 ℃/h), pole piece adhesion (the adhesion between the coated membrane and a positive plate under the conditions of 3MPa, 10min and 95 ℃) and the expansion coefficient of the membrane used at the battery end (after the membrane and the pole piece are wound and injected with electrolyte in a hot-pressing mode, the temperature is 70 ℃, sealing is kept for 20d, the thickness expansion coefficient of the battery is tested, the expansion coefficient = the thickness after the sealing is swelled for 20 d/the thickness during sealing) and the capacity retention rate (the battery is cycled for 400 times under 0.6C charge and discharge, the capacity before and after the cycle is tested, and the capacity retention rate = the capacity after the cycle/the capacity before the cycle).
[ example 2 ]
In the embodiment, the width of the inorganic dotted coating is 480 mu m, the height of the inorganic dotted coating is 2.8 mu m, the distance between each point and each dot is 1900 mu m, and the coverage rate is 6.4%; the particle size of the organic dot-shaped coating is 450 mu m, the thickness is 6.0 mu m, the coverage rate is 5.4 percent, and the areal density is 0.5g/m2Otherwise, the same procedure as in example 1 was repeated.
[ example 3 ]
In the embodiment, the width of the inorganic dotted coating is 350 mu m, the height of the inorganic dotted coating is 0.8 mu m, the distance between each point and each point is 1500 mu m, and the coverage rate is 5.4%; the particle size of the organic dot-shaped coating is 300um, the thickness is 4.7 mu m, the coverage rate is 10.4 percent, and the areal density is 0.5g/m2Otherwise, the same procedure as in example 1 was repeated.
Comparative example 1
The width of the inorganic dotted coating in the comparative example 1 is 300 mu m, the height of the inorganic dotted coating is 0.4 mu m, the distance between a point and a point is 1200 mu m, and the coverage rate is 6.3%; the particle size of the organic dot-shaped coating is 250 mu m, the thickness is 4.2 mu m, the coverage rate is 10.4 percent, and the areal density is 0.5g/m2Otherwise, the same procedure as in example 1 was repeated.
Comparative example 2
In the comparative example, the width of the inorganic dotted coating is 450 mu m, the height of the inorganic dotted coating is 3.5 mu m, the distance between each point and each dot is 1200 mu m, and the coverage rate is 14.1%; the particle size of the organic dot-shaped coating is 300 mu m, the thickness is 3.0 mu m, the coverage rate is 16.2 percent, and the areal density is 0.5g/m2Otherwise, the same procedure as in example 1 was repeated.
Comparative example 3
Preparing slurry: mixing 100 parts of alumina with the particle size of 0.8 mu m and 250 parts of water at 1500rpm, stirring for 1h, adding 10 parts of carboxymethyl cellulose, quickly stirring for 1h at 1500rpm, then adding 15 parts of butadiene styrene rubber, stirring for 30min at 1000rpm, and finally adding 5 parts of sodium dodecyl sulfate, stirring for 30min at low speed of 200rpm to obtain heat-resistant layer slurry;
micro-gravure coating: and (3) fully coating the inorganic ceramic layer on the diaphragm by using a 100-line-number 50-mum-depth twill roller, and drying and rolling to obtain the coated diaphragm.
Comparative example 4
Preparing slurry: the slurry of the heat-resistant layer was the same as in comparative example 3, and the slurry of the organic dot coating was the same as in example 1;
coating a micro-gravure plate: the same as comparative example 3;
spraying an organic dot coating: and spraying a discontinuous organic dot coating on the basis of the comparative example 3, and drying and rolling to obtain the coating diaphragm.
The test results of the air permeability, the thermal shrinkage performance, the adhesion with the pole piece, the expansion coefficient and the capacity retention rate of the diaphragm are summarized in table 1.
TABLE 1
As can be seen from table 1, the air permeability values and the heat shrinkability parameters in the examples and comparative examples were not large, i.e., whether or not the dot-shaped coating layer was provided did not affect the air permeability and the heat shrinkability of the coated separator.
Regarding the adhesion force with the pole piece, the data of the adhesion force between the coated diaphragm and the pole piece in the examples 1 to 3 is larger, and the adhesion force between the coated diaphragm and the pole piece is smaller compared with the adhesion force without the inorganic dot coating, in the comparative example 2, the adhesion force between the organic dot coating and the pole piece is prevented due to the fact that the inorganic dot coating is too high, and in the comparative example 3, the adhesion force between the coated diaphragm and the pole piece is not generated due to the fact that the organic dot coating is not generated.
In addition, the expansion coefficient of the diaphragm in the embodiment 1-3 is 1.0, which shows that the battery bulge can not be caused when the diaphragm in the embodiment is used in the battery end, and in the comparative example 1, because the inorganic dot coating is too low, the organic dot coating is swelled by the electrolyte after being hot-pressed, and the inorganic dot coating has insufficient space for swelling the organic dot coating, the battery thickness is expanded, and the bulge phenomenon is generated; comparative example 4 since the inorganic dot coating layer was not provided, the organic dot coating layer directly causes swelling of the battery after hot pressing and swelling.
Finally, the inorganic dot-shaped coating in the embodiments 1 to 3 can provide enough space for storing the electrolyte, and the capacity retention rate is high after circulation; in the comparative example 1, the inorganic point-shaped coating is too low, and no extra space is provided for storing the electrolyte, so that the capacity retention rate is high after the circulation; the comparative example 3 and the comparative example 4 have no inorganic point coating, so the electrolyte is stored without space, and the capacity retention rate is lower after circulation.
In conclusion, the separators in examples 1 to 3 have good air permeability and thermal shrinkage, high adhesion with the pole piece, no bulge at the battery end, and high retention rate of the battery cycle capacity. Some of the separators of the comparative examples had poor adhesion, some were liable to cause cell swelling, and some had low capacity retention after cycles, and the performances were inferior to those of examples 1 to 3.
Although the illustrative embodiments of the present application have been described in order to enable those skilled in the art to understand the present application, the present application is not limited to these embodiments, and various modifications can be made within the spirit and scope of the present application as defined and defined by the appended claims.
Claims (23)
1. A coated separator, comprising:
the base membrane is a porous film;
a heat-resistant layer disposed on at least one side surface of the base film;
the point-shaped coating is arranged on one side of the heat-resistant layer and comprises inorganic point-shaped coatings and organic point-shaped coatings, the inorganic point-shaped coatings are regularly distributed, and the organic point-shaped coatings are randomly distributed among and/or on the inorganic point-shaped coatings.
2. The coated separator of claim 1, wherein the porous film is a polypropylene film, a polyethylene film or a polyethylene/polypropylene composite film.
3. A coated membrane according to claim 1, wherein the thickness of the heat resistant layer is 0.5-3.5 μm.
4. A coated separator according to claim 1, wherein said heat resistant layer and inorganic dot coating comprise ceramic particles, stabilizers, glues and wetting agents.
5. The coated separator of claim 4, wherein the ceramic particles are one or more of alumina, boehmite, silica, aluminum hydroxide.
6. A coated separator according to claim 4, wherein the stabilizer is one or more of gelatin, methyl cellulose, carboxymethyl cellulose, sodium polyacrylate, polyethylene oxide, polyvinyl alcohol.
7. The coated membrane of claim 4 wherein the glue is one or more of acrylic, styrene butadiene, polystyrene, polyacrylate.
8. The coated separator of claim 4, wherein the wetting agent is one or more of sodium lauryl sulfate, fatty alcohol, ethylene oxide, sodium butylnaphthalene sulfonate, and polyoxyethylene nonylphenol ether.
9. The coated membrane according to claim 4, wherein the ceramic particles of the heat-resistant layer have a particle size of 0.5 to 2 μm.
10. A coated separator according to claim 4, wherein the ceramic particles of the inorganic dot coating have a particle size of 0.2-1 μm.
11. A coated separator according to claim 4, wherein the ceramic particles of the inorganic dot coating are porous ceramic.
12. A coated separator according to claim 1, wherein the inorganic dot coating has a thickness of 0.5-3 μm.
13. A coated membrane according to claim 1, wherein the width of the inorganic dot coating is 200 μm and 500 μm.
14. A coated membrane according to claim 1, wherein the distance between two of said inorganic dot-like coatings is 1000-.
15. A coated separator according to claim 1, wherein the coverage of the inorganic dot coating is 1-25%.
16. A coated separator according to claim 1, wherein the organic dot coating has a particle size in the range of 50-500 μm.
17. A coated separator according to claim 1, wherein the organic dot coating has a thickness of 3-7 μm.
18. A coated separator according to claim 1, wherein the coverage of the organic dot coating is 5-20%.
19. A coated membrane according to claim 1, wherein the organic dot coating comprises an organic binder and glue.
20. The coated separator of claim 19, wherein the organic binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, and polymethyl methacrylate.
21. The coated membrane of claim 19 wherein the glue is one or more of acrylic, styrene butadiene glue, polystyrene, polyacrylate.
22. A method of preparing a coated separator according to claim 1, comprising the steps of:
preparing heat-resistant layer slurry, inorganic dot coating slurry and organic dot coating slurry;
coating the heat-resistant layer slurry on at least one side surface of the base film, and drying to form the heat-resistant layer;
coating the inorganic dotted coating slurry on the heat-resistant layer by using a dotted micro-concave roller, and drying to form the inorganic dotted coating;
and coating the organic dot coating slurry on the inorganic dot coating by using a spraying technology to form the organic dot coating which is randomly distributed.
23. Use of a coated separator according to any one of claims 1 to 21 or a coated separator obtained by the method of preparing a coated separator according to claim 22 in a lithium battery.
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| CN114649638B (en) | 2022-09-06 |
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