CN111341982B - Coated diaphragm and preparation method, doped boehmite, ceramic slurry, lithium battery - Google Patents

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a coating diaphragm, a preparation method of the coating diaphragm, doped boehmite, ceramic slurry and a lithium battery. The present coated separator includes: the coating comprises a base film and a boehmite ceramic coating layer positioned on the surface of the base film; wherein the boehmite ceramic coating comprises the following raw materials: doped boehmite, a dispersing agent, a thickening agent, a binder, a wetting agent and a solvent. The boehmite-doped ceramic slurry is prepared by adopting the doped boehmite, so that the internal space of the boehmite coating can be increased, the porosity of the boehmite coating is improved, and the liquid storage capacity of the electrolyte is further improved.

Description

Coated diaphragm and preparation method, doped boehmite, ceramic slurry, lithium battery

technical field

The invention belongs to the technical field of lithium batteries, and in particular relates to a coated diaphragm and a preparation method, doped boehmite, ceramic slurry, and a lithium battery.

Background technique

The boehmite coating of conventional separators is densely packed inside and has low porosity, which can hold a small amount of electrolyte. In order to improve the problem of low porosity of the boehmite coating, the present invention uses boehmite nanofibers and rhomboid boehmite to be doped in a certain proportion, so that the boehmite coating presents a bridging structure with bridges, increasing the porosity of the boehmite coating. The internal space of the boehmite coating increases the porosity of the boehmite coating and increases the storage capacity of the electrolyte.

Contents of the invention

The invention provides a coated diaphragm and a preparation method, doped boehmite, ceramic slurry and a lithium battery.

In order to solve the above technical problems, the present invention provides a coated diaphragm, comprising: a base film and a boehmite ceramic coating on the surface of the base film; wherein the boehmite ceramic coating includes the following raw materials: doped boehmite stone, dispersant, thickener, binder, wetting agent, solvent.

In the second aspect, the present invention also provides a doped boehmite, including: nanofiber boehmite, rhomboid boehmite; and both are suitable for forming a bridge structure.

In the third aspect, the present invention also provides a boehmite ceramic slurry, including the following raw materials: doped boehmite, dispersant, thickener, binder, wetting agent, solvent; each raw material is suitable for dispersing Uniformly, the boehmite ceramic slurry is formed.

In a fourth aspect, the present invention also provides a method for preparing a coated diaphragm, comprising: preparing boehmite ceramic slurry; coating the boehmite ceramic slurry on the surface of the base film and drying to form boehmite ceramic coating.

In a fifth aspect, the present invention also provides a lithium battery, comprising: a separator; the separator is the above-mentioned coated separator.

The beneficial effect of the present invention is that, the coated diaphragm and preparation method, doped boehmite, ceramic slurry, and lithium battery of the present invention are made of boehmite ceramic slurry by doping boehmite, and coated on the base film The boehmite ceramic coating is formed on the surface, which can increase the internal space of the boehmite coating, increase the porosity of the boehmite coating, and then increase the liquid storage capacity of the electrolyte.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to make the above-mentioned objects, features and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the accompanying drawings.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

Fig. 1 is the preparation process flow diagram of coating diaphragm of the present invention;

Fig. 2 is a schematic diagram of a bridge structure doped with boehmite of the present invention;

Fig. 3 is the porosity contrast figure of coating membrane of the present invention and traditional membrane;

Fig. 4 is the comparison chart of the liquid storage capacity of coating diaphragm of the present invention and traditional diaphragm;

In Fig. 2: nanofiber boehmite 1, rhombohedral boehmite 2.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. the embodiment. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

first part:

The boehmite coating of conventional separators is densely packed inside and has low porosity, which can hold a small amount of electrolyte. In order to improve the problem of low porosity of the boehmite coating, the present invention provides a coated diaphragm (that is, a high liquid storage capacity boehmite coated diaphragm), including: a base film and boehmite located on the surface of the base film Ceramic coating; wherein the boehmite ceramic coating includes the following raw materials: doped boehmite, dispersant, thickener, binder, wetting agent, and solvent.

Optionally, the base film includes, but is not limited to, polymer films such as PP film, PE film, PI film, PET film, and composite films thereof.

In the raw material of boehmite ceramic coating, the mass ratio of boehmite, dispersant, thickener, binder and wetting agent is 1:0.004-0.016:0.003-0.03:0.022-0.09:0.001 -0.006, an appropriate amount of solvent is used to prepare boehmite ceramic slurry for coating on the surface of the base film. Optionally, the mass ratio of boehmite, dispersant, thickener, binder and wetting agent is 1:0.01:0.006:0.05:0.004. Optionally, the mass ratio of boehmite, dispersant, thickener, binder and wetting agent is 1:0.007:0.01:0.08:0.003.

At the same time, some specific substances corresponding to the raw materials of the boehmite ceramic coating are listed in order to facilitate the understanding of the scheme, as follows:

The dispersants include silicates (such as water glass), alkali metal phosphates (such as sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, etc.), organic dispersants; wherein the organic dispersants include: three At least one of ethylhexyl phosphoric acid, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, guar gum, fatty acid polyethylene glycol ester.

The thickener includes, but is not limited to, sodium carboxymethacrylate.

The binder includes but not limited to various water-based binders such as acrylic.

The wetting agent includes, but is not limited to, at least one of anionic and nonionic surfactants and the like.

The solvent includes, but is not limited to, pure water.

As an optional embodiment of doping boehmite.

As shown in FIG. 2 , the doped boehmite includes: nanofiber boehmite 1 and rhomboid boehmite 2 (or rectangular rhomboid boehmite); and the two are suitable for forming a bridge structure. And the mass ratio of the nanofiber boehmite and rhomboid boehmite is (1-11):(1-11), and may be (1-3):(3-1).

Optionally, the nanofibrous boehmite is a thread-like material with a length of 0.5-10 μm, optionally 3 μm, 5 μm, or 8 μm; and the rhomboid boehmite has a particle size D50 of 0.3-5.0 μm, which can 1 μm and 3 μm are selected.

The doped boehmite in this embodiment uses boehmite nanofibers and rhomboid boehmite to dope in a certain proportion, so that the boehmite coating presents a bridging structure with a bridge frame, increasing the internal space of the boehmite coating , to increase the porosity of the boehmite coating, thereby increasing the electrolyte storage capacity.

As mentioned above, see FIG. 2 , the present invention also provides a doped boehmite, including: nanofiber boehmite 1 , rhomboid boehmite 2 ; and both are suitable for forming a bridge structure.

As mentioned above, the present invention also provides a boehmite ceramic slurry, including the following raw materials: doped boehmite, dispersant, thickener, binder, wetting agent, solvent; each raw material is suitable for uniformly dispersed to form the boehmite ceramic slurry. Wherein, the dispersion method includes but not limited to high-speed dispersion using a double planetary or sand mill.

As mentioned above, see Figure 1, the present invention also provides a method for preparing a coated diaphragm, comprising: preparing boehmite ceramic slurry; coating the boehmite ceramic slurry on the surface of the base film and drying, To form a boehmite ceramic coating, the coated membrane, ie, a high storage capacity boehmite coated membrane, is produced.

Optionally, the method for preparing boehmite ceramic slurry includes: selecting nanofiber boehmite and diamond-shaped boehmite, and doping the two in proportion; then adding dispersant, wetting agent, bonding agent, thickener, and pure water, and disperse evenly by stirring, sand milling and other dispersion methods to make boehmite ceramic slurry.

As mentioned above, the present invention also provides a lithium battery, comprising: a separator; the separator adopts the above-mentioned coated separator.

the second part:

Example 1

(1) Preparation of doped boehmite.

Firstly, 8 kg of nanofiber boehmite with a length of 5 μm and 10.5 kg of diamond-shaped boehmite with a particle size D50 of 0.8 μm are sand-milled and mixed to form doped boehmite.

(2) Prepare boehmite ceramic slurry.

Add 20.4kg of pure water to the mixing tank, then add 0.094kg of alkali metal phosphates for stirring and dispersing; then add 18.0kg of doped boehmite for stirring and dispersing; then add 5.3kg of sodium carboxymethylacrylate solution , carry out stirring and sand milling; then add 5.6kg of acrylic binder and stir; then add 0.46kg of wetting agent solution, stir and disperse, and make boehmite ceramic slurry.

(3) Coating.

The boehmite ceramic slurry is coated on the 12 μm PE film to form a boehmite ceramic coating on the surface of the PE film. The coating specification is 12+4 (that is, the base film thickness is 12 μm, and the coating thickness is 4 μm), which is made into a boehmite-coated diaphragm with a high liquid storage capacity.

Example 2

(1) Preparation of doped boehmite.

First, 1 kg of nanofiber boehmite with a length of 0.5 μm and 11 kg of diamond-shaped boehmite with a particle size D50 of 0.3 μm are sand-milled and mixed to form doped boehmite.

(2) Prepare boehmite ceramic slurry.

Add 12kg of pure water in the mixing tank, then add 0.04kg of alkali metal phosphates for stirring and dispersing; then add 10kg of doped boehmite for stirring and dispersing; then add 0.03kg of sodium carboxymethylacrylate solution for Stir and sand mill; then add 0.22kg of acrylic binder and stir; then add 0.06kg of wetting agent solution, stir and disperse to prepare boehmite ceramic slurry.

(3) Coating.

The boehmite ceramic slurry is coated on the PI film with a diameter of 12 μm, and a boehmite ceramic coating is formed on the surface of the PI film. The coating specification is 12+4 (that is, the base film thickness is 12 μm, and the coating thickness is 4 μm), which is made into a boehmite-coated diaphragm with a high liquid storage capacity.

Example 3

(1) Preparation of doped boehmite.

First, 11 kg of nanofibrous boehmite with a length of 2 μm and 1 kg of rhombohedral boehmite with a particle size D50 of 1 μm are sand-milled and mixed to form doped boehmite.

(2) Prepare boehmite ceramic slurry.

Add 12kg of pure water to the mixing tank, then add 0.16kg of methyl amyl alcohol for stirring and dispersing; then add 10kg of doped boehmite for stirring and dispersing; then add 0.3kg of sodium carboxymethylacrylate solution for stirring Sand milling; then add 0.9kg of acrylic binder and stir; then add 0.04kg of wetting agent solution, stir and disperse to prepare boehmite ceramic slurry.

(3) Coating.

The boehmite ceramic slurry is coated on the PP film with a thickness of 12 μm to form a boehmite ceramic coating on the surface of the PP film. The coating specification is 12+4 (that is, the base film thickness is 12 μm, and the coating thickness is 4 μm), which is made into a boehmite-coated diaphragm with a high liquid storage capacity.

Example 4

(1) Preparation of doped boehmite.

Firstly, 4 kg of nanofiber boehmite with a length of 6 μm and 12 kg of diamond-shaped boehmite with a particle diameter D50 of 3 μm are sand-milled and mixed to form doped boehmite.

(2) Prepare boehmite ceramic slurry.

Add 12kg of pure water to the mixing tank, then add 0.1kg of methyl amyl alcohol for stirring and dispersing; then add 10kg of doped boehmite for stirring and dispersing; then add 0.06kg of sodium carboxymethylacrylate solution for stirring Sand milling; then add 0.05kg of acrylic binder and stir; then add 0.01kg of wetting agent solution, stir and disperse to prepare boehmite ceramic slurry.

(3) Coating.

The boehmite ceramic slurry is coated on the PP film with a thickness of 12 μm to form a boehmite ceramic coating on the surface of the PP film. The coating specification is 12+4 (that is, the base film thickness is 12 μm, and the coating thickness is 4 μm), which is made into a boehmite-coated diaphragm with a high liquid storage capacity.

Example 5

(1) Preparation of doped boehmite.

First, 12 kg of nanofiber boehmite with a length of 1 μm and 4 kg of diamond-shaped boehmite with a particle size D50 of 1 μm are sand-milled and mixed to form doped boehmite.

(2) Prepare boehmite ceramic slurry.

Add 12kg of pure water to the mixing tank, then add 0.12kg of methyl amyl alcohol for stirring and dispersing; then add 10kg of doped boehmite for stirring and dispersing; then add 0.2kg of sodium carboxymethylacrylate solution for stirring Sand grinding; then add 0.8kg of acrylic binder and stir; then add 0.02kg of wetting agent solution, stir and disperse, and make boehmite ceramic slurry;

(3) Coating.

The boehmite ceramic slurry is coated on the PP film with a thickness of 12 μm to form a boehmite ceramic coating on the surface of the PP film. The coating specification is 12+4 (that is, the base film thickness is 12 μm, and the coating thickness is 4 μm), which is made into a boehmite-coated diaphragm with a high liquid storage capacity.

comparative example

Choose rhombohedral boehmite with a particle size D50 of 0.8 μm, configure 50kg of long-cycle coating slurry, use 12 μm PE film, and use a coating specification of 12+4 to make a traditional diaphragm.

Example 6

See Fig. 3, Fig. 4, this embodiment 6 compares the high-reserved boehmite-coated diaphragm (corresponding to the new type in Fig. 3 or Fig. 4) prepared in Example 1 and the traditional diaphragm (corresponding to Fig. 3 or Conventional in Figure 4) for porosity and liquid storage testing. It can be seen that the porosity of the boehmite-coated diaphragm with high liquid storage capacity of the present invention is 70%, and its liquid storage capacity is 40g; while the porosity of the traditional diaphragm is 45%, and its liquid storage capacity is 25g. It can be seen that the porosity and liquid storage capacity of the boehmite-coated separator with high liquid storage capacity have been greatly improved, mainly due to the doping of boehmite nanofibers and rhomboid boehmite in a certain proportion. The heteroboehmite has a bridge structure, which increases the internal space of the boehmite coating and increases the porosity of the boehmite coating, thereby increasing the liquid storage capacity of the electrolyte.

In summary, the coating diaphragm and preparation method, doped boehmite, ceramic slurry, and lithium battery of the present invention use boehmite nanofibers and rhomboid boehmite to be doped in a certain proportion to form doped boehmite The boehmite has a bridging structure of a bridge, and the boehmite ceramic slurry is prepared from this, and the boehmite ceramic coating is formed on the surface of the base film, which can increase the internal space of the boehmite coating and improve the quality of the boehmite coating. Porosity, thereby increasing the liquid storage capacity of the electrolyte.

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (5)

1. A coating diaphragm, characterized in that, comprising: A base film and a boehmite ceramic coating on the surface of the base film; wherein The boehmite ceramic coating includes the following raw materials: doped boehmite, dispersant, thickener, binder, wetting agent, solvent; The doped boehmite includes: nanofiber boehmite, rhombohedral boehmite; and The two are suitable for forming a bridge structure; The nanofiber boehmite is a wire-like material with a length of 0.5-10 μm; The particle size D50 of the rhombohedral boehmite is 0.3-5.0 μm; The mass ratio of the nanofiber boehmite to rhomboid boehmite is (1-11): (1-11); The thickness of the boehmite ceramic coating is 4 μm. 2. The coated membrane of claim 1, wherein The mass ratio of the doped boehmite, dispersant, thickener, binder and wetting agent is 1:0.004-0.016:0.003-0.03:0.022-0.09:0.001-0.006. 3. The coated membrane of claim 1, wherein Described dispersant comprises silicate, alkali metal phosphate, organic dispersant; Wherein The organic dispersant includes: at least one of triethylhexyl phosphoric acid, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, gull gum, and fatty acid polyethylene glycol ester. 4. a preparation method of coating diaphragm as claimed in claim 1, is characterized in that, comprises: Prepare boehmite ceramic coating slurry; The boehmite ceramic coating slurry is coated on the surface of the base film and dried to form the boehmite ceramic coating. 5. A lithium battery, characterized in that, comprising: diaphragm; The diaphragm adopts the coated diaphragm according to claim 1.

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