CN108305972B

CN108305972B - Ceramic coating diaphragm and preparation method and application thereof

Info

Publication number: CN108305972B
Application number: CN201711490079.0A
Authority: CN
Inventors: 姚坤; 王哲; 张辉; 乔井会
Original assignee: Shenzhen Zhongxing New Material Technology Co ltd
Current assignee: Shenzhen Zhongxing New Material Technology Co ltd
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2021-08-17
Anticipated expiration: 2037-12-29
Also published as: CN108305972A

Abstract

The application discloses a ceramic coating diaphragm and a preparation method and application thereof. The ceramic coating diaphragm comprises a base film and a ceramic coating coated on at least one surface of the base film, wherein the ceramic coating is formed by coating inorganic particles with polyethylene glycol grafted on the surface. The ceramic coating diaphragm of this application, the inorganic granule of the creative adoption surface grafting polyethylene glycol prepares ceramic coating for the interface cohesion of inorganic granule and base film is better, has improved the holistic peel strength of ceramic coating diaphragm, keeps ceramic coating characteristics such as high temperature resistant, has solved inorganic granule again and has droed, fall the powder problem. The inorganic particles with the surfaces grafted with the polyethylene glycol have better dispersion effect in water, so that the ceramic coating diaphragm has better uniformity. The ceramic coating formed by the inorganic particles with the surfaces grafted with the polyethylene glycol has higher imbibition rate and higher imbibition rate, and forms gel after absorbing electrolyte, so that the ceramic coating diaphragm can be better attached to the surface of the electrode.

Description

Ceramic coating diaphragm and preparation method and application thereof

Technical Field

The application relates to the field of lithium ion battery diaphragms, in particular to a ceramic coating diaphragm and a preparation method and application thereof.

Background

The lithium ion battery separator is a porous membrane. The lithium ion battery diaphragm has the main functions of isolating the positive electrode and the negative electrode of the battery and preventing the internal short circuit of the battery; provides a passage for lithium ions to migrate during charge and discharge, and allows lithium ions to pass through. The previously commercialized separator is mainly classified into a dry-process uniaxially stretched separator and a wet-process biaxially stretched separator. See patents US5480745, JP 2004323820.

In order to further improve the electrolyte absorption capacity of the lithium battery diaphragm, the thermal stability of the diaphragm and the lithium dendrite resistance capacity of the diaphragm, a high-temperature-resistant coating is usually compounded on the surface of the diaphragm. The ceramic can be dispersed in water, so that the environment-friendly performance is good, and the ceramic is widely used for coating the diaphragm at present so as to prepare the high-temperature resistant ceramic coating diaphragm with good thermal stability. But the ceramic is used as an inorganic material, and stress conduction does not exist among ceramic particles, so that the mechanical strength of the ceramic coating diaphragm is seriously reduced; and the compatibility of the inorganic material of the ceramic particles and the base film of the organic diaphragm is poor, so that the ceramic particles are easy to fall off, namely fall off powder, the high temperature resistance of the ceramic coating diaphragm is reduced, and the performance of the battery is influenced.

Disclosure of Invention

The application aims to provide a novel ceramic coating diaphragm, a preparation method and application.

In order to achieve the purpose, the following technical scheme is adopted in the application:

one aspect of the present application discloses a ceramic coating diaphragm, which comprises a base film and a ceramic coating layer coated on at least one surface of the base film, wherein the ceramic coating layer is formed by coating inorganic particles with polyethylene glycol grafted on the surface.

The ceramic coating is prepared by creatively adopting the inorganic particles with the surfaces grafted with the polyethylene glycol, so that on one hand, the ceramic coating diaphragm has good thermal stability, high temperature resistance and better lithium dendrite resistance; on the other hand, the inorganic particles with the polyethylene glycol grafted on the surface have better interface binding force with the base membrane, are not easy to fall off, have no powder falling phenomenon, and ensure that the liquid absorption rate of the ceramic coating diaphragm is higher, the liquid absorption rate is higher, and the gel is easy to form after absorbing electrolyte, so that the gel can be better attached to the surface of the electrode. The liquid absorption speed is high, and the production efficiency of the battery can be improved; the high liquid absorption rate can accelerate the charging and discharging rate of the battery and prolong the service life of the battery; the gel state, namely the adhesive state, is formed, the electrode surface can be favorably attached, the consistency of internal resistance can be improved after the electrode surface is attached, and the service life of the battery is prolonged. In addition, the inorganic particle of surface grafting polyethylene glycol that this application adopted, dispersion effect in aqueous is better for the ceramic coating of preparation is more even, and then makes the ceramic coating diaphragm performance of this application more reliable and stable.

It is understood that the key point of the present application is to prepare the ceramic coating using inorganic particles with polyethylene glycol grafted on the surface, and as for the specific type of inorganic particles, reference can be made to the inorganic particles used in the existing ceramic coating. However, in a preferred embodiment of the present invention, the inorganic particles are particularly limited to achieve a more preferable effect, and the following technical means will be described in detail.

Preferably, the peel strength of the ceramic coated membrane of the present application is greater than 40N/m at an angle of 180 degrees.

It should be noted that, the ceramic coating diaphragm of the application, because the inorganic particle of surface grafting polyethylene glycol is adopted to prepare the ceramic coating, make the cohesion of ceramic coating and base film better, be difficult for droing, the powder phenomenon does not fall, and, in the implementation of the application, the peel strength of ceramic coating diaphragm at 180 degrees angle of this application is greater than 40N/m, peel strength all is above 70N/m in the embodiment of this application, can reach 98N/m the highest, the cohesion of ceramic coating and base film is strong, each performance of ceramic coating diaphragm has been ensured, the influence of ceramic coating droing to diaphragm or battery has been avoided.

Preferably, the base film is a polyolefin microporous film. More preferably, the polyolefin microporous membrane is a polyethylene microporous membrane, a polypropylene microporous membrane or a two-layer or multi-layer composite membrane consisting of the polyethylene microporous membrane and the polypropylene microporous membrane.

Preferably, the inorganic particles are selected from at least one of aluminum oxide, silicon dioxide, zirconium dioxide, titanium dioxide, zinc oxide, magnesium oxide, calcium carbonate, magnesium hydroxide, aluminum hydroxide, and boehmite.

Preferably, the base film has a thickness of 5 to 60 μm, a porosity of 10 to 60%, and a pore diameter of 0.01 to 0.5 μm.

The application also discloses application of the ceramic coating diaphragm in a lithium ion battery.

The other side of the application discloses a lithium ion battery that adopts the ceramic coating diaphragm of the application.

The ceramic coating diaphragm is not easy to fall off, so that the powder falling phenomenon is avoided, the influence of the powder falling on the performance of the lithium ion battery is avoided, and the stability and the safety of the lithium ion battery are improved; and, the ceramic coating diaphragm imbibition rate of this application is fast, the imbibition rate is higher to form the gel form behind the absorption electrolyte and make better laminating of diaphragm at the electrode surface, make lithium ion battery's wholeness ability better.

Still another aspect of the present application discloses a method for preparing a ceramic coated membrane of the present application, comprising the steps of,

dispersing the inorganic particles into ethanol, adding an aminosilane coupling agent, reacting for 1-4 hours at the temperature of 20-80 ℃ and the pH value of 6-8, and washing and drying a reaction product to obtain the inorganic particles with amino groups on the surfaces; mixing a condensing agent, inorganic particles with amino on the surface and polyethylene glycol with carboxyl on the end group, stirring and reacting for 1-8 hours at 20-50 ℃, and then washing to obtain inorganic particles with polyethylene glycol grafted on the surface;

dispersing inorganic particles with polyethylene glycol grafted on the surface into water, and uniformly stirring to prepare coating slurry;

the preparation method of the ceramic coating diaphragm comprises the following steps: coating a coating slurry on at least one surface of the base film to obtain the ceramic coating separator.

It should be noted that, in the preparation method of the present application, compared with other methods of surface grafting polymers, the step of preparing the inorganic particles with the surface grafted with the polyethylene glycol does not need an organic solvent, and is more environment-friendly and safer.

Preferably, the condensing agent is at least one of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, 2-chloro-4, 6-dimethoxy-1, 3, 5-triazine and N-hydroxysuccinimide.

The condensing agent is used for causing the amino group on the surface of the inorganic particle to perform condensation reaction with the carboxyl group of the polyethylene glycol, so that the polyethylene glycol is grafted on the surface of the inorganic particle; based on this principle, it is not excluded that other chemical agents that can promote the condensation reaction may also be used, and are not specifically limited herein.

Preferably, the step of preparing the ceramic coating membrane further comprises coating the coating slurry on at least one surface of the base membrane, and heating to volatilize water to obtain the ceramic coating membrane; wherein the heating temperature is 30-80 deg.C, and the heating time is 5-72 s.

Preferably, the coating is performed by at least one of a blade coating method, a meyer bar coating method, a reverse roll coating method, a gravure roll coating method, a dip coating method, and a brush coating method.

Due to the adoption of the technical scheme, the beneficial effects of the application are as follows:

the ceramic coating diaphragm of this application, the inorganic granule of creative adoption surface grafting polyethylene glycol prepares ceramic coating for the interface cohesion of inorganic granule and base film is better, has improved the holistic peel strength of ceramic coating diaphragm, and, when having remain ceramic coating's characteristics such as high temperature resistant, fine solution inorganic granule again drops, the problem of falling the powder. The inorganic particles with the surfaces grafted with the polyethylene glycol have better dispersion effect in water, so that the prepared ceramic coating diaphragm has better uniformity. The ceramic coating formed by the inorganic particles with the polyethylene glycol grafted on the surface has higher imbibition rate and higher imbibition rate, and is easy to form gel after absorbing electrolyte, so that the ceramic coating diaphragm can be better attached to the surface of an electrode, and the overall comprehensive performance of the lithium ion battery is improved.

Drawings

FIG. 1 is a schematic illustration of the peel strength test in an example of the present application;

fig. 2 is a schematic structural view of a ceramic-coated diaphragm in an embodiment of the present application.

Detailed Description

In the existing ceramic coating diaphragm, inorganic particles are easy to fall off and the phenomenon of powder falling occurs, so that the ceramic coating diaphragm is a difficult problem. The application discovers that the characteristics of the ceramic coating can be kept and the problem of falling off of inorganic particles can be well solved by adopting the inorganic particles with the polyethylene glycol grafted on the surface to prepare the ceramic coating in the process of carrying out long-term production practice and research on the ceramic coating diaphragm.

According to the above research, the present application provides a ceramic coating membrane comprising a base membrane and a ceramic coating layer coated on at least one surface of the base membrane, wherein the ceramic coating layer is coated with inorganic particles with polyethylene glycol grafted on the surface. The ceramic coating diaphragm of the present application has a structure as shown in fig. 2, wherein inorganic particles with polyethylene glycol grafted on the surface actually form a polyethylene glycol coating layer 211 on the surface of the inorganic particles 21 to form particles with a core-shell structure, and then coat on the surface of the base film 22. The inorganic particles with the surface grafted with the polyethylene glycol have better interface bonding force with the base membrane and are not easy to fall off, thereby solving the powder falling problem of the ceramic coating diaphragm.

The present application is described in further detail below with reference to specific embodiments and the attached drawings. The following examples are intended to be illustrative of the present application only and should not be construed as limiting the present application.

Example 1

The embodiment adopts a polypropylene microporous membrane with the thickness of 16 mu m, the porosity of 40 percent and the pore diameter of 0.02-0.03 mu m of Shenzhen Zhongxing Innovation materials technology Limited company as a base membrane; preparing the ceramic coating diaphragm by adopting the aluminum oxide with the surface grafted with the polyethylene glycol; wherein the alumina is purchased from Nippon Sumitomo and has a particle size of D500.50-0.82 μm. The preparation method comprises the following steps:

1. preparation of surface grafted polyethylene glycol aluminum oxide

Dispersing aluminum oxide particles into ethanol, adding an aminosilane coupling agent, reacting for 3 hours at the temperature of 60 ℃ and the pH value of about 6.5, and washing and drying a reaction product to obtain aluminum oxide with amino groups on the surface; mixing the condensing agent, the aluminum oxide with amino on the surface and the polyethylene glycol with carboxyl on the end group, stirring and reacting for 1 hour at 50 ℃, and then washing to obtain the aluminum oxide with the polyethylene glycol grafted on the surface. The condensing agents used in this example were 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

2. Preparation of coating slurries

40g of prepared aluminum oxide with polyethylene glycol grafted on the surface, 1g of carboxymethyl cellulose viscosity regulator and 1g of polyacrylate adhesive are directly dispersed into 58g of deionized water, and the mixture is stirred for 1 to 3 hours to prepare coating slurry.

The prepared coating slurry was uniformly coated on one surface of the base film by a roll coating method, and then dried in an oven at 70 ℃ to volatilize water, thereby obtaining a ceramic coating membrane having a coating thickness of 4 μm according to this example.

Examples 2 to 7

Examples 2 to 7 respectively prepared silica, zirconia, titania, zinc oxide, magnesia, and calcium carbonate with polyethylene glycol grafted on the surface for preparing a ceramic coating membrane. The method comprises the following specific steps:

example 2 is similar to example 1, except that silica is used instead of alumina to form silica with polyethylene glycol grafted on the surface for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the particle size of the silicon dioxide is D500.50-0.61 μm.

Example 3 similar to example 1, except that zirconium dioxide was used instead of aluminum oxide to form polyethylene glycol surface-grafted zirconium dioxide for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the grain diameter of the zirconium dioxide is D500.82-1.13 μm.

Example 4 is similar to example 1, except that titanium dioxide is used instead of alumina to form polyethylene glycol surface-grafted titanium dioxide for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the particle diameter of the titanium dioxide is D500.38-0.67 μm.

Example 5 is similar to example 1, except that zinc oxide is used instead of aluminum oxide to form zinc oxide with polyethylene glycol grafted on the surface for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the particle size of the zinc oxide is D500.63-0.99 μm.

Example 6 is similar to example 1, except that magnesium oxide is used instead of aluminum oxide to form magnesium oxide with polyethylene glycol grafted on the surface for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the particle diameter of the magnesium oxide is D500.58-0.85 μm.

Example 7 is similar to example 1, except that calcium carbonate is used instead of alumina to form calcium carbonate with polyethylene glycol grafted on the surface for preparing a ceramic-coated separator. The remaining conditions were the same as in example 1. Wherein the particle size of the calcium carbonate is D500.66-0.83 μm.

Comparative examples 1 to 7

Comparative examples 1 to 7 correspond to examples 1 to 7 in this order, except that the ceramic-coated separator was prepared directly using inorganic particles without surface grafting, as follows:

comparative example 1 the same source and specification of alumina as in example 1 was directly dispersed in water to prepare a coating slurry, the components and the amounts of which were the same as in example 1, and then the same preparation method was used to obtain a ceramic coating separator having the same coating thickness. The same as example 1 was conducted except that the alumina was not surface-grafted with polyethylene glycol, including the base film and the like.

Comparative example 2 a coating slurry was prepared by directly dispersing silica having the same source and specification as in example 2 in water, and the components and the amounts of the coating slurry were the same as in example 2, and then a ceramic coating separator having the same coating thickness was obtained by the same preparation method. The same as example 2 except that the silica was not surface-grafted with polyethylene glycol, including a base film, etc.

Comparative example 3 the same sources and specifications of zirconium dioxide as in example 3 were directly dispersed in water to prepare a coating slurry, the components and amounts of which were the same as in example 3, and then the same preparation method was used to obtain a ceramic coating membrane having the same coating thickness. The same as example 3 was conducted except that the zirconia was not surface-grafted with polyethylene glycol, including a base film and the like.

Comparative example 4 the same titania of the same source and specification as in example 4 was directly dispersed in water to prepare a coating slurry, the components and the amounts of which were the same as in example 4, and then the ceramic coating separator of the same coating thickness was obtained by the same preparation method. The same as in example 4 except that titanium dioxide was not surface-grafted with polyethylene glycol, including a base film and the like.

Comparative example 5 the same zinc oxide source and specification as in example 5 was directly dispersed in water to prepare a coating slurry, the components and amounts of which were the same as in example 5, and then the same preparation method was used to obtain a ceramic coating separator having the same coating thickness. The same as example 5 was conducted except that the zinc oxide was not surface-grafted with polyethylene glycol, including a base film and the like.

Comparative example 6 magnesium oxide of the same source and specification as in example 6 was directly dispersed in water to prepare a coating slurry, the components and amounts of which were the same as in example 6, and then a ceramic coating separator of the same coating thickness was obtained using the same preparation method. The same as example 6 was conducted except that the magnesium oxide was not surface-grafted with polyethylene glycol, including a base film and the like.

Comparative example 7 the same source and specification of calcium carbonate as in example 7 were directly dispersed in water to prepare a coating slurry, the components and amounts of which were the same as in example 7, and then the same preparation method was used to obtain a ceramic coating separator having the same coating thickness. The same as example 7 was conducted except that calcium carbonate was not surface-grafted with polyethylene glycol, including a base film and the like.

The ceramic-coated separators of the above examples and comparative examples were tested for peel strength, high temperature resistance, liquid absorption rate, and pole piece adhesion. The specific test method is as follows:

the peel strength was measured by reference to GB/T2792-1998, and 5 samples 20-80 mm in size were cut in the MD direction of the film, and as shown in FIG. 1, the samples were adhered to a stainless steel plate 2 with 3M standard tape 3, and then peeled in the 180 DEG direction on a three-wire electric tensile machine at a speed of 300mm/min to peel the base film 11 and the coating 12, and after the experiment was completed, the software was automatically processed to output the peel strength value of the samples. The average value of the peel strength of 5 samples is the peel strength.

The high temperature resistance performance, namely thermal shrinkage, is tested by referring to GB/T12027-2004, 5 samples which are larger than or equal to 100mm multiplied by 100mm are taken along the MD and TD directions of the film, the actual size of the samples is measured, then the samples are clamped between two pieces of A4 paper, after the temperature of an oven is stabilized, the samples are put into the oven, heated for 1h at 120 ℃, taken out, the size after heating is measured, and the shrinkage rate is calculated. The average of the heat shrinkages of the 5 sheets of samples was its heat shrinkage.

And (3) the liquid absorption rate is obtained by cutting 5 samples with the size of 100 x 100mm, weighing the mass, immersing each sample in the conventional electrolyte for 10min, taking out the sample, sucking the electrolyte on the surface by using filter paper, weighing the mass again, and calculating the percentage of the mass increase after the electrolyte is immersed, namely the liquid absorption rate. The average value of the liquid absorption rates of the 5 samples is the liquid absorption rate.

Cutting 5 samples with the size of 20 x 100mm and 5 ternary positive electrodes with the size of 30 x 65mm into pole pieces, hot-pressing for 5min under the conditions of 0.9Mpa pressure and 90 ℃, and then testing the adhesive force of the diaphragm and the pole pieces according to a peel strength testing method.

The results of the tests are shown in Table 1.

Table 1 separator performance test results

The results in table 1 show that the peel strength of the separator in each embodiment of the present application is greatly improved compared with the comparative example, so that the problem of powder falling of the product in the use process is avoided, and the safety performance of the battery is improved. Meanwhile, the diaphragm and the pole piece of the comparative example have no adhesive force, the diaphragm and the pole piece of each example have better adhesive force, and the adhesive force of the diaphragm and the pole piece can improve the consistency of the internal resistance of the battery and prolong the service life of the battery; and if the diaphragm and the pole piece are not well bonded, a gap is formed between the diaphragm and the pole piece, so that the internal resistance of the battery at the position is high, the problems of lithium precipitation and the like are easily caused, the hardness of the battery is improved, and the deformation of the battery in the long-term use process is reduced. In addition, compared with a comparative example, the liquid absorption of each example of the application is improved by about 20%, the formation process is further shortened, and the rapid charge and discharge performance of the battery is improved. The heat shrinkage performance of the diaphragm of each embodiment of the application is equivalent to that of the diaphragm of the comparative example, and the heat shrinkage performance of the diaphragm of the embodiment is guaranteed to be the same as that of the existing product.

The foregoing is a more detailed description of the present application in connection with specific embodiments thereof, and it is not intended that the present application be limited to the specific embodiments thereof. It will be apparent to those skilled in the art from this disclosure that many more simple derivations or substitutions can be made without departing from the spirit of the disclosure.

Claims

1. A preparation method of a ceramic coating diaphragm is characterized by comprising the following steps: the ceramic coating diaphragm comprises a base film and a ceramic coating coated on at least one surface of the base film, wherein the ceramic coating is formed by coating inorganic particles with polyethylene glycol grafted on the surface,

dispersing the inorganic particles into ethanol, adding an aminosilane coupling agent, stirring and reacting for 1-4h at the temperature of 20-80 ℃ and the pH value of 6-8, and washing and drying a reaction product to obtain the inorganic particles with amino groups on the surfaces; mixing a condensing agent, inorganic particles with amino on the surface and polyethylene glycol with carboxyl on the end group, stirring and reacting for 1-8 hours at 20-50 ℃, and then washing to obtain inorganic particles with polyethylene glycol grafted on the surface;

preparing coating slurry, namely dispersing the inorganic particles with the surfaces grafted with the polyethylene glycol into water, and uniformly stirring to prepare the coating slurry;

the preparation method of the ceramic coating diaphragm comprises the following steps: coating the coating slurry on at least one surface of the base film to obtain the ceramic coating separator.

2. The method of claim 1, wherein: the condensing agent is at least one of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, 2-chloro-4, 6-dimethoxy-1, 3, 5-triazine and N-hydroxysuccinimide.

3. The method of claim 1, wherein: the step of preparing the ceramic coating diaphragm further comprises the steps of coating the coating slurry on at least one surface of the base film, and heating to volatilize water to obtain the ceramic coating diaphragm; the heating temperature is 30-80 ℃ and the heating time is 5-72 s.

4. The method of claim 1, wherein: the coating adopts at least one of a scraper coating method, a Meyer bar coating method, a reverse roll coating method, a gravure roll coating method, dip coating and brush coating.

5. The production method according to any one of claims 1 to 4, characterized in that: the peel strength of the ceramic coating diaphragm at an angle of 180 degrees is greater than 40N/m.

6. The production method according to any one of claims 1 to 4, characterized in that: the base film is a polyolefin microporous film, and the polyolefin microporous film is a polyethylene microporous film, a polypropylene microporous film or a two-layer or multi-layer composite film consisting of the polyethylene microporous film and the polypropylene microporous film.

7. The production method according to any one of claims 1 to 4, characterized in that: the inorganic particles are selected from at least one of aluminum oxide, silicon dioxide, zirconium dioxide, titanium dioxide, zinc oxide, magnesium oxide, calcium carbonate, magnesium hydroxide, aluminum hydroxide and boehmite.

8. The production method according to any one of claims 1 to 4, characterized in that: the thickness of the basement membrane is 5-60 mu m, the porosity is 10% -60%, and the pore diameter is 0.01-0.5 mu m.

9. The ceramic coated separator produced by the production method according to any one of claims 1 to 8.

10. Use of the ceramic coated separator of claim 9 in a lithium ion battery.

11. A lithium ion battery employing the ceramic coated separator of claim 9.