CN115588820A - A low-cost lithium battery separator with high electrolyte wettability and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of lithium battery diaphragms, in particular to a low-cost lithium battery diaphragm with high electrolyte wettability, which comprises a base film and polymer coatings coated on any one side or two sides of the base film, wherein the polymer coatings comprise PVDF (polyvinylidene fluoride) and PMMA (polymethyl methacrylate) materials; the polymer slurry consists of mixed powder, a compatilizer, a dispersing agent, a thickening agent, a binder, a wetting agent, a defoaming agent and ultrapure water, wherein the mixed powder is a mixture of PVDF and PMMA. Compared with the traditional PMMA-simple substance coated lithium battery coating diaphragm, the invention effectively inhibits the excessive swelling condition of PMMA by a small amount of PVDF homopolymer, thereby improving the ionic conductivity and reducing the cost, and develops the compatilizer which is beneficial to the compatibility of PVDF and PMMA, so that PVDF and PMMA can obtain better compatibility in the slurry, and the stability of the slurry and the coating uniformity are improved.

Description

A low-cost lithium battery separator with high electrolyte wettability and preparation method thereof

technical field

The invention relates to the technical field of lithium battery separators, in particular to a low-cost lithium battery separator with high electrolyte wettability and a preparation method thereof.

Background technique

The structure of a lithium battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The main function of the separator is to separate the positive and negative electrodes of the battery to avoid short circuits between the positive and negative electrodes. Therefore, the separator needs to maintain good ion permeability and electronic insulation. In industrial production, the diaphragm made of polyolefin materials is generally called the base film. However, because the base film may have various performance deficiencies, the surface of the base film is often coated to make up for its various properties. Performance flaws.

In order to improve the bonding ability between the separator and the pole piece, an organic coating is often applied on the surface of the base film to improve its bonding property. The more mature one is to use PVDF as the organic coating. In actual use, it is often not the homopolymer of PVDF that is coated, but the copolymer of PVDF-HFP (polyvinylidene fluoride and hexafluoropropylene) is usually coated because of the swelling of the homopolymer of PVDF The performance is poor and the ionic conductivity is low, so the PVDF copolymer is modified by HPF before coating. However, the cost of using PVDF-HFP materials is very high, which is a relatively large burden on enterprises.

PMMA (polymethyl methacrylate, commonly known as acrylic) has become one of the materials that can replace PVDF-HFP due to its affinity electrolyte, low price and easy control of glass transition temperature. However, there is a problem of excessive swelling when simply using PMMA material for coating. Excessive swelling of PMMA will block the pores of the diaphragm and reduce the ionic conductivity of the diaphragm.

Therefore, we propose a low-cost lithium battery separator with high electrolyte wettability and its preparation method to solve the above problems.

Contents of the invention

The purpose of the present invention is to solve the shortcomings in the prior art, and propose a low-cost lithium battery diaphragm with high electrolyte wettability and a preparation method thereof.

A low-cost lithium battery separator with high electrolyte wettability, including a base film and a polymer coating coated on either side or both sides of the base film, the polymer coating includes PVDF and PMMA materials;

The polymer slurry is composed of the following raw materials in weight percentage: mixed powder 6%-13%, compatibilizer 5%-15%, dispersant 0.3%-1.2%, thickener 2.5%-7%, adhesive Agent 5%~13.5%, wetting agent 0.1%~0.35%, defoamer 0.1%~0.35%, and the rest is ultrapure water;

The mixed powder is a mixture of PVDF and PMMA, and the weight ratio is PVDF:PMMA=5-30:70-95.

Preferably, the base film is a polyolefin separator.

Preferably, the dispersant is aliphatic amides, the thickener is sodium hydroxymethylcellulose, the binder is polyacrylic acid, and the wetting agent is alkyl sulfate. Described defoamer is polyether type defoamer.

Preferably, the dispersant is polyacrylamide, octadecylamine acetate, alkyl quaternary ammonium salt, aminopropylamine dioleate, polyethylene glycol polyol, polyethyleneimine derivative, oil One of amino oleic acid esters, the adhesive is cyanoacrylate derivative adhesive, cyanoacrylate polyethylene glycol adhesive, acrylic adhesive, vinyl acetate polymer latex adhesive One of the wetting agents, the wetting agent is one of polyoxyethylene surfactants, fatty acid surfactants, and silanol nonionic surfactants, and the defoaming agent is a high-carbon alcohol fatty acid ester Compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropanolamine ether, polyoxypropylene glyceryl ether, polyoxypropylene polyoxyethylene glyceryl ether and polydimethylsiloxane.

Preferably, the compatibilizer is composed of the following raw materials in parts by weight: 40-80 parts of PVDF homopolymer powder, and 20-60 parts of methyl methacrylate liquid.

A method for preparing a low-cost lithium battery diaphragm with high electrolyte wettability, comprising the following steps:

S1, prepare polymer slurry:

S1-1. Take 0.3%-1.2% dispersant and 6%-13% mixed powder according to the mass ratio and put them into ultrapure water for pre-mixing to obtain the first intermediate;

S1-2. Add 5% to 13.5% of binder and 2.5% to 7% of thickener to the first intermediate by mass ratio and continue stirring to obtain a second intermediate;

S1-3. Add 0.1%-0.35% wetting agent and 0.1%-0.35% defoamer to the second intermediate by mass ratio, stir, and filter to remove iron to obtain polymer slurry;

S2, preparation compatibilizer:

S2-1. Put the PVDF homopolymer powder and methyl methacrylate liquid in the ratio of 40-80:20-60 into ultrapure water for stirring and mixing to obtain a mixed solution;

S2-2. Place the aforementioned mixed solution in a gamma ray environment, take it out after sufficient irradiation, and obtain a compatibilizer;

S3. Modifying the aforementioned polymer slurry: putting 5-15 parts of compatibilizer into 85-95 parts of polymer slurry, stirring and mixing, and then standing still to obtain the modified polymer slurry;

S4. Preparing the separator: uniformly coating the prepared modified polymer slurry on the separator, baking, and rolling up for later use.

Preferably, in step S1-1, the premixing time is 10-120 minutes, and the rotation speed is 400-900 rpm.

Preferably, in step S1-2, the mixing time is 20-80 minutes, and the rotation speed is 350-700 rpm.

Preferably, in the step of S1-3, the mixing time is 20-80 minutes, and the rotation speed is 150-550 rpm.

Preferably, in step S4, a micro-gravure roll coating process is used to uniformly roll-coat the modified polymer slurry on the separator through a coating machine.

The beneficial effects of the present invention are:

1. Compared with the traditional PMMA single substance coated lithium battery coating diaphragm, the present invention effectively suppresses the excessive swelling of PMMA through a small amount of PVDF homopolymer, thereby improving the ion conductivity, and compared with Traditional PVDF-HFP material reduces cost.

2. The present invention has developed a kind of compatibilizer that is beneficial to PVDF and PMMA compatibility, and this compatibilizer is main chain with PVDF, through gamma ray irradiation at PVDF main chain graft MMA branch, makes PVDF and PMMA in slurry It can obtain better compatibility, improve the stability of slurry and the uniformity of coating.

3. The present invention uses water-based coating to prepare the diaphragm, which has less pollution and lower cost than oil-based coating.

detailed description

The present invention will be further explained below in conjunction with specific embodiments.

Embodiment one:

A low-cost lithium battery separator with high electrolyte wettability, including a base film and a polymer coating coated on either side or both sides of the base film, the polymer coating includes PVDF and PMMA materials; the base film is polyolefin diaphragm.

The polymer slurry is composed of the following raw materials in weight percentage: 6% mixed powder, 5% compatibilizer, 0.3% dispersant, 2.5% thickener, 5% binder, 0.1% wetting agent, defoaming agent Agent 0.1%, mixed powder is a mixture of PVDF and PMMA, PVDF:PMMA=5:95.

In the above polymer slurry, the dispersant used is polyacrylamide, octadecylamine acetate, alkyl quaternary ammonium salt, aminopropylamine dioleate, polyethylene glycol polyol, polyethylene One of imine derivatives and oleyl amino oleate.

The thickener is sodium carboxymethylcellulose (CMC glue).

The adhesive is one of cyanoacrylate derivative adhesives, cyanoacrylate polyethylene glycol adhesives, acrylic adhesives, and vinyl acetate polymer latex adhesives.

The wetting agent is one of polyoxyethylene surfactants, fatty acid surfactants, and silanol nonionic surfactants.

The defoaming agent is high carbon alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glyceryl ether, polyoxypropylene polyoxyethylene glyceryl ether and polydimethyl One of the base siloxanes.

A method for preparing a low-cost lithium battery diaphragm with high electrolyte wettability, comprising the following steps:

S1, prepare polymer slurry:

S1-1. Take 0.3% dispersant and 6% mixed powder according to the mass ratio and put them into ultrapure water and stir for 10 minutes at a stirring speed of 400rpm to obtain the first intermediate;

S1-2. Add 5% binder and 2.5% thickener to the obtained first intermediate and continue stirring for 20 minutes at a stirring speed of 350 rpm to obtain the second intermediate;

S1-3. Add 0.1% wetting agent and 0.1% defoamer to the obtained second intermediate and continue stirring for 20 minutes at a stirring speed of 150 rpm to obtain polymer slurry.

S2, preparation compatibilizer:

S2-1. Put PVDF homopolymer powder and MMA (methyl methacrylate) liquid into ultrapure water at a ratio of 45:55 and stir to obtain a mixed solution. The stirring time is 20 minutes, and the stirring speed is 500 rpm;

S2-2. Place the aforementioned mixed solution in a gamma ray environment, take it out after sufficient irradiation, and obtain a compatibilizer.

S3. Modification of the aforementioned polymer slurry: 5 parts of compatibilizer and 95 parts of polymer slurry were mixed and stirred for 20 minutes at a stirring speed of 500 rpm to obtain modified polymer slurry.

S4. Preparation of the separator: using a micro-gravure roll coating process, the prepared modified polymer slurry was uniformly rolled on the polyolefin separator by a coating machine, and then rolled up after being baked in a 70°C oven for later use.

The stirring speed and stirring time in this example and the following examples are for reference only, and it is only necessary to ensure sufficient mixing.

Embodiment two:

A low-cost lithium battery separator with high electrolyte wettability, including a base film and a polymer coating coated on either side or both sides of the base film, the polymer coating includes PVDF and PMMA materials; the base film is polyolefin diaphragm.

The polymer slurry is composed of the following raw materials in weight percentage: 8% mixed powder, 10% compatibilizer, 0.92% dispersant, 10.5% thickener, 3.8% binder, 0.25% wetting agent, defoaming agent Agent 0.25%, mixed powder is a mixture of PVDF and PMMA, PVDF:PMMA=10:90.

In the above polymer slurry, the dispersant used is polyacrylamide, octadecylamine acetate, alkyl quaternary ammonium salt, aminopropylamine dioleate, polyethylene glycol polyol, polyethylene One of imine derivatives and oleyl amino oleate.

The thickener is sodium carboxymethylcellulose (CMC glue).

The adhesive is one of cyanoacrylate derivative adhesives, cyanoacrylate polyethylene glycol adhesives, acrylic adhesives, and vinyl acetate polymer latex adhesives.

The wetting agent is one of polyoxyethylene surfactants, fatty acid surfactants, and silanol nonionic surfactants.

The defoaming agent is high carbon alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glyceryl ether, polyoxypropylene polyoxyethylene glyceryl ether and polydimethyl One of the base siloxanes.

A method for preparing a low-cost lithium battery diaphragm with high electrolyte wettability, comprising the following steps:

S1, prepare polymer slurry:

S1-1. Put 0.92% dispersant and 8% mixed powder into ultrapure water according to mass ratio and stir for 60 minutes at a stirring speed of 600rpm to obtain the first intermediate;

S1-2. Add 3.8% binder and 10.5% thickener to the obtained first intermediate and continue stirring for 40 minutes at a stirring speed of 600 rpm to obtain the second intermediate;

S1-3. Add 0.25% wetting agent and 0.25% defoamer to the obtained second intermediate and continue stirring for 30 minutes at a stirring speed of 200 rpm to obtain polymer slurry.

S2, preparation compatibilizer:

S2-1. Put PVDF homopolymer powder and MMA (methyl methacrylate) liquid into ultrapure water at a ratio of 55:45 and stir to obtain a mixed solution. The stirring time is 20 minutes, and the stirring speed is 500 rpm;

S2-2. Place the aforementioned mixed solution in a gamma ray environment, take it out after sufficient irradiation, and obtain a compatibilizer.

S3. Modification of the aforementioned polymer slurry: 10 parts of compatibilizer and 90 parts of polymer slurry were mixed and stirred for 20 minutes at a stirring speed of 500 rpm to obtain modified polymer slurry.

S4. Preparation of the diaphragm: using a micro-gravure roll coating process, the prepared modified polymer slurry was evenly rolled onto the polyolefin diaphragm by a coating machine, and then rolled up after baking in a 70°C oven for later use.

Embodiment three:

A low-cost lithium battery separator with high electrolyte wettability, including a base film and a polymer coating coated on either side or both sides of the base film, the polymer coating includes PVDF and PMMA materials; the base film is polyolefin diaphragm.

Polymer slurry is composed of the following raw materials in weight percentage: 13% mixed powder, 20% compatibilizer, 1.2% dispersant, 13.5% thickener, 7% binder, 0.35% wetting agent, defoaming agent Agent 0.35%, mixed powder is a mixture of PVDF and PMMA, PVDF:PMMA=30:70.

In the above polymer slurry, the dispersant used is polyacrylamide, octadecylamine acetate, alkyl quaternary ammonium salt, aminopropylamine dioleate, polyethylene glycol polyol, polyethylene One of imine derivatives and oleyl amino oleate.

The thickener is sodium carboxymethylcellulose (CMC glue).

The adhesive is one of cyanoacrylate derivative adhesives, cyanoacrylate polyethylene glycol adhesives, acrylic adhesives, and vinyl acetate polymer latex adhesives.

The wetting agent is one of polyoxyethylene surfactants, fatty acid surfactants, and silanol nonionic surfactants.

The defoaming agent is high carbon alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glyceryl ether, polyoxypropylene polyoxyethylene glyceryl ether and polydimethyl One of the base siloxanes.

A method for preparing a low-cost lithium battery diaphragm with high electrolyte wettability, comprising the following steps:

S1, prepare polymer slurry:

S1-1. Take 1.2% dispersant and 13% mixed powder 1 according to the mass ratio and put them into ultrapure water and stir for 120 minutes at a stirring speed of 900 rpm to obtain the first intermediate;

S1-2. Add 7% binder and 13.5% thickener to the obtained first intermediate and continue to stir for 80 minutes at a stirring speed of 700rpm to obtain the second intermediate;

S1-3. Add 0.35% wetting agent and 0.35% defoamer to the obtained second intermediate and continue stirring for 80 minutes at a stirring speed of 550 rpm to obtain polymer slurry.

S2, preparation compatibilizer:

S2-1. Put PVDF homopolymer powder and MMA (methyl methacrylate) liquid into ultrapure water at a ratio of 80:20 and stir to obtain a mixed solution. The stirring time is 20 minutes and the stirring speed is 500 rpm;

S2-2. Place the aforementioned mixed solution in a gamma ray environment, take it out after sufficient irradiation, and obtain a compatibilizer.

S3. Modification of the aforementioned polymer slurry: 15 parts of compatibilizer and 85 parts of polymer slurry were mixed and stirred for 20 minutes at a stirring speed of 500 rpm to obtain modified polymer slurry.

S4. Preparation of the diaphragm: using a micro-gravure roll coating process, the prepared modified polymer slurry was evenly rolled onto the polyolefin diaphragm by a coating machine, and then rolled up after baking in a 70°C oven for later use.

Comparative example one:

Aiming at the above-mentioned embodiments, a comparative example 1 is provided, in which pure PMMA organic particles are used for coating.

Prepare slurry:

Put 0.92% dispersant and 8% PMMA powder into ultrapure water according to the mass ratio and stir for 60 minutes, the stirring speed is 600rpm, add 3.8% binder and 10.5% thickener to the obtained solution to continue Stir for 40 minutes at a stirring speed of 600 rpm, continue to add 0.25% of a wetting agent and 0.25% of an antifoaming agent and continue stirring for 30 minutes at a stirring speed of 200 rpm to obtain a PMMA coating slurry.

Prepare the diaphragm:

Using the micro-gravure roller coating process, the prepared PMMA Tugu slurry is evenly rolled on the polyolefin separator through a coating machine, and it is rolled up after being baked in a 70°C oven for later use.

Comparative example two:

In view of the above-mentioned embodiments, a comparative example 2 is provided, which uses PVDF homopolymer organic particles for coating.

Prepare slurry:

Put 0.92% dispersant and 8% PVDF powder into ultrapure water according to the mass ratio and stir for 60 minutes at a stirring speed of 600rpm, add 3.8% binder and 10.5% thickener to the obtained solution to continue Stir for 40 minutes at a stirring speed of 600 rpm, continue to add 0.25% of a wetting agent and 0.25% of an antifoaming agent and continue stirring for 30 minutes at a stirring speed of 200 rpm to obtain a PMMA coating slurry.

Prepare the diaphragm:

Using the micro-gravure roller coating process, the prepared PVDF coating slurry is evenly rolled on the polyolefin separator through a coating machine, and it is rolled up after being baked in a 70°C oven for later use.

The performance comparisons of the composite diaphragms prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1:

Table 1. Comparison of various properties of the composite diaphragms prepared in Examples 1-3 and Comparative Examples 1-2

It can be seen from experiments that under the preparation conditions of Examples 1-3 and the same coating thickness, Compared with Comparative Example 1, Examples 1-3 obviously have better puncture resistance, while compared with Comparative Example 2 , Examples 1-3 again have better liquid uptake and peel strength because of their higher liquid uptake and thus better ionic conductivity of the separator.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (10)

1. A low-cost lithium battery diaphragm with high electrolyte wettability is characterized by comprising a base film and polymer coatings coated on any one side or two sides of the base film, wherein the polymer coatings comprise PVDF and PMMA materials;

the polymer slurry is composed of the following raw materials in percentage by weight: 6 to 13 percent of mixed powder, 5 to 15 percent of compatilizer, 0.3 to 1.2 percent of dispersant, 2.5 to 7 percent of thickening agent, 5 to 13.5 percent of binder, 0.1 to 0.35 percent of wetting agent, 0.1 to 0.35 percent of defoaming agent and the balance of ultrapure water;

the mixed powder is a mixture of PVDF and PMMA, and the weight ratio of PVDF: PMMA =5 to 30:70 to 95.

2. The high electrolyte wettability low cost lithium battery separator as claimed in claim 1, wherein said base film is a polyolefin separator.

3. The high electrolyte wettability low cost lithium battery separator as claimed in claim 1, wherein said dispersant is aliphatic amide, said thickener is hydroxymethyl cellulose sodium, said binder is polyacrylic acid, said wetting agent is alkyl sulfate, said antifoaming agent is polyether antifoaming agent.

4. The high electrolyte wettability low cost lithium battery separator as claimed in claim 3, wherein said dispersant is one of polyacrylamide, octadecylamine acetate, alkyl quaternary ammonium salt, aminopropylamine dioleate, polyethylene glycol type polyol, polyethyleneimine derivative, and oleyl aminooleate, said binder is one of cyanoacrylate derivative binder, cyanoacrylate polyethylene glycol binder, acrylic binder, and vinyl acetate polymer latex binder, said wetting agent is one of polyoxyethylene type surfactant, fatty acid surfactant, and silanol type nonionic surfactant, and said defoaming agent is one of higher alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glyceryl ether, polyoxypropylene polyoxyethylene glyceryl ether, and polydimethylsiloxane.

5. The high-electrolyte-wettability low-cost lithium battery separator according to claim 1, wherein said compatibilizer comprises the following raw materials in parts by weight: 40-80 parts of PVDF homopolymer powder and 20-60 parts of methyl methacrylate liquid.

6. A preparation method of a lithium battery diaphragm with high electrolyte wettability and low cost is characterized by comprising the following steps:

s1, preparing polymer slurry:

s1-1, adding 0.3-1.2% of dispersing agent and 6-13% of mixed powder into ultrapure water according to the mass ratio for premixing to obtain a first intermediate;

s1-2, adding 5-13.5% of binder and 2.5-7% of thickener into the first intermediate according to the mass ratio, and continuously stirring to obtain a second intermediate;

s1-3, adding 0.1-0.35% of wetting agent and 0.1-0.35% of defoaming agent into the second intermediate according to the mass ratio, stirring, and filtering to remove iron to obtain polymer slurry;

s2, preparing a compatilizer:

s2-1, mixing PVDF homopolymer powder and methyl methacrylate liquid according to the weight ratio of 40-80: putting the mixture into ultrapure water in a proportion of 20-60, and stirring and mixing to obtain a mixed solution;

s2-2, placing the mixed solution in a gamma ray environment, fully irradiating, and taking out to obtain a compatilizer;

s3, modifying the polymer slurry: 5-15 parts of compatilizer is added into 85-95 parts of polymer slurry, stirred and mixed, and then the mixture is kept stand to obtain the modified polymer slurry;

s4, preparing a diaphragm: and uniformly coating the prepared modified polymer slurry on a diaphragm, baking and rolling for later use.

7. The method for preparing a lithium battery separator with high electrolyte wettability and low cost according to claim 6, wherein in the step S1-1, the premixing time is 10-120 min, and the rotation speed is 400-900 rpm.

8. The method for preparing a lithium battery separator with high electrolyte wettability and low cost according to claim 6, wherein in the step S1-2, the mixing time is 20-80 min, and the rotation speed is 350-700 rpm.

9. The method for preparing a lithium battery separator with high electrolyte wettability and low cost according to claim 6, wherein in the step S1-3, the mixing time is 20-80 min, and the rotation speed is 150-550 rpm.

10. The method for preparing a lithium battery separator with high electrolyte wettability and low cost as claimed in claim 6, wherein in the step S4, the modified polymer slurry is uniformly roll-coated on the separator by a coater through a micro gravure roll coating process.