Preparation process of high-temperature-resistant latticed aramid fiber coated diaphragm for lithium battery

Abstract

The invention relates to the technical field of preparation of lithium battery diaphragms, in particular to a preparation process of a high-temperature-resistant latticed aramid fiber coated diaphragm for a lithium battery. The preparation method comprises the following steps: adding SiO2 into a mixed solution in an ultrasonic mixing manner to prepare slurry, and coating the surface of a base membrane with the slurry to obtain the high-temperature-resistant latticed aramid fiber coating diaphragm for the lithium battery. The SiO2 nanowires have good high temperature resistance and heat conduction performance, and the SiO2 nanowires are selected as a coating material to be added into the slurry component, so that the heat resistance of the coating is improved, and the heat resistance of the diaphragm is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium battery diaphragm preparation, in particular to a preparation process of an aramid coated diaphragm for a high temperature resistant grid-shaped lithium battery. Background Art

[0002] In the structure of lithium batteries, the diaphragm is one of the key inner components. The performance of the diaphragm determines the interface structure and internal resistance of the battery, directly affecting the battery's capacity, cycle and safety performance. A diaphragm with excellent performance plays an important role in improving the overall performance of the battery. The main function of the diaphragm is to separate the positive and negative electrodes of the battery to prevent the two electrodes from contacting and short-circuiting. In addition, it also has the function of allowing electrolyte ions to pass through. The diaphragm material is non-conductive, and its physical and chemical properties have a great influence on the performance of the battery. Different types of batteries use different diaphragms. For lithium battery series, since the electrolyte is an organic solvent system, a diaphragm material resistant to organic solvents is required, and a high-strength thin-film polyolefin porous membrane is generally used. The Chinese invention patent with application number 201510457866.X discloses a lithium-ion battery diaphragm coated with an aramid polymer and a preparation method thereof. However, the high temperature resistance of the lithium-ion battery diaphragm is poor. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a preparation process of an aramid coated diaphragm for a high temperature resistant grid-shaped lithium battery, wherein the diaphragm has good high temperature resistance.

[0004] In order to solve the above problems, the following technical solutions are provided:

[0005] The preparation process of the high temperature resistant grid-shaped lithium battery aramid coated diaphragm of the present invention is characterized by comprising the following steps: the first step is to prepare a slurry

[0006] (1) POSS, aramid fiber and ionic liquid are mixed to obtain a mixed solution; wherein the ionic liquid is composed of a main solvent and a co-solvent, the main solvent is NVP, DMI or DMPU, and the co-solvent is CsCl, KCl or NaCl; the amounts of POSS, aramid fiber and co-solvent are 3wt% to 28wt%, 2wt% to 10wt% and 1wt% to 3wt% of the weight of the main solvent, respectively.

[0007] (2) adding SiO2 nanowire powder to the mixed solution, and stirring the mixed solution with the added SiO2 nanowire powder for 2 to 3 hours at 40 to 50 kHz using an ultrasonic stirrer to obtain a mixed solution containing SiO2; wherein the amount of SiO2 nanowire powder added is 3 to 5 parts by mass per 100 parts of the mixed solution;

[0008] (3) Add alkali to the mixed solution containing SiO2 to adjust the pH value to >4 to obtain a slurry.

[0009] Step 2: Coating

[0010] The slurry prepared in the first step is coated on one or both sides of the base film, placed in a precipitant for precipitation and then dried to obtain a high-temperature resistant grid-shaped aramid coated separator for lithium batteries.

[0011] The aramid is one or more of meta / para aramid fiber, meta / para aramid pulp, and meta / para aramid polymer, and the molecular weight of the aramid is 3,000 to 70,000.

[0012] The POSS is eight-arm vinyl silsesquioxane, eight-amyl silsesquioxane or trifluorinated propyl-POSS.

[0013] The base film is a polypropylene microporous film or a polyethylene microporous film.

[0014] The base film has a thickness of 24-34 μm.

[0015] The slurry is applied to one or both sides of the base film in a thickness of 0.1-0.5 μm.

[0016] The above solution has the following advantages:

[0017] According to the preparation process of the high temperature resistant mesh-shaped lithium battery aramid coated diaphragm of the present invention, SiO2 is added to the mixed liquid by ultrasonic mixing to obtain a slurry, and the slurry is coated on the surface of the base film to obtain the high temperature resistant mesh-shaped lithium battery aramid coated diaphragm. SiO2 nanowires have good high temperature resistance and thermal conductivity. Selecting SiO2 nanowires as coating materials and adding them to the slurry components is conducive to improving the heat resistance of the coating, thereby improving the heat resistance of the diaphragm. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to the embodiments.

[0019] Example 1

[0020] A preparation process of an aramid coated diaphragm for a high temperature resistant grid-shaped lithium battery comprises the following steps:

[0021] Step 1: Prepare slurry

[0022] (1) First, 100 g of NVP solvent and 1 g of CsCl solvent were weighed and added to a stirrer respectively, and stirred with a magnetic stirrer at 42° C. until CsCl was completely dissolved to form an ionic liquid.

[0023] (2) then, 3 g of V-POSS and 2 g to 10 g of meta-aramid fiber with a molecular weight of 1000 were added to the ionic solution, respectively, and stirred with a magnetic stirrer at 40° C. until the meta-aramid fiber was completely dissolved and no meta-aramid staple fibers were visible in the solution, thereby obtaining a mixed solution;

[0024] (3) Weigh 100 g of the mixed solution and add it into an ultrasonic mixer.

[0025] (4) Add 3 g of SiO2 nanowire powder to the mixed solution, set the frequency of the ultrasonic stirrer to 40-50 kHz, and mix for 2 h to obtain a mixed solution containing SiO2.

[0026] (5) adding alkali to the mixed solution containing SiO2 to adjust the pH value to greater than 4 to obtain a slurry;

[0027] Step 2: Coating

[0028] The slurry was coated on a 25 μm PP base film for lithium batteries using a wire rod, with a coating thickness of 0.5 μm. The coated wet film was placed in deionized water for 30 seconds and then taken out. After drying, a high temperature resistant grid-shaped aramid coated separator for lithium batteries was obtained.

[0029] Example 2

[0030] A preparation process of an aramid coated diaphragm for a high temperature resistant grid-shaped lithium battery comprises the following steps:

[0031] Step 1: Prepare slurry

[0032] (1) First, 100 g of NVP solvent and 3 g of CsCl solvent were weighed and added to a stirrer respectively, and stirred with a magnetic stirrer at 42° C. until CsCl was completely dissolved to form an ionic liquid.

[0033] (2) then, 28 g of V-POSS and 10 g of meta-aramid fiber with a molecular weight of 1000 were added to the ionic solution, respectively, and stirred with a magnetic stirrer at 40° C. until the meta-aramid fiber was completely dissolved and no meta-aramid staple fibers were visible in the solution, thereby obtaining a mixed solution;

[0034] (3) Weigh 100 g of the mixed solution and add it into an ultrasonic mixer.

[0035] (4) Add 5 g of SiO2 nanowire powder to the mixed solution, set the frequency of the ultrasonic stirrer to 40-50 kHz, and mix for 3 h to obtain a mixed solution containing SiO2.

[0036] (5) adding alkali to the mixed solution containing SiO2 to adjust the pH value to greater than 4 to obtain a slurry;

[0037] Step 2: Coating

[0038] The slurry was coated on a 28 μm PP base film for lithium batteries using a wire rod, with a coating thickness of 0.2 μm. The coated wet film was placed in deionized water for 30 seconds and then taken out. After drying, a high temperature resistant grid-shaped aramid coated separator for lithium batteries was obtained.

[0039] Example 3

[0040] A preparation process of an aramid coated diaphragm for a high temperature resistant grid-shaped lithium battery comprises the following steps:

[0041] Step 1: Prepare slurry

[0042] (1) First, 100 g of NVP solvent and 2CsCl solvent were weighed and added to a stirrer respectively, and stirred with a magnetic stirrer at 42° C. until CsCl was completely dissolved to form an ionic liquid.

[0043] (2) then, 15 g of V-POSS and 6 g of meta-aramid fiber with a molecular weight of 1000 were added to the ionic solution, respectively, and stirred at 40° C. with a magnetic stirrer until the meta-aramid fiber was completely dissolved and no meta-aramid staple fibers were seen in the solution, thereby obtaining a mixed solution;

[0044] (3) Weigh 100 g of the mixed solution and add it into an ultrasonic mixer.

[0045] (4) Add 4 g of SiO2 nanowire powder to the mixed solution, set the frequency of the ultrasonic stirrer to 40-50 kHz, and mix for 2.5 hours to obtain a mixed solution containing SiO2.

[0046] (5) adding alkali to the mixed solution containing SiO2 to adjust the pH value to greater than 4 to obtain a slurry;

[0047] Step 2: Coating

[0048] The slurry was coated on a 34 μm PP base film for lithium batteries using a wire rod, with a coating thickness of 0.3 μm. The coated wet film was placed in deionized water for 30 seconds and then taken out. After drying, a high temperature resistant grid-shaped aramid coated separator for lithium batteries was obtained.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that no SiO2 is added and a pure meta-aramid coating film is directly prepared.

[0051] Comparative Example 2

[0052] The difference from Example 1 is that SiO2 is added, but ordinary mechanical stirring is used instead of ultrasonic stirring.

[0053] The following table shows the results of the performance tests of the coated diaphragms obtained in Examples 1, 2, 3 and Comparative Examples 1 and 2.

[0054] Conclusion: From the comparison of the data in the table, it can be seen that the present invention adds SiO2 to the mixed liquid by ultrasonic mixing to obtain a slurry, and then applies the slurry to the surface of the base film to obtain a high-temperature resistant grid-shaped aramid coated diaphragm for lithium batteries. SiO2 nanowires have good high temperature resistance and thermal conductivity. Selecting SiO2 nanowires as a coating material and adding them to the slurry component is beneficial to improving the heat resistance of the coating, thereby improving the heat resistance of the diaphragm.

Claims

1. A process for preparing an aramid-coated diaphragm for a high-temperature resistant grid-shaped lithium battery, characterized in that: The steps include: Step 1: Prepare slurry (1) POSS, aramid fiber and ionic liquid are mixed to obtain a mixed solution; wherein the ionic liquid is composed of a main solvent and a co-solvent, the main solvent is NVP, DMI or DMPU, and the co-solvent is CsCl, KCl or NaCl; the amounts of POSS, aramid fiber and co-solvent are 3wt% to 28wt%, 2wt% to 10wt% and 1wt% to 3wt% of the weight of the main solvent respectively; (2) adding SiO2 nanowire powder to the mixed solution, and stirring the mixed solution with the added SiO2 nanowire powder for 2 to 3 hours at 40 to 50 kHz using an ultrasonic stirrer to obtain a mixed solution containing SiO2; wherein the amount of SiO2 nanowire powder added is 3 to 5 parts by mass per 100 parts of the mixed solution; (3) adding alkali to the mixed solution containing SiO2 to adjust the pH value to greater than 4 to obtain a slurry; Step 2: Coating The slurry prepared in the first step is coated on one or both sides of the base film, placed in a precipitant for precipitation and then dried to obtain a high-temperature resistant grid-shaped aramid coated separator for lithium batteries.

2. The process for preparing the high temperature resistant grid-shaped lithium battery aramid coated diaphragm according to claim 1, characterized in that: The aramid is one or more of meta / para aramid fiber, meta / para aramid pulp, and meta / para aramid polymer, and the molecular weight of the aramid is 3,000 to 70,000.

3. The process for preparing the high temperature resistant grid-shaped lithium battery aramid coated diaphragm according to claim 1, characterized in that: The POSS is eight-arm vinyl silsesquioxane, eight-amyl silsesquioxane or trifluorinated propyl-POSS.

4. The process for preparing the high temperature resistant grid-shaped lithium battery aramid coated diaphragm according to claim 1, characterized in that: The base film is a polypropylene microporous film or a polyethylene microporous film.

5. The process for preparing the high temperature resistant grid-shaped lithium battery aramid coated diaphragm according to claim 1, characterized in that: The base film has a thickness of 25-34 μm.

6. The process for preparing the high temperature resistant grid-shaped lithium battery aramid coated diaphragm according to claim 1, characterized in that: The slurry is applied to one or both sides of the base film in a thickness of 0.1-0.5 μm.

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