阅读说明：本技术 一种锂离子电池隔膜及其制备方法 (Lithium ion battery diaphragm and preparation method thereof ) 是由 邓江红 于 2020-12-10 设计创作，主要内容包括：本发明公开了一种锂离子电池隔膜及其制备方法,包括将商用纸平铺在玻璃器皿中,然后将氧化石墨烯加入到蒸馏水中,超声40～60min使其分散,然后加入多巴胺超声搅拌,缓慢倒入玻璃器皿中,然后加入tril-HCl缓冲液,调节其pH值至8.5～9,静置26～30h,然后取出用无水乙醇进行洗涤,备用；将聚偏氟乙烯加入到N,N-二甲基甲酰胺中,完全溶解,搅拌8～12h得到粘性溶液,然后取步骤S1中的备用的商用纸,用真空抽滤的方法,反复抽滤3～6次,制备出均匀孔径的隔膜前体；将隔膜前体在55～70℃下真空干燥12～16h,然后用辊压机加压,使纤维黏连,其中辊压机的压力为32～38MPa,然后用冲片机切成直径19毫米的隔膜。本发明隔膜具有优异的电解质湿润性,机械性能和导电性能。(The invention discloses a lithium ion battery diaphragm and a preparation method thereof, wherein the preparation method comprises the steps of flatly paving commercial paper in a glass ware, adding graphene oxide into distilled water, carrying out ultrasonic treatment for 40-60 min to disperse the graphene oxide, adding dopamine, carrying out ultrasonic stirring, slowly pouring the mixture into the glass ware, adding a tri-HCl buffer solution, adjusting the pH value of the buffer solution to 8.5-9, standing for 26-30 h, taking out the buffer solution, and washing the buffer solution with absolute ethyl alcohol for later use; adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 8-12 h to obtain a viscous solution, and repeatedly performing suction filtration for 3-6 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare a diaphragm precursor with uniform aperture; and (3) drying the diaphragm precursor in vacuum at 55-70 ℃ for 12-16 h, then pressurizing by using a roller press to bond the fibers, wherein the pressure of the roller press is 32-38 MPa, and then cutting into diaphragms with the diameter of 19 mm by using a punching machine. The diaphragm of the invention has excellent electrolyte wettability, mechanical property and conductivity.)

1. The lithium ion battery diaphragm is characterized in that a base material of the diaphragm is cellulose commercial paper, then micropores of the commercial paper are modified by polydopamine, and then polyvinylidene fluoride is used for filling, so that the diaphragm with high porosity is obtained.

2. The preparation method of the lithium ion battery separator according to claim 1, wherein the preparation method comprises the following steps:

s1: flatly paving commercial paper in a glass ware, adding graphene oxide into distilled water, performing ultrasonic treatment for 40-60 min to disperse the graphene oxide, adding dopamine, performing ultrasonic stirring, slowly pouring the mixture into the glass ware, adding a tri-HCl buffer solution, adjusting the pH value of the mixture to 8.5-9, standing for 26-30 h, taking out the mixture, and washing the mixture with absolute ethyl alcohol for later use;

s2: adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 8-12 h to obtain a viscous solution, and repeatedly performing suction filtration for 3-6 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare a diaphragm precursor with uniform aperture;

s3: and (3) drying the diaphragm precursor in vacuum at 55-70 ℃ for 12-16 h, then pressurizing by using a roller press to bond the fibers, wherein the pressure of the roller press is 32-38 MPa, and then cutting into diaphragms with the diameter of 19 mm by using a punching machine.

3. The preparation method of the lithium ion battery separator according to claim 2, wherein the addition amount of the graphene oxide is 14-28 wt%.

4. The preparation method of the lithium ion battery separator according to claim 2, wherein the mass-to-volume ratio of the dopamine to the tri-HCl buffer solution is (0.21-0.26) g (115-160) mL.

5. The preparation method of the lithium ion battery separator according to claim 2, wherein the mass ratio of the viscous solution is 6.2-8.6 wt.%.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery diaphragm and a preparation method thereof.

Background

The diaphragm is one of the important components of the battery, can avoid short circuit caused by direct contact of the anode and the cathode, and simultaneously ensures the rapid transfer of lithium ions, and is of great importance to the performance and the safety of the battery. At present, the commonly used single-layer or multi-layer polyolefin microporous membrane has superior electrochemical stability and higher mechanical strength, but the hydrophobicity of the membrane causes poor electrolyte affinity, thereby affecting the rate performance of the battery.

In recent years, since cellulose is renewable, excellent characteristics such as biocompatibility and high electrolyte affinity are considered to be excellent choices in the field of manufacturing of separators for energy storage, and cellulose separators exhibit excellent thermal stability, high strength, and excellent electrolyte wettability, many researchers have employed various cellulose-based separators to improve the safety performance and electrochemical performance of lithium ion batteries. Therefore, commercial paper made of cellulose has great potential as a substrate of a lithium ion battery separator. However, the micropores between the fibers of commercial paper cause short circuits when it is used as a separator.

Disclosure of Invention

Aiming at the problem that the commercial paper is large in pore diameter when being used as a diaphragm material, the invention aims to provide a lithium ion battery diaphragm, wherein the base material of the diaphragm is cellulose commercial paper, then polydopamine is used for modifying micropores of the commercial paper, and then polyvinylidene fluoride is used for filling, so that the diaphragm with high porosity is obtained.

The invention also aims to provide a preparation method of the lithium ion battery diaphragm, which comprises the following steps:

s1: spreading commercial paper in a glass ware, adding graphene oxide into distilled water, performing ultrasonic treatment for 40-60 min to disperse the graphene oxide, adding dopamine, performing ultrasonic stirring, slowly pouring the mixture into the glass ware, adding a tri-HCl buffer solution, adjusting the pH value of the mixture to 8.5-9, standing for 26-30 h, taking out the mixture, and washing the mixture with absolute ethyl alcohol for later use.

S2: and (3) adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 8-12 h to obtain a viscous solution, and repeatedly performing suction filtration for 3-6 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare the diaphragm precursor with uniform aperture.

S3: and (3) drying the diaphragm precursor in vacuum at 55-70 ℃ for 12-16 h, then pressurizing by using a roller press to bond the fibers, wherein the pressure of the roller press is 32-38 MPa, and then cutting into diaphragms with the diameter of 19 mm by using a punching machine.

Preferably, the addition amount of the graphene oxide is 14-28 wt%.

Preferably, the mass-to-volume ratio of the dopamine to the tril-HCl buffer solution is (0.21-0.26) g (115-160) mL.

Preferably, the mass ratio of the viscous solution is 6.2 to 8.6 wt.%.

Compared with the prior art, the invention has the following beneficial effects:

in the invention, commercial paper is used as a base material, polydopamine is firstly used for modification, and the polydopamine has stronger adsorption energy to lithium ions, so that the nucleation barrier of lithium is favorably reduced, the ion transmission is adjusted, the electrochemical deposition of lithium on a negative electrode material is uniform, and the formation of lithium dendrites is avoided; and then filled again with polyvinylidene fluoride, strong hydrogen bonds are formed between F atoms in PVDF and H atoms in — OH groups in cellulose, giving the separator high thermal stability and mechanical strength.

Drawings

Fig. 1 is an SEM image of the separator prepared in example 1 of the present invention.

Detailed Description

The following embodiments of the present invention are described in detail, and the embodiments are implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Example 1

A preparation method of a lithium ion battery diaphragm specifically comprises the following steps:

s1: spreading commercial paper in a glass ware, adding graphene oxide into distilled water, wherein the addition amount of the graphene oxide is 14 wt%, performing ultrasonic agitation for 40min to disperse the graphene oxide, adding dopamine, performing ultrasonic agitation, wherein the mass-to-volume ratio of the dopamine to the tri-HCl buffer solution is 0.21g:115mL, slowly pouring the mixture into the glass ware, adding the tri-HCl buffer solution, adjusting the pH value of the mixture to 8.5, standing the mixture for 26h, taking the mixture out, and washing the mixture with absolute ethyl alcohol for later use.

S2: and (2) adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 8 hours to obtain a viscous solution with the mass ratio of 6.2 wt.%, and repeatedly performing suction filtration for 3 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare the diaphragm precursor with uniform aperture.

S3: the membrane precursor was vacuum dried at 55 ℃ for 12 hours and then pressed with a roll press having a pressure of 32MPa to bind the fibers, and then cut into a membrane having a diameter of 19 mm with a punch.

Example 2

A preparation method of a lithium ion battery diaphragm specifically comprises the following steps:

s1: spreading commercial paper in a glass ware, adding graphene oxide into distilled water, wherein the addition amount of the graphene oxide is 28 wt%, performing ultrasonic agitation for 60min to disperse the graphene oxide, adding dopamine, performing ultrasonic agitation, wherein the mass-to-volume ratio of the dopamine to the tri-HCl buffer solution is 0.26g:160mL, slowly pouring the mixture into the glass ware, adding the tri-HCl buffer solution, adjusting the pH value of the mixture to 9, standing the mixture for 30h, taking the mixture out, and washing the mixture with absolute ethyl alcohol for later use.

S2: and (2) adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 12 hours to obtain a viscous solution with the mass ratio of 8.6 wt.%, and repeatedly performing suction filtration for 6 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare the diaphragm precursor with uniform aperture.

S3: the membrane precursor was vacuum dried at 70 ℃ for 16h and then pressed with a roller press having a pressure of 38MPa to bind the fibers, and then cut into a membrane having a diameter of 19 mm with a punch.

Example 3

A preparation method of a lithium ion battery diaphragm specifically comprises the following steps:

s1: spreading commercial paper in a glass ware, adding graphene oxide into distilled water, wherein the addition amount of the graphene oxide is 18 wt%, performing ultrasonic stirring for 45min to disperse the graphene oxide, adding dopamine, performing ultrasonic stirring, wherein the mass-to-volume ratio of the dopamine to the tri-HCl buffer solution is 0.23g:130mL, slowly pouring the mixture into the glass ware, adding the tri-HCl buffer solution, adjusting the pH value of the mixture to 8.6, standing the mixture for 27h, taking the mixture out, and washing the mixture with absolute ethyl alcohol for later use.

S2: and (2) adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 10 hours to obtain a viscous solution with the mass ratio of 7.6 wt.%, and repeatedly performing suction filtration on the commercial paper for standby in the step S1 for 4 times by using a vacuum suction filtration method to prepare the diaphragm precursor with uniform aperture.

S3: the membrane precursor was vacuum dried at 60 ℃ for 13 hours and then pressed with a roll press having a pressure of 34MPa to bind the fibers, and then cut into a membrane having a diameter of 19 mm with a punch.

Example 4

A preparation method of a lithium ion battery diaphragm specifically comprises the following steps:

s1: spreading commercial paper in a glass ware, adding graphene oxide into distilled water, wherein the addition amount of the graphene oxide is 26 wt%, performing ultrasonic agitation for 55min to disperse the graphene oxide, adding dopamine, performing ultrasonic agitation, wherein the mass-to-volume ratio of the dopamine to the tri-HCl buffer solution is 0.25g:150mL, slowly pouring the mixture into the glass ware, adding the tri-HCl buffer solution, adjusting the pH value of the mixture to 8.8, standing the mixture for 28h, taking the mixture out, and washing the mixture with absolute ethyl alcohol for later use.

S2: and (2) adding polyvinylidene fluoride into N, N-dimethylformamide, completely dissolving, stirring for 11 hours to obtain a viscous solution with the mass ratio of 8.2 wt.%, and repeatedly performing suction filtration for 5 times by using a vacuum suction filtration method on the commercial paper for later use in the step S1 to prepare the diaphragm precursor with uniform aperture.

S3: the membrane precursor was vacuum dried at 65 ℃ for 15 hours and then pressed with a roll press having a pressure of 36MPa to bind the fibers, and then cut into a membrane having a diameter of 19 mm with a punch.

Experimental example: the separators prepared in examples 1 to 4 were subjected to the following performance tests,

and (3) performance testing: the thermal stability performance test adopts a thermal weight loss method, and the thermal shrinkage rate of the diaphragm is tested at a heating rate of 5 ℃/min under the nitrogen atmosphere;

the mechanical property is tested by adopting a tensile testing machine, and the tensile is carried out at the strain rate of 1 mm/min; the imbibition rate test was performed by placing a diaphragm in the electrolyte (1M LiPF)₆Dissolving in EC/DMC/EMC 1:1:1), weighing the diaphragm mass after absorption saturation, and calculating the liquid absorption rate by the following formula:

wherein EU is the liquid absorption rate, W₀And W is the weight of the separator before and after soaking in the electrolyte;

the conductivity was measured using an electrochemical workstation, with a frequency range of 100mHz to 100kHz, calculated by the following formula:

where σ is the ionic conductivity, d is the thickness of the separator, R is the bulk resistance, and A is the electrode area;

the porosity was measured using a surface area tester, the porosity was measured by soaking in n-butanol, calculated using the following formula:

where ρ is the n-butanol density, W₂Is the mass of the diaphragm after absorbing n-butanol, W₁Is the dry membrane mass, all the above test results are reported in table 1,

table 1. results of performance testing:

as can be seen from Table 1, the thermal stability of the diaphragm prepared in the embodiments 1-4 can reach more than 300 ℃, which shows that the diaphragm material of the invention has excellent thermal stability; meanwhile, the mechanical strength is more than 36MPa, the liquid absorption rate and the porosity are respectively more than 223 wt.% and 80%, and the conductivity is about 0.71 mS/cm, which shows that the diaphragm material has excellent ionic conductivity.