阅读说明：本技术 一种高性能纤维素基锂离子电池隔膜的制备方法 (Preparation method of high-performance cellulose-based lithium ion battery diaphragm ) 是由 付宇 王永勤 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种高性能纤维素基锂离子电池隔膜的制备方法,属于锂离子电池技术领域。本发明所述的纤维素基锂离子电池隔膜的制备方法是,将UIO-67纳米粒子分散在有机溶剂中,加入醋酸纤维素(CA)和聚氨酯(PU),采用静电纺丝工艺制备CA/PU/UIO-67隔膜。本发明提供的方法制备的CA/PU/UIO-67隔膜具有锂离子迁移数高、热稳定好、孔径分布均匀、孔径较小等优点,可以有效延缓锂枝晶的成核速率,提高锂离子电池的电化学性能。(The invention discloses a preparation method of a high-performance cellulose-based lithium ion battery diaphragm, and belongs to the technical field of lithium ion batteries. The preparation method of the cellulose-based lithium ion battery diaphragm comprises the steps of dispersing UIO-67 nano particles in an organic solvent, adding Cellulose Acetate (CA) and Polyurethane (PU), and preparing the CA/PU/UIO-67 diaphragm by adopting an electrostatic spinning process. The CA/PU/UIO-67 diaphragm prepared by the method provided by the invention has the advantages of high transference number of lithium ions, good thermal stability, uniform pore size distribution, small pore size and the like, can effectively delay the nucleation rate of lithium dendrites, and improves the electrochemical performance of a lithium ion battery.)

1. A preparation method of a high-performance cellulose-based lithium ion battery diaphragm is characterized by comprising the following steps:

s1, dispersing UIO-67 nano particles in an organic solvent;

s2, adding cellulose acetate and polyurethane into the dispersion liquid prepared in the step S1;

s3, performing electrostatic spinning on the dispersion liquid obtained in the step S2 to obtain a membrane, and performing vacuum drying on the membrane to obtain the CA/PU/UIO-67 diaphragm.

2. The method for preparing the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the UIO-67 nanoparticles are prepared by the following method: zirconium chloride and 4,4' -bi-linkedPhthalic acid and acetic acid in N, N-dimethylformamide/H₂Stirring and heating the O mixed solution to 110 ℃ for reaction; after the reaction is finished, cooling, centrifuging, and washing the product by using water and ethanol to obtain the UIO-67 nano particles.

3. The preparation method of the high-performance cellulose-based lithium ion battery separator as claimed in claim 2, wherein the UIO-67 nanoparticles are prepared from the following raw materials in parts by weight: zirconium chloride 7.5g, 4,4' -Biphenyldicarboxylic acid 7.8g, acetic acid 93mL, N, N-dimethylformamide 500mL, H₂O 75mL。

4. The preparation method of the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the UIO-67 nanoparticles are present in the organic solvent in an amount of 0.6 to 0.8 wt% in step S1.

5. The method for preparing the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the organic solvent in the step S1 is a mixed solvent of N, N-dimethylformamide and acetone, and the volume ratio of the mixed solvent to the mixed solvent is (7-8) to (2-3).

6. The method for preparing the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the mass ratio of the cellulose acetate to the polyurethane in the step S2 is 7: 3.

7. The preparation method of the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the mass fraction of the cellulose acetate and the polyurethane in the dispersion liquid in the step S2 is 7-8 wt%.

8. The method for preparing the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the cellulose acetate has an acetyl content of 39.5 wt% and a hydroxyl content of 3.5 wt%; the polyurethane is a thermoplastic polyurethane.

9. The method for preparing the high-performance cellulose-based lithium ion battery separator according to claim 1, wherein the electrostatic spinning parameters in step S3 are set as follows: the distance between the nozzle and the receiver is 12-15cm, the applied voltage is 18-20kV, the supply rate is 2-2.5mL/h, and the rotation speed of the roller is 800-.

10. The application of the CA/PU/UIO-67 diaphragm prepared by the preparation method of the high-performance cellulose-based lithium ion battery diaphragm as claimed in any one of claims 1 to 9 in a lithium ion battery.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a high-performance cellulose-based lithium ion battery diaphragm.

Background

Lithium ion batteries are a very promising and important energy storage technology. The separator serves as a key component of a lithium ion battery, and although the separator does not directly participate in the electrochemical reaction of the battery, the performance and structure of the separator play a key role in influencing the battery performance (including energy density, power density, safety and service life). Many factors should be considered in selecting a suitable separator for use in a lithium ion battery. Existing lithium ion battery separators typically employ polyolefins such as polyethylene and polypropylene. However, the shortfalls of polyolefin separators are also apparent, and they are difficult to meet the requirements of future development. From the practical standpoint, the polyolefin-based separator has two greatest drawbacks of poor thermal stability and poor wettability with an electrolyte. In addition, polyolefin based membranes rely on limited fossil energy sources and are not renewable, sustainable or biodegradable. Therefore, more new materials are being investigated as membrane substitutes.

Compared with polyolefin diaphragms, lithium ion battery diaphragms prepared by taking cellulose as a raw material overcome the defects. The heat-resistant temperature of the cellulose diaphragm can reach more than 230 ℃, and the cellulose diaphragm has the characteristics of good wettability and high liquid absorption rate on electrolyte, but the mechanical strength of the cellulose membrane is poor, and the existing cellulose diaphragm still has certain problems. Therefore, designing and preparing a high performance cellulose-based lithium ion battery separator remains a significant challenge.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a preparation method for preparing a high-performance cellulose-based lithium ion battery diaphragm with good electrochemical performance and thermal stability.

In order to achieve the purpose, the invention is realized by the following technical scheme.

A preparation method of a high-performance cellulose-based lithium ion battery diaphragm comprises the following steps:

s1, dispersing UIO-67 nano particles in an organic solvent;

s2, adding Cellulose Acetate (CA) and Polyurethane (PU) into the dispersion liquid prepared in the step S1;

s3, performing electrostatic spinning on the dispersion liquid obtained in the step S2 to obtain a membrane, and performing vacuum drying on the membrane to obtain the CA/PU/UIO-67 diaphragm.

The UIO-67 nano particles are prepared by the following method: dissolving zirconium chloride, 4' -biphenyldicarboxylic acid and acetic acid in N, N-dimethylformamide/H₂Stirring and heating the O mixed solution to 110 ℃ for reaction; after the reaction is finished, cooling, centrifuging, and washing the product by using water and ethanol to obtain the UIO-67 nano particles.

Preferably, the UIO-67 nanoparticles are prepared from the following raw materials: zirconium chloride 7.5g, 4,4' -Biphenyldicarboxylic acid 7.8g, acetic acid 93mL, N, N-dimethylformamide 500mL, H₂O 75mL。

The specific surface area of the UIO-67 nano particle prepared by the method is 1600-1700m²The pore size is 0.7-1.2nm, and the pore size can effectively promote the transmission of lithium ions and inhibit PF₆ ^-And (4) transmission of anions.

Preferably, the mass fraction of the UIO-67 nanoparticles in the organic solvent in the step S1 is 0.6-0.8 wt%.

Preferably, the organic solvent in step S1 is a mixed solvent of N, N-dimethylformamide and acetone, and the volume ratio of the mixed solvent is (7-8) to (2-3).

Preferably, the mass ratio of the cellulose acetate to the polyurethane in the step S2 is 7: 3.

Preferably, the mass fraction of the cellulose acetate and the polyurethane in the dispersion liquid in the step S2 is 7-8 wt%.

Preferably, the cellulose acetate has an acetyl content of 39.5 wt% and a hydroxyl content of 3.5 wt%; the polyurethane is thermoplastic polyurethane, and is sold under the trade name 2795.

Preferably, the parameters of the electrostatic spinning in step S3 are set as follows: the distance between the nozzle and the receiver is 12-15cm, the applied voltage is 18-20kV, the supply rate is 2-2.5mL/h, and the rotation speed of the roller is 800-.

The thickness of the CA/PU/UIO-67 diaphragm prepared by the method is 60-100 mu m, the aperture is 10-100 nm, and the porosity is 30-50%.

The invention also provides application of the high-performance cellulose-based lithium ion battery diaphragm prepared by the preparation method in a lithium ion battery, and the diaphragm of the conventional lithium ion battery is replaced by the CA/PU/UIO-67 diaphragm prepared by the invention.

The invention has the following beneficial effects:

(1) the diaphragm prepared by the method contains the UIO-67 nano particles with large specific surface area, so that the infiltration performance of the diaphragm to electrolyte can be obviously improved; meanwhile, the pore diameter structure of the nano particle can effectively promote Li⁺And suppressing the PF₆ ^-And the transmission of anions further improves the transference number of lithium ions.

(2) The diaphragm prepared by the invention contains UIO-67 nano particles with excellent thermal stability, and the thermal stability of the diaphragm can be obviously improved.

(3) The membrane matrix prepared by the invention contains cellulose, and the cellulose contains a large amount of hydroxyl which can be mixed with PF₆ ^-The anions form hydrogen bonds, so that the transmission of the anions is effectively inhibited, and the transference number of the lithium ions is further improved.

(4) The diaphragm of the invention has the advantages of uniform pore distribution, small pore diameter and the like, and can promote Li⁺The uniform deposition on the surface of the negative electrode delays the nucleation rate of lithium dendrites.

(5) Compared with a polyolefin diaphragm, the diaphragm substrate adopted by the invention has high heat-resistant temperature and better thermal stability, and meanwhile, the defect of poor mechanical property of the cellulose membrane is made up by the good mechanical property of polyurethane.

Drawings

FIG. 1(a) shows the contact angle of Celgard 2400 separator with an electrolyte; FIG. 1(b) is a contact angle of the CA/PU/UIO-67 separator prepared in example 1 with an electrolyte.

FIG. 2 is a graph of the cycling performance of a CA/PU/UIO-67 separator assembled lithium ion battery prepared in example 1.

Detailed Description

The technical solutions of the present invention will be described in detail and fully with reference to the following specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

Example 1

A preparation method of a high-performance cellulose-based lithium ion battery diaphragm comprises the following steps:

(1) preparation of UIO-67 nanoparticles

7.5g of zirconium chloride, 7.8g of 4,4' -biphenyldicarboxylic acid and 93mL of acetic acid were dissolved in 500mL of N, N-dimethylformamide and 75mLH₂Heating the mixed solution of O to 110 ℃, stirring and reacting for 60 minutes, cooling to room temperature after the reaction is finished, centrifuging for 5 minutes at the rotating speed of 8000r/min, collecting a solid product, and washing with water and ethanol to obtain the UIO-67 nano particles.

(2) Preparation of CA/PU/UIO-67 separator

S1, ultrasonically dispersing UIO-67 nano particles in a DMF/acetone mixed solvent, wherein the volume ratio of DMF to acetone is 8:2, and the mass fraction of the UIO-67 nano particles is 0.6 wt%;

s2, adding CA and PU with the mass ratio of 7:3 into the dispersion prepared in the step S1, and stirring at room temperature for 24 hours, wherein the mass fraction of the CA and the PU is 7 wt%;

s3, transferring the dispersion liquid obtained in the step S2 into a plastic injector, and performing electrostatic spinning in an air atmosphere to obtain an electrostatic spinning film; and drying the electrostatic spinning membrane under the vacuum condition, and removing residual organic solvent in the membrane to obtain the CA/PU/UIO-67 diaphragm. The parameters of the electrostatic spinning process are as follows: the distance between the nozzle and the receiver is 12 cm; the applied voltage was 20 kV; the feed rate was 2mL/h and the rotational speed of the drum was 1000 r/min.

The thickness of the CA/PU/UIO-67 diaphragm prepared by the embodiment is 100 mu m, the aperture is 10-100 nm, and the porosity is 38.7%.

Example 2

The preparation method of the high-performance cellulose-based lithium ion battery diaphragm is similar to that of the UIO-67 nano-particles in example 1, and the preparation method of the CA/PU/UIO-67 diaphragm comprises the following steps:

s1, ultrasonically dispersing UIO-67 nano particles in a DMF/acetone mixed solvent, wherein the volume ratio of DMF to acetone is 7:3, and the mass fraction of the UIO-67 nano particles is 0.8 wt%;

s2, adding CA and PU with the mass ratio of 7:3 into the dispersion prepared in the step S1, and stirring at room temperature for 12 hours, wherein the mass fraction of the CA and the PU is 8 wt%;

s3, transferring the dispersion liquid obtained in the step S2 into a plastic injector, and performing electrostatic spinning in an air atmosphere to obtain an electrostatic spinning film; and drying the electrostatic spinning membrane under the vacuum condition, and removing residual organic solvent in the membrane to obtain the CA/PU/UIO-67 diaphragm. The parameters of the electrostatic spinning process are as follows: the distance between the nozzle and the receiver is 15 cm; the applied voltage was 18 kV; the feed rate was 2.5mL/h and the drum rotation speed was 800 r/min.

The thickness of the CA/PU/UIO-67 diaphragm prepared by the embodiment is 60 mu m, the aperture is 10-100 nm, and the porosity is 49.5%.

Example 3

The preparation method of the high-performance cellulose-based lithium ion battery diaphragm is similar to that of the UIO-67 nano-particles in example 1, and the preparation method of the CA/PU/UIO-67 diaphragm comprises the following steps:

s1, ultrasonically dispersing UIO-67 nano particles in a DMF/acetone mixed solvent, wherein the volume ratio of DMF to acetone is 7.5:2.5, and the mass fraction of the UIO-67 nano particles is 0.75 wt%;

s2, adding CA and PU with the mass ratio of 7:3 into the dispersion prepared in the step S1, and stirring at room temperature for 18h, wherein the mass fraction of CA and PU is 7.5 wt%;

s3, transferring the dispersion liquid obtained in the step S2 into a plastic injector, and performing electrostatic spinning in an air atmosphere to obtain an electrostatic spinning film; and drying the electrostatic spinning membrane under the vacuum condition, and removing residual organic solvent in the membrane to obtain the CA/PU/UIO-67 diaphragm. The parameters of the electrostatic spinning process are as follows: the distance between the nozzle and the receiver is 14 cm; the applied voltage was 19 kV; the feed rate was 2.3mL/h and the drum rotation speed was 900 r/min.

The thickness of the CA/PU/UIO-67 diaphragm prepared by the embodiment is 100 mu m, the aperture is 10-100 nm, and the porosity is 48.5%.

Example 4

The preparation method of the high-performance cellulose-based lithium ion battery diaphragm is similar to that of the UIO-67 nano-particles in example 1, and the preparation method of the CA/PU/UIO-67 diaphragm comprises the following steps:

s1, ultrasonically dispersing UIO-67 nano particles in a DMF/acetone mixed solvent, wherein the volume ratio of DMF to acetone is 8:2, and the mass fraction of the UIO-67 nano particles is 0.7 wt%;

s2, adding CA and PU with the mass ratio of 7:3 into the dispersion prepared in the step S1, and stirring at room temperature for 20 hours, wherein the mass fraction of the CA and the PU is 7 wt%;

s3, transferring the dispersion liquid obtained in the step S2 into a plastic injector, and performing electrostatic spinning in an air atmosphere to obtain an electrostatic spinning film; and drying the electrostatic spinning membrane under the vacuum condition, and removing residual organic solvent in the membrane to obtain the CA/PU/UIO-67 diaphragm. The parameters of the electrostatic spinning process are as follows: the distance between the nozzle and the receiver is 15 cm; the applied voltage was 18 kV; the feed rate was 2.5mL/h and the rotational speed of the drum was 850 r/min.

The thickness of the CA/PU/UIO-67 diaphragm prepared by the embodiment is 100 mu m, the aperture is 10-100 nm, and the porosity is 44.8%.

Comparative example

Commercial polypropylene septum Celgard 2400 was used as a comparison. FIG. 1(a) shows the contact angle of Celgard 2400 separator with the electrolyte, and FIG. 1(b) shows the contact angle of CA/PU/UIO-67 separator prepared in example 1 with the electrolyte, and it can be seen that the CA/PU/UIO-67 separator prepared by the present invention has a smaller contact angle with the electrolyte and better wettability.

The CA/PU/UIO-67 diaphragms prepared in the examples 1 to 4 and diaphragms of the comparative examples are respectively assembled into NCM523 lithium ion batteries for performance test.

Transference number of lithium ion: a5 mV polarization voltage was applied to the assembled cell by a chronoamperometry method, and the initial polarization current value and the stabilized polarization current value were recorded. The calculation formula is as follows:

wherein, t_Li+Is the transport number of lithium ions, I_SSThe current value (A), R after polarization stabilization_SSFor impedance after polarization stabilization，I_OThe current value (A), R is the initial value of polarization_OFor impedance after polarization stabilizationAnd Δ V is a polarization voltage value (V).

Charge-discharge cycle performance: the charge-discharge cycle test is carried out at 25 ℃ and 1C, and the voltage test range is 3.0-4.2V.

The test results are shown in table 1.

Table 1 results of performance testing

Examples	Transference number of lithium ion	900 cycle capacity fading rate (%)
			Example 1	0.71	21.68
Example 2	0.73	21.62
			Example 3	0.72	21.57
Example 4	0.71	21.63
			Comparative example	0.62	48.42

The CA/PU/UIO-67 diaphragm prepared by the method has the advantage of high transference number of lithium ions, and meanwhile, due to the high porosity and small pore diameter of the diaphragm, the nucleation rate of lithium dendrites can be effectively delayed, so that the cycle performance of the lithium ion battery is improved.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.