CN-122025997-A - High-performance polyolefin diaphragm and preparation method and application thereof

Abstract

A process for preparing high-performance polyolefin diaphragm includes such steps as washing polyolefin diaphragm, surface treating by plasma surface treating equipment, preparing in-situ growth precursor solution from heteropolyacid with high ion conducting power, metal source and organic ligand, immersing the diaphragm in the precursor solution, hydrothermal reaction, washing with solvent and absolute alcohol, and vacuum drying. The invention combines the synergistic effect of plasma surface activation and supported heteropolyacid/metal organic framework, and builds the high-performance ion conductive coating through an in-situ growth process. Meanwhile, the ionic conductivity, the thermal stability and the cycling stability of the polyolefin diaphragm are improved, the process flow is simplified, and the production efficiency and the product consistency are higher.

Inventors

• WANG MENG
• JIANG RUI
• Ling Ruijing
• LIU XINGXING
• LI YUSI

Assignees

• 北京理工大学重庆创新中心

Dates

Publication Date

20260512

Application Date

20260317

Claims (10)

1. 1. A method for preparing a high-performance polyolefin membrane, which is characterized by comprising the following steps: A. Cleaning a polyolefin diaphragm, and then adopting plasma surface treatment equipment to carry out surface treatment on the diaphragm; B. selecting heteropoly acid with high ion conduction capacity, a metal source and an organic ligand, preparing an in-situ growth precursor solution with a solvent, soaking a diaphragm subjected to plasma surface treatment in the precursor solution, and performing hydrothermal reaction; C. And washing the membrane subjected to the hydrothermal reaction by using a solvent and absolute ethyl alcohol in sequence, and drying in vacuum to obtain the membrane.
2. 2. The polyolefin separator according to claim 1 may be a polypropylene separator, a polyethylene separator, a polypropylene or a polyethylene composite separator.
3. 3. The method of claim 1, wherein in step a, the plasma surface treatment atmosphere is one or more of oxygen, nitrogen and argon, the treatment time is 1 s-1 min, and the power is 10 w-80 w.
4. 4. The process according to claim 1, wherein in the step B, the heteropolyacid is one or more selected from the group consisting of silicotungstic acid, phosphotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid Dawson acid, phosphomolybdic acid Dawson acid, arsenic tungstic acid, germanium tungstic acid, cobalt molybdic acid, the metal source is one or more selected from the group consisting of zirconium salt, titanium salt, aluminum salt, iron salt, chromium salt, the organic ligand is one or more selected from the group consisting of 2-amino terephthalic acid, trimesic acid, 2-methylimidazole, and the solvent is one or more selected from the group consisting of N, N-dimethylformamide, acetic acid, ethanol, deionized water, and dimethyl sulfoxide.
5. 5. The method according to claim 1, wherein in the step B, the total concentration of the metal source and the organic ligand in the solution is 0.1wt% to 5wt%, and the mass ratio of the metal source to the organic ligand is 0.1 to 3:1.
6. 6. The method of claim 1, wherein the concentration of the heteropoly acid in the solution is 0.1wt% to 2wt%.
7. 7. The method according to claim 1, wherein in the step B, the hydrothermal reaction is performed at 80 ℃ to 200 ℃ for 12h to 48h.
8. 8. The method according to claim 1, wherein in step C, the drying is performed in a vacuum drying oven at 60 ℃ to 100 ℃ for 1h to 24h.
9. 9. A high performance polyolefin separator, characterized in that the high performance polyolefin separator is prepared by the preparation method according to any one of the preceding claims 1-8.
10. 10. Use of the high-performance polyolefin separator according to claim 9 in a lithium ion battery, wherein the high-performance polyolefin separator is used as a battery separator of the lithium ion battery.

Description

High-performance polyolefin diaphragm and preparation method and application thereof Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a high-performance polyolefin diaphragm and a preparation method and application thereof. Background The lithium ion battery diaphragm is used as a physical isolation layer and an ion conduction channel between an electrolyte and a positive electrode and a negative electrode, and the performance of the lithium ion battery diaphragm plays a vital role in the safety, the cycle life and the electrochemical performance of the battery. Conventional polyolefin separators are widely used in commercial lithium ion batteries due to their excellent mechanical strength, chemical stability and processability. However, polyolefin separators still face the outstanding problems that, due to the characteristics of the materials, ① electrolyte wettability is poor, polypropylene is a typical nonpolar material, surface energy is low, compatibility with polar electrolyte is poor, electrolyte is difficult to infiltrate into the separator rapidly, so that the transmission rate of lithium ions is limited, the rate capability and uniform deposition characteristics of a battery are affected, and ② thermal stability is insufficient, namely, polypropylene is easy to thermally shrink or even melt under high temperature conditions, electrode short circuit is possibly caused, and serious thermal runaway risks are caused. The problem is particularly obvious in the application of high-power or high-energy density batteries, and becomes a bottleneck for improving the safety of the lithium ion batteries, and the ③ polyolefin diaphragm has high mechanical strength, but the surface structure of the diaphragm is easily damaged in multiple charge and discharge cycles, so that the long-term stability of the diaphragm is affected. To overcome the above problems, researchers have proposed a method of surface modifying polyolefin separator. Among them, the surface coating technology is receiving attention because of its simple process and its ability to significantly improve separator performance. The common coating materials comprise inorganic particles (such as alumina, silicon dioxide, boron nitride and the like) and organic polymers (such as polyvinylidene fluoride, polyimide, polydopamine and the like), wherein the inorganic particles can obviously improve the thermal stability and mechanical strength of the diaphragm, but the coating has insufficient adhesive force with a polypropylene matrix, is easy to fall off in long-time use and affects the stability of the coating, and the organic coating has good electrolyte wettability and flexibility, but the single organic coating is difficult to meet the comprehensive performance requirement of the diaphragm. In recent years, methods such as plasma surface treatment, inorganic coating, polymer modification, and the like have been widely used to improve polyolefin separator performance. However, physical coatings have poor interfacial affinity with nonpolar substrates, are prone to shedding in long cycles, and single Metal Organic Framework (MOF) coatings have low conductivity, while heteropolyacid species have high conductivity but are very prone to loss in electrolytes. Therefore, the composite system with high cycle retention rate, fast ion transmission and excellent heat resistance is constructed by utilizing the synergistic effect of the MOF structural support and the fast heteropoly acid transmission capability by utilizing the plasma surface activation to strengthen the interface anchoring. Disclosure of Invention The invention aims to solve the problems in the prior art and provide a high-performance polyolefin diaphragm and a preparation method and application thereof. The technical scheme adopted by the invention is that the preparation method of the high-performance polyolefin diaphragm comprises the following steps: A. Cleaning a polyolefin diaphragm, and then adopting plasma surface treatment equipment to treat the surface of the diaphragm to form active sites on the surface of the diaphragm; B. Selecting heteropoly acid with high ion conduction capability, a metal source and an organic ligand, preparing the heteropoly acid and the organic ligand with a mixed solvent into an in-situ growth precursor solution, soaking a diaphragm subjected to plasma surface treatment in the precursor solution, and performing hydrothermal reaction to fully diffuse reaction components and effectively adsorb the reaction components on the surface of the diaphragm and in a micropore structure; C. and washing the membrane subjected to the hydrothermal reaction by using a synthetic mixed solvent and absolute ethyl alcohol in sequence, and drying in vacuum to obtain the membrane. In the step a, the atmosphere of the plasma surface treatment is one or more of oxygen, nitrogen and argon, the treatment time is 1 s-1 min (for exa