阅读说明：本技术 一种基于核孔膜的固态电解质隔膜及其制备方法 (Solid electrolyte diaphragm based on nuclear pore membrane and preparation method thereof ) 是由 刘建德 刘杰 孙友梅 姚会军 莫丹 段敬来 曹殿亮 陈永辉 于 2020-11-18 设计创作，主要内容包括：本发明公开了一种基于核孔膜的固态电解质隔膜及其制备方法。本发明采用聚酰亚胺重离子径迹刻蚀多孔膜作为基膜,聚酰亚胺耐高温达400℃,可在-200～300℃的温度范围内稳定工作,收缩性极低,具有优异的力学性能和绝缘性。聚酰亚胺薄膜的优良性能,保证了制备的电解质隔膜的高的力学性能和热稳定性。重离子径迹刻蚀技术制备的膜(核孔膜)具有孔径一致,大小可控,孔密度方便可调的优点。聚酰亚胺重离子径迹刻蚀膜的纳米孔中填充的高分子链电解质,定向排列的纳米孔的空间限域效应使高分子链沿着纳米孔方向伸展,降低了聚合物的玻璃化转变温度,提高了聚合物电解质的锂离子电导率,使全固态锂离子电池或锂金属电池具有优异的安全性能和电池性能。(The invention discloses a solid electrolyte diaphragm based on a nuclear pore membrane and a preparation method thereof. The polyimide heavy ion track etching porous membrane is used as a base membrane, the polyimide has high temperature resistance of 400 ℃, can stably work at the temperature of-200-300 ℃, has extremely low contractility, and has excellent mechanical property and insulativity. The excellent performance of the polyimide film ensures the high mechanical property and thermal stability of the prepared electrolyte diaphragm. The membrane (nuclear pore membrane) prepared by the heavy ion track etching technology has the advantages of consistent aperture, controllable size and convenient and adjustable pore density. The polymer chain electrolyte is filled in the nano holes of the polyimide heavy ion track etching film, and the space confinement effect of the nano holes in the directional arrangement enables the polymer chain to extend along the direction of the nano holes, so that the glass transition temperature of the polymer is reduced, the lithium ion conductivity of the polymer electrolyte is improved, and the all-solid-state lithium ion battery or the lithium metal battery has excellent safety performance and battery performance.)

1. A solid electrolyte separator is composed of a base film and an electrolyte;

the base membrane is a nuclear pore membrane with pore channels uniformly distributed;

the electrolyte is uniformly distributed in the pore channels of the nuclear pore membrane.

2. The solid electrolyte membrane according to claim 1, characterized in that: the base film is made of polyimide or polyethylene terephthalate;

the pore channel is a straight-through hole;

the arrangement mode of the pore channels is directional arrangement;

the pore diameter of the pore channel is 0.01-5 mu m;

the thickness of the base film is 5-30 mu m; in particular 6 μm;

the pore density of the base film was 10⁵～2×10¹⁰Per square centimeter;

the electrolyte is a lithium salt electrolyte; in particular, a PEO polymer lithium salt electrolyte.

3. A method of producing the solid electrolyte membrane of claim 1 or 2, comprising:

1) performing vertical surface incidence irradiation on the polyimide film, and adjusting the intensity and irradiation time of heavy ion beam to ensure that the ion number irradiated on the polyimide film is 10⁵～2×10¹⁰ions/cm²Obtaining an irradiated PI film;

2) carrying out hole etching on the irradiated PI film obtained in the step 1) to obtain a porous PI film;

3) coating a lithium salt polymer coating on the surface of the porous PI film, and removing the solvent to obtain the porous PI film coated with the electrolyte on the surface;

the lithium salt polymer coating consists of a lithium salt polymer and an organic solvent;

4) and 3) melting the electrolyte of the porous PI film with the electrolyte coated on the surface obtained in the step 3) in an inert atmosphere, filling the electrolyte in the pores of the porous PI film, and cooling to obtain the solid electrolyte diaphragm.

4. The method of claim 3, wherein: in the step 1), the LET value (linear energy transfer) of the heavy ions in the polyimide material is more than 4.5 eV/nm;

the heavy ions are heavy ions of bismuth or tantalum;

the ion energy is 0.1-100 MeV/u; specifically 9.8 MeV/u;

irradiation density of 10⁵-2×10¹⁰Each square centimeter of ions; in particular 2 x 10⁸Each square centimeter of ions;

in the step 2), in the step of etching the holes, the etchant is aqueous solution of hypochlorite; the hypochlorite is at least one selected from sodium hypochlorite, potassium hypochlorite, lithium hypochlorite and calcium hypochlorite; (ii) a

The mass percentage of the available chlorine in the hypochlorite aqueous solution is 5-15%; in particular to 12 percent;

the etching time is 3-150 minutes; in particular 20-40 minutes; more specifically 30 minutes;

in the step 3), the organic solvent is acetonitrile;

in the lithium salt polymer coating, the dosage ratio of the lithium salt polymer to the organic solvent is 5-30 mg: 30 ml;

the coating method is spin coating, dipping or blade coating;

the method for removing the solvent is vacuum drying; the temperature of the vacuum drying is specifically 40-80 ℃; in particular 60 ℃; the time is 8-20 hours;

in the step 4), the temperature in the melting step is 200-230 ℃; in particular 220 ℃; the time is 8-20 hours;

the inert atmosphere is nitrogen atmosphere or argon atmosphere.

5. Use of the solid electrolyte separator as claimed in any one of claims 1 or 2 in the manufacture of a battery.

6. A battery comprising the solid electrolyte membrane according to claim 1 or 2 as an electrolyte membrane.

7. The use according to claim 5 or the battery according to claim 6, characterized in that: the battery is a solid-state lithium ion battery or a lithium metal battery.

Technical Field

The invention relates to a solid electrolyte diaphragm based on a nuclear pore membrane and a preparation method thereof.

Background

Lithium ion batteries are widely used due to their advantages of high energy density, high operating voltage, long charge-discharge life, no memory effect, and little environmental pollution. There is a conflict between the high performance and safety of lithium batteries, resulting in catastrophic battery failures that continue to increase with the demand for high energy density lithium ion batteries. The all-solid-state lithium battery has higher theoretical capacity and good safety, is considered as an ideal choice for future energy storage equipment, and the preparation of the thin electrolyte membrane with self-supporting performance and high lithium ion conductivity is the key for realizing the high-performance lithium secondary battery and is the core of the preparation of the all-solid-state lithium ion battery and the lithium metal battery. The solid electrolyte mainly includes a solid organic polymer electrolyte and an inorganic compound electrolyte. Organic polymer electrolytes have the advantages of light weight, good film-forming property, convenient preparation and the like, are considered to be preferred electrolytes for solid lithium ion batteries, and particularly have attracted much attention as polyethylene oxide (PEO) polymer electrolytes. However, the application of the polymer electrolyte in the all-solid-state lithium battery is limited by low lithium ion conductivity, poor mechanical property, no high temperature resistance and the like. The preparation of solid electrolyte separators with excellent mechanical strength, high temperature resistance and high lithium ion conductivity is a key to the development of solid lithium ion batteries and lithium metal batteries.

The investigation of PEO polymer electrolytes began in 1973 with the discovery of the conductivity of polyethylene oxide complexes with alkali metal ions by Wright et al. In 1979, Armand et al, France reported that the ionic conductivity of PEO alkali metal salt complex reached 10 at 40-60 deg.C^-5S/cm and has good film forming property. Polyethylene oxide (PEO) electrolytes, with excellent flexibility and good interfacial compatibility, have made PEO polymers considered to be the most promising electrolyte materials for solid state lithium batteries to date. However, PEO has high crystallinity and high glass transition temperature, which limits the lithium ion conductivity of PEO electrolyte, and the PEO film has poor mechanical properties and low mechanical strength, which limits the application of the PEO film in batteries. The main methods of increasing the conductivity of PEO electrolytes are to inhibit crystallization of the polymer chains and to increase the concentration of the carrier ions. The method of copolymerization, crosslinking, blending, plasticization, addition of inorganic materials and the like can effectively reduce the crystallinity of the polymer and improve the proportion of an amorphous region, and simultaneously increase the ion-carrying concentration in the system, thereby improving the lithium ion conductivity of the PEO polymer electrolyte system.

However, it is difficult to improve both the conductivity of lithium ions and the mechanical properties of the reinforced film by the conventional method for improving the conductivity of lithium ions. The PEO polymer film has insufficient mechanical strength, is not suitable for preparing a solid-state battery, and even brings hidden danger to the safety of the solid-state battery. The low ionic conductivity and insufficient mechanical strength of the existing polymer electrolytes have largely limited their application in all solid-state lithium secondary batteries.

Disclosure of Invention

Aiming at the problem that the existing improved PEO-based polymer solid electrolyte is difficult to simultaneously take the conductivity and the mechanical strength of lithium ion into consideration, the invention provides a solid electrolyte diaphragm based on a nuclear pore membrane and a preparation method thereof.

The solid electrolyte diaphragm provided by the invention consists of a base film and an electrolyte;

the base membrane is a nuclear pore membrane with pore channels uniformly distributed;

the electrolyte is uniformly distributed in the pore channels of the nuclear pore membrane.

In the solid electrolyte membrane, the base membrane is made of polyimide or polyethylene terephthalate;

the pore channel is a straight-through hole;

the arrangement mode of the pore channels is directional arrangement;

the pore diameter of the pore channel is 0.01-5 mu m;

the thickness of the base film is 5-30 mu m; in particular 6 μm;

the pore density of the base film was 10⁵～2×10¹⁰Per square centimeter;

the electrolyte is a lithium salt electrolyte; in particular, a PEO polymer lithium salt electrolyte.

The method for preparing the solid electrolyte membrane comprises the following steps:

1) performing vertical surface incidence irradiation on the polyimide film, and adjusting the intensity and irradiation time of heavy ion beam to ensure that the ion number irradiated on the polyimide film is 10⁵～2×10¹⁰ions/cm²Obtaining an irradiated PI film;

2) carrying out hole etching on the irradiated PI film obtained in the step 1) to obtain a porous PI film;

3) coating a lithium salt polymer coating on the surface of the porous PI film, and removing the solvent to obtain the porous PI film coated with the electrolyte on the surface;

the lithium salt polymer coating consists of a lithium salt polymer and an organic solvent;

4) and 3) melting the electrolyte of the porous PI film with the electrolyte coated on the surface obtained in the step 3) in an inert atmosphere, filling the electrolyte in the pores of the porous PI film, and cooling to obtain the solid electrolyte diaphragm.

In the step 1) of the method, the LET value (linear energy transfer) of the heavy ions in the polyimide material is greater than 4.5eV/nm, so that damage tracks generated by the heavy ions in the polyimide can be ensured to etch uniform and continuous holes;

the heavy ions are heavy ions of bismuth or tantalum;

the ion energy is 0.1-100 MeV/u; specifically 9.8 MeV/u;

irradiation density of 10⁵-2×10¹⁰Each square centimeter of ions; in particular 2 x 10⁸Each square centimeter of ions;

in the step 2), in the step of etching the holes, the etchant is aqueous solution of hypochlorite; the hypochlorite is at least one selected from sodium hypochlorite, potassium hypochlorite, lithium hypochlorite and calcium hypochlorite; (ii) a

The mass percentage of the available chlorine in the hypochlorite aqueous solution is 5-15%; in particular to 12 percent;

the etching time is 3-150 minutes; in particular 20-40 minutes; more specifically 30 minutes;

in the step 3), the organic solvent is acetonitrile;

in the lithium salt polymer coating, the dosage ratio of the lithium salt polymer to the organic solvent is 5-30 mg: 30 ml;

the coating method is spin coating, dipping or blade coating;

the method for removing the solvent is vacuum drying; the temperature of the vacuum drying is specifically 40-80 ℃; in particular 60 ℃; the time is 8-20 hours; in particular 12-16 hours;

in the step 4), the temperature in the melting step is 200-230 ℃; in particular 220 ℃; the time is 8-20 hours; in particular 12-16 hours;

the inert atmosphere is nitrogen atmosphere or argon atmosphere.

In addition, the application of the solid electrolyte membrane provided by the invention in the preparation of batteries and the batteries using the solid electrolyte membrane as the electrolyte membrane also belong to the protection scope of the invention. Specifically, the battery is a solid-state lithium ion battery or a lithium metal battery.

The solid electrolyte membrane provided by the invention adopts the polyimide heavy ion track etching membrane (nuclear pore membrane) containing nano pores with uniform size as the base membrane, so that the solid electrolyte membrane has excellent mechanical property and high temperature resistance. And then, the lithium salt Polymer Electrolyte (PEO) filled in the nano-pores is directionally arranged along the direction of the pores by utilizing the space confinement effect of the nano-pores of the base film, so that the conductivity of lithium ions is increased. The invention combines high lithium ion conductivity, excellent mechanical property and stable electrochemical property in the polymer electrolyte, can ensure that the solid lithium ion battery or the lithium metal battery has excellent battery performance and safety performance, and provides a preferable method for preparing the solid lithium ion electrolyte.

The polyimide film with directional arrangement, no cross and uniform diameter and column-shaped through holes can be obtained by the method, and PEO polymer lithium salt electrolyte is filled in the nano holes of the polyimide film. The porous polyimide film has excellent mechanical property and thermal property, and the PEO electrolyte reduces the glass transition temperature thereof through the confinement effect of the nano-pores, thereby improving the conductivity of the lithium ion. Therefore, the solid electrolyte diaphragm which has high lithium ion conductivity and high mechanical strength and is used for a solid lithium ion battery or a lithium metal battery can be prepared by the method.

The polyimide heavy ion track etching porous membrane is used as a base membrane, the polyimide has high temperature resistance of 400 ℃, can stably work at the temperature of-200-300 ℃, has extremely low contractility, and has excellent mechanical property and insulativity. The excellent performance of the polyimide film ensures the high mechanical property and thermal stability of the prepared electrolyte diaphragm. The membrane (nuclear pore membrane) prepared by the heavy ion track etching technology has the advantages of consistent aperture, controllable size and convenient and adjustable pore density. The polymer chain electrolyte is filled in the nano holes of the polyimide heavy ion track etching film, and the space confinement effect of the nano holes in the directional arrangement enables the polymer chain to extend along the direction of the nano holes, so that the glass transition temperature of the polymer is reduced, the lithium ion conductivity of the polymer electrolyte is improved, and the all-solid-state lithium ion battery or the lithium metal battery has excellent safety performance and battery performance.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention.

FIG. 2 is an optical diagram of a polyimide film after heavy ion irradiation.

FIG. 3 is an electron microscope image of the polyimide film after heavy ion irradiation and etching.

Fig. 4 is a topographical view of a solid electrolyte separator prepared for use in a solid lithium ion battery or a lithium metal battery.

Fig. 5 is a Nyquist plot of solid electrolyte membranes tested at different temperatures using the blocking electrode method and Arrhenius curves characterizing ionic conductivity.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

The invention relates to a high-strength lithium battery solid electrolyte diaphragm based on a nuclear pore membrane and a preparation method thereof, wherein the nuclear pore membrane has the advantages of uniform aperture, convenience and controllability, and is used for preparing a polyimide nuclear pore membrane with high mechanical strength; the polymer solid electrolyte filled in the holes is arranged along the direction of the holes by utilizing the space confinement effect of the nano holes, so that the glass transition temperature of the polymer electrolyte is reduced, and the conductivity of lithium ion is improved. Thereby preparing the solid electrolyte diaphragm with excellent mechanical strength and high lithium ion conductivity, and being convenient for preparing solid lithium ion batteries or lithium metal batteries.

Examples 1,

1) The high-energy heavy ion beam current provided by the heavy ion accelerator is heavy ion bismuth (the LET value (linear energy transfer) of the heavy ions in the polyimide material is more than 4.5eV/nm), the ion energy is 9.8MeV/u, the Polyimide (PI) film with the thickness of 6 microns is vertically irradiated, and the irradiation density is 2 x 10⁸The irradiated PI film is shown in fig. 2 per square centimeter of ions.

2) The heavy ion irradiated PI membrane was etched in a sodium hypochlorite solution with an available chlorine content of 12% at 60 ℃ for 30 minutes to obtain a PI nuclear pore membrane with a vertical nanopore diameter of 3 hundred nanometers, as shown in fig. 3.

3) Coating the prepared PI nuclear pore membrane with a PEO electrolyte solution containing lithium salt, evaporating at 60 ℃ for 12 hours to remove the solvent, heating to 220 ℃ in an inert atmosphere for 16 hours to ensure that the polymer electrolyte is thermally melted into the nano pores of the polyimide, as shown in figure 4, thereby obtaining the high-strength lithium battery solid electrolyte membrane based on the nuclear pore membrane for the solid lithium ion battery or the lithium metal battery.

The solid electrolyte membrane is composed of a base membrane and an electrolyte;

the base membrane is a nuclear pore membrane with pore channels uniformly distributed;

the electrolyte is uniformly distributed in the pore channels of the nuclear pore membrane.

In the solid electrolyte membrane, the material constituting the base film is polyimide;

the pore channel is a straight-through hole;

the arrangement mode of the pore channels is directional arrangement;

the pore diameter of the pore channel is 0.01-5 mu m;

the thickness of the base film is 5-30 mu m; in particular 6 μm;

the pore density of the base film was 10⁵～2×10¹⁰Per square centimeter;

the electrolyte is PEO polymer lithium salt electrolyte.

Fig. 1 is a schematic structural diagram of a solid electrolyte membrane for a solid lithium ion battery or a lithium metal battery according to the present invention, which includes a porous polyimide-based membrane and a lithium salt polymer electrolyte filled in a space-confining region in a nanopore. The polyimide basal membrane has high mechanical strength and thermal stability, and can ensure that the solid-state lithium ion battery or the lithium metal battery has high safety. The multiple nanopores of the polyimide-based membrane and the spatial confinement of the lithium salt polymer electrolyte enable the polymer electrolyte to be arranged along the nanopores, the glass transition temperature of the polymer electrolyte is reduced, and the lithium ion conductivity is improved, so that the solid-state lithium ion battery or the lithium metal battery is ensured to have excellent battery performance.

The electron micrograph of fig. 4 includes the front and back sides of a solid electrolyte separator for a solid lithium ion battery or a lithium metal battery. In an electron microscope picture, lithium salt polymer electrolyte is filled in the nanopores of the PI basal membrane no matter on the front surface or the back surface, so that the solid electrolyte diaphragm for the solid lithium ion battery or the lithium metal battery, which is prepared by the invention, has high mechanical strength and thermal stability, and has excellent lithium ion conductivity, so that the solid lithium ion battery or the lithium metal battery has excellent electrochemical performance.

Fig. 5 is a Nyquist plot and an Arrhenius curve representing ionic conductivity measured at different temperatures using the blocking electrode method for a solid electrolyte separator for a solid lithium ion battery or a lithium metal battery prepared according to the present invention. As can be seen from the Arrhenius curve, the prepared solid electrolyte membrane has higher lithium ion conductivity.