WO2023028900A1

WO2023028900A1 - Inorganic-organic composite electrolyte membrane, preparation method therefor, and application thereof

Info

Publication number: WO2023028900A1
Application number: PCT/CN2021/115850
Authority: WO
Inventors: 金超; 杨瑞枝; 彭琳; 陆正义; 孙家文
Original assignee: 苏州大学
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2023-03-09

Abstract

An inorganic-organic composite solid-state electrolyte membrane, which is composed of the following components: an inorganic ceramic solid-state electrolyte, lithium salt, unsaturated organic small molecules, and a film-forming polymer. A preparation method for the inorganic-organic composite solid-state electrolyte membrane. An inorganic-organic composite solid-state electrolyte membrane-based solid-state lithium battery, specifically comprises a lithium metal negative electrode, a positive electrode, and the inorganic-organic composite solid-state electrolyte membrane. The inorganic-organic composite solid-state electrolyte membrane has relatively high lithium-ion conductivity, excellent physical and mechanical properties, and good heat resistance and stability, while also having a wide electrochemical window and excellent electrochemical stability. The inorganic-organic composite solid-state electrolyte membrane can be used to construct various solid-state lithium batteries, effectively inhibit the growth of lithium dendrites, and improve the comprehensive performance of the battery.

Description

A kind of inorganic-organic composite electrolyte membrane and its preparation method and application

technical field

The invention belongs to the technical field of composite electrolyte membranes, specifically relates to an inorganic-organic composite electrolyte membrane, and also relates to a solid-state lithium battery comprising the inorganic-organic composite electrolyte membrane.

Background technique

At present, lithium-ion batteries have been widely developed and popularized in various portable electronic products, electric vehicles and other fields, but traditional lithium-ion batteries are limited by their energy density bottlenecks, making them unable to meet increasingly higher performance requirements. In addition, because the organic liquid electrolyte contained in traditional lithium-ion batteries has a series of safety hazards such as instability and flammability, it is easy to cause serious safety problems such as thermal runaway and explosion of the battery. In view of the above problems, the use of solid electrolytes instead of traditional liquid electrolytes and the preparation of solid-state lithium-ion batteries can effectively solve the safety problems of lithium-ion batteries, and become one of the most promising technical routes.

Solid electrolytes include inorganic ceramic solid electrolytes, polymer solid electrolytes, and inorganic-organic composite solid electrolytes. Inorganic ceramic solid electrolytes include perovskite solid electrolytes such as (Li _3x La _2/3x TiO ₃ ) (LLTO), NASICON solid electrolytes such as Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ (LATP), garnet solid electrolytes Electrolyte such as Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) and other inorganic solid electrolytes. In recent years, new inorganic solid electrolytes with high ionic conductivity have been reported: garnet-type oxide and sulfide solid electrolytes. Among them, the garnet-type oxide solid electrolyte LLZO has high lithium ion conductivity, wide electrochemical window and good stability to lithium, which has attracted extensive attention and application. However, the shortcomings of inorganic ceramic solid electrolytes lie in their rigidity and fragility, and their preparation process is complicated, requiring high-temperature sintering; in addition, the poor interface contact between solid electrolytes and electrodes leads to high interfacial charge transfer resistance, which hinders their use in batteries. practical use in the system. Polymer solid electrolytes are composed of organic polymers and metal salts, which have excellent mechanical properties. In 1979, Armand et al. successfully prepared a polyoxyethylene (PEO)-based polymer solid electrolyte, but the conductivity was only 10 ^-7 S·cm ^-1 . Polymer systems that are currently being studied include polyethylene oxide (PEO), polycarbonate (PC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA). Although polymer solid-state electrolytes have excellent mechanical properties, their electrical conductivity and oxidation resistance are not satisfactory, which seriously hinders the development of polymer solid-state electrolytes.

Inorganic-organic composite solid electrolytes include inorganic ceramic components and polymer matrix in physical composition, which is a compromise method to solve the poor mechanical properties of inorganic solid electrolytes and the low conductivity of polymer solid electrolytes. However, in the prior art, the lithium ion migration of the polymer component in the composite solid electrolyte is slow, which seriously affects the improvement and application of the conductivity of the composite solid electrolyte.

technical problem

The primary purpose of the present invention is to provide a method for preparing an inorganic-organic composite electrolyte membrane with higher ion conductivity and excellent mechanical properties. The present invention prepares a composite film by adding unsaturated organic small molecules to provide more lithium ion channels to improve the conductivity of the composite electrolyte. At the same time, the existence of unsaturated organic small molecules improves the compatibility between the composite electrolyte membrane and the electrode, and improves the inorganic-organic Ionic conductivity of composite solid electrolyte membranes. The existence of organic small molecules optimizes the interface contact between the inorganic-organic composite solid electrolyte and the positive and negative electrodes, reduces the interface resistance, improves the interface stability, and improves the electrochemical performance of the battery.

technical solution

In order to realize the purpose of the above invention, the technical solution adopted in the present invention is: an inorganic-organic composite solid electrolyte membrane, including unsaturated small organic molecules, film-forming polymers, lithium salts, and inorganic ceramic solid electrolytes. Preferably, the inorganic-organic composite solid electrolyte membrane disclosed in the present invention is composed of small unsaturated organic molecules, film-forming polymers, lithium salts, and inorganic ceramic solid electrolytes. Among them, the unsaturated organic small molecules are carboxy unsaturated organic small molecules, carbonyl unsaturated organic small molecules, urea group unsaturated organic small molecules, amino unsaturated organic small molecules, cyano unsaturated organic small molecules, hydroxyl unsaturated organic small molecules One or more of the molecules.

The invention discloses a preparation method of the above-mentioned inorganic-organic composite solid electrolyte membrane. The unsaturated organic small molecule, polymer, lithium salt, and inorganic ceramic solid electrolyte are mixed in a solvent to form a membrane to obtain the inorganic-organic composite solid electrolyte membrane.

In the present invention, film-forming polymers, lithium salts, inorganic ceramic solid electrolytes, and solvents are conventional materials for preparing lithium-ion batteries. For example, the film-forming polymers are polyethylene oxide (PEO), polycarbonate (PC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyacrylamide (PAM) ), polyethersulfone (PESF), etc.; lithium salts are LiClO ₄ , LiTFSI, LiFSI, LiPF ₆ , LiAsF ₆ , LiBF _{4 ,} etc.; solvents are N,N-dimethylformamide, acetonitrile, tetrahydrofuran, N-methyl - one or more of 2-pyrrolidone or dimethyl sulfoxide, etc.

In the present invention, the inorganic ceramic solid electrolyte is selected from oxide ceramic solid electrolytes, more specifically, oxide solid electrolytes or NASICON solid electrolytes with cubic phase garnet structure, preferably Li _7-x La ₃ Zr _2-x _Tax O ₁₂ (LLZTO), where 0≤X≤0.6; or Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ where 0≤X≤1.2. The particle diameter of the inorganic ceramic solid electrolyte is 200-2000 nm, preferably 200-400 nm.

In the present invention, the mass sum of unsaturated organic small molecules, film-forming polymers, lithium salts, and inorganic ceramic solid electrolytes is 100%: wherein the mass fraction of inorganic ceramic solid electrolytes is 5 wt.% to 15wt.%, preferably 7wt.～10 wt.%; the mass fraction of lithium salt is 15wt.%～25 wt.%, preferably 20 wt.%～25 wt.%; the mass fraction of unsaturated organic small molecules is 5 wt.%～40wt .%, preferably 10 wt.% to 30 wt.%; film-forming polymer is the balance. Preferably, the amount of small unsaturated organic molecules is 10-40% of the mass of the film-forming polymer, preferably 20-25%. Within the above mass ratio range, the obtained composite solid electrolyte membrane has excellent mechanical properties and high ion conductivity.

In the present invention, the thickness of the inorganic-organic composite solid electrolyte membrane is 50-200 um, preferably 50-100 um.

The invention provides a preparation method of the above-mentioned inorganic-organic composite solid electrolyte membrane, including a preparation method of an inorganic ceramic solid electrolyte and a preparation method of an inorganic-organic composite solid electrolyte membrane. The preparation methods of inorganic ceramic solid electrolyte include sol-gel method, solid phase synthesis method, etc.; the preparation methods of inorganic-organic composite solid electrolyte membrane include casting coating method, blade coating method, phase transformation method, etc.

In the present invention, the preparation method of the inorganic-organic composite solid electrolyte membrane comprises the following steps: (1) dissolving the film-forming polymer and unsaturated small organic molecules in a solvent to form a solution system.

(2) Adding an inorganic ceramic solid electrolyte and a lithium salt to the above solution system to obtain a slurry.

(3) The slurry is scraped or coated on the substrate, and then vacuum-dried to remove the solvent to obtain an inorganic-organic composite solid-state electrolyte membrane, which is stored in a glove box filled with argon; the substrate is selected from polytetrafluoroethylene One or more of vinyl fluoride plate, glass plate, aluminum foil, copper foil. According to the type of polymer, hot pressing can be selected after vacuum drying, which is a conventional technology. For example, when the polymer is PEO, take it out after vacuum drying and hot pressing to obtain an inorganic-organic composite solid electrolyte membrane.

The invention discloses a solid-state lithium battery with high safety performance, excellent electrochemical performance and low internal resistance, which includes a positive electrode, the above-mentioned inorganic-organic composite solid electrolyte membrane and a negative electrode, and can also include a conventional packaging structure. The preparation method of the solid-state lithium battery is as follows: coating the positive electrode material, conductive agent, and binder on the positive electrode current collector to obtain the positive electrode; assembling the positive electrode, the inorganic-organic composite solid electrolyte membrane, and the negative electrode to obtain the solid state lithium battery. . Optionally, a wetting agent is added dropwise on both sides of the inorganic-organic composite solid electrolyte membrane; and then assembled with the positive and negative electrodes. Among them, the positive pole is a conventional commercial electrode material, including one or more of positive electrode materials such as lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, etc., and also includes conductive agents, binders, and binders. The mass content of the conductive agent is 5wt.%～15 wt.%, the mass content of the conductive agent is 5 wt.%～15 wt.%; the negative electrode adopts one or more of metal lithium and lithium metal alloy negative electrodes, which are conventional commercial electrodes Materials; According to conventional methods, trace amounts of wetting solvents, including fluoroethylene carbonate (FEC), polycarbonate (PC), dimethyl carbonate (DMC), can be added dropwise on both sides of the above inorganic-organic composite solid electrolyte membrane , ethylene glycol dimethyl ether (DME), ethylene glycol dimethyl ether and other organic solvents suitable for lithium-ion batteries, preferably fluoroethylene carbonate (FEC), the amount of wetting solvent added is 1-20ul/cm ² , preferably 1.0-5ul/cm ² .

Beneficial effect

The beneficial effects of the above technical solution are as follows: the organic small molecule modified inorganic-organic composite electrolyte membrane disclosed for the first time in the present invention can provide more lithium ion migration paths, and improve the ion conductivity and lithium ion migration number of the composite electrolyte membrane. The inorganic-organic composite solid electrolyte of the present invention has the following characteristics: high lithium ion conductivity; excellent mechanical properties, flexibility, and bendability; compatible with lithium metal negative electrodes, and capable of inhibiting dendrite growth; when assembling a solid lithium battery, It has good interface contact with positive and negative electrodes, and has low polarization resistance, which is beneficial to improve the cycle performance and rate performance of the battery.

Description of drawings

FIG. 1 is a diagram showing the change in electrical conductivity of the composite electrolyte membrane with temperature in Example 1, Example 2, Example 2-1, and Comparative Example 1.

Fig. 2 is a graph showing the tensile strength of the inorganic-organic composite electrolyte membrane of Example 1.

Fig. 3 is a graph of the electrochemical window of the composite electrolyte membrane of Example 1, Example 2, Example 2-1, and Comparative Example 1.

Fig. 4 is a lithium symmetric cycle graph of the composite electrolyte membrane of Example 1 and Comparative Example 1.

5 is a microscopic topography diagram of the surface of the lithium metal negative electrode of the composite electrolyte membrane of Example 1 and Comparative Example 1 after the lithium symmetric cycle.

Fig. 6 is a cycle graph of the solid-state lithium iron phosphate full battery prepared by the film of Example 1 and Comparative Example 1.

Fig. 7 is a rate performance curve of the solid lithium iron phosphate full battery prepared by the film of Example 1.

Fig. 8 is a graph showing the voltage plateau of the solid-state lithium iron phosphate full battery prepared by the film of Example 1.

FIG. 9 is a diagram showing the variation of conductivity with temperature of the composite electrolyte membranes of Example 3 and Comparative Example 1. FIG.

Fig. 10 is a lithium symmetric cycle graph of the composite electrolyte membrane of Example 4 and Comparative Example 2.

Fig. 11 is a graph of the electrochemical window of the composite electrolyte membrane of Example 4 and Comparative Example 2.

12 is a microscopic topography diagram of the surface of the lithium metal negative electrode of the composite electrolyte membrane of Example 4 and Comparative Example 2 after the lithium symmetric cycle.

Fig. 13 is a graph showing the tensile strength of the inorganic-organic composite electrolyte membrane of Example 6.

Fig. 14 is a rate performance curve of the solid lithium iron phosphate full battery prepared by the film of Example 7.

Fig. 15 is a graph of the voltage plateau of the solid-state lithium iron phosphate full battery prepared by the film of Example 7.

Fig. 16 is a graph of the electrochemical window of the composite electrolyte membrane of Example 9 and Comparative Example 6.

Embodiments of the present invention

The composite solid electrolyte of the invention has high ion conductivity and wide electrochemical window, can effectively improve the contact between the electrolyte and the electrode, and improve the stable compatibility between the solid electrolyte and the electrode. The raw materials or reagents involved in the present invention can be purchased from the market and are conventional raw materials for lithium batteries. The specific preparation operation and test method of the present invention are conventional lithium battery methods. Specifically, the present invention uses a scanning electron microscope (Scan Electron Microscope, SEM) to characterize the microstructure of the prepared solid electrolyte film and the surface of the lithium sheet after cycling, specifically: The S-4700 scanning electron microscope of Hitachi, Japan; the solid-state lithium battery assembly of the present invention is carried out in a glove box with high-purity argon (99.999%), specifically the U.S. VAC-OMNI-LAB glove box, wherein oxygen and The water vapor content is less than 0.5ppm. The battery performance test is carried out on a charge-discharge instrument in the air, specifically Wuhan Landian charge-discharge instrument (LAND CT 2001A), and the charge-discharge current density is 0.01-10mA/cm ² . Linear sweep test and AC impedance test were carried out on Auto LAB electrochemical workstation. The current used for charging and discharging the battery and the specific capacity of the battery are calculated based on the effective area of the electrode.

The present invention will be further described below in conjunction with drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Synthesis example: _Synthesis _of Li ₇ La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) _inorganic _solid electrolyte by conventional sol-gel method: Lithium nitrate _, lanthanum nitrate, and Zirconium oxynitrate and tantalum pentoxide are evenly mixed in a mixed solvent of ethylene glycol and water, and the mass excess of lithium nitrate is 10 wt.%, so as to prevent loss of lithium during high-temperature sintering. Add citric acid monohydrate, the molar ratio of citric acid monohydrate to cations in LLZTO is 1.5:1; the molar ratio of citric acid monohydrate to ethylene glycol is 1:1. Stir the above solution in a water bath at 80°C for three hours to obtain a slightly yellow uniform sol system, then transfer the obtained sol to an oven at 160°C and dry for 40 minutes to obtain a loose and porous gel, burn it completely with alcohol, and burn the completely The material was calcined at 850°C for 12 hours in a muffle furnace to obtain a cubic phase oxide solid electrolyte. Take 1g of the oxide solid electrolyte and supplement its mass with 10wt.% LiOH. After tableting, the mother powder is covered and sintered, and the sintering temperature is 1200°C; the sintered LLZTO is crushed and ball-milled, and LLZTO powder of 200-400nm is obtained through a sieve, which is used for the following experiments .

Other inorganic ceramic solid electrolytes can be prepared according to existing methods, and are also commercially available.

Example 1: Preparation of inorganic-organic composite solid-state electrolyte membrane: Accurately weigh 0.75g of polyvinylidene fluoride (PVDF), add 9g of N,N-dimethylformamide (DMF) to 0.25g of maleic acid (MA) ), stirred at 50°C for 6 hours to obtain a solution system; accurately weighed 0.100g Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g LiClO ₄ in the glove box and dispersed in the above solution system, stirred at 50°C for 12h , to obtain a viscous slurry; scrape the viscous slurry on a polytetrafluoroethylene board with a scraper, then place it in a vacuum oven at 60°C for 24 hours, then take it out and place it in another vacuum oven, and dry it under vacuum at 120°C for 24 hours , to obtain the organic small molecule modified inorganic-organic composite solid electrolyte membrane that removes the solvent. The electrolyte membrane material is cut into a circular electrolyte sheet with a diameter of 19mm and stored in an argon-filled glove box for later use. The thickness of the membrane material is 100um.

Comparative Example 1: On the basis of Example 1, 0.25g maleic acid was replaced with 0.25g polyvinylidene fluoride, that is, 1g polyvinylidene fluoride (PVDF) was added to 9g N,N-dimethylformamide ( DMF); the rest remained unchanged, and an inorganic-organic composite solid electrolyte membrane was obtained with a thickness of 100um.

Example 2: Accurately weigh 0.9g of polyvinylidene fluoride (PVDF), add 0.1g of maleic acid (MA) into 9g of N,N-dimethylformamide (DMF), stir at 50°C for 6h to obtain a solution system ; Accurately weigh 0.100g of Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g of LiClO ₄ in the glove box and disperse in the above solution system, stir at 50°C for 12 hours to obtain a viscous slurry; The slurry was scraped on a polytetrafluoroethylene board, then placed in a vacuum oven at 60°C for 24 hours, then taken out and placed in another vacuum oven, and dried in a vacuum at 120°C for 24 hours to obtain a small organic molecule modified inorganic- Organic composite solid electrolyte membrane, the electrolyte membrane material is cut into circular electrolyte sheets with a diameter of 19mm and stored in an argon-filled glove box for later use, and the thickness of the membrane material is 100um.

Example 2-1: Accurately weigh 0.7g of polyvinylidene fluoride (PVDF), add 0.3g of maleic acid (MA) into 9g of N,N-dimethylformamide (DMF), stir at 50°C for 6h to obtain Solution system: Accurately weigh 0.100g Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g LiClO ₄ in the glove box and disperse in the above solution system, stir at 50°C for 12h to obtain a viscous slurry; The viscous slurry was scraped on a polytetrafluoroethylene board, then dried in a vacuum oven at 60°C for 24 hours, then taken out and placed in another vacuum oven, and dried in a vacuum at 120°C for 24 hours to obtain a small organic molecule modified product with the solvent removed. Inorganic-organic composite solid-state electrolyte membrane, the electrolyte membrane material is cut into a circular electrolyte sheet with a diameter of 19mm and stored in an argon-filled glove box for later use, and the thickness of the membrane material is 100um.

Product testing: The testing methods for impedance and ionic conductivity are: AC impedance testing also refers to the small-amplitude symmetrical sine wave AC impedance method. By controlling the small-amplitude symmetrical alternating current to change according to the law of sine waves, the alternating current impedance is measured to calculate the relevant electrochemical parameters. A CR2032 stainless steel sheet symmetric cell was assembled in a glove box, wherein the diameter of the stainless steel sheet was 16 mm. The resistance value of the stainless steel symmetrical battery was tested at different temperatures in the Autolab electrochemical workstation, the temperature range of the test was 30°C-80°C, and the frequency range was 0.1Hz-10MHz. The AC impedance spectrum obtained from the test is fitted by NOVA software to obtain the relevant resistance R parameters of the material, such as ohmic resistance, interface resistance, and bulk resistance. From the resistance R in the electrolyte AC impedance spectrum, the electrode area A and the thickness L of the electrolyte film, the ionic conductivity σ of the composite electrolyte can be obtained by the following formula:

.

The above-mentioned inorganic-organic composite electrolyte (CPE) was used to assemble a stainless steel symmetrical battery, and its ionic conductivity was tested at different temperatures. As shown in Figure 1, at 30°C, the conductivity of the composite membrane in Example 1 was 9.09× 10 ^-4 s cm ^-1 , better than the conductivity of the composite membrane in Comparative Example 1, which was 5.9×10 ^-4 s cm ^-1 .

Young's modulus test: cutting the inorganic-organic composite membrane material with a width of 1 cm and a length of 5 cm in the above-mentioned embodiment, accurately measure the thickness of the composite membrane material, and use 0.2 The film material is stretched at a speed of mm/s until the material breaks. A graph showing the relationship between tensile force and deformation is obtained, as shown in FIG. 2 , which is a graph of the tensile strength test of the composite electrolyte membrane in Example 1.

Electrochemical window test: The electrochemical window of the composite membrane material was tested by linear sweep voltammetry (LSV). In the LSV test, SS｜CPE｜Li batteries were assembled by conventional methods to explore their redox voltage, and stainless steel gaskets were used as working electrodes , At the same time, the metal lithium sheet is used as the counter electrode and the reference electrode. The electrochemical window of the composite electrolyte was tested by Autolab electrochemical workstation, the test range was 2.5V-6V, and the sweep rate was 5mV/s. As shown in Figure 3, the electrochemical window of the composite electrolyte membrane in Example 1 is greater than 5V, which is better than that of the inorganic-organic composite electrolyte membrane in Example 2, indicating that the composite membrane material has high pressure resistance and can be used with more Many positive electrode materials match.

Test of the inhibitory effect of the electrolyte membrane material on lithium dendrite growth: a lithium symmetric battery was assembled with the inorganic-organic composite membrane of Example 1 and the inorganic-organic composite membrane of Comparative Example 1, respectively. Add 1ul·cm ^-2 of FEC on the surface of lithium metal negative electrode to wet the interface. In the blue electric system, the charge and discharge cycles were performed for 1 hour at a current density of 0.1 mA·cm ^-2 . As shown in Figure 4, the lithium symmetric battery in Example 1 can be stably cycled for more than 500 hours, while the stable cycle of Comparative Example 1 is not more than 200 hours, indicating that the composite electrolyte membrane of Example 1 effectively inhibits dendrite growth. At the same time, a lithium symmetric battery was assembled from the composite electrolyte membrane in Example 1 and Comparative Example 1 and charged and discharged for 1 hour at a current density of 0.1 mA cm ^-2 , and the lithium symmetric battery after the cycle was removed to observe the lithium metal surface , carry out the scanning electron microscope test on the surface of the lithium metal negative electrode. As shown in Figure 5, the surface of the lithium metal negative electrode matched with the composite film in Example 1 is smooth, while the surface of the lithium metal negative electrode matched with the composite film in Comparative Example 1 is loose and pulverized, which further indicates that the addition of small organic molecules can effectively inhibit branching. crystal growth.

Full battery performance test: Lithium iron phosphate (LiFePO ₄ ) is used as the positive electrode, and lithium sheets are used as the negative electrode to assemble 2032 button cells by conventional methods, wherein the mass ratio of each material of the positive electrode material is LiFePO ₄ :Super P:PVDF=8:1 : 1; the above-mentioned substances are uniformly dispersed in NMP solvent to obtain lithium iron phosphate positive electrode slurry, and the positive electrode slurry is coated on the aluminum foil substrate with a scraper with a thickness of 75um, and the coated positive electrode sheet is vacuumed at 120°C Dry for 12 hours, and cut into 10mm circular positive electrode sheets after compaction. During battery assembly, the lithium metal negative electrode has a diameter of 16mm. Put the positive electrode sheet in the center of the positive electrode shell, add 1 ul/cm ² of FEC organic solvent dropwise on both sides of the above electrolyte membrane to wet the interface, cover the positive electrode, and finally stack the lithium metal negative electrode, gasket, and shrapnel on the electrolyte membrane in sequence Above, cover the negative electrode case, seal the battery with a pressure of 50 MPa in the battery packaging machine, and obtain the lithium iron phosphate button battery; stand at room temperature for 12 hours to be tested. The cycle performance and rate performance of the battery at room temperature were tested in the blue electric system, and the voltage range of the test was 2.5-4.0V.

As shown in Figure 6, it is the long-term cycle performance of the full battery with the inorganic-organic composite electrolyte membrane used as the electrolyte in Example 1 and Comparative Example 1. The performance of Example 1 is excellent under the condition of 0.2C. After 180 cycles The capacity retention rate is 83.5%, and the Coulombic efficiency is preserved at 100% during the cycle.

As shown in Figure 7 and Figure 8, the lithium iron phosphate full battery assembled with the composite membrane of Example 1 was tested for rate performance. The figure shows that the inorganic-organic composite electrolyte membrane added with organic small molecules exhibits excellent rate performance , indicating that it has great potential at the application level.

Example 3: Accurately weigh 0.8g of polyvinylidene fluoride (PVDF), add 0.2g of itaconic acid into 9g of N,N-dimethylformamide (DMF), stir at 50°C for 6h to obtain a solution system; in a glove box Accurately weigh 0.100g of Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g of LiClO ₄ and disperse in the above solution system, stir at 50°C for 12h to obtain a viscous slurry; scrape the viscous slurry on Teflon plate, then placed in a vacuum oven at 60°C for 24 hours, then taken out and placed in another vacuum oven, and dried at 120°C for 24 hours to obtain an inorganic-organic composite solid electrolyte membrane modified by organic small molecules without solvent , cutting the electrolyte membrane material into circular electrolyte sheets with a diameter of 19 mm and storing them in an argon-filled glove box for future use. The thickness of the membrane material is 100 um.

In the same way as above, the inorganic-organic composite electrolyte obtained in Example 3 was used to assemble a stainless steel symmetrical battery, and its ionic conductivity was tested at different temperatures, as shown in Figure 9, and Comparative Example 1 was used as a comparison.

Example 4: Accurately weigh 0.65g of polyethylene oxide (PEO), add 0.35g of 2-ureido-4[1H]-pyrimidinone (UPy) into 10g of tetrahydrofuran (THF), and stir for 6 hours to obtain a solution system; in the glove box Accurately weigh 0.100g of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) and 0.652 g of LiTFSI to disperse in the solution system, and stir for 12 hours to obtain a uniform slurry. The uniform slurry was poured into a polytetrafluoroethylene mold, then dried in a vacuum oven at 60°C for 24 hours, then taken out and hot-pressed at 15MPa at 80°C for 3 minutes to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane with solvent removed. The solvent-removed composite electrolyte membrane material was cut into circular electrolyte sheets with a diameter of 19 mm and stored in an argon-filled glove box for later use. The membrane material had a thickness of 150 um and a conductivity of 0.5×10 ^-4 s cm ^-1 at 30°C.

Comparative Example 2: On the basis of Example 4, 0.35g of 2-ureido-4[1H]-pyrimidinone was replaced with 0.35g of polyethylene oxide, that is, 1g of polyethylene oxide (PEO) was added to 10g of tetrahydrofuran (THF) ; the rest remained unchanged, and an inorganic-organic composite solid electrolyte membrane was obtained with a thickness of 150um and a conductivity of 0.29×10 ^-4 s cm ^-1 at 30°C.

The same method was used to assemble the lithium symmetric battery, and the cycle performance test was carried out. The results are shown in Figure 10. The electrochemical window of the composite membrane material was tested by linear sweep voltammetry (LSV) as above, and the results are shown in Figure 11. The cycled lithium symmetric battery was removed to observe the lithium metal surface, and a scanning electron microscope test was performed on the lithium metal negative electrode surface, as shown in Figure 12.

Example 5: Accurately weigh 0.85g of polyethylene oxide (PEO), add 0.15g of 2,2-dimethylethylboronic acid (EDBA) into 10g of tetrahydrofuran (THF), and stir for 6 hours to obtain a solution system; Weigh 0.100 g of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) and 0.652 g of LiTFSI to disperse in the solution system, and stir for 12 hours to obtain a uniform slurry. The uniform slurry was poured into a polytetrafluoroethylene mold, then dried in a vacuum oven at 60°C for 24 hours, then taken out and hot-pressed at 15MPa at 80°C for 3 minutes to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane with solvent removed. The solvent-removed composite electrolyte membrane material was cut into circular electrolyte sheets with a diameter of 19 mm and stored in an argon-filled glove box for later use. The thickness of the membrane material was 150 um, and the conductivity at 30°C was 2.4×10 ^-4 s cm ^-1 .

Example 6: Accurately weigh 0.8g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), add 0.2g of neopentyl glycol to 9g of N,N-dimethylpyrrolidone (NMP), and stir at 60°C for 6h A solution system was obtained; 0.072g of Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ (LATP) and 0.358g of LiFSI were accurately weighed in a glove box and dispersed in the solution system, and stirred at 60°C for 12 hours to obtain a uniform viscous slurry. Scrape-coat the uniform slurry on a glass plate, and then dry it in a vacuum oven at 80°C for 24 hours to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane that removes the solvent, and cut the electrolyte membrane material into a circle with a diameter of 19mm The electrolyte sheet is stored in an argon-filled glove box for standby use, and the thickness of the membrane material is 50um. See Figure 13 for tensile strength.

Comparative example three: on the basis of embodiment six, 0.2g neopentyl glycol is replaced by 0.2g polyvinylidene fluoride-hexafluoropropylene copolymer, is about 1g polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP ) was added to 9g of N,N-dimethylpyrrolidone (NMP); the rest remained unchanged to obtain an inorganic-organic composite solid electrolyte membrane with a thickness of 50um.

Example 7: Accurately weigh 0.931g polyacrylcyanide (PAN), add 0.069g cyclodextrin (CD) to 9g dimethyl sulfoxide (DMSO) and stir for 6 hours to obtain a solution system; accurately weigh 0.215g in the glove box Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ (LLZTO) and 0.215g LiPF ₆ were dispersed in the solution system and stirred for 12 hours to obtain a uniform viscous slurry. Scrape-coat the uniform slurry on a glass plate, and then dry it in a vacuum oven at 60°C for 24 hours to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane from which the solvent has been removed, and cut the electrolyte membrane material into a circle with a diameter of 19mm The electrolyte sheet is stored in an argon-filled glove box for standby use, and the thickness of the membrane material is 50um. As shown in Figure 14 and Figure 15, the composite membrane of Example 7 is a lithium iron phosphate full battery assembled as above and the rate performance test is performed. The figure shows that the inorganic-organic composite electrolyte membrane added with organic small molecules exhibits excellent performance. The rate performance shows that it has great potential at the application level.

Comparative Example 4: On the basis of Example 7, 0.069g of cyclodextrin was replaced with 0.069g of polyacrylonitrile (PAN), that is, 1g of polyacrylonitrile (PAN) was added to 9g of dimethyl sulfoxide (DMSO); the rest unchanged, an inorganic-organic composite solid electrolyte membrane with a thickness of 50um was obtained.

Example 8: Accurately weigh 0.43g of polyacrylamide (PAM), add 0.57g of 2,6-diaminoanthraquinone into 9g of acetonitrile and stir for 6 hours to obtain a solution system; accurately weigh 0.100g of Li _1.6 Al in a glove box _0.6 Ti _1.4 (PO ₄ ) ₃ (LATP) and 0.333g LiAsF6 were dispersed in the solution system and stirred at 50°C for 12h to obtain a uniform viscous slurry. Scrape-coat the uniform slurry on the polytetrafluoroethylene plate, and then dry it in a vacuum oven at 60°C for 24 hours to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane from which the solvent has been removed, and cut the electrolyte membrane material into a diameter of 19mm The circular electrolyte sheet is stored in an argon-filled glove box for later use, and the thickness of the membrane material is 100um.

Comparative example five: on the basis of embodiment eight, the 2,6-diaminoanthraquinone of 0.57g is replaced by 0.57g polyacrylamide (PAM), is about to add 1g polyacrylamide (PAM) in 9g acetonitrile; Change to obtain an inorganic-organic composite solid electrolyte membrane with a thickness of 100um.

Example 9: Accurately weigh 0.85g of polyethersulfone (PESF), add 0.15g of 4-vinylbenzoic acid into 9g of N,N-dimethylpyrrolidone (NMP), stir at 50°C for 6h to obtain a solution system; in the glove box Accurately weigh 0.100g of Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g of LiBF ₄ to disperse in the solution system, and stir at 50°C for 12h to obtain a uniform viscous slurry. Spread the uniform slurry on a flat aluminum foil, spray 5mL alcohol evenly on the aluminum foil with an airbrush for pre-curing, then soak it in 50mL isopropanol for 6 hours, take it out and place it in a vacuum at 80°C Dry in an oven for 24 hours to obtain an inorganic-organic composite solid electrolyte membrane modified by organic small molecules after removing the solvent. The electrolyte membrane material is cut into circular electrolyte sheets with a diameter of 19 mm and stored in an argon glove box for later use. The thickness of the membrane material is 100um.

Comparative Example 6: On the basis of Example 9, 0.15g of 4-vinylbenzoic acid was replaced by 0.15g of polyethersulfone (PESF), that is, 1g of polyethersulfone (PESF) was added to 9g of N,N-dimethylpyrrolidone (NMP); the rest remained unchanged, and an inorganic-organic composite solid electrolyte membrane was obtained with a thickness of 100um.

Using the same method as above, the inorganic-organic composite electrolytes obtained in Example 9 and Comparative Example 6 were used to assemble stainless steel symmetrical batteries, and their ionic conductivity was tested at different temperatures, as shown in FIG. 16 .

Example 10: Accurately weigh 0.70g polymethylmethacrylate (PMMA), add 0.3g riboflavin to 9g N,N-dimethylpyrrolidone (NMP), stir at 60°C for 6h to obtain a solution system; 0.100g of Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ (LLZTO) and 0.333g of LiTFSI were accurately weighed and dispersed in the solution system, and stirred at 60°C for 12 hours to obtain a uniform viscous slurry. Scrape-coat the uniform slurry on the polytetrafluoroethylene plate, and then dry it in a vacuum oven at 60°C for 24 hours to obtain an organic small molecule modified inorganic-organic composite solid electrolyte membrane from which the solvent has been removed, and cut the electrolyte membrane material into a diameter of 19mm The circular electrolyte sheet is stored in an argon-filled glove box for later use, and the thickness of the membrane material is 100um.

Comparative example seven: on the basis of embodiment ten, 0.3g riboflavin is replaced by 0.3g polymethylmethacrylate (PMMA), is about to add 1g polymethylmethacrylate to 9g N, N-dimethylpyrrolidone (NMP); the rest remained unchanged, and an inorganic-organic composite solid electrolyte membrane was obtained with a thickness of 100um.

The inorganic-organic composite electrolyte prepared by the invention is applied to the lithium ion battery, replacing the electrolyte solution and the diaphragm, and providing a medium for lithium ion transmission. Ionic conductivity is a key factor for composite electrolytes. In the process of assembling the lithium-ion battery, the invention provides a method for optimizing interface contact, so as to obtain a battery with excellent cycle performance and good rate performance to meet commercial applications. Compared with the existing composite solid electrolyte, the composite solid electrolyte added with small molecules of the present invention has higher conductivity and wider electrochemical window, and at the same time, the addition of small molecules improves the interfacial contact between the composite electrolyte and the electrode, In this way, excellent long-term cycle performance and rate performance of the full battery are obtained.

Claims

An inorganic-organic composite solid electrolyte membrane, characterized in that it includes unsaturated organic small molecules, film-forming polymers, lithium salts, and inorganic ceramic solid electrolytes; the unsaturated organic small molecules are carboxyl unsaturated organic small molecules, carbonyl One or more of unsaturated organic small molecules, urea group unsaturated organic small molecules, amino unsaturated organic small molecules, cyano unsaturated organic small molecules, hydroxyl unsaturated organic small molecules.
The inorganic-organic composite solid electrolyte membrane according to claim 1, wherein the small organic molecules are maleic acid, acrylic acid, itaconic acid, 4-vinylbenzoic acid, isophthalic acid, Kecon Acid disodium salt, 2-ureido-4[1H]-pyrimidinone, 1-vinylimidazole, 2,6-diaminoanthraquinone, 1,3,5-tris(4-formyl)benzene, riboflavin One or more of element, 2-amino-4-hydroxy-6-methylpyrimidine, cyclodextrin, neopentyl glycol, 2,2-dimethylethylboronic acid.
The inorganic-organic composite solid electrolyte membrane according to claim 1, characterized in that the amount of small unsaturated organic molecules is 10-40% of the mass of the film-forming polymer.
According to the described inorganic-organic composite solid electrolyte membrane of claim 1, it is characterized in that, take the mass sum of unsaturated organic small molecule, film-forming polymer, lithium salt, inorganic ceramic solid electrolyte as 100%: wherein the inorganic ceramic solid electrolyte The mass fraction is 5wt.%～15wt.%; the mass fraction of lithium salt is 15wt.%～25 wt.%; the mass fraction of unsaturated organic small molecules is 5 wt.%～40wt.%; quantity.
The preparation method of the inorganic-organic composite solid electrolyte membrane according to claim 1, characterized in that, the unsaturated organic small molecules, polymers, lithium salts, and inorganic ceramic solid electrolytes are mixed in a solvent to form a film to obtain an inorganic-organic composite solid electrolyte membrane. solid electrolyte membrane.
According to the preparation method of the inorganic-organic composite solid electrolyte membrane described in claim 5, it is characterized in that the film-forming polymer is polyethylene oxide, polycarbonate, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, One or more of polyacrylamide and polyethersulfone; lithium salt is one or more of LiClO 4 , LiTFSI, LiFSI, LiPF 6 , LiAsF 6 , LiBF 4 ; inorganic ceramic solid electrolyte is selected from oxide ceramics solid electrolyte.
A solid-state lithium battery, comprising a positive electrode and a negative electrode, characterized in that it also includes an inorganic-organic composite solid-state electrolyte membrane according to claim 1.
The preparation method of the solid-state lithium battery according to claim 7, characterized in that, the positive electrode material, the conductive agent, and the binder are coated on the positive electrode current collector to obtain the positive electrode; the positive electrode, the inorganic-organic composite solid electrolyte membrane, The negative electrode is assembled to obtain a solid-state lithium battery.
The application of unsaturated organic small molecules in the preparation of solid electrolyte films is characterized in that the unsaturated organic small molecules are carboxyl unsaturated organic small molecules, carbonyl unsaturated organic small molecules, urea group unsaturated organic small molecules, amino unsaturated organic small molecules, One or more of saturated organic small molecules, cyano unsaturated organic small molecules, and hydroxyl unsaturated organic small molecules.
The application of the inorganic-organic composite solid electrolyte membrane in claim 1 in the preparation of lithium batteries.