Electrolytes based on organometallic framework porous structures, batteries and methods of making the same

Abstract

The application discloses an electrolyte based on an organic metal skeleton porous structure, a battery and a preparation method thereof, and the preparation method comprises the following steps: mixing an ionic liquid electrolyte containing a lithium salt and an ionic liquid electrolyte with an organic solution of a metal salt and an organic ligand of the metal salt respectively to obtain a first mixed solution and a second mixed solution; mixing the first mixed solution and the second mixed solution again to obtain a precursor solution; and heating the precursor solution at 60-80 DEG C for 24-72 hours to obtain a composite gel electrolyte. The morphology and performance of the composite gel electrolyte obtained by the application are between those of a solid-state electrolyte and a liquid-state electrolyte, the composite gel electrolyte has excellent interface performance and ionic conductivity, and a lithium metal or lithium ion battery obtained from the composite gel electrolyte can be used as a new generation of semi-solid-state batteries.

Description

Technical Field

[0001] This invention relates to a composite gel electrolyte based on an organometallic porous structure and its preparation method, belonging to the field of chemical energy storage. Background Technology

[0002] Conventional liquid electrolytes have hindered the further application of lithium-ion batteries due to their flammability and toxicity. To improve the safety performance of lithium batteries, researchers have begun to explore the use of solid electrolytes to replace flammable organic liquid electrolytes. Compared with liquid electrolytes, solid electrolytes have the following advantages: 1) They are directly matched with metallic lithium, reducing the amount of lithium-intercalated graphite anode used, reducing anode mass, and increasing energy density; 2) They can suppress lithium dendrite growth to a certain extent, are not easily combustible, have no electrolyte leakage, are resistant to high temperatures, and have good safety; 3) They have a wide electrochemical window and can be well adapted to high-voltage materials. However, solid electrolytes have drawbacks such as low conductivity and high interfacial resistance between the electrode and the solid electrolyte, which limit their large-scale commercial application. Therefore, developing new electrolytes that can effectively overcome the defects of liquid and solid electrolytes and obtain electrolytes that can further improve the performance of lithium-ion batteries is an urgent problem to be solved by existing technologies. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to propose a new gel electrolyte and its preparation and application method. The electrolyte has a material form and properties between solid electrolytes and liquid electrolytes. It has a special gel polymer structure, combining the transport and diffusion capabilities of liquids with the cohesive characteristics of solids. It has excellent interfacial properties and ionic conductivity, and can be used as a new generation of semi-solid batteries.

[0004] The technical solution of the present invention is as follows:

[0005] The preparation method of composite gel electrolyte based on porous organometallic framework includes:

[0006] Organic solutions of metal salts and organic ligands were obtained separately, namely metal salt solutions and organic ligand solutions;

[0007] To obtain an ionic liquid electrolyte containing lithium salt and ionic liquid electrolyte;

[0008] A portion of the ionic liquid electrolyte is mixed with the metal salt solution to obtain a first mixture, and the remaining ionic liquid electrolyte is mixed with the organic ligand solution to obtain a second mixture.

[0009] The first mixture and the second mixture are mixed to obtain a precursor solution;

[0010] The precursor solution was heated at 60–80°C for 24–72 h to obtain the composite gel electrolyte.

[0011] The organic ligand is selected from organic acids, and the metal salt has a coordination site that coordinates with the organic ligand.

[0012] According to some preferred embodiments of the present invention, in the ionic liquid electrolyte, the concentration of lithium salt in the ionic liquid electrolyte is 0.5 mol / L.

[0013] According to some preferred embodiments of the present invention, the concentration of the metal salt solution is 0.5 mol / L.

[0014] According to some preferred embodiments of the present invention, the concentration of the organic ligand solution is 0.5 mol / L.

[0015] According to some preferred embodiments of the present invention, in the first mixture, the volume ratio of the metal salt solution to the ionic liquid electrolyte is 1 to 2:1.

[0016] According to some preferred embodiments of the present invention, in the second mixture, the volume ratio of the organic ligand solution to the ionic liquid electrolyte is 1 to 2:1.

[0017] According to some preferred embodiments of the present invention, the metal salt is selected from one or more of Fe(NO3)3 and / or its hydrate, (CH3COO)2Co and / or its hydrate, and C4H6O4Zn.

[0018] According to some preferred embodiments of the present invention, the organic ligand is selected from one or more of pyromellitic acid, dimethylimidazole, and benzoic acid.

[0019] According to some preferred embodiments of the present invention, the ionic liquid electrolyte is selected from one or more of [EMIMTFSI] ionic liquid, [BMITFSI] ionic liquid, and [TMPTFSI] ionic liquid.

[0020] Among them, [EMIMTFSI] ionic liquid refers to 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, [BMITFSI] ionic liquid refers to 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and [TMPTFSI] ionic liquid refers to tri-n-butylammonium bis(trifluoromethanesulfonyl)imide salt.

[0021] According to some preferred embodiments of the present invention, the lithium salt is selected from LiTFSI, namely lithium bis(trifluoromethanesulfonyl)imide.

[0022] According to some preferred embodiments of the present invention, the solvent of the organic solution is selected from ethanol.

[0023] The above preparation method of the present invention uses a solvent-gel method to synthesize a gel electrolyte structure containing a porous framework in one step. Metal ions and organic ligands are connected to form a porous structure by self-assembly with the metal ions as vertices and the organic ligands. At the same time, the liquid electrolyte is confined in it to obtain a composite gel electrolyte.

[0024] The present invention further provides a composite gel electrolyte prepared by the above preparation method.

[0025] This gel electrolyte is a metal-organic gel (MOG) material with a microstructure combining an inorganic porous framework and an organic electrolyte. The porous structure acts as a framework, providing mechanical strength. Simultaneously, open metal sites (OMS) on the framework interact with anions in the liquid electrolyte, confining it within. The liquid electrolyte provides lithium-ion transport channels, enabling liquid-like transport of lithium ions within the composite gel electrolyte.

[0026] The present invention further provides a lithium-containing battery, which contains a composite gel electrolyte and / or a composite electrolyte prepared by the above preparation method.

[0027] The lithium-containing battery can be a lithium-ion battery or a lithium metal battery.

[0028] The preparation method of this invention utilizes an in-situ sol-gel method to construct a gel electrolyte with a porous MOF framework in situ. The addition of glass fibers during preparation allows for further in-situ growth of the gel electrolyte on the glass fibers, forming a three-dimensional porous lithium-ion transport channel. The lithium-ion battery prepared by this method exhibits excellent electrolyte interface performance and ionic conductivity, a wide electrochemical window, and excellent cycle performance, making it suitable as a next-generation semi-solid-state battery. Attached Figure Description

[0029] Figure 1 These are scanning electron microscope images of the solid electrolytes prepared in Examples 1-4.

[0030] Figure 2 The ionic conductivity at room temperature of the electrolytes prepared in Examples 1-4.

[0031] Figure 3 The temperature-dependent properties of the electrolyte prepared in Example 1.

[0032] Figure 4 The electrochemical windows of the solid electrolytes prepared in Examples 1-4 are shown.

[0033] Figure 5 The electrochemical performance of the solid electrolyte prepared in Example 1 matched with the lithium iron phosphate electrode is shown. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The instruments used in the following embodiments include:

[0036] Scanning electron microscopy (SEM) test: Scanning electron microscope.

[0037] Conductivity testing: Electrochemical impedance spectroscopy was performed on the SS / electrolyte membrane / SS battery using an electrochemical workstation to obtain the ionic conductivity of the electrolyte. The test frequency was 10Hz-100kHz and the temperature range was 30℃-80℃.

[0038] Electrochemical window testing: Linear sweep voltammetry was performed on the Li / electrolyte membrane / SS battery using an electrochemical workstation to obtain the electrochemical stability window of the electrolyte.

[0039] Assembly and Testing of CR2032 Button Solid-State Battery: CR2032 solid-state button batteries were assembled in an argon-atmosphere glove box using lithium metal (Li) as the negative electrode, lithium iron phosphate as the positive electrode, and the electrolyte obtained in the previous example. The electrochemical performance of the assembled batteries was tested using a blue electrode tester at 30°C and a voltage range of 2.5-4.2V. The batteries were charged and discharged at 0.1C (1C = 170mAh / g) during the test.

[0040] Example 1

[0041] The composite gel electrolyte was prepared using the following steps:

[0042] (1) Weigh 0.287g of LiTFSI in an argon glove box and dissolve it in 2ml of ionic liquid [BMITFSI]1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. Stir for 10 hours under a stirrer to completely dissolve the lithium salt in the ionic liquid and prepare an electrolyte with a molar concentration of 0.5mol / L.

[0043] (2) Measure 0.414g Fe(NO3)·6H2O and 0.2102g pyromellitic acid (BTC) and dissolve them in 5ml ethanol, respectively. Then, sonicate them in an ultrasonic cleaner for 10min to promote the dissolution of the solutes, and obtain ethanol solutions of Fe(NO3)·6H2O and pyromellitic acid (BTC) with a molar concentration of 0.5mol / L.

[0044] (3) Take two small glass bottles and label them A and B respectively. Add 1 ml of Fe(NO3)·6H2O ethanol solution and 0.5 ml of the electrolyte obtained in step (1) to bottle A, and add 1 ml of pyromellitic acid (BTC) ethanol solution and 0.5 ml of the electrolyte obtained in step (1) to bottle B.

[0045] (4) Place bottles A and B on a magnetic stirrer until the liquids in them are mutually soluble. Then, while bottle B is being stirred continuously, pour the mixed liquid from bottle A into it and stir rapidly for 5-10 seconds to obtain an electrolyte precursor solution that has not gelled.

[0046] (5) The ungelled electrolyte precursor solution was placed in an 80°C oven and dried for 24 hours to obtain a gel electrolyte.

[0047] The microstructure of the obtained composite electrolyte was characterized, and its scanning electron microscope image is shown below. Figure 1 As shown in the image of Example 1, the obtained composite electrolyte has a porous structure, which ensures that lithium ions are conducted in a liquid flow manner within the composite electrolyte.

[0048] Furthermore, the positive electrode material lithium iron phosphate (LFP), conductive agent SuperP, and binder polyvinylidene fluoride (PVDF) are ground evenly in a mass ratio of 8:1:1 to form a slurry. The slurry is then evenly coated onto aluminum foil using a coating applicator and dried in a vacuum drying oven at 80°C for 12 hours to obtain the electrode sheet.

[0049] The obtained composite electrolyte, electrode sheet and lithium metal were assembled into a lithium-ion coin cell half cell. The battery was subjected to constant current charge and discharge test using a Blue Electric electrochemical workstation with a test voltage of 2.8V-4.2V.

[0050] The measured conductivity values ​​of the composite electrolyte are shown in the attached figure. Figure 2 As shown in the image of Example 1, it can be seen that its conductivity at room temperature can reach 10. -3 Orders of magnitude; the conductivity of the composite electrolyte under a temperature gradient of 30-80℃ is shown in the attached figure. Figure 3 As shown, the obtained electrolyte maintains the characteristic of increasing with increasing temperature, indicating that the lithium-ion conduction characteristics inside the gel electrolyte are similar to those of a liquid.

[0051] The measured electrochemical window of the composite electrolyte is shown in the attached figure. Figure 4 As shown in the image of Example 1, it can be seen from the figure that the electrochemical window of this electrolyte is relatively wide, reaching above 5V, which can meet the electrochemical window requirements of most cathode materials.

[0052] Furthermore, Figure 5The performance results of Li / MOG / LFP solid-state batteries matched with this electrolyte after 100 cycles at a 0.1C rate within a voltage range of 2.5-4.2V show that the battery capacity still remains at around 98% after 100 cycles, indicating that the electrolyte has good performance and can be adapted to a wide variety of cathode materials and lithium metal batteries.

[0053] Example 2

[0054] The composite gel electrolyte was prepared using the following steps:

[0055] (1) Weigh 0.287g of LiTFSI in an argon glove box and dissolve it in 2ml of ionic liquid [BMITFSI]1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. Stir for 10 hours under a stirrer to completely dissolve the lithium salt in the ionic liquid and obtain an electrolyte with a molar concentration of 0.5mol / L.

[0056] (2) 0.414g Fe(NO3)·9H2O and 0.2102g triphenyl benzoic acid (BTC) were respectively dissolved in 5ml ethanol and ultrasonicated for 10min in an ultrasonic cleaner to promote dissolution, so as to obtain iron salt solution and BTC solution with a molar concentration of 0.5mol / L.

[0057] (3) Take two small glass bottles and label them A and B respectively; add 1.5 ml of iron salt solution and 0.5 ml of electrolyte to bottle A, and add 1.5 ml of BTC solution and 0.5 ml of electrolyte to bottle B.

[0058] (4) Place bottles A and B on a magnetic stirrer until the solutions in them are miscible. Then, while bottle B is being stirred continuously, pour the mixed liquid from bottle A into it and stir rapidly for 5-10 seconds to obtain an electrolyte precursor solution that has not gelled.

[0059] (5) The ungelled electrolyte precursor solution was placed in an 80°C oven and dried for 24 hours to obtain a gel electrolyte.

[0060] The electrolyte obtained in Example 2 was characterized.

[0061] Figure 1 The image in Example 2 is a scanning electron microscope image of the obtained composite gel electrolyte, showing that the electrolyte still has a multi-pore structure, similar to that in Example 1. This structural feature can ensure that the ionic liquid electrolyte conducts lithium ions in a liquid flow manner.

[0062] Figure 2 The image in Example 2 shows the electrical conductivity value of the material. It can be seen that it maintains a high conductivity of 1.45 × 10⁻⁶ at room temperature. -3 S / cm.

[0063] Figure 4 The image in Example 2 shows the electrochemical window of the electrolyte, which is similar to that in Example 1. This indicates that changing the ratio of ionic liquid electrolyte has little effect on the pore structure of the composite gel electrolyte. That is, within a certain range, the porous MOG can adsorb a specific amount of electrolyte, indicating that the electrolyte still has stable electrochemical performance. This shows that changing the amount of ionic liquid added has no significant effect on the synthesis of the electrolyte structure.

[0064] Example 3

[0065] The composite gel electrolyte was prepared using the following steps:

[0066] (1) Weigh 0.287g of LiTFSI in an argon glove box and dissolve it in 2ml of ionic liquid [BMI][TFSI]. Stir for 10 hours under a stirrer to completely dissolve the lithium salt in the ionic liquid and obtain an electrolyte with a molar concentration of 0.5mol / L.

[0067] (2) 0.414g Fe(NO3)·9H2O and 0.2102g triphenyl benzoic acid (BTC) were respectively dissolved in 5ml ethanol and ultrasonicated for 10min in an ultrasonic cleaner to promote dissolution, so as to obtain iron salt solution and BTC solution with a molar concentration of 0.5mol / L.

[0068] (3) Take two small glass bottles and label them A and B respectively; add 1 ml of iron salt solution and 0.5 ml of electrolyte to bottle A, and add 1 ml of BTC solution and 0.5 ml of electrolyte to bottle B.

[0069] (4) Place bottles A and B on a magnetic stirrer until the solutions in them are miscible. Then, while bottle B is being stirred continuously, pour the mixed liquid from bottle A into it and stir rapidly for 5-10 seconds to obtain an electrolyte precursor solution that has not gelled.

[0070] (5) The ungelled composite electrolyte precursor solution was placed in a 60°C oven and dried for 72 hours to obtain the composite electrolyte.

[0071] Figure 1 The image in Example 3 is a scanning electron microscope image of the obtained composite electrolyte. It can be seen that the electrolyte synthesized at different drying temperatures and times has a similar porous structure to that in Example 1. This structural feature can still ensure that the ionic liquid electrolyte conducts lithium ions in a liquid flow manner.

[0072] Figure 2 The image in Example 3 shows the conductivity value of the obtained composite electrolyte. It can be seen that it maintains a high conductivity of 1.09 × 10⁻⁶ at room temperature. -3 / cm, which is much higher than the conductivity of existing solid electrolytes.

[0073] Figure 4 The image in Example 3 shows the electrochemical window of the obtained composite electrolyte, which is similar to that in Examples 1 and 2. It reaches above 5V and can be adapted to most cathode materials, indicating that the electrolyte still has stable structural and electrochemical properties. This shows that the temperature and time of the electrolyte synthesis are within a certain controllable range.

[0074] Example 4

[0075] The composite gel electrolyte was prepared using the following steps:

[0076] (1) Weigh 0.287g of LiTFSI in an argon glove box and dissolve it in 2ml of ionic liquid [TMPTFSI] tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. Stir for 10 hours under a stirrer to completely dissolve the lithium salt in the ionic liquid and obtain an electrolyte with a molar concentration of 0.5mol / L.

[0077] (2) 0.414g Fe(NO3)·9H2O and 0.2102g triphenyl benzoic acid (BTC) were respectively dissolved in 5ml ethanol and ultrasonicated for 10min in an ultrasonic cleaner to promote dissolution, so as to obtain iron salt solution and BTC solution with a molar concentration of 0.5mol / L.

[0078] (3) Take two small glass bottles and label them A and B respectively; add 1 ml of iron salt solution and 0.5 ml of electrolyte to bottle A, and add 1 ml of BTC solution and 0.5 ml of electrolyte to bottle B.

[0079] (4) Place bottles A and B on a magnetic stirrer until the solutions are miscible. Then, while stirring bottle B continuously, pour the mixed liquid from bottle A into it and quickly add glass fiber (GF). Mix well to obtain a non-gelled composite electrolyte precursor solution.

[0080] (5) The ungelled composite electrolyte precursor solution was placed in an 80°C oven and dried for 24 hours to obtain the composite electrolyte.

[0081] Figure 1 The image in Example 4 is a scanning electron microscope image of the obtained composite electrolyte. It can be seen that the electrolyte still has a rich pore structure, similar to that in Example 1. This structural feature can ensure that the ionic liquid electrolyte conducts lithium ions in a liquid flow manner.

[0082] Figure 2 The image in Example 4 shows the conductivity value of the obtained composite electrolyte. It can be seen that it maintains a high conductivity of 1.42 × 10⁻⁶ at room temperature. -3 / cm, which is higher than that in Examples 1 and 3, indicating that the electrolyte obtained by using the ionic liquid [TMPTFSI] in this example has faster lithium-ion transport.

[0083] Figure 4 The image in Example 4 shows the electrochemical window of the obtained composite electrolyte, which has a width of 4.8V, slightly lower than the previous three examples, but still relatively high.

[0084] The test results of the above embodiments show that the conductivity and electrochemical window of the composite electrolyte are affected by the type of ionic liquid, and the porous MOG structure often has more active sites. These sites have a certain chemical bonding effect on the electrolyte anions, so the composite structure exhibits superior performance. Changing the type of ionic liquid does not affect the structure of the gel electrolyte. The gel electrolytes synthesized using different ionic liquids in the above embodiments all have rich pore structures and excellent electrical properties.

[0085] The above embodiments are preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite gel electrolyte based on a porous structure of an organometallic framework, characterized in that, It includes: Organic solutions of metal salts and organic ligands were obtained separately, namely metal salt solutions and organic ligand solutions; To obtain an ionic liquid electrolyte containing lithium salt and ionic liquid electrolyte; A portion of the ionic liquid electrolyte is mixed with the metal salt solution to obtain a first mixture, and the remaining ionic liquid electrolyte is mixed with the organic ligand solution to obtain a second mixture. The first mixture and the second mixture are mixed to obtain a precursor solution; The precursor solution was heated at 60–80°C for 24–72 h to obtain the composite gel electrolyte. The organic ligand is selected from organic acids, and the metal salt has a coordination site that coordinates with the organic ligand.

2. The preparation method according to claim 1, characterized in that, The lithium salt concentration in the ionic liquid electrolyte is 0.5 mol / L; the concentration of the metal salt solution is 0.5 mol / L; and the concentration of the organic ligand solution is 0.5 mol / L.

3. The preparation method according to claim 1, characterized in that, In the first mixture, the volume ratio of the metal salt solution to the ionic liquid electrolyte is 1 to 2:

1.

4. The preparation method according to claim 1, characterized in that, In the second mixture, the volume ratio of the organic ligand solution to the ionic liquid electrolyte is 1 to 2:

1.

5. The preparation method according to claim 1, characterized in that, The metal salt is selected from one or more of Fe(NO3)3 and / or its hydrate, (CH3COO)2Co and / or its hydrate, and C4H6O4Zn.

6. The preparation method according to claim 1, characterized in that, The organic ligand is selected from one or more of pyromellitic acid, dimethylimidazole, and benzoic acid.

7. The preparation method according to claim 1, characterized in that, The ionic liquid electrolyte is selected from one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and tri-n-butylmethylammonium bis(trifluoromethanesulfonyl)imide salt.

8. The preparation method according to claim 1, characterized in that, The lithium salt is selected from LiTFSI; and / or the solvent of the organic solution is selected from ethanol.

9. The composite gel electrolyte prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery comprising the composite gel electrolyte of claim 9.

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