Composite solid electrolyte and preparation method and application thereof

Abstract

The application belongs to the field of battery materials, and discloses a composite solid electrolyte and a preparation method and application thereof.The composite solid electrolyte comprises M2SeBr6 material, PEO and a lithium salt, and M is any one or both of Cs and K.The M2SeBr6 material is applied to a polymer solid electrolyte, so that the conductivity and structural stability of the solid electrolyte can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of battery materials and relates to a solid electrolyte material, specifically a composite solid electrolyte and its preparation method and application. Background Technology

[0002] Currently, the most commonly used battery systems are ternary lithium / graphite, lithium iron phosphate / graphite, and ternary lithium / lithium titanate. Based on the properties of the raw materials used in these three types of batteries, the specific energy of a single lithium iron phosphate and lithium titanate battery cannot exceed 300Wh / kg, while only ternary lithium batteries currently meet this requirement. Although ternary lithium batteries surpass other batteries in energy density, they use a liquid electrolyte, posing significant safety risks. Solid-state lithium batteries can currently be divided into inorganic solid-state electrolyte batteries and polymer solid-state lithium batteries. The development of solid-state lithium batteries mainly depends on the development of solid electrolyte materials.

[0003] Currently, the most studied polymer solid electrolytes are PEO (polyethylene oxide) and its derivative lithium salt complex polymer electrolytes. PEO polymers also exhibit good ionic conductivity at high temperatures and have good processability. However, the high viscosity of PEO polymer electrolytes affects film formation and their poor conductivity, thus hindering their development and application. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, the present invention provides, firstly, a composite solid electrolyte; secondly, a method for preparing the composite solid electrolyte; and thirdly, a battery.

[0005] In a first aspect, the present invention provides a composite solid electrolyte comprising M2SeBr6 material, PEO and lithium salt, wherein M is any one or two of Cs and K.

[0006] Preferably, the M2SeBr6 material is any one or both of Cs2SeBr6 and K2SeBr6.

[0007] Preferably, the lithium salt is any one or more of LiPF6, LiTFSI, LiFSI, and LiBF4.

[0008] Preferably, the mass ratio of M2SeBr6 material to PEO is 5~10:100; the molar ratio of EO in PEO to lithium in lithium salt is 15~20:1.

[0009] Secondly, the present invention provides a method for preparing a composite solid electrolyte, comprising: ball milling and mixing M2SeBr6 material, PEO, lithium salt and organic solvent to obtain a slurry, coating the slurry onto a substrate and then vacuum drying it to obtain the final product.

[0010] Preferably, the organic solvent is any one or more of tetrahydrofuran, acetonitrile, and N,N-dimethylformamide.

[0011] Preferably, the solid-liquid ratio of the slurry is 1g:15~30mL.

[0012] Preferably, the ball milling speed is 300~500 rpm and the ball milling time is 2~6 hours.

[0013] Preferably, the drying temperature is 70~90℃ and the drying time is 6~12h.

[0014] Preferably, the preparation method of M2SeBr6 material includes: dispersing metal bromide and selenium dioxide in hydrobromic acid solution, heating and drying to obtain an intermediate product; and subjecting the obtained intermediate product to high-temperature sintering treatment to obtain the final M2SeBr6 material.

[0015] Preferably, the metal bromide is any one or both of potassium bromide and cesium bromide.

[0016] Preferably, the concentration of the hydrobromic acid solution is 6~10 mol / L.

[0017] Preferably, the molar ratio of the metal bromide, selenium dioxide, and HBr in hydrobromic acid is the same as the stoichiometric ratio of M2SeBr6.

[0018] Preferably, the heating reaction temperature is 70~90℃; the heating reaction time is 2~4h.

[0019] Preferably, the high-temperature sintering atmosphere is a nitrogen or argon atmosphere; the high-temperature sintering temperature is 500~700℃; and the high-temperature sintering time is 6~18h.

[0020] Thirdly, a battery comprising the aforementioned composite solid electrolyte or the composite solid electrolyte prepared by the aforementioned preparation method.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) Applying M2SeBr6 material to polymer solid electrolytes can effectively improve the conductivity and structural stability of solid electrolytes.

[0023] (2) The modification process of the present invention is simple and the process is short, making it easy to achieve large-scale production. Attached Figure Description

[0024] Figure 1 The results show the cycle performance test results of batteries assembled from the solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-4.

[0025] Figure 2The mechanical strength test diagram is shown for the solid electrolyte prepared in Example 1.

[0026] Figure 3 The mechanical strength test diagram is for the solid electrolyte prepared in Comparative Example 1. Detailed Implementation

[0027] The present invention provides the following specific technical solutions.

[0028] In a first aspect, the present invention provides a composite solid electrolyte comprising M2SeBr6 material, PEO and lithium salt, wherein M is any one or two of Cs and K.

[0029] Through research, the inventors discovered that the M2SeBr6 crystal structure contains abundant ion transport channels, which facilitates the rapid migration of lithium ions. PEO, as a polymer matrix, possesses certain flexibility and lithium ion solvation capabilities. The combination of the two can balance the high ion conductivity of inorganic materials with the interfacial compatibility of polymers, thereby synergistically improving the overall ionic conductivity of the electrolyte and meeting the requirements of high-power batteries. M2SeBr6 material can enhance the mechanical strength of the electrolyte, suppress lithium dendrite puncture, and improve battery safety. Meanwhile, the flexibility of PEO gives the composite electrolyte good processability, making it easy to prepare into thin films, which meets the needs of large-scale production of solid-state batteries.

[0030] Preferably, the M2SeBr6 material is any one or more of Cs2SeBr6 and K2SeBr6.

[0031] Preferably, the lithium salt is any one or more of LiPF6, LiTFSI, LiFSI, and LiBF4.

[0032] Preferably, the mass ratio of M2SeBr6 material to PEO is 5~10:100; the molar ratio of EO in PEO to lithium in lithium salt is 15~20:1.

[0033] Through research, the inventors discovered that PEO possesses good flexibility. When the M2SeBr6 ratio is appropriate, PEO can form a continuous matrix structure, ensuring that the electrolyte has a certain degree of flexibility and processability, facilitating close contact with the electrode and reducing interfacial resistance. This avoids the cost increase caused by a high proportion of inorganic materials. At the same time, as an inexpensive polymer matrix, PEO can reduce the overall cost while ensuring performance, making it more suitable for practical applications.

[0034] Secondly, the present invention provides a method for preparing a composite solid electrolyte, comprising: ball milling and mixing M2SeBr6 material, PEO, lithium salt and organic solvent to obtain a slurry, coating the slurry onto a substrate and then vacuum drying it to obtain the final product.

[0035] The preparation method provided by this invention is simple, easy to operate, and conducive to industrialization and marketization.

[0036] Preferably, the organic solvent is any one or more of tetrahydrofuran, acetonitrile, and N,N-dimethylformamide.

[0037] Preferably, the solid-liquid ratio of the slurry is 1g:15~30mL.

[0038] Preferably, the drying temperature is 70~90℃ and the drying time is 6~12h.

[0039] Preferably, the preparation method of M2SeBr6 material includes: dispersing metal bromide and selenium dioxide in hydrobromic acid solution for reaction, then drying, and sintering under a protective atmosphere to obtain solid particles, which are M2SeBr6 materials.

[0040] Preferably, the metal bromide is one of potassium bromide or cesium bromide.

[0041] Preferably, the concentration of the hydrobromic acid solution is 6~10 mol / L.

[0042] Preferably, the molar ratio of metal bromide, selenium dioxide, and HBr in hydrobromic acid is the same as the stoichiometric ratio of M2SeBr6. In practical applications, HBr in hydrobromic acid can be slightly in excess, i.e., the molar ratio of metal bromide, selenium dioxide, and HBr in hydrobromic acid is 2:1:4.05~4.2.

[0043] Preferably, the drying temperature is 70~90℃; the heating reaction time is 2~4h.

[0044] Preferably, the sintering temperature is 500~700℃; the sintering time is 6~18h.

[0045] Preferably, the protective atmosphere is provided by any one or more of nitrogen and argon.

[0046] Thirdly, a battery comprising the aforementioned composite solid electrolyte or the composite solid electrolyte prepared by the aforementioned preparation method.

[0047] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] Example 1:

[0051] A method for preparing a composite solid electrolyte includes the following steps:

[0052] Step 1, Preparation of Cs₂SeBr₆: 0.2 mol cesium bromide and 0.1 mol selenium dioxide were dispersed in 51 mL of 8 mol / L hydrobromic acid solution. After heating at 80 °C for 3 h, the solvent was evaporated to obtain an intermediate product. The obtained intermediate product was sintered at 580 °C for 10 h under a nitrogen atmosphere to obtain the final Cs₂SeBr₆ material.

[0053] Step 2: Take 3g of Cs2SeBr6, 36.7g of PEO, and 13.3g of LiTFSI obtained in Step 1, add them to 1000mL of tetrahydrofuran, and ball mill at 400rpm for 4h to obtain a slurry; then coat the slurry onto a polytetrafluoroethylene plate and dry it at 80℃ for 9h to obtain the composite solid electrolyte.

[0054] Example 2:

[0055] A method for preparing a composite solid electrolyte includes the following steps:

[0056] Step 1, Preparation of Cs₂SeBr₆: 0.2 mol cesium bromide and 0.1 mol selenium dioxide were dispersed in 67.5 mL of 6 mol / L hydrobromic acid solution. After heating at 70 °C for 4 h, the solvent was evaporated to obtain an intermediate product. The obtained intermediate product was sintered at 500 °C for 18 h under a nitrogen atmosphere to obtain the final Cs₂SeBr₆ material.

[0057] Step 2: Take 2.8g of Cs2SeBr6, 55.8g of PEO, and 24.2g of LiTFSI obtained in Step 1, add them to 1260mL of tetrahydrofuran, and ball mill at 300rpm for 6h to obtain a slurry; then coat the slurry onto a polytetrafluoroethylene plate and dry it at 70℃ for 12h to obtain the composite solid electrolyte.

[0058] Example 3:

[0059] A method for preparing a composite solid electrolyte includes the following steps:

[0060] Step 1, Preparation of K2SeBr6: 0.2 mol potassium bromide and 0.1 mol selenium dioxide were dispersed in 42 mL of 10 mol / L hydrobromic acid solution. After heating at 90 °C for 2 h, the solvent was evaporated to obtain an intermediate product. The obtained intermediate product was sintered at 700 °C for 6 h under a nitrogen atmosphere to obtain the final K2SeBr6 material.

[0061] Step 2: Take 2g of K2SeBr6, 20.06g of PEO, and 6.54g of LiTFSI obtained in Step 1, add them to 765mL of tetrahydrofuran, and ball mill at 500rpm for 2h to obtain a slurry; then coat the slurry onto a polytetrafluoroethylene plate and dry it at 90℃ for 6h to obtain the composite solid electrolyte.

[0062] Comparative Example 1:

[0063] A method for preparing a composite solid electrolyte includes the following steps:

[0064] The steps are as follows: 36.7g PEO and 13.3g LiTFSI are added to 1000mL of tetrahydrofuran and ball-milled at 400rpm for 4h to obtain a slurry; then the slurry is coated onto a polytetrafluoroethylene plate and dried at 90℃ for 6h to obtain the composite solid electrolyte.

[0065] The composite solid electrolytes prepared in Examples 1-3 and Comparative Example 1 were assembled into batteries.

[0066] The solid electrolytes obtained in Examples 1-3 and Comparative Example 1 were used as solid electrolyte components and assembled into coin cells, with Li 1.1 Mn 0.9 O2 is used as the positive electrode active material. It is weighed and ground according to a mass ratio of positive electrode material:conductive graphite:PVDF of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone (NMP) is added, and grinding and stirring are continued to form a uniform slurry. The slurry is then evenly coated onto aluminum foil using a mold to a thickness of 200 μm, and placed in a drying oven at 90°C for 10 hours. The resulting material is then cut into 12 mm diameter discs to form the positive electrode. Lithium sheets are used as the negative electrode. They are placed in a glove box filled with argon atmosphere for 4 hours to reduce the moisture adsorbed during the transfer process. Finally, they are assembled into CR2032 coin cells in the glove box.

[0067] After the battery assembly was completed and aged for 12 hours, charge-discharge tests were conducted at different potentials. The battery was activated for 3 cycles at a current density of 0.1C under a voltage of 2.7~4.8V, and then cycled for 100 cycles at a current density of 1C.

[0068] Figure 1The figures show the cycle performance test results of batteries assembled with solid electrolytes prepared in Examples 1-3 and Comparative Example 1. As can be seen from the figures, the battery assembled with the solid electrolyte containing M2SeBr6 material exhibits the best electrochemical performance, while the battery assembled with the solid electrolyte in Comparative Example 1 without M2SeBr6 material shows the worst electrochemical performance. The inventors suggest that this may be due to the excellent conductivity and ion transport properties exhibited by the composite of M2SeBr6 material and PEO-based electrolyte, as well as the excellent structural stability of M2SeBr6 material itself, all of which effectively improve the electrochemical performance of the battery.

[0069] Figure 2 The image shows the mechanical strength test results of the solid electrolyte prepared in Example 1. The solid electrolyte was subjected to a mechanical strength test under a pressure of 30 GPa. The solid electrolyte structure remained intact and there were no cracks.

[0070] Figure 3 The mechanical strength test diagram of the solid electrolyte prepared in Comparative Example 1 is shown. The solid electrolyte was placed under a pressure of 20 GPa for mechanical strength testing, and the solid electrolyte ruptured.

[0071] contrast Figure 2 and Figure 3 This demonstrates that the solid electrolyte provided by the present invention has excellent mechanical strength and safety performance.

[0072] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte, characterized in that, Including M2SeBr6 materials, PEO and lithium salts, where M is any one or both of Cs and K; The mass ratio of M2SeBr6 material to PEO is (5~10):100; The preparation method of the composite solid electrolyte includes: ball milling and mixing M2SeBr6 material, PEO, lithium salt and organic solvent to obtain a slurry, coating the slurry onto a substrate and then vacuum drying to obtain the composite solid electrolyte.

2. The composite solid electrolyte as described in claim 1, characterized in that, The M2SeBr6 material is any one or both of Cs2SeBr6 and K2SeBr6.

3. The composite solid electrolyte as described in claim 1, characterized in that, The lithium salt is any one or more of LiPF6, LiTFSI, LiFSI, and LiBF4.

4. The composite solid electrolyte as described in claim 1, characterized in that, The molar ratio of EO in PEO to lithium in lithium salt is (15~20):

1.

5. The composite solid electrolyte as described in claim 1, characterized in that, The organic solvent is any one or more of tetrahydrofuran, acetonitrile, and N,N-dimethylformamide.

6. The composite solid electrolyte as described in claim 1, characterized in that, The solid-liquid ratio of the slurry is 1g:(15~30)mL.

7. The composite solid electrolyte as described in claim 1, characterized in that, The preparation method of M2SeBr6 material includes: dispersing metal bromide and selenium dioxide in hydrobromic acid solution, heating and reacting for a certain time, evaporating the solvent to obtain an intermediate product; and subjecting the intermediate product to high-temperature sintering treatment to obtain the final M2SeBr6 material.

8. The composite solid electrolyte as described in claim 7, characterized in that, The metal bromide is any one or two of potassium bromide and cesium bromide; the concentration of the hydrobromic acid solution is 6~10 mol / L; the molar ratio of the metal bromide, selenium dioxide, and HBr in the hydrobromic acid solution is the same as the stoichiometric ratio of M2SeBr6; the heating reaction temperature is 70~90℃; and the heating reaction time is 2~4h.

9. A battery, characterized in that, Includes the composite solid electrolyte as described in any one of claims 1 to 8.

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