A composite solid electrolyte membrane and its preparation method and battery

Abstract

This invention discloses a composite solid electrolyte membrane, its preparation method, and a battery, belonging to the field of battery material technology. The preparation of the composite solid electrolyte membrane includes: mixing a first lithium salt, polyethylene oxide, and filler, followed by annealing and pressing into a membrane. The preparation of the filler includes: mixing succinic anionylene, a second lithium salt, and a metal-organic framework material under vacuum, followed by ultrasonic treatment. The metal-organic framework material confines the succinic anionylene molecules within its pores, significantly reducing the plasticizing effect of succinic anionylene on the polymer chain segments, which is beneficial for improving the mechanical properties of the polymer electrolyte. Simultaneously, with the increase of the metal-organic framework material content, the succinic anionylene in the pores forms a connected three-dimensional network structure, which can improve the conductivity of the electrolyte and reduce impedance; furthermore, due to the unique solid-state characteristics of the plastic crystal, the succinic anionylene molecules fixed inside the pores will not react with the lithium metal anode, which is beneficial for improving the battery's discharge specific capacity.

Description

Technical Field

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

[0002] Currently, lithium-ion batteries generally use liquid electrolytes, whose main components are flammable and volatile carbonate solvents. Solid-state batteries, on the other hand, use solid electrolytes, which have better safety than liquid electrolytes and eliminate the risk of electrolyte leakage.

[0003] Solid polymer electrolytes have the potential to become the mainstream approach for solid-state batteries due to their ease of processing and low cost; however, their ionic conductivity is typically low (σ). RT <10 -4 The S / cm ratio is mainly due to the fact that the transport of Li within the polymer depends on the movement of polymer chain segments, which move relatively slowly at room temperature.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a composite solid electrolyte membrane, its preparation method, and a battery, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing a composite solid electrolyte membrane, comprising the following steps: mixing a first lithium salt with polyethylene oxide to obtain an electrolyte;

[0008] The electrolyte and filler are mixed, then annealed and pressed into a membrane to obtain a composite solid electrolyte membrane.

[0009] The preparation of the filler includes: mixing succinate, a second lithium salt, and a metal-organic framework material under vacuum and then subjecting the mixture to ultrasonic treatment.

[0010] In an optional embodiment, the mass ratio of polyethylene oxide to the first lithium salt is 100:15 to 100:50;

[0011] And / or, the mass ratio of electrolyte to packing is 100:10 to 100:80.

[0012] In an optional embodiment, the first lithium salt includes at least one of LiTFSI, LiFSI, LiClO4, LiBF4, LiPF6, LDFOB, and LiBOB.

[0013] In an optional embodiment, the annealing temperature is 50°C to 80°C, and the annealing time is 5 hours to 10 hours.

[0014] In an optional embodiment, the pressing pressure is 0.1 MPa to 5.0 MPa.

[0015] In an optional embodiment, the second lithium salt includes at least one of LiTFSI, LiFSI, LiCIO4, LiBF4, LiPF6, LDFOB, and LiBOB;

[0016] And / or, the metal-organic framework material includes at least one of MOF-818 and MOF-919.

[0017] In an optional embodiment, the mass ratio of the second lithium salt to succinic anion is 0.1:1 to 0.5:1;

[0018] And / or, the total mass ratio of succinate and the second lithium salt to the metal-organic framework material is 0.05:1 to 0.2:1.

[0019] In an optional embodiment, the ultrasonic treatment temperature is 60℃~200℃, and the ultrasonic treatment time is 0.1h~2h.

[0020] Secondly, the present invention provides a composite solid electrolyte membrane, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0021] In an optional embodiment, the thickness of the composite solid electrolyte membrane is 30 μm to 100 μm.

[0022] Thirdly, the present invention provides a battery comprising the composite solid electrolyte membrane of the aforementioned embodiments.

[0023] The beneficial effects of this invention include:

[0024] In the preparation of the composite solid electrolyte membrane, this application first uses a metal-organic framework (MOF) material to confine succinic acid molecules within its pores, significantly reducing the plasticizing effect of succinic acid on polymer segments and thus improving the mechanical properties of the polymer electrolyte. Simultaneously, with the increase of MOF material content, the MOF particles come into contact with each other, promoting the formation of a connected three-dimensional network structure of succinic acid within the MOF pores, resulting in a substantial increase in electrolyte conductivity and a decrease in impedance. Furthermore, due to the unique solid-state characteristics of the plasticized crystals, the succinic acid molecules fixed within the MOF material do not react with the lithium metal anode, significantly improving the electrochemical performance of the battery.

[0025] Batteries containing the aforementioned composite solid electrolyte membrane can have a high discharge specific capacity. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0027] The composite solid electrolyte membrane, its preparation method, and the battery provided by this invention will be described in detail below.

[0028] This invention provides a method for preparing a composite solid electrolyte membrane, comprising the following steps: mixing a first lithium salt with polyethylene oxide to obtain an electrolyte;

[0029] The electrolyte and filler are mixed, then annealed and pressed into a membrane to obtain a composite solid electrolyte membrane.

[0030] The preparation of the filler includes: mixing succinate, a second lithium salt, and a metal-organic framework material under vacuum and then subjecting the mixture to ultrasonic treatment.

[0031] This application utilizes metal-organic framework materials in the preparation of composite solid electrolyte membranes, which reduces the crystallinity of the polymer and increases the mobility of polymer chain segments, thereby improving the conductivity of the solid polymer electrolyte. Simultaneously, the unique molecular motion characteristics of the plastic crystal molecule succinate endow it with excellent kinematic properties, thus making it suitable as a Li... + The carrier for conduction. However, it should be noted that simply mixing succinic anhydride with polymer electrolytes will significantly reduce the mechanical properties of the electrolyte. In addition, succinic anhydride readily reacts with lithium metal, thereby deteriorating the electrochemical performance of the battery.

[0032] This application employs a metal-organic framework (MOF) to confine succinic acid molecules within its pores, significantly reducing the plasticizing effect of succinic acid on polymer segments and thus improving the mechanical properties of the polymer electrolyte. Simultaneously, with the increase in MOF content, the MOF particles come into contact with each other, promoting the formation of a connected three-dimensional network structure of succinic acid within the MOF pores. This results in a substantial increase in electrolyte conductivity and a decrease in impedance. Furthermore, due to the unique solid-state characteristics of the plastic crystals, the succinic acid molecules fixed within the MOF will not react with the lithium metal anode, significantly enhancing the battery's electrochemical performance.

[0033] In some alternative embodiments, the mass ratio of polyethylene oxide to the first lithium salt can be from 100:15 to 100:50, such as 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100:45 or 100:50, or other values ​​within the range of 100:15 to 100:50.

[0034] The first lithium salt may, by way of example but not by way of limitation, include at least one of LiTFSI, LiFSI, LiClO4, LiBF4, LiPF6, LDFOB and LiBOB.

[0035] In some alternative embodiments, the mass ratio of electrolyte to filler can be from 100:10 to 100:80, such as 100:10, 100:20, 100:30, 100:40, 100:50, 100:60, 100:70 or 100:80, or other values ​​within the range of 100:10 to 100:80.

[0036] If the amount of filler is too small, it will hinder the construction of the lithium-ion conduction network inside the composite electrolyte; if the amount of filler is too large, it will hinder the maintenance of the flexibility of the composite solid electrolyte.

[0037] In some alternative embodiments, the annealing temperature can be 50°C to 80°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, or other values ​​within the range of 50°C to 80°C.

[0038] The annealing time can be 5h to 10h, such as 5h, 6h, 7h, 8h, 9h or 10h, or other values ​​within the range of 5h to 10h.

[0039] Annealing under the above conditions can promote thorough and uniform mixing of the electrolyte and filler.

[0040] In some alternative implementations, the pressing pressure can be 0.1MPa to 5.0MPa, such as 0.1MPa, 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa or 5MPa, etc., which can be adjusted according to actual needs.

[0041] In some alternative embodiments, the second lithium salt may, by way of example but not limitation, include at least one of LiTFSI, LiFSI, LiCIO4, LiBF4, LiPF6, LDFOB, and LiBOB.

[0042] Metal-organic framework materials may include, by way of example but not by way of limitation, at least one of MOF-818 and MOF-919.

[0043] In some alternative embodiments, the mass ratio of the second lithium salt to succinic anion can be from 0.1:1 to 0.5:1, such as 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1 or 0.5:1, or other values ​​within the range of 0.1:1 to 0.5:1.

[0044] If the amount of succinate is too small, it will not be conducive to the filling of MOF materials; if the amount of succinate is too large, it will not be conducive to the improvement of ionic conductivity.

[0045] The ratio of the total mass of succinate and the second lithium salt to the mass of the metal-organic framework material can be from 0.05:1 to 0.2:1, such as 0.05:1, 0.1:1, 0.15:1 or 0.2:1, or other values ​​within the range of 0.05:1 to 0.2:1.

[0046] If the amount of metal-organic framework material is too small, it will not be conducive to the full absorption of the mixture of succinate and second lithium salt; if the amount of metal-organic framework material is too large, it will not be conducive to improving the pore filling rate of MOF material, ultimately making it difficult to construct the composite electrolyte ion conduction network.

[0047] In some alternative embodiments, the temperature of the ultrasonic treatment can be 60°C to 200°C, such as 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, or other values ​​within the range of 60°C to 200°C.

[0048] The duration of ultrasonic treatment can be 0.1h to 2h, such as 0.1h, 0.5h, 1h, 1.5h or 2h, or other values ​​within the range of 0.1h to 2h.

[0049] The ultrasonic treatment described above can promote the composite of the mixture of succinic acid and the second lithium salt with the metal-organic framework material, allowing the mixture of succinic acid and the second lithium salt to effectively enter the porous structure of the metal-organic framework material.

[0050] Furthermore, the ultrasonically treated material can be frozen and pulverized. By first freezing the ultrasonically treated material (e.g., -40°C to -50°C), the subsequent pulverization operation is more favorable at this temperature, and the material is less likely to agglomerate.

[0051] Accordingly, the present invention also provides a composite solid electrolyte membrane, which is prepared by the above-described preparation method.

[0052] In some optional embodiments, the thickness of the composite solid electrolyte membrane can be 30 μm to 100 μm, such as 30 μm, 50 μm, 80 μm or 100 μm, or other values ​​in the range of 30 μm to 100 μm.

[0053] In addition, the present invention also provides a battery containing the above-described composite solid electrolyte membrane.

[0054] This battery possesses high ionic conductivity, mechanical properties, and cycle stability.

[0055] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0056] Example 1

[0057] This embodiment provides a composite solid electrolyte membrane, the preparation method of which includes:

[0058] S1: Preparation of packing material.

[0059] S11: Mix succinate and the second lithium salt (LiPF6) to obtain a mixture;

[0060] S12: After mixing the mixture with metal-organic framework material (MOF-818), place it in a vacuum environment, heat it to 100°C and sonicate it for 1 hour; then freeze it and grind it into powder.

[0061] The mass ratio of the second lithium salt to succinic anion is 0.3:1; the total mass ratio of the succinic anion and the second lithium salt to the metal-organic framework material is 0.1:1.

[0062] S2: Preparation of composite solid electrolyte membrane.

[0063] S21: The first lithium salt (LiPF6) is mixed with polyethylene oxide to obtain an electrolyte;

[0064] S22: The electrolyte and filler are mixed and kneaded, then annealed at 60°C for 8 hours, and then pressed into a membrane at 3MPa to obtain a composite solid electrolyte membrane.

[0065] The mass ratio of polyethylene oxide to the first lithium salt is 100:30; the mass ratio of electrolyte to filler is 100:10.

[0066] Example 2

[0067] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:20.

[0068] Example 3

[0069] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:30.

[0070] Example 4

[0071] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:40.

[0072] Example 5

[0073] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:50.

[0074] Example 6

[0075] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:60.

[0076] Example 7

[0077] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:70.

[0078] Example 8

[0079] The difference between this embodiment and Embodiment 1 is that the mass ratio of electrolyte to filler is 100:80.

[0080] Example 9

[0081] This embodiment provides a composite solid electrolyte membrane, the preparation method of which includes:

[0082] S1: Preparation of packing material.

[0083] S11: Mix succinate and the second lithium salt (LiBF4) to obtain a mixture;

[0084] S12: The mixture was mixed with metal-organic framework material (MOF-818) and placed in a vacuum environment, heated to 60°C and ultrasonically treated for 2 hours; then frozen and ground.

[0085] The mass ratio of the second lithium salt to succinic anion is 0.1:1; the total mass ratio of the succinic anion and the second lithium salt to the mass ratio of the metal-organic framework material is 0.05:1.

[0086] S2: Preparation of composite solid electrolyte membrane.

[0087] S21: The first lithium salt (LiBF4) is mixed with polyethylene oxide to obtain an electrolyte;

[0088] S22: The electrolyte and filler are mixed and kneaded, then annealed at 50°C for 10 hours, and then pressed into a membrane at 5MPa to obtain a composite solid electrolyte membrane.

[0089] The mass ratio of polyethylene oxide to the first lithium salt is 100:15; the mass ratio of electrolyte to filler is 100:10.

[0090] Example 10

[0091] This embodiment provides a composite solid electrolyte membrane, the preparation method of which includes:

[0092] S1: Preparation of packing material.

[0093] S11: Mix succinate and the second lithium salt (LiClO4) to obtain a mixture;

[0094] S12: The mixture is mixed with metal-organic framework material (MOF-919) and placed in a vacuum environment, heated to 200°C and ultrasonically treated for 0.1 h; then frozen and ground.

[0095] The mass ratio of the second lithium salt to the second succinic anion is 0.5:1; the total mass ratio of the succinic anion and the second lithium salt to the metal-organic framework material is 0.2:1.

[0096] S2: Preparation of composite solid electrolyte membrane.

[0097] S21: The first lithium salt (LiClO4) is mixed with polyethylene oxide to obtain an electrolyte;

[0098] S22: The electrolyte and filler are mixed and kneaded, then annealed at 80°C for 5 hours, and then pressed into a membrane at 0.1 MPa to obtain a composite solid electrolyte membrane.

[0099] The mass ratio of polyethylene oxide to the first lithium salt is 100:50; the mass ratio of electrolyte to filler is 100:10.

[0100] Comparative Example 1

[0101] This comparative example provides a composite solid electrolyte membrane, the preparation method of which includes:

[0102] S1: The first lithium salt (LiPF6) is mixed with polyethylene oxide to obtain the electrolyte;

[0103] S2: The electrolyte is mixed with succinate and kneaded, then annealed at 60°C for 8 hours, and then pressed into a membrane at 3MPa to obtain a composite solid electrolyte membrane.

[0104] The mass ratio of polyethylene oxide to the first lithium salt is 100:30; the mass ratio of electrolyte to succinic acid is 100:10.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:20.

[0107] Comparative Example 3

[0108] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:30.

[0109] Comparative Example 4

[0110] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:40.

[0111] Comparative Example 5

[0112] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:50.

[0113] Comparative Example 6

[0114] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:60.

[0115] Comparative Example 7

[0116] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:70.

[0117] Comparative Example 8

[0118] The difference between this comparative example and Comparative Example 1 is that the mass ratio of electrolyte to succinic acid is 100:80.

[0119] Comparative Example 9

[0120] The difference between this comparative example and Example 1 is that in S12, the ratio of the total mass of the second lithium salt and succinic anion to the mass of the metal-organic framework material is 0.4:1.

[0121] Comparative Example 10

[0122] The difference between this comparative example and Example 1 is that in S22, the mass ratio of electrolyte to filler is 100:5.

[0123] Comparative Example 11

[0124] The difference between this comparative example and Example 1 is that in S22, after the electrolyte and filler are mixed and kneaded, they are not annealed and are directly pressed into a film under a pressure of 3 MPa.

[0125] Comparative Example 12

[0126] The difference between this comparative example and Example 1 is that MOF-818 is replaced with an equal amount of MOF-808.

[0127] Comparative Example 13

[0128] The difference between this comparative example and Example 1 is that MOF-818 is replaced with an equal amount of UIO-66.

[0129] Test case

[0130] The composite solid electrolyte membranes obtained in Examples 1-10 and Comparative Examples 1-13 were assembled into button cells using the following method: a positive electrode (nickel-cobalt-manganese positive electrode) was placed in the center of the positive electrode shell, and the cut composite solid electrolyte membrane was placed on the positive electrode. Lithium metal was used as the negative electrode and placed on top of the electrolyte membrane. Then, a spacer, a spring, and a negative electrode shell were placed on top in sequence. After encapsulation, a button cell was obtained for testing the discharge specific capacity. The test conditions were 25°C, 0.1C, and 3V-4.3V.

[0131] In addition, the composite solid electrolyte membranes obtained in Examples 1-10 and Comparative Examples 1-13 were assembled into Li / Li batteries to test the deposition potential. The assembly process was the same as that of a coin cell, except that the positive electrode was replaced with lithium metal.

[0132] The test results are shown in Table 1.

[0133] Table 1 Test Results

[0134]

[0135]

[0136] As can be seen from Table 1, the composite solid electrolyte membrane prepared in the embodiments of the present invention has a low deposition potential and low impedance, which enables the battery to have a high discharge specific capacity.

[0137] In summary, this invention first uses a metal-organic framework (MOF) to confine succinic acid molecules within its pores, significantly reducing the plasticizing effect of succinic acid on polymer segments and thus improving the mechanical properties of the polymer electrolyte. Simultaneously, as the MOF content increases, the MOF particles come into contact with each other, promoting the formation of a connected three-dimensional network structure of succinic acid within the MOF pores, resulting in a substantial increase in the electrolyte's conductivity. Furthermore, due to the unique solid-state properties of the plastic crystals, the succinic acid molecules fixed within the MOF will not react with the lithium metal anode, significantly improving the battery's cycle stability.

[0138] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite solid-state electrolyte film, characterized by, The method comprises the following steps: mixing a first lithium salt with polyethylene oxide to obtain an electrolyte; mixing the electrolyte with a filler, followed by annealing, pressing into a film to obtain a composite solid electrolyte film; Preparation of the filler comprises: mixing malononitrile, a second lithium salt and a metal organic framework material under vacuum and ultrasonic treatment; The mass ratio of the polyethylene oxide to the first lithium salt is 100:15 to 100:50; The mass ratio of the electrolyte to the filler is 100:10 to 100:80; The mass ratio of the second lithium salt to malononitrile is 0.1:1 to 0.5:1; The ratio of the total mass of malononitrile and the second lithium salt to the mass of the metal organic framework material is 0.05:1 to 0.2:1; The metal organic framework material is selected from at least one of MOF-818 and MOF-919.

2. The production method according to claim 1, characterized by, The first lithium salt comprises at least one of LiTFSI, LiFSI, LiClO4, LiBF4, LiPF6, LDFOB and LiBOB.

3. The preparation method according to claim 1, characterized in that, The annealing temperature is 50-80℃, and the annealing time is 5-10h.

4. The method of claim 1, wherein, The pressing pressure is 0.1-5.0MPa.

5. The method of any one of claims 1 to 4, wherein the method further comprises the step of: The second lithium salt comprises at least one of LiTFSI, LiFSI, LiClO4, LiBF4, LiPF6, LDFOB and LiBOB.

6. The method of any one of claims 1 to 5, wherein the method further comprises the step of: The ultrasonic treatment temperature is 60-200℃, and the ultrasonic treatment time is 0.1-2h.

7. A composite solid-state electrolyte membrane, characterized by, Prepared by the preparation method of any one of claims 1-6.

8. A battery, characterized by The battery contains the composite solid electrolyte film of claim 7.

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