A high-voltage resistant composite solid electrolyte and preparation method thereof, and all-solid-state lithium battery

Abstract

The present invention discloses a high-voltage resistant composite solid electrolyte and a preparation method thereof, and an all-solid-state lithium battery, relating to the technical field of lithium-ion batteries, wherein a high-voltage resistant composite solid electrolyte is formed by hot pressing a first composite solid electrolyte layer and a second composite solid electrolyte layer; the first composite solid electrolyte layer includes a COFs matrix and a polymer electrolyte A loaded on the surface of the COFs matrix, and the polymer electrolyte A includes polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride; the second composite solid electrolyte layer includes a COFs matrix and a polymer electrolyte B loaded on the surface of the COFs matrix; the polymer electrolyte B includes polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride. The composite solid electrolyte of the present application not only broadens the electrochemical window of the solid electrolyte, reduces the interface resistance, improves the positive and negative electrode interface stability and lithium ion transmission performance, but also can be applied to both lithium metal negative electrodes and high-voltage ternary positive electrodes, thereby improving battery cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a high-voltage resistant composite solid electrolyte and a preparation method thereof, and an all-solid-state lithium battery. Background Art

[0002] In lithium-ion battery applications, solid electrolytes can significantly improve the energy density and safety of lithium-ion batteries compared to traditional liquid electrolytes, thus gaining widespread application. Currently, solid electrolytes are mainly divided into two categories: inorganic solid electrolytes and polymer solid electrolytes. However, in actual use, due to the large interfacial resistance of inorganic solid electrolytes, instability towards lithium metal anodes, and the low critical current density at which lithium dendrites penetrate the solid electrolyte and cause battery short circuits, the application of inorganic solid electrolytes in all-solid-state lithium batteries is limited. Polymer solid electrolytes, on the other hand, have high lithium ion conductivity, considerable mechanical integrity, and compatibility with electrodes, making them one of the popular candidate materials for solid batteries. However, during use, polymer solid electrolytes have a narrow electrochemical window, making them unsuitable for both lithium metal anodes and high-voltage ternary cathodes, thus limiting their large-scale promotion.

[0003] Therefore, how to improve the voltage window of polymer solid electrolytes, enhance their antioxidant capacity, and increase the actual energy density of solid batteries has become a hot topic in recent years. For example, the Chinese patent document, application number CN202011064037.2, discloses a composite solid electrolyte with two surfaces and its preparation method, which discloses a two-step method of coating antioxidant and anti-reduction polymer solid electrolytes on the surface of a three-dimensional ceramic skeleton, thereby widening the electrochemical window. However, due to the uneven microstructure of the ceramic matrix used, the actual thickness of the coated polymer solid electrolyte is uneven, resulting in uneven electric field distribution inside the solid electrolyte during charging and discharging, and a potential risk of lithium plating at the negative electrode, which in turn poses a safety hazard.

[0004] As well as the Chinese patent document, a double-layer composite solid electrolyte with application number 201910025818.1, its preparation method and application. Although the disclosed double-layer composite solid electrolyte improves the lithium ion conductivity, electrochemical window and mechanical strength of the composite solid electrolyte, it helps to inhibit the growth of lithium dendrites and improve the battery cycle performance; however, this system is suitable for sulfur-based positive electrodes and is difficult to be applied to lithium metal negative electrodes and high-voltage ternary positive electrodes at the same time. At the same time, because it includes oxide solid electrolytes, sulfide solid electrolytes and polymer solid electrolytes, there are many contact interfaces of different types of solid electrolytes, resulting in poor electrochemical stability and large interfacial internal resistance, which affects the cycle performance of lithium-ion batteries. Summary of the Invention

[0005] 1. Technical problem to be solved by the invention

[0006] In response to the technical problems of existing polymer solid electrolytes such as narrow electrochemical window, poor electrochemical stability and high interfacial internal resistance, the present invention provides a high-voltage resistant composite solid electrolyte and its preparation method, as well as an all-solid-state lithium battery. It can not only broaden the electrochemical window of the solid electrolyte and reduce the battery internal resistance, but also improve the electrochemical stability and lithium ion transport performance of the solid electrolyte, thereby extending the battery cycle life.

[0007] 2. Technical solution

[0008] In order to solve the above problems, the technical solution provided by the present invention is:

[0009] A high-voltage resistant composite solid electrolyte is formed by hot pressing a first composite solid electrolyte layer and a second composite solid electrolyte layer; wherein the first composite solid electrolyte layer comprises a COFs matrix and a polymer electrolyte A loaded on the surface of the COFs matrix, the polymer electrolyte A comprising polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride, and the mass ratio of the polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride is 70-90:2-6:10-30:1-5; the second composite solid electrolyte layer comprises a COFs matrix and a polymer electrolyte B loaded on the surface of the COFs matrix; the polymer electrolyte B comprises polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride, and the mass ratio of the polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride is 75-95:2-5:10-25:1-5.

[0010] Optionally, the COFs matrix includes an amino-modified porous nano-oxide substrate and a COFs layer supported on the amino-modified porous nano-oxide substrate, the COFs layer includes tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid, and the mass ratio of tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid is 10-20:5-15:50-200.

[0011] Optionally, the thickness of the COFs substrate is 30-200 μm.

[0012] At the same time, the present application also provides a method for preparing the above-mentioned high-voltage resistant composite solid electrolyte, comprising the following steps:

[0013] S1. Preparation of COFs matrix: a. Soak the porous nano-oxide substrate in deionized water, then in a hydrochloric acid solution, and then in a toluene solution containing 3-aminopropyltriethoxysilane. After completion, wash with alcohol to obtain an amino-modified porous nano-oxide substrate; b. Dissolve tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid in ethylene dioxide, ultrasonically disperse to obtain a light yellow transparent solution, and place the obtained light yellow transparent solution in a high-pressure reactor; dissolve terephthalic acid in ethylene dioxide to obtain a mixed solution, soak the amino-modified porous nano-oxide substrate obtained in step a in the mixed solution, take it out after completion, vertically place it in a high-pressure reactor, and heat it to obtain a COFs matrix;

[0014] S2. Preparation of the first composite solid electrolyte layer: dissolving polyethylene oxide, bismuth trioxide, lithium salt, and polyvinylidene fluoride in anhydrous acetonitrile, and ultrasonically dispersing the mixture to obtain a polymer electrolyte A solution; casting the polymer electrolyte A solution onto the COFs substrate obtained in step S1, and vacuum drying the mixture to obtain the first composite solid electrolyte layer;

[0015] S3. Preparation of the second composite solid electrolyte layer: dissolving polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride in anhydrous acetonitrile and ultrasonically dispersing to obtain a polymer electrolyte B solution; casting the polymer electrolyte B solution on the COFs substrate obtained in step S1 and vacuum drying to obtain a second composite solid electrolyte layer;

[0016] S4. The first composite solid electrolyte layer obtained in step S2 and the second composite solid electrolyte layer obtained in step S3 are composited by hot pressing in an inert atmosphere to obtain a high-pressure resistant composite solid electrolyte.

[0017] Optionally, in step a, the porous nano-oxide substrate is any one of a porous nano-aluminum oxide substrate, a porous nano-molybdenum oxide substrate, a porous nano-silicon oxide substrate, a porous nano-copper oxide substrate, a porous nano-indium oxide substrate, a porous nano-silver oxide substrate, and a porous nano-titanium oxide substrate; the deionized water temperature is 80-90°C, the immersion time in deionized water is 1-3h, the concentration of the hydrochloric acid solution is 0.5-1.0M / L, the immersion time in a toluene solution containing 3-aminopropyltriethoxysilane is 1-3h, and the substrate is rinsed 3-5 times with anhydrous ethanol.

[0018] Optionally, in step b, the mass ratio of tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid is 10-20:5-15:50-200, ultrasonic dispersion is performed for 10-30 minutes, the lining of the high-pressure reactor is polytetrafluoroethylene, the immersion temperature is 150-170°C, the immersion time is 0.5-2 hours, the heating temperature is 100-200°C, and the heating time is 70-80 hours.

[0019] Optionally, in step S2, the mass ratio of polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride is 70-90:2-6:10-30:1-5, ultrasonic dispersion is carried out for 1-2 hours, and the vacuum drying temperature is 20-30°C; in step S3, the mass ratio of polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride is 75-95:2-5:10-25:1-5, ultrasonic dispersion is carried out for 1-2 hours, and the vacuum drying temperature is 20-30°C.

[0020] Optionally, in step S4, the inert atmosphere is an argon atmosphere, the hot pressing environment pressure is 30-50 standard atmospheres, and the hot pressing temperature is 100-300°C.

[0021] In addition, the present application also provides an all-solid-state lithium battery, comprising the above-mentioned high-voltage resistant composite solid electrolyte or the high-voltage resistant composite solid electrolyte prepared by the above-mentioned method, a composite positive electrode sheet and a negative electrode sheet, wherein the high-voltage resistant composite solid electrolyte is located between the composite positive electrode sheet and the negative electrode sheet.

[0022] Optionally, the composite positive electrode sheet includes lithium titanium aluminum phosphate, a ternary positive electrode material and a conductive agent, and the mass ratio of the lithium titanium aluminum phosphate, the ternary positive electrode material and the conductive agent is 1-1.5:1-1.5:0.05-0.1.

[0023] 3. Beneficial effects

[0024] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0025] (1) A high-voltage composite solid electrolyte proposed in the embodiment of the present application utilizes covalent organic frameworks (COFs) with high specific surface area, adjustable pore size, structural predictability and stability, which can realize large-capacity lithium storage and fast ion transport channels. COFs can improve Li + affinity and periodic pores, which is beneficial to Li +The uniform distribution of flux is conducive to the smooth progress of Li transport and deposition. Therefore, by setting the first composite solid electrolyte layer and the second composite solid electrolyte layer to include a COFs matrix and compounding the polymer electrolyte in the COFs matrix, the interface resistance between the composite solid electrolyte layer and the electrode can be significantly improved, thereby improving the lithium ion transmission rate. At the same time, considering that the COFs matrix layer has high hardness and large interface resistance after contact with the polymer electrolyte, the Bi2O3 material has extremely high ionic conductivity at low temperature and can be used as a negative electrode material for lithium ion batteries. By adding Bi2O3 in the synthesis of the polymer electrolyte, the problem of large interface resistance after contact with the polymer electrolyte due to the high hardness of the COFs matrix layer can be effectively avoided, thereby further improving the lithium ion transmission rate. In addition, the main component of polymer electrolyte A is polyethylene oxide, so that the first composite solid electrolyte layer obtained has anti-reduction properties and contacts with the lithium negative electrode, and the main component of polymer electrolyte B is polymethyl methacrylate, so that the second composite solid electrolyte layer obtained has anti-oxidation properties and contacts with the high-voltage ternary positive electrode material, thereby improving the electrochemical stability and lithium ion transmission performance of the solid electrolyte. It can be seen from this that the high-voltage resistant composite solid electrolyte of the present application, through the synergistic effect between different components, not only broadens the electrochemical window of the polymer solid electrolyte, reduces the interface resistance, improves the positive and negative electrode interface stability and lithium ion transmission performance, but also can be applied to both lithium metal negative electrode and high-voltage ternary positive electrode, thereby improving the cycle performance of the battery.

[0026] (2) A high-voltage composite solid electrolyte proposed in the embodiment of the present application takes into account the relatively poor stability of Bi2O3 and its easy reduction in actual application, thereby reducing its ionic conductivity. By adding an appropriate amount of acetic acid to the components of the COFs layer and adjusting the pH of the system, the redox adsorption characteristics of the COFs material are improved. During the actual charge and discharge process, protons are preferentially adsorbed, reducing the reduction reaction of the Bi2O3 material, improving the stability of Bi2O3, and thus improving the conductivity of the COFs matrix; at the same time, porous COFs are prepared on an amino-modified oxide porous substrate, which can improve the synthesis efficiency of COFs and make COFs with uniform and controllable pore size, thereby improving the mechanical strength and lithium ion transport performance of the electrolyte, and contributing to the high stability of the Bi2O3 material, effectively reducing the interface resistance, and improving the battery internal resistance and cycle life.

[0027] (3) A high-pressure resistant composite solid electrolyte proposed in the embodiment of the present application can ensure that there are a rich number of channels inside the COFs matrix by limiting the thickness of the COFs matrix, thereby achieving large-capacity lithium storage and fast ion transmission channels while having a simple internal structure to avoid impurities in the electrolyte.

[0028] (4) The present application proposes a method for preparing a high-voltage resistant composite solid electrolyte. The high-voltage composite solid electrolyte prepared by this method, through the synergistic effect between different components, not only broadens the electrochemical window of the polymer solid electrolyte, reduces the interface resistance, and improves the positive and negative electrode interface stability and lithium ion transmission performance, but also has a stability of up to 4.1V. It can also be applied to both lithium metal negative electrodes and high-voltage ternary positive electrodes, thereby improving the cycle performance of the battery.

[0029] (5) The present application proposes a method for preparing a high-voltage resistant composite solid electrolyte. By loading amino groups on the surface of a porous nano-oxide substrate, the substrate surface can be activated. At the same time, the amino-modified porous nano-oxide substrate can fully adsorb terephthalic acid and ethylene dioxide solution in step b, thereby accelerating the reaction speed and improving the reaction efficiency.

[0030] (6) An all-solid-state lithium battery proposed in an embodiment of the present application, in application, uses the above-mentioned high-voltage resistant composite solid electrolyte to simultaneously make good contact with the lithium metal negative electrode and the high-voltage ternary positive electrode, thereby reducing the interface impedance, maintaining good conductivity, improving the positive and negative electrode interface stability and lithium ion transmission performance, and improving the battery's cycle performance. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] It should be noted that all reagents and raw materials involved in this application can be purchased from the market.

[0033] The present application provides a high-voltage resistant composite solid electrolyte, which is formed by hot pressing a first composite solid electrolyte layer and a second composite solid electrolyte layer; wherein the first composite solid electrolyte layer comprises a COFs matrix and a polymer electrolyte A loaded on the surface of the COFs matrix, the polymer electrolyte A comprises polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride, and the mass ratio of polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride is 70-90:2-6:10-30:1-5; the second composite solid electrolyte layer comprises a COFs matrix and a polymer electrolyte B loaded on the surface of the COFs matrix; The polymer electrolyte B comprises polymethyl methacrylate, bismuth trioxide, lithium salt, and polyvinylidene fluoride, wherein the mass ratio of the polymethyl methacrylate, bismuth trioxide, lithium salt, and polyvinylidene fluoride is 75-95:2-5:10-25:1-5. The COFs matrix comprises an amino-modified porous nano-oxide substrate and a COFs layer supported on the amino-modified porous nano-oxide substrate. The COFs layer comprises tetrakis-(4-anilino)methane, terephthalic acid, and acetic acid, wherein the mass ratio of the tetrakis-(4-anilino)methane, terephthalic acid, and acetic acid is 10-20:5-15:50-200. The COFs matrix has a thickness of 30-200 μm.

[0034] In this application, covalent organic frameworks (COFs) are used to achieve large-capacity lithium storage and fast ion transport channels due to their high specific surface area, adjustable pore size, structural predictability, and stability. COFs can improve the + affinity and periodic pores, which is beneficial to Li +The uniform distribution of flux is conducive to the smooth progress of Li transport and deposition. Therefore, by setting the first composite solid electrolyte layer and the second composite solid electrolyte layer to include a COFs matrix and compounding the polymer electrolyte in the COFs matrix, the interface resistance between the composite solid electrolyte layer and the electrode can be significantly improved, thereby improving the lithium ion transmission rate. At the same time, considering that the COFs matrix layer has high hardness and large interface resistance after contact with the polymer electrolyte, the Bi2O3 material has extremely high ionic conductivity at low temperature and can be used as a negative electrode material for lithium ion batteries. By adding Bi2O3 in the synthesis of the polymer electrolyte, the problem of large interface resistance after contact with the polymer electrolyte due to the high hardness of the COFs matrix layer can be effectively avoided, thereby further improving the lithium ion transmission rate. In addition, the main component of polymer electrolyte A is polyethylene oxide, so that the first composite solid electrolyte layer obtained has anti-reduction properties and contacts with the lithium negative electrode, and the main component of polymer electrolyte B is polymethyl methacrylate, so that the second composite solid electrolyte layer obtained has anti-oxidation properties and contacts with the high-voltage ternary positive electrode material, thereby improving the electrochemical stability and lithium ion transmission performance of the solid electrolyte. It can be seen from this that the high-voltage resistant composite solid electrolyte of the present application, through the synergistic effect between different components, not only broadens the electrochemical window of the polymer solid electrolyte, reduces the interface resistance, improves the positive and negative electrode interface stability and lithium ion transmission performance, but also can be applied to both lithium metal negative electrode and high-voltage ternary positive electrode, thereby improving the cycle performance of the battery.

[0035] At the same time, the present application also provides a method for preparing a high-voltage resistant composite solid electrolyte, comprising the following steps:

[0036] S1. Preparation of COFs matrix: a. Soak the porous nano-oxide substrate in 80-90°C deionized water for 1-3 hours, then immerse it in a hydrochloric acid solution with a concentration of 0.5-1.0M / L to activate the surface hydroxyl groups, and then soak it in a toluene solution containing 3-aminopropyltriethoxysilane for 1-3 hours. After the surface loading of amino groups is completed, rinse it with anhydrous ethanol 3-5 times to obtain an amino-modified porous nano-oxide substrate; wherein the porous nano-oxide substrate is any one of a porous nano-alumina substrate, a porous nano-molybdenum oxide substrate, a porous nano-silicon oxide substrate, a porous nano-copper oxide substrate, a porous nano-indium oxide substrate, a porous nano-silver oxide substrate, and a porous nano-titanium oxide substrate. In this step, by loading amino groups on the surface of the porous nano-oxide substrate, the substrate surface can be activated. At the same time, the amino-modified porous nano-oxide substrate can fully adsorb terephthalic acid and ethylene dioxide solution in step b, accelerate the reaction speed, and improve the reaction efficiency.

[0037] b. Tetrakis-(4-anilino)-methane, terephthalic acid, and acetic acid are dissolved in ethylene dioxide in a mass ratio of 10-20:5-15:50-200, and ultrasonically dispersed for 10-30 minutes to obtain a light yellow transparent solution, which is placed in a polytetrafluoroethylene-lined autoclave; terephthalic acid is dissolved in ethylene dioxide (mass fraction of 5-20%) to obtain a mixed solution, and the amino-modified porous nano-oxide substrate obtained in step a is immersed in the mixed solution at 150-170° C. for 0.5-2 hours. After the mixture is removed, the substrate is vertically placed in an autoclave and heated at 100-200° C. for 70-80 hours to obtain a COFs matrix with uniform pore size, wherein the thickness of the COFs matrix is ​​30-200 μm, wherein the COFs microstructure and pore size can be controlled by the amino-modified porous nano-oxide substrate, and the water and oxygen content in the environment do not exceed 10 ppm during the preparation process.

[0038] Considering the relatively poor stability of Bi2O3 and its easy reduction in practical applications, which reduces its ionic conductivity, the addition of an appropriate amount of acetic acid to the components of the COFs layer and the adjustment of the system's pH enhance the redox adsorption properties of the COFs material. During the actual charge and discharge process, protons are preferentially adsorbed, reducing the reduction reaction of the Bi2O3 material, improving the stability of Bi2O3, and thus the conductivity of the COFs matrix. Furthermore, the preparation of porous COFs on an amino-modified porous oxide substrate improves the COFs synthesis efficiency and produces COFs with uniform and controllable pore size, which in turn improves the mechanical strength and lithium ion transport performance of the electrolyte, contributes to the high stability of the Bi2O3 material, effectively reduces the interfacial resistance, and improves the battery's internal resistance and cycle life. Furthermore, by limiting the thickness of the COFs matrix, a rich number of pores can be ensured within the COFs matrix, achieving large-capacity lithium storage and rapid ion transport channels while maintaining a simple internal structure and avoiding impurities in the electrolyte.

[0039] S2. Preparation of the first composite solid electrolyte layer: dissolve polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride in anhydrous acetonitrile in a mass ratio of 70-90:2-6:10-30:1-5, and ultrasonically disperse for 1-2 hours to obtain a polymer electrolyte A solution; cast the polymer electrolyte A solution on the COFs substrate obtained in step S1, and vacuum evaporate the acetonitrile at 20-30°C to obtain the first composite solid electrolyte layer.

[0040] S3. Preparation of the second composite solid electrolyte layer: dissolve polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride in anhydrous acetonitrile in a mass ratio of 75-95:2-5:10-25:1-5, and ultrasonically disperse for 1-2 hours to obtain a polymer electrolyte B solution; cast the polymer electrolyte B solution on the COFs substrate obtained in step S1, and vacuum evaporate the acetonitrile at 20-30°C to obtain a second composite solid electrolyte layer.

[0041] In practical application, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium chlorate, lithium hexafluorophosphate, and lithium difluorooxalatoborate.

[0042] S4. The first composite solid electrolyte layer obtained in step S2 and the second composite solid electrolyte layer obtained in step S3 are hot-pressed and composited at 100-300° C. under 30-50 standard atmospheric pressure in an argon atmosphere to obtain a high-pressure resistant composite solid electrolyte.

[0043] In addition, the present application also provides an all-solid-state lithium battery, comprising the high-voltage resistant composite solid electrolyte described above or the high-voltage resistant composite solid electrolyte prepared by the method described above, a composite positive electrode sheet and a negative electrode sheet, wherein the high-voltage resistant composite solid electrolyte is located between the composite positive electrode sheet and the negative electrode sheet. Wherein, the composite positive electrode sheet comprises lithium titanium aluminum phosphate, a ternary positive electrode material and a conductive agent, and the mass ratio of the lithium titanium aluminum phosphate, the ternary positive electrode material and the conductive agent is 1-1.5:1-1.5:0.05-0.1; the negative electrode sheet is a lithium metal sheet. By adopting the above-mentioned high-voltage resistant composite solid electrolyte, the battery can simultaneously make good contact with the lithium metal negative electrode and the high-voltage ternary positive electrode, thereby reducing the interface impedance, maintaining good conductivity, improving the positive and negative electrode interface stability and lithium ion transmission performance, and improving the battery's cycle performance.

[0044] In actual application, the preparation process of the composite positive electrode sheet is as follows: lithium aluminum titanium phosphate, ternary positive electrode material and conductive agent are added to a high-energy vibration ball mill in a mass ratio of 1-1.5:1-1.5:0.05-0.1, ball milled at room temperature for 30-45 minutes, the mixed material is transferred to a molybdenum-based alloy mold, and pressed into a film at 30-40 standard atmospheres as a composite positive electrode sheet. Among them, the ternary positive electrode material used is LiNi X CoyMnzO2, wherein 0≤x<1, 0≤y<1, 0≤z<1, and x+y+z=1; the conductive agent used is one or more of Ketjen black, carbon black, carbon nanotubes, carbon nanofibers or conductive graphite.

[0045] In actual application, the preparation method of the all-solid-state lithium battery is as follows: under 30-40 standard atmospheric pressures, the above-mentioned composite positive electrode sheet is pressed on one side of the second composite solid electrolyte layer in the high-pressure resistant composite solid electrolyte, and the lithium metal sheet is pressed on the first composite solid electrolyte layer in the high-pressure resistant composite solid electrolyte under 30-40 standard atmospheric pressures to form a button-type all-solid-state lithium battery.

[0046] Example 1

[0047] The porous nano-alumina substrate was immersed in 86°C deionized water for 2 hours, then immersed in a hydrochloric acid solution with a concentration of 0.7M / L, and then immersed in a toluene solution containing 3-aminopropyltriethoxysilane for 2 hours. After the end, it was rinsed with anhydrous ethanol 4 times to obtain an amino-modified porous nano-oxide substrate; tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid were dissolved in ethylene dioxide in a mass ratio of 15:8:112, and ultrasonically dispersed for 18 minutes to obtain a light yellow transparent solution. The obtained light yellow transparent solution was placed in a polytetrafluoroethylene-lined in a high-pressure reactor; dissolving terephthalic acid in ethylene dioxide (mass fraction of 11%) to obtain a mixed solution, soaking the amino-modified porous nano-oxide substrate obtained above in the mixed solution at 158°C for 1 hour, taking it out after the end, vertically placing it in a high-pressure reactor, and heating it at 140°C for 75 hours to obtain a COFs matrix with uniform pore size, wherein the thickness of the COFs matrix is ​​125 μm, wherein the COFs microstructure and pore size can be controlled by the amino-modified porous nano-oxide substrate, and the environmental water and oxygen content during the preparation process does not exceed 10 ppm.

[0048] Polyethylene oxide, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 77:4:22:3, and ultrasonically dispersed for 1.5 hours to obtain a polymer electrolyte A solution; the polymer electrolyte A solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 24°C to obtain a first composite solid electrolyte layer; polymethyl methacrylate, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 78:4:20:3, and ultrasonically dispersed for 1.5 hours to obtain a polymer electrolyte B solution; the polymer electrolyte B solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 24°C to obtain a second composite solid electrolyte layer.

[0049] Finally, the first composite solid electrolyte layer and the second composite solid electrolyte layer obtained above were composited by hot pressing at 200° C. under 40 standard atmospheres in an argon atmosphere to obtain a high-pressure resistant composite solid electrolyte.

[0050] All-solid-state lithium battery preparation

[0051] Lithium aluminum titanium phosphate, LiNi 0.5 Co 0.2 Mn 0.3 O2 positive electrode material and Ketjen black are added to a high-energy vibration ball mill in a mass ratio of 1.2:1.2:0.07, and ball-milled at room temperature for 36 minutes. The mixed material is transferred to a molybdenum-based alloy mold and pressed into a film as a composite positive electrode sheet at 33 standard atmospheres. At 36 standard atmospheres, the above-obtained composite positive electrode sheet is pressed on one side of the second composite solid electrolyte layer in the high-pressure resistant composite solid electrolyte, and the lithium metal sheet is pressed on the first composite solid electrolyte layer in the high-pressure resistant composite solid electrolyte at 36 standard atmospheres to form a button-type all-solid-state lithium battery.

[0052] Example 2

[0053] The porous nano-alumina substrate was immersed in 90°C deionized water for 1 hour, then immersed in a hydrochloric acid solution with a concentration of 0.5M / L, and then immersed in a toluene solution containing 3-aminopropyltriethoxysilane for 3 hours. After the end, it was rinsed with anhydrous ethanol 5 times to obtain an amino-modified porous nano-alumina substrate; tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid were dissolved in ethylene dioxide at a mass ratio of 20:5; 50, and ultrasonically dispersed for 10 minutes to obtain a light yellow transparent solution. The obtained light yellow transparent solution was placed in a high-pressure water filter lined with polytetrafluoroethylene. in a high-pressure reactor; dissolving terephthalic acid in ethylene dioxide (mass fraction of 20%) to obtain a mixed solution, soaking the amino-modified porous nano-oxide substrate obtained above in the mixed solution at 170°C for 0.5h, taking it out after the end, vertically placing it in a high-pressure reactor, and heating it at 200°C for 80h to obtain a COFs matrix with uniform pore size, wherein the thickness of the COFs matrix is ​​200μm, wherein the COFs microstructure and pore size can be controlled by the amino-modified porous nano-oxide substrate, and the environmental water and oxygen content during the preparation process does not exceed 10ppm.

[0054] Polyethylene oxide, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 70:6:10:5 and ultrasonically dispersed for 2 hours to obtain a polymer electrolyte A solution; the polymer electrolyte A solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 20°C to obtain a first composite solid electrolyte layer; polymethyl methacrylate, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 95:2:10:5 and ultrasonically dispersed for 1 hour to obtain a polymer electrolyte B solution; the polymer electrolyte B solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 30°C to obtain a second composite solid electrolyte layer.

[0055] Finally, the first composite solid electrolyte layer and the second composite solid electrolyte layer obtained above were hot-pressed and composited at 300° C. in an argon atmosphere at 30 standard atmospheres to obtain a high-pressure resistant composite solid electrolyte.

[0056] The conditions for preparing the all-solid-state lithium battery are the same as those in Example 1.

[0057] Example 3

[0058] The porous nano-alumina substrate was immersed in 80°C deionized water for 3 hours, then immersed in a hydrochloric acid solution with a concentration of 1.0M / L, and then immersed in a toluene solution containing 3-aminopropyltriethoxysilane for 1 hour. After the end, it was rinsed with anhydrous ethanol 3 times to obtain an amino-modified porous nano-alumina substrate; tetra-(4-anilino)-methane, terephthalic acid and acetic acid were dissolved in ethylene dioxide in a mass ratio of 10:15:200, and ultrasonically dispersed for 30 minutes to obtain a light yellow transparent solution. The obtained light yellow transparent solution was placed in a polytetrafluoroethylene liner. Terephthalic acid is dissolved in ethylene dioxide (mass fraction is 5%) to obtain a mixed solution, and the amino-modified porous nano-oxide substrate obtained above is immersed in the mixed solution at 150° C. for 2 hours. After the mixture is immersed, the substrate is taken out and vertically placed in a high-pressure reactor, and heated at 100° C. for 70 hours to obtain a COFs substrate with uniform pore size. The thickness of the COFs substrate is 30 μm, wherein the COFs microstructure and pore size can be controlled by the amino-modified porous nano-oxide substrate. During the preparation process, the water and oxygen contents in the environment do not exceed 10 ppm.

[0059] Polyethylene oxide, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 90:2:30:1 and ultrasonically dispersed for 1 hour to obtain a polymer electrolyte A solution; the polymer electrolyte A solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 30°C to obtain a first composite solid electrolyte layer; polymethyl methacrylate, bismuth trioxide, lithium bis(trifluoromethanesulfonyl)imide and polyvinylidene fluoride were dissolved in anhydrous acetonitrile in a mass ratio of 95:2:25:1 and ultrasonically dispersed for 2 hours to obtain a polymer electrolyte B solution; the polymer electrolyte B solution was cast on the COFs substrate obtained above, and the acetonitrile was vacuum evaporated at 20°C to obtain a second composite solid electrolyte layer; the first composite solid electrolyte layer obtained above and the second composite solid electrolyte layer obtained above were hot-pressed at 300°C in an argon atmosphere at 50 standard atmospheres to obtain a high-voltage resistant composite solid electrolyte.

[0060] The conditions for preparing the all-solid-state lithium battery are the same as those in Example 1.

[0061] Example 4

[0062] Compared with Example 1, the difference is that lithium aluminum titanium phosphate, LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material and carbon nanotubes were added to a high-energy vibrating ball mill at a mass ratio of 1.5:1.5:0.05 and milled at room temperature for 30 minutes. The mixed material was then transferred into a molybdenum-based alloy mold and pressed into a film at 40 standard atmospheres of pressure to form a composite positive electrode sheet. The resulting composite positive electrode sheet was then pressed onto one side of the second composite solid electrolyte layer in a high-pressure resistant composite solid electrolyte at 40 standard atmospheres of pressure. A lithium metal sheet was then pressed onto the first composite solid electrolyte layer in the high-pressure resistant composite solid electrolyte at 40 standard atmospheres of pressure to form a button-type all-solid-state lithium battery. All other conditions were the same as in Example 1.

[0063] Comparative Example 1

[0064] Compared with Example 1, the difference is that in Comparative Example 1, Bi2O3 is not added to the polymer electrolyte A and polymer electrolyte B components, and the other conditions are the same as those in Example 1.

[0065] Comparative Example 2

[0066] Compared with Example 1, the difference is that in Comparative Example 2, no COFs matrix is ​​provided in the first composite solid electrolyte layer and the second composite solid electrolyte layer, and the other conditions are the same as those in Example 1.

[0067] Comparative Example 3

[0068] Compared with Example 1, the difference is that in Comparative Example 3, the main component polyethylene oxide is not added to the polymer electrolyte A, and the other conditions are the same as those in Example 1.

[0069] Comparative Example 4

[0070] Compared with Example 1, the difference is that in Comparative Example 4, the main component polymethyl methacrylate is not added to the polymer electrolyte B, and the other conditions are the same as those in Example 1.

[0071] Comparative Example 5

[0072] Compared with Example 1, the difference is that in Comparative Example 5, the first composite solid electrolyte layer and the second composite solid electrolyte layer are composed of only pure polyethylene oxide, and the other conditions are the same as those in Example 1;

[0073] Comparative Example 6

[0074] Compared with Example 1, the difference is that in Comparative Example 6, the first composite solid electrolyte layer and the second composite solid electrolyte layer are composed of only pure polymethyl methacrylate, and the other conditions are the same as those in Example 1.

[0075] Comparative Example 7

[0076] Compared with Example 1, the difference is that in Comparative Example 7, the second composite solid electrolyte layer is in contact with metallic lithium, while the first composite solid electrolyte layer is in contact with the ternary positive electrode. The other conditions are the same as in Example 1.

[0077] Comparative Example 8

[0078] Compared with Example 1, the difference is that the thickness of the COFs substrate in Comparative Example 8 is 300 μm, and the other conditions are the same as those in Example 1.

[0079] Battery performance test

[0080] The all-solid-state lithium batteries prepared in Examples 1-4 and Comparative Examples 1-8 were tested for internal resistance using AC impedance spectroscopy at room temperature in a frequency range of 1-10 6 HZ; at the same time, the cycle life was tested at 0.1C rate in the range of 2.7-4.1V at 65°C. As shown in Table 1, the performance test results of the high-voltage composite solid electrolytes prepared in Examples 1-4 and the solid electrolytes prepared in Comparative Examples 1-8.

[0081] Table 1

[0082] Group Internal resistance (Ω) Cycle life (times) Example 1 37.6 423 Example 2 38.1 414 Example 3 37.9 417 Example 4 38.3 410 Comparative Example 1 45.2 358 Comparative Example 2 52.7 253 Comparative Example 3 43.8 384 Comparative Example 4 46.6 335 Comparative Example 5 89.1 196 Comparative Example 6 87.2 208 Comparative Example 7 49.4 359 Comparative Example 8 47.6 236

[0083] As shown in Table 1, the high-voltage composite solid electrolytes prepared in Examples 1-4 have significantly lower AC impedance and longer battery cycle life at room temperature than those in Comparative Examples 1-8. This indicates that the high-voltage composite solid electrolytes prepared in this application can effectively improve the internal resistance and cycle life of all-solid-state batteries.

[0084] Combining the data of Example 1 and Comparative Examples 1-8, it can be seen that the high-pressure resistant composite solid electrolyte of the present application, especially combining Example 1 and Comparative Example 2, can realize large-capacity lithium storage and fast ion transport channels by utilizing covalent organic framework COFs with high specific surface area, adjustable pore size, structural predictability and stability. COFs can improve Li + affinity and periodic pores, which is beneficial to Li + The uniform distribution of flux is conducive to the smooth transmission and deposition of Li. Therefore, by setting the first composite solid electrolyte layer and the second composite solid electrolyte layer to include a COFs matrix and compounding the polymer electrolyte in the COFs matrix, the interface resistance between the composite solid electrolyte layer and the electrode can be significantly improved, and the lithium ion transmission rate can be increased.

[0085] At the same time, considering the high hardness of the COFs matrix layer and the large interface resistance after contact with the polymer electrolyte, the Bi2O3 material has extremely high ionic conductivity at low temperatures and can be used as a negative electrode material for lithium ion batteries. In particular, combined with the data of Example 1 and Comparative Example 1, it can be seen that by adding Bi2O3 in the synthesis of the polymer electrolyte, the problem of large interface resistance after contact with the polymer electrolyte due to the high hardness of the COFs matrix layer can be effectively avoided, thereby further improving the lithium ion transmission rate; and considering that Bi2O3 is relatively poor in stability and is easily reduced in practical applications, thereby reducing its ionic conductivity, by adding Bi2O3 in the COFs matrix layer, the lithium ion transmission rate can be further improved. By adding an appropriate amount of acetic acid to the components of the Fs layer and adjusting the pH of the system, the redox adsorption characteristics of the COFs material are improved. During the actual charge and discharge process, protons will be preferentially adsorbed, reducing the reduction reaction of the Bi2O3 material, improving the stability of Bi2O3, and thus improving the conductivity of the COFs matrix; at the same time, preparing porous COFs on an amino-modified oxide porous substrate can improve the synthesis efficiency of COFs and produce COFs with uniform and controllable pore size, thereby improving the mechanical strength and lithium ion transport performance of the electrolyte, and contributing to the high stability of the Bi2O3 material, effectively reducing the interface resistance, and improving the battery internal resistance and cycle life.

[0086] In addition, in combination with Example 1 and Comparative Example 7, it can be seen that the main component of polymer electrolyte A is polyethylene oxide, so that the first composite solid electrolyte layer obtained has anti-reduction properties and is in contact with the lithium negative electrode, and the main component of polymer electrolyte B is polymethyl methacrylate, so that the second composite solid electrolyte layer obtained has oxidation resistance and is in contact with the high-voltage ternary positive electrode material, thereby improving the electrochemical stability and lithium ion transmission performance of the solid electrolyte. It can be seen that the high-voltage resistant composite solid electrolyte of the present application, through the synergistic effect between different components, not only broadens the electrochemical window of the polymer solid electrolyte, reduces the interface resistance, improves the positive and negative electrode interface stability and lithium ion transmission performance, but also can be applied to both lithium metal negative electrodes and high-voltage ternary positive electrodes, thereby improving the cycle performance of the battery.

[0087] In conjunction with Example 1 and Comparative Example 8, the thickness of the COF substrate in this application needs to be maintained within an optimal range. Specifically, by limiting the thickness of the COF substrate, it is possible to ensure that the COF substrate has a rich number of pores, achieving large-capacity lithium storage and fast ion transport channels while maintaining a simple internal structure and preventing impurities in the electrolyte.

[0088] In summary, the high-voltage resistant composite solid electrolyte of the present application, by utilizing the synergistic effect between different components, broadens the electrochemical window of the polymer solid electrolyte, has a stability of up to 4.1V, reduces the interface resistance, improves the positive and negative electrode interface stability and lithium ion transmission performance, and can be applied to both lithium metal negative electrodes and high-voltage ternary positive electrodes, thereby improving the battery's cycle performance and providing an important technical reference for improving the energy density and cycle life of solid batteries.

[0089] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high-voltage composite solid electrolyte, characterized in that: It is formed by hot pressing a first composite solid electrolyte layer and a second composite solid electrolyte layer; wherein, the first composite solid electrolyte layer includes a COFs matrix and a polymer electrolyte A loaded on the surface of the COFs matrix, the polymer electrolyte A includes polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride, and the mass ratio of polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride is 70-90:2-6:10-30:1-5; the second composite solid electrolyte layer includes a COFs matrix and a polymer electrolyte B loaded on the surface of the COFs matrix; the polymer electrolyte B includes polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride, and the mass ratio of polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride is 75-95:2-5:10-25:1-5.

2. The high-voltage composite solid electrolyte according to claim 1, characterized in that: The COFs matrix includes an amino-modified porous nano-oxide substrate and a COFs layer supported on the amino-modified porous nano-oxide substrate. The COFs layer includes tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid. The mass ratio of the tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid is 10-20:5-15:50-200.

3. The high-voltage composite solid electrolyte according to claim 1, characterized in that The thickness of the COFs matrix is ​​30-200 μm.

4. A method for preparing a high-voltage resistant composite solid electrolyte according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparation of COFs matrix: a. Soak the porous nano-oxide substrate in deionized water, then in a hydrochloric acid solution, and then in a toluene solution containing 3-aminopropyltriethoxysilane. After completion, wash with alcohol to obtain an amino-modified porous nano-oxide substrate; b. Dissolve tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid in ethylene dioxide, ultrasonically disperse to obtain a light yellow transparent solution, and place the obtained light yellow transparent solution in a high-pressure reactor; dissolve terephthalic acid in ethylene dioxide to obtain a mixed solution, soak the amino-modified porous nano-oxide substrate obtained in step a in the mixed solution, take it out after completion, vertically place it in a high-pressure reactor, and heat it to obtain a COFs matrix; S2. Preparation of the first composite solid electrolyte layer: dissolving polyethylene oxide, bismuth trioxide, lithium salt, and polyvinylidene fluoride in anhydrous acetonitrile, and ultrasonically dispersing the mixture to obtain a polymer electrolyte A solution; casting the polymer electrolyte A solution onto the COFs substrate obtained in step S1, and vacuum drying the mixture to obtain the first composite solid electrolyte layer; S3. Preparation of the second composite solid electrolyte layer: dissolving polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride in anhydrous acetonitrile and ultrasonically dispersing to obtain a polymer electrolyte B solution; casting the polymer electrolyte B solution on the COFs substrate obtained in step S1 and vacuum drying to obtain a second composite solid electrolyte layer; S4. The first composite solid electrolyte layer obtained in step S2 and the second composite solid electrolyte layer obtained in step S3 are composited by hot pressing in an inert atmosphere to obtain a high-pressure resistant composite solid electrolyte.

5. The method for preparing a high-voltage resistant composite solid electrolyte according to claim 4, wherein: In step a, the porous nano-oxide substrate is any one of a porous nano-aluminum oxide substrate, a porous nano-molybdenum oxide substrate, a porous nano-silicon oxide substrate, a porous nano-copper oxide substrate, a porous nano-indium oxide substrate, a porous nano-silver oxide substrate, and a porous nano-titanium oxide substrate; the deionized water temperature is 80-90° C., the immersion time in deionized water is 1-3 hours, the concentration of the hydrochloric acid solution is 0.5-1.0 M / L, the immersion time in a toluene solution containing 3-aminopropyltriethoxysilane is 1-3 hours, and the substrate is rinsed with anhydrous ethanol 3-5 times.

6. The method for preparing a high-voltage resistant composite solid electrolyte according to claim 4, wherein: In step b, the mass ratio of tetrakis-(4-anilino)-methane, terephthalic acid and acetic acid is 10-20:5-15:50-200, ultrasonic dispersion is performed for 10-30 minutes, the inner lining of the high-pressure reactor is polytetrafluoroethylene, the immersion temperature is 150-170°C, the immersion time is 0.5-2 hours, the heating temperature is 100-200°C, and the heating time is 70-80 hours.

7. The method for preparing a high-voltage resistant composite solid electrolyte according to claim 4, wherein: In step S2, the mass ratio of polyethylene oxide, bismuth trioxide, lithium salt and polyvinylidene fluoride is 70-90:2-6:10-30:1-5, ultrasonic dispersion is performed for 1-2 hours, and the vacuum drying temperature is 20-30°C; in step S3, the mass ratio of polymethyl methacrylate, bismuth trioxide, lithium salt and polyvinylidene fluoride is 75-95:2-5:10-25:1-5, ultrasonic dispersion is performed for 1-2 hours, and the vacuum drying temperature is 20-30°C.

8. The method for preparing a high-voltage resistant composite solid electrolyte according to claim 4, wherein: In step S4, the inert atmosphere is an argon atmosphere, the hot pressing environment pressure is 30-50 standard atmospheres, and the hot pressing temperature is 100-300°C.

9. An all-solid-state lithium battery, characterized in that: It comprises the high-voltage resistant composite solid electrolyte according to any one of claims 1 to 3 or the high-voltage resistant composite solid electrolyte prepared by the method according to any one of claims 4 to 8, a composite positive electrode sheet and a negative electrode sheet, wherein the high-voltage resistant composite solid electrolyte is located between the composite positive electrode sheet and the negative electrode sheet.

10. The all-solid-state lithium battery according to claim 9, characterized in that: The composite positive electrode sheet comprises lithium titanium aluminum phosphate, a ternary positive electrode material and a conductive agent, and the mass ratio of the lithium titanium aluminum phosphate, the ternary positive electrode material and the conductive agent is 1-1.5:1-1.5:0.05-0.1.