Multifunctional composite diaphragm, preparation method thereof and application of multifunctional composite diaphragm in lithium-sulfur battery
The multifunctional composite separator prepared by electrospinning and structural engineering solves the problem of shuttle effect caused by pores in lithium-sulfur batteries, achieves efficient self-discharge inhibition and polysulfide catalysis, and improves the stability and electrochemical performance of the battery.
Patent Information
- Application Number
- CN202510496351.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-07-08
AI Technical Summary
The existing polyolefin separators have problems with the reduction of lithium-sulfur battery circulation performance and battery capacity due to the shuttle effect caused by their inherent pores.
Multifunctional composite separators are prepared by electrospinning combined with structural engineering, and self-discharge inhibitors and transition metal compound catalysts are used to form fiber mesh crosslinking structures, ammonia graft modification, and are supported in nanofibers or three-dimensional pore structures, inhibiting the shuttle between polysulfides and catalyzing the conversion of polysulfides in lithium-sulfur batteries.
Effectively inhibit polysulfide shuttle, improve the anti-self-discharge performance of the separator, enhance the stability and electrochemical performance of the battery, improve the utilization rate of active substances, reduce interface resistance, and achieve efficient battery performance.
Smart Images
Figure CN120280653A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery separator material preparation, and particularly relates to a multifunctional composite separator, a preparation method thereof, and an application thereof in a lithium-sulfur battery. Background Art
[0002] The lithium-sulfur battery is a new type of secondary energy storage device with a theoretical energy density (2600 Wh / kg) 2-5 times that of a lithium-ion battery. However, the commercialization of high-performance lithium-sulfur batteries has been severely hindered by rapid capacity decay caused by polysulfide shuttling and self-discharge, as well as low lifespan due to uncontrolled growth of lithium dendrites. The separator plays a key role in isolating the sulfur cathode and lithium anode while promoting lithium-ion and material transport and preventing internal short circuits.
[0003] Currently, although commercial polyolefin separators provide necessary lithium-ion transport channels through a micro-nano pore structure, they have serious limitations. Their inherent pores allow soluble polysulfides to migrate freely, leading to the shuttle effect, and reaching the surface of the lithium anode where reduction reactions occur. The polysulfides are reduced to insoluble Li2S2 or Li2S and deposited on the surface of the lithium anode, forming a passivation layer, increasing the internal resistance of the battery, and affecting the cycle performance of the battery. Secondly, these side reactions consume active substances, resulting in irreversible loss of sulfur at the cathode, thereby reducing the capacity of the battery. In addition, the lithium anode itself is prone to form dendrites during cycling, and the presence of polysulfides may exacerbate this problem, leading to battery short circuit or even thermal runaway. Functional separator modification is a promising solution to address these challenges. Summary of the Invention
[0004] Aiming at the deficiencies in the prior art, the present invention provides a multifunctional composite separator, a preparation method thereof, and an application thereof in a lithium-sulfur battery, which solves the problems of reduced battery cycle performance and battery capacity caused by the shuttle effect due to the inherent pores of existing polyolefin separators.
[0005] The present invention is achieved through the following technical solutions:
[0006] A preparation method of a multifunctional composite separator includes the following steps:
[0007] S1: Take a self-discharge inhibitor and polyacrylonitrile, dissolve them in N,N-dimethylformamide, perform electrospinning, and vacuum dry to obtain a negative electrode self-discharge inhibition layer film;
[0008] S2: Use the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, and load a transition metal compound catalyst through structural engineering to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer;
[0009] S3: Dissolve the grafting agent in a solution, and stir and reflux the double-layer composite separator obtained in step S2 in the grafting agent solution at 120 - 160 °C for ammoniation grafting to obtain a multifunctional composite separator.
[0010] Further, in step S1, the self-discharge inhibitor is any one or more of graphene oxide, reduced graphene oxide, graphene quantum dots, carboxylated carbon nanotubes, polyethyleneimine, silk fibroin, chitosan, cellulose, hyaluronic acid methacrylate, and graphdiyne.
[0011] Further, in step S1, the mass ratio of the self-discharge inhibitor to polyacrylonitrile is (1:1) - (1:10).
[0012] Further, in step S2, the transition metal compound catalyst is any one or more of metal oxides, metal sulfides, metal phosphides, metal selenides, and metal tellurides.
[0013] Further, the transition metal in the transition metal compound catalyst is any one or more of cobalt, zinc, nickel, manganese, iron, molybdenum, chromium, and copper.
[0014] Further, in step S2, the mass ratio of the self-discharge inhibitor to the transition metal compound catalyst is (1:1) - (1:10).
[0015] Further, in step S2, the structure engineering is any one of layer-by-layer electrospinning, thermal coating, atomic layer deposition, thermal spraying, chemical vapor deposition, magnetron sputtering, spin coating, and 3D printing.
[0016] Further, in step S3, the grafting agent is any one or more of ethylenediamine, aminobenzene, polyethyleneimine, chitosan, and alanine, the solution is any one or more of ethylene glycol, ethanol, and methanol, and the concentration of the grafting agent solution is 5 - 20 g / L.
[0017] A multifunctional composite separator is prepared by the above method. The multifunctional composite separator has a fiber network cross-linked structure. The self-discharge inhibitor and the transition metal compound catalyst are loaded or filled in the network cross-linked fibers, and the fiber surface is modified by amino grafting.
[0018] A lithium-sulfur battery includes a multifunctional composite separator. When the lithium-sulfur battery is cycled 1000 times at a 0.5C rate, the average capacity attenuation rate per cycle is less than 0.03%, and the self-discharge capacity attenuation loss rate after standing for 24 h is 2.1%.
[0019] Compared with the prior art, the present invention has the following beneficial technical effects:
[0020] The present invention can effectively improve the ability of the separator to inhibit the shuttle of polysulfides and enhance the self-discharge resistance performance of the separator through a self-discharge inhibitor; the metal compound of the transition metal compound catalyst is conducive to catalyzing the conversion of polysulfides in the lithium-sulfur battery, effectively improving the conversion efficiency between sulfur and polysulfides, inhibiting the shuttle of polysulfides, and increasing the utilization rate of the active substance sulfur and the electrochemical performance of the battery. Through the structural engineering method, the porosity of the functional separator and the electrolyte absorption rate can be effectively balanced, the interface between the electrode and the separator can be more effectively regulated and optimized. At the same time, ammoniation grafting is beneficial to reducing the interfacial resistance of the contact between the separator and the negative electrode and forming a stable solid electrolyte film, thereby improving the stability of the battery. The multifunctional composite separator prepared by the present invention through electrospinning combined with structural engineering solves the problem of low porosity caused by the blockage of the pores of the separator, while retaining the ion and substance transport channels, which is simple, efficient and highly independent, and can be mass-produced.
[0021] In the present invention, the transition metal is conducive to the synergistic exertion of the catalytic effects of various transition metal compound catalysts.
[0022] The grafting agent of the ammoniation grafting reaction of the present invention can effectively achieve the full and effective grafting of the surface functional groups of the polyacrylonitrile nanofibers, thereby increasing the content of nitrogen-containing and oxygen-containing functional groups on the surface of the separator to improve the inhibition of polysulfide shuttle and the stability of the negative electrode interface.
[0023] The mass ratio of the self-discharge inhibitor to the transition metal compound catalyst in the present invention is (1:1) to (1:10). At this ratio, the self-discharge inhibitor and the transition metal compound catalyst can be evenly distributed inside or on the surface of the matrix, forming a rich three-dimensional structure, providing more reaction active sites, and realizing the maximization of both the self-discharge inhibition effect and the polysulfide adsorption-catalysis function.
[0024] The multifunctional composite separator provided by the present invention has a fiber network cross-linked structure. The fiber network cross-linked structure is conducive to the loading of the self-discharge inhibitor and the transition metal compound catalyst, further conducive to the distribution of active sites, increasing the number of electrochemically reactive sites, and providing more electron and ion transport channels, which is beneficial to the mass transfer of the electrolyte and improves the electrochemical performance. The fiber network cross-linked structure loaded with the self-discharge inhibitor can react well with polysulfide anions to achieve the self-discharge resistance effect; while the transition metal compound catalyst can effectively improve the chemical adsorption and catalytic conversion of polysulfides, and synergistically with ammoniation grafting to alleviate the irregular growth of lithium dendrites and improve the cycle stability of the battery, having excellent electrochemical performance. Description of the Drawings
[0025] Figure 1 SEM image and elemental surface distribution map of the multifunctional composite separator provided for Example 1;
[0026] Figure 2Digital photo of the flexibility test of the multifunctional composite separator provided for Example 2;
[0027] Figure 3 Self-discharge performance test curve of the multifunctional composite separator provided for Example 3;
[0028] Figure 4 Cycling performance curve of the multifunctional composite separator provided for Example 4. Detailed implementation manners
[0029] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art for the present invention. In case of conflict, the definitions in this specification shall prevail.
[0030] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.
[0031] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges shall be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).
[0032] In this article, unless otherwise specified, terms such as "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".
[0033] The present invention provides a multifunctional composite separator, a preparation method thereof, and an application in a lithium-sulfur battery.
[0034] A preparation method of a multifunctional composite separator includes the following steps:
[0035] S1: Take a self-discharge inhibitor and polyacrylonitrile and dissolve them in N,N-dimethylformamide, spin at 15 kV for 12 hours, and vacuum dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0036] Among them, the self-discharge inhibitor is any one or more of graphene oxide, reduced graphene oxide, graphene quantum dots, carboxylated carbon nanotubes, polyethyleneimine, silk fibroin, chitosan, cellulose, hyaluronic acid methacrylate, and graphdiyne. The mass ratio of the self-discharge inhibitor to polyacrylonitrile is 1:1 to 1:10, and the concentration of polyacrylonitrile in the N,N-dimethylformamide solution is 100 to 300 g / L.
[0037] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, a double-layer composite separator with a composite positive electrode adsorption-catalytic layer is obtained by loading a transition metal compound catalyst through structural engineering.
[0038] Among them, the transition metal compound catalyst is any one or more of metal oxides, metal sulfides, metal phosphides, metal selenides, and metal tellurides; the transition metal is any one or more of cobalt, zinc, nickel, manganese, iron, molybdenum, chromium, or copper; the structural engineering is one of layer-by-layer electrospinning, thermal coating, atomic layer deposition, thermal spraying, chemical vapor deposition, magnetron sputtering, spin coating, 3D printing; the mass ratio of the self-discharge inhibitor to the transition metal compound catalyst is (1:1) to (1:10), and the thickness of the positive electrode adsorption-catalytic layer is 30 to 120 μm.
[0039] S3: The double-layer composite separator obtained in step S2 is subjected to ammoniation grafting by stirring and refluxing in a solution containing a grafting agent with a concentration of 5 to 20 g / L at 120 to 160 °C for 8 hours. After the reaction ends and the temperature drops to room temperature, it is washed three times with deionized water and ethanol each, and vacuum dried at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0040] Among them, the grafting agent is any one or more of ethylenediamine, aminobenzene, polyethyleneimine, deacetylated chitin, and alanine; the solution is any one or more of ethylene glycol, ethanol, and methanol.
[0041] The multifunctional composite separator prepared by the above method has a fiber network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of less than 0.03% per cycle after 1000 cycles at a 0.5C rate, and the self-discharge capacity decay loss rate after standing for 24 h is 2.1%.
[0042] The present invention provides a new method for preparing a multifunctional composite separator by electrospinning combined with structural engineering. A surface ammoniated grafted multifunctional composite separator with a self-discharge inhibitor and a transition metal compound catalyst uniformly loaded in nanofibers or a three-dimensional pore structure is prepared by electrospinning, structural engineering and ammoniation grafting reaction. The present invention prepares a high-performance multifunctional separator for lithium-sulfur batteries by a simpler, more efficient and highly independent method, which can be mass-produced. The prepared multifunctional separator has excellent electrolyte affinity and mechanical / thermal stability, and the battery containing the multifunctional composite separator also has excellent electrochemical performance. The method of the present invention is highly efficient and controllable, and can be used for the mass production and large-scale application of multifunctional composite separators.
[0043] In the following examples, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following examples, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturers. In the following examples, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.
[0044] The technical solutions adopted to achieve the object of the present invention are as follows:
[0045] Weigh a self-discharge inhibitor and polyacrylonitrile (PAN) and dissolve them in N,N-dimethylformamide (DMF) to prepare a spinning solution. Electrospin to obtain a negative electrode self-discharge inhibition layer film. Then, using the negative electrode self-discharge inhibition layer film as a base film, load a transition metal compound catalyst through structural engineering to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, and perform ammoniation grafting on it to obtain a multifunctional composite separator; use it in a lithium-sulfur battery and test its electrochemical performance.
[0046] Example 1
[0047] A method for preparing a multifunctional composite separator includes the following steps:
[0048] S1: Weigh 0.1 g of graphene oxide and 1 g of polyacrylonitrile and uniformly disperse them in 10 mL of N,N-dimethylformamide, stir at 40 °C for 12 h to obtain a spinning solution, electrospin for 12 hours at 15 kV, and vacuum dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0049] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as a base film, load 0.25 g of cobalt tetroxide by layer-by-layer electrospinning to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, where the thickness of the positive electrode adsorption-catalysis layer is 65 μm;
[0050] S3: The double-layer composite separator obtained in step S2 is subjected to ammoniation grafting by stirring and refluxing in a 50 mL ethylene glycol solution containing 0.5 g of polyethyleneimine at 140 °C for 8 hours. After the reaction is completed and cooled to room temperature, it is washed three times with deionized water and ethanol respectively, and then dried in vacuum at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0051] As Figure 1 shown, it can be seen that the obtained multifunctional composite separator presents a fiber network cross-linked structure, and according to the elemental surface distribution map, it can be known that the prepared separator is a double-layer structure and the carbon, nitrogen, oxygen and cobalt elements are evenly distributed inside and on the surface of the fibers. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.026% per cycle after 1000 cycles at a rate of 0.5C, and the self-discharge capacity decay loss rate after standing for 24 h is 2.5%.
[0052] Example 2
[0053] A preparation method of a multifunctional composite separator includes the following steps:
[0054] S1: Weigh 0.2 g of hyaluronic acid methacrylate and 1.6 g of polyacrylonitrile and disperse them evenly in 16 mL of N,N-dimethylformamide. Stir at 40 °C for 12 h to obtain a spinning solution, spin for 12 hours at 15 kV, and dry the spun film in vacuum at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0055] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, load 0.2 g of molybdenum disulfide and copper sulfide by 3D printing to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, where the thickness of the positive electrode adsorption-catalysis layer is 70 μm;
[0056] S3: The double-layer composite separator obtained in step S2 is subjected to ammoniation grafting by stirring and refluxing in a 50 mL mixed solution of ethylene glycol and methanol containing 1 g of ethylenediamine at 150 °C for 8 hours. After the reaction is completed and cooled to room temperature, it is washed three times with deionized water and ethanol respectively, and then dried in vacuum at 80 °C for 12 hours to obtain the multifunctional composite separator. It can be Figure 2 seen that the prepared multifunctional composite separator (Figure b) has better flexibility compared with the commercial polyolefin separator (Figure a), which is beneficial to adapting to the volume strain of the reaction substances in the battery and improving the safety and stability of the battery.
[0057] The multifunctional composite separator prepared by the above method is a fiber network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.024% per cycle after 1000 cycles at a rate of 0.5C, and the self-discharge capacity decay loss rate after standing for 24 h is 2.2%.
[0058] Example 3
[0059] A preparation method of a multifunctional composite separator includes the following steps:
[0060] S1: Weigh 0.3 g of graphene quantum dots and 1.5 g of polyacrylonitrile and uniformly disperse them in 10 mL of N,N-dimethylformamide. Stir for 12 h at 40 °C to obtain a spinning solution. Spin for 12 hours at 15 kV, and vacuum dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0061] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as a base film, load 0.9 g of nickel telluride and iron diselenide through atomic layer deposition to obtain a double-layer composite separator with a composite positive electrode adsorption-catalytic layer, where the thickness of the positive electrode adsorption-catalytic layer is 30 μm;
[0062] S3: Subject the double-layer composite separator obtained in step S2 to ammoniation grafting by stirring and refluxing in a 60 mL ethanol solution containing 0.3 g of chitosan for 8 hours at 130 °C. After the reaction ends and the temperature drops to room temperature, wash three times with deionized water and ethanol respectively, and vacuum dry at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0063] The multifunctional composite separator prepared by the above method has a fiber network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.022% per cycle at a 0.5C rate after 1000 cycles. From Figure 3 (a), it can be seen that the capacity decay rate of the battery without rest after the second cycle is 8.1% after the first cycle. After standing for 24 h, from Figure 3 (b), it can be seen that the capacity decay rate between the second cycle and the first cycle is 10.5%. Therefore, the self-discharge capacity decay loss rate of the lithium-sulfur battery containing this multifunctional composite separator after standing for 24 h is 2.4%. This value is much smaller than the self-discharge capacity loss rate of commercial polyolefin separators, and the battery performance is much better than the separators and batteries of existing research and inventions, which also reflects the advantage of the multifunctional composite separator prepared by the present invention in suppressing self-discharge.
[0064] Example 4
[0065] A preparation method of a multifunctional composite separator includes the following steps:
[0066] S1: Weigh 0.12 g of graphdiyne and 1.2 g of polyacrylonitrile and uniformly disperse them in 10 mL of N,N-dimethylformamide. Stir for 12 h at 40 °C to obtain a spinning solution. Spin for 12 hours at 15 kV, and vacuum dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0067] S2: Using the negative electrode self-discharge suppression layer film prepared in step S1 as the base film, 0.96g of cobalt phosphide and chromium trioxide are loaded by magnetron sputtering to obtain a double-layer composite diaphragm of a composite positive electrode adsorption-catalytic layer, wherein the thickness of the positive electrode adsorption-catalytic layer is 120μm;
[0068] S3: The double-layer composite diaphragm obtained in step S2 is subjected to ammonia grafting in a 40 mL methanol solution containing 0.2 g alanine, and stirred under reflux at 120°C for 8 hours. After the reaction is completed and the temperature is cooled to room temperature, it is washed with deionized water and ethanol three times each, and vacuum dried at 80°C for 12 hours to obtain the multifunctional composite diaphragm.
[0069] The multifunctional composite separator prepared by the above method is a fiber mesh cross-linked structure. The self-discharge capacity attenuation loss rate of the lithium-sulfur battery containing the multifunctional composite separator after standing for 24 hours is 2.8%. Figure 4 It can be seen that the lithium-sulfur battery containing the multifunctional composite membrane has an average capacity decay rate of 0.023% per cycle after 1000 cycles at a rate of 0.5C, which is much better than the commercial polyolefin membrane and the membranes and batteries prepared by existing reports and other inventions, demonstrating the great advantages of the present invention in improving the electrochemical stability of lithium-sulfur batteries, and also demonstrating the advancement and high originality of the present invention.
[0070] Example 5
[0071] A method for preparing a multifunctional composite diaphragm comprises the following steps:
[0072] S1: Weigh 0.2g chitosan and 1g polyacrylonitrile and evenly disperse them in 10mL N,N-dimethylformamide, stir at 40℃ for 12h to obtain a spinning solution, spin at 15kV for 12h, and dry the film obtained by spinning at 80℃ in vacuum to obtain a negative electrode self-discharge inhibition layer film;
[0073] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, 1.4 g of cobalt diselenide and zinc selenide are loaded by chemical vapor deposition to obtain a double-layer composite diaphragm of a composite positive electrode adsorption-catalytic layer, wherein the thickness of the positive electrode adsorption-catalytic layer is 60 μm;
[0074] S3: The double-layer composite diaphragm obtained in step S2 is subjected to ammonia grafting in a mixed solution of 50 mL of ethylene glycol and ethanol containing 1 g of aminobenzene, and stirred under reflux at 160°C for 8 hours. After the reaction is completed and the temperature is cooled to room temperature, it is washed with deionized water and ethanol three times each, and vacuum dried at 80°C for 12 hours to obtain the multifunctional composite diaphragm.
[0075] The multifunctional composite separator prepared by the above method is a fibrous network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.023% per cycle after 1000 cycles at a rate of 0.5C, and a self-discharge capacity decay loss rate of 2.1% after standing for 24 hours.
[0076] Example 6
[0077] A preparation method of a multifunctional composite separator includes the following steps:
[0078] S1: Weigh 0.1 g of silk fibroin and 1 g of polyacrylonitrile and uniformly disperse them in 10 mL of N,N-dimethylformamide, stir at 40 °C for 12 h to obtain a spinning solution, spin for 12 hours at 15 kV, and vacuum-dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0079] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, load 1 g of iron phosphide by magnetron sputtering to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, where the thickness of the positive electrode adsorption-catalysis layer is 40 μm;
[0080] S3: For the double-layer composite separator obtained in step S2, carry out ammoniation grafting by stirring and refluxing in a 20 mL ethylene glycol solution containing 0.2 g of chitosan for 8 hours at 150 °C. After the reaction ends and cools to room temperature, wash it three times with deionized water and ethanol respectively, and vacuum-dry at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0081] The multifunctional composite separator prepared by the above method is a fibrous network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.027% per cycle after 1000 cycles at a rate of 0.5C, and a self-discharge capacity decay loss rate of 2.3% after standing for 24 hours.
[0082] Example 7
[0083] A preparation method of a multifunctional composite separator includes the following steps:
[0084] S1: Weigh 3 g of cellulose and 3 g of polyacrylonitrile and uniformly disperse them in 10 mL of N,N-dimethylformamide, stir at 40 °C for 12 h to obtain a spinning solution, spin for 12 hours at 15 kV, and vacuum-dry the spun film at 80 °C to obtain a negative electrode self-discharge inhibition layer film;
[0085] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, load 3 g of manganese dioxide by thermal coating to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, where the thickness of the positive electrode adsorption-catalysis layer is 80 μm;
[0086] S3: The double-layer composite separator obtained in step S2 is subjected to ammoniation grafting by stirring and refluxing in a 10 mL mixed solution of ethylene glycol and ethanol containing 0.18 g of ethylenediamine and polyethyleneimine at 130 °C for 8 hours. After the reaction is completed and cooled to room temperature, it is washed three times with deionized water and ethanol respectively, and then dried in vacuum at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0087] The multifunctional composite separator prepared by the above method has a fiber network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.023% per cycle during 1000 cycles at a rate of 0.5C, and a self-discharge capacity decay loss rate of 2.2% after standing for 24 h.
[0088] Example 8
[0089] A preparation method of a multifunctional composite separator includes the following steps:
[0090] S1: Weigh 0.8 g of reduced graphene oxide, 2.4 g of silk fibroin and polyacrylonitrile, and disperse them evenly in 12 mL of N,N-dimethylformamide. Stir at 40 °C for 12 h to obtain a spinning solution, spin for 12 hours at 15 kV, and dry the spun film in vacuum at 80 °C to obtain a negative electrode self-discharge inhibition layer film.
[0091] S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, spin-coat and load 4 g of iron phosphide and cobalt oxide to obtain a double-layer composite separator with a composite positive electrode adsorption-catalysis layer, where the thickness of the positive electrode adsorption-catalysis layer is 90 μm.
[0092] S3: The double-layer composite separator obtained in step S2 is subjected to ammoniation grafting by stirring and refluxing in a 20 mL mixed solution of ethylene glycol and methanol containing 0.24 g of chitosan and alanine at 140 °C for 8 hours. After the reaction is completed and cooled to room temperature, it is washed three times with deionized water and ethanol respectively, and then dried in vacuum at 80 °C for 12 hours to obtain the multifunctional composite separator.
[0093] The multifunctional composite separator prepared by the above method has a fiber network cross-linked structure. The lithium-sulfur battery containing this multifunctional composite separator has an average capacity decay rate of 0.029% per cycle during 1000 cycles at a rate of 0.5C, and a self-discharge capacity decay loss rate of 2.8% after standing for 24 h.
[0094] The present invention provides a new method for preparing a multifunctional composite separator through electrospinning combined with structural engineering. An ammoniated grafted multifunctional composite separator with a self-discharge inhibitor and a transition metal compound catalyst uniformly loaded in nanofibers or a three-dimensional pore structure is prepared through electrospinning, structural engineering, and ammoniated grafting reaction. The present invention prepares a high-performance multifunctional separator for a lithium-sulfur battery by a simpler, more efficient, and more independent method, which can be mass-produced. The prepared multifunctional separator has excellent electrolyte affinity and mechanical / thermal stability, and a battery containing the multifunctional composite separator also has excellent electrochemical performance. The method of the present invention is highly efficient and controllable, and can be used for the mass production and large-scale application of the multifunctional composite separator.
[0095] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.
Claims
1. A preparation method of a multifunctional composite diaphragm, characterized in that, It includes the following steps: S1: Take a self-discharge inhibitor and polyacrylonitrile and dissolve them in N,N-dimethylformamide, electrospinning, and vacuum drying to obtain a negative electrode self-discharge inhibition layer film; S2: Using the negative electrode self-discharge inhibition layer film prepared in step S1 as the base film, load a transition metal compound catalyst through structural engineering to obtain a double-layer composite separator with a composite positive electrode adsorption-catalytic layer; S3: Take a grafting agent and dissolve it in a solution, and stir and reflux the double-layer composite separator obtained in step S2 in the grafting agent solution at 120-160 °C for ammoniation grafting to obtain a multifunctional composite separator.
2. The preparation method of a multifunctional composite diaphragm according to claim 1, wherein, In step S1, the self-discharge inhibitor is any one or more of graphene oxide, reduced graphene oxide, graphene quantum dots, carboxylated carbon nanotubes, polyethyleneimine, silk fibroin, chitosan, cellulose, hyaluronic acid methacrylate, graphdiyne.
3. The preparation method of a multifunctional composite diaphragm according to claim 1, wherein, In step S1, the mass ratio of the self-discharge inhibitor to polyacrylonitrile is (1:1) to (1:10).
4. The preparation method of a multifunctional composite diaphragm according to claim 1, characterized in that, In step S2, the transition metal compound catalyst is any one or more of metal oxides, metal sulfides, metal phosphides, metal selenides, metal tellurides.
5. The preparation method of a multifunctional composite diaphragm according to claim 4, characterized in that, The transition metal in the transition metal compound catalyst is any one or more of cobalt, zinc, nickel, manganese, iron, molybdenum, chromium or copper.
6. The preparation method of a multifunctional composite diaphragm according to claim 1, characterized in that, In step S2, the mass ratio of the self-discharge inhibitor to the transition metal compound catalyst is (1:1) to (1:10).
7. The preparation method of a multifunctional composite diaphragm according to claim 1, characterized in that In step S2, the structural engineering is any one of layer-by-layer electrospinning, thermal coating, atomic layer deposition, thermal spraying, chemical vapor deposition, magnetron sputtering, spin coating, 3D printing.
8. The preparation method of a multifunctional composite diaphragm according to claim 1, characterized in that, In step S3, the grafting agent is any one or more of ethylenediamine, aminobenzene, polyethyleneimine, chitosan, alanine, and the solution is any one or more of ethylene glycol, ethanol, methanol, and the concentration of the grafting agent solution is 5-20 g / L.
9. A multifunctional composite diaphragm, characterized in that, Prepared by the method according to any one of claims 1-8, the multifunctional composite separator is a fiber network cross-linked structure, and the self-discharge inhibitor and the transition metal compound catalyst are loaded or filled in the network cross-linked fibers, and the fiber surface is modified by amino grafting.
10. A lithium-sulfur battery, characterized in that, Containing the multifunctional composite separator according to claim 9, the lithium-sulfur battery has an average capacity decay rate of less than 0.03% per cycle after 1000 cycles at a rate of 0.5C, and the self-discharge capacity decay loss rate after standing for 24 h is 2.1%.