High-specific-volume lithium-sulfur battery
By using a combination of cesium iodide and molybdenum disulfide in lithium-sulfur batteries, the problems of cathode kinetic lag and catalyst deactivation were solved, achieving lithium-sulfur battery performance with high specific capacity and long cycle life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2026-03-27
AI Technical Summary
In lithium-sulfur batteries, the cathode kinetic hysteresis problem leads to a decrease in specific capacity and an increase in polarization. Furthermore, Lewis acid catalysts are prone to deactivation during cycling, which affects battery performance.
An electrolyte and membrane combination containing cesium iodide as an electrolyte additive and molybdenum disulfide as a Lewis acid catalyst is used to accelerate the conversion of sulfur species, avoid catalyst surface gelation, and maintain catalyst activity.
It improves the specific capacity and cycle stability of lithium-sulfur batteries, extends battery life, and enhances battery charge-discharge performance.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of lithium-sulfur batteries, and particularly relates to a high specific capacity lithium-sulfur battery. BACKGROUND
[0002] Developing high specific capacity secondary batteries is of vital importance to prolong the standby time of portable electronic devices such as mobile phones and computers and to improve the driving range of electric vehicles. Lithium-sulfur batteries have a theoretical energy density of up to 2600 Wh / kg, and are one of the most promising next-generation high specific capacity secondary battery technologies.
[0003] However, the positive electrode kinetics lag problem in lithium-sulfur batteries significantly restricts the development of high-performance lithium-sulfur batteries. Specifically, the positive electrode side undergoes a multi-phase multi-electron conversion process between solid elemental sulfur, soluble polysulfides, and solid lithium sulfide during the charging and discharging process. The reaction number is large, the reaction speed is slow, and the reaction degree is low. The above-mentioned many kinetic bottlenecks directly lead to the decrease of the specific capacity and the increase of the polarization of the battery, that is, the actual performance of the battery is greatly reduced.
[0004] In previous studies, the method of introducing Lewis acid catalysts is often used to solve the problem of positive electrode kinetics. For example, some researchers use nickel diselenide as a Lewis acid catalyst, which can modulate the surface structure of the positive electrode, interact with the Lewis base sites of sulfur species, change the conformational energy of sulfur species on it, and thus reduce the activation energy of the reaction. However, it cannot be ignored that during the battery cycle, the Lewis acid catalyst not only interacts with the Lewis base sites of sulfur species, but also interacts with the Lewis base sites on other components such as organic solvents and lithium salts. The above-mentioned interaction will induce the cationic polymerization of the solvent, and then produce a gel layer on the surface of the catalyst, which will cause the deactivation of the catalyst and reduce the catalytic conversion efficiency of sulfur species.
[0005] Therefore, in order to realize high-performance lithium-sulfur batteries, it is necessary to prevent the deactivation phenomenon caused by the surface gelation of the catalyst while promoting the kinetics. SUMMARY
[0006] The purpose of the present application is to overcome the problems of low specific capacity and rapid decay of specific capacity with cycles of lithium-sulfur batteries in the prior art, and to provide a high specific capacity lithium-sulfur battery. The combination of electrolyte additives in the electrolyte and Lewis acid catalysts in the separator of the lithium-sulfur battery can realize the rapid conversion of sulfur species while ensuring that the Lewis acid catalyst always maintains high activity, effectively building high-performance lithium-sulfur batteries.
[0007] In order to achieve the above-mentioned purpose, one aspect of the present application provides a lithium-sulfur battery, wherein the lithium-sulfur battery comprises a positive electrode material, a negative electrode material, a separator and an electrolyte.
[0008] The electrolyte comprises an organic solvent, an organic lithium salt and an electrolyte additive, and the electrolyte additive is cesium iodide.
[0009] The separator comprises a carbon material, a polymer base material, a binder and a Lewis acidic catalyst, and the Lewis acidic catalyst is molybdenum disulfide.
[0010] Preferably, the concentration of the electrolyte additive in the electrolyte is 100-200 mmol / L, preferably 120-180 mmol / L.
[0011] Preferably, the surface loading of the Lewis acidic catalyst in the separator is 0.5-1 mg / cm 2 , preferably 0.6-0.9 mg / cm 2 .
[0012] Through the above technical solution, the beneficial effects are as follows:
[0013] The lithium-sulfur battery provided by the application contains a Lewis acidic catalyst in the separator, which can accelerate the conversion kinetics of sulfur species, and the electrolyte additive contained in the electrolyte can effectively prevent the surface gelation of the Lewis acidic catalyst from occurring, avoid the deactivation of the Lewis acidic catalyst, ensure the long-term working performance of the Lewis acidic catalyst, and ensure the high activity of the lithium-sulfur battery while realizing the rapid conversion of sulfur species, thereby improving the specific capacity and long cycle stability of the lithium-sulfur battery. DETAILED DESCRIPTION
[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the application. The endpoints of the ranges and any numerical values should be interpreted as approximately including values that are near the recited values that are not to be construed as limited to only the precise numerical values. For values that are less than one, one unit is considered to be 0.001. For values that are fractions of one, at least one unit is considered to be 0.0001. For values that have only one significant figure, at least one unit is considered to be 1. The use of "about" or "approximately" in connection with a value means that the exact value is not critical and that the disclosed range is to be understood as encompassing values near the stated value within the precision of the measurement, measurement instrument, and / or the accuracy of the measurement.
[0015] In one aspect, the application provides a lithium-sulfur battery, wherein the lithium-sulfur battery comprises a positive electrode material, a negative electrode material, a separator and an electrolyte.
[0016] The electrolyte comprises an organic solvent, an organic lithium salt and an electrolyte additive, and the electrolyte additive is cesium iodide.
[0017] The separator comprises a carbon material, a polymer base material, a binder and a Lewis acidic catalyst, and the Lewis acidic catalyst is molybdenum disulfide.
[0018] In the present application, the lithium-sulfur battery comprises a Lewis acid catalyst in the separator, which can accelerate the conversion kinetics of sulfur species, and the electrolyte additive contained in the electrolyte can effectively prevent the occurrence of gelation on the surface of the Lewis acid catalyst, avoid the deactivation of the Lewis acid catalyst, ensure the long-term working of the Lewis acid catalyst, and ensure the high activity of the lithium-sulfur battery while realizing the rapid conversion of sulfur species, thereby improving the specific capacity and long cycle stability of the lithium-sulfur battery.
[0019] According to the present application, preferably, the concentration of the electrolyte additive in the electrolyte is 100-200 mmol / L, for example, 100 mmol / L, 110 mmol / L, 120 mmol / L, 130 mmol / L, 140 mmol / L, 150 mmol / L, 160 mmol / L, 170 mmol / L, 180 mmol / L, or any range between any two of them, preferably 120-180 mmol / L.
[0020] In the present application, the addition of an appropriate amount of the above-mentioned electrolyte additive can prevent the occurrence of gelation on the surface of the Lewis acid catalyst, ensure the activity of the Lewis acid catalyst, and the concentration of the electrolyte additive that is too high can cause the active sites on the surface of the Lewis acid catalyst to be occupied too much, thereby reducing its catalytic activity; and the concentration of the electrolyte additive that is too low cannot prevent the polymerization and gelation of the electrolyte on the surface of the Lewis acid catalyst, thereby causing the catalyst to be deactivated.
[0021] According to the present application, the organic solvent can be selected from a wide range of conventional organic solvents in the art. Preferably, the organic solvent is ethylene glycol dimethyl ether and / or 1,3-dioxolane, preferably 1,3-dioxolane.
[0022] In the present application, the use of the above-mentioned organic solvent can improve the solubility of the organic lithium salt, improve the conductivity of the lithium-sulfur battery electrolyte, provide a fast conversion reaction kinetics for the positive electrode of the lithium-sulfur battery, and realize a high energy density of the lithium-sulfur battery.
[0023] According to the present application, the type of the organic lithium salt is not particularly limited and can be a conventional organic lithium salt in the art, and a person skilled in the art can select a suitable organic lithium salt. Preferably, the organic lithium salt is lithium bis(trifluoromethylsulfonyl)imide and / or lithium bis(fluorosulfonyl)imide.
[0024] According to the present application, preferably, the concentration of the organic lithium salt in the electrolyte is 300-1800 mmol / L, for example 500 mmol / L, 600 mmol / L, 700 mmol / L, 800 mmol / L, 900 mmol / L, 1000 mmol / L, or any range between any two of them, preferably 500-1000 mmol / L. In the present application, the use of an appropriate amount of the above-mentioned organic lithium salt can provide more active lithium ions in the electrolyte, thereby improving the cycle performance of the lithium-sulfur battery.
[0025] In the present application, the preparation method of the electrolyte is not particularly limited, and according to a preferred embodiment of the present application, the method comprises the following steps: mixing the organic lithium salt, the organic solvent and the electrolyte additive under a protective atmosphere to obtain the electrolyte.
[0026] In the present application, the protective atmosphere has the conventional interpretation in the art, which refers to an atmosphere free of oxygen, preferably at least one selected from argon, nitrogen and helium.
[0027] In the present application, the mixing condition is not particularly limited, and the organic lithium salt, the organic solvent and the electrolyte additive are mixed until no solid is precipitated, and a uniformly mixed electrolyte is obtained.
[0028] In the present application, the separator contains a Lewis acidic catalyst, which can accelerate the conversion kinetics of the sulfur species of the positive electrode material, improve the conversion rate of the sulfur species, inhibit the diffusion and irreversible loss of the sulfur species to the negative electrode side, and is conducive to realizing a lithium-sulfur battery with high discharge specific capacity and long cycle stability.
[0029] According to the present application, preferably, the surface loading of the Lewis acidic catalyst in the separator is 0.5-1 mg / cm 2 , for example 0.5 mg / cm 2 , 0.55 mg / cm 2 , 0.6 mg / cm 2 , 0.65 mg / cm 2 , 0.7 mg / cm 2 , 0.75 mg / cm 2 , 0.8 mg / cm 2 , 0.85 mg / cm 2 , 0.9 mg / cm 2 , 0.95 mg / cm 2 , 1 mg / cm 2 , or any range between any two of them, preferably 0.6-0.9 mg / cm 2In the present application, too high content of Lewis acidic catalyst in the separator increases the mass of non-active substances in the lithium-sulfur battery, which is not conducive to achieving high energy density of the lithium-sulfur battery, and too low content cannot fully play the effect of improving reaction kinetics, which is not conducive to achieving high specific capacity.
[0030] According to the present application, the type and source of the carbon material are not particularly limited, which is a conventional carbon material for lithium-sulfur batteries in the art and can be commercially available or prepared by existing methods. The carbon material is selected from at least one of acetylene black, graphene, ketjen black and conductive graphite.
[0031] According to the present application, preferably, the surface loading of the carbon material in the separator is 0.05-0.2 mg / cm 2 , preferably 0.08-0.12 mg / cm 2 In the present application, the addition of an appropriate amount of carbon material can improve the electrical conductivity of the Lewis acidic catalyst and synergistically promote its promotion of reaction kinetics.
[0032] According to the present application, the type and source of the binder are not particularly limited, which is a conventional binder for battery materials in the art and can be commercially available or prepared by existing methods. Preferably, the binder is selected from at least one of polyethylene oxide, poly(vinylidene fluoride) and polytetrafluoroethylene.
[0033] According to the present application, preferably, the surface loading of the binder in the separator is 0.005-0.02 mg / cm 2 , for example 0.005 mg / cm 2 , 0.008 mg / cm 2 , 0.01 mg / cm 2 , 0.012 mg / cm 2 , 0.015 mg / cm 2 , 0.018 mg / cm 2 , 0.02 mg / cm 2 , or any range between any two of them, preferably 0.008-0.015 mg / cm 2 .
[0034] According to the present application, the high molecular substrate is a conventional separator material in the art, and preferably the high molecular substrate is selected from at least one of polypropylene film, polyethylene film and polyvinylidene fluoride film, preferably polypropylene film.
[0035] In the present application, the size and thickness of the high molecular substrate are not particularly limited, and those skilled in the art can adaptively adjust the size and thickness of the high molecular substrate according to the capacity and size of the lithium-sulfur battery. Preferably, the thickness of the high molecular substrate is 10-30 microns, preferably 15-25 microns.
[0036] In the present application, the preparation method of the separator is not particularly limited, according to a preferred embodiment of the present application, the preparation method of the separator comprises:
[0037] (1) mixing and dispersing the carbon material, the binder and the Lewis acidic catalyst in water to form a slurry;
[0038] (2) drying the slurry obtained in (1) on a polymer substrate after suction filtration to obtain the lithium-sulfur battery separator.
[0039] In the present application, the mixing method of step (1) is not particularly limited, and the carbon material, the binder and the Lewis acidic catalyst can be uniformly mixed. The ratio of the mixture of the carbon material, the binder and the Lewis acidic catalyst to water is not particularly limited, and a uniform slurry can be formed.
[0040] In the present application, the drying conditions in step (2) are not particularly limited, and the conventional drying conditions in the art can be used.
[0041] In the present application, the lithium-sulfur battery comprises a positive electrode material, a negative electrode material, a separator and an electrolyte. By combining the electrolyte containing the electrolyte additive cesium iodide and the separator containing the Lewis acidic catalyst molybdenum disulfide, the rapid conversion of sulfur species in the lithium-sulfur battery can be ensured, the surface gelation of the Lewis acidic catalyst can be reduced, the high activity of the Lewis acidic catalyst can be maintained, and the specific capacity and cycle performance of the lithium-sulfur battery can be improved.
[0042] In the present application, the type and source of the positive electrode material are not particularly limited, and it is a conventional lithium-sulfur battery positive electrode material in the art, which can be commercially available or prepared by existing methods. According to a preferred embodiment of the present application, the positive electrode material is a carbon-sulfur composite positive electrode.
[0043] In the present application, the type of the lithium-sulfur battery negative electrode material is not particularly limited, and it is a conventional negative electrode material in the art. According to a preferred embodiment of the present application, the negative electrode material is metallic lithium.
[0044] In the present application, the lithium-sulfur battery is assembled by using the positive electrode material, the negative electrode material, the electrolyte and the separator, and the charge-discharge performance and the cycle performance are tested. The test is carried out at 25℃, and the specific capacity of the lithium-sulfur battery positive electrode in the button cell is higher than 1000mAh / g, the cycle number of the capacity reaching 80% of the first circle is more than 100 circles, and the cycle life and the coulombic efficiency of the lithium-sulfur battery are improved.
[0045] In the present application, the assembly method of the positive electrode material, the negative electrode material, the separator and the electrolyte of the lithium-sulfur battery is not particularly limited, and the lithium-sulfur button cell can be assembled according to the conventional method in the art.
[0046] According to a particularly preferred embodiment of the present application, a high specific capacity lithium-sulfur battery, wherein the lithium-sulfur battery comprises a positive electrode material, a negative electrode material, a separator and an electrolyte;
[0047] The electrolyte comprises an organic solvent, an organic lithium salt and an electrolyte additive, and the electrolyte additive is cesium iodide.
[0048] The separator comprises a carbon material, a polymer substrate, a binder and a Lewis acidic catalyst, and the Lewis acidic catalyst is molybdenum disulfide.
[0049] The concentration of the electrolyte additive in the electrolyte is 120-180 mmol / L.
[0050] The surface loading of the Lewis acidic catalyst in the separator is 0.6-0.9 mg / cm 2 .
[0051] The present application will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, the reagents used in the present application are commercially available.
[0052] Example 1
[0053] 1) Preparation of electrolyte: In an argon atmosphere glove box, an organic lithium salt (lithium bis(trifluoromethylsulfonyl)imide) was weighed according to the ratio and added to a reagent bottle, then an organic solvent 1,3-dioxolane and an electrolyte additive cesium iodide were slowly added, and the organic lithium salt and the electrolyte additive were fully dissolved in the organic solvent by stirring, so that the concentration of lithium salt in the electrolyte was 1000 mmol / L, and the concentration of electrolyte additive was 150 mmol / L.
[0054] 2) Preparation of separator: The carbon material acetylene black, the binder polyethylene oxide and the Lewis acidic catalyst molybdenum disulfide were mixed according to the ratio and dispersed in water to form a slurry, and the slurry was suction filtered on a polymer substrate polypropylene film and dried, and the thickness of the polypropylene film was 25 microns, so that the surface loading of the carbon material was 0.1 mg / cm 2 , the surface loading of the binder was 0.01 mg / cm 2 , and the surface loading of the Lewis acidic catalyst was 0.75 mg / cm 2 , thereby obtaining the lithium-sulfur battery separator.
[0055] Comparative Example 1
[0056] Based on Example 1, the difference is that in step 1), no electrolyte additive is added, and in step 2), no Lewis acidic catalyst is added, and other components and preparation processes remain the same as in Example 1.
[0057] Comparative Example 2
[0058] On the basis of Example 1, the difference is that no electrolyte additive is added in step 1), and other ingredients and preparation process remain consistent with Example 1.
[0059] Comparative Example 3
[0060] On the basis of Example 1, the difference is that no Lewis acid catalyst is added in step 2), and other ingredients and preparation process remain consistent with Example 1.
[0061] Example 2
[0062] On the basis of Example 1, the difference is that the concentration of electrolyte additive in the electrolyte in step 1) is 100 mmol / L, and other ingredients and preparation process remain consistent with Example 1.
[0063] Example 3
[0064] On the basis of Example 1, the difference is that the concentration of electrolyte additive in the electrolyte in step 1) is 200 mmol / L, and other ingredients and preparation process remain consistent with Example 1.
[0065] Example 4
[0066] On the basis of Example 1, the difference is that the surface loading of Lewis acid catalyst in the separator in step 2) is 0.5 mg / cm 2 , and other ingredients and preparation process remain consistent with Example 1.
[0067] Example 5
[0068] On the basis of Example 1, the difference is that the surface loading of Lewis acid catalyst in the separator in step 2) is 1 mg / cm 2 , and other ingredients and preparation process remain consistent with Example 1.
[0069] Example 6
[0070] 1) Preparation of electrolyte: In an argon atmosphere glove box, organic lithium salt bis(fluorosulfonyl) imide lithium is weighed according to the metering ratio and added to the reagent bottle, then organic solvent 1,3-dioxolane and electrolyte additive cesium iodide are slowly added, and the organic lithium salt and electrolyte additive are fully dissolved in the organic solvent by stirring, so that the lithium salt concentration in the electrolyte is 500 mmol / L, and the concentration of electrolyte additive is 120 mmol / L.
[0071] 2) Preparation of the separator: carbon material acetylene black, binder polyethylene oxide and Lewis acidic catalyst molybdenum disulfide were mixed in a metered ratio and dispersed in water to form a slurry, the slurry was suction filtered on a polymeric substrate polyethylene film and dried, the film thickness was 15 microns, so that the face loading of the carbon material was 0.08 mg / cm 2 , the face loading of the binder was 0.015 mg / cm 2 , the face loading of the Lewis acidic catalyst was 0.55 mg / cm 2 , thus obtaining the lithium-sulfur battery separator.
[0072] Test Examples
[0073] The lithium-sulfur battery electrolyte and separator prepared in the examples and comparative examples were tested in lithium-sulfur button cells, the results of the first cycle energy density and cycle life when the capacity reached 80% of the initial are shown in Table 1.
[0074] Lithium-sulfur button cell:
[0075] The positive electrode material had a thickness of 140 microns and a sulfur face loading of 6 mg / cm 2 , and the electrode size was a round piece with a diameter of 13.0 mm;
[0076] The negative electrode material was metallic lithium, with a thickness of 50 microns and an electrode size of a round piece with a diameter of 16.0 mm;
[0077] The separator was the separator prepared in the examples and comparative examples, with a thickness of 15-25 microns and a size of a round piece with a diameter of 19.0 mm;
[0078] The amount of electrolyte was 45 μL;
[0079] The button cell configuration was a lithium-sulfur button cell in the 2032 standard configuration, which was left to stand for 2 hours after assembly, and was subjected to constant current charge and discharge at 0.3 C, with a voltage range of 1.7-2.6 V. The specific capacity of the first cycle was the first cycle battery discharge capacity divided by the mass of elemental sulfur. The number of stable cycles was the number of cycles when the capacity reached 80% of the first cycle capacity.
[0080] Table 1
[0081]
[0082] As can be seen from the results of Table 1, compared with Comparative Example 1 and Comparative Example 1, the specific capacity and cycle performance of the lithium-sulfur battery are greatly improved after adding the Lewis acid catalyst and the electrolyte additive. Comparative Example 1 and Comparative Example 2 show that after adding the Lewis acid catalyst but not adding the electrolyte additive, the specific capacity and cycle performance of the battery are improved to a certain extent, but still not as good as Example 1, which shows that the addition of the Lewis acid catalyst can promote the positive electrode kinetics, but due to the appearance of surface gelation, the catalyst is deactivated, that is, the long-term performance of the catalytic conversion cannot be guaranteed. Comparative Example 1 and Comparative Example 3 show that after adding the electrolyte additive but not adding the Lewis acid catalyst, the specific capacity and cycle performance of the battery are basically not improved, far inferior to the performance of Example 1, which shows that the electrolyte additive cannot work alone, and it can only be used in combination with the Lewis acid catalyst to eliminate surface gelation and further improve the performance of the catalytic conversion of the catalyst. In summary of the above comparison, the example of adding the Lewis acid catalyst and the electrolyte additive at the same time has the best specific capacity and cycle performance, which confirms the effectiveness of the electrolyte and the separator used in the present application for building high-performance lithium-sulfur batteries.
[0083] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.
Claims
1. A lithium-sulfur battery, characterized in that, The lithium-sulfur battery includes a positive electrode material, a negative electrode material, a separator, and an electrolyte; The electrolyte comprises an organic solvent, an organic lithium salt, and an electrolyte additive, wherein the electrolyte additive is cesium iodide; The membrane comprises carbon material, a polymer substrate, a binder, and a Lewis acid catalyst, wherein the Lewis acid catalyst is molybdenum disulfide.
2. The lithium-sulfur battery according to claim 1, wherein, The concentration of electrolyte additives in the electrolyte is 100-200 mmol / L, preferably 120-180 mmol / L.
3. The lithium-sulfur battery according to claim 1 or 2, wherein, The organic solvent is ethylene glycol dimethyl ether and / or 1,3-dioxolane, preferably 1,3-dioxolane.
4. The lithium-sulfur battery according to any one of claims 1-3, wherein, The organolithium salt is lithium bis(trifluoromethylsulfonyl)imide and / or lithium bis(fluorosulfonyl)imide.
5. The lithium-sulfur battery according to any one of claims 1-4, wherein, In the electrolyte, the concentration of the organic lithium salt is 300-1800 mmol / L, preferably 500-1000 mmol / L.
6. The lithium-sulfur battery according to any one of claims 1-5, wherein, The areal loading of the Lewis acidic catalyst in the membrane is 0.5-1 mg / cm³. 2 The preferred concentration is 0.6-0.9 mg / cm³. 2 .
7. The lithium-sulfur battery according to any one of claims 1-6, wherein, The carbon material is selected from at least one of acetylene black, graphene, Ketjen black, and conductive graphite.
8. The lithium-sulfur battery according to any one of claims 1-7, wherein, The areal loading of carbon material in the diaphragm is 0.05-0.2 mg / cm². 2 The preferred concentration is 0.08-0.12 mg / cm³. 2 .
9. The lithium-sulfur battery according to any one of claims 1-8, wherein, The adhesive is selected from at least one of polyethylene oxide, poly(vinylidene fluoride) and polytetrafluoroethylene; Preferably, the areal loading of the adhesive in the diaphragm is 0.005-0.02 mg / cm³. 2 The preferred concentration is 0.008-0.015 mg / cm³. 2 .
10. The lithium-sulfur battery according to any one of claims 1-9, wherein, The polymer substrate is selected from at least one of polypropylene film, polyethylene film and polyvinylidene fluoride film; Preferably, the thickness of the polymer substrate is 10-30 micrometers, and more preferably 15-25 micrometers.