CN110649213A - Coating diaphragm material for lithium-sulfur secondary battery and application thereof - Google Patents

Coating diaphragm material for lithium-sulfur secondary battery and application thereof Download PDF

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CN110649213A
CN110649213A CN201910837680.5A CN201910837680A CN110649213A CN 110649213 A CN110649213 A CN 110649213A CN 201910837680 A CN201910837680 A CN 201910837680A CN 110649213 A CN110649213 A CN 110649213A
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diaphragm
parts
coating material
lithium
separator
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CN110649213B (en
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段晓波
赵致远
王昆
蔡欣
张蕾
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Xian University of Science and Technology
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Xian University of Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a diaphragm coating material for a lithium-sulfur secondary battery and application thereof, belonging to the field of lithium-sulfur secondary batteries. The diaphragm coating material comprises one or more metal hydrides, wherein the metal elements in the metal hydrides comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co and Zr. The auxiliary material for coating the diaphragm also comprises a high molecular binder and an additive, and the material for coating the diaphragm comprises 20-98 parts of metal hydride, 1-50 parts of the high molecular binder and 0-30 parts of carbon black according to parts by weight. The metal hydride in the diaphragm coating material has stronger chemical adsorption capacity to polysulfide in the lithium-sulfur secondary battery, can effectively obstruct the diffusion of the polysulfide, and improves the comprehensive electrochemical performance of the lithium-sulfur secondary battery.

Description

Coating diaphragm material for lithium-sulfur secondary battery and application thereof
Technical Field
The invention relates to a diaphragm coating material for a lithium-sulfur secondary battery and application thereof, belonging to the field of lithium-sulfur secondary batteries.
Background
The lithium-sulfur secondary battery takes a sulfur-containing substance as a positive electrode and metal lithium as a negative electrode, has the advantages of high theoretical energy density, low cost, environmental friendliness and the like, is considered to be the first choice of a next-generation high-specific-energy chemical power source following a lithium ion battery, and is widely valued by countries in the world.
Although lithium-sulfur secondary batteries have a series of advantages such as high energy density, the indexes such as self-discharge performance, coulombic efficiency and cycle performance of lithium-sulfur secondary batteries still cannot be compared with those of lithium-ion batteries. The main reason is that lithium polysulfide, a discharge intermediate product of a sulfur positive electrode, can be dissolved in a large amount in an electrolyte and shuttles back and forth between the positive electrode and the negative electrode, resulting in poor self-discharge, cycle performance and coulombic efficiency. Therefore, the key to improving the performance of the lithium sulfur secondary battery is to suppress the shuttling effect of the lithium sulfur secondary battery. An effective method adopted by the academia at present is to coat a polar compound on the surface of the diaphragm, and utilize the adsorption effect of the compound on polysulfide to block the diffusion of polysulfide from a positive electrode to a negative electrode. Among them, many coating compounds are oxides, sulfides, and the like, but these materials generally have a high specific gravity and a low conductivity, and affect the electron transfer ability of the sulfur positive electrode.
Disclosure of Invention
In view of the above problems, the present invention provides a separator coating material and a separator having high conductivity and good sulfur blocking effect, which aims to block shuttling of lithium polysulfide and improve the dynamic properties of a lithium sulfur secondary battery.
A separator coating material for a lithium-sulfur secondary battery, comprising one or more metal hydrides, wherein the metal elements comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co, Zr.
Further, the metal hydride includes a metal hydride containing one metal element or a metal hydride containing a plurality of metal elements.
Furthermore, the diaphragm coating material also comprises a polymer binder and an additive, and the diaphragm coating material comprises 20-98 parts of metal hydride, 1-50 parts of the polymer binder and 0-30 parts of carbon black according to parts by weight.
Further, the particle size of the metal hydride is less than 100 μm.
Further, the purity of the metal hydride is more than 90%.
Further, the metal hydride is preferably a metal hydride in which the metal element is one or more of Mg, Ti, V, Cr, Ni, and Fe, in view of hydride stability and cost.
Preferably, TiH is an index which comprehensively considers the improvement effect on the battery performance, the cost, the operation simplicity, whether the current industrial-grade supply capacity is available or not, and the like2With MgH2Mixtures are a relatively good choice.
Preferably, the separator coating material comprises TiH in parts by weight245 portions of MgH245 parts of high molecular adhesive and 5 parts of carbon black.
A preparation method of a separator coating material for a lithium-sulfur secondary battery comprises the following steps: under the protection of inert gas, ball-milling the metal hydride until the granularity is lower than 100 mu m, dissolving 1-50 parts of the polymer binder in a solvent with the weight of 15-20 times that of the polymer binder, uniformly mixing 20-98 parts of the refined metal hydride and 0-30 parts of carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
Further, the inert gas includes argon or nitrogen.
A separator comprising the separator coating material described above.
The preparation method of the diaphragm comprises the following steps: coating the diaphragm coating slurry on a high-molecular porous diaphragm, wherein the thickness of a coating layer is 30-150 mu m, and cutting and forming as required after drying.
A lithium sulfur secondary battery comprising the separator described above.
The effective component of the diaphragm coating material is metal hydride which contains metal bonds, has free electrons and has high conductivity at the metal level. In the prior art, metal hydrides are mainly used as power source negative electrode materials in alkaline electrolyte, such as metal hydride graphene batteries of CN109037666A public cloth, and are used as battery negative electrode materials. In lithium ion batteries, researchers also propose that a few hydrides have certain lithium intercalation capacity at 0-0.5V (metallic lithium is the standard potential) and have potential to be used as a lithium ion battery cathode material, but lithium is difficult to remove under the current technical conditions, the cycle performance is poor, and no practicability exists.
In the earlier research process, the invention discovers that metal hydride is easy to chemically adsorb polysulfide ions and is suitable for being used as a coating material of a lithium-sulfur secondary battery diaphragm. Although the mechanism of the hydride to adsorb polysulfide ions is not clear at present, and presumably may be related to the surface polarity or reducibility of the hydride, the technical effect is significant.
The beneficial effects of the invention include:
(1) the metal hydride has stronger chemical adsorption capacity to polysulfide in an oxidation state, can effectively hinder the diffusion of the polysulfide and improve the comprehensive electrochemical performance of the battery.
(2) The metal hydride has higher conductivity and can not reduce the electron transfer capability of the sulfur anode.
(3) The metal hydride is relatively easy to synthesize, has brittleness similar to inorganic ceramic, and can easily realize the regulation and control of the particle size by mechanical means such as ball milling and the like.
Drawings
For a clearer explanation of the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a first charge and discharge curve of the battery in example 1.
Fig. 2 is a first charge and discharge curve of the battery in example 2.
Fig. 3 is a first charge and discharge curve of the battery in example 3.
Fig. 4 is a first charge and discharge curve of the battery in example 4.
Fig. 5 is a first charge and discharge curve of the battery in example 5.
Fig. 6 is a first charge and discharge curve of the battery of example 6.
Fig. 7 is a first charge and discharge curve of the battery in example 7.
Fig. 8 is a first charge and discharge curve of the battery of example 8.
Fig. 9 is a first charge and discharge curve of the battery in example 9.
Fig. 10 is a first charge-discharge curve of the battery in example 10.
Fig. 11 is a first charge and discharge curve of the battery in example 11.
Fig. 12 is a first charge and discharge curve of the battery of example 12.
Fig. 13 is a first charge and discharge curve of the battery in example 13.
Fig. 14 is a first charge and discharge curve of the battery of example 14.
Fig. 15 is a first charge and discharge curve of the battery in example 15.
Fig. 16 is a first charge and discharge curve of the battery of example 16.
Fig. 17 is a first charge-discharge curve of the battery in example 17.
Fig. 18 is a first charge-discharge curve of the battery in the comparative example.
Fig. 19 is an electron Scanning Electron Microscope (SEM) photograph of the hydride powder of example 17.
FIG. 20 is a graph showing the charge and discharge curves of the hydride powder of example 17 in the range of 1-3V operating voltage.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, belong to the scope of protection of the present invention.
Example 1
Under the protection of Ar gas, TiH2Ball-milling the powder until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 90 parts of refined TiH2And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 2
Under the protection of Ar gas, MgH2Ball-milling the powder until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 90 parts of refined MgH2And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 3
Under the protection of Ar gas, LaNi is added5H6Ball-milling the powder to a particle size of less than 100 μm, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 15 times the weight of N-methylpyrrolidone (NMP) and mixing with 90 parts of refined LaNi5H6And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 30 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 4
Under the protection of Ar gas, TiCoH1.4Ball-milling the powder to a particle size of less than 100 μm, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 15 times the weight of N-methylpyrrolidone (NMP) and mixing with 90 parts of refined TiCoH1.4Mixing the powders uniformlyAnd (4) uniformly obtaining diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 50 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 5
VH is treated under the protection of Ar gas2Ball-milling the powder to a particle size of less than 100 μm, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times the weight of N-methylpyrrolidone (NMP) and mixing with 90 parts of refined VH2And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 150 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 6
Under the protection of Ar gas, ZrNi5H4Ball-milling the powder to a particle size of less than 100 μm, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times the weight of N-methylpyrrolidone (NMP) and mixing with 90 parts of refined ZrNi5H4And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 7
Under the protection of Ar gas, TiFeH1.9Ball-milling the powder to a particle size of less than 100 μm, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times the weight of N-methylpyrrolidone (NMP) and mixing with 90 parts of refined TiFeH1.9And uniformly mixing the powder to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 8
Under the protection of Ar gas, TiH2And MgH2The powder is mixed according to the weight ratio of 5:1 and then ball-milled until the granularity is less than 100 mu m,dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 9
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 4:1, ball-milling until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 10
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 3:1, ball-milling until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 11
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 2:1, ball-milling until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2Uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurryAnd drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 12
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 1:1, ball-milling until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 13
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 0.5:1, ball-milling until the particle size is less than 100 mu m, dissolving 10 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 80 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 10 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 14
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 1:1, ball-milling until the particle size is less than 100 mu m, dissolving 1 part of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 98 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 1 part of high-purity carbon black to obtain a diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 15
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 1:1, ball-milling until the particle size is less than 100 mu m, dissolving 50 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 20 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 30 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 16
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 1:1, ball-milling until the particle size is less than 100 mu m, dissolving 30 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 40 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 30 parts of high-purity carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
Example 17
Under the protection of Ar gas, TiH2And MgH2Mixing the powder according to the weight ratio of 1:1, ball-milling until the particle size is less than 100 mu m, dissolving 5 parts of polyvinylidene fluoride (PVDF) in 20 times of N-methylpyrrolidone (NMP) by weight, and mixing with 90 parts of refined TiH2And MgH2And uniformly mixing the mixed powder and 5 parts of high-purity carbon black to obtain a diaphragm coating slurry, and drying to obtain the diaphragm coating material.
And coating the diaphragm coating slurry on a Celgard2325 diaphragm, wherein the coating thickness is 100 mu m, and cutting and forming as required after drying to obtain the diaphragm of the invention.
The separator coated with metal hydride prepared in the above example is cut into a circular piece with the diameter of 19mm, and is applied to a CR2025 button cell for electrochemical performance test of a lithium-sulfur secondary battery, meanwhile, a untreated Celgard2325 commercial separator is taken as a control example, and in the test results, the hundred-time cycle retention rate and the coulombic efficiency are shown in table 1, and the first charge-discharge curve is shown in attached fig. 1-17. In the electrochemical performance test, the positive plate is a self-made sulfur electrode, the counter electrode is metal lithium, the electrolyte is 1mol/L lithium bistrifluorosulfonate imine solution, and the solvent is a mixed solution of ethylene glycol dimethyl ether (DME) solution and 1,3 Dioxolane (DOL) in a volume ratio of 1: 1.
The preparation method of the positive plate comprises the following steps: 70 parts of elemental sulfur and 20 parts of multi-walled carbon nano-tubes are mixed and heated for 5 hours at the temperature of 150 ℃, 10 parts of polyvinylidene fluoride (PVDF) are added and mixed evenly, and a proper amount of N-methyl pyrrolidone (NMP) is added to prepare viscous slurry. The slurry was uniformly coated on aluminum foil and dried at 60 ℃ for 24 hours, cut into disks 14mm in diameter. The sulfur loading is 5-6mg/cm2In the meantime.
TABLE 1
Examples of the invention Retention ratio (%) of one hundred cycles Coulombic efficiency (%)
Example 1 73.6 91.2
Example 2 73.1 90.6
Example 3 65.3 86.4
Example 4 64.5 89.3
Example 5 66.4 89.9
Example 6 63.5 90.3
Example 7 70.4 90.1
Example 8 71.5 91.0
Example 9 75.4 91.0
Example 10 76.7 91.8
Example 11 77.9 91.9
Example 12 79.7 93.1
Example 13 75.6 90.4
Example 14 77.5 90.6
Example 15 68.7 83.3
Example 16 74.0 90.3
Example 17 82.6 95.9
Comparative example 54.2 46.1
As can be seen from table 1 and fig. 1 to 17, compared with the comparative example, the indexes such as the hundred-cycle retention rate and the coulombic efficiency of the embodiments are all significantly improved, and the specific capacity of most of the embodiments is also significantly better than that of the comparative example. By optimizing the species and the composition proportion of the mixed hydride and the proportion of the hydride, the conductive additive and the adhesive in the formula of the diaphragm, the technical effect of the hydride diaphragm is improved.
Comprehensively considering indexes such as cost, simplicity and convenience in operation, actual effect and the like, TiH2With MgH2Mixtures are relatively good choices. Comparative examples 8 to 13 show that TiH2With MgH2At a weight ratio of 1:1, the metal hydride is changedThe best electrochemical performance of the battery is possible to be combined with TiH2Good stability but high density, MgH2Poor stability but low density. TiH2With MgH2The proportions of the mixed powder, the polymer adhesive and the carbon black are respectively 95: 5: at 5, the separator barrier polysulfide property is best at this time as seen from the hundred cycle retention and coulombic efficiency of the battery. As can be seen from fig. 19, the metal hydride particles are large and strongly adsorbed to polysulfides; the carbon black particles have weak adsorbability on polysulfide, but fine particles, developed pores and good conductivity; the adhesive has no adsorbability and poor conductivity but can play an indispensable bonding role, so the three should have reasonable proportion, ensure to form a conductive diaphragm with firm bonding and good liquid absorption, and simultaneously increase the content of hydrogenated matters in the diaphragm as much as possible. Fig. 20 shows that the hydride used has almost no lithium intercalation/deintercalation capacity in the range of 1-3V (standard potential of metallic lithium) and has only very small electric double layer capacity, so that the metal hydride separator used contributes negligibly to the capacity of a lithium-sulfur secondary battery, and the battery performance is improved substantially by virtue of its adsorption capacity and conductivity to polysulfide ions.

Claims (9)

1. A separator coating material for a lithium-sulfur secondary battery, comprising one or more metal hydrides, wherein the metal elements of the metal hydrides comprise one or more of rare earth elements, Mg, Ca, Ti, V, Cr, Ni, Fe, Co, Zr.
2. The separator coating material according to claim 1, wherein the metal hydride comprises a metal hydride containing one metal element or a metal hydride containing a plurality of metal elements.
3. The membrane coating material as claimed in claim 1, further comprising a polymer binder and an additive, wherein the membrane coating material comprises 20-98 parts by weight of metal hydride, 1-50 parts by weight of polymer binder and 0-30 parts by weight of carbon black.
4. Separator coating material according to claim 3, wherein the particle size of the metal hydride is below 100 μm.
5. The separator coating material according to claim 4, wherein the purity of the metal hydride is 90% or more.
6. A method for preparing the separator coating material according to any one of claims 1 to 5, comprising the steps of: under the protection of inert gas, ball-milling the metal hydride until the granularity is lower than 100 mu m, dissolving 1-50 parts of the high-molecular binder in a solvent with the weight of 15-20 times, uniformly mixing 20-98 parts of refined metal hydride and 0-30 parts of carbon black to obtain diaphragm coating slurry, and drying to obtain the diaphragm coating material.
7. A separator coated with the separator coating material according to claim 6.
8. The preparation method of the separator according to claim 7, wherein the separator coating slurry is coated on a polymer porous separator with a thickness of 30-150 μm, dried and cut to shape as required.
9. A lithium sulfur secondary battery comprising the separator of claim 7.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113506953A (en) * 2021-06-02 2021-10-15 郑州轻工业大学 Application of lithium vanadium phosphate in coating of lithium-sulfur battery diaphragm

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