Lithium-sulfur battery diaphragm modified by metal-based nutgall coordination polymer and preparation method of lithium-sulfur battery diaphragm

Abstract

The invention discloses a novel lithium-sulfur battery diaphragm modification material, and particularly relates to a lithium-sulfur battery diaphragm modified by a metal-based nutgall coordination polymer and a preparation method of the lithium-sulfur battery diaphragm. The metal-based nutgall coordination polymer, the conductive agent and the binder are ground and mixed and then blended into slurry in N-methyl pyrrolidone, and the surface of the diaphragm is coated with the slurry. The modified diaphragm has a relatively strong adsorption effect on soluble polysulfide, and meanwhile, metal cations have good catalytic activity on an oxidation-reduction reaction in a battery charging and discharging process. And excellent cycle performance and rate capability are shown in the lithium-sulfur battery.

Description

Technical Field

[0001] The invention relates to the technical field of lithium-sulfur battery separators, and in particular to a lithium-sulfur battery separator modified by a metal-based gallon coordination polymer and a preparation method thereof. Background Art

[0002] At present, commercial lithium-ion battery cathode materials include LiCoO2, LiFePO4, and ternary layered materials LiNi x Co y Mn (1-x-y) O2. However, the theoretical specific capacity of this type of negative electrode is currently expected to be less than 300 mAh g -1 , its electrochemical properties are gradually approaching its theoretical limit. With the continuous increase in the production of lithium-ion batteries, metal resources (such as cobalt, nickel, manganese, etc.) are in short supply, and the development of lithium-ion batteries faces huge challenges. Using elemental sulfur as the positive electrode material, a theoretical specific capacity 3-5 times higher than that of commercial lithium-ion batteries (1675mAh g -1 ) and theoretical energy density (2600Wh·kg -1 ), and elemental sulfur resources are abundant, environmentally friendly, and low in cost. Therefore, lithium-sulfur battery is a new energy storage method with great application prospects.

[0003] However, due to the poor conductivity of elemental sulfur and the sulfides it generates, the charge transfer efficiency in the electrochemical process decreases and the electrode reaction polarization is serious. Due to the dissolution and transfer of polysulfide intermediates, the positive electrode material is lost during charging and discharging. Polysulfides can enter the negative electrode and be reduced at the negative electrode. Lithium-sulfur batteries have a "shuttle effect", which seriously affects the cycle life and rate performance. At the same time, the volume effect of sulfur positive electrode materials and "lithium dendrites" and other problems have also become bottlenecks restricting its industrialization process.

[0004] The active materials used to modify the lithium-sulfur battery separator in the prior art often have complex synthesis routes and have limited improvement on the overall electrochemical performance of lithium-sulfur batteries. Therefore, it is very necessary to provide a separator-modified active material with a simple synthesis method and improved redox kinetics. Summary of the invention

[0005] In view of the defects existing in the prior art, the present invention provides a lithium-sulfur battery separator modified by a metal-based gallon coordination polymer and a preparation method thereof.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a metal-based gallon coordination polymer, comprising:

[0008] Gallic acid and a metal weak acid salt are mixed and ground in a molar ratio of 2:1 and added into a ball mill, and ball milled at a rotation speed of 500-1000 r / min to obtain a solid product. The obtained solid product is washed with deionized water and an organic solvent in turn, filtered, and dried in a vacuum oven at 60° C. to obtain a metal-based gallic coordination polymer.

[0009] Furthermore, a method for preparing a metal-based gallon coordination polymer is provided, wherein the metal weak acid salt comprises one or more of cobalt acetate, ferrous acetate, cupric acetate, nickel acetate and manganese acetate.

[0010] Furthermore, in a method for preparing a metal-based gallon coordination polymer, the ball milling temperature range is 10-60°C.

[0011] Furthermore, a method for preparing a metal-based gallon coordination polymer is provided, wherein the ball milling time is 6-24 hours.

[0012] Furthermore, a method for preparing a metal-based gallon coordination polymer is provided, wherein the organic solvent comprises one or more of ether, ethanol, acetone and glycerol.

[0013] The second aspect of the present invention provides a metal-based gallic acid coordination polymer modified lithium-sulfur battery separator and a preparation method thereof, comprising:

[0014] The metal-based gallic coordination polymer, conductive agent and binder are ground and mixed, stirred in an organic solvent to form a slurry, and coated on one side of the diaphragm. After drying in a vacuum oven at 60° C. for 12 hours, a lithium-sulfur battery diaphragm modified with a metal-based gallic coordination polymer is obtained.

[0015] Furthermore, a metal-based gallic acid coordination polymer modified lithium-sulfur battery separator and a preparation method thereof, wherein the ratio of the metal-based gallic acid coordination polymer, the conductive agent and the binder is 70-80:20-10:10.

[0016] Furthermore, a metal-based gallon coordination polymer modified lithium-sulfur battery separator and a preparation method thereof, wherein the conductive agent is one of conductive carbon black, acetylene black and Ketjen black.

[0017] Furthermore, a metal-based gallon coordination polymer modified lithium-sulfur battery separator and a preparation method thereof, wherein the separator is one of polypropylene and polyethylene separators.

[0018] Compared with the prior art, the advantages and technical effects of the present invention are as follows:

[0019] The invention prepares the metal-based gallon coordination polymer by a simple mechanical ball milling method and uses the metal-based gallon coordination polymer to modify the lithium-sulfur battery separator. The preparation method has a short process flow and simple preparation operation.

[0020] The metal-based gallic coordination polymer modified diaphragm provided by the present invention has obvious adsorption-catalysis effect on soluble polysulfides, which is because the metal-based gallic coordination polymer has abundant micropores and physically intercepts polysulfides. At the same time, the metal cation has good catalytic activity on the redox reaction of sulfur substances during the battery charging and discharging process, effectively inhibiting the shuttle effect of polysulfides, so that the lithium-sulfur battery exhibits excellent cycle and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD pattern of the cobalt-based gallon coordination polymer prepared in Example 2 of the present invention.

[0022] Figure 2 This is a SEM image of the cobalt-based gallon coordination polymer prepared in Example 2 of the present invention.

[0023] Figure 3 This is a cross-sectional SEM image of the cobalt-based gallon coordination polymer modified diaphragm prepared in Example 4 of the present invention.

[0024] Figure 4 This is a rate performance diagram of lithium-sulfur batteries with different separators according to Example 5 of the present invention.

[0025] Figure 5 This is a graph showing the cycle performance of lithium-sulfur batteries with different separators according to Example 5 of the present invention.

[0026] Figure 6 This is a cyclic voltammetry curve of a lithium-sulfur battery with different separators according to Example 5 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Embodiment 1:

[0029] A method for preparing a cobalt-based gallic coordination polymer comprises the following specific steps: mixing gallic acid and cobalt acetate tetrahydrate in a molar ratio of 2:1, grinding the mixture, adding the mixture into a ball mill, and ball milling the mixture for 6 hours at a rotation speed of 500 r / min to obtain a solid product.

[0030] The obtained solid product was washed with deionized water and anhydrous ethanol in sequence, filtered, and dried in a vacuum oven at 60° C. to obtain a cobalt-based gallon coordination polymer.

[0031] Embodiment 2:

[0032] A method for preparing a cobalt-based gallic coordination polymer comprises the following specific steps: gallic acid and cobalt acetate tetrahydrate are mixed and ground in a molar ratio of 2:1, added into a ball mill, and ball milled for 12 hours at a rotation speed of 500 r / min to obtain a solid product.

[0033] The obtained solid product was washed with deionized water and anhydrous ethanol in turn, filtered, and dried in a vacuum oven at 60°C to obtain a cobalt-based gallic coordination polymer. The XRD and SEM images of the prepared cobalt-based gallic coordination polymer are shown in FIG. Figure 1 and Figure 2 shown.

[0034] Embodiment 3:

[0035] A method for preparing a cobalt-based gallon coordination polymer comprises the following specific steps: mixing gallic acid and cobalt acetate tetrahydrate in a molar ratio of 2:1, grinding the mixture, adding the mixture into a ball mill, and ball milling the mixture for 24 hours at a rotation speed of 500 r / min to obtain a solid product.

[0036] The obtained solid product was washed with deionized water and anhydrous ethanol in sequence, filtered, and dried in a vacuum oven at 60° C. to obtain a cobalt-based gallon coordination polymer.

[0037] Embodiment 4:

[0038] A lithium-sulfur battery separator modified with a cobalt-based gallic coordination polymer and a preparation method thereof, wherein the cobalt-based gallic coordination polymer, the conductive agent and the binder in Example 2 are ground at a ratio of 7:2:1 for 0.5 h, mixed in N-methylpyrrolidone and stirred into a slurry, and coated on one side of a polypropylene separator using a scraper, and dried in a vacuum oven at 60°C for 12 h to obtain a lithium-sulfur battery separator modified with a cobalt-based gallic coordination polymer. The cross-section SEM of the modified separator is as follows: Figure 3 shown.

[0039] Embodiment 5:

[0040] The modified diaphragm obtained in Example 4 was cut into 16 mm discs, which were assembled into CR2032 button cells with sulfur positive electrode, lithium negative electrode and lithium sulfur electrolyte in a glove box, and subjected to rate, cycle and cyclic voltammetry tests. The test results are shown in FIG. Figure 4 , Figure 5 and Figure 6 The test results show that the modified separator battery has excellent electrochemical performance, and the cobalt-based gallic acid coordination polymer has good catalytic activity for polysulfide conversion.

[0041] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing a metal-based gallon coordination polymer, It is characterized in that include: (1) Gallic acid and a metal salt are mixed and ground in a molar ratio of 2:1, added into a ball mill, and ball milled at a rotation speed of 500 r / min to obtain a solid product; (2) The obtained solid product is washed with deionized water and an organic solvent in sequence, filtered, and dried in a vacuum oven at 60° C. to obtain a metal-based gallon coordination polymer.

2. The method for preparing the metal-based gallon coordination polymer according to claim 1, It is characterized in that The metal weak acid salt in step (1) includes one or more transition metal weak acid salts such as cobalt acetate, ferrous acetate, cupric acetate, nickel acetate and manganese acetate.

3. The method for preparing the metal-based gallon coordination polymer according to claim 1, It is characterized in that The ball milling temperature in step (1) is in the range of 10-60°C.

4. The method for preparing the metal-based gallon coordination polymer according to claim 1, It is characterized in that The ball milling time in step (1) is 6-24h.

5. The method for preparing the metal-based gallon coordination polymer as claimed in claim 1, It is characterized in that The organic solvent in step (2) includes one or more of ether, ethanol, acetone and triacetin.

6. A method for preparing a lithium-sulfur battery separator modified by a metal-based gallon coordination polymer, It is characterized in that include: The metal-based gallic coordination polymer, conductive agent and binder described in claim 1 are ground and mixed, and stirred into slurry in an organic solvent, the slurry is coated on one side of the diaphragm, and dried in a vacuum oven at 60° C. for 12 hours to obtain a lithium-sulfur battery diaphragm modified with a metal-based gallic coordination polymer.

7. The method for preparing the metal-based gallon coordination polymer modified lithium-sulfur battery separator as claimed in claim 6, It is characterized in that The ratio of the metal-based gallon coordination polymer, the conductive agent and the binder is 70-80:20-10:

10.

8. The method for preparing the metal-based gallon coordination polymer modified lithium-sulfur battery separator as claimed in claim 6, It is characterized in that The conductive agent is one of conductive carbon black, acetylene black and Ketjen black.

9. The method for preparing the metal-based gallon coordination polymer modified lithium-sulfur battery separator as claimed in claim 6, It is characterized in that The diaphragm is one of a polypropylene diaphragm and a polyethylene diaphragm.

10. Use of the modified lithium-sulfur battery separator according to claim 6 in lithium-sulfur batteries.

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