Indium-based oxide catalysts, finishing coatings, finishing separators, and lithium-sulfur batteries

Abstract

The application discloses an indium-based oxide catalyst, which is prepared by the following method: step one, adding indium nitrate, isophthalic acid, DMF, acetonitrile, imidazole and nitric acid into a reaction kettle, reacting at 80 DEG C for 12 hours, then heating to 100 DEG C and reacting for 24 hours, washing with DMF and anhydrous ethanol respectively, and vacuum drying for 12 hours to obtain an In-MOF precursor; step two, keeping the In-MOF precursor under the condition of nitrogen atmosphere and 200-600 DEG C for 4 hours, and naturally cooling to room temperature to obtain the indium-based oxide catalyst. Most of the prepared indium-based oxide catalysts still retain the corresponding three-dimensional hierarchical porous framework structure of the original MOF; the indium-based oxide catalyst contains highly dispersed metal active sites inside, effectively reduces the aggregation of metal oxides or metal elements, and thus exhibits more excellent catalytic activity; the organic ligand isophthalic acid generates a large amount of carbon material through pyrolysis under an inert atmosphere, greatly improving the conductivity of the indium-based oxide catalyst.

Description

Technical Field

[0001] This application relates to the field of lithium-sulfur battery technology, and in particular to an indium-based oxide catalyst, a modifying coating, a modified separator, and a lithium-sulfur battery. Background Technology

[0002] Lithium-sulfur batteries are known for their theoretically high energy density (≈2600Wh / kg). -1 Li-S batteries are promising for future battery technologies due to their low cost and environmental friendliness. However, the poor conductivity of sulfur and solid-state discharge products (Li2S / Li2S2), the large volume change (≈80%) of sulfur cathodes during cycling, the "shuttle effect" of soluble LiPSs, the slow sulfur reduction oxidation reaction (SRR) kinetics, and the volume expansion of the cathode during the reaction process have hindered the further development of Li-S batteries.

[0003] To address these issues, the physical confinement of porous carbon and the chemical anchoring of polar substrates are typically employed to suppress the shuttle effect. However, both strategies are inherently passive solutions. Catalysis has been introduced into lithium-sulfur batteries in recent years as an active strategy to accelerate polysulfide conversion and thus address the shuttle effect. Sulfides, nitrides, phosphides, and their heterostructures have been widely used as catalysts. In particular, they have directly described the electron transfer number to characterize electrocatalytic sulfur reduction and confirmed catalysis as a promising approach to solving the fundamental challenges of lithium-sulfur batteries. However, current catalysts used in lithium-sulfur batteries exhibit poor electrochemical performance, making practical application difficult. Summary of the Invention

[0004] In order to solve at least one of the above-mentioned technical problems and develop a catalyst that can be applied to lithium-sulfur batteries, this application provides an indium-based oxide catalyst, a modified coating, a modified separator, and a lithium-sulfur battery.

[0005] On the one hand, the indium-based oxide catalyst provided in this application is prepared by the following method:

[0006] Step 1: Indium nitrate, isophthalic acid, DMF, acetonitrile, imidazole and nitric acid are added to the reaction vessel and reacted at 80°C for 12 h. Then the mixture is heated to 100°C and reacted for 24 h. The mixture is washed with DMF and anhydrous ethanol respectively and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0007] Step 2: The In-MOF precursor is kept in a nitrogen atmosphere at 200-600℃ for 4 hours and then naturally cooled to room temperature to obtain the indium-based oxide catalyst.

[0008] Optionally, in step one, the weight-to-volume ratio of indium nitrate, isophthalic acid, DMF, acetonitrile, imidazole, and nitric acid is: 0.9–2.7 g : 0.9–2.7 g : 3–10 ml : 3–10 ml : 0.6–6 ml : 0.6–6 ml.

[0009] Optionally, in step two, the In-MOF precursor is kept in a nitrogen atmosphere at 200°C for 2 hours, and then heated to 500°C and kept for 2 hours, with a heating rate of 5°C / min.

[0010] Secondly, this application provides a modifying coating comprising the indium-based oxide catalyst, carbon black, and polyvinylidene fluoride prepared above; the indium-based oxide catalyst, carbon black, and polyvinylidene fluoride are ground and mixed, and NMP solvent is added and continuously stirred for 12 hours to obtain the modifying coating.

[0011] Optionally, the weight ratio of indium-based oxide catalyst, carbon black, and polyvinylidene fluoride is 2–4:5–7:1.

[0012] Thirdly, this application provides a modified diaphragm, wherein the modified coating prepared above is uniformly coated onto the diaphragm using a 200μm doctor blade and dried under vacuum at 60°C for 6–12 hours.

[0013] Optionally, the diaphragm mentioned above is made of PP membrane.

[0014] Fourthly, this application provides a lithium-sulfur battery, including a modified separator, wherein the modified separator is coated with the above-mentioned modified coating on the side facing the positive electrode.

[0015] In summary, this application includes at least one of the following beneficial technical effects:

[0016] 1. Most of the prepared indium-based oxide catalysts still retain the corresponding three-dimensional hierarchical porous framework structure of the original MOF; the indium-based oxide catalysts contain highly dispersed metal active sites, which effectively reduces the aggregation of metal oxides or metal elements, thus exhibiting superior catalytic activity; the organic ligand isophthalic acid generates a large amount of carbon material through pyrolysis under an inert atmosphere, which greatly improves the conductivity of the indium-based oxide catalysts.

[0017] 2. The membrane functional modification layer material of this application, which has electrocatalytic function, provides physical confinement and chemical catalysis and exhibits selective catalysis for PSs: In2O3 inhibits the conversion of S8 to Li2S during discharge. n Conversion, promoting Li2S n The conversion to Li₂S. During the charging process, the latter facilitates the conversion of Li₂S to Li₂S. nThe In2O3 / C material bidirectionally promotes the rapid conversion of LiPSs in Li-S batteries, suppresses the shuttle effect, improves the utilization rate of active material sulfur, and exhibits the best electrochemical performance.

[0018] 3. By improving the physical limitation of PSs by improving the pore size of the membrane itself, and at the same time, the chemical adsorption and electrocatalytic performance of LiPSs by In2O3 / C loaded on the membrane are synergistically inhibited to suppress the "shuttle effect" of PSs, thereby improving the cycle stability of lithium-sulfur batteries;

[0019] 4. The lithium-sulfur battery assembled with the electrocatalytic membrane of this application has greatly improved cycle stability and rate performance. Moreover, the preparation process of the functional membrane of this invention is simple and easy to operate, which is conducive to industrial production. Attached Figure Description

[0020] Figure 1 The XRD pattern of the In-MOF precursor prepared in Example 1;

[0021] Figure 2 The XRD pattern of the indium-based oxide catalyst prepared in Example 1;

[0022] Figure 3 SEM image of the indium-based oxide catalyst prepared in Example 1;

[0023] Figure 4 TEM image of the indium-based oxide catalyst prepared in Example 1;

[0024] Figure 5 HRTEM image of the indium-based oxide catalyst prepared in Example 1;

[0025] Figure 6 The image shows a SEM image of the modified diaphragm prepared in Example 11.

[0026] Figure 7 The graph shows the cycle performance of the lithium-sulfur battery prepared in Example 1.

[0027] Figure 8 The graph shows the rate performance of the lithium-sulfur battery prepared in Example 1. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] In the following embodiments of this application, unless otherwise specified, the main raw materials are all purchased from commercially available products.

[0030] The positive electrode used in this application is an existing positive electrode. The specific preparation method is as follows: 160 mg of sulfur and 20 mg of carbon black are weighed and mixed thoroughly, then kept at 155°C in a nitrogen atmosphere for 12 hours to obtain a C / S positive electrode material. The C / S positive electrode material, polyvinylidene fluoride, and carbon black are thoroughly mixed and ground in a ratio of 8:1:1, transferred to a weighing bottle, and an appropriate amount of NMP organic solvent is added. The mixture is continuously stirred for 12 hours to form a uniform slurry. This slurry is then uniformly coated onto aluminum foil using a 200 μm blade and placed in a vacuum drying oven at 60°C for 12 hours to obtain the positive electrode.

[0031] Examples 1-5 were used to prepare indium-based oxide catalysts.

[0032] Preparation Example 1

[0033] 0.9 g indium nitrate, 0.9 g isophthalic acid, 3 ml DMF, 3 ml acetonitrile, 0.6 ml imidazole and 0.6 ml nitric acid were added to a reaction vessel and reacted at 80 °C for 12 h. Then the mixture was heated to 100 °C and reacted for 24 h. The mixture was washed with DMF and anhydrous ethanol, respectively, and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0034] The In-MOF precursor was placed in a crucible and transferred to a tube furnace filled with nitrogen. The furnace was held at 200°C for 2 hours, then heated to 500°C and held for another 2 hours at a rate of 5°C / min. After natural cooling to room temperature, the indium-based oxide catalyst was obtained.

[0035] Preparation Example 2

[0036] 1.8 g indium nitrate, 0.9 g isophthalic acid, 5 ml DMF, 5 ml acetonitrile, 3 ml imidazole and 3 ml nitric acid were added to the reaction vessel and reacted at 80 °C for 12 h. Then the mixture was heated to 100 °C and reacted for 24 h. The mixture was washed with DMF and anhydrous ethanol respectively and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0037] The In-MOF precursor was placed in a crucible and transferred to a tube furnace filled with nitrogen, where it was maintained at 400°C for 4 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the indium-based oxide catalyst was obtained.

[0038] Preparation Example 3

[0039] 2.7 g indium nitrate, 0.9 g isophthalic acid, 10 ml DMF, 10 ml acetonitrile, 6 ml imidazole and 6 ml nitric acid were added to the reaction vessel and reacted at 80 °C for 12 h. Then the mixture was heated to 100 °C and reacted for 24 h. The mixture was washed with DMF and anhydrous ethanol respectively and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0040] The In-MOF precursor was placed in a crucible and transferred to a tube furnace filled with nitrogen, where it was maintained at 600°C for 4 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the indium-based oxide catalyst was obtained.

[0041] Preparation Example 4

[0042] 1.8 g indium nitrate, 1.8 g isophthalic acid, 5 ml DMF, 5 ml acetonitrile, 3 ml imidazole and 3 ml nitric acid were added to the reaction vessel and reacted at 80 °C for 12 h. Then the mixture was heated to 100 °C and reacted for 24 h. The mixture was washed with DMF and anhydrous ethanol respectively and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0043] The In-MOF precursor was placed in a crucible and transferred to a tube furnace filled with nitrogen. The furnace was held at 200°C for 2 hours, then heated to 500°C and held for another 2 hours at a rate of 5°C / min. After natural cooling to room temperature, the indium-based oxide catalyst was obtained.

[0044] Preparation Example 5

[0045] 0.9 g indium nitrate, 2.7 g isophthalic acid, 3 ml DMF, 3 ml acetonitrile, 0.6 ml imidazole and 0.6 ml nitric acid were added to the reaction vessel and reacted at 80 °C for 12 h. Then the mixture was heated to 100 °C and reacted for 24 h. The mixture was washed with DMF and anhydrous ethanol, respectively, and dried under vacuum for 12 h to obtain the In-MOF precursor.

[0046] The In-MOF precursor was placed in a crucible and transferred to a tube furnace filled with nitrogen. The furnace was held at 200°C for 2 hours, then heated to 500°C and held for another 2 hours at a rate of 5°C / min. After natural cooling to room temperature, the indium-based oxide catalyst was obtained.

[0047] Preparation Examples 6-10 were used to prepare decorative coatings.

[0048] Preparation Example 6

[0049] Take 40 mg of the indium-based oxide catalyst, 140 mg of conductive carbon black and 20 mg of polyvinylidene fluoride prepared in Preparation Example 1, add them to a mortar and mix and grind them. Add an appropriate amount of NMP solvent and stir continuously for 12 h to obtain the modified coating.

[0050] Preparation Example 7

[0051] Take 40 mg of the indium-based oxide catalyst, 140 mg of conductive carbon black and 20 mg of polyvinylidene fluoride prepared in Preparation Example 2, add them to a mortar and mix and grind them. Add an appropriate amount of NMP solvent and stir continuously for 12 h to obtain the modified coating.

[0052] Preparation Example 8

[0053] Take 40 mg of the indium-based oxide catalyst, 140 mg of conductive carbon black and 20 mg of polyvinylidene fluoride prepared in Preparation Example 3, add them to a mortar and mix and grind them. Add an appropriate amount of NMP solvent and stir continuously for 12 h to obtain the modified coating.

[0054] Preparation Example 9

[0055] Take 60 mg of the indium-based oxide catalyst, 120 mg of conductive carbon black and 20 mg of polyvinylidene fluoride prepared in Preparation Example 4, add them to a mortar and mix and grind them. Add an appropriate amount of NMP solvent and stir continuously for 12 h to obtain the modified coating.

[0056] Preparation Example 10

[0057] Take 80 mg of the indium-based oxide catalyst, 100 mg of conductive carbon black and 20 mg of polyvinylidene fluoride prepared in Preparation Example 5, add them to a mortar and mix and grind them. Add an appropriate amount of NMP solvent and stir continuously for 12 h to obtain the modified coating.

[0058] Preparation Examples 11-15 were used to prepare modified diaphragms.

[0059] The modification coatings prepared in Preparation Examples 6 to 10 were uniformly applied to Celgard-2400PP membranes using a 200 μm doctor blade, and then transferred to an oven to be vacuum dried at 60°C overnight (6 to 12 h) to obtain modified membranes. Specific Implementation

[0061] Examples 1-5 were used to prepare lithium-sulfur batteries, wherein the modified separators of the lithium-sulfur batteries were prepared using the modified separators prepared in Examples 11-15, respectively.

[0062] Place the cut positive electrode sheet and separator into the glove box, and then assemble the CR2032 coin cell in the following order: positive electrode shell, positive electrode sheet, electrolyte, separator, electrolyte, negative electrode sheet, gasket, spring, and negative electrode shell. The electrolyte used is 1M LiTFSI, DME:DOL = 1:1V%, 0.1M LiNO3.

[0063] The charge-discharge performance of the assembled button cells was tested at room temperature using a LandCT2001A battery testing system and a CHI760E electrochemical workstation.

[0064] Example 1

[0065] This embodiment uses the modified separator prepared in Preparation Example 11 to prepare a lithium-sulfur battery. After three activation cycles, the lithium-sulfur battery prepared in this embodiment exhibits a first-cycle discharge specific capacity of 636.3 mAh / g at 1C, and after 1200 long cycles, its capacity remains at 237.2 mAh / g, with a capacity decay rate of 0.052% per cycle. At 3C, it releases a high discharge specific capacity of 507 mAh / g, and when the current density returns from 3C to 0.2C, the discharge specific capacity gradually recovers to 784.1 mAh / g.

[0066] Example 2

[0067] In this embodiment, a lithium-sulfur battery was prepared using the modified separator prepared in Preparation Example 11. After three activation cycles, the lithium-sulfur battery prepared in this embodiment exhibited a first-cycle discharge specific capacity of 645.2 mAh / g at 1C, and after 1200 long cycles, its capacity remained at 241.2 mAh / g, with a capacity decay rate of 0.052% per cycle. At 3C, it released a high discharge specific capacity of 512 mAh / g, and when the current density returned from 3C to 0.2C, the discharge specific capacity gradually recovered to 798.4 mAh / g.

[0068] Example 3

[0069] This embodiment uses the modified separator prepared in Preparation Example 11 to prepare a lithium-sulfur battery. After three activation cycles, the lithium-sulfur battery prepared in this embodiment exhibits a first-cycle discharge specific capacity of 651.9 mAh / g at 1C, and after 1200 long cycles, its capacity remains at 245.8 mAh / g, with a capacity decay rate of 0.052% per cycle. At 3C, it releases a high discharge specific capacity of 515 mAh / g, and when the current density returns from 3C to 0.2C, the discharge specific capacity gradually recovers to 799.5 mAh / g.

[0070] Example 4

[0071] This embodiment uses the modified separator prepared in Preparation Example 11 to prepare a lithium-sulfur battery. After three activation cycles, the lithium-sulfur battery prepared in this embodiment exhibits a first-cycle discharge specific capacity of 623.4 mAh / g at 1C, and after 1200 long cycles, its capacity remains at 243.5 mAh / g, with a capacity decay rate of 0.051% per cycle. At 3C, it releases a high discharge specific capacity of 503 mAh / g, and when the current density returns from 3C to 0.2C, the discharge specific capacity gradually recovers to 789.1 mAh / g.

[0072] Example 5

[0073] This embodiment uses the modified separator prepared in Preparation Example 11 to prepare a lithium-sulfur battery. After three activation cycles, the lithium-sulfur battery prepared in this embodiment exhibits a first-cycle discharge specific capacity of 605.1 mAh / g at 1C, and after 1200 long cycles, its capacity remains at 241.1 mAh / g, with a capacity decay rate of 0.050% per cycle. At 3C, it releases a high discharge specific capacity of 501 mAh / g, and when the current density returns from 3C to 0.2C, the discharge specific capacity gradually recovers to 786.2 mAh / g.

[0074] Figure 1 and 2 It can be observed that the In-MOF precursor and the indium-based oxide catalyst exhibit obvious characteristic peaks of In-MOF and In2O3, which fully demonstrates the successful preparation of the In-MOF precursor and the indium-based oxide catalyst.

[0075] exist Figure 3 and Figure 4 The SEM and TEM images show that the In-MOF cubic structure remains intact, and the backscattered image of the SEM of the indium-based oxide catalyst shows that the generated In2O3 is very uniformly dispersed without obvious large-scale agglomeration, indicating that the advantage of the dispersed metal active sites of MOF can be fully utilized to effectively suppress agglomeration.

[0076] Figure 5 This is an HRTEM image of an indium-based oxide catalyst. Figure 6 This is a SEM image of the modified membrane, showing that the slurry formed by the indium-based oxide catalyst is uniformly coated on one side of the PP membrane surface.

[0077] Figure 7 This is a graph showing the cycle performance of a lithium-sulfur battery assembled with a modified separator. Figure 7 As can be seen from the figure, after three activation cycles, its first discharge capacity at 1C is 636.3 mAh / g, and after 1200 long cycles, its capacity is still maintained at 237.2 mAh / g, with a capacity decay rate of 0.052% per cycle.

[0078] Figure 8 This is a rate performance graph of a lithium-sulfur battery assembled with a modified separator. The lithium-sulfur battery assembled with the modified separator exhibits a high discharge specific capacity of 507 mAh / g at 3C, and the discharge specific capacity gradually recovers to 784.1 mAh / g when the current density returns from 3C to 0.2C.

[0079] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A finishing coating, characterized in that, The modification coating includes an indium-based oxide catalyst, carbon black, and polyvinylidene fluoride; the indium-based oxide catalyst, carbon black, and polyvinylidene fluoride are mixed by grinding, NMP solvent is added, and continuous stirring is performed for 12 hours to obtain the modification coating. The indium-based oxide catalyst is prepared by the following preparation method: Step one: indium nitrate, isophthalic acid, DMF, acetonitrile, imidazole, and nitric acid are added to a reaction kettle, and reaction is performed at 80°C for 12 hours, and then heated to 100°C for 24 hours, washed with DMF and anhydrous ethanol, and vacuum dried for 12 hours to obtain an In-MOF precursor; Step two: the In-MOF precursor is kept at 200-600°C for 4 hours under a nitrogen atmosphere, and naturally cooled to room temperature to obtain the indium-based oxide catalyst.

2. A finish as defined in claim 1, wherein The weight ratio of the indium-based oxide catalyst, carbon black, and polyvinylidene fluoride is 2-4:5-7:

1.

3. A finish according to claim 1, characterised in that In step one, the weight / volume ratio of indium nitrate, isophthalic acid, DMF, acetonitrile, imidazole, and nitric acid is 0.9-2.7g:0.9-2.7g:3-10mL:3-10mL:0.6-6mL:0.6-6mL.

4. The finish of claim 1 wherein, In step two, the In-MOF precursor is kept at 200°C for 2 hours under a nitrogen atmosphere, and then heated to 500°C for 2 hours at a heating rate of 5°C / min.

5. A modified separator, characterized by, The modification coating of claim 1 is uniformly coated on the separator by a 200μm doctor blade, and dried at 60°C under vacuum for 6-12 hours.

6. A modified separator as defined in claim 5, characterized in that The separator is a PP separator.

7. A lithium-sulfur battery, characterized by, The modification separator includes the modification coating of claim 1 coated on one side facing the positive electrode.

Images