Indium-based heterogeneous complex, preparation method and application

Abstract

The present invention discloses an indium-based heterogeneous composite, preparation method, and application. The indium-based heterogeneous composite comprises: In2O3, a hexagonal hollow tube that provides In / O sites; and ZnIn2S4, a two-dimensional sheet grown on the inner and outer surfaces of the In2O3 tube, providing Zn / In sites. The indium-based heterogeneous composite is a multifunctional catalytic ZnIn2S4@In2O3 catalyst, composed of highly adsorbed In2O3 and highly conductive and catalytically active ZnIn2S4. This ensures rapid capture-conversion of LiPSs (Lithium Polystyrene Polystyrene Sulfur) and improves the cycling stability of lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur battery materials, and in particular relates to a preparation method of an indium-based modified diaphragm with multifunctional catalysis and application thereof in lithium-sulfur batteries. Background Art

[0002] Lithium-sulfur (Li-S) batteries have a high theoretical energy density (2600Whkg -1 ), low cost, and environmental friendliness, it is considered to be the most promising next-generation secondary battery. However, the inherent defects of lithium-sulfur batteries limit their practical application, including: 1) poor conductivity of sulfur and intermediate product LiPSs (LiPSs), resulting in slow reaction kinetics of sulfur redox reaction (SRR); 2) the shuttle effect of LiPSs leads to rapid capacity decay and negative electrode corrosion; 3) the volume expansion of sulfur during charge and discharge leads to positive electrode pulverization. Among them, solving the shuttle effect of LiPSs is the top priority for the commercialization of lithium-sulfur batteries. Therefore, it is of great significance to develop a more effective strategy to inhibit the shuttling of LiPSs.

[0003] To address these issues, various strategies have been employed to improve sulfur electrochemistry, including the use of conductive host materials, binder modification, lithium anode protection, electrolyte modification, and functionalized separator modification. Among these, the introduction of functional interlayers or separator modification is one of the most promising strategies for blocking LiPS migration without affecting Li+ transport. Simultaneously, catalysis has been introduced into Li-S batteries, accelerating the conversion of LiPSs to insoluble products and considered one of the most effective strategies for suppressing the shuttle effect. To ensure rapid conversion of LiPSs, catalysts should simultaneously possess high adsorption capacity for LiPSs, good electron transfer conductivity, and high catalytic activity to enhance conversion kinetics. However, it is difficult to simultaneously impart these properties in a single catalyst. For example, metal oxides such as TiO2, Fe3O4, In2O3, and Co3O4 have a strong affinity for LiPSs but poor conductivity. Sulfides such as SnS2, MoS2, and Co3S4 generally exhibit good conductivity and catalytic performance but have weak adsorption capacity for LiPSs. The functional separator obtained by combining it with a commercial separator has a single function, poor conversion efficiency of LiPSs, and cannot fundamentally solve the "shuttle effect" of LiPSs in lithium-sulfur batteries. Therefore, a multifunctional composite catalyst, ZnIn2S4@In2O3, which can be constructed from two or more substances to form a new catalyst with high adsorption, high conductivity and high catalytic activity, has been proposed as a sulfur electrochemical catalyst. Its use in lithium-sulfur battery separator modification can ensure the smooth capture and conversion of LiPSs. Summary of the Invention

[0004] In response to the problems of the prior art, the present invention proposes an indium-based heterogeneous complex, a preparation method, a modified coating, a modified diaphragm and a lithium-sulfur battery. The indium-based heterogeneous complex is a multifunctional catalytic ZnIn2S4@In2O3 catalyst, which is composed of In2O3 with high adsorption and ZnIn2S4 with high catalytic activity. It can ensure the rapid capture-conversion of LiPSs and improve the cycle stability of the lithium-sulfur battery.

[0005] The technical solution is as follows:

[0006] One of the objects of the present invention is to provide an indium-based heterocomposite, comprising:

[0007] In2O3, a hexagonal hollow tube, provides In / O sites;

[0008] ZnIn2S4 is a two-dimensional sheet that grows on the inner and outer surfaces of the In2O3 tube, providing Zn / In sites.

[0009] A second object of the present invention is to provide a method for preparing an indium-based heterogeneous complex, which is prepared by a three-step solvothermal-pyrolysis-hydrothermal method, wherein a hexagonal MIL-68 precursor is obtained by solvothermal method; the hexagonal MIL-68 precursor is calcined under an inert gas, the organic ligand is partially decomposed by heat, and metal oxides are formed in situ on its carbon skeleton to form a hollow tubular In2O3; and a two-dimensional sheet ZnIn2S4 is self-grown on the inner and outer surfaces of the hollow tubular In2O3 by a low-temperature hydrothermal method to obtain a ZnIn2S4@In2O3 composite material, which comprises the following steps:

[0010] The MIL-68(In) precursor was calcined in a muffle furnace and then cooled to obtain light yellow powder In2O3;

[0011] Light yellow powder In2O3 and an appropriate amount of acidic deionized water were mixed and stirred, and zinc source, indium source and sulfur source were added in sequence. After stirring evenly, the mixture was heated at 80°C for 2h using a low-temperature hydrothermal method to obtain an indium-based heterogeneous complex.

[0012] The preparation method of the above-mentioned MIL-68(In) precursor is as follows:

[0013] In(NO3)3·xH2O, PTA and DMF were added to the container in sequence, stirred evenly and placed in a 120°C oil bath for 3 h. After cooling naturally to room temperature, the product was centrifuged and washed several times with anhydrous ethanol to obtain the MIL-68 precursor, which was then transferred to a 60°C vacuum oven for vacuum drying for later use.

[0014] A third object of the present invention is to provide an indium-based heterogeneous composite modified coating, comprising:

[0015] adhesive

[0016] Conductive carbon black

[0017] and the above-mentioned indium-based heterocomplex.

[0018] A fourth object of the present invention is to provide an indium-based heterocomplex modified diaphragm, comprising:

[0019] PP diaphragm;

[0020] and the above-mentioned indium-based heterogeneous complex modified coating, which is coated on the PP separator.

[0021] A fifth object of the present invention is to provide a lithium-sulfur battery, comprising:

[0022] positive electrode, electrolyte, negative electrode; and

[0023] The above-mentioned indium-based heterogeneous complex modifies the diaphragm, and the diaphragm is arranged between the positive electrode and the negative electrode, and the coating faces the positive electrode.

[0024] The present invention loads a composite of ZnIn2S4@In2O3, SupperP (conductive carbon black) and PVDF (binder) on the positive electrode side of a polypropylene membrane (PP), physically restricts LiPSs by improving the pore size of the membrane itself, and synergistically suppresses the "shuttle effect" of LiPSs with the chemical adsorption and electrocatalytic performance of ZnIn2S4@In2O3 loaded on the membrane, thereby improving the cycle stability of the lithium-sulfur battery. The technical principles are as follows: First, In2O3 containing In / O sites can accelerate the conversion of S8 to LiPSs during discharge; second, ZnIn2S4 containing Zn / In sites can effectively catalyze the conversion of long-chain LiPSs to Li2S, and the two-dimensional sheet-like ZnIn2S4 network structure with good conductivity shortens the lithium ion migration distance and provides more catalytic active sites; at the same time, new adsorption sites are re-exposed, realizing the self-cleaning function of the active sites and continuously anchoring LiPSs; third, during the charging stage, due to the strong interaction between the Zn / In active sites and Li2S, ZnIn2S4 further promotes the decomposition of Li2S. The combined effect of the above factors can effectively chemically anchor and catalyze LiPSs, and provide a large number of active sites on the membrane surface, efficiently catalyzing the conversion between LiPSs.

[0025] The beneficial effects of the present invention are as follows: (1) The functional modified layer material of the diaphragm with electrocatalytic function of the present invention provides more catalytic active sites and exhibits selective catalytic function for LiPSs: In2O3 containing In / O sites can accelerate the conversion of S8 to LiPs during discharge; at the same time, ZnIn2S4 containing Zn / In sites can effectively catalyze the conversion of long-chain LiPSs to Li2S. It also helps to reduce the decomposition energy barrier of Li2S during the catalytic process;

[0026] (2) The three-dimensional conductive network structure composed of polar In2O3 nanoparticles and two-dimensional ZnIn2S4 nanosheets with excellent conductivity contained in the functional modification layer material of the diaphragm with electrocatalytic function of the present invention provides a lithium ion diffusion path, shortens the lithium ion migration energy barrier, and has a rapid adsorption-conversion effect on LiPSs generated during the cycle;

[0027] (3) The diaphragm with electrocatalytic function of the present invention has extraordinary electrolyte affinity and mechanical strength. The former is conducive to the rapid and uniform infiltration of the electrolyte, thereby facilitating the rapid diffusion of lithium ions; the latter can effectively alleviate the volume expansion of the electrode material during the charge and discharge process, avoid the pulverization and failure of the electrode structure, and extend the battery life;

[0028] (4) The lithium-sulfur battery assembled with the diaphragm having electrocatalytic function of the present invention has greatly improved cycle stability and rate performance, and the preparation process of the functional diaphragm of the present invention is simple and easy to operate, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the XRD pattern of the ZnIn2S4@In2O3 heterostructure composite material prepared in Example 1;

[0030] Figure 2 is a SEM image of the ZnIn2S4@In2O3 heterostructure composite material prepared in Example 1;

[0031] Figure 3 is a TEM image of the ZnIn2S4@In2O3 heterostructure composite material prepared in Example 1;

[0032] Figure 4 is a digital photograph of the ZnIn2S4@In2O3-modified membrane prepared in Example 1;

[0033] Figure 5 is the SEM image of the ZnIn2S4@In2O3-modified diaphragm prepared in Example 1 after cycling;

[0034] Figure 6 This is a graph showing the cycling performance of a lithium-sulfur battery assembled with a ZnIn2S4@In2O3-modified separator prepared in Example 1;

[0035] Figure 7 This is a rate performance diagram of a lithium-sulfur battery assembled with a ZnIn2S4@In2O3-modified diaphragm prepared in Example 1. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0037] Example 1

[0038] (1) 160 mg of sulfur (S) and 20 mg of carbon black (CB) were weighed and mixed at a ratio of 8:1, then ground thoroughly. The mixture was then incubated in a tube furnace at 155°C under a nitrogen atmosphere for 12 h to obtain a C / S cathode. The cathode was then mixed with LA133 binder at a mass ratio of 9:1 and an appropriate solvent (n-propanol:water = 3:1) was added to form a uniform slurry. The slurry was then coated on aluminum foil and dried in a vacuum at 60°C to obtain a C / S electrode for later use.

[0039] (2) Preparation of ZnIn2S4@In2O3 composite material: First, 180 mg of In(NO3)3·xH2O and PTA (terephthalic acid) were weighed and added to a 250 mL round-bottom flask, followed by the addition of 120 mL of DMF (dimethylformamide) and stirring on a magnetic stirrer for 10 min. The mixture was then placed in a 120°C oil bath for 3 h. After cooling naturally to room temperature, the mixture was centrifuged and washed several times with anhydrous ethanol to obtain the desired product, MIL-68(In), which was then placed in a 60°C vacuum oven for vacuum drying. Subsequently, the prepared MIL-68(In) was transferred to a muffle furnace, calcined at 120°C for 2 h, and then calcined at 500°C for 2 h, with a heating rate of 5°C min -1 . After cooling naturally to room temperature, the light yellow powder was collected, which was hexagonal hollow tubular In2O3. Finally, 22.5 mg of hollow tubular In2O3 and 30 mL of deionized water (pH = 2.5) were weighed and added to a 30 mL glass bottle and stirred evenly on a magnetic stirrer for 30 minutes. 81.6 mg of ZnCl2, 132.6 mg of InCl3 and 30 mg of TAA were added thereto in turn. After stirring for another 10 minutes, the mixture was transferred to an oil bath at 80°C and kept warm for 2 hours. Continuous stirring was maintained during the insulation period. After cooling naturally and standing, the supernatant was poured out, and the precipitate was filtered and washed 3 times with deionized water and anhydrous ethanol. Finally, it was vacuum dried at 60°C in a vacuum drying oven to obtain the ZnIn2S4@In2O3 composite material.

[0040] Figure 1 The XRD pattern of ZnIn2S4@In2O3 heterostructure composite material is shown in Figure 2. Figure 1 It can be observed that the ZnIn2S4@In2O3 composite material exhibits characteristic peaks of In2O3 and ZnIn2S4, which fully demonstrates the successful preparation of the ZnIn2S4@In2O3 heterostructure composite material.

[0041] Figure 2 is the SEM image of the ZnIn2S4@In2O3 heterostructure composite material; Figure 3 This is the TEM image of the ZnIn2S4@In2O3 heterostructure composite material; Figure 2 and Figure 3 The SEM and TEM images show that two-dimensional sheet-like ZnIn2S4 grows evenly on both sides of the hollow In2O3 tube, forming a well-defined ZnIn2S4@In2O3 heterostructure composite material.

[0042] (3) Preparation of ZnIn2S4@In2O3-modified membrane and assembly of lithium-sulfur battery: 40 mg ZnIn2S4@In2O3, 140 mg CB and 20 mg PVDF were weighed in a ratio of 2:7:1, added to a mortar and ground thoroughly, and then transferred to a weighing bottle. An appropriate amount of NMP solvent was added and stirred continuously on a magnetic stirrer to obtain a uniform slurry. The obtained slurry was evenly coated on a commercial membrane with a 200 μm scraper and vacuum dried at 60 ° C for 12 h to obtain a ZnIn2S4@In2O3-modified membrane. The loading amount of ZnIn2S4@In2O3 on the modified membrane was 0.6 mg cm -2 .

[0043] The Li-S battery assembly process is as follows: The cut positive electrode sheets and separator are placed in a glove box. CR2032 button cells are then assembled in the following order: positive electrode shell, positive electrode, electrolyte, separator, electrolyte, negative electrode, gasket, spring, and negative electrode shell. The electrolyte used is 1M LiTFSI, DME:DOL = 1:1 V%, and 0.1M LiNO3.

[0044] The charge and discharge performance of the assembled button batteries were tested at room temperature using a LandCT2001A battery testing system and a CHI760E electrochemical workstation.

[0045] Figure 4 This is a digital photo of the ZnIn2S4@In2O3-modified diaphragm. Figure 5 This is the SEM image of the ZnIn2S4@In2O3-modified membrane after cycling. It can be seen that the slurry formed by ZnIn2S4@In2O3 is evenly coated on one side of the commercial PP membrane surface.

[0046] Figure 6 The cycle performance diagram of lithium-sulfur battery assembled with ZnIn2S4@In2O3-modified separator is shown in Figure 1. Figure 6 It can be seen that the lithium-sulfur battery assembled with ZnIn2S4@In2O3-modified membrane maintains a capacity of 369.8mAh / g after 1000 cycles at a high current density of 2C, and the capacity decay rate is only 0.021% during the last 800 cycles.

[0047] Figure 7This is a graph showing the rate performance of a lithium-sulfur battery assembled with a ZnIn2S4@In2O3-modified separator. The lithium-sulfur battery assembled with a ZnIn2S4@In2O3-modified separator released a high discharge capacity of 665.6 mAh / g at 2C, and when the current density returned from 2C to 0.1C, the discharge capacity gradually recovered to 960.5 mAh / g.

[0048] Example 2

[0049] (1) 160 mg of S and 20 mg of CB were weighed and mixed at a ratio of 8:1, and the mixture was thoroughly ground. The mixture was then incubated in a tube furnace at 155°C under a nitrogen atmosphere for 12 h to obtain a C / S cathode. The cathode was then mixed with LA133 binder at a mass ratio of 9:1 and an appropriate solvent (n-propanol:water = 3:1) was added to form a uniform slurry. The slurry was then coated on aluminum foil and dried in a vacuum at 60°C to obtain a C / S electrode for later use.

[0050] (2) Preparation of ZnIn2S4@In2O3 composite material: First, 180 mg of In(NO3)3·xH2O and PTA were weighed and added to a 250 mL round-bottom flask, followed by the addition of 120 mL of DMF and stirring on a magnetic stirrer for 10 min. The mixture was then placed in a 120°C oil bath for 3 h. After cooling naturally to room temperature, the mixture was centrifugally washed several times with anhydrous ethanol to obtain the desired product, MIL-68(In), which was then placed in a 60°C vacuum oven for vacuum drying. Subsequently, the prepared MIL-68(In) was transferred to a muffle furnace, calcined at 120°C for 2 h, and then calcined at 500°C for 2 h, with a heating rate of 5°C min -1 . After cooling naturally to room temperature, the light yellow powder collected is hexagonal hollow tubular In2O3. Finally, 45 mg of hollow tubular In2O3 and 30 mL of deionized water (pH = 2.5) were weighed and added to a 30 mL glass bottle and stirred evenly on a magnetic stirrer for 30 minutes. ZnCl2 (81.6 mg), InCl3 (132.6 mg) and TAA (30 mg) were added thereto in turn. After stirring for another 10 minutes, the mixture was transferred to an oil bath at 80°C and kept warm for 2 hours. Continuous stirring was maintained during the insulation period. After cooling naturally and standing, the supernatant was poured out, and the precipitate was filtered and washed 3 times with deionized water and anhydrous ethanol. Finally, it was vacuum dried at 60°C in a vacuum drying oven to obtain the ZnIn2S4@In2O3 composite material.

[0051] (3) Preparation of ZnIn2S4@In2O3-modified membrane and assembly of lithium-sulfur battery: 40 mg, 140 mg, and 20 mg of ZnIn2S4@In2O3, CB, and PVDF were weighed in a ratio of 2:7:1, respectively, added to a mortar, and ground thoroughly. After that, they were transferred to a weighing bottle, to which an appropriate amount of NMP solvent was added and stirred continuously on a magnetic stirrer to obtain a uniform slurry. The obtained slurry was evenly coated on a commercial membrane with a 200 μm scraper, and vacuum dried at 60 ° C for 12 h to obtain a ZnIn2S4@In2O3-modified membrane. The loading amount of ZnIn2S4@In2O3 on the modified membrane was 0.6 mg cm -2 .

[0052] The Li-S battery assembly process is as follows: The cut positive electrode sheets and separator are placed in a glove box. CR2032 button cells are then assembled in the following order: positive electrode shell, positive electrode, electrolyte, separator, electrolyte, negative electrode, gasket, spring, and negative electrode shell. The electrolyte used is 1M LiTFSI, DME:DOL = 1:1 V%, and 0.1M LiNO3.

[0053] Example 3

[0054] (1) 160 mg of S and 20 mg of CB were weighed and mixed at a ratio of 8:1, and the mixture was thoroughly ground. The mixture was then incubated in a tube furnace at 155°C under a nitrogen atmosphere for 12 h to obtain a C / S cathode. The cathode was then mixed with LA133 binder at a mass ratio of 9:1 and an appropriate solvent (n-propanol:water = 3:1) was added to form a uniform slurry. The slurry was then coated on aluminum foil and dried in a vacuum at 60°C to obtain a C / S electrode for later use.

[0055] (2) Preparation of ZnIn2S4@In2O3 composite material: First, 180 mg of In(NO3)3·xH2O and PTA were weighed and added to a 250 mL round-bottom flask, followed by the addition of 120 mL of DMF and stirring on a magnetic stirrer for 10 min. The mixture was then placed in a 120°C oil bath for 3 h. After cooling naturally to room temperature, the mixture was centrifugally washed several times with anhydrous ethanol to obtain the desired product, MIL-68(In), which was then placed in a 60°C vacuum oven for vacuum drying. Subsequently, the prepared MIL-68(In) was transferred to a muffle furnace, calcined at 120°C for 2 h, and then calcined at 500°C for 2 h, with a heating rate of 5°C min -1. After cooling naturally to room temperature, the light yellow powder collected is hexagonal hollow tubular In2O3. Finally, 12 mg of hollow tubular In2O3 and 30 mL of deionized water (pH = 2.5) are weighed and added to a 30 mL glass bottle and stirred evenly on a magnetic stirrer for 30 minutes. ZnCl2 (81.6 mg), InCl3 (132.6 mg) and TAA (30 mg) are added thereto in turn. After stirring for another 10 minutes, the mixture is transferred to an oil bath at 80°C and kept warm for 2 hours. Continuous stirring is still maintained during the insulation period. After cooling naturally and standing, the supernatant is poured out, and the precipitate is filtered and washed 3 times with deionized water and anhydrous ethanol. Finally, it is vacuum dried at 60°C in a vacuum drying oven to obtain the ZnIn2S4@In2O3 composite material.

[0056] (3) Preparation of ZnIn2S4@In2O3-modified membrane and assembly of lithium-sulfur battery: 40 mg, 140 mg, and 20 mg of ZnIn2S4@In2O3, CB, and PVDF were weighed in a ratio of 2:7:1, respectively, added to a mortar, and ground thoroughly. After that, they were transferred to a weighing bottle, to which an appropriate amount of NMP solvent was added and stirred continuously on a magnetic stirrer to obtain a uniform slurry. The obtained slurry was evenly coated on a commercial membrane with a 200 μm scraper, and vacuum dried at 60 ° C for 12 h to obtain a ZnIn2S4@In2O3-modified membrane. The loading amount of ZnIn2S4@In2O3 on the modified membrane was 0.6 mg cm -2 The Li-S battery assembly process is as follows: Place the cut positive electrode sheet and separator in a glove box. Then, assemble the CR2032 button cell in the following order: positive electrode shell, positive electrode, electrolyte, separator, electrolyte, negative electrode, gasket, spring, and negative electrode shell. The electrolyte used is 1M LiTFSI, DME:DOL = 1:1V%, and 0.1M LiNO3.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same.

Claims

1. A lithium-sulfur battery, characterized in that include: cathode, electrolyte, anode and indium-based heterogeneous composite modified separator; The indium-based heterogeneous complex modified separator includes a PP separator and an indium-based heterogeneous complex modified coating, wherein the indium-based heterogeneous complex modified coating is coated on the PP separator, and the PP separator is arranged between the positive electrode and the negative electrode, and the indium-based heterogeneous complex modified coating faces the positive electrode; The indium-based heterogeneous composite modified coating comprises a binder, conductive carbon black, and an indium-based heterogeneous composite; The indium-based heterogeneous composite comprises: In2O3, which is a hexagonal hollow tube that provides In / O sites; and ZnIn2S4 is a two-dimensional sheet that grows on the inner and outer surfaces of the In2O3 tube, providing Zn / In sites.

2. The lithium-sulfur battery according to claim 1, characterized in that The method for preparing the indium-based heterogeneous composite comprises the following steps: The In-MIL-68 precursor was calcined in a muffle furnace and then cooled to obtain light yellow powder In2O3; Light yellow powder In2O3 and an appropriate amount of acidic deionized water were mixed and stirred, and zinc source, indium source and sulfur source were added in sequence. After stirring evenly, the mixture was heated at 80℃ for 2 h by low-temperature hydrothermal method to obtain indium-based heterogeneous complex.

3. The lithium-sulfur battery according to claim 2, characterized in that The preparation method of the In-MIL-68 precursor is as follows: In(NO3)3·xH2O, PTA and DMF were added to the container in sequence, stirred evenly and placed in a 120℃ oil bath for 3 h. After cooling naturally to room temperature, the product was centrifuged and washed several times with anhydrous ethanol to obtain the MIL-68 precursor, which was then transferred to a 60℃ vacuum oven for vacuum drying.

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