Preparation method of Co9S8 / ZnS@C microrod composite material as negative electrode material for lithium-ion / sodium-ion batteries

Abstract

The present invention belongs to the field of electrochemistry and battery technology and is a negative electrode material for lithium ion / sodium ion batteries and a preparation method thereof. A negative electrode material for lithium ion / sodium ion batteries and a preparation method thereof include the following steps: (1) dissolving ZnSO4 and CoSO4 in a mixed solution of ethylene glycol and deionized water, adding H2C2O4·2H2O, stirring, and hydrothermally treating in an autoclave to obtain a ZnCo2(C2O4)3 micron rod precursor; (2) adding a certain amount of dopamine hydrochloride to carbon-coat the precursor to obtain ZnCo2(C2O4)3@PDA; and (3) calcining a sulfur source and ZnCo2(C2O4)3@PDA in a quartz calcined boat in an inert reducing atmosphere and naturally cooling to obtain a lithium ion / sodium ion battery Co9S8 / ZnS@C micron rod composite material.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a cobalt-zinc bimetallic sulfide negative electrode material for lithium-ion / sodium-ion batteries and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices and hybrid vehicles due to their high energy density, long cycle life, and environmental friendliness. As an important component of lithium-ion batteries, negative electrode materials play a key role in improving the energy density of lithium-ion batteries. However, the low specific capacity of traditional commercial graphite negative electrode materials cannot meet the needs of high-energy-density lithium-ion batteries. Therefore, the development of new negative electrode materials with high specific capacity is particularly important. However, with the widespread application of lithium-ion batteries, people have gradually realized the limitations brought about by the scarcity of lithium resources and the rising cost of batteries. Sodium has similar physical and chemical properties to lithium, and its resources are abundant and the cost is low. Therefore, sodium-ion batteries are considered to be the next generation of potential secondary energy storage batteries.

[0003] Sodium-ion batteries consist of five major components: a positive electrode, a negative electrode, electrolyte, separator, and casing. The negative electrode material plays a key role in the battery's energy density and electrochemical performance. However, sodium ions have a weak interaction with graphite layers, making it difficult for them to form stable intercalation compounds with graphite, resulting in a low sodium storage capacity. Therefore, developing a high-performance negative electrode material for sodium-ion batteries is a key factor in advancing their development.

[0004] Cobalt-based sulfides have become a research hotspot for anode materials due to their various advantages, including high capacity, diverse chemical compositions, and unique crystal structures. However, their poor electronic conductivity and large volume changes during lithium insertion and extraction lead to poor structural stability during charge and discharge. This causes separation of the material from the current collector and repeated reactions with the electrolyte, resulting in poor cycling and rate performance, which seriously hinders their practical application. Therefore, it is extremely important to develop cobalt-based sulfides with high specific capacity, good cycling stability, and long cycle life. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a Co9S8 / ZnS@C microrod composite material, a negative electrode material for lithium / sodium ion batteries with high stability and long cycle life.

[0006] The technical solution adopted by the present invention to further solve the technical problem is:

[0007] A method for preparing a Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium / sodium ion batteries comprises the following steps:

[0008] (1) ZnSO4 and CoSO4 were dissolved in a mixture of ethylene glycol and deionized water, H2C2O4·2H2O was added, stirred, and hydrothermally treated in an autoclave to obtain a ZnCo2(C2O4)3 micron rod precursor;

[0009] (2) Weigh a certain amount of ZnCo2(C2O4)3 micron rods and add them to a solution of dopamine hydrochloride and anhydrous ethanol, stirring for 10-30 minutes;

[0010] (3) adding a certain amount of ammonia solution to the mixed solution obtained in step (2) and continuing stirring for 4-8 hours. After stirring is completed, filtering, washing, and drying to obtain ZnCo2(C2O4)3@PDA;

[0011] (4) The ZnCo2(C2O4)3@PDA obtained in step (3) is placed in a ceramic ark near the gas outlet, and a sulfur source is placed in the ceramic ark near the gas inlet. Then, after the tubular furnace is sealed, an inert reducing gas is introduced for calcination to obtain a Co9S8 / ZnS@C microrod composite material.

[0012] In the present invention, preferably, in step (1), the molar ratio of ZnSO4 to CoSO4 is 1:1.5-2.5.

[0013] In the present invention, preferably, in step (1), the temperature of the hydrothermal treatment is 100-150° C., and the time is 10-24 h.

[0014] In the present invention, preferably, in step (1), the volume ratio of ethylene glycol to deionized water is 3-5:1.

[0015] In the present invention, preferably, in step (4), the sulfur source is one or more of sulfur powder, thiourea, thioacetamide and ammonium sulfide.

[0016] In the present invention, preferably, in step (4), the mass ratio of the sulfur source to ZnCo2(C2O4)3@PDA is 3-8:1, the calcination time is 500-700°C, the time is 2-5h, and the heating rate is 1-5°C / min.

[0017] The present invention forms a Co9S8 / ZnS@C microrod composite material with a heterojunction structure by atomic-scale mixing. The introduction of ZnS forms a heterojunction structure with Co9S8. The heterojunction structure can generate a built-in electric field and improve the Li + / Na +The carbon shell further enhances the conductivity of the composite material and suppresses the volume change of the Co9S8 / ZnS during charge and discharge. The material prepared by this invention is an ideal anode material for lithium-ion and sodium-ion batteries with great application prospects.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] (1) The Co9S8 / ZnS@C microrod composite material prepared by the present invention is a negative electrode material for lithium / sodium ion batteries. The prepared Co9S8 / ZnS@C microrod composite material has a diameter of 2-4 μm, high purity, strong crystallinity, and uniform morphology;

[0020] (2) The Co9S8 / ZnS@C microrod composite material obtained by the present invention is made into a lithium / sodium ion battery electrode, which can achieve high specific capacity, excellent cycle performance and rate performance;

[0021] (3) The solvent thermal method, in-situ polymerization and solid phase vulcanization methods used in the present invention have short processes, simple processes, cheap and readily available raw materials, high yields, and uniform and easily controllable product structures and morphologies, meeting the requirements of large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD pattern of the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention.

[0023] Figure 2 This is the SEM image of the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention.

[0024] Figure 3 This is the first charge and discharge curve of the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention after being made into a lithium-ion battery.

[0025] Figure 4 This is a graph showing the cycling performance of a lithium-ion battery made from the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention at a current density of 200 mA / g.

[0026] Figure 5 This is a graph showing the cycling performance of a lithium-ion battery made from the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention at a current density of 1 A / g.

[0027] Figure 6 This is the first charge and discharge curve of the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention after being made into a sodium ion battery.

[0028] Figure 7 This is a graph showing the cycling performance of a sodium ion battery made from the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention at a current density of 200 mA / g.

[0029] Figure 8 This is a cycling performance diagram of a sodium ion battery made from the Co9S8 / ZnS@C microrod composite material obtained in Example 1 of the present invention at a current density of 500 mA / g. DETAILED DESCRIPTION

[0030] In order to express the present invention more clearly, the present invention is further described below through examples.

[0031] Example 1

[0032] (1) 0.29 g ZnSO4·7H2O and 0.58 g CoSO4·7H2O were weighed and dissolved in a mixed solution of 30 mL ethylene glycol and 10 mL deionized water. 0.39 g H2C2O4·2H2O was added and stirred for 0.5 h. The mixed solution was transferred to an autoclave and hydrothermally treated at 120 °C for 20 h. The obtained solution was then filtered, washed, and dried to obtain a ZnCo2(C2O4) 3-μm rod precursor.

[0033] (2) Weigh 0.5 g of ZnCo2(C2O4) 3-μm rods and add them to 80 ml of deionized water. Ultrasonicate for 30 min to disperse them evenly.

[0034] (3) Weigh 0.5 g of dopamine hydrochloride and 25 ml of anhydrous ethanol and add them to the suspension obtained in step (3) in sequence, and continue stirring for 30 minutes;

[0035] (4) 10 ml of ammonia solution was added to the mixed solution obtained in step (3), and the mixture was stirred for 6 h. After the stirring was completed, the mixture was filtered, washed, and dried to obtain ZnCo2(C2O4)3@PDA;

[0036] (5) The ZnCo2(C2O4)3@PDA obtained in step (4) is placed in the ceramic ark near the air outlet, and thiourea is placed in the ceramic ark near the air inlet, with the mass ratio of thiourea to ZnCo2(C2O4)3@PDA being 3.5:1. The tubular furnace is sealed and an inert reducing gas is introduced, and the mixture is heated at 600°C for 5 hours and naturally cooled to room temperature to obtain a Co9S8 / ZnS@C microrod composite material.

[0037] The Co9S8 / ZnS@C microrod composite material obtained in Example 1 was subjected to XRD analysis. The XRD analysis results are shown in FIG. Figure 1 ,from Figure 1It can be seen that there are two phases of Co9S8 and ZnS in the Co9S8 / ZnS@C microrod composite material.

[0038] The Co9S8 / ZnS@C microrod composite material obtained in Example 1 was subjected to SEM analysis. The SEM analysis structure is as follows: Figure 2 , it can be seen that the Co9S8 / ZnS@C composite material presents a micron-scale rod-like structure.

[0039] 0.015g of CMC as a binder was weighed and added to deionized water with stirring to dissolve. Then, 0.075g of the prepared Co9S8 / ZnS@C composite material and 0.015g of acetylene black as a conductive agent were added and stirred for 8 hours to form a uniform suspension. The slurry was then drawn onto copper foil to form a sheet, which was then dried in an 80°C oven. In an argon-filled glove box, CR2032 button cells were assembled using metal lithium / sodium sheets as counter electrodes.

[0040] At 25°C, constant current charge and discharge cycle tests were carried out in the voltage range of 0.01-3.0V at a current density of 200mA / g. When used as a negative electrode material for lithium-ion batteries, the obtained Co9S8 / ZnS@C has an initial discharge capacity of 1436.7mAh / g and a charge capacity of 1147.3mAh / g. The initial charge and discharge curve of the battery is shown in Figure 2. Figure 3 As shown. Figure 4 As shown in Figure 2, after 200 cycles at a current density of 200 mA / g at 25°C, its reversible specific capacity is 767.4 mAh / g. Figure 5 As shown, after 500 cycles at a current density of 1 A / g at 25°C, its reversible specific capacity is 618.9 mAh / g, with high capacity retention and good stability, showing excellent electrochemical performance.

[0041] At 25°C, constant current charge and discharge cycle tests were carried out in the voltage range of 0.01-3.0V at a current density of 200mA / g. When used as a negative electrode material for sodium ion batteries, the obtained Co9S8 / ZnS@C has an initial discharge capacity of 740.6mAh / g and a charge capacity of 390.2mAh / g. The initial charge and discharge curve of the battery is shown in Figure 2. Figure 6 As shown. Figure 7 As shown in Figure 2, after 200 cycles at a current density of 200 mA / g at 25°C, its reversible specific capacity is 328.6 mAh / g. Figure 8 As shown in Figure 3, after 500 cycles at a current density of 500 mA / g at 25°C, its reversible specific capacity is 251.3 mAh / g.

[0042] Example 2

[0043] (1) 0.29 g ZnSO4·7H2O and 0.58 g CoSO4·7H2O were weighed and dissolved in a mixed solution of 40 mL ethylene glycol and 10 mL deionized water. 0.39 g H2C2O4·2H2O was added and stirred for 1 h. The mixed solution was transferred to an autoclave and hydrothermally treated at 150 °C for 12 h. The obtained solution was then filtered, washed, and dried to obtain a ZnCo2(C2O4) 3-μm rod precursor.

[0044] (2) Weigh 0.25 g of ZnCo2(C2O4) 3-μm rods and add them to 60 ml of deionized water. Ultrasonicate for 30 min to disperse them evenly.

[0045] (3) Weigh 0.5 g of dopamine hydrochloride and 25 ml of anhydrous ethanol and add them to the suspension obtained in step (3) in sequence, and continue stirring for 30 minutes;

[0046] (4) 10 ml of ammonia solution was added to the mixed solution obtained in step (3), and the mixture was stirred for 6 h. After the stirring was completed, the mixture was filtered, washed, and dried to obtain ZnCo2(C2O4)3@PDA;

[0047] (5) The ZnCo2(C2O4)3@PDA obtained in step (4) is placed in the ceramic ark near the air outlet, and thiourea is placed in the ceramic ark near the air inlet. The mass ratio of thioacetamide to ZnCo2(C2O4)3@PDA is 6:1. The tubular furnace is sealed and an inert reducing gas is introduced. The mixture is heated at 700°C for 5 hours and naturally cooled to room temperature to obtain a Co9S8 / ZnS@C microrod composite material.

[0048] 0.015g of CMC as a binder was weighed and added to deionized water with stirring to dissolve. Then, 0.075g of the prepared Co9S8 / ZnS@C composite material and 0.015g of acetylene black as a conductive agent were added and stirred for 8 hours to form a uniform suspension. The slurry was then drawn onto copper foil to form a sheet, which was then dried in an 80°C oven. In an argon-filled glove box, CR2032 button cells were assembled using metal lithium / sodium sheets as counter electrodes.

[0049] Constant current charge-discharge cycling tests were conducted at 25°C at a current density of 200mA / g in the voltage range of 0.01-3.0V. When used as a negative electrode material for lithium-ion batteries, the resulting Co9S8 / ZnS@C exhibited an initial discharge capacity of 1357.6mAh / g and a charge capacity of 1098.8mAh / g. After 200 cycles at a current density of 200mA / g at 25°C, its reversible capacity was 589.8mAh / g. After 500 cycles at a current density of 1A / g at 25°C, its reversible capacity was 445.5mAh / g, demonstrating high capacity retention and good stability, demonstrating excellent electrochemical performance.

[0050] Constant current charge-discharge cycling tests were conducted at 25°C at a current density of 200 mA / g in the voltage range of 0.01-3.0 V. When used as a negative electrode material for sodium-ion batteries, the resulting Co9S8 / ZnS@C exhibited an initial discharge capacity of 628 mAh / g and a charge capacity of 466.5 mAh / g. After 200 cycles at a current density of 200 mA / g at 25°C, its reversible capacity was 324.1 mAh / g. After 500 cycles at a current density of 500 mA / g at 25°C, its reversible capacity was 222.2 mAh / g.

[0051] Example 3

[0052] (1) 0.29 g ZnSO4·7H2O and 0.58 g CoSO4·7H2O were weighed and dissolved in a mixed solution of 40 mL ethylene glycol and 8 mL deionized water. 0.39 g H2C2O4·2H2O was added and stirred for 1 h. The mixed solution was transferred to an autoclave and hydrothermally treated at 130 °C for 20 h. The obtained solution was then filtered, washed, and dried to obtain a ZnCo2(C2O4) 3-μm rod precursor.

[0053] (2) Weigh 0.1 g of ZnCo2(C2O4) 3-μm rods and add them to 60 ml of deionized water. Ultrasonicate for 30 min to disperse them evenly.

[0054] (3) Weigh 0.3 g of dopamine hydrochloride and 25 ml of anhydrous ethanol and add them to the suspension obtained in step (3) in sequence, and continue stirring for 30 minutes;

[0055] (4) 10 ml of ammonia solution was added to the mixed solution obtained in step (3), and the mixture was stirred for 6 h. After the stirring was completed, the mixture was filtered, washed, and dried to obtain ZnCo2(C2O4)3@PDA;

[0056] (5) The ZnCo2(C2O4)3@PDA obtained in step (4) is placed in the ceramic ark near the air outlet, and thiourea is placed in the ceramic ark near the air inlet. The mass ratio of sulfur powder to ZnCo2(C2O4)3@PDA is 8:1. The tubular furnace is sealed and an inert reducing gas is introduced. The mixture is heated at 700°C for 3 hours and naturally cooled to room temperature to obtain a Co9S8 / ZnS@C microrod composite material.

[0057] The Co9S8 / ZnS@C microrod composite material obtained in Example 3 was subjected to XRD analysis. The XRD analysis structure showed that two phases, Co9S8 and ZnS, existed in the Co9S8 / ZnS@C microrod composite material.

[0058] The Co9S8 / ZnS@C microrod composite material obtained in Example 3 was subjected to SEM analysis. The SEM analysis results showed that the Co9S8 / ZnS@C composite material exhibited a micron-scale rod-like structure.

[0059] 0.015g of CMC as a binder was weighed and added to deionized water with stirring to dissolve. Then, 0.075g of the prepared Co9S8 / ZnS@C composite material and 0.015g of acetylene black as a conductive agent were added and stirred for 8 hours to form a uniform suspension. The slurry was then drawn onto copper foil to form a sheet, which was then dried in an 80°C oven. In an argon-filled glove box, CR2032 button cells were assembled using metal lithium / sodium sheets as counter electrodes.

[0060] Constant current charge-discharge cycling tests were conducted at 25°C at a current density of 200mA / g in the voltage range of 0.01-3.0V. When used as a negative electrode material for lithium-ion batteries, the resulting Co9S8 / ZnS@C exhibited an initial discharge capacity of 1453mAh / g and a charge capacity of 1119.3mAh / g. After 200 cycles at a current density of 200mA / g at 25°C, its reversible capacity was 696mAh / g. After 500 cycles at a current density of 1A / g at 25°C, its reversible capacity was 453mAh / g, demonstrating high capacity retention and good stability, demonstrating excellent electrochemical performance.

[0061] Constant current charge-discharge cycling tests were conducted at 25°C at a current density of 200 mA / g in the voltage range of 0.01-3.0 V. When used as a negative electrode material for sodium-ion batteries, the resulting Co9S8 / ZnS@C exhibited an initial discharge capacity of 631.6 mAh / g and a charge capacity of 472.2 mAh / g. After 200 cycles at a current density of 200 mA / g at 25°C, its reversible capacity was 323.7 mAh / g. After 500 cycles at a current density of 500 mA / g at 25°C, its reversible capacity was 288.3 mAh / g.

[0062] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing a Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium-ion / sodium-ion batteries, characterized in that: The following steps are involved: (1) ZnSO4 and CoSO4 were dissolved in a mixture of ethylene glycol and deionized water, H2C2O4·2H2O was added, stirred, and hydrothermally treated in an autoclave to obtain a ZnCo2(C2O4)3 micron rod precursor; (2) Weigh a certain amount of ZnCo2(C2O4)3 micron rod precursor and add it to a solution of dopamine hydrochloride and anhydrous ethanol, stirring for 10-30 minutes; (3) adding a certain amount of ammonia solution to the mixed solution obtained in step (2) and continuing stirring for 4-8 hours. After stirring is completed, filtering, washing, and drying to obtain ZnCo2(C2O4)3@PDA; (4) The ZnCo2(C2O4)3@PDA obtained in step (3) is placed in a ceramic ark near the gas outlet, and a sulfur source is placed in the ceramic ark near the gas inlet. Then, after the tubular furnace is sealed, an inert reducing gas is introduced for calcination to obtain a Co9S8 / ZnS@C microrod composite material.

2. The method for preparing the Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium / sodium ion batteries according to claim 1, characterized in that: In step (1), the molar ratio of ZnSO4 to CoSO4 is 1:1.5-2.

5.

3. The method for preparing the Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium / sodium ion batteries according to claim 1, characterized in that: In step (1), the volume ratio of ethylene glycol to deionized water is 3-5:

1.

4. The method for preparing the Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium / sodium ion batteries according to claim 1, characterized in that: In step (4), the sulfur source is one or more of sulfur powder, thiourea, thioacetamide and ammonium sulfide.

5. The method for preparing the Co9S8 / ZnS@C microrod composite material as a negative electrode material for lithium / sodium ion batteries according to claim 1, characterized in that: In step (4), the mass ratio of the sulfur source to ZnCo2(C2O4)3@PDA is 3-8:1, the calcination temperature is 500-700°C, the time is 2-5h, and the heating rate is 1-5°C / min.

6. A Co9S8 / ZnS@C microrod composite material prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The Co9S8 / ZnS@C has a rod-like structure with a diameter between 2-4 μm.

7. Use of the Co9S8 / ZnS@C microrod composite material according to claim 6 in lithium-ion / sodium-ion batteries.

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