A composite electrode and a preparation method and application thereof

Abstract

The present application belongs to the technical field of lithium battery negative electrode, and particularly relates to a composite electrode and a preparation method and application thereof. The composite electrode provided by the present application comprises a carbon matrix and modified gallium nitride nanowires loaded on the carbon matrix, the modified gallium nitride nanowires comprise gallium nitride nanowires and sheet-layered molybdenum disulfide wrapped on the surface of the gallium nitride nanowires; a heterojunction is formed between the sheet-layered molybdenum disulfide and the gallium nitride nanowires. The gallium nitride nanowires in the composite electrode provided by the present application have a relatively high specific surface area, can provide more active sites, are beneficial to the adsorption of lithium ions and charge transfer, and improve the utilization rate of active sites; the sheet-layered molybdenum disulfide is wrapped on the surface of the gallium nitride nanowires, a heterojunction is formed at the interface due to the difference in electrostatic potential, a built-in electric field is generated, the transfer efficiency of charges at the interface can be promoted, the conductivity of the electrode material is improved, and the electrochemical performance of the composite electrode is further improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery anode technology, specifically relating to a composite electrode, its preparation method, and its application. Background Technology

[0002] With the development of new energy vehicles and portable electronic devices, and the increasing demands for new clean energy technologies, the development of lithium-ion batteries has received widespread attention. However, currently available commercial carbon anode materials have a relatively low theoretical capacity (372 mAh·g). -1 The poor cycle performance of lithium-ion batteries has limited their development and hindered their further industrial application.

[0003] Gallium nitride (GaN) possesses excellent physical and chemical stability, resulting in superior lithium storage performance. However, further improvements in the electrochemical performance of GaN electrode materials are limited by the low utilization rate of the electrode material due to its limited number of active sites, and the poor conductivity of GaN itself. Summary of the Invention

[0004] The purpose of this invention is to provide a composite electrode, its preparation method, and its application. The active material on the composite electrode provided by this invention has high utilization rate and conductivity.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a composite electrode comprising a carbon matrix and modified gallium nitride nanowires supported on the carbon matrix, wherein the modified gallium nitride nanowires comprise gallium nitride nanowires and sheet-like molybdenum disulfide wrapped around the surface of the gallium nitride nanowires;

[0007] A heterogeneous interface is formed between the layered molybdenum disulfide and gallium nitride nanowires.

[0008] Preferably, the gallium nitride nanowire has a diameter of 50 nm to 250 nm and an aspect ratio of 40 to 100.

[0009] Preferably, the mass ratio of the modified gallium nitride nanowires to the carbon matrix is ​​1:2 to 10;

[0010] The mass ratio of the layered molybdenum disulfide and gallium nitride nanowires is 1 to 3:1.

[0011] The present invention also provides a method for preparing the composite electrode described in the above technical solution, comprising the following steps;

[0012] Gallium source and elemental carbon were mixed, and gallium nitride nanowires were grown on the surface of a carbon substrate by chemical vapor deposition in an ammonia atmosphere, resulting in a carbon substrate with gallium nitride nanowires grown on it.

[0013] The carbon substrate on which gallium nitride nanowires are grown is immersed in a mixture containing a molybdenum source and a sulfur source, and a hydrothermal reaction is carried out to obtain the composite electrode.

[0014] Preferably, the gallium source comprises gallium-containing oxides and / or gallium-containing inorganic salts; the elemental carbon comprises carbon powder;

[0015] The mass ratio of the gallium source to elemental carbon is 3 to 10:1.

[0016] Preferably, the flow rate of the ammonia gas is 100-150 sccm.

[0017] Preferably, the temperature of the chemical vapor deposition is 950–1050°C, and the holding time is 15–30 min.

[0018] Preferably, the molybdenum source comprises sodium molybdate and / or ammonium molybdate; the sulfur source comprises thiourea and / or thioacetamide;

[0019] The molar ratio of the molybdenum source to the sulfur source is 1:2 to 4;

[0020] The ratio of the carbon matrix on which gallium nitride nanowires are grown to the mixture containing molybdenum and sulfur sources is 1–2 g: 20–50 mL.

[0021] Preferably, the temperature of the hydrothermal reaction is 180–200°C, and the holding time is 24–48 h.

[0022] The present invention also provides the application of the composite electrode described in the above technical solution or the composite electrode prepared by the preparation method described in the above technical solution as a negative electrode in a lithium battery.

[0023] This invention provides a composite electrode comprising a carbon matrix and modified gallium nitride nanowires loaded on the carbon matrix. The modified gallium nitride nanowires include gallium nitride nanowires and lamellar molybdenum disulfide (MoD2) coating the surface of the gallium nitride nanowires. A heterogeneous interface is formed between the lamellar MoD2 and the gallium nitride nanowires. In this invention, the gallium nitride nanowires on the carbon matrix have a high specific surface area, thus providing more active sites, which is beneficial for lithium ion adsorption and charge transfer, improving the utilization rate of active sites. The lamellar MoD2, coating the surface of the gallium nitride nanowires, forms a heterogeneous interface at the interface due to the difference in electrostatic potential between the two materials when they are combined, generating a built-in electric field. The formation of this built-in electric field can promote the efficiency of charge transfer at the interface, thereby improving the conductivity of the electrode material and enhancing the electrochemical performance of the composite electrode. Attached Figure Description

[0024] Figure 1 The image shows the SEM image of the composite electrode obtained in Example 1.

[0025] Figure 2 The constant current charge-discharge curve of the lithium-ion battery obtained in Test Example 2;

[0026] Figure 3 This is a schematic diagram of the process flow provided by the present invention. Detailed Implementation

[0027] The present invention provides a composite electrode comprising a carbon matrix and modified gallium nitride nanowires supported on the carbon matrix, wherein the modified gallium nitride nanowires comprise gallium nitride nanowires and sheet-like molybdenum disulfide wrapped around the surface of the gallium nitride nanowires;

[0028] A heterogeneous interface is formed between the layered molybdenum disulfide and gallium nitride nanowires.

[0029] In this invention, the diameter of the gallium nitride nanowire is preferably 50 nm to 250 nm, more preferably 100 nm to 200 nm, and even more preferably 150 nm to 180 nm; the aspect ratio is preferably 40 to 100, more preferably 50 to 90, and even more preferably 60 to 80.

[0030] In this invention, the mass ratio of the modified gallium nitride nanowires to the carbon matrix is ​​preferably 1:2 to 10, more preferably 1:3 to 8, and even more preferably 1:5 to 7. In this invention, the mass ratio of the layered molybdenum disulfide to gallium nitride nanowires is preferably 1 to 3:1, and even more preferably 2:1.

[0031] In this invention, the carbon carrier preferably includes carbon paper or carbon fiber.

[0032] The present invention also provides a method for preparing the composite electrode described in the above technical solution, comprising the following steps;

[0033] Gallium source and elemental carbon were mixed, and gallium nitride nanowires were grown on the surface of a carbon substrate by chemical vapor deposition in an ammonia atmosphere, resulting in a carbon substrate with gallium nitride nanowires grown on it.

[0034] The carbon substrate on which gallium nitride nanowires are grown is immersed in a mixture containing a molybdenum source and a sulfur source, and a hydrothermal reaction is carried out to obtain the composite electrode.

[0035] In this invention, unless otherwise specified, all raw materials are commercially available products well known to those skilled in the art.

[0036] This invention mixes gallium source and elemental carbon, and grows gallium nitride nanowires on the surface of a carbon substrate by chemical vapor deposition in an ammonia atmosphere, thereby obtaining a carbon substrate with gallium nitride nanowires grown on it.

[0037] In this invention, the gallium source preferably comprises gallium-containing oxides and / or gallium-containing inorganic salts; the gallium-containing oxides preferably comprise gallium oxide, and the gallium-containing inorganic salts preferably comprise gallium nitrate or gallium chloride. In this invention, the elemental carbon preferably comprises carbon powder; the mass ratio of the gallium source to elemental carbon is preferably 3–10:1, more preferably 4–9:1, more preferably 5–8:1, and most preferably 6–7:1. In this invention, the mixing method is preferably grinding. This invention does not impose any special limitations on the grinding process; any process well-known to those skilled in the art can be used. In a specific embodiment of this invention, the grinding is preferably performed in an agate mortar.

[0038] In this invention, the flow rate of the ammonia gas is preferably 100-150 sccm, more preferably 110-140 sccm, and even more preferably 120-130 sccm.

[0039] In this invention, the temperature for chemical vapor deposition is preferably 950–1050°C, more preferably 960–1030°C, and even more preferably 980–1000°C; the heating rate to the chemical vapor deposition temperature is preferably 5–10°C / min; and the holding time is preferably 15–30 min, more preferably 18–28 min, and even more preferably 20–25 min. In this invention, the chemical vapor deposition is preferably performed in a tube furnace.

[0040] In this invention, the chemical vapor deposition process preferably includes:

[0041] The mixture of gallium source and elemental carbon is placed in a ceramic boat, which is then placed in the middle of a tube furnace. The carbon matrix is ​​then positioned between the ceramic boat and the gas outlet of the tube furnace.

[0042] The tubular furnace is evacuated, then nitrogen is introduced and heated. When the temperature of the tubular furnace reaches the vapor phase chemical deposition temperature, the nitrogen is replaced with ammonia to perform the vapor phase chemical deposition.

[0043] In this invention, the distance between the carbon substrate and the ceramic boat is preferably 15-20 cm. In a specific embodiment of this invention, the size of the carbon substrate is preferably 5 cm * 2 cm.

[0044] In this invention, the flow rate of nitrogen gas is preferably 130–180 sccm. In this invention, the heating rate is preferably 5–10 °C / min.

[0045] Following the chemical vapor deposition, the present invention preferably includes naturally cooling the resulting carbon matrix to room temperature. In this invention, the natural cooling is preferably performed under a nitrogen atmosphere. In this invention, the nitrogen flow rate is preferably 130–180 sccm.

[0046] After obtaining a carbon substrate with gallium nitride nanowires grown on it, the present invention immerses the carbon substrate with gallium nitride nanowires grown on it in a mixed solution containing a molybdenum source and a sulfur source to carry out a hydrothermal reaction to obtain the composite electrode.

[0047] In this invention, the molybdenum source preferably includes sodium molybdate and / or ammonium molybdate; the sulfur source preferably includes thiourea and / or thioacetamide; the molar ratio of the molybdenum source to the sulfur source is preferably 1:2 to 4, more preferably 1:3. In this invention, the preferred ratio of the carbon substrate with gallium nitride nanowires grown to the mixed solution containing the molybdenum source and the sulfur source is 1 to 2 g: 20 to 50 mL. This invention does not impose any special limitations on the impregnation process; the carbon substrate with gallium nitride nanowires grown can be directly impregnated entirely in the mixed solution.

[0048] In this invention, the temperature of the hydrothermal reaction is preferably 180–200°C, more preferably 182–195°C, and even more preferably 185–190°C; the holding time is preferably 24–48 h, more preferably 30–40 h, and even more preferably 32–36 h. In this invention, the hydrothermal reaction is preferably carried out in a hydrothermal reactor.

[0049] Following the hydrothermal reaction, the present invention preferably further includes cooling the resulting matrix to room temperature.

[0050] The process flow diagram provided by this invention is as follows: Figure 3 As shown.

[0051] This invention also provides the application of the composite electrode described in the above-described technical solutions, or the composite electrode prepared by the preparation method described in the above-described technical solutions, as a negative electrode in a lithium battery. This invention does not impose any special limitations on the specific implementation of the application; any process well-known to those skilled in the art can be used.

[0052] To further illustrate the present invention, a composite electrode, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] Grind 1.5g of gallium oxide and 0.5g of carbon powder in an agate mortar. Place the resulting mixture in a ceramic boat and place the ceramic boat in the middle of a tube furnace. Place a piece of carbon paper measuring 5cm*2cm between the ceramic boat and the air outlet of the tube furnace, with a distance of 15cm between the carbon paper and the ceramic boat.

[0055] The tubular furnace was evacuated, and then nitrogen gas was introduced at a flow rate of 150 sccm. The furnace was heated at a heating rate of 8 °C / min until it reached 1000 °C. Then, nitrogen gas was replaced with ammonia gas at a flow rate of 120 sccm for vapor phase chemical deposition, and the temperature was maintained for 20 min. After deposition, ammonia gas was replaced with nitrogen gas at a flow rate of 150 sccm, and the furnace was allowed to cool naturally to room temperature to obtain carbon paper with gallium nitride nanowires grown on it.

[0056] 40 mL of a mixture containing ammonium molybdate and thiourea (where the molar concentration of ammonium molybdate is 1 mol / L and the molar concentration of thiourea is 0.5 mol / L) was placed in a hydrothermal reactor. Carbon paper with gallium nitride nanowires grown on it was immersed in the mixture. The hydrothermal reaction was carried out at 200 °C for 48 h. After cooling to room temperature, the composite electrode was obtained (wherein, the diameter of the gallium nitride nanowires is 100 nm and the aspect ratio is 80; the mass ratio of lamellar molybdenum disulfide to gallium nitride is 3:1; and the mass ratio of gallium nitride nanowires coated with lamellar molybdenum disulfide to carbon paper is 1:5).

[0057] Example 2

[0058] Grind 1.5g of gallium oxide and 0.5g of carbon powder in an agate mortar. Place the resulting mixture in a ceramic boat and place the ceramic boat in the middle of a tube furnace. Place a piece of carbon paper measuring 5cm*2cm between the ceramic boat and the air outlet of the tube furnace, with a distance of 15cm between the carbon paper and the ceramic boat.

[0059] The tubular furnace was evacuated, and then nitrogen gas was introduced at a flow rate of 150 sccm. The furnace was heated at a heating rate of 8 °C / min until the temperature reached 1000 °C. Then, nitrogen gas was replaced with ammonia gas at a flow rate of 150 sccm for vapor phase chemical deposition, and the temperature was maintained for 30 min. After deposition, ammonia gas was replaced with nitrogen gas at a flow rate of 150 sccm, and the furnace was allowed to cool naturally to room temperature to obtain carbon paper with gallium nitride nanowires grown on it.

[0060] A 40 mL mixture containing ammonium molybdate and thiourea (with a molar concentration of 1 mol / L for ammonium molybdate and 0.5 mol / L for thiourea) was placed in a hydrothermal reactor. Carbon paper with gallium nitride nanowires was immersed in the mixture, and a hydrothermal reaction was carried out at 200 °C for 48 h. After cooling to room temperature, the composite electrode was obtained (wherein, the diameter of the gallium nitride nanowires is 150 nm and the aspect ratio is 100; the mass ratio of lamellar molybdenum disulfide to gallium nitride is 2:1; and the mass ratio of gallium nitride nanowires coated with lamellar molybdenum disulfide to carbon paper is 1:4).

[0061] Performance testing

[0062] Test Example 1

[0063] The composite electrode obtained in Example 1 was subjected to scanning electron microscopy (SEM) testing, and the resulting SEM image is shown below. Figure 1 As shown, from Figure 1 It can be seen that GaN nanowires were successfully obtained by chemical vapor deposition on carbon paper; in the subsequent hydrothermal process, the layered molybdenum disulfide structure was tightly attached to the gallium nitride nanowires, and a heterogeneous interface was formed between the surface molybdenum disulfide and the inner gallium nitride nanowires.

[0064] Test Example 2

[0065] The electrochemical performance of the composite electrodes obtained in Examples 1 and 2 was tested;

[0066] Using the composite electrode obtained in Examples 1-2 as the negative electrode, lithium metal sheet as the positive electrode, and lithium hexafluorophosphate as the electrolyte, lithium-ion batteries were assembled in a glove box filled with nitrogen, as sample group 1 and sample group 2.

[0067] Assemble lithium-ion batteries using molybdenum disulfide or gallium nitride as active materials:

[0068] Active materials, conductive carbon black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1 to obtain a slurry, which was coated on copper foil, dried, and then pressed to obtain a negative electrode sheet. Lithium metal sheet was used as the positive electrode and lithium hexafluorophosphate was used as the electrolyte. Lithium-ion batteries were assembled in a glove box filled with nitrogen as control group 1 (molybdenum disulfide) and control group 2 (gallium nitride).

[0069] Electrochemical performance tests were performed on sample groups 1-2 and control groups 1-2, and the constant current charge-discharge test curves obtained are shown below. Figure 2 As shown, where Figure 2 a represents control group 1. Figure 2 b is control group 2. Figure 2 c represents sample group 1. Figure 2 d represents sample group 2;

[0070] from Figure 2 It can be seen that when molybdenum disulfide is used alone as the negative electrode active material, its performance at 0.1 A·g -1 The capacity after 200 cycles at the current density is 216.2 mAh·g. -1 When gallium nitride is used alone as the negative electrode active material, its performance at 0.1 A·g -1 The capacity after 200 cycles at the current density is 391.6 mAh·g. -1 The composite electrode-1 (sample group 1) provided by this invention, at 0.1 A·g -1 The capacity after 200 cycles at the current density is 723.1 mAh·g. -1The composite electrode-2 (sample group 2) provided by this invention, at 0.1 A·g -1 The capacity after 200 cycles at the current density is 874.6 mAh·g. -1 This indicates that by designing nanostructures and constructing heterostructure interfaces, the charge transfer efficiency was enhanced and the lithium-ion storage performance of the composite electrode was improved, thus improving the electrochemical performance of the composite electrode.

[0071] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A composite electrode, characterized in that, It consists of a carbon matrix and modified gallium nitride nanowires supported on the carbon matrix. The modified gallium nitride nanowires are composed of gallium nitride nanowires and lamellar molybdenum disulfide wrapped on the surface of the gallium nitride nanowires. The carbon matrix is ​​carbon paper. A heterogeneous interface is formed between the lamellar molybdenum disulfide and gallium nitride nanowires; The method for preparing the composite electrode includes the following steps; Gallium source and elemental carbon were mixed, and gallium nitride nanowires were grown on the surface of a carbon substrate by chemical vapor deposition in an ammonia atmosphere, resulting in a carbon substrate with gallium nitride nanowires grown on it. The carbon substrate on which gallium nitride nanowires are grown is immersed in a mixture containing a molybdenum source and a sulfur source, and a hydrothermal reaction is carried out to obtain the composite electrode.

2. The composite electrode according to claim 1, characterized in that, The gallium nitride nanowires have a diameter of 50 nm to 250 nm and an aspect ratio of 40 to 100.

3. The composite electrode according to claim 1 or 2, characterized in that, The mass ratio of the modified gallium nitride nanowires to the carbon matrix is ​​1:2 to 10; The mass ratio of the layered molybdenum disulfide and gallium nitride nanowires is 1 to 3:

1.

4. The method for preparing the composite electrode according to any one of claims 1 to 3, characterized in that, Includes the following steps; Gallium source and elemental carbon were mixed, and gallium nitride nanowires were grown on the surface of a carbon substrate by chemical vapor deposition in an ammonia atmosphere, resulting in a carbon substrate with gallium nitride nanowires grown on it. The carbon substrate on which gallium nitride nanowires are grown is immersed in a mixture containing a molybdenum source and a sulfur source, and a hydrothermal reaction is carried out to obtain the composite electrode.

5. The preparation method according to claim 4, characterized in that, The gallium source includes gallium-containing oxides and / or gallium-containing inorganic salts; the elemental carbon includes carbon powder. The mass ratio of the gallium source to elemental carbon is 3 to 10:

1.

6. The preparation method according to claim 4, characterized in that, The flow rate of the ammonia gas is 100-150 sccm.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The chemical vapor deposition temperature is 950–1050℃, and the holding time is 15–30 min.

8. The preparation method according to claim 4, characterized in that, The molybdenum source includes sodium molybdate and / or ammonium molybdate; the sulfur source includes thiourea and / or thioacetamide. The molar ratio of the molybdenum source to the sulfur source is 1:2 to 4; The ratio of the carbon matrix on which gallium nitride nanowires are grown to the mixture containing molybdenum and sulfur sources is 1–2 g: 20–50 mL.

9. The preparation method according to claim 4 or 8, characterized in that, The hydrothermal reaction temperature is 180–200℃, and the holding time is 24–48 h.

10. The composite electrode according to any one of claims 1 to 3 or the composite electrode prepared by the preparation method according to any one of claims 4 to 9 is used as a negative electrode in a lithium battery.

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