Ni2(OH)3Cl nanosheet / multilayer graphene sodium ion battery negative electrode composite material and preparation method thereof

Abstract

The application discloses a kind of Ni2 (OH) 3Cl nanosheet / multilayer graphene sodium ion battery negative composite material and preparation method thereof.Multilayer graphene is prepared by ultrasonic treatment of expanded graphite, and since it is not subjected to oxidation treatment, the surface carbon ring structure of the multilayer graphene is complete, and the surface oxygen-containing functional groups are few, so it has good conductivity.Ni2 (OH) 3Cl is uniformly distributed on the surface of the multilayer graphene.Ni2 (OH) 3Cl is in the form of nanosheet, the thickness of the nanosheet is less than 10 nm, and the size of the two-dimensional plane of the nanosheet is between 50 nm and 200 nm.Most of the nanosheets are parallel to the surface of the multilayer graphene, and a few of the nanosheets are at an angle.The composite material of the technical scheme has excellent sodium storage performance and can be used as a negative material for sodium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, and specifically relates to a Ni2(OH)3Cl nanosheet / multilayer graphene sodium-ion battery anode composite material and its preparation method. The material of this invention has potential applications in sodium-ion battery anodes. Background Technology

[0002] Sodium-ion batteries operate on the same principle as lithium-ion batteries. With rising lithium prices, the price advantage of sodium-ion batteries makes them a promising candidate for commercial application. However, sodium ions have a much larger ionic radius than lithium ions, and the insertion / extraction of sodium ions causes greater volume expansion than in lithium-ion battery materials. Therefore, developing new sodium-ion battery materials and obtaining sodium-ion battery materials with good nanostructures has become a research hotspot.

[0003] Ni₂(OH)₃Cl is a basic salt, and research on its use as an anode material in sodium-ion batteries is currently very limited. However, we have found that Ni₂(OH)₃Cl is entirely suitable for use as an anode material in sodium-ion batteries; the only challenge is finding a suitable method to prepare Ni₂(OH)₃Cl with a good nanostructure. Furthermore, Ni₂(OH)₃Cl has low conductivity, resulting in slow electron movement within it when used as an electrode in sodium-ion batteries, leading to low specific capacity, poor rate performance, and poor cycle performance. Therefore, its poor conductivity must be addressed by combining it with highly conductive materials before its application.

[0004] Carbon materials possess excellent electrical conductivity and are commonly used conductive substrates for preparing composite materials. However, carbon materials have low surface chemical activity. In the preparation of carbon composites, carbon materials are often oxidized to introduce active functional groups before chemical synthesis. However, oxidation increases the preparation cost and generates more wastewater. Furthermore, oxidation reduces the electrical conductivity of carbon materials, thus affecting their electrochemical performance. Therefore, it is necessary to find a solution for preparing Ni₂(OH)₃Cl-carbon composites on carbon material surfaces without introducing active groups.

[0005] In view of the deficiencies of the existing technology, the present invention proposes a technical solution to solve the technical problems existing in the existing technology. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention employs liquid-phase exfoliation of multilayer graphene as a carbon substrate and has developed a process for directly preparing Ni2(OH)3Cl nanosheets on the surface of multilayer graphene without relying on surface-active groups. This results in a Ni2(OH)3Cl nanosheet / multilayer graphene composite material, which exhibits excellent electrochemical performance and can be used as a negative electrode material for sodium-ion batteries.

[0007] To address the technical problems existing in the prior art, the technical solution of the present invention is as follows:

[0008] This invention discloses a composite material of Ni2(OH)3Cl nanosheets and multilayer graphene sodium-ion battery anode. The Ni2(OH)3Cl nanosheets are uniformly distributed on the surface of the multilayer graphene, with most nanosheets parallel to the surface and a few at an angle. There are voids between the Ni2(OH)3Cl nanosheets. The Ni2(OH)3Cl is in nanosheet form, with a thickness of less than 10 nm and a two-dimensional planar dimension of 50-200 nm. The multilayer graphene is obtained from expanded graphite through ultrasonication. The multilayer graphene surface has a complete carbon ring structure and very few oxygen-containing functional groups, exhibiting good structural integrity and electrical conductivity.

[0009] This invention also discloses a method for preparing a Ni2(OH)3Cl nanosheet and multilayer graphene sodium-ion battery anode composite material, comprising the following steps:

[0010] Step S10: Measure DMF and deionized water in a volume ratio of 8:2, mix them evenly and use them as a mixed solvent. Weigh out expanded graphite and add it to the mixed solvent. Perform ultrasonic treatment at 200W power for 4 hours to obtain a multilayer graphene dispersion. The concentration of expanded graphite relative to the mixed solvent is 0.5-2 mg / mL.

[0011] Step S20: Weigh 15-25 mg / mL of nickel chloride hexahydrate relative to the mixed solvent and add it to the multilayer graphene solution. Add the magnetic rotor to the glass bottle and stir for 15 minutes at room temperature.

[0012] Step S30: Add ammonia water (25-28 wt%) to the reaction solution. The volume ratio of ammonia water to the mixed solvent is 0.01-0.025:1. Then, place the mixture in a water bath at 80-95℃ and stir magnetically for 5 hours.

[0013] In step S40, after cooling the reaction solution, it was washed three times with deionized water and three times with alcohol by centrifugation at a speed of 6000 rpm. After washing, it was placed in an oven at 70°C for 24 hours to dry. After drying, Ni2(OH)3Cl nanosheets / multilayer graphene composite material was obtained.

[0014] As a further improvement, multilayer graphene does not require oxidation to introduce active groups; instead, Ni2(OH)3Cl is deposited directly on the surface of multilayer graphene through molecular forces.

[0015] As a further improvement, obtaining Ni2(OH)3Cl nanosheets does not require the addition of additional directing agents or inhibitors.

[0016] As a further improvement, Ni₂(OH)₃Cl nanosheets are connected to multilayer graphene through molecular forces. The electron clouds of the carbon atoms in the multilayer graphene and Ni₂(OH)₃Cl overlap, resulting in low resistance and fast electron movement between them.

[0017] As a further improvement, Ni₂(OH)₃Cl nanosheets are uniformly distributed on the surface of multilayer graphene, with large gaps between the nanosheets. These gaps facilitate electrolyte penetration, resulting in a large contact area between the active material and the electrolyte. Simultaneously, the nanosheet structure of Ni₂(OH)₃Cl also allows the material to achieve a large specific surface area. The combined effect of these two factors improves the specific capacitance, rate performance, and cycle life of the composite material.

[0018] As a further improvement, composite materials can be used as anode materials for sodium-ion batteries, exhibiting high capacity density and excellent cycle performance.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The preparation of multilayer graphene substrate is simple and low cost. Ni2(OH)3Cl nanosheets can be deposited without the need for activation treatment of the multilayer graphene surface.

[0021] (2) Ni2(OH)3Cl nanosheets are connected to multilayer graphene through molecular forces. The electron clouds between the carbon atoms of multilayer graphene and Ni2(OH)3Cl overlap, resulting in low resistance and fast movement of electrons between them.

[0022] (3) Ni2(OH)3Cl is in the form of nanosheets, exhibiting minimal volume change during the charge-discharge process of sodium ions. This improves its structural stability during charge-discharge, thereby enhancing its stability as a negative electrode material for sodium-ion batteries.

[0023] (4) Most of the Ni2(OH)3Cl nanosheets are parallel to the multilayer graphene, while a few nanosheets are at an angle to the multilayer graphene. The parallel Ni2(OH)3Cl nanosheets and the multilayer graphene exhibit good contact and stability. The angled Ni2(OH)3Cl nanosheets create larger gaps between the Ni2(OH)3Cl nanosheets and between the multilayer graphene layers, thus facilitating electrolyte penetration. Simultaneously, the multilayer graphene exhibits good electrical conductivity, further improving the conductivity of the composite material. These structural characteristics of the composite material enable it to possess high capacity, rate performance, and cycle performance as a negative electrode for sodium-ion batteries.

[0024] (5) Compared with other nickel-containing compound / carbon composite materials, the Ni2(OH)3Cl nanosheet / multilayer graphene composite material of this invention has a lower preparation temperature and does not require the high-pressure equipment required for hydrothermal methods. Therefore, the required preparation cost is low, making it suitable for large-scale industrial production. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation steps of the Ni2(OH)3Cl nanosheet / multilayer graphite composite material in Example 1 of the present invention.

[0026] Figure 2 The XRD pattern of the Ni2(OH)3Cl nanosheet / multilayer graphite composite material prepared in Example 1 of this invention;

[0027] Figure 3 This is a low-magnification scanning electron microscope image of the Ni2(OH)3Cl nanosheet / multilayer graphite composite material prepared in Example 1 of this invention;

[0028] Figure 4 This is a high-magnification scanning electron microscope image of the Ni2(OH)3Cl nanosheet / multilayer graphite composite material prepared in Example 1 of this invention;

[0029] Figure 5 This is a TEM image of the Ni2(OH)3Cl nanosheet / multilayer graphite composite material prepared in Example 1 of this invention;

[0030] Figure 6 The rate curve of the Ni2(OH)3Cl nanosheet / multilayer graphite composite sodium-ion battery anode prepared in Example 1 of this invention;

[0031] Figure 7 The cycling curve of the Ni2(OH)3Cl nanosheet / multilayer graphite composite sodium-ion battery anode prepared in Example 1 of this invention; Detailed Implementation

[0032] To better illustrate the process and solution of the present invention, the following description is provided in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] To address the technical problems existing in the current technology, see [link to relevant documentation]. Figure 1 The diagram shows a flowchart of the preparation method for uniformly distributing sheet-like nano-iron oxide particles on multilayer graphene, as proposed in this invention, including the following steps:

[0034] Step S10: Measure DMF and deionized water in a volume ratio of 8:2, mix them evenly and use them as a mixed solvent. Weigh out expanded graphite and add it to the mixed solvent. Perform ultrasonic treatment at 200W power for 4 hours to obtain a multilayer graphene dispersion. The concentration of expanded graphite relative to the mixed solvent is 0.5-2 mg / mL.

[0035] Step S20: Weigh 15-25 mg / mL of nickel chloride hexahydrate relative to the mixed solvent and add it to the multilayer graphene solution. Add the magnetic rotor to the glass bottle and stir for 15 minutes at room temperature.

[0036] Step S30: Add ammonia water (25-28 wt%) to the reaction solution. The volume ratio of ammonia water to the mixed solvent is 0.01-0.025:1. Then, place the mixture in a water bath at 80-95℃ and stir magnetically for 5 hours.

[0037] In step S40, after cooling the reaction solution, it was washed three times with deionized water and three times with alcohol by centrifugation at a speed of 6000 rpm. After washing, it was placed in an oven at 70°C for 24 hours to dry. After drying, Ni2(OH)3Cl nanosheet / multilayer graphene composite material was obtained.

[0038] Example 1:

[0039] 8 mL of LDM and 2 mL of deionized water were measured and mixed thoroughly to form a mixed solvent. 20 mg of expanded graphite was weighed and added to the mixed solvent. The mixture was then sonicated at 200 W for 4 hours to obtain a multilayer graphene dispersion. 200 mg of nickel chloride hexahydrate was weighed and added to the multilayer graphene solution, and the mixture was magnetically stirred for 15 minutes at room temperature. 200 μL of ammonia water was added to the reaction solution, and the mixture was placed in a 90 °C water bath and magnetically stirred for 5 hours. After cooling, the reaction solution was washed three times with deionized water and three times with alcohol by centrifugation at 6000 rpm. After washing, the solution was dried in an oven at 70 °C for 24 hours. The dried solution yielded a Ni₂(OH)₃Cl nanosheet / multilayer graphene composite material.

[0040] The XRD pattern of the Ni2(OH)3Cl nanosheet / multilayer graphene composite material synthesized in this example is shown below. Figure 2 As shown. The diffraction angles at 16.5°, 33.0°, 36.9°, 47.1°, 58.5°, and 61.1° in the spectrum belong to the (001), (002), (101), (102), (110), and (103) crystal planes of Ni2(OH)3Cl (JCPDS 02-1085). Low-magnification and high-magnification scanning electron microscope images of the composite material are shown below. Figure 3 and 4 As shown. Transmission electron micrographs of the composite material are shown below. Figure 5As shown in the images, scanning electron microscopy and transmission electron microscopy reveal that Ni₂(OH)₃Cl is uniformly distributed on the surface of the multilayer graphene. The Ni₂(OH)₃Cl is in the form of nanosheets, with a thickness of less than 10 nm and a two-dimensional dimension of 50-200 nm in the planar direction. Most of the nanosheets are parallel to the surface of the multilayer graphene, while a few are at an angle.

[0041] The composite material, acetylene black, and PVDF binder (in a mass ratio of 8:1:1) were weighed and stirred evenly with NMP as solvent to obtain a slurry of suitable viscosity. The slurry was coated onto the surface of a copper sheet and dried in a vacuum oven at 100℃ for 12 hours. After removal, it was pressed into a tablet using a tablet press at a pressure of 10 MPa. The resulting composite electrode sheet was then assembled into a button cell for testing. The prepared electrode sheet was used as the working electrode, glass fiber (Whatman GF / C) as the separator, a 1.0 M sodium hexafluorophosphate (NaPF6) solution dissolved in diethylene glycol dimethyl ether as the electrolyte, and a sodium metal sheet as the counter and reference electrodes. Figure 6 The results show the rate performance of the composite material electrode. As can be seen from the figure, the discharge specific capacity at charge / discharge current densities of 100, 200, 500, 1000, and 2000 mA / g are 350, 300, 268, 245, and 208 mAh / g, respectively. When the charge / discharge current returns to 100 mA / g, the capacity recovers to 322 mA / g. Figure 7 These are the cycle performance test results for the composite electrode. At a charge / discharge current density of 100 mA / g, the initial discharge specific capacity is 432 mAh / g, and the discharge specific capacity after 100 cycles is 332 mAh / g. This composite material exhibits excellent rate capability and cycle performance.

[0042] Example 2:

[0043] 8 mL of LDM and 2 mL of deionized water were measured and mixed thoroughly to form a mixed solvent. 20 mg of expanded graphite was weighed and added to the mixed solvent, and the mixture was sonicated for 4 hours to obtain a multilayer graphene dispersion. 250 mg of nickel chloride hexahydrate was weighed and added to the multilayer graphene solution, and the mixture was magnetically stirred for 15 minutes at room temperature. 250 μL of ammonia water was added to the reaction solution, and the mixture was placed in a 90°C water bath and magnetically stirred for 5 hours. After cooling, the reaction solution was washed three times with deionized water and three times with alcohol by centrifugation at 6000 rpm. After washing, the solution was dried in an oven at 70°C for 24 hours. The dried solution yielded a Ni₂(OH)₃Cl nanosheet / multilayer graphene composite material.

[0044] Example 3:

[0045] 8 mL of LDM and 2 mL of deionized water were measured and mixed thoroughly to form a mixed solvent. 5 mg of expanded graphite was weighed and added to the mixed solvent, and the mixture was sonicated for 4 hours to obtain a multilayer graphene dispersion. 150 mg of nickel chloride hexahydrate was weighed and added to the multilayer graphene solution, and the mixture was magnetically stirred for 15 minutes at room temperature. 100 μL of ammonia water was added to the reaction solution, and the mixture was placed in an 80°C water bath and magnetically stirred for 5 hours. After cooling, the reaction solution was washed three times with deionized water and three times with alcohol by centrifugation at 6000 rpm. After washing, the solution was dried in an oven at 70°C for 24 hours. The dried solution yielded a Ni₂(OH)₃Cl nanosheet / multilayer graphene composite material.

[0046] Example 4:

[0047] 8 mL of LDM and 2 mL of deionized water were measured and mixed thoroughly to form a mixed solvent. 15 mg of expanded graphite was weighed and added to the mixed solvent, and the mixture was sonicated for 4 hours to obtain a multilayer graphene dispersion. 180 mg of nickel chloride hexahydrate was weighed and added to the multilayer graphene solution, and the mixture was magnetically stirred for 15 minutes at room temperature. 180 μL of ammonia water was added to the reaction solution, and the mixture was placed in an 85°C water bath and magnetically stirred for 5 hours. After cooling, the reaction solution was washed three times with deionized water and three times with alcohol by centrifugation at 6000 rpm. After washing, the solution was dried in an oven at 70°C for 24 hours. The dried solution yielded a Ni₂(OH)₃Cl nanosheet / multilayer graphene composite material.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Ni2(OH)3Cl nanosheet / multilayer graphene sodium-ion battery anode composite material, characterized in that, Ni2(OH)3Cl forms nanosheets that are uniformly dispersed on the surface of multilayer graphene, with gaps between them. The thickness of the nanosheets is less than 10 nm, and the two-dimensional planar dimensions are 50-200 nm. Most of the nanosheets are parallel to the surface of the multilayer graphene, while a few are at an angle. The multilayer graphene is obtained by ultrasonication of expanded graphite in a mixed organic solvent. The carbon ring structure on the surface of the multilayer graphene obtained by mechanical exfoliation is intact. The number of graphite layers in the multilayer graphene is less than 100, and the surface contains very few oxygen-containing functional groups, resulting in good electrical conductivity.

2. The preparation method of the Ni2(OH)3Cl nanosheet / multilayer graphene sodium-ion battery anode composite material according to claim 1, characterized in that, Includes the following steps: Step S10: Measure DMF and deionized water in a volume ratio of 8:2, mix them evenly and use them as a mixed solvent. Weigh out expanded graphite and add it to the mixed solvent. Perform ultrasonic treatment at 200W power for 4 hours to obtain a multilayer graphene dispersion. The concentration of expanded graphite relative to the mixed solvent is 0.5~2mg / mL. Step S20: Weigh 15-25 mg / mL of nickel chloride hexahydrate relative to the mixed solvent and add it to the multilayer graphene solution. Add the magnetic rotor to the glass bottle and stir for 15 minutes at room temperature. Step S30: Add ammonia water to the reaction solution, with the volume ratio of ammonia water to the mixed solvent being 0.01-0.025:

1. Then, place the mixture in a water bath at 80-95℃ and stir magnetically for 5 hours. In step S40, after the reaction solution is cooled, it is washed three times with deionized water and three times with alcohol by centrifugation at a speed of 6000 rpm. After washing, it is placed in an oven at 70°C for 24 hours to dry. After drying, Ni2(OH)3Cl nanosheets / multilayer graphene composite material is obtained.

3. The method for preparing the composite material according to claim 2, characterized in that, Ni2(OH)3Cl can be deposited directly on the surface of multilayer graphene through molecular forces, without the need for additional directing agents or inhibitors.

4. The method for preparing the composite material according to claim 2, characterized in that, The Ni2(OH)3Cl nanosheets are connected to the multilayer graphene through molecular forces; the electron clouds between the carbon atoms of the multilayer graphene and Ni2(OH)3Cl overlap, resulting in low resistance and fast movement of electrons between them.

5. The method for preparing the composite material according to claim 2, characterized in that, Ni2(OH)3Cl nanosheets are uniformly distributed on the surface of multilayer graphene, with large gaps between the nanosheets. These gaps facilitate the penetration of the electrolyte, resulting in a large contact area between the active material and the electrolyte. At the same time, the nanosheet structure of Ni2(OH)3Cl also enables the material to achieve a large specific surface area. The combined effect of these two factors improves the specific capacitance, rate performance, and cycle performance of the composite material.

6. The method for preparing the composite material according to claim 2, characterized in that, Composite materials are used as anode materials for sodium-ion batteries, exhibiting high capacity density and excellent cycle performance.

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