CN110323429A - Niobium pentaoxide/redox graphene composite negative pole material preparation method - Google Patents

Abstract

A method for preparing a niobium pentoxide/reduced graphene oxide composite negative electrode material, comprising the following steps: (1) mixing graphene oxide nanosheets with water, stirring, and ultrasonically dispersing to obtain a dispersion liquid of graphene oxide nanometers; (2) Dissolve niobium pentachloride in water, stir to obtain niobium pentachloride suspension, add organic cosolvent and hexamethylenetetramine successively in niobium pentachloride suspension, stir, obtain white solution; (3 ) mix the dispersion liquid of graphene oxide nanometer with the white solution, stir until the dispersion is uniform, and obtain a mixed solution, and put the obtained mixed solution into an autoclave for hydrothermal reaction; (4) after the hydrothermal reaction is completed, the obtained The precipitate is washed and dried to obtain a solid powder; (5) The solid powder is heat-treated under an argon atmosphere, and the product is ready. The invention has convenient operation and controllable reaction conditions, and the lithium battery installed with the lithium battery negative electrode made of the obtained composite negative electrode material has excellent cycle and rate performance.

Description

Preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material

technical field

The invention relates to a preparation method of a lithium-ion rechargeable battery composite negative electrode material, in particular to a preparation method of a niobium oxide negative electrode material composed of niobium pentoxide/reduced graphene oxide.

Background technique

Lithium-ion rechargeable batteries are commonly used as energy storage devices. Compared with lead-acid batteries and nickel-cadmium batteries, they have the characteristics of higher voltage, high energy density, long service life, environmental friendliness and no memory effect. Since Since its commercialization, it has played a pivotal role and has been widely used in mobile electronic devices, communication equipment and backup power supplies.

With the rapid development of electric vehicles and hybrid vehicles, lithium-ion batteries are considered to be ideal candidates for the power system of electric vehicles due to their unique advantages. High power density, high energy density and long service life have become the most urgent problems to be solved in the research and development of lithium-ion batteries for electric vehicles at this stage. The performance of energy storage devices largely depends on the properties of the materials used. The anode material is an important part of the lithium-ion secondary battery. The anode material of the traditional lithium-ion battery is mainly graphite anode, which has good conductivity, but its rate performance is poor, and it is difficult to meet the high-current charging and discharging requirements of the lithium-ion battery. Require. Most other anode materials work at low voltages, which can lead to problems such as lithium dendrites. Therefore, anode materials for lithium-ion batteries with high operating voltage, better rate performance, and long cycle life have been widely concerned and studied.

The transition metal oxide niobium pentoxide (Nb ₂ O ₅ ) has unique embedded pseudocapacitive properties, and is a new type of lithium-ion battery anode material with good safety and good rate performance. In bulk Nb ₂ O ₅ materials, there is no phase transition during the de-lithiation/intercalation process, and its charge storage properties are not controlled by the semi-infinite diffusion process like most battery materials, but by the surface transformation process, resulting in its The unusually high rate performance, which makes it a capacitive process with a fast response time, is a lithium-ion electrode material that can achieve fast charging and fast discharging. However, Nb ₂ O ₅ has low electrical conductivity (~3×10-6 S cm ^-1 ), and it is easy to pulverize during charge and discharge, which leads to capacity fading, making it difficult to meet the needs of high-performance batteries. Therefore, effectively enhancing its electrical conductivity and electrode structure stability is the key to improving the electrochemical performance of Nb ₂ O ₅ anode materials. Due to its special energy band structure, ultra-high mobility and novel transport properties, graphene material has become an ideal system for exploring new physical properties and developing new quantum electronic devices. Combining graphene materials with niobium pentoxide not only improves the storage capacity of lithium ions, but also enhances the transport capacity of electrolyte ions due to the porous structure of graphene. The flexibility of the graphene structure and the construction of a three-dimensional framework are conducive to Buffering the volume expansion brought about by the deintercalation process of lithium ions, the resulting lithium-ion battery not only has a high volume capacity, but also has a large charge-discharge rate performance and long cycle stability. Therefore, graphene can effectively improve the performance of niobium Based oxides are used for the specific capacity, rate performance and cycle performance of lithium-ion battery anode materials.

CN108493427A discloses a method for preparing Nb2O5 powder lithium-ion battery electrode materials by hydrothermal method. In this method, micro-nano-scale Nb2O5 powder is first synthesized by hydrothermal method, and then uniformly mixed with graphene to prepare lithium-ion electrode materials. However, the Nb2O5 powder material has relatively large particles, which are micron-sized, and has serious agglomeration, which cannot effectively solve the problem of capacity fading due to poor structural stability of the Nb2O5 negative electrode material during charge and discharge. There are gaps between the Nb2O5 micron particles synthesized by this method, which is not conducive to the electronic conduction process of the material, and cannot maximize the effect of graphene on improving the conductivity of the Nb2O5 negative electrode material. Part of the synthesis process in this method requires higher temperature, longer time and greater energy consumption.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art, and provide a stable structure, good electrical conductivity, excellent rate performance, simple preparation process, low energy consumption, low cost, and suitable for industrial production. A preparation method of diniobium/reduced graphene oxide nanocomposite negative electrode material.

The technical solution adopted by the present invention to solve the technical problem is as follows: a preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material, comprising the following steps:

(1) Mix graphene oxide nanosheets with water, stir, and ultrasonically disperse to obtain a dispersion of graphene oxide nanoparticles;

(2) Dissolve and disperse niobium pentachloride in water, stir to obtain a suspension of niobium pentachloride, add organic co-solvent to the suspension of niobium pentachloride, stir to obtain a clear solution, add six times to the clear solution Methyltetramine was stirred to obtain a white solution;

(3) Mixing the dispersion of graphene oxide nanoparticles obtained in step (1) with the white solution obtained in step (2), stirring until uniformly dispersed to obtain a mixed solution, and putting the obtained mixed solution into an autoclave for hydrothermal reaction;

(4) After the hydrothermal reaction is completed, the precipitate produced by the hydrothermal reaction is collected, and the obtained precipitate is washed and dried to obtain a solid powder;

(5) Heat-treating the solid powder obtained in step (4) under an argon atmosphere to obtain a niobium pentoxide/reduced graphene oxide composite negative electrode material.

Further, in step (1), the concentration of the graphene oxide nanometer dispersion is 0.5-2 mg/mL.

Further, in step (2), the concentration of the niobium pentachloride suspension is 5-15 mg/mL.

Further, in step (2), the organic co-solvent is at least one of oxalic acid, acetic acid or oxalic acid.

Further, in step (2), the method for dissolving and dispersing the niobium pentachloride is magnetic stirring: the mixed solution of niobium pentachloride and water is placed in a water bath for magnetic stirring, and the speed of the magnetic stirring is 300-500 r /min, the temperature of magnetic stirring is 10-40 ℃, and the time of magnetic stirring is 0.5 h-3 h.

Further, in step (3), the volume ratio of the graphene oxide nano-dispersion and the white solution is 1:1-1:3;

Further, in step (3), the temperature of the hydrothermal reaction is 140-200° C., and the time is 8-24 h.

Further, in step (4), the drying method is at least one of freeze drying, blast drying or vacuum drying.

Further, in step (5), the heating rate of the heat treatment is 1-20 °C/min, the heating temperature is 400 °C-1000 °C, and the holding time is 1-3 h.

The advantages of the present invention are: (1) The present invention has simple process, low energy consumption and low cost; (2) In the niobium pentoxide/reduced graphene oxide composite negative electrode material prepared by the present invention, the niobium pentoxide nanowires are confined in the two-dimensional nanospace of the graphene nanosheets, and the diameter of the niobium pentoxide nanowires is 5-10 nm, length 50-200 nm, in-situ growth on the surface of reduced graphene oxide with a sheet thickness of 5-10 nm, can effectively enhance its structural stability and electrical conductivity, thereby effectively improving its electrochemical performance, It provides a new idea for the development and research of new high-performance electrode materials; (3) The niobium pentoxide/reduced graphene oxide composite negative electrode material prepared by the present invention has better electrochemical performance when applied to the negative electrode of lithium batteries, and the electrochemical performance is better at 1 C ( At a current density of 1 C= 200 mA/g), the discharge capacity can be as high as 170 mAh/g; at a current density of 10 C (1 C= 200 mA/g), the discharge specific capacity can be as high as 100 mAh/g, indicating that Due to the existence of graphene, the agglomeration of niobium pentoxide can be prevented, the electrical conductivity of niobium pentoxide can be enhanced, and the lithium storage capacity of the material can be significantly improved.

Description of drawings

Fig. 1 is the XRD pattern of niobium pentoxide/reduced graphene oxide composite negative electrode material of embodiment 1 of the present invention;

Fig. 2 is the scanning electron microscope picture of niobium pentoxide/reduced graphene oxide composite negative electrode material of embodiment 1 of the present invention;

Fig. 3 is the transmission electron microscope picture of niobium pentoxide/reduced graphene oxide composite negative electrode material of embodiment 1 of the present invention;

Fig. 4 is a comparison chart of the charge and discharge curves of the first cycle and the second cycle of the niobium pentoxide/reduced graphene oxide composite negative electrode material and the pure phase niobium pentoxide negative electrode material of Example 1 of the present invention;

Fig. 5 is a rate performance test chart of the niobium pentoxide/reduced graphene oxide composite negative electrode material in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

The chemical reagents used in the examples of the present invention were obtained through conventional commercial channels unless otherwise specified.

Example 1

This embodiment includes the following steps:

(1) Mix 0.0435 g graphene oxide nanosheets with 40 ml deionized water, stir for 0.5 h, and ultrasonically disperse for 0.5 h to obtain a graphene oxide nano-dispersion;

(2) Disperse 0.872 g of niobium pentachloride in 40 mL of deionized water and stir for 0.5 h to obtain a suspension of niobium pentachloride; add 2 g of oxalic acid to the suspension obtained above and stir for 0.5 h to obtain a clear solution; 1.12 g of hexamethylenetetramine was added to the above clear solution and stirred for 0.5 h to obtain a white solution;

(3) Mix the white solution obtained in step (2) with the graphene oxide nano-dispersion obtained in step (1), stir for 0.5 h to obtain a mixed solution, put the mixed solution in a high-pressure reactor, and conduct 14 The hydrothermal reaction of h;

(4) After the completion of the hydrothermal reaction, the obtained precipitate was centrifuged and washed three times with deionized water at a speed of 6000 r/min, and dried in a blast drying oven at 60 °C for 12 h to obtain a solid powder;

(5) The solid powder was heat-treated at 600 °C for 3 h at a heating rate of 5 °C/min in an argon atmosphere to obtain a niobium pentoxide/reduced graphene oxide composite negative electrode material.

Figure 1 is the XRD pattern of the niobium pentoxide/reduced graphene oxide composite negative electrode material prepared in this example. Compared with the standard card, it can be seen that the material is hexagonal niobium pentoxide without other impurity phases. Fig. 2 is the SEM picture of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this embodiment, it can be seen that the loose and fluffy network structure of the reduced graphene oxide is very obvious, and the niobium pentoxide nanowires Agglomerates of particles grow in the middle of graphene sheets. Figure 3 is a transmission electron microscope image of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this example. By this method, a very thin reduced graphene oxide monolayer with a thickness of 5 to 10 nm can be obtained Within, the niobium pentoxide nanowires grow on the single-layer graphene sheet, the size distribution is 5-10 nm in diameter, 50-200 nm in length, and the agglomeration phenomenon is not obvious.

Battery assembly: mix niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material with carbon black and PVDF in a mass ratio of 8:1:1 in this example, and use NMP as a dispersant to mix and grind, and then evenly spread on copper foil surface, to obtain niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material pole piece; Working electrode, metal lithium sheet as the counter electrode, microporous polypropylene membrane as the diaphragm, 1mol/L LiPF ₆ /EC:DMC (volume ratio 1:1) as the electrolyte, assembled into a CR2025 button battery for charging and discharging test.

It can be seen from Figure 4 that, in the voltage range of ^0-3 V, the first cycle and The charge-discharge curve of the second cycle shows that the capacity of the first cycle of niobium pentoxide/reduced graphene oxide nanocomposite anode material is increased from 520 mAh/g to 900 mAh/g compared with the pure phase of niobium pentoxide. , the second cycle increased from 250 mAh/g to 540 mAh/g. It shows that the composite of reduced graphene oxide can greatly improve the electrochemical performance of niobium pentoxide as the negative electrode of lithium-ion batteries. As shown in Figure 5, the battery assembled with niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material according to the embodiment of the present invention has a current density of 0.1 C (1 C=200 mA/g) in the voltage range of 0-3 V , the discharge capacity can be stabilized at 295 mAh/g; at a current density of 5 C, the discharge specific capacity can be as high as 100 mAh/g, indicating that the presence of graphene can prevent the agglomeration of niobium pentoxide nanoparticles and enhance the five The conductivity of niobium oxide significantly improves the lithium storage performance of the material.

Example 2

This embodiment includes the following steps:

(1) Mix 0.0435 g graphene oxide nanosheets with 40 mL deionized water, stir for 0.5 h, and ultrasonically disperse for 0.5 h to obtain graphene oxide nanodispersion;

(2) Disperse 0.872 g of niobium pentachloride in 40 mL of deionized water and stir for 0.5 h to obtain a suspension of niobium pentachloride; add 2 g of oxalic acid to the suspension obtained above and stir for 0.5 h to obtain a clear solution; 1.12 g of hexamethylenetetramine was added to the above clear solution and stirred for 0.5 h to obtain a white solution;

(3) Mix the white solution obtained in step (2) with the graphene oxide nano-dispersion obtained in step (1), stir for 0.5 h to obtain a mixed solution, put the mixed solution in a high-pressure reactor, and conduct 8 The hydrothermal reaction of h;

(4) After the completion of the hydrothermal reaction, the precipitate obtained from the hydrothermal reaction was centrifuged and washed three times with deionized water at a speed of 6000 r/min, and dried in a blast drying oven at 60 °C for 12 h to obtain solid powder;

(5) The solid powder was heat-treated at 600 °C for 3 h at a heating rate of 5 °C/min in an argon atmosphere to obtain niobium pentoxide/reduced graphene oxide nanocomposite anode materials.

The XRD pattern of the material obtained in this embodiment is compared with the standard card, and it can be seen that the material is hexagonal niobium pentoxide, and there is no other impurity phase. The SEM picture of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this example shows that the loose and fluffy network structure of the reduced graphene oxide is very obvious, and the niobium pentoxide nanowires grow as secondary particles in the middle of the graphene sheets. The transmission electron microscope image of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this example, the reduced graphene oxide sheet with very thin sheets can be obtained by this method, and the niobium pentoxide nanowires grow on the single layer graphene On-chip, the reunion phenomenon is not obvious.

Battery assembly: the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material of this example is mixed with carbon black and PVDF at a mass ratio of 8:1:1, and NMP is used as a solvent to mix and grind, and then evenly spread on the copper foil On the surface, a nanoscale reduced graphene oxide composite niobium oxide negative electrode material smear was obtained; then, in an airtight glove box filled with argon gas, the pole piece of niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material was used as the working electrode of the battery , metal lithium sheet as counter electrode, microporous polypropylene membrane as diaphragm, 1mol/L LiPF ₆ /EC:DMC (volume ratio 1:1) as electrolyte, assembled into a CR2025 button battery, and carried out charge and discharge tests. The charging and discharging performance is similar to that of Example 1, indicating that the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this embodiment can prevent the agglomeration of niobium pentoxide nanoparticles due to the existence of graphene, and strengthen the The conductivity of diniobium improves the lithium storage performance of the material.

Example 3

This embodiment includes the following steps:

(1) Mix 0.0435 g of graphene oxide nanosheets with 40 ml of deionized water, stir for 0.5 h, and ultrasonically disperse for 0.5 h to obtain a graphene oxide nanodispersion;

(2) Disperse 0.872 g of niobium pentachloride in 40 ml of deionized water and stir for 0.5 h to obtain a suspension of niobium pentachloride; add 2 g of oxalic acid to the suspension obtained above and stir for 0.5 h to obtain a clear solution; 1.12 g of hexamethylenetetramine was added to the above clear solution and stirred for 0.5 h to obtain a white solution;

(3) The above white solution was mixed with the graphene oxide nano-dispersion, and stirred for 0.5 h to obtain a mixed solution. The mixed solution was put into an autoclave, and a hydrothermal reaction was carried out at 180 °C for 24 h.

(4) After the completion of the hydrothermal reaction, the precipitate obtained from the hydrothermal reaction was centrifuged and washed three times with deionized water at a speed of 6000 r/min, and dried in a blast drying oven at 60 °C for 12 h to obtain solid powder;

(5) The solid powder was heat-treated at 600 °C for 3 h at a heating rate of 5 °C/min in an argon atmosphere to obtain niobium pentoxide/reduced graphene oxide nanocomposite anode materials.

The XRD pattern of the material obtained in this embodiment is compared with the standard card, and it can be seen that the material is hexagonal niobium pentoxide, and there is no other impurity phase. The SEM picture of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this example shows that the loose and fluffy network structure of the reduced graphene oxide is very obvious, and the niobium pentoxide nanowires grow as secondary particles in the middle of the graphene sheets. The transmission electron microscope image of the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this example, the reduced graphene oxide sheet with very thin sheets can be obtained by this method, although the niobium pentoxide nanowires grow on the monolayer On the graphene sheet, but the agglomeration phenomenon is more obvious, indicating that the hydrothermal time is too long to easily lead to the agglomeration of the primary particles of niobium pentoxide, and the particle growth is uneven.

Battery assembly: the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material of this example is mixed with carbon black and PVDF at a mass ratio of 8:1:1, and NMP is used as a solvent to mix and grind, and then evenly spread on the copper foil On the surface, a nanoscale reduced graphene oxide composite niobium oxide negative electrode material smear was obtained; then, in an airtight glove box filled with argon gas, the pole piece of niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material was used as the working electrode of the battery , metal lithium sheet as counter electrode, microporous polypropylene membrane as diaphragm, 1mol/L LiPF ₆ /EC:DMC (volume ratio 1:1) as electrolyte, assembled into a CR2025 button battery, and carried out charge and discharge tests. The charging and discharging performance is similar to that of Example 1, indicating that the niobium pentoxide/reduced graphene oxide nanocomposite negative electrode material obtained in this embodiment can prevent the agglomeration of niobium pentoxide nanoparticles due to the existence of graphene, and strengthen the The conductivity of diniobium improves the lithium storage performance of the material.

The results of the examples show that the present invention can uniformly grow niobium pentoxide nanowires on thin reduced graphene oxide nanosheets by controlling the hydrothermal time conditions of the hydrothermal method, and the content and size of niobium pentoxide are uniform and controllable . When this material is used as an anode material for lithium-ion batteries, it shows much higher lithium storage capacity and excellent rate performance than pure-phase niobium pentoxide, and can be used as an anode material for next-generation high-performance lithium-ion batteries.

Claims (9)

1. a preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material, is characterized in that, comprises the following steps: (1) Mix graphene oxide nanosheets with water, stir, and ultrasonically disperse to obtain a dispersion of graphene oxide nanoparticles; (2) Dissolve and disperse niobium pentachloride in water, stir to obtain a suspension of niobium pentachloride, add organic co-solvent to the suspension of niobium pentachloride, stir to obtain a clear solution, add six times to the clear solution Methyltetramine was stirred to obtain a white solution; (3) Mixing the dispersion of graphene oxide nanoparticles obtained in step (1) with the white solution obtained in step (2), stirring until uniformly dispersed to obtain a mixed solution, and putting the obtained mixed solution into an autoclave for hydrothermal reaction; (4) After the hydrothermal reaction is completed, the precipitate produced by the hydrothermal reaction is collected, and the obtained precipitate is washed and dried to obtain a solid powder; (5) Heat-treating the solid powder obtained in step (4) under an argon atmosphere to obtain a niobium pentoxide/reduced graphene oxide composite negative electrode material. 2. The preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material according to claim 1, characterized in that, in step (1), the concentration of the graphene oxide nanometer dispersion is 0.5-2 mg/mL. 3. The preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material according to claim 1 or 2, characterized in that, in step (2), the concentration of the niobium pentachloride suspension is 5 ~15 mg/mL. 4. The method for preparing niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 3, characterized in that, in step (2), the organic co-solvent is oxalic acid, acetic acid or ethyl at least one of the diacids. 5. The method for preparing niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 4, characterized in that, in step (2), the method for dissolving and dispersing said niobium pentachloride is Magnetic stirring: put the mixed solution of niobium pentachloride and water in a water bath for magnetic stirring, the speed of magnetic stirring is 300-500 r/min, the temperature of magnetic stirring is 10-40 ℃, and the time of magnetic stirring is 0.5 h ~ 3 h. 6. The method for preparing niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 5, characterized in that, in step (3), the dispersion liquid of the graphene oxide nanometer and the The mixing volume ratio of the white solution is 1:1-3. 7. The preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 6, characterized in that, in step (3), the temperature of the hydrothermal reaction is 140 to 200 ℃, the time is 8-24 h. 8. The method for preparing niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 7, characterized in that, in step (4), the drying method is freeze drying, blasting Dry or vacuum dry. 9. The preparation method of niobium pentoxide/reduced graphene oxide composite negative electrode material according to any one of claims 1 to 8, characterized in that, in step (5), the heating rate of the heat treatment is 1 to 20 °C /min, the heating temperature is 400 ℃ ~ 1000 ℃, and the holding time is 1 ~ 3 h.