CN111785955B - High-capacity VNb9O25Nano-sheet lithium ion battery cathode material and preparation method thereof - Google Patents

Abstract

The invention discloses a high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material and a preparation method thereof, comprising the following steps: dissolving niobium pentachloride in ethanol, adding a certain amount of vanadyl acetylacetonate to the solution powder, after the mixed solution is completely dissolved by ultrasonic vibration, the aqueous solution of tetramethylammonium hydroxide is added dropwise to the mixed solution, and the mixture is stirred at a uniform speed to dissolve it completely. Then, the obtained solution is put into an autoclave for heating and reaction; after cooling, washing, drying and roasting are carried out to obtain VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material. The VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material prepared by the invention has nanometer scale and good dispersibility, and has the advantages of high specific capacity, good cycle performance and the like when applied as a lithium ion battery negative electrode material.

Description

A high-capacity VNb9O25 nanosheet lithium ion battery negative electrode material and preparation method thereof

technical field

The invention belongs to the field of lithium ion battery materials, in particular to a high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material and a preparation method thereof.

Background technique

With the enhancement of people's awareness of environmental protection, electric vehicles have attracted more and more attention. Lithium-ion batteries have the characteristics of high energy density, high operating voltage, small size, long service life, and environmental friendliness, and are considered to be an ideal power source for electric vehicles. However, the current commercial lithium-ion batteries cannot meet the requirements of electric vehicles in terms of charging speed, cruising range and safety. Therefore, the development of high-performance power lithium-ion batteries has always been the tireless pursuit of people. Electrode materials are the core and key of lithium-ion batteries, and have a decisive impact on the performance of batteries. Therefore, the focus of research and development of high-performance lithium-ion batteries is to develop high-performance electrode materials.

As an important component of Li-ion batteries, a satisfactory anode material is necessary because it plays a key role in enhancing its electrochemical performance. However, conventional anode material graphite cannot fully meet these requirements due to its relatively poor performance. The high-power kinetics are attributed to its poor Li-ion conductivity and safety issues stemming from the formation of Li dendrites at low operating potentials (relative to Li/Li ⁺ ). To solve the above problems, other types of anodes have been explored and developed. For example, titanium-based compounds show good performance in certain aspects. However, their low storage capacity severely limits their widespread application. Therefore, there is a strong desire to develop new anode materials with larger capacity and better safety.

In order for Li-ion batteries to better adapt to market demands, further improvements are essential in terms of high capacity, high electronic conductivity, and excellent capacity retention. In recent years, niobium-based compounds, such as _Nb2O5 , have received high attention from the scientific community as lithium _- ion anode materials, showing high power density, good structural stability, low cost, and environmental friendliness. Unfortunately, however, its inherent poor conductivity and capacity retention during charging/discharging have limited its practical use in Li-ion batteries. Therefore, it is crucial to develop anode materials with similar advantages to niobium pentoxide but with higher electrical conductivity.

Doping vanadium to niobium pentoxide can achieve larger discharge specific capacity, higher lithium ion diffusion coefficient and better cycle performance and stability than niobium pentoxide.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to aim at the deficiencies of the prior art, and to provide a method for preparing high-capacity VNb ₉ O ₂₅ nanosheets for lithium ion battery negative electrode materials with simple process and low cost. The ₉ O ₂₅ nanosheet lithium ion battery anode material has excellent electrochemical performance, discharge specific capacity, higher lithium ion diffusion coefficient and better cycle performance and stability.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A preparation method of a high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material, comprising the following steps:

(1) Dissolve niobium pentachloride in absolute ethanol and stir for 0.5-1 hour to completely dissolve it;

(2) adding vanadyl acetylacetonate powder as the vanadium source to the solution prepared in (1), and then ultrasonically oscillating for 0.5-1 hour to completely dissolve it;

(3) Add 20 mL of tetramethylammonium hydroxide aqueous solution to the solution prepared in (2) at a constant rate, and stir to dissolve it completely;

(4) Transfer the solution obtained in (3) to a stainless steel reaction kettle lined with polytetrafluoroethylene, and place it in a constant temperature drying oven for heating and reaction;

(5) Wash the reaction precipitate obtained in (4) with acetone, ethanol and deionized water for several times until the solution is neutral, and then place it in a vacuum drying oven to dry;

(6) The powder obtained in (5) is calcined in a muffle furnace to obtain a VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material.

Further, in the step (2), the molar ratio of vanadium ion to niobium ion is 1:9-1:5.

Further, in the described step (3), the concentration of the aqueous solution of tetramethyl ammonium hydroxide is 25%, the ratio of the amount of the total substance of vanadyl acetylacetonate and niobium pentachloride and the amount of substance of tetramethyl ammonium hydroxide It is 1:20-1:40, preferably 1:25.6-1:32.

Further, in the step (3), the dropping rate of the aqueous solution of tetramethylammonium hydroxide is 0.6 mL/min.

Further, the temperature of the heating reaction in the step (4) is 240° C., and the reaction time is 12-15 hours.

Further, in the step (5), the vacuum drying temperature is 60-90° C., and the drying time is 20-24 hours.

Further, in the step (6), the calcination temperature is 400° C., and the calcination time is 4-5 hours.

A high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material prepared by the preparation method.

Further, the VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material is formed by assembling VNb ₉ O ₂₅ microspheres and nanosheets, and the thickness of the nanosheets is 3-4 nanometers.

Beneficial effects of the present invention: the present invention adopts commercial niobium pentachloride as the niobium source, and vanadyl acetylacetonate as the vanadium source, and adopts the hydrothermal method to prepare, the process is simple, the cost is low, and it is suitable for industrial production; The molar ratio, calcination temperature and calcination time are used to control the particle size and dispersion degree of the material, and a high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material with good dispersion and controllable morphology is prepared; the VNb prepared by the present invention is used. ₉ O ₂₅ nanosheet material is used as the negative electrode of lithium ion battery, which has extremely high discharge specific capacity and good cycle performance.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the VNb ₉ O ₂₅ nanosheet material prepared in Example 1;

2 is a scanning electron microscope (SEM) photo of the VNb ₉ O ₂ 5 nanosheet material prepared in Example 1;

3 is a transmission electron microscope (TEM) photo of the VNb ₉ O ₂₅ nanosheet material prepared in Example 1;

4 is a graph showing the rate performance of the coin cell with the VNb ₉ O ₂₅ nanosheet material prepared in Example 1 as the negative electrode under different currents;

5 is a graph showing the cycle stability performance of a coin cell with the VNb ₉ O ₂₅ nanosheet material prepared in Example 1 as a negative electrode at a current of 2 A/g;

6 is the X-ray diffraction pattern of the VNb ₉ O ₂₅ nanorod material prepared in Example 2;

7 is a scanning electron microscope (SEM) photo of the VNb ₉ O ₂₅ nanorod material prepared in Example 2;

8 is a transmission electron microscope (TEM) photo of the VNb ₉ O ₂₅ nanorod material prepared in Example 2;

9 is a graph of the rate performance of the coin cell with the VNb ₉ O ₂₅ nanorod material prepared in Example 2 as the negative electrode under different currents;

FIG. 10 is a graph showing the rate performance of the coin cell with the VNb ₉ O ₂₅ nanosheet material prepared in Example 3 as the negative electrode at different currents.

FIG. 11 is a graph showing the rate performance of the coin cell using the Nb ₂ O ₅ nanosheet material prepared in Example 5 as the negative electrode at different currents.

Detailed ways

The present invention will be further described below with reference to specific embodiments. It should be understood that the following examples are only used to illustrate the present invention rather than to limit the scope of the present invention, and those skilled in the art can make some non-essential improvements and adjustments according to the content of the above invention.

Example 1

The preparation method of the high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material of the present embodiment is as follows:

(1) Dissolve 2.7 mmol of niobium pentachloride (0.73 g) in 36 ml of absolute ethanol, and stir for 0.5-1 hour to completely dissolve it;

(2) Add 0.3 mmol of vanadyl acetylacetonate powder to the solution as the vanadium source, at this time V:Nb is 1:9, and then ultrasonically vibrate for 0.5-1 hour to completely dissolve it;

(3) 20 mL of 25% tetramethylammonium hydroxide aqueous solution was added dropwise to the mixed solution at a rate of 0.6 mL/min, and stirred until a clear solution was formed. At this time (vanadyl acetylacetonate + five The molar ratio of niobium chloride) to tetramethylammonium hydroxide is 1:25.6;

(4) The obtained solution was then transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, placed in a constant temperature drying oven for heating reaction, the temperature of the heating reaction was 240°C, and the reaction time was 12 hours;

(5) The obtained reaction precipitate was washed several times with acetone, ethanol and deionized water respectively until the solution was neutral, and then placed in a vacuum drying oven to dry at a vacuum drying temperature of 60 °C and a drying time of 24 hours;

(6) The powder obtained after drying is calcined in a muffle furnace at a calcination temperature of 400° C. and a calcination time of 4 hours, and then taken out for cooling and grinding to obtain a VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material.

The negative electrode material of the VNb ₉ O ₂₅ nanosheet lithium ion battery prepared in this example was characterized by X-ray diffractometer and electron scanning electron microscope, respectively, and the results are shown in FIG. 1 and FIG. 2 . It can be seen from Figure 1 that the diffraction peak of the material sample is completely consistent with the diffraction peak of VNb ₉ O ₂₅ in the standard PDF card, and no other impurity peaks are found, indicating that the synthesized sample is relatively pure. As shown in Figure 2, the sample has good morphology and good dispersion, and the size of the microspheres is about 1-2 microns. As shown in Fig. 3, the thickness of the nanosheets on the surface of the microspheres is about 3-4 nm.

The VNb ₉ O ₂₅ nanosheet material prepared in this example is used as the negative electrode material of the lithium ion battery to prepare a button battery, wherein the VNb ₉ O ₂₅ nanosheet material is the active material, the conductive agent is Ketjen black, and the binder is polyvinylidene fluoride. Ethylene, the ratio of the three is 8:1:1 (mass ratio). Then the electrochemical performance of the coin cell was tested, and the cell test range was 1.0-3.0 V. As shown in Figure 4, the cycle performance of the tested samples at different magnifications, it can be seen from the figure that the samples have good cycle performance at 0.2 A/g, 0.4A/g, 1 A/g, 2 A/g The discharge specific capacities of the samples are about 500, 445, 325, and 300 mAh/g, respectively, and they still have high discharge specific capacities (about 140 mAh/g) even at a rate of 10 A/g. Figure 5 shows that the coin cell prepared with this material still has a discharge specific capacity of 290 mAh/g after 2000 cycles at a current of 2 A/g.

Example 2

(1) Dissolve 2.7 mmol of niobium pentachloride (0.73 g) in 36 ml of absolute ethanol, and stir for 0.5-1 hour to completely dissolve it;

(2) Add 0.3 mmol of vanadyl acetylacetonate powder to the solution as the vanadium source, at this time V:Nb is 1:9, and then ultrasonically vibrate for 0.5-1 hour to completely dissolve it;

(3) Add 30 mL of tetramethylammonium hydroxide aqueous solution dropwise to the mixed solution at a rate of 0.6 mL/min, stir to dissolve completely, at this time (vanadyl acetylacetonate + niobium pentachloride) and tetramethylammonium The molar ratio of methylammonium hydroxide is 1:38.3;

(4) The obtained solution was then transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, placed in a constant temperature drying oven for heating reaction, the temperature of the heating reaction was 240°C, and the reaction time was 12 hours;

(5) The obtained reaction precipitate was washed several times with acetone, ethanol and deionized water, respectively, until the solution was neutral, and then placed in a vacuum drying oven to dry at a vacuum drying temperature of 60°C and a drying time of 24 hours;

(6) The powder obtained after drying is calcined in a muffle furnace at a calcination temperature of 700° C. and a calcination time of 4 hours, and then taken out for cooling and grinding to obtain a VNb ₉ O ₂₅ nanorod lithium ion battery negative electrode material. Due to the high calcination temperature, the hydrothermally synthesized nanosheet precursors were transformed into _{VNb9O25 nanorods} .

The negative electrode material of the VNb ₉ O ₂₅ nanorod lithium ion battery prepared in this example was characterized by X-ray diffractometer and electron scanning electron microscope, respectively, and the results are shown in FIG. 6 and FIG. 7 . It can be seen from Figure 6 that the diffraction peak of the material sample is completely consistent with the diffraction peak of VNb ₉ O ₂₅ in the standard PDF card, and no other impurity peaks are found, indicating that the synthesized sample is relatively pure. As shown in Figure 7, the sample has good morphology and good dispersion, the diameter of the nanorods is about 20-50 nanometers, and the length is about 200-400 nanometers. Figure 8 is a transmission electron microscope (TEM) photo of VNb ₉ O ₂₅ nanorods;

The VNb ₉ O ₂₅ nanorod material prepared in this example is used as the negative electrode material of the lithium ion battery to prepare a button battery, wherein the VNb ₉ O ₂₅ nanorod material is the active material, the conductive agent is Ketjen black, and the binder is polyvinylidene fluoride. Ethylene, the ratio of the three is 8:1:1 (mass ratio), and then the electrochemical performance of the coin cell was tested. As shown in Figure 9, the cycle performance of the test samples at different rates is about 250, 200, 125, and 100 mAh/g at 0.2, 0.4, 1, and 2 A/g. The coin-cell battery prepared with VNb ₉ O ₂₅ nanosheet material as the negative electrode material, the discharge specific capacity at the same current decreased significantly.

Example 3

The preparation method of the high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material of the present embodiment is as follows:

(1) Dissolve 3 mmol of niobium pentachloride (0.81 g) in 36 ml of absolute ethanol and stir for 0.5-1 hour to completely dissolve it;

(2) Add 0.6 mmol of vanadyl acetylacetonate powder to the solution as the vanadium source, at this time V:Nb is 1:5, and then ultrasonically vibrate for 0.5-1 hour to completely dissolve it;

(3) Add 35 mL of 25% tetramethylammonium hydroxide aqueous solution dropwise to the mixed solution at a rate of 0.6 mL/min, stir to dissolve it completely, at this time (vanadyl acetylacetonate + five The molar ratio of niobium chloride) to tetramethylammonium hydroxide is 1:37.3;

(4) The obtained solution was then transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, placed in a constant temperature drying oven for heating reaction, the temperature of the heating reaction was 240°C, and the reaction time was 12 hours;

(5) The obtained reaction precipitate was washed several times with acetone, ethanol and deionized water, respectively, until the solution was neutral, and then placed in a vacuum drying oven to dry at a vacuum drying temperature of 60°C and a drying time of 24 hours;

(6) The powder obtained after drying is calcined in a muffle furnace, the calcination temperature is 500°C, and the calcination time is 4 hours, and then the powder is taken out for cooling and grinding to obtain a nano-sheet lithium-ion battery negative electrode with a VNb ₉ O ₂₅ crystal phase. Material.

The VNb ₉ O ₂₅ nanosheet material prepared in this example is used as the negative electrode material of the lithium ion battery to prepare a button battery, wherein the VNb ₉ O ₂₅ nanosheet material is the active material, the conductive agent is ketjen black, and the binder is polyvinylidene fluoride Ethylene, the ratio of the three is 8:1:1 (mass ratio). Then the electrochemical performance of the coin cell was tested, and the cell test range was 1.0-3.0 V. As shown in Figure 10, the cycle performance of the test sample at different rates is shown. It can be seen from the figure that the sample has good rate cycle performance. , 250, 200 mAh/g, compared with the coin cell battery prepared with 400 ℃ VNb ₉ O ₂₅ nanosheet material as the negative electrode material, the discharge specific capacity at the same current decreased significantly. Compared with the coin-cell battery prepared with VNb ₉ O ₂₅ nanorod material (Fig. 9) as the anode material, the discharge specific capacity at the same current is significantly improved.

Example 4

The preparation method of the high-capacity VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material of the present embodiment is as follows:

(1) Dissolve 3 mmol of niobium pentachloride (0.81 g) in 36 ml of absolute ethanol and stir for 0.5-1 hour to completely dissolve it;

(2) Add 0.6 mmol of vanadyl acetylacetonate powder to the solution as the vanadium source, at this time V:Nb is 1:5, and then ultrasonically vibrate for 0.5-1 hour to completely dissolve it;

(3) 25 mL of 25% tetramethylammonium hydroxide aqueous solution was added dropwise to the mixed solution at a rate of 0.6 mL/min, and stirred to dissolve completely. At this time (vanadyl acetylacetonate + pentachloride) The molar ratio of niobium) to tetramethylammonium hydroxide is 1:26.6;

(4) The obtained solution was then transferred to a stainless steel reaction kettle lined with polytetrafluoroethylene, placed in a constant temperature drying oven for heating reaction, the temperature of the heating reaction was 240°C, and the reaction time was 12 hours;

(5) The obtained reaction precipitate was washed several times with acetone, ethanol and deionized water, respectively, until the solution was neutral, and then placed in a vacuum drying oven to dry at a vacuum drying temperature of 60°C and a drying time of 24 hours;

(6) The powder obtained after drying is calcined in a muffle furnace at a calcination temperature of 400° C. and a calcination time of 4 hours, and then taken out for cooling and grinding to obtain a VNb ₉ O ₂₅ nanosheet lithium ion battery negative electrode material.

Example 5

(1) Dissolve 3 mmol of niobium pentachloride (0.81 g) in 36 ml of absolute ethanol, and stir for 0.5-1 hour to completely dissolve it;

(2) Add 25 mL of tetramethylammonium hydroxide aqueous solution dropwise to the mixed solution at a rate of 0.6 mL/min, and stir to dissolve it completely. At this time, the moles of niobium pentachloride and tetramethylammonium hydroxide are The ratio is 1:32;

(4) then transfer the obtained solution to a stainless steel reaction kettle lined with polytetrafluoroethylene, place it in a constant temperature drying oven for heating reaction, the temperature of heating reaction is 240 ℃, and the reaction time is 12 hours;

(5) The obtained reaction precipitate was washed several times with acetone, ethanol and deionized water, respectively, until the solution was neutral, and then placed in a vacuum drying oven to dry at a vacuum drying temperature of 60°C and a drying time of 24 hours;

(6) The powder obtained after drying is placed in a muffle furnace for calcination, the calcination temperature is 400°C, and the calcination time is 4 hours, and then the powder is taken out for cooling and grinding, that is, a vanadium-free Nb ₂ O ₅ nanosheet lithium ion battery negative electrode is obtained Material.

The Nb ₂ O ₅ nanosheet material prepared in this example is used as the negative electrode material of the lithium ion battery to prepare a button battery, wherein the Nb ₂ O ₅ nanosheet material is the active material, the conductive agent is ketjen black, and the binder is polyvinylidene fluoride Ethylene, the ratio of the three is 8:1:1 (mass ratio). Then the electrochemical performance of the coin cell was tested, and the cell test range was 1.0-3.0 V. As shown in Figure 11, the cycle performance of the test sample at different rates is shown. It can be seen from the figure that the sample has good rate cycle performance. About 162, 158, 151, 138, 103, 53 mAh/g, compared with 400 ℃ VNb ₉ O ₂₅ nanosheet material (Fig. 4) as the negative electrode material of the button battery, the discharge specific capacity under the same current is obvious decline.

The foregoing has shown and described the basic principles and main features of the present invention, as well as the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. High-capacity VNb₉O₂₅The preparation method of the nano-sheet lithium ion battery cathode material is characterized by comprising the following steps of:

(1) dissolving niobium pentachloride in absolute ethyl alcohol, and stirring for 0.5-1 hour to completely dissolve the niobium pentachloride;

(2) adding vanadyl acetylacetonate powder as a vanadium source into the solution prepared in the step (1), and then carrying out ultrasonic oscillation for 0.5-1 hour to completely dissolve the vanadyl acetylacetonate powder;

(3) adding tetramethyl ammonium hydroxide aqueous solution into the solution obtained in the step (2) at a constant speed, and stirring to completely dissolve the tetramethyl ammonium hydroxide aqueous solution;

(4) transferring the solution obtained in the step (3) into a stainless steel reaction kettle lined with polytetrafluoroethylene, and placing the stainless steel reaction kettle in a constant-temperature drying box for heating reaction;

(5) washing the reaction precipitate obtained in the step (4) with acetone, ethanol and deionized water for several times respectively until the solution is neutral, and then placing the solution in a vacuum drying oven for drying;

(6) placing the powder obtained in the step (5) in a muffle furnace for roasting at 400-500 ℃ to obtain VNb₉O₂₅A nanoplate lithium ion battery negative electrode material;

the mass fraction of the tetramethylammonium hydroxide aqueous solution in the step (3) is 25%, and the ratio of the total amount of vanadyl acetylacetonate and niobium pentachloride to the amount of tetramethylammonium hydroxide is 1:20-1: 40;

the dropping rate of the tetramethylammonium hydroxide aqueous solution is 0.6 mL/min;

the heating reaction temperature in the step (4) is 240 ℃, and the reaction time is 12-15 hours.

2. The VNb of claim 1₉O₂₅The preparation method of the nano-sheet lithium ion battery cathode material is characterized by comprising the following steps: in the step (2), the molar ratio of the vanadium ions to the niobium ions is 1:9-1: 5.

3. The VNb of claim 1₉O₂₅The preparation method of the cathode material of the nano-sheet lithium ion battery is characterized in that the vacuum drying temperature in the step (5) is 60-90 ℃, and the drying time is 20-24 hours.

4. The VNb of claim 1₉O₂₅Nano-sheet lithium ion battery cathode materialThe preparation method of the material is characterized in that the roasting temperature in the step (6) is 400 ℃, and the roasting time is 4-5 hours.

5. A high capacity VNb produced by the production method of any one of claims 1 to 4₉O₂₅A nano-sheet negative electrode material for lithium ion batteries.

6. The high-capacity VNb of claim 5₉O₂₅The nano-sheet lithium ion battery cathode material is characterized in that: the VNb₉O₂₅The negative electrode material of the nano-sheet lithium ion battery consists of VNb₉O₂₅The thickness of the nano-sheet is 3-4 nanometers.

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