CN112928246B - Composite material, preparation method and application thereof - Google Patents

Abstract

The invention provides a composite material, a preparation method and application thereof. The composite material is a core-shell structure in which a nano-carbon layer coats a single crystal H-Nb ₂ O ₅ , wherein the core is a single crystal H-Nb ₂ O ₅ particle, The longest dimension is 2-10 μm, and the shell is a nano-carbon layer with a thickness of 10-20 nm. The nano-carbon layer-coated single-crystal H-Nb ₂ O ₅ composite material obtained according to the preparation method of the present invention has a reversible capacity as high as 270 mAh/g; and the single-crystal H-Nb ₂ O ₅ has intrinsically high lithium ion diffusivity , the uniform nano _- carbon layer improves the electronic conductivity of the material, and ensures the ultra _- high rate charge-discharge capability and long-cycle stability of the material. Lithium precipitation does not occur under the current density, so the safety is good.

Description

A kind of composite material, its preparation method and application

technical field

The invention relates to the technical field of single crystal H-Nb ₂ O ₅ materials, in particular to a composite material, a preparation method and application thereof.

Background technique

With the continuous innovation of terminal application technology and the increase of market demand, it is imperative to develop higher-performance energy storage equipment, especially the development of energy storage technology with high capacity, fast charging and discharging, and good safety. Lithium-ion batteries and lithium-ion capacitors are currently the most commonly used high-rate energy storage technologies. Electrode materials are the main body of energy storage and directly determine the overall performance of energy storage batteries or capacitors. Therefore, the optimization and innovation of key electrode materials is the key to improving performance. The properties of anode materials directly affect the power performance and safety performance of energy storage batteries or capacitors.

For lithium-ion batteries, graphite-based anodes are the most commonly used anode materials for commercial lithium-ion batteries, with a theoretical specific capacity of 372mAh/g and low lithium intercalation potential (<0.2V, vs. Li ⁺ /Li). However, at high current density, the overpotential of graphite negative electrode lithium intercalation increases, and there is a risk of lithium precipitation, which may cause battery circuit and cause battery safety problems, so it is not suitable for high-rate charge and discharge. Lithium titanate (Li ₄ Ti ₅ O ₁₂ , LTO) has a lithium intercalation potential of 1.55V (vs. Li ⁺ /Li) and small volumetric strain during charge and discharge. Anode material for discharge. However, due to its high potential and low specific capacity (175mAh/g), its energy density is difficult to meet the demand for high specific energy batteries. The silicon-based composite anode material is an emerging high specific capacity anode, and its actual specific capacity can reach 600-2000mAh/g, and good high-rate charge-discharge performance can be achieved through material nanoization. However, the inherent huge volume expansion of the material during the lithium intercalation process affects its cycle life, and there are problems such as low first charge and discharge coulombs, and complex material fabrication processes, which make it difficult for silicon-based anodes to achieve large-scale practical applications. Li-ion capacitors use the fast lithium storage properties of adsorption and desorption to achieve high-rate charge and discharge, but their capacity is limited. Combining traditional capacitor cathode materials and high-rate redox anode materials to form hybrid capacitors can effectively improve their energy density. Therefore, exploring suitable anode materials is a hot and difficult point in the development of next-generation high-rate and high-safety energy storage technologies.

SUMMARY OF THE INVENTION

Based on the disadvantages of lithium ion battery negative electrode materials in the prior art, such as lithium precipitation, low energy density, short cycle life and limited capacity of lithium ion capacitors, the present invention provides a composite material, which can be used as a negative electrode for lithium ion batteries and lithium ion batteries. In ion capacitors, the single crystal H-Nb ₂ O ₅ coated with nano-carbon layer has suitable lithium intercalation potential, high reversible capacity and good safety.

The single crystal H-Nb ₂ O ₅ in this application is a variant of Nb ₂ O ₅ , and the crystal structure of Nb ₂ O ₅ is related to the preparation method.

According to one aspect of the present application, a composite material is provided, the composite material is a core-shell structure in which a nano-carbon layer coats a single crystal H-Nb ₂ O ₅ , wherein the core is a single crystal H-Nb ₂ O ₅ particle , the longest dimension is 2-10 μm, and the shell is a nano-carbon layer with a thickness of 10-20 nm.

Optionally, the carbon content in the nano-carbon layer-coated single crystal H-Nb ₂ O ₅ is 2.0-4.0 wt %.

Preferably, the carbon content in the nano-carbon layer-coated single crystal H-Nb ₂ O ₅ is 2.5-3.5 wt %.

The present application also provides a method for preparing the above-mentioned composite material, the method comprising at least the following steps:

a) obtaining single crystal H-Nb ₂ O ₅ ;

b) react and carbonize the mixture containing the single crystal H-Nb ₂ O ₅ and the carbon source to obtain the single crystal H-Nb ₂ O ₅ covered by the nano-carbon layer.

Optionally, the method for obtaining the single crystal H-Nb ₂ O ₅ in step a) includes: calcining the raw material containing the niobium source to obtain the single crystal H-Nb ₂ O ₅ .

Optionally, the niobium source includes at least one of niobium carbide, niobium hydroxide, niobium oxalate, niobium pentachloride, niobium ethoxide, niobium dioxide, niobium monoxide, and lithium niobate.

Optionally, the conditions of the calcination are: the reaction temperature is 900-1200° C.; and the reaction time is 6-24 h.

Optionally, the carbon source includes at least one carbon source including dopamine, methoxypolyethylene glycol-dopamine, and sulfhydryl-polyethylene glycol-dopamine.

Optionally, the reaction is a polymerization reaction.

Optionally, the mass ratio of the carbon source to the single crystal H-Nb ₂ O ₅ in step b) is 1:10˜1:4.

Preferably, the mass ratio of the carbon source to the single crystal H-Nb ₂ O ₅ in step b) is 1:8˜1:6.

Optionally, the reaction time is 6-48h.

Preferably, the reaction time is 12-16 h.

Common carbonization treatment conditions can be used in this application, and those skilled in the art can select appropriate reaction conditions according to actual production needs. Preferably, the conditions of the carbonization treatment are as follows: the reaction temperature is 800-1000°C; the reaction heating rate is 1-5°C/min; and the reaction time is 2-6h.

Optionally, the carbonization is carried out in an inert atmosphere.

Optionally, the inert atmosphere includes an inert atmosphere and a nitrogen atmosphere.

Commonly used cooling conditions after carbonization treatment can be used in this application, and those skilled in the art can select appropriate reaction conditions according to actual production needs. Preferably, the temperature is lowered after the carbonization treatment is completed, and the cooling rate is 1-10° C./min.

The obtaining of the mixture in step b) at least includes the following steps: mixing the dispersion liquid containing the single crystal H-Nb ₂ O ₅ and the solution containing the carbon source to obtain the mixture.

Optionally, the solid content of the dispersion liquid of the single crystal H-Nb ₂ O ₅ is 0.05-5.0 wt %.

Preferably, the solid content of the dispersion liquid of the single crystal H-Nb ₂ O ₅ is 0.5-2 wt %.

Optionally, the dispersion liquid of the single crystal H-Nb ₂ O ₅ includes a solution buffer; the solution buffer includes tris (Tris), potassium dihydrogen phosphate, sodium dihydrogen phosphate at least one of them.

Optionally, the pH of the dispersant is 8-9.

Optionally, the solution includes a solvent; the solvent includes at least one of water, methanol, ethanol, propanol, and ethylene glycol.

Optionally, the concentration of the solution is 0.05-0.5 mol/L.

Optionally, the step B) includes at least the following steps:

(1) adding the solution containing the carbon source into the dispersion liquid containing the single crystal H-Nb ₂ O ₅ under stirring conditions, and stirring and polymerizing to obtain the single crystal H-Nb ₂ O ₅ covered by the carbon precursor;

(2) carbonizing the single crystal H-Nb ₂ O ₅ coated with the carbon precursor to obtain the composite material.

Preferably, the step b) includes at least the following steps: continuously stirring the single crystal H-Nb ₂ O ₅ dispersion, while slowly adding the dopamine solution to the single crystal H-Nb ₂ O ₅ dispersion at a rate of 20～100mL/min; after adding, continue to stir the mixed solution for 6～48h, after the dopamine monomer undergoes polymerization reaction, wash, separate and dry to obtain polydopamine-coated single crystal H-Nb ₂ O ₅ .

Optionally, the solvent used in the washing is at least one of water, methanol, ethanol, and propanol.

Common drying conditions can be used in this application, and those skilled in the art can select appropriate reaction conditions according to actual production needs. Preferably, the drying treatment temperature is 70-100° C., and the treatment time is 12-48 h.

Optionally, the step of carbonizing treatment at least includes: placing the obtained single crystal H-Nb ₂ O ₅ coated with carbon precursor in an inert atmosphere tube furnace for high temperature carbonizing treatment to obtain a nano-carbon layer coated single crystal. Crystalline H _{- Nb2O5} composite.

Optionally, the preparation method of the single crystal H-Nb ₂ O ₅ dispersion liquid is as follows: the single crystal H-Nb ₂ O ₅ is uniformly dispersed in a Tris buffer aqueous solution by ultrasonic waves for 15 to 60 minutes.

The present application also provides a negative electrode material, comprising at least one of the above-mentioned composite material and the composite material prepared according to the above-mentioned method.

The present application also provides a lithium ion battery, comprising at least one of the above composite material, the composite material prepared according to the above method, and the above negative electrode material.

In addition, the present application provides a lithium ion capacitor, comprising at least one of the above-mentioned composite material, the composite material prepared according to the above-mentioned method, and the above-mentioned negative electrode material.

The beneficial effects that this application can produce include:

1) Compared with the Nb ₂ O ₅ prepared by the conventional preparation method, the nano-carbon layer-coated single crystal H-Nb ₂ O ₅ material prepared according to the preparation method of the present invention has a reversible capacity as high as 270mAh/g;

2) The single crystal H-Nb ₂ O ₅ material has intrinsically high lithium ion diffusivity, the uniform nano-carbon layer improves the electronic conductivity of the material, and ensures the ultra-high rate charge-discharge capability and long-cycle stability of the material;

3) The single crystal H-Nb ₂ O ₅ covered by the nano-carbon layer has a suitable lithium intercalation potential, and no lithium precipitation occurs at a large current density, so the safety is good.

Description of drawings

Fig. 1 is the XRD pattern of the single crystal H-Nb ₂ O ₅ coated with nano-carbon layer obtained in Example 1;

Fig. 2 is the TEM image of the single crystal H-Nb ₂ O ₅ coated with the nano-carbon layer obtained in Example 1;

Fig. 3 is the SEM image of the single crystal H-Nb ₂ O ₅ coated with nano-carbon layer obtained in Example 1;

Fig. 4 is the charge-discharge curve at 0.25C of the single-crystal H-Nb ₂ O ₅ coated with the nano-carbon layer obtained in Example 1;

5 is a rate performance diagram of the single-crystal H-Nb ₂ O ₅ material coated with the nano-carbon layer obtained in Example 1;

FIG. 6 is a 1000 cycle performance diagram of the nano-carbon layer-coated single-crystal H-Nb ₂ O ₅ material obtained in Example 1. FIG.

Detailed ways

The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

The instrument used for SEM test is scanning electron microscope/JSM-7800F;

The instrument used for XRD test is X-ray powder diffractometer/RigakuUltima IV;

The TEM test uses an environmental projection electron microscope/Titan Themis ETEM G3;

The instrument used for TGA test is thermogravimetric analyzer/PYRIS Diamond;

The battery used for the battery performance test is a CR2016 button battery, and the instrument used is the blue battery test system/CT2001A.

Example 1

Preparation of single crystal H-Nb ₂ O ₅ (1#):

Put the corundum crucible containing 5g of niobium carbide into a muffle furnace, and heat it up to 1000°C at a heating rate of 2°C/min; after heat treatment at this temperature for 12 hours, it is lowered to room temperature at a rate of 10°C/min to obtain a single crystal H-Nb ₂ O ₅ (1#);

Preparation of sample material (A1):

Weigh 1 g of the obtained single crystal H-Nb ₂ O ₅ (1#) material and uniformly disperse it in a Tris buffer aqueous solution with pH=8.5 by ultrasonic for 30 minutes, and continuously stir the single crystal H-Nb ₂ O ₅ (1#) dispersion; Dissolve 0.36g of dopamine in 10mL of deionized water to prepare a dopamine solution; add the obtained dopamine solution dropwise to the stirring single crystal H-Nb ₂ O ₅ (1#) dispersion, and continue stirring for 24h, dopamine polymerizes on the surface of the material After the polymerization reaction is completed, wash three times with ethanol, centrifuge to obtain the product, and place the product in an oven at 90 ° C for drying for 12 hours; transfer the dried product to a porcelain boat and put it into a tube furnace, in an argon atmosphere for 5 The temperature was raised to 850°C at ℃/min, and the temperature was maintained for 2 hours. After the carbonization reaction was completed, the temperature was lowered to room temperature at 5°C/min to obtain a composite sample material (A1).

Preparation of half-cell (B1):

The sample material (A1) was used as the electrode active material to prepare an electrode; the material composition of the electrode was: the mass ratio of composite material (A1), carbon black and PVdF was 8:1:1, the current collector was aluminum foil, and the electrolyte was LBC0305, The obtained electrode and metal lithium formed a half-cell to test the performance of the battery.

Example 2

The single crystal H-Nb ₂ O ₅ used in Example 2 is the single crystal H-Nb ₂ O ₅ (1#) prepared in Example 1.

Preparation of sample material (A2):

The difference between the preparation of the sample material (A2) and the preparation method of the sample material (A1) is: when the dopamine solution is added dropwise to the stirring single crystal H-Nb ₂ O ₅ dispersion, the continuous stirring time becomes 12h, and the other reaction steps and conditions are the same as in Example 1.

Preparation of half-cell (B2):

The steps and conditions for preparing the half-cell (B2) from the sample material (A2) as the electrode active material are the same as in Example 1.

Example 3

The single crystal H-Nb ₂ O ₅ used in Example 3 is the single crystal H-Nb ₂ O ₅ (1#) prepared in Example 1.

Preparation of sample material (A3):

The difference between the preparation of the sample material (A3) and the preparation method of the sample material (A1) is: when the dopamine solution is added dropwise to the stirring single crystal H-Nb ₂ O ₅ dispersion, the continuous stirring time becomes 48h, and the other reaction steps and conditions are the same as in Example 1.

Preparation of half-cell (B3):

The steps and conditions for preparing the half-cell (B3) from the sample material (A3) as the electrode active material were the same as those in Example 1.

Example 4

Preparation of single crystal H-Nb ₂ O ₅ (2#):

The corundum crucible containing 5g of niobium dioxide was put into a muffle furnace, and the temperature was raised to 1000°C at a heating rate of 2°C/min. Crystalline H-Nb ₂ O ₅ (2#).

Preparation of sample material (A4):

Weigh 1 g of the obtained single crystal H-Nb ₂ O ₅ (2#) and evenly disperse it in a Tris buffer aqueous solution with pH=8.5 by ultrasonic for 30 minutes, and continuously stir the single crystal H-Nb ₂ O ₅ (2#) dispersion; 0.36g of dopamine was dissolved in 10mL of deionized water to prepare a dopamine solution; the obtained dopamine solution was added dropwise to the stirring single crystal H-Nb ₂ O ₅ (2#) dispersion, and the stirring was continued for 24h, the dopamine polymerized on the surface of the material ; After the polymerization reaction is completed, wash with ethanol three times, centrifuge to obtain the product, and dry the product at 90 °C for 12 h; transfer the dried product to a porcelain boat and put it in a tube furnace, and heat up at 5 °C/min in an argon atmosphere. to 850° C., and kept for 2 h. After the carbonization reaction was completed, the composite sample material (A4) was obtained after the temperature was lowered to room temperature at 5° C./min.

Preparation of half-cell (B4):

The steps and conditions for preparing the half-cell (B4) from the sample material (A4) as the electrode active material were the same as in Example 1.

Example 5

Preparation of polycrystalline Nb ₂ O ₅ (3#):

The difference between the preparation method of polycrystalline Nb ₂ O ₅ (3#) and the preparation method of single crystal H-Nb ₂ O ₅ (2#) is that niobium hydroxide is used, and other reaction steps and conditions are the same as in Example 4 .

Preparation of sample material (A5):

The sample material (A5) was prepared in the same way as the sample material (A4).

Preparation of half-cell (B5):

The steps and conditions for preparing the half-cell (B5) from the sample material (A5) as the electrode active material are the same as in Example 1.

Comparative Example 1

The single crystal H-Nb ₂ O ₅ used in Comparative Example 1 is the single crystal H-Nb ₂ O ₅ (1#) prepared in Example 1. The obtained single crystal H-Nb ₂ O ₅ (1#) was directly used as the sample material (A6) of Comparative Example 1

The steps and conditions for preparing the half-cell (B6) from the sample material (A6) as the electrode active material are the same as in Example 1.

Comparative Example 2

Preparation of single crystal T-Nb ₂ O ₅ (4#):

Put the corundum crucible containing 5g of niobium carbide into a muffle furnace, and heat it up to 700°C at a heating rate of 2°C/min; after heat treatment at this temperature for 12 hours, it is lowered to room temperature at a rate of 10°C/min to obtain a single crystal T-Nb ₂ O ₅ (4#);

Preparation of sample material (A7):

Weigh 1 g of the obtained single crystal T-Nb ₂ O ₅ (4#) material and uniformly disperse it in a Tris buffered aqueous solution with pH=8.5 by ultrasonic for 30 minutes, and continuously stir the single crystal T-Nb ₂ O ₅ (4#) dispersion; Dissolve 0.36 g of dopamine in 10 mL of deionized water to prepare a dopamine solution; add the obtained dopamine solution dropwise to the stirring single crystal T-Nb ₂ O ₅ (4#) dispersion, and continue stirring for 24 hours, dopamine polymerizes on the surface of the material After the polymerization reaction is completed, wash three times with ethanol, centrifuge to obtain the product, and place the product in an oven at 90 ° C for drying for 12 hours; transfer the dried product to a porcelain boat and put it into a tube furnace, in an argon atmosphere for 5 The temperature was raised to 700°C at ℃/min, and the temperature was maintained for 2 h. After the carbonization reaction was completed, the temperature was lowered to room temperature at 5°C/min to obtain a composite sample material (A7).

Preparation of half-cell (B7):

The steps and conditions for preparing the half-cell (B7) from the sample material (A7) as the electrode active material were the same as in Example 1.

Comparative Example 3

Preparation of polycrystalline Nb ₂ O ₅ (5#):

Put the corundum crucible containing 5g of niobium carbide into a muffle furnace, and heat it up to 1400°C at a heating rate of 2°C/min; after maintaining this temperature for 12 hours of heat treatment, drop to room temperature at a rate of 10°C/min to obtain polycrystalline Nb ₂ O ₅ (5#);

Preparation of sample material (A8):

Weigh 1 g of the obtained polycrystalline Nb ₂ O ₅ (5#) material and uniformly disperse it in a Tris buffered aqueous solution with pH=8.5 by ultrasonic for 30 minutes, and continuously stir the polycrystalline Nb ₂ O ₅ (5#) dispersion; weigh 0.36 g of dopamine Dissolve in 10 mL of deionized water to prepare a dopamine solution; add the obtained dopamine solution dropwise to the stirring polycrystalline Nb ₂ O ₅ (5#) dispersion, and continue stirring for 24 hours, the dopamine polymerizes on the surface of the material; when the polymerization is completed , washed three times with ethanol, and centrifuged to obtain the product, which was dried in an oven at 90 °C for 12 h; the dried product was transferred to a porcelain boat and placed in a tube furnace, and heated to 850 °C at 5 °C/min in an argon atmosphere. ℃, keep the temperature for 2 h, and after the carbonization reaction is completed, reduce to room temperature at 5 ℃/min to obtain a composite sample material (A8).

Preparation of half-cell (B8):

The steps and conditions for preparing the half-cell (B8) from the sample material (A8) as the electrode active material were the same as in Example 1.

Comparative Example 4

Preparation of polycrystalline Nb ₂ O ₅ (6#):

Put the corundum crucible containing 5g of niobium carbide into a muffle furnace, and heat it up to 1400°C at a heating rate of 2°C/min; after heat treatment at this temperature for 6 hours, drop to room temperature at a rate of 10°C/min to obtain polycrystalline Nb ₂ O ₅ (6#);

Preparation of sample material (A9):

Weigh 1 g of the obtained polycrystalline Nb ₂ O ₅ (6#) material and uniformly disperse it in a Tris buffer aqueous solution with pH=8.5 by ultrasonic for 30 minutes, and continuously stir the dispersion liquid of single crystal polycrystalline Nb ₂ O ₅ (6#); weigh 0.36 g dopamine was dissolved in 10 mL of deionized water to prepare a dopamine solution; the obtained dopamine solution was added dropwise to the stirring polycrystalline Nb ₂ O ₅ (5#) dispersion liquid, and the stirring was continued for 24 hours, the dopamine polymerized on the surface of the material; to be polymerized The reaction was completed, washed three times with ethanol, and centrifuged to obtain the product, which was dried in an oven at 90 °C for 12 h; the dried product was transferred to a porcelain boat and placed in a tube furnace, and the temperature was raised at 5 °C/min in an argon atmosphere. At 850°C, the temperature was kept for 2 hours. After the carbonization reaction was completed, the temperature was lowered to room temperature at 5°C/min to obtain a composite sample material (A9).

Preparation of half-cell (B9):

The steps and conditions for preparing the half-cell (B9) from the sample material (A9) as the electrode active material were the same as in Example 1.

Comparative Example 5

Preparation of polycrystalline Nb ₂ O ₅ (7#):

Put the corundum crucible containing 5g of niobium carbide into a muffle furnace, and heat it up to 1400°C at a heating rate of 2°C/min; after maintaining this temperature for 48 hours of heat treatment, it is lowered to room temperature at a rate of 10°C/min to obtain polycrystalline Nb ₂ O ₅ (7#);

Preparation of sample material (A10):

The sample material (A10) was prepared in the same way as the sample material (A9).

Preparation of half-cell (B10):

The steps and conditions for preparing the half-cell (B10) from the sample material (A10) as the electrode active material were the same as in Example 1.

Example 6 XRD structure characterization of Nb ₂ O ₅ samples (1#～7#)

The structures of samples 1# to 7# were characterized respectively. XRD test showed that pure phase micron-sized single crystal H-Nb ₂ O ₅ could be obtained by calcining niobium carbide and niobium dioxide as raw materials and calcining at 1000℃ for 12h in oxygen. ; Using niobium carbide as raw material, calcined in oxygen for 12h at a temperature lower than the optional temperature (700°C) to obtain single crystal T-Nb ₂ O ₅ ; Using niobium hydroxide as raw material, calcining in oxygen at a temperature of 1000°C After calcining for 12h, polycrystalline Nb ₂ O ₅ can be obtained; using niobium carbide as raw material, calcining in oxygen for 12h at a temperature higher than the optional temperature (1400°C) or for calcination in oxygen at a calcination temperature of 1000°C for a time outside the optional time range (6h). and 48h) to obtain polycrystalline Nb ₂ O ₅ ;

Taking sample 1# as a typical representative, Figure 1 is the XRD pattern of sample 1#.

Example 7 XRD structure characterization of sample materials (A1-A10)

The sample materials A1-A10 were characterized respectively, and the XRD test showed that the crystal phases of all the sample materials A1-A10 were exactly the same as the corresponding Nb ₂ O ₅ samples.

Taking sample A1 as a typical representative, Figure 1 is the XRD pattern of sample A1.

TEM structure characterization of sample materials (A1-A10) in Example 8

The structure of the sample materials A1~A10 was characterized respectively, and the TEM test showed that the carbon shell thickness of the sample material with a polymerization reaction time of 24h and a carbonization temperature of 850℃ was about 10 nm; the carbon shell thickness of the sample material with a polymerization reaction time of 12h and a carbonization temperature of 850℃ About 6 nm; the carbon shell thickness of the sample material with a polymerization reaction time of 48 h or a carbonization temperature of 700 °C is about 20 nm.

Taking sample A1 as a typical representative, Fig. 2 is the TEM image of sample A1.

SEM Morphology Characterization of Sample Materials (A1-A5) in Example 9

The morphology of the sample materials A1~A10 was characterized respectively, and the SEM test showed that the particle size of the sample material in the longest direction could be obtained by calcining at 1000℃ for 12h in oxygen; 700℃) calcination for 12h or calcination time in oxygen at 1000℃ for 6h, the longest dimension of the sample material particles obtained is 2-3μm; The calcination time at 1000°C calcination time is 48h, and the particle size of the sample material in the longest direction is 6-10 μm.

Taking sample A1 as a typical representative, FIG. 3 is the SEM image of sample A1.

Example 10 Thermogravimetric analysis of composite materials (A1-A3)

Thermogravimetric analysis was performed on sample materials A1 to A10 using a thermogravimetric analyzer, and the carbon content data shown in Table 1 were obtained. 3.5wt%); the sample material with a polymerization reaction time of 12h and a carbonization temperature of 850°C has a lower carbon content (2.1wt%); a sample material with a polymerization reaction time of 48h or a carbonization temperature of 700°C has a higher carbon content (4.2-4.5 wt%).

Table 1 Carbon content of sample materials A1~A10

Example 11 Performance test of half cells (B1-B10)

The rate performance and cycle performance of the half cells B1~B10 were tested respectively, and the electrochemical performance data shown in Table 2 were obtained. The electrochemical performance test showed that the carbon layer effectively improved the rate performance and cycle stability of the sample material half cell; single crystal The H-Nb ₂ O ₅ sample has higher capacity and cycle stability than single crystal T-Nb ₂ O ₅ and polycrystalline Nb ₂ O ₅ ; the composite material of single crystal H-Nb ₂ O ₅ prepared in the present invention has suitable The particle size and carbon layer thickness showed excellent electrochemical performance. Taking the half-cell B1 as a typical representative, Figure 4 shows the charge-discharge curve of the half-cell B1, Figure 5 shows the rate performance of the half-cell B1, and Figure 6 shows the cycle performance of the half-cell B1.

Table 2 Performance test of half cells (B1～B10)

The above are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Without departing from the scope of the technical solution of the present application, any changes or modifications made by using the technical content disclosed above are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims (7)

1. a lithium ion battery or lithium ion capacitor, is characterized in that, comprises negative electrode material; The negative electrode material comprises a composite material; The composite material is a core-shell structure in which a nano-carbon layer coats a single crystal H-Nb ₂ O ₅ ; Among them, the core is a single crystal H-Nb ₂ O ₅ particle, the longest dimension is 2~5μm, and the shell is a nano-carbon layer with a thickness of 10~20nm; The preparation method of the composite material at least includes the following steps: a) Obtaining single crystal H-Nb ₂ O ₅ ; b) react and carbonize the mixture containing the single crystal H-Nb ₂ O ₅ and the carbon source to obtain the single crystal H-Nb ₂ O ₅ covered by the nano-carbon layer; The method for obtaining the single crystal H-Nb ₂ O ₅ in step a) includes: heating the raw material containing the niobium source to 1000 ^o C at a heating rate of 2 ^o C/min; after maintaining the temperature for heat treatment for 12 h, Lowering to room temperature at a speed of 10 ^o C/min to obtain the single crystal H-Nb ₂ O ₅ ; The niobium source is niobium carbide or niobium dioxide; The carbon source is dopamine; Step b) includes at least the following steps: b-1) Add the solution containing the carbon source to the dispersion containing the single crystal H-Nb ₂ O ₅ under stirring conditions, and stir the polymerization reaction for 12~48 h to obtain the single crystal H-Nb ₂ coated with the carbon precursor. O ₅ ; b-2) carbonizing the single-crystal H-Nb ₂ O ₅ coated with the carbon precursor at a carbonization temperature of 850 ^o C to obtain the composite material; The composite material has a reversible capacity of 270 mAh/g. 2 . The lithium ion battery or lithium ion capacitor according to claim 1 , wherein the carbon content in the nano-carbon layer-coated single crystal H-Nb ₂ O ₅ is 2.0-4.0 wt %. 3 . 3. lithium ion battery or lithium ion capacitor according to claim 1, is characterized in that, the mass ratio of carbon source described in step b) and described single crystal H-Nb ₂ O ₅ is 1:10～1: 4. 4. The lithium-ion battery or lithium-ion capacitor according to claim 1, wherein, The conditions of the carbonization treatment are: The reaction heating rate is 1~5 ^o C/min; the reaction time is 2~6h; The carbonization is carried out in an inert atmosphere. 5. lithium ion battery or lithium ion capacitor according to claim 1, is characterized in that, cooling is carried out after described carbonization; Cooling speed is 1～10 ^o C/min. 6. The lithium-ion battery or lithium-ion capacitor according to claim 1, characterized in that, The solid content of the dispersion liquid of the single crystal H-Nb ₂ O ₅ is 0.05-5.0 wt %; The dispersion liquid of the single crystal H-Nb ₂ O ₅ includes a solution buffer; The pH of the dispersion is 8 to 9; The solution buffer is at least one of tris(hydroxymethyl)aminomethane hydrochloride (Tris), potassium dihydrogen phosphate and sodium dihydrogen phosphate. 7. The lithium ion battery or lithium ion capacitor according to claim 1, wherein the concentration of the solution is 0.05-0.5 mol/L; the solution comprises a solvent; The solvent includes at least one of water, methanol, ethanol, propanol, and ethylene glycol.

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