A niobate / carbon composite material, its preparation method and application

Abstract

The application discloses a niobate / carbon composite material and a preparation method and application thereof, and relates to the technical field of lithium ion battery negative electrode materials. The prepared niobate / carbon composite material has a porous structure, and the niobate belongs to an orthorhombic system. The preparation method comprises the following steps: using terephthalic acid and metal salt as raw materials to perform a solvothermal reaction to generate a precursor metal organic framework (MOFs), performing centrifugal drying, and then performing a solvothermal reaction on the MOFs precursor and a niobate solution, and performing washing, drying and heat treatment to obtain the niobate / carbon composite material. The niobate / carbon composite material has excellent cycle and rate performance as a lithium ion battery negative electrode material. The composite material prepared by the application has a porous structure, and has excellent cycle and rate performance as a lithium ion battery negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to a niobate / carbon composite material, its preparation method, and its application. Background Technology

[0002] With the development of new energy technologies, electricity has been widely used as a clean energy source. Among them, lithium-ion batteries have received widespread attention due to their high-performance energy storage technology. However, to gain a wider market share, lithium-ion batteries not only need high capacity and energy density, but also stable cycleability, fast charge and discharge rates, and long cycle life. Niobium-based oxides are common high-rate anode materials, possessing higher theoretical capacity and superior safety and cycle stability than graphite electrodes, making them promising for lithium-ion battery applications. However, niobium-based oxides generally have poor electronic / ionic conductivity, leading to rapid energy / power density decay at high rates, which limits their large-scale application.

[0003] Currently, the main methods to improve the above-mentioned problems are the design of micro / nano structures of materials and their composite with conductive matrices. Micro / nano structures can shorten the diffusion paths of lithium ions and electrons, thereby increasing the transport rate of lithium ions and electrons and improving rate performance; composites with conductive matrices can provide fast electron transport channels, improving the overall electronic conductivity of the electrode. Carbon materials, with their high conductivity, large surface area, and stable physicochemical properties, have become the most widely used composite conductive matrices. Currently, researchers often combine niobium-based oxides with various carbon materials such as porous carbon, graphene, and carbon nanotubes to improve their electrochemical performance, but their conductivity is still limited. In addition, the contact area between niobium-based oxide particles and the electrolyte is also one of the important factors affecting its high-rate performance.

[0004] Chinese patent CN 111969197A discloses a calcium-based niobate compound potassium-ion battery anode material with a framework structure and its preparation method. Using Ca2Nb2O7 particles of several hundred nanometers as the anode material, it exhibits good cycle stability and a stable voltage plateau. However, the solid structure of the Ca2Nb2O7 particles is not conducive to sufficient electrolyte wetting. Furthermore, this material is pure Ca2Nb2O7 without any composite conductive material, resulting in poor conductivity and limiting its high-rate performance.

[0005] Chinese patent CN 109767925A discloses a T-Nb2O5 / egg white carbon composite material for lithium-ion supercapacitors and its preparation method. Using niobium oxalate as the Nb source and egg white as the C source, a nitrogen-rich porous T-Nb2O5 / egg white carbon composite material can be prepared via a two-step hydrothermal-annealing method. This material can effectively alleviate the stacking and aggregation of Nb2O5 nanoparticles, thereby increasing the effective specific surface area and the utilization rate of active materials. However, in the Nb2O5 / carbon composite material obtained by adding an additional carbon source, the binding force between Nb2O5 and carbon is relatively poor, which is detrimental to long-term cycling stability. Summary of the Invention

[0006] To address the problems in the prior art, the present invention aims to solve at least one of the technical problems existing in the prior art by providing a niobate / carbon composite material, its preparation method, and its applications. The present invention uses metal-organic frameworks (MOFs) as precursor templates. High-temperature heat treatment to form a nanoporous structure increases the contact area between the niobate-based oxide electrode and the electrolyte, providing more central sites for electrochemical reactions and effectively accelerating the lithium-ion insertion / extraction process. The MOF-derived conductive matrix composite provides a fast electron transport channel, improving the overall electronic conductivity of the electrode. Simultaneously, niobate, as a MOF derivative, has a tight bond with MOF-derived carbon materials, which is beneficial for cycle stability. Furthermore, MOFs have a unique and controllable structure, providing an effective template for subsequent structural design. The combination of these strategies greatly promotes the reaction kinetics of the niobate-based oxide electrode. When used as a negative electrode material for lithium-ion batteries, this electrode material exhibits high capacity and long cycle life.

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention provides a method for preparing a niobate / carbon composite material, comprising: adding terephthalic acid and a metal salt to an organic solvent A, mixing to obtain a solution A, and subjecting solution A to a solvothermal reaction to obtain MOF precursor powder;

[0009] Niobium salt was dissolved in organic solvent B, and the MOF precursor powder was added. After mixing, a solvothermal reaction was carried out to obtain powder α. Powder α was then heat-treated to obtain a niobate / carbon composite material.

[0010] As a preferred embodiment of the present invention, the preparation method of the niobate / carbon composite material of the present invention specifically includes the following steps:

[0011] (1) Add terephthalic acid and metal salt to organic solvent A and stir to obtain solution A;

[0012] (2) The solution A obtained in step (1) is transferred to a reaction vessel for solvothermal reaction, and then washed and dried to obtain MOF precursor powder;

[0013] (3) Niobium salt is dissolved in organic solvent B, and then MOF precursor from step (2) is added. After stirring and sonicating, it is placed in a reaction vessel for solvothermal reaction. After washing and drying, powder α is obtained. After heat treatment of powder α, niobate / carbon composite material is obtained.

[0014] In step (1), the synthesis of MOF precursors uses the following proportions of components:

[0015] Organic solvent A, 10-25 ml;

[0016] 1-2 mmol of terephthalic acid;

[0017] Metal salt 0.3-3.5 mmol;

[0018] In step (1), the metal salt is at least one of cobalt acetate, cobalt nitrate, cobalt chloride, ferric chloride, ferric nitrate, ferric acetate, nickel acetate, nickel nitrate, and nickel chloride.

[0019] In step (1), the organic solvent A is at least one of N,N-2-methylformamide, diethylformamide, and dimethyl sulfoxide.

[0020] In step (1), the solution needs to be stirred for at least 5 minutes, preferably 5-15 minutes.

[0021] In step (2), the solvothermal reaction temperature and time are 100-130℃ and 15-24 hours, respectively.

[0022] In step (3), the synthesis of the niobate / carbon composite material uses the following component ratios:

[0023] Organic solvent B, 25-50 ml;

[0024] MOF precursor 160-450mg;

[0025] Niobium salt 0.13-0.59 mmol;

[0026] In step (3), the niobium salt is at least one of niobium oxalate, niobium acetate, and niobium chloride; the organic solvent B is at least one of ethanol and N,N-2-methylformamide.

[0027] In step (3), the solution needs to be stirred and sonicated for at least 10 minutes, and the stirring and sonication time is preferably 10-30 minutes.

[0028] In step (3), the solvothermal reaction temperature and time are 150-180℃ and 20-30 hours, respectively.

[0029] In step (3), the protective atmosphere for heat treatment is nitrogen or argon, and the reaction temperature and time for heat treatment are 600-900℃ and 1-3 hours, respectively.

[0030] A second aspect of this invention provides a niobate / carbon composite material prepared using the above method. This invention uses MOFs as a precursor and prepares a niobate / carbon porous composite electrode through a combination of solvothermal and heat treatment of a niobate salt solution, maintaining the porous structure after calcination. That is, the niobate / carbon composite material prepared by this invention has a porous structure, and the niobate belongs to the orthorhombic crystal system.

[0031] Specifically, in this invention, the niobate is at least one of iron niobate, cobalt niobate, and nickel niobate.

[0032] A third aspect of the present invention provides the application of the niobate / carbon composite material as a negative electrode material for lithium-ion batteries.

[0033] As a preferred embodiment of the present invention, the obtained niobate / carbon composite material is mixed with conductive agent Super P and binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1 to form a slurry, which is then coated onto a copper current collector. A 1.2 cm diameter disc is then stamped out to serve as the electrode for assembling a lithium-ion battery. A microporous polypropylene membrane is used as the separator, and a 1 mol / L... -1 A button cell is assembled using LiPF6 as the solute, ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 as the solvent, and lithium foil as the negative electrode.

[0034] After the assembled lithium-ion battery was placed for 12 hours, a constant current charge-discharge test was performed. The charge-discharge voltage was 3V-0.01V. The capacity, rate performance, and charge-discharge cycle performance of the negative electrode of the lithium-ion battery were measured in an environment of 25±1℃.

[0035] Tests have shown that batteries prepared using the niobate / carbon composite material of this invention as the negative electrode material for lithium-ion batteries exhibit excellent cycle and rate performance.

[0036] This invention has at least one of the following beneficial effects:

[0037] (1) First, this invention uses a solvothermal method with phthalic acid and metal salts to prepare MOF precursor powder. The MOF precursor powder is the basis for forming a carbon network. Compared with the prior art, the MOF precursor powder prepared by this invention has the characteristics of uniform particle size and simple preparation. Second, the prepared MOF precursor powder is subjected to a solvothermal reaction with niobium salt to obtain powder α. This invention uses a simple solvothermal method to prepare niobate / carbon composite porous materials. Compared with the commonly used solid-state sintering of niobate (above 1000℃), the heat treatment temperature is reduced, saving energy consumption. The synthesis method is simple and effective. In addition, the niobate material prepared by the solvothermal method has a more uniform morphology and a more nano-sized size, which is conducive to promoting electrode reaction kinetics and improving the electrochemical performance of lithium-ion batteries. Then, the powder α is heat-treated under a protective atmosphere. In this invention, the powder α is heat-treated at a temperature of 600-900℃ for 1-3 hours to form niobate and MOF-derived carbon. The formed niobate is a MOF derivative and has a tight bond with the MOF-derived carbon material, thereby forming a niobate / carbon composite material with a porous structure. The applicant found in the study that the temperature and time of heat treatment are key conditions for the formation of niobates and MOF-derived carbon. Too low a treatment temperature is not conducive to the formation of high-conductivity MOF-derived carbon; too high a treatment temperature will destroy the porous structure of niobates and lead to agglomeration.

[0038] (2) The introduction of MOFs in this invention brings structural adjustability. The tunable structure of the precursor can effectively increase the specific surface area of ​​niobate, constructing a loose porous structure that is beneficial for electrolyte wetting. In addition, MOF-derived carbon also provides an external electron transport channel for iron niobate. At the same time, the in-situ coating of niobate with MOF-derived carbon can improve the bonding force between the two phases, effectively improve the stability of the electrode structure, and at the same time, slow down the aggregation of active materials during electrochemical cycling.

[0039] (3) Compared with traditional niobate electrodes, the niobate / carbon composite porous material prepared by this invention exhibits a nanoscale microstructure, which shortens the diffusion path of lithium ions and electrons, improves the transport rate of lithium ions and electrons, and promotes electrochemical reaction kinetics. Attached Figure Description

[0040] Figure 1 The X-ray diffraction (XRD) pattern of the iron niobate / carbon composite material prepared in Example 1;

[0041] Figure 2 (a) and (b) are scanning electron microscope (SEM) images of the precursor MOFs prepared in Example 1 at different magnifications;

[0042] Figure 3 (a) and (b) are SEM images of the iron niobate / carbon composite material prepared in Example 1 at different magnifications;

[0043] Figure 4 The battery cycle performance of the iron niobate / carbon composite electrode material prepared in Example 1;

[0044] Figure 5 The battery rate performance of the iron niobate / carbon composite electrode material prepared in Example 1 is shown. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0046] Example 1:

[0047] (1) Add 1.2 mmol of terephthalic acid and 2.5 mmol of ferric chloride to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0048] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 110 °C for 20 hours. Then wash and dry with anhydrous ethanol to obtain a solution based on the central ion Fe. 3+ MOF precursor powder with terephthalic acid as the ligand;

[0049] (3) Dissolve 0.2 mmol of niobium pentachloride in 35 ml of ethanol, then add 200 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reactor and react at 170 °C for 20 hours. After washing with anhydrous ethanol and drying, powder α is obtained. After heat treatment at 750 °C for 2 hours under nitrogen, black powder is obtained, which is the iron niobate / carbon composite material.

[0050] Figure 1 The image shows the XRD pattern of the iron niobate / carbon composite material prepared in Example 1. Figure 1 It can be seen that the phase of the iron niobate / carbon composite material prepared in Example 1 is orthogonal FeNb2O6 (JCPDS 72-0483). Figure 2 (a) and (b) are SEM images of precursor MOFs at different magnifications. The precursor MOFs are uniform dodecahedral particles with a size of approximately 500 nm. Figure 3 (a) and (b) are SEM images of the iron niobate / carbon composite material at different magnifications, showing a porous structure.

[0051] Example 2:

[0052] (1) Add 1.2 mmol of terephthalic acid and 2.5 mmol of ferric chloride to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0053] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 110 °C for 20 hours. Then wash and dry with anhydrous ethanol to obtain a solution based on the central ion Fe. 3+ MOF precursor powder with terephthalic acid as the ligand;

[0054] (3) Dissolve 0.13 mmol of niobium pentachloride in 35 ml of ethanol, then add 160 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reaction vessel and react at 170 °C for 20 hours. After washing with anhydrous ethanol and drying, powder α is obtained. After heat treatment at 750 °C for 2 hours under nitrogen, black powder is obtained, which is the iron niobate / carbon composite material.

[0055] Example 3:

[0056] (1) Add 1.2 mmol of terephthalic acid and 2.5 mmol of ferric chloride to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0057] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 110 °C for 20 hours. Then wash and dry with anhydrous ethanol to obtain a solution based on the central ion Fe. 3+ MOF precursor powder with terephthalic acid as the ligand;

[0058] (3) Dissolve 0.59 mmol of niobium acetate in 35 ml of ethanol, then add 450 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reactor and react at 170 °C for 20 hours. After washing with anhydrous ethanol and drying, powder α is obtained. After heat treatment at 750 °C for 2 hours under nitrogen, black powder is obtained, which is the iron niobate / carbon composite material.

[0059] Example 4:

[0060] (1) Add 1.2 mmol of terephthalic acid and 2.5 mmol of ferric chloride to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0061] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 110 °C for 20 hours. Then wash and dry with anhydrous ethanol to obtain a solution based on the central ion Fe. 3+ MOF precursor powder with terephthalic acid as the ligand;

[0062] (3) Dissolve 0.2 mmol of niobate in 35 ml of ethanol, then add 200 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reactor and react at 170 °C for 20 hours. After washing and drying with anhydrous ethanol, powder α is obtained. After heat treatment at 750 °C for 2 hours under nitrogen, black powder is obtained, which is the iron niobate / carbon composite material.

[0063] Example 5:

[0064] (1) Add 2 mmol of terephthalic acid and 3.5 mmol of cobalt acetate to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0065] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 130 °C for 24 hours. Then wash and dry with anhydrous ethanol to obtain the solution based on the central ion Co. 2+ MOF precursor powder with terephthalic acid as the ligand;

[0066] (3) Dissolve 0.3 mmol of niobium pentachloride in 35 ml of ethanol, then add 200 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reactor and react at 200 °C for 20 hours. After washing with anhydrous ethanol and drying, powder α is obtained. Heat treatment at 750 °C for 2 hours under nitrogen to obtain black powder, which is the cobalt niobate / carbon composite material.

[0067] Example 6:

[0068] (1) Add 1 mmol of terephthalic acid and 0.3 mmol of nickel nitrate to 15 ml of N,N-2-methylformamide and stir for 10 minutes to obtain solution A;

[0069] (2) Transfer the solution A obtained in step (1) to a 100 ml reaction vessel and react at 100 °C for 15 hours. Then wash and dry with anhydrous ethanol to obtain the solution based on the central ion Ni. 2+ MOF precursor powder with terephthalic acid as the ligand;

[0070] (3) Dissolve 0.2 mmol of niobium pentachloride in 35 ml of ethanol, then add 200 mg of MOF precursor from step (2), stir and sonicate for 20 minutes, then put it into a 100 ml reactor and react at 150 °C for 30 hours. After washing and drying with anhydrous ethanol, powder α is obtained. After heat treatment at 750 °C for 2 hours under nitrogen, black powder is obtained, which is nickel niobate / carbon composite material.

[0071] Comparative Example 1:

[0072] The difference from Example 1 is that step (3) does not involve heat treatment of powder α, that is, it does not involve heat treatment at 750°C for 2 hours under nitrogen to obtain black powder, but otherwise it is the same as Example 1.

[0073] Comparative Example 2:

[0074] The difference from Example 1 is that the synthesis of MOF precursors in steps (1) and (2) is not performed. Instead, 2 mmol of niobium pentachloride is directly dissolved in 35 ml of ethanol, followed by the addition of 1 mmol of ferric chloride. After stirring and sonicating for 20 minutes, the mixture is placed in a 100 ml reactor and reacted at 200 °C for 24 hours. Powder α is obtained after washing and drying with anhydrous ethanol. Iron niobate powder is obtained after heat treatment at 750 °C for 2 hours under nitrogen.

[0075] Comparative Example 3:

[0076] The difference from Example 1 is that the temperature of the heat-treated powder α in step (3) is changed, that is, the black powder is obtained after heat treatment at 500°C for 2 hours under nitrogen. The rest is the same as in Example 1.

[0077] Comparative Example 4:

[0078] The difference from Example 1 is that the temperature of the heat-treated powder α in step (3) is changed, that is, the black powder is obtained after heat treatment at 1000°C for 2 hours under nitrogen. The rest is the same as in Example 1.

[0079] The niobate / carbon composite powder materials obtained in step (3) of Examples 1-6 and Comparative Examples 1-4 were mixed with conductive agent SuperP and binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1 to form a slurry. This slurry was then coated onto a copper current collector, and a 1.2 cm diameter disc was stamped out to serve as the lithium-ion battery electrode for battery assembly. A microporous polypropylene membrane was used as the separator, and 1 mol / L... -1 A button cell was assembled using LiPF6 as the solute and a 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the solvent, along with a lithium electrode. The charge / discharge voltage range was set to 3V-0.01V, and constant current charge / discharge tests were performed on the assembled lithium-ion battery.

[0080] With changes in the ratio and type of niobium salt and precursor MOFs, lithium-ion batteries exhibit different electrochemical performances. Table 1 shows the maximum discharge capacity of a niobate / carbon composite powder material used as a lithium-ion electrode material in Examples 1-6 when assembled into a lithium-ion battery at different current densities.

[0081] Table 1

[0082]

[0083]

[0084] As can be seen from Table 1, when the ratio of niobium salt and MOFs is changed, decreasing the ratio of niobium salt and MOFs leads to a decrease in the overall performance of the electrode material. This indicates that decreasing the ratio of niobium salt and MOFs is not conducive to the formation of iron niobate. Increasing the ratio of niobium salt and MOFs results in an initial capacity of the electrode material that is better than that of Example 1, but the decay is more severe under high current. The reason may be that although increasing the ratio of niobium salt and MOFs is conducive to the formation of iron niobate, the accumulation of a large number of iron niobate particles leads to poor performance under high current. When the niobium source is changed, the material also shows good electrochemical performance (Example 4). However, when cobalt acetate and nickel nitrate are used as metal salts for synthesizing precursor MOFs (Examples 5 and 6), the performance under high current is not as good as that of Example 1, but it is still better than that of the traditional niobate electrode.

[0085] A comparison of the data from Examples 1-6 with Comparative Example 1 shows that heat treatment is a necessary condition for the formation of MOF-derived carbon and niobates. Omitting the heat treatment step will result in a significant decrease in the performance of the final material.

[0086] A comparison of the data from Examples 1-6 with Comparative Example 2 shows that MOFs, as precursors, are the basis for the formation of carbon networks. Omitting the preparation process of MOF precursors will lead to a significant decrease in the performance of the final material.

[0087] A comparison of the data from Examples 1-6 with Comparative Examples 3 and 4 shows that the heat treatment temperature is a key condition for the formation of niobate and MOF-derived carbon. Too low a treatment temperature is detrimental to the formation of MOF-derived carbon; too high a treatment temperature will destroy the porous structure of niobate. Both lead to a significant decrease in the properties of the final prepared material.

[0088] Figure 4 This is a graph showing the cycle performance of the lithium-ion battery in Example 1. As can be seen from the graph, the lithium-ion battery achieves good cycle performance at a current density of 1 A g. -1 It exhibited good electrochemical performance, maintaining a capacity of 240.6 mAh g after 280 cycles. -1 The capacity. Figure 5 The following is a rate curve of the lithium-ion battery in Example 1, showing the rate of change at 0.1, 0.2, 0.5, 1, and 2 A g. -1 The maximum discharge capacities at the specified current densities were 614.3, 242.2, 178.9, 125.8, and 71.1 mAh g, respectively. -1 It exhibits good rate performance.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a niobate / carbon composite material, characterized by, The application relates to a preparation method of a niobate / carbon composite material. Terephthalic acid and a metal salt are added into an organic solvent A to obtain a solution A, the solution A is subjected to a solvothermal reaction to obtain MOFs precursor powder; A niobate salt is dissolved in an organic solvent B, the MOFs precursor powder is added, and then the mixture is subjected to a solvothermal reaction to obtain powder alpha, and the powder alpha is subjected to heat treatment to obtain the niobate / carbon composite material; The metal salt is at least one of cobalt acetate, cobalt nitrate, cobalt chloride, iron chloride, iron nitrate, iron acetate, nickel acetate, nickel nitrate and nickel chloride; The organic solvent A is at least one of N,N-2-methylformamide, diethylformamide and dimethyl sulfoxide; The solvothermal reaction temperature of the solution A is 100-130 DEG C, and the reaction time is 15-24 hours; The niobate salt is at least one of niobium oxalate, niobium acetate and niobium chloride; The organic solvent B is at least one of ethanol and N,N-2-methylformamide; The solvothermal reaction temperature of the mixture of the niobate salt and the MOFs precursor powder is 150-180 DEG C, and the reaction time is 20-30 hours; The heat treatment of the powder alpha is carried out in a nitrogen or argon atmosphere, the heat treatment temperature is 600-900 DEG C, and the heat treatment time is 1-3 hours.

2. The method for preparing a niobate / carbon composite material according to claim 1, characterized in that, In the synthesis of the MOFs precursor powder, the component usage ratio is as follows: The organic solvent A is 10-25 ml; Terephthalic acid is 1-2 mmol; The metal salt is 0.3-3.5 mmol.

3. The method for preparing a niobate / carbon composite material according to claim 1, characterized in that, In the synthesis of the powder alpha, the component usage ratio is as follows: The organic solvent B is 25-50 ml; The MOFs precursor powder is 160-450 mg; The niobate salt is 0.13-0.59 mmol.

4. The niobate / carbon composite material produced by the method according to any one of claims 1 to 3, characterized by The niobate / carbon composite material has a porous structure, and the niobate belongs to an orthorhombic system.

5. Application of the niobate / carbon composite material as a lithium ion battery negative electrode material.

Images