Preparation method and energy storage application of niobium pentoxide / carbon composite negative electrode material

Abstract

The invention relates to a preparation method and energy storage application of a niobium pentoxide / carbon composite negative electrode material, and belongs to the technical field of lithium ion battery materials. The method comprises the following steps: dissolving niobium oxalate ammonium salt in an organic solvent to form a homogeneous solution, adding a polymer and the like, and continuously heating and stirring to prepare a spinning precursor solution; niobium-containing organic fibers are prepared through an electrostatic spinning technology; and carrying out programmed heating treatment on the fiber in an inert atmosphere to finally obtain the niobium pentoxide / carbon composite structure negative electrode material. According to the preparation process, in-situ compounding of niobium pentoxide and a carbon conductive substrate is realized through design of a molecular-level precursor and combination of an electrostatic spinning-pyrolysis technology, and a three-dimensional continuous conductive network structure is formed. When the obtained composite material is used as a negative electrode of a lithium ion battery, high specific capacity, excellent rate capability and long cycle stability are shown. The method has the characteristics of simple and efficient process, controllable product purity, high raw material utilization rate and the like, does not need complex post-treatment equipment, meets the green chemical requirements, and has remarkable industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a preparation method of a niobium pentoxide / carbon composite anode material and its energy storage application. Background Art

[0002] As the current mainstream rechargeable energy storage device, lithium-ion batteries have advantages such as high energy density and long cycle life, and occupy a core position in the fields of consumer electronics, electric vehicles and large-scale energy storage. As a key component determining the battery performance, the development of the anode material needs to take into account high specific capacity, fast ion / electron transport ability and excellent structural stability. At present, commercial graphite anodes have problems such as low theoretical capacity and slow lithium ion diffusion speed, and it is increasingly difficult to meet the requirements of high power density devices; while silicon-based and tin-based lithium battery anode materials have high capacities, but face serious problems such as severe volume expansion and poor cycle stability during charge and discharge.

[0003] At present, transition metal oxides have become a research hotspot due to their high theoretical capacity and safety. Among them, niobium pentoxide has attracted much attention due to its unique layered structure and pseudocapacitive energy storage mechanism. The octahedral voids in its crystal can provide fast lithium ion transport channels, and the low working potential can also effectively inhibit the growth of lithium dendrites, thus significantly improving safety. However, niobium pentoxide has low intrinsic electronic conductivity and insufficient ion mobility, resulting in poor rate performance and fast capacity decay, and it is difficult to meet the requirements of high-loading electrodes. In addition, the traditional preparation process of niobium pentoxide requires high-temperature sintering, with high energy consumption and no cost advantage in production. Therefore, developing a preparation method with controllable process, low cost and precise regulation of the niobium pentoxide / carbon interface structure is of great significance for promoting the practical application process of high-power lithium-ion battery anode materials. Summary of the Invention

[0004] Aiming at the technical problems faced by the existing niobium pentoxide-based lithium-ion battery anode materials, the present invention provides a preparation method of a niobium pentoxide / carbon composite anode material and its energy storage application. Compared with the existing technology, the present invention realizes the in-situ composite of niobium pentoxide and a carbon conductive matrix through molecular-level precursor design and combines electrospinning-pyrolysis technology, thereby forming a composite material with a three-dimensional continuous conductive network structure. The application of this composite anode material in lithium batteries shows high specific capacity, excellent rate performance and long cycle stability.

[0005] To achieve the above effects, the present invention adopts the following technical solutions:

[0006] (1) Prepare a niobium-containing precursor solution and stir it in a water bath for an appropriate time;

[0007] (2) Add a polymer to step (1), heat and stir in a water bath for an appropriate time to form a white viscous solution;

[0008] (3) Use the solution obtained in step (2) as the spinning solution, perform electrospinning to obtain an organic fiber membrane, and then dry it;

[0009] (4) Heat-treat the dried organic fiber membrane obtained in step (3) in an inert atmosphere to obtain a niobium pentoxide / carbon composite nanostructure;

[0010] Further, the niobium-containing precursor in step (1) is generally ammonium oxalate niobate, niobium salts such as niobium pentachloride, and ammonium oxalate niobate is preferred; the solvent is generally N,N-dimethylformamide, absolute ethanol, chloroform, etc., and N,N-dimethylformamide is preferred; the concentration of the niobium salt is generally 0.1 - 0.3 mol / L

[0011] Further, the water bath heating temperature in step (1) is generally 30 - 100 °C, and 60 °C is preferred; the stirring time is generally 10 - 60 minutes, and 20 minutes is preferred;

[0012] Further, the polymer added in step (2) is generally polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride, polylactic acid, polyurethane, etc., and polyacrylonitrile is preferred; the molecular weight of the polymer is generally between 20,000 and 150,000, and 85,000 is preferred; the concentration of the polymer is generally 5% - 25%, and 10% is preferred;

[0013] Further, the water bath heating temperature in step (2) is generally 30 - 100 °C, and 60 °C is preferred; the stirring time is generally 10 - 60 minutes, and 20 minutes is preferred;

[0014] Further, the electrospinning voltage in step (3) is generally 10 - 20 kV, and 15 kV is preferred; the advancing speed of the spinning solution is generally 0.2 - 1.5 ml / h, and 0.5 ml / h is preferred; the rotation speed of the spinning machine drum is generally 200 - 400 rpm, and 300 rpm is preferred; the needle head model is 23G;

[0015] Further, the drying temperature of the organic fiber membrane in step (3) is generally 50 - 120 °C, and 80 °C is preferred; the drying time is generally 10 - 24 hours, and 18 hours is preferred;

[0016] Further, the heat treatment method in step (4) is to first heat up to 200 - 300 °C, hold for 2 - 6 hours, preferably heat up to 240 °C and hold for 3 hours; then heat up to 500 - 800 °C and hold for 1 - 6 hours, preferably heat up to 600 °C and hold for 2 hours;

[0017] Further, in the step (4), the heating rate of the heat treatment is 5-15 °C / min, preferably 10 °C / min; the inert gas for the heat treatment is high-purity nitrogen, high-purity argon, high-purity carbon dioxide, or any mixture of the above gases.

[0018] The obtained niobium pentoxide / carbon composite nanostructure as described above is used as the negative electrode material of a lithium-ion battery, and is assembled into a lithium-ion battery for use as an electrochemical energy storage device.

[0019] The preparation method of the present invention has the advantages of simple process, high efficiency, controllable product purity, and high raw material utilization rate, and does not require complex post-treatment equipment, meeting the requirements of sustainable development of green chemistry. Through this method, the deficiencies of the prior art are overcome, and it has good industrial application prospects. Description of the Drawings

[0020] Figure 1 It is the SEM picture of the niobium pentoxide / carbon composite nanostructure;

[0021] Figure 2 It is the XRD pattern of the niobium pentoxide / carbon composite nanostructure;

[0022] Figure 3 It is the long-term cycling performance graph of the half-cell at a rate of 0.1C with the niobium pentoxide / carbon composite nanostructure as the negative electrode material. Detailed Embodiments

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0024] Embodiment 1, the present invention provides a preparation method and energy storage application of a niobium pentoxide / carbon composite negative electrode material. Taking the preparation of 0.001 mol of the niobium pentoxide / carbon composite negative electrode material as an example, the specific steps include:

[0025] Step 1, weigh 0.001 mol of ammonium oxalate niobate hydrate and put it into a 50 ml beaker, add 10 ml of N,N-dimethylformamide, place it in a 45 °C water bath, and stir magnetically or mechanically for 15 minutes;

[0026] Step 2, take polyacrylonitrile (PAN) with a concentration of 10% and a molecular weight of 85000, add it to the beaker, place it in a 45 °C water bath, and stir magnetically or mechanically for 15 minutes to obtain a white viscous solution;

[0027] Step 3: Put the white viscous solution into an electrospinning machine. The spinning voltage is 15 kV, the advancing speed of the spinning solution is 0.5 ml / h, and the rotating speed of the roller of the spinning machine is 300 rpm to obtain an organic spinning film containing niobium salt;

[0028] Step 4: Dry the organic spinning film obtained in step (3) in an oven. The oven temperature is 90 °C and the drying time is 12 hours;

[0029] Step 5: Put the dried organic spinning film in step (4) into an atmosphere tube furnace for heat treatment. The heat treatment conditions are as follows: raise the temperature from room temperature of 25 °C to 250 °C at a heating rate of 10 °C / min, hold for 2 hours, then raise the temperature to 500 °C at a heating rate of 10 °C / min, hold for 2 hours, and then cool down naturally. During the whole heating and cooling process, high-purity nitrogen is continuously introduced. Finally, a niobium pentoxide / carbon composite negative electrode material is obtained, and its SEM pattern is as Figure 1 shown.

[0030] Example 2: The present invention provides a preparation method of a niobium pentoxide / carbon composite negative electrode material and its energy storage application. Taking the preparation of 0.003 mol of the niobium pentoxide / carbon composite negative electrode material as an example, the specific steps include:

[0031] Step 1: Weigh 0.003 mol of ammonium niobium oxalate hydrate and put it into a 50 ml beaker. Add 10 ml of absolute ethanol, put it into a water bath at 55 °C, and stir magnetically or mechanically for 10 minutes;

[0032] Step 2: Take polyvinyl alcohol with a concentration of 10% and a molecular weight of 90000, add it to the beaker, put it into a water bath at 50 °C, and stir magnetically or mechanically for 20 minutes to obtain a white viscous solution;

[0033] Step 3: Put the white viscous solution into an electrospinning machine. The spinning voltage is 15 kV, the advancing speed of the spinning solution is 0.4 ml / h, and the rotating speed of the roller of the spinning machine is 300 rpm to obtain an organic spinning film containing niobium salt;

[0034] Step 4: Dry the organic spinning film obtained in step (3) in an oven. The oven temperature is 80 °C and the drying time is 15 hours;

[0035] Step 5: Put the dried organic spinning film in step (4) into an atmosphere tube furnace for heat treatment. The heat treatment conditions are as follows: raise the temperature from room temperature of 25 °C to 200 °C at a heating rate of 10 °C / min, hold for 3 hours, then raise the temperature to 600 °C at a heating rate of 10 °C / min, hold for 2 hours, and then cool down naturally. During the whole heating and cooling process, high-purity nitrogen is continuously introduced. Finally, a niobium pentoxide / carbon composite negative electrode material is obtained, and its XRD pattern is as Figure 2 shown.

[0036] The results of the above embodiments have been precisely tested, realizing the preparation of the niobium pentoxide composite anode material. The application of this composite anode material in lithium batteries exhibits high specific capacity, excellent rate performance, and long cycle stability. Compared with the existing preparation methods, it has significant advantages such as simple operation, low requirements for equipment, high utilization rate of raw materials, high product purity, and being green and pollution-free. The above has made a detailed description of the specific implementation manners of the present invention in conjunction with the accompanying drawings, but these descriptions cannot be understood as limiting the scope of the present invention. The protection scope of the present invention is defined by the appended claims, and any modification based on the claims of the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application, characterized in that: The method mainly comprises the following steps: (1) preparing a niobium-containing precursor solution, heating it in a water bath and stirring it for an appropriate amount of time; (2) adding the polymer to step (1), heating in a water bath and stirring for an appropriate amount of time to form a white viscous solution; (3) using the solution obtained in step (2) as a spinning solution, performing electrospinning to obtain an organic fiber membrane, and then drying; (4) The organic fiber membrane dried in step (3) is heat-treated in an inert atmosphere to obtain a niobium pentoxide / carbon composite nanostructure.

2. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: The niobium-containing precursor in step (1) is generally niobium ammonium oxalate, niobium pentachloride and other niobium salts, preferably niobium ammonium oxalate; the solvent is generally N,N-dimethylamide, anhydrous ethanol, chloroform and the like, preferably N,N-dimethylamide; the concentration of the niobium salt is generally 0.1-0.3 mol / L.

3. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: In step (1), the water bath heating temperature is generally 30 to 100 degrees, preferably 60 degrees; the stirring time is generally 10 to 60 minutes, preferably 20 minutes.

4. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: The polymer added in step (2) is generally polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride, polylactic acid, polyurethane, etc., preferably polyacrylonitrile; the molecular weight of the polymer is generally between 20,000 and 150,000, preferably 85,000; the concentration of the polymer is generally 5% to 25%, preferably 10%.

5. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: In step (2), the water bath heating temperature is generally 30 to 100 degrees, preferably 60 degrees; the stirring time is generally 10 to 60 minutes, preferably 20 minutes.

6. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: In step (3), the electrospinning voltage is generally 10-20 kV, preferably 15 kV; the spinning solution advancement speed is generally 0.2-1.5 ml / h, preferably 0.5 ml / h; the spinning machine drum speed is generally 200-400 rpm, preferably 300 rpm; the needle model is 23G.

7. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: In step (3), the drying temperature of the organic fiber membrane is generally 50 to 120 degrees, preferably 80 degrees; the drying time is generally 10 to 24 hours, preferably 18 hours.

8. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: The heat treatment method in step (4) is to first heat the temperature to 200-300 degrees and keep it warm for 2-6 hours, preferably heat it to 240 degrees and keep it warm for 3 hours; then heat it to 500-800 degrees and keep it warm for 1-6 hours, preferably heat it to 600 degrees and keep it warm for 2 hours.

9. The method for preparing a niobium pentoxide / carbon composite negative electrode material and its energy storage application as claimed in claim 1, characterized in that: In step (4), the heating rate of the heat treatment is 5-15°C / min, preferably 10°C / min; the heat treatment inert gas is high-purity nitrogen, high-purity argon, high-purity carbon dioxide or any mixture of the above gases.

10. Use of a niobium pentoxide / carbon composite negative electrode material prepared by the method according to any one of claims 1 to 9 in a negative electrode material for a lithium battery, characterized in that: The material has an initial discharge specific capacity of greater than 600 mAh / g at a rate of 0.1C, and a capacity retention rate of greater than 80% after 120 cycles.

Images