Preparation method of negative electrode material for sodium ion capacitor with high rate performance

Abstract

The present invention relates to the technical field of sodium ion capacitors, and particularly to a preparation method of a negative electrode material for a sodium ion capacitor with high rate performance. The preparation method is as follows: Hydrothermal reaction is carried out on niobium oxide powder and an alkali solution in a reaction kettle; The supernatant is retained, and then the pH is adjusted with an acid solution of a certain concentration to generate product A; An M (M = Fe, Co, Ni, Mn, etc.) salt is added to product A, and a second hydrothermal reaction is carried out in a reaction kettle, which is washed with distilled water and freeze-dried to obtain product B; Product B is placed in a tubular furnace and high-temperature calcination is carried out by introducing an inert gas, and finally the product: ilmenite-type niobate is obtained. The present invention provides a method for preparing ilmenite-type niobate MNb2O6 material, and uses it as a negative electrode material for a sodium ion capacitor with high capacity, large rate and long life and can cooperate with a fast capacitive adsorption type positive electrode, so as to solve the problem that the energy density and power density output by the sodium ion capacitor under large current charge and discharge are relatively low.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion capacitors, and particularly to a preparation method of a negative electrode material for a sodium ion capacitor with high rate performance. Background Art

[0002] In recent years, with the increasingly serious problems of energy shortage and environmental pollution, the storage, utilization and conversion of renewable energy such as wind energy and solar energy have attracted much attention. The development of energy technology has received high attention in China. Therefore, the research and development of new energy storage devices with high performance, high efficiency and environmental friendliness have become a hot topic in the new energy field.

[0003] Metal ion capacitors are a new type of energy storage device between secondary batteries and supercapacitors. They combine the energy storage mechanisms of secondary batteries and supercapacitors, and have the characteristics of both. They have the advantages of high energy density, long cycle life, high power output, etc., and have become an important development direction for future sustainable new energy storage systems. At present, more research has been done on lithium ion and sodium ion capacitors. Compared with lithium, sodium is rich in resources, low in price, good in sustainability, and similar in physical and chemical properties to lithium, making sodium ion batteries and sodium ion capacitors effective alternatives to lithium ion energy storage systems, attracting the attention of many researchers.

[0004] However, the relatively large radius of sodium ions results in the kinetics of the bulk sodium insertion reaction in the negative electrode of sodium ion capacitors being much lower than the reversible adsorption / desorption process of the positive electrode, leading to lower energy density and power density output under high current charge and discharge, which has also become the main bottleneck in the practical application of such devices. Therefore, developing a negative electrode material for sodium ion capacitors with high capacity, high rate and long life and capable of cooperating with a fast capacitive adsorption type positive electrode is a challenging topic.

[0005] Currently, among the negative electrode materials for sodium ion capacitors, more research has been done on insertion type materials, including hard carbon, titanium-based oxides (such as Na2Ti3O7, TiO2, etc.) and niobium-based oxides (such as TiNb2O7, Nb2O5, etc.). Among them, hard carbon has a small volume change during the sodiation / desodiation process, so it has good cycle stability. However, the tap density of hard carbon is very poor, resulting in a low volume energy density. Among the titanium-based oxides, TiO2, as a sodium ion insertion material, has a low sodium storage potential (0.3V vs. Na + / Na), and the inherent pseudocapacitive behavior of TiO2 can improve the electrochemical performance of sodium ion capacitors. However, TiO2 belongs to a semiconductor material, and both the ion diffusion rate and the electronic conductivity are very low, which has a great impact on the performance of the assembled sodium ion capacitors. Niobium-based oxides have two redox pairs (Nb 5+ / Nb 4+ for each Nb atom during the charge and discharge process, and Nb4+ / Nb 3+ ) An oxidation-reduction reaction occurs, and its theoretical specific capacity is relatively high. At present, based on binary niobium-based oxides as electrode materials for sodium ion insertion and extraction, good electrochemical performance has been obtained. Since binary niobium-based oxides increase the redox couples in the reaction, they have a higher theoretical specific capacity. Niobite-type niobates MNb2O6, due to their unique properties, have M and Nb located at 4c and 8d positions in their structure and are surrounded by six oxygen atoms, forming MO6 and NbO6 octahedrons. They share edges and form independent zigzag chains along the c-axis. At the same time, these parallel MO6 and NbO6 layers are alternately arranged along the a-axis in the sequence of M-Nb-Nb-M-Nb-Nb-M. Due to the unique interconnected three-dimensional channels and low-energy-barrier migration positions in the structure of MNb2O6, it helps the rapid insertion and extraction of large-sized sodium ions, so it meets the basic requirements of the insertion-type negative electrode material for sodium ion capacitors. At present, niobite-type niobates MNb2O6 have received extensive attention and exploration in the fields of ferroelectricity, piezoelectricity, dielectric, and optics, but the research in the field of sodium ion capacitors is still immature.

[0006] Therefore, we propose the preparation method of the niobite-type niobate of the present invention and its application as a negative electrode material for sodium ion capacitors. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method of a niobite-type niobate MNb2O6 (M = Fe, Co, Ni, Mn, etc.) material, and use it as a negative electrode material for sodium ion capacitors with high capacity, high rate, and long life and can cooperate with a fast-capacitance-adsorption type positive electrode to solve the problem that the energy density and power density output by sodium ion capacitors under large-current charge and discharge are relatively low.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] The preparation method of niobite-type niobate includes the following steps:

[0010] Step 1, hydrothermally react niobium oxide powder with an alkali solution in a reaction kettle;

[0011] Retain the supernatant, and then adjust the pH to 7-8 with an acid solution of a certain concentration to generate product A: hydrated niobium pentoxide;

[0012] Step 2, add M salt to product A, and the molar ratio of niobium oxide to M salt is 1:1. Conduct a second hydrothermal reaction in a reaction kettle, wash it with distilled water, and freeze-dry it to obtain product B;

[0013] Step 3, put product B into a tube furnace, introduce an inert gas for high-temperature calcination, and then obtain the final product: niobite-type niobate.

[0014] Further, in Step 1, the alkali solution is a KOH solution; the acid solution is a hydrochloric acid solution.

[0015] Further, in Step 1, the hydrothermal reaction conditions are 240°C to 280°C, and the heating time is 10 h to 14 h.

[0016] Further, in Step 2, the M salt is at least one of the following:

[0017] NiCl2, FeCl3, CoCl2, MnCl2.

[0018] Further, in Step 2, the second hydrothermal reaction conditions are: the temperature is 160°C to 220°C, and the hydrothermal time is 16 to 24 h.

[0019] Further, in Step 3, the high-temperature calcination temperature is 600 to 1000°C, and the calcination time is 1 to 2 h.

[0020] Further, in Step 3, the inert gas is argon.

[0021] The present invention also provides an application of ilmenite-type niobate as a negative electrode material for a sodium-ion capacitor.

[0022] The present invention has at least the following beneficial effects:

[0023] The present invention provides a preparation method of an ilmenite-type niobate MNb2O6 (M = Fe, Co, Ni, Mn, etc.) material, and uses it as a negative electrode material for a sodium-ion capacitor with high capacity, high rate and long life and can cooperate with a fast-capacitance adsorption-type positive electrode, so as to solve the problem that the energy density and power density output by the sodium-ion capacitor under large-current charge and discharge are relatively low.

[0024] For the MNb2O6 prepared by the present invention, since each Nb atom has two electrode pairs (Nb 5+ / Nb 4+ , Nb 4+ / Nb 3+ ) during the charge and discharge process of the niobium-based oxide, its theoretical specific capacity is higher than that of the titanium-based oxide. And the binary niobium-based oxide niobate increases the redox electrode pairs of the reaction, and its theoretical specific capacity is higher than that of Nb2O5. Since MNb2O6 has a unique structure, large-sized sodium ions can be quickly inserted and extracted, providing an insertion-type negative electrode material for a high-capacity and high-rate sodium-ion capacitor, and helping to improve the kinetic matching of the positive and negative electrodes of the sodium-ion capacitor. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0026] Figure 1 : SEM image of the niobite-type niobate NiNb2O6 material obtained in Example 1;

[0027] Figure 2 : XRD pattern of the niobite-type niobate NiNb2O6 material obtained in Example 1;

[0028] Figure 3 : The charge-discharge curve of the niobite-type niobate NiNb2O6 material obtained in Example 1;

[0029] Figure 4 : Rate performance diagram of the niobite-type niobate NiNb2O6 material obtained in Example 1 at different current densities. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Example 1

[0032] This embodiment provides niobium iron ore type niobate NiNb2O6 as a negative electrode material for a sodium ion capacitor and a preparation method thereof, which is prepared by the following method:

[0033] 0.5g Nb2O5 and 3g KOH were dispersed in 70mL deionized water, stirred magnetically for 2h to form a dispersed solution, which was transferred to a reactor and placed in a blast drying oven for hydrothermal reaction at 260℃ for 12h. The supernatant was transferred to a beaker and 1mol / L hydrochloric acid solution was slowly added to adjust its pH value to 7-8. NiCl2 (the molar ratio of NiCl2 to Nb2O5 was 1:1) was added, and after sufficient stirring, it was transferred to a reactor for hydrothermal reaction at 180℃ for 20h. The obtained product was washed by centrifugation with distilled water 3 times and dried at 70℃ in a blast drying oven for 12h. Finally, the dried product was placed in a tubular furnace and calcined at 800℃ for 2h under argon protection.

[0034] The prepared niobium iron ore type niobate NiNb2O6 was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The test results showed that Figure 1and Figure 2 The prepared niobium iron ore type niobate NiNb2O6 was used as the negative electrode of sodium ion capacitor for electrochemical testing. The results showed that Figure 3 and Figure 4 .

[0035] Figure 1 The SEM image of the niobite-type niobate NiNb2O6 material shows that the NiNb2O6 material is a particle with a diameter of 50 nm. Figure 2 The XRD pattern of the obtained product corresponds to the standard card 31-0644, proving that it is NiNb2O6 material. Figure 3 It shows that NiNb2O6 material as the negative electrode of sodium ion capacitor has a high conductivity at 50mA·g -1 The charge-discharge curves from the first to the fifth cycle at a current density of . It can be seen from the figure that the specific capacity of the first discharge and charge is higher than that of other cycles, which is caused by the formation of the SEI film. In the subsequent reaction, the sodium ions are reversibly deintercalated in the electrode, and the specific capacity values ​​from the second to the fifth cycle are very small, indicating that the material has good stability and rate performance. Figure 4 The rate performance diagram of the material at different current densities is obtained through testing. At current densities of 0.05, 0.1, 0.2, 0.5, 1 and 2 A·g -1 The reversible specific capacities were 290, 245, 225, 196, 164 and 139 mA·h·g -1 When the current density returns to 0.05A·g -1 When the discharge capacity is 270mA·h·g -1 The capacity retention rate is 93.1%, showing excellent rate performance.

[0036] Example 2

[0037] This embodiment provides niobium iron ore type niobate FeNb2O6 as a negative electrode material for a sodium ion capacitor and a preparation method thereof, which is prepared by the following method:

[0038] 0.5g Nb2O5 and 3g KOH were dispersed in 70mL deionized water, stirred magnetically for 2h to form a dispersed solution, which was transferred to a reactor and placed in a blast drying oven for hydrothermal reaction at 260℃ for 12h. The supernatant was transferred to a beaker and 1mol / L hydrochloric acid solution was slowly added to adjust its pH value to 7-8. FeCl3 (the molar ratio of FeCl3 to Nb2O5 was 1:1) was added, and after sufficient stirring, it was transferred to a reactor for hydrothermal reaction at 180℃ for 20h. The obtained product was washed by centrifugation with distilled water 3 times and dried at 70℃ in a blast drying oven for 12h. Finally, the dried product was placed in a tubular furnace and calcined at 800℃ for 2h under argon protection.

[0039] Through charge and discharge tests, the current density is 0.05, 0.1, 0.2, 0.5, 1 and 2A·g -1 The specific capacities are 284, 247, 219, 188, 157, and 131 mA·h·g -1 , and when the current density returns to 0.05A·g -1 When the discharge capacity is 259mA·h·g -1 , maintaining 91.2% of the original charge and discharge capacity.

[0040] Example 3

[0041] This embodiment provides a niobium iron ore type niobate CoNb2O6 as a negative electrode material for a sodium ion capacitor and a preparation method thereof, which is prepared by the following method:

[0042] 0.5g Nb2O5 and 3g KOH were dispersed in 70mL deionized water, stirred magnetically for 2h to form a dispersed solution, which was transferred to a reactor and placed in a blast drying oven for hydrothermal reaction at 260℃ for 12h. The supernatant was transferred to a beaker and 1mol / L hydrochloric acid solution was slowly added to adjust its pH value to 7-8. CoCl2 (the molar ratio of CoCl2 to Nb2O5 was 1:1) was added, and after sufficient stirring, it was transferred to a reactor for hydrothermal reaction at 180℃ for 20h. The obtained product was washed by centrifugation with distilled water 3 times and dried at 70℃ in a blast drying oven for 12h. Finally, the dried product was placed in a tubular furnace and calcined at 800℃ for 2h under argon protection.

[0043] Through charge and discharge tests, the current density is 0.05, 0.1, 0.2, 0.5, 1 and 2A·g -1 When the specific capacities are 288, 243, 221, 193, 161, and 133 mA·h·g -1 , and when the current density returns to 0.05A·g -1 When the discharge capacity is 261mA·h·g -1 , maintaining 90.6% of the original charge and discharge capacity.

[0044] Example 4

[0045] This embodiment provides a niobium iron ore type niobate MnNb2O6 as a negative electrode material for a sodium ion capacitor and a preparation method thereof, which is prepared by the following method:

[0046] 0.5 g of Nb2O5 and 3 g of KOH were dispersed in 70 mL of deionized water and magnetically stirred for 2 h to form a dispersion solution, which was transferred to a reaction kettle and placed in a forced-air drying oven for hydrothermal reaction under the condition of heating at 260 °C for 12 h. The supernatant was transferred to a beaker, and a hydrochloric acid solution with a concentration of 1 mol / L was slowly added to adjust its pH value to 7 - 8. Then, MnCl2 (the molar ratio of MnCl2 to Nb2O5 was 1:1) was added. After sufficient stirring, it was transferred to a reaction kettle and hydrothermally reacted at 180 °C for 20 h. The obtained product was centrifugally washed with distilled water three times and dried in a forced-air drying oven at 70 °C for 12 h. Finally, the dried product was placed in a tubular furnace and calcined at 800 °C for 2 h under argon protection.

[0047] It was obtained through charge-discharge tests that at current densities of 0.05, 0.1, 0.2, 0.5, 1, and 2 A·g -1 , the specific capacities were 280, 233, 209, 175, 146, and 126 mA·h·g -1 , respectively, and when the current density returned to 0.05 A·g -1 , the discharge specific capacity returned to 248 mA·h·g -1 , maintaining 88.6% of the original charge-discharge specific capacity.

[0048] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only 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 improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Use of columbite-type niobate as a negative electrode material for a sodium ion capacitor, characterized in that, The preparation method of the ilmenite-type niobate comprises the following steps: Step 1: Hydrothermally react niobium oxide powder with an alkali solution in a reaction kettle; Retain the supernatant, and then adjust the pH to 7-8 with an acid solution of a certain concentration to generate product A: hydrated niobium pentoxide; Step 2: Add M salt to product A, and the molar ratio of niobium oxide to M salt is 1:

1. Conduct a second hydrothermal reaction in a reaction kettle, wash it with distilled water, and freeze-dry it to obtain product B; M salt is at least one of the following: NiCl2, FeCl3, CoCl2; Step 3: Put product B into a tubular furnace and introduce an inert gas for high-temperature calcination to obtain the final product: ilmenite-type niobate; the final product ilmenite-type niobate is at least one of the following: NiNb2O6, FeNb2O6, CoNb2O6.

2. Use of the columbite-type niobate as a negative electrode material for a sodium ion capacitor according to claim 1, characterized in that In Step 1, the alkali solution is a KOH solution; the acid solution is a hydrochloric acid solution.

3. Use of the columbite-type niobate as a negative electrode material for a sodium ion capacitor according to claim 1, characterized in that In Step 1, the hydrothermal reaction conditions are 240°C - 280°C, and the heating time is 10h - 14h.

4. Use of the columbite-type niobate as a negative electrode material for a sodium ion capacitor according to claim 1, characterized in that, In Step 2, the second hydrothermal reaction conditions are: the temperature is 160°C - 220°C, and the hydrothermal time is 16 - 24h.

5. Use of the columbite-type niobate as a negative electrode material for a sodium ion capacitor according to claim 1, characterized in that, In Step 3, the high-temperature calcination temperature is 600 - 1000°C, and the calcination time is 1 - 2h.

6. Use of the columbite-type niobate as a negative electrode material for a sodium ion capacitor according to claim 1, characterized in that, In Step 3, the inert gas is argon.

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