Manganese dioxide composite material for battery and preparation process of manganese dioxide composite material

Abstract

The invention belongs to the technical field of new energy, and particularly relates to a manganese dioxide composite material for a battery and a preparation process thereof. Comprising the following steps: preparing iron ion loaded cattail wool; synthesizing beta-manganese dioxide by a hydrothermal template method; and carrying out vacuum impregnation and calcination treatment on the precursor template. Fe < 3 + > ions are loaded on the surface of cattail wool, glucose is doped while beta-manganese dioxide is synthesized, oxygen atoms can be induced to be separated from crystal lattices so as to form oxygen vacancies during subsequent calcination, the surface of manganese dioxide is coated with residual carbon generated by pyrolysis, backfilling of the oxygen vacancies can be inhibited, and the oxygen vacancies can be effectively degraded. The oxygen vacancies formed after calcination can increase the storage sites of carriers (Zn < 2 + > and H < + >), and endow the subsequent manganese dioxide composite material with higher specific capacity, thereby effectively increasing the discharge specific capacity of the manganese dioxide composite material as the positive electrode of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy, and particularly relates to a manganese dioxide composite material for batteries and a preparation process thereof. Background Art

[0002] With the accelerating transformation of the global energy structure, electrochemical energy storage technology has become the core support for the efficient utilization of renewable energy. Among many energy storage systems, although traditional lithium-ion batteries have long dominated, their inherent bottlenecks are becoming increasingly prominent: on the one hand, the system based on organic electrolytes has safety hazards such as flammability and explosiveness, and may release highly toxic fluorides under thermal runaway conditions; on the other hand, the uneven geographical distribution of lithium resources and the rising extraction cost have continuously pressured the economy of the battery system.

[0003] Therefore, aqueous multivalent ion batteries have attracted extensive attention due to their intrinsic safety and cost advantages. Among them, aqueous zinc-ion batteries have high theoretical capacity, low price, and abundant zinc resources. Different from the single-electron transfer mechanism of lithium ions, zinc ions achieve charge storage through a two-electron reaction and can provide a higher volumetric energy density. However, the actual performance of this system highly depends on the reversible storage ability of the cathode material for Zn2 + ions.

[0004] Currently, common cathode materials for aqueous zinc-ion batteries mainly include manganese-based compounds, vanadium-based compounds, Prussian blue analogs, organic compounds, etc. Manganese-based cathode materials have become the most studied cathode materials for ZIBs due to their high theoretical capacity, high voltage window, non-toxicity, and abundant reserves. However, the poor intrinsic conductivity and large volume change during charge and discharge of manganese-based materials lead to phenomena such as low capacity, short cycle life, and slow reaction kinetics. Summary of the Invention

[0005] In order to solve the above technical defects, the present invention has developed a preparation process for a manganese dioxide composite material for batteries. When the prepared manganese dioxide composite material is used as a cathode material, it has a high specific capacity and long cycle stability, and has excellent electrochemical performance.

[0006] A preparation process for a manganese dioxide composite material for batteries includes the following steps:

[0007] S1: Preparation of iron ion-loaded cattail fluff

[0008] Wash the cattail fluff and immerse it in a 3-aminopropyltriethoxysilane solution for modification to obtain amino-functionalized cattail fluff. Immerse the amino-functionalized cattail fluff in an FeCl3 solution prepared by mixing FeCl3, sodium citrate, and deionized water. After oscillating and reacting, perform centrifugation, washing, and drying to obtain iron ion-loaded cattail fluff;

[0009] S2: Hydrothermal template synthesis of β-manganese dioxide

[0010] Under stirring, add MnSO4·H2O and (NH4)2S2O8 into the glucose aqueous solution until Mn 2+ The concentration is 0.2-0.3 mol / L, a manganese-glucose solution is obtained, and the iron ion-loaded cattail fluff is added and mixed evenly, and then transferred to an autoclave for hydrothermal reaction, centrifuged and washed, and then dried to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide;

[0011] S3: Vacuum impregnation and calcination of precursor template

[0012] Tetramethoxyphenylporphyrin cobalt and europium nitrate hexahydrate are uniformly mixed with anhydrous ethanol, and then an oxygen vacancy precursor template loaded with β-manganese dioxide is immersed therein and vacuum impregnated, taken out and dried, and then placed in a tubular vacuum furnace for vacuum calcination, cooled to room temperature, rinsed, and then dried to obtain a manganese dioxide composite material.

[0013] Furthermore, step S1, the preparation of cattail fluff loaded with iron ions, comprises the following steps:

[0014] S1.1: immerse the cattail fluff in an ethanol solution with a concentration of 25-30%, and then perform ultrasonic treatment for 25-30 minutes under the conditions of 200-220W and 30-35kHz, remove and dry in a vacuum drying oven at 60-65°C to obtain cleaned cattail fluff, mix 3-aminopropyltriethoxysilane and anhydrous ethanol in a volume ratio of 1:(15-20), adjust the pH to 5-5.5 with acetic acid, hydrolyze for 20-25 minutes, obtain a 3-aminopropyltriethoxysilane solution, immerse the cleaned cattail fluff in the 3-aminopropyltriethoxysilane solution at a solid-liquid ratio of 1:(10-15) g / mL, stir evenly, and stand at 45-50°C for 1-2 hours, filter and take out the solid residue, wash and dry, and obtain amino-functionalized cattail fluff;

[0015] S1.2: Mix FeCl3, sodium citrate and deionized water to prepare Fe 3+ The concentration of FeCl3 solution is 0.2-0.3 mol / L, and the concentration of sodium citrate is 0.04-0.05 mol / L, the pH is adjusted to 4.5-5, and then the amino-functionalized cattail fluff is immersed in the FeCl3 solution at a solid-liquid ratio of 1: (15-20) g / mL, transferred to a constant temperature oscillator for oscillation reaction for 2-3 hours, and then centrifuged at 4000-5000 rpm for 10-15 minutes. After washing, it is placed in a 60-65°C vacuum drying oven for drying to obtain iron ion loaded cattail fluff.

[0016] Further, the hydrothermal template method for synthesizing β-manganese dioxide in step S2 includes the following steps:

[0017] S2.1: Under stirring, add MnSO4·H2O and (NH4)2S2O8 to an aqueous glucose solution with a concentration of 0.1 - 0.2 mol / L at a molar ratio of 1:(1 - 1.2) until the Mn concentration in the solution is 0.2 - 0.3 mol / L, obtaining a manganese-glucose solution; 2+ Concentration is 0.2 - 0.3 mol / L, obtaining a manganese-glucose solution;

[0018] S2.2: Mix the iron ion-loaded cattail fluff and the manganese-glucose solution evenly at a solid-liquid ratio of 1:(60 - 80) g / mL, then place them in a stainless-steel autoclave with a polytetrafluoroethylene inner lining and seal it. Set the hydrothermal reaction temperature to 140 - 145 °C and the time to 12 - 13 hours. After the reaction, centrifuge the reaction solution, take the bottom precipitate, add 15 - 20 times the mass of anhydrous ethanol and centrifuge again. Collect the precipitate and dry it at 80 - 85 °C to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide.

[0019] Further, the vacuum impregnation and calcination treatment of the precursor template in step S3 includes the following steps:

[0020] S3.1: Add 6 - 6.5 parts by weight of europium nitrate hexahydrate powder and 3.5 - 4 parts by weight of cobalt tetramethoxyphenylporphyrin to 30 - 40 parts by weight of anhydrous ethanol. After stirring evenly, obtain a mixed impregnation solution. Immerse 6 - 8 parts by weight of the oxygen vacancy precursor template loaded with β-manganese dioxide in the mixed impregnation solution, then transfer it to a vacuum impregnation tank for vacuum impregnation. Take it out and transfer it to a blast drying oven, and dry it at 75 - 80 °C to obtain an oxygen vacancy precursor template coated with rare earth complexes;

[0021] S3.2: Place the oxygen vacancy precursor template coated with rare earth complexes in a tubular vacuum furnace. Under a vacuum condition of 0.1 - 0.5 Pa, heat it at a heating rate of 5 - 10 °C / min to 480 - 500 °C, then hold for 1 - 1.5 hours. After naturally cooling to room temperature, rinse it 2 - 3 times with deionized water, and then dry it at 60 - 65 °C to obtain a manganese dioxide composite material.

[0022] Further, the conditions for the oscillating reaction in step S1.2 are 25 °C and 150 - 200 rpm.

[0023] Further, the centrifugation speed for centrifugation in step S2.2 is 6000 - 8000 rpm, and the time is 10 - 15 minutes.

[0024] Further, the vacuum degree during the vacuum impregnation process in step S3.1 is 10 - 20 Pa, and the time is 30 - 35 minutes.

[0025] A manganese dioxide composite material for battery is prepared by the above-mentioned preparation process of the manganese dioxide composite material for battery.

[0026] The beneficial effects are as follows: 1. The present invention loads Fe on the surface of cattail fluff. 3+ ions, and then glucose is doped while synthesizing β-manganese dioxide. When calcined later, Fe 3+ Partially replace Mn 4+ At this time, the adjacent oxygen atoms tend to leave the lattice to form oxygen vacancies, and glucose is pyrolyzed under vacuum to generate reducing gases CO and H2, which induce oxygen atoms to leave the lattice of the composite material to form oxygen vacancies. The residual carbon generated by pyrolysis is coated on the surface of manganese dioxide, which can inhibit the backfilling of oxygen vacancies. The oxygen vacancies formed after calcination can increase the carriers (Zn 2+ and H + ) storage sites, giving the subsequent manganese dioxide composite material a higher specific capacity, thereby effectively increasing its discharge specific capacity as the battery positive electrode.

[0027] 2. The present invention uses cattail fluff as a template for the hydrothermal synthesis reaction of β-manganese dioxide to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide, and then forms a porous manganese dioxide flower ball composed of flaky manganese dioxide in the subsequent calcination process, and a continuous conductive skeleton is formed between the microcrystalline carbon remaining from the carbonization of the cattail fluff and the β-manganese dioxide, which not only improves the conductivity of the composite material and enhances the rate performance, but also stabilizes its structural framework. When used for battery positive electrode materials, it can maintain long-term cycle stability, greatly improve the capacity retention rate of the positive electrode material, and has long cycle stability.

[0028] 3. The present invention uses a vacuum impregnation method to coat tetramethoxyphenylporphyrin cobalt and europium nitrate on the surface of an oxygen vacancy precursor template loaded with β-manganese dioxide through coordination. The obtained rare earth complex-coated oxygen vacancy precursor template can further form a carbon conductive skeleton during calcination, and the cobalt therein can be coated with molten europium nitrate and infiltrated into β-manganese dioxide, thereby reducing the energy band gap of manganese dioxide, improving the conductive properties of the composite material, and stabilizing the crystal structure of β-manganese dioxide, further improving its electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the preparation process of the manganese dioxide composite material for batteries used in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment 1

[0032] A manganese dioxide composite material for a battery and its preparation process, as Figure 1 shown, includes the following steps:

[0033] S1: Preparation of iron ion-loaded cattail fluff

[0034] S1.1: Immerse cattail fluff in an ethanol solution with a concentration of 25%, then perform ultrasonic treatment for 25 minutes under the conditions of 200W and 30kHz, fish out and place it in a vacuum drying oven at 60°C for drying to obtain cleaned cattail fluff. Mix 3-aminopropyltriethoxysilane and absolute ethanol in a volume ratio of 1:15, adjust the pH to 5 with acetic acid, and hydrolyze for 20 minutes to obtain a 3-aminopropyltriethoxysilane solution. Immerse the cleaned cattail fluff in the 3-aminopropyltriethoxysilane solution at a solid-liquid ratio of 1:10 g / mL, stir evenly and then let it stand at 45°C for 1 hour, filter to obtain the solid filter residue for washing and drying to obtain amino-functionalized cattail fluff;

[0035] S1.2: Mix FeCl3, sodium citrate, and deionized water to prepare an Fe 3+ solution with an FeCl3 concentration of 0.2 mol / L and a sodium citrate concentration of 0.04 mol / L, adjust the pH to 4.5, then immerse the amino-functionalized cattail fluff in the FeCl3 solution at a solid-liquid ratio of 1:15 g / mL, transfer it to a constant temperature oscillator and oscillate for reaction for 2 hours. The oscillation reaction conditions are 25°C and 150 rpm, then centrifuge at 4000 rpm for 10 minutes, wash and place it in a vacuum drying oven at 60°C for drying to obtain iron ion-loaded cattail fluff.

[0036] S2: Hydrothermal template synthesis of β-manganese dioxide

[0037] S2.1: Under stirring, add MnSO4·H2O and (NH4)2S2O8 to a glucose aqueous solution with a concentration of 0.1 mol / L in a molar ratio of 1:1 until the Mn 2+ concentration in the solution is 0.2 mol / L to obtain a manganese-glucose solution;

[0038] S2.2: Mix the iron ion-loaded cattail fluff and the manganese-glucose solution evenly at a solid-liquid ratio of 1:60 g / mL, then seal it in a stainless-steel autoclave with a PTFE liner, set the hydrothermal reaction temperature at 140 °C and the time at 12 hours. After the reaction, centrifuge the reaction solution at a speed of 6000 rpm for 10 minutes. Take the bottom precipitate, add 15 times the mass of absolute ethanol and centrifuge again. Collect the precipitate and dry it at 80 °C to obtain the oxygen vacancy precursor template loaded with β-manganese dioxide.

[0039] S3: Vacuum impregnation and calcination treatment of the precursor template

[0040] S3.1: Add 6 parts by weight of europium nitrate hexahydrate powder and 3.5 parts by weight of cobalt tetramethoxyphenylporphyrin to 30 parts by weight of absolute ethanol. After stirring evenly, a mixed impregnation solution is obtained. Immerse 6 parts by weight of the oxygen vacancy precursor template loaded with β-manganese dioxide in the mixed impregnation solution, then transfer it to a vacuum impregnation tank for vacuum impregnation. Take it out and transfer it to a forced-air drying oven to dry at 75 °C to obtain the oxygen vacancy precursor template coated with rare-earth complexes.

[0041] S3.2: Place the oxygen vacancy precursor template coated with rare-earth complexes in a tubular vacuum furnace. Under a vacuum condition of 0.1 Pa, heat it to 480 °C at a heating rate of 5 °C / min and keep it warm for 1 hour. Naturally cool it to room temperature, rinse it twice with deionized water, and then dry it at 60 °C to obtain the manganese dioxide composite material.

[0042] Example 2

[0043] A manganese dioxide composite material for batteries and its preparation process, as Figure 1 shown, includes the following steps:

[0044] S1: Preparation of iron ion-loaded cattail fluff

[0045] S1.1: Immerse the cattail fluff in an ethanol solution with a concentration of 25%, then perform ultrasonic treatment at 200 W and 30 kHz for 25 minutes. After fishing it out, place it in a vacuum drying oven at 60 °C to dry and obtain the cleaned cattail fluff. Mix 3-aminopropyltriethoxysilane and absolute ethanol at a volume ratio of 1:20, adjust the pH to 5 with acetic acid, and hydrolyze for 20 minutes to obtain a 3-aminopropyltriethoxysilane solution. Immerse the cleaned cattail fluff in the 3-aminopropyltriethoxysilane solution at a solid-liquid ratio of 1:15 g / mL, stir evenly, and let it stand at 45 °C for 1 hour. Filter to obtain the solid residue, wash and dry it to obtain the amino-functionalized cattail fluff.

[0046] S1.2: Mix FeCl3, sodium citrate and deionized water to prepare Fe 3+An FeCl3 solution with a concentration of 0.3 mol / L and a sodium citrate concentration of 0.05 mol / L was adjusted to a pH of 4.5. Then, the amino-functionalized cattail fluff was immersed in the FeCl3 solution at a solid-liquid ratio of 1:20 g / mL, transferred to a constant temperature oscillator, and oscillated for 2 hours under the conditions of 25 °C and 150 rpm. Then, centrifugation was carried out at 4000 rpm for 10 minutes. After washing, it was placed in a vacuum drying oven at 60 °C for drying to obtain iron ion-loaded cattail fluff.

[0047] S2: Hydrothermal template synthesis of β-manganese dioxide

[0048] S2.1: Under stirring conditions, MnSO4·H2O and (NH4)2S2O8 were added to a 0.1 mol / L glucose aqueous solution at a molar ratio of 1:1.2 until the Mn concentration in the solution was 0.3 mol / L to obtain a manganese-glucose solution; 2+ The concentration was 0.3 mol / L, and a manganese-glucose solution was obtained;

[0049] S2.2: The iron ion-loaded cattail fluff and the manganese-glucose solution were mixed evenly at a solid-liquid ratio of 1:80 g / mL, then placed in a stainless steel autoclave with a polytetrafluoroethylene liner and sealed. The hydrothermal reaction temperature was set at 140 °C for 12 hours. After the reaction, the reaction solution was centrifuged at a speed of 6000 rpm for 10 minutes. The bottom precipitate was taken and centrifuged again with 15 times the mass of absolute ethanol. The precipitate was collected and dried at 80 °C to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide.

[0050] S3: Vacuum impregnation and calcination treatment of the precursor template

[0051] S3.1: 6.5 parts by weight of europium nitrate hexahydrate powder and 4 parts by weight of cobalt tetramethoxyphenylporphyrin were added to 30 parts by weight of absolute ethanol. After stirring evenly, a mixed impregnation solution was obtained. 8 parts by weight of the oxygen vacancy precursor template loaded with β-manganese dioxide was immersed in the mixed impregnation solution, then transferred to a vacuum impregnation tank for vacuum impregnation, taken out and transferred to a forced air drying oven, and dried at 75 °C to obtain an oxygen vacancy precursor template coated with rare earth complexes;

[0052] S3.2: The oxygen vacancy precursor template coated with rare earth complexes was placed in a tube-type vacuum furnace. Under a vacuum condition of 0.1 Pa, it was heated to 480 °C at a heating rate of 5 °C / min and held for 1 hour. After natural cooling to room temperature, it was rinsed twice with deionized water and then dried at 60 °C to obtain a manganese dioxide composite material.

[0053] Example 3

[0054] A manganese dioxide composite material for batteries and its preparation process, as Figure 1As shown, the following steps are included:

[0055] S1: Preparation of cattail fluff loaded with iron ions

[0056] S1.1: Immerse the cattail fluff in a 30% ethanol solution, then perform ultrasonic treatment at 220W and 35kHz for 30 minutes, remove and dry in a vacuum drying oven at 65°C to obtain cleaned cattail fluff, mix 3-aminopropyltriethoxysilane and anhydrous ethanol in a volume ratio of 1:15, adjust the pH to 5.5 with acetic acid, hydrolyze for 25 minutes, obtain a 3-aminopropyltriethoxysilane solution, immerse the cleaned cattail fluff in the 3-aminopropyltriethoxysilane solution at a solid-liquid ratio of 1:10g / mL, stir evenly, and stand at 50°C for 2 hours, filter and take out the solid residue, wash and dry, and obtain amino-functionalized cattail fluff;

[0057] S1.2: Mix FeCl3, sodium citrate and deionized water to prepare Fe 3+ The concentration of FeCl3 solution was 0.2 mol / L, and the concentration of sodium citrate was 0.04 mol / L. The pH was adjusted to 5. Then, the amino-functionalized cattail fluff was immersed in the FeCl3 solution at a solid-liquid ratio of 1:15 g / mL, and transferred to a constant temperature oscillator for oscillation reaction for 3 hours. The oscillation reaction conditions were 25°C, 200 rpm, and then centrifuged at 5000 rpm for 15 minutes. After washing, it was placed in a 65°C vacuum drying oven for drying to obtain iron ion loaded cattail fluff.

[0058] S2: Hydrothermal template synthesis of β-manganese dioxide

[0059] S2.1: Under stirring, add MnSO4·H2O and (NH4)2S2O8 in a molar ratio of 1:1 to a 0.2 mol / L aqueous glucose solution until Mn 2+ The concentration is 0.2 mol / L to obtain a manganese-glucose solution;

[0060] S2.2: The iron ion-loaded cattail fluff and manganese-glucose solution were mixed evenly at a solid-liquid ratio of 1:60 g / mL, and then placed in a stainless steel autoclave lined with polytetrafluoroethylene and sealed. The hydrothermal reaction temperature was set to 145°C and the reaction time was 13 hours. After the reaction, the reaction solution was centrifuged at a speed of 8000 rpm for 15 minutes. The bottom precipitate was taken and 20 times the mass of anhydrous ethanol was added and centrifuged again. The precipitate was collected and dried at 85°C to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide.

[0061] S3: Vacuum impregnation and calcination of precursor template

[0062] S3.1: Add 6 parts by weight of europium nitrate hexahydrate powder and 3.5 parts by weight of cobalt tetramethoxyphenylporphyrin into 30 parts by weight of absolute ethanol. After stirring evenly, a mixed impregnation solution is obtained. Immerse 6 parts by weight of the oxygen vacancy precursor template loaded with β-manganese dioxide into the mixed impregnation solution, then transfer it to a vacuum impregnation tank for vacuum impregnation. Take it out and transfer it to a forced air drying oven, and dry it at 80 °C to obtain an oxygen vacancy precursor template coated with rare earth complex;

[0063] S3.2: Place the oxygen vacancy precursor template coated with rare earth complex in a tubular vacuum furnace. Under a vacuum condition of 0.5 Pa, heat it to 500 °C at a heating rate of 10 °C / min and keep it warm for 1.5 hours. After natural cooling to room temperature, rinse it 3 times with deionized water, and then dry it at 65 °C to obtain a manganese dioxide composite material.

[0064] Comparative Example 1: The difference from Example 1 is that Fe is not loaded on the cattail fluff in Comparative Example 1 3+ , and replace the subsequent iron ion-loaded cattail fluff with the same mass of washed cattail fluff. The rest of the specific implementation manners are the same as those in Example 1.

[0065] Comparative Example 2: The difference from Example 1 is that in Comparative Example 2, the glucose aqueous solution in step S2.1 is replaced with the same mass of deionized water to prepare a manganese pre-reaction solution, and the subsequent manganese-glucose solution is replaced with the manganese pre-reaction solution. The rest of the specific implementation manners are the same as those in Example 1.

[0066] Comparative Example 3: The difference from Example 1 is that in Comparative Example 3, the cattail fluff in step S1.1 is replaced with the same mass of carbon cloth (W0S1011). The rest of the specific implementation manners are the same as those in Example 1.

[0067] Comparative Example 4: The difference from Example 1 is that in Comparative Example 4, step S3.1 is removed, and the oxygen vacancy precursor template coated with rare earth complex is replaced with the oxygen vacancy precursor template loaded with β-manganese dioxide. The rest of the specific implementation manners are the same as those in Example 1.

[0068] Crush the manganese dioxide composite materials prepared in Examples 1-3 and Comparative Examples 1-4 to obtain samples. Then, disperse each sample, conductive carbon black, and polyvinylidene fluoride in an N-methylpyrrolidone solution at a mass ratio of 7:2:1, and continuously stir for four hours to obtain a uniformly dispersed slurry. Uniformly coat it on the surface of a titanium foil, dry it and cut it to obtain a positive electrode sheet. Finally, assemble the positive electrode sheet, zinc foil (negative electrode), separator (glass fiber), and 2M ZnSO4 + 0.1M MnSO4 mixed solution (electrolyte) into a CR2032 type button battery.

[0069] Electrochemical performance test:

[0070] The constant current discharge specific capacity of the button cells assembled with the samples of Examples 1-3 and Comparative Examples 1-2 was tested using a battery test system at a test rate of 0.1C. Among them, during battery testing, 1C = 308 mAh / g. Three tests were conducted, and the test results are shown in Table 1.

[0071] Table 1: Discharge specific capacity of button cells assembled with various samples at 0.1C

[0072]

[0073] From the data of Examples 1-3 in Table 1, it can be seen that the button cells assembled with the samples prepared in Examples 1-3 all have high discharge specific capacity. While from Comparative Examples 1-2, it can be seen that without adding Fe 3+ ions or glucose will both cause a significant decrease in the discharge specific capacity, which can prove that loading Fe 3+ ions on the surface of cattail fluff and doping glucose during the synthesis of β-manganese dioxide can both effectively increase the discharge specific capacity of the manganese dioxide composite material as the battery cathode.

[0074] The rate performance and cycling performance of the button cells assembled with the samples of Examples 1-3 and Comparative Examples 3-4 were tested using a battery test system. The rate performance was tested at current densities of 200 mA / g, 400 mA / g, 600 mA / g, 800 mA / g, 1000 mA / g, 2000 mA / g, and 3000 mA / g. Five charge-discharge cycles were carried out at each rate, and the average discharge capacity of the five charge-discharge cycles was taken. The cycling performance was tested for the number of cycles with a specific capacity greater than 80% at 1C rate. The test results are shown in Table 2.

[0075] Table 2: Discharge specific capacity of button cells assembled with various samples at different current densities

[0076]

[0077]

[0078] From the data in Table 2, it can be seen that the button cells assembled with the samples prepared in Examples 1-3 all have excellent rate performance, and the number of cycles with a specific capacity greater than 80% at 1C rate also reaches a relatively high number, indicating good cycling stability. While for the button cells assembled with the samples prepared in Comparative Examples 3-4, both the rate performance and cycling stability have decreased, which can prove that using cattail fluff as a template molecule and doping cobalt tetramethoxyphenylporphyrin and europium nitrate during the calcination of manganese dioxide can both improve the conductivity and stability of the manganese dioxide composite material, enhancing the rate performance and cycling stability.

[0079] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the relevant technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation process of a manganese dioxide composite material for a battery, characterized in that, It includes the following steps: S1: Preparation of iron ion-loaded cattail fluff The cattail fluff is washed and then immersed in a 3-aminopropyltriethoxysilane solution for modification to obtain amino-functionalized cattail fluff. The amino-functionalized cattail fluff is immersed in an FeCl3 solution prepared by mixing FeCl3, sodium citrate, and deionized water. After oscillating the reaction, centrifugation, washing, and drying are carried out to obtain iron ion-loaded cattail fluff; S2: Hydrothermal template synthesis of β-manganese dioxide Under stirring conditions, MnSO4·H2O and (NH4)2S2O8 are added to the glucose aqueous solution until the Mn concentration in the solution is 0.2 - 0.3 mol / L to obtain a manganese-glucose solution. Iron ion-loaded cattail fluff is added and mixed evenly, and then it is transferred to an autoclave for hydrothermal reaction. After centrifugal washing and drying, an oxygen vacancy precursor template loaded with β-manganese dioxide is obtained. 2+ ​ S3: Vacuum impregnation and calcination treatment of the precursor template Tetramethoxyphenylporphyrin cobalt and europium nitrate hexahydrate are mixed evenly in absolute ethanol. Then, the oxygen vacancy precursor template loaded with β-manganese dioxide is immersed therein and subjected to vacuum impregnation. After taking it out and drying, it is placed in a tube-type vacuum furnace for vacuum calcination. After cooling to room temperature, it is rinsed clean and then dried to obtain a manganese dioxide composite material.

2. The preparation process of a manganese dioxide composite material for a battery according to claim 1, wherein, For the preparation of iron ion-loaded cattail fluff in step S1, it includes the following steps: S1.1: The cattail fluff is immersed in an ethanol solution with a concentration of 25-30%, and then ultrasonic treatment is carried out for 25-30 minutes under the conditions of 200-220W and 30-35kHz. After fishing it out, it is placed in a vacuum drying oven at 60-65°C for drying to obtain cleaned cattail fluff. 3-aminopropyltriethoxysilane and absolute ethanol are mixed at a volume ratio of 1:(15-20), and the pH is adjusted to 5-5.5 with acetic acid and hydrolyzed for 20-25 minutes to obtain a 3-aminopropyltriethoxysilane solution. The cleaned cattail fluff is immersed in the 3-aminopropyltriethoxysilane solution at a solid-liquid ratio of 1:(10-15) g / mL, stirred evenly, and then left standing at 45-50°C for 1-2 hours. The solid filter residue is filtered, washed, and dried to obtain amino-functionalized cattail fluff; S1.2: Mix FeCl3, sodium citrate and deionized water to prepare an FeCl3 solution with an Fe concentration of 0.2 - 0.3 mol / L and a sodium citrate concentration of 0.04 - 0.05 mol / L. Adjust the pH to 4.5 - 5, and then immerse the amino-functionalized cattail fluff into the FeCl3 solution at a solid-liquid ratio of 1:(15 - 20) g / mL. Transfer it to a thermostatic oscillator and oscillate for reaction for 2 - 3 hours. Then centrifuge at 4000 - 5000 rpm for 10 - 15 minutes, wash it, and place it in a vacuum drying oven at 60 - 65 °C for drying to obtain cattail fluff loaded with iron ions. 3+ ​ 3. The preparation process of a manganese dioxide composite material for a battery according to claim 2, characterized in that, For the hydrothermal template synthesis of β-manganese dioxide in step S2, it includes the following steps: S2.1: Under stirring conditions, add MnSO4·H2O and (NH4)2S2O8 to an aqueous glucose solution with a concentration of 0.1 - 0.2 mol / L in a molar ratio of 1:(1 - 1.2) until the Mn in the solution 2+ The concentration is 0.2 - 0.3 mol / L to obtain a manganese-glucose solution; S2.2: The iron ion-loaded cattail fluff and the manganese-glucose solution are mixed evenly at a solid-liquid ratio of 1:(60-80) g / mL, and then placed in a stainless steel autoclave with a polytetrafluoroethylene lining and sealed. The hydrothermal reaction temperature is set at 140-145°C and the time is 12-13 hours. After the reaction ends, the reaction solution is centrifuged. The bottom precipitate is taken and centrifuged again by adding 15-20 times the mass of absolute ethanol. The precipitate is collected and dried at 80-85°C to obtain an oxygen vacancy precursor template loaded with β-manganese dioxide.

4. The preparation process of a manganese dioxide composite material for a battery according to claim 3, characterized in that, For the vacuum impregnation and calcination treatment of the precursor template in step S3, it includes the following steps: S3.1: 6-6.5 parts by weight of europium nitrate hexahydrate powder and 3.5-4 parts by weight of tetramethoxyphenylporphyrin cobalt are added to 30-40 parts by weight of absolute ethanol, and after stirring evenly, a mixed impregnation solution is obtained. 6-8 parts by weight of the oxygen vacancy precursor template loaded with β-manganese dioxide is immersed in the mixed impregnation solution, and then transferred to a vacuum impregnation tank for vacuum impregnation. After taking it out, it is transferred to a blast drying oven and dried at 75-80°C to obtain an oxygen vacancy precursor template coated with rare earth complexes; S3.2: Place the oxygen vacancy precursor template coated with rare earth complex in a tubular vacuum furnace. Under the vacuum condition of 0.1 - 0.5 Pa, heat it at a heating rate of 5 - 10 °C / min to 480 - 500 °C, then hold for 1 - 1.5 hours. After naturally cooling to room temperature, rinse it 2 - 3 times with deionized water, and then dry it at 60 - 65 °C to obtain the manganese dioxide composite material.

5. The preparation process of a manganese dioxide composite material for a battery according to claim 2, characterized in that, The conditions for the oscillating reaction in step S1.2 are 25 °C and 150 - 200 rpm.

6. The preparation process of a manganese dioxide composite material for a battery according to claim 3, characterized in that, The centrifugal speed for centrifugation in step S2.2 is 6000 - 8000 rpm, and the time is 10 - 15 minutes.

7. The preparation process of a manganese dioxide composite material for a battery according to claim 4, characterized in that, The vacuum degree for the vacuum impregnation process in step S3.1 is 10 - 20 Pa, and the time is 30 - 35 minutes.

8. A manganese dioxide composite material for a battery, characterized in that, It is prepared by the preparation process of a manganese dioxide composite material for a battery according to any one of claims 1 - 7 above.

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