A positive electrode material of polyaniline-coated manganese dioxide nanorolls and a preparation method thereof

Abstract

The application discloses a kind of positive electrode material of polyaniline-coated manganese dioxide nanometer roll and its preparation method, polyaniline (PANI) conductive polymer is compounded with manganese dioxide, the polyaniline is overlapped with ultrathin sheet layered structure and forms the three-dimensional network conductive protective layer of manganese dioxide nanometer roll, for improving electrode conductivity, the polyaniline-coated manganese dioxide nanometer roll (MnO2 / PANI) for aqueous zinc ion battery positive electrode, the battery positive electrode obtained shows excellent rate performance and cycle stability, the coating of the polyaniline will play a protective role to manganese dioxide, inhibit the dissolution of manganese dioxide, improve battery cycle stability.The polyaniline-coated manganese dioxide nanometer roll material prepared in the application effectively improves the problem of low intrinsic conductivity of traditional manganese dioxide, polyaniline (PANI) conductive polymer is compounded with manganese dioxide, the prepared positive electrode material has reversible electrochemical capacity and excellent cycle performance, further improves the electrochemical performance of manganese dioxide.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to a positive electrode material of polyaniline-coated manganese dioxide nanorolls and its preparation method. Background Technology

[0002] Among existing energy storage devices, lithium-ion batteries are widely used due to their high operating voltage, wide operating temperature range, and long cycle life. However, the flammability of organic electrolytes, safety concerns, and the scarcity of lithium resources hinder the large-scale application of lithium-ion batteries in the future. Furthermore, low-cost sodium-ion and potassium-ion batteries also face safety issues. These drawbacks of organic electrolyte systems have prompted researchers to explore next-generation energy storage systems that offer high capacity, low cost, and high safety.

[0003] Multivalent metal ion rechargeable batteries, such as those using Ca, Al, and Zn, have seen widespread development due to their high energy density, low cost, and abundant resources. Among these, only zinc anodes exhibit high compatibility with aqueous electrolytes. Furthermore, the inherent safety and environmental friendliness of aqueous electrolytes contribute to battery chemistry, making rechargeable aqueous zinc-ion batteries a promising candidate for large-scale energy storage systems. MnO2 has gradually become the most widely used cathode material for aqueous zinc-ion batteries, but issues such as structural collapse due to continuous phase transitions during charging and discharging, and low electron mobility still require further improvement.

[0004] Existing public patents ( CN110265649A By forming a metal oxide coating on the surface of manganese dioxide, large volume changes in the material during charge and discharge processes can be suppressed, and direct contact between the electrode material and the electrolyte can be prevented to avoid the dissolution of manganese in the electrode material. However, problems such as the poor chemical stability of manganese dioxide materials during charge and discharge processes still need to be solved. Therefore, other coated manganese dioxide materials besides metal oxides need further development. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention aims to provide a positive electrode material of polyaniline-coated manganese dioxide nanorolls and its preparation method. This method is simple to operate, uses widely available raw materials, and has controllable conditions, possessing the potential for mass production. The prepared polyaniline-coated manganese dioxide nanoroll material effectively improves the problem of low intrinsic conductivity of traditional manganese dioxide. By combining polyaniline (PANI) conductive polymer with manganese dioxide, the prepared positive electrode material exhibits reversible electrochemical capacity and excellent cycle performance, further enhancing the electrochemical performance of manganese dioxide.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A positive electrode material with polyaniline-coated manganese dioxide nanorolls is disclosed. Polyaniline (PANI) conductive polymer is composited with manganese dioxide. The polyaniline forms a three-dimensional network conductive protective layer of manganese dioxide nanorolls in an ultrathin sheet-like layered structure to improve electrode conductivity. The polyaniline-coated manganese dioxide nanorolls (MnO2 / PANI) are used as the positive electrode in an aqueous zinc-ion battery. The resulting battery positive electrode exhibits excellent rate performance and cycle stability. The polyaniline coating protects the manganese dioxide, inhibits its dissolution, and enhances battery cycle stability.

[0008] A method for preparing a positive electrode material with polyaniline-coated manganese dioxide nanorolls includes the following steps;

[0009] Step 1: Add phytic acid to deionized water, sonicate, then add aniline monomer and sonicate until completely dissolved to obtain solution A;

[0010] Step 2: Add ammonium persulfate to deionized water and sonicate until completely dissolved to obtain solution B. Freeze solutions A and B simultaneously. Add solution B dropwise into solution A and sonicate rapidly to obtain solution C. Place solution C in ice water to cool and age for a certain period of time to finally obtain polyaniline gel.

[0011] Step 3: Wash the polyaniline gel obtained in Step 2 with deionized water three times, add deionized water and stir continuously to obtain polyaniline dispersion D;

[0012] Step 4: Disperse manganese dioxide in deionized water to obtain dispersion E. Add dispersion D to dispersion E while stirring. After continuous stirring, dry the mixture to obtain polyaniline-coated manganese dioxide material.

[0013] The specific steps for preparing the manganese dioxide added in step 4 include:

[0014] a. Mix potassium permanganate and ammonium chloride in a molar ratio of 1.5-4.5:1, add to 50-70 ml of deionized water, and sonicate for 15 min to form a uniformly dispersed mixed solution;

[0015] b. Transfer the resulting mixed solution to a 100ml high-pressure hydrothermal reactor lined with polytetrafluoroethylene, and heat it in an oil bath at 120-160℃ for 24-60 hours, stirring continuously at a speed of 2000-4000rpm.

[0016] c. Collect the precipitate, wash it three times with deionized water, and dry it under vacuum to obtain manganese dioxide.

[0017] In step 1, the molar ratio of aniline monomer to phytic acid molecules in the mixed aqueous solution of phytic acid and aniline monomer is (1-7):1. The mixture is sonicated for 15 minutes in step 1 to ensure the aniline monomer is fully dissolved in the phytic acid solution. After the reaction, an aniline phytate solution is formed. Since one phytic acid molecule can react with one aniline molecule to form a salt or with multiple aniline molecules, and one phytic acid molecule can react with a maximum of six aniline molecules, this process avoids the formation of a small amount of precipitation in the solution when aniline is slightly in excess, and also avoids the formation of a solid solution in the solution when aniline is extremely in excess, which would prevent the subsequent polymerization reaction from continuing.

[0018] In step 2, the molar ratio of aniline to ammonium persulfate is (2.4-1.0):1. Solutions A and B are simultaneously frozen for 10 minutes and then sonicated for 10 seconds. This lowers the reaction temperature, slows down the polymerization rate, and ensures a more complete polymerization reaction.

[0019] In step 2, the water is cooled to 0-4°C and aged for 1-2 hours, preferably 2 hours.

[0020] The polyaniline gel obtained in step 2 is dark green in color.

[0021] In step 3, the mass density of the polyaniline gel dispersion D is 10 mg / ml.

[0022] The mass ratio of polyaniline to manganese dioxide in the polyaniline dispersion D in step 4 is (0.05-0.20):1.

[0023] In step 4, 100 mg of manganese dioxide is dispersed in 10 ml of deionized water to obtain dispersion E. Dispersion D is added to dispersion E while stirring. After stirring for 12 hours, the mixture is dried to obtain a polyaniline-coated manganese dioxide material.

[0024] The manganese dioxide described in step 4 is a nanoroll structure with a length of approximately ≥2 μm. This unique ultralong nanoroll structure has a high specific surface area, providing more active sites.

[0025] The drying method in step 4 is one of vacuum drying, forced air drying, or freeze drying.

[0026] The beneficial effects of this invention are:

[0027] This invention is simple to operate, uses widely available raw materials, and operates under controllable conditions, possessing the potential for mass production. It combines polyaniline (PANI) conductive polymer with manganese dioxide. In the composite electrode, the polyaniline forms a three-dimensional network conductive protective layer of manganese dioxide nanorolls through an ultrathin, layered structure, effectively improving electrode conductivity. This results in excellent rate performance and cycle stability when the polyaniline-coated manganese dioxide nanorolls (MnO2 / PANI) are used as the positive electrode in aqueous zinc-ion batteries. Simultaneously, the polyaniline coating protects the manganese dioxide, inhibiting its dissolution and further enhancing battery cycle stability. Attached image description:

[0028] Figure 1 This is a SEM image of a polyaniline-coated manganese dioxide nanofiber material prepared in Example 1 of the present invention.

[0029] Figure 2 This is a TEM image of a polyaniline-coated manganese dioxide nanoroll material prepared in Example 1 of the present invention.

[0030] Figure 3 The image shows the XRD pattern of a polyaniline-coated manganese dioxide nanofiber material prepared in Example 1 of this invention.

[0031] Figure 4 The image shows the Raman spectrum of a polyaniline-coated manganese dioxide nanofiber material prepared in Example 1 of this invention.

[0032] Figure 5 This is a rate capability diagram of a polyaniline-coated manganese dioxide nanofiber material prepared in Example 1 of this invention as a positive electrode material for an aqueous zinc-ion battery.

[0033] Figure 6 This is a cycle diagram of a polyaniline-coated manganese dioxide nanofiber material prepared in Example 1 of the present invention as a positive electrode material for an aqueous zinc-ion battery. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the embodiments.

[0035] Example 1:

[0036] Step 1: Add 0.92 ml (1 mmol) of phytic acid to 2 ml of deionized water, sonicate for 15 min, then add 0.46 ml (3 mmol) of aniline monomer and sonicate until completely dissolved to obtain solution A.

[0037] Step 2: Add 0.286g (1.25mmol) of ammonium persulfate to 0.5ml of deionized water and sonicate until completely dissolved to obtain solution B. Freeze solutions A and B simultaneously for 10min. Drop solution B into solution A and quickly place it in an ultrasonic machine and sonicate for 10s to obtain solution C. Cool solution C in ice water to 0-4℃ and age for 1h. After freeze-drying, the final polyaniline gel is obtained.

[0038] Step 3: Wash the polyaniline gel obtained in Step 2 three times with deionized water, add deionized water and stir continuously to obtain dispersion D.

[0039] Step 4: Disperse 100 mg of manganese dioxide in 10 ml of deionized water to obtain dispersion E. While stirring, add 0.5 ml of dispersion D to dispersion E, and continue stirring for 12 h. Then freeze-dry to obtain polyaniline-coated manganese dioxide nanorolls.

[0040] The morphology of MnO2 / PANI materials was observed using scanning electron microscopy and transmission electron microscopy. SEM images of the MnO2 / PANI samples are shown below. Figure 1 The images show that polyaniline forms a compact and dense structure on the outer layer of manganese dioxide nanorolls. Transmission electron microscopy images of the MnO2 / PANI sample (…) Figure 2 It can be seen that polyaniline forms a three-dimensional network conductive protective layer of manganese dioxide nanorolls through an ultrathin sheet-like layered structure, thereby improving the conductivity of the electrode.

[0041] The crystal structure and composition of MnO2 / PANI were further investigated using X-ray diffraction (XRD) and Raman spectroscopy. The XRD pattern of manganese dioxide composite with polyaniline is shown below. Figure 3 The results showed that the characteristic peaks of both samples at the (110) crystal plane at 12.7°, the (200) crystal plane at 18.1°, the (310) crystal plane at 28.8°, and the (211) crystal plane at 37.5° all matched well with the α-MnO2 standard card (JCPDS No. 44-0141). Compared with the MnO2 material, the MnO2 / PANI material showed the characteristic peak of polyaniline at 25.7°, and the position of the MnO2 characteristic peak did not shift, further indicating that polyaniline was successfully coated on the surface of manganese dioxide. Figure 4 The Raman spectrum of the MnO2 / PANI sample shown indicates that at 632 cm⁻¹... -1 The absorption peak generated by the octahedral Mn-O stretching vibration of MnO6 in MnO2 is weakened, which is due to the outer coating of polyaniline. Additionally, the absorption peak of the MnO2 / PANI sample at 1583 cm⁻¹ is... -1 1486cm -1 1345cm -1 and 1166cm -1The absorption peaks generated are due to the stretching vibrations of C=C in the quinone ring of polyaniline, the stretching vibrations of C=C in the benzene ring, the stretching vibrations of Ar-N in aromatic amines, and the bending vibrations within the CH plane of the benzene ring. This further proves the successful composite of polyaniline with manganese dioxide. Furthermore, the absorption peaks on the quinone ring framework are slightly stronger than those on the benzene ring framework, indicating that polyaniline is in a semi-oxidized state.

[0042] A commercial zinc foil was used as the negative electrode, a mixed aqueous solution of 1M ZnSO4 and 0.1M MnSO4 was used as the electrolyte, a CR2032 button cell casing was used, and a glass fiber separator was used to assemble an aqueous zinc-ion battery for electrochemical performance testing. Figure 5 As shown, MnO2 / PANI exhibits current densities of 300, 278, 239, 198, 156, and 150 mAh g at current densities of 0.2C, 0.5C, 1C, 2C, 3C, and 4C, respectively. -1 The specific capacity of the MnO2 electrode is only 175, 169, 149, 110, 98, and 52 mAh g, compared to that of the MnO2 electrode. -1 The specific capacity shows that polyaniline coating significantly enhances the rate performance of the material. Furthermore, polyaniline encapsulation also greatly enhances the cycling performance of the electrode, such as... Figure 6 As shown, the MnO2 electrode decreased from its initial 210 mAh g after 100 cycles. -1 The specific capacity dropped to only 80mAh g -1 The MnO2 / PANI electrode only decreased by 290 mAh g after 100 cycles. -1 Reduced to 260mAh g -1 The electrochemical capacity retention increased from 38.1% to 89.7%. This is because the polyaniline coating reduces the direct contact between manganese dioxide and the electrolyte, thereby reducing the dissolution of manganese dioxide during discharge. At the same time, polyaniline, as a conductive polymer material, provides sufficient ion transport channels for the charging and discharging process of manganese dioxide.

[0043] Example 2:

[0044] Step 1: Add 0.92 ml (1 mmol) of phytic acid to 2 ml of deionized water, sonicate for 15 min, then add 1.07 ml (7 mmol) of aniline monomer and sonicate until completely dissolved to obtain solution A.

[0045] Step 2: Add 0.8008g (3.5mmol) of ammonium persulfate to 0.5ml of deionized water and sonicate until completely dissolved to obtain solution B. Freeze solutions A and B simultaneously for 10min. Drop solution B into solution A and quickly place it in an ultrasonic machine and sonicate for 10s to obtain solution C. Cool solution C in ice water to 0-4℃ and age for 1h. After freeze-drying, the final polyaniline gel is obtained.

[0046] Step 3: Wash the polyaniline gel obtained in Step 2 three times with deionized water, add deionized water and stir continuously to obtain dispersion D.

[0047] Step 4: Disperse 100 mg of manganese dioxide in 10 ml of deionized water to obtain dispersion E. While stirring, add 1 ml of dispersion D to dispersion E, and continue stirring for 12 h. Then, vacuum dry to obtain polyaniline-coated manganese dioxide nanorolls.

[0048] Example 3:

[0049] Step 1: Add 0.92 ml (1 mmol) of phytic acid to 2 ml of deionized water, sonicate for 15 min, then add 0.15 ml (1 mmol) of aniline monomer and sonicate until completely dissolved to obtain solution A.

[0050] Step 2: Add 0.2288g (1mmol) of ammonium persulfate to 0.5ml of deionized water and sonicate until completely dissolved to obtain solution B. Freeze solutions A and B simultaneously for 10min. Drop solution B into solution A and quickly place it in an ultrasonic machine and sonicate for 10s to obtain solution C. Cool solution C in ice water to 0-4℃ and age for 2h. After freeze-drying, the final polyaniline gel is obtained.

[0051] Step 3: Wash the polyaniline gel obtained in Step 2 three times with deionized water, add deionized water and stir continuously to obtain dispersion D.

[0052] Step 4: Disperse 100 mg of manganese dioxide in 10 ml of deionized water to obtain dispersion E. While stirring, add 2 ml of dispersion D to dispersion E, continue stirring for 12 h, and then dry with a forced air to obtain polyaniline-coated manganese dioxide nanorolls.

Claims

1. A method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls, characterized in that, Includes the following steps; Step 1: Add phytic acid to deionized water, sonicate, then add aniline monomer and sonicate until completely dissolved to obtain solution A; Step 2: Add ammonium persulfate to deionized water and sonicate until completely dissolved to obtain solution B. Freeze solutions A and B simultaneously. Add solution B dropwise into solution A and sonicate rapidly to obtain solution C. Place solution C in ice water to cool and age for a certain period of time to finally obtain polyaniline gel. Step 3: Wash the polyaniline gel obtained in Step 2 with deionized water three times, add deionized water and stir continuously to obtain polyaniline dispersion D; Step 4: Disperse manganese dioxide in deionized water to obtain dispersion E. Add dispersion D to dispersion E while stirring. After continuous stirring, dry the mixture to obtain polyaniline-coated manganese dioxide material. The specific steps for preparing the manganese dioxide added in step 4 include: a. Mix potassium permanganate and ammonium chloride in a molar ratio of 1.5-4.5:1, add to 50-70 ml of deionized water, and sonicate for 15 min to form a uniformly dispersed mixed solution; b. Transfer the resulting mixed solution to a 100ml high-pressure hydrothermal reactor lined with polytetrafluoroethylene, and heat it in an oil bath at 120-160℃ for 24-60 hours, stirring continuously at a speed of 2000-4000rpm. c. Collect the precipitate, wash it three times with deionized water, and dry it under vacuum to obtain manganese dioxide; A positive electrode material of polyaniline-coated manganese dioxide nanorolls is disclosed. Polyaniline (PANI) conductive polymer is composited with manganese dioxide. The polyaniline forms a three-dimensional network conductive protective layer of manganese dioxide nanorolls in an ultrathin sheet-like layered structure to improve electrode conductivity. This polyaniline-coated manganese dioxide nanoroll (MnO2 / PANI) is used as the positive electrode in an aqueous zinc-ion battery. The resulting battery positive electrode exhibits excellent rate performance and cycle stability. The polyaniline coating protects the manganese dioxide, inhibits its dissolution, and enhances battery cycle stability.

2. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 1, the molar ratio of aniline monomer to phytic acid molecule in the mixed aqueous solution of phytic acid and aniline monomer is (1-7):1, and the ultrasonic treatment is performed for 15 minutes.

3. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 2, the molar ratio of aniline to ammonium persulfate is (2.4-1.0):

1. Solutions A and B are simultaneously frozen for 10 minutes and then sonicated for 10 seconds in an ultrasonic machine.

4. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 2, the water is cooled to 0-4°C and aged for 1-2 hours. The polyaniline gel obtained in step 2 is dark green in color.

5. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 3, the mass density of the polyaniline gel dispersion D is 10 mg / ml.

6. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 4, the mass ratio of polyaniline to manganese dioxide in the polyaniline dispersion D is (0.05-0.20):

1.

7. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, In step 4, 100 mg of manganese dioxide is dispersed in 10 ml of deionized water to obtain dispersion E. Dispersion D is added to dispersion E while stirring. After stirring for 12 h, the mixture is dried to obtain a polyaniline-coated manganese dioxide material.

8. The method for preparing a positive electrode material of polyaniline-coated manganese dioxide nanorolls according to claim 1, characterized in that, The manganese dioxide mentioned in step 4 has a nanoroll structure with a nanoroll length ≥ 2 μm. The drying method in step 4 is one of vacuum drying, forced air drying, or freeze drying.

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