Positive electrode material and preparation method thereof, positive electrode and supercapacitor

Abstract

The invention discloses a positive electrode material and a preparation method thereof, a positive electrode and a supercapacitor, the positive electrode material is prepared by dipping cobalt-doped manganese dioxide in a sodium borohydride solution, the positive electrode material is in a nanorod shape, the length of the positive electrode material is 500-3000 nm, the positive electrode material can be used as the positive electrode, and the cobalt-doped manganese dioxide can be used as the negative electrode. The positive electrode can be used as a positive electrode of a supercapacitor. The preparation method has the beneficial effects that cobalt doping is performed on the manganese dioxide material, and defect engineering treatment is performed, so that the prepared positive electrode material has higher oxygen vacancy concentration, and on the premise that the morphology and the crystal form of the treated manganese dioxide material are not changed, the conductivity and the cycling stability of manganese dioxide are improved; and moreover, the synthesis process is green, pollution-free and low in cost, and the prepared manganese dioxide material can be widely applied to the field of supercapacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and in particular to a positive electrode material and a preparation method thereof, a positive electrode and a super capacitor. Background Art

[0002] With the consumption of energy and the resulting environmental problems, new energy sources are receiving more and more attention worldwide. As a new type of energy storage device, supercapacitors have attracted much attention. The electrode material of supercapacitors is the main factor affecting the energy storage performance of supercapacitors. Metal oxides are widely used as electrode materials for supercapacitors due to their high energy density, high specific capacitance and excellent reversibility. MnO 2 It is the most promising transition metal oxide and has also been a research hotspot in recent years.

[0003] At present, manganese oxide as a supercapacitor electrode material faces the following problems:

[0004] Poor conductivity: Manganese oxide itself has poor conductivity, which limits its performance in supercapacitors. The low conductivity of the electrode material will lead to slow electron transfer rate, affecting the charge and discharge efficiency and power density of the capacitor.

[0005] Poor cycle stability: During the charge and discharge process of supercapacitors, manganese oxide electrodes are prone to structural damage and performance degradation, which is mainly due to the insufficient stability of their lattice structure in repeated redox reactions.

[0006] Difficulty in controlling morphology and crystal form: The morphology and crystal form of manganese oxide have a great influence on its electrochemical properties. However, during the synthesis process, it is a challenge to precisely control its morphology and crystal form, which is directly related to the performance of the electrode material.

[0007] Limited electrochemically active surface area: The electrochemically active surface area of ​​manganese oxide has a great influence on its Faraday capacity. How to increase its active surface area and increase its charge storage capacity is a key issue in research.

[0008] Cost and environmental impact: Although manganese oxide raw materials are abundant and inexpensive, its preparation process may involve environmental pollution. How to achieve a green and low-cost synthesis method is an important aspect in promoting the commercialization of manganese oxide-based supercapacitors.

[0009] Optimization of doping and composite materials: It is a common strategy to improve the performance of manganese oxide by doping or compounding other materials. However, how to select suitable dopants or composite materials, and how to optimize their component ratios and structures, are the focus of current research.

[0010] In summary, the research on manganese oxide as a supercapacitor electrode material requires in-depth exploration in improving conductivity, cycle stability, electrochemically active surface area, and optimizing preparation process in order to achieve its wide application in the field of supercapacitors. Summary of the invention

[0011] In order to solve the above technical problems, the present invention provides a positive electrode material with good conductivity and cycle stability and a preparation method thereof for application in the positive electrode of a supercapacitor.

[0012] The technical solution is as follows: In a first aspect, the present invention provides a method for preparing a positive electrode material, the gist of which is that it comprises the following steps:

[0013] Cobalt-doped manganese dioxide is prepared, and the cobalt-doped manganese dioxide is immersed in a sodium borohydride solution to obtain a positive electrode material.

[0014] Preferably, the immersion time is 1-4 hours.

[0015] Preferably, the preparation of the cobalt-doped manganese dioxide comprises: dissolving a manganese salt, an ammonium salt and a cobalt salt in a solvent and reacting them to obtain the cobalt-doped manganese dioxide.

[0016] Preferably, the molar ratio of the manganese salt, the ammonium salt and the cobalt salt is 10:10:1.

[0017] Preferably: the reaction time is 20-25h, and the reaction temperature is 150-200°C;

[0018] The solvent is deionized water.

[0019] Preferably: the manganese salt is manganese sulfate monohydrate, wherein the manganese sulfate monohydrate is analytically pure;

[0020] The ammonium salt is ammonium persulfate, wherein the ammonium persulfate is analytically pure;

[0021] The cobalt salt is cobalt nitrate hexahydrate, wherein the cobalt nitrate hexahydrate is analytically pure.

[0022] The second aspect of the present invention provides a positive electrode material, which is prepared according to the preparation method described in the first aspect of the present invention.

[0023] Preferably, the positive electrode material is in the shape of nanorods, and the length thereof is 500-3000 nm.

[0024] The third aspect of the present invention provides a positive electrode, comprising the positive electrode material prepared according to the preparation method described in the first aspect of the present invention or the positive electrode material described in the second aspect of the present invention.

[0025] The fourth aspect of the present invention provides a supercapacitor, comprising the positive electrode described in the third aspect of the present invention.

[0026] Compared with the prior art, the present invention has the following beneficial effects: by cobalt-doping the manganese dioxide material and performing defect engineering treatment, the prepared positive electrode material has a higher concentration of oxygen vacancies. On the premise that the morphology and crystal form of the treated manganese dioxide material do not change, the conductivity and cycle stability of manganese dioxide are improved, the charge storage capacity is increased, and the synthesis process is green, pollution-free, and low-cost. The prepared manganese dioxide material can be widely used in the field of supercapacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 XRD data diagram of CoMO and CoMO-D;

[0028] Figure 2 This is a scanning electron microscope image of CoMO-D;

[0029] Figure 3 This is a transmission electron micrograph of CoMO-D;

[0030] Figure 4 Mapping data map of CoMO-D;

[0031] Figure 5 This is the STEM-HAADF data diagram of CoMO-D;

[0032] Figure 6 XPS data of CoMO and CoMO-D;

[0033] Figure 7 High-resolution XPS spectra of CoMO and CoMO-D in the O1s region;

[0034] Figure 8 This is the EPR data diagram of CoMO-D;

[0035] Fig. 9 CV curve diagram of electrochemical data of CoMO;

[0036] Fig.10 GCD curve diagram of electrochemical data of CoMO;

[0037] Fig.11 CV curve diagram of electrochemical data of CoMO-D;

[0038] Fig.12 GCD curve diagram of electrochemical data of CoMO-D;

[0039] Fig.13 It is the rate performance diagram of CoMO and CoMO-D;

[0040] Fig.14The electrochemical impedance data of CoMO and CoMO-D are shown in Figure 2.

[0041] Fig.15 Cycling data diagram of supercapacitor CoMO / / AC;

[0042] Fig.16 Energy density vs power density of supercapacitor CoMO-D / / AC;

[0043] Fig.17 This is the cycle data diagram of CoMO-D / / AC. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with embodiments and drawings.

[0045] Preparation of cathode materials

[0046] Example 1

[0047] 5 mmol of manganese sulfate monohydrate, 5 mmol of ammonium persulfate and 0.5 mmol of cobalt nitrate hexahydrate were dissolved in 50 ml of deionized water and stirred for 30 minutes to obtain a homogeneous solution.

[0048] The homogeneous solution was placed in a hydrothermal reactor and kept at 180 degrees for 24 hours, then filtered and washed with water and ethanol alternately for 3 times to obtain cobalt-doped manganese dioxide with a chemical formula of Co 0.05 Mn 0.95 O 2 , abbreviated as CoMO.

[0049] The CoMO was immersed in a 0.01 mol / L sodium borohydride solution for 2 h to obtain a positive electrode material, whose chemical formula is Co 0.05 Mn 0.95 O 2-x , where the value range of x is (0.1≤x≤0.5). In cobalt-doped manganese dioxide, x represents the number of O atoms lost due to impregnation, which means that the obtained positive electrode material has certain oxygen vacancy defects, abbreviated as CoMO-D.

[0050] Example 2

[0051] 5 mmol of manganese sulfate monohydrate, 5 mmol of ammonium persulfate and 0.5 mmol of cobalt nitrate hexahydrate were dissolved in 50 ml of deionized water and stirred for 30 minutes to obtain a homogeneous solution.

[0052] The homogeneous solution was placed in a hydrothermal kettle and kept warm at 150 degrees for 20 hours, and then filtered and washed alternately with water and ethanol for 3 times to obtain cobalt-doped manganese dioxide.

[0053] The CoMO was immersed in a 0.01 mol / L sodium borohydride solution for 1 hour to obtain a positive electrode material.

[0054] Example 3

[0055] 5 mmol of manganese sulfate monohydrate, 5 mmol of ammonium persulfate and 0.5 mmol of cobalt nitrate hexahydrate were dissolved in 50 ml of deionized water and stirred for 30 minutes to obtain a homogeneous solution.

[0056] The homogeneous solution was placed in a hydrothermal kettle at 200 degrees for 25 hours, and then filtered and washed alternately with water and ethanol for 3 times to obtain cobalt-doped manganese dioxide.

[0057] The CoMO was immersed in a 0.01 mol / L sodium borohydride solution for 4 hours to obtain a positive electrode material.

[0058] CoMO and CoMO-D in Example 1 were selected and their structures, doping and defects were observed using electron microscopy.

[0059] like Figure 1 As shown, the XRD data patterns of CoMO and CoMO-D show that, compared with the PDF card of 24-0735, the XRD patterns of CoMO and CoMO-D are basically consistent, which shows that compared with CoMO, the crystal shape and crystal structure of CoMO-D doped with cobalt and obtaining defects by impregnation have not changed.

[0060] like Figure 2 As shown, scanning electron microscope imaging of CoMO-D shows that CoMO-D is a nanorod structure with a length of 500nm-3000nm and a relatively rough surface.

[0061] like Figure 3 and Figure 4 As shown, the transmission electron microscope image of CoMO-D and the mapping data spectrum of CoMO-D. The transmission spectrum further shows that CoMO-D has a typical nanorod structure with a length of 500nm-3000nm. The mapping data spectrum shows the successful doping of Co element, and Co, Mn and O are evenly distributed on the nanorods.

[0062] like Figure 5 As shown, the STEM-HAADF data image of CoMO-D shows that it has a typical tetragonal crystal structure inside and a 2nm amorphous structure on the surface.

[0063] like Figure 6As shown, the XPS data of CoMO and CoMO-D show that CoMO and CoMO-D contain Co, Mn and O elements, and the carbon element signal comes from the contaminated carbon in the test, with the carbon element 284.8eV as the standard reference result; Figure 7 and Figure 8 As shown in the figure, the two are respectively the high-resolution XPS spectra of CoMO and CoMO-D in the O1s region and the EPR data of CoMO and CoMO-D. Figure 7 and Figure 8 It can be seen that CoMO-D has a higher oxygen vacancy concentration than CoMO, where the greater the peak intensity in the EPR data of CoMO-D, the higher the oxygen vacancy concentration. Oxygen vacancies refer to the vacancy formed by the oxygen atoms (oxygen ions) in the lattice of metal oxides or other oxygen-containing compounds detaching from each other, resulting in oxygen deficiency. In simple terms, it refers to the defects left by the escape of oxygen ions from its lattice, so the higher the oxygen vacancy concentration, the higher the defect.

[0064] Test Case

[0065] The CoMO and CoMO-D in Example 1 were prepared into electrode sheets respectively, and then assembled into supercapacitors, and the performance of the two supercapacitors was tested. The specific steps are as follows:

[0066] 1) Preparation of electrode sheets

[0067] Weigh CoMO-D or CoMO, conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, mix the three substances in an agate mortar, add 6 ml of N-methylpyrrolidone, and grind them evenly with a mortar. Transfer the mixed electrode material to the coating equipment and apply it evenly on the nickel foam with a scraper. Put the nickel foam coated with the electrode material into a vacuum drying oven at 60°C, dry it for 24 hours, and punch it into a circular electrode sheet with a diameter of 14 mm.

[0068] 2) Capacitor assembly

[0069] The activated carbon material was used as the negative electrode, the circular electrode sheet prepared above was used as the positive electrode, the glass fiber filter paper was used as the diaphragm, and 1 mol / L Na 2 SO 4 As the electrolyte, a gasket and a spring are put in, and then assembled into a CR 2016 button supercapacitor and sealed.

[0070] 3) Battery performance test

[0071] The assembled supercapacitors were placed for 12 hours and then subjected to electrochemical tests. The cycle test and electrochemical impedance spectroscopy test of the experimental supercapacitors were completed on a VMP-3 (Bio-Logic electrochemical workstation, France) at room temperature with a voltage range of 0-2.0 V. The frequency range of the electrochemical impedance spectroscopy test was 0.1-100 KHz.

[0072] like Fig. 9 and Fig.10 As shown in the figure, the two are the electrochemical data CV curve and GCD curve of CoMO, showing that CoMO at 1Ag -1 With 222Fg -1 The highest specific capacity. Fig.11 and Fig.12 The CV curve and GCD curve of the electrochemical data of CoMO-D show that CoMO-D has better electrochemical performance than CoMO, and at 1Ag -1 With 342Fg -1 The highest specific capacity.

[0073] like Fig.13 As shown, the rate performance diagram of CoMO and CoMO-D shows that CoMO-D has higher rate performance than CoMO.

[0074] like Fig.14 As shown, the electrochemical impedance data of CoMO and CoMO-D show that the diffusion resistance of CoMO-D is lower than that of CoMO.

[0075] like Fig.15 As shown, the supercapacitor CoMO / / AC cycle data graph shows that CoMO still has a capacity retention rate of 94.3% after 5000 cycles.

[0076] like Fig.16 As shown, the energy density vs power density graph of the supercapacitor CoMO-D / / AC shows that it is 45.4Whkg -1 The energy density is highest when Fig.17 The CoMO-D / / AC cycling data graph shows an 89% capacity retention after 10,000 cycles.

[0077] The beneficial effects of the present invention are as follows: the present invention dopes the manganese dioxide material with cobalt and performs defect engineering treatment, so that the prepared positive electrode material has a higher concentration of oxygen vacancies. On the premise that the morphology and crystal form of the treated manganese dioxide material do not change, the conductivity and cycle stability of manganese dioxide are improved, and the charge storage capacity is increased. The synthesis process is green, pollution-free, and low-cost. The prepared manganese dioxide material can be widely used in the field of supercapacitors.

[0078] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that: The following steps are involved: Cobalt-doped manganese dioxide is prepared, and the cobalt-doped manganese dioxide is immersed in a sodium borohydride solution to obtain a positive electrode material.

2. The preparation method according to claim 1, characterized in that: The immersion time is 1-4 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The preparation of cobalt-doped manganese dioxide comprises: dissolving manganese salt, ammonium salt and cobalt salt in a solvent and reacting them to obtain the cobalt-doped manganese dioxide.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the manganese salt, the ammonium salt and the cobalt salt is 10:10:

1.

5. The preparation method according to claim 3, characterized in that: The reaction time is 20-25h, and the reaction temperature is 150-200°C; The solvent is deionized water.

6. The preparation method according to claim 3, characterized in that: The manganese salt is manganese sulfate monohydrate; The ammonium salt is ammonium persulfate; The cobalt salt is cobalt nitrate hexahydrate.

7. A positive electrode material, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

8. The positive electrode material according to claim 7, characterized in that: The positive electrode material is in the shape of a nanorod, and the length thereof is 500-3000nm.

9. A positive electrode, characterized in that: It includes the positive electrode material prepared by the preparation method according to any one of claims 1 to 6 or the positive electrode material according to claim 7 or 8.

10. A supercapacitor, characterized in that: Comprising the positive electrode as claimed in claim 9.

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