Manganese oxide containing cathode active material for supercapacitors

Abstract

The present invention relates to a positive electrode active material for a supercapacitor comprising a manganese oxide composite nanofiber containing a metal element.

Description

Technology Field

[0001] The present invention relates to a positive electrode active material for a manganese oxide-containing supercapacitor. Background Technology

[0002] Supercapacitors have superior input / output characteristics and high cycle reliability compared to secondary batteries such as lithium-ion batteries, making them a field where development is currently booming in relation to environmental issues. They are promising, for example, as primary and auxiliary power sources for electric vehicles or as power storage devices for renewable energy sources such as solar and wind power. Furthermore, they are expected to be utilized as devices capable of extracting large currents in a short period of time in uninterruptible power supplies (UPS), where demand is increasing alongside IT advancements.

[0003] Among them, the electric double layer capacitor has a structure in which a pair or multiple polarized electrodes (positive and negative electrodes), mainly composed of carbon materials, are placed facing each other with a separator in between and immersed in an electrolyte. At this time, the principle is to accumulate electric charge in the electric double layer formed at the interface between the polarized electrodes and the electrolyte.

[0004] Meanwhile, pseudocapacitors have high energy storage capacity based on oxidation-reduction reactions and primarily use transition metal oxides as electrodes to create an environment where oxidation-reduction reactions occur readily on the surface. Generally, pseudocapacitors are known to have higher capacitance values ​​compared to electric double-layer capacitors.

[0005] The basic structure of a pseudo-capacitor is as shown in Figure 1 below. It consists of a current collector, electrodes, an electrolyte, and a separator from both sides.

[0006] In general, active materials used as the main materials for electrochemical capacitors are advantageous for electron generation at the interface using a large specific surface area, but because their conductivity is relatively poor, nanometer-sized conductive materials are generally added to achieve the required characteristics. For example, oxides of Ru, Ir, Co, and Mn are widely used as positive active materials for conventional capacitors, and these materials are currently widely used in the manufacture of lithium-ion batteries.

[0007] However, oxides such as Ru and Ir have disadvantages including atmospheric and water pollution, toxicity, and high unit costs, while Co oxides destroy the surrounding environment along with greenhouse gas emissions during the mineral extraction process, and the exploitation of African child labor is a serious issue.

[0008] In addition, while Mn oxide is environmentally friendly and inexpensive, it has the disadvantage of having electrical conductivity and capacitance values ​​that fall short of expectations. Prior art literature

[0009] Republic of Korea Registered Patent No. 10-2030866 (Published Oct. 10, 2019) Republic of Korea Registered Patent No. 10-0305436 (Published Nov. 07, 2001) The problem to be solved

[0010] The problem that the present invention aims to solve is to provide a positive electrode active material for a supercapacitor composed of a metal-substituted manganese oxide that is environmentally friendly and has excellent electrical conductivity and capacitance values. means of solving the problem

[0011] In one embodiment, the present invention provides a positive electrode active material for a manganese oxide-containing supercapacitor comprising a manganese oxide composite nanofiber containing a metal element.

[0012] In addition, the metal element may be one or more selected from the group consisting of magnesium (Mg), aluminum (Al), silica (Si), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), molybdenum (Mo), silver (Ag), indium (In), and tin (Sn).

[0013] In addition, the metallic element can be Ca.

[0014] In addition, manganese oxide composite nanofibers can have a spinel structure.

[0015] In addition, manganese in the crystal structure of manganese oxide composite nanofibers can be substituted with metal elements.

[0016] The present invention provides a supercapacitor comprising the aforementioned manganese oxide-containing positive electrode active material in another embodiment. Effects of the invention

[0017] According to the present invention, the purpose is to provide a positive electrode active material for a supercapacitor composed of a metal-substituted manganese oxide that is environmentally friendly and has excellent electrical conductivity and capacitance values. Brief explanation of the drawing

[0018] Figure 1 shows the basic structure of a conventional pseudo-capacitor. Figure 2 is a flowchart showing the manufacturing process of an electrode. FIG. 3 is a three-electrode device for testing the electrochemical characteristics of the positive electrode active material of the present invention. Figure 4 is an SEM image of manganese oxide according to the CMO800 0.7 g condition in Table 1. Figure 5 is an SEM image of manganese oxide according to the CMO800 1.0 g condition in Table 1. Figure 6 is an SEM image of manganese oxide according to the CMO800 1.3 g condition in Table 1. Figure 7 is an SEM image of manganese oxide according to the CMO900 0.7 g condition in Table 1. Figure 8 is an SEM image of manganese oxide according to the CMO900 1.0 g condition in Table 1. Figure 9 is an SEM image of manganese oxide according to the CMO900 1.3 g condition in Table 1. Figure 10 is an SEM image of manganese oxide according to the CMO1000 0.7 g condition of Table 1. Figure 11 is an SEM image of manganese oxide according to the CMO1000 1.0 g condition in Table 1. Figure 12 is an SEM image of manganese oxide according to the CMO1000 1.3 g condition of Table 1. Figure 13 shows the XRD diffraction pattern analysis results of manganese oxide prepared under conditions of CMO800 1.0 g, CMO900 1.0 g, and CMO1000 1.0 g. Figures 14 A to 14 C are TEM images of manganese oxide according to the CMO800 1.0 g condition of Table 1. Figures 15 A to 15 C are TEM images of manganese oxide according to the CMO900 1.0 g condition of Table 1. Figures 16 A to 16 D are TEM images of manganese oxide according to the CMO1000 1.0 g condition of Table 1. Figure 17 shows the cyclic voltammetry (CV) results of cathode active materials containing manganese oxide prepared under conditions of CMO800 1.0 g, CMO900 1.0 g, and CMO1000 1.0 g. Figure 18 shows the GCD (Galvanostatic charge discharge (GCD) results of cathode active materials containing manganese oxide prepared under conditions of CMO800 1.0 g, CMO900 1.0 g, and CMO1000 1.0 g. Figure 19 shows the Electrochemical Impedance Spectroscopy (EIS) results of cathode active materials containing manganese oxide prepared under conditions of CMO800 1.0 g, CMO900 1.0 g, and CMO1000 1.0 g. Specific details for implementing the invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different embodiments and is not limited to the embodiments described herein. Throughout the specification, similar parts are denoted by the same reference numerals.

[0021] In one embodiment, the present invention provides a positive electrode active material for a manganese oxide-containing supercapacitor comprising a manganese oxide composite nanofiber containing a metal element.

[0022] The manganese oxide composite nanofiber containing a metal element according to the present invention means that it contains a metal element other than manganese (hereinafter simply referred to as a "metal element").

[0023] The metal-substituted manganese oxide composite nanofiber according to the present invention has improved battery characteristics compared to conventional manganese oxide.

[0024] In addition, the metal element in the present invention may include not only the metal element, but also metal ions, metal compounds, and metal compound particles.

[0025] The metal element contained in the manganese oxide composite nanofiber containing the metal element of the present invention is a metal element other than manganese (Mn), and may be one or more selected from the group consisting of magnesium (Mg), aluminum (Al), silica (Si), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), molybdenum (Mo), silver (Ag), indium (In), and tin (Sn), specifically may be calcium, and more specifically may be a calcium cation.

[0026] In addition, manganese oxide composite nanofibers can have a spinel structure.

[0027] In addition, manganese oxide composite nanofibers can have manganese substituted with metal elements within their crystal structure.

[0028] Manganese oxide composite nanofibers can be obtained by mixing and stirring calcium, manganese, PVP (Polyvinylpyrrolidone), a solvent, and acetic acid, followed by electrospinning and heat treatment.

[0029] The PVP used in the present invention serves to control the viscosity of the fiber.

[0030] The solvent used in the present invention may be methanol, and the methanol can be used to produce nanofibers with a small fiber diameter.

[0031] Acetic acid plays a role in inhibiting Calcium nitrate tetrahydrate and Manganese(II) acetate tetrahydrate from reacting with moisture in the air during the production of manganese oxide.

[0032] Manganese oxide composite nanofibers can be prepared by mixing 0.32 g of calcium, 0.68 g of manganese, 1.0 g of PVP, 8 ml of solvent, and 2 ml of acetic acid. If the above range is exceeded, the nanofibers may not be prepared completely, and the electrical properties of the cathode active material may be degraded.

[0033] Calcium is Calcium nitrate tetrahydrate, and manganese is Manganese(II) acetate tetrahydrate.

[0034] In addition, heat treatment can be performed at a temperature of 920 to 950 ℃ for 4 to 6 hours, and specifically, at a temperature of 900 ℃ for 5 hours at a heating rate of 1 ℃ / min.

[0035] If the heat treatment temperature deviates from the aforementioned range, the nanofibers break, leading to a problem where electrical properties deteriorate.

[0036] The manganese oxide composite nanofiber containing a metal element manufactured according to the present invention may have a diameter of about 0.287 nm.

[0037] The present invention provides a supercapacitor comprising the aforementioned manganese oxide-containing positive electrode active material in another embodiment.

[0038] In addition, the supercapacitor can have a capacitance of about 437 F / g.

[0040] The present invention will be described in more detail below using examples. These examples are solely for the purpose of more specifically explaining the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not limited by them.

[0041] <실시예>

[0042] CaMn2O4 was prepared according to the amount of PVP added and heat treatment conditions.

[0043] CaMn2O4 was synthesized by electrospinning and heat treating after adding 0.32 g of Ca, 0.68 g of Mn, 8 ml of methanol, and 2 ml of acetic acid, along with the PVP content indicated in Table 1 below.

[0044] At this time, electrospinning was performed with Syringe: 10 ml, Tip diameter: 30 G, Flow rate: 30 μl / min, Voltage: 21.5 kV, and heat treatment was performed at 800, 900, and 1000 ℃ at 1℃ / min for 5h.

[0045] PVP 함량열처리 조건 0.7 g 1.0 g 1.3 g 800 ℃, 1℃ / min, 5h CMO800 0.7 g CMO800 1.0 g CMO800 1.3 g 900 ℃, 1℃ / min, 5h CMO900 0.7 g CMO900 1.0 g CMO900 1.3 g 1,000 ℃, 1℃ / min, 5h CMO1000 0.7 g CMO1000 1.0 g CMO1000 1.3 g

[0046] <시험예>

[0047] Test Example 1: Analysis of XRD diffraction, SEM, and TEM

[0048] XRD diffraction, SEM, and TEM of the manganese oxide prepared according to Table 1 above were analyzed.

[0049] Referring to Fig. 13, it was confirmed that the manganese oxide prepared under the condition of 1.0 g of CMO800 contained both CaMn3O6 and CaMn3O8. On the other hand, for 1.0 g of CMO900 and 1.0 g of CMO1000, a pure peak containing only CaMn3O4 could be observed.

[0050] As a result, it can be confirmed that secondary phases coexist when heat-treated at low temperatures.

[0051] Referring to FIGS. 4 to 12 and FIGS. 14 to 16, it can be seen that breakage occurred in the manganese oxide prepared under the condition of 1.0 g of CMO800 and the manganese oxide nanofiber prepared under the condition of 1.0 g of CMO1000, whereas no breakage was observed in the manganese oxide nanofiber prepared under the condition of 1.0 g of CMO900.

[0052] The above results suggest that when manufacturing active materials using manganese oxide nanofibers, it may affect the ion conductivity value.

[0054] Test Example 2: CV, GCD, and EIS Measurement

[0055] Electrodes were prepared using a cathode active material containing CaMn2O4 prepared according to Table 1, and CV, GCD, and EIS values ​​were measured.

[0056] Figure 3 shows a three-electrode apparatus for testing the electrochemical characteristics of a positive electrode active material, and Table 2 below shows the configuration of the electrodes and measurement conditions.

[0057] Fabrication of CaMn 2 O 4 working electrode Active material : CNT : PVDF 8:1:1 (wt%) Current collector With foam : 2x1 cm 2 Cyclic voltammetry Potential window (V vs Ag / AgCl) 0 ~ 0.5 V Galvanostatic charge-discharge Potential window(V vs Ag / AgCl) 0 ~ 0.5 V Current density 2, 4, 6, 8, 10 A / g

[0058] Referring to Figures 17 to 19, it can be seen that CaMn2O4 heat-treated at 900 ℃ has a superior CV curve compared to CaMn2O4 heat-treated at 800 and 1,000 ℃. The above results show that CaMn2O4 heat-treated at 900 ℃ in Figure 18 has superior capacitance values, and the capacitance value is expected to increase from 800 ℃ to 900 ℃ and then decrease thereafter.

[0059] In addition, CaMn2O4 heat-treated at 800 ℃ had poor electrical conductivity due to high internal resistance caused by secondary phases, whereas CaMn2O4 heat-treated at 900 ℃ and 1000 ℃ showed similar levels of internal resistance.

[0060] In addition, the electrical conductivity value was better at 1000 ℃ than at 900 ℃, but the capacitance value was better at CaMn2O4 heat-treated at 900 ℃.

[0061] This is because the small size of the nanofibers increased the specific surface area, leading to a significant number of redox reactions occurring on the surface.

[0063] Consequently, the present invention can provide an excellent positive electrode active material for supercapacitors by producing a manganese oxide composite nanofiber containing a metal element through substitution of calcium cations in a specific ratio and heat treatment under specific conditions.

[0065] Although preferred embodiments of the present invention have been described above with reference to the attached drawings, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all technical ideas of the present invention. Therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0066] Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting, and the scope of the invention is defined by the claims set forth below rather than by the detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the invention.

Claims

Claim 1 A positive electrode active material for a manganese oxide-containing supercapacitor, comprising a manganese oxide composite nanofiber containing a metal element, wherein the manganese oxide composite nanofiber containing a metal element is CaMn2O4, has a spinel structure, in which manganese in the crystal structure is substituted with calcium (Ca), and is heat-treated at a temperature of 900 ℃ for 5 hours at a heating rate of 1 ℃ / min. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 A supercapacitor comprising the positive active material of claim 1.

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