CN102376452B - Super capacitor assembled by manganese series oxide electrodes with meshed nano-structures - Google Patents

Abstract

The invention relates to a super capacitor assembled by manganese series oxide electrodes with meshed nano-structures, which is large in specific capacity and low in cost. The super capacitor assembled by the manganese series oxide electrodes with the meshed nano-structures is characterized by comprising at least one manganese series oxide electrode with a unique meshed nano-structure, a membrane soaking in an electrolyte solution is clamped between the manganese series oxide electrode with the unique meshed nano-structure and a congeneric electrode or other electrodes such as an active carbon electrode and the like, a shell is coated outside and a negative wire and a positive wire are led out, thus the super capacitor is assembled. The super capacitor assembled by the manganese series oxide electrodes with the meshed nano-structures adopts composite oxides of transition metal manganese, which are abundant in material, as electrode material instead of precious metal, so that the super capacitor is low in cost.

Description

A supercapacitor assembled with mesh-like nanostructured manganese-based oxide electrodes

technical field

The invention relates to a supercapacitor with large specific capacity and low cost assembled by manganese oxide electrodes with mesh nanostructure. the

Background technique

Supercapacitor is a new type of energy storage device between chemical batteries and ordinary electrostatic capacitors. Its energy storage energy density is much higher than that of electrostatic capacitors, and its discharge power density is much higher than that of chemical batteries. It is used in electric vehicles, satellites and pulse power supplies. All have good application prospects, and can assist or even begin to replace the currently used battery system when high-power discharge is required. The capacity of the original ordinary capacitors can only reach the order of microfarads, and the energy that can be stored is extremely small. They are used as filters, AC coupling devices, and oscillation circuit components in electronic circuits. The ability of supercapacitors to store charges is several orders of magnitude higher than that of ordinary capacitors, which is why they are called "super". However, the names of supercapacitors are not uniform at present. There are supercapacitors (Supercapacitor), ultracapacitors (Ultracapacitor), electrochemical capacitors (Electrochemical Capacitor), electric double layer capacitors (Electrical Double Layer Capacitor, EDLC) or electric double layer capacitors (Double Layer Capacitor, DLC) etc. The reason is that when the electrode materials and electrolytes of this type of capacitor are different, the charge storage and discharge mechanisms are different, which are generally divided into two types of charge storage and discharge mechanisms: electric double layer capacitance and Faraday quasi-capacitance. On the one hand, its capacitive performance depends on the electric double layer of the electrode, so the larger the specific surface area of the electrode, the greater the capacitance. At present, the activated carbon electrode supercapacitor with the largest output is mainly an electric double layer capacitor with this mechanism; Range, fast, reversible, no phase transition Faradaic reaction occurs on the surface of the electrode, accompanied by the underpotential deposition of protons or ions or "intercalation" in the lattice to realize the storage and release of charge, that is, energy, its capacitance value is not only It is related to the electric double layer and is also related to the Faraday reaction on the electrode surface. Therefore, the capacitance value is generally 10 to 100 times that of an electric double layer capacitor. Metal oxide electrode supercapacitors generally belong to electrochemical capacitors with this type of mechanism. Far greater than the electric double layer capacitance of carbon materials, metal oxide electrode materials have received extensive attention in recent years. the

Metal oxide electrode materials mainly include ruthenium oxide, nickel oxide, cobalt oxide, manganese oxide, iron oxide, and aluminum oxide. The most successful metal oxide-based supercapacitor is the ruthenium oxide electrode/H ₂ SO ₄ aqueous solution system, which was first discovered by Conway ^[1] in Canada. It is characterized by a cyclic voltammetry curve that is almost symmetrical and rectangular, without sharp oxidation Reduction peak. Park ^[2] et al. prepared RuO ₂ thin film electrodes by cathodic electrodeposition, and the specific capacity of a single electrode is as high as 788F·g ^-1 . However, the high price and toxicity of RuO ₂ limit its large-scale commercialization, and it is imperative to find cheap electrode materials. Kyung W N ^[3] et al. prepared porous NiO _x films by electrochemically depositing Ni(OH) ₂ and then heat treatment. The specific capacity of a single electrode was 277 F·g ^-1 . Anderson ^[4] and others used sol-gel method and electrochemical deposition method to prepare MnO ₂ respectively, and found that the specific capacity of MnO ₂ prepared by sol-gel method was one-third higher than that prepared by electrodeposition method. But so far, no new metal oxide material that can completely replace _RuO2 in terms of performance has been found. Moreover, the current publications are all single-electrode specific capacitance values, rather than the capacitance assembled into a capacitor.

Chinese Patent No. ZL200710176693.X Patent ^[5] proposes a method for preparing a manganese oxide electrode with a nano-mesh structure. The electrode preparation cost is low and it is an environmentally friendly green material. The invention provides a capacitor assembled with the manganese-based oxide of such a nano-mesh structure as an electrode. The capacitor not only has a larger mass than capacitance, but also has a relatively low cost.

References:

[1]Conway B E. Transition from super capacitor to battery behavior in electrochemical energy storage[J]. Electrochem Soc, 1991, 138(6):1539-1548.

[2] Park B O, Lokhande D C, Park H S, Jung K D, Joo O S. Performance of supercapacitor with electrodeposited ruthenium oxide film electroded-effect of film thickness[J]. Power Source, 2004,134(1) :148-152.

[3] Kyung Wan Nam, Kwang Bum Kim. A study of the NiO _x electrode via electrochemical route for supercapacitor applications and their charge storage mechanism[J]. Electrochem Soc,2002,149(3):346-354.

[4] Anderson M A, Pang S C, Chapman T W. Novel electrode material for thin film ultracapacitors: comparison of electrochemical properties of sol-gel derived and electrode deposited manganese dioxide[J]. Electrochem , Soc1,420(2) :444-450.

[5] Meng Huimin, Shi Yanhua, Sun Dongbai, Yu Hongying, Fan Zishuan, Wang Xudong. A mesh-like nanostructure manganese oxide coating and its preparation method [P]. Patent number: ZL200710176693.X.

Contents of the invention

The object of the present invention is to use a mesh-like nanostructure manganese oxide electrode, sandwich a diaphragm soaked in an electrolyte solution with the same electrode, or with other electrodes such as activated carbon electrodes, wrap a shell and draw out the negative pole pole and the positive pole pole , assembled into supercapacitors with large specific capacity and low cost. the

The technical solution of the present invention is as follows: a supercapacitor assembled with a manganese-based oxide electrode with a mesh-like nanostructure, characterized in that: the supercapacitor includes at least one manganese-based oxide electrode with a unique mesh-like nanostructure; A manganese-based oxide electrode with a unique mesh-like nanostructure and other electrodes such as the same electrode or activated carbon electrode are sandwiched by a diaphragm soaked in an electrolyte solution, wrapped in a casing and drawn out from the negative and positive wires, and assembled into a supercapacitor. the

Further: the manganese-based oxide electrode with a unique mesh-like nanostructure, the manganese-based oxide includes Mn-O, Mn-Mo-O, Mn-Mo-Fe-O, Mn-Mo-VO, Mn - Manganese-based oxides in which MnO ₂ is doped with other elements such as Fe-VO.

Further: the capacitor diaphragm is other diaphragms such as glass fiber film, polypropylene film, agar film, etc. the

Further: the capacitor electrolyte is an inorganic aqueous electrolyte, or an organic electrolyte, or a mixed inorganic and organic electrolyte, or a solid electrolyte or a gel electrolyte. the

Further: the electrodes and separators of the capacitor are flat sheets or the flat sheets are rolled. the

Further: the capacitor is a single capacitor assembled with two electrodes, or a multi-electrode capacitor assembled with multiple electrodes. the

The beneficial effects of the present invention are:

1. The composite oxide of transition metal manganese with rich raw materials is used as the electrode material, and precious metals are not used, so that the cost of the supercapacitor is low.

2. A high-performance manganese-based oxide electrode with a unique three-dimensional mesh-like nanostructure is used as at least one electrode of the supercapacitor, so that the supercapacitor has high capacitance performance and high energy storage density. the

Description of drawings

Accompanying drawing 1 is the structure diagram of the supercapacitor assembled with multiple sets of flat sheet electrodes and diaphragms. the

Accompanying drawing 2 is the microscopic morphology of the surface of the manganese oxide electrode with mesh-like nanostructure used in the present invention. In the figure a. Mn-O electrode, b. Mn-Mo-O electrode, c. Mn-Mo-Fe-O electrode, d. Mn-Mo-V-O electrode, e. Mn-Fe-V-O electrode

Accompanying drawing 3 is the pore size distribution diagram of the surface of the manganese oxide electrode with mesh-like nanostructure used in the present invention.

Accompanying drawing 4 is the cyclic voltammetry curve of the mesh-like nanostructure Mn-Mo-Fe-O electrode. the

Accompanying drawing 5 is the cyclic voltammetry curve of the symmetric supercapacitor assembled with the mesh nanostructure Mn-Mo-Fe-O oxide electrode. the

Detailed ways

Accompanying drawing 1 is the structure diagram of the supercapacitor assembled with multiple sets of flat sheet electrodes and diaphragms. 1. Shell, 2. Negative pole, 3. Positive pole, 4. Electrode, 5. Diaphragm. A diaphragm soaked in electrolyte solution is sandwiched between the two electrodes, and multiple sets of negative and positive electrodes are respectively exported to the negative pole and the positive pole with conductive busbars, and the outer casing is encapsulated to form a complete supercapacitor. the

The mass specific capacitance (Cst) of the supercapacitor is calculated according to the formula:

                                                                   

                                                                   

In the formula, C _st — mass specific capacitance;

Q——volt-ampere charge;

φ2－φ1——potential interval;

m - mass;

v——Cyclic voltammetry test scan speed.

Accompanying drawing 2 is the microscopic morphology of the surface of several manganese oxide electrodes with a unique mesh-like nanostructure manufactured by the ZL200710176693.X patent method. The surface morphology of the nano-scale manganese oxide coating doped with Mo, Fe or V was observed by field emission electron microscopy. The doped manganese oxide coating has a three-dimensional mesh-like nanostructure. Although the manganese oxide is Mn The mixed oxide of two or three elements of , Mo, Fe and V elements, but still maintains the typical γ-MnO ₂ crystal phase structure, and the doping elements Fe, Mo and V are respectively Fe ³⁺ and Mo ⁶⁺ , The form of V ⁵⁺ solid dissolves into the γ-MnO ₂ phase, and its organization is a fully crystalline nanocrystal. The oxides deposited by anodic electrodeposition have different pore structures and higher specific surface areas. Mn-O and Mn-Fe-VO oxides have larger pore structures on the anode surface, while Mn-Mo-O, Mn-Mo- The meshes of VO and Mn-Mo-Fe-O are fine and dense. The meshes of Mn-O oxides are lamellar structures intertwined with each other, and the skeletons of the meshes are relatively thick, while the skeletons of the meshes of Mn-Fe-VO oxides are thinner.

Accompanying drawing 3 is the pore size distribution map of several three-dimensional mesh-like nanostructure manganese oxide electrodes. The main distribution range of Mn-O oxide pore size is 3.6~9.4 nm, and the mesopores larger than 2 nm are the main ones. The pore sizes of Mn-Mo-O, Mn-Mo-V-O, and Mn-Fe-V-O oxides are mainly distributed in the range of 0.85-2.5 nm, with micropores less than 2 nm being the main ones. The pore sizes of Mn-Mo-Fe-O oxides The main distribution range is 0.5~2.5 nm, and most of the micropores are smaller than 2 nm. The ratio of the micropore volume of Mn-Mo-O, Mn-Mo-V-O, Mn-Mo-Fe-O, and Mn-Fe-V-O oxides to the entire pore volume is higher than that of Mn-O oxides. After doping Mo, Fe, and V elements in manganese oxide, the nanostructure of manganese oxide is refined, the size of the nanostructure is significantly refined, the real specific surface area of the electrode is greatly increased, and the number of surface active points is significantly increased. The doped manganese oxide has a small three-dimensional mesh-like nanostructure, and the mesh structure makes it easier for the electrolyte to enter the bulk phase of the electrode, which can increase the real surface area of the oxide coating in contact with the solution and increase the quasi- The probability of capacitive reaction can further increase the capacitance of the capacitor assembled with manganese oxide as the electrode. the

Accompanying drawing 4 is the cyclic voltammetry curve of the three-dimensional mesh nanostructure Mn-Mo-Fe-O oxide electrode tested by the electrochemical three-electrode test system, so that the capacitance performance of the electrode can be analyzed. The mesh-like nanostructured Mn-Mo-Fe-O oxide electrode is used as the working electrode, the saturated calomel electrode (SCE) is used as the reference electrode, the platinum sheet is used as the auxiliary electrode, and the electrolyte is 0.5 mol·dm ^-3 at 25 °C Na ₂ SO ₄ solution with a scan rate of 10 mV·s ^-1 . The cyclic voltammetry curve measured by CHI660B electrochemical workstation is shown in Figure 3. It shows that the Mn-Mo-Fe-O oxide electrode has a good rectangular feature in the 0-1 V potential range, and the cathode process and the anode process are basically symmetrical, showing the quasi-capacitance characteristics of a pure capacitor, indicating that the electrode is in this potential range. Charge and discharge with a constant current, and the size of the reversible quasi-capacitance is related to the potential, which is an important feature to distinguish the electric double layer capacitor; a pair of weak redox peaks appear in the CV curve between 0.4 and 0.6 V, which correspond to Mn ⁴⁺ /Mn ³⁺ conversion process; the electrode has good charge and discharge performance, and the capacitance generated by working in the 0-1 V potential range is mainly the Faraday capacitance generated by the redox reaction of the electroactive material. Therefore, the formation of the three-dimensional nano-network structure Mn-Mo-Fe-O oxide electrode capacitance has at least two charge storage mechanisms: electric double layer capacitance and Faraday quasi-capacitance, and its capacitance performance depends on the one hand on the three-dimensional nano-network structure. The electric double layer with large specific surface area, on the one hand, depends on the fast and reversible redox faradaic reaction between Mn(IV) and Mn(III) in the electrochemical window. Moreover, according to the capacitor energy storage calculation formula E=C(ΔV) ² /2, the energy storage density is proportional to the specific capacitance of the capacitor and the square of the working potential window. The potential window of the Mn-Mo-Fe-O oxide electrode is 1V. It shows that its energy storage density is very high. According to the mass specific capacitance (C _st ) of the supercapacitor, the mass specific capacitance C _st of the Mn-Mo-Fe-O oxide electrode reaches 515.22 F·g ^-1 calculated according to the formula. The voltammetric curve test of multiple cycles also shows that the capacitance of the electrode can still be maintained above 95% after multiple cycles, indicating that the supercapacitor with Mn-Mo-Fe-O oxide as the electrode active material has good cycle performance and capacitive stability.

Example 1

A symmetrical manganese-based oxide supercapacitor is assembled by using two mesh-like nanostructured manganese-based oxide electrodes, and the electrolyte is an aqueous solution of an inorganic electrolyte such as KCl. Two Mn-Mo-Fe-O oxide electrodes with a three-dimensional mesh-like nanostructure are sandwiched by a glass fiber membrane diaphragm soaked in a 2 mol dm ^-3 KCl electrolyte solution to assemble a single capacitor with a symmetrical structure. The cyclic voltammetry curve was tested in the voltage range of -0.5~0.5V at room temperature, and the scanning speed was 5mV·s ^-1 . The test results are shown in Figure 6. The Mn-Mo-Fe-O oxide single supercapacitor has a good rectangular characteristic in the potential window range of -0.5~+0.5V, and is basically symmetrical with respect to the zero current line. The obvious redox peak and the current response value are almost constant, indicating that the cathode process and the anode process are basically symmetrical, indicating that the supercapacitor is charged and discharged at a constant rate, and the potential change of the electrode has no obvious impact on the capacity of the electrode. The electrode has a typical Capacitive characteristics, the charge exchange between the electrode and the electrolyte proceeds at a constant rate. From the two ends of the curve, it can be seen that when the scanning direction changes, there is a rapid current response, and the current turns rapidly, indicating that the internal resistance of the electrode is small, and the charging and discharging process of the electrode has good kinetic reversibility. According to the mass specific capacitance (C _st ) of the supercapacitor, the mass specific capacitance C _st of the Mn-Mo-Fe-O oxide electrode reaches 515.22 F·g ^-1 calculated according to the formula. Moreover, according to the capacitor energy storage calculation formula E=C(ΔV) ² /2, the energy storage density is proportional to the specific capacitance of the capacitor and the square of the working potential window. The potential window of the Mn-Mo-Fe-O oxide electrode is 1V. It shows that its energy storage density is very high, and the energy density can reach 71.59 Wh·Kg ^-1 , which is higher than the energy density of 66.35 Wh·Kg ^-1 measured in the potential window of 0~0.8V of the RuO ₂ thin film electrode prepared by cathodic electrodeposition. , which is slightly lower than the energy density of 78.52 Wh·Kg ^-1 measured in the potential window of 0~0.9V of MnO ₂ prepared by sol-gel method and electrodeposition method.

Example 2

A symmetrical manganese-based oxide supercapacitor is assembled by using two three-dimensional mesh-like nanostructured manganese-based oxide electrodes, and an organic electrolyte is used for the electrolyte. Two mesh-like nanostructured Mn-Fe-VO electrode oxide electrodes are sandwiched by a glass fiber membrane separator impregnated with 1.36 mol·dm ^-3 MgCl ₂ /EtOH organic electrolyte solution to assemble a single capacitor with a symmetrical structure . The MgCl ₂ /EtOH organic electrolyte solution in this embodiment is prepared by dissolving the inorganic electrolyte MgCl ₂ in an organic solvent absolute ethanol (EtOH). The cyclic voltammetry curve of the capacitor using organic electrolyte also has a good rectangular characteristic in the range of -0.5~+0.5V potential window, and is basically symmetrical with respect to the zero current line, there is no obvious redox peak, and the current response value is almost For constant, the cathode process and the anode process are basically symmetrical, which indicates that the electrode capacitor is charged and discharged at a constant rate, the potential change of the electrode has no obvious influence on the capacity of the electrode, and the electrode has typical capacitance characteristics. It also states that the charge exchange between the electrodes and the electrolyte takes place at a constant rate. When the scanning direction of the cyclic voltammetry curve changes, there is a rapid current response, and the current turns rapidly, indicating that the internal resistance of the electrode is small, and the charging and discharging process of the electrode has good kinetic reversibility. Due to the difference in the composition, concentration, and organic solvent of the organic electrolyte, the supercapacitor with such a symmetrical structure has a mass specific capacitance in the range of 50-350 F·g ^-1 , and the stability of the capacitance is good.

Example 3

Assemble an asymmetric manganese-based oxide supercapacitor, that is, one electrode uses a manganese-based oxide electrode with a mesh-like nanostructure, and the opposite electrode uses other electrodes such as activated carbon electrodes. The mesh-like nanostructured Mn-Mo-VO oxide electrode and the activated carbon electrode are sandwiched by a glass fiber membrane diaphragm impregnated with a 0.5 mol dm ^-3 Na ₂ SO ₄ electrolyte solution to assemble a single capacitor with an asymmetric structure . The activated carbon electrode of this embodiment is prepared by mixing activated carbon with conductive graphite, polytetrafluoroethylene, etc., drying them, and pressing them onto nickel foam. The three-dimensional mesh-like nanostructured manganese-based oxide supercapacitor with asymmetric structure has a cyclic voltammetry curve shape similar to that of the symmetrically structured manganese-based oxide supercapacitor, and has a good performance in the potential window range of -0.5~+0.5V. The rectangular feature is basically symmetrical with respect to the zero current line, there is no obvious redox peak, the current response value is almost constant, the cathode process and the anode process are basically symmetrical, indicating that the supercapacitor is still charging and discharging at a constant rate, and the potential of the electrode The change has no obvious effect on the capacity of the electrode, the electrode has typical capacitive characteristics, and the charging and discharging process of the electrode has good kinetic reversibility. Due to the differences in the composition and manufacturing process of other electrodes such as activated carbon electrodes, such asymmetric supercapacitors have a mass specific capacitance in the range of 60-180 F·g ^-1 and good capacitance stability.

Claims (5)

1. ultracapacitor with mesh nano-structure manganese series oxides electrode assembling, it is characterized in that: described ultracapacitor comprises that at least one has the manganese series oxides electrode of unique mesh nanostructure; The manganese series oxides electrode of described unique mesh nanostructure and electrode of the same race or activated carbon electrodes therebetween are to be soaked with the barrier film of electrolyte solution, and bag is with shell and draw negative pole and positive wire, is assembled into ultracapacitor;

Described manganese series oxides electrode with unique mesh nanostructure, this manganese series oxides are Mn-O or Mn-Mo-O or Mn-Mo-Fe-O or Mn-Mo-V-O or Mn-Fe-V-O; Mn ?O oxide aperture distribution be 3.6～9.4nm; And Mn ?Mo ?O, Mn ?Mo ?V ?O, Mn ?Fe ?V ?O oxide aperture distribution be 0.85～2.5nm; Mn ?Mo ?Fe ?O oxide aperture distribution 0.5～2.5nm.

2. ultracapacitor according to claim 1 is characterized in that: described capacitor diaphragm is glass fibre membrane or polypropylene film or agar membrane barrier film.

3. ultracapacitor according to claim 1 is characterized in that: electrolyte is a water based inorganic electrolyte in the described capacitor, or organic electrolyte, or inorganic and organic mixed electrolytic solution, or solid electrolyte or gel electrolyte.

4. ultracapacitor according to claim 1 is characterized in that: the electrode of described capacitor and barrier film are plain film or plain film are carried out around volume.

5. a kind of ultracapacitor according to claim 1 is characterized in that: described capacitor is the monolithic capacitor of two electrodes assembling, or the multielectrode capacitance device of a plurality of electrode assembling.

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