Supercapacitor is a new type of energy storage element, which is widely used in starting power supply, pulse power supply, military, mobile communication device, computer and electric vehicle due to its advantages of large capacity, fast charging and discharging of large current, and long cycle life. and other research fields. According to the different energy storage mechanisms, supercapacitors can be divided into the following three types: electric double-layer capacitors, Faraday pseudocapacitors and hybrid supercapacitors.

Electric double-layer capacitors mainly store energy through the electric double layer formed at the interface between electrodes/electrolytes, and these capacitors have high power density and excellent cycle performance.

Faraday pseudocapacitors mainly store energy through fast and reversible chemical adsorption/desorption or redox reactions on the surface of the electrode or in the two-dimensional space in the bulk phase. The reaction is characterized by the generation of Faraday current, and its theoretical specific capacitance And the energy density is 100 times higher than that of electric double layer capacitors.

The two electrodes of the hybrid supercapacitor adopt different energy storage mechanisms respectively, one electrode is made of pseudocapacitor or secondary battery electrode material, and the other electrode is made of electric double layer capacitor carbon material. Hybrid supercapacitors mainly use metal oxides as positive electrode materials and carbon materials as negative electrode materials. The electrode material is the main performance index that directly affects the supercapacitor. The metal oxide materials initially used as anode materials are mainly noble metal oxides such as ruthenium oxide (RuO2) or iridium oxide (IrO2). The specific capacitance of the thin film electrode made of RuO2 can reach 760 F/g, but its high price and high environmental pollution limit its wide application. Manganese dioxide (MnO2) has similar functions to RuO2, and its advantages such as abundant resources, non-toxicity, easy preparation, and environmental friendliness have become one of the candidate materials to replace precious metals.

At present, the methods for preparing MnO2 mainly include hydrothermal method, liquid deposition method, high-temperature solid-phase method, etc. However, MnO2 prepared by most methods has poor performance as a cathode material for supercapacitors, mainly due to low discharge specific capacitance and poor cycle stability. And other issues. This limits the large-scale application of MnO2 in the supercapacitor industry.

In order to improve the problems of low discharge specific capacitance and poor cycle stability of the MnO2 electrode material, the present invention designs a preparation method capable of simply and quickly synthesizing the supercapacitor electrode material MnO2.

The present invention is achieved through the following technical solutions:

Preparation method of supercapacitor electrode material manganese dioxide:

(O get raw material pyrrole (purifying under reduced pressure before use) and potassium permanganate respectively, the mol ratio of pyrrole and potassium permanganate is 1:0.5-1:1;

(2) the obtained pyrrole monomer is dispersed and dissolved in water, fully stirred to obtain solution A; The volume ratio of pyrrole and water is 1:25-1:50;

(3) water-soluble potassium permanganate is obtained to obtain solution B; the volume of gained solution B is 2-3 times of the volume of solution A;

(4) solution B is slowly added in solution A, and stirring reaction 6-12 hours under 0 ~ 5 ℃ of temperature conditions;

(5) filter the reaction solution to obtain solid powder product, wash with deionized water and ethanol solvent respectively, until the filtrate is colorless; (6) dry the washed solid powder product at 50-80 ° C for 12-24 hours , that is, the electrode material MnO2 powder is obtained, which is used to prepare the positive electrode material of the supercapacitor.

Compared with the prior art, the present invention has the following advantages:

1. The MnO2 electrode material prepared by the method of the present invention is a powdery amorphous material, which not only has high specific capacitance, but also has good electrochemical stability, and is an excellent supercapacitor positive electrode material.

2. The preparation method of MnO2 of the present invention is simple and fast, and solves the problem of difficulty in large-scale application of MnO2 in the supercapacitor industry.

How to make it?

The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

The following is the characterization and analysis of the prepared MnO2 by XRD, FT-IR, SEM, TEM, etc. using various analytical instruments. In the following examples, the pyrrole in the raw material was purified by vacuum distillation before use, and the molar ratio of pyrrole to potassium permanganate was the molar ratio of pyrrole to potassium permanganate after purification.

(1) get raw material pyrrole and potassium permanganate respectively, the mol ratio of pyrrole and potassium permanganate is 1:0.6;

(2) the obtained pyrrole monomer is dispersed and dissolved in water, fully stirred to obtain solution A; The volume ratio of pyrrole and water is 1:25;

(3) water-soluble potassium permanganate is obtained to obtain solution B; the volume of gained solution B is 3 times of the volume of solution A;

(4) solution B is slowly added in solution A, and stirring reaction 8 hours under 5 ℃ of temperature conditions;

(5) filter the reaction product to obtain solid powdery precipitate, wash the precipitate with deionized water and ethanol solvent respectively, until the filtrate is colorless;

(6) vacuum-drying the washed solid powder product at 60° C. for 18h to obtain electrode material MnO powder, which can be used to prepare supercapacitor positive electrode material.