CN116715847A - High-magnification polypyrrole electrode material, preparation method thereof and application thereof in organic potassium battery - Google Patents

Abstract

The application belongs to the field of organic positive electrode materials of double-ion potassium batteries, and discloses a high-rate polypyrrole electrode material, a preparation method thereof and application thereof in organic potassium batteries. The preparation method of the polypyrrole comprises the following steps: under the protection of inert gas, under the ice water bath condition, slowly dripping a dispersion liquid of ferric (III) sulfate oxidant into a mixed solution of pyrrole monomers and doping agents, and controlling the reaction temperature and the dripping speed of the oxidant to ensure that the generated polypyrrole electrode material shows ultra-high rate performance, and under the current density of 0.05A/g, the specific capacity of the battery can reach 112mAh/g; when the current density is increased by 2.0A/g, the specific capacity value of 97mAh/g can be still maintained, the ultrahigh capacity retention rate is shown, and the method has important research value in the aspect of application of the quick-charging battery.

Description

High-magnification polypyrrole electrode material, preparation method thereof and application thereof in organic potassium battery

Technical Field

The application belongs to the field of organic positive electrode materials of double-ion potassium batteries, and particularly relates to a polypyrrole electrode material, a preparation method thereof and application thereof in high-rate batteries.

Background

With the rapid increase in demand for lithium ion batteries, the supply of lithium resources is becoming increasingly intense. In the age background of energy transformation, key mineral resources such as lithium, nickel, cobalt and the like have become the focus of attention and competition worldwide. China is the first importation country of global lithium resources, and if the use scale of lithium ion batteries is continuously enlarged, for example, more electric automobiles and energy storage power stations are produced, the current situation becomes more severe. In the long term strategic aspect, these batteries that rely on non-renewable mineral resources can face the problem of resource shortage, which can have adverse effects on energy safety and stability. To meet the different needs of various fields, various battery systems have been vigorously developed. Among them, the potassium ion battery with abundant resource reserves and low cost is one of ideal alternatives. However, the larger ionic radius of potassium ions can lead to irreversible phase changes in the electrode structure, resulting in poor cycling stability. In addition, slow ion transport kinetics can lead to difficult enhancement of battery rate performance. Therefore, the development of a positive electrode material having excellent rate performance and long-cycle stability is of great significance for the practical use of potassium ion batteries.

The organic material mainly comprises elements such as carbon, hydrogen, oxygen, nitrogen, sulfur and the like, can be obtained from renewable resources, is easy to degrade and recycle, and has the advantage of environmental friendliness. More importantly, the organic electrode material has molecular designability, and can be subjected to purposeful structural design according to the requirement of battery performance. Electrochemical energy storage and conversion based on organic electrode materials have wide application prospects and important research values, and are considered to be an important development direction for realizing sustainable battery technology. The polypyrrole has good conductivity and electrochemical redox reversibility, and has strong charge storage capacity and good chemical stability, and has great development potential in the aspect of serving as an electrode active material of a secondary battery. However, polypyrrole conductivity is very limited to levels that can be achieved, which severely limits the performance of the active material during battery cycling and electron conduction at high rates. Although conductivity may be improved by the addition of a conductive agent, the addition of a non-electrochemically active additive is detrimental to improving the energy density of the battery system. Thus, the synthesis of polypyrroles with intrinsically high reaction kinetics is critical to the solution of the problem. The main synthesis conditions affecting the properties of the conductive polypyrrole are: the nature of the medium, the concentration of the oxidant, the type, amount and concentration of the dopant, the reaction time, the reaction temperature, etc. How to obtain polypyrrole electrode materials with excellent properties by adjusting polymerization reaction conditions, it is of great importance to develop organic potassium batteries with high voltage, high specific capacity, high rate performance and good cycle stability.

Development of a novel low-cost sustainable electrochemical energy storage technology is a key to efficient utilization of renewable energy. The potassium battery is used as an important supplementary technology of a lithium battery in the field of large-scale energy storage, has important economic value and strategic significance, and is currently applicable to the problem that the multiplying power performance of the positive electrode material of the potassium battery is difficult to improve.

Disclosure of Invention

In order to solve the above problems, the present application aims to provide a polypyrrole electrode material that can be used as a positive electrode material of a potassium battery and to investigate its performance as a potassium battery. The polypyrrole has good air stability, high conductivity and environmental friendliness, and the preparation process of the chemical oxidation synthesis method is simple and easy to operate, has low cost and is suitable for mass production. The potassium secondary battery applying the polypyrrole disclosed by the application is found in a half-battery test, and the material has higher specific capacity and working potential, is excellent in cycle life and rate capability, has great practical value, and can be used for large-scale energy storage equipment of smart grid peak shaving, distributed power stations, backup power sources or communication base stations.

The application provides a polypyrrole-based high-magnification organic positive electrode material, which has the following synthetic route and structural general formula:

the second purpose of the application is to provide a preparation method of the environment-friendly low-cost polypyrrole, which comprises the following steps:

step 1: performing reduced pressure distillation on crude pyrrole to obtain purified pyrrole monomer, purifying pyrrole by using a reduced pressure distillation method, dispersing the purified pyrrole monomer in 4-sodium toluene sulfonate aqueous solution, and stirring under the conditions of protective atmosphere and ice water bath to obtain solution a;

step 2: dispersing ferric (III) sulfate hydrate into water, vigorously stirring and ultrasonically dispersing to obtain a solution b;

step 3: under the protection of inert gas, slowly dropwise adding the solution b into the solution a under the ice water bath condition, and continuously and vigorously stirring;

step 4: after the dripping is finished, stirring is continued for 4.0 hours under the conditions of protective atmosphere and ice water bath;

step 5: and collecting a product obtained by the reaction, filtering the crude product, centrifugally cleaning the crude product with deionized water for a plurality of times, and drying the crude product in vacuum to obtain black polypyrrole powder.

In the step 1, the temperature of reduced pressure distillation is 50-60 ℃, argon or nitrogen is introduced for protection during distillation, and the distillation is carried out well, and the distillation is sealed and stored in a dark place.

In step 2, the iron (iii) sulfate hydrate is subjected to thermogravimetric analysis to determine the number of crystal water contained in the sample.

In the step 1, the molar ratio of pyrrole to 4-sodium toluene sulfonate is 1:2; in the solution a, the concentration of pyrrole is 0.7-0.8mol/L, and the concentration of 4-toluenesulfonic acid sodium is 1.4-1.6mol/L.

In the step 2, the concentration of the ferric sulfate (III) in the solution b is 0.6-0.65mol/L.

In the step 2, the time of intense stirring and ultrasonic dispersion is 1-2 h, and the ultrasonic power is 450-600W.

In the step 3, the molar ratio of the ferric sulfate (III) to the pyrrole is 1.25:1.

In step 3, the rate of adding solution b to solution a is controlled to be 1-2 drops per minute.

Preferably, the drop speed is controlled to be one drop per minute at the initial stage of the reaction, and after the addition amount exceeds 2/3, the drop speed is controlled to be two drops per minute.

The application further provides application of the high-rate polypyrrole electrode material prepared by the method in potassium batteries.

The preparation method of the positive electrode of the potassium battery comprises the steps of mixing the obtained polypyrrole, conductive carbon and a binder in water to form a sticky substance, coating the sticky substance on a current collector, vacuum drying at 60-80 ℃ for 24-36 hours, and cutting the dried pole piece to a proper size to obtain the positive electrode of the battery.

Wherein the polypyrrole material accounts for 60 to 80 weight percent, the conductive carbon accounts for 10 to 30 weight percent, and the binder accounts for no more than 10 weight percent.

The fourth object of the application is to provide an organic potassium battery, which comprises the battery anode, the cathode material, the diaphragm and the electrolyte;

wherein,,

the negative electrode material comprises metal potassium;

the diaphragm is a glass fiber membrane or a PP diaphragm;

the electrolyte is a liquid electrolyte composed of an organic solvent and potassium salt, wherein the organic solvent is one or more than two mixed ester solvents selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and fluoroethylene carbonate; the potassium salt is potassium hexafluorophosphate;

compared with the prior art, the application has the following beneficial effects:

the conductivity of the conductive polypyrrole is mainly dependent on the structure and the morphology of the polypyrrole formed during polymerization, polymerization at low temperature (about 0 ℃) is beneficial to improving the molecular weight of polyaniline and obtaining a polymer with narrower molecular weight distribution, and the generation of popcorn is avoided by controlling the dropping speed of the oxidant, so that the polypyrrole with high conductivity is obtained. The preparation method has simple synthesis steps, mild conditions and low price, and can be used for industrial production. The polypyrrole material is applied to a positive electrode material of a potassium battery, and experimental tests prove that the polypyrrole material has higher rate performance, and the specific capacity of the battery can reach 112mAh/g under the current density of 0.05A/g; when the current density was increased by 2.0A/g, a specific volume value of 97mA h/g was maintained.

Drawings

FIG. 1 is a Fourier transform infrared spectrum of polypyrrole obtained in example 1.

FIG. 2 is a scanning electron micrograph of the polypyrrole obtained in example 1.

FIG. 3 is a transmission electron micrograph of the polypyrrole obtained in example 1.

FIG. 4 is a cyclic voltammogram (sweep rate of 0.1mV s) of polypyrrole prepared in example 2 in a potassium cell ^-1 )。

FIG. 5 is a graph showing charge and discharge curves (current density of 0.05A/g) of polypyrrole prepared in example 2 in a potassium cell.

FIG. 6 is a graph showing the cycle performance (current density of 0.1A/g) of polypyrrole prepared in example 2 in a potassium cell.

Fig. 7 is an electrochemical impedance spectrum of polypyrrole prepared in example 2 in a potassium cell.

FIG. 8 is a graph showing the rate performance (current densities of 0.05, 0.1, 0.2, 0.5, 1.0, 2.0A/g, respectively) of polypyrrole prepared in example 2 in a potassium cell.

Detailed Description

In order to make the technical purpose, technical scheme and beneficial effect of the present application more clear, the technical scheme of the present application is further described below with reference to the accompanying drawings and specific embodiments.

Example 1

A preparation method of a high-magnification silicon-based hard carbon material comprises the following steps:

s1, preparing a solution a: 1.0g of the purified pyrrole monomer and 5.78g of sodium 4-toluenesulfonate were dissolved in 20mL of deionized water and stirred on a magnetic stirrer under ice water bath and nitrogen atmosphere for 30min.

S2, preparing a solution b, namely dispersing 7.45g of ferric (III) sulfate in 30mL of deionized water, and carrying out vigorous stirring and ultrasonic dispersion, wherein the ultrasonic time is 1-2 h, and the ultrasonic power is 450-600W, so as to obtain a mixture of uniformly dispersing ferric sulfate particles in water.

And S3, dropwise adding the solution b into the solution a under vigorous stirring through a dropping funnel, wherein the dropwise adding speed at the initial stage of the reaction is controlled to be one drop per minute under the conditions of ice-water bath and nitrogen atmosphere in the whole process, and after the adding amount of the solution b exceeds 2/3, the dropwise adding speed is controlled to be two drops per minute.

And S4, after the dropwise addition of the solution b is finished, the reaction is continuously stirred for 4 hours under the conditions of protective atmosphere and ice water bath. And centrifuging the black precipitate obtained by vacuum filtration with deionized water for 3 times, and freeze-drying and then placing to obtain polypyrrole black powder.

Fig. 1 is a fourier transform infrared spectrum of polypyrrole. Characteristic bands of polypyrrole appear in the infrared spectrum, wherein the stretching vibration peak of the pyrrole ring is 1549cm ^-1 ，1160-1200cm ^-1 The stretching vibration of S=O in sulfonate anions can be attributed to, and the successful synthesis of the 4-sodium toluene sulfonate doped polypyrrole is proved.

Fig. 2 and 3 are scanning electron microscope and transmission electron microscope photographs of the polypyrrole obtained in example 1, respectively, from which the morphology and particle size of the prepared polypyrrole were observed, and as can be seen from fig. 2 and 3, the prepared polypyrrole exhibited well-dispersed and uniformly sized particles having a particle size of 200 to 500 nm.

Example 2

The polypyrrole obtained in this example was used as the positive electrode of a potassium cell:

70wt.% of the polypyrrole material prepared in the embodiment is weighed, 20wt.% of acetylene black is used as a conductive agent, 10wt.% of sodium carboxymethylcellulose (CMC) is added as a binder, 150wt.% of water is used as a solvent, uniform black paste slurry is obtained after full grinding, the slurry is coated on an aluminum foil current collector to serve as a positive plate, a metal potassium plate is used as a comparison electrode to be assembled into a button cell, an electrolyte of 0.8M organic electrolyte (potassium salt is potassium hexafluorophosphate, the solvent is a mixed solution of ethylene carbonate and diethyl carbonate with volume ratio of 1:1), glass fiber is used as a diaphragm, CR2032 stainless steel is used as a cell shell to be assembled into the button cell, and the cell performance is tested.

The application of polypyrrole organic positive electrode in potassium cell and its performance are shown in fig. 4-8.

Fig. 4 is a cyclic voltammogram of polypyrrole in potassium cells prepared in example 2. From fig. 4, it can be seen that polypyrrole has a pair of redox peaks at 2.3V and 3.0V, indicating that polypyrrole has good redox reversibility and stable electrochemical activity.

Fig. 5 is a constant current charge-discharge curve of polypyrrole prepared in example 2 in a potassium cell. As can be seen from FIG. 5, the reversible specific charge/discharge capacity of the polypyrrole electrode was 112mAh/g at a current density of 0.05A/g.

Fig. 6 is a cycle stability test of polypyrrole prepared in example 2 in potassium cells. As can be seen from FIG. 6, the polypyrrole electrode was made of 0.1Ag ^-1 The current density of the alloy shows good circulation stability, and after 200 times of circulation, the reversible capacity reaches 106mAh/g.

Fig. 7 is an electrochemical impedance test of polypyrrole prepared in example 2 in a potassium cell. As can be seen from fig. 7, the potassium cell based on the polypyrrole electrode showed a smaller impedance, indicating that polypyrrole had better conductivity.

Fig. 8 shows the rate performance profile of polypyrrole prepared in example 2 in potassium cells. As can be seen from fig. 8, when the current densities are respectively 0.05, 0.1, 0.2, 0.5, 1.0 and 2.0A/g, the reversible capacities of the batteries are respectively 112, 104, 101, 100, 99 and 97mAh/g, and the reversible capacities exhibit ultrahigh capacity retention rates, thus proving the application potential of polypyrrole as an electrode material of a high-rate battery.

The foregoing is merely exemplary embodiments of the present application, and detailed technical solutions or features that are well known in the art have not been described in detail herein. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present application, and these should also be regarded as the protection scope of the present application, which does not affect the effect of the implementation of the present application and the practical applicability of the patent. The protection scope of the present application is subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.

Claims (10)

1. The preparation method of the high-rate polypyrrole electrode material is characterized by comprising the following steps of:

step 1: performing reduced pressure distillation on crude pyrrole to obtain purified pyrrole monomer, purifying pyrrole by using a reduced pressure distillation method, dispersing the purified pyrrole monomer in 4-sodium toluene sulfonate aqueous solution, and stirring under the conditions of protective atmosphere and ice water bath to obtain solution a;

step 2: dispersing ferric sulfate hydrate into water, vigorously stirring and ultrasonically dispersing to obtain a solution b;

step 3: under the protection of inert gas, slowly dropwise adding the solution b into the solution a under the ice water bath condition, and continuously and vigorously stirring;

step 4: after the dripping is finished, stirring is continued for a certain time under the conditions of protective atmosphere and ice water bath;

step 5: and collecting a product obtained by the reaction, filtering the crude product, centrifugally cleaning the crude product with deionized water for a plurality of times, and drying the crude product in vacuum to obtain black polypyrrole powder.

2. The method of claim 1, wherein in step 1, the molar ratio of pyrrole monomer to sodium 4-toluene sulfonate is 1:2.

3. The process according to claim 1, wherein the concentration of the pyrrole monomer in the solution a of step 1 is 0.7 to 0.8mol/L and the concentration of the sodium 4-toluenesulfonate is 1.4 to 1.6mol/L.

4. The process according to claim 1, wherein the concentration of iron sulfate in the solution b of step 2 is 0.6 to 0.65mol/L.

5. The method of claim 1, wherein in step 2, the time of vigorous stirring and ultrasonic dispersion is 1 to 2 hours, and the ultrasonic power is 450 to 600W.

6. The method of claim 1, wherein in step 3, the molar ratio of ferric sulfate to pyrrole monomer is 1.25:1 after solution b is added to solution a;

the rate of addition of solution b to solution a was controlled to be 1-2 drops per minute.

7. The method of claim 1, wherein in step 4, the stirring time is 4.0 hours.

8. Use of the high-rate polypyrrole electrode material prepared by the preparation method of any one of claims 1 to 7 in potassium batteries.

9. The use according to claim 8, comprising the steps of:

uniformly mixing polypyrrole, a conductive agent and a binder in deionized water, stirring and preparing into black slurry, coating the black slurry on a current collector, drying, and cutting to obtain a battery anode;

wherein the mass ratio of polypyrrole, the conductive agent and the binder is (60-80): (10-30): 10;

the conductive agent is one or a mixture of more than two of Super-P, acetylene black, ketjen black, carbon nano tubes or graphene in any proportion;

the binder is one or a mixture of two of sodium carboxymethyl cellulose CMC or polytetrafluoroethylene PTFE dispersion liquid in any proportion;

the current collector is aluminum foil.

10. An organic potassium cell comprising the cell positive electrode of claim 9, further comprising: a negative electrode material, a separator, and an electrolyte;

wherein,,

the electrolyte is a liquid electrolyte composed of an organic solvent and potassium salt, wherein the organic solvent is one or more than two mixed ester solvents selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and fluoroethylene carbonate; the potassium salt is potassium hexafluorophosphate;

the negative electrode material is selected from metal potassium;

the separator is selected from glass fiber separator or PP separator.