Methods to improve the capacity of polypyrrole electrodes

Abstract

This invention provides a method for improving the capacity of a polypyrrole electrode. The method includes the following steps: S1, using a polypyrrole electrode as the working electrode and forming a three-electrode system with a platinum electrode, a calomel electrode, and an electrolyte; S2, running an electrochemical activation program on the three-electrode system. This method is based on the fact that the polypyrrole electrode material completes the energy storage and release process through the insertion and extraction of ions in the electrolyte. It increases the number of ions that can be inserted into the polypyrrole molecular chain through a negative potential activation method, thereby improving its capacity. This activation process alters the structure of the polypyrrole molecular chain, giving it more ion doping sites, representing an improvement at the molecular chain level. This method can be used for pure polypyrrole electrodes and polypyrrole composite electrodes.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a method for improving the capacity of polypyrrole electrodes. Background Technology

[0002] Supercapacitors can assist energy devices such as batteries, playing a crucial role in applications requiring instantaneous high power output. Their rapid charging and discharging capabilities, along with their long lifespan, make them promising candidates for applications in transportation, energy, industry, microgrids, and aerospace. Polypyrrole exhibits significant pseudocapacitive energy storage characteristics, is easily integrated with fabrics, and is relatively inexpensive, making it a promising candidate for large-scale production of flexible electrode materials. However, the capacity of fabric-based polypyrrole electrodes still needs improvement.

[0003] To improve the capacity of fabric-based polypyrrole electrodes, a common approach is to utilize the synergistic effect of the conductivity and energy storage properties of multi-component materials, such as combining polypyrrole with carbon-based materials, metal oxides, sulfides, and double hydroxides. Another approach is to increase charge storage sites, such as building scaffold structures on the fiber surface to increase the polypyrrole loading, thereby increasing the number of energy storage units on the electrode; or to control the micro / nano morphology of polypyrrole to obtain a higher specific surface area.

[0004] In the prior art, Chinese patent application number 202311745198.1 discloses a polypyrrole-coated VS2-PPy composite material and its preparation method. This composite material has good capacity and cycling stability, and the polypyrrole conductive network formed during cycling greatly improves the conductivity of the composite material. Chinese patent application number 202211523880.1 discloses a method for preparing a hierarchical polypyrrole / NiCoAl-LDH / cotton fiber flexible electrode material, in which three-dimensional double metal hydroxides (LDHs) derived using metal-organic frameworks (MOFs) as templates are novel electrode materials with tunable morphology and high specific capacitance. However, combining polypyrrole with other conductive or energy storage materials increases the mass of the electrode, thereby reducing its specific capacity.

[0005] In view of this, it is necessary to design an improved method to increase the capacity of polypyrrole electrodes in order to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a method for improving the capacity of polypyrrole electrodes. This method is based on the fact that polypyrrole electrode materials rely on the insertion and extraction of electrolyte ions to complete the energy storage and release process. By using a negative potential activation method, the number of ions capable of intercalating into the polypyrrole molecular chain is increased, thereby improving its capacity. This activation process alters the structure of the polypyrrole molecular chain, giving it more ion doping sites, representing a molecular chain-level improvement. Even when subsequent charging and discharging occur within a positive potential range, more ions will participate in doping, thus increasing the capacity of the polypyrrole. This method can be used for both pure polypyrrole electrodes and polypyrrole composite electrodes.

[0007] To achieve the above objectives, the present invention provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0008] S1, a three-electrode system is formed by using a polypyrrole electrode with a polypyrrole molecular chain structure as the working electrode, a platinum sheet as the counter electrode, a calomel electrode as the reference electrode, and an electrolyte.

[0009] S2, perform negative potential electrochemical activation treatment on the three-electrode system in step S1 to obtain an electrochemically activated polypyrrole electrode.

[0010] Further, in step S2, the negative potential electrochemical activation treatment refers to cyclic voltammetric activation treatment, the parameters of which are set as follows: the maximum voltage limit is 0V, the minimum voltage limit is between -0.4V and -1.0V, the scan starts from 0V, the scan rate is between 0.1mV / s and 100mV / s, and the number of scan cycles is between 1 and 100.

[0011] Further, in step S2, the negative potential electrochemical activation treatment refers to constant current charge-discharge activation treatment, the parameters of which are set as follows: the maximum voltage limit is 0V, the minimum voltage limit is between -0.4V and -1.0V, the operation starts from 0V, the charge-discharge current is between 0.1mA and 20.0mA, and the number of charge-discharge cycles is between 1 and 100.

[0012] Further, in step S1, the polypyrrole electrode is an electrode material with a polypyrrole molecular chain structure prepared by chemical oxidative polymerization or electrochemical polymerization.

[0013] Further, in step S1, the electrolyte is one or a mixture of NaCl solution, Na2SO4 solution, KCl solution, and K2SO4 solution, and the concentration range of each ion in the electrolyte is 0.01-4.5 mol / L.

[0014] Further, in step S1, the polypyrrole electrode is a pure polypyrrole electrode, a rigid polypyrrole electrode, a flexible polypyrrole electrode, or a multi-electrode active material electrode containing polypyrrole.

[0015] Furthermore, the pure polypyrrole electrode is made of polypyrrole powder; the rigid polypyrrole electrode is obtained by electrodepositing polypyrrole onto a rigid substrate such as metal or conductive glass, or by first preparing a conductive slurry from polypyrrole powder with an adhesive and carbon black and then coating it onto a rigid substrate such as metal or conductive glass; the flexible polypyrrole electrode is obtained by loading polypyrrole onto a polymer film material or aerogel framework material as a substrate, wherein the polymer film material is a fiber material, hydrogel material, or rubber; the polypyrrole-containing multi-element active material electrode is a composite electrode containing one or more active materials in addition to polypyrrole, such as carbon materials, conductive polymers, metal oxides, metal sulfides, metal hydroxides, organometallic frameworks, and covalent organic frameworks.

[0016] Furthermore, the electrolyte is a NaCl solution or a KCl solution, and the concentration range of the NaCl solution or KCl solution is 0.01-4.5 mol / L.

[0017] Furthermore, the electrolyte is a K2SO4 solution with a concentration range of 0.01-2.25 mol / L.

[0018] Furthermore, the electrolyte is a mixture of NaCl solution and KCl solution, and the concentration of each ion in the electrolyte ranges from 0.01 to 4.5 mol / L.

[0019] The beneficial effects of this invention are:

[0020] 1. The method for improving the capacity of polypyrrole electrodes provided by this invention increases the number of ions embedded in the polypyrrole molecular chain through activation technology within a negative potential range, rather than using other electroactive composite components. This avoids the problem of significantly increasing electrode mass associated with traditional methods of improving electrode capacity through composite material technology, thus offering excellent application prospects. This activation process alters the structure of the polypyrrole molecular chain, providing more ion doping sites, representing an improvement at the molecular chain level. Because the types of doping ions at negative potentials differ from those at positive potentials, this invention alters the polypyrrole molecular chain structure through negative potential activation. This structure can also be doped with corresponding ions under positive potential conditions. Therefore, even if subsequent charging and discharging occur within a positive potential range, more ions will participate in doping, further improving the capacity of the polypyrrole.

[0021] 2. The method for improving the capacity of polypyrrole electrodes provided by this invention is novel and simple. This activation method is also effective for polypyrrole that has been stored for a long time. Due to prolonged disuse, the conductivity of polypyrrole will decrease, thereby reducing the capacitance. However, after activation by this method, the long-stored polypyrrole electrode has essentially the same capacity as the newly prepared polypyrrole electrode. Attached Figure Description

[0022] Figure 1 The graph shows the performance test results of activated and unactivated polypyrrole electrodes after the activation method used in Example 1.

[0023] Figure 2 This is a graph of the negative potential activation process in Example 1.

[0024] Figure 3 The graphs show the performance of activated and unactivated polypyrrole electrodes after activation using the activation method described in Example 1, and the performance of the polypyrrole electrode in Comparative Example 1.

[0025] Figure 4 The graphs show the performance of activated and unactivated polypyrrole electrodes after activation using the activation method described in Example 7, and the performance of the polypyrrole electrode in Comparative Example 2.

[0026] Figure 5 This is a graph of the negative potential activation process in Example 7.

[0027] Figure 6 This is a performance test graph of activated and unactivated polypyrrole electrodes that have been left unused for 75 days after the activation method used in Example 8. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0030] This invention provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0031] S1, a three-electrode system is formed by using a polypyrrole electrode with a polypyrrole molecular chain structure as the working electrode, a platinum sheet as the counter electrode, a calomel electrode as the reference electrode, and an electrolyte.

[0032] The polypyrrole electrode is an electrode material with a polypyrrole molecular chain structure prepared by chemical oxidative polymerization or electrochemical polymerization.

[0033] The polypyrrole electrode is a pure polypyrrole electrode, a rigid polypyrrole electrode, a flexible polypyrrole electrode, or a multi-electrode active material electrode containing polypyrrole.

[0034] The pure polypyrrole electrode is made from polypyrrole powder; the rigid polypyrrole electrode is obtained by electrodepositing polypyrrole onto a rigid substrate such as metal or conductive glass, or by first preparing a conductive slurry from polypyrrole powder with an adhesive and carbon black and then coating it onto a rigid substrate such as metal or conductive glass; the flexible polypyrrole electrode is obtained by loading polypyrrole onto a polymer film material or aerogel framework material as a substrate, wherein the polymer film material is a fiber material, hydrogel material, or rubber; the multi-element active material electrode containing polypyrrole is a composite electrode containing one or more active materials in addition to polypyrrole, such as carbon materials, conductive polymers, metal oxides, metal sulfides, metal hydroxides, organometallic frameworks, and covalent organic frameworks.

[0035] The electrolyte is one or a mixture of NaCl solution, Na2SO4 solution, KCl solution, and K2SO4 solution, and the concentration of each ion in the electrolyte ranges from 0.01 to 4.5 mol / L.

[0036] S2, perform negative potential electrochemical activation treatment on the three-electrode system in step S1 to obtain an electrochemically activated polypyrrole electrode.

[0037] The negative potential electrochemical activation treatment refers to cyclic voltammetric activation treatment, with the following parameters: the highest voltage limit is 0V, the lowest voltage limit is between -0.4V and -1.0V, the scan starts from 0V, the scan rate is between 0.1mV / s and 100mV / s, and the number of scan cycles is between 1 and 100.

[0038] Alternatively, the negative potential electrochemical activation treatment refers to constant current charge-discharge activation treatment, with the following parameters: the highest voltage limit is 0V, the lowest voltage limit is between -0.4V and -1.0V, operation starts from 0V, the charge-discharge current is between 0.1mA and 20.0mA, and the number of charge-discharge cycles is between 1 and 100.

[0039] The preparation method of the method for improving the capacity of polypyrrole electrodes provided by the present invention will be described below with reference to specific embodiments.

[0040] Example 1

[0041] This embodiment provides a method for improving the capacity of a polypyrrole electrode, including the following steps:

[0042] S1, a polypyrrole / nanofiber modified nonwoven fabric composite material prepared by chemical oxidative polymerization is used as the working electrode and forms a three-electrode system with a platinum electrode, a calomel electrode and a 2 mol / L NaCl electrolyte.

[0043] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.8V to 0V, scan starting from 0V, scan rate 5mV / s, and scan number of cycles 2.

[0044] Tests showed that the capacity of the polypyrrole electrode activated in this way was 2.2 times higher than that of the unactivated polypyrrole electrode.

[0045] Please see Figure 1 The figure shows the performance test graphs of activated and unactivated polypyrrole electrodes after the activation method used in Example 1. It can be seen that the area of ​​the electrode curve measured after activation is larger, indicating a higher capacity.

[0046] Figure 2 The graph shows the negative potential activation process in Example 1. A clear redox peak can be seen in the graph, indicating that the electrolyte ions have doped the polypyrrole.

[0047] Comparative Example 1

[0048] Comparative Example 1 provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0049] Step S1 is the same as step S1 in Example 1;

[0050] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from 0V to 0.8V, scanning starts from 0V, scanning rate is 5mV / s, and the number of scanning cycles is 2.

[0051] Testing showed that the capacity of the polypyrrole electrode activated in this way increased by only about 0.13 times compared to the unactivated polypyrrole electrode, indicating that negative potential activation is more effective than positive potential activation.

[0052] Figure 3 The figures show performance test graphs of activated and unactivated polypyrrole electrodes after activation using the method described in Example 1, and performance test graphs of the polypyrrole electrode in Comparative Example 1 (performance test graph of the polypyrrole electrode after activation in the positive potential range). It is evident that negative potential activation significantly improves electrode capacity compared to positive potential activation.

[0053] Example 2

[0054] Example 2 provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0055] S1 uses a polypyrrole electrode prepared by chemical oxidative polymerization as the working electrode and forms a three-electrode system with a platinum electrode, a calomel electrode, and a 0.01 mol / L KCl electrolyte.

[0056] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.4V to 0V, scan starting from 0V, scan rate 100mV / s, and scan number of 100 cycles.

[0057] Tests showed that the capacity of the polypyrrole electrode activated in this way was 0.4 times higher than that of the unactivated polypyrrole electrode.

[0058] Example 3

[0059] Example 3 provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0060] S1, using a polypyrrole / carbon cloth composite material prepared by electrochemical polymerization as the working electrode, and forming a three-electrode system with a platinum electrode, a calomel electrode, and a 1 mol / L NaCl electrolyte;

[0061] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from -1.0V to 0V, scan starting from 0V, scan rate 0.1mV / s, and scan cycle number 1.

[0062] Tests showed that the capacity of the polypyrrole electrode activated in this way was 1.3 times higher than that of the unactivated polypyrrole electrode.

[0063] Example 4

[0064] S1 uses a polypyrrole / carbon cloth composite material prepared by electrochemical polymerization as the working electrode and forms a three-electrode system with a platinum electrode, a calomel electrode, and a 2.25 mol / L Na2SO4 electrolyte.

[0065] S2, run the constant current charge-discharge activation program on the three-electrode system; the program parameters are set as follows: voltage from -1.0V to 0V, start running from 0V, charge-discharge current 20.0mA, and charge-discharge times 2.

[0066] Tests showed that the capacity of the polypyrrole electrode activated in this way was 0.5 times higher than that of the unactivated polypyrrole electrode.

[0067] Example 5

[0068] S1, using a polypyrrole / polyester nonwoven composite material prepared by chemical oxidative polymerization as the working electrode, and forming a three-electrode system with a platinum electrode, a calomel electrode, and a 0.5 mol / L K2SO4 electrolyte;

[0069] S2, run the constant current charge-discharge activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.4V to 0V, start running from 0V, charge-discharge current 1mA, and charge-discharge cycles 100 times.

[0070] Tests showed that the capacity of the polypyrrole electrode activated in this way was 2.2 times higher than that of the unactivated polypyrrole electrode.

[0071] Example 6

[0072] S1, a three-electrode system is formed by using a polypyrrole / polyester nonwoven composite material prepared by chemical oxidative polymerization as the working electrode and a mixed electrolyte consisting of a platinum electrode, a calomel electrode, and a 1 mol / L NaCl solution + a 1 mol / L KCl solution.

[0073] S2, run the constant current charge-discharge activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.8V to 0V, start running from 0V, charge-discharge current 0.1mA, and charge-discharge times 1.

[0074] Tests showed that the capacity of the polypyrrole electrode activated in this way was 0.6 times higher than that of the unactivated polypyrrole electrode.

[0075] Example 7

[0076] S1, a polypyrrole / nanofiber modified nonwoven fabric composite material prepared by chemical oxidative polymerization is used as the working electrode and forms a three-electrode system with a platinum electrode, a calomel electrode and a 2 mol / L NaCl electrolyte.

[0077] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.8V to 0V, scan starting from 0V, scan rate 100mV / s, and scan number of 2 cycles.

[0078] Tests showed that the capacity of the polypyrrole electrode activated in this way was 1.3 times higher than that of the unactivated polypyrrole electrode.

[0079] Figure 5 The graph shows the negative potential activation process in Example 7. A clear redox peak can be seen in the graph, indicating that the electrolyte ions have doped the polypyrrole.

[0080] Comparative Example 2

[0081] Comparative Example 2 provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0082] Step S1 is the same as step S1 in Example 7;

[0083] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from 0V to 0.8V, scanning starts from 0V, scanning rate is 100mV / s, and the number of scanning cycles is 2.

[0084] Testing showed that the capacity of the polypyrrole electrode activated in this way increased by only about 0.03 times compared to the unactivated polypyrrole electrode, indicating that negative potential activation is more effective than positive potential activation.

[0085] Figure 4 The figures show performance test graphs of activated and unactivated polypyrrole electrodes after activation using the method described in Example 7, and performance test graphs of the polypyrrole electrode in Comparative Example 2 (performance test graph of the polypyrrole electrode after activation in the positive potential range). It is evident that negative potential activation significantly improves electrode capacity compared to positive potential activation.

[0086] Example 8

[0087] Example 8 provides a method for improving the capacity of a polypyrrole electrode, comprising the following steps:

[0088] S1 uses a polypyrrole / nanofiber modified nonwoven fabric composite material prepared by chemical oxidative polymerization and left unused for 75 days as the working electrode, and forms a three-electrode system with a platinum electrode, a calomel electrode and a 2 mol / L NaCl electrolyte.

[0089] S2, run the cyclic voltammetry activation program on the three-electrode system; the program parameters are set as follows: voltage from -0.8V to 0V, scan starting from 0V, scan rate 5mV / s, and scan number of cycles 2.

[0090] After testing, the capacity of the polypyrrole electrode activated by this method and left unused for 75 days was increased by 8.6 times compared with the unactivated polypyrrole electrode in Example 1. The capacity of the polypyrrole electrode left unused for 75 days was only 40% of that of the unactivated polypyrrole electrode in Example 1 due to the decline in performance after prolonged storage. However, after activation by this method, the capacity of the polypyrrole electrode after prolonged storage was basically equal to the capacity directly measured after preparation.

[0091] Please see Figure 6 The figure shows the performance test results of activated and unactivated polypyrrole electrodes that had been left unused for 75 days after the activation method used in Example 8. Figure 6 The area of ​​the curve after activation and Figure 1 The activated curve areas are basically similar. This shows that this activation method has the same effect on polypyrrole electrodes that have been stored for a long time.

[0092] In summary, this invention provides a method for improving the capacity of a polypyrrole electrode by increasing the number of ions capable of embedding into the polypyrrole molecular chain through negative potential activation. This activation process alters the structure of the polypyrrole molecular chain, providing more ion doping sites, representing an improvement at the molecular chain level. This method can be used for both pure polypyrrole electrodes and polypyrrole composite electrodes. Furthermore, this activation method is effective for polypyrrole electrodes that have been stored for a long time. Due to prolonged disuse, the conductivity of polypyrrole decreases, resulting in a reduction in capacitance; however, after activation using this method, the stored polypyrrole electrode exhibits essentially the same capacity as a newly prepared polypyrrole electrode.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the capacity of a polypyrrole electrode, characterized in that, Includes the following steps: S1, a three-electrode system is formed by using a polypyrrole electrode with a polypyrrole molecular chain structure as the working electrode, a platinum sheet as the counter electrode, a calomel electrode as the reference electrode, and an electrolyte; the polypyrrole electrode is an electrode material with a polypyrrole molecular chain structure prepared by chemical oxidative polymerization or electrochemical polymerization. S2, perform negative potential electrochemical activation treatment on the three-electrode system in step S1 to change the structure of the polypyrrole molecular chain and make it have more ion doping sites. After electrochemical activation, the capacity of the polypyrrole electrode increases in the positive potential range; The negative potential electrochemical activation treatment does not use other electroactive composite components; during the negative potential electrochemical activation treatment, the highest voltage limit is 0V, and the lowest voltage limit is between -0.4V and -1.0V.

2. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: In step S2, the negative potential electrochemical activation treatment refers to cyclic voltammetric activation treatment, with the following parameters: starting the scan from 0V, the scan rate is between 0.1mV / s and 100mV / s, and the number of scan cycles is between 1 and 100.

3. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: In step S2, the negative potential electrochemical activation treatment refers to the constant current charge-discharge activation treatment, the parameters of which are set as follows: starting from 0V, the charge-discharge current is between 0.1mA and 20.0mA, and the number of charge-discharge cycles is between 1 and 100.

4. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: In step S1, the electrolyte is one or a mixture of NaCl solution, Na2SO4 solution, KCl solution, and K2SO4 solution, and the concentration of each ion in the electrolyte ranges from 0.01 to 4.5 mol / L.

5. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: In step S1, the polypyrrole electrode is a pure polypyrrole electrode, a rigid polypyrrole electrode, a flexible polypyrrole electrode, or a multi-electrode active material electrode containing polypyrrole.

6. The method for improving the capacity of a polypyrrole electrode according to claim 5, characterized in that: The pure polypyrrole electrode is made of polypyrrole powder; the rigid polypyrrole electrode is obtained by electrodepositing polypyrrole onto a rigid metal or conductive glass substrate, or by first preparing a conductive slurry from polypyrrole powder with an adhesive and carbon black and then coating it onto a rigid metal or conductive glass substrate; the flexible polypyrrole electrode is obtained by loading polypyrrole onto a polymer film material or aerogel framework material as a substrate, wherein the polymer film material is a fiber material, hydrogel material, or rubber; the multi-element active material electrode containing polypyrrole is a composite electrode containing one or more active materials in addition to polypyrrole, such as carbon materials, conductive polymers, metal oxides, metal sulfides, metal hydroxides, organometallic frameworks, and covalent organic frameworks.

7. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: The electrolyte is a NaCl solution or a KCl solution, and the concentration range of the NaCl solution or KCl solution is 0.01-4.5 mol / L.

8. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: The electrolyte is a K2SO4 solution or a Na2SO4 solution, and the concentration range of the K2SO4 solution or Na2SO4 solution is 0.01-2.25 mol / L.

9. The method for improving the capacity of a polypyrrole electrode according to claim 1, characterized in that: The electrolyte is a mixture of NaCl and KCl solutions, with the concentration of each ion in the electrolyte ranging from 0.01 to 4.5 mol / L.

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