An Evaluation Method for the Doping Effect of Modifiers on Supercapacitor Activated Carbon Electrode Materials

Abstract

The present application relates to a method for evaluating the doping effect of a modifier for a supercapacitor activated carbon electrode material, including: obtaining the specific surface area of activated carbon prepared under a first working condition and a second working condition, its specific capacitance in a two-electrode system, and its specific capacitance in a three-electrode system, and calculating the two-electrode system index and the three-electrode system index of the activated carbon under the second working condition; preliminarily judging the doping effect of the modifier based on the two-electrode system index and the three-electrode system index, retaining the activated carbon prepared under the working condition where the doping effect meets the conditions, otherwise using other modifiers; calculating the polarization loss rate based on the two-electrode system index and the three-electrode system index, and further calculating the effective specific surface area of the activated carbon under the second working condition based on the specific surface area of the activated carbon prepared under the first working condition and the second working condition; calculating the capacitance contribution rate based on the specific surface area and the effective specific surface area of the activated carbon under the second working condition; and judging the final doping effect of the modifier based on the capacitance contribution rate.

Description

Technical Field

[0001] The present application relates to the technical field of doping effects of modifiers, and particularly to a method for evaluating the doping effect of a modifier for an activated carbon electrode material of a supercapacitor. Background Art

[0002] Supercapacitors have characteristics such as high energy density, high stability, and long cycle life, and are a hot topic in the field of energy storage. The electrode material is the key to affecting the performance of the capacitor, and activated carbon is a porous structure material. Its special pores and high specific surface area can improve its electrochemical performance. Activated carbon with a higher specific surface area has richer pores, which can provide more active sites to store charges, increasing the specific capacitance of the capacitor. However, after the specific surface area reaches a certain value, the improvement of the specific capacitance is very small because the difference in conductivity causes some active sites to be unable to adsorb electrons. Blindly increasing the specific surface area will only make the part that cannot adsorb electrons larger. Therefore, many researchers use modifiers containing heteroatoms such as N, P, O, and S for doping to improve the wettability of the surface of the activated carbon material and increase the electron adsorption rate.

[0003] Currently, during the process of doping modification using modifiers, researchers cannot quickly and accurately evaluate the doping effect. Usually, the performance of the final product is used to measure the doping effect, but this cannot guarantee the doping effect under different preparation conditions, which leads to the problem of how to quickly select a suitable modifier during the research process. Summary of the Invention

[0004] Based on this, it is necessary to provide a method for evaluating the doping effect of a modifier for an activated carbon electrode material of a supercapacitor, and this method includes:

[0005] S1: During the preparation of the activated carbon electrode material of the supercapacitor, the working condition of preparing by adding only any one activator is used as the first working condition, and the working condition of adding any one or more modifiers for doping on the basis of the first working condition is used as the second working condition;

[0006] S2: Obtain the specific surface area of the activated carbon prepared under the first working condition and the second working condition, its specific capacitance in the two-electrode system, and its specific capacitance in the three-electrode system, and calculate the two-electrode system index and the three-electrode system index of the activated carbon under the second working condition;

[0007] S3: Based on the two-electrode system index and the three-electrode system index, preliminarily judge the doping effect of the modifier, retain the activated carbon prepared under the working condition where the doping effect meets the conditions, otherwise return to S1 and use other modifiers;

[0008] S4: For the activated carbon prepared under the retention condition, calculate the polarization loss rate of the activated carbon between the two electrode systems based on the two - electrode system index and the three - electrode system index, and then calculate the effective specific surface area of the activated carbon under the second condition based on the specific surface areas of the activated carbon prepared under the first condition and the second condition.

[0009] S5: Based on the specific surface area and the effective specific surface area of the activated carbon under the second condition, calculate the capacitance contribution rate; judge the final doping effect of the modifier based on the capacitance contribution rate, and there is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

[0010] Preferably, the calculation formula for the three - electrode system index of the activated carbon under the second condition is:

[0011] ;

[0012] Among them, represents the three - electrode system index of the activated carbon under the m - th second condition; represents the specific surface area of the activated carbon prepared under the i - th first condition; represents the specific surface area of the activated carbon prepared under the m - th second condition; represents the specific capacitance of the activated carbon prepared under the i - th first condition in the three - electrode system; represents the specific capacitance of the activated carbon prepared under the m - th second condition in the three - electrode system.

[0013] Preferably, the calculation formula for the two - electrode system index of the activated carbon under the second condition is:

[0014] ;

[0015] Among them, represents the two - electrode system index of the activated carbon under the m - th second condition; represents the specific surface area of the activated carbon prepared under the i - th first condition; represents the specific surface area of the activated carbon prepared under the m - th second condition; represents the specific capacitance of the activated carbon prepared under the i - th first condition in the two - electrode system; represents the specific capacitance of the activated carbon prepared under the m - th second condition in the two - electrode system.

[0016] Preferably, in S3, it includes:

[0017] Calculate the contribution degree of the sacrificed specific surface area of the activated carbon under the second condition to the specific capacitance based on the two - electrode system index and the three - electrode system index;

[0018] When the contribution degree is greater than or equal to 1, retain the activated carbon prepared under the corresponding second condition;

[0019] Otherwise, return to S1 and use other modifiers.

[0020] Preferably, the calculation formula for the contribution degree is:

[0021] ;

[0022] where AB represents the contribution degree of the specific surface area sacrificed by the activated carbon to the specific capacitance under the second working condition; m represents the number of the second working conditions; represents the three - electrode system index of the activated carbon under the m - th second working condition; represents the two - electrode system index of the activated carbon under the m - th second working condition.

[0023] Preferably, the calculation formula for the polarization loss rate is:

[0024] ;

[0025] where represents the polarization loss rate of the activated carbon prepared under the m - th second working condition between the two electrode systems; represents the specific capacitance of the activated carbon prepared under the m - th second working condition in the three - electrode system; represents the specific capacitance of the activated carbon prepared under the m - th second working condition in the two - electrode system.

[0026] Preferably, the calculation formula for the effective specific surface area is:

[0027] ;

[0028] where represents the effective specific surface area of the activated carbon prepared under the m - th second working condition, and the effective specific surface area is the part of the specific surface area that can provide charge storage; represents the three - electrode system index of the activated carbon under the m - th second working condition; represents the two - electrode system index of the activated carbon under the m - th second working condition; represents the polarization loss rate of the activated carbon prepared under the m - th second working condition between the two electrode systems; represents the specific surface area of the activated carbon prepared under the i - th first working condition; represents the specific surface area of the activated carbon prepared under the m - th second working condition.

[0029] Preferably, the calculation formula for the capacitance contribution rate is:

[0030] ;

[0031] ;

[0032] where It represents the capacitance contribution rate of the modifier used under the m-th second working condition; It represents the average value of the effective specific surface area of the activated carbon prepared under the m second working conditions; It represents the effective specific surface area of the activated carbon prepared under the m-th second working condition; It represents the specific surface area of the activated carbon prepared under the m-th second working condition; m represents the number of second working conditions.

[0033] Beneficial effects: This method can achieve the quantitative evaluation of the doping effect of the modifier, which can bring great benefits to the preparation of activated carbon electrode materials. It can not only stably prepare high-performance electrode materials, but also save the cost of trial and error, and help researchers further understand the doping mechanism. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 It is a flowchart of the method for evaluating the doping effect of the modifier of the activated carbon electrode material of the supercapacitor in the embodiment of the present application. Detailed Embodiments

[0036] In order to make the above objects, features and advantages of the present application more obvious and understandable, the following will describe the detailed embodiments of the present application with reference to the drawings. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0037] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0038] As Figure 1 shown, this embodiment provides a method for evaluating the doping effect of the modifier of the activated carbon electrode material of the supercapacitor. The method includes:

[0039] S1: During the preparation of the activated carbon electrode material for the supercapacitor, the working condition of adding only any one activating agent for preparation is taken as the first working condition, and the working condition of doping by adding any one or more modifying agents on the basis of the first working condition is taken as the second working condition.

[0040] In this embodiment, the activating agent is KOH.

[0041] S2: Obtain the specific surface area of the activated carbon prepared under the first working condition and the second working condition, its specific capacitance in the two-electrode system, and its specific capacitance in the three-electrode system, and calculate the two-electrode system index and the three-electrode system index of the activated carbon under the second working condition.

[0042] Specifically, the calculation formula for the three-electrode system index of the activated carbon under the second working condition is:

[0043] ;

[0044] Among them, represents the three-electrode system index of the activated carbon under the m-th second working condition; represents the specific surface area of the activated carbon prepared under the i-th first working condition; represents the specific surface area of the activated carbon prepared under the m-th second working condition; represents the specific capacitance of the activated carbon prepared under the i-th first working condition in the three-electrode system; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in the three-electrode system.

[0045] The calculation formula for the two-electrode system index of the activated carbon under the second working condition is:

[0046] ;

[0047] Among them, represents the two-electrode system index of the activated carbon under the m-th second working condition; represents the specific surface area of the activated carbon prepared under the i-th first working condition; represents the specific surface area of the activated carbon prepared under the m-th second working condition; represents the specific capacitance of the activated carbon prepared under the i-th first working condition in the two-electrode system; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in the two-electrode system.

[0048] S3: Based on the two-electrode system index and the three-electrode system index, preliminarily judge the doping effect of the modifying agent, retain the activated carbon prepared under the working condition where the doping effect meets the conditions, otherwise return to S1 and use other modifying agents.

[0049] Specifically, based on the two-electrode system index and the three-electrode system index, calculate the contribution degree of the specific surface area sacrificed by the activated carbon to the specific capacitance under the second working condition;

[0050] When the contribution degree is greater than or equal to 1, retain the activated carbon prepared under the corresponding second working condition;

[0051] Otherwise, return to S1 and use other modifiers.

[0052] Furthermore, the calculation formula for the contribution degree is:

[0053] ;

[0054] where AB represents the contribution degree of the specific surface area sacrificed by the activated carbon to the specific capacitance under the second working condition; m represents the number of the second working conditions; represents the three-electrode system index of the activated carbon under the m-th second working condition; represents the two-electrode system index of the activated carbon under the m-th second working condition.

[0055] S4: For the activated carbon prepared under the retained working conditions, based on the two-electrode system index and the three-electrode system index, calculate the polarization loss rate of the activated carbon between the two electrode systems, and then based on the specific surface areas of the activated carbon prepared under the first working condition and the second working condition, calculate the effective specific surface area of the activated carbon under the second working condition.

[0056] Specifically, the calculation formula for the polarization loss rate is:

[0057] ;

[0058] where represents the polarization loss rate of the activated carbon prepared under the m-th second working condition between the two electrode systems; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in the three-electrode system; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in the two-electrode system.

[0059] For the same activated carbon electrode material, due to polarization, the specific capacitance in the two-electrode system will have a difference from the specific capacitance in the three-electrode system. Therefore, in this embodiment, the polarization loss rate represents the ratio of this difference to the specific capacitance in the three-electrode system.

[0060] Furthermore, the calculation formula for the effective specific surface area is:

[0061] ;

[0062] where represents the effective specific surface area of the activated carbon prepared under the m-th second working condition; It represents the three - electrode system index of activated carbon under the m - th second working condition; It represents the two - electrode system index of activated carbon under the m - th second working condition; It represents the polarization loss rate of the activated carbon prepared under the m - th second working condition between the two electrode systems; It represents the specific surface area of the activated carbon prepared under the i - th first working condition; It represents the specific surface area of the activated carbon prepared under the m - th second working condition.

[0063] It should be noted that the larger the specific surface area of the activated carbon material, the more electric charge it stores (i.e., the larger the specific capacitance). However, it cannot be said that the larger the specific surface area, the larger the specific capacitance. The reason is that heteroatom doping can improve the charge aggregation ability of the material. Therefore, there are cases where activated carbon materials with a small specific surface area have a larger specific capacitance, and this situation occurs commonly. Therefore, it is necessary to study the part of the specific surface area that can provide charge storage. In this embodiment, the effective specific surface area is used as the part of the specific surface area that can provide charge storage, which characterizes the pore structure and the specific capacitance of the activated carbon electrode material.

[0064] S5: Based on the specific surface area and the effective specific surface area of the activated carbon under the second working condition, calculate the capacitance contribution rate; judge the final doping effect of the modifier based on the capacitance contribution rate. There is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

[0065] Specifically, the calculation formula of the capacitance contribution rate is:

[0066] ;

[0067] ;

[0068] Among them, It represents the capacitance contribution rate of the modifier used under the m - th second working condition; It represents the average value of the effective specific surface area of the activated carbon prepared under the m second working conditions; It represents the effective specific surface area of the activated carbon prepared under the m - th second working condition; It represents the specific surface area of the activated carbon prepared under the m - th second working condition; m represents the number of the second working conditions.

[0069] Taking the ratio of the effective specific surface area to the specific surface area as the capacitance contribution rate of the modifier to the working condition, the larger the value of the capacitance contribution rate, the better the improvement effect of the corresponding modifier on the electrochemical performance of the activated carbon, that is, the better the doping effect of the corresponding modifier.

[0070] To verify the accuracy of evaluating the modifier through the capacitance contribution rate, a comparative experiment was carried out. The working condition parameters used in the comparative experiment are shown in Table 1;

[0071] Table 1 is the parameter table of working conditions;

[0072]

[0073] For the above 7 second working conditions, the capacitance contribution rate is calculated respectively by the method provided in this embodiment , and the calculation results are shown in Table 2;

[0074] Table 2 is the calculation table of the capacitance contribution rate of 7 second working conditions;

[0075]

[0076] It can be seen from Table 2 that the capacitance contribution rate of urea is the highest among other modifiers in 7 working conditions, which is 43%, that is, the doping effect of urea is better than that of other modifiers. Through the method provided in this embodiment, the doping effect of the modifier can be judged quickly and accurately.

[0077] The method for evaluating the doping effect of the modifier of the activated carbon electrode material of the supercapacitor provided in this embodiment can realize the quantitative evaluation of the doping effect of the modifier, which can bring great convenience to the preparation of the activated carbon electrode material. It can not only stably prepare high-performance electrode materials, but also save the cost of trial and error, and help researchers further understand the doping mechanism.

[0078] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0079] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for evaluating the doping effect of a modifier on a supercapacitor activated carbon electrode material, characterized in that Including: S1: In the preparation process of the activated carbon electrode material for supercapacitors, the working condition of adding only any one activator for preparation is taken as the first working condition, and the working condition of doping by adding any one or more modifiers on the basis of the first working condition is taken as the second working condition; S2: Obtain the specific surface area of the activated carbon prepared under the first working condition and the second working condition, its specific capacitance in the two-electrode system, and its specific capacitance in the three-electrode system, and calculate the two-electrode system index and the three-electrode system index of the activated carbon under the second working condition; The calculation formula for the three-electrode system index of the activated carbon under the second working condition is: ； Among them, represents the three - electrode system index of activated carbon under the m - th second working condition; represents the specific surface area of the activated carbon prepared under the i - th first working condition; represents the specific surface area of the activated carbon prepared under the m - th second working condition; represents the specific capacitance of the activated carbon prepared under the i - th first working condition in the three - electrode system; represents the specific capacitance of the activated carbon prepared under the m - th second working condition in the three - electrode system; The calculation formula for the two-electrode system index of the activated carbon under the second working condition is: ； Among them, represents the two - electrode system index of activated carbon under the m - th second working condition; represents the specific surface area of the activated carbon prepared under the i - th first working condition; represents the specific surface area of the activated carbon prepared under the m - th second working condition; represents the specific capacitance of the activated carbon prepared under the i - th first working condition in the two - electrode system; represents the specific capacitance of the activated carbon prepared under the m - th second working condition in the two - electrode system; S3: Based on the two-electrode system index and the three-electrode system index, preliminarily judge the doping effect of the modifier, retain the activated carbon prepared under the working condition where the doping effect meets the conditions, otherwise return to S1 and use other modifiers; S4: For the activated carbon prepared under the retained working condition, calculate the polarization loss rate of the activated carbon between the two electrode systems based on the two-electrode system index and the three-electrode system index, and then calculate the effective specific surface area of the activated carbon under the second working condition based on the specific surface areas of the activated carbon prepared under the first working condition and the second working condition; The calculation formula for the effective specific surface area is: ； Among them, represents the effective specific surface area of the activated carbon prepared under the m-th second working condition, and the effective specific surface area is the part of the specific surface area that can provide charge storage; represents the three-electrode system index of the activated carbon under the m-th second working condition; represents the two-electrode system index of the activated carbon under the m-th second working condition; represents the polarization loss rate of the activated carbon prepared under the m-th second working condition between the two electrode systems; represents the specific surface area of the activated carbon prepared under the i-th first working condition; represents the specific surface area of the activated carbon prepared under the m-th second working condition; S5: Calculate the capacitance contribution rate based on the specific surface area and the effective specific surface area of the activated carbon under the second working condition; the calculation formula for the capacitance contribution rate is: ； ； Among them, represents the capacitance contribution rate of the modifier used under the m-th second working condition; represents the average value of the effective specific surface area of the activated carbon prepared under the m second working conditions; represents the effective specific surface area of the activated carbon prepared under the m-th second working condition; represents the specific surface area of the activated carbon prepared under the m-th second working condition; m represents the number of second working conditions; the final doping effect of the modifier is judged based on the capacitance contribution rate, and there is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

2. The evaluation method for the doping effect of the modifier of the supercapacitor activated carbon electrode material according to claim 1, characterized in that In S3, including: Calculate the contribution degree of the sacrificed specific surface area of the activated carbon under the second working condition to the specific capacitance based on the two-electrode system index and the three-electrode system index; When the contribution degree is greater than or equal to 1, retain the activated carbon prepared under the corresponding second working condition; Otherwise, return to S1 and use other modifiers.

3. The evaluation method for the doping effect of the modifier of the supercapacitor activated carbon electrode material according to claim 2, characterized in that The calculation formula for the contribution degree is: ； Among them, AB represents the contribution degree of the specific surface area sacrificed by activated carbon to the specific capacitance under the second working condition; m represents the number of the second working conditions; represents the three-electrode system index of the activated carbon under the m-th second working condition; represents the two-electrode system index of the activated carbon under the m-th second working condition.

4. The evaluation method for the doping effect of the modifier of the supercapacitor activated carbon electrode material according to claim 1, wherein The calculation formula for the polarization loss rate is: ； Among them, represents the polarization loss rate of the activated carbon prepared under the m-th second working condition between two electrode systems; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in a three-electrode system; represents the specific capacitance of the activated carbon prepared under the m-th second working condition in a two-electrode system.

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