Method for evaluating doping effect of active carbon electrode material modifier of supercapacitor

Abstract

The invention relates to a supercapacitor active carbon electrode material modifier doping effect evaluation method, which comprises the following steps: acquiring the specific surface area of active carbon prepared under a first working condition and a second working condition, the specific capacitance of the active carbon in a two-electrode system and the specific capacitance of the active carbon in a three-electrode system, calculating a two-electrode system index and a 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 that the doping effect meets the condition, and otherwise, adopting other modifiers; calculating a 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 a 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 modifier doping effects, and in particular to a method for evaluating the doping effects of modifiers for activated carbon electrode materials of supercapacitors. Background Art

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

[0003] At present, in the process of using modifiers for doping modification, researchers cannot quickly and accurately evaluate the doping effect. The doping effect is usually measured by the performance of the final product, but this cannot guarantee the doping effect under different preparation conditions. This leads to the problem of how to quickly select suitable modifiers 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 a supercapacitor activated carbon electrode material, the method comprising: S1: In the process of preparing the activated carbon electrode material for 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 adding any one or more modifiers for doping on the basis of the first working condition is taken as the second working condition; S2: obtaining the specific surface area of ​​the activated carbon prepared under the first working condition and the second working condition and the specific capacitance in the two-electrode system and the specific capacitance in the 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; S3: Preliminarily judge the doping effect of the modifier based on the two-electrode system index and the three-electrode system index, and retain the activated carbon prepared under the working conditions where the doping effect meets the conditions, otherwise return to S1 to use other modifiers; S4: For the activated carbon prepared under the reserved working condition, the polarization loss rate of the activated carbon between the two electrode systems is calculated based on the two-electrode system index and the three-electrode system index, and then the effective specific surface area of ​​the activated carbon under the second working condition is calculated based on the specific surface areas of the activated carbon prepared under the first working condition and the second working condition; S5: Based on the specific surface area and effective specific surface area of ​​the activated carbon under the second working condition, the capacitance contribution rate is calculated; based on the capacitance contribution rate, the final doping effect of the modifier is judged, and there is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

[0005] Preferably, the calculation formula of the three-electrode system index of activated carbon under the second working condition is: ; in, represents the three-electrode system index of activated carbon under the mth 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 mth 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 mth second working condition in the three-electrode system.

[0006] Preferably, the calculation formula of the two-electrode system index of activated carbon under the second working condition is: ; in, represents the two-electrode system index of activated carbon under the mth 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 mth second working condition; represents the specific capacitance of the activated carbon prepared under the i-th first working condition in the two-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

[0007] Preferably, S3 includes: The contribution of the sacrificial specific surface area of ​​activated carbon to the specific capacitance under the second working condition is calculated based on the two-electrode system index and the three-electrode system index; When the contribution degree is greater than or equal to 1, the activated carbon prepared under the corresponding second working condition is retained; Otherwise, return to S1 to use other modifiers.

[0008] Preferably, the calculation formula for the contribution degree is: ; Wherein, AB represents the contribution of the sacrificed specific surface area of ​​activated carbon to the specific capacitance under the second working condition; m represents the number of the second working condition; represents the three-electrode system index of activated carbon under the mth second working condition; Represents the two-electrode system index of activated carbon under the mth second working condition.

[0009] Preferably, the calculation formula for the polarization loss rate is: ; in, represents the polarization loss rate of the activated carbon prepared under the mth second working condition between the two electrode systems; represents the specific capacitance of the activated carbon prepared under the mth second working condition in the three-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

[0010] Preferably, the calculation formula for the effective specific surface area is: ; in, represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition, wherein the effective specific surface area is the portion of the specific surface area that can provide charge storage; represents the three-electrode system index of activated carbon under the mth second working condition; represents the two-electrode system index of activated carbon under the mth second working condition; represents the polarization loss rate of the activated carbon prepared under the mth 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 mth second working condition.

[0011] Preferably, the capacitance contribution rate is calculated as: ; ; in, represents the capacitance contribution rate of the modifier used in the mth second operating condition; represents the average effective specific surface area of ​​the activated carbon prepared under m second working conditions; represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition; represents the specific surface area of ​​the activated carbon prepared under the mth second operating condition; m represents the number of second operating conditions.

[0012] Beneficial effects: This method can realize 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 trial and error costs, and help researchers further understand the modification and doping mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 This is a flow chart of a method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode materials in an embodiment of the present application. DETAILED DESCRIPTION

[0015] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0016] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0017] like Figure 1 As shown, this embodiment provides a method for evaluating the doping effect of a modifier for a supercapacitor activated carbon electrode material, the method comprising: S1: In the process of preparing supercapacitor activated carbon electrode materials, the working condition of adding only any one activator for preparation is taken 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 taken as the second working condition.

[0018] In this embodiment, the activating agent is KOH.

[0019] S2: Obtain the specific surface area of ​​the activated carbon prepared under the first working condition and the second working condition and its specific capacitance in the two-electrode system and the 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.

[0020] Specifically, the calculation formula of the three-electrode system index of activated carbon under the second working condition is: ; in, represents the three-electrode system index of activated carbon under the mth 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 mth 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 mth second working condition in the three-electrode system.

[0021] The calculation formula of the two-electrode system index of activated carbon under the second working condition is: ; in, represents the two-electrode system index of activated carbon under the mth 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 mth second working condition; represents the specific capacitance of the activated carbon prepared under the i-th first working condition in the two-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

[0022] S3: Preliminarily judge the doping effect of the modifier based on the two-electrode system index and the three-electrode system index, and retain the activated carbon prepared under the working conditions where the doping effect meets the conditions, otherwise return to S1 to use other modifiers.

[0023] Specifically, the contribution of the sacrificial specific surface area of ​​the activated carbon to the specific capacitance under the second working condition is calculated based on the two-electrode system index and the three-electrode system index; When the contribution degree is greater than or equal to 1, the activated carbon prepared under the corresponding second working condition is retained; Otherwise, return to S1 to use other modifiers.

[0024] Furthermore, the calculation formula for the contribution degree is: ; Wherein, AB represents the contribution of the sacrificed specific surface area of ​​activated carbon to the specific capacitance under the second working condition; m represents the number of the second working condition; represents the three-electrode system index of activated carbon under the mth second working condition; Represents the two-electrode system index of activated carbon under the mth second working condition.

[0025] S4: For the activated carbon prepared under the retention condition, the polarization loss rate of the activated carbon between the two electrode systems is calculated based on the two-electrode system index and the three-electrode system index, and then the effective specific surface area of ​​the activated carbon under the second working condition is calculated based on the specific surface areas of the activated carbon prepared under the first working condition and the second working condition.

[0026] Specifically, the calculation formula for the polarization loss rate is: ; in, represents the polarization loss rate of the activated carbon prepared under the mth second working condition between the two electrode systems; represents the specific capacitance of the activated carbon prepared under the mth second working condition in the three-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

[0027] For the same activated carbon electrode material, the specific capacitance in a two-electrode system will differ from that in a three-electrode system due to polarization. Therefore, in this embodiment, the polarization loss rate is used to represent the ratio of the difference to the specific capacitance in the three-electrode system.

[0028] Furthermore, the calculation formula of the effective specific surface area is: ; in, represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition; represents the three-electrode system index of activated carbon under the mth second working condition; represents the two-electrode system index of activated carbon under the mth second working condition; represents the polarization loss rate of the activated carbon prepared under the mth 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 mth second working condition.

[0029] It is worth noting that the larger the specific surface area of ​​the activated carbon material, the more charge it can store (i.e., the larger the specific capacitance), but it cannot be said that the larger the specific surface area, the larger the specific capacitance; the reason is that heteroatom doping can enhance the material's ability to accumulate charges, so there are activated carbon materials with small specific surface areas, but their specific capacitance is indeed larger, and this situation generally occurs. 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 specific capacitance of the activated carbon electrode material.

[0030] S5: Based on the specific surface area and effective specific surface area of ​​the activated carbon under the second working condition, the capacitance contribution rate is calculated; based on the capacitance contribution rate, the final doping effect of the modifier is judged, and there is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

[0031] Specifically, the calculation formula for the capacitance contribution rate is: ; ; in, represents the capacitance contribution rate of the modifier used in the mth second operating condition; represents the average effective specific surface area of ​​the activated carbon prepared under m second working conditions; represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition; represents the specific surface area of ​​the activated carbon prepared under the mth second operating condition; m represents the number of second operating conditions.

[0032] The ratio of the effective specific surface area to the specific surface area is taken as the capacitance contribution rate of the modifier to the working condition. The larger the value of the capacitance contribution rate, the better the effect of the corresponding modifier on improving the electrochemical properties of activated carbon, that is, the better the doping effect of the corresponding modifier is.

[0033] In order to verify the accuracy of evaluating the modifier by capacitance contribution rate, a comparative experiment was conducted. The working conditions used in the comparative experiment are shown in Table 1; Table 1 is the working condition parameter table;

[0034] For the above 7 second working conditions, the capacitance contribution rate is calculated by the method provided in this embodiment. , the calculation results are shown in Table 2; Table 2 is a calculation table of capacitance contribution rates of seven second working conditions;

[0035] It can be seen from Table 2 that the capacitance contribution rate of urea is the highest among the seven working conditions compared with other modifiers, which is 43%. That is, the doping effect of urea is better than that of other modifiers. The method provided in this embodiment can quickly and accurately determine the doping effect of the modifier.

[0036] The method for evaluating the doping effect of modifiers on supercapacitor activated carbon electrode materials provided in this embodiment can realize 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 trial and error costs, and help researchers further understand the modification and doping mechanism.

[0037] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode materials, characterized in that: include: S1: In the process of preparing the activated carbon electrode material for 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 adding any one or more modifiers for doping on the basis of the first working condition is taken as the second working condition; S2: obtaining the specific surface area of ​​the activated carbon prepared under the first working condition and the second working condition and the specific capacitance in the two-electrode system and the specific capacitance in the 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; S3: Preliminarily judge the doping effect of the modifier based on the two-electrode system index and the three-electrode system index, and retain the activated carbon prepared under the working conditions where the doping effect meets the conditions, otherwise return to S1 to use other modifiers; S4: For the activated carbon prepared under the reserved working condition, the polarization loss rate of the activated carbon between the two electrode systems is calculated based on the two-electrode system index and the three-electrode system index, and then the effective specific surface area of ​​the activated carbon under the second working condition is calculated based on the specific surface areas of the activated carbon prepared under the first working condition and the second working condition; S5: Based on the specific surface area and effective specific surface area of ​​the activated carbon under the second working condition, the capacitance contribution rate is calculated; based on the capacitance contribution rate, the final doping effect of the modifier is judged, and there is a positive correlation between the final doping effect of the modifier and the value of the capacitance contribution rate.

2. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: The calculation formula of the three-electrode system index of activated carbon under the second working condition is: ； in, represents the three-electrode system index of activated carbon under the mth 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 mth 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 mth second working condition in the three-electrode system.

3. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: The calculation formula of the two-electrode system index of activated carbon under the second working condition is: ； in, represents the two-electrode system index of activated carbon under the mth 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 mth second working condition; represents the specific capacitance of the activated carbon prepared under the i-th first working condition in the two-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

4. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: S3 includes: The contribution of the sacrificial specific surface area of ​​activated carbon to the specific capacitance under the second working condition is calculated based on the two-electrode system index and the three-electrode system index; When the contribution degree is greater than or equal to 1, the activated carbon prepared under the corresponding second working condition is retained; Otherwise, return to S1 to use other modifiers.

5. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 4, characterized in that: The calculation formula for contribution degree is: ； Wherein, AB represents the contribution of the sacrificed specific surface area of ​​activated carbon to the specific capacitance under the second working condition; m represents the number of the second working condition; represents the three-electrode system index of activated carbon under the mth second working condition; Represents the two-electrode system index of activated carbon under the mth second working condition.

6. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: The calculation formula of polarization loss rate is: ； in, represents the polarization loss rate of the activated carbon prepared under the mth second working condition between the two electrode systems; represents the specific capacitance of the activated carbon prepared under the mth second working condition in the three-electrode system; It represents the specific capacitance of the activated carbon prepared under the mth second working condition in the two-electrode system.

7. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: The calculation formula for the effective specific surface area is: ； in, represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition, wherein the effective specific surface area is the portion of the specific surface area that can provide charge storage; represents the three-electrode system index of activated carbon under the mth second working condition; represents the two-electrode system index of activated carbon under the mth second working condition; represents the polarization loss rate of the activated carbon prepared under the mth 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 mth second working condition.

8. The method for evaluating the doping effect of a modifier for supercapacitor activated carbon electrode material according to claim 1, characterized in that: The calculation formula for capacitance contribution is: ； ； in, represents the capacitance contribution rate of the modifier used in the mth second operating condition; represents the average effective specific surface area of ​​the activated carbon prepared under m second working conditions; represents the effective specific surface area of ​​the activated carbon prepared under the mth second working condition; represents the specific surface area of ​​the activated carbon prepared under the mth second operating condition; m represents the number of second operating conditions.

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