CN114709084A

CN114709084A - Electrode based on construction of porous carbon skeleton in wood tracheid, preparation method and supercapacitor

Info

Publication number: CN114709084A
Application number: CN202210418254.XA
Authority: CN
Inventors: 罗勇锋; 欧阳杰; 王小满; 周璀; 陈洪
Original assignee: Central South University of Forestry and Technology
Current assignee: Central South University of Forestry and Technology
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-07-05
Anticipated expiration: 2042-04-21

Abstract

An electrode based on a porous carbon skeleton constructed in a wood tracheid comprises a carbonized wood sheet substrate, wherein a tracheid structure is arranged in the carbonized wood sheet substrate, and the porous carbon skeleton is constructed in the tracheid structure of the carbonized wood sheet through a glucose and sodium chloride template; the concentration of glucose is 3-5 mol/L, and the concentration of sodium chloride is 1-3 mol/L. In the invention, a three-dimensional porous carbon structure is constructed inside the wood derived carbon tube cell by utilizing the abundant functional groups on the surface of the pre-carbonized wood. After the potassium hydroxide etching, the structure and the hydrophilicity of the E-PCS @ WC electrode are greatly improved. The electrode has high hydrophilicity, high volume energy density and excellent cycling stability.

Description

Electrode based on construction of porous carbon skeleton in wood tracheid, preparation method and supercapacitor

Technical Field

The invention relates to an electrode material, in particular to an electrode for a super capacitor based on construction of a porous carbon skeleton in a wood tracheid and a preparation method thereof.

Background

The Super Capacitor (SC) is a green energy storage device and has the advantages of stable electrochemical performance, long service life, high charge-discharge rate, high power density, convenience in manufacturing and the like. Among them, the electrode material is the core component of SC, and the carbon electrode materials (such as activated carbon, carbon aerogel, carbon nanotube and graphene) adopted in the current commercialization have high specific surface area, but their specific capacity is far from ideal. Meanwhile, for such carbon electrode materials, the thickness of the electrode is increased along with the increase of the active substance, the rate performance and the structural stability are poor, and the further improvement of the capacitance performance of the material is limited. Therefore, the establishment of a stable three-dimensional porous carbon skeleton with good pore distribution realizes high-speed charge transfer and rapid dynamic ion transmission, and is the key for obtaining the high-performance SC electrode.

The natural wood can retain the three-dimensional oriented carbon skeleton inherent in the wood tracheids after carbonization. The wood-derived carbon retains the structure and simultaneously shows excellent conductivity and structural stability, and has the advantage of being unique as a self-supporting electrode material of a super capacitor. Has been reported in the literature using MnO₂、Co(OH)₂And polypyrrole and other active substances are used for filling tracheids of basswood, poplar and paulownia wood to prepare a series of SC electrodes. On the basis, the needle leaf wood processing residue is taken as a base material, and a series of high-performance SC electrode materials are developed, wherein the high-performance SC electrode materials comprise wood derived carbon with a chemical method, active substances with a core-shell structure and the like. However, the wood tracheid cavities account for about 80% of the volume, so the above studies have low utilization of both the space of the tracheids and the active substances.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a supercapacitor electrode based on the construction of a porous carbon skeleton in a wood tracheid, which has high hydrophilicity, high volume energy density and excellent cycling stability, and a preparation method thereof.

In order to solve the technical problems, the technical scheme provided by the invention is as follows: an electrode based on a porous carbon skeleton constructed in a wood tracheid comprises a carbonized wood sheet substrate, wherein a tracheid structure is arranged in the carbonized wood sheet substrate, and the porous carbon skeleton is constructed in the tracheid structure of the carbonized wood sheet through a glucose and sodium chloride template; the concentration of the glucose is 3-5 mol/L, and the concentration of the sodium chloride is 1-3 mol/L.

Preferably, the carbonized wood chips with the porous carbon skeletons built are etched by potassium hydroxide; the concentration of the potassium hydroxide is 1mol/L-3 mol/L.

The preparation method of the electrode based on the construction of the porous carbon skeleton in the wood tracheid comprises the following steps:

1) cutting the wood chips with the tracheid structure into preset sizes;

2) pre-carbonizing wood chips in a drying oven

3) Soaking the pre-carbonized wood chips in a mixed solution of 3-5 mol/L glucose and 1-3 mol/L sodium chloride, and vacuum soaking for more than 10 hours;

4) drying the wood chips soaked in the step 3), calcining and carbonizing under the protection of inert gas, wherein the calcining temperature is 300-850 ℃, and the calcining time is 2-6 hours; washing with deionized water after calcination; the electrode obtained in step 4) is marked as PCS @ WC.

5) Putting the wood chips obtained in the step 4) into a potassium hydroxide solution, wherein the concentration of potassium hydroxide is 1-3 mol/L, soaking for 2-6 hours in vacuum, and drying;

6) calcining the wood chips obtained in the step 5) for 1-3 hours under the protection of inert gas, wherein the calcining temperature is 650-850 ℃;

7) washing the excessive potassium hydroxide on the wood chips by using HCl solution, and washing the wood chips to be neutral by using deionized water, wherein the concentration of the HCl solution is 3-6 mol/L; and obtaining an electrode based on the construction of a porous carbon skeleton in the wood tracheid, and marking the electrode as E-PCS @ WC.

In the preparation method of the electrode based on the construction of the porous carbon skeleton in the wood tracheid, the pre-carbonization temperature is preferably 200-300 ℃, and the time is preferably 3-6 hours.

In the above preparation method for constructing the electrode with the porous carbon skeleton in the wood tracheid, preferably, the mass ratio of the carbonized wood chips put into the potassium hydroxide solution in the step 5) to the potassium hydroxide solution is 1: 3.

A super capacitor comprises the electrode based on the construction of the porous carbon skeleton in the wood tracheid.

Compared with the prior art, the invention has the advantages that: according to the invention, a three-dimensional porous carbon structure is constructed in the wood derived carbon tube cell by utilizing abundant functional groups on the surface of the pre-carbonized wood. After the potassium hydroxide etching, the structure and the hydrophilicity of the E-PCS @ WC electrode are greatly improved. The electrode has high hydrophilicity, high volume energy density and excellent cycle stability. At a current density of 5mAcm⁻²The area/volume capacitance of the E-PCS @ WC electrode is 7.29Fcm⁻²/145.8Fcm⁻³. E-PCS @ WC// E-PCS @ WC SSC device with power density of 2.5mW cm⁻²The area/volume capacity and the volume energy density were 1.75Fcm, respectively⁻²/34.99Fcm⁻³And 4.86mWhcm⁻³. At 50mAcm⁻³The capacity retention ratio of 20000 cycles is 98.5%.

Drawings

FIG. 1 is a flow chart of the preparation of the E-PCS @ WC electrode.

FIG. 2 is a top SEM image of WC wood chips

Fig. 3 is a cross-sectional SEM image of WC wood chips.

Fig. 4 is an enlarged SEM image of a cross section of WC wood chips.

Fig. 5 is a further enlarged SEM image of a cross section of WC wood chips.

FIG. 6 is a top SEM image of a PCS @ WC electrode.

FIG. 7 is an enlarged top SEM image of a PCS @ WC electrode.

FIG. 8 is an enlarged top SEM image of PCS @ WC electrode channels

FIG. 9 is a top SEM image of an E-PCS @ WC electrode.

FIG. 10 is an enlarged top SEM image of an E-PCS @ WC electrode.

FIG. 11 is an enlarged top SEM image of an E-PCS @ WC electrode channel.

FIG. 12 is a cross-sectional SEM image of an E-PCS @ WC electrode.

FIG. 13 is an enlarged cross-sectional SEM image of a PCS @ WC electrode channel.

FIG. 14 is an enlarged cross-sectional SEM image of an E-PCS @ WC electrode channel.

Fig. 15 is an infrared plot of untreated wood chips versus pre-carbonized wood chips.

FIG. 16 is an XPS plot of WC, PCS @ WC and E-PCS @ WC electrodes.

Fig. 17 is a high resolution C1 spectrum of WC.

FIG. 18 is a high resolution C1 spectrum of PCS @ WC.

FIG. 19 is a high resolution C1 spectrum of E-PCS @ WC.

FIG. 20 is a Raman plot of WC, PCS @ WC, and E-PCS @ WC electrodes.

FIG. 21 is a graph showing the nitrogen adsorption and desorption curves of PCS @ WC and E-PCS @ WC electrodes.

FIG. 22 is a graph of the pore size distribution of PCS @ WC and E-PCS @ WC electrodes.

Fig. 23 is a graph of the contact angle of WC.

FIG. 24 is a graph of the contact angle of PCS @ WC.

FIG. 25 is a graph of the contact angle of E-PCS @ WC.

Fig. 26 is a CV curve of the WC electrode at different sweep rates.

FIG. 27 is a CV curve for PCS @ WC electrode at various sweep rates.

FIG. 28 is a CV curve for the E-PCS @ WC electrode at various sweep rates.

Figure 29 is a GCD plot of WC electrodes at different current densities.

FIG. 30 is a GCD plot of PCS @ WC electrodes at different current densities.

FIG. 31 is a graph of GCD for E-PCS @ WC electrode at different current densities.

FIG. 32 shows the area and volume capacitances for WC, PCS @ WC, and E-PCS @ WC electrodes at different current densities.

FIG. 33 is a CV curve of WC// WC at different sweep rates.

FIG. 34 is a CV curve for PCS @ WC// PCS @ WC at different sweep rates.

FIG. 35 is a GCD plot of WC// WC at different current densities.

FIG. 36 is a graph of GCD for PCS @ WC// PCS @ WC at different current densities.

FIG. 37 is a CV curve for E-PCS @ WC// E-PCS @ WC at different sweep rates.

FIG. 38 is a graph of GCD at different current densities for E-PCS @ WC// E-PCS @ WC.

FIG. 39 is a plot of area capacitance and volume capacitance for E-PCS @ WC// E-PCS @ WC at different current densities.

FIG. 40 shows WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC at 50mA cm⁻²Long cycling efficiency at current density.

FIG. 41 is a Nyquist plot of WC// WC, PCS @ WC// PCS @ WC, and E-PCS @ WC// E-PCS @ WC.

FIG. 42 shows the area energy density and volumetric energy density for WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC at different power densities.

Detailed Description

In order to facilitate an understanding of the present invention, the present invention will be described more fully and in detail with reference to the preferred embodiments, but the scope of the present invention is not limited to the specific embodiments described below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Example 1

A preparation method of an electrode based on construction of a porous carbon skeleton in a wood tracheid comprises the following steps:

the fir chips were cut to a size of 3 mm by 20 mm by 40 mm and also pre-carbonized in an air-blast drying oven at 250 ℃ for 6 h, and the resulting electrodes were marked as WC electrodes. Then, the pre-carbonized wood chips were soaked in a mixed solution containing glucose (concentration: 3 ‒ 5M) and sodium chloride (concentration: 1 ‒ 3M), vacuum soaked for 12 hours, and the soaked wood chips were dried at 60 ℃ for 24 hours. Finally, the wood chips are respectively calcined for 2 h, 4 h and 4 h at 300 ℃, 750 ℃ and 850 ℃ under the protection of argon, and the temperature rise rate is 5 ℃/min. After being ground to 0.5 mm on sandpaper, the sandpaper was washed with deionized water to remove impurities and a sodium chloride template, which was labeled as PCS @ WC.

And putting the obtained PCS @ WC electrode into 10ml of KOH solution for vacuum soaking for 4 h, wherein the mass ratio of the PCS @ WC electrode to the KOH solution is 1:3, and the concentration of the KOH solution is 1mol/L-3 mol/L. After drying at 60 ℃, calcining for 2 h at 750 ℃ under the protection of argon, wherein the heating rate is 5 ℃/min. Finally, excess KOH was washed off with 6M HCl and neutralized with deionized water. The resulting electrode was labeled E-PCS @ WC.

In this example, in order to test the performance of an electrode based on the construction of a porous carbon skeleton in wood tracheids, its electrochemical performance was tested on an electrochemical workstation (vertex.one/vertex.c, IVIUM, Holland) using a three-electrode device. SCE as reference electrode, platinum sheet as counter electrode and 1M Na₂SO₄Is an electrolyte. When the all-solid-state symmetrical supercapacitor is assembled, non-woven fabric is taken as a diaphragm, PVA gel is taken as electrolyte (polyvinyl alcohol (PVA) solution (10 mL, 0.12 g/mL) and 1 g of Na₂SO₄(1mol/L) and stirred at 60 ℃ for 30 min).

In this embodiment, fig. 1 is a flow chart of the preparation of the electrode based on the construction of the porous carbon skeleton in the wood tracheid. The wood chips are pre-carbonized and pyrolyzed in an air environment at 250 ℃ to generate a large amount of oxygen-containing functional groups. The pre-carbonized wood chips were then soaked in a solution of glucose and sodium chloride. The oxygen-containing functional groups on the surface of the pre-carbonized wood chips and glucose have strong intermolecular force, so that the tracheids are completely filled with the glucose and sodium chloride. This is favorable to constructing good porous carbon skeleton in the tracheid during the subsequent carbonization process. After carbonization, the NaCl crystal template is removed by deionized water to form a porous structure, and then KOH is used for etching an electrode to form a three-dimensional porous structure with micro-nano holes.

It can be seen from fig. 2 and 3 that WC having a top-to-bottom through-cell structure provides a large volume of cavities. At the same time, the dense tracheid walls make the wood-derived carbon electrode have good mechanical strength, and are also an advantageous basis for constructing a porous framework, as shown in fig. 4 and 5. From the top view of PCS @ WC, as shown in FIGS. 6 and 7, the tracheids of the PCS @ WC sheet are filled in a large amount, and the porous carbon skeleton is firmly bonded to the tracheids. In the drying process, NaCl crystals and glucose are separated out together and have a divergent dendritic structure, so that the inherent crystal structure of the NaCl crystals is maintained during subsequent carbonization. Therefore, the cross-sectional view (figure 8) enlarged through PCS @ WC can observe that after the NaCl template is removed, the porous structure and the dendritic carbon skeleton formed by NaCl crystal particle clusters are remained in the pore channels. Meanwhile, the tracheid filling rate of E-PCS @ WC is not changed after KOH corrosion (figure 9), and the constructed tracheid structure is proved to have good stability. FIGS. 10 and 11 are enlarged views of the structure of E-PCS @ WC with the dendritic carbon skeleton missing in the tracheid channels, exposing the entire porous structure. This is due to the reaction of the dendritic carbon skeleton in the tracheid channel with KOH at high temperature:

6KOH+2C→2K₂CO₃+2K+3H₂

the clean pores reduce the resistance of the electrolyte to the E-PCS @ WC phase and provide a convenient and fast channel for ion transmission. Cross-sectional SEM images of PCS @ WC and E-PCS @ WC electrodes were observed to characterize the internal structure of the electrode tube cells. FIG. 12 shows that the tracheids of WC can be efficiently filled and formed into a continuous porous structure by the sodium chloride template. Compared with the pore structures (figure 13 and figure 14) in electrode tube cells of PCS @ WC and E-PCS @ WC, the dendritic frameworks in the pore channels of the E-PCS @ WC are obviously reduced, and meanwhile, a large number of small holes are etched in the surface of the rough porous carbon framework. This compensates for the reduction in specific surface area caused by the clean dendritic carbon skeleton structure.

To demonstrate that glucose efficiently constructs a porous carbon skeleton in wood tracheids, natural wood and pre-carbonized wood were characterized using infrared spectroscopy. As shown in fig. 15, the pre-carbonized wood is very different from the untreated wood. At wavenumbers of 3356, 2952, 1719, 1602, 1209 and 767cm^-1When this occurs, the pre-carbonized wood exhibits a distinct infrared absorption band. This is due to the fact that the pre-carbonization process results in the decomposition of part of the lignin, hemicellulose and cellulose in the wood to produce a large amount of organic greasy substances. After removal of the organic grease, the pre-carbonized wood was at 3356, 2952 and 1209cm^-1The infrared absorption at wavenumbers is attributed to free hydroxyl (-OH), methyl/methylene (-CH) groups on the polyheterocycles₃/-CH₂-) and a carbon-oxygen bond (-C-O-). Due to the fact thatBenzene rings are present in lignin, and the absorption wave numbers are 1719, 1602 and 767cm^-1Functional groups corresponding to C = O, -OH and adjacent substituents on the phenyl ring, respectively. The infrared spectrum shows that the surface of the pre-carbonized wood has rich functional groups and is an important bridge for constructing a porous carbon skeleton of the wood tracheid. Furthermore, the kind and content of oxygen-containing functional groups in the WC, PCS @ WC, E-PCS @ WC electrodes were investigated by XPS, as shown in FIG. 16 ‒ 19. Analysis of the C1s spectrum revealed four peaks at 288.9, 287.4, 284.5 and 283.4 eV, corresponding to COOR, C = O, C-O and C-C, respectively. We found that COOR functional groups are only present on the WC electrode. In contrast, PCS @ WC and E-PCS @ WC electrodes have only C = O and C-O functional groups, demonstrating that the type of oxygen-containing functional groups on the electrode surface can be altered by building a carbon backbone in the tracheid using glucose. The oxygen-containing functional group contents on the surfaces of WC, PCS @ WC and E-PCS @ WC were found to be 33.7%, 37.9% and 52.5%, respectively, by calculation. E-PCS @ WC possesses more oxygen-containing functional groups than WC and PCS @ WC, because KOH can attach oxygen-containing functional groups to the carbon surface during etching and cleaning. Also, the KOH treated E-PCS @ WC had a higher defect level as shown in FIG. 20. The more oxygen-containing functional groups, the higher the defect level, indicating that E-PCS @ WC may have better energy storage performance.

The nitrogen adsorption/desorption curves and pore size distribution curves of PCS @ WC and E-PCS @ WC are shown in FIGS. 21 and 22. Compared with WC electrode, the specific surface area is only 365.5m²g^-1The specific surface areas of PCS @ WC and E-PCS @ WC are remarkably increased and are respectively 648.7 m²g^-1And 695.2m²g^-1. By constructing a porous carbon structure in the tracheids, 3 ‒ 4 nm mesopores are formed in a carbon skeleton (as shown in figure 22), and the specific surface area of the material is greatly increased under the action of a NaCl template, and meanwhile, the utilization rate of the cavity is improved. The specific surface area of E-PCS @ WC was slightly increased, which is consistent with the effect of KOH on the PCS @ WC structure. WC, PCS @ WC and E-PCS @ WC serve as electrode materials of the super capacitor, and the hydrophilicity of the electrode materials is also an important reference factor (FIG. 23 ‒, FIG. 25). The contact angles of the WC, PCS @ WC and E-PCS @ WC electrodes and water drops are 104.9, 84.9 and 49.5 respectively. Although the hydrophilicity of PCS @ WC is slightly improved, the porous carbon structure of E-PCS @ WC is more excellent, and the content of oxygen-containing functional groups is higherAnd the contact angle of E-PCS @ WC is smaller, and the hydrophilicity is better. The large specific surface area and good hydrophilicity are the premise that E-PCS @ WC has higher specific capacity and energy density.

WC, PCS @ WC and E-PCS @ WC electrodes, firstly, cyclic volt-ampere (CV) and constant current charge-discharge (GCD) tests of a single electrode are carried out on a three-electrode system. WC, PCS @ WC and E-PCS @ WC are in 1.0M Na₂SO₄CV tests were performed in the electrolyte at different scan speeds, as shown in fig. 26 ‒ and fig. 28. The CV curves for WC, PCS @ WC, and E-PCS @ WC are rectangular, showing typical capacitive behavior. The CV curve area of the E-PCS @ WC electrode is the largest within a voltage window range of-1-0V, and the maximum capacity of the E-PCS @ WC electrode is shown. At 5 ‒ 30mAcm⁻²GCD testing at current density (FIG. 29 ‒, FIG. 31) indicated that PCS @ WC and E-PCS @ WC have ideal isosceles triangles with lower IR drop, and that both electrochemical performance and electrolyte transfer rate were faster than WC. The calculation shows that the concentration is 5, 10, 15, 20 and 30mAcm⁻²The area specific capacitances of E-PCS @ WC at current densities were 7.29, 6.68, 5.93, 5.33, and 4.62 Fcm⁻². And at 5mAcm⁻²Under the current density, the specific area capacities of WC and PCS @ WC are respectively only 3.14 and 1.76 Fcm⁻². E-PCS @ WC has excellent area specific capacitance and rate performance. Notably (FIG. 32), a 0.5 mm thick E-PCS @ WC electrode was at 5mAcm⁻²Has ultrahigh volume specific capacity of 145.8Fcm under current density⁻³When the current density reaches 30mAcm⁻²The product still has 92.4 Fcm⁻³Volume to capacity of (a). This is due to the efficient utilization of the tracheid cavity. WC and PCS @ WC at 5mAcm⁻²The corresponding volume specific capacitance at current density was 35.3 and 62.8Fcm respectively⁻³. Experimental results show that the constructed tracheid structure improves the utilization rate and the specific surface area of the cavity and can directly double the capacity of the electrode. In addition, the hydrophilicity of the material is improved through KOH cleaning, the electrolyte can better permeate into an electrode structure, the ion migration is promoted, the structural advantage of E-PCS @ WC is greatly exerted, and the specific surface area of the material is improved by 4 times. The volume ratio of E-PCS @ WC is 145.8Fcm⁻³Further develops the application potential of the wood derived carbon.

In addition, a Symmetrical Super Capacitor (SSC) of WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC is assembled, and the non-woven fabric is used as a diaphragm and 1.0M Na₂SO₄And preparing a neutral gel electrolyte. The CV curves and GCD curves of SSC devices for WC// WC and PCS @ WC// PCS @ WC are shown in FIG. 33 ‒ and FIG. 36. The results show that the electrochemical behavior of SSC devices of WC// WC and PCS @ WC// PCS @ WC changes and is 2mAcm⁻²Under the current density, the area specific capacities of WC// WC and PCS @ WC// PCS @ WC are only 1.6 and 78 mFcm respectively⁻². This is because WC and PCS @ WC electrodes have poor hydrophilicity, and thus gel electrolyte cannot penetrate into the bulk phase of the electrode, and thus structural advantages of the electrode cannot be exerted. Surprisingly, E-PCS @ WC// E-PCS @ WC shows typical capacitance characteristics in the voltage range of-1 to 0V (FIG. 37), and ranges from 2 to 12 mVs⁻¹The range exhibits excellent rate performance. In addition, the GCD curves also showed significant double layer capacitive behavior (fig. 38), indicating that the E-PCS @ WC electrode surface has rapid reversible adsorption/desorption of ions. At 5, 10, 15, 20 and 30mAcm⁻²The area specific capacitances of E-PCS @ WC// E-PCS @ WC were 1.75, 1.42, 1.26, 1.16, and 1.02 Fcm, respectively, at current density⁻². It is noteworthy that at this current density, the corresponding volumetric specific volumes are as high as 34.99, 28.42, 25.29, 23.28 and 20.34 Fcm, respectively⁻³(FIG. 39). The clean hydrophilic porous structure in the E-PCS @ WC tube promotes the permeation of hydrogel electrolyte, and a large number of oxygen-containing functional groups on the surface of the porous carbon skeleton are utilized, so that the E-PCS @ WC shows excellent energy storage capacity. FIG. 40 shows the cycle performance of SSC devices for WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC. The capacity of SSC devices for WC// WC and PCS @ WC// PCS @ WC fluctuates greatly over long periods. The E-PCS @ WC// E-PCS @ WC SSC device is 50mAcm⁻²The stable capacitance of 98.5% is still maintained after 20000 cycles. The clean and hydrophilic porous structure ensures the stable energy storage effect of an SSC device of E-PCS @ WC// E-PCS @ WC. FIG. 41 is a Nyquist plot of SSC devices for WC// WC, PCS @ WC// PCS @ WC, and E-PCS @ WC// E-PCS @ WC. R of three SSC devices_ΩThe resistances are 17.83, 9.53 and 9.47 omega, respectively, indicating that the WC, PCS @ WC and E-PCS @ WC electrodes are in effective contact with the electrolyteShowing excellent ion transfer performance. Meanwhile, the SSC devices assembled by the PCS @ WC and the E-PCS @ WC have good dynamic performance.

Energy density is an important parameter index for supercapacitors. The power density is 1 ‒ 15mWcm⁻²The areal and volumetric energy densities for WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC SSC devices are shown in Table 1. FIG. 42 shows that at a power density of 2.5mWcm⁻²The volume energy density of an SSC device of the E-PCS @ WC// E-PCS @ WC is 4.86mWhcm⁻³. When the power density reaches 15mWcm⁻²When the energy density is kept at 2.83mWhcm⁻³。

Table 1 shows the area energy density and the volume energy density for WC// WC, PCS @ WC// PCS @ WC and E-PCS @ WC// E-PCS @ WC.

In this example, a three-dimensional porous carbon structure was built inside the wood-derived carbon nanotube cells using the abundant functional groups on the surface of the pre-carbonized wood. After the potassium hydroxide etching, the structure and the hydrophilicity of the E-PCS @ WC electrode are greatly improved. The electrode has high hydrophilicity, high volume energy density and excellent cycling stability. At a current density of 5mAcm⁻²The area/volume capacitance of the E-PCS @ WC electrode is 7.29Fcm⁻²/145.8Fcm⁻³. E-PCS @ WC// E-PCS @ WC SSC device with power density of 2.5mW cm⁻²The area/volume capacity and the volume energy density were 1.75Fcm, respectively⁻²/34.99Fcm⁻³And 4.86mWhcm⁻³. At 50mAcm⁻³The capacity retention ratio of 20000 cycles is 98.5%.

Claims

1. The utility model provides an electrode based on construct porous carbon skeleton in timber tracheid, includes the wood chip base member of carbomorphism, the inside tracheid structure that has of wood chip base member of carbomorphism, its characterized in that: a porous carbon skeleton is constructed in a tracheid structure of the carbonized wood sheet through a glucose and sodium chloride template; the concentration of the glucose is 3-5 mol/L, and the concentration of the sodium chloride is 1-3 mol/L.

2. The electrode based on the construction of a porous carbon skeleton in wood tracheids according to claim 1, characterized in that: the carbonized wood chips with porous carbon skeletons are etched by potassium hydroxide; the concentration of the potassium hydroxide is 1mol/L-3 mol/L.

3. The method for preparing an electrode based on the construction of a porous carbon skeleton in wood tracheids according to claim 1 or 2, characterized in that: the method comprises the following steps:

1) cutting the wood chips with the tracheid structure into preset sizes;

2) pre-carbonizing wood chips in a drying oven

4) drying the wood chips soaked in the step 3), calcining and carbonizing under the protection of inert gas, wherein the calcining temperature is 300-850 ℃, and the calcining time is 2-6 hours; washing with deionized water after calcination;

7) washing the wood chips with HCl solution to remove redundant potassium hydroxide, and washing the wood chips with deionized water to be neutral, wherein the concentration of the HCl solution is 3-6 mol/L; and obtaining the electrode based on the construction of the porous carbon skeleton in the wood tracheids.

4. The method for preparing an electrode based on the construction of a porous carbon skeleton in wood tracheids according to claim 3, characterized in that: the temperature of the pre-carbonization is 200-300 ℃, and the time is 3-6 hours.

5. The method for preparing an electrode based on the construction of a porous carbon skeleton in wood tracheids according to claim 3, wherein: the mass ratio of the carbonized wood chips put into the potassium hydroxide solution in the step 5) to the potassium hydroxide solution is 1: 3.

6. A supercapacitor, characterized by: an electrode based on the construction of a porous carbon skeleton in wood tracheids comprising the electrode according to claim 1 or claim.