CN114030046B

CN114030046B - Preparation method of isotropic conductive paper

Info

Publication number: CN114030046B
Application number: CN202111315748.7A
Authority: CN
Inventors: 郭洪武; 张伟业; 刘毅; 王蓓蓓; 孙璟萌
Original assignee: Beijing Forestry University
Current assignee: Beijing Forestry University
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2022-07-22
Anticipated expiration: 2041-11-08
Also published as: CN114030046A

Abstract

The invention discloses a preparation method of isotropic conductive paper, which comprises the following steps: slicing the wood along the direction vertical to the growth direction to obtain a cross-section wood substrate; immersing the substrate into a delignification buffer solution, and heating for delignification treatment; immersing the delignified wood substrate in a ferric trichloride solution, and freeze-drying after the impregnation; and pressing the obtained sample by using a cold press to obtain a conductive substrate, then sealing the sample and the pyrrole solution together, and synthesizing polypyrrole on the surface of the conductive substrate in situ by using an in-situ chemical vapor deposition method to obtain the isotropic conductive paper. The method has the advantages of simple preparation process, mild reaction conditions and wide application prospect in the fields of electrochemistry, electromagnetic shielding and the like.

Description

Preparation method of isotropic conductive paper

Technical Field

The invention relates to a preparation method of a composite material, in particular to a preparation method of isotropic conductive paper, and belongs to the field of composite materials.

Background

In recent years, flexible wearable electronic devices are expected to have high application values in portable electronic devices, implantable medical devices and flexible displays, and thus have attracted great research interests. Among the various devices, flexible supercapacitors are of great interest for their high power density, fast charge-discharge characteristics, long cycle life and good safety. The design of a flexible electrode with good electrochemical performance, high stability and excellent mechanical performance is one of the keys for preparing a high-performance flexible supercapacitor. Flexible substrate materials (fibers, paper, films and fabrics) have been used to prepare flexible electrodes. Among them, paper-based electrodes are considered as potential components of wearable electronic devices due to their low cost, light weight and degradability. The paper/cellulose substrate has a microporous structure and a large number of hydrophilic groups, so that a plurality of carbon materials (graphene, carbon nanotubes and the like) can be easily attached to the cellulose/paper substrate and can be used as a self-supporting supercapacitor electrode. The conductive papers currently used as the electrodes of the supercapacitor are classified into two types. One is that the traditional paper prepared by paper pulp, bleaching and wet forming technology is used as base material (ordinary printing paper or filter paper), then the electrochemical active material is loaded by soaking polymerization, electrochemical deposition and vacuum filtration, because the traditional paper is affected by strong acid or strong base in the preparation process, the mechanical strength is lower, and the preparation process is complex; another method is to extract nanocellulose from plants, mix it with electrochemically active materials using a suction filtration method to prepare cellulose conductive paper, the nanocellulose fibers are usually obtained by mechanical disintegration or acid hydrolysis, wherein the mechanical method usually requires a pretreatment such as 2,2,6, 6-tetramethylpiperidine oxide mediated oxidation or enzymatic pretreatment to reduce the energy requirement during mechanical defibrillation, and this process usually requires a huge energy consumption, resulting in a waste of resources.

Recently, there has been much interest in using natural wood to prepare supercapacitor electrodes in a top-down method. As a sustainable and abundant carbon resource, the natural wood has a unique three-dimensional microstructure, has a hierarchical communication channel in the growth direction, and transports water and ions to cultivate the growth of trees. The unique structure of wood makes it a great potential for the fabrication of advanced supercapacitor electrodes. However, wood is electrically insulating and cannot be used directly as an electrode. Zhang et al, which uses balsa wood as a base material, makes it have high conductivity by high-temperature carbonization, then hydrothermally loads manganese dioxide and graphene quantum dots to prepare a composite electrode material, and the obtained electrode has a medium area ratioCapacitor (Current density 1.0mA cm)^-2When the concentration is 2712mF cm^-2) Good rate performance and excellent cycle stability (retention rate 95.3% after 2000 cycles). Lv et al use a cross section of wood as a flexible scaffold and reduced graphene oxide as an active material to prepare an electrode having good surface capacitance (102 mF. cm)^-2) And excellent cycle stability (capacity retention of 98.9% after 5000 cycles). Zhang et al uses a delignification process followed by a carbon nanotube coating process to convert a rigid and electrically insulating wood film into a flexible and electrically conductive material. Subsequently, the silver nanoparticles and the poly 3, 4-ethylenedioxythiophene-polystyrene sulfonate are loaded to prepare a flexible supercapacitor electrode, and the electrode shows high area capacitance (at 20 mV. s)^-1Lower 266.7 mF. cm^-2) And good long-term circulation stability (5 mA-cm)^-2The capacity retention after the next 5000 cycles was 84.3%). Although high conductivity can be achieved by charring or coating with conductive materials, the anisotropic nature of wood causes significant differences in anisotropic properties between different electrodes of the same batch, and in addition, existing wood-based electrodes have poor tensile properties, thereby hindering commercial application of the electrodes.

To prepare isotropic conductive paper, an active material is required in addition to the wood substrate. Currently, the most commonly used materials include Carbon Nanotubes (CNTs), graphene, metal oxides, and two-dimensional metal carbonitrides, among which carbon nanotubes show great potential in supercapacitor devices. The carbon nano tube has a one-dimensional tubular structure and excellent electrical property and mechanical stability, so that the CNT serving as a substrate meets the requirements of high conductivity, expandability and long-cycle stability of the flexible supercapacitor. However, its low capacitance limits its application in supercapacitor devices. The new trend of the composite material of CNT and conductive polymer to synthesize the composite material of supercapacitor, among the conductive polymers, polypyrrole (PPy) has high conductivity, high energy storage capacity, low cost, simple synthesis and environmental friendliness, and thus is considered as a promising material of supercapacitor. Patent CN106469808B discloses graphene conductive paper, which is mainly prepared from a carbon material, paper pulp and an auxiliary agent in a mass ratio of 5-10:34-57:6-9, and the conductive paper applied to the field of paper batteries has the advantages of improving specific capacity, stabilizing battery performance, prolonging battery life and the like; patent CN108257791A discloses a two-dimensional metal carbon nitride (MXene) paper electrode and a preparation method thereof, and a micro supercapacitor and a preparation method thereof. The preparation method of the MXene paper electrode adopts the spraying technology to prepare the MXene paper electrode, so that the MXene paper electrode is used for a miniature super capacitor, the miniature super capacitor is light and thin and has good flexibility, and the pasting function of the miniature capacitor is easy to realize. The preparation method has complex preparation process and poor mechanical strength of the electrode. Therefore, it is a very urgent subject to invent a supercapacitor electrode derived from wood and having excellent electrochemical and mechanical properties.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a top-down method for preparing isotropic conductive paper by utilizing anisotropic natural wood, and the prepared conductive paper is used for a supercapacitor electrode and has excellent mechanical property and electrochemical property.

Specifically, the invention is achieved by the following technical scheme:

a preparation method of isotropic conductive paper comprises the following steps:

(1) the wood is sliced perpendicular to the growth direction to obtain a wood substrate with a cross section.

(2) And (2) immersing the wood substrate obtained in the step (1) into a delignification buffer solution, heating for reaction, taking out a sample after the reaction is finished, washing, and absorbing deionized water on the surface by using filter paper.

(3) Immersing the delignified wood substrate obtained in the step (2) in ferric trichloride (FeCl)₃) In the solution, after the immersion, the solution is freeze-dried.

(4) Compressing the sample obtained in the step (3) with a cold press at a certain pressure.

(5) Sealing the sample obtained in step (4) and a vial of pyrrole monomer in a beaker, and transferring into a refrigerator for cooling. And taking out after the reaction is finished to obtain the isotropic conductive paper.

Preferably, the wood in step (1) is selected from wood with lower density, such as balsa wood, poplar wood, paulownia wood, etc.

Preferably, the thickness of the wood substrate in step (1) is 0.3-1mm, most preferably 0.4 mm.

Preferably, the wood substrate obtained in step (1) is washed with deionized water and then dried at room temperature for 24 hours for use.

Preferably, the delignification buffer in the step (2) is sodium hydroxide (NaOH) and sodium sulfite (Na)₂SO₃) The mixed solution of (1).

Preferably, the concentration of the NaOH solution in the step (2) is 1-5mol/L, preferably 2.5 mol/L; na (Na)₂SO₃The concentration of the solution is 0.1 to 1mol/L, preferably 0.4 mol/L.

Preferably, in step (2), NaOH solution and Na₂SO₃The volume ratio of the solution was 1: 1.

Preferably, the reaction in step (2) is carried out by heating in a water bath at 85 ℃ for 1-6 h.

Most preferably, the reaction time in step (2) is 2 h.

Preferably, the washing in the step (2) is washing with ethanol and deionized water in sequence.

Preferably, the filter paper in the step (2) is a high-speed quantitative filter paper.

Preferably, the delignified wood substrate obtained in step (2) is placed in FeCl₃Transferred to a vacuum drying oven, and vacuum impregnated.

More preferably, the operation of step (3) is repeated 2 to 3 times.

Preferably, FeCl as described in step (3)₃The concentration of the solution was 0.3 mol/L.

Preferably, FeCl is said in step (3)₃The solution was prepared as follows:

40.575g of FeCl were weighed with a tray balance₃·6H₂Adding the O solid into a beaker, adding 500mL of deionized water into the beaker, and stirring for 1-2h to obtain FeCl₃And (3) solution.

More preferably, in step (3)FeCl of₃Solution, FeCl used₃·6H₂O is analytically pure grade.

Preferably, the sample impregnated in step (3) is first rinsed with deionized water to remove the residual solution, and then freeze-dried for 24 h.

Preferably, the pressure of the cold pressing in step (4) is selected in the range of 0.3-5MPa, most preferably 1 MPa.

Preferably, the cold pressing time in step (4) is selected to be 3-15min, most preferably 7 min.

Preferably, the pyrrole in step (5) is of analytical grade.

Preferably, the volume of pyrrole in step (5) is 1 mL.

Preferably, the volume of the beaker in step (5) is 50 mL.

Preferably, the reaction time of the sample with pyrrole in the refrigerator is 3, 5, 7 and 9 days, most preferably 7 days.

Preferably, the reaction device for the beaker and the sample in the step (5) is placed in a refrigerating chamber of a refrigerator.

According to the method, lignin and hemicellulose are partially removed from wood to obtain a base material, and PPy is generated on the surface of the base material in situ by adopting an in-situ chemical vapor deposition method, so that continuous loading and high purity of an active material can be realized, and isotropic conductive paper with excellent electrochemical performance and mechanical performance is obtained. Compared with the prior art, the invention has the following advantages and excellent effects:

(1) in the process of preparing the isotropic conductive paper, the base material is made of natural wood with wide sources, environmental protection and low cost, non-degradable plastics and materials such as cellulose paper, plastics and the like with complex preparation processes are replaced, and the PPy is loaded by adopting an in-situ chemical vapor deposition method to ensure that the conductive paper has high conductivity, while the PPy generated by the traditional solution chemical polymerization has low purity and poor continuity.

(2) The cold pressing not only enhances the mechanical property of the conductive paper, but also removes the interference of wood anisotropy on the electrochemical property of the conductive paper, ensures the stability of the electrochemical property of the conductive paper and provides reference significance for the development of biomass-based electronic equipment.

Drawings

FIG. 1 is a schematic view of charging and discharging isotropic conductive paper

Detailed Description

The invention provides a preparation method of a conductive wood aerogel, which aims to solve the problems in the background art. The technical solutions of the present invention will be further described below with reference to specific examples, but the scope and embodiments of the present invention are not limited thereto.

Example 1:

(1) barsha wood was sliced in the direction of growth to obtain a wood substrate having a thickness of 0.4mm and a length and width dimension of 15X 10 mm.

(2) Repeatedly washing the wood substrate obtained in the step (1) with deionized water, and then standing at room temperature for 24h for later use.

(3) Putting the sample in the step (2) into 2.5mol/L NaOH and 0.4mol/L Na₂SO₃The mixed aqueous solution of (1) was heated in a water bath at 85 ℃ for 2 hours.

(4) Washing the partially delignified wood substrate in the step (3) with ethanol and deionized water in sequence, putting a sample into FeCl₃The solution was placed in a beaker and then transferred to a vacuum oven for vacuum impregnation for 2 h.

(5) Washing the sample obtained in the step (4) with deionized water to remove excessive solution, and freeze-drying at-45 ℃ for 24 h.

(6) And (5) cold-pressing the sample obtained in the step (5) for 7min by using a cold press, wherein the pressure is 1 MPa.

(7) The sample obtained in step (6) was sealed with a vial of pyrrole (1mL) in a beaker and placed in a refrigerator at 0 ℃ for 7 days.

(8) As shown in figure 1, when the prepared isotropic conductive paper is used as an electrode, the specific capacitance reaches 2576mF/cm²。

Example 2:

(1) the poplar was sliced along the growth direction to obtain a wood substrate with a thickness of 0.4mm and a length and width dimension of 15X 10 mm.

(7) The sample obtained in step (6) was sealed in a beaker with a vial of pyrrole (1mL) and placed in a refrigerator at 0 ℃ for 7 days.

(8) When the prepared isotropic conductive paper is used as an electrode, the specific capacitance reaches 2344mF/cm²。

Example 3:

(1) paulownia wood is sliced along the growth direction to obtain a wood substrate with the thickness of 0.4mm and the length and width of 15 multiplied by 10 mm.

(4) Washing the partial delignified wood substrate in the step (3) with ethanol and deionized water in sequence, and putting a sample in FeCl₃The solution was placed in a beaker and then transferred to a vacuum oven for vacuum impregnation for 2 h.

(8) When the prepared isotropic conductive paper is used as an electrode, the specific capacitance reaches 2134mF/cm²。

Claims

1. A preparation method of isotropic conductive paper is characterized by comprising the following steps:

(1) slicing the wood along the direction vertical to the growth direction to obtain a wood substrate with the cross section thickness of 0.4mm and the length and width dimensions of 15 multiplied by 10 mm;

(2) immersing the wood substrate obtained in the step (1) into a delignification buffer solution, wherein the delignification buffer solution is 2.5mol/L NaOH and 0.4mol/L Na₂SO₃Aqueous solution, taking out the sample after the reaction is finished, washing, and then immersing the sample in 0.3mol/L FeCl₃Vacuum soaking for 2h in the solution, then washing the sample with ethanol and deionized water in sequence, and drying, wherein the drying is to freeze the sample in a refrigerator for 12h, and then transfer the sample to a freeze dryer for freeze drying at-45 ℃ for 24 h;

(3) pressing the sample obtained in the step (2) for 7min by using a cold press under the pressure of 1 Mpa;

(4) the sample obtained in step (3) was sealed in a beaker with 1mL of the pyrrole solution, and then the beaker was moved into a refrigerator and left for 7 days.