A carbon material for electrodes that can be converted into electrolyte components and a preparation method thereof

Abstract

The present invention belongs to the field of electrode materials and their applications, and particularly relates to a carbon material for electrodes composite with a component that can be converted into an electrolyte and a preparation method thereof. The prepared carbon material intrinsically has a carbon pore structure, but a large amount of phosphorus pentoxide that can be converted into an electrolyte after absorbing water is contained in the carbon pore structure. It can be used as an electrode carbon material in a battery or capacitor in an aqueous phase with phosphoric acid as the electrolyte. Due to the presence of phosphorus pentoxide in the pores of the material, this carbon material has good hydrophilicity, and the phosphorus pentoxide contained in the material pores in-situ generates a phosphoric acid electrolyte after absorbing water, enabling the electrolyte solution to be uniformly dispersed in the carbon material and filling pores of various sizes, which can significantly improve the electrochemical performance of the electrode material.

Description

Technical Field

[0001] The present invention belongs to the field of electrode materials and their applications, and particularly relates to a carbon material for electrodes composite with electrolyte components that can be transformed and an application method thereof. Background Art

[0002] Battery electrode materials generally adopt carbon materials with large specific surface areas having porous or hierarchical pore structures. CN114171326A discloses a preparation method of nitrogen-doped ultrathin 2D porous carbon nanosheets. Using crushed and sieved fruit shell biomass such as hazelnut shells and walnut shells as carbon sources and γ-polyglutamic acid as nitrogen sources, through chemical cross-linking, freeze-drying, and then activating with any one of potassium hydroxide, zinc chloride, phosphoric acid, potassium carbonate, etc. as an activator, and finally performing pickling and water washing to remove the possibly remaining activator and then drying to prepare carbon nanosheets with a 2D porous sheet structure, high microporosity, and a relatively large specific surface area. This invention adopts traditional activation methods, with complex steps. Although the prepared 2D porous carbon has a large specific surface area and element doping, its hydrophilicity is poor, and it is difficult for the electrolyte to penetrate into the pores, making it actually difficult to apply in practice.

[0003] CN114141548A discloses a preparation method of mesoporous structure carbon-based nanocages for high-performance supercapacitors. Using basic magnesium carbonate as a raw material to prepare mesoporous magnesium oxide, then reacting with zinc nitrate to obtain a template, and finally depositing carbon nanocages on the template under atmosphere protection, and finally removing the template through pickling immersion and water washing, etc. The carbon nanocages obtained by this method have effects such as high specific surface area, high conductivity, and coexistence of hierarchical pores, but the efficiency is low, the steps are long, and the cost and energy consumption are also very high. Especially when used as an electrode, it is difficult for the electrolyte to effectively penetrate.

[0004] CN113979434A discloses a biomass-based carbon electrode material, its preparation method and application. Using biomass cattail as a precursor and biomass carbon material, and KOH solution as an activator, a porous carbon material with a relatively large specific surface area is obtained through long-term soaking and high-temperature activation. In fact, it mainly relies on the initial structure of the special raw material cattail and adopts traditional processes for activation, without wide raw material applicability, and the subsequent treatment processes will be very complicated. In addition, its inventor points out that it can only be applied to the preparation of the positive electrode of supercapacitors. This usually means its application in asymmetric capacitors, and the principle of this kind of capacitor generally relies on the pseudocapacitance generated by redox reactions, and the charge and discharge speed is usually relatively slow.

[0005] However, with the in-depth research and application, technicians found that simply improving the porous structure and specific surface area of the electrode carbon has very limited improvement on the electrode performance. The main reason is that the surface tension of the electrolyte solution makes it difficult for the electrolyte to effectively penetrate and distribute in the electrode carbon. At the same time, the Faraday effect on the surface during the charging state will also hinder the mass transfer of the electrolyte in the micropores. This means that the problem of the effective distribution of the electrolyte in the electrode carbon must be solved. Summary of the Invention

[0006] In order to avoid the difficulty of electrolyte infiltration after the carbon material electrode is made, the present invention aims to adopt the method of pre-burying the material that can be converted into the electrolyte in the electrode carbon material to solve the problem of the effective distribution of the electrolyte in the electrode carbon.

[0007] The preparation method of the electrode carbon material compounded with the component that can be converted into the electrolyte provided by the present invention is specifically implemented as follows:

[0008] The material used as the carbon source, phosphoric acid and conductive carbon black are fully ground and mixed evenly in a mortar. The evenly mixed raw materials are reacted in an autoclave at 150 - 250 °C and 5 - 15 Mpa for 60 - 600 minutes to form a uniform black liquid; after the black liquid is dried, it is heated to 700 - 900 °C under nitrogen protection for activation for 40 - 180 minutes, and then cooled and ball-milled into a powdery electrode carbon material compounded with the component that can be converted into the electrolyte.

[0009] Among them, the carbon source is one or several of lignosulfonate, lignin, and cellulose.

[0010] The phosphoric acid is chemically pure, which can promote the dehydration of the carbon source in the autoclave, promote the carbon formation and pore formation of the carbon material during high-temperature activation, and finally be converted into phosphorus pentoxide and buried in the electrode carbon material.

[0011] The conductive carbon black mainly promotes the conductivity of the carbon material and prevents the poor conductivity of the carbon material itself due to the multiphase structure.

[0012] The electrode carbon material compounded with the component that can be converted into the electrolyte prepared by the method of the present invention has the following composition by mass percentage: carbon source: 25 - 69%, phosphoric acid: 30 - 70%, conductive carbon black: 1 - 5%.

[0013] The carbon material prepared by the present invention intrinsically has a carbon pore structure, but a large amount of phosphorus pentoxide that can be converted into the electrolyte after absorbing water is contained in the carbon pore structure, and it can be used as the electrode carbon material in a battery or capacitor with phosphoric acid as the electrolyte in the aqueous phase.

[0014] Due to the presence of phosphorus pentoxide in the pores of the material, the usage method of the carbon material of the present invention is as follows: The carbon material is ground into a slurry with conductive carbon black and a binder in a solvent in proportion, and then coated or roll-pressed onto a conductive substrate to form an electrode sheet. The electrode sheet needs to be pre-soaked in water for 48 hours before use, and the electrolyte medium during use should be a phosphoric acid solution. The phosphorus pentoxide contained in the pores of the carbon material absorbs water and in-situ generates a phosphoric acid electrolyte, making the electrolyte solution disperse evenly in the carbon material and cover pores of various sizes, thus enabling better electrochemical performance. However, due to the simple treatment without complex processes such as pickling and drying, the material is granular and has a large bulk density. Therefore, a better device energy density can be obtained with the electrodes of the present invention.

[0015] Beneficial effects

[0016] In the carbon material of the electrode of the present invention, a phosphorus pentoxide component that can be converted into a phosphoric acid electrolyte is compounded. Utilizing the characteristic that phosphorus pentoxide is extremely easy to absorb water and convert into phosphoric acid, compared with the traditional electrode carbon preparation process, both the preparation method and the post-treatment process are greatly simplified, and the activation conditions are relatively mild, with lower corrosion to the environment compared to the commonly used alkali activation environment. Although the specific capacitance of the electrode carbon material will decrease when tested alone due to the non-separation of the components that can be converted into the electrolyte, due to the lack of complex processes such as pickling and drying, the material is granular and has a large bulk density. Therefore, a better device energy density can be obtained with the electrodes of the present invention. The carbon material of the electrode compounded with the components that can be converted into the electrolyte of the present invention can be applied in both supercapacitors and electrolyte batteries. Description of the drawings

[0017] Figure 1 It is the process flow chart of the present invention.

[0018] Figure 2 It is the electron microscope image of the electrode material prepared in Example 1 of the present invention. Detailed implementation manners

[0019] The following examples are used to further illustrate the technical features of the present invention, but the protection scope of the present invention is not limited to the following examples.

[0020] Example 1

[0021] Formula: Lignin 69%; Phosphoric acid 30%; Conductive carbon black: 1%.

[0022] Preparation method: Grind the lignin, phosphoric acid, and conductive carbon black in the above formula evenly in a mortar. The uniformly mixed raw materials are reacted in an autoclave at 150 °C and 5 Mpa for 600 minutes to form a uniform black liquor. After the black liquor is dried, it is heated to 900 °C under nitrogen protection for activation for 40 minutes, and then cooled and ball-milled into a powdery carbon material for electrodes compounded with components that can be converted into the electrolyte.

[0023] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and an electrode sheet is made by coating it on conductive carbon paper with a thickness of 0.05 mm. The prepared electrode sheet can be used after being soaked in pure water for 48 hours.

[0024] Example 2

[0025] Formulation: Calcium lignosulfonate 15%; Cellulose 10%; Phosphoric acid 70%; Conductive carbon black 5%;

[0026] Preparation method: Grind calcium lignosulfonate, cellulose, phosphoric acid and conductive carbon black in the above formulation evenly in a mortar. The evenly mixed raw materials are reacted in a high-pressure reactor at 250 °C and 15 Mpa for 60 minutes to form a uniform black liquor; after the black liquor is dried, it is heated to 700 °C under nitrogen protection for activation for 180 minutes, and after cooling, it is ball-milled into a powdery carbon material for electrodes that can be converted into electrolyte components.

[0027] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and an electrode sheet is made by coating it on conductive carbon paper with a thickness of 0.05 mm. The prepared electrode sheet can be used after being soaked in pure water for 48 hours.

[0028] Example 3

[0029] Formulation: Sodium lignosulfonate 15%; Cellulose 10%; Calcium lignosulfonate 25%; Phosphoric acid 47%; Conductive carbon black 3%;

[0030] Preparation method: Grind sodium lignosulfonate, cellulose, calcium lignosulfonate, phosphoric acid and conductive carbon black in the above formulation evenly in a mortar. The evenly mixed raw materials are reacted in a high-pressure reactor at 200 °C and 10 Mpa for 260 minutes to form a uniform black liquor; after the black liquor is dried, it is heated to 800 °C under nitrogen protection for activation for 100 minutes, and after cooling, it is ball-milled into a powdery carbon material for electrodes that can be converted into electrolyte components.

[0031] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and an electrode sheet is made by coating it on conductive carbon paper with a thickness of 0.05 mm. The prepared electrode sheet can be used after being soaked in pure water for 48 hours.

[0032] Example 4

[0033] Formulation: Sodium lignosulfonate 20%; Cellulose 15%; Calcium lignosulfonate 15%; Phosphoric acid 49%; Conductive carbon black 1%;

[0034] Preparation method: Grind sodium lignosulfonate, cellulose, calcium lignosulfonate, phosphoric acid and conductive carbon black in the above formula evenly in a mortar. The evenly mixed raw materials are reacted in an autoclave at 200 °C and 10 Mpa for 260 minutes to form a uniform black liquor. After the black liquor is dried, it is heated to 800 °C under nitrogen protection for activation for 100 minutes, and then ground into a powder after cooling to obtain a carbon material for electrodes that can be converted into electrolyte components.

[0035] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and coated on conductive carbon paper with a thickness of 0.05 mm to make an electrode sheet. The made electrode sheet can be used after being soaked in pure water for 48 hours.

[0036] Example 5

[0037] Formula: Lignin 50%; Phosphoric acid 49%; Conductive carbon black: 1%.

[0038] Preparation method: Grind lignin, phosphoric acid and conductive carbon black in the above formula evenly in a mortar. The evenly mixed raw materials are reacted in an autoclave at 150 °C and 5 Mpa for 600 minutes to form a uniform black liquor. After the black liquor is dried, it is heated to 900 °C under nitrogen protection for activation for 40 minutes, and then ground into a powder after cooling to obtain a carbon material for electrodes that can be converted into electrolyte components.

[0039] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and coated on conductive carbon paper with a thickness of 0.05 mm to make an electrode sheet. The made electrode sheet can be used after being soaked in pure water for 48 hours.

[0040] Comparative Example 1

[0041] Formula: Lignin 69%; Red phosphorus 30%; Conductive carbon black: 1%.

[0042] Preparation method: Grind lignin, red phosphorus and conductive carbon black in the above formula evenly in a mortar. The evenly mixed raw materials are reacted in an autoclave at 150 °C and 5 Mpa for 600 minutes to form a uniform black liquor. After the black liquor is dried, it is heated to 900 °C under nitrogen protection for activation for 40 minutes, and then ground into a powder after cooling to obtain a carbon material for electrodes that can be converted into electrolyte components.

[0043] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and coated on conductive carbon paper with a thickness of 0.05 mm to make an electrode sheet. The made electrode sheet is soaked in pure water for 48 hours

[0044] Comparative Example 2

[0045] Formula: Lignin 51%; Phosphoric acid 49%.

[0046] Preparation method: Grind the lignin and phosphoric acid in the above formula evenly in a mortar. The uniformly mixed raw materials are reacted in an autoclave at 150 °C and 5 Mpa for 600 minutes to form a uniform black liquor. After the black liquor is dried, it is heated to 900 °C under nitrogen protection for activation for 40 minutes, and then cooled and ball-milled into a powdery carbon material for electrodes that can be converted into electrolyte components.

[0047] The prepared carbon material is directly ground into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, and coated on conductive carbon paper with a thickness of 0.05 mm to make an electrode sheet. The made electrode sheet is soaked in pure water for 48

[0048] Comparative Example 3

[0049] Use the commercially available Kuraray YP-50, which is the most commonly used in supercapacitors, as the electrode active material, grind it into a slurry in absolute ethanol according to the ratio of 8:1:1 with conductive carbon black and binder, coat it on conductive carbon paper with a thickness of 0.05 mm to make an electrode sheet, and conduct comparative tests.

[0050] The performance of the carbon materials prepared in each example and comparative example is shown in Table 1.

[0051] Table 1

[0052]

Claims

1. Application of a carbon material for an electrode containing components convertible into electrolyte components, characterized in that, The preparation method of the carbon material for the electrode is as follows: (1) Thoroughly grind the carbon source, phosphoric acid and conductive carbon black evenly in a mortar; (2) Heat and mix the uniformly mixed raw materials in an autoclave to form a uniformly mixed black liquid; (3) After the uniformly mixed black liquid is dried by vacuum pumping, it is heated and carbonized under nitrogen protection, and after cooling, it is ball-milled into a powdery carbon material for the electrode that can be converted into electrolyte components; Among them, the composition by mass percentage is: carbon source: 25 - 69%, phosphoric acid: 30 - 70%, conductive carbon black: 1 - 5%; The carbon material is ground into a slurry with conductive carbon black and a binder in a solvent, coated or roll-pressed on a conductive substrate to make an electrode sheet. The electrode sheet needs to be soaked in water for 48 hours before use. When in use, the electrolyte medium is a phosphoric acid solution; the phosphorus pentoxide contained in the pores of the carbon material absorbs water and in-situ generates a phosphoric acid electrolyte, so that the electrolyte solution is uniformly dispersed in the carbon material and fills large, medium and small pores, obtaining good electrochemical performance.

2. The application material containing carbon materials for electrodes that can be converted into electrolyte components according to claim 1, characterized in that, The carbon source in step (1) is one or more of lignosulfonate, lignin, and cellulose.

3. Use of the carbon material for electrodes that can be converted into electrolyte components according to claim 1, characterized in that, In step (2), the reaction temperature of the autoclave is: 150 - 250 °C, the pressure is 5 - 15 MPa, and the reaction time is: 60 - 600 minutes.

4. Use of the carbon material for an electrode capable of being converted into an electrolyte component according to claim 1, characterized in that, In step (3), the carbonization temperature is: 700 - 900 °C, and the carbonization time is: 40 - 180 minutes.

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