Porous carbon nanomaterial based on direct carbonization and preparation method and application thereof

Abstract

The application belongs to the technical field of battery materials, and discloses a porous carbon nanomaterial obtained based on direct carbonization, and a preparation method and application thereof. The preparation method comprises the following steps: first temperature rising carbonization of a carbon source, oxidation to eliminate surface effect after cooling, and second temperature rising carbonization to obtain the porous carbon nanomaterial; the first temperature rising carbonization is that the carbon source is placed in a tube furnace, inert gas is introduced into the tube furnace, the temperature is raised to 600-800 DEG C at a temperature rising rate of 1-10 DEG C / min, and then the temperature is kept for 1-3 hours; the cooling is cooling to room temperature under a nitrogen atmosphere; the oxidation to eliminate surface effect is that air is introduced into the tube furnace for 1-3 hours to oxidize the carbonization product so as to eliminate surface effect; the second temperature rising carbonization is that inert gas is introduced into the tube furnace again, the temperature is raised to 1200-2400 DEG C at a temperature rising rate of 1-10 DEG C / min, and then the temperature is kept for 1-3 hours, and the porous carbon nanomaterial is obtained after natural cooling.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and specifically relates to a porous carbon nanomaterial obtained by direct carbonization, its preparation method, and its application. Background Technology

[0002] The natural abundance of lithium resources is as low as 0.0065%, making it difficult to support the industry's continued battery demand. Overexploitation of lithium resources has led to a lithium crisis, causing prices to soar and making the development of new rechargeable batteries to replace lithium batteries an urgent need. Among various rechargeable batteries, potassium has a low redox potential and can be intercalated into graphite to form a stable graphite intercalation compound, KC8. It has advantages such as abundant resources and low price. Sodium-ion batteries work on a similar principle to lithium-ion batteries and have a significant cost advantage. Sodium / potassium rechargeable batteries are considered two of the most promising battery systems to replace lithium-ion batteries. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology and develop efficient electrode materials to meet the demand for high performance and low cost, the primary objective of this invention is to provide a method for preparing porous carbon nanomaterials based on direct carbonization.

[0004] Another object of the present invention is to provide a porous carbon nanomaterial prepared by the above preparation method.

[0005] Another object of the present invention is to provide an application of the above-mentioned porous carbon nanomaterials.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing porous carbon nanomaterials based on direct carbonization includes the following steps: heating and carbonizing a carbon source for the first time, oxidizing it after cooling to eliminate surface effects, and then heating and carbonizing it a second time to obtain porous carbon nanomaterials.

[0008] The carbon source is one or both of bismuth ammonium citrate and bismuth citrate.

[0009] The first heating carbonization involves placing the carbon source in a tube furnace, introducing inert gas into the tube furnace, heating the temperature to 600-800℃ at a heating rate of 1-10℃ / min, and then holding the temperature for 1-3 hours.

[0010] The cooling process involves cooling to room temperature under a nitrogen atmosphere; the oxidation process involves introducing air into the tube furnace for 1-3 hours to oxidize the carbonization products and thus eliminate the surface effect.

[0011] The second heating carbonization involves introducing inert gas into the tube furnace again, heating it to 1200-2400℃ at a heating rate of 1-10℃ / min, holding it at that temperature for 1-3 hours, and then allowing it to cool naturally to obtain porous carbon nanomaterials.

[0012] A porous carbon nanomaterial prepared by the above-described preparation method.

[0013] The above-mentioned porous carbon nanomaterials are used in the anode materials of sodium / potassium ion secondary batteries.

[0014] A battery electrode sheet for sodium / potassium ion secondary battery anode material prepared from the above-mentioned porous carbon nanomaterials is obtained by placing porous carbon nanomaterials, conductive agent and binder together in a mass ratio of 70-90:5-15:5-15 into a ball mill, adding N-methylpyrrolidone to prepare an electrode slurry, coating the obtained electrode slurry onto copper foil, drying it in an oven at 70°C for 10 hours, and cutting it into sheets to obtain the battery electrode sheet for sodium / potassium ion secondary battery anode material.

[0015] The conductive agent is one or more of Super P, acetylene black, and Ketjen black, and the binder is polyvinylidene fluoride.

[0016] A sodium / potassium ion secondary battery is assembled from sodium / potassium sheets, a separator, an electrolyte, button cell springs, gaskets, positive and negative electrode shells, and battery electrode sheets made of the aforementioned sodium / potassium ion secondary battery negative electrode material.

[0017] The present invention has the following advantages and effects compared with the prior art:

[0018] (1) The present invention adopts an extremely simple method to successfully prepare carbon nanomaterials with porous structures, which provides the possibility for large-scale industrial production; and the prepared carbon nanomaterials have excellent performance. After 700 charge-discharge tests at a current density of 0.1A / g, the cycle performance can still be maintained at 150mAh / g.

[0019] (2) The porous carbon nanomaterials prepared by this invention facilitate the insertion and extraction of sodium / potassium ions between the carbon nanomaterials and the electrolyte, thereby solving the technical problem that the conductivity and cycle stability of the negative electrode materials of sodium / potassium ion batteries need to be improved in the prior art. Therefore, the material of this invention has high initial discharge capacity and cycle stability, and is suitable for the development requirements of negative electrode materials for sodium / potassium ion batteries. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the porous carbon nanomaterial prepared in Example 1 of the present invention;

[0021] Figure 2Transmission electron microscope (TEM) image of the porous carbon nanomaterial prepared in Example 1 of this invention;

[0022] Figure 3 The XRD energy spectrum of the porous carbon nanomaterial prepared in Example 1 of this invention;

[0023] Figure 4 The graph shows the charge-discharge performance of a sodium / potassium ion battery anode assembled using the porous carbon nanomaterial prepared in Example 1 of this invention as the anode material, under a current density of 0.1 A / g for the first 700 constant current cycle. Detailed Implementation

[0024] The following specific embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention.

[0025] Example 1

[0026] (1) Place the carbon source, bismuth ammonium citrate, in a tube furnace and pass an inert protective gas (nitrogen).

[0027] (2) Heat the tubular furnace to 600°C at a heating rate of 5°C / min, and hold it at the temperature for 2 hours after reaching the temperature.

[0028] (3) After the heat preservation is completed, cool to room temperature in a nitrogen atmosphere, and then slowly introduce air for 1 hour to oxidize the carbonized products and thus eliminate the surface effect.

[0029] (4) Inert protective gas (nitrogen) is introduced into the tube furnace again, and the temperature is raised to 1400°C at a heating rate of 5°C / min. Then the temperature is held for 2 hours and the porous carbon nanomaterial is obtained after natural cooling.

[0030] (5) Test the material using an in-situ analytical XRD diffractometer to determine whether bismuth has been completely removed. For example... Figure 3 As shown, there are only pure carbon diffraction peaks, with no other impurities.

[0031] (6) Observation using transmission electron microscopy, such as Figure 2 As shown, scanning electron microscopy observations are as follows: Figure 1 As shown, the desired carbon nanomaterial is a porous carbon nanomaterial.

[0032] (7) Preparation method of sodium / potassium ion battery negative electrode sheet: The porous carbon nanomaterials, conductive agent and binder prepared above are put into a ball mill and ball milled for 10 minutes in a mass ratio of 8:1:1. Then, N-methylpyrrolidone is added to make an electrode slurry. The obtained electrode slurry is coated onto copper foil and dried in an oven at 70°C for 10 hours. The sheet is then cut to obtain the sodium / potassium ion secondary battery negative electrode sheet.

[0033] (8) Preparation method of potassium-ion secondary battery: potassium sheet, separator (glass fiber), electrolyte (4M KFSI inDME), button cell spring, gasket, positive and negative electrode shell and the above-obtained potassium-ion secondary battery negative electrode sheet are assembled.

[0034] (9) Preparation method of sodium-ion secondary battery: Sodium sheet, separator (glass fiber), electrolyte (1.0M NaPF6in DME), button cell spring, gasket, positive and negative electrode shell and the sodium-ion secondary battery negative electrode sheet obtained above are assembled.

[0035] (10) Test method: The potassium-ion secondary battery or sodium-ion secondary battery prepared above was subjected to constant current charge-discharge test. The current density was 0.1 A / g, and the charge-discharge voltage range was 0.01 V-3 V. The constant current cycle charge-discharge performance curves for the first 700 cycles are shown in the figure. Figure 4 As shown.

[0036] Example 2

[0037] (1) Place the carbon source, bismuth ammonium citrate, in a tube furnace and pass an inert protective gas (nitrogen).

[0038] (2) Heat the tubular furnace to 700°C at a heating rate of 2°C / min, and hold it at the temperature for 3 hours after reaching the temperature.

[0039] (3) After the heat preservation is completed, cool to room temperature in a nitrogen atmosphere, and then slowly introduce air for 1.5 hours to oxidize the carbonized products and thus eliminate the surface effect.

[0040] (4) Inert protective gas (nitrogen) is introduced into the tube furnace again, and the temperature is raised to 1600℃ at a heating rate of 2℃ / min. Then the temperature is held for 2 hours and the porous carbon nanomaterial is obtained after natural cooling.

[0041] (5) Preparation method of sodium / potassium ion battery negative electrode sheet: The porous carbon nanomaterials, conductive agent and binder prepared above are put into a ball mill and ball milled for 10 minutes in a mass ratio of 8:1:1. Then, N-methylpyrrolidone is added to make an electrode slurry. The obtained electrode slurry is coated onto copper foil and dried in an oven at 70°C for 10 hours. The sheet is cut to obtain the sodium / potassium ion secondary battery negative electrode sheet.

[0042] (6) Preparation method of potassium-ion secondary battery: potassium sheet, separator (glass fiber), electrolyte (4M KFSI inDME), button cell spring, gasket, positive and negative electrode shell and the above-obtained potassium-ion secondary battery negative electrode sheet are assembled.

[0043] (7) Preparation method of sodium-ion secondary battery: Sodium sheet, separator (glass fiber), electrolyte (1.0M NaPF6in DME), button cell spring, gasket, positive and negative electrode shell and the sodium-ion secondary battery negative electrode sheet obtained above are assembled.

[0044] (8) Test method: The potassium-ion secondary battery or sodium-ion secondary battery prepared above was subjected to constant current charge and discharge test, with a current density of 0.1A / g and a charge and discharge voltage range of 0.01V-3V.

[0045] Example 3

[0046] (1) Place the carbon source, bismuth ammonium citrate, in a tube furnace and pass an inert protective gas (nitrogen).

[0047] (2) Heat the tubular furnace to 900℃ at a heating rate of 10℃ / min, and hold it at the temperature for 1 hour after reaching the temperature.

[0048] (3) After the heat preservation is completed, cool to room temperature in a nitrogen atmosphere, and then slowly introduce air for 2 hours to oxidize the carbonized products and thus eliminate the surface effect.

[0049] (4) Inert protective gas (nitrogen) is introduced into the tube furnace again, and the temperature is raised to 2000℃ at a heating rate of 5℃ / min. Then the temperature is held for 2 hours and the porous carbon nanomaterial is obtained after natural cooling.

[0050] (5) Preparation method of sodium / potassium ion battery negative electrode sheet: The porous carbon nanomaterials, conductive agent and binder prepared above are put into a ball mill and ball milled for 10 minutes in a mass ratio of 8:1:1. Then, N-methylpyrrolidone is added to make an electrode slurry. The obtained electrode slurry is coated onto copper foil and dried in a 70-degree oven for 10 hours. The sheet is cut to obtain the sodium / potassium ion secondary battery negative electrode sheet.

[0051] (6) Preparation method of potassium-ion secondary battery: potassium sheet, separator (glass fiber), electrolyte (4M KFSI inDME), button cell spring, gasket, positive and negative electrode shell and the above-obtained potassium-ion secondary battery negative electrode sheet are assembled.

[0052] (7) Preparation method of sodium-ion secondary battery: Sodium sheet, separator (glass fiber), electrolyte (1.0M NaPF6in DME), button cell spring, gasket, positive and negative electrode shell and the sodium-ion secondary battery negative electrode sheet obtained above are assembled.

[0053] (8) Test method: The potassium-ion secondary battery or sodium-ion secondary battery prepared above was subjected to constant current charge and discharge test, with a current density of 0.1A / g and a charge and discharge voltage range of 0.01V-3V.

[0054] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing porous carbon nanomaterials based on direct carbonization, characterized in that... The following steps are included: (1) Place the carbon source in a tube furnace for the first heating carbonization. Inert gas is introduced into the tube furnace and the temperature is raised to 600-800℃ at a heating rate of 1-10℃ / min. Then the temperature is maintained for 1-3 hours. The carbon source is one or both of bismuth ammonium citrate and bismuth citrate. (2) Cool to room temperature in a nitrogen atmosphere, and introduce air into the tube furnace for 1-3 hours to oxidize the carbonization products and thus eliminate the surface effect; (3) Inert gas is introduced into the tube furnace again, and the temperature is raised to 1200-2400℃ at a heating rate of 1-10℃ / min. Then the temperature is maintained for 1-3 hours. After natural cooling, porous carbon nanomaterials are obtained.

2. A porous carbon nanomaterial prepared by the preparation method described in claim 1.

3. The application of the porous carbon nanomaterials according to claim 2 in the negative electrode material of sodium-ion or potassium-ion secondary batteries.

4. A battery electrode sheet for a sodium-ion or potassium-ion secondary battery negative electrode material prepared from the porous carbon nanomaterials described in claim 2, characterized in that: This battery electrode is made by putting porous carbon nanomaterials, conductive agents and binders into a ball mill in a mass ratio of 70-90:5-15:5-15, adding N-methylpyrrolidone to make an electrode slurry, coating the obtained electrode slurry onto copper foil, drying it in an oven at 70°C for 10 hours, and cutting it into sheets to obtain a battery electrode material for sodium-ion or potassium-ion secondary batteries.

5. The battery electrode sheet of the sodium-ion or potassium-ion secondary battery negative electrode material according to claim 4, characterized in that: The conductive agent is one or more of Super P, acetylene black, and Ketjen black, and the adhesive is polyvinylidene fluoride.

6. A sodium-ion or potassium-ion secondary battery, characterized in that: The battery is assembled using sodium or potassium sheets, along with a separator, electrolyte, button cell spring, gasket, positive and negative electrode shells, and the sodium-ion or potassium-ion secondary battery negative electrode material as described in claim 4.

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