A modified non-graphite carbon material, its preparation method and application

Abstract

The present invention belongs to the technical field of rechargeable batteries, and particularly relates to a modified non-graphitic carbon material, a preparation method thereof, and an application thereof. The present invention provides a modified non-graphitic carbon material, which comprises a doped carbon carrier and a coated carbon coated on the doped carbon carrier; the doped carbon carrier comprises non-graphitic carbon and nitrogen and / or phosphorus doped in the non-graphitic carbon. In the present invention, the introduction of nitrogen and / or phosphorus can significantly improve the reversible capacity of the carbon material. The first reversible capacity of the modified carbon material in the lithium battery system is above 450 mAh / g, and the first reversible capacity of the modified carbon material in the sodium battery system is above 350 mAh / g. The modified non-graphitic carbon material provided by the present invention can be used as a negative electrode material to improve the energy density of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of rechargeable batteries, and particularly relates to a modified non-graphite carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] Rechargeable batteries (secondary batteries) are widely used in the fields of power batteries and energy storage batteries due to their advantages of good stability, high energy density, and no memory effect. Currently, the negative electrode materials of commercial secondary batteries are mainly graphite negative electrodes. However, the theoretical specific capacity of graphite negative electrodes is relatively low, only 372 mAh / g, and it is difficult to effectively improve the high-rate continuous charge and discharge ability and low-temperature performance.

[0003] Common non-graphite carbon negative electrode materials include soft carbon, hard carbon, or activated carbon. Due to the lack of graphitization treatment, they have a large interlayer spacing, and thus exhibit excellent rate performance and low-temperature performance. During the preparation process, a large number of micropores will be generated on the material surface. The microporous structure on the surface is extremely easy to absorb moisture and difficult to remove. The increase in moisture content will, on the one hand, reduce its specific capacity, and at the same time, consume the active lithium / sodium ions during the charge and discharge process, resulting in a decrease in the first Coulomb efficiency. At the same time, lattice defects will also be generated in the internal structure of non-graphite carbon materials. These lattice defects will cause lithium ions / sodium ions not only to intercalate into the carbon atom layers but also into these lattice defects during the deintercalation process, resulting in irreversible ion loss, thereby further leading to a low energy density of secondary batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified non-graphite carbon material, a preparation method thereof, and an application thereof. The modified non-graphite carbon material provided by the present invention can improve the energy density of the battery as a negative electrode material.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a modified non-graphite carbon material, including a doped carbon carrier and a coated carbon coated on the doped carbon carrier;

[0007] The doped carbon carrier includes non-graphite carbon and nitrogen and / or phosphorus doped in the non-graphite carbon.

[0008] Preferably, the mass ratio of the doped carbon carrier to the coated carbon is 100:2 to 15;

[0009] The mass of the nitrogen and / or phosphorus accounts for 0.1 to 1% of the mass of the non-graphite carbon;

[0010] The coated carbon is located on the surface and in the pores of the doped carbon carrier.

[0011] The present invention also provides a method for preparing the modified non-graphitic carbon material described in the above technical solution, which includes the following steps:

[0012] Mix non-graphitic carbon, doping raw materials and water for the first time, and obtain a pretreated carbon carrier through hydrothermal reaction; the doping raw materials include nitrogen-containing compounds and / or phosphorus-containing compounds;

[0013] Sinter the pretreated carbon carrier to obtain a doped carbon carrier;

[0014] Mix the doped carbon carrier and the carbon coating material for the second time, and obtain the modified non-graphitic carbon material through pressing and calcination in sequence.

[0015] Preferably, the nitrogen-containing compounds include one or more of ammonium carbonate, ammonium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, ammonium polyphosphate, ammonium nitrate, ammonium chloride and ammonium acetate;

[0016] The phosphorus-containing compounds include one or more of sodium phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate and ammonium polyphosphate;

[0017] The mass ratio of the doping raw materials to the non-graphitic carbon is 1-20:100;

[0018] The mass ratio of the doping raw materials to water is 0.5-5:100.

[0019] Preferably, the temperature of the hydrothermal reaction is 100-300°C, the heat preservation time is 1-10h; the pressure is 1-7MPa.

[0020] Preferably, the sintering is carried out in an atmosphere of air or nitrogen;

[0021] The temperature of the sintering is 200-600°C, and the heat preservation time is 2-10h.

[0022] Preferably, the carbon coating material includes one or more of asphalt, polyethylene, polystyrene, polypropylene, polyethylene glycol, polyacrylic acid, polymethacrylic acid, polymethyl methacrylate, polyacrylonitrile and sodium alginate;

[0023] The mass ratio of the doped carbon carrier to the carbon coating material is 100:3-10.

[0024] Preferably, the pressure of the pressing is 10-200MPa, and the pressure maintaining time is 1-30min.

[0025] Preferably, the calcination is carried out in an inert atmosphere;

[0026] The temperature of the calcination is 700-1200°C, and the heat preservation time is 2-10h.

[0027] The present invention also provides an application of the modified non-graphitic carbon material described in the above solution or the modified non-graphitic carbon material prepared by the preparation method described in the above technical solution as a negative electrode material.

[0028] The present invention provides a modified non-graphitic carbon material, comprising a doped carbon carrier and a coated carbon coated on the doped carbon carrier; the doped carbon carrier comprises non-graphitic carbon and nitrogen and / or phosphorus doped in the non-graphitic carbon. By doping nitrogen and / or phosphorus in the non-graphitic carbon, the present invention can significantly improve the specific capacity of the material, thereby improving the energy density of the battery; at the same time, carbon coating is performed on the doped non-graphitic carbon, which can significantly reduce the specific surface area of the non-graphitic carbon, enhance the air stability of the non-graphitic carbon, reduce the water content, and reduce the loss of active ions during the charge and discharge process; and can effectively isolate the negative electrode material and the electrolyte during the charge and discharge process, reduce the side reaction of the battery during the charge and discharge process, and contribute to the formation of a stable electrode and electrolyte interface; in addition, the modified non-graphitic carbon material provided by the present invention has a large carbon layer spacing, which is more conducive to the insertion and extraction of metal ions, and has a stable structure and small volume expansion, thereby improving the energy density of the battery. Description of the Drawings

[0029] Figure 1 and Figure 2 is the SEM image of the modified non-graphitic carbon material obtained in Example 1;

[0030] Figure 3 is the XRD pattern of the modified non-graphitic carbon material obtained in Example 1;

[0031] Figure 4 is the first charge-discharge curve of the lithium-ion half-cell assembled with the modified non-graphitic carbon material obtained in Example 1;

[0032] Figure 5 is the first charge-discharge curve of the sodium-ion half-cell assembled with the modified non-graphitic carbon material obtained in Example 1. Detailed Embodiments

[0033] The present invention provides a modified non-graphitic carbon material, comprising a doped carbon carrier and a coated carbon coated on the doped carbon carrier;

[0034] the doped carbon carrier comprises non-graphitic carbon and nitrogen and / or phosphorus doped in the non-graphitic carbon.

[0035] In the present invention, the non-graphitic carbon preferably comprises one or more of soft carbon, hard carbon and activated carbon. In the present invention, the carbon layer spacing of the non-graphitic carbon is preferably 0.36-0.42 nm.

[0036] In the present invention, the mass of the nitrogen and / or phosphorus preferably accounts for 0.1-1% of the mass of the non-graphitic carbon, more preferably 0.2-0.9%, and even more preferably 0.3-0.8%.

[0037] In the present invention, the mass ratio of the doped carbon carrier to the carbon coating is preferably 100:2-15, more preferably 100:5-12, and even more preferably 100:8-10. In the present invention, the thickness of the carbon coating is preferably 10-500 nm, more preferably 50-450 nm, and even more preferably 100-400 nm. In the present invention, the carbon coating is preferably amorphous carbon and is located on the surface and in the pores of the doped carbon carrier.

[0038] In the present invention, the specific surface area of the modified non-graphitic carbon material is preferably 1-6 m 2 / g, more preferably 2-5 m 2 / g, and even more preferably 3-4 m 2 / g.

[0039] In the present invention, the D10 particle size of the modified non-graphitic carbon material is preferably ≥1 μm.

[0040] In the present invention, the carbon layer spacing of the modified non-graphitic carbon material is preferably 0.36-0.42 nm.

[0041] The present invention also provides a method for preparing the modified non-graphitic carbon material described in the above technical solution, including the following steps:

[0042] Mix the non-graphitic carbon, the doping raw material, and water for the first time, and obtain a pretreated carbon carrier through a hydrothermal reaction; the doping raw material includes a nitrogen-containing compound and / or a phosphorus-containing compound;

[0043] Sinter the pretreated carbon carrier to obtain a doped carbon carrier;

[0044] Mix the doped carbon carrier and the carbon coating material for the second time, and obtain the modified non-graphitic carbon material through pressing and calcination in sequence.

[0045] In the present invention, without special instructions, all preparation raw materials are commercially available products well-known to those skilled in the art.

[0046] In the present invention, the non-graphitic carbon, the doping raw material, and water are mixed for the first time, and a pretreated carbon carrier is obtained through a hydrothermal reaction; the doping raw material includes a nitrogen-containing compound and / or a phosphorus-containing compound.

[0047] In the present invention, the non-graphitic carbon is preferably obtained through preparation; the preparation method preferably includes the following steps:

[0048] Sinter the carbon raw material to obtain the non-graphitic carbon.

[0049] In the present invention, the carbon raw material preferably includes one or more of fructose, mannose, sucrose, glucose, galactose, galactan, amino sugar, ribose, deoxyribose, starch, cellulose, polysaccharide, pectin, pentose, mannose, mannan, chitin, maltose, gum arabic, glycogen, inulin, chitin, straw, sawdust, walnut shell, bagasse, rice bran, wheat shell, coconut shell, apricot shell, peanut shell, wood, lignin, acrylic resin, phenolic resin, and epoxy resin; when the carbon raw material preferably includes two or more of the above selections, the present invention has no special limitation on the proportion of specific substances, and they can be mixed in any proportion.

[0050] In the present invention, the sintering temperature is preferably 1000 - 1800 °C, more preferably 1100 - 1700 °C, and even more preferably 1200 - 1600 °C; the heating rate to the sintering temperature is preferably 3 °C / min; the heat preservation time is preferably 6 h. In the present invention, the sintering is preferably carried out in a nitrogen atmosphere.

[0051] In the present invention, the equipment used for sintering is preferably a box furnace, a tube furnace, a rotary kiln, a roller hearth kiln, a pusher kiln, or a shuttle kiln. In the present invention, the oxygen content in the furnace chamber of the equipment is preferably less than 100 ppm. In the present invention, the temperature difference in the area where the materials are placed in the furnace chamber is preferably lower than 20 °C. In the present invention, the stacking height of the carbon raw material in the furnace chamber is preferably below 10 cm.

[0052] In the present invention, the doping raw material includes a nitrogen-containing compound and / or a phosphorus-containing compound. In the present invention, the nitrogen-containing compound preferably includes one or several of ammonium carbonate, ammonium bicarbonate, ammonium phosphate, ammonium dihydrogen phosphate, ammonium polyphosphate, ammonium nitrate, ammonium chloride, and ammonium acetate; the phosphorus-containing compound preferably includes one or several of sodium phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, and ammonium polyphosphate; when the doping raw material preferably includes two or more of the above selections, the present invention has no special limitation on the proportion of specific substances, and they can be mixed in any proportion.

[0053] In the present invention, the mass ratio of the doping raw material to the non-graphite carbon is preferably 1 - 20:100, more preferably 5 - 18:100, and even more preferably 10 - 15:100. In the present invention, the mass ratio of the doping raw material to water is preferably 0.5 - 5:100, more preferably 1.0 - 4.5:100, and even more preferably 1.5 - 4.0:100. The present invention has no special limitation on the process of the first mixing, and it can be carried out by using a process well-known to those skilled in the art.

[0054] In the present invention, the temperature of the hydrothermal reaction is preferably 100 - 300 °C, more preferably 150 - 280 °C, and even more preferably 180 - 250 °C; the heat preservation time is preferably 1 - 10 h, more preferably 2 - 9 h, and even more preferably 3 - 8 h; the pressure is preferably 1 - 7 MPa, more preferably 2 - 6 MPa, and even more preferably 3 - 5 MPa.

[0055] In the present invention, the doping raw material and the non-graphitic carbon can be more uniformly mixed through the hydrothermal reaction.

[0056] After the hydrothermal reaction, the present invention preferably further includes drying the obtained product. The present invention has no special limitation on the drying process, and it can be carried out by a process well-known to those skilled in the art.

[0057] After obtaining the pretreated carrier, the present invention sinters the pretreated carbon carrier to obtain a doped carbon carrier.

[0058] In the present invention, the sintering is preferably carried out in an atmosphere of air or nitrogen. In the present invention, the temperature of the sintering is preferably 200 - 600 °C, more preferably 250 - 550 °C, and even more preferably 300 - 500 °C; the heating rate to the sintering temperature is preferably 3 °C / min; the heat preservation time is preferably 2 - 10 h, more preferably 3 - 9 h, and even more preferably 4 - 8 h. In the present invention, during the sintering process, the doping raw material will be thermally decomposed, and the generated nitrogen element and / or phosphorus element will be partially solidified inside the carbon material to form N - C and / or P - C bonds, realizing in-situ doping; the introduction of the nitrogen element and / or phosphorus element can significantly improve the specific capacity of the negative electrode material, thereby improving the energy density of the secondary battery.

[0059] After obtaining the doped carbon carrier, the present invention performs a second mixing of the doped carbon carrier and the carbon coating material, and then successively performs pressing and calcination to obtain the modified carbon.

[0060] In the present invention, the carbon coating material preferably includes one or more of asphalt, polyethylene, polystyrene, polypropylene, polyethylene glycol, polyacrylic acid, polymethacrylic acid, polymethyl methacrylate, polyacrylonitrile, and sodium alginate; the asphalt preferably includes one or more of natural asphalt, coal tar pitch, and petroleum asphalt; when the carbon coating material is preferably two or more of the above selections, the present invention has no special limitation on the proportion of specific substances, and they can be mixed in any proportion.

[0061] In the present invention, the mass ratio of the doped carbon carrier to the carbon coating material is preferably 100:3 - 10; more preferably 100:4 - 9, and even more preferably 100:5 - 8.

[0062] In the present invention, the second mixing method preferably includes solid-phase mixing or liquid-phase mixing.

[0063] In the present invention, the solid-phase mixing is preferably: putting the doped carbon carrier and the carbon-coated material into a mixer and stirring.

[0064] In the present invention, the rotation speed of the stirring is preferably 300 - 1000 rpm, more preferably 400 - 900 rpm, and even more preferably 500 - 800 rpm; the time is preferably 1 - 4 h, more preferably 2 - 3 h. In the present invention, the mixer preferably includes a plowshare mixer, a ribbon mixer, a VC mixer, a fluid mixer, a high-speed stirrer or a three-eccentric mixer.

[0065] In the present invention, the liquid-phase mixing is preferably: mixing the doped carbon carrier, the carbon-coated material and an organic solvent, and placing them in a dispersion tank for stirring.

[0066] In the present invention, the organic solvent preferably includes one or more of alcohol organic solvents, ether organic solvents and ketone organic solvents; the alcohol organic solvents are further preferably one or more of ethanol, ethylene glycol, propanol, isopropanol and butanol.

[0067] In the present invention, the solid content of the mixed slurry obtained by mixing is preferably 10 - 40 wt%, more preferably 20 - 30 wt%. In the present invention, the rotation speed of the stirring is preferably 300 - 1000 rpm, more preferably 400 - 900 rpm, and even more preferably 500 - 800 rpm; the time is preferably 1 - 4 h, more preferably 2 - 3 h. After the stirring, the present invention further preferably includes drying the obtained slurry. The present invention has no special limitation on the drying process, and it can be carried out by using a process well-known to those skilled in the art.

[0068] In the present invention, the pressure of the pressing is preferably 10 - 200 MPa, more preferably 50 - 180 MPa, and even more preferably 100 - 150 MPa; the pressure holding time is preferably 1 - 30 min. The present invention has no special limitation on the pressing process, and it can be carried out by using a process well-known to those skilled in the art. In the present invention, the pressing is preferably carried out in an isostatic press, a single-column hydraulic press, a four-column hydraulic press, a mechanical press or a hot press.

[0069] In the present invention, the calcination temperature is preferably 700 to 1200 °C, more preferably 800 to 1100 °C, and still more preferably 900 to 1000 °C; the heating rate to the calcination temperature is preferably 3 to 8 °C / min; the heat preservation time is preferably 2 to 10 h, more preferably 3 to 9 h, and still more preferably 4 to 8 h. In the present invention, the calcination is preferably carried out in an inert atmosphere; the inert atmosphere preferably includes one or more of nitrogen, helium, neon, and argon. In the present invention, the calcination is preferably carried out in a box furnace, a tube furnace, a rotary kiln, a roller hearth kiln, a pusher kiln, or a shuttle kiln.

[0070] After the calcination, the present invention preferably further includes successively crushing, screening, classifying, and demagnetizing the obtained material.

[0071] The present invention has no special limitation on the crushing process, and the process well-known to those skilled in the art can be used. In the present invention, the particle size D50 of the material obtained by crushing is preferably 5 to 10 μm. The present invention has no special limitation on the screening process, and the process well-known to those skilled in the art can be used. In the present invention, the aperture of the sieve used for screening is preferably 200 to 400 mesh. In the present invention, the particle size D100 of the material obtained after screening is preferably ≤60 μm. The present invention has no special limitation on the classification process, and the process well-known to those skilled in the art can be used. In the present invention, the particle size D10 of the material obtained after classification is preferably ≥1 μm. The present invention has no special limitation on the demagnetizing process, and the process well-known to those skilled in the art can be used. In the present invention, the total amount of magnetic substances removed by demagnetization is preferably ≤2 ppm.

[0072] The present invention also provides the use of the modified non-graphitic carbon material described in the above technical solution or the modified non-graphitic carbon material prepared by the preparation method described in the above technical solution as a negative electrode material. The present invention has no special limitation on the specific implementation manner of the use, and the manner well-known to those skilled in the art can be used.

[0073] To further illustrate the present invention, the following describes in detail a modified non-graphitic carbon material and its preparation method and use provided by the present invention with reference to the drawings and examples, but they should not be construed as limiting the protection scope of the present invention.

[0074] Example 1

[0075] Put 10 kg of starch into a box furnace (the stacking height is 3 cm and the temperature difference in the material area is less than 20 °C), introduce nitrogen until the oxygen content in the furnace chamber of the box furnace is less than 100 ppm, and heat it to 1300 °C at a heating rate of 3 °C / min for sintering, and the heat preservation time is 6 h to obtain non-graphitic carbon;

[0076] After mixing 1 kg of non-graphitic carbon, 0.1 kg of ammonium phosphate, and 10 kg of water, put them into a hydrothermal reactor and carry out hydrothermal reaction at a pressure of 4 MPa and a temperature of 200 °C for 5 h. After drying, a pretreated carrier is obtained;

[0077] Put 1 kg of the pretreated carrier into a box furnace, heat it to 500 °C at a heating rate of 3 °C / min under a nitrogen atmosphere, and keep it for 4 h to obtain a doped carbon carrier;

[0078] Put 800 g of the doped carbon carrier and 50 g of polypropylene into a mixer, stir at a speed of 600 rpm for 2 h, and then put it into a four-column hydraulic press and press it at 100 MPa. The pressure holding time is 10 min;

[0079] Then put the pressed material into a tube furnace, heat it to 950 °C at a heating rate of 3 °C / min under a nitrogen atmosphere, and keep it for 6 h;

[0080] After calcination, crush the obtained material to obtain a material with a D50 particle size of 8.6 μm; then screen it with a 325-mesh sieve to remove large particles to obtain a material with a D100 particle size of 37.2 μm; then through classification treatment, obtain a material with a D10 particle size of 3.1 μm, and finally obtain a modified non-graphitic carbon material after demagnetization (where the doping mass percentage content of nitrogen element is 0.23%, and the doping mass percentage content of phosphorus element is 0.16%).

[0081] Example 2

[0082] Put 10 kg of glucose into a rotary kiln (the stacking height is 6 cm, and the temperature difference in the material area is less than 20 °C), introduce nitrogen until the oxygen content in the furnace of the rotary kiln is less than 100 ppm, heat it to 1700 °C at a heating rate of 3 °C / min for sintering, and keep it for 4 h to obtain non-graphitic carbon;

[0083] After mixing 1 kg of non-graphitic carbon, 0.2 kg of ammonium chloride, and 40 kg of water, put them into a hydrothermal reactor and carry out hydrothermal reaction at a pressure of 2 MPa and a temperature of 150 °C for 10 h. After drying, a pretreated carrier is obtained;

[0084] Put 1 kg of the pretreated carrier into a tube furnace, heat it to 600 °C at a heating rate of 3 °C / min under a nitrogen atmosphere, and keep it for 8 h to obtain a doped carbon carrier;

[0085] Put 1 kg of the doped carbon carrier and 100 g of asphalt into a mixer, stir at a speed of 700 rpm for 3 h, and then put it into an isostatic press and press it at 200 MPa. The pressure holding time is 1 min;

[0086] Then place the pressed material in a tubular furnace, heat it to 1150 °C at a heating rate of 3 °C / min under a nitrogen atmosphere for calcination, and keep the temperature for 4 h;

[0087] After the calcination is completed, crush the obtained material to obtain a material with a D50 particle size of 9.5 μm; then screen it with a 400-mesh sieve to remove large particles to obtain a material with a D100 particle size of 41.8 μm; then through classification treatment, obtain a material with a D10 particle size of 4.7 μm, and finally obtain a modified non-graphite carbon material after demagnetization (where the doping mass percentage content of nitrogen element is 0.76%).

[0088] Example 3

[0089] Put 10 kg of coconut shells into a roller hearth kiln (the stacking height is 9 cm and the temperature difference in the material area is less than 20 °C), introduce nitrogen until the oxygen content in the furnace chamber of the roller hearth kiln is less than 100 ppm, heat it to 1200 °C at a heating rate of 3 °C / min for sintering, and keep the temperature for 2 h to obtain non-graphite carbon;

[0090] Mix 1 kg of non-graphite carbon, 0.2 kg of ammonium polyphosphate and 5 kg of water, put them into a hydrothermal reaction kettle, carry out hydrothermal reaction at a pressure of 7 MPa and a temperature of 300 °C for 2 h, and obtain a pretreated carrier after drying;

[0091] Put 1 kg of the pretreated carrier into a box furnace, heat it to 200 °C at a heating rate of 3 °C / min under an air atmosphere for sintering, and keep the temperature for 2 h to obtain a doped carbon carrier;

[0092] Put 1 kg of the doped carbon carrier and 50 g of polyacrylonitrile into a mixer, stir at a speed of 700 rpm for 3 h, then place it in a single-column hydraulic press and press it at 50 MPa, and keep the pressure for 30 min;

[0093] Then place the pressed material in a box furnace, heat it to 800 °C at a heating rate of 3 °C / min under a nitrogen atmosphere for calcination, and keep the temperature for 10 h;

[0094] After the calcination is completed, crush the obtained material to obtain a material with a D50 particle size of 7.2 μm; then screen it with a 200-mesh sieve to remove large particles to obtain a material with a D100 particle size of 34.7 μm; then through classification treatment, obtain a material with a D10 particle size of 2.9 μm, and finally obtain a modified non-graphite carbon material after demagnetization (where the doping mass percentage content of nitrogen element is 0.47% and the doping mass percentage content of phosphorus element is 0.31%).

[0095] Example 4

[0096] Put 10 kg of phenolic resin into a pusher kiln (the stacking height is 6 cm and the temperature difference in the material area is less than 20 °C), introduce nitrogen until the oxygen content in the furnace of the roller kiln is less than 100 ppm, heat it up to 1000 °C at a heating rate of 3 °C / min for sintering, and keep the temperature for 6 h to obtain non-graphitic carbon;

[0097] Mix 1 kg of non-graphitic carbon, 0.3 kg of potassium phosphate and 10 kg of water, put them into a hydrothermal reactor, and carry out hydrothermal reaction at a pressure of 1.5 MPa and a temperature of 260 °C for 6 h. After drying, a pretreated carrier is obtained;

[0098] Put 1 kg of the pretreated carrier into a box furnace, heat it up to 600 °C at a heating rate of 3 °C / min in a nitrogen atmosphere for sintering, and keep the temperature for 10 h to obtain a doped carbon carrier;

[0099] Put 1 kg of the doped carbon carrier and 100 g of polymethyl methacrylate into a mixer, stir at a speed of 800 rpm for 2 h, then put it into a hot press and press it at 150 MPa, and keep the pressure for 15 min;

[0100] Then put the pressed material into a box furnace, heat it up to 850 °C at a heating rate of 3 °C / min in a nitrogen atmosphere for calcination, and keep the temperature for 7 h;

[0101] After calcination, crush the obtained material to obtain a material with a D50 particle size of 5.8 μm; then screen it with a 325-mesh sieve to remove large particles to obtain a material with a D100 particle size of 36.1 μm; then through classification treatment, obtain a material with a D10 particle size of 2.2 μm, and finally obtain a modified non-graphitic carbon material after demagnetization (where the doping mass percentage of phosphorus element is 0.59%).

[0102] Comparative Example 1

[0103] Prepare the modified non-graphitic carbon material in the same manner as in Example 1, except that nitrogen and phosphorus doping are not carried out.

[0104] Comparative Example 2

[0105] Prepare the modified non-graphitic carbon material in the same manner as in Example 1. The difference is that after adding nitrogen-containing compounds and / or phosphorus-containing compounds, doping is not carried out in the hydrothermal reactor, but directly mixed.

[0106] Comparative Example 3

[0107] Prepare the modified non-graphitic carbon material in the same manner as in Example 1, except that carbon coating is not carried out.

[0108] Comparative Example 4

[0109] The modified non-graphitic carbon material was prepared in the same manner as in Example 1, except that after adding the carbon coating material, the pressing process was not carried out.

[0110] Performance Test

[0111] Test Example 1

[0112] The modified non-graphitic carbon material obtained in Example 1 was subjected to scanning electron microscopy (JSM-7800F) for scanning electron microscopy test, and the obtained SEM images are as Figure 1 and Figure 2 shown. It can be seen from Figure 1 and Figure 2 that the modified non-graphitic carbon material obtained in the present invention has good particle consistency, uniform distribution, and no obvious fine powder.

[0113] Test Example 2

[0114] The modified non-graphitic carbon material obtained in Example 1 was subjected to nitrogen element test using an oxygen, nitrogen, and hydrogen analyzer (ONH836). It was tested that the mass percentage content of nitrogen element on the modified non-graphitic carbon material provided in Example 1 was 0.23%.

[0115] Test Example 3

[0116] The modified non-graphitic carbon material obtained in Example 1 was subjected to element content test using a SPECTRO ICP-OES plasma emission spectrometer GREEN from Germany. It was tested that the mass percentage content of phosphorus element on the modified non-graphitic carbon material provided in Example 1 was 0.16%.

[0117] Test Example 4

[0118] The modified non-graphitic carbon material obtained in Example 1 was subjected to X-ray diffraction test using an XRD diffractometer (PANalytical X'Pert PRO MPD from the Netherlands), and the obtained XRD pattern is as Figure 3 shown. According to the Scherrer formula, the carbon layer spacing of the modified non-graphitic carbon material provided in this example can be calculated to be 0.38 nm.

[0119] Test Example 5

[0120] Test the electrochemical performance of the non-graphitic carbon materials obtained in Test Examples 1 to 4 and Comparative Examples 1 to 4;

[0121] 1. Lithium battery button cell test method:

[0122] The non-graphitic carbon materials obtained in Examples 1-4 and Comparative Examples 1-4 were used as the negative electrode active material. The active material, conductive carbon black, and binder were mixed in pure water at a mass ratio of 96:1:3, homogenized, and the solid content was controlled at 48%. It was coated on a copper foil current collector and vacuum baked at 100-110 °C for 4-8 h. After pressing into shape, it was punched into a negative electrode sheet. A button-type half-cell was assembled in a glove box filled with argon. The counter electrode was a lithium metal sheet, the separator used was PE, and the electrolyte was 1 mol / L LiPF6 in EC / DMC (Vol 1:1). The button-type battery was subjected to charge and discharge tests, and the test process was 0.2C DC to 0V, 0.05C DC to 0V, 0V CV 50 μA, 0.01C DC to 0V, 0V CV 20 μA, Rest 10 min, 0.2C CC to 2V. The first reversible capacity and efficiency of the button-type half-cell were tested; the test equipment for the button-type battery was the LAND battery test system of Wuhan Blue Electronic Co., Ltd.; the test results obtained are shown in Table 1; among them, the first charge-discharge curve obtained from the modified non-graphitic carbon material of Example 1 is as shown in Figure 4 shown;

[0123] 2. Sodium battery button cell test method:

[0124] The non-graphitic carbon materials obtained in Examples 1-4 and Comparative Examples 1-4 were used as the sodium positive electrode material. In a dry room with a humidity less than 10%, the sodium positive electrode material, conductive carbon black, and binder were mixed in NMP at a mass ratio of 90:5:5, homogenized, and the solid content was controlled at 45%. It was coated on an aluminum foil current collector and vacuum baked at 100-110 °C for 4-8 h. After pressing into shape, it was punched into a sodium positive electrode sheet. A button-type half-cell was assembled in a glove box filled with argon. The counter electrode was a sodium metal sheet, the separator used was PE, and the electrolyte was 1 mol / L NaPF6 in EC / DMC (Vol 1:1). The button-type battery was subjected to charge and discharge tests, and the test process was 0.1C CC 4.0V, 4.0V CV 0.03C, 0.1C DC 2V. The first reversible capacity and efficiency of the button-type half-cell were tested; the test equipment for the button-type battery was the commercial LAND battery test system of Wuhan Blue Electronic Co., Ltd.; the test results are shown in Table 1; among them, the first charge-discharge curve obtained from the modified non-graphitic carbon material of Example 1 is as shown in Figure 5 shown;

[0125] Table 1 Electrochemical performance of half-cells assembled with carbon materials obtained in Examples and Comparative Examples

[0126]

[0127] It can be seen from Table 1 that in the non-graphitic carbon of the present invention, after doping with nitrogen and / or phosphorus elements, the first reversible capacity and first efficiency of the material can be significantly improved.

[0128] In Comparative Example 1, the modified non-graphitic carbon material is not doped with nitrogen and / or phosphorus, and the initial reversible capacity of the obtained material is significantly reduced. The initial reversible capacity in the lithium battery is only 401.3 mAh / g, and the initial reversible capacity in the sodium battery is only 290.6 mAh / g.

[0129] In Comparative Example 2, after adding a nitrogen-containing compound and / or a phosphorus-containing compound to the modified non-graphitic carbon material, doping is not carried out in a hydrothermal reaction kettle, but direct mixing is performed, and the initial reversible capacity and the initial efficiency of the obtained material will also decrease.

[0130] In Comparative Example 3, the modified non-graphitic carbon material is not carbon-coated, the initial reversible capacity decreases, and the initial efficiency decreases significantly. Especially in the lithium battery test system, the initial efficiency is only 71.2%.

[0131] In Comparative Example 4, after adding a carbon coating material to the modified non-graphitic carbon material, the pressing process is not carried out, and the initial reversible capacity and the initial efficiency of the obtained material will both decrease.

[0132] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A preparation method of a modified non-graphite carbon material, characterized in that, The steps are as follows: Put 10 kg of coconut shell into a roller hearth kiln with a stacking height of 9 cm and a temperature difference in the material area of less than 20 °C. Introduce nitrogen until the oxygen content in the furnace of the roller hearth kiln is less than 100 ppm. Heat it to 1200 °C at a heating rate of 3 °C / min for sintering, and keep the temperature for 2 h to obtain non-graphitic carbon; Mix 1 kg of non-graphitic carbon, 0.2 kg of ammonium polyphosphate and 5 kg of water, then put them into a hydrothermal reactor and carry out hydrothermal reaction at a pressure of 7 MPa and a temperature of 300 °C for 2 h. After drying, a pretreated carrier is obtained; Put 1 kg of the pretreated carrier into a box furnace, heat it to 200 °C at a heating rate of 3 °C / min in an air atmosphere for sintering, and keep the temperature for 2 h to obtain a doped carbon carrier; Put 1 kg of the doped carbon carrier and 50 g of polyacrylonitrile into a mixer, stir at a speed of 700 rpm for 3 h, then put it into a single-column hydraulic press and press it at 50 MPa with a pressure holding time of 30 min; Then put the pressed material into a box furnace, heat it to 800 °C at a heating rate of 3 °C / min in a nitrogen atmosphere for calcination, and keep the temperature for 10 h; After the calcination is completed, crush the obtained material to obtain a material with a D50 particle size of 7.2 μm; then screen it with a 200-mesh sieve to remove large particles to obtain a material with a D100 particle size of 34.7 μm; then through classification treatment, obtain a material with a D10 particle size of 2.9 μm, and finally obtain a modified non-graphitic carbon material after demagnetization, wherein the doping mass percentage content of nitrogen element is 0.47%, and the doping mass percentage content of phosphorus element is 0.31%.

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