A doped and modified porous carbon anode material and its preparation method

Abstract

The present invention discloses a doped and modified porous carbon anode material and a preparation method thereof, which relates to the technical field of electrode materials. When preparing the doped and modified porous carbon anode material of the present invention, first, the sugarcane bagasse pretreated with vinyltrimethoxysilane reacts with bis(4-chlorophenyl)phosphine oxide, then reacts with 2,4,6-triethylbenzene-1,3,5-trimethylamine, and then reacts with bis(4-chlorophenyl)phosphine oxide to obtain phosphorus-containing sugarcane bagasse. Secondly, the phosphorus-containing sugarcane bagasse reacts with 1,4-diamino-2,5-divinylbenzene, and then reacts with terephthalaldehyde and p-phenylenediamine to obtain modified sugarcane bagasse; the modified sugarcane bagasse and ferrous acetate are mixed, and then mixed with polydimethylsilane, and the modified porous carbon anode material is obtained by drying, calcining, grinding and pressing. The doped and modified porous carbon anode material prepared by the present invention has wide raw material sources, low cost, good electrochemical performance and good cycle stability.

Description

Technical Field

[0001] The present invention relates to the field of electrode materials, and particularly to a doped and modified porous carbon anode material and a preparation method thereof. Background Art

[0002] With the progress of technology, the requirements for energy storage devices in fields such as electronic products, electric vehicles, medical equipment, and aerospace are increasing day by day. Among many energy storage devices, batteries with high energy density, small volume, and long cycle life have gradually become a research hotspot.

[0003] Generally speaking, the main materials studied as battery anode materials are as follows: carbon materials, tin-based materials, silicon-based materials, nitrides, phosphides, and transition metal oxides, etc. Considering comprehensive factors such as cycle capacity, specific capacity, and production cost, the most ideal anode material at present is carbon materials. The most widely used anode material in the current market is still graphite-based anode materials. However, the theoretical specific capacity of graphite anodes is only 372 mAh / g, and the energy density is relatively low. At the same time, the "lithium precipitation" phenomenon of graphite anode materials in the application of lithium-ion batteries has relatively large potential safety hazards. These problems have greatly restricted the application of graphite anodes in batteries. Therefore, improving the specific capacity and cycle stability of batteries has become the key to their further development. To solve the above problems, it is necessary to modify carbon materials. Currently, the modification methods mainly include heteroatom doping of carbon materials, nanostructure design, and porous structure design, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a doped and modified porous carbon anode material and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A doped and modified porous carbon anode material, characterized in that the doped and modified porous carbon anode material is obtained by mixing modified bagasse and ferrous acetate, and then mixing with polydimethylsilane, followed by drying, calcining, grinding, and pressing into tablets.

[0007] As an optimization, the modified bagasse is obtained by reacting bagasse pretreated with vinyltrimethoxysilane with bis(4-chlorophenyl)phosphine oxide, then reacting with 2,4,6-triethylbenzene-1,3,5-trimethylamine, then reacting with bis(4-chlorophenyl)phosphine oxide to obtain phosphorus-containing bagasse, reacting the phosphorus-containing bagasse with 1,4-diamino-2,5-divinylbenzene, and then reacting with terephthalaldehyde and p-phenylenediamine.

[0008] A preparation method of a doped and modified porous carbon anode material, comprising the following preparation steps:

[0009] (1) Mix the pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Kaster catalyst, and N,N-dimethylformamide in a mass ratio of 1:(0.5 - 0.7):(0.001 - 0.003):(20 - 30). Heat the mixture to 100 - 120 °C and react for 20 - 22 h. After the reaction, filter and redisperse it in N,N-dimethylformamide with a mass 20 - 30 times that of the pretreated bagasse. Add 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide, and stir at 15 - 20 °C for 4 - 6 h. Then add bis(4-chlorophenyl)phosphine oxide with a mass 1.8 - 2.0 times that of the pretreated bagasse, heat to 25 - 30 °C and react for 4 - 6 h. After the reaction, filter and wash with pure water 5 times, and dry at 80 °C for 24 h to obtain phosphorus-containing bagasse;

[0010] (2) Mix the phosphorus-containing bagasse, Kaster catalyst, 1,4-diamino-2,5-divinylbenzene, and N,N-dimethylformamide in a mass ratio of 1:(0.001 - 0.003):(2 - 3):(20 - 30). Heat the mixture to 100 - 120 °C and react for 20 - 22 h. After the reaction, filter and redisperse it in toluene with a mass 20 - 30 times that of the pretreated bagasse. Under nitrogen protection, add terephthalaldehyde with a mass 1.5 - 1.8 times that of the phosphorus-containing bagasse and p-phenylenediamine with a mass 1.5 - 1.8 times that of the phosphorus-containing bagasse, heat to 110 - 120 °C and reflux and stir for 2 - 3 h. Filter and wash with ethanol 3 - 4 times, and dry at 80 °C for 24 h to obtain modified bagasse;

[0011] (3) Mix the modified bagasse and 10 wt% ferrous acetate solution in a mass ratio of 1:(10 - 12), stir at room temperature for 22 - 24 h, filter and redisperse it in a polydimethylsiloxane solution with a mass 10 - 12 times that of the modified bagasse, stir for 5 - 10 min, filter after stirring, and calcine it using a programmed calcination method in an argon tube furnace. After calcination, grind it through a 100-mesh sieve to obtain the modified anode material;

[0012] (4) Prepare a negative electrode sheet from the modified anode material, conductive agent, and binder in a mass ratio of 8:1:1 by the tabletting method to obtain a doped and modified porous carbon negative electrode material.

[0013] As an optimization, the preparation method of the pretreated bagasse in step (1) is: dry the bagasse at 80 °C for 6 h, then crush it with a high-speed crusher, pass through a 100-mesh sieve, mix the sieved bagasse and a 6% vinyltrimethoxysilane-acetone solution in a mass ratio of 1:20 for 4 h, filter and wash with pure water 5 times, and dry at 80 °C for 24 h to obtain the pretreated bagasse.

[0014] As an optimization, the mass ratio of the pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylammonium, sodium hydroxide, and tetrabutylammonium bromide in step (1) is 1:(0.8 - 1.0):(0.3 - 0.5):(0.4 - 0.6).

[0015] As an optimization, the Karstedt catalyst described in step (2) and step (3) is bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum.

[0016] As an optimization, the programmed calcination method described in step (3) is to heat up to 350 °C at a rate of 3 °C / min and hold for 1 h, then heat up to 800 °C at a rate of 5 °C / min and hold for 2 h, and then cool to room temperature.

[0017] As an optimization, the polydimethylsiloxane solution is obtained by mixing polydimethylsiloxane and n-hexane at a mass ratio of 1:10. The model of polydimethylsiloxane is DC184, purchased from Dow Corning Corporation.

[0018] As an optimization, the conductive agent is acetylene black and the binder is polyvinylidene fluoride.

[0019] As an optimization, the preparation method of the negative electrode sheet is as follows: Mix the binder and N-methylpyrrolidone at a mass ratio of 1:20, ultrasonically disperse for 2 h, and let it stand in a drying dish for 7 days to obtain a binder solution; Mix the modified negative electrode material, conductive agent, and binder solution, and then add N-methylpyrrolidone with a mass 0.15 times that of the modified negative electrode material, and stir for 1 h under sealed conditions to obtain a slurry; Fix the copper foil on a glass plate, coat the slurry on the copper foil with a coating thickness of 150 μm, then put it into a vacuum drying oven at 105 °C and dry for 10 h, cut it into a pole piece with a diameter of 6 mm using a slicing machine, and perform pressing treatment with a powder press to obtain the negative electrode sheet.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] When the present invention prepares the doped and modified porous carbon negative electrode material, first, after the bagasse pretreated with vinyltrimethoxysilane reacts with bis(4-chlorophenyl)phosphine oxide, then reacts with 2,4,6-triethylbenzene-1,3,5-trimethylammonium, and then reacts with bis(4-chlorophenyl)phosphine oxide to obtain phosphorus-containing bagasse. Secondly, after the phosphorus-containing bagasse reacts with 1,4-diamino-2,5-divinylbenzene, then reacts with terephthalaldehyde and p-phenylenediamine to obtain modified bagasse; Mix the modified bagasse and ferrous acetate, and then mix with polydimethylsilane, and obtain the modified porous carbon negative electrode material through drying, calcination, grinding, and pressing.

[0022] First of all, as a biomass waste, sugarcane bagasse is low-cost and widely available. It has a loose structure, a hollow vascular bundle shape, a smooth surface, and a small amount of pore structure. It provides a basis for the preparation of porous carbon materials. The sugarcane bagasse pretreated with vinyl trimethoxysilane contains abundant double bonds, which can react with bis(4-chlorophenyl)phosphine oxide under the action of a catalyst to make the sugarcane bagasse carry phosphorus and chlorophenyl. Then, it reacts with 2,4,6-triethylbenzene-1,3,5-trimethylamine and bis(4-chlorophenyl)phosphine oxide to obtain phosphorus-containing sugarcane bagasse. The phosphorus-containing sugarcane bagasse contains not only phosphorus and nitrogen, but also 2,4,6-triethylbenzene-1,3,5-trimethylamine and bis(4-chlorophenyl)phosphine oxide. The molecular cage structure obtained by the reaction of phosphine oxide with 1-(2-nitrogen)-2-nitrogen; the molecular cage structure will form a porous structure on the surface during the subsequent calcination and carbonization process, thereby increasing the specific surface area of the material; taking lithium-ion batteries as an example, doping atoms can improve the conductivity of the carbon negative electrode, expand the interlayer spacing and increase defect sites, thereby improving the electrode kinetics. Nitrogen is one of the most important doping elements of carbon materials. The electron donor performance of phosphorus atoms will affect the local charge density of the carbon matrix, provide free charge carriers, and facilitate the rapid migration of electrons. Phosphorus atoms will combine with the dangling bonds of carbon materials to form CP bonds. The larger atomic radius can expand the carbon layer spacing and introduce topological defects. These defects will create new active sites and enhance the contact characteristics with the electrolyte.

[0023] Secondly, after the phosphorus-containing sugarcane bagasse and 1,4-diamino-2,5-divinylbenzene are reacted, the sugarcane bagasse is again subjected to the action of a catalyst to allow the diphenylamine structure to be present. Through the subsequent Schiff base reaction with terephthalaldehyde and p-phenylenediamine, a polymer containing a Schiff base is generated on the sugarcane bagasse. The Schiff base polymer on the sugarcane bagasse has a complexing effect on metal ions. When the modified sugarcane bagasse and ferrous acetate are mixed, ferrous ions can be more evenly distributed on the sugarcane bagasse. During the subsequent calcination process, iron oxide is generated, which can undergo a reversible redox reaction with metallic lithium. Then, energy is stored by means of a large amount of electron transfer during the reaction, thereby improving the specific capacity.

[0024] Finally, the modified bagasse and ferrous acetate are mixed and then mixed with polydimethylsilane. The modified porous carbon negative electrode material is obtained by drying, calcining, grinding and pressing. The carbon material obtained after calcination is not only doped with nitrogen and phosphorus elements, but also contains iron oxide and silicon oxide. The synergistic effect of the above substances can further improve the electrical properties of the porous carbon negative electrode material. DETAILED DESCRIPTION

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The Karstedt catalyst used in the following examples and comparative examples is bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum; the polydimethylsiloxane solution used is obtained by mixing polydimethylsiloxane and n-hexane at a mass ratio of 1:10. The model of polydimethylsiloxane is DC184 and is purchased from Dow Corning Corporation; the conductive agent used is acetylene black; the binder used is polytetrafluoroethylene.

[0027] Example 1:

[0028] A preparation method of a doped and modified porous carbon negative electrode material, the preparation method of the doped and modified porous carbon negative electrode material includes the following preparation steps:

[0029] (1) Dry the bagasse at 80 °C for 6 h, then pulverize it with a high-speed pulverizer, pass through a 100-mesh sieve, mix the sieved bagasse and a 6% vinyltrimethoxysilane-acetone solution by mass ratio of 1:20 for 4 h, filter and wash with pure water 5 times, and dry at 80 °C for 24 h to obtain pretreated bagasse; weigh pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide according to a mass ratio of 1:0.8:0.3:0.4; mix pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Karstedt catalyst, and N,N-dimethylformamide according to a mass ratio of 1:0.5:0.001:20, heat up to 120 °C and react for 22 h. After the reaction is completed, filter and redisperse it in N,N-dimethylformamide 20 times the mass of the pretreated bagasse, add 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, tetrabutylammonium bromide, stir at 20 °C for 6 h, then add bis(4-chlorophenyl)phosphine oxide 1.8 times the mass of the pretreated bagasse, heat up to 30 °C and react for 6 h. After the reaction is completed, filter and wash with pure water 5 times, and dry at 80 °C for 24 h to obtain phosphorus-containing bagasse;

[0030] (2) Mix phosphorous-containing bagasse, Kast catalyst, 1,4-diamino-2,5-divinylbenzene, and N,N-dimethylformamide in a mass ratio of 1:0.001:2:20, heat up to 120 °C and react for 22 h. After the reaction, filter and redisperse it in toluene with a mass 20 times that of the pretreated bagasse. Under nitrogen protection, add terephthalaldehyde with a mass 1.5 times that of the phosphorous-containing bagasse and p-phenylenediamine with a mass 1.5 times that of the phosphorous-containing bagasse, heat up to 120 °C and reflux and stir for 3 h, filter and wash with ethanol 4 times, and dry at 80 °C for 24 h to obtain modified bagasse;

[0031] (3) Mix the modified bagasse and 10 wt% ferrous acetate solution in a mass ratio of 1:10, stir at room temperature for 24 h, filter and redisperse it in a polydimethylsiloxane solution with a mass 10 times that of the modified bagasse, stir for 10 min, filter after stirring, and use the method of programmed calcination in an argon tube furnace. Heat up to 350 °C at a rate of 3 °C / min and hold for 1 h, then heat up to 800 °C at a rate of 5 °C / min and hold for 2 h, and then cool to room temperature. After calcination, grind it through a 100-mesh sieve to obtain the modified anode material;

[0032] (4) Weigh the modified anode material, conductive agent, and binder in a mass ratio of 8:1:1. Mix the binder and N-methylpyrrolidone in a mass ratio of 1:20, ultrasonically disperse for 2 h, and let it stand in a drying dish for 7 days to obtain the binder solution; Mix the modified anode material, conductive agent, and binder solution, and then add N-methylpyrrolidone with a mass 0.15 times that of the modified anode material, stir for 1 h under sealed conditions to obtain the slurry; Fix the copper foil on the glass plate, coat the slurry on the copper foil with a coating thickness of 150 μm, then put it into a vacuum drying oven at 105 °C and dry for 10 h, cut it into pole pieces with a diameter of 6 mm using a slicing machine, and perform pressing treatment with a powder press to obtain the negative electrode sheet.

[0033] Example 2:

[0034] A preparation method of a doped and modified porous carbon anode material, the preparation method of the doped and modified porous carbon anode material includes the following preparation steps:

[0035] (1) The bagasse was dried at 80 °C for 6 h, then pulverized with a high-speed pulverizer, passed through a 100-mesh sieve. The sieved bagasse and a 6% (mass fraction) vinyltrimethoxysilane-acetone solution were mixed at a mass ratio of 1:20 for 4 h, filtered and washed 5 times with pure water, and dried at 80 °C for 24 h to obtain pretreated bagasse; The pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide were weighed at a mass ratio of 1:0.9:0.4:0.5; The pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Kaster catalyst, and N,N-dimethylformamide were mixed at a mass ratio of 1:0.6:0.002:25, heated to 110 °C and reacted for 21 h. After the reaction, it was filtered and redispersed in N,N-dimethylformamide 25 times the mass of the pretreated bagasse. 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide were added, and stirred at 17 °C for 5 h. Then, bis(4-chlorophenyl)phosphine oxide 1.9 times the mass of the pretreated bagasse was added, heated to 27 °C and reacted for 5 h. After the reaction, it was filtered and washed 5 times with pure water, and dried at 80 °C for 24 h to obtain phosphorus-containing bagasse;

[0036] (2) The phosphorus-containing bagasse, Kaster catalyst, 1,4-diamino-2,5-divinylbenzene, and N,N-dimethylformamide were mixed at a mass ratio of 1:0.002:2.5:25, heated to 110 °C and reacted for 21 h. After the reaction, it was filtered and redispersed in toluene 25 times the mass of the pretreated bagasse. Under nitrogen protection, terephthalaldehyde 1.6 times the mass of the phosphorus-containing bagasse and p-phenylenediamine 1.7 times the mass of the phosphorus-containing bagasse were added, heated to 115 °C and refluxed and stirred for 2.5 h, filtered and washed 3 times with ethanol, and dried at 80 °C for 24 h to obtain modified bagasse;

[0037] (3) The modified bagasse and a 10 wt% ferrous acetate solution were mixed at a mass ratio of 1:11, stirred at room temperature for 23 h, filtered and redispersed in a polydimethylsiloxane solution 11 times the mass of the modified bagasse, stirred for 7 min, filtered after stirring, and calcined in an argon tube furnace using a programmed calcination method. It was heated to 350 °C at a rate of 3 °C / min and held for 1 h, then heated to 800 °C at a rate of 5 °C / min and held for 2 h, and then cooled to room temperature. After calcination, it was ground and passed through a 100-mesh sieve to obtain the modified anode material;

[0038] (4) Weigh the modified anode material, conductive agent, and binder according to a mass ratio of 8:1:1. Mix the binder and N-methylpyrrolidone according to a mass ratio of 1:20, ultrasonically disperse for 2 h, and let it stand in a drying dish for 7 days to obtain a binder solution. Mix the modified anode material, conductive agent, and binder solution, and then add N-methylpyrrolidone that is 0.15 times the mass of the modified anode material. Stir for 1 h under sealed conditions to obtain a slurry. Fix the copper foil on a glass plate, coat the slurry on the copper foil with a coating thickness of 150 μm, then place it in a vacuum drying oven at 105 °C and dry for 10 h. Cut it into pole pieces with a diameter of 6 mm using a slicing machine, and perform pressing treatment with a powder press to obtain the negative electrode sheet.

[0039] Example 3:

[0040] A preparation method of a doped and modified porous carbon anode material, the preparation method of the doped and modified porous carbon anode material includes the following preparation steps:

[0041] (1) Dry the bagasse at 80 °C for 6 h, then crush it with a high-speed crusher, pass through a 100-mesh sieve. Mix the sieved bagasse and a 6% mass fraction of vinyltrimethoxysilane-acetone solution according to a mass ratio of 1:20 for 4 h, filter and wash 5 times with pure water, and dry at 80 °C for 24 h to obtain pretreated bagasse. Weigh the pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide according to a mass ratio of 1:1.0:0.5:0.6. Mix the pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Kaster catalyst, and N,N-dimethylformamide according to a mass ratio of 1:0.7:0.003:30, heat up to 100 °C and react for 20 h. After the reaction, filter and redisperse it in N,N-dimethylformamide that is 30 times the mass of the pretreated bagasse. Add 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, tetrabutylammonium bromide, and stir at 15 °C for 4 h. Then add bis(4-chlorophenyl)phosphine oxide that is 2.0 times the mass of the pretreated bagasse, heat up to 25 °C and react for 4 h. After the reaction, filter and wash 5 times with pure water, and dry at 80 °C for 24 h to obtain phosphorus-containing bagasse.

[0042] (2) Mix the phosphorus-containing bagasse, Kaster catalyst, 1,4-diamino-2,5-divinylbenzene, and N,N-dimethylformamide according to a mass ratio of 1:0.003:3:30, heat up to 100 °C and react for 20 h. After the reaction, filter and redisperse it in toluene that is 30 times the mass of the pretreated bagasse. Under nitrogen protection, add terephthalaldehyde that is 1.8 times the mass of the phosphorus-containing bagasse and p-phenylenediamine that is 1.8 times the mass of the phosphorus-containing bagasse, heat up to 110 °C and reflux and stir for 2 h. Filter and wash 3 times with ethanol, and dry at 80 °C for 24 h to obtain modified bagasse.

[0043] (3) Mix the modified bagasse and a 10 wt% ferrous acetate solution at a mass ratio of 1:12, stir at room temperature for 22 h, filter, and then redisperse in a polydimethylsiloxane solution 12 times the mass of the modified bagasse. Stir for 5 min, filter after stirring, and perform calcination in an argon tube furnace using a programmed calcination method. Heat to 350 °C at a rate of 3 °C / min and hold for 1 h, then heat to 800 °C at a rate of 5 °C / min and hold for 2 h, and then cool to room temperature. After calcination, grind and pass through a 100-mesh sieve to obtain the modified anode material;

[0044] (4) Weigh the modified anode material, conductive agent, and binder at a mass ratio of 8:1:1. Mix the binder and N-methylpyrrolidone at a mass ratio of 1:20, ultrasonically disperse for 2 h, and let stand in a drying dish for 7 days to obtain the binder solution. Mix the modified anode material, conductive agent, and binder solution, and then add N-methylpyrrolidone 0.15 times the mass of the modified anode material. Stir for 1 h under sealed conditions to obtain the slurry. Fix the copper foil on a glass plate, coat the slurry on the copper foil with a coating thickness of 150 μm, then place it in a vacuum drying oven at 105 °C and dry for 10 h. Cut it into a pole piece with a diameter of 6 mm using a slicing machine, and perform pressing treatment with a powder press to obtain the negative electrode sheet.

[0045] Comparative Example 1:

[0046] The preparation method of the doped and modified porous carbon anode material in Comparative Example 1 is different from that in Example 2 in that step (2) is not included, and step (1) is modified as follows: Dry the bagasse at 80 °C for 6 h, then crush it with a high-speed crusher, pass through a 100-mesh sieve, mix the sieved bagasse and a 6 wt% vinyltrimethoxysilane-acetone solution at a mass ratio of 1:20 for 4 h, filter and wash 5 times with pure water, and dry at 80 °C for 24 h to obtain the modified bagasse.

[0047] Comparative Example 2:

[0048] The preparation method of the doped and modified porous carbon anode material of Comparative Example 2 is different from that of Example 2 in that it does not contain step (2), and step (1) is modified as follows: Bagasse is dried at 80 °C for 6 h, then pulverized with a high-speed pulverizer, screened through a 100-mesh sieve, and the sieved bagasse and a 6% by mass vinyltrimethoxysilane-acetone solution are mixed at a mass ratio of 1:20 for 4 h, filtered and washed 5 times with pure water, and dried at 80 °C for 24 h to obtain pretreated bagasse; Weigh pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide at a mass ratio of 1:0.9:0.4:0.5; Mix pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Kaster catalyst, and N,N-dimethylformamide at a mass ratio of 1:0.6:0.002:25, heat up to 110 °C and react for 21 h. After the reaction is completed, filter and redisperse it in N,N-dimethylformamide 25 times the mass of the pretreated bagasse, add 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, tetrabutylammonium bromide, stir at 17 °C for 5 h, then add bis(4-chlorophenyl)phosphine oxide 1.9 times the mass of the pretreated bagasse, heat up to 27 °C and react for 5 h. After the reaction is completed, filter and wash 5 times with pure water, and dry at 80 °C for 24 h to obtain modified bagasse.

[0049] Test Example 1:

[0050] Button cell assembly: The doped and modified porous anode material is vacuum-dried at 105 °C for 10 h and then put into a vacuum glove box for assembling a button cell. A lithium metal sheet is used as the electrode, the electrolyte is obtained by mixing dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) of 1 mol / L LiPF6 at a mass ratio of 2:2:1, the separator is a Celgard 2400 type porous polypropylene membrane, and the model of the battery case is CR2025. Finally, the assembled button cell is sealed on a sealing machine with the positive electrode facing up, left standing for 24 h to allow the electrolyte to fully contact the electrode sheet, and then the electrochemical performance is tested.

[0051] Test of battery performance:

[0052] Test method: Use a Shenzhen Neware BTS-5V / 2.2A battery performance tester to test the capacity and cycle performance of the battery. The test voltage range is: 0.01 - 2.0 V, the current density for the cycle performance of the material is 100 mA / g, one discharge and one charge are recorded as one cycle, record the battery discharge capacity at the 100th cycle, and calculate the capacity retention rate. The results are shown in Table 1 below.

[0053] Table 1

[0054]

[0055]

[0056] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-2 in Table 1, it can be found that the doped and modified porous carbon anode material prepared by the present invention has good electrical properties.

[0057] By comparison, the electrical properties of Examples 1-3 are better than those of Comparative Examples 1-2, indicating that, firstly, the bagasse pretreated with vinyltrimethoxysilane contains rich double bonds, which can react with bis(4-chlorophenyl)phosphine oxide under the action of a catalyst to make the bagasse carry phosphorus elements and chlorophenyl groups, and then react with 2,4,6-triethylbenzene-1,3,5-trimethylamine, and then react with bis(4-chlorophenyl)phosphine oxide to obtain phosphorus-containing bagasse. The phosphorus-containing bagasse not only contains phosphorus elements and nitrogen elements, but also contains a molecular cage structure obtained by the reaction of 2,4,6-triethylbenzene-1,3,5-trimethylamine and bis(4-chlorophenyl)phosphine oxide; during the subsequent calcination and carbonization process, the molecular cage structure will form a porous structure on the surface, increasing the specific surface area of the material; taking a lithium-ion battery as an example, doped atoms can improve the conductivity of the carbon anode, expand the interlayer spacing and increase the defect sites, thereby improving the electrode kinetics. Nitrogen is one of the main doping elements in carbon materials. The electron donor property of phosphorus atoms will affect the local charge density of the carbon matrix, provide free charge carriers, and is conducive to the rapid migration of electrons. Phosphorus atoms will combine with the dangling bonds of the carbon material to form C-P bonds. The larger atomic radius can expand the carbon layer spacing and introduce topological defects. These defects will create new active sites and at the same time enhance the contact characteristics with the electrolyte;

[0058] Secondly, after reacting the phosphorus-containing bagasse with 1,4-diamino-2,5-divinylbenzene, the bagasse is made to contain a diphenylamine structure through the action of a catalyst again. Through the subsequent Schiff base reaction with terephthalaldehyde and p-phenylenediamine, a polymer containing Schiff base is formed on the bagasse; the Schiff base polymer on the bagasse has a complexing effect on metal ions. When the modified bagasse and ferrous acetate are mixed, ferrous ions can be more evenly distributed on the bagasse, and iron oxides are formed during the subsequent calcination process, which can undergo a reversible redox reaction with metallic lithium, and then energy storage is carried out by means of a large amount of electron transfer during the reaction process, increasing the specific capacity.

[0059] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claim concerned.

Claims

1. A preparation method of a doped and modified porous carbon negative electrode material, characterized in that, It includes the following preparation steps: (1) Mix pretreated bagasse, bis(4-chlorophenyl)phosphine oxide, Karstedt's catalyst, and N,N-dimethylformamide at a mass ratio of 1:(0.5 - 0.7):(0.001 - 0.003):(20 - 30), heat up to 100 - 120 °C and react for 20 - 22 h. After the reaction, filter and redisperse it in N,N-dimethylformamide with a mass 20 - 30 times that of the pretreated bagasse. Add 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide, stir at 15 - 20 °C for 4 - 6 h, then add bis(4-chlorophenyl)phosphine oxide with a mass 1.8 - 2.0 times that of the pretreated bagasse, heat up to 25 - 30 °C and react for 4 - 6 h. After the reaction, filter and wash with pure water 5 times, dry at 80 °C for 24 h to obtain phosphorus-containing bagasse; (2) Mix phosphorus-containing bagasse, Karstedt's catalyst, 1,4-diamino-2,5-divinylbenzene, and N,N-dimethylformamide at a mass ratio of 1:(0.001 - 0.003):(2 - 3):(20 - 30), heat up to 100 - 120 °C and react for 20 - 22 h. After the reaction, filter and redisperse it in toluene with a mass 20 - 30 times that of the pretreated bagasse. Under nitrogen protection, add terephthalaldehyde with a mass 1.5 - 1.8 times that of the phosphorus-containing bagasse and p-phenylenediamine with a mass 1.5 - 1.8 times that of the phosphorus-containing bagasse, heat up to 110 - 120 °C and reflux and stir for 2 - 3 h, filter and wash with ethanol 3 - 4 times, dry at 80 °C for 24 h to obtain modified bagasse; (3) Mix modified bagasse and 10 wt% ferrous acetate solution at a mass ratio of 1:(10 - 12), stir at room temperature for 22 - 24 h, filter and redisperse it in a polydimethylsiloxane solution with a mass 10 - 12 times that of the modified bagasse, stir for 5 - 10 min, filter after stirring, and calcine it in an argon tube furnace using a programmed calcination method. After calcination, grind it through a 100-mesh sieve to obtain the modified anode material; (4) Prepare a negative electrode sheet from the modified anode material, conductive agent, and binder at a mass ratio of 8:1:1 by the tabletting method to obtain a doped and modified porous carbon negative electrode material.

2. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, characterized in that, The preparation method of the pretreated bagasse described in step (1) is as follows: Dry the bagasse at 80 °C for 6 h, then crush it with a high-speed crusher, pass through a 100-mesh sieve, mix the sieved bagasse and a 6% vinyltrimethoxysilane-acetone solution at a mass ratio of 1:20 for 4 h, filter and wash with pure water 5 times, dry at 80 °C for 24 h to obtain the pretreated bagasse.

3. The preparation method of a doped and modified porous carbon anode material according to claim 1, wherein, The mass ratio of the pretreated bagasse, 2,4,6-triethylbenzene-1,3,5-trimethylamine, sodium hydroxide, and tetrabutylammonium bromide described in step (1) is 1:(0.8 - 1.0):(0.3 - 0.5):(0.4 - 0.6).

4. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, characterized in that, The Karstedt's catalyst described in steps (1) and (2) is bis(1,3-divinyl-1,1,3,3-tetramethyldisiloxane)platinum.

5. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, characterized in that, The program calcination method described in step (3) is to heat up to 350 °C at a rate of 3 °C / min and hold for 1 h, then heat up to 800 °C at a rate of 5 °C / min and hold for 2 h, and then cool to room temperature.

6. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, characterized in that, The polydimethylsiloxane solution described in step (3) is obtained by mixing polydimethylsiloxane and n-hexane in a mass ratio of 1:10, and the model of polydimethylsiloxane is DC184.

7. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, characterized in that, The conductive agent described in step (4) is acetylene black, and the binder is polyvinylidene fluoride.

8. The preparation method of a doped and modified porous carbon negative electrode material according to claim 1, wherein The preparation method of the negative electrode sheet described in step (4) is as follows: mix the binder and N-methylpyrrolidone in a mass ratio of 1:20, ultrasonically disperse for 2 h, and let stand in a drying dish for 7 days to obtain a binder solution; mix the modified negative electrode material, conductive agent, and binder solution, and then add N-methylpyrrolidone 0.15 times the mass of the modified negative electrode material, and stir for 1 h under sealed conditions to obtain a slurry; fix the copper foil on a glass plate, coat the slurry on the copper foil, with a coating thickness of 150 μm, then place it in a vacuum drying oven at 105 °C and dry for 10 h, cut it into a pole piece with a diameter of 6 mm using a slicing machine, and perform pressing treatment with a powder press to obtain the negative electrode sheet.

9. A doped and modified porous carbon negative electrode material prepared by the preparation method of the doped and modified porous carbon negative electrode material according to any one of claims 1-8.

Images