Preparation method of high-performance biomass-based hard carbon negative electrode material

Abstract

The application discloses a preparation method of a high-performance biomass-based hard carbon negative electrode material and belongs to the technical field of ion batteries. The application adopts bamboo to prepare a precursor, and prepares pre-carbonized bamboo, carbon particles and hard carbon particles; the obtained hard carbon particles are mixed with a binder and a conductive agent to obtain a negative electrode material, and then super-pure water is added, and the obtained mixed slurry is the hard carbon negative electrode material. The application can reduce the cost of a sodium ion battery, improve the performance of the battery, improve the competitiveness of the battery in the energy storage market and promote the application of the sodium ion battery in the large-scale energy storage field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ion batteries, and particularly relates to a preparation method of a high-performance biomass-based hard carbon negative electrode material. BACKGROUND

[0002] The hard carbon negative electrode has become a key material for replacing lithium ion batteries in the large-scale energy storage field of sodium ion batteries due to its advantages of stable structure, low working potential, high specific capacity and high tap density. At present, the hard carbon precursor is mainly resin and biomass. For example, the patent application No. CN202110287252.7 discloses a nano-carbon composite resin hard carbon electrode material and its preparation method and application. The resin precursor has the characteristics of high purity and high carbon content, but it is expensive and the process is complex, which is not conducive to large-scale commercial use and the low-cost advantage of sodium ion batteries, and cannot improve the competitive advantage of sodium ion batteries. In addition, the patent application No. CN202311660219.X discloses a hard carbon electrode material with a wide interlayer spacing and a preparation method thereof, and the precursor is coconut shell. Therefore, biomass precursors should have the advantages of wide distribution, low price and renewable to promote the development of biomass-based hard carbon. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of a high-performance biomass-based hard carbon negative electrode material, which uses abundant, inexpensive and renewable bamboo as a precursor, can reduce the cost of sodium ion batteries, improve the battery performance, improve its competitiveness in the energy storage market, and promote the application of sodium ion batteries in the large-scale energy storage field.

[0004] The technical scheme adopted by the present application to achieve the above purpose is as follows:

[0005] A preparation method of a high-performance biomass-based hard carbon negative electrode material, comprising the following steps:

[0006] S1. heating and raising the temperature of the bamboo precursor, and performing heat preservation treatment at 300-800 DEG C to obtain pre-carbonized bamboo;

[0007] S2. crushing the pre-carbonized bamboo to obtain pre-carbonized bamboo particles, soaking the pre-carbonized bamboo particles in an alkaline solution and an acid solution respectively, washing to neutral and drying to obtain carbon particles;

[0008] S3. heating and raising the temperature of the carbon particles, and performing carbonization treatment, cooling to 20-30 DEG C to obtain a hard carbon material; crushing and screening the obtained hard carbon material to obtain hard carbon particles;

[0009] S4. stirring and mixing the hard carbon particles with a binder and a conductive agent to obtain a negative electrode material, adding ultrapure water, and the obtained mixed slurry is the hard carbon negative electrode material.

[0010] In step S1, the heating and temperature maintaining of the bamboo precursor are carried out under the protection of inert gas, the inert gas is nitrogen, and the flow rate of the inert gas is controlled to be 10-100 sccm;

[0011] In step S1, the heating rate is controlled to be 1-10 ℃ / min, and the temperature maintaining time is 2-8 h;

[0012] In step S1, the bamboo precursor is prepared as follows: the bamboo is crushed to obtain bamboo fibers, and the bamboo fibers are cleaned and dried to obtain the bamboo precursor; the diameter of the crushed bamboo fibers ranges from 0.5 mm to 5 mm; the bamboo fibers are cleaned with deionized water and dried with hot air at a temperature of 50-100 ℃.

[0013] In step S2, the particle size of the crushed pre-carbonized bamboo particles ranges from 25 μm to 35 μm;

[0014] In step S2, the pH of the alkaline solution is 9-14, and the pH of the acid solution is 2-5; the alkaline solution is soaked for 10-24 h, and the acid solution is soaked for 10-24 h;

[0015] In step S2, deionized water is used for washing, and the drying temperature is 50-100 ℃, and the drying time is 10-24 h.

[0016] In step S3, the heating and carbonization of the carbon particles are carried out under the protection of inert gas, the inert gas is nitrogen, and the flow rate of the inert gas is controlled to be 10-100 sccm;

[0017] In step S3, the heating rate is controlled to be 1-10 ℃ / min, and the carbonization temperature is controlled to be in the range of 1000-1600 ℃; the carbonization time is 1-5 h;

[0018] In step S3, the hard carbon material is mechanically crushed or air-flow crushed; the particle size of the obtained hard carbon particles ranges from 5 μm to 15 μm.

[0019] In step S4, the conductive agent is one or more of Super P, graphene, acetylene black, Ketjen black, conductive carbon black, and carbon nanotube;

[0020] In step S4, the mass ratio of the hard carbon particles, the binder, and the conductive agent is 1-10:0.5-1.5:0.5-1.5;

[0021] In step S4, the solid content in the obtained mixed slurry ranges from 40% to 80%;

[0022] In step S4, the stirring speed is 150-300 r / min, and the stirring time is 5-24 h.

[0023] The binder in step S4 is one or more of sodium alginate, sodium carboxymethyl cellulose, cross-linked polyimide, and modified cross-linked polyimide; the modified cross-linked polyimide is obtained by polymerization and imidization of a dianhydride compound with 1,5-diaminonaphthalene and / or 2-(4-aminophenyl)-5-aminobenzimidazole.

[0024] The above technical solution is used to prepare a bamboo precursor from abundant, inexpensive and renewable bamboo, for preparing a bio-based hard carbon material, which can reduce the cost of sodium ion batteries, improve the competitiveness of the sodium ion batteries in the energy storage market, and promote the application of the sodium ion batteries in large-scale energy storage fields.

[0025] The binder for preparing the negative electrode material is modified cross-linked polyimide, which is obtained by polymerization and imidization of a dianhydride compound with 1,5-diaminonaphthalene and / or 2-(4-aminophenyl)-5-aminobenzimidazole; the binder can improve the electrochemical performance of the obtained sodium ion battery, and significantly improve the initial coulombic efficiency and capacity retention rate of the battery. This may be because the modified cross-linked polyimide has good bonding strength and mechanical properties, and the modified cross-linked polyimide, under the action of a cross-linking agent, helps to form intermolecular hydrogen bonds and physical entanglements, and helps to form a good conductive network in the obtained negative electrode material. Moreover, the modified cross-linked polyimide obtained by the reaction of the dianhydride compound with 1,5-diaminonaphthalene and / or 2-(4-aminophenyl)-5-aminobenzimidazole helps to combine hydrogen bonds in the negative electrode material due to the presence of benzothiazole and / or benzimidazole groups therein, forms a conductive network between the components of the electrode, promotes the diffusion of sodium ions in the process of charging and discharging, and improves the capacity retention capability of the electrode. In addition, the introduction of heteroatoms in the binder modified cross-linked polyimide also helps to form hydrogen bonds in the obtained negative electrode material, and provides a strong interaction force between the components.

[0026] According to an aspect of the present application, a hard carbon negative electrode sheet is provided, which comprises a current collector and a functional layer attached to the current collector, the current collector is a copper foil or an aluminum foil, and the functional layer comprises the obtained hard carbon negative electrode material.

[0027] According to an aspect of the present application, a preparation method of a hard carbon negative electrode sheet is provided, which comprises coating the obtained hard carbon negative electrode material on a current collector, vacuum drying, cooling to room temperature, and cutting to obtain a sodium ion battery hard carbon negative electrode sheet.

[0028] Preferably, the current collector is a copper foil or an aluminum foil, the thickness of the current collector is 10-30 μm, the coating thickness of the hard carbon negative electrode material is 10-300 μm, the temperature for vacuum drying is 50-100 °C, and the drying time is 10-48 h.

[0029] According to an aspect of the present application, a sodium ion battery is provided, which comprises a positive electrode material prepared from a sodium sheet and the above-mentioned hard carbon negative electrode sheet.

[0030] According to one aspect of the present application, a binder for negative electrode material of ion battery is provided, comprising modified cross-linked polyimide. The modified cross-linked polyimide is obtained by polymerization and imidization of dianhydride compound with 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0031] According to one aspect of the present application, a method for preparing modified cross-linked polyimide is provided, comprising the following steps:

[0032] Dissolve diphenyl sulfone tetracarboxylic dianhydride in dimethylacetamide (DMAc), then add 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole, and stir the mixture at 20-30℃ under argon atmosphere for 10-48h to obtain modified polyamic acid;

[0033] Stir the obtained modified polyamic acid and cross-linking agent at 20-30℃ under argon atmosphere for 4-10h to obtain modified cross-linked polyamic acid;

[0034] After vacuum drying the obtained modified cross-linked polyamic acid, heat treatment is performed to obtain modified cross-linked polyimide through imidization reaction.

[0035] Further, in the process of preparing modified polyamic acid, ethylene glycol is added to the DMAc solution of diphenyl sulfone tetracarboxylic dianhydride before adding 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole, and the molar ratio of diphenyl sulfone tetracarboxylic dianhydride to ethylene glycol is 3-6:1.

[0036] Preferably, in the process of preparing modified polyamic acid, the mass-volume ratio of diphenyl sulfone tetracarboxylic dianhydride to dimethylacetamide is 1g:0.5-3mL; the mass ratio of diphenyl sulfone tetracarboxylic dianhydride to 1,5-diaminonaphthalene is 4.5-8:1; and the mass ratio of diphenyl sulfone tetracarboxylic dianhydride to 2-(4-aminophenyl)-5-aminobenzimidazole is 4.5-8:0.5-1.5.

[0037] Preferably, the cross-linking agent is trimesic acid; and the mass ratio of diphenyl sulfone tetracarboxylic dianhydride to cross-linking agent is 30-100:1.

[0038] Further, when vacuum drying the obtained modified cross-linked polyamic acid, the drying temperature is 60-90℃, and the drying time is 6-24h.

[0039] Further, in the imidization reaction of the modified crosslinking polyamic acid, the temperature is first increased to 120-160 DEG C at a rate of 5-15 DEG C / min, and then heated for 20-60 min, and then the temperature is further increased to 200-270 DEG C at a rate of 5-15 DEG C / min, and then heated for 20-60 min, and then the temperature is further increased to 300-400 DEG C at a rate of 5-15 DEG C / min, and then heated for 20-60 min.

[0040] Further, in the preparation method of the modified crosslinking polyimide, the crosslinking agent comprises trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid, and the mass ratio of the diphenyl sulfone tetracarboxylic dianhydride to the crosslinking agent is 30-100:1; the mass ratio of the trimesic acid to the 2-phosphonobutane-1,2,4-tricarboxylic acid is 1:0.5-3.

[0041] Further, in the preparation process of the modified crosslinking polyimide, the modified polyamic acid and the trimesic acid are stirred at 20-30 DEG C for 2-5 h under an argon atmosphere, and then the 2-phosphonobutane-1,2,4-tricarboxylic acid is added, and then the stirring is continued at 20-30 DEG C for 2-5 h under an argon atmosphere; and the modified crosslinking polyamic acid is obtained.

[0042] In the preparation process of the modified crosslinking polyimide, the trimesic acid and the 2-phosphonobutane-1,2,4-tricarboxylic acid are used as the crosslinking agent, and compared with using the trimesic acid alone as the crosslinking agent, the first coulombic efficiency and the capacity retention rate of the sodium ion battery using the obtained modified crosslinking polyimide as the binder can be further improved. This may be because after the 2-phosphonobutane-1,2,4-tricarboxylic acid is added, the crosslinking structure of the obtained modified crosslinking polyamic acid can be further changed, and the phosphonic acid group in the 2-phosphonobutane-1,2,4-tricarboxylic acid can help the formation of intermolecular hydrogen bonds, and the phosphonic acid group and the related groups of 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in the modified polyamic acid can interact with each other, which can help to increase the sodium ion intercalation sites of the obtained binder, improve the intercalation and deintercalation capacity of sodium ions, and thus improve the electrochemical performance of the obtained sodium ion battery.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] 1. The bamboo precursor is prepared from abundant, inexpensive and renewable bamboo, which is used to prepare a bio-based hard carbon material, and a method for preparing a sodium ion battery negative electrode material by using the bio-based hard carbon material is provided, which can reduce the cost of the sodium ion battery, improve its competitiveness in the energy storage market, and promote the application of the sodium ion battery in the large-scale energy storage field.

[0045] 2. In the process of preparing hard carbon negative electrode material, modified cross-linked polyimide is used as binder, and the modified cross-linked polyimide is obtained by polymerization and imidization of dianhydride compound with 1,5-diaminonaphthalene and / or 2-(4-aminophenyl)-5-aminobenzimidazole; which can greatly improve the initial coulombic efficiency and capacity retention rate of the obtained sodium ion battery. The modified cross-linked polyimide has good bonding strength and mechanical properties, which is helpful to the formation of intermolecular hydrogen bonds and physical entanglement, and is helpful to the formation of good conductive network in the obtained negative electrode material; the use of 1,5-diaminonaphthalene and / or 2-(4-aminophenyl)-5-aminobenzimidazole helps the combination of hydrogen bonds in the negative electrode material, promotes the diffusion of sodium ions, and the introduction of heteroatoms also helps the formation of hydrogen bonds in the obtained negative electrode material, providing stronger interaction force between components.

[0046] 3. In the process of preparing modified cross-linked polyimide, using trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid as cross-linking agent, compared with using trimesic acid alone as cross-linking agent, it can further improve the initial coulombic efficiency and capacity retention rate of sodium ion battery using the obtained modified cross-linked polyimide as binder. This may be because the phosphonic acid group in 2-phosphonobutane-1,2,4-tricarboxylic acid helps the formation of intermolecular hydrogen bonds, and the phosphonic acid group and the related groups of 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in modified polyamic acid interact with each other, which helps to increase the sodium ion intercalation sites of the obtained binder, improve the ability of sodium ion intercalation and deintercalation, and thus improve the electrochemical performance of the obtained sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 SEM image of hard carbon particles obtained in Example 1 of the present application;

[0048] Figure 2 XRD pattern of hard carbon particles of Example 2 of the present application;

[0049] Figure 3 The relationship between the potential and specific capacity of the sodium ion battery obtained in Example 1 during the first cycle charge and discharge process;

[0050] Figure 4 Infrared spectrum of modified polyimide obtained in Example 3. DETAILED DESCRIPTION

[0051] The technical solutions of the present application are further described in detail below in combination with specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0052] Example 1

[0053] Preparation of biomass-based hard carbon negative electrode material

[0054] S1. Preparation of pre-carbonized bamboo: bamboo is crushed to obtain bamboo fibers, and the bamboo fibers are washed and dried to obtain a bamboo precursor; the bamboo precursor is heated and raised in temperature under inert gas protection, and is treated at 500 DEG C for heat preservation to obtain pre-carbonized bamboo;

[0055] S2. Preparation of carbon particles: the pre-carbonized bamboo obtained in step S1 is crushed to obtain pre-carbonized bamboo particles, which are soaked in an alkaline solution and an acid solution respectively, washed to neutral and dried to obtain carbon particles;

[0056] S3. Preparation of hard carbon particles: the carbon particles obtained in step S2 are heated and raised in temperature under inert gas protection, and are carbonized and treated, and are cooled to 25 DEG C to obtain a hard carbon material; the hard carbon material is crushed and sieved to obtain hard carbon particles;

[0057] S4. Preparation of hard carbon negative electrode material: the hard carbon particles obtained in step S3 are mixed with a binder and a conductive agent by stirring to obtain a negative electrode material, and ultrapure water is added, and the obtained mixed slurry is the hard carbon negative electrode material.

[0058] In step S1, the diameter of the crushed bamboo fibers ranges from 0.5 to 5 mm;

[0059] In step S1, the bamboo fibers are washed with deionized water and dried with a hot air stream at 80 DEG C;

[0060] In step S1, the inert gas is argon, and the flow rate of the inert gas is controlled at 80 sccm;

[0061] In step S1, the temperature rising rate is controlled at 5 DEG C / min, and the heat preservation time is 5 h.

[0062] In step S2, the particle size of the crushed pre-carbonized bamboo particles is about 30 μm;

[0063] In step S2, the pH of the alkaline solution is 12, and the pH of the acid solution is 5; the alkaline solution is soaked for 12 h, and the acid solution is soaked for 12 h;

[0064] In step S2, deionized water is used for washing; the drying temperature is 80 DEG C, and the drying time is 12 h.

[0065] In step S3, the inert gas is argon, and the flow rate of the inert gas is controlled at 80 sccm;

[0066] In step S3, the temperature rising rate is controlled at 5 DEG C / min, and the carbonization temperature is controlled in the range of 1400 DEG C; the heat preservation time is 2 h;

[0067] In step S3, the hard carbon material is mechanically pulverized or air-jet pulverized; the particle size of the hard carbon particles obtained by screening is 5~15μm.

[0068] In step S4, the binder is sodium alginate, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder and conductive agent is 8:1:1.

[0069] In step S4, the solid content of the resulting mixed slurry is 50%.

[0070] In step S4, the stirring speed is 200 r / min and the stirring time is 12 h.

[0071] In this embodiment, the SEM image of the hard carbon particles obtained at a carbonization temperature of 1400℃ is shown below. Figure 1 .Depend on Figure 1 As can be seen, the hard carbon particles obtained in this embodiment exhibit irregular shapes and smooth surfaces without obvious pores, with a particle size of approximately 8 μm. This irregularly shaped hard carbon structure facilitates dense packing on the current collector, thereby improving the electrochemical performance of the sodium-ion battery anode material.

[0072] Preparation of hard carbon negative electrode sheet

[0073] The hard carbon anode material obtained above is coated on the current collector, vacuum dried and cooled to room temperature. According to the battery size, an electrode sheet with a diameter of 15 mm is cut out, which is the hard carbon anode electrode sheet for sodium-ion batteries.

[0074] The current collector is made of copper foil with a thickness of 15 μm; the coating thickness of the hard carbon anode material is 100 μm; the vacuum drying temperature is 80℃ and the drying time is 12 h.

[0075] Preparation of sodium-ion batteries

[0076] Using a sodium sheet of the same size as the negative electrode as the positive electrode material, a CR2025 button cell was assembled in a glove box under an argon atmosphere, following standard operating procedures: positive electrode shell, negative electrode shell, glass fiber separator, sodium sheet (15mm in diameter, 1mm thick), and nickel foam. The electrolyte was a 1M NaPF6 solution, and the solvent was a 1:1 volume ratio mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The assembled cells were sealed using a button cell sealing machine.

[0077] Example 2

[0078] The difference between this embodiment and Embodiment 1 is that in the preparation of the biomass-based hard carbon anode material, step S3 uses a carbonization temperature of 1100℃.

[0079] All other conditions and steps are the same.

[0080] In this embodiment, the XRD pattern of the hard carbon particles obtained at a carbonization temperature of 1100°C is shown below. Figure 2 .like Figure 2 As shown in the XRD diagram 2 θ = 23° and 2 θ The appearance of a rounded peak near 43° indicates that the carbon obtained at this carbonization temperature has a disordered amorphous structure, consistent with the characteristics of hard carbon, and the interlayer spacing is approximately 0.388 nm. Therefore, the hard carbon obtained in this invention has a large interlayer spacing, which is beneficial for improving the effective capacity of sodium-ion batteries.

[0081] Example 3

[0082] The difference between this embodiment and Embodiment 1 is that in the preparation process of biomass-based hard carbon anode material, in step S4, the binder is modified cross-linked polyimide, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder, and conductive agent is 8:1:1.

[0083] All other conditions and steps are the same.

[0084] The preparation method of the modified crosslinked polyimide is as follows:

[0085] Diphenylsulfone tetracarboxylic dianhydride was dissolved in DMAc, and then 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole were added. The mixture was stirred at 25°C and 200 r / min for 24 h under an argon atmosphere to obtain modified polyamic acid.

[0086] The obtained modified polyamic acid and crosslinking agent were reacted with each other under an argon atmosphere at 25°C and 200 r / min for 6 h to obtain modified crosslinked polyamic acid;

[0087] The obtained modified crosslinked polyamic acid was vacuum dried and then heated to undergo an imidization reaction to obtain modified crosslinked polyimide.

[0088] In the preparation of modified polyamic acid, the mass-to-volume ratio of diphenylsulfone tetracarboxylic dianhydride and dimethylacetamide is 1 g:1 mL; the mass ratio of diphenylsulfone tetracarboxylic dianhydride to 1,5-diaminonaphthalene is 6:1; and the mass ratio of diphenylsulfone tetracarboxylic dianhydride to 2-(4-aminophenyl)-5-aminobenzimidazole is 6:1.5.

[0089] Furthermore, in the preparation of modified polyamic acid, before adding 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole, ethylene glycol is added to the DMAc of diphenylsulfonetetracarboxylic dianhydride, with a molar ratio of diphenylsulfonetetracarboxylic dianhydride to ethylene glycol of 4:1.

[0090] Furthermore, the crosslinking agent is pyromellitic acid, and the mass ratio of diphenylsulfone tetracarboxylic dianhydride to the crosslinking agent is 40:1.

[0091] The modified cross-linked polyamide acid obtained is vacuum dried at a drying temperature of 80℃ for 12h.

[0092] During the imidization reaction of the modified cross-linked polyamide acid, the temperature is first increased to 150℃ at a rate of 10℃ / min, and then kept constant for 30min, then continuously increased to 250℃ at a rate of 10℃ / min, and then kept constant for 30min, and then continuously increased to 350℃ at a rate of 10℃ / min, and then kept constant for 30min.

[0093] The modified cross-linked polyimide is characterized by using an IS50 type Fourier infrared spectrometer, the sample is prepared by potassium bromide tabletting method, the scanning wavelength range is 4000cm -1 -500cm -1 , the scanning line number is 32, and the resolution is 4cm -1 ; the obtained infrared spectrum is shown in Figure 4 . The absorption peak near 3300cm -1 is the absorption peak of O-H bond. The absorption peaks near 2920cm -1 and 2850cm -1 are the asymmetric and symmetric stretching vibration absorption peaks of C-H. The absorption peaks near 1775cm -1 and 1720cm -1 are the stretching vibration peaks of C=O bond in imide structure. The absorption peaks near 1600cm -1 and 1500cm -1 are the vibration peaks of benzene ring skeleton. The absorption peak near 1370cm -1 is the stretching vibration absorption peak of C-N bond. The absorption peaks near 1240cm -1 and 1200cm -1 are the symmetric and asymmetric stretching vibration peaks of -CO-O-. The absorption peak near 1025cm -1 is the stretching vibration peak of S=O bond. The above can prove the successful preparation of the modified polyimide.

[0094] Example 4

[0095] The difference between this embodiment and Example 1 is that in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is modified cross-linked polyamide, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder and conductive agent is 8:1.2:1.

[0096] The other conditions and steps are the same.

[0097] The preparation method of the modified cross-linked polyamide is the same as that of Example 3.

[0098] Example 5

[0099] The difference between this embodiment and Example 1 is that in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is modified cross-linked polyimide, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder and conductive agent is 8:1.5:1.

[0100] The other conditions and steps are the same.

[0101] The preparation method of the modified cross-linked polyimide is the same as that of Example 3.

[0102] Example 6

[0103] The difference between this embodiment and Example 1 is that in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is modified cross-linked polyimide, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder and conductive agent is 8:1:1.

[0104] The other conditions and steps are the same.

[0105] The preparation method of the modified cross-linked polyimide is different from that of Example 3 in that the cross-linking agent includes trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid, the obtained modified polyamic acid is stirred at 25℃ and 200r / min for 3h under an argon atmosphere after adding trimesic acid, and then 2-phosphonobutane-1,2,4-tricarboxylic acid is added and stirred at 25℃ and 200r / min for 3h under an argon atmosphere; the modified cross-linked polyamic acid is obtained; the mass ratio of diphenyl sulfone tetraacid dianhydride to cross-linking agent is 40:1; and the mass ratio of trimesic acid to 2-phosphonobutane-1,2,4-tricarboxylic acid is 1:1.

[0106] Example 7

[0107] The difference between this embodiment and Example 1 is that in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is modified cross-linked polyimide, the conductive agent is conductive carbon black, and the mass ratio of hard carbon particles, binder and conductive agent is 8:1:1.

[0108] The other conditions and steps are the same.

[0109] The preparation method of the modified cross-linked polyimide is different from that of Example 3 in that the cross-linking agent comprises benzene-1,3,5-tricarboxylic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid, the obtained modified polyamic acid is stirred at 25°C and 200 r / min for 3h under an argon atmosphere, then 2-phosphonobutane-1,2,4-tricarboxylic acid is added, and the stirring is continued at 25°C and 200 r / min for 3h under an argon atmosphere; the modified cross-linked polyamic acid is obtained; the mass ratio of benzene-1,3,5-tricarboxylic acid to 2-phosphonobutane-1,2,4-tricarboxylic acid is 1:2.

[0110] Comparative Example 1

[0111] The difference between the present comparative example and Example 1 is that, in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is the modified cross-linked polyimide, and the conductive agent is the conductive carbon black, and the mass ratio of the hard carbon particles, the binder and the conductive agent is 8:1:1.

[0112] The other conditions and steps are the same.

[0113] The preparation method of the modified cross-linked polyimide is different from that of Example 3 in that 1,5-diaminonaphthalene is replaced by an equal amount of 2-(4-aminophenyl)-5-aminobenzimidazole; the other conditions and steps are the same.

[0114] Comparative Example 2

[0115] The difference between the present comparative example and Example 1 is that, in the preparation process of the biomass-based hard carbon negative electrode material, in step S4, the binder is the modified cross-linked polyimide, and the conductive agent is the conductive carbon black, and the mass ratio of the hard carbon particles, the binder and the conductive agent is 8:1:1.

[0116] The other conditions and steps are the same.

[0117] The preparation method of the modified cross-linked polyimide is different from that of Example 3 in that 1,5-diaminonaphthalene is replaced by an equal amount of 2-(4-aminophenyl)-5-aminobenzimidazole; the other conditions and steps are the same.

[0118] Test Example

[0119] The battery performance tester LAND CT3002A produced by Wuhan Blue Electronic Co., Ltd. is used to test the performance of the batteries obtained in Examples 1-7 and Comparative Examples 1-2. The test voltage range is 0.001-2.5V, and the cycle test is carried out at a current density of 0.1C (1C = 372 mAg -1 ) for 1 cycle, and the initial coulombic efficiency of the sodium ion battery is calculated.

[0120] Figure 3 This table shows the relationship between potential and specific capacity of the sodium-ion battery obtained in Example 1 during the first charge-discharge cycle. Table 1 shows the initial coulombic efficiency of the sodium-ion batteries obtained in each example and comparative example.

[0121] Table 1. Initial coulombic efficiency of sodium-ion batteries obtained in each embodiment and comparative example.

[0122]

[0123] Depend on Figure 3 Based on the data in Table 1, the sodium-ion battery prepared using the hard carbon material obtained in Example 1 has a discharge capacity of over 300 mAh / g and an initial coulombic efficiency of over 85%. Therefore, the sodium-ion battery using the biomass-based hard carbon anode material obtained in Example 1 has high capacity and initial efficiency.

[0124] Referring to the data in Table 1, the initial coulombic efficiency of the sodium-ion battery prepared using the hard carbon material obtained in Example 2 is not significantly different from that of the sodium-ion battery prepared using the hard carbon material obtained in Example 1. It can be seen that in the process of preparing bio-based hard carbon anode material, when the temperature for carbonizing carbon particles to obtain hard carbon particles is 1100℃ or 1400℃, it has little effect on the initial coulombic efficiency of the resulting sodium-ion battery.

[0125] Referring again to the data in Table 1, compared to Example 1, the initial coulombic efficiency of the batteries obtained in Examples 3-7 and Comparative Examples 1-2 increased by 8.4%, 9.9%, 11.4%, 13.9%, 14.8%, 2.9%, and 1.9%, respectively. It is evident that in the preparation of sodium-ion batteries, using modified cross-linked polyimide as a binder, compared to sodium alginate, can significantly improve the initial coulombic efficiency of the resulting batteries.

[0126] The initial coulombic efficiency of the batteries obtained in Examples 3-5 showed an increasing trend. It can be seen that, in the process of preparing sodium-ion battery anode materials, increasing the amount of modified cross-linked polyimide as a binder within a certain range helps to improve the initial efficiency of the obtained sodium-ion batteries.

[0127] Based on the data from Comparative Examples 1-2, compared to Example 3, the initial coulombic efficiency of the battery obtained in Comparative Example 1 decreased by 5.0%, and the initial coulombic efficiency of the battery obtained in Comparative Example 2 decreased by 6.0%. It is evident that compared to using 1,5-diaminonaphthalene alone or 2-(4-aminophenyl)-5-aminobenzimidazole alone in reaction with diphenylsulfonetetracarboxylic dianhydride, the combined use of 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in combination with diphenylsulfonetetracarboxylic dianhydride has a more significant impact on the initial coulombic efficiency of sodium-ion batteries.

[0128] Compared with Example 3, the first coulombic efficiency of the batteries obtained in Examples 6-7 is increased by 5.0%, 5.9% respectively. It can be seen that, in the process of preparing the negative electrode material of the sodium ion battery, the modified cross-linked polyimide is reacted with 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in combination with diphenyl sulfone tetraacid dianhydride, and the trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid are used as cross-linking agents. Compared with using only trimesic acid as a cross-linking agent, the first coulombic efficiency of the obtained sodium ion battery can be further improved. And within a certain range, the first coulombic efficiency of the obtained sodium ion battery is positively correlated with the amount of 2-phosphonobutane-1,2,4-tricarboxylic acid used in the preparation process of the modified cross-linked polyimide adhesive.

[0129] The battery performance tester LAND CT3002A produced by Wuhan Blue Electronic Co., Ltd. was used to test the performance of the batteries obtained in Examples 1-7 and Comparative Examples 1-2. The voltage range was 0.001-2.5 V, and the cycle test was carried out at a current density of 0.1 C (1 C = 372 mAg -1 ) for 180 cycles, and the cycle stability of each sodium ion battery was compared. Table 2 shows the capacity retention rate of the sodium ion batteries obtained in each example and comparative example after 180 cycles.

[0130] Table 2 Capacity retention rate of the sodium ion batteries obtained in each example and comparative example after 180 cycles

[0131]

[0132] According to the data in Table 1, the battery prepared using the hard carbon material obtained in Example 1 still has a capacity retention rate of more than 85% after 180 cycles. Therefore, the sodium ion battery using the biomass-based hard carbon negative electrode material obtained in Example 1 has good cycle stability.

[0133] According to the data in Table 1, the capacity retention rate of the battery prepared using the hard carbon material obtained in Example 2 after 180 cycles is not much different from that of Example 1. It can be seen that when the temperature is 1100°C or 1400°C during the carbonization treatment of the carbon particles to obtain hard carbon particles in the preparation of the biomass-based hard carbon negative electrode material, the capacity retention rate of the obtained sodium ion battery is not much affected.

[0134] Continuing to refer to the data in Table 1, compared with Example 1, the capacity retention rates of the batteries obtained in Examples 3-7 and Comparative Examples 1-2 are increased by 8.4%, 9.8%, 10.9%, 13.9%, 14.5%, 2.8% and 2.2% respectively. It can be seen that, in the process of preparing the sodium ion battery, compared with sodium alginate, using modified cross-linked polyimide as the adhesive can significantly improve the capacity retention rate of the obtained battery.

[0135] The capacity retention rate of the batteries obtained in Examples 3-5 shows an upward trend, which indicates that, in the process of preparing the negative electrode material of the sodium ion battery, increasing the amount of the modified cross-linked polyimide as the binder within a certain range helps to improve the initial efficiency of the obtained sodium ion battery.

[0136] In combination with the data of Comparative Example 1-2, the capacity retention rate of the battery obtained in Comparative Example 1 is reduced by 5.2% after 180 cycles, and the capacity retention rate of the battery obtained in Comparative Example 2 is reduced by 5.8% after 180 cycles. It can be seen that, compared with the modified cross-linked polyimide obtained by using 1,5-diaminonaphthalene alone or by using 2-(4-aminophenyl)-5-aminobenzimidazole alone and reacting with diphenyl sulfone tetraacid dianhydride, the modified cross-linked polyimide obtained by using 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in combination and reacting with diphenyl sulfone tetraacid dianhydride has a more significant effect on the capacity retention rate of the sodium ion battery.

[0137] Compared with Example 3, the capacity retention rates of the batteries obtained in Examples 6-7 are increased by 5.0% and 5.6%, respectively. It can be seen that, in the process of preparing the negative electrode material of the sodium ion battery, the binder modified cross-linked polyimide is prepared by using 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole in combination and reacting with diphenyl sulfone tetraacid dianhydride, and using trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid as the cross-linking agent, which can further improve the capacity retention rate of the obtained sodium ion battery compared with using only trimesic acid as the cross-linking agent; and within a certain range, the capacity retention rate of the obtained sodium ion battery is positively correlated with the amount of 2-phosphonobutane-1,2,4-tricarboxylic acid used in the preparation process of the binder modified cross-linked polyimide.

[0138] The conventional operations in the operation steps of the present application are well known to those skilled in the art, and will not be described here.

[0139] The above-described examples have described the technical solutions of the present application in detail, and it should be understood that the above-described examples are only specific embodiments of the present application and are not intended to limit the present application. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a high-performance biomass-based hard carbon negative electrode material, comprising the following steps: S1. heating and warming a bamboo precursor, and treating at 300-800 ℃ to obtain a pre-carbonized bamboo; S2. crushing the pre-carbonized bamboo to obtain pre-carbonized bamboo particles, which are soaked in an alkaline solution and an acid solution respectively, washed to neutral and dried to obtain carbon particles; S3. heating and warming the carbon particles, and carbonizing to obtain a hard carbon material, which is crushed and screened to obtain hard carbon particles after cooling to 20-30 ℃; S4. mixing the hard carbon particles with a binder and a conductive agent to obtain a negative electrode material, and adding ultrapure water, and the obtained mixed slurry is the hard carbon negative electrode material; the binder in step S4 is modified cross-linked polyimide; the preparation method of the modified cross-linked polyimide comprises the following steps: dissolving diphenyl sulfone tetraacid dianhydride in dimethylacetamide, then adding 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole, stirring at 20-30 ℃ for 10-48 h under an argon atmosphere to obtain modified polyamic acid, and stirring the obtained modified polyamic acid and a cross-linking agent at 20-30 ℃ for 4-10 h under an argon atmosphere to obtain modified cross-linked polyamic acid, and vacuum drying the obtained modified cross-linked polyamic acid, heating and treating to undergo imidization to obtain modified cross-linked polyimide; in the preparation of the modified polyamic acid, ethylene glycol is added to the dimethylacetamide solution of diphenyl sulfone tetraacid dianhydride before adding 1,5-diaminonaphthalene and 2-(4-aminophenyl)-5-aminobenzimidazole, the molar ratio of diphenyl sulfone tetraacid dianhydride to ethylene glycol is 3-6:1, the mass ratio of diphenyl sulfone tetraacid dianhydride to 1,5-diaminonaphthalene is 4.5-8:1, the mass ratio of diphenyl sulfone tetraacid dianhydride to 2-(4-aminophenyl)-5-aminobenzimidazole is 4.5-8:0.5-1.5, the mass-volume ratio of diphenyl sulfone tetraacid dianhydride to dimethylacetamide is 1 g:0.5-3 mL, and the mass ratio of diphenyl sulfone tetraacid dianhydride to the cross-linking agent is 30-100:1; the cross-linking agent is trimesic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid, and the mass ratio of trimesic acid to 2-phosphonobutane-1,2,4-tricarboxylic acid is 1:0.5-3. 2.The method for preparing a high-performance biomass-based hard carbon negative electrode material according to claim 1, wherein in step S1, the heating and warming and the heat preservation treatment of the bamboo precursor are both carried out under the protection of an inert gas, the inert gas is nitrogen, and the flow rate of the inert gas is controlled at 10-100 sccm; in step S1, the heating rate is controlled at 1-10 ℃ / min, and the heat preservation time is 2-8 h. 3.The method for preparing a high-performance biomass-based hard carbon negative electrode material according to claim 1, wherein in step S2, the particle size of the crushed pre-carbonized bamboo particles is 25-35 μm. ​ ​ In step S2, the pH of the alkaline solution is 9-14, and the pH of the acid solution is 2-5; the soaking time for the alkaline solution is 10-24 hours, and the soaking time for the acid solution is 10-24 hours.

4. The method for preparing high-performance biomass-based hard carbon anode material according to claim 1, characterized in that, In step S3, the heating and carbonization of the carbon particles are carried out under the protection of an inert gas, which is nitrogen, and the flow rate of the inert gas is controlled at 10~100 sccm. In step S3, the heating rate is controlled at 1~10℃ / min, the carbonization temperature is controlled in the range of 1000~1600℃, and the carbonization time is 1~5 h; In step S3, the hard carbon material is mechanically pulverized or air-jet pulverized; the resulting hard carbon particles have a particle size of 5~15μm.

5. The method for preparing high-performance biomass-based hard carbon anode material according to claim 1, characterized in that, In step S4, the conductive agent is one or more of Super P, graphene, acetylene black, Ketjen black, conductive carbon black, and carbon nanotubes. In step S4, the mass ratio of hard carbon particles, binder, and conductive agent is 1~10:0.5-1.5:0.5-1.5; In step S4, the solid content of the resulting mixed slurry is 40%-80%.

6. A hard carbon negative electrode sheet, characterized by, It includes a current collector and a functional layer attached to the current collector, wherein the current collector is a copper foil or an aluminum foil, and the functional layer includes a hard carbon anode material prepared by the method of claim 1.

7. A sodium-ion battery comprising the hard carbon negative electrode sheet as described in claim 6.

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