Hierarchical porous sodium-hard carbon negative electrode material and preparation method thereof

Abstract

The application discloses a kind of hierarchical pore sodium electric hard carbon negative material and preparation method thereof, wherein the steps of preparation method include: S1, after mixing hard carbon precursor material and pore former 1, low-temperature pre-carbonization is carried out to obtain first composite material;S2, first composite material is crushed to obtain fine powder material;S3, fine powder material is mixed with pore former 2 to obtain mixed material;S4, mixed material is carried out first high-temperature carbonization to obtain surface porous first composite material;S5, metal salt solution is added to surface porous first composite material and dried to obtain dried material;S6, carbon source is deposited on dried material to obtain second composite material;S7, second composite material is carried out second high-temperature carbonization to obtain third composite material;S8, third composite material is purified and dried to obtain purified material;S9, the purified material is coated to obtain hierarchical pore sodium electric hard carbon negative material.The hierarchical pore sodium electric hard carbon negative material prepared by the preparation method has microporous, mesoporous, carbon nanotube and coating structure, thereby significantly improving the initial efficiency and rate performance of sodium-ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery negative electrode materials, and particularly relates to a hierarchical pore sodium battery hard carbon negative electrode material and a preparation method thereof. BACKGROUND

[0002] Hard carbon as an electrode material is widely used in the field of electrochemical energy storage, especially in sodium ion batteries. Traditional hard carbon materials have significant advantages in ion diffusion dynamics and platform sodium storage due to their abundant microporous structure, far superior to lithium graphite. However, the pore structure of hard carbon materials has a profound impact on their electrochemical performance. The opening and closing of micropores directly affect the specific surface area and platform sodium storage capacity of the material: increasing closed pores can improve the platform sodium storage capacity, while increasing open pores can improve the specific surface area and ion diffusion dynamics.

[0003] In order to improve the kinetic performance of hard carbon materials, the mainstream method is to improve the pore structure and introduce more pore structures. However, the microporous structure is usually introduced, which can significantly increase the specific surface area of the hard carbon material. However, high specific surface area hard carbon materials are prone to side reactions with electrolyte during the first charge and discharge process, resulting in reduced battery first efficiency. In addition, high specific surface area also increases the contact area of the material with the electrolyte, accelerating the degradation of the material and affecting the rate performance of the battery.

[0004] Therefore, there is an urgent need for a hierarchical pore sodium battery hard carbon negative electrode material and a preparation method thereof to solve the problems of the prior art. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a hierarchical pore sodium battery hard carbon negative electrode material and a preparation method thereof. The hierarchical pore sodium battery hard carbon negative electrode material prepared by the preparation method has microporous, mesoporous, carbon nanotube and coating layer structures, which can optimize the ion transport path and electronic conduction and reduce the occurrence of side reactions, thereby significantly improving the first efficiency and rate performance of the sodium ion battery.

[0006] To achieve the above purpose, the first aspect of the present application provides a preparation method of a hierarchical pore sodium battery hard carbon negative electrode material, comprising the following steps:

[0007] S1, mixing a hard carbon precursor material and a pore former 1 to prepare a first composite material by low-temperature pre-carbonization;

[0008] S2, crushing the first composite material to obtain a fine powder material;

[0009] S3, stirring and mixing the fine powder material with a pore former 2 to obtain a mixed material;

[0010] S4, performing first high-temperature carbonization on the mixed material to obtain a surface porous first composite material;

[0011] S5, adding a metal salt solution having a catalytic CNT generation effect into the porous first composite material on the surface, drying to obtain a dried material;

[0012] S6, depositing a carbon source on the dried material by high-temperature vapor deposition in an inert atmosphere to obtain a second composite material;

[0013] S7, performing a second high-temperature carbonization on the second composite material to obtain a third composite material;

[0014] S8, purifying, filtering, washing, and drying the third composite material to obtain a purified material;

[0015] S9, coating the purified material with a coating agent to obtain a hierarchical pore sodium electrochemical hard carbon negative electrode material.

[0016] Compared with the prior art, in the S1 step, the hard carbon precursor material is mixed with the pore former 1 and is pre-carbonized at a low temperature, which can form a large number of mesoporous structures in the hard carbon material, increase the specific surface area of the material, and be beneficial to the storage and transmission of sodium ions. In the S3 step, the pore former 2 occupies the pore structure exposed outside the fine powder, so that the pore structure is retained after the first high-temperature carbonization in the S4 step, and finally the pore former 1 and the pore former 2 are washed away in the purification in the S8 step to obtain a material rich in mesoporous and microporous structures. In addition, the metal salt solution having a catalytic CNT generation effect added in the S5 step acts as a catalyst in the high-temperature vapor deposition process in the S6 step, promotes the decomposition of the carbon-containing gas, and thus forms carbon nanotubes (CNT) with excellent electronic conductivity on the surface and inside of the hard carbon material. The carbon nanotubes themselves have a one-dimensional tubular structure, have a large cavity inside, and have a rich surface outside, which provides additional transmission paths for sodium ions. Therefore, by preparing a hierarchical pore sodium electrochemical hard carbon negative electrode material with microporous, mesoporous, and carbon nanotube structures, the sodium ions can not only migrate along the mesopores and micropores in the hard carbon material, but also transmit through the inner and outer surfaces of the carbon nanotubes, which can significantly optimize the ion transmission path and electronic conduction, and thus improve the rate performance of the sodium ion battery. In addition, in the S9 step, the purified material is coated with a coating agent, and the coating layer can reduce the direct contact of the hard carbon material with the electrolyte, reduce the occurrence of side reactions, and further improve the initial efficiency and rate performance of the sodium ion battery. In summary, the hierarchical pore sodium electrochemical hard carbon negative electrode material prepared by the preparation method of the present application has microporous, mesoporous, carbon nanotube, and coating layer structures, which can optimize the ion transmission path and electronic conduction and reduce the occurrence of side reactions, thereby significantly improving the initial efficiency and rate performance of the sodium ion battery.

[0017] As an embodiment, the hard carbon precursor material is selected from at least one of phenolic resin, polyacrylonitrile, polystyrene, polyfurfural, and polyfuran resin. Preferably, the hard carbon precursor is selected from coconut shell.

[0018] As an embodiment, the pore forming agent 1 is selected from at least one of NaCl, NaOH, KOH, ZnCl2, Na2CO3. Preferably, the pore forming agent 1 is selected from NaCl.

[0019] As an embodiment, the pore forming agent 2 is selected from at least one of NaOH, KOH, ZnCl2. Preferably, the pore forming agent 2 is selected from ZnCl2.

[0020] As an embodiment, the metal salt solution having catalytic CNT generation effect is selected from a chloride salt or nitrate salt of a metal M, the metal M being iron, cobalt or nickel.

[0021] As an embodiment, the temperature for the low-temperature pre-carbonization in S1 is 350℃-650℃, and the time is 0.5h-10h. Specifically, the temperature for the low-temperature pre-carbonization can be, but is not limited to, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃, 510℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 630℃, 650℃; and the time can be, but is not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h.

[0022] As an embodiment, the mass of the pore forming agent 1 in S1 accounts for 0.1%-10% of the mass of the hard carbon precursor material; as an example, the mass of the pore forming agent 1 accounts for 0.1%, 0.7%, 1.2%, 1.5%, 1.8%, 3%, 3.5%, 4.5%, 5%, 5.5%, 6.5%, 7.5%, 8.5%, 10% of the mass of the hard carbon precursor material, but is not limited to the listed values, and other values within the range are also applicable.

[0023] As an embodiment, the pulverization in S2 includes first performing roll crushing and then using air flow pulverization; specifically, first using roll equipment to roll crush the first composite material to 2mm, and then using an air flow pulverizer to pulverize.

[0024] As an embodiment, the Dv10 of the fine powder material in S2 is 2μm-4μm, the Dv50 is 4-8μm, the Dv90 is 8-14μm, the Dv99 is below 45μm, and the value of (Dv90-Dv10) / Dv50 is 1.2-1.5.

[0025] As an embodiment, the mass of the pore former 2 in S3 is 0.1% to 10% of the mass of the hard carbon precursor material; as examples, the mass of the pore former 2 is 0.1%, 0.7%, 1.2%, 1.5%, 1.8%, 3%, 3.5%, 4.5%, 5%, 5.5%, 6.5%, 7.5%, 8.5%, 10% of the mass of the hard carbon precursor material, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0026] As an embodiment, the mass of the metal salt having a catalytic CNT generation effect in S5 is 0.1% to 5% of the mass of the hard carbon precursor material; as examples, the mass of the metal salt having a catalytic CNT generation effect is 0.1%, 0.7%, 1.2%, 1.5%, 1.8%, 3%, 3.5%, 4.5%, 5% of the mass of the hard carbon precursor material, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0027] As an embodiment, the temperature of the drying in S5 is ≥80°C, and the time of the drying is ≥2h; the temperature of the drying can be, for example, but is not limited to, 80°C, 83°C, 86°C, 88°C, 90°C, 93°C, 97°C, 100°C, 102°C, 105°C, 108°C, 110°C; the time of the drying can be, for example, but is not limited to, 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, 8.5h, 9.0h, 9.5h, 10.0h, 10.5h, 11.0h, 11.5h, 12.0h. The drying process can remove the water in the hard carbon material, ensuring that the material does not have an adverse reaction due to the presence of water in the subsequent high-temperature vapor deposition process.

[0028] As an embodiment, the gas of the inert atmosphere in S6 is selected from at least one of nitrogen and argon; preferably, the gas of the inert atmosphere is selected from nitrogen.

[0029] As an embodiment, the carbon source in S6 is at least one of methane, acetylene, and ethylene. Preferably, the carbon source is acetylene.

[0030] As an embodiment, the temperature of the high-temperature vapor deposition method in S6 is 700-1000°C, and the time is 0.5-5 h; specifically, the temperature of the high-temperature vapor deposition method can be, but is not limited to, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C; and specifically, the time can be, but is not limited to, 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h. Specifically, the high-temperature vapor deposition method is performed in a CVD furnace, and the temperature rising rate is 3-6°C / min, preferably, the temperature rising rate is 5°C / min.

[0031] As an embodiment, the temperature of the second high-temperature carbonization in S7 is 1100-1600°C, and the time is 0.5-10 h; specifically, the temperature of the high-temperature carbonization can be, but is not limited to, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C; and specifically, the time can be, but is not limited to, 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h, 6.5 h, 7.0 h, 7.5 h, 8.0 h, 8.5 h, 9.0 h, 9.5 h, 10.0 h. The S7 step can further stabilize the structure of the hard carbon material and improve the electrochemical performance.

[0032] As an embodiment, the purification in S8 includes soaking the third composite material with an acid agent; for example, the acid agent can be, but is not limited to, at least one of hydrochloric acid, hydrofluoric acid, and nitric acid; and the filtering and washing includes controlling the pH of the filtrate after filtering and washing to be ≥6.5.

[0033] As an embodiment, the temperature of the drying in S8 is ≥80°C, and the time is ≥2 h; for example, the temperature of the drying can be, but is not limited to, 80°C, 83°C, 86°C, 89°C, 93°C, 96°C, 98°C, 100°C, 103°C, 106°C, 108°C, 110°C; and the drying time can be, but is not limited to, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h.

[0034] As an embodiment, the ash content of the purified material in S8 is ≤0.5%. The S8 step can remove impurities and moisture that can exist in the material, ensuring the purity of the material, which is very important for improving the electrochemical stability of the material.

[0035] As an embodiment, the coating agent in S9 is selected from at least one of pitch, resin, and starch; preferably, the coating agent is selected from phenolic resin.

[0036] As an embodiment, the temperature for coating in S9 is 1000℃-1600℃, and the holding time is 0.5h-10h; the temperature for coating can be specifically but not limited to 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃; the time can be specifically but not limited to 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, 8.5h, 9.0h, 9.5h, 10.0h.

[0037] As an embodiment, in S9, the Dv10 of the hierarchical pore sodium electrochemical hard carbon negative material is 1-3μm, the Dv50 is 3-7μm, the Dv90 is 7-13μm, the Dv99 is below 40μm, and the value of (Dv90-Dv10) / Dv50 is 1.4-2.0.

[0038] Correspondingly, the second aspect of the present application also provides a hierarchical pore sodium electrochemical hard carbon negative material prepared by the above-mentioned preparation method of the hierarchical pore sodium electrochemical hard carbon negative material. DETAILED DESCRIPTION

[0039] In order to better illustrate the purpose, technical scheme and beneficial effects of the present application, the present application will be further described below in combination with examples. It should be noted that the following implementation of the method is a further explanation and description of the present application, and should not be regarded as a limitation of the present application.

[0040] Example 1

[0041] The present embodiment provides a preparation method of a hierarchical pore sodium electrochemical hard carbon negative material, the steps of which include:

[0042] S1, mix 5kg of coconut shell particles and 500g of NaCl in a VC mixer, then pour into a graphite crucible, put the graphite crucible into a box furnace, adjust the nitrogen atmosphere in the furnace, the nitrogen flow rate is 1L / min, adjust the heating rate to 5℃ / min, and keep the material at 500℃ for 2h, then take out the graphite crucible after cooling, and obtain 2000g of first composite material;

[0043] S2, use a pair of roller equipment to crush the first composite material to 2mm, then use an air flow pulverizer to finely crush it to a particle size Dv10 controlled at 2μm, a particle size Dv50 controlled at 5μm, a particle size Dv90 controlled at 10μm, and a particle size Dv99 controlled at 13μm, and the value of particle size distribution (Dv90-Dv10) / Dv50 is 1.6, to obtain 1600g of fine powder material;

[0044] S3, add the fine powder and 104 g of ZnCl2crystals into a beaker, then pour 2 L of deionized water into the beaker to stir and mix the mixture evenly to obtain a mixed material;

[0045] S4, put the mixed material into a heat treatment at 800℃ for 1 h to obtain a surface-porous first composite material;

[0046] S5, add 42 g of a ferric chloride solution having a catalytic CNT generation effect into the surface-porous first composite material, and then dry the mixture in a blast drying oven at 110℃ for 6 h to obtain 1544 g of a dried material;

[0047] S6, place the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to be nitrogen, adjust the nitrogen flow rate to be 1 L / min, adjust the temperature rising rate to be 5℃ / min to make the material at 850℃, adjust the carbon-containing gas to be acetylene, adjust the acetylene flow rate to be 3 L / min, and keep the temperature for 3 h, then take out the material after cooling to obtain 1440 g of a second composite material;

[0048] S7, place the second composite material into a graphite crucible, place the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to be nitrogen, adjust the nitrogen flow rate to be 1 L / min, adjust the temperature rising rate to be 5℃ / min to make the material at 1600℃, keep the temperature for 2 h, then take out the graphite crucible after cooling to obtain 1332 g of a third composite material;

[0049] S8, place the third composite material into a beaker, add 160 g of hydrochloric acid to perform acid bubbling, perform filtration and washing of the third composite material using a positive pressure filter until the pH of the washing filtrate is 7, then place the third composite material into a blast drying oven to dry at 110℃ for 3 h to obtain 549 g of a purified material;

[0050] S9, place the purified material into a beaker, add 216 g of a phenolic resin solution diluted with alcohol to a concentration of 60% to stir and mix, then place the mixture into a graphite crucible, place the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to be nitrogen, adjust the nitrogen flow rate to be 1 L / min, adjust the temperature rising rate to be 5℃ / min to make the material at 1600℃, keep the temperature for 2 h, then take out the graphite crucible after cooling to obtain 727 g of a hierarchical-pore sodium-doped hard carbon negative electrode material.

[0051] Example 2

[0052] The embodiment provides a preparation method of a hierarchical-pore sodium-doped hard carbon negative electrode material, and the steps include:

[0053] S1, pour 5.0 kg of coconut shell particles and 250 g of NaCl into a graphite crucible after mixing them in a VC mixer, place the graphite crucible in a box furnace, adjust the nitrogen atmosphere in the furnace to a nitrogen flow rate of 1 L / min, adjust the heating rate to 5 ℃ / min to keep the material at 600 ℃ for 2.3 h, take out the graphite crucible after cooling, and obtain 1650 g of a first composite material;

[0054] S2, use a pair of roller equipment to crush the first composite material to 2 mm, and then use an air flow mill to finely crush it to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, to obtain 1320 g of a fine powder material;

[0055] S3, add the fine powder material and 52 g of ZnCl2 crystals into a beaker, pour 2 L of deionized water into the beaker, and stir to obtain a mixture;

[0056] S4, place the mixture into a heat treatment at 900 ℃ for 0.6 h to obtain a porous first composite material;

[0057] S5, add 21 g of an iron chloride solution having a catalytic CNT generation effect into the porous first composite material, and then dry the mixture in a blast drying oven at 100 ℃ for 8 h to obtain 1366 g of a dried material;

[0058] S6, place the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, adjust the nitrogen flow rate to 1 L / min, adjust the heating rate to 5 ℃ / min to keep the material at 1000 ℃, adjust the carbon-containing gas to acetylene, adjust the acetylene flow rate to 3 L / min, and keep the material at 1000 ℃ for 3 h, take out the material after cooling, and obtain 1216 g of a second composite material;

[0059] S7, place the second composite material into a graphite crucible, place the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, adjust the nitrogen flow rate to 1 L / min, adjust the heating rate to 5 ℃ / min to keep the material at 1500 ℃ for 3.5 h, take out the graphite crucible after cooling, and obtain 1194 g of a third composite material;

[0060] S8, place the third composite material into a beaker, add 160 g of hydrochloric acid to perform acid bubbling, perform filtration and washing of the third composite material using a positive pressure filter until the pH of the washing filtrate is 7, and then place the third composite material into a blast drying oven to dry at 100 ℃ for 4 h to obtain 456 g of a purified material;

[0061] S9, put the purified material into a beaker, add 144g of phenolic resin solution with a concentration of 60% after dilution with alcohol, and stir and mix, then put it into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1L / min, adjust the heating rate to 5℃ / min, and keep the material at 1500℃ for 3.5h, take out the graphite crucible after cooling, and obtain 599g of hierarchical pore sodium electric hard carbon negative material.

[0062] Example 3

[0063] The embodiment provides a preparation method of a hierarchical pore sodium electric hard carbon negative material, and the steps comprise:

[0064] S1, mix 5.0kg of coconut shell particles and 700g of NaCl in a VC mixer, then pour them into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1L / min, adjust the heating rate to 5℃ / min, and keep the material at 450℃ for 4.5h, take out the graphite crucible after cooling, and obtain 2450g of a first composite material;

[0065] S2, use a pair of roller equipment to crush the first composite material to 2mm, and then use an air flow pulverizer to finely crush it to a discharge particle size Dv10 controlled at 2μm, a particle size Dv50 controlled at 5μm, a particle size Dv90 controlled at 10μm, a particle size Dv99 controlled at 13μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, to obtain 1760g of a fine powder material;

[0066] S3, add the fine powder material and 156g of NaOH crystals into a beaker, pour 2L of deionized water into the beaker, and stir and mix uniformly to obtain a mixed material;

[0067] S4, put the mixed material into a heat treatment at 760℃ for 2h to obtain a surface porous first composite material;

[0068] S5, add 63g of a nickel chloride solution with a catalytic CNT generation effect into the surface porous first composite material, and then dry it in a 80℃ air drying oven for 12h to obtain 1740g of a dried material;

[0069] S6, put the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1L / min, adjust the heating rate to 5℃ / min, keep the material at 1100℃, adjust the carbon-containing gas to acetylene, the acetylene flow rate is 3L / min, keep it for 2.5h, take out the material after cooling, and obtain 1601g of a second composite material;

[0070] S7, the second composite material is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is kept at 1400 ℃ for 5 h, after cooling, the graphite crucible is taken out, and 1608 g of the third composite material is obtained;

[0071] S8, the third composite material is placed in a beaker, 160 g of hydrochloric acid is added for acid bubbling, after acid bubbling for 3 h, the third composite material is filtered and washed using a positive pressure filter until the pH of the washing filtrate is 7, then the third composite material is put into a forced air drying oven for drying at 85 ℃ for 6 h, and 486 g of the purified material is obtained;

[0072] S9, the purified material is put into a beaker, 288 g of a phenolic resin solution diluted with alcohol and having a concentration of 60% is added for stirring and mixing, after mixing, the mixture is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is kept at 1300 ℃ for 5.5 h, after cooling, the graphite crucible is taken out, and 759 g of the hierarchical pore sodium electric hard carbon negative electrode material is obtained.

[0073] Example 4

[0074] The difference between the present example and example 1 is that, in the present example, S9 is that the purified material is put into a beaker, 72 g of a phenolic resin solution diluted with alcohol and having a concentration of 60% is added for stirring and mixing, after mixing, the mixture is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is kept at 1600 ℃ for 2 h, after cooling, the graphite crucible is taken out, and 590 g of the hierarchical pore sodium electric hard carbon negative electrode material is obtained.

[0075] The rest is the same as in example 1.

[0076] Example 5

[0077] The difference between the present example and example 1 is that, in the present example, S9 is that the purified material is put into a beaker, 144 g of a phenolic resin solution diluted with alcohol and having a concentration of 60% is added for stirring and mixing, after mixing, the mixture is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is kept at 1600 ℃ for 2 h, after cooling, the graphite crucible is taken out, and 658 g of the hierarchical pore sodium electric hard carbon negative electrode material is obtained.

[0078] The rest is the same as in example 1.

[0079] Example 6

[0080] The difference between this embodiment and embodiment 1 is only that the S9 of this embodiment is: the purified material is put into a beaker, 288 g of phenolic resin solution diluted with alcohol to a concentration of 60% is added for stirring and mixing, after mixing is completed, the mixture is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the heating rate is adjusted to be 5 ℃ / min, and the material is kept at 1600 ℃ for 2 h, after cooling, the graphite crucible is taken out, and 795 g of the hierarchical pore sodium electric hard carbon negative electrode material is obtained;

[0081] The rest is the same as embodiment 1.

[0082] Comparative example 1

[0083] This comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, and the steps include:

[0084] S1, 5 kg of coconut shell particles are poured into a graphite crucible, the graphite crucible is put into a box furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the heating rate is adjusted to be 5 ℃ / min, and the material is kept at 500 ℃ for 2 h, after cooling, the graphite crucible is taken out, and 1500 g of a first composite material is obtained;

[0085] S2, the first composite material is crushed to 2 mm by using a pair of roller equipment, and then finely crushed to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6 by using an air flow pulverizer, and 1200 g of a fine powder material is obtained;

[0086] S3, the fine powder material is added into a beaker, and then 2 L of deionized water is poured in for stirring and mixing to obtain a mixed material;

[0087] S4, the mixed material is put into heat treatment at 800 ℃ for 1 h to obtain a surface porous first composite material;

[0088] S5, the surface porous first composite material is dried in a blast drying oven at 110 ℃ for 6 h to obtain 1080 g of a dried material;

[0089] S6, the dried material is put into a CVD furnace, the protective atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the heating rate is adjusted to be 5 ℃ / min, the material is kept at 850 ℃ for 3 h, after cooling, the material is taken out, and 864 g of a second composite material is obtained;

[0090] S7, the second composite material is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, and the material is kept at 1600 ℃ for 2 h, the graphite crucible is taken out after cooling, and 778 g of a third composite material is obtained;

[0091] S8, the third composite material is placed in a beaker, 160 g of hydrochloric acid is added for acid bubbling, the third composite material is filtered and washed using a positive pressure filter after acid bubbling for 3 h, until the pH of the washing filtrate is 7, the third composite material is put into a forced air drying oven for drying at 110 ℃ for 3 h, and 622 g of a purified material is obtained;

[0092] S9, the purified material is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, and the material is kept at 1600 ℃ for 2 h, the graphite crucible is taken out after cooling, and 591 g of a sodium electric hard carbon negative electrode material with hierarchical pores is obtained.

[0093] Comparative Example 2

[0094] The present comparative example provides a preparation method of a sodium electric hard carbon negative electrode material with hierarchical pores, and the steps comprise:

[0095] S1, 5 kg of coconut shell particles and 250 g of NaCl are mixed in a VC mixer, then poured into a graphite crucible, the graphite crucible is put into a box furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, and the material is kept at 500 ℃ for 2 h, the graphite crucible is taken out after cooling, and 1750 g of a first composite material is obtained;

[0096] S2, the first composite material is crushed to 2 mm by using a pair of roller equipment, and then finely crushed to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6 by using an air flow pulverizer, and 1400 g of a fine powder material is obtained;

[0097] S3, the fine powder material is added into a beaker, and then 2 L of deionized water is poured into the beaker for stirring and mixing uniformly to obtain a mixed material;

[0098] S4, the mixed material is subjected to heat treatment at 800 ℃ for 1 h to obtain a first composite material with a porous surface;

[0099] S5, the first composite material with a porous surface is dried in a 110 ℃ forced air drying oven for 6 h to obtain 1260 g of a dried material;

[0100] S6, put the dried material into the CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material at 850 ℃, then adjust the carbon-containing gas to acetylene, the acetylene flow rate is 3 L / min, and keep the temperature for 3 h, then take out the material after cooling, and 1058 g of second composite material is obtained;

[0101] S7, put the second composite material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material at 1600 ℃, keep the temperature for 2 h, then take out the graphite crucible after cooling, and 977 g of third composite material is obtained;

[0102] S8, put the third composite material into a beaker, add 160 g of hydrochloric acid for acid bubbling, filter and wash the third composite material using a positive pressure filter after acid bubbling for 3 h until the pH of the washing filtrate is 7, then put the third composite material into a forced air drying oven for drying at 110 ℃ for 3 h to obtain 582 g of purified material;

[0103] S9, put the purified material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material at 1600 ℃, keep the temperature for 2 h, then take out the graphite crucible after cooling, and 553 g of hierarchical pore sodium electric hard carbon negative electrode material is obtained.

[0104] Comparative Example 3

[0105] The present comparative example provides a preparation method of hierarchical pore sodium electric hard carbon negative electrode material, the steps comprising:

[0106] S1, mix 5 kg of coconut shell particles and 500 g of NaCl in a VC mixer, then pour into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material at 500 ℃, keep the temperature for 2 h, then take out the graphite crucible after cooling, and 2000 g of first composite material is obtained;

[0107] S2, use a pair of roller equipment to crush the first composite material to 2 mm, then use an air flow pulverizer to finely crush it to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, and 1600 g of fine powder material is obtained;

[0108] S3, add the fine powder material into a beaker, then pour 2 L of deionized water into the beaker for stirring and mixing uniformly to obtain a mixed material;

[0109] S4, the mixture is put into heat treatment at 800 DEG C for 1h to obtain a surface porous first composite material;

[0110] S5, the surface porous first composite material is dried in a 110 DEG C air drying oven for 6h to obtain 1440g of dried material;

[0111] S6, the dried material is put into a CVD furnace, the protective atmosphere in the furnace is adjusted to nitrogen, the nitrogen flow rate is 1L / min, the heating rate is adjusted to 5 DEG C / min, the material is treated at 850 DEG C, the carbon-containing gas is adjusted to acetylene, the acetylene flow rate is 3L / min, and the material is treated for 3h, then the material is taken out after cooling, and 1252g of a second composite material is obtained;

[0112] S7, the second composite material is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to nitrogen, the nitrogen flow rate is 1L / min, the heating rate is adjusted to 5 DEG C / min, the material is treated at 1600 DEG C for 2h, then the graphite crucible is taken out after cooling, and 1177g of a third composite material is obtained;

[0113] S8, the third composite material is put into a beaker, 160g of hydrochloric acid is added for acid bubbling, the third composite material is filtered and washed using a positive pressure filter after acid bubbling for 3h until the pH of the washing filtrate is 7, then the third composite material is put into an air drying oven and dried at 110 DEG C for 3h to obtain 541g of purified material;

[0114] S9, the purified material is put into a graphite crucible, the graphite crucible is put into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to nitrogen, the nitrogen flow rate is 1L / min, the heating rate is adjusted to 5 DEG C / min, the material is treated at 1600 DEG C for 2h, then the graphite crucible is taken out after cooling, and 514g of a hierarchical pore sodium electric hard carbon negative electrode material is obtained.

[0115] Comparative Example 4

[0116] The present comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, comprising the following steps:

[0117] S1, 5kg of coconut shell particles and 750g of NaCl are mixed in a VC mixer, then poured into a graphite crucible, the graphite crucible is put into a box furnace, the atmosphere in the furnace is adjusted to nitrogen, the nitrogen flow rate is 1L / min, the heating rate is adjusted to 5 DEG C / min, the material is treated at 500 DEG C for 2h, then the graphite crucible is taken out after cooling, and 2250g of a first composite material is obtained;

[0118] S2, the first composite material is crushed to 2 mm by using a pair of roller equipment, and then the first composite material is finely crushed to a particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6 by using an air flow mill, to obtain 1600 g of fine powder material;

[0119] S3, the fine powder material is added into a beaker, and then 2 L of deionized water is poured into the beaker to stir and mix the fine powder material uniformly to obtain a mixed material;

[0120] S4, the mixed material is subjected to heat treatment at 800 ℃ for 1 h to obtain a surface porous first composite material;

[0121] S5, the surface porous first composite material is dried in a blast drying oven at 110 ℃ for 6 h to obtain 1620 g of dried material;

[0122] S6, the dried material is placed into a CVD furnace, the protective atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is subjected to heat treatment at 850 ℃, the carbon-containing gas is adjusted to be acetylene, the acetylene flow rate is 3 L / min, and the material is subjected to heat treatment for 3 h, to obtain 1446 g of a second composite material;

[0123] S7, the second composite material is placed into a graphite crucible, the graphite crucible is placed into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is subjected to heat treatment at 1600 ℃ for 2 h, and the graphite crucible is taken out after cooling to obtain 1376 g of a third composite material;

[0124] S8, the third composite material is placed into a beaker, 160 g of hydrochloric acid is added to the beaker to perform acid bubbling, the third composite material is filtered and washed by using a positive pressure filter after acid bubbling for 3 h, until the pH of the washing filtrate is 7, and then the third composite material is placed into a blast drying oven to perform drying at 110 ℃ for 3 h to obtain 501 g of purified material;

[0125] S9, the purified material is placed into a graphite crucible, the graphite crucible is placed into a high-temperature atmosphere furnace, the atmosphere in the furnace is adjusted to be nitrogen, the nitrogen flow rate is 1 L / min, the temperature rising speed is adjusted to be 5 ℃ / min, the material is subjected to heat treatment at 1600 ℃ for 2 h, and the graphite crucible is taken out after cooling to obtain 476 g of a hierarchical pore sodium electric hard carbon negative electrode material.

[0126] Comparative Example 5

[0127] The present comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, and the steps include:

[0128] S1, pour 5 kg of coconut shell particles and 1000 g of NaCl into a graphite crucible after mixing them in a VC mixer, put the graphite crucible into a box furnace, adjust the nitrogen atmosphere in the furnace, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, and keep the material at 500 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 2500 g of first composite material;

[0129] S2, use a pair of roller equipment to crush the first composite material to 2 mm, and then use an air flow mill to finely crush it to an outlet particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, to obtain 1600 g of fine powder material;

[0130] S3, add the fine powder material into a beaker, pour 2 L of deionized water into the beaker, and stir to mix uniformly to obtain a mixed material;

[0131] S4, put the mixed material into a heat treatment at 800 ℃ for 1 h to obtain a surface porous first composite material;

[0132] S5, dry the surface porous first composite material in a 110 ℃ air drying oven for 6 h to obtain 1800 g of dried material;

[0133] S6, put the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, keep the material at 850 ℃, adjust the carbon-containing gas to acetylene, the acetylene flow rate is 3 L / min, and keep the temperature for 3 h, take out the material after cooling, and obtain 1640 g of second composite material;

[0134] S7, put the second composite material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, keep the material at 1600 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 1576 g of third composite material;

[0135] S8, put the third composite material into a beaker, add 160 g of hydrochloric acid for acid bubbling, filter and wash the third composite material using a positive pressure filter after acid bubbling for 3 h until the washing filtrate pH is 7, and then put the third composite material into an air drying oven for 110 ℃ drying for 3 h to obtain 461 g of purified material;

[0136] S9, put the purified material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material keep at 1600 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 438 g of the hierarchical pore sodium electric hard carbon negative electrode material.

[0137] Comparative Example 6

[0138] The present comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, comprising the following steps:

[0139] S1, mix 5 kg of coconut shell particles and 500 g of NaCl in a VC mixer, then pour into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material keep at 500 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 2000 g of the first composite material;

[0140] S2, use a pair of roller equipment to crush the first composite material to 2 mm, and then use an air flow mill to finely crush it to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, to obtain 1600 g of fine powder material;

[0141] S3, add the fine powder material and 52 g of ZnCl2 crystals into a beaker, then pour into 2 L of deionized water to stir and mix uniformly to obtain a mixed material;

[0142] S4, put the mixed material into heat treatment at 900 ℃ for 0.6 h to obtain a surface porous first composite material;

[0143] S5, add 21 g of iron chloride solution with catalytic CNT effect to the surface porous first composite material, and then dry in a 110 ℃ air drying oven for 6 h to obtain 1492 g of dried material;

[0144] S6, put the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material keep at 850 ℃, then adjust the carbon-containing gas to acetylene, the acetylene flow rate is 3 L / min, keep for 3 h, take out the material after cooling, and obtain 1346 g of the second composite material;

[0145] S7, put the second composite material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, and keep the material at 1600 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 1254 g of third composite material;

[0146] S8, put the third composite material into a beaker, add 160 g of hydrochloric acid for acid bubbling, filter and wash the third composite material using a positive pressure filter after acid bubbling for 3 h until the pH of the washing filtrate is 7, then put the third composite material into a forced air drying oven for drying at 110 ℃ for 3 h to obtain 545 g of purified material;

[0147] S9, put the purified material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, and keep the material at 1600 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 518 g of hierarchical pore sodium electric hard carbon negative electrode material.

[0148] Comparative Example 7

[0149] This comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, the steps comprising:

[0150] S1, mix 5 kg of coconut shell particles and 500 g of NaCl in a VC mixer, then pour into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min, and keep the material at 500 ℃ for 2 h, take out the graphite crucible after cooling, and obtain 2000 g of first composite material;

[0151] S2, use a pair of roller equipment to crush the first composite material to 2 mm, then use an air flow pulverizer to finely crush it to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, to obtain 1600 g of fine powder material;

[0152] S3, add the fine powder material and 104 g of ZnCl2 crystals into a beaker, then pour into 2 L of deionized water for stirring and mixing uniformly to obtain a mixed material;

[0153] S4, heat the mixed material to 900 ℃ for 0.6 h to obtain a surface porous first composite material;

[0154] S5, add 42 g of iron chloride solution with catalytic CNT effect to the surface porous first composite material, then dry in a 110 ℃ forced air drying oven for 6 h to obtain 1544 g of dried material;

[0155] S6, put the dried material into the CVD furnace, adjust the protective atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material under the condition of 850 ℃, then adjust the carbon-containing gas to acetylene, the acetylene flow rate is 3 L / min, keep warm for 3 h, take out the material after cooling, and obtain 1440 g of second composite material;

[0156] S7, put the second composite material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material under the condition of 1600 ℃, keep warm for 2 h, take out the graphite crucible after cooling, and obtain 1332 g of third composite material;

[0157] S8, put the third composite material into a beaker, add 160 g of hydrochloric acid for acid bubbling, filter and wash the third composite material using a positive pressure filter after acid bubbling for 3 h, until the pH of the washing filtrate is 7, then put the third composite material into a forced air drying oven for drying at 110 ℃ for 3 h, and obtain 549 g of purified material;

[0158] S9, put the purified material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material under the condition of 1600 ℃, keep warm for 2 h, take out the graphite crucible after cooling, and obtain 521 g of hierarchical pore sodium electric hard carbon negative electrode material.

[0159] Comparative Example 8

[0160] This comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, the steps comprising:

[0161] S1, mix 5 kg of coconut shell particles and 500 g of NaCl in a VC mixer, then pour into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to 5 ℃ / min to make the material under the condition of 500 ℃, keep warm for 2 h, take out the graphite crucible after cooling, and obtain 2000 g of first composite material;

[0162] S2, use a pair of roller equipment to crush the first composite material to 2 mm, then use an air flow mill to finely crush it to a discharge particle size Dv10 controlled at 2 μm, a particle size Dv50 controlled at 5 μm, a particle size Dv90 controlled at 10 μm, a particle size Dv99 controlled at 13 μm, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6, and obtain 1600 g of fine powder material;

[0163] S3, add the fine powder and 156 g of ZnCl2crystals into a beaker, then pour 2 L of deionized water into the beaker to stir and mix the mixture evenly to obtain a mixed material;

[0164] S4, put the mixed material into a heat treatment at 900 DEG C for 0.6 h to obtain a porous first composite material;

[0165] S5, add 63 g of iron chloride solution with catalytic CNT effect into the porous first composite material, then dry the mixture in a blast drying oven at 110 DEG C for 6 h to obtain 1596 g of dried material;

[0166] S6, put the dried material into a CVD furnace, adjust the protective atmosphere in the furnace to be nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to be 5 DEG C / min to make the material at 850 DEG C, then adjust the carbon-containing gas to be acetylene, the acetylene flow rate is 3 L / min, and keep the temperature for 3 h, then take out the material after cooling to obtain 1534 g of a second composite material;

[0167] S7, put the second composite material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to be nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to be 5 DEG C / min to make the material at 1600 DEG C, keep the temperature for 2 h, then take out the graphite crucible after cooling to obtain 1409 g of a third composite material;

[0168] S8, put the third composite material into a beaker, add 160 g of hydrochloric acid to perform acid bubbling, perform filtration and washing of the third composite material using a positive pressure filter until the pH of the washing filtrate is 7, then put the third composite material into a blast drying oven to dry at 110 DEG C for 3 h to obtain 552 g of purified material;

[0169] S9, put the purified material into a graphite crucible, put the graphite crucible into a high-temperature atmosphere furnace, adjust the atmosphere in the furnace to be nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to be 5 DEG C / min to make the material at 1600 DEG C, keep the temperature for 2 h, then take out the graphite crucible after cooling to obtain 525 g of a hierarchical pore sodium electric hard carbon negative electrode material.

[0170] Comparative Example 9

[0171] The present comparative example provides a preparation method of a hierarchical pore sodium electric hard carbon negative electrode material, the steps comprising:

[0172] S1, mix 5 kg of coconut shell particles and 500 g of NaCl in a VC mixer, then pour the mixture into a graphite crucible, put the graphite crucible into a box furnace, adjust the atmosphere in the furnace to be nitrogen, the nitrogen flow rate is 1 L / min, adjust the heating rate to be 5 DEG C / min to make the material at 500 DEG C, keep the temperature for 2 h, then take out the graphite crucible after cooling to obtain 2000 g of a first composite material;

[0173] S2, the first composite material is crushed to 2mm by using a pair of roller equipment, and then the first composite material is finely crushed to a particle size Dv10 controlled at 2um, a particle size Dv50 controlled at 5um, a particle size Dv90 controlled at 10um, a particle size Dv99 controlled at 13um, and a particle size distribution (Dv90-Dv10) / Dv50 value of 1.6 by using an air flow pulverizer, so as to obtain 1600g of fine powder material;

[0174] S3, the fine powder material and 208g of ZnCl2crystals are added into a beaker, and then 2L of deionized water is poured into the beaker to uniformly stir and mix the fine powder material and the ZnCl2crystals, so as to obtain a mixed material;

[0175] S4, the mixed material is subjected to heat treatment at 900℃ for 0.6h to obtain a porous first composite material;

[0176] S5, 84g of iron chloride solution having a catalytic CNT effect is added into the porous first composite material, and then the porous first composite material is dried in a blast drying oven at 110℃ for 6h to obtain 1648g of dried material;

[0177] S6, the dried material is placed into a CVD furnace, a nitrogen atmosphere is adjusted in the CVD furnace, a nitrogen flow rate is 1L / min, a temperature rising speed is adjusted to 5℃ / min, the material is subjected to heat treatment at 850℃, acetylene is adjusted as a carbon-containing gas, an acetylene flow rate is 3L / min, and the material is subjected to heat treatment for 3h, so as to obtain 1628g of a second composite material;

[0178] S7, the second composite material is placed into a graphite crucible, the graphite crucible is placed into a high-temperature atmosphere furnace, a nitrogen atmosphere is adjusted in the high-temperature atmosphere furnace, a nitrogen flow rate is 1L / min, a temperature rising speed is adjusted to 5℃ / min, the material is subjected to heat treatment at 1600℃, and the material is subjected to heat treatment for 2h, so as to obtain 1487g of a third composite material;

[0179] S8, the third composite material is placed into a beaker, 160g of hydrochloric acid is added into the beaker to perform acid bubbling, the third composite material is filtered and washed by using a positive pressure filter after the acid bubbling for 3h, until the pH of the washing filtrate is 7, and then the third composite material is placed into a blast drying oven to perform drying at 110℃ for 3h, so as to obtain 556g of purified material;

[0180] S9, the purified material is placed into a graphite crucible, the graphite crucible is placed into a high-temperature atmosphere furnace, a nitrogen atmosphere is adjusted in the high-temperature atmosphere furnace, a nitrogen flow rate is 1L / min, a temperature rising speed is adjusted to 5℃ / min, the material is subjected to heat treatment at 1600℃, and the material is subjected to heat treatment for 2h, so as to obtain 528g of a sodium-superhard carbon negative electrode material.

[0181] The particle size of the graded-pore sodium-hard carbon negative electrode material of Examples 1-6 and Comparative Examples 1-9 was tested by using a Malvern laser particle size analyzer MS2000; the specific surface area of the graded-pore sodium-hard carbon negative electrode material of Examples 1-6 and Comparative Examples 1-9 was tested by using a CANTAB specific surface area tester NOVA2000e; and the test results are shown in Table 1.

[0182] The graded-pore sodium-hard carbon negative electrode material of Examples 1-6 and Comparative Examples 1-9 was applied to a half-cell according to the following method:

[0183] The graded-pore sodium-hard carbon negative electrode material, SBR, CMC and conductive SP were mixed in a mass ratio of 95:2.5:1.5:1, uniformly coated on an aluminum foil, and the coated electrode sheet was placed in a vacuum drying oven at a temperature of 110°C for vacuum drying for 4 hours for standby, and then punched into small round sheets with a diameter of 14 mm. Then, the small round sheets were transferred into a glove box of Germany Microna, which was filled with argon, to assemble a 2430 type button cell, with a 1 mol / L NaClO4 three-component mixed solvent, a mixture of EC:PC(1:1)+5% FEC(v / v) as the electrolyte, a metal sodium sheet as the counter electrode, and a 16 μm thick Ube separator as the separator film, to form a half-cell.

[0184] The assembled half-cell was subjected to electrochemical performance testing on an American Arbin electrochemical testing system: first, the battery was subjected to 3 cycles of 0.2C formation to ensure that the electrode material was fully activated and a stable SEI film was formed. Then, the battery was subjected to charge-discharge testing at a rate of 0.5C, and the gram capacity and initial efficiency were recorded. Then, the battery was subjected to charge-discharge testing at a rate of 1.0C, and the discharge capacity was recorded, and the capacity ratio was calculated, which was the ratio of the 1.0C discharge capacity to the gram capacity multiplied by 100%. The test results are shown in Table 1.

[0185] Table 1

[0186]

[0187]

[0188]

[0189] Comparing Comparative Examples 1-5, it can be seen that an increase in the proportion of the pore-forming agent 1 will result in an increase in the number of pore structures in the hard carbon material, and more pore structures will significantly increase the specific surface area of the material, and the increase in the specific surface area will help to improve the electrochemical performance of the material, especially the capacity performance.

[0190] It can be seen from the comparative analysis of Comparative Examples 6 to 9 that adjusting the content of the pore-forming agent 2 in step S3 and the content of the metal salt solution having a catalytic effect in step S5 will affect the specific surface area of the material, which indicates that the introduction of micropores and carbon nanotubes has a significant effect on the total specific surface area. With the increase of the specific surface area, the capacity of the material is improved, but at the same time, the first efficiency will decrease.

[0191] Comparing Comparative Examples 6 to 9 and Examples 1, 4 to 6, it can be seen that adjusting the content of the coating agent will also affect the specific surface area of the material. After coating, the specific surface area of the hierarchical-pore sodium-electric hard carbon negative electrode material can be reduced to 2 to 4 m 2 / g, and the capacity of the material not only does not decrease, but also slightly increases, and the first efficiency is also improved.

[0192] In summary, the hierarchical-pore sodium-electric hard carbon negative electrode material prepared by the preparation method of the present application can significantly improve the first efficiency and rate performance of the sodium ion battery. This is because the hierarchical-pore sodium-electric hard carbon negative electrode material prepared by the present application has a microporous, mesoporous, carbon nanotube and coating layer structure, so that the sodium ions can not only migrate along the mesopores and micropores in the hard carbon material, but also transport through the inner and outer surfaces of the carbon nanotubes, which can significantly optimize the ion transport path and electron conduction, thereby improving the rate performance of the sodium ion battery. In addition, the coating layer can reduce the direct contact of the hard carbon material with the electrolyte and reduce the occurrence of side reactions, further improving the first efficiency and rate performance of the sodium ion battery.

[0193] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it is not limited to the examples listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A preparation method of hierarchical pore sodium electrochemically hard carbon negative material, characterized by the steps of The application relates to a preparation method of a hierarchical-pore sodium-electric hard carbon negative electrode material. S1, mixing a hard carbon precursor material and a pore-forming agent 1 to prepare a first composite material through low-temperature pre-carbonization; S2, crushing the first composite material to prepare a fine powder material; S3, stirring and mixing the fine powder material with a pore-forming agent 2 to prepare a mixed material; S4, performing first high-temperature carbonization on the mixed material to obtain a surface-porous first composite material; S5, adding a metal salt solution with a CNT generation effect into the surface-porous first composite material, and performing drying treatment to obtain a dried material; S6, depositing a carbon source on the dried material through a high-temperature vapor deposition method in an inert atmosphere to obtain a second composite material; S7, performing second high-temperature carbonization on the second composite material to obtain a third composite material; S8, performing purification, filtration washing and drying on the third composite material to obtain a purified material; S9, coating the purified material with a coating agent to obtain the hierarchical-pore sodium-electric hard carbon negative electrode material.

2. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The hard carbon precursor material is at least one selected from phenolic resin, polyacrylonitrile, polystyrene, polyfurfural and polyfuran resin.

3. The method for preparing hierarchical porous sodium-hard carbon anode material as described in claim 1, characterized in that, The pore-forming agent 1 is at least one selected from NaCl, NaOH, KOH, ZnCl2 and Na2CO3.

4. The method for preparing hierarchical porous sodium-hard carbon anode material as described in claim 1, characterized in that, The pore-forming agent 2 is at least one selected from NaOH, KOH and ZnCl2.

5. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The metal salt solution with the CNT generation effect is a chloride salt or nitrate salt of a metal M, and the metal M is iron, cobalt or nickel.

6. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The temperature of the low-temperature pre-carbonization in S1 is 350 DEG C to 650 DEG C, and the time is 0.5 h to 10 h.

7. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The carbon source in S6 is at least one selected from methane, acetylene and ethylene.

8. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The hierarchical-pore sodium-electric hard carbon negative electrode material in S9 has a Dv10 of 1 mu m to 3 mu m, a Dv50 of 3 to 7 mu m, a Dv90 of 7 to 13 mu m, a Dv99 of 40 mu m or less, and a value of (Dv90-Dv10) / Dv50 of 1.4 to 2.

0.

9. The method for preparing hierarchical porous sodium-carbon hard anode material as described in claim 1, characterized in that, The application further discloses a hierarchical-pore sodium-electric hard carbon negative electrode material prepared by the method. The mass of the pore-forming agent 1 in S1 accounts for 0.1% to 10% of the mass of the hard carbon precursor material. The crushing in S2 comprises: first performing roller crushing and then adopting airflow crushing. The fine powder material in S2 has a Dv10 of 2 mu m to 4 mu m, a Dv50 of 4 to 8 mu m, a Dv90 of 8 to 14 mu m, a Dv99 of 45 mu m or less, and a value of (Dv90-Dv10) / Dv50 of 1.2 to 1.

5. The mass of the pore-forming agent 2 in S3 accounts for 0.1% to 10% of the mass of the hard carbon precursor material. The temperature of the first high-temperature carbonization in S4 is 700 DEG C to 900 DEG C, and the time is 0.5 h to 5 h. The mass of the metal salt with the CNT generation effect in S5 accounts for 0.1% to 5% of the mass of the hard carbon precursor material. The temperature of the drying in S5 is greater than or equal to 80 DEG C, and the time is greater than or equal to 2 h. The gas of the inert atmosphere in S6 is at least one selected from nitrogen and argon. The temperature of the high-temperature vapor deposition method in S6 is 700 DEG C to 1000 DEG C, and the time is 0.5 h to 5 h. (10) The second high-temperature carbonization in S7 is at a temperature of 1100-1600°C for 0.5-10 hours; (11) The purification in S8 includes soaking the third composite material with an acid agent; the drying temperature is ≥80°C for ≥2 hours; (12) The ash content of the purified material in S8 is ≤0.5%; (13) The coating agent in S9 is selected from at least one of pitch, resin, and starch; (14) The coating temperature in S9 is 1000-1600°C for 0.5-10 hours.

10. A hierarchical porous sodium electrochemically hard carbon negative material, characterized in that, The preparation method of the hierarchical-pore sodium electrochemical hard carbon negative electrode material according to any one of claims 1-9.

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