Hard carbon negative electrode material and preparation method and application thereof

Abstract

The application provides a hard carbon negative electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) performing acid washing and ash removal treatment on a hard carbon precursor to obtain an acid washing precursor, and mixing acid washing precursors with different particle sizes to obtain mixed acid washing precursors; (2) performing fluidized bed oxidation treatment on the mixed acid washing precursors and then performing screening to obtain oxidized materials with different particle sizes; and (3) performing sintering treatment on small-particle-size oxidized materials to obtain the hard carbon negative electrode material; wherein the median particle size D50 of the small-particle-size acid washing precursor is less than or equal to 30 microns, and the median particle size D50 of the small-particle-size oxidized material is less than or equal to 30 microns. The application solves the problems of a large number of impurity components in the negative electrode material, uneven pre-oxidation, high energy consumption and an unsatisfactory particle size distribution, improves the fluidization state and pre-oxidation effect of the fluidized bed ultra-fine viscous particles, realizes efficient preparation of high-quality hard carbon materials, and provides better negative electrode materials for power batteries and energy storage systems.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a hard carbon anode material, its preparation method and application. Background Technology

[0002] Currently, lithium-ion batteries are widely used in mobile electronic devices, new energy vehicles, and power tools due to their high energy density and excellent safety performance. However, the limited availability and high cost of lithium resources restrict their application in large-scale energy storage systems. In contrast, sodium resources are abundant in the Earth's crust and inexpensive, making sodium-ion batteries a promising candidate for large-scale energy storage systems.

[0003] Sodium ions have a larger radius than lithium ions, making it difficult for them to intercalate into the interlayer spacing of graphite anodes. Therefore, graphite anodes are not suitable as anode materials for sodium-ion batteries. However, amorphous hard carbon, due to its disordered and bent carbon layers, can store sodium through multiple methods such as intercalation, adsorption, and pore filling, resulting in higher capacity. Therefore, hard carbon has great potential for practical application as anode material for sodium-ion batteries.

[0004] Unlike hard carbon, soft carbon materials prepared from raw materials such as coal tar pitch / petroleum pitch / coal / heavy carbon have better electrical conductivity, but their high carbon layer order and small interplanar spacing result in poor electrochemical performance when directly applied to the anode of sodium-ion batteries. A common modification method is to pre-oxidize the precursor to obtain a cross-linked structure, thereby increasing the disorder of the carbon layer and the interplanar spacing, further improving sodium storage performance. However, for precursors with varying physicochemical properties, conventional static pre-oxidation methods (muffle furnace, tube furnace, fixed bed) are unlikely to enhance the pre-oxidation effect. The entire process suffers from significant influence from impurities in the precursor particles, diverse particle distribution, and limitations in oxidation methods, leading to incomplete or excessive oxidation reactions, unsatisfactory particle size distribution, long process cycles, and high energy consumption. This increases the difficulty of obtaining an ideal cross-linked structure to form hard carbon materials with high sodium storage capacity and excellent rate capability.

[0005] CN115188952A discloses a method for air oxidation modification of pitch using a kneading pan. Through steps such as molecular distillation, oxidation treatment, pulverization, air stabilization, and high-temperature carbonization, the process for preparing hard carbon materials is optimized, ultimately forming a negative electrode material with excellent electrochemical performance. However, this patent does not solve the problem of oxidation uniformity, which may affect the consistency of material performance; the lack of in-depth treatment of impurities in coal tar pitch may affect the conductivity and cycle performance of the hard carbon; and the limited particle size control precision may pose a challenge to the consistency of electrode fabrication.

[0006] CN107986254A proposes a method for preparing hard carbon anode materials through kneading, carbonization, and high-temperature carbonization steps. This method involves mixing aggregates with asphalt, improving the surface oxygen-containing functional groups through oxidation modification, and then performing a two-step carbonization process to prepare hard carbon materials with high lithium storage porosity and a reasonable particle size distribution. However, the oxidation modification in this patent requires strict control of airflow rate and kneading uniformity, making the operation complex; it does not mention impurity removal processes, which may affect material purity; and the method is highly dependent on high-temperature equipment, potentially increasing industrialization costs.

[0007] CN118454887A proposes a deep deashing and dechlorination process and system for high-chlorine coal. It employs technologies such as pre-screening, jigging, liquid-solid fluidized bed, and flotation to achieve efficient removal of chlorine and ash from coal. Simultaneously, it combines improved H2O2 oxidation and ultrasonic treatment technologies to further remove sulfur content and improve the quality of clean coal. However, the process is complex and heavily reliant on jigging machines, multi-stage equipment, and ultrasonic equipment. The preparation of iron-doped carbon dots is also cumbersome and may increase costs. The industrial applicability and economic viability of some processing steps require further verification. Summary of the Invention

[0008] The purpose of this invention is to provide a hard carbon anode material, its preparation method, and its application. This invention solves the problems of multiple impurity components, uneven pre-oxidation, high energy consumption, and unsatisfactory particle size distribution in anode materials. It improves the fluidization state and pre-oxidation effect of ultrafine viscous particles in fluidized beds, and realizes the efficient preparation of high-quality hard carbon materials, providing better anode materials for power batteries and energy storage systems.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a hard carbon anode material, the method comprising the following steps:

[0011] (1) Acid washing and deashing treatment is performed on the first particle size hard carbon precursor and the second particle size hard carbon precursor to obtain the first particle size acid washing precursor and the second particle size acid washing precursor. The first particle size acid washing precursor and the second particle size acid washing precursor are mixed to obtain a mixed acid washing precursor.

[0012] (2) After the mixed pickling precursor is subjected to fluidized bed oxidation treatment, it is screened to obtain oxidized material with first particle size and oxidized material with second particle size.

[0013] (3) The first particle size oxide is sintered to obtain the hard carbon anode material;

[0014] Among them, the median particle size D50 of the first particle size pickling precursor is ≤ 30 μm, the median particle size D50 of the second particle size pickling precursor is > 30 μm, the median particle size D50 of the first particle size oxidized material is ≤ 30 μm, and the median particle size D50 of the second particle size oxidized material is > 30 μm.

[0015] For the first particle size hard carbon precursor and the second particle size hard carbon precursor of the present invention, they can be mixed first and then pickled, or pickled separately and then mixed. There is no clear limitation here.

[0016] In the present invention, by introducing pickling and deashing, the pre-oxidation process of matching coarse and fine particles in a fluidized bed, and precise particle size control technology, high-quality hard carbon materials are prepared. By adopting the pre-oxidation process of matching coarse and fine particles in a fluidized bed, the precursor particles can uniformly contact the oxidant in the fluidized environment, thereby significantly improving the oxidation uniformity and ensuring the stability of product performance.

[0017] Preferably, the median particle size 2 μm ≤ D50 ≤ 30 μm of the first particle size hard carbon precursor, for example: 2 μm, 5 μm, 10 μm, 20 μm or 30 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The median particle size 30 μm < D50 ≤ 200 μm of the second particle size hard carbon precursor, for example: 35 μm, 50 μm, 100 μm, 150 μm or 200 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] The median particle size 2 μm ≤ D50 ≤ 30 μm of the first particle size pickling precursor, for example: 2 μm, 5 μm, 10 μm, 20 μm or 30 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The median particle size 30 μm < D50 ≤ 200 μm of the second particle size pickling precursor, for example: 35 μm, 50 μm, 100 μm, 150 μm or 200 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] The median particle size 2 μm ≤ D50 ≤ 30 μm of the first particle size oxidized material, for example: 2 μm, 5 μm, 10 μm, 20 μm or 30 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The median particle size 30 μm < D50 ≤ 200 μm of the second particle size oxidized material, for example: 35 μm, 50 μm, 100 μm, 150 μm or 200 μm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] Preferably, in step (2), after the second particle size oxidant is crushed and screened to obtain an oxidant with a median particle size of 2μm≤D50≤30μm, it is mixed with a new second particle size pickling precursor and the fluidized bed oxidation treatment and screening steps of step (2) are repeated.

[0021] This invention improves particle flow properties by supplementing the fluidized bed with larger-sized raw materials (new second-size pickling precursors) and reducing the risk of agglomeration of ultrafine, sticky particles from smaller-sized raw materials (crushed second-size oxidized materials). This cyclical process significantly improves heat and mass transfer within the fluidized bed. Furthermore, by sieving the raw materials and subjecting them to secondary crushing (less than 30 μm) and secondary oxidation, the particle size is controlled before and after fluidized bed oxidation, ensuring that the particle size distribution meets electrode fabrication requirements and improving battery conductivity and cycle stability.

[0022] Preferably, in step (1), the first particle size hard carbon precursor and the second particle size hard carbon precursor are obtained by crushing, grinding, sieving and drying the precursor carbon material.

[0023] The first-size hard carbon precursor and the second-size hard carbon precursor of the present invention can be obtained from the same batch of precursor materials through crushing, grinding, sieving and drying, or they can be obtained from different batches of precursor materials through crushing, grinding, sieving and drying.

[0024] Preferably, the precursor carbon material includes any one or a combination of at least two of coal tar pitch, petroleum pitch, coal, biomass carbon material, or heavy carbon material. Typical but non-limiting combinations include combinations of coal tar pitch and petroleum pitch, combinations of coal and biomass carbon material, or combinations of petroleum pitch and coal, etc.

[0025] Preferably, the drying temperature is 100℃~110℃, for example: 100℃, 102℃, 105℃, 108℃ or 110℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the acid washing and deashing treatment in step (1) includes hydrochloric acid washing and hydrofluoric acid washing.

[0027] Preferably, the hydrochloric acid used for the hydrochloric acid washing has a mass concentration of 15% to 20%, such as 15%, 16%, 17%, 18%, 19%, or 20%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the solid-liquid mass-to-volume ratio of the hydrochloric acid wash is 1:(5-15)g / mL, for example: 1:5g / mL, 1:8g / mL, 1:10g / mL, 1:12g / mL or 1:15g / mL, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, stirring is performed during the hydrochloric acid washing process.

[0030] Preferably, the stirring speed is 50 rpm to 150 rpm, for example: 50 rpm, 80 rpm, 100 rpm, 120 rpm or 150 rpm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the stirring time is 10h to 15h, for example: 10h, 11h, 12h, 13h, 14h or 15h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, after washing with hydrochloric acid, the mixture is allowed to stand and then washed with water. Silver nitrate is added to the water washing solution, and after no white precipitate is formed, the mixture is dried.

[0033] Preferably, the settling time is 1h to 3h, for example: 1h, 1.5h, 2h, 2.5h or 3h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the drying temperature is 100℃~110℃, for example: 100℃, 102℃, 105℃, 108℃ or 110℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the drying time is 10h to 15h, for example: 10h, 11h, 12h, 13h, 14h or 15h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the mass concentration of hydrofluoric acid used in the hydrofluoric acid pickling is 35% to 45%, for example: 35%, 38%, 40%, 42% or 45%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the solid-liquid mass-to-volume ratio of the hydrofluoric acid washing is 1:(5-10)g / mL, for example: 1:5g / mL, 1:6g / mL, 1:8g / mL, 1:9g / mL or 1:10g / mL, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, stirring is performed during the hydrofluoric acid washing process.

[0039] Preferably, the stirring speed is 50 rpm to 150 rpm, for example: 50 rpm, 80 rpm, 100 rpm, 120 rpm or 150 rpm.

[0040] Preferably, the stirring time is 20h to 30h, for example: 20h, 22h, 25h, 28h or 30h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, after hydrofluoric acid washing, the mixture is allowed to stand and then washed with water. Calcium chloride is added to the water washing solution, and after no white precipitate is formed, the mixture is dried.

[0042] Preferably, the settling time is 2h to 4h, for example: 2h, 2.5h, 3h, 3.5h or 4h.

[0043] Preferably, the drying temperature is 100℃~110℃, for example: 100℃, 102℃, 105℃, 108℃ or 110℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the drying time is 10h to 15h, for example: 10h, 11h, 12h, 13h, 14h or 15h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] In step (2), the mass ratio of the first particle size pickling precursor to the second particle size pickling precursor is 1:(2-5), for example: 1:2, 1:2.5, 1:3, 1:4 or 1:5, etc. It is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0046] Preferably, the atmosphere of the fluidized bed oxidation treatment in step (2) includes oxygen-containing gas.

[0047] Preferably, the gas flow rate of the fluidized bed oxidation process in step (2) is 700 mL / min to 800 mL / min, for example: 700 mL / min, 720 mL / min, 750 mL / min, 780 mL / min or 800 mL / min, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the heating rate of the fluidized bed oxidation treatment in step (2) is 0.4℃ / min to 1℃ / min, for example: 0.4℃ / min, 0.5℃ / min, 0.6℃ / min, 0.8℃ / min, 0.9℃ / min or 1℃ / min, etc.

[0049] Preferably, the temperature of the fluidized bed oxidation treatment in step (2) is 200℃~350℃, for example: 200℃, 220℃, 250℃, 300℃ or 350℃, etc.

[0050] Preferably, the fluidized bed oxidation treatment in step (2) includes a first-stage fluidized bed oxidation treatment and a second-stage fluidized bed oxidation treatment.

[0051] Preferably, the temperature of the first fluidized bed oxidation treatment is 200℃~300℃, for example: 220℃, 230℃, 240℃, 260℃ or 280℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the time for the first fluidized bed oxidation treatment is 2h to 6h, for example: 2h, 3h, 4h, 5h or 6h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] Preferably, the temperature of the second fluidized bed oxidation treatment is 300℃~350℃, for example: 300℃, 310℃, 320℃, 340℃ or 350℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0054] Preferably, the second fluidized bed oxidation treatment time is 3h to 5h, for example: 3h, 3.5h, 4h, 4.5h or 5h.

[0055] Preferably, the atmosphere for the sintering process in step (3) includes an inert gas.

[0056] Preferably, the sintering temperature in step (3) is 1200℃~1500℃, for example: 1200℃, 1250℃, 1300℃, 1400℃ or 1500℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] Preferably, the sintering time in step (3) is 3h to 8h, for example: 3h, 4h, 5h, 6h, 7h or 8h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0058] Preferably, after the sintering process described in step (3), an airflow grading and shaping process is performed.

[0059] Preferably, after the airflow staged shaping process, the median particle size D50 of the hard carbon anode material is 2μm to 10μm, for example: 2μm, 3μm, 5μm, 8μm or 10μm, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0060] In a second aspect, the present invention provides a hard carbon anode material, which is prepared by the preparation method described in the first aspect.

[0061] Thirdly, the present invention provides a negative electrode sheet comprising the hard carbon negative electrode material as described in the second aspect.

[0062] Fourthly, the present invention provides a battery comprising a negative electrode as described in the third aspect.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] (1) The present invention adopts acid washing and deashing and fluidized bed pre-oxidation process, which greatly shortens the preparation cycle and reduces energy consumption. Compared with the traditional static oxidation method, the production efficiency is increased by more than 100%, and the consistency of hard carbon material performance is improved.

[0065] (2) Through the synergistic optimization of oxidation, sieving and high-temperature carbonization, the present invention enables the obtained hard carbon material to have high specific capacity and cycle stability, and is especially suitable for high-rate charge and discharge applications.

[0066] (3) The present invention adopts precise screening and acid washing and deashing process in the precursor treatment stage, which significantly reduces the impact of inorganic impurities on material properties, reduces energy consumption and by-product generation in the subsequent carbonization stage, and is environmentally friendly and economical. At the same time, it reduces the difficulty of pre-oxidation of larger particles in the pre-oxidation process and greatly reduces production costs. Attached Figure Description

[0067] Figure 1 This is a process flow diagram of the preparation process of hard carbon anode material provided in the embodiments of the present invention, wherein the first particle size is a small particle size and the second particle size is a large particle size. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0069] Example 1

[0070] This embodiment provides a hard carbon anode material, and the preparation process flow diagram of the hard carbon anode material is shown below. Figure 1 As shown, the preparation method of the hard carbon negative electrode material comprises the following steps:

[0071] (1) First, crush the coal tar pitch using a jaw crusher (5E-JCA), pre-dry it at 105 °C in a forced-air drying oven, then grind it using a pulverizer (5E-PCIX100), sieve it using a standard sieve shaker, and select the first particle size hard carbon precursor with a median particle size D50 of 2 μm to 30 μm and the second particle size hard carbon precursor with a median particle size D50 of 50 μm to 200 μm. Dry them at 105 °C for 4 h. Mix the first particle size hard carbon precursor and the second particle size hard carbon precursor with 18% mass fraction of HCl at a ratio of 1:10 g / mL, stir and wash the coal at a speed of 100 rpm for 12 h, let it stand for 2 h, and repeatedly wash it with distilled water until there is no Cl - (Checked using AgNO3, no white precipitate) Filter, dry it in a forced-air drying oven at 105 °C for 12 h to obtain the demineralized raw material. Weigh the demineralized raw material and mix it with 40% mass concentration of hydrofluoric acid at a ratio of 1:7.5 g / mL, stir at a speed of 100 rpm for 24 h, let it stand for 3 h, filter, and wash the filter cake with distilled water, wash it many times (mix the filter cake with distilled water in a beaker and filter by suction many times) until there is no F - (Checked using CaCl2), then dry it at 105 °C for 12 h to obtain the first particle size pickled precursor and the second particle size pickled precursor. Mix the first particle size pickled precursor and the second particle size pickled precursor according to a mass ratio of 1:3 to obtain the mixed pickled precursor;

[0072] (2) Place the mixed pickled precursor in a fluidized bed. In an air atmosphere, select an air velocity of 740 mL / min; at a heating rate of 0.5 °C / min, heat from room temperature to 260 °C, carry out the first-stage fluidized bed pre-oxidation treatment for 4 h, and then heat to 330 °C at the same heating rate to carry out the second-stage fluidized bed pre-oxidation treatment for 4 h. Screen the material after fluidized bed pre-oxidation, and collect the particles with a median particle size of 2 μm ≤ D50 ≤ 30 μm (the first particle size oxidized material) as the material for high-temperature carbonization; crush the particles with a median particle size of 30 μm < D50 ≤ 200 μm (the second particle size oxidized material) to particles with a median particle size of 2 μm ≤ D50 ≤ 30 μm as the next fluidized bed pre-oxidation material to obtain the first particle size pickled precursor, mix it with the new second particle size pickled precursor, and repeat the fluidized bed oxidation treatment and screening steps in step (2), repeat the fluidized bed pre-oxidation and crushing and screening steps N times;

[0073] (3) Place the first particle size oxidized material in the constant temperature zone of a tube furnace, heat it to 1400 °C at a heating rate of 1 °C / min in an argon atmosphere and keep it at a constant temperature for 5 h. After airflow classification and shaping treatment, obtain the hard carbon negative electrode carbon material with a median particle size D50 of 2 μm to 10 μm.

[0074] Example 2

[0075] This embodiment provides a hard carbon anode material, and the preparation process flow diagram of the hard carbon anode material is shown below. Figure 1 As shown, the preparation method of the hard carbon anode material includes the following steps:

[0076] (1) First, the heavy carbon (liquefaction residue) was crushed using a jaw crusher (5E-JCA) and pre-dried at 105℃ in a forced-air drying oven. Then, it was ground using a pulverizer (5E-PCIX100) and sieved using a standard vibrating sieve. The first-size hard carbon precursor with a median particle size D50 of 2μm to 5μm and the second-size hard carbon precursor with a median particle size D50 of 40μm to 200μm were selected and dried at 105℃ for 4 hours. The first-size and second-size hard carbon precursors were then mixed with 20% HCl at a ratio of 1:5 g / mL, stirred at 50 rpm for 15 hours, allowed to stand for 3 hours, and repeatedly washed with distilled water until no Cl was found. - (No white precipitate was observed using AgNO3 test) Filter, dry in a forced-air drying oven at 100℃ for 15 hours to obtain demineralized raw material. Weigh the demineralized raw material and mix it with 40% hydrofluoric acid at a ratio of 1:10 g / mL. Stir at 150 rpm for 20 hours, let stand for 4 hours, filter, and wash the filter cake with distilled water multiple times (the filter cake should be stirred and mixed with distilled water in a beaker and filtered repeatedly) until no F is found. - (CaCl2 detection), and then dried at 100℃ for 15h to obtain the first particle size pickling precursor and the second particle size pickling precursor. The first particle size pickling precursor and the second particle size pickling precursor are mixed at a mass ratio of 1:2 to obtain the mixed pickling precursor.

[0077] (2) Place the mixed pickling precursor in a fluidized bed, and in an air atmosphere, select an air velocity of 700 mL / min; raise the temperature from room temperature to 200℃ at a heating rate of 0.8℃ / min, and perform the first stage of fluidized bed pre-oxidation treatment for 6 hours, and then heat it to 320℃ at the same heating rate for the second stage of fluidized bed pre-oxidation treatment for 3 hours. Screen the material after fluidized bed pre-oxidation, and collect the particles with a median particle size of 2μm≤D50≤5μm (the first particle size oxidant) as the material for high-temperature carbonization; crush the particles with a median particle size of 40μm≤D50≤200μm (the second particle size oxidant) to particles with a median particle size of 2μm≤D50≤5μm as the material for the next fluidized bed pre-oxidation to obtain the first particle size pickling precursor, mix it with the new second particle size pickling precursor, and repeat the fluidized bed oxidation treatment and screening steps in step (2) again, and repeat the fluidized bed pre-oxidation and crushing and screening steps N times;

[0078] (3) The first particle size of the oxide material is placed in the constant temperature zone of the tube furnace and heated to 1500℃ at a heating rate of 1℃ / min under argon atmosphere and kept at the temperature for 3h. After airflow classification and shaping treatment, a hard carbon negative electrode carbon material with a median particle size D50 of 2μm~10μm is obtained.

[0079] Example 3

[0080] This embodiment provides a hard carbon anode material, and the preparation process flow diagram of the hard carbon anode material is shown below. Figure 1 As shown, the preparation method of the hard carbon anode material includes the following steps:

[0081] (1) First, the long-flame coal was crushed using a jaw crusher (5E-JCA) and pre-dried at 110℃ in a forced-air drying oven. Then, it was ground using a pulverizer (5E-PCIX100) and sieved using a standard vibrating screen. The first-size hard carbon precursor with a median particle size D50 of 2μm to 20μm and the second-size hard carbon precursor with a median particle size D50 of 50μm to 200μm were selected and dried at 110℃ for 4 hours. The first-size and second-size hard carbon precursors were then mixed with 20% HCl at a ratio of 1:15 g / mL, respectively. The mixture was stirred and washed at 150 rpm for 10 hours, allowed to stand for 1 hour, and repeatedly washed with distilled water until no Cl was found. - (No white precipitate was observed using AgNO3 test) Filter, dry in a forced-air drying oven at 100℃ for 15 hours to obtain demineralized raw material. Weigh the demineralized raw material and mix it with 40% hydrofluoric acid at a ratio of 1:5 g / mL. Stir at 50 rpm for 30 hours, let stand for 4 hours, filter, and wash the filter cake with distilled water multiple times (the filter cake should be stirred and mixed with distilled water in a beaker and filtered repeatedly) until no F is found. - (CaCl2 detection), and then dried at 100℃ for 15h to obtain the first particle size pickling precursor and the second particle size pickling precursor. The first particle size pickling precursor and the second particle size pickling precursor are mixed at a mass ratio of 1:5 to obtain the mixed pickling precursor.

[0082] (3) Place the mixed pickling precursor in a fluidized bed, in an oxygen atmosphere, select a gas velocity of 800 mL / min; raise the temperature from room temperature to 300℃ at a heating rate of 1℃ / min, perform the first stage fluidized bed pre-oxidation treatment for 2 hours, and then heat it to 350℃ at the same heating rate for the second stage fluidized bed pre-oxidation treatment for 5 hours. Screen the material after fluidized bed pre-oxidation, collect the particles with a median particle size of 2μm≤D50≤20μm (first particle size oxidant) as the material for high-temperature carbonization; crush the particles with a median particle size of 50μm≤D50≤200μm (second particle size oxidant) to particles with a median particle size of 2μm≤D50≤20μm as the material for the next fluidized bed pre-oxidation to obtain the first particle size pickling precursor, mix it with the new second particle size pickling precursor, and repeat the fluidized bed oxidation treatment and screening steps of step (2) again, repeating the fluidized bed pre-oxidation and crushing and screening steps N times;

[0083] (3) The first particle size of the oxide material is placed in the constant temperature zone of the tube furnace and heated to 1200℃ at a heating rate of 1℃ / min under argon atmosphere and kept at the temperature for 8h. After airflow classification and shaping treatment, a hard carbon negative electrode carbon material with a median particle size D50 of 2μm~10μm is obtained.

[0084] Example 4

[0085] The only difference between this embodiment and Embodiment 1 is that only one fluidized bed oxidation process is performed at a temperature of 330°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0086] Example 5

[0087] The only difference between this embodiment and Embodiment 1 is that in the mixed pickling precursor, the mass ratio of the first particle size pickling precursor to the second particle size pickling precursor is 1:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0088] Example 6

[0089] The only difference between this embodiment and Embodiment 1 is that in the mixed pickling precursor, the mass ratio of the first particle size pickling precursor to the second particle size pickling precursor is 1:6. All other conditions and parameters are exactly the same as in Embodiment 1.

[0090] Example 7

[0091] The only difference between this embodiment and Embodiment 1 is that the gas flow rate of the fluidized bed oxidation treatment is 600 mL / min, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0092] Example 8

[0093] The only difference between this embodiment and Embodiment 1 is that the gas flow rate of the fluidized bed oxidation treatment is 900 mL / min, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0094] Example 9

[0095] The only difference between this embodiment and Embodiment 3 is that only one fluidized bed oxidation process is performed at a temperature of 300°C, while the other conditions and parameters are exactly the same as in Embodiment 3.

[0096] Comparative Example 1

[0097] The only difference between this comparative example and Example 1 is that acid washing and deashing treatment is not performed; all other conditions and parameters are exactly the same as in Example 1.

[0098] Comparative Example 2

[0099] The only difference between this comparative example and Example 1 is that a single large-particle-size (50μm~200μm) acid-washing precursor was used; all other conditions and parameters were exactly the same as in Example 1.

[0100] Comparative Example 3

[0101] The only difference between this comparative example and Example 1 is that a single small-particle-size (2μm~30μm) acid-washed precursor was used; all other conditions and parameters were exactly the same as in Example 1.

[0102] Comparative Example 4

[0103] The only difference between this comparative example and Example 1 is that a tubular furnace oxidation is used instead of a fluidized bed oxidation; all other conditions and parameters are exactly the same as in Example 1.

[0104] Comparative Example 5

[0105] The only difference between this comparative example and Example 3 is that a tubular furnace oxidation is used instead of a fluidized bed oxidation; all other conditions and parameters are exactly the same as in Example 3.

[0106] Performance testing:

[0107] The hard carbon anode materials prepared in the examples and comparative examples were ground, bonded, and magnetically stirred according to the mass ratio of active material: SP:CMC:SBR = 90:4:2:4 to form a slurry. Specific process parameters were: stirring in a single-cup homogenizer for 27 minutes at 1950 rpm, followed by degassing for 3 minutes at 2150 rpm.

[0108] The coating process used a thickness of 100 μm and an areal density controlled at 2.5 mg / cm³. 2 After the electrodes are dried, they are rolled, cut directly, and weighed. The battery testing was conducted with a 7-hour resting period. The testing environment was: temperature 25±1℃; humidity 40%RH.

[0109] Using the above-mentioned electrode as the negative electrode, sodium as the positive electrode, and 1 mol / L NaPF6 dissolved in EC:DMC (1:1) as the electrolyte, and glass fiber (GF / D) as the separator, electrochemical tests were performed. The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] As shown in Table 1, and based on Examples 1-8, the battery made from the hard carbon anode material of the present invention can achieve a specific capacity of over 300 mAh / g at 0.1C, over 265 mAh / g at 1C, and over 230 mAh / g at 5C. The initial coulombic efficiency can reach over 88.6%, and the capacity retention rate after 100 cycles can reach over 83.4%. During the preparation of the hard carbon anode material of the present invention, the carbonization temperature, oxidation atmosphere, and fluidized bed oxidation conditions significantly affect the microporous structure, specific capacity, and cycle performance of the material. By appropriately increasing the carbonization temperature to 1400℃ and optimizing oxidation conditions (such as fluidized bed gas velocity and segmented oxidation control), the specific capacity and initial coulombic efficiency of hard carbon materials can be effectively improved. The specific capacity at 0.1C charging can reach over 310mAh / g, the specific capacity at 1C charging can reach over 275mAh / g, the specific capacity at 5C charging can reach over 240mAh / g, the initial coulombic efficiency can reach over 90.6%, and the capacity retention rate after 100 cycles can reach over 87.5%.

[0114] A comparison of Examples 1 and 4 shows that, in the preparation process of the hard carbon anode material of the present invention, the use of segmented fluidized bed oxidation treatment (such as two-stage temperature control) can significantly improve the oxidation uniformity and the final electrochemical performance of the material. Single-stage oxidation treatment, due to insufficient oxidation depth, results in a significant decrease in material performance compared to Example 1, manifested as a reduction in specific capacity and cycle performance.

[0115] A comparison of Examples 1 and 5-6 shows that the ratio of the first-size pickling precursor to the second-size pickling precursor affects the performance of the hard carbon anode material of the present invention during its preparation. Controlling the mass ratio of the first-size pickling precursor to the second-size pickling precursor at 1:(2-5) yields a hard carbon anode material with better performance. If the proportion of the first-size pickling precursor (small particle size) is too high, it will lead to severe particle agglomeration, uneven fluidized bed oxidation, microporous structure imbalance, and a decrease in initial coulombic efficiency and cycle performance. If the proportion of the first-size pickling precursor (small particle size) is too low, the particle surface area is insufficient, the oxidation reaction depth is limited, the specific capacity decreases, and the rate performance is poor.

[0116] A comparison of Examples 1 and 7-8 shows that the gas flow rate during the preparation of the hard carbon anode material of the present invention affects its performance. Controlling the gas flow rate during the fluidized bed oxidation process to 700 mL / min to 800 mL / min results in a hard carbon anode material with better performance. If the gas flow rate during the fluidized bed oxidation process is too high, the particles will be suspended erratically, the oxidation reaction will be uneven, which may lead to sintering on the material surface or destruction of the microporous structure, resulting in a decrease in electrochemical performance. If the gas flow rate during the fluidized bed oxidation process is too low, the particles will be insufficiently suspended, the gas distribution will be uneven, the oxidation depth will be limited, resulting in insufficient micropore formation and a decrease in the initial coulombic efficiency and specific capacity.

[0117] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention uses acid washing and deashing and fluidized bed pre-oxidation processes to significantly shorten the preparation cycle and reduce energy consumption. Compared with the traditional static oxidation method, the production efficiency is increased by more than 100%, and the consistency of hard carbon material performance is improved.

[0118] As can be seen from the comparison of Example 1 and Comparative Examples 2-3, the present invention improves the flow properties of particles by compounding carbon precursors of different particle sizes, reduces the risk of agglomeration of small-sized ultrafine sticky carbon particles, and significantly improves the heat transfer and mass transfer effect in the fluidized bed.

[0119] As can be seen from the comparison between Example 1 and Comparative Example 4, the fluidized bed oxidation process of the present invention significantly improves the oxidation uniformity, oxidation efficiency, and production controllability compared to tubular furnace oxidation. In the fluidized bed, particles can fully contact the oxidizing gas, avoiding local over-oxidation or incomplete oxidation phenomena in tubular furnace oxidation, ultimately improving the specific capacity, initial coulombic efficiency, and circulation performance of hard carbon materials.

[0120] Comparative analysis of Examples 3, 9, and Comparative Example 5 shows that the differences in the oxidation process of the hard carbon anode material preparation method of the present invention significantly affect the performance of the final hard carbon material. Compared to Example 3, the oxidation process in Example 9 is simpler, with only one pre-oxidation step. This may result in a looser microstructure of the final hard carbon material, and the degree of carbonization during the carbonization process may not be as high as in Example 3. The difference between Comparative Example 5 and Example 3 lies in the choice of oxidation method. Comparative Example 5 uses tubular furnace oxidation instead of fluidized bed oxidation, with all other parameters being exactly the same as in Example 3. Tubular furnace oxidation may result in less uniform gas flow during the oxidation process compared to fluidized bed oxidation, thus affecting the degree of oxidation and surface structure of the material, and consequently affecting the performance of the final hard carbon material. In summary, by comparing Examples 3, 9, and Comparative Example 5, it can be seen that fluidized bed oxidation treatment, compared to tubular furnace oxidation and single-stage oxidation treatment, is more conducive to the uniformity of particle size distribution and carbonization effect of the hard carbon material, thereby significantly improving the electrochemical performance of the hard carbon anode material.

[0121] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, The preparation method includes the following steps: (1) Acid washing and deashing treatment is performed on the first particle size hard carbon precursor and the second particle size hard carbon precursor to obtain the first particle size acid washing precursor and the second particle size acid washing precursor. The first particle size acid washing precursor and the second particle size acid washing precursor are mixed to obtain a mixed acid washing precursor. (2) The mixed pickling precursor is subjected to fluidized bed oxidation treatment and then screened to obtain oxidized material with first particle size and second particle size; (3) The first particle size oxidant is sintered to obtain the hard carbon anode material; Wherein, the median particle size D50 of the first particle size pickling precursor is ≤30μm, the median particle size D50 of the second particle size pickling precursor is >30μm, the median particle size D50 of the first particle size oxidant is ≤30μm, and the median particle size D50 of the second particle size oxidant is >30μm.

2. The preparation method according to claim 1, characterized in that, The median particle size of the first-size hard carbon precursor is 2 μm ≤ D50 ≤ 30 μm, and the median particle size of the second-size hard carbon precursor is 30 μm. <D50≤200μm; The median particle size of the first-particle-size pickling precursor is 2 μm ≤ D50 ≤ 30 μm, and the median particle size of the second-particle-size pickling precursor is 30 μm. <D50≤200μm; The median particle size of the first particle size oxidant is 2μm ≤ D50 ≤ 30μm, and the median particle size of the second particle size oxidant is 30μm. <D50≤200μm。 3. The preparation method according to claim 1, characterized in that, Step (2): After the second particle size oxidant is crushed and screened to obtain an oxidant with a median particle size of 2μm≤D50≤30μm, it is mixed with a new second particle size pickling precursor and the fluidized bed oxidation treatment and screening steps of step (2) are repeated.

4. The preparation method according to claim 1, characterized in that, Step (1) The first particle size hard carbon precursor and the second particle size hard carbon precursor are obtained by crushing, grinding, sieving and drying the precursor carbon material.

5. The preparation method according to claim 4, characterized in that, The precursor carbon material includes any one or a combination of at least two of coal tar pitch, petroleum pitch, coal, biomass carbon materials, or heavy carbon materials.

6. The preparation method according to claim 4, characterized in that, The drying temperature is 100℃~110℃.

7. The preparation method according to claim 1, characterized in that, The acid washing and deashing treatment in step (1) includes hydrochloric acid washing and hydrofluoric acid washing.

8. The preparation method according to claim 7, characterized in that, The hydrochloric acid used for the washing process has a mass concentration of 15% to 20%.

9. The preparation method according to claim 7, characterized in that, The solid-liquid mass-to-volume ratio of the hydrochloric acid wash is 1:(5~15)g / mL.

10. The preparation method according to claim 7, characterized in that, Stirring is performed during the hydrochloric acid washing process.

11. The preparation method according to claim 10, characterized in that, The stirring speed is 50 rpm to 150 rpm.

12. The preparation method according to claim 10, characterized in that, The stirring time is 10h~15h.

13. The preparation method according to claim 7, characterized in that, After being washed with hydrochloric acid, the mixture is allowed to stand and then washed with water. Silver nitrate is added to the water washing solution, and after no white precipitate is formed, it is dried.

14. The preparation method according to claim 13, characterized in that, The settling time is 1 to 3 hours.

15. The preparation method according to claim 13, characterized in that, The drying temperature is 100℃~110℃.

16. The preparation method according to claim 13, characterized in that, The drying process takes 10 to 15 hours.

17. The preparation method according to claim 7, characterized in that, The hydrofluoric acid used in the hydrofluoric acid pickling process has a mass concentration of 35% to 45%.

18. The preparation method according to claim 7, characterized in that, The solid-liquid mass-to-volume ratio of the hydrofluoric acid washing is 1:(5~10)g / mL.

19. The preparation method according to claim 7, characterized in that, Stirring is performed during the hydrofluoric acid washing process.

20. The preparation method according to claim 19, characterized in that, The stirring speed is 50 rpm to 150 rpm.

21. The preparation method according to claim 19, characterized in that, The stirring time is 20h~30h.

22. The preparation method according to claim 7, characterized in that, After hydrofluoric acid washing, the mixture is allowed to stand and then washed with water. Calcium chloride is added to the water washing solution, and after no white precipitate is formed, it is dried.

23. The preparation method according to claim 22, characterized in that, The settling time is 2 to 4 hours.

24. The preparation method according to claim 22, characterized in that, The drying temperature is 100℃~110℃.

25. The preparation method according to claim 22, characterized in that, The drying process takes 10 to 15 hours.

26. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the first particle size pickling precursor to the second particle size pickling precursor is 1:(2~5).

27. The preparation method according to claim 1, characterized in that, The atmosphere for the fluidized bed oxidation process in step (2) includes oxygen-containing gas.

28. The preparation method according to claim 1, characterized in that, The gas flow rate of the fluidized bed oxidation process in step (2) is 700 mL / min to 800 mL / min.

29. The preparation method according to claim 1, characterized in that, The heating rate of the fluidized bed oxidation treatment in step (2) is 0.4℃ / min to 1℃ / min.

30. The preparation method according to claim 1, characterized in that, The temperature of the fluidized bed oxidation treatment in step (2) is 200℃~350℃.

31. The preparation method according to claim 1, characterized in that, The fluidized bed oxidation process in step (2) includes a first-stage fluidized bed oxidation process and a second-stage fluidized bed oxidation process.

32. The preparation method according to claim 31, characterized in that, The temperature of the first fluidized bed oxidation treatment is 200℃~300℃.

33. The preparation method according to claim 31, characterized in that, The first stage of fluidized bed oxidation treatment lasts for 2 to 6 hours.

34. The preparation method according to claim 31, characterized in that, The temperature of the second stage fluidized bed oxidation treatment is 300℃~350℃.

35. The preparation method according to claim 31, characterized in that, The second stage of fluidized bed oxidation treatment lasts for 3 to 5 hours.

36. The preparation method according to claim 1, characterized in that, The atmosphere for the sintering process in step (3) includes an inert gas.

37. The preparation method according to claim 1, characterized in that, The sintering temperature in step (3) is 1200℃~1500℃.

38. The preparation method according to claim 1, characterized in that, The sintering process in step (3) takes 3 to 8 hours.

39. The preparation method according to claim 1, characterized in that, After the sintering process described in step (3), the airflow classification and shaping process is carried out.

40. The preparation method according to claim 39, characterized in that, After the airflow classification and shaping process, the median particle size D50 of the hard carbon anode material is 2μm~10μm.

41. A hard carbon anode material, characterized in that, The hard carbon anode material is prepared by the preparation method according to any one of claims 1-40.

42. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the hard carbon negative electrode material as described in claim 41.

43. A battery, characterized in that, The battery includes the negative electrode as described in claim 42.

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