Sodium-ion battery hard carbon induced by waste graphite negative electrode, preparation method and application thereof

Abstract

The application provides a kind of waste graphite negative electrode induced sodium ion battery hard carbon, the recovered waste lithium ion battery negative electrode graphite is repaired and purified as induction growth seed, biomass carbon is used as precursor, mixed construction has three-dimensional space graphite and biomass carbon precursor contact induction growth interface, after calcination carbonization and removal of the graphite that plays an induction role, form makes sodium ion fast embeds and the hard carbon negative electrode material that exports. The preparation method is to mix the waste lithium battery graphite negative electrode waste material after repair with biomass carbon precursor, and to be equipped with graphite sheet to form a sandwich structure with three-dimensional space, after calcination carbonization, ultrasonic removal of the repaired graphite that plays an induction role, washing, drying and grinding to obtain a hard carbon negative electrode material. The hard carbon negative electrode material of the application makes full use of waste raw materials, is low in price, reduces the cost at the same time, solves the problem that sodium ion battery negative electrode material is difficult to consider the first coulomb efficiency and reversible specific capacity, and can be applied to sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a method for preparing and applying a hard carbon anode material for sodium-ion batteries, which is induced to form a hard carbon anode material using graphite anode material from waste lithium-ion batteries. Background Technology

[0002] Currently, with the rapid development of electronic products and electric vehicles, lithium-ion batteries occupy a large market share. However, lithium resources are not abundant and their distribution is extremely uneven.

[0003] Sodium and lithium belong to the same group of elements and have similar electrochemical properties. Sodium is abundant (its reserves are approximately 430 times that of lithium), widely distributed, and inexpensive, making sodium-ion batteries a promising next-generation energy storage battery technology suitable for large-scale renewable energy applications. Hard carbon, due to its unique structure, possesses a unique sodium storage mechanism and boasts advantages such as abundant raw materials, low cost, excellent conductivity, environmental friendliness, and high specific capacity—even higher than commercial graphite—making it a highly promising anode material for sodium-ion batteries. However, hard carbon suffers from low initial coulombic efficiency in sodium-ion batteries, significantly reducing the battery capacity and limiting its industrial application.

[0004] As the demand for lithium-ion batteries continues to grow, a wave of retired lithium-ion batteries is also arriving, leading to the problem of recycling and disposing of a large number of used lithium batteries. If the graphite anode material in lithium batteries is discarded or incinerated, it will bring serious environmental risks, including particulate pollution and greenhouse gas emissions. Existing technologies for treating graphite anodes include high-temperature heat treatment, alkaline leaching, and acid leaching. High-temperature heat treatment requires a large amount of energy, while high-concentration alkaline leaching and acid leaching processes will cause significant environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a sodium-ion battery hard carbon induced by graphite anode material from waste lithium-ion batteries.

[0006] The sodium-ion battery hard carbon induced by waste graphite negative electrode provided by this invention is formed by repairing and purifying recycled waste lithium-ion battery negative electrode graphite as an induction growth seed, using biomass carbon as a precursor, mixing and constructing a three-dimensional graphite and biomass carbon precursor to fully contact and induce growth interface, calcining and carbonizing, and removing the graphite that plays an induction role to form a hard carbon negative electrode material that enables sodium ions to be rapidly inserted and extracted.

[0007] This invention also provides a method for preparing hard carbon for sodium-ion batteries induced by the above-mentioned waste graphite negative electrode, comprising the following steps:

[0008] S1 involves screening and classifying the recycled and dismantled waste lithium battery graphite anode material, centrifuging, washing, and drying to obtain pretreated graphite anode material with a particle size of 5-50 μm.

[0009] S2 involves calcining the pretreated graphite anode waste in an inert atmosphere to remove impurities and obtain repaired high-purity graphite.

[0010] S3 mixes the repaired high-purity graphite with biomass carbon precursors and adds graphite sheets to form a three-dimensional sandwich structure. It is then carbonized in a tube furnace under an inert atmosphere by segmented gradient calcination at low temperature (250℃~500℃) and high temperature (900℃~1400℃) to transform the biomass carbon precursors into hard carbon with a highly ordered structure.

[0011] S4 Remove the carbonized product from the atmosphere furnace, remove the graphite sheet used for clamping, and then ultrasonically treat the mixed powder of high-purity graphite and hard carbon in the middle layer to remove the high-purity graphite that plays an inductive role in the repair.

[0012] S5 cleans the product obtained in step S4, and then dries and grinds it to obtain hard carbon anode material for sodium-ion batteries.

[0013] This invention also provides the application of the sodium-ion battery hard carbon anode material prepared by the above method in sodium-ion batteries.

[0014] This invention repairs and purifies recycled lithium-ion battery negative electrode graphite, using it as an induced growth seed. Biomass carbon is used as a precursor, and the two are thoroughly mixed mechanically. Graphite sheets are then used to enclose the biomass carbon precursor and the repaired and purified negative electrode graphite mixture, forming a sandwich-like structure. This creates an induced growth interface in three-dimensional space where graphite and biomass carbon precursor are in full contact. The biomass carbon is then held near its relatively low pyrolysis temperature for a certain period, followed by further high-temperature calcination. The calcined product is then subjected to low-power, short-time ultrasonic treatment to completely peel off and remove the added graphite, thereby preparing a high-efficiency hard carbon material with a highly ordered structure.

[0015] This invention utilizes inexpensive and widely available biomass carbon, such as rush pith, eggshells, petroleum coke, asphalt, sugarcane, bamboo, bark, straw, bagasse, corn cobs, or sawdust, as a precursor, supplemented by recycled graphite from waste lithium batteries. This process utilizes waste materials to prepare hard carbon anode materials, significantly reducing their cost. The preparation method is simple and the process is short. The resulting hard carbon anode material exhibits high specific capacity, good conductivity, low polarization, high initial coulombic efficiency, and reversible specific capacity, along with good cycle performance. It solves the problem of sodium-ion battery anode materials struggling to achieve both initial coulombic efficiency and reversible specific capacity, and can be applied to various alkali metal battery anode materials, demonstrating excellent application prospects.

[0016] This invention also provides the application of the hard carbon anode material prepared by the above method in sodium-ion batteries.

[0017] Applying this hard carbon anode material to sodium-ion batteries can reduce the cost of sodium-ion batteries, improve their electrochemical performance such as initial efficiency and high capacity, and promote the commercial application of hard carbon anodes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the preparation of the hard carbon anode material constructed from graphite and biomass carbon precursors with three-dimensional space according to the present invention.

[0019] Figure 2 This is a transmission electron microscope (TEM) image of the hard carbon anode material prepared in Example 1 of the present invention;

[0020] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the hard carbon anode material prepared in Example 1 of this invention.

[0021] Figure 4 The image shows the electrochemical performance of the hard carbon anode material prepared in Example 1 of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] See Figure 1This invention first provides a method for inducing hard carbon for sodium-ion batteries using waste graphite negative electrodes. The method involves repairing and purifying recycled waste lithium-ion battery negative electrode graphite, using it as an induction growth seed. Biomass carbon is used as a precursor. The repaired and purified negative electrode graphite is mixed with the biomass carbon precursor, which is sandwiched within the graphite sheet, forming a sandwich-like structure. This creates a three-dimensional interface for full contact and induction of growth between the graphite and the biomass carbon precursor. Through calcination and carbonization, the carbon atoms within the biomass carbon precursor undergo disordered movement during calcination, inducing growth by the graphite sheet. The surface of the biomass carbon precursor in contact with the graphite sheet is "catalyzed," the disordered movement of carbon atoms near the graphite sheet is weakened, and the ordered recombination is enhanced. After a long period of induction, the carbon atoms gradually become ordered during the high-temperature insulation process. At the same time, the interlayer spacing of the biomass carbon precursor is expanded, and the number of sodium storage sites increases. Ultimately, the hard carbon surface in contact with the biomass carbon precursor and the graphite sheet forms "long-range order," that is, highly ordered lattice stripes, with an interlayer spacing of more than 0.39 nm. After removing the graphite that plays an inductive role, channels are formed that allow sodium ions to be rapidly inserted and extracted. This is beneficial for the storage of sodium ions in the channels and their rapid transport in the carbon layer, thereby improving the electrochemical performance of the hard carbon anode material.

[0024] This invention also provides a method for preparing hard carbon for sodium-ion batteries induced by the above-mentioned waste graphite negative electrode, comprising the following steps:

[0025] S1 involves screening and classifying the recycled and dismantled waste lithium battery graphite anode material, followed by centrifugation, washing, and drying to obtain pretreated graphite anode material with a particle size of 5–50 μm.

[0026] This step involves discharging recycled waste lithium batteries, such as waste ternary lithium batteries, waste lithium iron phosphate batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries. After discharge treatment, the graphite anode waste is disassembled and separated by physical methods such as mechanical crushing, magnetic separation, and sieving. After centrifugation, washing, and drying, waste graphite anode powder with a coarse particle size of 5-50 μm is obtained.

[0027] S2 involves calcining the pretreated graphite anode waste (powder) under an inert atmosphere to remove impurities and obtain repaired high-purity graphite powder.

[0028] Because the waste graphite anode material contains a variety of impurities in different forms, this step involves calcining the pretreated graphite anode material in a microwave heating device under a N2 or Ar2 atmosphere, controlling the temperature at 300℃~500℃. The first calcination lasts for 5~30 minutes to completely decompose and remove the binders and conductive agents remaining on the graphite surface. Then, the temperature is raised to 1500℃~2500℃ and calcined for another 30~120 minutes to further remove the metallic impurities in the graphite anode material, resulting in high-purity graphite powder.

[0029] S3 mixes the repaired high-purity graphite powder with biomass carbon precursors and adds graphite sheets to form a three-dimensional sandwich structure. The biomass carbon precursors are then carbonized in a tube furnace under an inert atmosphere using a segmented gradient calcination process at low temperatures of 250℃~500℃ and high temperatures of 900℃~1400℃, transforming them into hard carbon with a highly ordered structure.

[0030] The biomass carbon precursor in this step is obtained by sequentially soaking the biomass carbon precursor raw materials in alkaline and acidic solutions. The biomass carbon precursor raw materials are widely available and inexpensive, selected from one of the following: rush pith, eggshells, petroleum coke, asphalt, sucrose, bamboo, bark, straw, bagasse, corn cobs, or sawdust. These raw materials are pulverized before soaking. The alkaline solution includes at least one of NaOH, NH3H2O, and KOH, with a concentration of 3.0–18.5 wt%. The acidic solution includes at least one of H2SO4, HCl, and HNO3, with a concentration of 3.5–15 wt%. The soaking time is 10–60 minutes. Pre-treatment of the biomass carbon precursor raw materials with alkaline and acidic solutions removes some metallic impurities such as iron, copper, and nickel, thereby avoiding side reactions caused by the presence of these elements during calcination and the presence of numerous defects in the product.

[0031] The mass ratio of the high-purity graphite powder to the biomass carbon precursor is 1:10 to 1:50. The mixture is stirred at room temperature for 0.5 to 8 hours at a stirring rate of 200 to 800 r / min. The mass ratio of graphite sheets to biomass carbon precursor is 30:1 to 1:1. The length, width and height of the graphite sheets are 5cm × 3cm × 0.2cm.

[0032] Specifically, the repaired graphite powder and the pulverized biomass carbon precursor are thoroughly and evenly mixed mechanically (such as by a mixer) to maximize the contact between the two substances. The mixture is then spread evenly on the surface of a graphite sheet to a thickness of about 0.5 cm, and another graphite sheet is placed on the other side of the mixture. This sandwich structure, where the mixture of repaired high-purity graphite powder and biomass carbon precursor is sandwiched between graphite sheets, further enhances the contact between the biomass carbon precursor powder and the graphite powder. Since both are granular, there is point contact between the particles, achieving a full contact interface between the graphite and the biomass carbon precursor, which serve as the seed for induced growth.

[0033] In this step, the sandwich structure composed of repaired high-purity graphite, biomass carbon precursor and graphite sheet is placed in a tube furnace and calcined at a pyrolysis temperature of 250℃~500℃ for 8-24h under N2, Ar2 or N2 / Ar2 mixed atmosphere. Then, the temperature is raised to 900℃~1400℃ at a heating rate of 0.5℃ / min~5℃ / min and held for 3h~12h. At the pyrolysis temperature, the disordered movement of carbon atoms begins. After the addition of graphite powder, the carbon atoms recombine and arrange themselves in an ordered manner under its induction. Subsequently, when the temperature is raised to 900℃~1400℃, the carbon atoms inside the biomass carbon precursor begin to move. Without graphite induction, the movement is mostly disordered, eventually forming a disordered structure or a short-range ordered structure. However, when the biomass carbon precursor is mixed with graphite, the surface in contact with the graphite is "catalyzed," which weakens the disordered movement of nearby carbon atoms and enhances the ordered recombination and arrangement. After a long period of induction, the arrangement and growth of carbon atoms can be perfected, eventually forming "long-range ordered," that is, highly ordered lattice fringes. At the same time, after the addition of repaired high-purity graphite, the interlayer spacing between graphite and biomass carbon precursor is expanded, with the interplanar spacing being above 0.39nm, making it easier for sodium ions to insert and extract. In addition, the conductivity of the hard carbon material is further improved through subsequent high-temperature calcination. Thus, the slow kinetics of sodium-ion batteries is improved through low-temperature + high-temperature gradient calcination, which can improve the cycle performance and rate performance of the battery.

[0034] In this step, the repaired high-purity graphite can be mechanically mixed and used in combination with any of the raw materials in the biomass carbon precursor, maintaining the consistency and sufficient contact of the biomass carbon precursor and ensuring efficient preparation of hard carbon. The segmented gradient calcination method reduces equipment requirements and hard carbon manufacturing costs. Furthermore, by maintaining the biomass carbon near its relatively low pyrolysis temperature for a certain period, the ordered formation process of the biomass carbon is ensured, thereby improving the electrochemical performance of the hard carbon.

[0035] S4 Remove the carbonized product from the atmosphere furnace, remove the outer layer of the sandwich structure containing the graphite sheet, and then ultrasonically treat the mixed powder composed of the repaired high-purity graphite in the middle layer and the hard carbon with a highly ordered structure converted from the biomass carbon precursor, in order to remove the high-purity graphite that plays an inductive role in the repair.

[0036] The ultrasonic treatment in this step uses a power of 10W to 50W, a time of 5 to 30 minutes, and a temperature of 20℃ to 40℃. This process removes the high-purity graphite powder that plays an inductive role in the repair process from the carbonized product, thereby obtaining high-purity hard carbon with a highly ordered structure. Since the high-purity graphite powder in the carbonized product is removed, only hard carbon is retained. This results in hard carbon having a large number of micropores and active sites that are conducive to sodium ion storage, which can effectively improve the first-cycle coulombic efficiency, long-cycle stability, and rate performance of hard carbon.

[0037] S5. Clean the product obtained in step S4, dry and grind it to obtain a hard carbon anode material for sodium-ion batteries, with a reversible specific capacity of 335 mAh g. -1 The Coulomb efficiency is above 94%.

[0038] In the above preparation method, firstly, microwave heating is used to purify and recover graphite from lithium-sodium ion battery anodes, which is then used as an induced growth seed in the preparation of hard carbon anodes for sodium-ion batteries. Simultaneously, inexpensive and widely available biomass carbon materials are used as precursors. These two materials are mixed to construct a three-dimensional graphite-biomass carbon precursor interface that fully contacts and induces growth. Through calcination and carbonization to remove the induced growth seed, a high-efficiency hard carbon material with a highly ordered structure is prepared. The hard carbon material prepared by this method exhibits high initial coulombic efficiency and reversible specific capacity, solving the problem that sodium-ion battery anode materials struggle to simultaneously achieve both initial coulombic efficiency and reversible specific capacity. It also provides a new, economical, and effective approach for the recycling and reuse of spent lithium-ion batteries.

[0039] The hard carbon anode material prepared by this invention can be applied to sodium-ion batteries, which not only reduces the manufacturing cost of sodium-ion batteries but also further improves the electrochemical performance of sodium-ion batteries.

[0040] The following detailed description of the above-mentioned method for preparing hard carbon for sodium-ion batteries induced by waste graphite negative electrodes, with reference to specific embodiments, provides further details. Example 1:

[0041] S1 sieves and classifies 100mg of industrially dismantled graphite anode waste after recycling to remove impurities and obtain graphite particles with a particle size of 50μm. Then, it is centrifuged at 800 rpm for 10 min, washed with deionized water, and dried in a vacuum oven at 60 ℃ to obtain pretreated graphite anode waste.

[0042] S2. 80mg of pretreated graphite anode waste was placed in a microwave heating device and calcined under a nitrogen atmosphere at a controlled temperature of 500℃ for 5 minutes. Then the temperature was raised to 2000℃ and calcined for another 30 minutes under a nitrogen atmosphere. This process repaired the graphite structure and removed residual metal impurities from the graphite anode waste. After cooling in the furnace, the repaired high-purity graphite was obtained.

[0043] S3 chopped pine bark, the raw material for biomass carbon precursor, was pretreated by soaking it in 4.5wt% NaOH and 5.5wt% HCl solutions for 60 min, then washed with deionized water and anhydrous ethanol, and dried at 80℃ to obtain pine bark biomass carbon precursor.

[0044] High-purity graphite and pine bark biomass carbon precursor were taken from the reconstituted materials and mixed mechanically at a ratio of 1:50 for 8 hours at room temperature with a stirring rate of 600 r / min. Simultaneously, 5 cm × 3 cm × 0.2 cm graphite sheets were added, with a graphite sheet to biomass carbon precursor mass ratio of 10:1, forming a sandwich-like sandwich structure with a layer thickness of 0.5 cm. The mixture was calcined and carbonized in a tube furnace under an Ar2 / H2 mixed atmosphere (H2 content of 5%) at a controlled temperature of 420℃ for 8 hours. Subsequently, the temperature was raised to 1200℃ at a rate of 2℃ / min and held for 8 hours. Afterward, the mixture was cooled to room temperature with the furnace, transforming the pine bark biomass carbon precursor into hard carbon with a highly ordered structure.

[0045] S4 Remove the carbonized product from the atmosphere furnace, remove the clamping graphite sheet, and then ultrasonically treat the mixed powder of high-purity graphite and hard carbon in the middle layer for 20 minutes at a temperature of 30°C and an ultrasonic power of 30 W to remove the high-purity graphite that plays an inductive role in the external repair.

[0046] S5 is used to wash the product obtained in step S4 with deionized water, then vacuum dried for 3 hours, and then ground to obtain hard carbon anode material for sodium-ion batteries.

[0047] See Figure 2 The hard carbon anode material prepared in Example 1 differs from the disordered porous structure reported in conventional literature. The hard carbon prepared by this process has a highly ordered microstructure, which is a long-range ordered structure with expanded interlayer spacing. This ordered tunnel structure allows sodium ions to be rapidly inserted and extracted, improving the kinetic performance and thus helping to improve the electrochemical performance of the battery, such as the first charge-discharge efficiency, cycle stability, and rate performance.

[0048] See Figure 3The hard carbon anode material prepared in Example 1 shows two broad-ranging envelope peaks around 26° and 43° in the XRD pattern of conventional hard carbon materials, indicating the disorder of the material. However, the curve in this example shows a sharp peak similar to graphite, indicating that the prepared hard carbon material tends towards a crystalline structure. Figure 2 The TEM images correspond to each other, with clearly visible lattice fringes and long-range ordered interlayer structure, which will greatly improve the electrochemical performance of the battery, such as initial charge-discharge efficiency, cycle stability, and rate performance.

[0049] See Figure 4 The sodium-ion battery prepared using the hard carbon anode material in Example 1 has an initial charge-discharge coulombic efficiency (ICE) of 94.0% and a reversible specific capacity of 338.1 mAh / g. Example 2:

[0050] S1 sieves and classifies 100mg of industrially dismantled graphite anode waste after recycling to remove impurities and obtain graphite particles with a particle size of 30μm. Then, it is centrifuged at 1000 rpm for 8 min, washed with deionized water, and dried in a vacuum oven at 60 ℃ to obtain pretreated graphite anode waste.

[0051] S2. 80mg of pretreated graphite anode waste was placed in a microwave heating furnace and calcined in an Ar2 atmosphere at a controlled temperature of 300℃ for 20 minutes. Then the temperature was raised to 2500℃ and calcined for another 30 minutes in an Ar2 atmosphere. This process repaired the graphite structure and removed residual metal impurities from the graphite anode waste. After cooling in the furnace, the repaired high-purity graphite was obtained.

[0052] S3 was pretreated by soaking petroleum coke in 5wt% NaOH and 6.5wt% HCl solutions for 30 min, then washed with deionized water and anhydrous ethanol, and dried at 80℃ to obtain petroleum coke biomass carbon precursor.

[0053] High-purity graphite and petroleum coke biomass carbon precursor were taken and mechanically mixed at room temperature for 3 hours at a stirring rate of 300 r / min, with a mass ratio of 3:97. At the same time, 5cm×3cm×0.2cm graphite sheets were added, with a mass ratio of graphite sheets to biomass carbon precursor of 15:1, forming a sandwich-like sandwich structure with a layer thickness of 0.3cm. The mixture was calcined and carbonized in a tube furnace under a mixed atmosphere of Ar2 / H2 (5% H2) at a controlled temperature of 280℃ for 12 hours. Then, the temperature was raised to 1300℃ at a heating and cooling rate of 2℃ / min for 4 hours. After that, the mixture was cooled to room temperature with the furnace, which transformed the petroleum coke biomass carbon precursor into hard carbon with a highly ordered structure.

[0054] S4 Remove the carbonized product from the atmosphere furnace, remove the clamping graphite sheet, and then ultrasonically treat the mixed powder of high-purity graphite and hard carbon in the middle layer for 20 minutes at a temperature of 30°C and an ultrasonic power of 25 W to remove the high-purity graphite that plays an inductive role in the external repair.

[0055] S5 is used to wash the product obtained in step S4 with deionized water, then vacuum dried for 3 hours, and then ground to obtain hard carbon anode material for sodium-ion batteries. Example 3:

[0056] S1 sieves and classifies 100mg of industrially dismantled graphite anode waste after recycling to remove impurities and obtain graphite particles with a particle size of 20μm. Then, it is centrifuged at 900 rpm for 6 min, washed with deionized water, and dried in a vacuum oven at 60 ℃ to obtain pretreated graphite anode waste.

[0057] S2. 100mg of pretreated graphite anode waste was placed in a microwave heating furnace and calcined under N2 atmosphere at a controlled temperature of 400℃ for 10 minutes. Then the temperature was raised to 2000℃ and calcined for another 30 minutes under N2 atmosphere. This process repaired the graphite structure and removed residual metal impurities from the graphite anode waste. After cooling in the furnace, the repaired high-purity graphite was obtained.

[0058] S3 chopped the raw material straw for biomass carbon precursor, and pretreated the straw chopped material by soaking it in 4.5% NaOH and 5.5% HCl solutions for 45 min in sequence. Then it was washed with deionized water and anhydrous ethanol, and dried at 80℃ to obtain the straw biomass carbon precursor.

[0059] High-purity graphite and corn stalk biomass carbon precursor were taken and mechanically mixed at room temperature for 5 hours at a stirring rate of 500 r / min, with a mass ratio of 5:95. At the same time, 5cm×3cm×0.2cm graphite sheets were added, with a mass ratio of graphite sheets to biomass carbon precursor of 25:1, forming a sandwich-like sandwich structure with a layer thickness of 0.5cm. The mixture was calcined and carbonized in a tube furnace under an Ar2 / H2 mixed atmosphere (H2 content of 5%), with a temperature of 480℃ and a holding time of 8 hours. The temperature was then raised to 1300℃ at a heating / cooling rate of 2℃ / min and held for 4 hours. After that, the mixture was cooled to room temperature with the furnace, which transformed the corn stalk biomass carbon precursor into hard carbon with a highly ordered structure.

[0060] S4 Remove the carbonized product from the atmosphere furnace, remove the clamping graphite sheet, and then ultrasonically treat the mixed powder of high-purity graphite and hard carbon in the middle layer for 20 minutes at a temperature of 30°C and an ultrasonic power of 20 W to remove the high-purity graphite that plays an inductive role in the external repair.

[0061] S5 is used to wash the product obtained in step S4 with deionized water, then vacuum dried for 4 hours, and then ground to obtain hard carbon anode material for sodium-ion batteries.

[0062] The above embodiments of the present invention are only part of the preferred embodiments of the present invention and should not be construed as limiting the present invention. Any modifications, equivalent substitutions and improvements made by those skilled in the art without departing from the spirit of the present invention shall be within the protection scope of the present invention.

Claims

1. A spent graphite negative electrode-induced sodium-ion battery hard carbon, characterized in that, The recovered waste lithium ion battery negative electrode graphite is repaired and purified as an induced growth seed, biomass carbon is used as a precursor, and a three-dimensional space interface of graphite and biomass carbon precursor is constructed by mixing to induce growth, after calcination and carbonization and removal of the graphite for induction, a hard carbon negative electrode material for rapid embedding and extraction of sodium ions is formed.

2. The method of claim 1, wherein the method is characterized by: The method comprises the following steps: S1: screening and grading the recovered and disassembled waste lithium battery graphite negative electrode waste material, and obtaining pretreated graphite negative electrode waste material with a particle size of 5-50 μm after centrifugation, washing and drying; S2: calcining the pretreated graphite negative electrode waste material under an inert atmosphere to remove impurities in the graphite negative electrode waste material, and obtaining repaired high-purity graphite; S3: mixing the repaired high-purity graphite and biomass carbon precursor, and simultaneously adding graphite sheets to form a sandwich structure with a three-dimensional space, and performing staged gradient calcination and carbonization under an inert atmosphere in a tube furnace at a low temperature of 250-500 ℃ and a high temperature of 900-1400 ℃, so that the biomass carbon precursor is converted into hard carbon with a highly ordered structure; wherein the raw material of the biomass carbon precursor is treated by soaking with an alkaline solution and an acidic solution in sequence, the alkaline solution comprises at least one of NaOH, NH3H2O and KOH, and has a concentration of 3.0-18.5 wt.%, the acidic solution comprises at least one of H2SO4, HCL and HNO3, and has a concentration of 3.5-15 wt.%, the soaking treatment time is 10-60 min; the mass ratio of the repaired high-purity graphite to the biomass carbon precursor is 1:10-1:50, the mixing and stirring are performed at room temperature for 0.5-8 h, and the stirring rate is 200-800 r / min; the mass ratio of the graphite sheets to the biomass carbon precursor is 30:1-1:1, and the length, width and height of the graphite sheets are 5 cm, 3 cm and 0.2 cm respectively; S4: taking out the product after carbonization from the atmosphere furnace, removing the graphite sheets used for clamping, and ultrasonic treating the mixed powder of the repaired high-purity graphite and the hard carbon in the middle layer to remove the repaired high-purity graphite for induction; S5: cleaning the product obtained in the step S4, drying and grinding to obtain a hard carbon negative electrode material for sodium ion batteries. 3.The method of claim 2, wherein the method further comprises the step of: In the step S2, the pretreated graphite negative electrode waste material is calcined under N2 or Ar2 atmosphere, the temperature is controlled to be 300-500 ℃, first calcination is performed for 5-30 min, then the temperature is raised to 1500-2500 ℃, and then calcination is performed for 30-120 min. ​ 4. The method of claim 2, wherein the method is characterized by: The raw material of the biomass carbon precursor is one of lamp wick grass, eggshell, petroleum coke, pitch, sucrose, bamboo, tree bark, straw, sugarcane residue, corn cob or wood chips. 5.The method of claim 2, wherein the method further comprises the step of: In the step S3, the sandwich structure composed of the repaired high-purity graphite, the biomass carbon precursor and the graphite sheets is placed in a tube furnace, calcination is performed under N2, Ar2 or N2 / Ar2 mixed atmosphere at a cracking temperature of 250-500 ℃ for 8-24 h, then the temperature is raised to 900-1400 ℃, and the temperature is kept for 3-12 h. ​ 6.The method of claim 5, wherein the method is characterized by, The temperature increasing rate in the S3 step is 0.5-5 DEG C / min.

7. The method of claim 2, wherein the method is characterized by: In the S4 step, the ultrasonic treatment power of the product after carbonization is 10-50w, the time is 5-30min, and the temperature is 20-40 DEG C.

8. The application of the sodium-ion battery hard carbon negative material prepared by the method in any one of claims 2-7 to a sodium-ion battery.

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