Sodium-ion battery negative electrode material, preparation method thereof, negative electrode sheet containing the negative electrode material, and sodium-ion battery

Abstract

The present disclosure relates to a kind of sodium ion battery negative electrode material, its preparation method, the negative electrode sheet and sodium ion battery comprising the negative electrode material, the method comprises: S1: first calcination is carried out to hard carbon precursor, and hard carbon particles are obtained;S2: petroleum coke is contacted with the mixed solution of sulfuric acid and nitric acid and reacts, and the solid after reaction is obtained;S3: the solid after reaction is mixed with first alkaline solution, and supernatant is separated from the mixture material;The supernatant is mixed with acidic solution, and solid phase material is separated out, the solid phase material is mixed with second alkaline solution as coating layer carbon material, and coating layer carbon material dispersion is obtained;S4: the coating layer carbon material dispersion is mixed with the hard carbon particles, then dry, and the dry mixture is obtained;The dry mixture is subjected to second calcination.The negative electrode material prepared by the present disclosure can be used for sodium ion battery, can effectively reduce irreversible capacity loss, improve battery first week coulomb efficiency.

Description

Technical Field

[0001] This disclosure relates to the field of sodium-ion battery anode material technology, specifically to a sodium-ion battery anode material, its preparation method, an anode electrode containing the anode material, and a sodium-ion battery. Background Technology

[0002] Sodium-ion batteries have more abundant resources than lithium-ion batteries, and sodium and lithium are in the same group, resulting in lower development costs. Sodium-ion batteries also offer advantages such as higher capacity and better rate performance, making them a more suitable battery system for large-scale energy storage. However, the electrochemical performance of sodium-ion batteries is mainly limited by the development of electrode materials; therefore, the rational design of electrode material structures has become a research hotspot.

[0003] Carbon materials are commonly used as anode materials in rechargeable batteries. Because sodium has a larger radius than lithium, traditional graphite-based anodes cannot achieve reversible sodium ion insertion / extraction. Therefore, finding suitable anode materials for sodium ion insertion / extraction is crucial for improving the performance of sodium-ion batteries. Hard carbon materials are difficult to graphitize and exhibit a short-range ordered, long-range disordered carbon layer arrangement. The ordered carbon layers have a large interlayer spacing, enabling reversible sodium ion insertion / extraction. Simultaneously, they possess abundant nanopores and defect structures that can provide storage sites for sodium ions. However, biomass-based hard carbon materials have a low carbon yield, resulting in relatively higher costs. Furthermore, the presence of numerous pores and defects after calcination leads to low initial coulombic efficiency and reduced reversible capacity in the battery.

[0004] Compared to other biomass-based materials, lignin-based carbon materials have advantages such as high carbon yield, wide availability, and low cost. However, the presence of numerous pores and defects on the surface of lignin-based carbon materials currently results in extremely low coulombic efficiency (less than 40%) in the first cycle of the battery. Therefore, there is an urgent need to develop a novel preparation method that facilitates the reversible insertion and extraction of sodium ions. Summary of the Invention

[0005] The purpose of this disclosure is to provide a sodium-ion battery anode material, its preparation method, an anode sheet containing the anode material, and a sodium-ion battery. The raw material components of the anode material are all widely available and inexpensive, which can effectively reduce the cost of the product. The anode material can be used in sodium-ion batteries, which can effectively reduce irreversible capacity loss and improve the first-cycle coulombic efficiency of the battery.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a sodium-ion battery anode material, the method comprising the following steps:

[0007] S1: The hard carbon precursor is first calcined to obtain hard carbon particles;

[0008] S2: Petroleum coke is reacted with a mixed solution of sulfuric acid and nitric acid to obtain the solid after the reaction;

[0009] S3: The reacted solid is mixed with a first alkaline solution, and a supernatant is obtained from the mixture; the supernatant is mixed with an acidic solution, and a solid phase material is separated; the solid phase material is used as a coating carbon material and mixed with a second alkaline solution to obtain a coating carbon material dispersion.

[0010] S4: Mix the coating carbon material dispersion with the hard carbon particles, and then dry them to obtain a dried mixture; then calcine the dried mixture a second time.

[0011] Optionally, the hard carbon precursor includes one of alkaline lignin, dealkalized lignin, and sodium lignin sulfonate, preferably dealkalized lignin; the petroleum coke includes one of needle coke, petroleum pitch, and coated pitch, preferably needle coke.

[0012] Optionally, the volume ratio of nitric acid to sulfuric acid in S2 is 1:1 to 4, preferably 1:1 to 3;

[0013] The conditions for the contact reaction include: a contact temperature of 60–100°C, preferably 60–80°C, and a contact time of 1–4 h, preferably 2–4 h.

[0014] Optionally, the first alkaline solution is an inorganic alkaline solution, preferably a sodium hydroxide solution; the pH of the first alkaline solution is 11-13; and the weight ratio of the solid after the reaction to the first alkaline solution is 1:10-100.

[0015] In S3, mixing the supernatant with the acidic solution includes adjusting the pH of the mixed solution to 1-2 using the acidic solution;

[0016] The acidic solution is an inorganic acid solution, preferably hydrochloric acid, and the mass percentage concentration of the hydrochloric acid is 25% to 40%.

[0017] The second alkaline solution is an inorganic alkaline solution with a pH of 9 to 13; the weight ratio of the coating carbon material to the second alkaline solution is 1:(5 to 20), preferably 1:(8 to 15).

[0018] Optionally, the first calcination includes calcining the hard carbon precursor under an inert atmosphere; the inert atmosphere includes one of nitrogen, helium, and argon.

[0019] The conditions for the first calcination include: a temperature of 800℃ to 1600℃, preferably 1000℃ to 1400℃; a time of 2 to 6 hours, preferably 2 to 4 hours; and an inert atmosphere flow rate of 5 to 200 mL / min, preferably 100 to 180 mL / min.

[0020] Optionally, the mass ratio of the coating carbon material dispersion to the hard carbon particles in S3 is 1:5 to 20, preferably 1:8 to 15.

[0021] Optionally, before step S3, the method further includes: washing the reacted solid with water until the pH of the filtrate is 6.5 to 7.5, and then filtering it.

[0022] Optionally, in step S4, the mixing includes: stirring to evaporate the solvent;

[0023] The mixing conditions include: a temperature of 30–90°C and a time of 6–12 hours; the stirring rate is 100–600 rpm.

[0024] The drying conditions include: a temperature of 80–120°C, preferably 90–110°C; and a time of 20–26 h, preferably 22–26 h.

[0025] Optionally, the second calcination includes calcining the dried mixture under an inert atmosphere; the inert atmosphere includes one of nitrogen, helium, and argon.

[0026] The conditions for the second calcination include: a temperature of 800℃ to 1600℃, preferably 1000℃ to 1400℃; a time of 2 to 6 hours, preferably 2 to 4 hours; and an inert atmosphere flow rate of 5 to 200 mL / min, preferably 100 to 180 mL / min.

[0027] The second aspect of this disclosure provides a sodium-ion battery anode material prepared by the method described in the first aspect of this disclosure.

[0028] The third aspect of this disclosure provides a sodium-ion battery anode material, the anode material comprising composite carbon material particles with a core-shell structure, wherein the core of the composite carbon material particles is a hard carbon particle and the shell of the composite carbon material particles is an amphiphilic carbon material.

[0029] Optionally, the amphiphilic carbon material is prepared by the following steps:

[0030] S1: Petroleum coke is reacted with a mixed solution of sulfuric acid and nitric acid to obtain the solid after the reaction;

[0031] S2: The reacted solid is mixed with a first alkaline solution, and a supernatant is obtained from the mixture; the supernatant is mixed with an acidic solution, and a solid phase is separated.

[0032] Optionally, the hard carbon particles have a particle size of 15–75 μm and a BET specific surface area of ​​6.5–8 m². 2 / g; the XRD pattern of the hard carbon particles shows characteristic peaks between 2θ values ​​of 20–25° and 40–45°, and the interlayer spacing of the hard carbon particles calculated based on the characteristic peaks between 2θ values ​​of 20–25° is: above;

[0033] The composite carbon material has a particle size of 15–125 μm and a BET specific surface area of ​​2.5–7.5 m². 2 / g; The XRD pattern of the composite carbon material shows characteristic peaks between 2θ values ​​of 20–25° and 40–45°. The interlayer spacing of the composite carbon material calculated based on the characteristic peaks between 2θ values ​​of 20–25° is: above.

[0034] Optionally, by weight percentage, the negative electrode material comprises 1-20% of a coating carbon material and 80-99% of hard carbon particles; preferably, the weight percentage of the coating carbon material is 5%-10%, and the weight percentage of the hard carbon particles is 90%-95%.

[0035] This disclosure provides a fourth aspect of a sodium-ion secondary battery negative electrode sheet, the negative electrode sheet comprising: a current collector, a binder, and the negative electrode material described in the third aspect of this disclosure.

[0036] This disclosure provides a sodium-ion secondary battery, the sodium-ion secondary battery comprising the negative electrode, positive electrode, electrolyte and separator between the positive electrode and the negative electrode as described in the fourth aspect of this disclosure;

[0037] The positive electrode is one of sodium manganate, sodium cobaltate, sodium vanadium phosphate, or sodium iron phosphate.

[0038] Through the above technical solution, this disclosure prepares hard carbon particles with a large interlayer spacing suitable for sodium storage using a hard carbon precursor. Simultaneously, an amphiphilic carbon material is introduced, allowing the amphiphilic carbon material to uniformly coat the surface of the hard carbon particles, effectively covering the numerous pores and defect sites formed during the calcination of the hard carbon precursor. The raw material components of the negative electrode material provided in this disclosure are all widely available and inexpensive, effectively reducing product costs. This negative electrode material can be used in sodium-ion batteries, effectively reducing irreversible capacity loss and improving the first-cycle coulombic efficiency of the battery.

[0039] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0040] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0041] Figure 1This is the XRD pattern of the carbon coating material in Example 1.

[0042] Figure 2 This is the XRD pattern of the hard carbon particles in Example 1.

[0043] Figure 3 This is the XRD pattern of the negative electrode material prepared in Example 1.

[0044] Figure 4 This is a charge-discharge curve of the sodium-ion battery prepared in Example 1 during the first and second weeks.

[0045] Figure 5 This is a charge-discharge curve of the sodium-ion battery prepared in Comparative Example 1 during the first and second weeks.

[0046] Figure 6 This is a SEM image of the negative electrode material prepared in Comparative Example 1.

[0047] Figure 7 This is a SEM image of the negative electrode material prepared in Example 1. Detailed Implementation

[0048] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0049] The first aspect of this disclosure provides a method for preparing a sodium-ion battery anode material, the method comprising the following steps:

[0050] S1: The hard carbon precursor is first calcined to obtain hard carbon particles;

[0051] S2: Petroleum coke is reacted with a mixed solution of sulfuric acid and nitric acid to obtain the solid after the reaction;

[0052] S3: The reacted solid is mixed with a first alkaline solution, and a supernatant is obtained from the mixture; the supernatant is mixed with an acidic solution, and a solid phase material is separated; the solid phase material is used as a coating carbon material and mixed with a second alkaline solution to obtain a coating carbon material dispersion.

[0053] S4: Mix the coating carbon material dispersion with the hard carbon particles, and then dry them to obtain a dried mixture; then calcine the dried mixture a second time.

[0054] The method disclosed herein overcomes the problem in existing technologies where the removal of heteroatoms after high-temperature calcination of hard carbon precursors results in numerous defect sites and residual impurities, leading to large irreversible capacity and low initial coulombic efficiency. The negative electrode material prepared by the method disclosed herein can be used in sodium-ion batteries, effectively reducing irreversible capacity loss and improving the initial coulombic efficiency of the battery.

[0055] According to this disclosure, the hard carbon precursor includes one of alkaline lignin, dealkalized lignin, and sodium lignin sulfonate, preferably dealkalized lignin; the petroleum coke includes one of needle coke, petroleum pitch, and coated pitch, preferably needle coke. The above embodiments utilize widely available and inexpensive precursors, making the method of this disclosure highly operable and possessing significant practical application value.

[0056] According to one embodiment of this disclosure, the volume ratio of nitric acid to sulfuric acid in S2 is 1:1 to 4, preferably 1:1 to 3, and more preferably 3:7; the contact reaction conditions include: a contact temperature of 60 to 100°C, preferably 60 to 80°C, and a contact time of 1 to 4 hours, preferably 2 to 4 hours. In a further embodiment, the mass percentage concentration of the nitric acid can be 60% to 70%, preferably 62% to 68%, and more preferably 65%; the mass percentage concentration of the sulfuric acid can be 98% or more, preferably 98%.

[0057] According to one embodiment of this disclosure, the first alkaline solution is an inorganic alkaline solution, preferably a sodium hydroxide solution; the pH of the first alkaline solution is 11-13, preferably pH=12; the weight ratio of the reacted solid to the first alkaline solution is 1:10-100, preferably 1:10-80; in step S3, mixing the supernatant with the acidic solution includes adjusting the pH of the mixed solution to 1-2, preferably pH=1, using the acidic solution; the acidic solution is an inorganic acid solution, preferably hydrochloric acid, and the mass percentage concentration of the hydrochloric acid can be 25%-40%, preferably 37%. The above embodiment is advantageous for preparing amphiphilic carbon materials. This amphiphilic carbon is soluble in both alkaline solvents and polar organic solvents. The second alkaline solution is an inorganic alkaline solution with a pH of 9-13; the weight ratio of the coating carbon material to the second alkaline solution is 1:(5-20), preferably 1:(8-15).

[0058] According to one embodiment of this disclosure, before step S3, the method further includes: washing the reacted solid with water until the pH of the filtrate is 6.5 to 7.5, preferably, the pH of the filtrate is 7, and then filtering.

[0059] According to one embodiment of this disclosure, the first calcination includes calcining the hard carbon precursor under an inert atmosphere; further, the inert atmosphere includes one of nitrogen, helium, and argon; the conditions for the first calcination include: a temperature of 800℃ to 1600℃, preferably 1000℃ to 1400℃; a time of 2 to 6 hours, preferably 2 to 4 hours; and an inert atmosphere flow rate of 5 to 200 mL / min, preferably 100 to 180 mL / min. The above embodiment is advantageous for preparing hard carbon particles with a large interlayer spacing suitable for sodium storage.

[0060] According to one embodiment of this disclosure, the hard carbon particles have a particle size of 15–75 μm and a BET specific surface area of ​​6.5–8 m². 2 / g; the XRD pattern of the hard carbon particles shows characteristic peaks between 2θ values ​​of 20–25° and 40–45°, with the characteristic peak between 2θ values ​​of 20–25° attributed to the 002 crystal plane and the characteristic peak between 2θ values ​​of 40–45° attributed to the 100 crystal plane; the interlayer spacing calculated based on the characteristic peaks between 2θ values ​​of 20–25° can be... The particle size is the smallest sieve opening that the particle can pass through in its most advantageous orientation. The above-described implementation results in hard carbon particles with a large interlayer spacing, suitable for sodium storage.

[0061] According to another embodiment of this disclosure, the mass ratio of the coating carbon material dispersion to the hard carbon particles in S3 is 1:5 to 20, preferably 1:8 to 15. This embodiment facilitates the uniform coating of the hard carbon material onto the surface of the hard carbon particles after curing, effectively covering the numerous pores formed during calcination and the defect sites resulting from heteroatom removal, thereby further obtaining a negative electrode material that can improve the first-cycle coulombic efficiency of the battery.

[0062] According to another embodiment of this disclosure, the hard carbon particles, the coating carbon material, and the second alkaline solution are mixed in a mass ratio of 1:(5-20):(5-20), preferably 1:(8-15):(8-15), and more preferably 1:10:10. This embodiment facilitates the uniform coating of the hard carbon particles with the cured coating carbon material, effectively covering the numerous pores formed during the calcination of the hard carbon particles and the defect sites formed by the removal of heteroatoms, thereby obtaining a negative electrode material that can improve the first-cycle coulombic efficiency of the battery.

[0063] According to one embodiment of this disclosure, in step S4, the mixing includes: stirring to evaporate the solvent; the solvent evaporation includes evaporating the solvent completely. The mixing conditions include: the temperature can be 30-90°C, preferably 60-80°C; the time can be adjusted according to the solvent evaporation, for example, the time can be 6-12 hours, preferably 8-12 hours; the stirring speed can be 100-600 rpm, preferably 200-500 rpm.

[0064] According to another embodiment of this disclosure, the mixing includes stirring at a first temperature, followed by stirring at a second temperature to evaporate the solvent. The first temperature can be 20–40°C, preferably 25–35°C; the mixing time at the first temperature can be 2–6 hours; the second temperature is 60–90°C, preferably 60–80°C; and the stirring rate can be 100–600 rpm, preferably 200–500 rpm.

[0065] According to one embodiment of this disclosure, the second calcination includes subjecting the dried mixture to a second calcination under an inert atmosphere; the inert atmosphere includes one of nitrogen, helium, and argon; the conditions for the second calcination include: a temperature of 800°C to 1600°C, preferably 1000°C to 1400°C; a time of 2 to 6 hours, preferably 2 to 4 hours; and an inert atmosphere flow rate of 5 to 200 mL / min, preferably 100 to 180 mL / min. The above embodiments are advantageous for obtaining coated carbon materials suitable for sodium deintercalation / intercalation.

[0066] According to one embodiment of this disclosure, the drying conditions include: a temperature of 80–120°C, preferably 90–110°C; and a drying time of 20–26 hours, preferably 22–26 hours. The drying apparatus can be a conventional drying apparatus in the art, such as a forced-air drying oven.

[0067] The above-described embodiments utilize the characteristic that the coating carbon material can dissolve in alkaline aqueous solutions. By mixing it evenly with hard carbon particles, the solidified coating carbon material can uniformly coat the surface of the hard carbon particles during the calcination process. This effectively covers the numerous pores formed during the calcination of the hard carbon particles and the defect sites formed due to the removal of heteroatoms, thereby obtaining a negative electrode material that can improve the first-cycle coulombic efficiency of the battery.

[0068] The second aspect of this disclosure provides a sodium-ion battery anode material prepared by the method described in the first aspect of this disclosure.

[0069] The third aspect of this disclosure provides a sodium-ion battery anode material, the anode material comprising a core-shell structured composite carbon material, wherein the core of the composite carbon material is a hard carbon particle and the shell of the composite carbon material is an amphiphilic carbon material.

[0070] According to one embodiment of this disclosure, the amphiphilic carbon material is prepared by the following steps:

[0071] S1: Petroleum coke is reacted with a mixed solution of sulfuric acid and nitric acid to obtain the solid after the reaction;

[0072] S2: The reacted solid is mixed with a first alkaline solution, and a supernatant is obtained from the mixture; the supernatant is mixed with an acidic solution, and a solid phase is separated.

[0073] According to one embodiment of this disclosure, the negative electrode material comprises, by weight percentage, 1-20% of a coating carbon material and 80-99% of hard carbon particles; preferably, the weight percentage of the coating carbon material is 5%-10%, and the weight percentage of the hard carbon particles is 90%-95%. The percentages of each component of the negative electrode material are calculated based on the dry weight added during the preparation process.

[0074] According to one embodiment of this disclosure, the composite carbon material has a particle size of 15–125 μm and a BET specific surface area of ​​2.5–7.5 m². 2 / g, preferably 2.5-6m 2 / g; the XRD pattern of the composite carbon material shows characteristic peaks between 2θ values ​​of 20–25° and 40–45°, and the interlayer spacing calculated based on the characteristic peaks between 2θ values ​​of 20–25° can be... The above are preferred. above.

[0075] This disclosure provides a fourth aspect of a sodium-ion battery negative electrode sheet, the negative electrode sheet comprising: a current collector, a binder, and the negative electrode material described in the third aspect of this disclosure.

[0076] This disclosure provides a sodium-ion battery in a fifth aspect, comprising the negative electrode, positive electrode, electrolyte, and separator between the positive and negative electrodes as described in the fourth aspect of this disclosure; the positive electrode is one of sodium manganate, sodium cobaltate, sodium vanadium phosphate, or sodium iron phosphate. The electrolyte can be a conventional electrolyte in the art, for example, the electrolyte salt can be one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, or sodium bis(trifluoromethanesulfonyl)imide, and the electrolyte solvent can be one or more of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), and methyl ethyl carbonate (EMC); the separator can be a conventional separator in the art, for example, a glass fiber separator or a polyolefin porous membrane.

[0077] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0078] In the following embodiments of this disclosure, X-ray scanning diffraction (XRD) was performed on an X-ray powder diffractometer from Philips Corporation in the United States. The test method used a Cu target anode Kα radiation source with a step width of 0.02°, a scanning speed of 2° / min, and 2θ = 10°-80°.

[0079] Scanning electron microscopy (SEM) was performed on a QUANTA 400 instrument;

[0080] Electrochemical performance tests were conducted on a CT3001A1U-5V 5mA instrument from Wuhan Landian Company.

[0081] The BET specific surface area was measured on a JW-BK instrument from Jingwei Gaobo Company.

[0082] The dealkalized lignin was a product of the brand Innochem purchased from Beijing Innochem Technology Co., Ltd.

[0083] The electrolyte was a sodium-ion battery-specific electrolyte purchased from Suzhou Duoduo Reagent Co., Ltd.

[0084] The adhesive is a product of Beijing Innochem Technology Co., Ltd.;

[0085] All raw materials and reagents used in the following examples and comparative examples are battery grade;

[0086] Unless otherwise specified, the chemical reagents used in the following examples and comparative examples are commercially available products.

[0087] Example 1

[0088] (1) 6g of dealkalized lignin was evenly placed in a corundum boat, placed in a tube furnace, and calcined at 1000℃ for 2 hours after nitrogen gas was introduced. Hard carbon particles were obtained and denoted as L1000. The BET specific surface area of ​​the obtained hard carbon particles was 7.52m². 2 / g.

[0089] (2) Take appropriate amounts of nitric acid and sulfuric acid, mix them evenly at a volume ratio of 3:7, and heat them in a water bath to 80°C. The mass percentage concentration of the sulfuric acid used is 98%, and the mass percentage concentration of the nitric acid used is 65%. After keeping it at this temperature for a period of time, slowly add needle-shaped coke powder and stir at 80°C for 3 hours. Dispense the resulting mixed solution into centrifuge tubes, centrifuge and wash with water multiple times until the supernatant is neutral, and filter to obtain a solid. Dissolve the solid in a sodium hydroxide solution with pH=12 and stir for 6 hours. After standing for 24 hours, take the supernatant, add dilute hydrochloric acid to the supernatant to adjust the pH to 1, and let it stand for 24 hours to obtain a precipitate. Place the precipitate in a forced-air drying oven at 110°C and dry for 24 hours to obtain the coated carbon material. The mass percentage concentration of the dilute hydrochloric acid used is 37%.

[0090] (3) Take the coated carbon material, L1000, and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then, place the material in a tube furnace and calcine it at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1200℃, and a calcination time of 2 hours. The resulting negative electrode material is obtained and denoted as ACM@L1000-1200. The BET specific surface area of ​​the obtained negative electrode material is 2.8 m². 2 / g.

[0091] (4) Preparation of sodium-ion battery negative electrode sheet. The above-mentioned sodium-ion battery negative electrode material and 20% sodium alginate binder were weighed at a mass ratio of 9:1. The mixture was stirred magnetically for 6 hours to ensure thorough mixing. The mixture was then coated onto copper foil using a 150 μm thick scraper. The coated copper foil was dried in an 80°C oven for 12 hours. Subsequently, the coated copper foil was cut into electrode sheets with a diameter of 12 mm using a die-cutting machine. Electrode sheets with uniform coating and similar mass were selected using a microbalance to obtain the sodium-ion battery negative electrode. The sodium alginate binder was prepared by first placing sodium alginate powder into a 25*25 mm weighing bottle, adding an appropriate amount of deionized water, and then stirring the sodium alginate and deionized water under magnetic stirring to form a uniform gel-like solution.

[0092] (5) Assembly of sodium-ion half-cells. Using metallic sodium as the counter electrode, 1 mol / L NaPF6-EC / DMC as the electrolyte, the aforementioned sodium-ion negative electrode sheet as the working electrode, and a Whatman GF / D glass fiber membrane as the battery separator, a CR2032 experimental button-shaped symmetrical cell was assembled in a glove box filled with argon atmosphere to evaluate the electrochemical performance of the aforementioned sodium-ion battery negative electrode material.

[0093] Example 2

[0094] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1000℃ for 2 hours to obtain hard carbon particles, which are denoted as L1000.

[0095] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0096] (3) Take the coating carbon material, L1000 and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine it at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1000℃, and a calcination time of 2 hours. The negative electrode material is obtained. It is denoted as ACM@L1000-1000.

[0097] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0098] Example 3

[0099] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1000℃ for 2 hours to obtain hard carbon particles, which are denoted as L1000.

[0100] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0101] (3) Take the coating carbon material, L1000 and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine at 1400℃ for 2 hours under a nitrogen atmosphere with a flow rate of 150 mL / min. The anode material is then obtained and denoted as ACM@L1000-1400.

[0102] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0103] Example 4

[0104] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1200℃ for 2 hours to obtain hard carbon particles, which are denoted as L1200.

[0105] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0106] (3) Take the coating carbon material, L1200 and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine it at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1000℃, and a calcination time of 2 hours. The negative electrode material is obtained. It is denoted as ACM@L1200-1000.

[0107] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0108] Example 5

[0109] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1200℃ for 2 hours to obtain hard carbon particles, which are denoted as L1200.

[0110] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0111] (3) Take the coating carbon material, L1200 carbon material, and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine it at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1200℃, and a calcination time of 2 hours. The negative electrode material is obtained. It is denoted as ACM@L1200-1200.

[0112] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0113] Example 6

[0114] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1400℃ for 2 hours to obtain hard carbon particles, which are denoted as L1400.

[0115] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0116] (3) Take the coating carbon material, L1400 and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine at 1200℃ for 2 hours under a nitrogen atmosphere with a flow rate of 150 mL / min. The resulting anode material is then obtained and denoted as ACM@L1400-1200.

[0117] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0118] Example 7

[0119] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1000℃ for 2 hours to obtain hard carbon particles, which are denoted as L1000.

[0120] (2) The preparation method of the coating carbon material is the same as in Example 1.

[0121] (3) Take the coating carbon material, L1000 and 0.1 mol / L sodium hydroxide solution and mix them evenly in a mass ratio of 1:4:10. Stir continuously at 80℃ until the water evaporates completely. Place the resulting evenly mixed material in a forced-air drying oven at 110℃ and dry for 24 hours. Then place the material in a tube furnace and calcine at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1200℃, and a calcination time of 2 hours. The negative electrode material is then obtained.

[0122] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0123] Comparative Example 1

[0124] (1) 6g of dealkalized lignin was evenly placed in a corundum boat, placed in a tube furnace, and calcined at 1000℃ for 2 hours after nitrogen gas was introduced. Hard carbon particles, denoted as L1000, were obtained. The BET specific surface area of ​​the obtained hard carbon particles was 7.5m². 2 / g.

[0125] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0126] Comparative Example 2

[0127] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1000℃ for 2 hours to obtain hard carbon particles, which are denoted as L1000.

[0128] (2) Take an appropriate amount of nitric acid and sulfuric acid and mix them evenly in a volume ratio of 3:7. Heat the mixture in a water bath to 80°C. The mass percentage concentration of the sulfuric acid used is 98% and the mass percentage concentration of the nitric acid used is 65%. After keeping it warm for a period of time, slowly add needle-shaped coke powder and stir at 80°C for 3 hours. Dispense the resulting mixed solution into centrifuge tubes and centrifuge and wash with water multiple times until the supernatant is neutral to obtain the coated carbon material.

[0129] (3) Take the coating carbon material, L1000 and 0.1 mol / L sodium hydroxide solution and mix them evenly at a mass ratio of 1:10:10. Stir continuously at 80°C until the water evaporates completely. Place the resulting uniformly mixed material in a forced-air drying oven at 110°C and dry for 24 hours. Then place the material in a tube furnace and calcine it at a nitrogen atmosphere flow rate of 150 mL / min, a high-temperature calcination temperature of 1200°C, and a calcination time of 2 hours. The negative electrode material is obtained. It is denoted as ACM@L1000-1200. The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half-cell are the same as in Example 1.

[0130] Comparative Example 3

[0131] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen for a period of time, and calcine at 1000℃ for 2 hours to obtain hard carbon particles, which are denoted as L1000.

[0132] (2) Take appropriate amounts of nitric acid and sulfuric acid, mix them evenly at a volume ratio of 3:7, and heat them in a water bath to 80°C. The mass percentage concentration of the sulfuric acid used is 98%, and the mass percentage concentration of the nitric acid used is 65%. After keeping it at this temperature for a period of time, slowly add needle-shaped coke powder and stir at 80°C for 3 hours. Dispense the resulting mixed solution into centrifuge tubes, centrifuge and wash with water multiple times until the supernatant is neutral to obtain amphiphilic carbon material. Dissolve the amphiphilic carbon material in a sodium hydroxide solution with a pH of 12 and stir for 6 hours. After standing for 24 hours, take the supernatant and add dilute hydrochloric acid to adjust the pH of the supernatant to 1. After standing for 24 hours, obtain the precipitate. Place the obtained precipitate in a forced-air drying oven at 110°C and dry for 24 hours to obtain the coated carbon material.

[0133] (3) Take the coating carbon material and L1000 and mix them at a mass ratio of 1:10. Place them in a tube furnace and calcine them at a nitrogen atmosphere flow rate of 150 mL / min, a high temperature of 1200℃, and a calcine time of 2 h. The negative electrode material is then obtained.

[0134] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0135] Comparative Example 4

[0136] (1) Take 6g of dealkalized lignin and place it evenly in a corundum boat. Put it in a tube furnace, introduce nitrogen gas for a period of time, and then calcine it at 1000℃ for 2 hours to obtain hard carbon particles.

[0137] (2) Take 1g of the above-mentioned hard carbon particles and 2g of coated asphalt, add an appropriate amount of water, ball mill for 2 hours, and dry in a forced-air drying oven at 110℃ for 24 hours. Put the above-mentioned mixed material into a tube furnace, purge with nitrogen for a period of time, and calcine at 800℃ for 2 hours to obtain the negative electrode material.

[0138] The preparation of the sodium-ion battery negative electrode sheet and the assembly of the sodium-ion half cell are the same as in Example 1.

[0139] Test Example 1

[0140] The electrochemical performance of the solar cells from Examples 1-7 and Comparative Examples 1-4 was tested under the following conditions: 0.1C (1C = 300 mAg). -1 Under the given rate, constant current charging and discharging was performed within a cutoff voltage range of 0.01V to 3V. The test results are shown in Table 1.

[0141] Table 1

[0142]

[0143] Based on the data in Table 1, and through comparison of the examples and comparative examples, it can be seen that the negative electrode material prepared by the method of this disclosure, when used in sodium-ion batteries, can effectively improve the first-cycle coulombic efficiency and effectively reduce irreversible capacity loss. A comparison of Example 7 and Example 1 shows that, within the preferred mass ratio range of the coating carbon material and the main hard carbon particles of this disclosure, the negative electrode material prepared for use in sodium-ion batteries can further improve the first-cycle coulombic efficiency.

[0144] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0145] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0146] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, The method includes the following steps: S1: The hard carbon precursor is first calcined to obtain hard carbon particles; S2: Petroleum coke is reacted with a mixed solution of sulfuric acid and nitric acid to obtain the solid after the reaction; S3: The reacted solid is mixed with a first alkaline solution, and a supernatant is obtained from the mixture; the supernatant is mixed with an acidic solution, and a solid phase material is separated; the solid phase material is used as a coating carbon material and mixed with a second alkaline solution to obtain a coating carbon material dispersion. S4: Mix the coating carbon material dispersion with the hard carbon particles, and then dry them to obtain a dried mixture; subject the dried mixture to a second calcination. S3 involves mixing the supernatant with the acidic solution, including adjusting the pH of the mixed solution to 1-2 using the acidic solution. The pH of the first alkaline solution is 11-13; The second alkaline solution is an inorganic alkaline solution with a pH of 9-13. The mass ratio of the coating carbon material dispersion to the hard carbon particles in S3 is 1:5~20.

2. The method according to claim 1, wherein, The hard carbon precursor includes one of alkaline lignin, dealkalized lignin, and sodium lignin sulfonate, and the petroleum coke is needle coke.

3. The method according to claim 1, wherein, The hard carbon precursor is alkali-degraded lignin.

4. The method according to claim 1, wherein, The volume ratio of nitric acid to sulfuric acid in S2 is 1:1~4; The conditions for the contact reaction include: a contact temperature of 60~100℃ and a contact time of 1~4h.

5. The method according to claim 1, wherein, The volume ratio of nitric acid to sulfuric acid in S2 is 1:1~3.

6. The method according to claim 1, wherein, The contact temperature of the contact reaction is 60~80℃.

7. The method according to claim 1, wherein, The contact time for the contact reaction is 2 to 4 hours.

8. The method according to claim 1, wherein, The first alkaline solution is an inorganic alkaline solution; the weight ratio of the solid after the reaction to the first alkaline solution is 1:10~100; The acidic solution is an inorganic acid solution; The weight ratio of the coating carbon material to the second alkaline solution is 1:(5~20).

9. The method according to claim 1, wherein, The first alkaline solution is a sodium hydroxide solution.

10. The method according to claim 1, wherein, The acidic solution is hydrochloric acid, and the mass percentage concentration of the hydrochloric acid is 25%~40%.

11. The method according to claim 1, wherein, The weight ratio of the coating carbon material to the second alkaline solution is 1:(8~15).

12. The method according to claim 1, wherein, The first calcination includes calcining the hard carbon precursor under an inert atmosphere; the inert atmosphere includes one of nitrogen, helium and argon. The conditions for the first calcination include: a temperature of 800℃~1600℃, a time of 2~6h, and an inert atmosphere flow rate of 5~200mL / min.

13. The method according to claim 1, wherein, The first calcination temperature is 1000~1400℃.

14. The method according to claim 1, wherein, The first calcination time is 2-4 hours.

15. The method according to claim 1, wherein, The inert atmosphere flow rate for the first calcination is 100~180 mL / min.

16. The method according to claim 1, wherein, The mass ratio of the coating carbon material dispersion to the hard carbon particles in S3 is 1:8~15.

17. The method according to claim 1, wherein, Before step S3, the method further includes: washing the reacted solid with water until the pH of the filtrate is 6.5-7.5, and then filtering it.

18. The method according to claim 1, wherein, In step S4, the mixing includes: stirring to evaporate the solvent; The mixing conditions include: a temperature of 30~90℃ and a time of 6~12h; the stirring rate is 100~600rpm. The drying conditions include a temperature of 80~120℃ and a time of 20~26h.

19. The method according to claim 1, wherein, In step S4, the drying temperature is 90~110℃.

20. The method according to claim 1, wherein, In step S4, the drying time is 22-26 hours.

21. The method according to claim 1, wherein, The second calcination includes calcining the dried mixture under an inert atmosphere; the inert atmosphere includes one of nitrogen, helium, and argon. The conditions for the second calcination include: a temperature of 800℃~1600℃, a time of 2~6h, and an inert atmosphere flow rate of 5~200mL / min.

22. The method according to claim 1, wherein, The second calcination temperature is 1000~1400℃.

23. The method according to claim 1, wherein, The second calcination time is 2-4 hours.

24. The method according to claim 1, wherein, The inert atmosphere flow rate for the second calcination is 100~180 mL / min.

25. The sodium-ion battery anode material prepared by the method according to any one of claims 1 to 24.

26. The negative electrode material according to claim 25, wherein, The negative electrode material includes a core-shell structured composite carbon material, wherein the core of the composite carbon material is a hard carbon particle and the shell of the composite carbon material is an amphiphilic carbon material.

27. The negative electrode material according to claim 26, wherein, The hard carbon particles have a particle size of 15~75μm and a BET specific surface area of ​​6.5~8m². 2 / g; the XRD pattern of the hard carbon particles is in 2 θ Characteristic peaks exist between 20~25° and 40~45°, according to 2 θ The interlayer spacing of hard carbon particles calculated for the characteristic peaks between 20 and 25° is greater than 3.8 Å; The composite carbon material has a particle size of 15~125μm and a BET specific surface area of ​​2.5~7.5m². 2 / g; The XRD pattern of the composite carbon material is in 2 θ Characteristic peaks exist between 20~25° and 40~45°, according to 2 θ The interlayer spacing of the composite carbon material calculated for the characteristic peaks between 20 and 25° is greater than 3.8 Å.

28. The negative electrode material according to claim 26, wherein, By weight percentage, the negative electrode material comprises 1-20% of coating carbon material and 80-99% of hard carbon particles.

29. The negative electrode material according to claim 28, wherein, The coating carbon material has a weight percentage of 5% to 10%, and the hard carbon particles have a weight percentage of 90% to 95%.

30. A sodium-ion battery negative electrode sheet, characterized in that, The negative electrode sheet comprises: a current collector, a binder, and the negative electrode material according to any one of claims 25 to 29.

31. A sodium-ion battery, characterized in that, Includes the negative electrode, positive electrode, electrolyte, and separator between the positive electrode and the negative electrode as described in claim 30; The positive electrode is one of sodium manganate, sodium cobaltate, sodium vanadium phosphate, or sodium iron phosphate.

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