Preparation method of jackfruit shell biomass hard carbon material for negative electrode of sodium ion battery

Abstract

The invention discloses a preparation method of a jackfruit shell biomass hard carbon material for the negative electrode of a sodium ion battery, belonging to the technical field of sodium ion batteries. The invention uses jackfruit shells as raw materials, and after soaking in an alkali mixed solution, low-temperature pre-carbonization, alkali solution soaking, acid solution soaking, and high-temperature carbonization, a biological hard carbon material that can be used for the negative electrode of a sodium ion battery is obtained. The biological hard carbon material has a large number of lamellar structures and honeycomb network structures, which can enable sodium ions to be effectively inserted and extracted from the negative electrode, has good electrochemical performance, provides a new idea for the research and development of sodium ion battery technology, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and particularly to a preparation method of a jackfruit shell biomass hard carbon material for the negative electrode of a sodium-ion battery. Background Art

[0002] Sodium-ion batteries and lithium-ion batteries have similar working principles, and sodium resources are rich in reserves, low in cost, and have excellent low-temperature performance and cycle life, showing broad application prospects in the fields of large-scale energy storage, power batteries, and drones. At present, the technologies of the positive electrode materials, separators, electrolytes, etc. of sodium-ion batteries have been relatively mature, but the lack of high-performance negative electrode materials has limited the industrial development of sodium-ion batteries to a certain extent. The sodium ion radius (about 0.1 nm) is much larger than the lithium ion radius (about 0.06 nm). Theoretically, graphite materials used in lithium-ion batteries have a small interlayer spacing, which is not conducive to the insertion and extraction of sodium ions, and will greatly reduce the storage capacity of sodium ions in graphite. Moreover, a stable intercalation compound cannot be formed between sodium and graphite, and this thermodynamic instability makes it difficult for graphite to be used as the negative electrode material of sodium-ion batteries, further affecting the development of sodium-ion battery technology.

[0003] Different from the lithium storage mechanism of graphite, the sodium storage mechanism of hard carbon is relatively complex, mainly including an intercalation reaction mechanism, an alloying reaction mechanism, and a conversion reaction mechanism. Sodium ions can be stored in three positions in hard carbon: the edges and defects on the surface of hard carbon, the voids between graphite layers, and the micropores formed between randomly oriented graphites. At present, coconut shell biomass materials and phenolic resins are used as hard carbon precursors. Although they can bring a stable structure, there are still problems such as poor cycle stability, high cost, and poor rate performance, which further affect the performance of the battery. Therefore, it is urgent to find a suitable negative electrode material to solve problems such as low capacity retention rate and low Coulomb efficiency of sodium-ion batteries. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention prepares a jackfruit shell biological hard carbon material for the negative electrode of a sodium-ion battery. The preparation method has a simple process flow, low cost, is environmentally friendly, and the sodium-ion battery assembled with the prepared jackfruit shell biological hard carbon material has advantages such as high specific capacity, obvious improvement in the first Coulomb efficiency, and excellent cycle performance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions to solve the technical problems:

[0006] On the one hand, the present invention provides a preparation method of a jackfruit shell biological hard carbon material for the negative electrode of a sodium-ion battery, including the following steps:

[0007] S1. Wash, dry, crush, soak in an alkali solution and then dry the jackfruit shell to obtain a precursor;

[0008] S2. Low-temperature and oxygen-free pre-carbonization etching of the precursor to obtain pyrolytic carbon;

[0009] S3. Immerse the pyrolytic carbon in alkali solution and acid solution respectively, wash until neutral, and dry to obtain an intermediate;

[0010] S4. Perform secondary oxygen-free high-temperature carbonization on the intermediate to obtain the final product, namely jackfruit shell biomass hard carbon.

[0011] Preferably, the drying temperature is 50-120 °C and the drying time is 12-72 h.

[0012] Preferably, in step S1, the alkali solution is one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, and ammonia water, and the concentration is 0.2-5 mol / L.

[0013] Preferably, in step S1, the soda solution is obtained by soaking the crushed jackfruit shell in the alkali solution, and the mass ratio of the jackfruit shell in the alkali solution is 10-50%.

[0014] Preferably, in step S2, the low-temperature pre-carbonization is carried out in an inert gas, the low-temperature pre-carbonization temperature is 400-600 °C, the time is 2-7 h, and the heating rate is 2-10 °C / min.

[0015] Preferably, in step S3, the acid solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, etc., and the concentration is 3-6 mol / L.

[0016] Preferably, in step S3, the alkali solution is one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia water and other solutions, and the concentration is 3-6 mol / L.

[0017] Preferably, in step S4, the high-temperature carbonization temperature is carried out in an inert gas, the high-temperature carbonization temperature is 900-1500 °C, the time is 5-12 h, and the heating rate is 5-15 °C / min.

[0018] On the one hand, the present invention provides the jackfruit shell bio-hard carbon material prepared by the preparation method described above.

[0019] On the other hand, the present invention also provides a sodium-ion battery, including a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and a casing, wherein the negative electrode sheet includes the jackfruit shell bio-hard carbon material described in claim 9.

[0020] Based on low-temperature carbonization, the present invention uses one or several types of alkali solutions containing sodium hydroxide, barium hydroxide, and potassium hydroxide. Sodium hydroxide or potassium hydroxide can react with impurities doped in the original biomass to improve the purity of the subsequent prepared hard carbon material. It can also act on the acidic functional groups of the material, and through redox reactions, it can further etch the material surface to increase the pore and pore wall structures, and cause the carbon skeleton of the pores to swell, increasing the pore diameter, improving the pore structure of the hard carbon material, and enhancing the specific surface area and adsorption performance. At the same time, the alkali also undergoes an acid-base neutralization reaction with the acidic functional groups in the jackfruit shell, causing certain corrosion on the surface, increasing the pore and pore wall structures. And the alkali can react with the graphite oxide groups in the biomass carbon at high temperatures, causing the destruction of the carbonaceous skeleton and forming new functional groups, further increasing the density and activity of the pore and pore wall, improving the adsorption performance of the material, and thus enabling it to accommodate more sodium ions.

[0021] In addition, low-temperature pre-carbonization can also reduce the release of volatile substances in the biomass raw material, enabling more carbon elements to be retained in the solid product, thereby increasing the yield and purity of hard carbon. Then, after impurity removal through alkali soaking and acid soaking, a high-performance jackfruit shell-based hard carbon anode material is finally obtained through high-temperature carbonization treatment.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention uses jackfruit shells as raw materials, and through alkali solution soaking, low-temperature pre-carbonization, alkali solution soaking, acid solution soaking, and high-temperature carbonization, a biological hard carbon material that can be used as the anode of a sodium-ion battery is prepared. The biological hard carbon material has a large number of lamellar structures and honeycomb-like reticular structures, enabling sodium ions to effectively intercalate and deintercalate at the anode, having good electrochemical performance, providing new ideas for the research and development of sodium-ion battery technology, and having broad application prospects.

[0024] The preparation method of the present invention is green and environmentally friendly, simple to operate, can be mass-produced industrially, uses jackfruit shells as raw materials, has rich sources and low costs, and is conducive to sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the present invention, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a scanning electron microscope image of the intermediate after pore-forming treatment with sodium hydroxide in Example 1 at a magnification of 5000 times.

[0027] Figure 2It is a scanning electron microscope image of the intermediate treated with sodium hydroxide for pore formation in Example 1 at a magnification of 10,000 times.

[0028] Figure 3 It is a scanning electron microscope image of the intermediate without pore formation treatment in Comparative Example 1 at a magnification of 5,000 times.

[0029] Figure 4 It is a scanning electron microscope image of the intermediate without pore formation treatment in Comparative Example 1 at a magnification of 10,000 times.

[0030] Figure 5 It is a cycle curve graph of a sodium-ion battery prepared from the jackfruit shell-based hard carbon negative electrode material after being treated with sodium hydroxide for pore formation in Example 1.

[0031] Figure 6 It is a cycle curve graph of a sodium-ion battery prepared from the jackfruit shell-based hard carbon negative electrode material without pore formation treatment in Comparative Example 1.

[0032] Figure 7 It is a charge-discharge curve graph of the first three cycles of a sodium-ion battery. In the figure, A is the sodium-ion battery prepared from the jackfruit shell-based hard carbon negative electrode material after being treated with sodium hydroxide for pore formation in Example 1; B is the sodium-ion battery prepared from the jackfruit shell-based hard carbon negative electrode material without sodium hydroxide pore formation treatment in Comparative Example 1. Detailed implementation mode

[0033] The following combines specific embodiments to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Unless otherwise specified, the test methods used in the following examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0035] Example 1

[0036] A preparation method of a jackfruit shell biomass hard carbon material, the preparation method specifically includes the following steps:

[0037] 1. Wash the jackfruit shell with deionized water, cut it into small pieces, shake it in an ultrasonic machine for 30 minutes, then rinse it with deionized water and dry it to constant weight, and use a wall breaker to grind it into powder to obtain a powdery raw material of jackfruit shell.

[0038] 2. Put the above-mentioned jackfruit shell powdery raw material into a beaker, add deionized water to submerge the sample, and place it in an oil bath at 80 °C for 2 h. Then transfer it to a 1 mol / L sodium hydroxide solution until completely submerged, where the mass of the sample in the alkali solution is 30%. Stir and soak at 60 °C for 2 h, and then put it into a blast drying oven at 60 °C to dry the moisture to obtain a precursor uniformly mixed with sodium hydroxide.

[0039] 3. Transfer the precursor to a nitrogen-purged tube furnace and heat it at a rate of 2 °C / min to 550 °C and hold for 5 h to obtain pre-carbonized carbon.

[0040] 4. Grind the pre-carbonized carbon into powder, pass it through a 1200-mesh sieve, stir and soak it in a 3 mol / L sodium hydroxide solution for 12 h, then wash it to neutrality, transfer it to a 3 mol / L hydrochloric acid solution, stir and soak it for 12 h, and then wash it to neutrality to obtain an intermediate.

[0041] 5. Transfer the intermediate to a nitrogen-purged tube furnace and heat it to 1300 °C at a rate of 10 °C / min and hold for 10 h to obtain the jackfruit shell bio-hard carbon anode material.

[0042] Example 2

[0043] A preparation method of a jackfruit shell biomass hard carbon material, the preparation method specifically includes the following steps:

[0044] 1. Wash the jackfruit shell with deionized water, cut it into small pieces, shake it in an ultrasonic machine for 30 min, then rinse it with deionized water and dry it to constant weight, and use a wall breaker to grind it into powder to obtain the jackfruit shell powdery raw material.

[0045] 2. Put the above-mentioned jackfruit shell powdery raw material into a beaker, add deionized water to submerge the sample, and place it in an oil bath at 80 °C for 2 h. Then transfer it to 1 mol / L sodium hydroxide until completely submerged, where the mass of the sample in the alkali solution is 30%. Stir and soak at 60 °C for 2 h, and then put it into a blast drying oven at 60 °C to dry the moisture to obtain a precursor uniformly mixed with sodium hydroxide.

[0046] 3. Transfer the precursor to a nitrogen-purged tube furnace and heat it at a rate of 2 °C / min to 400 °C and hold for 7 h to obtain pre-carbonized carbon.

[0047] 4. Grind the pre-carbonized carbon into powder, pass it through a 1200-mesh sieve, stir and soak it in a 3 mol / L sodium hydroxide solution for 12 h, then wash it to neutrality, transfer it to a 3 mol / L hydrochloric acid solution, stir and soak it for 12 h, and then wash it to neutrality to obtain an intermediate.

[0048] 5. Transfer the intermediate to a nitrogen-purged tube furnace and heat it to 1500 °C at a rate of 10 °C / min and hold for 5 h to obtain the jackfruit shell bio-hard carbon anode material.

[0049] Example 3

[0050] A preparation method of jackfruit shell biomass hard carbon material, the preparation method specifically includes the following steps:

[0051] 1. Wash the jackfruit shell with deionized water, cut it into small pieces, shake it in an ultrasonic machine for 30 minutes, then rinse it with deionized water and dry it to constant weight, and use a wall breaker to grind it into powder to obtain the powdery raw material of jackfruit shell.

[0052] 2. Put the above-mentioned powdery raw material of jackfruit shell into a beaker, add deionized water to submerge the sample, and place it in an oil bath at 80 °C for 2 hours, then transfer it to a 2 mol / L potassium hydroxide solution until it is completely submerged, where the mass of the sample in the alkali solution is 50%. Stir and soak at 60 °C for 2 hours, and then put it into a blast drying oven at 60 °C to dry the moisture to obtain a precursor uniformly mixed with potassium hydroxide.

[0053] 3. Transfer the precursor to a nitrogen-purged tubular furnace and heat it at a heating rate of 10 °C / min, and keep it at 600 °C for 2 hours to obtain pre-carbonized carbon.

[0054] 4. Ball-mill the pre-carbonized carbon into powder, pass it through a 1200-mesh sieve, stir and soak it in a 3 mol / L potassium hydroxide solution for 12 hours, then wash it to neutral, transfer it to a 3 mol / L hydrochloric acid solution, stir and soak it for 12 hours, and then wash it to neutral to obtain an intermediate.

[0055] 5. Transfer the intermediate to a nitrogen-purged tubular furnace and heat it to 900 °C at a rate of 10 °C / min and keep it at 900 °C for 12 hours to obtain the jackfruit shell biological hard carbon anode material.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 is not treated with alkali solution etching, and the others are the same.

[0058] 1. Wash the jackfruit shell with deionized water, cut it into small pieces, shake it in an ultrasonic machine for 30 minutes, then rinse it with deionized water and dry it, and use a wall breaker to grind it into powder to obtain the powdery raw material of jackfruit shell.

[0059] 2. Put the above-mentioned powdery raw material of jackfruit shell into a 500 - 1000 mL beaker, add deionized water to submerge the sample, and place it in an oil bath at 80 °C for 2 hours, then put it into a blast drying oven at 60 °C to dry to obtain a precursor.

[0060] 3. Transfer the precursor to a nitrogen-purged tubular furnace and heat it at a heating rate of 2 °C / min, and keep it at 550 °C for 5 hours to obtain pre-carbonized carbon.

[0061] 4. Grind the preheated carbonized pomelo peel into powder, sieve it through a 1200-mesh sieve, stir and soak it in 3 mol / L sodium hydroxide solution for 12 h, then wash it to neutrality, transfer it to 3 mol / L hydrochloric acid solution, stir and soak it for 12 h, and then wash it to neutrality to obtain an intermediate.

[0062] 5. Transfer the intermediate to a nitrogen-purged tubular furnace, heat it to 1300 °C at a rate of 10 °C / min, and hold for 10 h to obtain the pomelo peel biohard carbon anode material.

[0063] Test Example 1

[0064] I. Use a scanning electron microscope to characterize the surface morphology of the pomelo peel biohard carbon anode materials prepared in Example 1 and Comparative Example 1, respectively.

[0065] It can be seen from Figures 1-4 that the pomelo peel biohard carbon anode material prepared in Example 1 has obvious large-scale lamellar structures and honeycomb-like reticular structures, which are more conducive to the storage of sodium ions; while the pomelo peel biohard carbon anode material prepared in Comparative Example 1 without treatment with the alkali mixture has a relatively small particle size, but there are no obvious layered structures and etched defect hole structures on the surface.

[0066] II. Electrochemical performance test:

[0067] Weigh 420 mg of the above-prepared biomass hard carbon material and 20 mg of conductive carbon black, grind them in an agate mortar for 20 min, then add them to a solution of 40 mg of PVDF and 400 mg of NMP, continuously stir for 10 h to form a homogeneous mixture, and then uniformly coat it on a copper foil with a thickness of 200 μm. Place it in an oven at 60 °C and dry it for 24 h, then use a slicing machine to make it into a circular electrode with a diameter of 12 mm. Use this electrode as the negative electrode, a glass fiber (Whitman, GF / D) disc as the battery separator, metallic sodium as the counter electrode and reference electrode, and use a solution of 1 mol / L sodium hexafluorophosphate (NaPF6) dissolved in ethylene carbonate (EC): dimethyl carbonate (DMC) = 1:1 plus 5% wt fluoroethylene carbonate as the electrolyte, and assemble a sodium-ion battery in a glove box filled with high-purity argon according to the structure of a CR2032 standard coin cell.

[0068] The assembled battery is subjected to cyclic charge and discharge tests on a Neware battery testing device, and the current density is set to 0.2 A / g.

[0069] It can be seen from Figures 5-6 that the pomelo peel biohard carbon anode material of Example 1 has good cycle stability and a high capacity at a current density of 0.2 A / g; while the pomelo peel biohard carbon anode material of Comparative Example 1 has general cycle stability, and its initial efficiency is much lower, and the capacity is low at a current density of 0.2 A / g.

[0070] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of a jackfruit shell-derived hard carbon material for the negative electrode of a sodium-ion battery, characterized in that, It includes the following steps: S1. Wash, dry, crush, soak in alkali solution and then dry the jackfruit shell to obtain a precursor; S2. Carry out low-temperature anaerobic pre-carbonization etching of the precursor at 400-600 °C to obtain pyrolytic carbon; S3. Soak the pyrolytic carbon in alkali solution and acid solution respectively, wash to neutrality, and dry to obtain an intermediate; S4. Carry out secondary anaerobic high-temperature carbonization of the intermediate at 900-1500 °C to obtain the final product, namely jackfruit shell biomass hard carbon; In step S1, the soaking in alkali solution is to soak the crushed jackfruit shell in alkali solution, stir and soak at 60 °C for 2 h, and then put it into a blast drying oven at 60 °C to dry the moisture to obtain a precursor uniformly mixed with sodium hydroxide; the mass ratio of the jackfruit shell in the alkali solution is 10-50%.

2. The preparation method according to claim 1, wherein In step S1, the drying temperature is 50-120 °C and the drying time is 12-72 h.

3. The preparation method according to claim 1, wherein In step S1, the concentration of the alkali solution is 0.2-5 mol / L.

4. The preparation method according to claim 1, wherein In step S2, the low-temperature pre-carbonization is carried out in an inert gas, the low-temperature pre-carbonization time is 2-7 h, and the heating rate is 2-10 °C / min.

5. The preparation method according to claim 1, characterized in that, In step S3, the acid solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, and hydrofluoric acid, and the concentration is 1-6 mol / L.

6. The preparation method according to claim 1, wherein In step S3, the alkali solution is one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, and ammonia water, and the concentration is 1-6 mol / L.

7. The preparation method according to claim 1, characterized in that, In step S4, the high-temperature carbonization temperature is carried out in an inert gas, the high-temperature carbonization time is 5-12 h, and the heating rate is 5-15 °C / min.

8. The jackfruit shell bio-hard carbon material prepared by the preparation method according to any one of claims 1-7.

9. A sodium-ion battery, characterized in that, It includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and a casing. Among them, the negative electrode sheet includes the jackfruit shell bio-hard carbon material according to claim 8.

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