A biomass composite material for sodium-ion battery anode and its preparation method

Abstract

This invention discloses a biomass composite material for sodium-ion battery anodes and its preparation method, belonging to the field of sodium-ion battery technology. The composite material comprises 90-98 parts of biomass-based hard carbon and 2-10 parts of bismuth / antimony salt solution or bismuth / antimony oxide, and its preparation method is provided. This invention uses low-cost natural agricultural / industrial waste as a carbon source and bismuth / antimony or its compounds as important active materials. First, a porous carbon structure is formed through pre-carbonization. Then, bismuth / antimony or its compounds are mixed with the carbides. Next, bismuth / antimony is tightly encapsulated with carbon using medium-temperature pitch and activating gases, forming a bismuth / antimony core-shell composite material. This method introduces bismuth / antimony at low cost, improving the electrochemical activity of the hard carbon material, while simultaneously utilizing the carbon coating to suppress system expansion during sodium storage of bismuth / antimony, thus enhancing the material's stability. The method is simple, the composition is easily adjustable, the performance is high, and it has wide applications and promising prospects.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a biomass composite material for the negative electrode of a sodium-ion battery and its preparation method. Background Technology

[0002] Lithium-ion batteries have achieved mature industrial-scale production. Compared to lithium-ion batteries, sodium-ion batteries have widely available raw materials, lower economic costs, better safety, and superior low-temperature performance, thus showing promising research prospects. However, current sodium-ion batteries generally exhibit low reversible charge-discharge capacity and initial efficiency, severely hindering their development. The negative electrode material is the carrier of ions and electrons during the charge-discharge process of a sodium-ion battery, determining energy storage and release. Currently, amorphous carbon, metal compounds, and alloy materials are available for use in sodium-ion batteries.

[0003] Bismuth and antimony alloys and their oxides possess theoretical capacities of 660–1300 mAh / g, making them potential anode materials for sodium-ion batteries. However, these alloys exhibit volume changes exceeding 150% during charge-discharge, resulting in severe pulverization and significantly impacting the cycle stability of sodium-ion battery anodes. To improve the cycle stability of such electrode materials, extensive research has focused on preparing ultrafine nanoparticles and combining these materials with carbon-based materials. For example, antimony is mixed with multi-walled carbon nanotubes / graphene, and antimony-carbon nanocomposite fibers are synthesized using electrospinning. Current synthesis methods include: mass separation soft landing, coprecipitation, atomic layer deposition, hydrothermal synthesis, and electrostatic adsorption. Among these, mass separation soft landing requires ultra-high vacuum preparation conditions, making large-scale production difficult; coprecipitation is often used to prepare high-content multi-component composite materials; atomic layer deposition requires specific equipment to prepare nanoparticles, limiting its development; hydrothermal synthesis involves certain safety hazards due to the hydrothermal reaction, hindering industrial production; and in electrostatic adsorption, the spatial distribution of functional groups on the carrier is usually uneven, and various types of surface defects can have a significant impact on the adsorption behavior of metal complexes. These traditional preparation methods are complex, costly, and cannot be applied on a large scale.

[0004] Based on the above problems, a biomass composite material for sodium-ion battery anodes and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a biomass composite material for sodium-ion battery anodes and its preparation method, so as to solve the problems in the background art.

[0006] To achieve the above objectives, the present invention provides a biomass composite material for the negative electrode of a sodium-ion battery, comprising 90-98 parts of biomass-based hard carbon and 2-10 parts of bismuth / antimony salt solution or bismuth / antimony oxide.

[0007] Preferably, the biomass-based hard charcoal is one or more of the following: moso bamboo, tea bamboo and its waste bamboo powder, bamboo handicraft tailings, packaging paper / boxes, camellia shells and almond shells.

[0008] Preferably, the bismuth / antimony salt solution is a bismuth / antimony nitrate solution or a bismuth / antimony acetate solution.

[0009] This invention also provides a method for preparing the above-mentioned biomass composite material for sodium-ion battery negative electrode, comprising the following steps:

[0010] S1. Pre-treat the biomass raw materials, then stir and soak them in organic solvents, acids or oxidants in sequence, and wash them with water to obtain the precursor;

[0011] S2. The precursor is carbonized under the protection of an inert gas to obtain carbonized material;

[0012] S3. Mix the carbide material with a bismuth / antimony salt solution or bismuth / antimony oxide in a certain proportion, add a closed-cell reagent, and then pass an inert gas through it for carbonization treatment or directly carry out carbonization treatment in an activated gas to obtain a bismuth / antimony carbide composite material.

[0013] Preferably, in S1, the biomass raw material is one of the following: moso bamboo, tea bamboo and its waste bamboo powder, bamboo handicraft tailings, packaging paper / box, camellia shell and almond shell;

[0014] The pretreatment process for raw materials involves crushing, and the median particle size of the crushed material obtained after crushing is 25–75 μm.

[0015] Preferably, in S1, the organic solvent is one or more of petroleum ether, acetone, ethanol, methanol, and isopropanol; the acid is one of hydrofluoric acid, hydrochloric acid, and sulfuric acid, with a concentration of 1 mol / L to saturation concentration; and the oxidant is one of sodium hypochlorite or sodium chlorite, with a concentration of 1 wt.% to 10 wt.%.

[0016] The soaking time using organic solvents is 6–12 hours, and the temperature is 20–60℃; the soaking time using acids or oxidants is 6–12 hours, and the temperature is 20–80℃.

[0017] Preferably, in S1, the organic solvent is ethanol or methanol, the acid is hydrochloric acid with a concentration of 2 mol / L, and the oxidant is sodium chlorite with a concentration of 5 wt.%.

[0018] The soaking time in organic solvents was 6 hours at a temperature of 25°C; the soaking time in acid or oxidizing agents was 6 hours at a temperature of 25°C.

[0019] Preferably, in step S2, the carbonization temperature is 350–800°C, the heating rate is 5–10°C / min, and the processing time is 1–4 hours.

[0020] Preferably, in step S2, the carbonization temperature is 500–600°C and the processing time is 3 hours.

[0021] Preferably, in step S3, the mass ratio of bismuth / antimony salt solution to carbide is 1:10 to 2:98, and the carbide and bismuth / antimony salt solution are dried at 80°C after mixing.

[0022] The bismuth / antimony oxide and carbide are mixed by ball milling for 6 to 48 hours, with a ball-to-material ratio of 20:1 to 40:1.

[0023] Preferably, the bismuth / antimony oxide and the carbide are mixed by ball milling, with a ball-to-material ratio of 30:1 and a ball milling time of 6 hours.

[0024] Preferably, in step S3, during the carbonization process after adding the closing-cell reagent and introducing an inert gas, the closing-cell reagent is medium-temperature asphalt or a sugar substance, wherein the softening temperature of the medium-temperature asphalt is 60-80°C, the sugar substance is glucose or fructose, and the proportion of the closing-cell reagent is 1 wt.%-10 wt.%; the inert gas is argon or nitrogen, the flow rate is 30-150 sccm, the carbonization temperature is 600-950°C, and the time is 0.5-6 h.

[0025] Preferably, in the process of carbonization treatment directly in the activating gas in S3, the activating gas is one of acetylene, propyne, a mixture of methane and nitrogen, or a mixture of methane and argon, the proportion of the activating gas is 5% to 15%, the carbonization treatment temperature is 600 to 950°C, the carbonization time is 2 to 6 hours, and the activating gas is a closed-pore reagent.

[0026] Therefore, the biomass composite material for sodium-ion battery negative electrode and its preparation method of the present invention have the following beneficial effects:

[0027] (1) The bismuth / antimony particles obtained by the method protected by this invention have a small particle size, <300nm, and a high degree of bonding between the particles and carbon, which is beneficial to suppress the rapid decline in stability caused by volume expansion during charging and discharging. Moreover, the sodium-ion anode material prepared has a first charge-discharge specific capacity >400mAh / g and a first coulombic efficiency >88% under the condition of 50mA / g, which is good performance. Furthermore, the raw materials used in this method are widely available and the preparation method is simple, which has high application value in sodium-ion battery anode materials.

[0028] (2) This invention uses low-cost natural agricultural / industrial waste as a carbon source and bismuth / antimony or compounds as important active substances. First, a porous carbon structure is formed through pre-carbonization, and then bismuth / antimony or compounds are mixed with carbides. Then, bismuth / antimony and carbon are tightly wrapped by medium-temperature asphalt and activation gas to form a bismuth / antimony core-shell composite material. This not only introduces bismuth / antimony at low cost and improves the electrochemical activity of hard carbon materials, but also uses the effect of carbon coating to suppress the system expansion during the bismuth / antimony sodium storage process and improve the stability of the material.

[0029] (3) The bismuth / antimony carbide composite material prepared by the present invention has a very low mesopore distribution as a battery negative electrode material. At the same time, carbon encapsulates bismuth / antimony with high active sites, which improves the reversible capacity of sodium storage. The carbon coating of bismuth / antimony inhibits the volume expansion of bismuth / antimony, which is beneficial to the stability of sodium storage. The method is simple to operate, the ratio of bismuth / antimony is easy to control, the performance is high, the process is simple, the carbonization temperature is low, and it has a wide range of applications and good application prospects.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 The above are charge-discharge curves of the materials obtained in Examples 1 and 2 of this invention.

[0032] Figure 2 This is a charge-discharge curve of the material obtained in Example 3 of the present invention;

[0033] Figure 3 These are SEM images of the materials obtained in Example 2 and Comparative Example 1 of the present invention;

[0034] Figure 4 The BET diagrams are those of the materials obtained in Embodiment 2 and Comparative Example 1 of this invention;

[0035] Figure 5 This is a TEM image of the material prepared in Example 1 of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0038] Example 1

[0039] Hard carbon materials were prepared from 3-5 year old moso bamboo from Taojiang County, Yiyang City, Hunan Province. The steps are as follows:

[0040] S1. Pulverize the bamboo to a median particle size of 75 μm, then soak it in pure bioethanol at 25°C for 6 h, followed by pressure filtration and water washing; then soak it in 2 mol / L hydrochloric acid at 25°C for 6 h, followed by pressure filtration and water washing until neutral, and then dry to obtain the precursor.

[0041] S2. The obtained precursor was carbonized at 600°C for 2 hours in a nitrogen atmosphere and then pulverized to obtain carbonized material.

[0042] S3. Place the carbonized material in an ethanol solution of bismuth nitrate, wherein the mass ratio of bismuth nitrate to carbon is 1:9. Freeze-dry to remove ethanol to obtain a dried product. Place the dried product in a rotary kiln and perform carbon coating under a mixed gas of methane (10%) / argon (90%). The carbonization gas flow rate is 0.075 g / min, the carbonization temperature is 900℃, the heating rate is 10℃ / min, the carbonization time is 3h, and after cooling to room temperature, a hard carbon material is obtained.

[0043] Example 2

[0044] Hard carbon materials were prepared from camellia fruit shells in Zhangjiajie City, Hunan Province. The steps are as follows: S1. Camellia fruit shells were crushed to a median particle size of 45 μm, then soaked in pure bio-methanol at 25℃ for 6 h, followed by pressure filtration and washing with water, then soaked in 2 mol / L hydrofluoric acid at 25℃ for 6 h, followed by pressure filtration and washing with water until neutral, and then dried to obtain the precursor.

[0045] S2. The obtained precursor was carbonized at 600°C for 2 hours in a nitrogen atmosphere and then pulverized to obtain carbonized material.

[0046] S3. Place the carbonized material in an ethanol solution of antimony nitrate, with a mass ratio of antimony nitrate to carbon of 5:95. Freeze-dry to remove ethanol and obtain a dried product. Mix and grind the dried product with medium-temperature pitch at a ratio of 9:1. Place the mixture in a rotary kiln and perform carbon coating under nitrogen. The carbonization gas flow rate is 50 sccm, the carbonization temperature is 900℃, the heating rate is 10℃ / min, and the carbonization time is 3h. After cooling to room temperature, hard carbon material is obtained.

[0047] Example 3

[0048] The steps for preparing hard carbon materials from discarded cardboard boxes are as follows:

[0049] S1. The waste packaging cardboard boxes are crushed to a median particle size of 25μm, then soaked in petroleum ether at 25℃ for 6h to remove impurities such as ink, filtered under pressure and vacuum dried at 60℃; then soaked in 2mol / L hydrochloric acid at 25℃ for 6h, then filtered under pressure, washed with water until neutral, and dried to obtain the precursor.

[0050] S2. The obtained precursor was carbonized at 500°C for 2 hours in a nitrogen atmosphere to obtain carbonized material.

[0051] S3. Place the carbide material and bismuth oxide powder in a ball mill and ball mill for 6 hours at a ball-to-material ratio of 30:1 and a rotation speed of 40 rpm to obtain ball milling material. Then, carbonize the obtained ball milling material under a mixture of acetylene (10%) and argon (90%) gas. The carbonization gas flow rate is 100 sccm, the carbonization temperature is 650℃, the heating rate is 5℃ / min, and the carbonization time is 3 hours. After cooling to room temperature, hard carbon material is obtained.

[0052] Comparative Example 1

[0053] Hard carbon materials were prepared from camellia fruit shells from Zhangjiajie City, Hunan Province, following the steps below;

[0054] S1. The camellia fruit shell was crushed to a median particle size of 45μm, then soaked in pure bio-methanol at 25℃ for 6h, then filtered and washed with water, then soaked in 2mol / L hydrofluoric acid at 25℃ for 6h, then filtered and washed with water until neutral, and dried to obtain the precursor.

[0055] S2. The obtained precursor was placed in an ethanol solution of antimony nitrate, with a mass ratio of antimony nitrate to carbon of 5:95. The ethanol was removed by freeze drying to obtain a dried product. The dried product was then carbonized at 500°C for 2 hours under a nitrogen atmosphere to obtain a carbonized product.

[0056] S3. The obtained carbonized product is placed in a rotary kiln and subjected to secondary carbonization under nitrogen. The carbonization gas flow rate is 50 sccm, the carbonization temperature is 1300℃, the heating rate is 2℃ / min, the carbonization time is 3h, and the hard carbon material is obtained after cooling to room temperature.

[0057] The difference between Comparative Example 1 and Example 2 is that no carbon coating was performed, but high-temperature carbonization was used in the comparative example to reduce the specific surface area.

[0058] Comparative Example 2

[0059] Hard carbon materials were prepared from 3-5 year old moso bamboo from Taojiang County, Yiyang City, Hunan Province. The steps are as follows:

[0060] S1. Pulverize the bamboo to a median particle size of 75μm, then soak it in pure bioethanol at 25℃ for 6h, then filter and wash with water, then soak it in 2mol / L hydrochloric acid at 25℃ for 6h, then filter and wash with water until neutral, and dry to obtain the precursor.

[0061] S2. The obtained precursor was carbonized at 600°C for 2 hours in a nitrogen atmosphere, and then pulverized to obtain carbonized material.

[0062] S3. The obtained carbonized material is placed in a rotary kiln and carbonized under a mixture of methane (10%) and argon (90%). The carbonization gas flow rate is 0.075 g / min, the carbonization temperature is 900℃, the heating rate is 10℃ / min, the carbonization time is 3h, and the hard carbon material is obtained after cooling to room temperature.

[0063] The difference between Comparative Example 2 and Example 1 is that no bismuth / antimony doping was performed.

[0064] The hard carbon materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested for specific surface area and specific capacity. The specific surface area and pore structure of the hard carbon were determined using an ASAP2020 automated adsorption analyzer. High-purity N2 was used as the adsorbate, and the adsorption isotherm of the sample was determined at 77 K using a volumetric method. The total specific surface area of ​​the hard carbon was calculated using the Brunauer-Emett-Teller (BET) method from the obtained adsorption isotherms. The specific surface area and pore volume of the micropores were calculated using the t-plot method, and the specific surface area and pore volume of the micropores were calculated using the Barret-Joyner-Halenda (BJH) method. For the specific capacity test, the prepared hard carbon material was coated on copper foil as the working electrode, pure sodium was used as the counter electrode, NaPF6 (1M) was used as the electrolyte solute, and EC:DMC = 1:1 was used as the solvent. The test was conducted at 50 mA·cm⁻¹. -2 The current density was measured at that current density.

[0065] The specific test results are shown in Table 1:

[0066] Table 1 Performance Test Results

[0067] Specific surface area First effect Specific capacity Example 1 4 92 <![CDATA[413mA·h·g -1 ]]> Example 2 6 88 <![CDATA[435mA·h·g -1 ]]> Example 3 6 88 <![CDATA[430mA·h·g -1 ]]> Comparative Example 1 17 72 <![CDATA[270mA·h·g -1 ]]> Comparative Example 2 6 89 <![CDATA[325mA·h·g -1 ]]>

[0068] The charge-discharge curves of Example 1 and Example 2 are plotted as follows: Figure 1 As shown, the moso bamboo in Example 1 exhibits a higher initial coulombic efficiency due to its ordered porous characteristics. However, the specific capacity of Example 1 is slightly lower than that of the camellia fruit shell and waste cardboard box in Examples 2 and 3, due to their lower oxygen content and slightly lower number of active sites. Comparing Examples 2 and 3, the performance of the two materials is similar. The charge-discharge curve of Example 3 is shown in the figure. Figure 2 As shown.

[0069] Table 1 shows that the performance of Comparative Example 1 is much lower than that of Example 2, indicating that traditional high-temperature carbonization is difficult to effectively improve the first coulombic efficiency of hard carbon and the pore-closing effect is not ideal. Coating has a better effect on pore sealing.

[0070] The morphology of the hard carbon materials obtained in Example 2 and Comparative Example 1 was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 3 As shown, it can be seen that the surface of hard carbon has no pores, while the surface of high-temperature carbonized materials still has a large number of channels distributed, such as... Figure 4 The BET plot shows that the specific surface area results also confirm this finding.

[0071] Comparing Example 1 and Comparative Example 2 in Table 1, the performance of Comparative Example 2 is lower than that of Example 1, indicating that the incorporation of bismuth / antimony significantly improves the specific capacity of the material. The hard carbon material obtained in Example 1 was characterized using transmission electron microscopy (TEM), as shown... Figure 5 As shown, bismuth / antimony nanoparticles are encapsulated by a carbon layer, forming a core-shell structure.

[0072] Therefore, this invention provides a biomass composite material for sodium-ion battery anodes and its preparation method. Using low-cost natural agricultural / industrial waste as a carbon source and bismuth / antimony or its compounds as key active materials, the method first forms a porous carbon structure through pre-carbonization. Then, bismuth / antimony or its compounds are mixed with carbides, and finally, bismuth / antimony is tightly encapsulated with carbon using medium-temperature pitch and activating gases to form a bismuth / antimony core-shell composite material. This method introduces bismuth / antimony at low cost, improving the electrochemical activity of hard carbon materials, while simultaneously utilizing the carbon coating to suppress system expansion during sodium storage of bismuth / antimony, thus enhancing material stability. The method is simple, the composition is easily adjustable, the performance is high, and it has wide applications and promising prospects.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biomass composite material for a sodium-ion battery negative electrode, characterized in that: The biomass composite material for the negative electrode of sodium-ion batteries comprises 90-98 parts of biomass-based hard carbon and 2-10 parts of bismuth / antimony salt solution or bismuth / antimony oxide; the biomass-based hard carbon is one or more of moso bamboo, tea bamboo and its waste bamboo powder, bamboo handicraft tails, packaging paper / boxes, camellia shells and almond shells; the bismuth / antimony salt solution is a bismuth / antimony nitrate solution or a bismuth / antimony acetate solution. The method for preparing the biomass composite material for the sodium-ion battery negative electrode includes the following steps: S1. Pre-treat the biomass raw materials, then stir and soak them in organic solvents, acids or oxidants in sequence, and wash them with water to obtain the precursor; S2. The precursor is carbonized under the protection of an inert gas to obtain carbonized material; S3. Mix the carbide material with a bismuth / antimony salt solution or bismuth / antimony oxide in a certain proportion, add a closed-cell reagent, and then pass an inert gas through it for carbonization treatment or directly perform carbonization treatment in an activating gas to obtain a bismuth / antimony carbide composite material; wherein, the closed-cell reagent is a medium-temperature asphalt or a sugar substance, with a proportion of 1wt.%~10wt.%; the activating gas is one of acetylene, propyne, a mixture of methane and nitrogen, or a mixture of methane and argon, with a proportion of 5%~15%; the carbonization treatment temperature is 600~950℃, and the carbonization time is 2~6h.

2. The method for preparing a biomass composite material for a sodium-ion battery negative electrode according to claim 1, characterized in that: In S1, the biomass raw material is one of the following: moso bamboo, tea bamboo and its waste bamboo powder, bamboo handicraft tail material, packaging paper / box, camellia shell and almond shell.

3. The method for preparing a biomass composite material for a sodium-ion battery negative electrode according to claim 1, characterized in that: In S1, the organic solvent is one or more of petroleum ether, acetone, ethanol, methanol, and isopropanol; the acid is one of hydrofluoric acid, hydrochloric acid, and sulfuric acid; and the oxidant is one of sodium hypochlorite or sodium chlorite. The soaking time using organic solvents is 6-12 hours at a temperature of 20-60℃; the soaking time using acids or oxidants is 6-12 hours at a temperature of 20-80℃.

4. The method for preparing a biomass composite material for a sodium-ion battery negative electrode according to claim 1, characterized in that: In step S2, the carbonization temperature is 350~800℃, the heating rate is 5~10℃ / min, and the processing time is 1~4h.

5. The method for preparing a biomass composite material for a sodium-ion battery negative electrode according to claim 1, characterized in that: In step S3, the mass ratio of bismuth / antimony salt solution to carbide is 1:10~2:98, and the carbide and bismuth / antimony salt solution are dried at 80°C after mixing. The bismuth / antimony oxide and carbide are mixed by ball milling for 6 to 48 hours.

6. The method for preparing a biomass composite material for a sodium-ion battery negative electrode according to claim 1, characterized in that: In step S3, after adding the closed-cell reagent, an inert gas is introduced for carbonization. The inert gas is argon or nitrogen, with a flow rate of 30-150 sccm, a carbonization temperature of 600-950℃, and a time of 0.5-6h.

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