Preparation method of high-performance sodium ion battery hard carbon negative electrode material

Abstract

The invention relates to the technical field of battery materials, in particular to a preparation method of a high-performance sodium ion battery hard carbon negative electrode material. The preparation method comprises the following steps: mixing and heating a biomass precursor and a PEG raw material, coating the biomass precursor with the PEG raw material, and carbonizing; the carbonization temperature is 1000 to 1800 DEG C; the precursor is coconut shell; and the PEG type raw material comprises PEG (polyethylene glycol) 1000, PEG 2000, PEG 4000, PEG 8000 or PEG 20000. According to the invention, the performance of the carbonized biomass material is improved; according to the hard carbon material, the specific capacity performance of biomass hard carbon is improved from 280 mAh / g to 389 mAh / g, and the first-circle coulombic efficiency is improved from 82% to 89% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a method for preparing a high-performance hard carbon negative electrode material for a sodium ion battery. Background Art

[0002] As a potential alternative to lithium-ion batteries, sodium-ion batteries (SIBs) have attracted widespread attention in recent years due to their abundant resources, low cost, and environmental friendliness. They demonstrate significant advantages in large-scale energy storage and transportation, and their importance is becoming increasingly prominent in the context of the increasing shortage of lithium resources. However, compared to SIBs, the development of anode materials for SIBs still faces numerous challenges. In SIBs, the anode material plays a crucial role in overall performance. Currently studied anode materials include carbon-based materials, titanium-based materials, metal oxides, and alloys. Among these, hard carbon, a carbon-based material, is considered one of the most promising anode materials for SIBs due to its high theoretical specific capacity, good cycling stability, and low cost. Due to its unique amorphous structure and large interlayer spacing, hard carbon materials enable a variety of sodium storage mechanisms, including adsorption, intercalation, and pore filling. However, despite its promising application prospects, SIBs often face challenges in practical production, including high cost, complex processes, and difficulties in mass production, making them difficult to meet practical application requirements. Existing technologies mainly use biomass materials in the design and preparation of hard carbon negative electrode materials, but there are still many performance defects. The first coulombic efficiency, low-voltage platform capacity, rate performance and cycle stability of biomass hard carbon negative electrode materials need to be improved. Summary of the Invention

[0003] In response to the above technical problems, the present invention provides a new hard carbon negative electrode material preparation technology, which aims to overcome the defects of the existing technology and promote the commercial application of sodium ion batteries.

[0004] The present invention adopts the following technical solutions:

[0005] The present invention provides a method for preparing a hard carbon negative electrode material, which comprises mixing and heating a biomass precursor and a PEG-based raw material, coating the biomass precursor with the PEG-based raw material, and carbonizing the mixture; the carbonization temperature is 1000-1800°C.

[0006] In the above technical solution, further, the biomass precursor is coconut shell or bamboo charcoal; the PEG raw material includes PEG-800, PEG1000, PEG2000, PEG4000, PEG8000 or PEG20000.

[0007] In the above technical solution, further, the method includes the following steps:

[0008] (1) The biomass precursor is crushed by ball mill and passed through a 200-600 mesh sieve;

[0009] (2) The PEG raw material and the biomass precursor are mixed and heated to a paste-like mobile phase, so that the PEG raw material covers the biomass precursor;

[0010] (3) Filter at 60-120°C to remove uncoated PEG-based raw materials and cool;

[0011] (4) High temperature carbonization: 1000-1800℃ for 1-4h.

[0012] In the above technical solution, further, the heating temperature in step (2) is 40-200°C.

[0013] In the above technical solution, further, the filtration in step (3) is filter paper filtration.

[0014] In the above technical solution, further, the mass ratio of the PEG raw material to the biomass precursor is 1:1-10.

[0015] In the above technical solution, further, in the step (1), the biomass precursor is pre-carbonized before use, with the pre-carbonization temperature being 200-400° C. and the time being 4-12 h.

[0016] The present invention also provides a hard carbon negative electrode material prepared by the above-mentioned preparation method.

[0017] The present invention also provides the use of the aforementioned preparation method or the aforementioned hard carbon negative electrode material in the preparation of a sodium ion battery.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention is achieved by fully mixing a biomass precursor and a non-ionic surfactant, and utilizing the high wettability of the surfactant to uniformly coat the precursor. During the high-temperature activation process, PEG dissolves and penetrates into the coconut shell precursor. During the carbonization process, PEG decomposes into hydrocarbon radicals and hydroxyl radicals, promoting the development of a carbon layer inside the hard carbon, thereby achieving a high closed-pore structure and a short-range ordered carbon layer structure that are conducive to sodium storage, and improving the kinetic performance and specific capacity during the charge and discharge process. At the same time, the PEG on the surface decomposes, deposits, and carbonizes to form a uniform carbon layer, shielding the damage of the hard carbon end group defects to the solid electrolyte layer (SEI film) during the charge and discharge process, thereby improving the first efficiency and achieving performance improvement of the carbonized biomass material. The hard carbon material of the present invention increases the specific capacity performance of biomass hard carbon from 280mAh / g to 389mAh / g, and the first-cycle coulomb efficiency from 82% to more than 89%.

[0020] The preparation method of the present invention is simple, the material cost is low, the processing process is safe, and the obtained hard carbon material retains the original morphology of the biomass raw material and has a high true density of 1.75g / cm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Transmission electron microscope images; A. hard carbon negative electrode material sample of Example 1, B. sample of Comparative Example 1;

[0022] Figure 2 Scanning electron microscope images; A. hard carbon negative electrode material sample of Example 1, B. sample of Comparative Example 1;

[0023] Figure 3 Specific capacity result diagram; A. hard carbon negative electrode material sample of Example 1, B. sample of Comparative Example 1. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific examples, but the present invention is not limited thereto in any way.

[0025] Example 1

[0026] Preparation of hard carbon negative electrode material using coconut shell as raw material includes the following steps:

[0027] (1) The coconut shell precursor was washed with water to remove excess impurities, filtered and dried at 60°C, and the dried coconut shell was pre-carbonized to obtain a biomass precursor; the pre-carbonization temperature was 200°C and the time was 12 hours.

[0028] (2) Crush the coconut shell precursor. After crushing, add the precursor powder into a ball mill at a speed of 200 rpm for 2 h. The ball-milled sample is sieved through a 200-mesh sieve and collected.

[0029] (3) 1.5 g of PEG-20000 was heated to 200° C. in a constant temperature heating furnace until it melted, and 3 g of the sieved precursor from step (2) was added in small amounts and multiple times, gradually processing it into a black paste-like mobile phase, so that the PEG-based raw material coated the biomass precursor.

[0030] (4) Transfer the mobile phase onto filter paper, filter at 90°C to remove uncoated PEG-20000, and cool to a solid state.

[0031] (5) The precursor treated in step (4) was placed in a high-temperature vacuum furnace under nitrogen protection at 1300° C. for 4 h. The obtained sample was collected to obtain a hard carbon material.

[0032] Example 2

[0033] Preparation of hard carbon negative electrode material using coconut shell as raw material includes the following steps:

[0034] (1) The coconut shell precursor was washed with water to remove excess impurities, filtered and dried at 60°C, and the dried biomass was pre-carbonized to obtain a biomass precursor; the pre-carbonization temperature was 200°C and the time was 4 hours.

[0035] (2) Crush the coconut shell precursor. After crushing, add the precursor powder into a ball mill at a speed of 300 rpm for 4 h. The ball-milled sample is sieved through a 200-mesh sieve and collected.

[0036] (3) 1.5 g of PEG-2000 was heated to 60° C. in a constant temperature heating furnace until it melted, and 3 g of the sieved precursor from step (2) was added in small amounts and multiple times, gradually processing it into a black paste-like mobile phase.

[0037] (4) Transfer the mobile phase onto filter paper, filter at 90°C to remove uncoated PEG-2000, and cool to a solid state.

[0038] (5) The precursor treated in step (4) was placed in a high-temperature vacuum furnace under nitrogen protection at 1300° C. for 4 h. The obtained sample was collected to obtain a hard carbon material.

[0039] Example 3

[0040] Preparation of hard carbon negative electrode material using coconut shell as raw material includes the following steps:

[0041] (1) The coconut shell precursor was washed with water to remove excess impurities, filtered and dried at 60°C, and the dried biomass was pre-carbonized to obtain a biomass precursor; the pre-carbonization temperature was 300°C and the time was 12 hours.

[0042] (2) Grind the coconut shell precursor. After grinding, add the precursor powder into a ball mill, mill at a speed of 300 pm for 4 h, and sieve the milled sample through a 300-mesh sieve before collecting.

[0043] (3) 1 g of PEG-1000 was heated to 40° C. in a constant temperature heating furnace until it melted, and 3 g of the sieved precursor from step (2) was added in small amounts and multiple times, gradually processing it into a black paste-like mobile phase.

[0044] (4) Transfer the mobile phase onto filter paper to remove uncoated PEG-1000 and cool to a solid state.

[0045] (5) The precursor treated in step (4) is placed in a high-temperature vacuum furnace under nitrogen protection at 1800°C for 2 hours. The obtained sample is collected to obtain a hard carbon material.

[0046] Comparative Example 1

[0047] Preparation of hard carbon material HC from coconut shell

[0048] (1) The coconut shell precursor was washed with water to remove excess impurities, filtered and dried at 60°C, and the dried biomass was pre-carbonized to obtain a biomass precursor; the pre-carbonization temperature was 200°C and the time was 12 hours.

[0049] (2) The hard carbon precursor was placed in a high-temperature vacuum furnace under nitrogen protection at 1300°C for 4 hours. The obtained sample was collected to obtain a hard carbon material.

[0050] Example 4 Performance Test The testing method of the materials in the present invention is as follows:

[0051] 1. Prepare a slurry of the hard carbon anode material samples prepared in Example 1 and Example 2 with sodium carboxymethyl cellulose, styrene-butadiene rubber, and carbon black in a ratio of 8:0.5:0.5:1. Ball mill the mixture until uniform. Apply the slurry to copper foil using an automatic coating machine. Cut the active material-loaded copper foil into electrode pieces with a diameter of 12 mm. Store the slurry in a vacuum drying oven at 50°C for 8 hours.

[0052] 2. Combine the negative electrode and sodium foil to form a CR2032 button cell. Test under 0.1C constant current charge and discharge conditions.

[0053] 3. The hard carbon treated according to Comparative Example 1 was used as a control sample.

[0054] Depend on Figure 1 It can be seen that Example 1 has more closed-pore structures and more ordered carbon layer structures than Comparative Example 1.

[0055] Depend on Figure 2 It can be seen that compared with Comparative Example 1, Example 1 does not change the microstructure of the hard carbon and maintains the consistency of the structure.

[0056] Depend on Figure 3 As can be seen from Table 1, compared with Example 1, Example 2 and Comparative Example 1, Example 1 has higher specific capacity and first-cycle coulombic efficiency.

[0057] Table 1

[0058] HC (Comparative Example 1) HC-P2000 (Example 2) HC-P20000 (Example 1) Specific capacity (mAh / g) 274 331 389.7 First effect (%) 82.67 86.39 89.51 <![CDATA[True density (g / cm 3 )]]> 1.67 1.73 1.75

Claims

1. A method for preparing a hard carbon negative electrode material, characterized in that: The method comprises mixing a biomass precursor with a PEG raw material, heating the mixture, coating the biomass precursor with the PEG raw material, and carbonizing the mixture; the carbonization temperature is 1000-1800°C.

2. The preparation method according to claim 1, characterized in that The biomass precursor is coconut shell or bamboo charcoal; the PEG raw material includes PEG-800, PEG1000, PEG2000, PEG4000, PEG8000 or PEG20000.

3. The preparation method according to claim 1 or 2, characterized in that The method comprises the following steps: (1) The biomass precursor is crushed by ball mill and passed through a 200-600 mesh sieve; (2) The PEG raw material and the biomass precursor are mixed and heated to a paste-like mobile phase, so that the PEG raw material covers the biomass precursor; (3) Filter at 60-120°C to remove uncoated PEG-based raw materials and cool; (4) High temperature carbonization: 1000-1800℃ for 1-4h.

4. The preparation method according to claim 3, characterized in that The heating temperature in step (2) is 40-200°C.

5. The preparation method according to claim 3, characterized in that The filtration in step (3) is performed by filtering with filter paper.

6. The preparation method according to claim 3, characterized in that The mass ratio of the PEG raw material to the biomass precursor is 1:1-10.

7. The preparation method according to claim 3, characterized in that In the step (1), the biomass precursor is pre-carbonized before use, with the pre-carbonization temperature being 200-400° C. and the time being 4-12 hours.

8. A hard carbon negative electrode material, characterized in that The compound is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the preparation method according to claims 1 to 7 or the hard carbon negative electrode material according to claim 8 in the preparation of sodium ion batteries.

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