Hard carbon negative electrode material, and preparation method therefor and use thereof
By preparing hard carbon anode materials with specific particle size ratios and combining them with amorphous carbon coating layers, the high cost and low performance problems of hard carbon anode materials have been solved, enabling battery applications with high energy density, excellent cycle performance, and rate performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NINGBO RONBAY LITHIUM BATTERY MATERIAL CO LTD
- Filing Date
- 2025-06-30
- Publication Date
- 2026-07-02
AI Technical Summary
Existing hard carbon anode materials suffer from high prices, insufficient production capacity, low compaction density, low tap density, and low capacity, which affect the energy density, cycle performance, and rate performance of batteries.
Hard carbon anode materials are prepared by using first and second hard carbon anode materials with different particle sizes in a specific volume ratio, combined with an amorphous carbon coating layer, and through hydrothermal reaction, crushing, low-temperature oxygen doping modification and high-temperature calcination, thereby improving compaction density and reducing side reactions.
It improves the energy density, cycle performance, and rate performance of batteries, reduces production costs, simplifies the manufacturing process, and is suitable for widespread application.
Smart Images
Figure CN2025106347_02072026_PF_FP_ABST
Abstract
Description
A hard carbon anode material, its preparation method and application
[0001] This application claims priority to Chinese Patent Application No. 202411951775.7, filed on December 26, 2024, entitled "A Hard Carbon Anode Material and Its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to a hard carbon anode material, its preparation method, and its application, belonging to the field of secondary battery technology. Background Technology
[0003] Sodium-ion batteries, with their advantages of abundant raw material reserves, low cost, and good low-temperature performance, are considered an effective complement to lithium-ion batteries, and have enormous application potential in electric two-wheelers, low-speed electric vehicles, and energy storage systems. Currently, the bottleneck in the industrialization of sodium-ion batteries lies mainly in the anode material. The mainstream anode material is hard carbon, but existing hard carbon anode materials suffer from high prices, insufficient production capacity, and low industry maturity.
[0004] Currently, the main method for preparing hard carbon anode materials is through biomass to reduce the cost and increase the production capacity of hard carbon anode materials. However, hard carbon anode materials prepared using biomass have problems such as low compaction density and low tap density, which affect the energy density of the battery. Furthermore, the capacity of biomass hard carbon is relatively low, resulting in poor cycle performance and rate performance of the battery. Summary of the Invention
[0005] This application provides a hard carbon anode material, its preparation method, and its application. The special composition and morphology of the hard carbon anode material enable it to improve the cycle performance, rate performance, and energy density of batteries when applied to batteries.
[0006] This application provides a method for preparing the above-mentioned hard carbon anode material. This method can prepare the above-mentioned hard carbon anode material. The preparation method is simple to operate and is suitable for widespread application.
[0007] This application provides a battery comprising the aforementioned hard carbon anode material, which has excellent cycle performance, rate performance, and energy density.
[0008] This application provides a hard carbon anode material, the hard carbon anode material comprising a hard carbon core and an amorphous carbon coating layer covering at least a portion of the surface of the hard carbon core; the hard carbon anode material comprises a first hard carbon anode material and a second hard carbon anode material, the first hard carbon anode material having an average particle size of 4-10 μm, and the second hard carbon anode material having an average particle size of 10.1-18 μm; the volume ratio of the first hard carbon anode material to the second hard carbon anode material is (0.4-1.2):1.
[0009] In the hard carbon anode material described above, the carbon interlayer spacing of the amorphous carbon coating layer is 0.35-0.37 nm; and / or, the thickness of the amorphous carbon coating layer is 1-20 nm.
[0010] The hard carbon anode material described above has a particle size distribution of 1-4.
[0011] The hard carbon anode material described above has a carbon layer spacing of [missing information].
[0012] The hard carbon anode material described above has a powder impedance of 8.0*10⁻⁶. - 3 ~7.0*10 -2 Ohm; and / or, the electronic conductivity of the hard carbon anode material is 10-90 S / cm.
[0013] The hard carbon anode material described above has a compaction density of 0.9-1.1 m³. 2 / g; and / or, the specific surface area of the hard carbon anode material is 0.5-7m². 2 / g; and / or, the content of metal impurities in the hard carbon anode material is below 100ppm; and / or, the ash content of the hard carbon anode material is ≤0.2%.
[0014] This application provides a method for preparing the hard carbon anode material as described above, comprising: subjecting a carbon source to a hydrothermal reaction, followed by pulverization to obtain a first spherical precursor and a second spherical precursor, wherein the first spherical precursor has a D 50 The diameter of the second spherical precursor is 4-10 μm. 50 The thickness is 10.1-18 μm; the first spherical precursor and the second spherical precursor are mixed to form a composite precursor, wherein the volume ratio of the first spherical precursor to the second spherical precursor in the composite precursor is (0.4-1.2):1; the composite precursor is mixed with a coating agent and then calcined to obtain a hard carbon anode material including an amorphous carbon coating layer; the calcination process is carried out at a temperature of 1100-1600℃ for 1-10 hours.
[0015] In the preparation method described above, the hydrothermal reaction is carried out at a temperature of 200-360°C for 12-48 hours; and / or the coating agent includes at least one of petroleum asphalt, coal tar pitch, β-resin, phenolic resin, and epoxy resin.
[0016] The preparation method described above further includes, before mixing the composite precursor with the coating agent, performing a low-temperature oxygen-doping modification treatment on the composite precursor.
[0017] As described above, after the low-temperature oxygen-doping modification treatment, the pH of the composite precursor is 3-4.5, and the oxygen content of the composite precursor is 15-30 wt%; and / or, in the low-temperature oxygen-doping modification treatment, the temperature is 150-350℃, and the time is 4-48h.
[0018] This application provides a battery comprising the hard carbon anode material as described above.
[0019] This application provides a hard carbon anode material, its preparation method, and its application, which has the following advantages:
[0020] The hard carbon anode material of this application includes a first hard carbon anode material and a second hard carbon anode material with different particle sizes in a specific volume ratio. When the hard carbon anode material is applied to a battery, the smaller particle size of the first hard carbon anode material can fill the voids of the larger particle size of the second hard carbon anode material, resulting in an anode sheet with high compaction density, thereby improving the energy density of the battery. Furthermore, the amorphous carbon coating layer of the hard carbon anode material can reduce the probability of side reactions between the hard carbon anode material and the electrolyte, effectively improving the cycle performance and rate performance of the battery.
[0021] The preparation method of the hard carbon anode material of this application can prepare the above-mentioned hard carbon anode material. The preparation method is simple to operate and suitable for widespread application. In addition, the preparation method adopts one-step high-temperature calcination, which can reduce the number of calcination times and reduce the production cost of hard carbon anode material.
[0022] The battery of this application includes the aforementioned hard carbon anode material. Based on the aforementioned hard carbon anode material, the battery has excellent cycle performance, rate performance, and energy density. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 is a SEM image of the hard carbon anode material in Example 1 of this application;
[0025] Figure 2 is a SEM image of the hard carbon anode material in Comparative Example 4 of this application;
[0026] Figure 3 is the XRD pattern of the hard carbon anode material of Example 1 of this application;
[0027] Figure 4 is the XRD pattern of the amorphous carbon coating layer in Example 4 of this application;
[0028] Figure 5 is the XRD pattern of the hard carbon anode material in Comparative Example 4 of this application;
[0029] Figure 6 is a first-cycle charge-discharge curve of the battery using the hard carbon anode material in Embodiment 1 of this application;
[0030] Figure 7 shows the first charge-discharge curve of the hard carbon anode material in Comparative Example 4 of this application.
[0031] Figure 8 is a high-resolution transmission electron microscope image of the amorphous coating layer in Example 4 of this application. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0033] The first aspect of this application provides a hard carbon anode material, which includes a hard carbon core and an amorphous carbon coating layer covering at least a portion of the surface of the hard carbon core.
[0034] The hard carbon anode material includes a first hard carbon anode material and a second hard carbon anode material. The average particle size of the first hard carbon anode material is 4-10 μm, and the average particle size of the second hard carbon anode material is 10.1-18 μm.
[0035] The volume ratio of the first hard carbon anode material to the second hard carbon anode material is (0.4-1.2):1.
[0036] In this application, the amorphous carbon coating layer has an amorphous hard carbon structure, which is a non-graphitized amorphous carbon layer structure. It can be understood that the amorphous carbon coating layer of this application can coat the entire surface of the hard carbon core, or it can coat only a portion of the surface of the hard carbon core. The hard carbon anode material of this application has a core-shell structure comprising a hard carbon core and an amorphous carbon coating layer from the inside out.
[0037] For example, the average particle size of the first hard carbon anode material with smaller particle size can be a range of 4, 6, 8, 10 μm or any combination thereof, and the average particle size of the second hard carbon anode material with larger particle size can be a range of 10.1, 12, 14, 15, 18 μm or any combination thereof.
[0038] The hard carbon anode material of this application includes a first hard carbon anode material with a smaller particle size and a second hard carbon anode material with a larger particle size, and the volume ratio of the first hard carbon anode material to the second hard carbon anode material is (0.4-1.2):1, for example, 0.4:1, 1:1, 1.2:1 or any combination thereof.
[0039] Understandably, when the densities (true densities) of the first hard carbon anode material and the second hard carbon anode material are close to or equal, their volume ratio can be approximated as or equal to their mass ratio.
[0040] In some embodiments, a high-resolution transmission electron microscope (TEM) can be used to test the hard carbon anode material and obtain a TEM image of the hard carbon anode material. Based on the TEM image, it can be determined whether the hard carbon anode material includes an amorphous coating layer. In addition, a solid-state electron microscope (SEM) can be performed on the hard carbon anode material to obtain an SEM image. Based on the SEM image, a first hard carbon anode material and a second hard carbon anode material can be identified. In the SEM image, the hard carbon anode material is divided into a first hard carbon anode material with a particle size less than or equal to 10 μm and a second hard carbon anode material with a particle size greater than 10 μm, using 10 μm as the dividing line. The average particle size of the first hard carbon anode material and the second hard carbon anode material are measured and calculated respectively. At the same time, the volumes of the first hard carbon anode material and the second hard carbon anode material can also be obtained, and the volume ratio between the two can be calculated.
[0041] The hard carbon anode material of this application includes a first hard carbon anode material and a second hard carbon anode material with different particle sizes in a specific volume (mass) ratio. When the hard carbon anode material is applied to a battery, the smaller particle size of the first hard carbon anode material can fill the voids of the larger particle size of the second hard carbon anode material, resulting in an anode sheet with high compaction density, thereby improving the energy density of the battery. Furthermore, the amorphous carbon coating layer of the hard carbon anode material can reduce the probability of side reactions between the hard carbon anode material and the electrolyte, effectively improving the cycle performance and rate performance of the battery.
[0042] In some embodiments of this application, the (002) carbon interlayer spacing of the amorphous carbon coating layer is 0.35-0.37 nm.
[0043] In some embodiments, the (002) carbon interlayer spacing of the amorphous carbon coating can be obtained from the XRD pattern of the hard carbon anode material. When the (002) carbon interlayer spacing of the amorphous carbon coating meets the above-mentioned range, the carbon interlayer spacing of the amorphous carbon coating is large, which can increase the sodium storage active sites and the reversible capacity of the hard carbon anode material.
[0044] In some embodiments of this application, when the thickness of the amorphous carbon coating layer is 1-20 nm, the amorphous carbon coating layer can better protect the hard carbon core while ensuring the capacity of the hard carbon anode material, avoiding side reactions between the hard carbon core and the electrolyte, and improving the cycle performance and rate performance of the battery. In some embodiments, the thickness of the amorphous coating layer can be obtained by TEM.
[0045] In some embodiments of this application, the particle size distribution of the hard carbon anode material is 1-4.
[0046] Particle size distribution SPAN = (D 90 -D 10 ) / D 50 When the particle size and volume distribution of the hard carbon anode material meets the above-mentioned range, the larger second hard carbon anode material and the smaller first hard carbon anode material can be better matched, thereby improving the energy density of the battery.
[0047] The inventors also discovered in their research that when the carbon interlayer spacing of the (002) hard carbon anode material is... In this case, hard carbon anode materials have more sodium storage active sites, which can further improve the reversible capacity of hard carbon anode materials. In some embodiments, the (002) carbon layer spacing of hard carbon anode materials can be obtained from the XRD pattern of hard carbon anode materials.
[0048] In some embodiments of this application, the powder impedance of the hard carbon anode material is 8.0*10. - 3 ~7.0*10 -2 Ohm.
[0049] In this application, the powder impedance of the hard carbon anode material refers to the powder impedance of the hard carbon anode material at 16-20 MPa. When the powder impedance of the hard carbon anode material meets the above range, the hard carbon anode material can further improve the rate performance of the battery.
[0050] Furthermore, when the electronic conductivity of the hard carbon anode material is 10-90 S / cm, the resulting battery exhibits superior rate performance.
[0051] In some embodiments of this application, the compaction density of the hard carbon anode material is 0.9-1.1 m³. 2 / g.
[0052] In this application, the compaction density of the hard carbon anode material refers to the compaction density of the hard carbon anode material under a pressure of 1T. When the compaction density of the hard carbon anode material meets the above-mentioned range, the energy density of the battery can be further improved.
[0053] The inventors also discovered that when the specific surface area of the hard carbon anode material is 0.5-7m², 2 When the hard carbon anode material is applied to batteries at a rate of / g, it can undergo more complete electrochemical reactions, thereby improving the battery's rate performance, energy density, and cycle performance.
[0054] Furthermore, the content of metal impurities in the hard carbon anode material is below 100 ppm; and / or the ash content of the hard carbon anode material is ≤0.2%, indicating that the hard carbon anode material of this application has high purity, which can further improve the rate performance, energy density, and cycle performance of the battery. In some embodiments, the total metal impurity content of the hard carbon anode material can be tested using inductively coupled plasma optical emission spectrometry (ICP-OES).
[0055] A second aspect of this application provides a method for preparing the above-mentioned hard carbon anode material, comprising:
[0056] After the carbon source undergoes a hydrothermal reaction, it is pulverized to obtain a first spherical precursor and a second spherical precursor. The first spherical precursor has a D... 50 The second spherical precursor has a diameter of 4-10 μm. 50 The range is 10.1-18 μm;
[0057] A composite precursor is formed by mixing a first spherical precursor and a second spherical precursor, wherein the volume ratio of the first spherical precursor to the second spherical precursor in the composite precursor is (0.4-1.2):1.
[0058] The composite precursor and the coating agent are mixed and then calcined to obtain a hard carbon anode material including an amorphous coating layer. The calcination process is carried out at a temperature of 1100-1600℃ for 1-10 hours.
[0059] Specifically, the carbon source undergoes a hydrothermal reaction to form a spherical precursor, which is then pulverized to obtain spherical precursors of different particle sizes. 50 The first spherical precursor with a diameter of 4-10 μm and D 50 A composite precursor is formed by mixing second spherical precursors with a particle size of 10.1-18 μm at a volume ratio of (0.4-1.2):1.
[0060] After mixing the composite precursor with the coating agent, the mixture is calcined at 1100-1600℃ for 1-10 hours. During the calcination process, the coating agent forms an amorphous hard carbon coating layer that coats the surface of the hard carbon core. The first spherical precursor fills part of the voids formed by the second spherical precursor, resulting in a hard carbon anode material with excellent spherical morphology.
[0061] The preparation method of the hard carbon anode material of this application can obtain the above-mentioned hard carbon anode material, and the preparation method adopts one-step high-temperature calcination, which can reduce the number of calcination times and reduce the production cost of hard carbon anode material.
[0062] This application does not specifically limit the carbon source; the carbon source can be any material commonly used in the art that can form carbon after calcination. In some embodiments, the carbon source can be a biomass carbon source; further, the carbon source can be at least one of glucose, starch, and sucrose. Since glucose, starch, and sucrose contain relatively few impurities, using glucose, starch, and sucrose as carbon sources not only yields hard carbon anode materials with low impurity content and low ash content, but also eliminates the need for additional, complex purification processes, avoiding impurity removal steps such as acid washing, alkali washing, and water washing, which helps reduce environmental pollution and lowers the production cost of hard carbon anode materials.
[0063] In some embodiments, the pulverization process can be air-jet grinding. After pulverization, the precursor is sieved to obtain spherical precursors with a particle size of 4-18 μm.
[0064] This application does not specifically limit the coating agent; the coating agent can be any material commonly used in the art that forms a carbon coating layer after calcination. For example, the coating agent can be at least one selected from petroleum asphalt, coal tar pitch, β-resin, phenolic resin, and epoxy resin. Furthermore, the amount of coating agent added can be 0.5-20% of the total mass of the composite precursor and the coating agent, thereby forming an amorphous carbon coating layer with a thickness of 1-20 nm.
[0065] In some embodiments of this application, when the temperature is 200-360°C and the time is 12-48h in the hydrothermal reaction, the carbon source can be more fully converted into a spherical precursor with less impurities, promoting the subsequent reaction and obtaining a hard carbon anode material with excellent comprehensive performance.
[0066] In some embodiments of this application, before mixing the composite precursor with the coating agent, the process further includes: subjecting the composite precursor to low-temperature oxygen-doping modification treatment.
[0067] Specifically, it also includes: performing low-temperature oxygen-doping modification on the composite precursor to obtain an oxygen-doped composite precursor, then mixing the oxygen-doped composite precursor with a coating agent and performing calcination treatment to obtain a hard carbon anode material including an amorphous coating layer.
[0068] In some embodiments, low-temperature oxygen doping modification treatment can be carried out in an oxygen-containing atmosphere, which can be at least one of air, oxygen, and oxygen-containing nitrogen.
[0069] Before mixing the composite precursor with the coating agent, this application also performs low-temperature oxygen doping modification on the composite precursor, which can hinder the graphitization of the composite precursor, increase the carbon layer spacing of the hard carbon anode material (002), and thus increase the sodium storage sites and reversible capacity of the hard carbon anode material.
[0070] Furthermore, after low-temperature oxygen doping modification, the pH of the composite precursor is 3-4.5, and the oxygen doping content of the composite precursor is 15-30 wt%. And / or, in the low-temperature oxygen doping modification, when the temperature is 150-350℃ and the time is 4-48h, the graphitization of the composite precursor can be further hindered, the carbon layer spacing of the hard carbon anode material (002) can be increased, and the sodium storage sites and reversible capacity of the hard carbon anode material can be increased.
[0071] In some embodiments, the hard carbon anode material can be further pulverized and sieved to obtain hard carbon anode material of the target size. Further, the mesh size of the sieve can be 300-500 mesh.
[0072] A third aspect of this application provides a battery comprising the hard carbon anode material of the first aspect.
[0073] In this application, hard carbon anode material can be prepared into a negative electrode sheet using methods commonly used in the art, and then the negative electrode sheet can be assembled with a positive electrode sheet commonly used in the art to obtain a battery.
[0074] The battery of this application, due to including the hard carbon anode material of the first aspect, has excellent rate performance, energy density and cycle performance.
[0075] The technical solution of this application will be further explained and illustrated below with reference to specific embodiments.
[0076] Example 1
[0077] Preparation of hard carbon anode materials
[0078] 1) After the biomass raw material undergoes a hydrothermal reaction, it is then subjected to gas crushing to obtain a first spherical precursor and a second spherical precursor. The first spherical precursor and the second spherical precursor are then mixed to form a composite precursor.
[0079] The biomass feedstock is glucose; the hydrothermal reaction is carried out at a temperature of 200℃ for 12 hours; the first spherical precursor D... 50 The second spherical precursor has a diameter of 6 μm. 50The thickness is 15 μm; in the composite precursor, the volume ratio (R) of the first spherical precursor to the second spherical precursor is 0.4:1;
[0080] 2) The composite precursor was subjected to low-temperature oxygen-doping modification treatment in an oxygen-containing atmosphere to obtain an oxygen-doped composite precursor.
[0081] The oxygen-containing atmosphere was air; the pH of the oxygen-doped composite precursor was 3.6, and the oxygen doping content was 24% (obtained using EDS testing); the low-temperature oxygen doping modification treatment was carried out at a temperature of 300℃ for 8 hours.
[0082] 3) The composite precursor modified by low temperature oxygen doping and the coating agent are mixed to form a mixture, and calcined under nitrogen protection to obtain a hard carbon anode material including an amorphous carbon coating layer.
[0083] The coating agent is coal tar pitch; the mass percentage of the coating agent in the mixture is 5%; in the calcination treatment, the temperature is raised from room temperature to 1300℃ at a heating rate of 3℃ / min and held for 5h, and the thickness of the amorphous carbon coating layer is 20nm.
[0084] 4) The hard carbon anode material balls are crushed and passed through a 325-mesh sieve to obtain 325-mesh hard carbon anode material.
[0085] Example 2
[0086] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that in step 1), the volume ratio of the first spherical precursor to the second spherical precursor is 1:1; other conditions remain unchanged.
[0087] Example 3
[0088] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that in step 2), the temperature in the low-temperature oxygen doping modification treatment is 150°C; other conditions remain unchanged.
[0089] Example 4
[0090] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that in step 2), the temperature in the low-temperature oxygen doping modification treatment is 250°C.
[0091] In step 3), the coating agent in the mixture is β resin; other conditions remain unchanged.
[0092] Example 5
[0093] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that in step 3), the coating agent in the mixture is β resin and the mass percentage of the coating agent is 3%; other conditions remain unchanged.
[0094] Example 6
[0095] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that: in step 3), the coating agent in the mixture is β resin and the mass percentage of the coating agent is 3%; the calcination temperature is 1500℃; and other conditions remain unchanged.
[0096] Example 7
[0097] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that:
[0098] (excluding step 2);
[0099] In step 3), the composite precursor and the coating agent are mixed to form a mixture; other conditions remain unchanged.
[0100] Example 8
[0101] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that:
[0102] D of the first spherical precursor 50 The second spherical precursor has a diameter of 4 μm. 50 The thickness is 10.1 μm; in the composite precursor, the volume ratio (R) of the first spherical precursor to the second spherical precursor is 1.2:1; other conditions remain unchanged.
[0103] Example 9
[0104] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that:
[0105] D of the first spherical precursor 50 The second spherical precursor has a diameter of 10 μm. 50 The size is 18 μm; in the composite precursor, the volume ratio (R) of the first spherical precursor to the second spherical precursor is 0.8:1; other conditions remain unchanged.
[0106] Example 10
[0107] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that:
[0108] D of the first spherical precursor 50 The second spherical precursor has a diameter of 6 μm.50 The size is 12 μm; in the composite precursor, the volume ratio (R) of the first spherical precursor to the second spherical precursor is 1:1; other conditions remain unchanged.
[0109] Example 11
[0110] The preparation method of the hard carbon anode material in this embodiment is basically the same as that in Example 1, except that:
[0111] Step 2 is excluded, meaning the low-temperature oxygen doping modification treatment is not included; other conditions remain unchanged.
[0112] Comparative Example 1
[0113] The preparation method of the hard carbon anode material in this comparative example is basically the same as that in Example 1, except that:
[0114] In step 1), after the biomass feedstock undergoes a hydrothermal reaction, it is then subjected to gas-shearing to obtain D. 50 It is a spherical precursor with a diameter of 15 μm;
[0115] (excluding step 2);
[0116] In step 3), the spherical precursor is calcined under nitrogen protection to obtain hard carbon anode material.
[0117] Comparative Example 2
[0118] The preparation method of the hard carbon anode material in this comparative example is basically the same as that in Example 1, except that:
[0119] In step 1), after the biomass feedstock undergoes a hydrothermal reaction, it is then subjected to gas-shearing to obtain D. 50 It is a spherical precursor with a diameter of 15 μm;
[0120] In step 2), the spherical precursor is subjected to low-temperature oxygen doping modification treatment under an oxygen-containing atmosphere to obtain the spherical precursor after low-temperature oxygen doping modification treatment.
[0121] In step 3), the spherical precursor after low-temperature oxygen-doped modification is calcined under nitrogen protection to obtain hard carbon anode material.
[0122] Comparative Example 3
[0123] The preparation method of the hard carbon anode material in this comparative example is basically the same as that in Example 1, except that:
[0124] In step 1), after the biomass feedstock undergoes a hydrothermal reaction, it is then subjected to gas-shearing to obtain D. 50 It is a spherical precursor with a diameter of 15 μm.
[0125] Comparative Example 4
[0126] The preparation method of the hard carbon anode material in this comparative example is basically the same as that in Example 1, except that:
[0127] In step 3), no coating agent is added.
[0128] Test case
[0129] Batteries were fabricated using the hard carbon anode materials from the examples and comparative examples, specifically including:
[0130] 1) Preparation of negative electrode sheet
[0131] Hard carbon anode material, conductive carbon black, and sodium carboxymethyl cellulose were placed in a slurry mixer in a mass ratio of 80:10:10. Then, nitrogen-methylpyrrolidone solvent was added and mixed evenly to obtain anode slurry. The anode slurry was evenly coated on both surfaces of carbon-coated aluminum foil and dried in a vacuum drying oven at 100°C for 12 hours to obtain anode sheet.
[0132] 2) Battery manufacturing
[0133] The CR2032 battery was assembled using sodium metal as the counter electrode and the negative electrode sheet from step 1), glass fiber as the separator, and 1.5 mol / L sodium hexafluorophosphate (NaPF6) in dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) (volume ratio 2:1:2) as the electrolyte.
[0134] Performance testing
[0135] 1) SEM testing
[0136] SEM images of the hard carbon anode materials in Example 1 and Comparative Example 4 were obtained respectively. Figure 1 is the SEM image of the hard carbon anode material in Example 1 of this application; Figure 2 is the SEM image of the hard carbon anode material in Comparative Example 4 of this application. As can be seen from Figures 1 and 2, the hard carbon anode material in Example 1 has a coating layer. Furthermore, the average particle size of the hard carbon anode material was measured using a Nano Measurer 1.2 on the SEM images. The average particle size of the hard carbon in Example 1 in Figure 1 is 10.51 μm, and the average particle size of the hard carbon in Comparative Example 4 in Figure 2 is 10.70 μm.
[0137] 2) XRD testing
[0138] Using the calcination parameters in Example 4, the β resin was calcined under a nitrogen protective atmosphere to obtain an amorphous carbon coating layer with a thickness of 20 nm.
[0139] XRD patterns of the hard carbon anode material in Example 1, the amorphous carbon coating in Example 4, and the hard carbon anode material in Comparative Example 4 were obtained respectively.
[0140] Figure 3 is the XRD pattern of the hard carbon anode material in Example 1 of this application; Figure 4 is the XRD pattern of the amorphous carbon coating layer in Example 4 of this application; Figure 5 is the XRD pattern of the hard carbon anode material in Comparative Example 4 of this application. As can be seen from Figure 3, the hard carbon anode material in Example 1 of this application has two large bulge peaks (typical amorphous carbon characteristic peaks), and its (002) interplanar spacing d(002) is... As shown in Figure 4, an amorphous carbon coating layer was formed in Example 4, and the (002) interplanar spacing of the amorphous carbon coating layer was 0.35 nm. Combining Figures 3 and 4, it can be seen that in the preparation of the hard carbon anode material in Example 1, the coating agent, after high-temperature carbonization, forms a non-graphitized amorphous carbon layer structure, similar to the amorphous hard carbon structure. Therefore, the XRD pattern of the hard carbon anode material in Example 1 has no other characteristic peaks besides the two large bump peaks.
[0141] As shown in Figure 5, the X-ray diffraction pattern of the hard carbon anode material in Comparative Example 4 of this application has two large bulge peaks, exhibiting typical characteristics of amorphous carbon. Its (002) interplanar spacing d(002) is...
[0142] 3) Powder impedance
[0143] The powder impedance was measured using the four-probe method according to the national standard GB / T 30835-2014.
[0144] 4) Electronic conductivity
[0145] The electronic conductivity was obtained by using the four-probe method, according to the national standard GB / T 30835-2014.
[0146] 5) BET
[0147] The specific surface area (BET) was obtained using Bestech 3H-2000BET-A, according to the national standard GB / T 19587-2017.
[0148] 6) Compacted density
[0149] The compacted powder density was obtained according to the national standard GB / T 24533-2019, using a pressure mold and tested under 1.0T pressure for 30s.
[0150] 7) Average particle size of the first hard carbon anode material A1, average particle size of the second hard carbon anode material A2, and SPAN
[0151] SEM testing was performed on the hard carbon anode material to obtain its SEM image. Based on the SEM image, the first and second hard carbon anode materials were identified. In the SEM image, the hard carbon anode material was divided into a first hard carbon anode material with a particle size less than or equal to 10 μm and a second hard carbon anode material with a particle size greater than 10 μm, using 10 μm as the dividing line. The average particle size of the first and second hard carbon anode materials was measured and calculated. The volumes of the first and second hard carbon anode materials were also obtained, and their volume ratio R was calculated.
[0152] The SPAN value is calculated from the particle size distribution data obtained by testing the overall hard carbon anode material using a Malvern 3000 laser particle size analyzer. SPAN = (D... 90 -D 10 ) / D 50 .
[0153] 8) Thickness of the amorphous carbon coating layer
[0154] The thickness of the amorphous carbon coating was measured using high-resolution transmission electron microscopy (HRTEM) images. Figure 8 shows an HRTEM image of the amorphous coating in Example 4, with a measured thickness of approximately 8 nm.
[0155] 9) The content of metallic impurities and ash content
[0156] The content of metallic impurities was determined by inductively coupled plasma optical emission spectrometry (ICP-OES); the ash content was determined according to the national standard GB / T 17664-1999.
[0157] 10) Charge and discharge performance
[0158] The button cell was subjected to constant current charge-discharge test at 25°C on the Newway multi-channel test system. Its voltage was 0-2.0V, the rate was 0.1C, and 1C = 300mA / g.
[0159] Figure 6 shows the first charge-discharge curve of the battery including the hard carbon anode material in Example 1 of this application; Figure 7 shows the first charge-discharge curve of the battery including the hard carbon anode material in Comparative Example 4 of this application. As can be seen from Figures 6 and 7, the hard carbon anode material in Example 1 has a high reversible specific capacity and first coulombic efficiency, with a reversible specific capacity of 330 mAh / g and a first coulombic efficiency of 93%.
[0160] Test results
[0161] Table 1
[0162] Table 2
[0163] Table 3
[0164] As can be seen from Tables 1, 2 and 3, the hard carbon anode material in the embodiments of this application has the characteristics of high compaction density, low impurities, high reversible specific capacity, and good cycle performance and rate performance of the battery.
[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A hard carbon anode material, characterized in that, The hard carbon anode material includes a hard carbon core and an amorphous carbon coating layer covering at least a portion of the surface of the hard carbon core; The hard carbon anode material includes a first hard carbon anode material and a second hard carbon anode material, wherein the average particle size of the first hard carbon anode material is 4-10 μm and the average particle size of the second hard carbon anode material is 10.1-18 μm. The volume ratio of the first hard carbon anode material to the second hard carbon anode material is (0.4-1.2):
1.
2. The hard carbon anode material according to claim 1, characterized in that, The carbon interlayer spacing of the amorphous carbon coating is 0.35-0.37 nm; and / or, The thickness of the amorphous carbon coating layer is 1-20 nm.
3. The hard carbon anode material according to claim 1 or 2, characterized in that, The particle size distribution of the hard carbon anode material is 1-4.
4. The hard carbon anode material according to any one of claims 1-3, characterized in that, The carbon layer spacing of the hard carbon anode material is:
5. The hard carbon anode material according to any one of claims 1-4, characterized in that, The powder impedance of the hard carbon anode material is 8.0*10. -3 ~7.0*10 -2 Ohm; and / or, The electronic conductivity of the hard carbon anode material is 10-90 S / cm.
6. The hard carbon anode material according to any one of claims 1-5, characterized in that, The compaction density of the hard carbon anode material is 0.9-1.1 m³. 2 / g; and / or, The specific surface area of the hard carbon anode material is 0.5-7 m². 2 / g; and / or, The content of metallic impurities in the hard carbon anode material is below 100 ppm; and / or the ash content of the hard carbon anode material is ≤0.2%.
7. A method for preparing the hard carbon anode material according to any one of claims 1-6, characterized in that, include: After the carbon source undergoes a hydrothermal reaction, it is pulverized to obtain a first spherical precursor and a second spherical precursor. The first spherical precursor has a D... 50 The diameter of the second spherical precursor is 4-10 μm. 50 The range is 10.1-18 μm; The first spherical precursor and the second spherical precursor are mixed to form a composite precursor, wherein the volume ratio of the first spherical precursor to the volume of the second spherical precursor in the composite precursor is (0.4-1.2):
1. The composite precursor is mixed with a coating agent and then calcined to obtain a hard carbon anode material including an amorphous carbon coating layer; the calcination process is carried out at a temperature of 1100-1600℃ for 1-10 hours.
8. The preparation method according to claim 7, characterized in that, In the hydrothermal reaction, the temperature is 200-360℃ and the time is 12-48h; And / or, the coating agent includes at least one of petroleum asphalt, coal tar pitch, β resin, phenolic resin, and epoxy resin.
9. The preparation method according to claim 7 or 8, characterized in that, Before the composite precursor is mixed with the coating agent, the method further includes: subjecting the composite precursor to low-temperature oxygen-doping modification treatment.
10. The preparation method according to claim 9, characterized in that, After the aforementioned low-temperature oxygen-doping modification treatment, the pH of the composite precursor is 3-4.5, and the oxygen doping content of the composite precursor is 15-30 wt%; and / or, In the aforementioned low-temperature oxygen-doping modification treatment, the temperature is 150-350℃ and the time is 4-48h.
11. A battery, characterized in that, Includes the hard carbon anode material as described in any one of claims 1-6.