Preparation method of hard carbon negative electrode material, hard carbon negative electrode material and application thereof

Abstract

The application relates to the technical field of batteries, in particular to a preparation method of a hard carbon negative electrode material, the hard carbon negative electrode material and application thereof. The preparation method of the hard carbon negative electrode material comprises the following steps: first mixing treatment of urea, a copper source and water, drying treatment, to obtain first materials; heat treatment of the first materials, to obtain Cu quantum dots; second mixing treatment of the Cu quantum dots and a saccharide carbon source, and carbonization treatment. According to the method, the saccharide is used as a carbon source precursor, Cu quantum dots are introduced, hard carbon negative electrode material with large interlayer spacing and few defects is obtained through carbonization at a high temperature, and the hard carbon negative electrode material has good conductivity and high rate capacity.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a method for preparing a hard carbon anode material, the hard carbon anode material itself, and its applications. Background Technology

[0002] With the rapid development of the new energy industry, the market demand for lithium-ion batteries is increasing, creating an urgent need for alternatives. Sodium is widely distributed and inexpensive, making sodium-ion batteries a promising supplementary alternative to lithium-ion batteries and attracting the attention of researchers.

[0003] Sodium-ion batteries are a promising next-generation electrochemical energy storage technology, boasting advantages such as no resource limitations, low cost, and high safety. Furthermore, due to the low solvation effect of sodium ions, their low-temperature performance is highly anticipated. Hard carbon materials possess suitable plateau potentials, good structural stability, and excellent reversible capacity, making them the most commercially viable anode material for sodium-ion batteries. However, compared to graphite, hard carbon exhibits poor conductivity, resulting in a low sodium-ion diffusion coefficient in the low-potential plateau region, leading to lower rate performance that fails to meet the requirements for large-scale application of sodium-ion batteries. Improving the rate performance of hard carbon materials is one of the major bottlenecks that urgently need to be addressed for the commercialization of sodium-ion batteries.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] One objective of this invention is to provide a method for preparing a hard carbon anode material, thereby addressing the technical problems of low sodium ion diffusion coefficient and low rate performance in the low potential plateau region of existing hard carbon materials. The hard carbon anode material of this invention exhibits a large interlayer spacing, fewer defects, good electrical performance, and high capacity.

[0006] Another objective of this invention is to provide a hard carbon anode material that has the characteristics of large interlayer spacing, few defects, good electrical performance, and high capacity.

[0007] Another object of the present invention is to provide a negative electrode.

[0008] Another object of the present invention is to provide a battery.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] A method for preparing a hard carbon anode material includes the following steps:

[0011] Urea, copper source and water are first mixed and then dried to obtain the first material. The first material is then heat-treated to obtain Cu quantum dots.

[0012] The Cu quantum dots and the sugar carbon source are subjected to a second mixing treatment, followed by carbonization treatment.

[0013] In some embodiments, the carbohydrate carbon source includes at least one selected from glucose, sucrose, starch, cellulose, hemicellulose, maltose, and fructose.

[0014] In some embodiments, the mass ratio of the carbohydrate carbon source to the Cu quantum dots is 1:(0.01 to 0.1).

[0015] In some embodiments, the second mixing process is performed by ball milling; the ball milling speed is 200-500 r / min, and the ball milling time is 1-6 h.

[0016] In some embodiments, the carbonization temperature is 1350–1500°C, and the carbonization time is 2–6 hours.

[0017] In some embodiments, the atmosphere for the carbonization process is selected from at least one of Ar, N2, He, H2, and NH3.

[0018] In some embodiments, the heating rate of the carbonization treatment is 1–20 °C / min.

[0019] In some embodiments, the ratio of the amount of urea, the amount of copper source and the amount of water is (8-15):(250-300):(15-30) mL.

[0020] In some embodiments, the copper source includes CuCl2·2H2O.

[0021] In some implementations, the first mixing process takes 0.5 to 3 hours.

[0022] In some embodiments, the drying process is carried out at a temperature of 70–90°C.

[0023] In some embodiments, the heat treatment temperature is 400–600°C, and the heat treatment time is 1–3 hours.

[0024] In some embodiments, the heating rate of the heat treatment is 15–30 °C / min.

[0025] A hard carbon anode material is prepared by the method described above.

[0026] In some embodiments, the interlayer spacing of the hard carbon anode material is 0.39–0.42 nm.

[0027] In some embodiments, the hard carbon anode material has a capacity of 240 mAh / g or higher at a current density of 1 A / g.

[0028] A negative electrode sheet includes a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector; the negative electrode material layer comprises a hard carbon negative electrode material, which is prepared by the method for preparing the hard carbon negative electrode material.

[0029] A battery comprising the aforementioned negative electrode.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The preparation method of the hard carbon anode material of the present invention uses sugar as a carbon source precursor. By introducing Cu quantum dots and carbonizing at a higher temperature, Cu quantum dots can adjust the hard carbon structure and conductivity, and anode material with excellent electrical performance can be obtained. As the temperature increases, the CC ratio of sp2 and sp3 hybrid orbitals of sugar carbon source changes, forming an ordered and disordered microcrystalline carbon structure with an extended graphite region (interlayer spacing) and fewer defects. As a sodium-ion battery anode material, it has a high rate capacity.

[0032] (2) The hard carbon anode material of the present invention has a large interlayer spacing, fewer defects, and good conductivity. The interlayer spacing of the hard carbon anode material is 0.39 to 0.42 nm, and the capacity of the hard carbon anode material is above 240 mAh / g at a current density of 1 A / g.

[0033] (3) The battery of the present invention has excellent rate capability and safety performance. Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0035] According to one aspect of the present invention, the present invention relates to a method for preparing a hard carbon anode material, comprising the following steps:

[0036] Urea, copper source, and water are first mixed and dried to obtain a first material. The first material is then heat-treated to obtain Cu quantum dots. The Cu quantum dots and carbon source are then mixed and carbonized.

[0037] This invention provides a method for preparing a hard carbon anode material. Using sugars as a carbon source precursor, Cu quantum dots are introduced and carbonized at a high temperature. The Cu quantum dots doping into the hard carbon material can adjust the hard carbon structure and conductivity, resulting in an anode material with good electrical performance. As the temperature increases, the C / C ratio of the sp2 and sp3 hybrid orbitals of the sugar carbon source changes, forming a microcrystalline carbon structure with ordered and disordered distribution. This structure has an extended graphite region (interlayer spacing) and fewer defects, making it a high-rate capacity as a sodium-ion battery anode material.

[0038] In some embodiments, the carbohydrate carbon source includes at least one selected from glucose, sucrose, starch, cellulose, hemicellulose, maltose, and fructose. The carbohydrate carbon source of the present invention may be selected from any one of the above-mentioned carbon sources, or a combination of at least two, such as a combination of glucose and sucrose, a combination of starch and cellulose, a combination of maltose, starch, and cellulose, a combination of maltose, fructose, and cellulose, etc.

[0039] In some embodiments, the carbohydrate carbon source is selected from maltose, starch and cellulose; the mass ratio of maltose, cellulose and starch is (1-2):(1-2):(6-8), for example, but not limited to 1:1:8, 2:1:7, 1:2:7, 2:2:6, or any range between the two.

[0040] In some embodiments, the mass ratio of the carbohydrate carbon source to the Cu quantum dots is 1:(0.01 to 0.1), for example, but not limited to 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, or 1:0.1, or any value within a range of both. In this invention, the appropriate mass ratio of the carbohydrate carbon source and Cu quantum dots allows for better synergistic effects, resulting in a larger interlayer spacing graphite domain and fewer defects in the anode material, accelerating the Na... + The embedding and diffusion between layers can improve the conductivity of hard carbon anode materials, improve the bulk sodium ion transport kinetics, and ultimately effectively improve the rate performance of the material under the synergistic effect of rapid bulk phase and kinetics.

[0041] In some embodiments, the second mixing process employs ball milling; the ball milling speed is 200–500 r / min, for example, but not limited to 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, etc., or any range between the two. The ball milling time is 1–6 h, for example, but not limited to 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, or 6 h, etc., or any range between the two. This invention uses suitable ball milling speed and time to better mix and composite the materials, ensuring subsequent carbonization treatment and guaranteeing the electrochemical performance of the final negative electrode material.

[0042] In some embodiments, the carbonization temperature is 1350–1500°C, for example, but not limited to, 1350°C, 1380°C, 1400°C, 1420°C, 1450°C, 1480°C, 1500°C, etc., or any value between any two of the above. The carbonization time is 2–6 hours, for example, but not limited to, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or 6 hours, etc., or any value between any two of the above. In some embodiments, the carbonization atmosphere is selected from at least one of Ar, N2, He, H2, and NH3, for example, a combination of H2 and NH3, a combination of Ar and N2, etc. The heating rate of the carbonization process is 1–20°C / min, for example, but not limited to, 1°C / min, 2°C / min, 5°C / min, 10°C / min, 15°C / min, or 20°C / min, etc., or any value between any two of the above. This invention employs a suitable combination of carbonization temperature and time to ensure the carbonization effect, resulting in a negative electrode material with a large interlayer graphite domain and fewer defects, thus exhibiting better conductivity.

[0043] In some embodiments, the ratio of urea, copper source, and water is (8-15):(250-300):(15-30) mL, for example, but not limited to, 8:250:15, 10:260:20, 12:270:25, 15:280:30, 15:300:30, or any range between the two. In some embodiments, the copper source includes CuCl2·2H2O. In some embodiments, the first mixing treatment time is 0.5-3 hours, for example, but not limited to, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, or any range between the two. In some embodiments, the drying treatment temperature is 70-90°C, for example, but not limited to, 70°C, 75°C, 80°C, 85°C, 90°C, or any range between the two. In some embodiments, the heat treatment temperature is 400–600°C, for example, but not limited to 400°C, 450°C, 500°C, 550°C, 600°C, or any value between the two. The heat treatment time is 1–3 hours, for example, but not limited to 1 hour, 1.5 hours, 2 hours, 3 hours, or any value between the two. The heating rate of the heat treatment is 15–30°C / min, for example, but not limited to 15°C / min, 20°C / min, 25°C / min, 30°C / min, or any value between the two. This invention uses the above-mentioned suitable conditions to prepare Cu quantum dots, thereby ensuring the performance of Cu quantum dots and further improving the structure and conductivity of hard carbon materials.

[0044] In a preferred embodiment, the preparation method of the hard carbon anode material includes the following steps:

[0045] (1) Urea, CuCl2·2H2O and water are subjected to a first mixing treatment. The ratio of urea, copper source and water is (8-15):(250-300):(15-30) mL. The first mixing treatment time is 0.5-3 h. Then, the mixture is dried at a temperature of 70-90 °C to obtain the first material. The first material is then subjected to heat treatment at a temperature of 400-600 °C for 1-3 h under a protective gas condition. The heating rate of the heat treatment is 15-30 °C / min to obtain Cu quantum dots.

[0046] (2) The Cu quantum dots and the sugar carbon source are subjected to a second mixing treatment, and the mass ratio of the sugar carbon source to the Cu quantum dots is 1:(0.01~0.1); the second mixing treatment is carried out by ball milling, the ball milling speed is 200~500r / min, and the ball milling time is 1~6h; then carbonization treatment is carried out, the carbonization treatment temperature is 1350~1500℃, the carbonization treatment time is 2~6h, the carbonization treatment atmosphere is selected from at least one of Ar, N2, He, H2 and NH3, and the heating rate of the carbonization treatment is 1~20℃ / min.

[0047] According to another aspect of the present invention, the present invention also relates to a hard carbon anode material, which is prepared by the method for preparing the hard carbon anode material.

[0048] The hard carbon anode material of the present invention has a large interlayer spacing, fewer defects, and good conductivity.

[0049] In some embodiments, the interlayer spacing of the hard carbon anode material is 0.39 to 0.42 nm, such as 0.39 nm, 0.395 nm, 0.4 nm, 0.402 nm, 0.405 nm, 0.408 nm, 0.41 nm, 0.42 nm, or any value between the two mentioned above.

[0050] In some embodiments, the hard carbon anode material has a capacity of 240 mAh / g or higher at a current density of 1 A / g, such as 241 mAh / g, 242 mAh / g, 243 mAh / g, 245 mAh / g, 247 mAh / g, 248 mAh / g, 249 mAh / g, 250 mAh / g, or any value between the two.

[0051] According to another aspect of the present invention, the present invention also relates to a negative electrode sheet, comprising a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector; the negative electrode material layer comprises a hard carbon negative electrode material, the hard carbon negative electrode material being prepared by the method for preparing the hard carbon negative electrode material. The negative electrode material layer of the negative electrode sheet of the present invention further comprises a conductive agent and a binder.

[0052] According to another aspect of the invention, the invention also relates to a battery comprising the aforementioned negative electrode.

[0053] The battery of this invention has excellent cycle performance, rate performance and safety performance.

[0054] The battery of the present invention includes the above-mentioned negative electrode, positive electrode, separator and electrolyte.

[0055] The following explanation, in conjunction with specific embodiments and comparative examples, further clarifies the situation.

[0056] Example 1

[0057] A method for preparing a hard carbon anode material includes the following steps:

[0058] (1) Preparation of Cu quantum dots: 10g of urea and 268mg of CuCl2·2H2O were dissolved in 20mL of distilled water and stirred for 2h, then dried at 80℃. The mixture was heated to 550℃ at a rate of 25℃ / min under an argon atmosphere and held for 2h. After cooling, Cu quantum dots (Cu@C3N4) were obtained.

[0059] (2) Mix 100g of sucrose and 2g of Cu@C3N4 by ball milling at 300r / min for 2h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0060] Example 2

[0061] A method for preparing a hard carbon anode material includes the following steps:

[0062] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0063] (2) Mix 100g of sucrose and 4g of Cu@C3N4 by ball milling at 350r / min for 2h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0064] Example 3

[0065] A method for preparing a hard carbon anode material includes the following steps:

[0066] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0067] (2) Mix 100g of sucrose and 6g of Cu@C3N4 by ball milling at a speed of 400r / min for 1.5h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0068] Example 4

[0069] A method for preparing a hard carbon anode material includes the following steps:

[0070] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0071] (2) Mix 100g of sucrose and 8g of Cu@C3N4 by ball milling at a speed of 400r / min for 2h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0072] Example 5

[0073] A method for preparing a hard carbon anode material includes the following steps:

[0074] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0075] (2) Mix 100g of sucrose and 10g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0076] Example 6

[0077] A method for preparing a hard carbon anode material includes the following steps:

[0078] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0079] (2) Mix 100g of fructose and 5g of Cu@C3N4 by ball milling at 350r / min for 1.5h. Place the mixed composite material in a tube furnace under a He atmosphere and heat it to 1400℃ at 2℃ / min, holding for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0080] Example 7

[0081] A method for preparing a hard carbon anode material includes the following steps:

[0082] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0083] (2) Mix 100g of potato starch and 5g of Cu@C3N4 by ball milling at a speed of 500r / min for 1.5h. Place the mixed composite material into a tube furnace under a He atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0084] Example 8

[0085] A method for preparing a hard carbon anode material includes the following steps:

[0086] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0087] (2) Mix 100g of corn starch and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material into a tube furnace under a He atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0088] Example 9

[0089] A method for preparing a hard carbon anode material includes the following steps:

[0090] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0091] (2) Mix 100g of glucose and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0092] Example 10

[0093] A method for preparing a hard carbon anode material includes the following steps:

[0094] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0095] (2) Mix 100g of cellulose and 5g of Cu@C3N4 by ball milling at a speed of 400r / min for 1.5h. Place the mixed composite material into a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0096] Example 11

[0097] A method for preparing a hard carbon anode material includes the following steps:

[0098] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0099] (2) Mix 100g of hemicellulose and 5g of Cu@C3N4 by ball milling at a speed of 350r / min for 1.5h. Place the mixed composite material in a tube furnace under N2 atmosphere, heat to 1400℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0100] Example 12

[0101] A method for preparing a hard carbon anode material includes the following steps:

[0102] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0103] (2) Mix 100g of cellulose and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material into a tube furnace under an Ar atmosphere, heat to 1400℃ at a rate of 1℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0104] Example 13

[0105] A method for preparing a hard carbon anode material includes the following steps:

[0106] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0107] (2) Mix 100g of cellulose and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material into a tube furnace under an Ar atmosphere, heat to 1400℃ at a rate of 5℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0108] Example 14

[0109] A method for preparing a hard carbon anode material includes the following steps:

[0110] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0111] (2) Mix 100g of cellulose and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material into a tube furnace under an Ar atmosphere, heat to 1450℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0112] Example 15

[0113] A method for preparing a hard carbon anode material includes the following steps:

[0114] (1) Cu quantum dots Cu@C3N4 were prepared according to the method in Example 1.

[0115] (2) Mix 100g of cellulose and 5g of Cu@C3N4 by ball milling at a speed of 450r / min for 1.5h. Place the mixed composite material into a tube furnace under an Ar atmosphere, heat to 1500℃ at a rate of 2℃ / min, and hold for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0116] Example 16

[0117] A method for preparing a hard carbon anode material includes the following steps:

[0118] (1) Preparation of Cu quantum dots: 10g of urea and 268mg of CuCl2·2H2O were dissolved in 20mL of distilled water and stirred for 2.5h, then dried at 70℃. The mixture was heated to 580℃ at a rate of 20℃ / min under an argon atmosphere and held for 1.5h. After cooling, Cu quantum dots (Cu@C3N4) were obtained.

[0119] (2) Mix 30g of cellulose, 70g of potato starch and 2g of Cu@C3N4 by ball milling at 500r / min for 1h. Place the mixed composite material in a tube furnace under a He atmosphere and heat to 1400℃ at 2℃ / min, holding for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0120] Example 17

[0121] A method for preparing a hard carbon anode material includes the following steps:

[0122] (1) Preparation of Cu quantum dots: 10g of urea and 268mg of CuCl2·2H2O were dissolved in 20mL of distilled water and stirred for 2.5h, then dried at 70℃. The mixture was heated to 530℃ at a rate of 20℃ / min under an argon atmosphere and held for 2.5h. After cooling, Cu quantum dots (Cu@C3N4) were obtained.

[0123] (2) Mix 20g maltose, 20g cellulose, 60g potato starch, and 2g Cu@C3N4 by ball milling at 500r / min for 1h. Place the mixed composite material in a tube furnace under a He atmosphere and heat to 1400℃ at 2℃ / min, holding for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0124] Example 18

[0125] A method for preparing a hard carbon anode material includes the following steps:

[0126] (1) Preparation of Cu quantum dots: 10g of urea and 268mg of CuCl2·2H2O were dissolved in 20mL of distilled water and stirred for 2.5h, then dried at 70℃. The mixture was heated to 530℃ at a rate of 20℃ / min under an argon atmosphere and held for 2.5h. After cooling, Cu quantum dots (Cu@C3N4) were obtained.

[0127] (2) Mix 5g maltose, 15g cellulose, 80g potato starch, and 2g Cu@C3N4 by ball milling at 500r / min for 1h. Place the mixed composite material in a tube furnace under a He atmosphere and heat to 1400℃ at 2℃ / min, holding for 3h. Cool to room temperature to obtain the hard carbon anode material.

[0128] Comparative Example 1

[0129] A method for preparing a hard carbon anode material includes the following steps:

[0130] 100g of sucrose was placed in a tube furnace under an Ar atmosphere, and the temperature was increased to 1400℃ at a rate of 2℃ / min and held for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0131] Comparative Example 2

[0132] A method for preparing a hard carbon anode material includes the following steps:

[0133] 100g of cellulose was placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 2℃ / min, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0134] Experimental Example

[0135] Sodium-ion batteries were prepared using the hard carbon anode materials of each embodiment and comparative example, specifically including:

[0136] A negative electrode sheet was prepared using hard carbon anode material. The preparation method was as follows: the prepared hard carbon anode material, conductive agent SP, binder CMC, SBR, and deionized water were mixed and stirred. The mass ratio of the carbon anode material, conductive agent SP, binder CMC, and SBR was 95%:1.5%:1.5%:2%, resulting in a negative electrode slurry with a solid content of 30%. The slurry was uniformly coated onto aluminum foil and dehydrated under vacuum at 100℃. The dried electrode sheet was then punched to obtain the negative electrode sheet. Sodium was used as the positive electrode. The electrolyte was 1 mol of NaFP6 dissolved in a solvent of EC, DEC, and DMC (volume ratio 1:1:1). The separator was Celgard 2400.

[0137] The interlayer spacing of the hard carbon anode materials in each embodiment and comparative example and the specific capacity of the battery during the first discharge at a current density of 1 A / g were tested.

[0138] Interlayer spacing d002: Bragg's equation 2dsinθ=nλ, where λ is the wavelength of X-rays. The diffraction series n can be any positive integer.

[0139] The test results are shown in Table 1.

[0140] Table 1 Test Results

[0141]

[0142]

[0143] As shown in Table 1, the hard carbon anode materials obtained by the methods of the various embodiments of the present invention have a large interlayer spacing of 0.401 nm and above; the batteries obtained by the anode materials of the embodiments have excellent rate performance, with a first discharge specific capacity of 241.2 mAh / g and above at 1 A / g.

[0144] The hard carbon anode materials obtained by the methods of Comparative Example 1 and Comparative Example 2 have relatively small interlayer spacing, and the resulting batteries have relatively poor specific capacity at the first discharge of 1A / g, which are 122.6 mAh / g and 124.8 mAh / g, respectively.

[0145] 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 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 the present invention.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, Includes the following steps: Urea, copper source and water are first mixed and then dried to obtain the first material. The first material is then heat-treated to obtain Cu quantum dots. The Cu quantum dots and sugar carbon source are subjected to a second mixing treatment, followed by carbonization treatment.

2. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The carbohydrate carbon source includes at least one of glucose, sucrose, starch, cellulose, hemicellulose, maltose, and fructose.

3. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The mass ratio of the carbohydrate carbon source to the Cu quantum dots is 1:(0.01~0.1).

4. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The second mixing process employs ball milling; the ball milling speed is 200~500 r / min, and the ball milling time is 1~6 h.

5. The method for preparing the hard carbon anode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The carbonization temperature is 1350~1500℃ and the carbonization time is 2~6h; (2) The atmosphere for the carbonization treatment is selected from at least one of Ar, N2, He, H2 and NH3; (3) The heating rate of the carbonization treatment is 1~20℃ / min.

6. The method for preparing the hard carbon anode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (7): (1) The ratio of the amount of urea, the amount of copper source and the amount of water is (8~15):(250~300):(15~30) mL; (2) The copper source includes CuCl2·2H2O; (3) The time for the first mixing treatment is 0.5~3h; (4) The drying temperature is 70~90℃; (5) The heat treatment temperature is 400~600℃, and the heat treatment time is 1~3h; (6) The heating rate of the heat treatment is 15~30℃ / min; (7) The heat treatment is carried out under protective gas conditions.

Images