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

Abstract

The invention discloses a preparation method of a hard carbon negative electrode material, the hard carbon negative electrode material and application of the hard carbon negative electrode material, the preparation method of the hard carbon negative electrode material comprises the following steps: placing coconut shell hard carbon in an ethanol-water solution of manganese salt, and carrying out solvothermal reaction to obtain a first precursor; and carbonizing the first precursor to obtain the hard carbon negative electrode material.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and in particular to a preparation method of a hard carbon negative electrode material, a hard carbon negative electrode material and applications thereof. Background Art

[0002] Sodium-ion batteries have a similar energy storage mechanism to lithium-ion batteries. Graphite materials that exhibit excellent electrochemical performance in lithium-ion batteries, when used in sodium-ion batteries, exhibit lower actual capacity because their interlayer spacing cannot match the larger sodium ions. Therefore, hard carbon with a larger interlayer spacing and higher sodium storage capacity has become the best negative electrode material for sodium-ion batteries. However, the existing hard carbon material preparation process is complicated, and the prepared hard carbon materials exhibit problems such as low first coulomb efficiency and poor rate performance. Summary of the invention

[0003] In view of this, the present application provides a hard carbon negative electrode material and a preparation method and application thereof that can solve the above-mentioned technical problems.

[0004] The first aspect of the present application provides a method for preparing a hard carbon negative electrode material, comprising the following steps:

[0005] The coconut shell hard carbon is placed in an ethanol-water solution of a manganese salt to perform a solvothermal reaction to obtain a first precursor;

[0006] The first precursor is carbonized to obtain a hard carbon negative electrode material.

[0007] In some embodiments, the manganese salt includes at least one of manganese chloride, manganese oxalate, or manganese acetate.

[0008] In some embodiments, the mass of the manganese salt is 3% to 30% of the mass of the coconut shell-based hard carbon.

[0009] In some embodiments, in the ethanol-water solution, the volume ratio of ethanol to water is 60:(0-3).

[0010] In some embodiments, the temperature of the solvothermal reaction is 120° C. to 150° C., and the time of the solvothermal reaction is 10 h to 15 h.

[0011] In some embodiments, the carbonization treatment includes at least one of the following conditions:

[0012] (1) The temperature of the carbonization treatment is 1000° C. to 1500° C., and after reaching the temperature of the carbonization treatment, the temperature is kept warm for 3 h to 5 h;

[0013] (2) The atmosphere of the carbonization treatment is an inert gas;

[0014] (3) The heating rate of the carbonization treatment is 4°C / min to 6°C / min.

[0015] In some embodiments, the inert gas is argon.

[0016] A second aspect of the present application provides a hard carbon negative electrode material, which is prepared by the above-mentioned preparation method.

[0017] A third aspect of the present application provides a negative electrode sheet, which includes the above-mentioned hard carbon negative electrode material.

[0018] A fourth aspect of the present application provides a battery, comprising the above-mentioned negative electrode sheet.

[0019] The present invention uses coconut shell hard carbon as a carbon source, uses an ethanol-water solution of manganese salt to perform a solvent thermal reaction on the coconut shell hard carbon, and can introduce the transition metal element manganese into the coconut shell hard carbon; and then undergoes a carbonization treatment to obtain a hard carbon negative electrode material. The method is simple and easy to implement, and the obtained hard carbon negative electrode material has excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 and 2 are X-ray diffraction patterns of the hard carbon negative electrode materials of Example 1 and Comparative Example 1 of the present application.

[0021] Figure 2 This is a schematic diagram of the first cycle charge and discharge performance of Example 1 of the present application.

[0022] Figure 3 This is a schematic diagram of the charge and discharge performance of cycles 0 to 100 of Example 1 of the present application.

[0023] Figure 4 This is a schematic diagram of the rate performance of Example 1 of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application. The reagents and materials described in the following embodiments can all be obtained from commercial sources.

[0025] The first aspect of the present application provides a method for preparing a hard carbon negative electrode material, comprising the following steps:

[0026] The coconut shell hard carbon is placed in an ethanol-water solution of a manganese salt to perform a solvothermal reaction to obtain a first precursor;

[0027] The first precursor is carbonized to obtain a hard carbon negative electrode material.

[0028] Hard carbon, by definition, refers to carbon that is difficult to graphitize, and is difficult to graphitize even at high temperatures above 2500°C. Currently, there are many precursors for synthesizing hard carbon, including polymers, biomass and fossil fuels; polymers include resins, cellulose, polyaniline, etc., biomass includes coconut shells, starch, sucrose, wood, straw, etc., and fossil fuels include coal and asphalt, etc. In this application, "coconut shell hard carbon" refers to hard carbon obtained using coconut shell as a precursor.

[0029] In some embodiments, the manganese salt comprises at least one of manganese chloride, manganese oxalate, or manganese acetate.

[0030] In some specific embodiments, the mass of the manganese salt is 3% to 30% of the mass of the coconut shell hard carbon. For example, the mass of the manganese salt is 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30% of the mass of the coconut shell hard carbon or within the range formed by any two of the above values. The mass ratio of the manganese salt to the mass of the coconut shell hard carbon within the above range is beneficial to improving the first discharge specific capacity and the first coulomb efficiency of the battery.

[0031] In some specific embodiments, in the ethanol-water solution, the volume ratio of ethanol to water is 60:(0-3), for example, the volume ratio of ethanol to water is 60mL:0mL, 60mL:0.5mL, 60mL:1mL, 60mL:1.5mL, 60mL:2mL, 60mL:2.5mL, 60mL:3mL or within the range of any two of the above values. The appropriate ratio of ethanol to water is conducive to the introduction of transition metal element manganese during the solvothermal reaction of coconut shell hard carbon, thereby improving the first discharge specific capacity and first coulombic efficiency of the battery.

[0032] In some specific embodiments, the temperature of the solvothermal reaction is 120°C to 150°C, and the time of the solvothermal reaction is 10h to 15h. For example, the temperature of the solvothermal reaction is 120°C, 125°C, 130°C, 135°C, 140°C, 150°C, or within a range consisting of any two of the above values. For example, the time of the solvothermal reaction is 10h, 11h, 12h, 13h, 14h, 15h, or within a range consisting of any two of the above values. Suitable solvothermal reaction temperature and time can ensure the effective introduction of transition metal elements.

[0033] In some specific embodiments, after the solvothermal reaction step, a drying process is further included, and the drying process temperature is 80° C. to 100° C., for example, 80° C., 85° C., 90° C., 95° C., 100° C. or in a range consisting of any two of the above values. The drying process is used to remove moisture from the material.

[0034] In some specific embodiments, the temperature of the carbonization treatment is 1000° C. to 1500° C. For example, the temperature of the carbonization treatment is 1000° C., 1100° C., 1200° C., 1300, 1400, 1500° C. or in a range consisting of any two of the above values.

[0035] In some specific embodiments, the carbonization temperature is reached and then the temperature is kept warm for 3 to 5 hours. For example, the carbonization temperature is kept warm for 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or within a range consisting of any two of the above values.

[0036] In some specific embodiments, the heating rate of the carbonization treatment is 4-6°C / min, such as 4°C / min, 5°C / min, 6°C / min, or within the range consisting of any two of the above values.

[0037] By matching the above-mentioned suitable carbonization treatment temperature, heating rate and holding time, the high specific capacity and high first coulombic efficiency of the hard carbon negative electrode material are ensured.

[0038] In some specific embodiments, after the first precursor is carbonized, the first precursor is further cooled to room temperature.

[0039] The second aspect of the present application provides a hard carbon negative electrode material prepared by the above-mentioned preparation method.

[0040] The third aspect of the present application provides a negative electrode sheet comprising the hard carbon negative electrode material. The negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer contains the hard carbon negative electrode material.

[0041] The fourth aspect of the present application provides a battery comprising the above-mentioned negative electrode sheet, the battery also comprising a positive electrode sheet, a separator and an electrolyte. The battery may be a sodium ion battery.

[0042] The technical solution of the present application is further explained below in conjunction with specific implementation methods.

[0043] Example 1

[0044] A method for preparing a hard carbon negative electrode material comprises the following steps:

[0045] 700 mg of dried coconut shell hard carbon was placed in an ethanol-water solution of manganese chloride, wherein the amount of manganese chloride was 70 mg, the volume of ethanol was 60 mL, and the volume of water was 1 mL. Solvothermal reaction was carried out at 150°C for 12 hours. After the reaction was completed, drying was carried out at 90°C to obtain the first precursor.

[0046] The first precursor was placed in a tubular furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, then kept warm for 2 hours, and then heated to 1350°C at a rate of 5°C / min in an argon atmosphere and kept warm for 4 hours.

[0047] After cooling to room temperature, the hard carbon negative electrode material can be obtained.

[0048] Example 2

[0049] A method for preparing a hard carbon negative electrode material comprises the following steps:

[0050] 700 mg of dried coconut shell hard carbon was placed in an ethanol-water solution of manganese chloride, wherein the amount of manganese chloride was 21 mg, the volume of ethanol was 60 mL, and the volume of water was 1 mL. Solvothermal reaction was carried out at 150°C for 12 hours. After the reaction was completed, drying was carried out at 90°C to obtain the first precursor.

[0051] The first precursor was placed in a tubular furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, then kept warm for 2 hours, and then heated to 1350°C at a rate of 5°C / min in an argon atmosphere and kept warm for 4 hours.

[0052] After cooling to room temperature, the hard carbon negative electrode material can be obtained.

[0053] Example 3

[0054] A method for preparing a hard carbon negative electrode material comprises the following steps:

[0055] 700 mg of dried coconut shell hard carbon was placed in an ethanol-water solution of manganese chloride, wherein the amount of manganese chloride was 140 mg, the volume of ethanol was 60 mL, and the volume of water was 1 mL. Solvothermal reaction was carried out at 150°C for 12 hours. After the reaction was completed, drying was carried out at 90°C to obtain the first precursor.

[0056] The first precursor was placed in a tubular furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, then kept warm for 2 hours, and then heated to 1350°C at a rate of 5°C / min in an argon atmosphere and kept warm for 4 hours.

[0057] After cooling to room temperature, the hard carbon negative electrode material can be obtained.

[0058] Example 4

[0059] A method for preparing a hard carbon negative electrode material comprises the following steps:

[0060] 700 mg of dried coconut shell hard carbon was placed in an ethanol-water solution of manganese acetate, wherein the amount of manganese acetate was 210 mg, the volume of ethanol was 60 mL, and the volume of water was 1 mL. Solvothermal reaction was carried out at 150°C for 12 hours. After the reaction was completed, it was dried at 90°C to obtain the first precursor.

[0061] The first precursor was placed in a tubular furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, then kept warm for 2 hours, and then heated to 1000°C at a rate of 5°C / min in an argon atmosphere and kept warm for 4 hours.

[0062] After cooling to room temperature, the hard carbon negative electrode material can be obtained.

[0063] Example 5

[0064] A method for preparing a hard carbon negative electrode material comprises the following steps:

[0065] 700 mg of dried coconut shell hard carbon was placed in an ethanol-water solution of manganese oxalate, wherein the amount of manganese oxalate was 210 mg, the volume of ethanol was 60 mL, and the volume of water was 1 mL. Solvothermal reaction was carried out at 150°C for 12 hours. After the reaction was completed, it was dried at 90°C to obtain the first precursor.

[0066] The first precursor was placed in a tubular furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, and then kept warm for 2 hours. The temperature was then raised to 1500°C at a rate of 5°C / min in an argon atmosphere and kept warm for 4 hours.

[0067] After cooling to room temperature, the hard carbon negative electrode material can be obtained.

[0068] Example 6

[0069] The only difference between Example 6 and Example 1 is that the amount of manganese chloride used is 7 mg, that is, the mass of manganese chloride is 1% of the mass of coconut shell hard carbon, and the rest of the preparation method and steps are the same as Example 1.

[0070] Example 7

[0071] The only difference between Example 7 and Example 1 is that the amount of manganese chloride used is 280 mg, that is, the mass of manganese chloride is 40% of the mass of coconut shell hard carbon, and the rest of the preparation method and steps are the same as Example 1.

[0072] Comparative Example 1

[0073] The same coconut shell hard carbon as in Example 1 was obtained without any treatment.

[0074] Comparative Example 2

[0075] 700 mg of coconut shell hard carbon as in Example 1 was placed in a tube furnace in an argon atmosphere, heated to 400°C at a rate of 5°C / min, then kept at that temperature for 2 hours, and then heated to 1350°C at a rate of 5°C / min in an argon atmosphere and kept at that temperature for 4 hours. The mixture was cooled to room temperature to obtain a negative electrode material.

[0076] The hard carbon negative electrode material of Example 1 and the coconut shell hard carbon of Comparative Example 1 were placed in the same X-ray diffraction analyzer, and the X-ray diffraction patterns of the two were obtained as shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the coconut shell hard carbon modified by manganese salt does not destroy the original properties of the coconut shell hard carbon.

[0077] The negative electrode materials of each embodiment and comparative example were prepared into batteries according to the following methods, specifically including:

[0078] The negative electrode materials prepared in each embodiment or comparative example were respectively used as active materials and mixed with a binder, sodium alginate, and a conductive agent, acetylene black, in a mass ratio of 80:10:10. Deionized water was added to prepare a negative electrode slurry. The negative electrode slurry was evenly coated on an aluminum foil current collector with a coating thickness of 50±1 μm. After vacuum drying, a circular electrode sheet with a diameter of 12 mm was prepared.

[0079] Sodium metal sheet was used as the positive electrode and the electrolyte was 1.5M NaFP 6 Dissolved in a mixed solution of ethylene carbonate, dimethylcarbonamide and ethyl methyl carbonate, wherein the volume ratio of ethylene carbonate, dimethylcarbonamide and ethyl methyl carbonate is 1:2:2; assembled sodium ion half-cells in a glove box containing argon, sealed with a button cell sealer, and allowed to stand at room temperature for 10 hours after being taken out of the glove box.

[0080] The battery test was conducted using a Xinwei battery test system. The test method used constant current and constant voltage discharge and constant current charging. The charge and discharge test was conducted at a current density of 60 mAh / g. The test voltage range was 0.01-2.0 V. The first cycle electrochemical performance of the half-cell corresponding to the hard carbon negative electrode material of Example 1 is shown in Figure 2 As shown, Figure 2 It shows that the specific capacity of the half-cell corresponding to the hard carbon negative electrode material of Example 1 can reach 396.1 mAh / g in the first charge and discharge. Figure 3 As shown, the half-cell corresponding to the hard carbon negative electrode material of Example 1 was subjected to a cycle test, and the capacity retention rate of the discharge after 100 cycles was as high as 93%, wherein the capacity retention rate after 100 cycles was calculated as the ratio of the specific capacity at the 100th cycle to the specific capacity at the second cycle.

[0081] The rate performance of the half-cell corresponding to the hard carbon negative electrode material prepared in Example 1 was tested using a LAND CT200 1A tester. Specifically, the discharge specific capacity of the battery was obtained by testing at current densities of 60 mA / g, 150 mA / g, 300 mA / g, 600 mA / g, 1.5 A / g and 3 A / g in the voltage range of 0.01 to 2 V, as shown in the attached figure. Figure 4 As shown, it exhibits good rate performance.

[0082] The first discharge specific capacity and first coulombic efficiency of each half-cell at a current density of 60 mA / g are shown in Table 1.

[0083] Table 1.

[0084]

[0085] It can be seen from Table 1 that compared with Comparative Examples 1 and 2, the present application uses coconut shell hard carbon as the carbon source, adopts an ethanol-water solution of manganese salt to perform a solvent thermal reaction on the hard carbon, and then performs a high-temperature carbonization treatment. The obtained hard carbon negative electrode material has both high first discharge specific capacity and high first coulombic efficiency. At a current density of 60mA / g, the capacity reaches 396mAh / g, and the first coulombic efficiency reaches 86.0%.

[0086] The coconut shell hard carbon of Comparative Example 1 was not subjected to solvent thermal reaction treatment with an ethanol-water solution of manganese salt, and was not subjected to high-temperature carbonization. The first discharge specific capacity and the first coulombic efficiency of the half-cell prepared by the obtained hard carbon material were significantly reduced. Comparative Example 2 was not subjected to solvent thermal reaction treatment with an ethanol-water solution of manganese salt, and the first discharge specific capacity and the first coulombic efficiency of the half-cell prepared by the obtained hard carbon material were both reduced.

[0087] Compared with Example 6 and Example 7, it can be seen that the ratio of hard carbon to manganese salt is within a suitable range, which is beneficial to improving the first discharge specific capacity and the first coulombic efficiency of the half-cell.

[0088] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application is described in detail with reference to the above implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a hard carbon negative electrode material, characterized in that: The following steps are involved: The coconut shell hard carbon is placed in an ethanol-water solution of a manganese salt to perform a solvothermal reaction to obtain a first precursor; The first precursor is carbonized to obtain a hard carbon negative electrode material.

2. The method for preparing a hard carbon negative electrode material according to claim 1, characterized in that: The manganese salt includes at least one of manganese chloride, manganese oxalate or manganese acetate.

3. The method for preparing the hard carbon negative electrode material according to claim 1, characterized in that: The mass of the manganese salt is 3% to 30% of the mass of the coconut shell hard carbon.

4. The method for preparing a hard carbon negative electrode material according to claim 1, characterized in that: In the ethanol-water solution, the volume ratio of ethanol to water is 60:(0-3).

5. The method for preparing a hard carbon negative electrode material according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 120° C. to 150° C., and the time of the solvent thermal reaction is 10 h to 15 h.

6. The method for preparing a hard carbon negative electrode material according to claim 1, characterized in that: The carbonization treatment includes at least one of the following conditions: (1) The temperature of the carbonization treatment is 1000° C. to 1500° C., and after reaching the temperature of the carbonization treatment, the temperature is kept warm for 3 h to 5 h; (2) The atmosphere of the carbonization treatment is an inert gas; (3) The heating rate of the carbonization treatment is 4°C / min to 6°C / min.

7. The method for preparing a hard carbon negative electrode material according to claim 6, characterized in that: The inert gas is argon.

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

9. A negative electrode sheet, characterized in that: The negative electrode sheet comprises the hard carbon negative electrode material according to claim 8.

10. A battery, characterized in that: The battery comprises the negative electrode sheet according to claim 9.

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