Hard carbon material and preparation method thereof, negative active material, negative pole piece and battery

Abstract

The invention provides a hard carbon material and a preparation method thereof, a negative electrode active material, a negative electrode pole piece and a battery, and the method for preparing the hard carbon material comprises the following steps: mixing active carbon and a carbon source, and carrying out a pyrolytic reaction with the temperature in a reactor being 400-700 DEG C and the pressure in the reactor being 1-50 MPa to obtain an intermediate product; the reactor is heated for the second time under the protective atmosphere to be calcined, the temperature in the reactor ranges from 800 DEG C to 2000 DEG C, cooling is carried out, the hard carbon material is obtained, and in a Raman spectrum of the hard carbon material, ID / IG ranges from 0.4 to 1.15. According to the method for preparing the hard carbon material, the activated carbon and the carbon source are subjected to the pyrolytic reaction under the high-pressure condition, the activated carbon and the carbon source can make full contact, mass transfer in the pyrolysis process is improved, structural rearrangement of carbon atoms in the activated carbon is promoted, defects in the activated carbon are reduced, and the first effect of the sodium ion battery is improved; the reduction of the defects can also improve the transmission rate of sodium ions, so that the rate capability of the sodium ion battery is improved.

Description

Technical Field

[0001] The invention relates to the field of batteries, and in particular to hard carbon materials and preparation methods thereof, negative electrode active materials, negative electrode plates and batteries. Background Art

[0002] As a new type of secondary battery, sodium-ion batteries have the advantages of abundant raw materials, low cost and high safety, and are considered to be an important candidate to replace lithium-ion batteries in the future. However, the development of sodium-ion batteries also faces some challenges, one of which is the lack of high-performance negative electrode materials. At present, the negative electrode materials of sodium-ion batteries mainly include metallic sodium, carbon materials, metal alloys, oxides, etc. Among them, carbon materials have received extensive attention and research due to their excellent chemical stability, electrical conductivity, cycle life and other characteristics. Carbon materials can be divided into soft carbon, hard carbon, graphite, carbon nanotubes, graphene, etc. according to their microstructure and morphology. Among them, hard carbon is an amorphous carbon material with large interlayer spacing, small specific surface area, abundant micropores and mesopores, etc. These characteristics enable hard carbon to effectively embed and extract sodium ions. However, there are many defects in hard carbon materials in related technologies, which will reduce the first efficiency and rate performance of sodium-ion batteries. Summary of the invention

[0003] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0004] The first aspect of the present application provides a method for preparing a hard carbon material, the method comprising: mixing activated carbon and a carbon source in a reactor, heating the reactor for a first time to perform a pyrolysis reaction, the temperature in the reactor being 400°C-700°C, and the pressure in the reactor being 1MPa-50MPa, to obtain an intermediate product; heating the reactor for a second time under a protective atmosphere to perform calcination, the temperature in the reactor being 800°C-2000°C, and cooling to obtain the hard carbon material, wherein in the Raman spectrum of the hard carbon material, I D / I G It is 0.4-1.15.

[0005] The method for preparing hard carbon materials proposed in this application is to make the decomposed carbon source uniformly nucleate and grow on the surface of activated carbon through high-pressure chemical vapor deposition, and the activated carbon and the carbon source are pyrolyzed under high pressure conditions, so that the activated carbon and the carbon source can be fully in contact, improve the mass transfer during the pyrolysis process, and the carbon source can be cracked and carbonized at a lower temperature, improve the utilization rate of the carbon source, make the reaction more uniform, and promote the structural rearrangement of carbon atoms inside the activated carbon, reduce the defects inside the activated carbon, reduce the content of sodium ions adsorbed or embedded in the defects, and improve the first efficiency of the sodium ion battery. The reduction of defects can also increase the transmission rate of sodium ions, thereby improving the rate performance of the sodium ion battery. At the same time, the hard carbon material proposed in this application has abundant active sites and can also improve the specific capacity of the sodium ion battery.

[0006] According to some embodiments of the present application, the specific surface area of ​​the activated carbon is 800 m 2 / g-2000m 2 / g.

[0007] According to some embodiments of the present application, the heating rate of the first heating is 1°C / min-10°C / min, and the pyrolysis reaction time is 1h-10h. Thus, controlling the decomposition of the carbon source can further improve product quality and performance.

[0008] According to some embodiments of the present application, the heating rate of the second heating is 1°C / min-10°C / min, and the calcination time is 1h-10h. Thus, the prepared hard carbon material has a high yield and is easy to operate and control.

[0009] According to some embodiments of the present application, the carbon source includes at least one of a gaseous carbon source and a liquid carbon source, the gaseous carbon source includes at least one of methane, acetylene, ethylene, propylene, and propane, and the liquid carbon source includes at least one of benzene, toluene, ethylbenzene, xylene, styrene, cyclohexane, n-hexane, n-octane, n-heptane, ethanol, acetonitrile, glycerol, perfluorohexane, and thiol.

[0010] According to some embodiments of the present application, the ratio of the volume of the gaseous carbon source in the reactor to the volume of the reactor is (1-20):1; and / or the ratio of the volume of the liquid carbon source in the reactor to the volume of the reactor is (0.1-0.8):1.

[0011] The second aspect of the present application provides a hard carbon material, which is prepared by the method provided by the first aspect of the present application. The pore volume of the hard carbon material is 0.05 cm 3 / g-0.15cm 3 / g, and the porosity of the hard carbon material is 20%-60%.

[0012] The third aspect of the present application provides a negative electrode active material, including the hard carbon material prepared by the method provided in the first aspect of the present application or the hard carbon material provided in the second aspect of the present application.

[0013] The fourth aspect of the present application provides a negative electrode plate, comprising the negative electrode active material provided in the third aspect of the present application.

[0014] The fifth aspect of the present application provides a battery, comprising the negative electrode plate provided in the fourth aspect of the present application, wherein the battery satisfies at least one of the following conditions: the first-cycle discharge specific capacity of the battery is 255mAh / g-355mAh / g; the first coulombic efficiency of the battery is 80%-90%; the 50C discharge specific capacity of the battery is 117mAh / g-197mAh / g; the battery has a 1000-cycle capacity retention rate of 80%-96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0016] Figure 1 A schematic flow chart of a method for preparing a hard carbon material according to an embodiment of the present application is shown.

[0017] Figure 2 The Raman spectrum of the hard carbon material prepared in Example 6 of the present application is shown.

[0018] Figure 3 The Raman spectrum of the hard carbon material prepared in Comparative Example 1 of the present application is shown.

[0019] Figure 4 The Raman spectrum of the hard carbon material prepared in Comparative Example 2 of the present application is shown. DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the document in this area or the product specification are used. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0021] The first aspect of the present application provides a method for preparing a hard carbon material, the method comprising: mixing activated carbon and a carbon source in a reactor, heating the reactor for a first time to perform a pyrolysis reaction, the temperature in the reactor being 400°C-700°C, and the pressure in the reactor being 1MPa-50MPa, to obtain an intermediate product; heating the reactor for a second time under a protective atmosphere to perform calcination, the temperature in the reactor being 800°C-2000°C, and cooling to obtain the hard carbon material, wherein in the Raman spectrum of the hard carbon material, I D / I G It is 0.4-1.15.

[0022] The method for preparing hard carbon materials proposed in this application is to make the decomposed carbon source uniformly nucleate and grow on the surface of activated carbon through high-pressure chemical vapor deposition, and the activated carbon and the carbon source are pyrolyzed under high pressure conditions, so that the activated carbon and the carbon source can be fully in contact, improve the mass transfer during the pyrolysis process, and the carbon source can be cracked and carbonized at a lower temperature, improve the utilization rate of the carbon source, make the reaction more uniform, and promote the structural rearrangement of carbon atoms inside the activated carbon, reduce the defects inside the activated carbon, reduce the content of sodium ions adsorbed or embedded in the defects, and improve the first efficiency of the sodium ion battery. The reduction of defects can also increase the transmission rate of sodium ions, thereby improving the rate performance of the sodium ion battery. At the same time, the hard carbon material proposed in this application has abundant active sites and can also improve the specific capacity of the sodium ion battery.

[0023] In the Raman spectrum of hard carbon materials, the D peak usually appears at 1300 cm -1 The D peak is near the carbon atom lattice, which represents the defects of the C atom lattice. In carbon materials, the appearance of the D peak indicates the existence of structural defects or disorder in the material. The intensity of the D peak (I D ) is proportional to the defect density in the material, so I D The stronger it is, the more defects there are in the hard carbon material.

[0024] The G peak usually appears at 1580 cm -1 Nearby, representing the C atom sp 2 The intensity of the G peak (I G ) and shape can reflect the topological structure of the sample.

[0025] I D / I G The larger it is, the more defects there are in the hard carbon material.

[0026] As an example, I D / I G It may be 0.4, 0.6, 0.8, 1, 1.15, etc., or may be a range consisting of any of the above values.

[0027] The method proposed in this application is described in detail below. Figure 1 , the method comprising:

[0028] S10: Mixing the activated carbon and the carbon source in a reactor, heating the reactor for the first time to perform a pyrolysis reaction, the temperature in the reactor is 400° C.-700° C., and the pressure in the reactor is 0-50 MPa, to obtain an intermediate product

[0029] According to some embodiments of the present application, activated carbon is placed in a stainless steel reactor, a carbon source is added, the stainless steel reactor is sealed, and the stainless steel reactor is heated for the first time to perform a pyrolysis reaction. The temperature in the reactor is 400°C-700°C, and the pressure in the reactor is 1MPa-50MPa to obtain an intermediate product.

[0030] During the pyrolysis reaction, high-pressure chemical vapor deposition can promote full contact between the carbon source and the activated carbon, improve mass transfer during the pyrolysis process, and allow the carbon source to be cracked and carbonized at a lower temperature, thereby improving the utilization rate of the carbon source, making the reaction more uniform, and promoting the structural rearrangement of carbon atoms inside the activated carbon, reducing defects inside the activated carbon, and reducing the content of sodium ions adsorbed or embedded in the defects, thereby improving the initial efficiency of the sodium ion battery. The reduction of defects can also increase the transmission rate of sodium ions, thereby improving the rate performance of the sodium ion battery.

[0031] As an example, the pressure in the reactor may be 1 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, etc., or may be a range consisting of any of the above values.

[0032] As an example, the temperature of the reactor during the pyrolysis process can be 400° C., 500° C., 600° C., 700° C., etc., or can be a range consisting of any of the above values.

[0033] According to some embodiments of the present application, the specific surface area of ​​the activated carbon can be 800m 2 / g-2000m 2 / g. For example, it can be 800m 2 / g、1000m 2 / g、1200m 2 / g、1400m 2 / g、1600m 2 / g、1800m 2 / g, 2000m 2 / g, etc., or may be within the range consisting of any of the above values.

[0034] According to some embodiments of the present application, the heating rate of the first heating is 1°C / min-10°C / min, and the time of the pyrolysis reaction is 1h-10h.

[0035] As an example, the heating rate of the first heating can be 1°C / min, 3°C / min, 5°C / min, 7°C / min, 9°C / min, 10°C / min, etc., or can be a range consisting of any of the above numerical values.

[0036] As an example, the pyrolysis reaction time can be 1 h, 3 h, 5 h, 7 h, 9 h, 10 h, etc., or can be a range consisting of any of the above numerical values.

[0037] Therefore, by making the heating rate and pyrolysis time of the first heating within the above range, the carbon source can be better decomposed, while the yield of the hard carbon material is increased, which facilitates the control of the pyrolysis reaction.

[0038] According to some embodiments of the present application, the carbon source includes at least one of a gaseous carbon source and a liquid carbon source, the gaseous carbon source includes at least one of methane, acetylene, ethylene, propylene, and propane, and the liquid carbon source includes at least one of benzene, toluene, ethylbenzene, xylene, styrene, cyclohexane, n-hexane, n-octane, n-heptane, ethanol, acetonitrile, glycerol, perfluorohexane, and thiol.

[0039] According to some embodiments of the present application, the ratio of the volume of the gaseous carbon source in the reactor to the volume of the reactor is (1-20): 1. For example, it can be 1:1, 5:1, 10:1, 15:1, 20:1, etc., or can be a range consisting of any of the above values.

[0040] According to some embodiments of the present application, the ratio of the volume of the liquid carbon source in the reactor to the volume of the reactor is (0.1-0.8): 1. For example, it can be 0.1: 1, 0.3: 1, 0.5: 1, 0.7: 1, 0.8: 1, etc., or can be a range consisting of any of the above values.

[0041] S20: heating the reactor for a second time under a protective atmosphere for calcination, wherein the temperature in the reactor is 800° C.-2000° C., and cooling to obtain the hard carbon material

[0042] According to some embodiments of the present application, the reactor is heated for a second time under a protective atmosphere for calcination, the temperature in the reactor is 800° C.-2000° C., and then cooled to room temperature to obtain the hard carbon material.

[0043] As an example, the protective atmosphere includes at least one of nitrogen and argon.

[0044] As an example, the temperature in the reactor can be 800°C, 1000°C, 1200°C, 1400°C, 1600°C, 1800°C, 2000°C, etc., or can be a range consisting of any of the above values.

[0045] The second aspect of the present application provides a hard carbon material, which is prepared by the method provided by the first aspect of the present application. The pore volume of the hard carbon material is 0.05 cm 3 / g-0.15cm 3 / g, and the porosity of the hard carbon material is 20%-60%.

[0046] The hard carbon material proposed in this application has fewer internal defects, which can reduce the content of sodium ions adsorbed or embedded in the defects, improve the initial efficiency of the sodium ion battery, and the reduction of defects can also increase the transmission rate of sodium ions, thereby improving the rate performance of the sodium ion battery. At the same time, the hard carbon material proposed in this application has abundant active sites and can also improve the specific capacity of the sodium ion battery.

[0047] In the present application, the pore volume of the hard carbon material is tested by N2 adsorption-desorption test, namely, BET specific surface area full pore test method.

[0048] The third aspect of the present application provides a negative electrode active material, including the hard carbon material prepared by the method provided in the first aspect of the present application or the hard carbon material provided in the second aspect of the present application.

[0049] The fourth aspect of the present application provides a negative electrode plate, comprising the negative electrode active material provided in the third aspect of the present application.

[0050] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes the hard carbon material proposed in this application.

[0051] As an example, the negative electrode active material layer may further include a binder, wherein the binder includes at least one of sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride.

[0052] The fifth aspect of the present application provides a battery, comprising the negative electrode plate provided in the fourth aspect of the present application. The battery provided in the present application has a high specific capacity and first efficiency, and has excellent cycle performance.

[0053] According to some embodiments of the present application, the first-cycle discharge specific capacity of the battery is 255mAh / g-355mAh / g.

[0054] According to some embodiments of the present application, the first coulombic efficiency of the battery is 80%-90%.

[0055] According to some embodiments of the present application, the discharge specific capacity of the battery 50C is 117 mAh / g-197 mAh / g.

[0056] According to some embodiments of the present application, the battery has a capacity retention rate of 80%-96% after 1,000 cycles.

[0057] The battery proposed in this application includes a sodium ion battery.

[0058] Sodium-ion batteries include a positive electrode, a negative electrode, a separator and an electrolyte.

[0059] The electrolyte includes an electrolyte salt and a solvent, the electrolyte salt includes at least one of NaPF6 and NaClO4, and the solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate.

[0060] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the document in this area or the product specification are used. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0061] Example 1

[0062] Weigh 5g of the specific surface area of ​​800m 2 / g of activated carbon was added into a steel kettle, and then 200mL of methane gas was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 1.5MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0063] Example 2

[0064] Weigh 5g of the specific surface area of ​​800m 2 / g of activated carbon was added into a steel kettle, and then 500mL of methane gas was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 3.7MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0065] Example 3

[0066] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 1000mL of methane gas was introduced. After the reactor was sealed, the temperature was raised to 700℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 7MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0067] Example 4

[0068] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 10mL of benzene was introduced. After the reactor was sealed, the temperature was raised to 400℃ at a heating rate of 5℃ / min, and kept for 3h. The reaction pressure was 8MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0069] Example 5

[0070] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 10mL of benzene was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept for 3h. The reaction pressure was 15MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0071] Example 6

[0072] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 20mL of benzene was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept for 3h. The reaction pressure was 27MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0073] Example 7

[0074] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 25mL of benzene was introduced. After the reactor was sealed, the temperature was raised to 700℃ at a heating rate of 5℃ / min, and kept for 3h. The reaction pressure was 40MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0075] Example 8

[0076] Weigh 5g of the specific surface area of ​​1500m 2 / g of activated carbon was added into a steel kettle, and then 25mL of benzene was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 35MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0077] Example 9

[0078] Weigh 5g of the specific surface area of ​​1500m 2 / g of activated carbon was added into a steel kettle, and then 25mL of xylene was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 26MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0079] Example 10

[0080] Weigh 5g of the specific surface area of ​​1800m 2 / g of activated carbon was added into a steel kettle, and then 25mL of xylene was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and the temperature was kept for 3h. The reaction pressure was 24MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0081] Embodiment 11

[0082] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 25mL of cyclohexane was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and the temperature was kept for 3h. The reaction pressure was 26MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0083] Example 12

[0084] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 25mL of n-octane was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and the temperature was kept for 3h. The reaction pressure was 27MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0085] Example 13

[0086] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 12mL of acetonitrile was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept for 3h. The reaction pressure was 26MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0087] Embodiment 14

[0088] Weigh 5g of the specific surface area of ​​1000m 2 / g of activated carbon was added into a steel kettle, and then 20mL of ethyl mercaptan was introduced. After the reactor was sealed, the temperature was raised to 600℃ at a heating rate of 5℃ / min, and kept warm for 3h. The reaction pressure was 26MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, the desired hard carbon material was obtained.

[0089] Comparative Example 1

[0090] Weigh 5g of the specific surface area of ​​1000m 2 / g activated carbon was added into a steel kettle without gas or organic carbon source. The reactor was sealed and heated to 600℃ at a heating rate of 5℃ / min for 3h. The reaction pressure was 0.3MPa. After cooling to room temperature, the reacted powder was heated to 1400℃ at a rate of 5℃ / min in a nitrogen atmosphere and calcined for 2h. After cooling to room temperature, a hard carbon material was obtained.

[0091] Comparative Example 2

[0092] Weigh 5g of the specific surface area of ​​1000m 2 / g activated carbon was directly heated to 1400℃ at a rate of 5℃ / min and calcined for 2h, and then cooled to room temperature to obtain hard carbon material.

[0093] Weigh 0.47g of the hard carbon material prepared in Examples 1 to 14, Comparative Examples 1 and 2 and 30mg of carboxymethyl cellulose, add appropriate amount of deionized water and use a planetary ball mill to ball mill for 2h, apply the milled slurry on the current collector, vacuum dry it at 80°C for 12h, and cut it into negative electrode sheets with a diameter of 12mm. Metallic sodium is used as the counter electrode and reference electrode, a glass fiber diaphragm is used as the diaphragm, a NaPF6 concentration of 1 mol / L is used as the electrolyte, and the solvent is a mixed solution of diethyl carbonate and ethylene carbonate (volume ratio of 1:1), and the button batteries are assembled in a glove box with an argon atmosphere.

[0094] The detailed test method of electrochemical performance is as follows:

[0095] 1. First cycle charging capacity test method

[0096] On the Xinwei test system, the assembled button battery is charged and discharged in a constant current charging and discharging mode. The voltage window is set to 0-2V, and the test current density is 0.1C (1C=100mA / g), that is, a current density of 10mA / g is used for the charge and discharge test. First, it is discharged to 0V at 0.1C, and then charged to 2V at 0.1C. The discharge capacity is recorded as C1, the charging capacity is recorded as C2, and the first coulomb efficiency is calculated as C2 / C1×100%.

[0097] 2. 50C discharge specific capacity test method

[0098] The test method is the same as above, the current density is 500mA / g. The first charge specific capacity is recorded as C3, and the charge specific capacity after 1000 cycles at a current density of 50C is recorded as C4. The corresponding capacity retention rate is C4 / C3×100%.

[0099] Raman spectroscopy is used to test the degree of defects in hard carbon materials.

[0100] Table 1

[0101]

[0102] As can be seen from Table 1, the use of the hard carbon material prepared in this application as the negative electrode active material of the battery can improve the first coulombic efficiency, first charge specific capacity and cycle life of the battery, and the 50C discharge specific capacity is also high, indicating that the battery has excellent rate performance. D / I G It is relatively small, indicating that the present application can reduce defects in hard carbon materials and improve the electrochemical properties of hard carbon materials by adopting high-pressure vapor chemical deposition.

[0103] Depend on Figure 2-Figure 4It can be seen from the comparison that the hard carbon material prepared by high pressure gas phase method in Example 6 of the present application has a significantly weakened D peak compared with Comparative Examples 1 and 2. D / I G Further decrease indicates the reduction of defects in hard carbon materials.

[0104] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing a hard carbon material, characterized in that: include: Mixing activated carbon and a carbon source in a reactor, heating the reactor for a first time to perform a pyrolysis reaction, wherein the temperature in the reactor is 400° C.-700° C. and the pressure in the reactor is 1 MPa-50 MPa, to obtain an intermediate product; The reactor is heated for a second time under a protective atmosphere for calcination, the temperature in the reactor is 800° C.-2000° C., and then cooled to obtain the hard carbon material. In the Raman spectrum of the hard carbon material, I D / I G It is 0.4-1.

15.

2. The method according to claim 1, characterized in that The specific surface area of ​​the activated carbon is 800m 2 / g-2000m 2 / g.

3. The method according to claim 1 or 2, characterized in that: The heating rate of the first heating is 1°C / min-10°C / min, and the pyrolysis reaction time is 1h-10h.

4. The method according to claim 3, characterized in that The heating rate of the second heating is 1°C / min-10°C / min, and the calcination time is 1h-10h.

5. The method according to claim 4, characterized in that The carbon source comprises at least one of a gaseous carbon source and a liquid carbon source, and the gaseous carbon source comprises at least one of methane, acetylene, ethylene, propylene, and propane; and / or The liquid carbon source includes at least one of benzene, toluene, ethylbenzene, xylene, styrene, cyclohexane, n-hexane, n-octane, n-heptane, ethanol, acetonitrile, glycerol, perfluorohexane, and mercaptan.

6. The method according to claim 5, characterized in that The ratio of the volume of the gaseous carbon source in the reactor to the volume of the reactor is (1-20):1; and / or The ratio of the volume of the liquid carbon source in the reactor to the volume of the reactor is (0.1-0.8):

1.

7. A hard carbon material, characterized in that: The hard carbon material is prepared by the method according to any one of claims 1 to 6, wherein the pore volume of the hard carbon material is 0.05 cm 3 / g-0.15cm 3 / g, and the porosity of the hard carbon material is 20%-60%.

8. A negative electrode active material, characterized in that: The hard carbon material comprises the hard carbon material prepared by the method according to any one of claims 1 to 6 or the hard carbon material provided by claim 7.

9. A negative electrode plate, characterized in that: Comprising the negative electrode active material according to claim 8.

10. A battery, characterized in that: The battery comprises the negative electrode sheet according to claim 9, and the battery satisfies at least one of the following conditions: The first cycle discharge specific capacity of the battery is 255mAh / g-355mAh / g; The first coulombic efficiency of the battery is 80%-90%; The discharge specific capacity of the battery 50C is 117mAh / g-197mAh / g; The battery has a capacity retention rate of 80% to 96% after 1,000 cycles.

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