Hard carbon negative electrode material, preparation method for hard carbon negative electrode material, and sodium-ion battery

Abstract

The present invention relates to a hard carbon negative electrode material, a preparation method for a hard carbon negative electrode material, and a sodium-ion battery. The hard carbon negative electrode material has a closed pore volume of 0.01 cm3 / g<Vcp<0.5 cm3 / g, and the following relationship is satisfied: Vcp=1 / ρtrue-1 / (2.26×0.3354 / d002act), wherein ρtrue is the true density of the hard carbon negative electrode material, d002act is the interlayer spacing of a 002 crystal plane measured by X-ray diffraction, and the true density of the hard carbon negative electrode material satisfies that: 0.5 g / cm3<ρtrue<2.26 g / cm3. By controlling temperature and pressure, the true density of the negative electrode material is directly controlled, and the proportion of a closed pore structure of the negative electrode material is indirectly controlled, so that the negative electrode material has high reversible specific capacity and high initial Coulombic efficiency, and an assembled sodium-ion battery has high energy density and excellent rate capability.

Description

Hard carbon negative electrode material, preparation method of hard carbon negative electrode material and sodium ion battery TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials and battery preparation, and particularly relates to a hard carbon negative electrode material, a preparation method of the hard carbon negative electrode material and a sodium ion battery prepared by using the hard carbon negative electrode material. BACKGROUND

[0002] Hard carbon is an amorphous carbon material, has a low platform potential, good structural stability and low cost, and is considered to be one of the most likely commercialized negative electrode materials in sodium ion batteries. However, hard carbon also has some shortcomings, such as a low first-cycle coulombic efficiency, a low specific capacity and poor rate performance.

[0003] In order to improve the sodium storage performance of hard carbon, a common method is to optimize the multi-scale structure and function of hard carbon by manufacturing closed pores, so as to improve the application performance of hard carbon in sodium ion batteries.

[0004] A Chinese patent application with the application number CN202311744491.6 discloses a negative electrode material and a sodium ion battery. The negative electrode material includes a carbon matrix with a three-dimensional porous structure, and a doping element loaded in the pores of the carbon matrix. The relationship between the doping element content and the gas adsorption amount of the negative electrode material is as follows: 0 < a / b x 10 3 ≤1; wherein a is the content of the doping element in the negative electrode material, in ppm; and b is the gas adsorption amount of the negative electrode material, in cm 3 / g. The doping element includes any one or a combination of at least two of P, S, N, O, H, B, Mg, Ti, Zn or Fe; and the carbon matrix includes hard carbon. By controlling the doping element content and the gas adsorption amount of the negative electrode material, the pore structure of the negative electrode material is adjusted, so that the negative electrode material has a high reversible specific capacity and a high first-cycle coulombic efficiency.

[0005] The method of the present application is different from the method of the above-mentioned publication. The present application directly controls the true density of the negative electrode material by controlling the temperature and the pressure, and indirectly controls the closed pore structure ratio of the negative electrode material, so that the negative electrode material has a high reversible specific capacity and a high first-cycle coulombic efficiency. SUMMARY

[0006] The present application provides a hard carbon negative electrode material, a preparation method of the hard carbon negative electrode material and a sodium ion battery. The true density of the negative electrode material is directly controlled by controlling the temperature and the atmosphere, and the closed pore structure ratio of the negative electrode material is indirectly controlled, so that the negative electrode material has a high reversible specific capacity and a high first-cycle coulombic efficiency, and the assembled sodium ion battery has a high energy density and excellent rate performance.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] A hard carbon negative electrode material, by regulating the reaction conditions under the set atmosphere, a three-dimensional carbon matrix with a large number of closed pores is formed; the reaction conditions include carbonization temperature and system pressure; the closed pore volume of the hard carbon negative electrode material is 0.01 cm 3 / g<V cp <0.5cm 3 / g; and satisfies V cp =1 / ρ 真 -1 / (2.26×0.3354 / d002 act ); wherein, ρ 真 is the true density of the hard carbon negative electrode material, unit g / cm 3 ; d002 act is the interlayer spacing of X-ray diffraction 002 lattice, unit nm; the true density of the hard carbon negative electrode material is 0.5 g / cm 3 <ρ 真 <2.26 g / cm 3 .

[0009] Further, the true density of the hard carbon negative electrode material ρ 真 =(0.75T / 620)ρ0-0.25(T / 1000)(P / P0) 0.3 ; wherein, ρ0 is the density of the initial carbon source; T is the carbonization temperature, and T=200-1500℃; P0 is the atmospheric pressure; P is the system pressure, and P=0.1-1.5 MPa.

[0010] Further, the set atmosphere is one or a combination of several of nitrogen, argon, helium, carbon dioxide, chlorine, water vapor, air.

[0011] Further, the hard carbon forming the three-dimensional carbon matrix is formed by high-temperature carbonization of an organic thermosetting precursor; the reaction conditions under the set atmosphere means that during the carbonization process of the organic thermosetting precursor, the pore structure and open / closed pore ratio of the carbonization product are adjusted by controlling the temperature curve, system pressure and system atmosphere, and then the true density of the carbonization product is controlled.

[0012] Further, the hard carbon includes one or more of pitch, cellulose, sucrose, glucose, phenolic resin, starch, coal, heavy oil.

[0013] Further, the X-ray diffraction pattern of the hard carbon negative electrode material has a characteristic peak specific to hard carbon in the range of 20°-30° and 35°-50°.

[0014] A preparation method of a hard carbon negative electrode material, comprising the following steps:

[0015] (1) crushing the carbon matrix raw material to a set particle size;

[0016] (2) mixing the carbon matrix raw material, and then pre-carbonizing the mixed carbon matrix raw material at a temperature of 200-1000 DEG C in an atmosphere of inert gas / air / carbon dioxide / water vapor;

[0017] (3) dispersing the pre-carbonized carbon matrix to a size of 3-20 microns to obtain a negative electrode material precursor;

[0018] (4) high-temperature carbonizing the negative electrode material precursor at a temperature of 1000-1800 DEG C, and in the process, precisely controlling the pore structure of different negative electrode material precursors by controlling the temperature, pressure and reaction atmosphere; and finally obtaining a hard carbon negative electrode material with a closed pore volume of 0.01 cm 3 / g cp <0.5 cm 3 / g.

[0019] Further, the carbon matrix raw material includes one or more of biomass and modified products thereof, coal and modified products thereof, pitch and modified products thereof, and resin and modified products thereof.

[0020] A sodium ion battery includes the hard carbon negative electrode material in the negative electrode of the sodium ion battery.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The present application mainly provides a hard carbon negative electrode material, a preparation method of the hard carbon negative electrode material, and a sodium ion battery. The carbon matrix of the hard carbon negative electrode material has a three-dimensional porous structure, and the true density of the negative electrode material is regulated by controlling the temperature and pressure. The relationship between the closed pore volume and the true density of the negative electrode material is as follows: V cp =1 / ρ 真 -1 / 2.26(d002 gr / d002 hard ), wherein d002 gr is the interlayer spacing of the graphite 002 lattice in X-ray diffraction, and d002 hard is the interlayer spacing of the hard carbon 002 lattice in X-ray diffraction. The characteristic pore range of the negative electrode material is the gas adsorption amount. When the closed pore volume and the true density satisfy the above relationship, the closed pores not only support the structure of the carbon material, but also form certain characteristic pores in the negative electrode material. In the charging and discharging process, sodium ions can form sodium clusters in the characteristic pores, thereby providing high specific capacity and affecting the intercalation and filling process of sodium ions, ultimately improving the reversible specific capacity and the first coulombic efficiency of the negative electrode material, and further making the assembled sodium ion battery have high energy density and excellent rate performance. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is an XRD diagram of the hard carbon negative electrode material prepared in Example 1 of the present application.

[0024] Figure 2 is an SEM diagram of the hard carbon negative electrode material prepared in Example 1 of the present application.

[0025] Figure 3 is a charge-discharge curve diagram of the hard carbon negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0026] The hard carbon negative electrode material according to the present application is formed by regulating the reaction conditions under a set atmosphere, to form a three-dimensional carbon matrix with a large number of closed pores; the reaction conditions include carbonization temperature and system pressure; the closed pore volume of the hard carbon negative electrode material is 0.01 cm 3 / g < V cp < 0.5 cm 3 / g; and satisfies V cp = 1 / ρ 真 - 1 / (2.26 x 0.3354 / d002 act ); wherein, ρ 真 is the true density of the hard carbon negative electrode material, in units of g / cm 3 ; d002 act is the interlayer distance of the X-ray diffraction 002 lattice, in units of nm; the true density of the hard carbon negative electrode material is 0.5 g / cm 3 < ρ 真 < 2.26 g / cm 3 .

[0027] Further, the true density ρ 真 of the hard carbon negative electrode material is ρ0-0.25(T / 1000)(P / P0) 0.3 ; wherein, ρ0is the density of the initial carbon source; T is the carbonization temperature, and T = 200-1500°C; P0is atmospheric pressure; P is the system pressure, and P = 0.1-1.5 MPa.

[0028] Further, the set atmosphere is one or a combination of several of nitrogen, argon, helium, carbon dioxide, chlorine, water vapor, and air.

[0029] Further, the hard carbon forming the three-dimensional carbon matrix is formed by high-temperature carbonization of an organic thermosetting precursor; the regulating of the reaction conditions under a set atmosphere refers to, during the carbonization process of the organic thermosetting precursor, adjusting the pore structure and open-closed pore ratio of the carbonization product by controlling the temperature rising curve, system pressure, and system atmosphere, to further control the true density of the carbonization product.

[0030] Further, the hard carbon includes one or more of pitch, cellulose, sucrose, glucose, phenolic resin, starch, coal, and heavy oil.

[0031] Further, the X-ray diffraction pattern of the hard carbon negative electrode material has characteristic peaks specific to hard carbon in the range of 20° to 30° and 35° to 50°.

[0032] The preparation method of the hard carbon negative electrode material comprises the following steps:

[0033] (1) crushing the carbon matrix raw material to a set particle size;

[0034] (2) mixing the carbon matrix raw material, and then pre-carbonizing at a temperature of 200 to 1000°C in an atmosphere of inert gas / air / carbon dioxide / water vapor;

[0035] (3) dispersing the pre-carbonized carbon matrix to 3 to 20 microns to obtain a negative electrode material precursor;

[0036] (4) high-temperature carbonizing the negative electrode material precursor at a temperature of 1000 to 1800°C, and in this process, precisely controlling the pore structure of different negative electrode material precursors by controlling the temperature, pressure, and reaction atmosphere; and finally obtaining a hard carbon negative electrode material with a closed pore volume of 0.01 cm 3 / g cp <0.5 cm 3 / g.

[0037] Further, the carbon matrix raw material comprises one or more of biomass and modified products thereof, coal and modified products thereof, pitch and modified products thereof, resin and modified products thereof.

[0038] The sodium ion battery comprises the hard carbon negative electrode material.

[0039] The hard carbon negative electrode material has a three-dimensional porous carbon matrix with a controllable closed pore structure, and the proportion of the closed pore volume of the hard carbon negative electrode material is: 0.5 cm 3 / g cp / cm OP+CP <1 cm 3 / g; in the formula, V cp is the closed pore volume of the hard carbon negative electrode material, and the unit is cm 3 / g; V OP+CP is the total pore volume of the sum of the open pores and the closed pores of the hard carbon negative electrode material, and the unit is cm 3 / g.

[0040] Further, the range of V cp is 0.01 to 0.5 cm 3 / g; and the range of V OP+CP is 0.01 to 2 cm 3 / g.

[0041] Preferably, the closed pore volume V cp satisfies: 0.1 cm 3 / g < V cp ≤ 0.5 cm 3 / g, for example, can be 0.1 cm 3 / g, 0.15 cm 3 / g, 0.2 cm 3 / g, 0.25 cm 3 / g or 0.3 cm 3 / g, etc., but is not limited to the listed values, and other unlisted values within the range are also applicable.

[0042] Generally, hard carbon is synthesized by high-temperature carbonization of organic thermosetting precursors such as cellulose, sucrose, glucose, phenolic resin, starch, coal, heavy oil, etc. During pyrolysis, the precursor carbon layer is prone to form a vortex layer and disordered microstructure graphite clusters composed of surface defects, nanopores or voids. In this process, sodium ions first appear in the defect sites of the inclined region hard carbon and are adsorbed (0.1-1 V vs Na / Na + ), and then sodium clusters are formed in the platform region (0-0.1 V vs Na / Na + ). The closed pores are mainly responsible for sodium storage in the low-pressure platform. Increasing the number of closed pores and the size of nanopores can maximize the capacity of the platform to generate hard carbon, and the number and proportion of closed pores are characterized and measured by the true density of the negative electrode material.

[0043] In the present application, the empirical relationship between the closed pore volume and the true density of the hard carbon negative electrode material is as follows: V cp = 1 / ρ 真 - 1 / (2.26 x 0.3354 / d002 act )

[0044] In the formula, ρ 真 is the true density of the hard carbon negative electrode material, with a unit of g / cm 3 .

[0045] In the present application, the true density ρ 真 of the hard carbon negative electrode material can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 or 2.2, etc.

[0046] During the carbonization process of the organic thermosetting precursor, molecular rearrangement and gas escape occur. By controlling the temperature rise curve, system pressure and system atmosphere, the present application adjusts the pore structure and open / closed pore ratio of the carbonization product, and further controls the true density of the carbonization product, i.e. ρ 真= (0.75T / 620) p0- 0.25 (T / 1000) (P / P0) 0.3 .

[0047] When the true density and the closed pore volume satisfy the relationship of the present application, the capacity and the coulombic efficiency of the negative electrode material can be improved. When the true density is lower than the limited range of the relationship, the characteristic pores will collapse due to the insufficient strength of the pore wall, thereby reducing the specific capacity; and when the true density is higher than the limited range of the relationship, no suitable characteristic pores will be generated, or the generated characteristic pores are insufficient, thereby reducing the specific capacity.

[0048] Preferably, the carbon matrix of the present application comprises hard carbon.

[0049] Preferably, as shown in Figure 1, the hard carbon negative electrode material of the present application has a characteristic peak in the range of 20°-30° in the X-ray diffraction (XRD) spectrum, and the half-peak width of the characteristic peak is 5-20, for example, it can be 5, 7, 10, 12, 15, 17 or 20, etc., but is not limited to the listed values, and other values not listed in this range are also applicable. The characteristic peak in the range of 20°-30° in the present application reflects the carbon layer spacing and the degree of interlayer order.

[0050] Preferably, the hard carbon negative electrode material of the present application has a characteristic peak in the range of 35°-50° in the X-ray diffraction spectrum, and the characteristic peak in the range of 35°-50° reflects the degree of carbon layer order and the grain size.

[0051] Preferably, the preparation method of the hard carbon negative electrode material of the present application is as follows:

[0052] (1) crushing the carbon matrix raw material to a set particle size;

[0053] (2) mixing the carbon matrix raw material, and then pre-carbonizing at a temperature of 200-600°C in an inert gas / air / carbon dioxide atmosphere;

[0054] (3) dispersing the pre-carbonized carbon matrix to 3-20 microns to obtain a negative electrode material precursor;

[0055] (4) high-temperature carbonizing the negative electrode material precursor at a temperature of 1000-1800°C to obtain the hard carbon negative electrode material.

[0056] When the preparation method of the hard carbon negative electrode material described above is used, the temperature, pressure and reaction atmosphere can be controlled to precisely control the pore structure of different negative electrode material precursors; the hard carbon negative electrode material obtained has a suitable pore size structure, and the closed pore volume is 0.01 cm 3 / g < V cp < 0.5 cm3 hard carbon negative electrode material.

[0057] Preferably, the carbon matrix raw material includes any one or a combination of two or more of biomass and modified products thereof, coal and modified products thereof, pitch and modified products thereof, resin and modified products thereof.

[0058] The application also provides a sodium ion battery, wherein the negative electrode of the sodium ion battery comprises the hard carbon negative electrode material.

[0059] The following examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0060] Example 1

[0061] A hard carbon negative electrode material is prepared in this example.

[0062] (1) The coal-based pitch is crushed to a particle size D50 less than 20 μm to obtain pitch powder;

[0063] (2) The pitch powder is heated to 900℃ at a speed of 0.5℃ / min in a mixed atmosphere of air and water vapor with an absolute humidity of 40% and a system pressure of 0.3 Mpa to obtain pre-carbonized powder;

[0064] (3) The pre-carbonized powder is dispersed to D50=6 μm to obtain a hard carbon negative electrode material precursor;

[0065] (4) The hard carbon negative electrode material precursor is subjected to high-temperature carbonization at a temperature of 1400℃ to obtain the hard carbon negative electrode material.

[0066] In this example, the hard carbon negative electrode material comprises a carbon matrix with a three-dimensional porous structure, the carbon matrix is hard carbon, and the true density of the hard carbon negative electrode material is 1.62 g / cm 3 .

[0067] In this example, the closed pore volume of the hard carbon negative electrode material is 0.185 cm 3 / g.

[0068] FIG. 1 shows the XRD pattern of the hard carbon negative electrode material in this example, which has a characteristic peak in the range of 20°-30°, the characteristic peak is a (002) peak, which reflects the carbon interlayer spacing and interlayer order degree, and d002 is 0.372 nm; it also has a characteristic peak in the range of 35°-50°, the characteristic peak is a (100) peak, which reflects the carbon intra-layer order degree and grain size.

[0069] FIG. 2 is a SEM image of the hard carbon negative electrode material in this example.

[0070] The performance test process of the hard carbon negative electrode material is as follows:

[0071] (1) The negative electrode material, polyvinylidene fluoride (PVDF) and conductive agent (SP) provided in the example and comparative examples were dispersed and dissolved in N-methyl pyrrolidone (NMP) at a mass ratio of 90:5:5, and after stirring and dispersion, a slurry with a solid mass content of 55% was obtained. After coating, drying and rolling, the original piece of the button cell was punched. A metal sodium sheet was used as the counter electrode, polypropylene (PP) was used as the separator material, a small amount of sodium ion battery electrolyte was dropped, and the negative electrode material button cell was prepared. The solute of the electrolyte is 1M NaPF6, and the solvent is an ethylene carbonate-dimethyl carbonate (EC-DMC) system.

[0072] In the voltage range of 0-2V, 1) stand for 2h; 2) rate discharge (0.1C, 0V); 3) stand for 10min; 4) rate discharge (0.02C, 0V); 5) stand for 30s; 6) rate charge (0.1C, 2.0V), record the first charge specific capacity and the first coulombic efficiency, and the test results are shown in FIG. 3.

[0073]

Example 2

[0074] A hard carbon negative electrode material was prepared in this example, and the preparation process was as follows:

[0075] (1) The phenolic resin was crushed to a particle size D50 less than 18μm; and a phenolic resin powder was obtained;

[0076] (2) The phenolic resin powder was heated to 900℃ at a rate of 0.25℃ / min in an air and carbon dioxide system with a system pressure of 0.1Mpa to obtain a pre-carbonized powder;

[0077] (3) The pre-carbonized powder was dispersed to D50=5μm to obtain a hard carbon negative electrode material precursor;

[0078] (4) The hard carbon negative electrode material precursor was subjected to high-temperature carbonization at a temperature of 1300℃ to obtain the hard carbon negative electrode material.

[0079] In this example, the hard carbon negative electrode material comprises a carbon matrix with a three-dimensional porous structure, and the carbon matrix is hard carbon. The true density of the hard carbon negative electrode material is 1.58g / cm 3 .

[0080] In this example, the closed pore volume of the hard carbon negative electrode material is 0.167cm 3 / g.

[0081] The performance test process of the hard carbon negative electrode material is the same as that of Example 1.

[0082]

Example 3

[0083] A hard carbon negative electrode material is prepared in this example, and the preparation process is as follows:

[0084] (1) The starch is crushed to a particle size D50 less than 18 μm; to obtain starch powder;

[0085] (2) The starch powder is heated to 900℃ at a speed of 0.3℃ / min in air with a system pressure of 0.15Mpa to obtain pre-carbonized powder;

[0086] (3) The pre-carbonized powder is dispersed to D50 = 5.5 μm to obtain a hard carbon negative electrode material precursor;

[0087] (4) The hard carbon negative electrode material precursor is high-temperature carbonized at a temperature of 1200℃ to obtain the hard carbon negative electrode material.

[0088] In this example, the hard carbon negative electrode material comprises a carbon matrix with a three-dimensional porous structure, and the carbon matrix is hard carbon. The true density of the hard carbon negative electrode material is 1.36 g / cm 3 .

[0089] In this example, the closed pore volume of the hard carbon negative electrode material is 0.158 cm 3 / g.

[0090] The performance test process of the hard carbon negative electrode material is the same as that of Example 1

[0091]

Comparative Example

[0092] The process for preparing the negative electrode material in this comparative example is as follows:

[0093] (1) The coal-based pitch is crushed to a particle size D50 less than 20 μm; to obtain pitch powder;

[0094] (2) The pitch powder is heated to 900℃ at a speed of 0.5℃ / min in an air and water vapor mixed atmosphere with an absolute humidity of 5% and a system pressure of 0.2Mpa to obtain pre-carbonized powder;

[0095] (3) The pre-carbonized powder is dispersed to D50 = 6 μm to obtain a hard carbon negative electrode material precursor;

[0096] (4) The hard carbon negative electrode material precursor is high-temperature carbonized at a temperature of 1400℃ to obtain the hard carbon negative electrode material.

[0097] In this comparative example, the hard carbon negative electrode material comprises a carbon matrix with a three-dimensional porous structure, and the carbon matrix is hard carbon. The true density of the hard carbon negative electrode material is 1.71 g / cm 3 .

[0098] The XRD pattern of the hard carbon negative electrode material in the comparative example also has a characteristic peak in the range of 20°-30°, which is a (002) peak, reflecting the carbon layer spacing and interlayer order degree, and the d002 is also 0.372 nm; it also has a characteristic peak in the range of 35°-50°, which is a (100) peak, reflecting the carbon layer order degree and grain size.

[0099] In the comparative example, the closed pore volume of the hard carbon negative electrode material is 0.153 cm 3 / g.

[0100] The negative electrode materials of Examples 1-3 and the comparative example were respectively prepared into negative electrode sheets, and each of the negative electrode sheets, positive electrode sheets and separators were assembled into sodium ion batteries. Among them, the preparation method of the positive electrode sheet was as follows: the active material, PVDF and SP were mixed in a mass ratio of 90:5:5 to prepare a positive electrode slurry, and a positive electrode sheet was obtained after coating; the solute of the electrolyte was 1M NaPF6, and the solvent was an ethylene carbonate-dimethyl carbonate (EC-DMC) system.

[0101] Charging and discharging tests were carried out at a voltage of 2.5-4.05 V and a rate of 0.2C, and the initial discharge capacity was recorded. The results are shown in Table 1.

[0102] Table 1: Initial charging and discharging results of negative electrode materials

[0103] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A hard carbon negative electrode material, characterized in that, By regulating the reaction condition under the set atmosphere, a three-dimensional carbon matrix with a large number of closed pores is formed; the reaction condition includes carbonization temperature and system pressure; the closed pore volume of the hard carbon negative electrode material is 0.01 cm 3 / g cp <0.5 cm 3 / g; and satisfies V cp =1 / ρ 真 -1 / (2.26×0.3354 / d002 act ); wherein ρ 真 is the true density of the hard carbon negative electrode material, in g / cm 3 ; d002 act is the interlayer distance of the X-ray diffraction 002 lattice, in nm; the true density of the hard carbon negative electrode material is 0.5 g / cm 3 < ρ 真 < 2.26 g / cm 3 . 2.The hard carbon negative electrode material of claim 1, characterized in that, The true density p of the hard carbon negative electrode material 真 = (0.75T / 620)p0- 0.25(T / 1000)(P / P0) 0.3 ; Wherein, ρ0 is the density of initial carbon source; T is carbonization temperature, and T = 200-1500℃; P0 is atmospheric pressure; P is system pressure, and P = 0.1-1.5 MPa. 3.The hard carbon negative electrode material of claim 1, characterized in that, The setting atmosphere is one or several combinations of nitrogen, argon, helium, carbon dioxide, chlorine, water vapor, and air. 4.The hard carbon negative electrode material of claim 1, characterized in that, The hard carbon forming a three-dimensional carbon matrix is formed by high-temperature carbonization of an organic thermosetting precursor; the reaction condition under the regulated setting atmosphere refers to adjusting the pore structure and open / close pore ratio of the carbonization product, and further controlling the true density of the carbonization product, by controlling the temperature rising curve, system pressure, and system atmosphere during the carbonization process of the organic thermosetting precursor.

5. The hard carbon negative electrode material of claim 4, wherein, The hard carbon includes one or more of pitch, cellulose, sucrose, glucose, phenolic resin, starch, coal, and heavy oil. 6.The hard carbon negative electrode material of claim 1, characterized in that, The hard carbon negative electrode material has characteristic peaks specific to hard carbon in the range of 20-30° and 35-50° in the X-ray diffraction pattern.

7. The method for preparing the hard carbon negative material according to any one of claims 1-6, characterized in that, The method comprises the following steps: (1) crushing the carbon matrix raw material to a set particle size; (2) mixing the carbon matrix raw material, and then pre-carbonizing at a temperature of 200-1000℃ under an atmosphere of inert gas / air / carbon dioxide / water vapor; (3) dispersing the pre-carbonized carbon matrix to 3-20 microns to obtain a negative electrode material precursor; (4) The negative material precursor is high-temperature carbonized at 1000-1800°C, in the process, the temperature, pressure and reaction atmosphere are controlled to precisely control the pore structure of different negative material precursors; and finally the hard carbon negative material with closed pore volume of 0.01 cm 3 / g cp <0.5 cm 3 / g is obtained. 8.The method of claim 7, wherein the hard carbon negative electrode material is prepared by the steps of: mixing a carbon source and a solvent to form a mixture; and heating the mixture to form the hard carbon negative electrode material. The carbon matrix raw material includes one or more of biomass and modified products thereof, coal and modified products thereof, pitch and modified products thereof, and resin and modified products thereof.

9. A sodium-ion battery, characterized in that, The hard carbon negative electrode material as claimed in any one of claims 1-6 is contained in the negative electrode of a sodium ion battery.

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