A sodium ion battery biomass hard carbon negative electrode material and its preparation method and application

Abstract

The present invention relates to the field of battery technology, and in particular to a biomass hard carbon negative electrode material for sodium ion batteries, its preparation method, and application. The preparation method comprises the following steps: S1. Preparing a pre-oxidized hard carbon precursor material using sodium lignin; S2. Evenly mixing a catalyst, a metal organic compound, and the pre-oxidized hard carbon precursor to prepare a porous metal-doped hard carbon precursor material; S3. Transferring the porous metal-doped hard carbon precursor material to a tubular furnace, introducing a carbon source mixed gas for carbonization, and obtaining a biomass hard carbon negative electrode material. The present invention obtains the pre-oxidized hard carbon precursor material by oxidizing sodium lignin, and chemically reacting it with the metal organic compound to improve the electronic conductivity and structural stability of the material.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a biomass hard carbon negative electrode material for a sodium ion battery, and a preparation method and application thereof. Background Art

[0002] Sodium-ion batteries are considered to be an important choice for the next generation of secondary batteries due to the abundant sodium content in the earth's crust and their high energy density. For the negative electrode, due to the large radius of sodium ions, graphite commonly used in traditional lithium-ion batteries is not suitable for use as a negative electrode material for sodium-ion batteries due to its narrow interlayer spacing. Hard carbon has a large interlayer spacing, which is conducive to the intercalation and deintercalation of sodium ions. However, its large amount of disordered structure inside will trigger a large number of side reactions and reduce the battery's first coulombic efficiency. The limited active sites and small interlayer spacing of soft carbon are also not conducive to sodium storage. Biomass-derived carbon materials retain the structural characteristics of biomass precursors and have the advantages of controllable structure and broad market prospects, and have attracted much attention. However, compared with hard carbon derived from organic polymers such as phenolic resin, the hard carbon (lignin) of biomass has a more irregular structure, and has problems such as large irreversible capacity and poor power performance, which greatly limits its application. Summary of the Invention

[0003] In order to improve the power performance of hard carbon materials, the composite material of the present invention utilizes N, B, and P heteroatom doping to provide more active sites, thereby increasing the specific capacity of the hard carbon material and vapor-deposited surface amorphous carbon, reducing surface defects and improving the initial efficiency.

[0004] A first aspect of the present invention provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery, the preparation method comprising the following steps:

[0005] S1. Preparation of pre-oxidized hard carbon precursor material using sodium lignin;

[0006] S2. The catalyst, the metal organic compound, and the pre-oxidized hard carbon precursor are mixed to prepare a porous metal-doped hard carbon precursor material;

[0007] S3. The porous metal-doped hard carbon precursor material is transferred to a tubular furnace, and a carbon source mixed gas is introduced for carbonization to obtain a biomass hard carbon negative electrode material.

[0008] In some embodiments, the S1 includes ultrasonically washing, drying, and heating sodium lignin to obtain a pre-oxidized hard carbon precursor material.

[0009] Furthermore, the S1 includes placing sodium lignin in an ultrasonic cleaning machine for ultrasonic washing, followed by filtration and drying to obtain a biomass precursor, which is then transferred to a tubular furnace for infrared heating to obtain a pre-oxidized hard carbon precursor material.

[0010] In some embodiments, the S2 includes configuring an N-methylpyrrolidone solution with a mass concentration of 1-10% catalyst, adding metal organic matter and pre-oxidized hard carbon precursor material and mixing them evenly, transferring the mixture to a high-pressure reactor, reacting at a temperature of 80-120°C and a pressure of 1-5Mpa for 1-6 hours, filtering, and freeze-drying at a temperature of -40°C for 24 hours to obtain a porous metal-doped hard carbon precursor material.

[0011] During the research, the applicant found that the simultaneous addition of catalysts and metal organics can increase the sodium storage capacity of the material's pores and improve the specific capacity, while the metal compound improves the electronic conductivity and power performance of the material. Furthermore, the mass ratio of the catalyst, metal organic, and pre-oxidized hard carbon precursor is (1-10): (1-10): 100. When the mass ratio of the three is controlled, both energy density and power performance can be taken into account. Too much metal organic content will lead to a decrease in energy density, while too little will result in limited improvement in power performance.

[0012] In some embodiments, the catalyst includes at least one of ferrocene, cobaltocene, nickelocene, titanocene, zirconocene, and magnesiumocene.

[0013] In some embodiments, the metal organic compound includes at least one of ferric isooctanoate, tin isooctanoate, chromium isooctanoate, bismuth neodecanoate, tin neodecanoate, and dibutyltin dilaurate. Applicants have discovered that, compared to conventional doping with metal powders or inorganic metal compounds, the addition of these metal organic compounds results in amorphous carbon after carbonization, which improves processing and compatibility with electrolytes. Furthermore, the presence of carboxyl groups in the organometallic compound facilitates pore formation in the material, increasing its specific capacity.

[0014] In some embodiments, the S3 includes transferring the porous metal-doped hard carbon precursor material into a tubular furnace, expelling the air in the tube with inert gas, introducing a carbon source mixed gas, heating the material to 300-500°C at a heating rate of 1-10°C / min and keeping the temperature for 1-6 hours, then heating the material to 700-1200°C at a heating rate of 1-10°C / min and keeping the temperature for 1-6 hours, and then naturally cooling the material to room temperature to obtain a hard carbon composite material.

[0015] Furthermore, the carbon source mixed gas is a mixture of a carbon source gas and a heteroatom gas.

[0016] In some embodiments, the volume ratio of the carbon source gas to the heteroatom gas is 10:(1-5).

[0017] In some embodiments, the heteroatom gas includes at least one of ammonia, diborane, and phosphine.

[0018] The applicant also found that adding heteroatom gas can improve the specific capacity of the material and its power performance, especially when the volume ratio of carbon source gas to heteroatom gas is 10: (1-5), it can effectively reduce the impedance of the material coating layer. Too much heteroatom gas will cause the surface structure of the material to become loose, reducing the tap density and structural stability, while too little heteroatom gas will not significantly improve the power performance of the material.

[0019] The second aspect of the present invention provides a biomass hard carbon negative electrode material for a sodium ion battery, wherein the material exhibits a core-shell structure, wherein the core is a metal-doped hard carbon material and the outer shell is a heteroatom-doped amorphous carbon.

[0020] The third aspect of the present invention provides the use of the preparation method or the sodium ion battery biomass hard carbon negative electrode material in the preparation of a secondary battery.

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

[0022] 1) A pre-oxidized hard carbon precursor material is obtained by oxidizing sodium lignin, and chemically reacting with metal organic matter to improve the electronic conductivity and structural stability of the material.

[0023] 2) Improve the electronic conductivity of the material and improve the rate performance through heteroatom gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is the SEM image of the sodium ion battery biomass hard carbon negative electrode material prepared in Example 1. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Example 1

[0028] A first aspect of this embodiment provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery, the method comprising the following steps:

[0029] Step S1: placing sodium lignin in deionized water and ultrasonically washing it in an ultrasonic cleaning machine, filtering it, and then drying it after suction filtration to obtain a biomass precursor, which was then transferred to a tube furnace and infrared heated (temperature 200° C., 3 h) to obtain a pre-carbonization treatment to obtain a pre-oxidized hard carbon precursor material;

[0030] Step S2: 5 g of the catalyst was added to 100 g of N-methylpyrrolidone to prepare a solution with a mass concentration of 5%, 5 g of the metal organic compound and 100 g of the pre-oxidized hard carbon precursor material were added and mixed evenly, and the mixture was transferred to an autoclave, reacted at a temperature of 100° C. and a pressure of 3 MPa for 3 h, filtered, and freeze-dried at a temperature of -40° C. for 24 h to obtain a porous metal-doped hard carbon precursor material; the catalyst was ferrocene and the metal organic compound was iron isooctanoate;

[0031] Step S3: Transfer the porous metal-doped hard carbon precursor material to a tubular furnace, introduce argon inert gas to expel the air in the tube, then introduce a carbon source mixed gas, heat it to 400°C at a heating rate of 5°C / min and keep it warm for 3 hours, then heat it to 950°C at a heating rate of 5°C / min and keep it warm for 3 hours, and naturally cool it to room temperature (25°C) to obtain a hard carbon composite material; the carbon source mixed gas is methane: ammonia = 10:3 (V / V).

[0032] A second aspect of this embodiment provides a biomass hard carbon negative electrode material for a sodium ion battery. The material has a core-shell structure, wherein the core is a metal-doped hard carbon material and the shell is a heteroatom-doped amorphous carbon.

[0033] The third aspect of this embodiment provides the use of the sodium ion battery biomass hard carbon negative electrode material in the preparation of a secondary battery.

[0034] Example 2

[0035] A first aspect of this embodiment provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery, the method comprising the following steps:

[0036] Step S1: placing sodium lignin in deionized water and ultrasonically washing it in an ultrasonic cleaning machine, filtering it, and then drying it after suction filtration to obtain a biomass precursor, which was then transferred to a tube furnace and infrared heated (temperature 200° C., 3 h) to obtain a pre-carbonization treatment to obtain a pre-oxidized hard carbon precursor material;

[0037] Step S2: 1g of the catalyst is added to 100g of N-methylpyrrolidone to prepare a solution with a mass concentration of 1%, 1g of the metal organic compound and 100g of the pre-oxidized hard carbon precursor material are added and mixed evenly, the mixture is transferred to an autoclave, reacted at a temperature of 80°C and a pressure of 5 MPa for 6 hours, filtered, and freeze-dried at a temperature of -40°C for 24 hours to obtain a porous metal-doped hard carbon precursor material; the catalyst is cobaltocene and the metal organic compound is tin isooctanoate;

[0038] Step S3: Transfer the porous metal-doped hard carbon precursor material to a tubular furnace, introduce argon inert gas to expel the air in the tube, then introduce a carbon source mixed gas, heat it to 300°C at a heating rate of 1°C / min and keep it warm for 6 hours, then heat it to 700°C at a heating rate of 1°C / min and keep it warm for 3 hours, and naturally cool it to room temperature (25°C) to obtain a hard carbon composite material; the carbon source mixed gas is acetylene: diborane = 10:1 (V / V).

[0039] The second aspect of this embodiment provides a biomass hard carbon negative electrode material for a sodium ion battery, and the specific implementation method is the same as that of Example 1.

[0040] The third aspect of this embodiment provides the use of the sodium ion battery biomass hard carbon negative electrode material in the preparation of a secondary battery.

[0041] Example 3

[0042] A first aspect of this embodiment provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery, the method comprising the following steps:

[0043] Step S1: placing sodium lignin in deionized water and ultrasonically washing it in an ultrasonic cleaning machine, filtering it, and then drying it after suction filtration to obtain a biomass precursor, which was then transferred to a tube furnace and infrared heated (temperature 200° C., 3 h) to obtain a pre-carbonization treatment to obtain a pre-oxidized hard carbon precursor material;

[0044] Step S2: adding 10 g of the catalyst to 100 g of N-methylpyrrolidone to prepare a 10% mass concentration solution, adding 10 g of the metal organic compound and 100 g of the pre-oxidized hard carbon precursor material and mixing them evenly, transferring the mixture to an autoclave, reacting at a temperature of 120° C. and a pressure of 1 MPa for 1 hour, filtering, and freeze-drying at a temperature of -40° C. for 24 hours to obtain a porous metal-doped hard carbon precursor material; the catalyst is nickelocene and the metal organic compound is chromium isooctanoate;

[0045] Step S3: Transfer the porous metal-doped hard carbon precursor material to a tubular furnace, introduce argon inert gas to expel the air in the tube, then introduce a carbon source mixed gas, heat it to 500°C at a heating rate of 10°C / min and keep it warm for 1 hour, then heat it to 1200°C at a heating rate of 10°C / min and keep it warm for 1 hour, and naturally cool it to room temperature (25°C) to obtain a hard carbon composite material; the carbon source mixed gas is ethylene: phosphine = 10:5 (V / V).

[0046] The second aspect of this embodiment provides a biomass hard carbon negative electrode material for a sodium ion battery, and the specific implementation method is the same as that of Example 1.

[0047] The third aspect of this embodiment provides the use of the sodium ion battery biomass hard carbon negative electrode material in the preparation of a secondary battery.

[0048] Comparative Example 1

[0049] This comparative example provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery. The specific implementation method is the same as that of Example 1, except that the carbon source mixed gas is methane.

[0050] Comparative Example 2

[0051] This comparative example provides a method for preparing a biomass hard carbon negative electrode material for a sodium ion battery. The specific implementation method is the same as that of Example 1, except that the preparation method includes the following steps:

[0052] Step S1: placing sodium lignin in deionized water and ultrasonically washing it in an ultrasonic cleaning machine, filtering it, and then drying it after suction filtration to obtain a biomass precursor, which was then transferred to a tube furnace and infrared heated (temperature 200° C., 3 h) to obtain a pre-carbonization treatment to obtain a pre-oxidized hard carbon precursor material;

[0053] Step S2: Transfer the pre-oxidized hard carbon precursor material to a tubular furnace, introduce argon inert gas to expel the air in the tube, then introduce a carbon source mixed gas, heat it to 400°C at a heating rate of 5°C / min and keep it warm for 3 hours, then heat it to 950°C at a heating rate of 5°C / min and keep it warm for 3 hours, and naturally cool it to room temperature (25°C) to obtain a hard carbon composite material; the carbon source mixed gas is methane: ammonia = 10:3 (V / V).

[0054] Performance Testing

[0055] (1) SEM test

[0056] The hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the results were as follows: Figure 1 As shown. Figure 1 It can be seen that the composite material presents a granular structure with a particle size between 10-15 μm.

[0057] (2) Physical and chemical properties and button battery testing

[0058] The conductivity, tap density, specific surface area, particle size, and powder OI value of the hard carbon composite materials obtained in Examples 1-3 and Comparative Examples 1-2 were tested according to the test methods specified in the standard GB / T-24533-2019, "Graphite-Based Anode Materials for Lithium-Ion Batteries." The test results are shown in Table 1.

[0059] The hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 served as negative electrodes and were assembled into button cells with a lithium sheet, electrolyte, and separator in a glove box containing argon and water content below 0.1 ppm. The separator was Celebard 2400, and the electrolyte was a LiPF6 solution. The LiPF6 concentration in the electrolyte was 1 mol / L, and the solvent was a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DMC) in a 1:1 weight ratio. The resulting button cells were labeled A-1, B-1, C-1, D-1, and E-1, respectively. The performance of the button cells was tested using a blue battery tester under the following test conditions: a 0.2C charge and discharge rate with a voltage range of 0.005-2V, followed by a 3-cycle cycle. The discharge capacity at 1C was then measured, and the 1C / 0.2C rate performance and cycle performance (25±3°C, 0.2C / 0.2C, 100 cycles) were calculated. The test results are shown in Table 1.

[0060] Table 1

[0061]

[0062] It can be seen from Table 1 that the electrical conductivity of the hard carbon composite materials prepared in Examples 1-3 is significantly higher than that in Comparative Examples 1-2. The reason may be that the graphite composite materials prepared in Examples 1-3 are doped with metal elements and elements such as nitrogen and boron with high electronic conductivity, which reduces the impedance and increases the specific surface area. At the same time, the electronic conductivity of the material is improved by doping with outer layer heteroatom gas, thereby improving the rate performance and cycle performance.

[0063] (3) Soft pack battery performance test

[0064] The graphite composite materials of Examples 1-3 and the hard carbon composite materials of Comparative Examples 1-2 were used as negative electrode active materials, and the positive electrode active materials were ternary materials (LiNi 1 / 3 Co 1 / 3 Mn 1 / 35Ah soft-pack batteries were assembled using a celegard 2400 separator and a LiPF6 solution (the solvent was a mixture of EC and DEC in a 1:1 volume ratio, with a LiPF6 concentration of 1.3 mol / L). The resulting soft-pack batteries were labeled A-2, B-2, C-2, D-2, and F-2, and their cycle and rate performance were tested. The test results are detailed in Table 2.

[0065] 3.1 Cycle performance: The battery cycle performance is tested at a charge and discharge rate of 1C / 1C, a voltage range of 2.8V-4.2V, and a temperature of 25±3℃;

[0066] 3.2 Rate performance: Charge the battery to 100% SOC at a rate of 2C using constant current + constant voltage mode, and then calculate the constant current ratio = constant current capacity / (constant current capacity + constant voltage capacity).

[0067] Table 2

[0068] Anode materials used in batteries Capacity retention rate after 500 cycles (%) Fast charging performance (constant current ratio) Example 1 92.42 93.2％ Example 2 93.88 91.5％ Example 3 92.39 92.7％ Comparative Example 1 86.11 85.1％ Comparative Example 2 87.34 83.4％

[0069] Table 2 shows that the cycle and rate performance of soft-pack batteries prepared using the hard carbon composite materials of Examples 1-3 as negative electrode materials are significantly superior to those prepared using the hard carbon composite materials of Comparative Examples 1-2. This is because the hard carbon composite materials of Examples 1-3, through oxidation of sodium lignin to produce a pre-oxidized hard carbon precursor material, undergo a chemical reaction with the metal organic compound to enhance the material's structural stability and improve cycle performance. Furthermore, the heteroatom gas increases the material's electronic conductivity and reduces the OI value, thereby improving rate performance.

[0070] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a biomass hard carbon negative electrode material for a sodium ion battery, characterized in that: The preparation method comprises the following steps: S1. Preparation of pre-oxidized hard carbon precursor material using sodium lignin; S2. The catalyst, the metal organic compound, the pre-oxidized hard carbon precursor are mixed to prepare a porous metal-doped hard carbon precursor material, wherein the catalyst comprises at least one of ferrocene, cobaltocene, nickelocene, titanocene, zirconocene, and magnesiumocene; S3. Transferring the porous metal-doped hard carbon precursor material to a tubular furnace and introducing a carbon source mixed gas for carbonization to obtain a biomass hard carbon anode material. The carbon source mixed gas is a mixture of a carbon source gas and a heteroatom gas, and the heteroatom gas includes at least one of ammonia, diborane, and phosphine.

2. The method for preparing a biomass hard carbon negative electrode material for a sodium ion battery according to claim 1, characterized in that: The S1 includes ultrasonically washing, drying, and heating sodium lignin to obtain a pre-oxidized hard carbon precursor material.

3. The method for preparing a biomass hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: The mass ratio of the catalyst, the metal organic compound and the pre-oxidized hard carbon precursor is (1-10): (1-10):

100.

4. The method for preparing a biomass hard carbon negative electrode material for a sodium ion battery according to claim 3, characterized in that: The metal organic compound includes at least one of ferric isooctanoate, tin isooctanoate, chromium isooctanoate, bismuth neodecanoate, tin neodecanoate, and dibutyltin dilaurate.

5. The method for preparing a biomass hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: The volume ratio of the carbon source gas to the heteroatom gas is 10:(1-5).

6. A sodium ion battery biomass hard carbon negative electrode material prepared by the method for preparing a sodium ion battery biomass hard carbon negative electrode material according to claim 1, characterized in that: The material presents a core-shell structure, wherein the core is a metal-doped hard carbon material and the shell is a heteroatom-doped amorphous carbon.

7. Use of the sodium ion battery biomass hard carbon negative electrode material according to claim 6 in the preparation of secondary batteries.

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