Hard carbon material for battery negative electrode, preparation method of hard carbon material and battery
The preparation of hard carbon materials through hydrothermal reaction and high-temperature annealing treatment has solved the poor fast charging performance and safety problems of existing hard carbon materials in the negative electrode of sodium ion batteries, and improved the degree of graphitization in lithium ion batteries, achieving higher battery capacity and better electrochemical performance.
Patent Information
- Application Number
- CN202510394729.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-05-23
AI Technical Summary
When existing hard carbon materials are used for the negative electrode of sodium ion batteries, there are problems such as poor fast charging performance, safety problems, unstable performance, and low degree of graphitization in lithium ion batteries.
The spherical carbon precursor is prepared by hydrothermal reaction of the aqueous sugar solution and subjected to high-temperature annealing in an atmosphere such as nitrogen to obtain a hard carbon material. During the hydrothermal reaction, gas is added to the hydrothermal kettle at the beginning to reduce the particle size of the hard carbon and increase the compaction density.
The compaction density and graphitization degree of hard carbon materials are improved, the load capacity of the electrode sheet and the charging and discharge capacity of the battery are improved, and the electrochemical performance and safety performance are improved.
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Figure BDA0005338329060000081
Abstract
Description
Technical Field
[0001] The present invention relates to the field of battery negative electrode materials, in particular to a hard carbon material for battery negative electrode and a preparation method thereof, and a battery. Background Art
[0002] Sodium-ion batteries are considered the core direction of the post-lithium era due to their high abundance of sodium resources (2.3% in the earth's crust, only 0.006% in lithium), low cost (the price of sodium carbonate is less than 1 / 10 of that of lithium carbonate), excellent low-temperature performance (capacity retention rate at -20°C > 80%), and fast charging potential (charging rate can reach more than 5C). However, the technology of negative electrode materials for sodium-ion batteries is not yet mature. Traditional graphite (interlayer spacing 0.335nm) fails because the radius of sodium ions (0.102nm) is much larger than the radius of lithium ions (0.076nm). Hard carbon materials have become the only negative electrode system that can be commercialized due to their disordered layered structure (interlayer spacing 0.38nm to 0.42nm) and abundant defect sites.
[0003] Hard carbon is the preferred material for the negative electrode of sodium-ion batteries. It can also be used for the negative electrode of lithium-ion batteries and potassium-ion batteries, and has excellent fast-charging performance. The hard carbon products currently on the market have large particle sizes and irregular edges. Due to the tip discharge effect, the fast-charging performance is poor and sodium metal is easily precipitated during fast charging and discharging, which leads to safety problems such as short circuit and thermal runaway. There are also problems such as unstable performance between batches, rapid capacity drop during fast charging, low long-cycle performance and first-cycle coulomb efficiency (less than 90%), and poor conductivity. The morphology and performance of hard carbon used in lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries in the prior art need to be further optimized in order to find hard carbon with better electrochemical and safety performance.
[0004] In addition, in the existing preparation method of hard carbon materials using hydrothermal reaction of glucose, the compaction density of the hard carbon is relatively low, which is not conducive to increasing the loading capacity of the electrode sheet and limits its application in industry. Moreover, the degree of graphitization of the produced hard carbon is relatively low, which is not conducive to its application in lithium-ion batteries. Summary of the invention
[0005] The first object of the present invention is to provide a method for preparing a hard carbon material for a battery negative electrode, which can increase the compaction density of the hard carbon and improve the loading capacity of the electrode sheet.
[0006] The second object of the present invention is to provide another method for preparing a hard carbon material for a negative electrode of a battery, which can improve the compaction density of the hard carbon, increase the loading capacity of the electrode sheet, and at the same time improve the degree of graphitization of the hard carbon.
[0007] The third object of the present invention is to provide a hard carbon material for battery negative electrode prepared by the above preparation method.
[0008] A fourth object of the present invention is to provide a battery having a battery negative electrode made of the above hard carbon material.
[0009] To achieve the above-mentioned first purpose, the present invention provides a method for preparing a hard carbon material for a battery negative electrode, comprising: adding a sugar aqueous solution to a hydrothermal kettle for a hydrothermal reaction, and during the hydrothermal reaction, after heating to a set temperature, adding gas to the hydrothermal kettle at the beginning of insulation; subjecting the product of the above-mentioned hydrothermal reaction to a high-temperature annealing treatment to obtain a hard carbon material.
[0010] It can be seen from the above scheme that the present invention obtains a spherical carbon precursor by subjecting a sugar aqueous solution to a hydrothermal reaction, and then performs a high-temperature annealing treatment in an atmosphere such as nitrogen to obtain a hard carbon material. In step one, gas is added to the hydrothermal kettle at the beginning of the insulation to reduce the particle size of the hard carbon, increase the compaction density of the hard carbon, increase the oxygen content, and increase the battery charge and discharge capacity.
[0011] A preferred solution is that the amount of gas added to the hydrothermal kettle at the beginning of the insulation is in the range of 1 to 8 atmospheres.
[0012] It can be seen from this that if the amount of supplemented gas is too small, the effect of improving the compaction density of hard carbon will be poor. If the amount of supplemented gas is too large, it may cause excessive pressure in the furnace and there is a risk of explosion.
[0013] A preferred solution is that the atmosphere of the high temperature annealing step is nitrogen.
[0014] A preferred solution is that during the high temperature annealing process, the heating rate is in the range of 0.5°C / min to 15°C / min, the reaction temperature is in the range of 800°C to 1900°C, and the holding time is in the range of 1 hour to 3 hours.
[0015] A preferred solution is to evacuate the annealing furnace before high-temperature annealing.
[0016] It can be seen that by evacuating the annealing furnace before high-temperature annealing, the compaction density of hard carbon can be further improved.
[0017] A preferred solution is to add gas to the annealing furnace before high temperature annealing.
[0018] It can be seen that by adding gas to the annealing furnace before high-temperature annealing and increasing the pressure in the annealing furnace, the graphitization degree of the hard carbon can be improved, so that when the hard carbon is used in lithium-ion batteries, the battery capacity is greatly improved.
[0019] In a further embodiment, the amount of gas added to the annealing furnace is in the range of 1 to 5 atmospheres.
[0020] To achieve the above-mentioned second purpose, the present invention provides another method for preparing a hard carbon material for a battery negative electrode, which is characterized in that it includes: step one, adding a sugar aqueous solution to a hydrothermal kettle for hydrothermal reaction; step two, filtering the product of the hydrothermal reaction obtained in step one, separating the filtrate and the filter residue, and drying the filter residue to obtain a spherical carbon precursor; step three, subjecting the spherical carbon precursor obtained in step two to high-temperature annealing to obtain a hard carbon material; wherein, in step three, before high-temperature annealing, the annealing furnace is first vacuumed; or before high-temperature annealing, gas is first added to the annealing furnace.
[0021] It can be seen that by evacuating the annealing furnace before high-temperature annealing, the compaction density of hard carbon can be significantly improved, thereby increasing the load of the electrode sheet. In addition, by adding gas to the annealing furnace before high-temperature annealing and increasing the pressure in the annealing furnace, the degree of graphitization of hard carbon can be increased, so that when the hard carbon is used in lithium-ion batteries, the battery capacity is greatly improved.
[0022] To achieve the third objective, the present invention provides a hard carbon material for a negative electrode of a battery, which is prepared by the above-mentioned preparation method.
[0023] To achieve the fourth objective, the present invention provides a battery, including a negative electrode, wherein the material of the negative electrode includes the hard carbon material described above. DETAILED DESCRIPTION
[0024] The preparation method of the hard carbon material for the negative electrode of the battery comprises the following steps:
[0025] Step 1, adding a saccharide aqueous solution with a concentration of 2.5% to 50% to a hydrothermal kettle for hydrothermal reaction. Preferably, the raw materials of the saccharide aqueous solution include at least one of glucose, sucrose, syrup, and sugarcane juice; the hydrothermal kettle is a high-pressure reactor; the atmosphere of the hydrothermal reaction can be air, nitrogen, or argon, etc. During the hydrothermal reaction, the heating rate is in the range of 1°C / min to 20°C / min, the reaction temperature is in the range of 180°C to 250°C, and the insulation time is in the range of 4 hours to 24 hours. During the hydrothermal reaction, after heating to the set temperature, gas is added to the hydrothermal kettle at the beginning of insulation, and the amount of added gas is in the range of 1 to 8 atmospheres.
[0026] Step 2: Filter the product of the hydrothermal reaction, separate the filtrate and the filter residue, and dry the filter residue to obtain a spherical carbon precursor.
[0027] Step 3: subjecting the spherical carbon precursor to high temperature annealing to obtain a hard carbon material. The atmosphere of the high temperature annealing step is nitrogen. During the high temperature annealing process, the heating rate is in the range of 0.5°C / min to 15°C / min, the reaction temperature is in the range of 800°C to 1900°C, and the holding time is in the range of 1 hour to 3 hours.
[0028] In addition, before high-temperature annealing, the annealing furnace can be evacuated, or before high-temperature annealing, nitrogen gas can be supplemented into the annealing furnace, and the amount of nitrogen gas supplemented is in the range of 1 to 5 atmospheres.
[0029] Example 1:
[0030] The preparation method of the hard carbon material in this example includes the following steps:
[0031] Step 1: Stir and dissolve 600 g of glucose in 2.4 L of deionized water to obtain a glucose aqueous solution with a concentration of 20%. The dissolved solution is filled into a 4 L high-pressure reactor, and the atmosphere in the high-pressure reactor is an air atmosphere. The high-pressure reactor is heated to 200 °C at a heating rate of 2 °C / min and held at this temperature for 6 h for hydrothermal reaction, and 5 atmospheres of air are supplemented into the hydrothermal reactor at the beginning of the holding.
[0032] Step 2: After the hydrothermal reaction is completed, filter the product of the hydrothermal reaction obtained in Step 1 to separate the filtrate and the filter residue, and dry the filter residue at a temperature of 65 °C to obtain a spherical carbon precursor.
[0033] Step 3: Place the spherical carbon precursor obtained in Step 2 in a tubular furnace or a box furnace, heat it to 1300 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, hold for 1 h, and wait for the temperature to naturally cool to room temperature to obtain a spheroidized hard carbon material. During the annealing process, the pressure in the annealing furnace is stabilized at 1 atmosphere.
[0034] Example 2:
[0035] The preparation method of the hard carbon material in this example includes the following steps:
[0036] Step 1: Stir and dissolve 600 g of glucose in 2.4 L of deionized water to obtain a glucose aqueous solution with a concentration of 20%. The dissolved solution is filled into a 4 L high-pressure reactor, and the atmosphere in the high-pressure reactor is an air atmosphere. The high-pressure reactor is heated to 200 °C at a heating rate of 2 °C / min and held at this temperature for 6 h for hydrothermal reaction.
[0037] Step 2: After the hydrothermal reaction is completed, filter the product of the hydrothermal reaction obtained in Step 1 to separate the filtrate and the filter residue, and dry the filter residue at a temperature of 65 °C to obtain a spherical carbon precursor.
[0038] Step 3: Place the spherical carbon precursor obtained in Step 2 in a tubular furnace or a box furnace used as an annealing furnace, evacuate the annealing furnace, then heat it to 1300 °C at a heating rate of 5 °C / min, hold for 1 h, and wait for the temperature to naturally cool to room temperature to obtain a spheroidized hard carbon material.
[0039] Embodiment 3:
[0040] As an explanation of the third embodiment of the present invention, only the differences from the first embodiment described above will be described below.
[0041] In this embodiment, step three is to place the spherical carbon precursor obtained in step two in a tubular furnace or a box furnace, and then maintain the pressure in the furnace stable at 2 atmospheres by adjusting the nitrogen intake and the back pressure valve, and then heat the furnace to 1300°C at a heating rate of 5°C / min under a nitrogen atmosphere, keep warm for 1 hour, and wait for the temperature to naturally cool to room temperature to obtain a spheroidized hard carbon material.
[0042] Embodiment 4:
[0043] The preparation method of the hard carbon material in this embodiment comprises the following steps:
[0044] Step 1: 600 g of glucose was stirred and dissolved in 2.4 L of deionized water to obtain a 20% glucose aqueous solution, and the dissolved solution was placed in a 4 L autoclave, the atmosphere in the autoclave was air atmosphere, the autoclave was heated to 200 ° C at a heating rate of 2 ° C / min, and kept at this temperature for 6 hours for hydrothermal reaction.
[0045] Step 2: After the hydrothermal reaction is completed, the product of the hydrothermal reaction obtained in step 1 is filtered, the filtrate and the filter residue are separated, and the filter residue is dried at a temperature of 65° C. to obtain a spherical carbon precursor.
[0046] Step three, place the spherical carbon precursor obtained in step two in a tubular furnace or a box furnace, and then adjust the nitrogen intake and the back pressure valve to keep the pressure in the furnace stable at 2 atmospheres, then heat it to 1300°C at a heating rate of 5°C / min under a nitrogen atmosphere, keep it warm for 1h, and wait for the temperature to naturally cool to room temperature to obtain a spheroidized hard carbon material.
[0047] Embodiment 5:
[0048] As an explanation of the fifth embodiment of the present invention, only the differences from the fourth embodiment described above will be described below.
[0049] In step three of this embodiment, the pressure in the furnace is kept stable at 6 atmospheres by adjusting the nitrogen intake and the back pressure valve.
[0050] Comparative Example:
[0051] As an explanation of a comparative example, only the differences from the above-mentioned embodiment 1 are explained below.
[0052] In this comparative example, in step 1, air was not added to the hydrothermal kettle at the beginning of the insulation.
[0053] Performance Testing
[0054] The spheroidized hard carbon materials obtained in Examples 1, 2 and the comparative example were coated on aluminum foil to make electrodes, and then assembled into CR2032 button sodium ion batteries. The electrochemical properties of the batteries were tested to obtain an electrochemical performance comparison table as shown in Table 1.
[0055] The spheroidized hard carbon materials obtained in the above Examples 3 to 5 and the comparative example were coated on copper foil to make electrodes, and then assembled into CR2032 button lithium ion batteries. The electrochemical properties of the batteries were tested to obtain an electrochemical performance comparison table as shown in Table 2.
[0056] Table 1 Comparison of electrochemical performance of Examples 1, 2 and Comparative Example
[0057]
[0058]
[0059] Table 2 Comparison of electrochemical performance of Examples 3-5 and Comparative Examples
[0060] High temperature carbonization nitrogen pressure (atm) Specific capacity (mAh / g) First cycle coulomb efficiency (%) Example 3 2 338 94.7 Example 4 2 361 95.6 Example 5 6 327 93 Comparative Example 1 292 88
[0061] As can be seen from Table 1, a spherical carbon precursor is obtained by hydrothermal reaction of a sugar aqueous solution, and then a high-temperature annealing treatment is performed in an atmosphere such as nitrogen to obtain a hard carbon material. The preparation method of the hard carbon material of the present invention not only has easy-to-obtain raw materials and low cost, but also has a simple preparation process. After the hard carbon materials prepared in Examples 1, 2 and the comparative example are used to make sodium ion batteries, the specific capacity at 0.1C in Examples 1 and 2 is more than 360mAh / g, and the first-cycle coulomb efficiency is close to or reaches 92%. Compared with the comparative example, the compacted density of the hard carbon in Examples 1 and 2 is increased to 1.8g / cm 3 , which greatly increases the loading capacity of the electrode sheet.
[0062] In Example 1, by adding gas to the hydrothermal reactor at the beginning of the heat preservation in step 1, the particle size of the hard carbon was reduced and the compacted density of the hard carbon was increased to 1.8 g / cm 3 , the oxygen content was increased (the oxygen content in the comparative example was 1.6%, and it was increased to 4.3% in Example 1), and the battery charge and discharge capacity was also increased to 372mAh / g, and the coulombic efficiency reached 92.0%. In Example 2, the compaction density of hard carbon was increased to 1.8g / cm 3 , the battery charge and discharge capacity is also increased to 366mAh / g, and the coulombic efficiency is also 91.8%. Therefore, by adding gas to the hydrothermal kettle at the beginning of the insulation in step 1 or by vacuumizing the annealing furnace before high-temperature annealing in step 3, the compaction density of hard carbon can be significantly improved.
[0063] It can be seen from Table 2 that by adding gas to the annealing furnace before high-temperature annealing to increase the pressure in the annealing furnace, the graphitization degree of the hard carbon can be improved, so that when the hard carbon is used in a lithium-ion battery, the battery capacity is greatly improved. When the hard carbon of the comparative example is used in a lithium-ion battery, its battery charge and discharge capacity is only more than 292mAh / g, and the first-cycle coulomb efficiency is only 88%. By adding 1 to 5 atmospheres of gas to the annealing furnace, the battery charge and discharge capacity reaches close to or reaches more than 330mAh / g, and the first-cycle coulomb efficiency also reaches more than 93%. At the same time, in Example 3, by adding gas to the hydrothermal autoclave at the beginning of the insulation in step 1, the compaction density of the hard carbon is also increased to 1.7g / cm 3 The above increases the loading capacity of the electrode sheet.
[0064] Examples of hard carbon materials for battery negative electrodes:
[0065] The hard carbon material for the battery negative electrode of this embodiment is prepared by the preparation method of the above preparation method embodiment.
[0066] Battery Example:
[0067] The battery of this embodiment includes a negative electrode, and the material of the negative electrode includes the hard carbon material of the hard carbon material embodiment. Optionally, the battery can be a lithium ion battery, a sodium ion battery or a potassium ion battery.
[0068] Finally, it should be emphasized that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a hard carbon material for a battery negative electrode, characterized in that: include: Adding the sugar aqueous solution into a hydrothermal kettle for hydrothermal reaction, during the hydrothermal reaction, after the temperature is raised to a set temperature, gas is added into the hydrothermal kettle at the beginning of heat preservation; The product of the hydrothermal reaction is subjected to high temperature annealing to obtain a hard carbon material.
2. The preparation method according to claim 1, characterized in that: The amount of gas added to the hydrothermal kettle at the beginning of the insulation is in the range of 1 to 8 atmospheres.
3. The preparation method according to claim 1, characterized in that: The atmosphere for the high temperature annealing step is nitrogen.
4. The preparation method according to any one of claims 1 to 3, characterized in that: During the high temperature annealing process, the heating rate is in the range of 0.5°C / min to 15°C / min, the reaction temperature is in the range of 800°C to 1900°C, and the holding time is in the range of 1 hour to 3 hours.
5. The preparation method according to any one of claims 1 to 3, characterized in that: Before high temperature annealing, the annealing furnace is evacuated.
6. The preparation method according to any one of claims 1 to 3, characterized in that: Before high temperature annealing, gas is added to the annealing furnace.
7. The preparation method according to claim 6, characterized in that: The amount of supplementary gas added to the annealing furnace is in the range of 1 to 5 atmospheres.
8. A method for preparing a hard carbon material for a battery negative electrode, characterized in that: include: Step 1, adding a sugar aqueous solution into a hydrothermal kettle for hydrothermal reaction; Step 2, filtering the product of the hydrothermal reaction obtained in step 1, separating the filtrate and the filter residue, and drying the filter residue to obtain a spherical carbon precursor; Step 3, subjecting the spherical carbon precursor obtained in step 2 to high temperature annealing to obtain a hard carbon material; Wherein, in step 3, before high temperature annealing, the annealing furnace is first vacuumized; or Before high temperature annealing, gas is added to the annealing furnace.
9. A hard carbon material for a negative electrode of a battery, characterized in that: The method is as described in any one of claims 1 to 8.
10. A battery comprising a negative electrode, characterized in that The material of the negative electrode includes the hard carbon material as claimed in claim 9.