A hard carbon anode material for sodium-ion batteries and its preparation method

Abstract

The present invention provides a hard carbon negative electrode material for a sodium ion battery and a preparation method thereof. The preparation method comprises the following steps: (1) mixing a resin precursor and an alcohol solvent, adding zinc oxide, and obtaining a hard carbon precursor after stirring and curing; (2) performing carbonization treatment on the hard carbon precursor obtained in step (1) under an inert atmosphere, and obtaining the hard carbon negative electrode material for the sodium ion battery after crushing, pickling and sieving. By adding a certain proportion of zinc oxide and alcohol as pore-forming agents in the resin precursor and acting synergistically, the present invention realizes the regulation and optimization of the surface defects and internal structure of the hard carbon material. The prepared hard carbon negative electrode material has a lower specific surface area, a larger interlayer spacing and a micropore pore volume. The specific capacity, the first Coulomb efficiency and the rate performance of the sodium ion battery prepared therefrom are effectively improved, realizing excellent comprehensive performance.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries and relates to a sodium ion battery hard carbon negative electrode material and a preparation method thereof. Background Art

[0002] The abundant reserves, wide distribution and low cost of metallic sodium make sodium-ion batteries have broad application prospects in large-scale energy storage. At present, the development of sodium-ion batteries has become the focus of attention. Hard carbon materials are considered to be the most promising sodium negative electrode materials for commercialization due to their excellent sodium storage capacity, long cycle life and low cost.

[0003] Hard carbon is mainly composed of disordered stacking of small-sized graphene sheets. The two sides of the graphene sheets, the edges of the graphene sheets, the holes around the sheet structure, and a large number of defects are all active sites for storing sodium ions. The charge and discharge curve of hard carbon contains a high potential slope (>0.10V) and a low potential platform (0.01-0.10V). Various mechanisms have been proposed for the charge and discharge behavior in different potential regions, but no conclusion has been reached. Some studies have linked the charge storage behavior to the interlayer distance (d002) and concluded that ordered graphene layers with d in the range of 0.36-0.40nm can store Na ions through interlayer insertion, providing high platform capacity, while some studies believe that Na ions (or clusters) filling the internal micropores (or gaps between graphene sheets) are responsible for the platform capacity.

[0004] Although there are different views on the charge storage mechanism, it is a recognized fact that the low potential platform region is the determining step of the ion diffusion rate in hard carbon. + The diffusion coefficient is 10 -11 ~10 - 9 cm 2 ·s -1 Between, platform area (10 -13 ~10 -10 cm 2 ·s -1 ) is two orders of magnitude lower (<0.10V). The diffusion rate of sodium ions is increased and the rate performance of hard carbon is improved by introducing more pores or defects in the hard carbon structure. However, the hard carbon prepared by this method usually has a high specific surface area, which reduces the initial Coulomb efficiency (ICE) and loses the platform capacity at low pressure (usually less than 50%), which is not conducive to the deintercalation and diffusion of sodium ions. Therefore, it is necessary to construct a hard carbon with a good microstructure to improve the rate performance of sodium storage of the material while maintaining the dominant platform capacity. Summary of the invention

[0005] The object of the present invention is to provide a hard carbon negative electrode material for a sodium-ion battery and a preparation method thereof. By adding a certain proportion of zinc oxide and alcohols as pore-forming agents to the resin precursor and synergistically acting, the present invention realizes the regulation and optimization of the surface defects and internal structure of the hard carbon material. The prepared hard carbon negative electrode material has a low specific surface area, a large interlayer spacing, and a micropore pore volume. The specific capacity, first Coulombic efficiency, and rate performance of the sodium-ion battery prepared therefrom are effectively improved, achieving excellent comprehensive performance.

[0006] To achieve the object of this invention, the following technical solutions are adopted in the present invention:

[0007] In the first aspect, the present invention provides a preparation method of a hard carbon negative electrode material for a sodium-ion battery, and the preparation method includes the following steps:

[0008] (1) Mix the resin precursor and an alcohol solvent, add zinc oxide, and obtain a hard carbon precursor after stirring and curing;

[0009] (2) Carbonize the hard carbon precursor obtained in step (1) under an inert atmosphere, and obtain the hard carbon negative electrode material for the sodium-ion battery after crushing, pickling, and sieving.

[0010] The present invention prepares a hard carbon material with a low specific surface area, a large interlayer spacing, and a high micropore pore volume through processes such as stirring, curing, carbonization, pickling, crushing, and sieving by adding a certain proportion of alcohol solvent and zinc oxide to the resin precursor. The obtained hard carbon material has a high charge-discharge specific capacity and first Coulombic efficiency, and excellent rate performance. Adding alcohol solvent and zinc oxide as pore-forming agents and synergistically acting, reasonably regulating the defects of the carbon plane, and constructing a hard carbon material with a good microstructure are beneficial to improving the sodium storage capacity and sodium ion diffusion rate, and enhancing the electrochemical performance of the hard carbon material.

[0011] Preferably, the resin precursor in step (1) includes any one or a combination of at least two of a phenolic resin precursor, a furan resin precursor, or a furfural resin precursor, and is preferably a phenolic resin precursor.

[0012] Preferably, the phenolic resin includes a thermoplastic phenolic resin and / or a thermosetting phenolic resin.

[0013] Preferably, the alcohol solvent in step (1) includes any one or a combination of at least two of ethanol, methanol, propanol, ethylene glycol, propylene glycol, or isopropanol.

[0014] Preferably, the morphology of the zinc oxide includes spherical, rod-shaped, nanowire, nanobelt, and flower-shaped, and further preferably, the morphology of the zinc oxide is spherical.

[0015] Preferably, the median particle size D of the zinc oxide 50is 400 - 800 nm, for example: 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, etc.

[0016] Preferably, the mass ratio of the resin precursor, alcohol solvent, and zinc oxide in step (1) is 25:(8 - 17):(1 - 3), for example: 25:10:2, 25:16.7:1.5, 25:8.33:2, 25:13.5:1.5, 25:10:1.8, etc.

[0017] Preferably, the stirring speed in step (1) is 400 - 600 rpm, for example: 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc.

[0018] Preferably, the stirring time is 2 - 4 h, for example: 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc.

[0019] Preferably, the curing temperature is 70 - 80 °C, for example: 70 °C, 72 °C, 75 °C, 78 °C, 80 °C, etc.

[0020] Preferably, the curing time is 3 - 5 h, for example: 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.

[0021] Preferably, the temperature of the carbonization treatment in step (2) is 1000 - 1500 °C, for example: 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C, 1500 °C, etc.

[0022] Preferably, the carbonization treatment time is 2 - 4 h, for example: 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc.

[0023] Preferably, the method of the crushing treatment includes ball milling, mechanical pulverization, or jet milling, preferably ball milling.

[0024] In a second aspect, the present invention provides a hard carbon negative electrode material for a sodium - ion battery, and the hard carbon negative electrode material for a sodium - ion battery is prepared by the method as described in the first aspect.

[0025] Preferably, the specific surface area of the hard carbon negative electrode material for a sodium - ion battery is 3 - 100 m 2 / g, for example: 5 m 2 / g, 10 m 2 / g, 20 m 2 / g, 50 m 2 / g, 80 m 2 / g, or 100 m 2 / g, etc.

[0026] Preferably, the average pore diameter of the hard carbon negative electrode material for the sodium-ion battery is 1 to 3 nm, such as: 1 nm, 1.5 nm, 2 nm, 2.5 nm, or 3 nm, etc.

[0027] Preferably, the d 002 layer spacing of the hard carbon negative electrode material for the sodium-ion battery is 0.37 to 0.40 nm, such as: 0.37 nm, 0.38 nm, 0.385 nm, 0.39 nm, or 0.4 nm, etc.

[0028] Preferably, the median particle size D50 of the hard carbon negative electrode material for the sodium-ion battery is 10 to 30 μm, such as: 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm, etc.

[0029] In the third aspect, the present invention provides a negative electrode plate, and the negative electrode plate includes the hard carbon negative electrode material for the sodium-ion battery as described in the second aspect.

[0030] In the fourth aspect, the present invention provides a sodium-ion battery, and the sodium-ion battery includes the negative electrode plate as described in the third aspect.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) By adding zinc oxide and an alcohol solvent to the resin in a synergistic manner, the present invention realizes the regulation and optimization of the carbon plane defects, and prepares a hard carbon structure with a low specific surface area, a large d 002 layer spacing, and a high micropore content. The specific capacity, rate performance, and first Coulomb efficiency of the sodium-ion battery made therefrom are effectively improved, and excellent comprehensive performance is achieved.

[0033] (2) The battery made of the hard carbon negative electrode material for the sodium-ion battery of the present invention can reach a first charging capacity of more than 263 mAh / g, a first discharge capacity of more than 285 mAh / g, a first Coulomb efficiency of more than 91%, and the capacity ratio in the plateau region exceeds 60% at 0.1C. After 50 cycles, the capacity retention rate can reach more than 93%. At 0.5C and 1C rates, the reversible capacity exceeds 248 mAh / g and 186 mAh / g. By adjusting the type of alcohol solution and the raw material ratio, the first charging capacity of the hard carbon negative electrode material for the sodium-ion battery can reach 281.87 mAh / g, the first discharge capacity can reach 305.82 mAh / g, the first Coulomb efficiency can reach 92.17%, the capacity ratio in the plateau region reaches 69.23%, and after 50 cycles, the capacity retention rate can reach 95.13%. At 0.5C and 1C rates, the discharge capacities are 277.68 and 204.93 mAh / g in sequence. Description of the Drawings

[0034] Figure 1It is the SEM image of the hard carbon negative electrode material described in Embodiment 1 of the present invention. Detailed implementation manners

[0035] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0036] Embodiment 1

[0037] This embodiment provides a hard carbon negative electrode material for a sodium-ion battery. The preparation method of the hard carbon negative electrode material for the sodium-ion battery is as follows:

[0038] (1) Dissolve 73.45 g of phenolic resin in 29.38 g of ethanol solution, then add 5.88 g of zinc oxide, stir with a stirring paddle at a speed of 450 rpm for 4 h, place the mixed solution in a blast drying oven at 80 °C for 4 h to cure, and obtain a hard carbon precursor material;

[0039] (2) After repeatedly evacuating the hard carbon precursor in a calcination furnace three times, heat it to 1300 °C at a heating rate of 5 °C / min under an argon atmosphere, and keep it heated for 4 h. After the carbonized material is cooled to room temperature, it is mechanically crushed, then 300 mL of 0.1 M dilute hydrochloric acid is added for ultrasonic washing for 6 h, then filtered by suction, washed with water until the filtrate is neutral, and dried at 100 °C. The obtained material is ball-milled in a ball mill at 450 rpm / min for 8 h, and passed through a 400-mesh sieve to obtain the hard carbon negative electrode material for the sodium-ion battery.

[0040] The SEM image of the hard carbon negative electrode material for the sodium-ion battery is as Figure 1 shown.

[0041] Embodiment 2

[0042] This embodiment provides a hard carbon negative electrode material for a sodium-ion battery. The preparation method of the hard carbon negative electrode material for the sodium-ion battery is as follows:

[0043] (1) Dissolve 73.45 g of phenolic resin in 39.58 g of ethylene glycol solution, then add 5.88 g of zinc oxide, stir with a stirring paddle at a speed of 450 rpm for 4 h, place the mixed solution in a blast drying oven at 80 °C for 4 h to cure, and obtain a hard carbon precursor material;

[0044] (2) Place the hard carbon precursor in a calcination furnace and evacuate it three times repeatedly. Then, under an argon atmosphere, heat it to 1300 °C at a heating rate of 5 °C / min and hold for 4 h. After the carbonized material is cooled to room temperature, it is mechanically crushed, then 300 mL of 0.1 M dilute hydrochloric acid is added for ultrasonic washing for 6 h, followed by suction filtration. After washing with water until the filtrate is neutral, it is dried at 100 °C. The obtained material is ball-milled in a ball mill at 450 rpm / min for 8 h and sieved through a 400-mesh sieve to obtain the hard carbon anode material for the sodium-ion battery.

[0045] Example 3

[0046] This example provides a hard carbon anode material for a sodium-ion battery. The preparation method of the hard carbon anode material for the sodium-ion battery is as follows:

[0047] (1) Dissolve 73.45 g of phenolic resin in 48.52 g of propylene glycol solution, then add 5.88 g of zinc oxide, and stir with a stirring paddle at 450 rpm for 4 h. The mixed solution is cured in a blast drying oven at 80 °C for 4 h to obtain a hard carbon precursor material;

[0048] (2) Place the hard carbon precursor in a calcination furnace and evacuate it three times repeatedly. Then, under an argon atmosphere, heat it to 1300 °C at a heating rate of 5 °C / min and hold for 4 h. After the carbonized material is cooled to room temperature, it is mechanically crushed, then 300 mL of 0.1 M dilute hydrochloric acid is added for ultrasonic washing for 6 h, followed by suction filtration. After washing with water until the filtrate is neutral, it is dried at 100 °C. The obtained material is ball-milled in a ball mill at 450 rpm / min for 8 h and sieved through a 400-mesh sieve to obtain the hard carbon anode material for the sodium-ion battery.

[0049] Example 4

[0050] The difference between this example and Example 1 is only that the mass of the ethanol solution is 37.72 g, and other conditions and parameters are exactly the same as those in Example 1.

[0051] Example 5

[0052] The difference between this example and Example 1 is only that the mass of the ethanol solution is 23.40 g, and other conditions and parameters are exactly the same as those in Example 1.

[0053] Example 6

[0054] The difference between this example and Example 1 is only that the mass of zinc oxide is 7.345 g, and other conditions and parameters are exactly the same as those in Example 1.

[0055] Example 7

[0056] The difference between this example and Example 1 is only that the mass of zinc oxide is 4.407 g, and other conditions and parameters are exactly the same as those in Example 1.

[0057] Comparative Example 1

[0058] The only difference between this comparative example and Example 1 is that zinc oxide is not added, and other conditions and parameters are exactly the same as those in Example 1.

[0059] Performance test:

[0060] The prepared hard carbon material was subjected to physical and chemical characterization tests, and the test results are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] The prepared hard carbon negative electrode material, carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose were homogenously mixed in a mass ratio of 95:1.5:1.5:2. During the homogenization process, an appropriate amount of water was added to adjust the viscosity to prepare an electrode slurry. The prepared electrode slurry was uniformly coated on aluminum foil and vacuum dried at 80 °C for 12 h, and then cut into (6×6) mm 2 electrode sheets, and the loading amount of the active material was controlled between 6 - 1.0 mg / cm 2 to obtain electrode sheets. Then, a button-type half-cell was assembled in a glove box filled with argon. Metallic sodium was used as the counter electrode, glass fiber was used as the separator, and the electrolyte used was 1 M NaClO4 in EC:DEC (volume ratio 1:1). The charge-discharge performance was tested using a LAND battery test system, the test voltage range was 0 - 3 V, and the nominal specific capacity was set to 300 mAh / g. The test results are shown in Table 2.

[0065] Table 2

[0066]

[0067] As can be seen from Table 2, it can be obtained from Examples 1-7 that for the battery made of the hard carbon negative electrode material of the sodium ion battery of the present invention, at 0.1C, the first charge capacity can reach more than 263 mAh / g, the first discharge capacity can reach more than 285 mAh / g, the first Coulombic efficiency can reach more than 91%, the capacity ratio in the plateau region exceeds 60%, and after 50 cycles, the capacity retention rate can reach more than 93%. At 0.5C and 1C rates, the reversible capacities exceed 248 mAh / g and 186 mAh / g respectively. By adjusting the type of alcohol solution and the raw material ratio, for the hard carbon negative electrode material of the sodium ion battery, at 0.1C, the first charge capacity can reach 281.87 mAh / g, the first discharge capacity can reach 305.82 mAh / g, the first Coulombic efficiency can reach 92.17%, the capacity ratio in the plateau region reaches 69.23%, and after 50 cycles, the capacity retention rate can reach 95.13%. At 0.5C and 1C rates, the discharge capacities are 277.68 mAh / g and 204.93 mAh / g respectively.

[0068] From the comparison between Example 1 and Examples 2-3, it can be obtained that the type of alcohol solution will affect the structural parameters and electrochemical performance of the prepared hard carbon negative electrode material. Compared with ethanol solvent, the pore structure of the hard carbon prepared using ethylene glycol and propylene glycol as solvents is more developed, the specific capacity and the capacity ratio in the plateau region are close, but the cycle stability and rate performance are poor.

[0069] From the comparison between Example 1 and Examples 4-7, it can be obtained that during the preparation process of the hard carbon negative electrode material of the sodium ion battery of the present invention, the addition amounts of the alcohol solvent and zinc oxide will affect the structural parameters and electrochemical performance of the prepared hard carbon negative electrode material of the sodium ion battery. The present invention controls the mass ratio of the resin precursor, the alcohol solvent and zinc oxide at 25:(8-14):(1-3), and the performance of the prepared hard carbon negative electrode material of the sodium ion battery is better. If too much ethanol and zinc oxide are added respectively, a large number of open pores will be formed, resulting in a large specific surface area of the material, low initial efficiency, and a decrease in the capacity in the plateau region.

[0070] From the comparison between Example 1 and Comparative Example 1, it can be obtained that by adding zinc oxide in the present invention, during the high-temperature carbonization process, bulk etching of the graphene layer is caused by the reaction ZnO + C = Zn + CO, resulting in an increase in the micropore content and an increase in the layer spacing at the same time.

[0071] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a hard carbon negative electrode material for a sodium-ion battery, characterized in that The preparation method comprises the following steps: (1) Mix a resin precursor and an alcohol solvent, add zinc oxide, and obtain a hard carbon precursor after stirring and curing; (2) Carry out carbonization treatment on the hard carbon precursor obtained in step (1) under an inert atmosphere, and obtain the hard carbon negative electrode material for the sodium-ion battery after crushing, pickling, and sieving; The resin precursor in step (1) includes any one or a combination of at least two of a phenolic resin precursor, a furan resin precursor, or a furfural resin precursor. The alcohol solvent includes any one or a combination of at least two of ethanol, methanol, propanol, ethylene glycol, propylene glycol, or isopropanol. The mass ratio of the resin precursor, the alcohol solvent, and zinc oxide is 25:(8-17):(1-3), and the curing temperature is 70-80°C; The temperature of the carbonization treatment in step (2) is 1000-1500°C.

2. The preparation method according to claim 1, characterized in that, The resin precursor in step (1) is a phenolic resin precursor.

3. The preparation method according to claim 2, characterized in that, The phenolic resin precursor includes a thermoplastic phenolic resin precursor and / or a thermosetting phenolic resin precursor.

4. The preparation method according to claim 1, characterized in that, The morphology of the zinc oxide includes any one or a combination of at least two of spherical, rod-shaped, nanowire, nanobelt, or flower-shaped.

5. The preparation method according to claim 1, characterized in that, The morphology of the zinc oxide is spherical.

6. The preparation method according to claim 1, characterized in that, The median particle size D50 of the zinc oxide is 400-800 nm.

7. The preparation method according to claim 1, characterized in that, The stirring speed in step (1) is 400-600 rpm.

8. The preparation method according to claim 1, characterized in that, The stirring time is 2-4 h.

9. The preparation method according to claim 1, wherein The curing time is 3-5 h.

10. The preparation method according to claim 1, characterized in that, The carbonization treatment time is 2-4 h.

11. The preparation method according to claim 1, characterized in that, The crushing method includes any one or a combination of at least two of ball milling, mechanical crushing, or jet milling.

12. The preparation method according to claim 11, wherein, The crushing method is ball milling.

13. A hard carbon negative electrode material for a sodium ion battery, characterized in that, The hard carbon negative electrode material for the sodium-ion battery is prepared by the method according to any one of claims 1-12.

14. The hard carbon negative electrode material for a sodium ion battery according to claim 13, wherein, The specific surface area of the hard carbon negative electrode material for the sodium ion battery is 3 to 100 m 2 / g.

15. The hard carbon negative electrode material for a sodium ion battery according to claim 13, characterized in that, The average pore size of the hard carbon negative electrode material for the sodium-ion battery is 1-3 nm.

16. The hard carbon negative electrode material for a sodium ion battery according to claim 13, wherein The d-spacing of the hard carbon anode material for the sodium-ion battery 002 is 0.37 to 0.40 nm.

17. The hard carbon negative electrode material for a sodium ion battery according to claim 13, wherein The median particle size D50 of the hard carbon negative electrode material for the sodium-ion battery is 10-30 μm.

18. A negative electrode plate, characterized in that, The negative electrode sheet contains the hard carbon negative electrode material for the sodium-ion battery according to any one of claims 13-17.

19. A sodium-ion battery, characterized in that, The sodium-ion battery contains the negative electrode sheet according to claim 18.

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