A carbon negative electrode material for sodium-ion batteries, its preparation method and application

Abstract

The present invention provides a method for preparing a carbon negative electrode material for a sodium-ion battery, comprising the following steps: (1) mixing coal powder and sodium bicarbonate and calcining at 270 °C to 350 °C; (2) stirring and reacting in an aqueous sodium hydroxide solution at 65 to 80 °C for 1.5 to 4 hours, collecting the solid mixture B after solid-liquid separation; (3) washing the solid mixture B with deionized water until neutral, collecting the solid mixture C and drying; (4) mixing the solid mixture C with nano-aluminum oxide and sodium hydride, and performing sintering treatment in an atmosphere of ethylene and inert gas to obtain a carbon negative electrode material for a sodium-ion battery, and the highest sintering temperature is 400 °C to 600 °C. The method for preparing the carbon negative electrode material for a sodium-ion battery of the present invention obtains a carbon negative electrode material for a sodium-ion battery coated with alumina, which improves the crystallinity and conductivity of the carbon negative electrode material for a sodium-ion battery; improves the capacity and cycle performance of the carbon negative electrode material for a sodium-ion battery, and the carbon negative electrode material for a sodium-ion battery of the present invention has relatively excellent comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and particularly relates to a carbon negative electrode material for a sodium-ion battery, a preparation method thereof, and an application thereof. Background Art

[0002] Among the existing negative electrode materials for sodium-ion batteries, carbon-based materials are the earliest and most studied negative electrode materials. Graphite has become the current widely used negative electrode material for lithium-ion batteries due to its high volume specific capacity and good cycling performance. However, the sodium storage capacity of graphite is very limited. A general view is that the insertion of sodium ions with large ionic radii into the graphite layer requires a large amount of energy. Disordered carbon has a lower degree of graphitization and a larger interlayer spacing, and is currently a carbon-based material with better performance. The volume expansion of carbon materials is relatively serious during charge and discharge, resulting in easy pulverization of the electrode and a relatively short cycle life. Summary of the Invention

[0003] An object of the present invention is to overcome the deficiencies of the prior art and provide a carbon negative electrode material for a sodium-ion battery, a preparation method thereof, and an application thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of a carbon negative electrode material for a sodium-ion battery, the preparation method comprising the following steps:

[0005] (1) Mix pulverized coal and sodium bicarbonate and calcine at 270°C to 350°C for 60 to 120 minutes, and obtain a mixture A after cooling;

[0006] (2) React the mixture A in an aqueous sodium hydroxide solution at 65 to 80°C with stirring for 1.5 to 4 hours, separate the solid and liquid, and collect a solid mixture B. The concentration of the aqueous sodium hydroxide solution is not less than 2 mol / L;

[0007] (3) Wash the solid mixture B with deionized water until neutral, collect a solid mixture C, and dry it;

[0008] (4) After mixing the solid mixture C with nano-aluminum oxide and sodium hydride, perform sintering treatment in an atmosphere of ethylene and an inert gas to obtain a carbon negative electrode material for a sodium-ion battery. The highest sintering temperature is 400°C to 600°C, the heat preservation time is 4 to 12 hours, and the weight ratio of the solid mixture C, nano-aluminum oxide, and sodium hydride is 100:(2 to 4):(5 to 12.5).

[0009] The preparation method of the above-mentioned carbon negative electrode material for sodium-ion batteries involves subjecting pulverized coal to calcination treatment with molten sodium bicarbonate and hydrothermal treatment with an aqueous sodium hydroxide solution in sequence, reducing the metal impurities in the pulverized coal raw material. Moreover, by combining nano-aluminum oxide and sodium hydride and performing sintering treatment at 400 - 600 °C in an ethylene and inert gas atmosphere, a carbon negative electrode material for sodium-ion batteries coated with aluminum oxide is obtained, improving the crystallinity and conductivity of the carbon negative electrode material for sodium-ion batteries; enhancing the capacity and cycling performance of the carbon negative electrode material for sodium-ion batteries, and having relatively excellent comprehensive performance.

[0010] Preferably, the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:7.5 - 10.

[0011] When the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride meets the above conditions, the crystallinity and conductivity of the carbon negative electrode material for sodium-ion batteries are further improved; the capacity and cycling performance of the carbon negative electrode material for sodium-ion batteries are enhanced, and it has relatively excellent comprehensive performance.

[0012] Preferably, in step (1), the weight ratio of pulverized coal to sodium bicarbonate is 100:(10 - 15).

[0013] Preferably, in step (2), the concentration of the aqueous sodium hydroxide solution is 2 - 11 mol / L, and the ratio of the aqueous sodium hydroxide solution to mixture A is 3 - 8 ml of aqueous sodium hydroxide solution per 1 g of mixture A.

[0014] Preferably, in step (4), the inert gas is nitrogen, helium, or argon. After introducing the inert gas to displace oxygen, the flow rate of ethylene during the calcination process is 80 - 150 ml / min.

[0015] Preferably, in step (3), solid mixture C is vacuum-dried at 105 - 115 °C for 2 - 5 hours.

[0016] Preferably, in step (4), the maximum sintering temperature is 500 - 600 °C. When the temperature is below 300 °C, it is heated to 300 °C at a rate of 8 - 12 °C / min, and then heated to the above maximum sintering temperature at a rate of 1.5 - 2.5 °C / min and held for 4 - 10 hours.

[0017] The present invention also provides a carbon negative electrode material for sodium-ion batteries prepared by the preparation method of any of the above-mentioned carbon negative electrode materials for sodium-ion batteries.

[0018] The present invention also provides a composition of a carbon negative electrode material for sodium-ion batteries, including the above-mentioned carbon negative electrode material for sodium-ion batteries, SP, CNT, CMC, SBR

[0019] The beneficial effects of the present invention are as follows: The present invention provides a carbon negative electrode material for sodium-ion batteries, its preparation method, and application. The present invention has the following advantages:

[0020] By analyzing the relevant data in the process of material preparation, the present invention optimizes the reaction conditions and preparation process, making the preparation method more simple and feasible. Compared with the traditional method, the present invention has the following advantages:

[0021] 1. Low cost: Using common pulverized coal as raw material reduces the cost of material preparation.

[0022] 2. Optimized process: Using sodium bicarbonate to activate pulverized coal and sintering with sodium hydride and nano-aluminum oxide, the preparation steps are simple.

[0023] 3. It can improve the energy density and cycle life of sodium batteries, reduce sodium loss and capacity degradation.

[0024] 4. By alumina coating and sodium hydride treatment, the contact between the electrolyte and alkaline solution and sodium is reduced, achieving the purpose of reducing gas generation, improving problems such as battery volume expansion and electrode / separator misalignment, and reducing battery life attenuation and safety problems.

[0025] 5. The process is simple, facilitating large-scale preparation. The preparation process is simple, suitable for industrial production, and can reduce production costs.

[0026] 6. Energy conservation and emission reduction: Sodium bicarbonate activates pulverized coal, reducing the subsequent use of alkali; the concentration of sodium hydroxide solution used in the preparation process is relatively low, and the pollution during the treatment process is small; the sintering temperature is low, and the energy consumption is small.

[0027] The preparation method of the carbon negative electrode material for sodium ion battery of the present invention is as follows: The pulverized coal is successively subjected to roasting treatment with molten sodium bicarbonate and hydrothermal treatment with aqueous sodium hydroxide solution, reducing the metal impurities in the pulverized coal raw material. Moreover, combined with nano-aluminum oxide and sodium hydride, after sintering treatment at 400-600 °C in an ethylene and inert gas atmosphere, a carbon negative electrode material for sodium ion battery with alumina coating is obtained, improving the crystallinity and conductivity of the carbon negative electrode material for sodium ion battery; improving the capacity and cycle performance of the carbon negative electrode material for sodium ion battery. The carbon negative electrode material for sodium ion battery of the present invention has excellent comprehensive performance. Brief Description of the Drawings

[0028] Figure 1 It is the SEM morphology structure diagram of the carbon negative electrode material for sodium ion battery of the embodiment of the present invention.

[0029] Figure 2 It is the comparison diagram of the alumina coating morphology of the carbon negative electrode material for sodium ion battery of the embodiment of the present invention

[0030] Figure 3 It is the XRD diffraction pattern diagram of the carbon negative electrode material for sodium ion battery of the comparative example of the present invention.

[0031] Figure 4Battery performance graph of the carbon anode material for sodium-ion batteries according to the embodiments of the present invention.

[0032] Figure 5 Gas generation situation of the slurry of the carbon anode material for sodium-ion batteries according to the embodiments of the present invention. Specific embodiments

[0033] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] As a preparation method of a carbon anode material for a sodium-ion battery according to an embodiment of the present invention, the method includes the following steps:

[0036] (1) After mixing pulverized coal and sodium bicarbonate according to a weight ratio of 100:10, roasting in a muffle furnace at 300 °C for 60 minutes, and cooling to obtain mixture A;

[0037] (2) After pulverizing mixture A, carrying out a hydrothermal reaction in a 7.5 mol / L sodium hydroxide aqueous solution at 70 °C for 3 hours, the liquid-solid ratio of mixture A to the sodium hydroxide aqueous solution is 4 mL / g; after solid-liquid separation, collect solid mixture B, and the method of solid-liquid separation is vacuum filtration;

[0038] (3) Wash solid mixture B with deionized water until neutral, then collect solid mixture C and vacuum dry at 105 °C for 4 hours;

[0039] (4) After mixing solid mixture C with nano-aluminum oxide and sodium hydride and placing them in a CVD furnace, the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:7.5. Pass argon to displace air, and pass ethylene at a gas flow rate of 100 mL / min for sintering treatment to obtain a carbon anode material for a sodium-ion battery. The sintering temperature is set to rise to 300 °C at a rate of 10 °C / min, then rise to 400 °C at a rate of 2 °C / min and hold for 2 hours, continue to rise to 500 °C at a rate of 2 °C / min and hold for 6 hours, and continue to rise to 600 °C at a rate of 2 °C / min and hold for 4 hours. The particle size of the nano-aluminum oxide is less than 1000 nanometers.

[0040] Elemental composition analysis of the solid mixture C (MX) after the treatment in step (3) is as shown in Table 1 below

[0041] Table 1 Elemental composition analysis of the initial pulverized coal and the solid mixture C after the treatment in step (3)

[0042]

[0043] Example 2

[0044] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is: (1) After the mixture A is pulverized, it is stirred in a 2.5 mol / L aqueous sodium hydroxide solution at 70 °C for 3 hours for hydrothermal reaction.

[0045] Example 3

[0046] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is: the weight ratio of the solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:5.

[0047] Example 4

[0048] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is: the weight ratio of the solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:10.

[0049] Example 5

[0050] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is: the weight ratio of the solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:12.5.

[0051] Comparative Example 1

[0052] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 1 is: Step (2) is not included. After Step (1) is completed, Steps (3) and (4) are directly carried out.

[0053] Comparative Example 2

[0054] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 1 is: sodium carbonate is used to replace sodium hydride in Step (4).

[0055] Comparative Example 3

[0056] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 1 is: in Step (4), sodium hydride is not added, and the mass of sodium hydride is supplemented with nano-aluminum oxide.

[0057] Comparative Example 4

[0058] As a preparation method of a carbon negative electrode material for a sodium-ion battery according to a comparative example of the present invention, the only difference between this comparative example and Embodiment 1 is: in Step (4), nano-aluminum oxide is not added, and the mass of nano-aluminum oxide is supplemented with sodium hydride.

[0059] Comparative Example 5

[0060] As a preparation method of a carbon negative electrode material for a sodium-ion battery as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that in step (4), nano-magnesium oxide is used to replace nano-aluminum oxide.

[0061] Comparative Example 6

[0062] As a preparation method of a carbon negative electrode material for a sodium-ion battery as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that in step (4), methane is used to replace ethylene.

[0063] Comparative Example 7

[0064] As a preparation method of a carbon negative electrode material for a sodium-ion battery as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride is 100:1:7.5.

[0065] Comparative Example 8

[0066] As a preparation method of a carbon negative electrode material for a sodium-ion battery as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride is 100:3:2.5.

[0067] Comparative Example 9

[0068] As a preparation method of a carbon negative electrode material for a sodium-ion battery as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that (1) after mixing pulverized coal and sodium bicarbonate in a weight ratio of 100:5, they are calcined in a muffle furnace at 300 °C for 60 minutes, and after cooling, mixture A is obtained.

[0069] Comparative Example 10

[0070] As a preparation method of a carbon negative electrode material for a sodium-ion battery of Example 1 of the present invention, the only difference between this example and Example 1 is that the weight ratio of solid mixture C, nano-aluminum oxide, and sodium hydride is 100:5:7.5.

[0071] The preparation method parameters of Examples 1 - 5 and Comparative Examples 1 - 10 are shown in Table 1.

[0072] Table 1 Parameters of the preparation method of the carbon negative electrode material for the sodium-ion battery

[0073]

[0074]

[0075] I. Samples to be measured

[0076] Prepare the carbon negative electrode materials for sodium-ion batteries according to the preparation methods of the carbon negative electrode materials for sodium-ion batteries in Examples 1-5 and Comparative Examples 1-10, and prepare the materials as samples according to the addition amount of 5 g of raw materials.

[0077] II. Detection methods

[0078] (I) Crystallinity detection.

[0079] Figure 3 For the XRD diffraction patterns of Example 1 and Comparative Example 4, crystallinity measurement.

[0080] Table 2 Crystallinity of carbon negative electrode materials for sodium-ion batteries

[0081] Characteristic peak Height FWHM Crystallinity Example 1 652.2 0.426 85.46％ Comparative Example 4 239.1 1.831 80.22％

[0082] Crystallinity calculation formula (XRD diffraction method):

[0083] Crystallinity = (Icr / Iam) * 100%

[0084] where Icr is the intensity of the crystalline peak

[0085] Iam is the intensity of the amorphous peak

[0086] The SEM micrograph of Example 1 is as Figure 1 shown. It can be seen that the carbon negative electrode material has a layered structure, and the alumina coating layer is uniform;

[0087] Figure 2 (a), Figure 2 (b), Figure 2 (c) are the SEM micrographs of Comparative Example 7, Example 1, and Comparative Example 10 respectively. It can be seen that the alumina coating layer of Comparative Example 7 is too thin and uneven, and the alumina coating layer of Comparative Example 10 is too thick, affecting the electrical properties of the material;

[0088] Figure 4 For the cycle performance comparison of Example 1, Comparative Example 1, and Comparative Example 3.

[0089] (II) Battery performance detection

[0090] Battery performance

[0091] The crystallinity and battery performance results of the carbon negative electrode materials for sodium-ion batteries in Examples 1-5 and Comparative Examples 1-10 are shown in Table 3.

[0092] Table 3 Crystallinity and battery performance of carbon negative electrode materials for sodium-ion batteries

[0093] (III) Gas generation detection

[0094] Assemble a button cell with the sodium-ion battery carbon anode material prepared above. Specifically, use a button cell formulation of 0.288 g of SP + 3 g of CNT + 8.1282 g of CMC colloidal solution + 5.4 g of sodium-ion battery carbon anode material + 0.525 g of SBR. Premix for 3 min at 200 r / min with a centrifugal degassing machine, mix for 10 min at 1000 r / min, and then perform vacuum degassing for 5 min to prepare a coating slurry. Take a certain amount of the slurry and place it in an aluminum-plastic film bag, and seal it after exhausting the gas with a vacuum packaging machine. Observe the gas production situation every 8 h, and calculate the volume change of the aluminum-plastic film bag after gas production and deformation by the water displacement method. The initial volume of the slurry plus the aluminum-plastic film bag after exhausting the gas is 20.0 ml;

[0095] Figure 5 is the situation of air bubbles generated in the slurry, Figure 5 a is Example 1, Figure 5 b is Comparative Example 4. Gas production in the slurry will affect the safety performance of the battery material.

[0096] Table 3 Battery performance results of sodium-ion battery carbon anode materials

[0097]

[0098]

[0099]

[0100] As can be seen from Table 3, for the preparation method of the sodium-ion battery carbon anode material of the present invention, the pulverized coal is successively subjected to molten sodium bicarbonate roasting treatment and sodium hydroxide aqueous solution hydrothermal treatment, reducing the metal impurities in the pulverized coal raw material. Moreover, combined with nano-aluminum oxide and sodium hydride, after sintering treatment at 400 - 600 °C in an ethylene and inert gas atmosphere, an alumina-coated sodium-ion battery carbon anode material is obtained, improving the crystallinity and conductivity of the sodium-ion battery carbon anode material; improving the capacity and cycling performance of the sodium-ion battery carbon anode material. As can be seen from Table 2 and Table 3, the sodium-ion battery carbon anode material of the present invention has more excellent comprehensive performance.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a carbon negative electrode material for a sodium ion battery, characterized in that: The preparation method comprises the following steps: (1) mixing coal powder and sodium bicarbonate, calcining the mixture in a muffle furnace at 270° C. to 350° C. for 60 to 120 minutes, and cooling the mixture to obtain a mixture A; (2) mixing the mixture A in a sodium hydroxide aqueous solution at 65 to 80° C. and stirring to react for 1.5 to 4 hours, collecting the solid mixture B after solid-liquid separation, and the concentration of the sodium hydroxide aqueous solution is not less than 2 mol / L; (3) washing the solid mixture B with deionized water until it is neutral, collecting the solid mixture C and drying it; (4) After mixing the solid mixture C with nano-alumina and sodium hydride, sintering the mixture in an atmosphere of ethylene and inert gas to obtain a carbon negative electrode material for a sodium ion battery. The maximum sintering temperature is 400-600° C., the insulation time is 4-12 hours, and the weight ratio of the solid mixture C, nano-alumina and sodium hydride is 100:(2-4):(5-12.5).

2. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: The weight ratio of the solid mixture C, nano-alumina and sodium hydride is 100:3:7.5-10.

3. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step (1), the weight ratio of coal powder to sodium bicarbonate is 100:(10-15).

4. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step (2), the concentration of the sodium hydroxide aqueous solution is 2-11 mol / L, and the ratio of the sodium hydroxide aqueous solution to the mixture A is 3-8 ml of the sodium hydroxide aqueous solution to 1 g of the mixture A.

5. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step (4), the inert gas is nitrogen, helium, or argon. After the inert gas is introduced to replace oxygen, the flow rate of ethylene during the calcination process is 80 to 150 ml / min.

6. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step (3), the solid mixture C is vacuum dried at 105-115° C. for 2-5 hours.

7. The method for preparing the carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step (4), the maximum sintering temperature is 500-600°C. When the temperature is lower than 300°C, the temperature is raised to 300°C at a rate of 8-12°C / min, and then the temperature is raised to the maximum sintering temperature at a rate of 1.5-2.5°C / min and kept at this temperature for 4-10 hours.

8. A sodium ion battery carbon negative electrode material prepared by the method for preparing a sodium ion battery carbon negative electrode material according to any one of claims 1 to 7.

9. A sodium ion battery carbon negative electrode material composition, comprising the sodium ion battery carbon negative electrode material as claimed in claim 8, conductive carbon black, carbon nanotubes, carboxymethyl cellulose and styrene-butadiene rubber.

Images