Carbon-based negative electrode material and preparation method thereof, negative electrode and sodium ion battery

Abstract

The present invention relates to the field of battery material technology, and discloses a carbon-based negative electrode material, a preparation method thereof, a negative electrode, and a sodium-ion battery. The preparation method of the carbon-based negative electrode material comprises: providing a mixed powder comprising starch and nano-sized boehmite powder; subjecting the mixed powder to pyrolysis of the boehmite at 400-500°C in a nitrogen atmosphere, allowing the boehmite to fully decompose into aluminum oxide and water, thereby etching the carbon material; and then carbonizing the starch at 1100-1500°C to form a mixture of aluminum, nitrogen, and aluminum oxide, which is coated on the carbon material. The carbon-based negative electrode material prepared by this preparation method of the present invention has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a carbon-based negative electrode material and a preparation method thereof, a negative electrode and a sodium ion battery. Background Art

[0002] To improve the sodium storage capacity and electrical performance of sodium batteries, starch can be considered as a carbon source to replace hard carbon from biomass, such as shells, bamboo, and reeds, which have poor raw material and morphological consistency. However, during the preparation process, starch carbon sources can foam, melt, and expand dramatically, making material preparation difficult. Furthermore, the irregular morphology of the foamed and melted material particles can also affect the final performance. To address this issue, the poor stability and suboptimal electrochemical performance of starch-based carbon anode materials have not yet been effectively addressed.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention aims to improve at least one of the problems mentioned in the background art.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for preparing a carbon-based negative electrode material, comprising:

[0007] Providing a mixed powder, the mixed powder comprising starch and nano-boehmite powder mixed with each other;

[0008] The mixed powder is placed at 400-500° C. to pyrolyze boehmite, so that the boehmite is fully decomposed to generate aluminum oxide; and then the starch is carbonized at 1100-1500° C. at high temperature.

[0009] In an optional embodiment, the time for pyrolyzing boehmite is 0.5 to 2 hours.

[0010] In an optional embodiment, the high-temperature carbonization time is 2 to 5 hours.

[0011] In an optional embodiment, the high-temperature carbonization process is performed in a nitrogen atmosphere.

[0012] In an optional embodiment, at least one of the following features (1) and (2) is included:

[0013] (1) The D50 and D90 of the starch are 4-9 μm and 10-20 μm, respectively;

[0014] (2) The mass ratio of starch to the nano-boehmite is 100:5~20.

[0015] In an optional embodiment, the starch is selected from at least one of corn starch, sweet potato starch, potato starch, cassava starch, sweet potato starch, water chestnut starch and lotus root starch.

[0016] In a second aspect, the present invention provides a carbon-based negative electrode material prepared by the preparation method described in any one of the aforementioned embodiments.

[0017] In a third aspect, the present invention provides a negative electrode, wherein the composition layer of the active coating comprises the carbon-based negative electrode material as described in the above embodiment.

[0018] In a fourth aspect, the present invention provides a sodium ion battery comprising the negative electrode described in the aforementioned embodiment.

[0019] The present invention has the following beneficial effects:

[0020] The preparation method provided by the present invention utilizes a mixture of nano-sized boehmite and starch for calcination, achieving localized physical barrier and constraint on the starch, effectively inhibiting foaming and fusion of starch particles during heating, improving particle morphology, and suppressing the ordered growth of the microcrystalline structure, thereby generating a more disordered sodium storage layer. Furthermore, after pyrolysis of the boehmite, the generated water vapor reacts with the starch to etch the material, creating pores and increasing capacity. The generated alumina, after high-temperature calcination, forms a mixture of aluminum nitrogen and aluminum oxide, which coats the starch surface and improves the material's conductivity. Furthermore, the aluminum nitrogen and aluminum oxide particles participate in the formation of the SEI film, increasing the high and low temperature stability of the SEI film, reducing side reactions, and improving the cycle life and rate performance of the battery cell. Using boehmite and starch as raw materials is low-cost, and the single-shot calcination process simplifies the production process. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0022] An embodiment of the present invention provides a method for preparing a carbon-based negative electrode material, comprising:

[0023] Providing a mixed powder, the mixed powder comprising starch and nano-sized boehmite powder mixed with each other;

[0024] The mixed powder is placed at 400-500° C. to pyrolyze boehmite, so that the boehmite is fully decomposed to generate alumina; and then the starch is carbonized at 1100-1500° C. at high temperature.

[0025] This preparation method utilizes a mixture of nano-sized boehmite and starch for calcination, achieving localized physical barrier and confinement of the starch. This effectively inhibits foaming and fusion of starch granules during heating, improving granule morphology. It also suppresses the ordered growth of the microcrystalline structure, generating more disordered sodium storage layers. Furthermore, after the boehmite is pyrolyzed, the generated water vapor reacts with the starch to etch the material, creating pores and increasing capacity. The resulting alumina, after high-temperature calcination, mixes and coats the starch surface, enhancing the material's conductivity. Furthermore, the alumina particles participate in the formation of the SEI membrane, increasing its high and low-temperature stability, reducing side reactions, and improving the cycle life and rate performance of the battery cell. Using boehmite and starch as raw materials is low-cost, and the single-fired process simplifies the production process.

[0026] Specifically, the preparation method is:

[0027] S1. Preparation of mixed powder

[0028] (1) The starch is ground and graded to obtain a powder with particle sizes D50 and D90 of approximately 4~9μm and 10~20μm, respectively.

[0029] Optionally, the starch is selected from at least one of corn starch, sweet potato starch, potato starch, tapioca starch, sweet potato starch, water chestnut starch and lotus root starch.

[0030] (2) Dry-mix the starch and nano-sized boehmite powder to obtain a mixed powder.

[0031] Optionally, the mass ratio of starch to nano-boehmite is 100:5-20 (eg, 100:5, 100:10, or 100:20).

[0032] S2. Heat treatment

[0033] The mixed powder is placed at 400-500°C (e.g., 400°C, 450°C, or 500°C) to pyrolyze boehmite, so that the boehmite is fully decomposed to generate alumina; and then the starch is high-temperature carbonized at 1100-1500°C (e.g., 1100°C, 1200°C, 1300°C, or 1500°C).

[0034] Preferably, the treatment time at 400-500° C. (eg, 400° C., 450° C., or 500° C.) is 0.5-2 h (eg, 0.5 h, 1 h, or 2 h).

[0035] Preferably, the treatment time at 1100-1500° C. is 2-5 h (eg, 2 h, 3 h, or 5 h).

[0036] Preferably, the high-temperature carbonization process is carried out in a nitrogen-containing atmosphere. At temperatures between 1100°C and 1500°C (e.g., 1100°C, 1200°C, 1300°C, or 1500°C), the starch is carbonized, and the aluminum oxide is partially reduced by carbon, which then reacts with the nitrogen-containing atmosphere to form a mixture of aluminum nitrogen and aluminum oxide. The resulting aluminum nitrogen also improves the material's conductivity and contributes to the formation of the SEI film, increasing its high- and low-temperature stability. Furthermore, nitrogen doping in the negative electrode material can further enhance electron mobility.

[0037] An embodiment of the present invention provides a carbon-based negative electrode material, which is prepared using the preparation method provided by the present invention.

[0038] An embodiment of the present invention provides a negative electrode, wherein the active coating of the negative electrode comprises the carbon-based negative electrode material provided by the embodiment of the present invention.

[0039] Specifically, the preparation method of the negative electrode is, for example:

[0040] The carbon-based material provided in an embodiment of the present invention is prepared into a slurry according to the ratio of carbon material: carbon black: CMC: SBR = 94:1.5:1.7:2.8, and the slurry is coated on aluminum foil to obtain a negative electrode sheet.

[0041] A sodium ion battery provided by an embodiment of the present invention includes the negative electrode provided by an embodiment of the present invention.

[0042] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0043] Example 1

[0044] Potato starch with a D50 and D90 of approximately 5 μm and 15 μm, respectively, and boehmite powder with a particle size range of 20 to 100 nm are uniformly mixed in a mass ratio of 100:10 to obtain a mixed powder;

[0045] Nitrogen was introduced into the sintering furnace, the mixed powder was placed in the sintering furnace, the temperature was raised to 450°C and sintered for 1 hour, and then the temperature of the sintering furnace was raised to 1200°C and high-temperature carbonization was performed for 3 hours to obtain a carbon-based material.

[0046] Example 2

[0047] Cassava starch with a D50 and D90 of approximately 4 μm and 10 μm, respectively, and boehmite powder with a particle size range of 20 to 100 nm are uniformly mixed in a mass ratio of 100:5 to obtain a mixed powder;

[0048] Nitrogen was introduced into the sintering furnace, the mixed powder was placed in the sintering furnace, the temperature was raised to 400°C and sintered for 2 hours, and then the temperature of the sintering furnace was raised to 1500°C and high-temperature carbonization was performed for 2 hours to obtain a carbon-based material.

[0049] Example 3

[0050] Corn starch with a D50 and D90 of approximately 9 μm and 15 μm, respectively, and boehmite powder with a particle size range of 20 to 100 nm are uniformly mixed in a mass ratio of 100:20 to obtain a mixed powder;

[0051] Nitrogen was introduced into the sintering furnace, the mixed powder was placed in the sintering furnace, the temperature was raised to 500°C and sintered for 0.5h, and then the temperature of the sintering furnace was raised to 1100°C and high-temperature carbonization was performed for 0.5h to obtain a carbon-based material.

[0052] Example 4

[0053] This embodiment is basically the same as embodiment 1, except that argon is introduced into the sintering furnace instead of nitrogen.

[0054] Comparative Example 1

[0055] This comparative example is basically the same as Example 2, except that after the mixed powder is placed in the sintering furnace, the temperature is directly raised to 1600° C. (the second temperature) and sintered for 2 hours.

[0056] Comparative Example 2

[0057] This comparative example is basically the same as Example 3, except that boehmite is replaced by nano-alumina, and the mass ratio of starch to alumina is 100:4.25.

[0058] Comparative Example 3

[0059] This comparative example is substantially the same as Example 3, except that no boehmite is added.

[0060] Comparative Example 4

[0061] This comparative example is basically the same as Example 1, except that starch is replaced with an equal amount of bamboo biomass powder.

[0062] Experimental Example 1

[0063] The negative electrode materials prepared in each embodiment and comparative example were prepared into negative electrode sheets. The specific method was as follows: a slurry was prepared in a ratio of carbon material: carbon black: CMC: SBR = 94:1.5:1.7:2.8 and coated on aluminum foil to obtain a negative electrode sheet.

[0064] The negative electrode sheets were assembled into a battery. The specific method was as follows: NFPP: carbon black: CNT: PVDF were mixed in a ratio of 96:1.2:1.1:1.7 to prepare a slurry, which was then coated on aluminum foil to make a positive electrode sheet; the positive electrode sheet, the prepared negative electrode sheet and the PP separator were assembled into a sodium ion battery, and the electrolyte was 1 mol / LNaPF6, 40% PC + 60% EMC.

[0065] The electrochemical performance of the battery was tested and the test results were recorded in Table 1.

[0066] Table 1 Performance statistics of batteries prepared in various embodiments and comparative examples

[0067]

[0068] It can be seen from Table 1 that the negative electrode materials prepared in various embodiments of the present invention have good electrochemical performance after being made into negative electrodes and assembled into batteries.

[0069] Comparing Example 4 with Example 1, the first effect of Example 4 is poor, which shows that when nitrogen-containing gas is introduced and nitrogen is doped in the obtained carbon-based negative electrode material, the surface of the material can be further modified and irreversible reactions can be reduced.

[0070] Comparing Comparative Example 1 with Example 2, the rate performance of Comparative Example 1 is significantly worse than that of Example 1, indicating that if the boehmite is not pyrolyzed at the first temperature and high-temperature carbonization is performed directly, the battery capacity will be reduced due to insufficient reaction.

[0071] Comparing Comparative Example 2 with Example 3, the rate performance of Comparative Example 2 is poor, indicating that if alumina is used to replace boehmite, the internal pore size of the obtained negative electrode material will be smaller, and the rate performance will be poor, because alumina will not decompose and etch the starch during the sintering process.

[0072] Comparing Comparative Example 3 with Example 3, the cycle of Comparative Example 3 is poor, indicating that if boehmite is not added during the preparation of the carbon-based material, there is no inhibitory effect on the foaming and melting of starch, and the cycle life of the obtained carbon-based material is poor;

[0073] Comparing Comparative Example 4 with Example 1, the cycle of Comparative Example 4 is poor, indicating that compared with biomass powder as a carbon source, starch has better consistency and more advantageous cycle life in the prepared carbon-based material.

[0074] In summary, the preparation method provided by the present invention has the following characteristics:

[0075] 1. In this application, starch is doped and sintered, which effectively inhibits the foaming and melting of starch particles during the heating process, improves the particle morphology, and inhibits the orderly growth of the microcrystalline structure to generate more disordered sodium storage layers.

[0076] 2. The finished product fired in this application contains aluminum nitrogen and aluminum oxide particles, which participate in the formation of the SEI film, increase the high and low temperature stability of the SEI film, reduce side reactions, improve the cycle life and rate performance of the battery cell, and improve the conductivity of the material.

[0077] 3. Water vapor etching is used in this application to increase the capacity of the material.

[0078] 4. The present application adopts low-cost starch raw material and boehmite mixed and fired once, which reduces the processing steps and is simple and low in cost.

[0079] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-based negative electrode material, characterized in that: include: Providing a mixed powder, the mixed powder comprising starch and nano-boehmite powder mixed with each other; placing the mixed powder at 400-500° C. to pyrolyze boehmite, so that the boehmite is fully decomposed to generate alumina; Then, the starch is carbonized at a temperature of 1100-1500° C.; The high-temperature carbonization process is carried out in a nitrogen atmosphere; The mass ratio of the starch to the nano-boehmite is 100:5-20.

2. The preparation method according to claim 1, characterized in that The time for thermal decomposition of boehmite is 0.5~2h.

3. The preparation method according to claim 1, characterized in that The high temperature carbonization time is 2~5h.

4. The preparation method according to claim 1, characterized in that The D50 and D90 of the starch are 4-9 μm and 10-20 μm, respectively.

5. The preparation method according to claim 1, characterized in that The starch is selected from at least one of corn starch, sweet potato starch, potato starch, cassava starch, sweet potato starch, water chestnut starch and lotus root starch.

6. A carbon-based negative electrode material, characterized in that The method is as described in any one of claims 1 to 5.

7. A negative electrode, characterized in that The active coating layer comprises the carbon-based negative electrode material as claimed in claim 6.

8. A sodium ion battery, characterized in that: Comprising the negative electrode according to claim 7.

Images