A micron-scale silicon monoxide composite anode material and its preparation method

Abstract

The present invention discloses a micron-sized silicon monoxide composite anode material and a preparation method thereof, belonging to the technical field of battery materials. In the present invention, N-Fe-MOF powder is placed in a tube furnace and heated to 850-900 °C at a heating rate of 5 °C / min under nitrogen protection, and kept for reaction for 2 h to obtain MOF-derived carbon. The micron-sized silicon monoxide composite anode material in the present invention coats the MOF-derived carbon on the surface of modified silicon monoxide by ball milling, so that the MOF-derived carbon can coat the modified silicon monoxide more uniformly, and plays an effect of inhibiting its volume expansion during the process of lithium intercalation into silicon monoxide. Iron ions and nitrogen atoms are introduced into the MOF-derived carbon in the form of coordination bonds, which can increase the conductivity of the silicon monoxide composite anode material, and at the same time play a synergistic effect with metals such as tin and iron in the modified silicon monoxide in terms of conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a micron-sized silicon monoxide composite anode material and a preparation method thereof. Background Art

[0002] With the wide application of lithium-ion batteries in electric vehicles, energy storage systems, and portable electronic devices, the development of anode materials with high energy density and long cycle life has become a key research direction. Silicon-based materials are regarded as the most promising alternatives due to their extremely high theoretical specific capacity. However, the severe volume expansion of silicon during charge and discharge processes leads to the pulverization of the electrode structure and the continuous rupture of the solid electrolyte interface (SEI) film, resulting in rapid capacity decay, which severely limits its commercial application.

[0003] A modified silicon monoxide / carbon nanotube composite anode material and a preparation method thereof with the publication number CN112678807B disclose a modified silicon monoxide / carbon nanotube composite anode material and a preparation method thereof. The silane coupling agent is pre-hydrolyzed, and the pre-hydrolyzed silane coupling agent, silicon monoxide, and surfactant are ultrasonically dispersed in a solvent to obtain a dispersion liquid. The dispersion liquid is heated and stirred in a reaction kettle under an inert atmosphere to obtain a modified silicon monoxide solution. The modified silicon monoxide solution is mixed with carbon nanotubes and ultrasonically dispersed, filtered, washed, dried, added to a carbon source for mixing and coating, and sintered and pulverized to obtain a modified silicon monoxide / carbon nanotube composite anode material. The present invention modifies the surface of silicon monoxide particles, adds an appropriate amount of carbon nanotubes to the silicon monoxide anode material, and coats a layer of carbon source on the surface of the modified silicon monoxide, effectively improving the cycle performance of the anode material.

[0004] During the first charge and discharge cycle of a lithium-ion battery, the positive electrode active material (such as layered oxide) undergoes a lithium ion deintercalation reaction, and lithium ions migrate through the electrolyte and embed into the lattice of the negative electrode active material. When silicon monoxide (SiOx) is used as the negative electrode, its lithium intercalation process is accompanied by significant volume expansion, and the mechanical stress generated by this lattice distortion will damage the solid electrolyte interface (SEI) film formed in-situ on the surface of the negative electrode. The rupture of the SEI film exposes the new electrode surface, resulting in continuous side reactions with the electrolyte and triggering the self-repair behavior of the SEI film. This dynamic reconstruction process will irreversibly consume the lithium salt in the electrolyte, causing a permanent loss of the active lithium inventory. As the number of cycles increases, this cumulative lithium loss will lead to a continuous decay of the reversible capacity of the battery and exacerbate the impedance growth at the electrode / electrolyte interface, ultimately resulting in the deterioration of the overall energy density and cycle life of the battery. Summary of the Invention

[0005] The object of the present invention is to provide a micron-scale silicon monoxide composite anode material and a preparation method thereof. By introducing iron ions and nitrogen atoms through MOF, and after carbonization, the MOF-derived carbon is coated on the surface of silicon monoxide doped with tin and iron, solving the problem of volume expansion of silicon monoxide during the lithium intercalation process, and achieving the beneficial effects of inhibiting the volume expansion of silicon monoxide and increasing the conductivity of silicon monoxide.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of a micron-scale silicon monoxide composite anode material, comprising the following steps:

[0008] Step 1: Put the N-Fe-MOF powder into a tubular furnace. Under nitrogen protection, raise the temperature to 850 - 900 °C at a heating rate of 5 °C / min, and keep the temperature for 2 h to obtain MOF-derived carbon.

[0009] Step 2: Stir and mix silicon, silicon dioxide, and a metal reducing agent under argon protection. Transfer the mixture to a tubular furnace, and raise the temperature to 1300 - 1450 °C at a rate of 5 °C / min under the condition of 1 - 10 Pa, keep the temperature for reaction for 15 - 20 h, cool down, and crush the product to obtain modified silicon monoxide.

[0010] Step 3: Wet ball-mill and mix the modified silicon monoxide and MOF-derived carbon, filter, wash, and dry to obtain a micron-scale silicon monoxide composite anode material.

[0011] The preparation process of the N-Fe-MOF powder is as follows:

[0012] Add trimesic acid, N,N-dimethylformamide, and a bipyridine derivative into a reaction kettle, stir at 20 - 25 °C and 500 - 800 r / min for 30 - 40 min, then add ferric chloride hexahydrate into the reaction kettle, and react at 150 - 160 °C and 500 - 800 r / min for 24 - 26 h. After cooling to room temperature, filter, wash, and dry to obtain the N-Fe-MOF powder.

[0013] Furthermore, the dosage ratio of trimesic acid, N,N-dimethylformamide, the bipyridine derivative, and ferric chloride hexahydrate is 8 - 10 g : 600 - 700 mL : 2 - 3 g : 1.5 - 2 g.

[0014] Furthermore, the bipyridine derivative is any one of 4,4'-dimethyl-2,2'-bipyridine and 4,4'-diethyl-2,2'-bipyridine.

[0015] Furthermore, in Step 2, the metal reducing agent is any one of tin, iron, or a mixture of the two.

[0016] Further, the mass ratio of silicon, silicon dioxide, and metal reducing agent is 100 - 150:80 - 120:6 - 16.

[0017] Further, in step three, the wet ball milling uses zirconia balls with a particle size of 8 mm, and the mass ratio of balls to powder is 40:1.

[0018] Further, in step three, the mass ratio of modified silicon monoxide and MOF-derived carbon is 45 - 50:5 - 8.

[0019] Advantages of the present invention:

[0020] In the micron-sized silicon monoxide composite anode material of the present invention, MOF-derived carbon is coated on the surface of modified silicon monoxide by ball milling, enabling the MOF-derived carbon to coat the modified silicon monoxide more uniformly, which has the effect of inhibiting its volume expansion during the lithium intercalation process of silicon monoxide. Iron and nitrogen atoms on the MOF-derived carbon increase the conductivity of the silicon monoxide composite anode material, and at the same time play a synergistic effect with metals such as tin and iron in the modified silicon monoxide in terms of conductivity, making the composite anode material have higher conductivity and initial Coulomb efficiency.

[0021] The MOF-derived carbon in the present invention first introduces iron ions and nitrogen atoms onto the MOF to form a double-ligand iron-based MOF, and then carbonizes it. Under the conditions of high temperature and nitrogen protection, using carbon as a reducing agent, the iron ions are reduced to nano-iron and are uniformly embedded in the carbon matrix with nitrogen atoms. The presence of nitrogen atoms increases the surface active sites of the carbon, which is beneficial to the formation of a conductive path, improves the electron mobility, and increases the conductivity of the anode material. Moreover, the MOF-derived carbon has abundant pores, which can provide ion transport channels, promote ion migration, and at the same time can provide storage sites to increase the specific capacity of the composite anode material.

[0022] The modified silicon monoxide in the present invention reduces silicon dioxide to silicon monoxide using tin and iron as metal reducing agents under high temperature and argon conditions. At the same time, under high temperature conditions, silicon, silicon dioxide, and tin-iron metals are in a gaseous state, which not only makes the reaction more complete, but also the addition of iron can prevent tin from agglomerating, enabling tin-iron and other metals to be more uniformly incorporated into silicon monoxide, increasing the conductivity of the anode material, maintaining the integrity of the electron path, and the formation of intermetallic compounds between iron and tin, and the stable crystal structure can effectively buffer the volume expansion generated during the lithium intercalation process of the anode material. Specific embodiments

[0023] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Example 1: This example provides a micron-sized silicon monoxide composite anode material, which is prepared through the following steps:

[0025] S1: Add 9 g of trimesic acid, 650 mL of N,N-dimethylformamide, and 2.5 g of 4,4'-dimethyl-2,2'-bipyridine into a reaction kettle, stir for 35 min under the conditions of 22 °C and 650 r / min, then add 1.7 g of ferric chloride hexahydrate into the reaction kettle, react for 25 h under the conditions of 155 °C and 650 r / min. After cooling to room temperature, centrifuge and filter, wash the filter cake 4 times with absolute ethanol, and dry at 85 °C for 11 h to obtain N-Fe-MOF powder.

[0026] S2: Put the N-Fe-MOF powder into a tubular furnace, under nitrogen protection, heat it to 875 °C at a heating rate of 5 °C / min, and hold for 2 h to obtain MOF-derived carbon.

[0027] S3: Add 125 g of silicon, 100 g of silicon dioxide, 5.5 g of tin, and 5.5 g of iron into a stirring kettle, stir for 1.5 h under argon protection and 750 r / min, transfer the mixture to a tubular furnace with a corundum lining, heat it to 1370 °C at a rate of 5 °C / min under the condition of 5 Pa, hold for 17.5 h, cool to room temperature, and crush the product through an air-flow crushing device to obtain modified silicon monoxide doped with tin and iron with a particle size of 4 - 5 μm.

[0028] S4: Add 47.5 g of modified silicon monoxide and 6.5 g of MOF-derived carbon into a ball mill. The zirconia balls used for ball milling are 8 mm in diameter, and the mass ratio of balls to powder is 40:1. Add 45 mL of deionized water and 25 mL of absolute ethanol, ball mill for 13 h under the condition of 450 r / min, centrifuge and filter, wash the filter cake 3 times with deionized water, and dry to constant weight to obtain the micron-sized silicon monoxide composite anode material.

[0029] Example 2: This example provides a micron-sized silicon monoxide composite anode material, which is prepared through the following steps:

[0030] S1: Add 8 g of trimesic acid, 600 mL of N,N-dimethylformamide, and 2 g of 4,4'-dimethyl-2,2'-bipyridine into a reaction kettle, stir for 30 min under the conditions of 20 °C and 500 r / min, then add 1.5 g of ferric chloride hexahydrate into the reaction kettle, and react for 24 h under the conditions of 150 °C and 500 r / min. After cooling to room temperature, carry out centrifugal filtration, wash the filter cake with absolute ethanol three times, and dry it at 80 °C for 10 h to obtain N-Fe-MOF powder.

[0031] S2: Put the N-Fe-MOF powder into a tubular furnace, under nitrogen protection, heat it to 850 °C at a heating rate of 5 °C / min, and keep the temperature for reaction for 2 h to obtain MOF-derived carbon.

[0032] S3: Add 100 g of silicon, 80 g of silicon dioxide, and 3 g of tin into a stirring kettle, stir for 1 h under argon protection and 500 r / min, transfer the mixture to a tubular furnace with a corundum inner lining, heat it to 1300 °C at a rate of 5 °C / min under the condition of 1 Pa, keep the temperature for reaction for 15 h, cool to room temperature, and crush the product through an air flow crushing device to obtain tin-doped modified silicon monoxide with a particle size of 4 - 5 μm.

[0033] S4: Put 45 g of modified silicon monoxide and 5 g of MOF-derived carbon into a ball mill, use 8 mm zirconia balls for ball milling, the mass ratio of balls to powder is 40:1, add 40 mL of deionized water and 20 mL of absolute ethanol, ball mill for 12 h under the condition of 400 r / min, carry out centrifugal filtration, wash the filter cake with deionized water twice, and dry it to constant weight to obtain a micron-sized silicon monoxide composite anode material.

[0034] Example 3: This example provides a micron-sized silicon monoxide composite anode material, which is prepared through the following steps:

[0035] S1: Add 10 g of trimesic acid, 700 mL of N,N-dimethylformamide, and 3 g of 4,4'-dimethyl-2,2'-bipyridine into a reaction kettle, stir for 40 min under the conditions of 25 °C and 800 r / min, then add 2 g of ferric chloride hexahydrate into the reaction kettle, and react for 26 h under the conditions of 160 °C and 800 r / min. After cooling to room temperature, carry out centrifugal filtration, wash the filter cake with absolute ethanol five times, and dry it at 90 °C for 12 h to obtain N-Fe-MOF powder.

[0036] S2: Put the N-Fe-MOF powder into a tubular furnace, under nitrogen protection, heat it to 900 °C at a heating rate of 5 °C / min, and keep the temperature for reaction for 2 h to obtain MOF-derived carbon.

[0037] S3: Add 150 g of silicon, 120 g of silicon dioxide, and 8 g of iron into a stirring kettle, stir for 2 h under the protection of argon and at 1000 r / min, transfer the mixture into a tubular furnace with a corundum liner, heat it to 1450 °C at a rate of 5 °C / min under the condition of 10 Pa, keep the temperature for reaction for 20 h, cool it to room temperature, and crush the product through an air flow crushing device to obtain iron-doped modified silicon monoxide with a particle size of 4 - 5 μm.

[0038] S4: Put 50 g of modified silicon monoxide and 8 g of MOF-derived carbon into a ball mill. The zirconia balls with a diameter of 8 mm are used for ball milling, and the mass ratio of balls to powder is 40:1. Add 50 mL of deionized water and 30 mL of absolute ethanol, ball mill for 14 h under the condition of 500 r / min, centrifuge and filter, wash the filter cake 4 times with deionized water, and dry it to constant weight to obtain a micron-sized silicon monoxide composite anode material.

[0039] Comparative Example 1: On the basis of Example 1, 4,4'-dimethyl-2,2'-bipyridine is not added in S1, and the remaining steps remain unchanged to prepare a micron-sized silicon monoxide composite anode material.

[0040] Comparative Example 2: On the basis of Example 1, ordinary carbon is used to replace MOF-derived carbon in S4, and the remaining steps remain unchanged to prepare a micron-sized silicon monoxide composite anode material.

[0041] Comparative Example 3: On the basis of Example 1, modified silicon monoxide is replaced by silicon monoxide in S4, and the remaining steps remain unchanged to prepare a micron-sized silicon monoxide composite anode material.

[0042] Mix the micron-sized silicon monoxide composite anode materials prepared in Examples 1 - 3 and Comparative Examples 1 - 3 with acetylene black and polyvinylidene fluoride according to a mass ratio of 8:1:1, grind them with N-methylpyrrolidone as a solvent until a uniform slurry is formed and coat it on a copper foil, dry it in vacuum at 90 °C for 24 h, and roll press to obtain an electrode sheet; cut the obtained negative electrode sheet into an electrode sheet with a diameter of 12 mm for battery assembly. The assembly process is carried out in a glove box filled with argon, and the water and oxygen content is less than 0.01 ppm. The battery uses a CR2032 type button battery, with a metal lithium sheet as the counter electrode, a polypropylene film as the separator, and 1 M lithium hexafluorophosphate as the electrolyte. Perform a 0.5C charge-discharge cycle performance test on the assembled button battery at 25 °C within a voltage range of 0.01 - 1.5 V, record the measured battery conductivity, initial Coulomb efficiency, percentage of volume change, and 100-cycle capacity retention rate, and the results are shown in Table 1:

[0043] Table 1 Performance Test Results Table

[0044] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Conductivity (S / cm) 47.2 46.5 46.1 43.8 37.5 41.1 Initial Coulombic efficiency (%) 89.5 89.1 89.9 88.6 83.3 85.5 Volume change percentage (%) 81 79 80 81 87 90 Capacity retention rate after 100 cycles (%) 85.1 84.1 85.4 84.2 76.5 83.5

[0045] As can be seen from Table 1, the conductivity of the micro-sized silicon monoxide composite anode materials prepared in Examples 1-3 is better than that of the micro-sized silicon monoxide composite anode materials prepared in Comparative Examples 1-3. In Comparative Example 2, ordinary carbon was used to replace the MOF-derived carbon, and its conductivity is lower than that of Examples 1-3. In Comparative Example 3, silicon monoxide was used to replace the modified silicon monoxide, and its conductivity is lower than that of Examples 1-3. This shows that the MOF-derived carbon and the modified silicon monoxide have a synergistic effect in increasing the conductivity of the composite anode material.

[0046] The initial Coulombic efficiency of the micro-sized silicon monoxide composite anode materials prepared in Examples 1-3 is higher than that of the micro-sized silicon monoxide composite anode materials prepared in Comparative Examples 1-3. In Comparative Example 2, ordinary carbon was used to replace the MOF-derived carbon, and its initial Coulombic efficiency is the lowest. This shows that the MOF-derived carbon plays a role in increasing the initial Coulombic efficiency in the composite anode material.

[0047] The percentage of volume change of the micro-sized silicon monoxide composite anode materials prepared in Examples 1-3 is lower than that of the micro-sized silicon monoxide composite anode materials prepared in Comparative Examples 1-3. In Comparative Example 2, ordinary carbon was used to replace the MOF-derived carbon, and in Comparative Example 3, silicon monoxide was used to replace the modified silicon monoxide. The percentage of volume change of both is higher than that of Examples 1-3. This shows that the combined action of the MOF-derived carbon and the modified silicon monoxide can effectively reduce the volume expansion of the micro-sized silicon monoxide composite anode material, and the effect of their combined action is better than that of a single action. This indicates that the MOF-derived carbon and the modified silicon monoxide have a synergistic effect in reducing the volume expansion of the composite anode material.

[0048] The 100-cycle capacity retention rate of the micro-sized silicon monoxide composite anode materials prepared in Examples 1-3 and Comparative Example 1 is higher than that of the micro-sized silicon monoxide composite anode materials prepared in Comparative Examples 2-3. In Comparative Example 2, ordinary carbon was used to replace the MOF-derived carbon, and in Comparative Example 3, silicon monoxide was used to replace the modified silicon monoxide. This shows that the MOF-derived carbon and the modified silicon monoxide have a certain synergistic effect in improving the 100-cycle capacity retention rate.

[0049] It should be noted that in this article, terms such as "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such a process, method, article or device.

[0050] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention.

Claims

1. A preparation method of a micron-sized silicon monoxide composite anode material, characterized in that, It includes the following steps: Step 1: Put the N-Fe-MOF powder into a tubular furnace. Under nitrogen protection, raise the temperature to 850 - 900 °C at a heating rate of 5 °C / min, keep it for 2 hours to obtain MOF-derived carbon; Step 2: Stir and mix silicon, silicon dioxide and a metal reducing agent under argon protection. Transfer the mixture to a tubular furnace, raise the temperature to 1300 - 1450 °C at a rate of 5 °C / min under the condition of 1 - 10 Pa, keep it for reaction for 15 - 20 hours, cool it, and crush the product to obtain modified silicon monoxide; Step 3: Wet ball-mill and mix the modified silicon monoxide and MOF-derived carbon, filter, wash, and dry to obtain a micron-scale silicon monoxide composite anode material; The preparation process of the N-Fe-MOF powder is as follows: Add trimesic acid, N,N-dimethylformamide and a bipyridine derivative into a reaction kettle, stir for 30 - 40 minutes under the conditions of 20 - 25 °C and 500 - 800 r / min, then add ferric chloride hexahydrate into the reaction kettle, react for 24 - 26 hours under the conditions of 150 - 160 °C and 500 - 800 r / min, after cooling to room temperature, filter, wash, and dry to obtain the N-Fe-MOF powder.

2. The preparation method of a micron-sized silicon monoxide composite anode material according to claim 1, characterized in that, The dosage ratio of the trimesic acid, N,N-dimethylformamide, bipyridine derivative and ferric chloride hexahydrate is 8 - 10 g : 600 - 700 mL : 2 - 3 g : 1.5 - 2 g.

3. The preparation method of a micron-scale silicon monoxide composite anode material according to claim 2, wherein The bipyridine derivative is any one of 4,4'-dimethyl-2,2'-bipyridine and 4,4'-diethyl-2,2'-bipyridine.

4. The preparation method of a micron-sized silicon monoxide composite anode material according to claim 1, characterized in that, The metal reducing agent in Step 2 is any one of tin and iron or a mixture of the two.

5. The preparation method of a micron-scale silicon monoxide composite anode material according to claim 1, characterized in that The mass ratio of the silicon, silicon dioxide and metal reducing agent in Step 2 is 100 - 150 : 80 - 120 : 6 - 16.

6. The preparation method of a micron-sized silicon monoxide composite anode material according to claim 1, characterized in that, The wet ball-milling in Step 3 uses zirconia balls with a particle size of 8 mm, and the mass ratio of the balls to the powder is 40 :

1.

7. The preparation method of a micron-scale silicon monoxide composite anode material according to claim 1, characterized in that The mass ratio of the modified silicon monoxide and MOF-derived carbon in Step 3 is 45 - 50 : 5 - 8.

8. A micron-sized silicon monoxide composite anode material, characterized in that, It is prepared by the preparation method of a micron-scale silicon monoxide composite anode material described in any one of claims 1 - 7.