A beta-cyclodextrin-based silicon-based material, a preparation method and application thereof

Abstract

The application discloses a kind of silicon-based materials based on beta-cyclodextrin and its preparation method and application.The preparation method comprises the following steps: to the water dispersion of nano-silicon, beta-cyclodextrin and silane coupling agent are added, stirring;After tin source and molybdenum source are added, composite precursor is obtained by reaction;The composite precursor is high-temperature carbonized.Compared with prior art, the preparation method provided by the application is simple, and the equipment requirement is low, which is convenient for large-scale production.On the other hand, the silicon-based negative electrode material prepared by the application has excellent rate performance and cycle stability, and has potential application value in the field of power lithium ion battery and digital lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a silicon-based material based on β-cyclodextrin, its preparation method, and its application. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and energy storage systems, the demand for high energy density, long lifespan, and high rate performance in lithium-ion batteries is becoming increasingly urgent. The theoretical specific capacity of traditional graphite anodes is only 372 mAh·g. -1 Silicon materials, due to their high theoretical specific capacity (4200 mAh·g), are no longer sufficient to meet the future development trend of high-energy-density batteries. -1 Silicon, with its high reserves, is considered the most promising next-generation lithium-ion battery anode material. However, silicon's volume expansion during lithium insertion and extraction can exceed 300%, leading to problems such as material pulverization, a sharp increase in active surface area, and repeated rupture and reconstruction of the SEI (solid electrolyte interphase) film, ultimately causing electrode structure failure and rapid capacity decay. To alleviate the volume effect of silicon materials, researchers have proposed a series of structural design strategies, including nanoscale silicon structures, carbon coating, silicon-carbon composites, porous structure construction, and metal alloying reinforcement. Although these methods have improved the cycle stability and conductivity of silicon-based anodes to some extent, they still have significant shortcomings. For example, while nanoscale silicon can buffer expansion, its excessively high specific surface area can cause severe SEI consumption; traditional carbon coating structures lack density or flexibility, making it difficult to adapt to long-term volume changes. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a silicon-based material based on β-cyclodextrin, its preparation method, and its applications. The silicon-based material provided by this invention utilizes a synergistic construction strategy of β-cyclodextrin-induced multi-metal alloying and carbon coating, achieving high structural stability, high conductivity, and excellent interfacial properties. This is of great significance for improving the cycle life and rate performance of silicon anodes.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a method for preparing silicon-based materials based on β-cyclodextrin, comprising the following steps: (1) Add β-cyclodextrin and silane coupling agent to the aqueous dispersion of nano-silicon and stir; (2) After adding tin source and molybdenum source, the reaction yields a composite precursor; (3) The composite precursor is carbonized at high temperature to obtain the silicon-based material.

[0005] In a preferred embodiment, in step (1), the particle size of the nano-silicon is 20~80 nm.

[0006] Preferably, the silane coupling agent is selected from at least one of aminopropyltriethoxysilane, N-ethylaminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0007] Preferably, the mass ratio of the nano-silicon, β-cyclodextrin and silane coupling agent is 10:(1~5):(0.1~1).

[0008] In a preferred embodiment, the stirring time in step (1) is 0.5 to 3 hours.

[0009] In a preferred embodiment, in step (2), the tin source is at least one of soluble tin salts, such as tin chloride, tin nitrate, or tin acetate; the molybdenum source is at least one of soluble molybdenum salts, such as ammonium molybdate, phosphomolybdic acid, or molybdic acid. Preferably, the mass ratio of the nano-silicon to the tin in the tin source and the molybdenum in the molybdenum source is 10:(0.05~1.5):(0.05~1.5).

[0010] In a preferred embodiment, in step (2), the addition of the tin source and the molybdenum source is carried out sequentially. In the technical solution of the present invention, adding the tin source first helps to form a uniform complex, avoids competitive reactions and molybdenum source precipitation, and ensures the high efficiency of the reaction and the stability of the product. Preferably, the reaction is carried out under stirring conditions; the stirring time is 0.5 to 3 h.

[0011] In some specific embodiments, step (2) is followed by a drying process; the drying temperature is 80~120°C.

[0012] In a preferred embodiment, in step (3), the temperature of the high-temperature carbonization is 800~1100℃; Preferably, the high-temperature carbonization time is 2-4 hours.

[0013] Preferably, the high-temperature carbonization is carried out in an inert atmosphere; in some specific embodiments, the inert atmosphere is nitrogen.

[0014] In some specific embodiments, the high-temperature carbonization in step (3) further includes post-treatment of washing and drying; the washing is ultrasonic washing with alcohol and deionized water; the drying is vacuum drying; the temperature of the vacuum drying is 60~90℃.

[0015] On the other hand, the present invention provides silicon-based materials obtained by the above preparation method.

[0016] In another aspect, the present invention provides the application of the above-mentioned silicon-based materials in the preparation of batteries.

[0017] Preferably, its application in the preparation of negative electrode materials.

[0018] Preferably, its application in the preparation of lithium-ion battery anode materials.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. β-Cyclodextrin (β-CD), as a natural cyclic polysaccharide, is rich in multiple hydroxyl groups and possesses advantages such as good coordination ability, spatially confined structure, and tunable pore structure after carbonization. This invention utilizes β-cyclodextrin (β-CD) as a structural unit with a triple function of "multi-point anchoring – spatial confinement – ​​carbon precursor" to prepare silicon-based materials. β-Cyclodextrin forms multi-point hydrogen bonds and coordination interactions with the silicon surface and metal precursors, enabling Sn... 2+ Mo 6+ Metal ions can be uniformly adsorbed and deposited on the silicon surface, avoiding the problems of severe metal salt agglomeration and uneven alloy phase in traditional systems, thus providing a good interface basis for subsequent high-temperature alloying.

[0020] 2. This invention uses a high-temperature carbonization reduction process to form a multi-element alloy phase of Sn, Mo and Si. These multi-element structures can disperse the stress of silicon, improve electronic conductivity and enhance the overall framework strength, significantly improving the stability of silicon-based anodes under high rate and long cycle conditions.

[0021] 3. The silicon-based anode material prepared by this invention has excellent rate performance and cycle stability, and has potential application value in the fields of power lithium-ion batteries and digital lithium-ion batteries. Attached Figure Description

[0022] Figure 1 These are charge-discharge curves of the silicon-based materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0023] Figure 2 These are charge-discharge curves of the silicon-based materials prepared in Examples 2-5 and Comparative Example 2 of this invention.

[0024] Figure 3 These are cycle performance test diagrams of the silicon-based materials prepared in Examples 1-4 of this invention.

[0025] Figure 4 These are cycle performance test diagrams of the silicon-based materials prepared in Example 5 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0026] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0028] Example 1 This embodiment provides a silicon-based material based on β-cyclodextrin, and the preparation method is as follows: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 1 g of β-cyclodextrin is added, followed by 0.1 g of aminopropyltriethoxysilane, and stirred for 3 h; (2) 0.1 g of SnCl2·2H2O and 0.1 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir and react for 3 h; the product obtained from the reaction is dried at 120℃ to obtain a composite precursor; (3) the composite precursor is carbonized at 1000℃ for 4 h in a tube furnace under nitrogen atmosphere; after cooling the product, it is ultrasonically cleaned in ethanol and deionized water; vacuum dried at 60℃ to obtain Si@C@Sn / Mo silicon-based material.

[0029] Example 2 This embodiment provides a silicon-based material based on β-cyclodextrin, and the preparation method is as follows: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 5 g of β-cyclodextrin is added, followed by 1 g of aminopropyltriethoxysilane, and the mixture is stirred for 0.5 h; (2) 1 g of SnCl2·2H2O and 1 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir the reaction for 0.5h; dry the product obtained by the reaction at 80℃ to obtain the composite precursor; (3) carbonize the composite precursor in a tube furnace under nitrogen atmosphere at 800℃ for 2h; after cooling the product, ultrasonically clean it in ethanol and deionized water; vacuum dry at 90℃ to obtain Si@C@Sn / Mo silicon-based material.

[0030] Example 3 This embodiment provides a silicon-based material based on β-cyclodextrin, and the preparation method is as follows: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 2 g of β-cyclodextrin is added, followed by 0.5 g of aminopropyltriethoxysilane, and stirred for 2 h; (2) 0.5 g of SnCl2·2H2O and 0.5 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir and react for 2 h; the product obtained from the reaction is dried at 100℃ to obtain a composite precursor; (3) the composite precursor is carbonized at 900℃ for 3 h in a tube furnace under nitrogen atmosphere; after cooling the product, it is ultrasonically cleaned in ethanol and deionized water; vacuum dried at 70℃ to obtain Si@C@Sn / Mo silicon-based material.

[0031] Example 4 This embodiment provides a silicon-based material based on β-cyclodextrin, and the preparation method is as follows: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 3 g of β-cyclodextrin is added, followed by 0.6 g of aminopropyltriethoxysilane, and stirred for 1 h; (2) 0.6 g of SnCl2·2H2O and 0.6 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir and react for 1 h; the product obtained from the reaction is dried at 100℃ to obtain a composite precursor; (3) the composite precursor is carbonized at 1000℃ for 4 h in a tube furnace under nitrogen atmosphere; after cooling the product, it is ultrasonically cleaned in ethanol and deionized water; vacuum dried at 80℃ to obtain Si@C@Sn / Mo silicon-based material.

[0032] Example 5 This embodiment provides a silicon-based material based on β-cyclodextrin, and the preparation method is as follows: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 1 g of β-cyclodextrin is added, followed by 0.5 g of aminopropyltriethoxysilane, and stirred for 2 h; (2) 0.3 g of SnCl2·2H2O and 0.3 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir and react for 3 h; the product obtained from the reaction is dried at 110℃ to obtain a composite precursor; (3) the composite precursor is carbonized at 950℃ for 3 h in a tube furnace under nitrogen atmosphere; after cooling the product, it is ultrasonically cleaned in ethanol and deionized water; vacuum dried at 80℃ to obtain Si@C@Sn / Mo silicon-based material.

[0033] Comparative Example 1 This comparative example provides a silicon-based material, prepared by the following method: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, 1 g of β-cyclodextrin is added, followed by 0.5 g of aminopropyltriethoxysilane, and stirred for 2 h; (2) the product obtained from the reaction is dried at 110 °C to obtain a composite precursor; (3) the composite precursor is carbonized at 950 °C for 3 h in a tube furnace under a nitrogen atmosphere; after cooling, the obtained product is ultrasonically cleaned in ethanol and deionized water; and vacuum dried at 80 °C to obtain Si@C silicon-based material.

[0034] Comparative Example 2 This comparative example provides a silicon-based material, prepared by the following method: (1) 10 g of nano-silicon (particle size of 50 nm) is dispersed in 100 mL of deionized water, and 0.3 g of SnCl2·2H2O and 0.3 g of (NH4)6Mo7O are added sequentially. 24 ·4H2O, stir for 3h; (2) dry the product obtained by reaction at 110℃ to obtain a composite precursor; (3) carbonize the composite precursor in a tube furnace under nitrogen atmosphere at 950℃ for 3h; after cooling the product, ultrasonically clean it in ethanol and deionized water; vacuum dry at 80℃ to obtain Si@Sn / Mo silicon-based material.

[0035] Performance testing The silicon-based materials prepared in the above examples and comparative examples were used to fabricate coin cells, and their performance was tested. The specific process was as follows: Silicon-based materials, conductive carbon black, and polyacrylic acid (PAA) were mixed uniformly in a mass ratio of 8:1:1 and coated onto copper foil. The mixture was then dried and perforated. In a glove box, a 2032 type coin cell was assembled: a lithium foil as the counter electrode, 1M LiPF6 as the electrolyte (a mixed solution of EC, DMC, and EMC in a volume ratio of 1:1:1), and a polyethylene composite microporous membrane as the separator. The assembled battery was then subjected to charge-discharge tests on a battery tester with a charge-discharge voltage of 0.005V. At 1.5 V and a charge / discharge rate of 0.1C, the charge / discharge capacity and initial charge / discharge efficiency were tested. Cycle performance and rate performance were tested using a 2032 coin cell assembled in a glove box with a negative electrode of 30% silicon and 70% graphite, a positive electrode of NCM523, and an electrolyte of 1M LiPF6 (a mixed solution of EC, DMC, and EMC in a 1:1:1 volume ratio). The test voltage was 3.0 V. 4.2V.

[0036] The test results are shown in Table 1. Figure 1-4 As shown, from Figure 1-2 As can be seen from Table 1, the initial charge-discharge efficiency and capacity retention at 3C rate of the sample in the embodiment are superior to those of the comparative example; from Figure 3-4As can be seen from Table 1, the sample of the embodiment has a better capacity retention rate than the comparative example after 100 cycles at 3C rate, indicating that it has good electrochemical performance.

[0037] Table 1

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing silicon-based materials based on β-cyclodextrin, characterized in that, Includes the following steps: (1) Add β-cyclodextrin and silane coupling agent to the aqueous dispersion of nano-silicon and stir; (2) After adding tin source and molybdenum source, the reaction yields a composite precursor; (3) The composite precursor is carbonized at high temperature to obtain the silicon-based material.

2. The preparation method according to claim 1, characterized in that, In step (1), the particle size of the nano-silicon is 20~80 nm; Preferably, the silane coupling agent is selected from at least one of aminopropyltriethoxysilane, N-ethylaminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; Preferably, the mass ratio of the nano-silicon, β-cyclodextrin and silane coupling agent is 10:(1~5):(0.1~1).

3. The preparation method according to claim 1, characterized in that, In step (1), the stirring time is 0.5~3h.

4. The preparation method according to claim 1, characterized in that, In step (2), the tin source is at least one of soluble tin salts; the molybdenum source is at least one of soluble molybdenum salts; Preferably, the mass ratio of the nano-silicon to the tin in the tin source and the molybdenum in the molybdenum source is 10:(0.05~1.5):(0.05~1.5).

5. The preparation method according to claim 1, characterized in that, In step (2), the addition of the tin source and the molybdenum source is done sequentially. Preferably, the reaction is carried out under stirring conditions; the stirring time is 0.5 to 3 h.

6. The preparation method according to claim 1, characterized in that, Step (2) is followed by a drying process; the drying temperature is 80~120℃.

7. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the high-temperature carbonization is 800~1100℃; Preferably, the high-temperature carbonization time is 2-4 hours; Preferably, the high-temperature carbonization is carried out in an inert atmosphere.

8. The preparation method according to claim 1, characterized in that, Step (3) after high-temperature carbonization also includes post-treatment of washing and drying; the washing is ultrasonic washing with alcohol and deionized water; the drying is vacuum drying; the temperature of vacuum drying is 60~90℃.

9. The silicon-based material obtained by any of the preparation methods described in claims 1-8.

10. The application of the silicon-based material according to claim 9 in the preparation of batteries; Preferably, its application in the preparation of negative electrode materials; Preferably, its application in the preparation of lithium-ion battery anode materials.

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