Amorphous copper nanolayer coated spherical porous silicon composite material and preparation method and application thereof

Abstract

The invention provides an amorphous copper nanolayer coated spherical porous silicon composite material and a preparation method and application thereof.The preparation method includes the step that the surface of spherical porous silicon is coated with an amorphous copper conductive nanolayer through a simple solution method.On the basis of the principle of replacement reaction, aluminum in aluminum-silicon alloy is replaced with copper to be coated on the surface of silicon, and the amorphous copper nanolayer coated spherical porous silicon composite material is obtained. And meanwhile, the rate of the replacement reaction is slowed down by utilizing different reaction activities of copper chloride in an organic solvent, so that the spherical morphology is kept, and meanwhile, the surface of silicon can be coated with a layer of amorphous copper nano layer with high conductivity. The invention also provides a preparation method of the material. Tests find that the conductivity of the material can be effectively improved due to the excellent conductivity of the copper nano layer, and the volume expansion effect of the material in the electrochemical cycle process can be effectively relieved due to the porous structure. Therefore, the combination of the two effectively improves the problems of poor conductivity and unstable structure of the silicon negative electrode material, and effectively improves the application performance of the silicon negative electrode material in the lithium ion battery negative electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to an amorphous copper nanolayer-coated spherical porous silicon composite material, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have become a core technology for modern energy storage systems, powering a wide range of applications from portable electronic devices to electric vehicles and renewable energy grids. Despite significant progress in the development of LIBs, the growing demand for higher energy density and longer life requires further innovation in electrode materials.

[0003] Silicon (Si) has abundant reserves, low discharge potential and extremely high theoretical specific capacity (4200mAhg -1 ), becoming one of the most promising anode materials to replace traditional graphite. However, the practical application of silicon anodes is severely hampered by their inherent limitations, primarily poor conductivity and a massive volume expansion (approximately 300%) during lithiation. This leads to mechanical disintegration and electrical isolation, resulting in the formation of an inactive layer—"dead silicon"—that loses capacity. This inactive layer, composed of broken silicon particles separated from the electrode, is non-conductive and cannot participate in the subsequent lithiation process, resulting in capacity loss.

[0004] In order to solve the inherent defects of silicon-based negative electrode materials and improve their electrochemical performance, current international research mainly revolves around two major strategies: one is nano-scaling, which reduces the size of silicon materials to the nanoscale to effectively alleviate their volume expansion during the lithium insertion / extraction process, reduce the mechanical stress concentration caused by lattice strain and shorten the lithium ion diffusion path; the other is composite construction, which aims to composite the silicon matrix with highly conductive components to construct a multi-scale and multi-dimensional structure, and reduce the direct contact between the silicon active material and the electrolyte by establishing a stable conductive matrix or network, thereby promoting the formation of a stable and uniform solid electrolyte interface (SEI) film and inhibiting the occurrence of harmful side reactions.

[0005] However, nanofabrication is limited by cost and operational complexity. Furthermore, common highly conductive components include graphite and amorphous-derived carbon. Graphite is rigid and suffers from uneven coating, while organic-derived carbon requires high-temperature carbonization, which results in high energy consumption and structural collapse. Therefore, the primary challenge is to effectively improve the conductivity of the silicon anode and maintain the structural stability of the silicon while minimizing cost and simplifying the operation. Summary of the Invention

[0006] In view of this, the present invention provides a spherical porous silicon composite material coated with an amorphous copper nanolayer, its preparation method and application. By using low-cost aluminum-silicon alloy powder and adopting a simple solution method, an amorphous copper nanolayer is coated on the surface of porous silicon, synthesizing a silicon-based material that not only has a porous structure to relieve volume expansion but also has excellent electrical conductivity, further improving the electrical conductivity of silicon while maintaining the porous structure of silicon.

[0007] The technical solution of the present invention is realized as follows: A preparation method of a spherical porous silicon composite material coated with an amorphous copper nanolayer, comprising the following steps: (1) Preparation of spherical porous silicon matrix: Mix aluminum-silicon alloy powder with a 0.8 - 1.2 mol / L solution of oxalic acid dihydrate according to a mass-volume ratio of 3 - 5 g:100 mL, stir and react for 6 - 10 hours, then wash with deionized water and dry to obtain porous silicon solid powder; (2) Loading of amorphous copper nanolayer: Disperse the porous silicon solid powder obtained in step (1) in N,N-dimethylformamide, add anhydrous copper chloride powder, stir and react for 10 - 48 hours, then wash with N,N-dimethylformamide and dry to obtain a precursor material; (3) Acid activation treatment: Place the precursor material obtained in step (2) in a 0.8 - 1.2 mol / L dilute hydrochloric acid according to a mass-volume ratio of 3 - 5 g:100 mL, stir and react for 20 - 28 hours, then wash with deionized water and dry to obtain the spherical porous silicon composite material coated with an amorphous copper nanolayer.

[0008] Further, the reaction temperature in step (1) is 20 - 40 °C, and the stirring rate is 200 - 500 r / min.

[0009] Further, the average particle size of the aluminum-silicon alloy powder in step (1) is 1 - 20 μm, and the silicon content is 10 - 30 wt%.

[0010] Further, the mass-volume ratio of the porous silicon solid powder, anhydrous copper chloride powder and N,N-dimethylformamide in step (2) is 1 - 4 g:2.5 - 3.5 g:100 mL.

[0011] Further, the reaction temperature in step (2) is 20 - 30 °C, and the stirring rate is 300 - 600 r / min.

[0012] Further, the reaction temperature in step (3) is 20 - 40 °C, and the stirring rate is 250 - 550 r / min.

[0013] Further, the drying in steps (1) - (3) is vacuum drying, the vacuum degree is -0.08 MPa to -0.1 MPa, the drying temperature is 60 - 120 °C, and the drying time is 24 - 48 h.

[0014] Further, the amorphous copper nanolayer-coated spherical porous silicon composite material prepared by the above method comprises a spherical porous silicon matrix, and an amorphous copper nanolayer with a thickness of 5-20 nm is coated on the surface of the spherical porous silicon matrix.

[0015] Further, the application of the amorphous copper nanolayer-coated spherical porous silicon composite material in a marine energy storage battery.

[0016] Further, the application in the marine energy storage battery is used as a negative electrode material for a marine energy storage lithium ion battery.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The product of the present invention has a uniform porous spherical morphology, which solves the problem that the silicon material has a large volume expansion and is easily pulverized during the cycling process, resulting in battery failure.

[0018] 2) The product of the present invention has a porous spherical silicon material coated with an amorphous copper layer, which can improve the conductivity and further enhance the performance of the lithium-ion silicon-based negative electrode.

[0019] 3) The present invention has low cost: cheap and easily available raw materials are used, reducing the production cost.

[0020] 4) The synthesis method is simple: a simple low-temperature solution method is adopted, the synthesis is simple, and large-scale production can be carried out.

[0021] In summary, the present invention prepares a spherical porous silicon composite material with controllable morphology and uniformly coated amorphous copper layer by a simple low-temperature solution method on the basis of using low-cost aluminum-silicon alloy powder. And it is found that the obtained copper-layer-coated spherical porous silicon material can maintain high conductivity during electrochemical cycling, while alleviating volume expansion, and still maintain a spherical morphology after cycling, which can further guide the rational design to obtain high-performance alloy-type silicon-based materials and can be used as a negative electrode material for lithium-ion batteries. Description of the Drawings [[ID=((29))]]

[0022] Figure 1 It is the SEM image of the porous silicon solid powder prepared in step (1) of Example 1; Figure 2 For Figure 1 The partial enlarged view of; Figure 3 It is the SEM image of the precursor material prepared in step (2) of Example 1; Figure 4 It is the mapping image of the precursor material prepared in step (2) of Example 1; Figure 5 It is the SEM image of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1; Figure 6 It is the mapping diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1; Figure 7 They are the HRTEM diagram and EDX diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1; Figure 8 It is for Figure 7 the partial enlarged view; Figure 9 It is the XPS diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1; Figure 10 It is the XRD diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1; Figure 11 It is the SEM diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 2; Figure 12 It is the SEM diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 3; Figure 13 It is the cycling performance diagram of the composite material prepared in Example 4 as the negative electrode active material of a lithium-ion battery in a half-cell (200 mA g -1 ); Figure 14 It is the voltage-capacity diagram of the composite material prepared in Example 4 as the negative electrode active material of a lithium-ion battery in a half-cell (200 mA g -1 ); Figure 15 It is the rate performance diagram of the composite material prepared in Example 4 as the negative electrode active material of a lithium-ion battery in a half-cell; Figure 16 It is the cycling performance diagram of the composite material prepared in Example 1 as the negative electrode active material of a lithium-ion battery in a full-cell with lithium iron phosphate as the positive electrode (0.2 C); Figure 17 It is the rate performance diagram of the composite material prepared in Example 1 as the negative electrode active material of a lithium-ion battery in a full-cell with lithium iron phosphate as the positive electrode. Detailed implementation manners

[0023] To better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0024] The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0025] The materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial channels unless otherwise specified.

[0026] Example 1 A spherical porous silicon composite coated with an amorphous copper nanolayer, comprising a spherical porous silicon matrix, on the surface of which is coated an amorphous copper nanolayer with a thickness of 5 - 20 nm.

[0027] The preparation method includes the following steps: (1) Weigh 4 g of an aluminum - silicon alloy powder with a silicon content of 20 wt% and an average particle size of 5 - 10 microns, mix it with 100 mL of a 0.1 mol oxalic acid dihydrate solution, stir at 30 °C and 300 r / min for 8 h, wash with deionized water, and then place it in a vacuum oven to dry at - 0.09 MPa and 80 °C for 24 hours to obtain a porous silicon solid powder; (2) Disperse 2 g of the porous silicon solid powder obtained in step (1) in 100 mL of DMF, add 3 g of anhydrous copper chloride powder, stir evenly, react at 25 °C and 400 r / min for 24 h, wash 3 times with DMF (50 mL each time), and vacuum - dry at - 0.09 MPa and 80 °C for 24 hours to obtain a precursor material; (3) Add 3 g of the precursor material obtained in step (2) to 100 mL of a 1.0 mol / L dilute hydrochloric acid, stir and react at 30 °C at a rate of 400 r / min for 24 hours. After the reaction, wash with deionized water until neutral (pH = 7), and vacuum - dry at - 0.09 MPa and 80 °C for 24 hours to obtain a spherical porous silicon composite coated with an amorphous copper nanolayer.

[0028] Through various characterization methods such as SEM, mapping, HRTEM, EDX, XPS, and XRD, the preparation process and products of the spherical porous silicon composite coated with an amorphous copper nanolayer were analyzed, and the following conclusions were obtained: During the preparation process, after the aluminum - silicon alloy was etched with oxalic acid dihydrate in step (1), the SEM images ( Figure 1 Figure 2 ) showed that the material successfully formed a spherical structure, and rough small holes appeared on the particle surface, indicating that the etching effect of oxalic acid on the alloy effectively constructed the basic morphology of the porous silicon matrix. After introducing anhydrous copper chloride to react with the porous silicon in DMF in step (), the SEM image ( Figure 3 ) confirmed that the spherical morphology was well maintained, and the mapping image ( Figure 4 ) visually presented that the copper element underwent a displacement reaction on the silicon surface and achieved preliminary uniform distribution, indicating that this step effectively realized the loading of the copper element. After being treated with dilute hydrochloric acid in step (3), the SEM and mapping images ( Figure 5 Figure 6 ), HRTEM and EDX images ( Figure 7 ​​​Figure 8 It further shows that the composite material finally forms a stable spherical porous structure, and the copper element is uniformly distributed on the surface of the spherical porous silicon, fully verifying that the entire preparation process can accurately control the material morphology and element distribution.

[0029] From the perspective of material structure and physical form, the XPS graph ( Figure 9 ) clearly confirms that copper chloride displaces copper elements through the reaction and tightly coats the surface of silicon elements; the XRD graph ( Figure 10 ) only shows the characteristic peaks of silicon elements and no crystal diffraction peaks of copper, indicating that copper exists in the composite material in an amorphous form. This series of characterization results together prove that the preparation method provided by the present invention can successfully prepare a spherical porous silicon composite material uniformly coated with an amorphous copper nanolayer through a simple solution reaction step, laying a solid material foundation for its application in fields such as lithium-ion battery energy storage.

[0030] Example 2 The present invention provides a method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer. In step (1), the silicon content of the aluminum-silicon alloy added is 30 wt%, and the remaining steps are the same as those in Example 1.

[0031] ( Figure 11 ) shows that increasing the silicon content can still maintain the spherical porous structure, confirming the universality of the oxalic acid dealumination method for the silicon content (10 - 30 wt%). Example 3 The present invention provides a method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer. In step (2), 3.5 g of anhydrous copper chloride powder is added, and the remaining steps are the same as those in Example 1.

[0032] ( Figure 12 ) shows that the thickness of the copper layer increases, but the spherical morphology is not damaged, and the uniformity of the copper element distribution remains good.

[0033] Example 4 The spherical porous silicon composite material coated with an amorphous copper nanolayer prepared in Example 1 is assembled as the negative electrode active material in a lithium-ion battery.

[0034] The cycling performance graph (200 mAg -1 ) of this material in the half-cell is as Figure 13 shown. After cycling 100 times at a current density of 200 mA / g, the silicon-copper composite material still reaches an excellent capacity retention rate. The charge-discharge curve ( Figure 14 ) and the rate performance graph ( Figure 15 ) show that the amorphous copper layer effectively improves the first Coulombic efficiency and high-rate performance.

[0035] Example 5 The amorphous copper nanolayer-coated spherical porous silicon composite prepared in Example 1 was assembled as the anode active material in a lithium-ion battery, and the cathode was lithium iron phosphate.

[0036] As Figure 16 shown, the lithium iron phosphate-silicon copper composite anode full battery of Example 5 was cycled 50 times at a rate of 0.2C, and the specific capacity remained stable at about 130 mAh / g all the time, and the Coulomb efficiency was maintained above 99%, indicating that the battery system constructed by this composite material had excellent cycle stability. The amorphous copper nanolayer coating structure effectively alleviated the volume expansion problem of the silicon-based material and ensured the stability of the structure and electrochemical performance during the battery cycle.

[0037] As Figure 17 shown, in the tests at different rates (0.2C - 1.0C), the specific capacity of the battery decayed regularly with the increase of the rate. The specific capacity was about 130 mAh / g at 0.2C and still maintained a certain capacity at 1.0C. And after the rate was adjusted back to 0.2C, the specific capacity could basically recover to the initial level (about 130 mAh / g), and the Coulomb efficiency always remained at a high level (about 99%). This shows that this composite material has good rate adaptability. The amorphous copper nanolayer enhances electron conduction and structural stability, enabling the battery to effectively output capacity and ensure electrochemical reversibility at different charge and discharge rates, demonstrating the potential as a lithium-ion battery anode material.

[0038] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of an amorphous copper nanolayer-coated spherical porous silicon composite material, characterized in that: It includes the following steps: (1) Preparation of spherical porous silicon matrix: Mix aluminum-silicon alloy powder with oxalic acid dihydrate solution with a concentration of 0.8 - 1.2 mol / L at a mass-to-volume ratio of 3 - 5 g:100 mL, stir and react for 6 - 10 hours, then wash with deionized water and dry to obtain porous silicon solid powder; (2) Loading of amorphous copper nanolayer: Disperse the porous silicon solid powder obtained in step (1) in N,N-dimethylformamide, add anhydrous copper chloride powder, stir and react for 10 - 48 hours, then wash with N,N-dimethylformamide and dry to obtain a precursor material; (3) Acid activation treatment: Place the precursor material obtained in step (2) in dilute hydrochloric acid with a concentration of 0.8 - 1.2 mol / L at a mass-to-volume ratio of 3 - 5 g:100 mL, stir and react for 20 - 28 hours, then wash with deionized water and dry to obtain the amorphous copper nanolayer-coated spherical porous silicon composite material.

2. The preparation method of an amorphous copper nano-layer coated spherical porous silicon composite material as described in claim 1, characterized in that: The temperature of the stirring reaction in step (1) is 20 - 40 °C, and the stirring rate is 200 - 500 r / min.

3. The preparation method of an amorphous copper nano-layer coated spherical porous silicon composite material according to claim 1, characterized in that: The average particle size of the aluminum-silicon alloy powder in step (1) is 1 - 20 μm, and the silicon content is 10 - 30 wt%.

4. The preparation method of an amorphous copper nanolayer-coated spherical porous silicon composite material according to claim 1, wherein: The mass-to-volume ratio of the porous silicon solid powder, anhydrous copper chloride powder, and N,N-dimethylformamide in step (2) is 1 - 4 g:2.5 - 3.5 g:100 mL.

5. The preparation method of an amorphous copper nanolayer-coated spherical porous silicon composite material according to claim 1, characterized in that: The temperature of the stirring reaction in step (2) is 20 - 30 °C, and the stirring rate is 300 - 600 r / min.

6. The preparation method of an amorphous copper nanolayer-coated spherical porous silicon composite material as described in claim 1, characterized in that: The temperature of the stirring reaction in step (3) is 20 - 40 °C, and the stirring rate is 250 - 550 r / min.

7. The preparation method of an amorphous copper nano-layer coated spherical porous silicon composite material according to claim 1, characterized in that: The drying in steps (1) - (3) is vacuum drying, the vacuum degree is -0.08 MPa to -0.1 MPa, the drying temperature is 60 - 120 °C, and the drying time is 24 - 48 h.

8. An amorphous copper nanolayer-coated spherical porous silicon composite material prepared by the method according to any one of claims 1-7, characterized in that: It includes a spherical porous silicon matrix, and the surface of the spherical porous silicon matrix is coated with an amorphous copper nanolayer with a thickness of 5 - 20 nm.

9. Application of the amorphous copper nanolayer-coated spherical porous silicon composite material as described in claim 8 in marine energy storage batteries.

10. The application according to claim 9, wherein The application in the marine energy storage battery is as the negative electrode material of the marine energy storage lithium-ion battery.

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