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

Abstract

The present invention provides a spherical porous silicon composite material coated with an amorphous copper nanolayer, and its preparation method and application. The method comprises coating an amorphous copper conductive nanolayer onto the surface of spherical porous silicon using a simple solution method. Based on the principle of replacement reaction, the aluminum in the aluminum-silicon alloy is replaced with copper and coated on the silicon surface. At the same time, the rate of the replacement reaction is slowed down by utilizing the different reactivity of copper chloride in organic solvents, so that the spherical morphology is maintained while a layer of highly conductive amorphous copper nanolayer is coated on the silicon surface. The present invention also provides a method for preparing the material. Tests have shown that the excellent conductive properties of the copper nanolayer can effectively improve the conductivity of the material, and the porous structure can effectively alleviate the volume expansion effect of the material during the electrochemical cycle. Therefore, the combination of the two effectively improves the problems of poor conductivity and structural instability of silicon negative electrode materials, and effectively improves their application performance in lithium-ion battery negative electrodes.

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 proposes an amorphous copper nanolayer-coated spherical porous silicon composite material, as well as its preparation method and application. Low-cost aluminum-silicon alloy powder is used and a simple solution method is adopted to coat a layer of amorphous copper nanolayer on the surface of porous silicon, thereby synthesizing a silicon-based material that has a porous structure that alleviates volume expansion and excellent electrical conductivity. While maintaining the porous structure of silicon, the conductivity of silicon is further improved.

[0007] The technical solution of the present invention is achieved as follows: a method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer, comprising the following steps:

[0008] (1) Preparation of spherical porous silicon substrate: Al-Si alloy powder was mixed with 0.8-1.2 mol / L oxalic acid dihydrate solution at a mass volume ratio of 3-5 g:100 mL, stirred for 6-10 hours, washed with deionized water, and dried to obtain a porous silicon solid powder;

[0009] (2) Amorphous copper nanolayer loading: The porous silicon solid powder obtained in step (1) is dispersed in N,N-dimethylformamide, anhydrous copper chloride powder is added, and the mixture is stirred for 10-48 hours, and then washed with N,N-dimethylformamide and dried to obtain a precursor material;

[0010] (3) Acid activation treatment: The precursor material obtained in step (2) is placed in dilute hydrochloric acid with a concentration of 0.8-1.2 mol / L at a mass volume ratio of 3-5 g:100 mL, stirred for reaction for 20-28 hours, washed with deionized water, and dried to obtain the amorphous copper nanolayer-coated spherical porous silicon composite material.

[0011] Furthermore, the reaction temperature in step (1) is 20-40° C., and the stirring rate is 200-500 r / min.

[0012] Furthermore, the aluminum-silicon alloy powder in step (1) has an average particle size of 1-20 μm and a silicon content of 10-30 wt%.

[0013] Furthermore, in step (2), the mass volume ratio of the porous silicon solid powder, anhydrous copper chloride powder and N,N-dimethylformamide is 1-4 g:2.5-3.5 g:100 mL.

[0014] Furthermore, the reaction temperature in step (2) is 20-30° C., and the stirring rate is 300-600 r / min.

[0015] Furthermore, the reaction temperature in step (3) is 20-40° C., and the stirring rate is 250-550 r / min.

[0016] Furthermore, the drying in steps (1) to (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.

[0017] Furthermore, the amorphous copper nanolayer-coated spherical porous silicon composite material prepared by the above method includes a spherical porous silicon substrate, the surface of the spherical porous silicon substrate is coated with an amorphous copper nanolayer with a thickness of 5-20 nm.

[0018] Furthermore, the amorphous copper nanolayer-coated spherical porous silicon composite material is used in marine energy storage batteries.

[0019] Furthermore, the application of the marine energy storage battery is as a negative electrode material of a marine energy storage lithium-ion battery.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The product of the present invention has a uniform porous spherical morphology, which solves the problem that silicon materials expand greatly and become pulverized easily during the cycle, leading to battery failure.

[0022] 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 battery silicon-based negative electrode.

[0023] 3) The present invention has low cost: it uses cheap and readily available raw materials, thereby reducing production costs.

[0024] 4) Simple synthesis method: It adopts a simple low-temperature solution method, which is simple to synthesize and can be produced on a large scale.

[0025] In summary, the present invention utilizes a simple low-temperature solution method, based on low-cost aluminum-silicon alloy powder, to prepare a spherical porous silicon composite material with controllable morphology and uniformly coated with an amorphous copper layer. Furthermore, the research found that the resulting copper-coated spherical porous silicon material can maintain high conductivity during electrochemical cycling while mitigating volume expansion, and can still maintain a spherical morphology after cycling. This can further guide the rational design of high-performance alloy-type silicon-based materials for use as negative electrode materials for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the porous silicon solid powder prepared in step (1) of Example 1;

[0027] Figure 2 for Figure 1 A partial enlarged view of

[0028] Figure 3 This is the SEM image of the precursor material prepared in step (2) of Example 1;

[0029] Figure 4 This is a mapping diagram of the precursor material prepared in step (2) of Example 1;

[0030] Figure 5 This is a SEM image of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1;

[0031] Figure 6 This is a mapping diagram of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1;

[0032] Figure 7 HRTEM and EDX images of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1;

[0033] Figure 8 for Figure 7 A partial enlarged view of

[0034] Figure 9 This is the XPS graph of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1;

[0035] Figure 10 The XRD pattern of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in step (3) of Example 1;

[0036] Figure 11 This is a SEM image of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 2;

[0037] Figure 12 This is a SEM image of the amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 3;

[0038] Figure 13 The cycle performance diagram of the composite material prepared in Example 4 as the negative electrode active material of lithium ion battery in half cell (200mAg -1 );

[0039] Figure 14 The voltage capacity diagram of the composite material prepared in Example 4 as the negative electrode active material of lithium ion battery in half cell (200mAg -1 );

[0040] Figure 15 This is a rate performance diagram of the composite material prepared in Example 4 as a negative electrode active material in a lithium-ion battery half-cell;

[0041] Figure 16This is a cycling performance diagram (0.2C) of the composite material prepared in Example 1 as a negative electrode active material for a lithium-ion battery in a full battery with lithium iron phosphate as the positive electrode;

[0042] Figure 17 This is a rate performance diagram of the composite material prepared in Example 1 as a negative electrode active material for a lithium-ion battery in a full battery with lithium iron phosphate as the positive electrode. DETAILED DESCRIPTION

[0043] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0044] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0045] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0046] Example 1

[0047] An amorphous copper nanolayer-coated spherical porous silicon composite material comprises a spherical porous silicon substrate, the surface of which is coated with an amorphous copper nanolayer with a thickness of 5-20 nm.

[0048] The preparation method comprises the following steps:

[0049] (1) Weigh 4 g of aluminum-silicon alloy powder with an average particle size of 5-10 μm and a silicon content of 20 wt% and mix it with 100 mL of 0.1 mol oxalic acid dihydrate solution, stir it at 30°C and 300 r / min for 8 h, wash it with deionized water, and dry it in a vacuum oven at -0.09 MPa and 80°C for 24 hours to obtain porous silicon solid powder;

[0050] (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 with DMF three times (50 mL each time), and vacuum dry at -0.09 MPa and 80 ° C for 24 h to obtain a precursor material;

[0051] (3) 3 g of the precursor material obtained in step (2) was added to 100 mL of 1.0 mol / L dilute hydrochloric acid, and the mixture was stirred at 400 r / min at 30°C for 24 hours. After the reaction, the mixture was washed with deionized water until neutral (pH = 7), and vacuum dried at -0.09 MPa and 80°C for 24 hours to obtain an amorphous copper nanolayer-coated spherical porous silicon composite material.

[0052] The preparation process and products of amorphous copper nanolayer-coated spherical porous silicon composite materials were analyzed by various characterization methods such as SEM, mapping, HRTEM, EDX, XPS and XRD, and the following conclusions were drawn:

[0053] In the preparation process, after etching the aluminum-silicon alloy with dihydrated oxalic acid in step (1), the SEM image ( Figure 1 、 Figure 2 ) shows that the material successfully formed a spherical structure, and rough small pores 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. Step (2) After introducing anhydrous copper chloride to react with porous silicon in DMF, the SEM image ( Figure 3 ) confirmed that the spherical morphology was well maintained, and the mapping image ( Figure 4 ) intuitively shows that the copper element undergoes a substitution reaction on the silicon surface and achieves a preliminary uniform distribution, indicating that this step effectively achieves the loading of copper elements. Step (3) After treatment with dilute hydrochloric acid, SEM and mapping images ( Figure 5 、 Figure 6 ), HRTEM and EDX images ( Figure 7 、 Figure 8 ) further showed that the composite material eventually formed a stable spherical porous structure, and the copper element was evenly distributed on the surface of the spherical porous silicon, which fully verified that the entire preparation process can accurately control the material morphology and element distribution.

[0054] From the perspective of material structure and material form, the XPS diagram ( Figure 9 ) clearly confirmed that copper chloride replaced copper element through reaction and was tightly coated on the surface of silicon element; XRD pattern ( Figure 10 ) showed only characteristic peaks for silicon, with no crystalline diffraction peaks for copper, indicating that the copper was present in an amorphous state within the composite. These characterization results demonstrate that the preparation method provided by this invention can successfully produce spherical porous silicon composites uniformly coated with amorphous copper nanolayers through a simple solution reaction step, laying a solid material foundation for their application in fields such as lithium-ion battery energy storage.

[0055] Example 2

[0056] 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 added aluminum-silicon alloy is 30 wt %, and the remaining steps are the same as those in Example 1.

[0057] ( Figure 11 ) showed that increasing the silicon content can still maintain the spherical porous structure, confirming that the oxalic acid dealumination method is universal for silicon content (10-30wt%)

[0058] Example 3

[0059] The present invention provides a method for preparing an amorphous copper nanolayer-coated spherical porous silicon composite material. In step (2), 3.5 g of anhydrous copper chloride powder is added, and the remaining steps are the same as in Example 1.

[0060] ( Figure 12 ) shows that the copper layer thickness increases without destroying the spherical morphology, and the uniformity of copper element distribution remains good.

[0061] Example 4

[0062] The amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 1 was assembled into a lithium-ion battery as a negative electrode active material.

[0063] Cycling performance diagram of the material in half-cell (200mAg -1 )like Figure 13 As shown in the figure, after 100 cycles at a current density of 200 mA / g, the silicon-copper composite material still achieves excellent capacity retention. Figure 14 ) and rate performance diagram ( Figure 15 ) showed that the amorphous copper layer effectively improved the first coulombic efficiency and high-rate performance.

[0064] Example 5

[0065] The amorphous copper nanolayer-coated spherical porous silicon composite material prepared in Example 1 was assembled into a lithium-ion battery as a negative electrode active material, and the positive electrode was lithium iron phosphate.

[0066] like Figure 16 As shown, the lithium iron phosphate-silicon copper composite negative electrode full battery of Example 5 was cycled 50 times at a rate of 0.2C, and the specific capacity was always stable at about 130mAh / g, and the coulombic efficiency was maintained at more than 99%, indicating that the battery system constructed by this composite material has excellent cycle stability, and the amorphous copper nanolayer coating structure effectively alleviates the volume expansion problem of silicon-based materials, ensuring the stability of the structure and electrochemical performance during the battery cycle.

[0067] like Figure 17 As shown, in tests at different rates (0.2C-1.0C), the battery's specific capacity decayed regularly with increasing rate, reaching approximately 130 mAh / g at 0.2C and maintaining a certain capacity at 1.0C. Furthermore, after the rate was adjusted back to 0.2C, the specific capacity essentially recovered to its initial level (approximately 130 mAh / g), and the coulombic efficiency remained consistently high (around 99%). This demonstrates the composite material's excellent rate adaptability. The amorphous copper nanolayer enhances electronic conduction and structural stability, enabling the battery to achieve both effective capacity output and electrochemical reversibility at varying charge and discharge rates, demonstrating its potential as a negative electrode material for lithium-ion batteries.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer, characterized by: The following steps are involved: (1) Preparation of spherical porous silicon substrate: Aluminum-silicon alloy powder was mixed with 0.8-1.2 mol / L dihydrate oxalic acid solution at a mass volume ratio of 3-5 g:100 mL, stirred for 6-10 hours, washed with deionized water, and dried to obtain a porous silicon solid powder; the aluminum-silicon alloy powder had an average particle size of 1-20 μm and a silicon content of 10-30 wt%. The stirring reaction temperature was 20-40°C and the stirring rate was 200-500 r / min; (2) Amorphous copper nanolayer loading: The porous silicon solid powder obtained in step (1) is dispersed in N,N-dimethylformamide, anhydrous copper chloride powder is added, and the mixture is stirred for 10-48 hours, and then washed with N,N-dimethylformamide and dried to obtain a precursor material; the mass volume ratio of the porous silicon solid powder, anhydrous copper chloride powder and N,N-dimethylformamide is 1-4g:2.5-3.5g:100mL, the stirring reaction temperature is 20-30°C, and the stirring rate is 300-600r / min; (3) Acid activation treatment: The precursor material obtained in step (2) is placed in dilute hydrochloric acid with a concentration of 0.8-1.2 mol / L at a mass volume ratio of 3-5 g:100 mL, stirred for reaction for 20-28 hours, washed with deionized water, and dried to obtain the amorphous copper nanolayer-coated spherical porous silicon composite material.

2. The method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer according to claim 1, wherein: The temperature of the stirring reaction in step (3) is 20-40° C., and the stirring rate is 250-550 r / min.

3. The method for preparing a spherical porous silicon composite material coated with an amorphous copper nanolayer according to claim 1, wherein: The drying in steps (1) to (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 hours.

4. An amorphous copper nanolayer-coated spherical porous silicon composite material prepared by the method according to any one of claims 1 to 3, characterized in that: The invention comprises a spherical porous silicon substrate, the surface of which is coated with an amorphous copper nanolayer, and the thickness of the amorphous copper nanolayer is 5-20nm.

5. Use of the amorphous copper nanolayer-coated spherical porous silicon composite material as claimed in claim 4 in marine energy storage batteries.

6. The use according to claim 5, characterized in that The application of the marine energy storage battery is as a negative electrode material of a marine energy storage lithium-ion battery.

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