Composite silicon-based negative electrode material and preparation method thereof, and battery

Abstract

The application belongs to the technical field of battery materials, and discloses a composite silicon-based negative electrode material, a preparation method thereof and a battery. The composite silicon-based negative electrode material comprises nano-silicon and a carbon network. The nano-silicon is distributed on the carbon network, and the nano-silicon and the carbon network are closely combined. The carbon network is doped with nitrogen elements, and the surface of the carbon network is loaded with nano-copper. In the silicon-based negative electrode material, the carbon material is doped with copper nano-points, which can promote electron conduction. The nitrogen-doped carbon network has higher stability, can provide better framework support for the copper nano-points and the nano-silicon, improve the structural stability and conductivity of the silicon-based negative electrode material, and relieve the volume change of the silicon-based negative electrode material. In addition, the nitrogen-doped carbon network loaded with the copper nano-points provides a stable composite layer for the nano-silicon material, can effectively inhibit the volume expansion of the silicon negative electrode, and improve the structural stability of the silicon negative electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and relates to a negative electrode material, in particular to a composite silicon-based negative electrode material and a preparation method thereof and a battery. BACKGROUND

[0002] With the continuous development of lithium ion battery technology, the development of high specific energy lithium ion batteries has become an unstoppable trend. In order to improve the specific energy of lithium ion batteries, it is necessary to proceed from two aspects of lithium ion battery structure design and new material development. The main method of battery structure design is to reduce the weight of structural parts, copper foil, aluminum foil and other non-active materials, thereby increasing the proportion of active materials and improving the specific energy of lithium ion batteries. The main method of new material development is to develop positive and negative electrode materials with higher capacity, and positive electrode materials with higher voltage, so as to improve the capacity and voltage of the battery and achieve the purpose of improving the energy density of the battery.

[0003] At present, the development direction of negative electrode materials is mainly to improve the capacity of the materials. For example, the capacity of the Si-based material which is now a relatively mature technology can reach more than 1000 mAh / g, which is much higher than that of graphite materials.

[0004] However, the silicon-based negative electrode material also has a serious volume expansion problem. In the fully embedded lithium state, the volume expansion of the Si negative electrode can reach 300%, which not only causes the particles of the Si negative electrode to break, but also damages the conductive network and the adhesive network of the electrode, resulting in loss of active materials, thereby seriously affecting the cycle performance of the silicon-based negative electrode material, which has become the main obstacle to the application of Si negative electrode materials. SUMMARY

[0005] In view of the defects and deficiencies of the prior art, in a first aspect, the application provides a composite silicon-based negative electrode material; in a second aspect, the application provides a preparation method of the composite silicon-based negative electrode material; and in a third aspect, the application provides a battery.

[0006] In a first aspect, the application provides a composite silicon-based negative electrode material, which comprises nano-silicon and a carbon network, the nano-silicon is distributed on the carbon network, and the nano-silicon and the carbon network are tightly combined; the carbon network is doped with nitrogen elements, and the surface of the carbon network is loaded with nano-copper.

[0007] Preferably, the size of the nano-silicon is 50-100 nm.

[0008] In a second aspect, the application provides a preparation method of the composite silicon-based negative electrode material, which comprises: mixing a copper-based nitrogen heterocyclic crown ether complex and nano-silicon, and sintering under a protective atmosphere to obtain the composite silicon-based negative electrode material.

[0009] Preferably, the mass ratio of the copper-based nitrogen heterocyclic crown ether complex to the nano-silicon is (0.1-0.8) : 1.

[0010] Preferably, the sintering temperature is 500~700℃ and the sintering time is 5~10h.

[0011] Preferably, the preparation method of the copper-based azirocrown ether complex includes: mixing azirocrown ether, copper salt and water, reacting for a certain period of time, centrifuging, washing with water and drying to obtain the final product.

[0012] Preferably, the azacrown ether is any one or more of pyridine-azacrown ether, aza-18-crown ether-6, 4,13-diaza-18-crown-6-ether, and aza-15-crown ether-5.

[0013] Preferably, the copper salt is any one or more of copper sulfate, copper chloride, and copper nitrate.

[0014] Preferably, the molar ratio of the azacrown ether to the copper salt is (5~10):1.

[0015] Preferably, the coordination reaction time is 10-20 hours.

[0016] Preferably, the protective atmosphere is provided by either nitrogen or argon, or both.

[0017] Thirdly, the present invention provides a battery comprising the aforementioned composite silicon-based anode material.

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) In this invention, carbon material is incorporated into silicon-based anode material. Copper nanoparticles in the carbon material can promote electron conduction. The nitrogen-doped carbon network loaded with copper nanoparticles provides a stable composite layer for the nano-silicon material, which can effectively suppress the volume expansion of the silicon anode and improve the structural stability of the silicon anode.

[0020] (2) Composite silicon-based anode materials are obtained by sintering copper-based nitrile crown ether complexes and nano-silicon. The preparation process is simple and easy to achieve large-scale production, which is conducive to commercialization and marketization. The silicon-based anode materials exhibit excellent cycle reversibility and structural stability. Attached Figure Description

[0021] Figure 1 Here is a SEM image of the composite silicon anode material prepared in Example 1;

[0022] Figure 2 EDS image of the composite silicon anode material prepared in Example 1;

[0023] Figure 3 The graph shows the cycle performance test results of the silicon anode materials prepared in Examples 1-3 and Comparative Examples 1-3, and the batteries assembled from nano-silicon.

[0024] Figure 4 SEM image of the electrode sheet made from the composite silicon anode material prepared in Example 1 after 50 cycles;

[0025] Figure 5 SEM image of the electrode sheet made from the composite silicon anode material prepared in Comparative Example 1 after 50 cycles.

[0026] Figure 6 SEM image of an electrode made of nano-silicon after 50 cycles. Detailed Implementation

[0027] The present invention provides the following specific technical solutions.

[0028] In a first aspect, the present invention provides a composite silicon-based anode material, comprising nano-silicon and a carbon mesh, wherein the nano-silicon is distributed on the carbon mesh and the nano-silicon and the carbon mesh are tightly bonded together; the carbon mesh is doped with nitrogen element, and the surface of the carbon mesh is loaded with nano-copper.

[0029] The inventors discovered that carbon mesh possesses excellent flexibility and elasticity. As a skeletal structure, the carbon mesh supports silicon particles, forming a stable overall electrode structure. This reduces the displacement and aggregation of silicon particles during charging and discharging, ensuring the structural stability of the electrode's interior. It also buffers the volume expansion and contraction of silicon during charging and discharging, reducing silicon particle pulverization. The carbon mesh has a large specific surface area and abundant pore structure, enabling better adsorption of electrolyte and promoting its uniform distribution within the electrode, thereby accelerating the diffusion rate of lithium ions. The copper nanodots on the carbon mesh surface promote electron conduction. The nitrogen-doped carbon mesh loaded with copper nanodots provides a stable composite layer for the nano-silicon material, effectively suppressing the volume expansion of the silicon anode and improving its structural stability.

[0030] Preferably, the size of the nano-silicon is 50~100nm.

[0031] Secondly, the present invention provides a method for preparing a composite silicon-based anode material, comprising: mixing a copper-based azirconium crown ether complex and nano-silicon, and sintering under a protective atmosphere to obtain the anode material.

[0032] Through research, the inventors discovered that by selecting copper-based nitrile crown ether complexes as one of the raw materials, the copper-based nitrile crown ether complexes decompose into nitrogen-doped carbon meshes during the sintering process, and nano-copper is uniformly loaded on the carbon meshes. The carbon meshes and nano-silicon composites produce silicon-based anode materials with good conductivity and structural stability, thus improving the cycle performance of the battery.

[0033] Preferably, the mass ratio of the copper-based azirconium crown ether complex to nano-silicon is (0.1~0.8):1.

[0034] Through research, the inventors discovered that within the above-mentioned preferred range, it is possible to ensure uniform mixing of nano-silicon and copper-based azirconium ether complexes, and to ensure sufficient carbon network generation, so that nano-silicon and the generated carbon network are evenly distributed, reducing the possibility of nano-silicon agglomeration.

[0035] Preferably, the sintering temperature is 500~700℃ and the sintering time is 5~10h.

[0036] Through research, the inventors discovered that under the aforementioned preferred sintering conditions, the organic groups in the copper-based azirconium crown ether complex can be completely decomposed into a carbon network, reducing the content of impurities and ensuring uniform distribution of each material, thus reducing the possibility of agglomeration.

[0037] In a specific embodiment, a method for preparing a composite silicon-based anode material includes the following steps:

[0038] Step 1, Preparation of copper-based azirocrown ether complex: Mix azirocrown ether, copper salt and water, allow to coordinate reaction for a certain time, then centrifuge, wash with water and dry to obtain the product;

[0039] Step 2, Preparation of composite silicon-based anode material: Mix the copper-based nitrogen crown ether complex obtained in step 1 with nano-silicon, and calcine under a protective atmosphere to obtain the final product.

[0040] Preferably, the azacrown ether is any one or more of pyridine-azacrown ether, aza-18-crown ether-6, 4,13-diaza-18-crown-6-ether, and aza-15-crown ether-5.

[0041] Preferably, the copper salt is any one or more of copper sulfate, copper chloride, and copper nitrate.

[0042] Preferably, the molar ratio of the azacrown ether to the copper salt is (5~10):1.

[0043] Preferably, the coordination reaction time is 10-20 hours.

[0044] In practical applications, coordination reactions are carried out at room temperature.

[0045] Preferably, the protective atmosphere is provided by either nitrogen or argon, or both.

[0046] Thirdly, the present invention provides a battery comprising the aforementioned composite silicon-based anode material.

[0047] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] Example 1:

[0051] A method for preparing a composite silicon anode includes the following steps:

[0052] Step 1: Dissolve 0.2 mol of pyridine-azacrown ether in 500 ml of deionized water, add 0.03 mol of copper sulfate to the above aqueous solution, and after coordination reaction for 15 h, centrifuge, wash with water and dry to obtain copper-based pyridine-azacrown ether complex.

[0053] Step 2: Mix 3g of the copper-based pyridine-azacrown ether complex obtained in Step 1 with 10g of nano-silicon material and sinter at 550℃ for 7h under a nitrogen atmosphere to obtain the composite silicon-based anode material.

[0054] Figure 1 The image shows a SEM image of the composite silicon anode material prepared in Example 1. Figure 1 It can be seen that the D50 of the silicon particles is about 50~100nm, and the silicon particles are evenly distributed and located inside the carbon network.

[0055] Figure 2 The image shown is the EDS diagram of the composite silicon anode material prepared in Example 1. Figure 2 It can be seen that the four elements Cu, N, C, and Si are evenly distributed in the material. The distribution of Cu and N overlaps with the distribution of C, proving that the copper-based nitrogen crown ether complex provided by this invention decomposes into a carbon network containing N element under the calcination process, and Cu is loaded on the carbon network.

[0056] Comparative Example 1:

[0057] A method for preparing a composite silicon anode includes the following steps:

[0058] Step 1: Mix 3g of pyridine-azacrown ether with 10g of nano-silicon material and sinter at 550℃ for 7h under nitrogen atmosphere to finally prepare composite silicon-based anode material.

[0059] Comparative Example 2:

[0060] A method for preparing a composite silicon anode includes the following steps:

[0061] Step 1: Mix 1.2g of nano-copper and 10g of nano-silicon materials and sinter at 550℃ for 7h under a nitrogen atmosphere to obtain the composite silicon-based anode material.

[0062] Comparative Example 3:

[0063] A method for preparing a composite silicon anode includes the following steps:

[0064] Step 1: Mix 1.2g of nano-copper, 0.2mol of pyridine-azacrown ether and 10g of nano-silicon material and sinter at 550℃ for 7h under a nitrogen atmosphere to obtain the composite silicon-based anode material.

[0065] Example 2:

[0066] A method for preparing a composite silicon anode includes the following steps:

[0067] Step 1: Dissolve 0.2 mol of aza-18-crown ether-6 in 500 ml of deionized water, add 0.02 mol of copper chloride to the above aqueous solution, and after coordination reaction for 10 h, centrifuge, wash with water and dry to obtain copper-based aza-18-crown ether-6 complex.

[0068] Step 2: Mix 1g of the copper-based aza-18-crown ether-6 complex obtained in Step 1 with 10g of nano-silicon material and sinter at 500℃ for 10h under a nitrogen atmosphere to obtain the composite silicon-based anode material.

[0069] Example 3:

[0070] A method for preparing a composite silicon anode includes the following steps:

[0071] Step 1: Dissolve 0.2 mol of 4,13-diaza-18-crown-6-ether in 500 ml of deionized water, add 0.04 mol of copper nitrate to the above aqueous solution, and after coordination reaction for 15 h, centrifuge, wash with water and dry to obtain copper-based 4,13-diaza-18-crown-6-ether complex.

[0072] Step 2: Mix 4g of the copper-based 4,13-diaza-18-crown-6-ether complex obtained in Step 1 with 5g of nano-silicon material and sinter at 700℃ for 5h under a nitrogen atmosphere to obtain the composite silicon-based anode material.

[0073] The silicon anode materials prepared in Examples 1-3 and Comparative Examples 1-3, along with nano-silicon, were used as active materials. These materials were mixed with conductive agent acetylene black (AB) and binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1. Using N-methylpyrrolidone (NMP) as a solvent, the mixture was stirred in a small beaker at 800 r / min for 2 hours to obtain a slurry. The slurry was coated onto a current collector copper foil using an automatic coating machine, laid flat on tempered glass, and dried in a vacuum drying oven at 85°C for 4 hours. After die-cutting to form electrode sheets with a diameter of 14 mm, the sheets were dried in a vacuum drying oven at 105°C for 4 hours. The sheets were then placed in a glove box filled with argon atmosphere for 4 hours to reduce the moisture adsorbed during transfer. Finally, the sheets were assembled into CR2032 coin cells in the glove box. The battery uses a 18mm diameter porous polyethylene membrane, model Celgard2300, as the separator, and a lithium sheet as the counter electrode.

[0074] After the battery assembly was completed and aged for 12 hours, a 2C rate charge-discharge test was then conducted within a voltage range of 0.1~3.0V.

[0075] Figure 3 The cycling performance test charts of the silicon anode materials prepared in Examples 1-3 and Comparative Examples 1-3, and the batteries assembled from nano-silicon, are presented by [the relevant authority / organization]. Figure 3 As can be seen from the comprehensive analysis of Example 1 and Comparative Examples 1-3, doping the silicon anode material with nitrogen-containing carbon materials or copper elements alone can improve its cycle performance. Furthermore, doping with both nitrogen-containing carbon materials and copper elements can further enhance the cycle performance. The silicon anode material provided by this invention not only contains carbon materials but also has copper nanodots loaded on the carbon materials. The silicon anode material with this special structure exhibits superior cycle performance, fully demonstrating the superior electrochemical stability of the modified silicon anode material and further proving its structural stability. The unmodified nano-silicon material exhibits the worst electrochemical performance, possibly due to the volume expansion of the silicon anode after electrochemical cycling, which directly affects the electrochemical capacity retention rate.

[0076] Figure 4 This is a SEM image of the electrode sheet made from the composite silicon anode material prepared in Example 1 after 50 cycles. Figure 4 As can be seen from the data, after cycling, the electrode surface is smooth and no cracks are generated, which proves that the composite silicon anode material provided by the present invention has good structural stability.

[0077] Figure 5 The image shows a SEM image of the electrode sheet made from the composite silicon anode material prepared in Comparative Example 1 after 50 cycles. Figure 5As can be seen, after cycling, obvious cracks appeared on the electrode, indicating that the silicon anode material made by combining a single nitrogen-containing carbon mesh and silicon material is also prone to volume expansion, and its structural stability is relatively poor compared with the composite silicon anode material provided by this invention.

[0078] Figure 6 SEM images of electrodes made of nano-silicon after 50 cycles. Figure 6 As can be seen, after cycling, the electrode developed obvious cracks, and the crack size was relatively large, which will greatly affect the electrochemical performance of the material. From... Figure 3 As can be clearly seen from the electrochemical performance graph, the electrochemical capacity decays rapidly in the later stages. This indicates that the drastic expansion of the silicon anode causes irreversibility of the silicon anode structure, which severely affects the electrochemical reversibility.

[0079] Combination Figures 3-6 This demonstrates that the carbon network loaded with copper nanodots and nitrogen doped by the present invention has better cycling performance and structural stability.

[0080] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite silicon-based anode material, characterized in that, It includes nano-silicon and carbon mesh, wherein the nano-silicon is distributed on the carbon mesh and the nano-silicon and the carbon mesh are tightly bonded; the carbon mesh is doped with nitrogen element, and the surface of the carbon mesh is loaded with nano-copper. The preparation method of the composite silicon-based anode material includes: mixing copper-based azirconium crown ether complex and nano-silicon, and sintering under a protective atmosphere to obtain the anode material; The mass ratio of copper-based azacrown ether complex to nano-silicon is (0.1~0.8):

1.

2. The composite silicon-based anode material as described in claim 1, characterized in that, The size of the silicon nanoparticles is 50~100nm.

3. The composite silicon-based anode material as described in claim 1, characterized in that, The sintering temperature is 500~700℃, and the sintering time is 5~10h.

4. The composite silicon-based anode material as described in claim 1, characterized in that, The preparation method of the copper-based azirocrown ether complex includes: mixing azirocrown ether, copper salt and water, reacting for a certain period of time, centrifuging, washing with water and drying to obtain the final product.

5. The composite silicon-based anode material as described in claim 4, characterized in that, The azacrown ether is any one or more of pyridine-azacrown ether, aza-18-crown ether-6, 4,13-diaza-18-crown-6-ether, and aza-15-crown ether-5; the copper salt is any one or more of copper sulfate, copper chloride, and copper nitrate; the molar ratio of azacrown ether to copper salt is (5~10):

1.

6. The composite silicon-based anode material as described in claim 4, characterized in that, The coordination reaction time is 10~20h.

7. A battery, characterized in that, Includes the composite silicon-based anode material as described in any one of claims 1 to 6.

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