A triazine-based covalent organic framework-coated nano-silicon negative electrode, a preparation method and applications thereof
By constructing a triazine-based covalent organic framework coating layer on the surface of nano-silicon, the problem of SEI film rupture during cycling of nano-silicon anodes was solved, achieving high cycle stability and long lifespan of lithium-ion battery anodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2024-10-11
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional graphite anodes are difficult to meet the requirements of high-energy lithium-ion batteries. During cycling, the solid-electrolyte interface (SEI) film of nano-silicon anodes breaks due to volume expansion, and cannot adapt to the huge volume expansion of silicon-based anodes, resulting in the formation of 'dead silicon'.
A triazine-based covalent organic framework (COF) coating layer was constructed on the surface of nano-silicon. The COF layer was formed by secondary amine bonds through van der Waals forces, electrostatic adsorption, and peptide bonds. During lithiation, the COF layer was converted into a high-modulus Li3N component, which enhanced the mechanical strength of the SEI film.
It improves the mechanical strength of the SEI film, prevents rupture, and enhances the cycle life of the lithium-ion battery anode and the long-term cycle stability of the electrode.
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Figure CN119419234B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a triazine-based covalent organic framework-coated nano-silicon anode, its preparation method, and its application, belonging to the field of lithium-ion battery technology. Background Technology
[0002] Currently, renewable energy technologies have been developed as a supplement or alternative to fossil fuels widely used in modern society. However, renewable energy is generated intermittently, making it impossible for the power grid to provide large-scale, long-term, and periodic power supply. Therefore, the development of large-scale energy storage systems is particularly important for the storage and conversion of renewable energy. Among various energy storage systems, lithium-ion batteries, with their advantages of long cycle life, high power density, and the fastest charge and discharge rates, have been widely used in various electronic devices, such as computers, mobile phones, power tools, industrial equipment, energy-saving hybrid ships, aircraft, drones, plug-in hybrid electric vehicles, and pure electric vehicles, for large-scale energy storage and conversion. However, traditional graphite anodes are insufficient to meet the growing demand for high-energy batteries. Nano-silicon (Si NPs), due to their high theoretical capacity (4200 mAh g / g), has become a promising alternative. -1 Silicon, with its relatively short ion / electron transport path, has attracted significant research interest as a promising anode material for next-generation lithium-ion batteries. However, its large specific surface area leads to the formation of a thick solid-electrolyte interface (SEI) film during the first cycle. This SEI typically has poor mechanical strength and cannot accommodate the massive volume expansion (~300%) of silicon-based anodes. During repeated lithiation / delithiation processes, it cracks and continues to grow, ultimately leading to the formation of "dead silicon." An effective approach to address these issues is to construct dense artificial SEIs with excellent mechanical properties on the silicon surface, such as organic / inorganic coatings rich in fluorides / nitrides. These can be converted in situ into components rich in LiF or Li3N during cycling, thereby increasing the SEI modulus and preventing SEI cracking during continuous lithiation / delithiation. Summary of the Invention
[0003] In view of this, the purpose of this invention is to provide a triazine-based covalent organic framework-coated nano-silicon anode, its preparation method, and its application.
[0004] To achieve the above objectives, the technical solution of the present invention is as follows.
[0005] A triazine-based covalent organic framework-coated nano-silicon anode is described, wherein melamine and nano-silicon are first bonded by one or more of the following forces: van der Waals forces, electrostatic adsorption, and peptide bonds. Then, pyromellitic anhydride and melamine are cross-linked through secondary amine bonds, ultimately forming a triazine-based covalent organic framework coating layer on the surface of the nano-silicon.
[0006] A method for preparing a triazine-based covalent organic framework-coated silicon nano-anode, comprising the following steps:
[0007] Nano-silicon powder and melamine were added to dimethyl sulfoxide (DMSO) and dispersed evenly by ultrasonication and stirring. Then, a DMSO solution of pyromellitic anhydride was added and mixed at a stirring rate of 100-400 rpm for 12-24 hours. After stirring, the mixture was centrifuged and dried to obtain a triazine-based covalent organic framework-coated nano-silicon anode (Si@COF).
[0008] Preferably, the mass ratio of nano-silicon powder, melamine, and pyromellitic anhydride is 1:1~2:1~2.
[0009] Preferably, the ultrasonic power is 200~300W, the stirring speed is 100~300rpm, and the dispersion time is 2~4 hours.
[0010] Preferably, the particle size of the nano-silicon powder is 50~100nm.
[0011] Preferably, a DMSO solution of pyromellitic anhydride is added and mixed at a stirring rate of 200-300 rpm for 14-16 hours.
[0012] An application of the triazine-based covalent organic framework-coated nano-silicon anode described in this invention, wherein the nano-silicon anode is used as a lithium-ion battery anode.
[0013] Beneficial effects
[0014] This invention provides a triazine-based covalent organic framework-coated silicon nanoparticle anode (Si@COF). A triazine-based covalent organic framework (COF) layer is formed on the surface of the silicon nanoparticles, and the triazine-based COF layers are linked together by secondary amine bonds. During lithiation, the C=N bonds on the triazine rings preferentially combine with lithium ions to form the inorganic Li3N component. Li3N has a high modulus, effectively improving the mechanical strength of the SEI film and preventing SEI film rupture due to the volume expansion of the silicon anode, thus enhancing the cycle life of the electrode. The synthesized Si@COF material exhibits excellent long-cycle stability when applied as a lithium-ion battery anode.
[0015] This invention provides a method for preparing a triazine-based covalent organic framework (COF)-coated silicon nanoparticle anode. Through self-assembly in solution, melamine is first mixed with silicon nanoparticle powder, and the two are bonded together by one or more of the following forces: van der Waals forces, electrostatic adsorption, and peptide bonds. Then, pyromellitic anhydride is added, and the two small-molecule monomers, melamine and pyromellitic anhydride, form a triazine-based COF layer on the surface of SiNPs. This triazine-based COF layer can form a high-modulus component rich in lithium nitride (Li3N) during electrochemical reactions, enhancing the mechanical properties of the SEI (Sediment Injection). This method uses mild reaction conditions and does not damage the bulk structure of the silicon anode. Attached Figure Description
[0016] Figure 1 The image shows a SEM image of Si@COF-1 prepared in Example 1.
[0017] Figure 2 The image shows the SEM image of the Si NPs in Comparative Example 1.
[0018] Figure 3 The graph shows the performance of Si@COF-1, Si NPs, Si@COF-2, and Si@COF-3 in Examples 1 and Comparative Examples 1-3, in the voltage range of 0.01-1.5V and 100 cycles at 0.3C.
[0019] Figure 4 The graph shows the performance of Si@COF-1, Si NPs, Si@COF-2, and Si@COF-3 in Examples and Comparative Examples 1-3, after 1000 cycles at 2C in the voltage range of 0.01-1.5V. Detailed Implementation
[0020] The present invention will be further described in detail below with reference to specific embodiments.
[0021] In the following examples and comparative examples, the nano-silicon powder was purchased from Kejing CW-Si-003 100nm nano-silicon powder, product model: CW-Si-003, standard packaging: 100g / bag, product code: 02005600.
[0022] Scanning electron microscopy (SEM) testing: The morphology of the material was tested using a JSM-6360LV scanning electron microscope.
[0023] Assembly and testing of CR2032 button batteries: The final products obtained in the comparative example and the embodiment were used as active materials. Acetylene black and polyacrylic acid binder were mixed in a mass ratio of 8:1:1 to form a slurry, which was then coated onto copper foil. The dried copper foil loaded with the slurry was cut into small circular pieces with a diameter of about 1 cm using a cutting machine to serve as positive electrodes. Lithium metal sheets were used as negative electrodes, Celgard 2300 was used as separators, and 1M carbonate solution was used as electrolyte (wherein the solvent is a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1, and the solute is LiPF6). CR2032 button batteries were assembled in an argon glove box (water pressure ≤ 0.01 ppm, oxygen pressure ≤ 0.01 ppm). The assembled CR2032 button batteries were subjected to constant current charge-discharge tests at different current densities using a CT2001A Land battery tester at a test temperature of 25℃.
[0024] Example 1
[0025] (1) Disperse 0.5 g of nano-silicon particles and 0.5 g of melamine in 32 ml of DMSO. Stir for 3 h under ultrasonic conditions at a stirring rate of 200 rpm. After complete dispersion, a mixed solution of nano-silicon / small molecule A is obtained.
[0026] (2) Dissolve 0.5 g of pyromellitic anhydride in 16 ml of DMSO, stir at room temperature for 3 h at a stirring rate of 200 rpm, and obtain a pyromellitic anhydride solution after complete dissolution.
[0027] (3) Mix the pyromellitic anhydride solution and the nano-silicon / melamine solution and stir for 12 hours at a stirring rate of 200 rpm to obtain the Si@COF-1 solution.
[0028] (4) The Si@COF-1 solution was centrifuged at a speed of 6000 rpm / min, and then washed three times with DMSO. The resulting product was dried in a vacuum oven at 60 °C for 12 h to obtain Si@COF-1 powder.
[0029] Comparative Example 1
[0030] Pure nano-silicon powder Si NPs is used as comparative example 1.
[0031] Comparative Example 2
[0032] (1) Disperse 0.5 g of nano-silicon particles and 0.25 g of melamine in 32 ml of DMSO. Stir for 3 h under ultrasonic conditions at a stirring rate of 200 rpm. After complete dispersion, a mixed solution of nano-silicon / melamine is obtained.
[0033] (2) Dissolve 0.25 g of pyromellitic anhydride in 16 ml of DMSO, stir at room temperature for 3 h at a stirring rate of 200 rpm, and obtain cyanuric acid solution after complete dissolution.
[0034] (3) After mixing the cyanuric acid solution and the nano-silicon / pyromellitic anhydride solution, stir for 12 hours at a stirring rate of 200 rpm to obtain the Si@COF-2 solution.
[0035] (4) The Si@COF-1 solution was centrifuged at a speed of 6000 rpm / min, and then washed three times with DMSO. The resulting product was dried in a vacuum oven at 60 °C for 12 h to obtain Si@COF-2 powder.
[0036] Comparative Example 3
[0037] (1) Disperse 0.5 g of nano-silicon particles and 0.75 g of melamine in 32 ml of DMSO. Stir for 3 h under ultrasonic conditions at a stirring rate of 200 rpm. After complete dispersion, a mixed solution of nano-silicon / melamine is obtained.
[0038] (2) Dissolve 0.75 g of pyromellitic anhydride in 16 ml of DMSO, stir at room temperature for 3 h at a stirring rate of 200 rpm, and obtain cyanuric acid solution after complete dissolution.
[0039] (3) Mix the pyromellitic anhydride solution and the nano-silicon / melamine solution and stir for 12 hours at a stirring rate of 200 rpm to obtain the Si@COF-3 solution.
[0040] (4) The Si@COF-3 solution was centrifuged at a speed of 6000 rpm / min, and then washed three times with DMSO. The resulting product was dried in a vacuum oven at 60 °C for 12 h to obtain Si@COF-3 powder.
[0041] SEM images of Si@COF-1 in Example 1 and Si NPs in Comparative Example 1 ( Figure 1 and Figure 2 The results show that the size of pure silicon nanoparticles is about 100 nm. After being coated with COF, the particle size did not change significantly, but the surface became rough, indicating the coating of the COF layer.
[0042] The cycling performance curves of Si@COF-1, Si@COF-2, Si@COF-3 and Si NPs electrodes at 0.3C in the voltage range of 0.01-1.5V are shown below. Figure 3As shown, except for Si@COF-1, the other three electrodes all exhibit a capacity decay trend. After 100 cycles, the discharge specific capacity of the Si@COF-2, Si@COF-3, and Si NPs electrodes all decreased to 500 mAhg. -1 The Si@COF-1 electrode still retains a capacity of 2011.0 mAh g even after 100 cycles. -1 This excellent capacity retention is mainly attributed to the in-situ generation of Li3N in the COF layer during the electrochemical reaction, which induces the formation of a dense, high-mechanical-strength SEI film on the silicon surface, thereby avoiding the formation of dead silicon and irreversible lithium loss.
[0043] The long-cycle performance curves of Si@COF-1, Si@COF-2, Si@COF-3, and Si NPs electrodes at a high rate of 2 C in the voltage range of 0.01-1.5V are shown below. Figure 4 As shown, the capacity of the comparative electrode exhibits rapid decay at high rates, approaching zero. It can be seen that Si@COF-2, Si@COF-3, and Si NPs cannot withstand prolonged cycling at high rates. The Si@COF-1 electrode, after stable cycling for 1000 cycles, still maintains a capacity of 1230.5 mAh g⁻¹. -1 The high capacity exhibited excellent cycle stability. It can be seen that an appropriate amount of triazine-based COF layer has a significant effect on improving the cycle stability of nano-silicon anodes, mainly due to the formation of a dense and mechanically strong SEI film on the silicon surface. Lower COF content may not be able to completely coat the silicon particles; higher COF content may lead to the formation of excess monomeric COF, which is detrimental to the silicon capacity.
[0044] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.
Claims
1. A triazine-based covalent organic framework-coated nanosilicon negative electrode, characterized in that: Melamine and nano-silicon are first bonded by one or more of the following forces: van der Waals forces, electrostatic adsorption, and peptide bonds. Then, pyromellitic anhydride and melamine are cross-linked through secondary amine bonds, and finally a triazine-based covalent organic framework coating layer is formed on the surface of nano-silicon. The nano-silicon anode was prepared by the following method: nano-silicon powder and melamine were added to dimethyl sulfoxide and dispersed evenly by ultrasonication and stirring. Then, a DMSO solution of pyromellitic anhydride was added and mixed and stirred at a stirring rate of 100-400 rpm for 12-24 hours. After stirring, the mixture was centrifuged and dried to obtain a triazine-based covalent organic framework-coated nano-silicon anode. The mass ratio of nano-silicon powder, melamine, and pyromellitic anhydride is 1:1~2:1~2.
2. The triazine-based covalent organic framework-coated nanosilicon anode of claim 1, wherein: The ultrasonic power is 200~300W, the stirring speed is 100~300rpm, and the dispersion time is 2~4 hours.
3. The triazine-based covalent organic framework-coated nanosilicon anode of claim 1, wherein: The particle size of the nano-silicon powder is 50~100nm.
4. The triazine-based covalent organic framework-coated nanosilicon anode of claim 1, wherein: Add a DMSO solution of pyromellitic anhydride and mix at a stirring rate of 200-300 rpm for 14-16 hours.
5. Use of a triazine-based covalent organic framework-coated nanosilicon anode according to claim 1, characterized in that: The nano-silicon anode is used as the anode in lithium-ion batteries.