A silicon carbon nitride material based on carbon lattice doped with silicon and nitrogen elements, and a preparation method and application thereof

Abstract

This invention discloses a silicon-carbon-nitrogen material based on carbon lattice doped with silicon and nitrogen, its preparation method, and its applications, belonging to the field of lithium-ion battery material technology. A silicon source, a nitrogen source, and a carbon source are dissolved in water to obtain a mixed solution; the mixed solution undergoes a hydrothermal reaction, and the resulting product is used as a precursor powder and calcined to obtain the silicon-carbon-nitrogen material based on carbon lattice doped with silicon and nitrogen. The silicon-carbon-nitrogen material prepared by this invention anchors Si elements within the carbon framework to form an atomic-level doped structure, fundamentally eliminating a series of problems caused by multiphase interfaces. Ultimately, it yields a novel carbon-based anode material with high carbon content, intercalation-dominated energy storage, and significantly superior capacity compared to graphite anodes, providing a new path for the development of high-energy-density lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a silicon-carbon-nitrogen material based on carbon lattice doped with silicon and nitrogen elements, its preparation method, and its application. Background Technology

[0002] With the rapid upgrading of new energy vehicles, smart terminals, and large-scale energy storage industries, the demand for high energy density and long-cycle stability in lithium-ion batteries is becoming increasingly urgent. Carbon materials, represented by graphite, have long dominated the anode of commercial lithium-ion batteries due to their excellent electronic conductivity, stable layered lithium intercalation structure, and low cost. However, the theoretical specific capacity of graphite is only 372 mAh·g. -1 The current technology is insufficient to meet the development needs of next-generation high-energy-density batteries. Therefore, modifying carbon-based anodes through element doping and structural regulation to improve capacity while maintaining their intercalation energy storage stability has become a core research direction in this field. Silicon (Si), with its unique electronic structure and lithium storage activity, has become a key candidate element for modifying carbon-based anodes.

[0003] Traditional silicon modification strategies for carbon-based anodes often employ methods such as physical mixing, mechanical coating, or surface deposition to form carbon (and its derivatives) with elemental silicon or silicon oxides (such as SiO2). x This type of traditional silicon-carbon material is essentially a multiphase composite of a carbon matrix and silicon-based components. The silicon-based components do not form a stable atomic-level bond with the carbon lattice, resulting in inherent structural defects: Firstly, the interfacial compatibility between carbon and silicon-based components is poor. During lithium-ion insertion / extraction, the silicon-based components undergo a volume expansion of up to 300% due to alloying reactions, easily leading to interfacial delamination, material cracking, and the shedding of active materials. Secondly, the presence of multiphase interfaces significantly increases electron transport resistance and lithium-ion diffusion barriers. Furthermore, unstable interfaces easily induce continuous growth of the SEI film, causing irreversible consumption of lithium resources, ultimately resulting in poor cycle stability and rate performance, severely limiting its commercial application.

[0004] To address the performance bottlenecks caused by multiphase composites, researchers have developed various optimization strategies. The core idea revolves around improving the interfacial bonding and structural stability between the carbon matrix and silicon-based components. For example, silicon-based components are nanoscaled (nanoparticles, nanowires, etc.) to alleviate volume expansion stress; dense carbon coatings are constructed using methods such as chemical vapor deposition to enhance interfacial constraint; or heteroatoms such as nitrogen and boron are introduced into the carbon matrix to regulate electronic structure and improve interfacial interactions. However, these strategies still do not overcome the inherent limitations of multiphase composites. Nanoscaled silicon-based components are prone to agglomeration, leading to a decrease in actual lithium storage capacity; the carbon coating is prone to cracking during long-term cycling, failing to provide sustained protection; while heteroatom doping can improve conductivity, its improvement on interfacial stability is limited, and excessive doping can disrupt the ordered intercalation structure of the carbon matrix, sacrificing some cycling stability. Existing strategies have consistently failed to achieve atomic-level fusion between the silicon-based components and the carbon lattice, and the performance trade-offs caused by multiphase interfaces (such as the contradiction between capacity improvement and cycling stability) remain fundamentally unresolved.

[0005] Therefore, developing a carbon-based anode design method that can achieve atomic-level bonding between silicon and carbon matrix, and improving lithium storage capacity while retaining the stability of the carbon material intercalation energy storage mechanism, has become the key to breaking through the current technological bottleneck. Summary of the Invention

[0006] To address the technical bottlenecks of existing silicon-carbon-based lithium-ion battery anode materials, such as multiphase interface delamination, volume expansion stress concentration, and difficulty in synergistically improving cycle stability and capacity, this invention provides a silicon-carbon-nitrogen material based on carbon lattice doping with silicon and nitrogen, along with its preparation method and applications. By anchoring Si elements inside the carbon framework to form an atomic-level doped structure, a series of problems caused by multiphase interfaces are eliminated at the source. Ultimately, a novel carbon-based anode material with high carbon content, intercalation-dominated energy storage, and significantly superior capacity compared to graphite anodes is obtained, providing a new path for the development of high-energy-density lithium-ion batteries.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing silicon-carbon-nitrogen materials based on carbon lattice doping with silicon nitrogen elements, comprising the following steps:

[0009] (1) Dissolve the silicon source, nitrogen source and carbon source in water to obtain a mixed solution;

[0010] (2) The mixed solution in step (1) is hydrothermally reacted at 120-200℃ for 12-24h, and the resulting product is used as a precursor powder. It is calcined at 800-1100℃ for 1-5h to obtain silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0011] The carbon source is graphene or sodium citrate;

[0012] The nitrogen source is urea or dicyandiamide;

[0013] The silicon source is tetraethyl orthosilicate or 3-aminopropyltrimethoxysilane;

[0014] The ratio of silicon source, nitrogen source and carbon source is 0.8-2.5 mL: 0.6 g: 1.29-3.87 g.

[0015] Furthermore, the heating rate during calcination in step (2) is 5-15 °C·min. -1 .

[0016] In a second aspect, the present invention provides a silicon-carbon-nitrogen material based on carbon lattice doped with silicon-nitrogen elements, prepared by the aforementioned preparation method.

[0017] In a third aspect, the present invention provides the application of the aforementioned silicon-carbon-nitrogen material based on carbon lattice doped with silicon-nitrogen elements in the preparation of lithium-ion batteries.

[0018] Furthermore, the silicon-carbon-nitrogen material doped with silicon nitrogen elements in a carbon lattice is used as an active material for the negative electrode of a lithium-ion battery.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] (1) This invention achieves atomic-level doping and stable bonding of Si elements in the carbon framework through a synergistic strategy of precursor anchoring and high-temperature carbonization. The prepared SiCN material has the core feature of "no multiphase interface". It not only retains the structural stability of carbon-based material intercalation lithium storage, but also improves the lithium storage capacity by regulating the electronic structure through silicon-nitrogen co-doping, which is significantly better than traditional graphite anode.

[0021] (2) This invention solves the problems of volume expansion and cracking and poor cycle stability caused by multiphase interface in traditional silicon-carbon composite materials. At the same time, it has the characteristics of simple preparation process, mild reaction conditions and wide source of raw materials. The battery assembly process is compatible with the existing industrial production system and has the potential for large-scale application.

[0022] (3) The synergistic doping of silicon and nitrogen elements in this invention can also optimize the electronic conductivity of carbon matrix and lithium-ion diffusion kinetics, and achieve synergistic improvement of capacity, cycle stability and rate performance, providing a new technical path for the development of high energy density lithium-ion battery anode materials. Attached Figure Description

[0023] Figure 1 SEM image of the silicon carbon nitride material based on carbon lattice doped silicon nitride prepared in Example 1;

[0024] Figure 2 TEM image of the silicon carbon nitride material based on carbon lattice doped silicon nitride prepared in Example 1;

[0025] Figure 3 The image shows an HRTEM image of the silicon carbon nitride material based on carbon lattice doped silicon nitride prepared in Example 1.

[0026] Figure 4 The image shows the XRD pattern of the silicon carbon nitride material based on carbon lattice doped silicon nitride prepared in Example 1.

[0027] Figure 5 XPS spectra of silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen prepared in Example 1, where (a) is C 1s spectrum, (b) is Si 2p spectrum, (c) is N 1s spectrum, and (d) is O 1s spectrum;

[0028] Figure 6 The charge-discharge performance diagram of the silicon carbon-nitrogen material based on carbon lattice doped silicon nitrogen prepared in Example 1 is shown.

[0029] Figure 7 The image shows the long-cycle performance of the silicon-carbon-nitrogen material based on carbon lattice doped with silicon nitrogen elements prepared in Example 1. Detailed Implementation

[0030] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0032] Example 1

[0033] (1) Mix 1.80 mL of 3-aminopropyltrimethoxysilane, 0.60 g of urea and 2.58 g of sodium citrate evenly, and then stir in 20 mL of deionized water for 0.5 h to obtain a colorless mixed solution;

[0034] (2) The colorless mixed solution in step (1) was transferred to a high-pressure reactor and hydrothermally reacted in an oven at 160 °C for 12 h to obtain a yellow solution. The yellow solution was placed in an oven and dried at 80 °C for 10 h in air atmosphere. After natural cooling, a yellow solid powder (precursor powder) was obtained. The yellow solid powder was placed in a tube furnace and dried at 5 °C·min. -1The temperature was increased to 1000 °C at a heating rate of 0.5, annealed in a nitrogen atmosphere for 2 h, and then naturally cooled to obtain a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0035] The SEM image of the silicon-carbon-nitrogen material prepared in Example 1 based on carbon lattice doped silicon-nitrogen elements is shown below. Figure 1 As shown, by Figure 1 It can be seen that silicon carbon nitrogen materials based on carbon lattice doped with silicon nitrogen elements exhibit a loose blocky morphology.

[0036] The HRTEM images of the silicon-carbon-nitrogen material prepared in Example 1 at different magnifications are shown in Figures 2 and 3, respectively. Figure 3 As shown in the figure, silicon-carbon-nitrogen materials based on carbon lattice doped with silicon-nitrogen elements exhibit a multi-layered, rolled-up morphology with short-range ordered and long-range disordered amorphous carbon lattice fringes.

[0037] The XRD pattern of the silicon-carbon-nitrogen material prepared in Example 1 based on carbon lattice doped silicon-nitrogen elements is shown below. Figure 4 As shown, by Figure 4 It can be seen that the characteristic peaks of carbon materials are observed at 23° and 42°, and the broad and gentle characteristic peaks indicate that the material has a high degree of disorder.

[0038] The XPS spectrum of the silicon-carbon-nitrogen material prepared in Example 1 based on carbon lattice doped silicon-nitrogen elements is shown below. Figure 5 As shown, (a) is the C 1s spectrum, (b) is the Si 2p spectrum, (c) is the N 1s spectrum, and (d) is the O 1s spectrum; from Figure 5 It can be seen that in the C 1s spectrum, the peaks at 285.5 and 284.8 eV correspond to C-O and C-C bonds. In the Si 2p spectrum, the peaks at 103.5 and 102.5 eV correspond to Si-O and Si-O-C bonds, indicating that the silicon component introduced by the silicon source is connected to the amorphous carbon structure through Si-O-C. In the N 1s spectrum, the peaks at 401.3, 399.8, and 398.6 eV correspond to graphitic N, pyrrole N, and pyridine N, proving the successful introduction of N. In the O 1s spectrum, the peaks at 533.2 and 531.9 eV correspond to Si-O and C-O bonds.

[0039] Example 2

[0040] Unlike Example 1, in Example 2, 3.87g of sodium citrate was added in step (1), and the other steps were the same as in Example 1, thus preparing a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0041] Example 3

[0042] Unlike Example 1, in step (1) of Example 3, 1.29g of sodium citrate was added, and the other steps were the same as in Example 1, thus preparing a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0043] Example 4

[0044] Unlike Example 1, in step (1) of Example 3, 2.50 mL of 3-aminopropyltrimethoxysilane was added, and the other steps were the same as in Example 1, thus preparing a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0045] Example 5

[0046] Unlike Example 1, in step (1) of Example 3, 0.80 mL of 3-aminopropyltrimethoxysilane was added, and the other steps were the same as in Example 1, thus preparing a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0047] Example 6

[0048] (1) Mix 1.80 mL of tetraethyl orthosilicate, 0.60 g of dicyandiamide and 2.58 g of graphene evenly, and then stir in 20 mL of deionized water for 0.5 h to obtain a colorless mixed solution;

[0049] (2) The colorless mixed solution in step (1) was transferred to a high-pressure reactor and hydrothermally reacted in an oven at 160 °C for 12 h. The reaction solution was then placed in an oven and dried at 80 °C for 10 h in air atmosphere. After natural cooling, a solid powder (precursor powder) was obtained. The solid powder was placed in a tube furnace and dried at 5 °C·min. -1 The temperature was increased to 1000℃ at a heating rate, annealed in a nitrogen atmosphere for 2 h, and then naturally cooled to obtain a silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements.

[0050] Example 7

[0051] Unlike Example 1, in step (2) of Example 8, the hydrothermal reaction temperature is 120°C and the reaction time is 20 h. The other steps are the same as in Example 1, and silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen is prepared.

[0052] Example 8

[0053] Unlike Example 1, in step (2) of Example 9, the hydrothermal reaction temperature is 200°C and the reaction time is 24 h. Other steps are the same as in Example 1, and silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen is prepared.

[0054] Example 9

[0055] Unlike Example 1, in step (2) of Example 10, the calcination temperature is 800℃ and the calcination time is 1 h. The other steps are the same as in Example 1, and silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen is prepared.

[0056] Example 10

[0057] Unlike Example 1, in step (2) of Example 11, the calcination temperature is 1100℃ and the calcination time is 5 h. The other steps are the same as in Example 1, and silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen is prepared.

[0058] Comparative Example 1

[0059] Unlike Example 1, Comparative Example 1 does not involve a hydrothermal reaction; the specific procedure is as follows:

[0060] (1) Mix 1.80 mL of 3-aminopropyltrimethoxysilane, 0.60 g of urea and 2.58 g of sodium citrate evenly, and then stir in 20 mL of deionized water for 0.5 h to obtain a colorless mixed solution;

[0061] (2) The colorless mixed solution was placed in an oven and dried at 80 °C for 10 h in air atmosphere. After natural cooling, the precursor powder was obtained. The precursor powder was placed in a tube furnace and dried at 5 °C·min. -1 The temperature was increased to 1000 °C at a heating rate of 0.5, annealed in a nitrogen atmosphere for 2 h, and then naturally cooled to obtain silicon carbon nitrogen material.

[0062] Electrochemical performance testing

[0063] The silicon carbon nitrogen (SiCN) materials prepared in Examples 1-10 and the comparative example were mixed with conductive carbon black and PVDF (the mass ratio of SiCN to conductive carbon black and PVDF was 8:1:1). The mixture was ground in a mortar for 20 minutes. The uniformly mixed powder was then dispersed in N-methylpyrrolidone to form an electrode slurry. The slurry was then coated onto copper foil and placed in a vacuum drying oven at 80°C for 24 hours. Finally, the dried copper foil containing the electrode material was cut into electrode sheets.

[0064] In the glove box, lithium metal sheets are used as the counter and reference electrodes, and the aforementioned SiCN-coated electrode sheet serves as the working electrode. The electrode material is immersed in a Li-containing solution. + A lithium-ion battery was assembled by separating the two electrodes in an electrolyte (LiPF6 solution) and then performing electrochemical performance tests. The results are shown in Table 1.

[0065] Table 1 Electrochemical performance test results

[0066] .

[0067] The lithium-ion battery charge-discharge test adopted a constant current charge-discharge test mode. The test steps were set as follows: first, discharge with a constant current to the discharge cutoff voltage, then rest for 2 minutes, and then charge with a constant current to the charging cutoff voltage. This sequence was used to perform cyclic charge-discharge tests on the battery. The charge-discharge performance of the silicon-carbon-nitrogen material based on carbon lattice doped with silicon nitrogen prepared in Example 1 is shown in the figure. Figure 6 As shown. At 0.05, 0.1, 0.2, 0.5, 1, and 5 A·g -1 At current densities of 1463.6, 1145.7, 936.4, 750.3, 624.1, 508.6 and 372.0 mAh·g -1 The capacity and current density return to 0.1 A·g -1 Even after that, it still has 1282 mAh·g -1 The capacity.

[0068] The long-cycle performance of the silicon-carbon-nitrogen material prepared in Example 1 based on carbon lattice doped silicon-nitrogen elements is shown in the figure below. Figure 7 As shown; at 1 A·g -1 It has a current density of 555.8 mAh·g -1 The capacity remains at 609.9 mAh·g after 2500 cycles. -1 The capacity is limited. This is because, in the initial stage of cycling, some sample particles did not fully participate in the energy storage reaction due to insufficient interfacial contact or incomplete wetting of the internal pores of the bulk phase. As cycling progresses, the electrolyte slowly wets the material interface and internal pores, and the conductive network of the silicon-carbon-nitrogen framework is gradually optimized, thereby activating the aforementioned unreacted sample particles.

Claims

1. A method for preparing silicon-carbon-nitrogen materials based on carbon lattice doping with silicon nitrogen elements, characterized in that, Includes the following steps: (1) Dissolve the silicon source, nitrogen source and carbon source in water to obtain a mixed solution; (2) The mixed solution in step (1) is hydrothermally reacted at 120-200℃ for 12-24h, and the resulting product is used as a precursor powder. It is calcined at 800-1100℃ for 1-5h to obtain silicon carbon nitrogen material based on carbon lattice doped with silicon nitrogen elements. The carbon source is graphene or sodium citrate; The nitrogen source is urea or dicyandiamide; The silicon source is tetraethyl orthosilicate or 3-aminopropyltrimethoxysilane; The ratio of silicon source, nitrogen source and carbon source is 0.8-2.5 mL: 0.6 g: 1.29-3.87 g.

2. The method for preparing silicon-carbon-nitrogen materials based on carbon lattice doping of silicon nitrogen elements according to claim 1, characterized in that, The heating rate for calcination in step (2) is 5-15 °C·min. -1 .

3. A silicon-carbon-nitrogen material based on carbon lattice doped with silicon-nitrogen elements, prepared by the preparation method of claim 1 or 2.

4. The application of a silicon carbon nitrogen material based on carbon lattice doped silicon nitrogen element prepared by the preparation method of claim 1 or 2, or the silicon carbon nitrogen material based on carbon lattice doped silicon nitrogen element as described in claim 3, in the preparation of lithium-ion batteries.

5. The application according to claim 4, characterized in that, The silicon-carbon-nitrogen material doped with silicon and nitrogen elements in a carbon lattice is used as an active material for the negative electrode of a lithium-ion battery.

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