I-sioc material, preparation method and application thereof

Abstract

The application discloses an I-SiOC material and a preparation method and application thereof, and belongs to the technical field of electrode materials. The preparation method of the I-SiOC material comprises the following steps: S1, silane and ethylene glycol are respectively used as a silicon source and a carbon source, iodine is used as an initiator, the iodine is dissolved after stirring and mixing, a reaction solution is obtained, and the reaction solution is subjected to a solvothermal reaction to obtain a precursor; and S2, the precursor is calcined in an inert atmosphere to obtain the I-SiOC material. The application provides a preparation method of an embedded I-SiOC material, the byproduct water of iodine-induced ethylene glycol condensation makes silane hydrolyze, the obtained silanol participates in the condensation process of ethylene glycol to obtain a precursor condensate, and the I-SiOC material with a SiO3C tetrahedral structure is obtained after high-temperature calcination, the I-SiOC material presents an embedded lithium storage mechanism, and the cycle stability is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to an I-SiOC material, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and portable electronic devices, the demand for high-energy-density lithium-ion batteries is becoming increasingly urgent. One effective way to improve energy density is to develop high-capacity anode materials with low lithium intercalation potential. Silicon anodes, due to their theoretical specific capacity of up to 4200 mAh / g and suitable lithium intercalation potential (approximately 0.4V vs. Li), are suitable for this purpose. + Silicon has attracted much attention due to its advantages in lithium (Li-Si) and cost. However, the Li-Si alloy phase formed during its lithiation process causes a volume expansion of about 400%, which leads to severe instability at the electrode / electrolyte interface and the electrode / current collector interface, resulting in rapid capacity decay. At the same time, the intrinsic semiconductor properties of silicon result in poor electronic / ionic conductivity, which severely limits its rate performance.

[0003] To alleviate the aforementioned problems, amorphous silicon carbide (SiOC) materials have been extensively studied. SiOC consists of mixed tetrahedral units (SiO4, SiO3C, SiO2C2, SiOC3) composed of Si, O, and C, a free carbon phase, and inherent nanopores. Its electrochemical performance stems from the synergistic contribution of each component. Recent studies have shown that the lithium storage behavior of each tetrahedral unit differs fundamentally: the SiO4 phase generates irreversible silicate and elemental Si during the first lithiation, with the former leading to a significant decrease in the initial coulombic efficiency (ICE), and the latter causing volume expansion due to the alloying reaction mechanism, resulting in deteriorated cycle stability; both SiO3C and SiO2C2 phases follow an intercalation-type lithium storage mechanism, which is completely reversible. Among them, SiO3C, due to its higher oxygen content, transfers more electrons per unit, resulting in a significantly better specific capacity than SiO2C2; while the SiOC3 phase completely transforms into irreversible SiC3 during the first lithiation and lacks electrochemical activity. In summary, the SiO3C phase combines high reversible capacity, excellent cycle stability, and a complete insertion mechanism, making it theoretically the most ideal active lithium storage unit.

[0004] However, existing SiOC materials and their preparation methods (such as the sol-gel method and polymer precursor pyrolysis method) suffer from key bottlenecks: the microstructure is "uncontrollable"—it is impossible to directionally synthesize SiO3C-rich tetrahedral structures, and the resulting products inevitably contain a mixture of multiple units, including phases such as SiO4 and SiOC3 with low or irreversible conductivity. This leads to low ICE (internal conductivity), complex capacity sources, difficulty in establishing stable structure-property relationships, and severely weakens the intrinsic advantages of SiO3C. In addition, to compensate for the insufficient intrinsic conductivity of SiOC, existing technologies mostly adopt "external" composite strategies such as surface carbon coating, heteroelement doping, or the construction of conductive networks. These typically require multiple complex processes (pre-carbonization, secondary coating, high-temperature treatment, etc.), increasing costs and introducing interfacial side reactions. At the same time, the slow expansion and capacity decay caused by irreversible phase transitions, microstructure collapse, and free carbon rearrangement during long-term cycling have not been fundamentally resolved. Summary of the Invention

[0005] To address the above problems, the purpose of this invention is to provide an I-SiOC material, its preparation method, and its applications.

[0006] In a first aspect, the present invention provides a method for preparing I-SiOC material, comprising the following steps: S1. Silane and ethylene glycol are used as silicon source and carbon source, respectively, and iodine is used as initiator. After stirring and mixing to dissolve the iodine, a reaction solution is obtained. The reaction solution is subjected to a solvothermal reaction to obtain the precursor. S2. After calcining the precursor in an inert atmosphere, I-SiOC material is obtained.

[0007] Preferably, in step S1, the silane is triethoxyvinylsilane, whose chemical structural formula is as follows: .

[0008] Preferably, in step S1, the volume ratio of silane to ethylene glycol is 1:(1~3).

[0009] Preferably, in step S1, the mass-to-volume ratio of iodine to ethylene glycol is (1~2.5)g:(10~30)mL.

[0010] Preferably, in step S1, the temperature of the solvothermal reaction is 160~180°C, and the time of the solvothermal reaction is 10~15h.

[0011] Preferably, in step S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0012] Preferably, in step S2, the calcination temperature is 800~1000℃ and the calcination time is 1~4h.

[0013] Secondly, the present invention provides an I-SiOC material, which is prepared by the aforementioned method.

[0014] Thirdly, the present invention provides a lithium battery comprising the aforementioned I-SiOC material.

[0015] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) The present invention provides a method for preparing an embedded I-SiOC material. Iodine initiates the condensation of ethylene glycol byproduct water, which causes silane hydrolysis. The silanol obtained by hydrolysis participates in the condensation process of ethylene glycol to obtain a precursor condensate. After high-temperature calcination, an I-SiOC material with a SiO3C tetrahedral structure is obtained, which exhibits an embedded lithium storage mechanism and achieves significantly improved cycle stability.

[0016] (2) The present invention uses a one-step solvothermal method combined with high-temperature calcination to prepare embedded I-SiOC materials. The precursor powder material is obtained after the solvothermal reaction, without the need for purification operations such as washing and filtration. The method is simple, has few steps, and has a low reaction temperature, which is conducive to large-scale production and has good application prospects in the field of lithium-ion battery anode materials. Attached Figure Description

[0017] Figure 1 This is the XRD pattern of Embodiment 1 of the present invention.

[0018] Figure 2 This is a TEM image of Embodiment 1 of the present invention.

[0019] Figure 3 This is the XPS spectrum of Embodiment 1 of the present invention.

[0020] Figure 4 This is a graph showing the first charge-discharge curve under constant current density in Embodiment 1 of the present invention.

[0021] Figure 5 This is a charge-discharge cycle performance diagram under constant current density in Embodiment 1 of the present invention.

[0022] Figure 6 This is the XRD pattern of Comparative Example 1 of the present invention.

[0023] Figure 7 This is a TEM image of Comparative Example 1 of the present invention.

[0024] Figure 8 This is the XPS spectrum of Comparative Example 1 of the present invention.

[0025] Figure 9 This is a graph showing the first charge-discharge curve under constant current density in Comparative Example 1 of the present invention.

[0026] Figure 10This is a charge-discharge cycle performance diagram of Comparative Example 1 of the present invention under constant current density.

[0027] Figure 11 This is the XRD pattern of Comparative Example 2 of the present invention.

[0028] Figure 12 This is a TEM image of Comparative Example 2 of the present invention.

[0029] Figure 13 This is the XPS spectrum of Comparative Example 2 of the present invention.

[0030] Figure 14 This is the first charge-discharge curve under constant current density in Comparative Example 2 of the present invention.

[0031] Figure 15 This is a charge-discharge cycle performance diagram of Comparative Example 2 of the present invention under constant current density.

[0032] Figure 16 This is the XRD pattern of Embodiment 2 of the present invention.

[0033] Figure 17 This is a TEM image of Embodiment 2 of the present invention.

[0034] Figure 18 This is the X-ray photoelectron spectrum of Embodiment 2 of the present invention.

[0035] Figure 19 This is the first charge-discharge curve under constant current density in Embodiment 2 of the present invention.

[0036] Figure 20 This is a charge-discharge cycle performance diagram under constant current density in Embodiment 2 of the present invention.

[0037] Figure 21 This is the XRD pattern of Embodiment 3 of the present invention.

[0038] Figure 22 This is a TEM image of Embodiment 3 of the present invention.

[0039] Figure 23 This is the XPS spectrum of Embodiment 3 of the present invention.

[0040] Figure 24 This is a graph showing the first charge-discharge curve under constant current density in Embodiment 3 of the present invention.

[0041] Figure 25 This is a charge-discharge cycle performance diagram under constant current density in Embodiment 3 of the present invention.

[0042] Figure 26 This is the XRD pattern of Embodiment 4 of the present invention.

[0043] Figure 27 This is a TEM image of Embodiment 4 of the present invention.

[0044] Figure 28 This is the XPS spectrum of Embodiment 4 of the present invention.

[0045] Figure 29 This is the first charge-discharge curve under constant current density in Embodiment 4 of the present invention.

[0046] Figure 30 This is a charge-discharge cycle performance diagram under constant current density in Embodiment 4 of the present invention. Detailed Implementation

[0047] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] As mentioned above, in a first aspect, the present invention provides a method for preparing I-SiOC material, comprising the following steps: S1. Silane and ethylene glycol are used as silicon source and carbon source, respectively, and iodine is used as initiator. After stirring and mixing to dissolve the iodine, a reaction solution is obtained. The reaction solution is subjected to a solvothermal reaction to obtain the precursor. S2. After calcining the precursor in an inert atmosphere, I-SiOC material is obtained.

[0049] This invention uses iodine as an initiator, utilizing the water byproduct generated during the condensation of ethylene glycol to initiate the in-situ and controllable hydrolysis of silanes (such as triethoxyvinylsilane). The silanols generated by hydrolysis further participate in the condensation process of ethylene glycol, forming precursor condensates with well-defined structures and homogeneous compositions. After high-temperature calcination, this invention successfully prepared I-SiOC materials with SiO3C tetrahedral units. In contrast, SiOC materials prepared by traditional methods contain four tetrahedral units: SiO4, SiO3C, SiO2C2, and SiOC3. Among them, the low-oxygen-content SiOC3 phase is completely irreversible, severely affecting the initial coulombic efficiency and cycling stability of the material. This invention, through a directional synthesis strategy, essentially eliminates the generation of irreversible phases, fundamentally solving the technical problem of uncontrollable SiOC material structure. Benefiting from the tetrahedral structure of SiO3C, the I-SiOC material described in this invention exhibits an intercalation-type lithium storage mechanism during lithium insertion / extraction, rather than the alloying reaction mechanism of traditional silicon-based materials. The appropriate oxygen content in the SiO3C unit ensures high reversible capacity while avoiding irreversible lithium consumption caused by excessively high oxygen content phases (such as SiO4) and structural collapse caused by excessively low oxygen content phases (such as SiOC3). This mechanism effectively suppresses volume expansion and structural damage during lithium-ion insertion / extraction, enabling the material to maintain a highly intact microstructure during long-term cycling and achieving ultra-high cycle stability. The I-SiOC material prepared in this invention has promising application prospects in the field of lithium-ion battery anode materials.

[0050] In some embodiments, in step S1, the silane is triethoxyvinylsilane.

[0051] In some embodiments, in step S1, the volume ratio of silane to ethylene glycol is 1:(1~3), including but not limited to: 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0052] By controlling the volume ratio of silane to ethylene glycol, it was ensured that the silanol generated by the hydrolysis of silane under iodine catalysis was in full contact with ethylene glycol and underwent in-situ co-condensation to form a precursor network dominated by Si-OC bonds. This enabled the directional synthesis of silicon-oxygen tetrahedra with specific carbon / oxygen ratios, achieving the directional and controllable synthesis of single silicon-oxygen tetrahedra.

[0053] In some embodiments, in step S1, the mass-to-volume ratio of iodine to ethylene glycol is (1~2.5)g:(10~30)mL, including but not limited to: 1:10, 1.5:10, 2.5:10, 1:20, 1.5:20, 2.5:20, 1:30, 1.5:30, 2.5:30, etc.

[0054] By controlling the mass-to-volume ratio of iodine to ethylene glycol, iodine is catalyzed at an appropriate concentration to condense ethylene glycol into water. This ensures a match between the silane hydrolysis rate and the ethylene glycol condensation rate, preventing insufficient hydrolysis or excessive cross-linking. The synergistic effect of these two parameters achieves a kinetic balance among silane hydrolysis, ethylene glycol condensation, and silanol co-condensation in the reaction system, providing a crucial process guarantee for the directional acquisition of I-SiOC materials with a single tetrahedral structure dominated by SiO3C after high-temperature calcination.

[0055] In some embodiments, in step S1, the temperature of the solvothermal reaction is 160~180℃, including but not limited to: 160℃, 165℃, 170℃, 175℃, 180℃, etc.

[0056] The solvothermal temperature of 160–180°C is a key window for achieving a single tetrahedral structure dominated by SiO3C: at this temperature, the rate of iodine-catalyzed ethylene glycol condensation to water production matches the rate of silane hydrolysis, ensuring sufficient hydrolysis of silane to form adequate silanol; simultaneously, this temperature promotes in-situ co-condensation of silanol and ethylene glycol, effectively forming a precursor coordination environment dominated by Si-OC bonds; furthermore, this temperature range can maintain the catalytic activity of iodine and control the uniform nucleation and growth of precursor particles, thereby directionally obtaining I-SiOC materials with a single tetrahedral structure dominated by SiO3C after high-temperature calcination, avoiding the problem of coexistence of four tetrahedral units (especially the irreversible phase SiOC3) in traditional SiOC.

[0057] In some embodiments, the solvothermal reaction time in step S1 is 10-15 hours, including but not limited to: 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, etc.

[0058] In some embodiments, in step S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0059] In some embodiments, in step S2, the calcination temperature is 800~1000℃ and the calcination time is 1~4h.

[0060] Secondly, the present invention provides an I-SiOC material, which is prepared by the aforementioned method.

[0061] Thirdly, the present invention provides a lithium battery comprising the aforementioned I-SiOC material.

[0062] The performance testing methods in the embodiments and comparative examples of this invention are as follows: X-ray powder diffraction was performed using a Bruker D8 advance XRD system from Germany. A Cu Kα target source was used as the X-ray source, with a scanning speed of 10° / min and a scanning range of 10°–80°.

[0063] The crystal structure and phase composition were studied using a field emission transmission electron microscope (TEM) of Thermo Fisher Scientific’s Talos F200S.

[0064] The composition of silicon tetrahedra was studied using a VG Scientific ESCALab220i XL X-ray photoelectron spectroscopy (XPS) system.

[0065] The battery assembly steps in this invention are as follows: Working electrode: I-SiOC material / SiOC material, conductive agent acetylene black and binder sodium alginate are mixed evenly in a mass ratio of 8:1:1. An appropriate amount of deionized water is added to the evenly mixed powder and the mixture is stirred for 8 hours. The resulting slurry is then coated onto copper foil by casting method. After vacuum drying at 80℃, it is cut into small round pieces with a diameter of 13mm.

[0066] Counter electrode: Φ16mm lithium metal sheet.

[0067] Separator: Celgard2325 PP / PE / PP separator.

[0068] Electrolyte: 1 M LiPF6 dissolved in an EC / EMC / DMC (volume ratio 1:1:1) solvent system containing 10 wt% FEC.

[0069] When the oxygen content in the water is less than 0.1 ppm, the battery can be assembled in the following order: positive electrode shell - working electrode plate - separator - lithium plate - gasket - spring plate - negative electrode shell, and electrolyte can be added to obtain a lithium half battery.

[0070] After the assembled lithium half-cell was left to stand for 12 hours, it was charged and discharged at a constant current density to obtain the cycle performance graph; the rate performance graph was obtained by charging and discharging at different current densities; the test voltage range was 0.01~3V; the test ambient temperature was 25℃.

[0071] Example 1 10 mL of vinyltriethoxysilane, 20 mL of ethylene glycol, and 1 g of iodine were mixed thoroughly by stirring for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 180 °C for 12 hours. After the reaction was completed, precursor powder was obtained. The precursor powder was calcined at 800 °C for 3 hours under an argon atmosphere. During the calcination process, iodine sublimated upon heating to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining the I-SiOC-1 material.

[0072] The XRD and TEM images of the I-SiOC-1 material prepared in this embodiment are shown below. Figure 1 and 2As shown, it can be seen that the silicon tetrahedrons and free carbon in the I-SiOC-1 material prepared in this embodiment are both amorphous structures.

[0073] The XPS image of the I-SiOC-1 material prepared in this embodiment is shown below. Figure 3 As shown, it can be seen that the silicon tetrahedron in the I-SiOC-1 material contains only the SiO3C component.

[0074] The I-SiOC-1 material prepared in this embodiment was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown in the figure. Figure 4 and 5 It can be seen that the half-cell has an initial coulombic efficiency of 73.5% at a current density of 1 A / g and a voltage window of 0.01-3 V; and a capacity retention of 82.0% after 500 cycles.

[0075] Comparative Example 1 Take 10 mL of vinyltriethoxysilane, 20 mL of ethylene glycol, and 10 mL of deionized water, stir for 4 hours to mix thoroughly, and adjust the pH of the solution to 4 to obtain a reaction solution. Place the reaction solution into a reaction vessel and carry out a solvothermal reaction at 180 °C for 12 hours. After the reaction is complete, filter, wash, and dry sequentially to obtain precursor powder. Calcine the precursor powder at 800 °C for 3 hours under an argon atmosphere to obtain SiOC-1 material.

[0076] XRD and TEM results of the SiOC-1 material prepared in this comparative example are as follows: Figure 6 and 7 As shown, it can be seen that both silicon tetrahedra and free carbon in SiOC-1 material are amorphous structures.

[0077] The XPS image of the SiOC-1 material prepared in this comparative example is shown below. Figure 8 As shown, it can be seen that the silicon tetrahedron in the SiOC-1 material contains four components: SiO4, SiO3C, SiO2C2, and SiOC3.

[0078] The SiOC-1 material prepared in this comparative example was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown below. Figure 9 and 10 The battery achieved an initial coulombic efficiency of 47.8% at a current density of 1 A / g and a voltage window of 0.01-3 V, and a capacity retention of 61.0% after 500 cycles.

[0079] Comparative Example 2 20 mL of ethylene glycol and 1 g of iodine were stirred for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 180 °C for 6 hours. 10 mL of vinyltriethoxysilane was then added to the reaction vessel, and the reaction was continued at 180 °C for another 6 hours to obtain a precursor powder. The precursor powder was calcined at 800 °C for 3 hours under an argon atmosphere. During the calcination process, iodine sublimated to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining the SiOC-2 material.

[0080] XRD and TEM results of the SiOC-2 material prepared in this comparative example are as follows: Figure 11 and 12 As shown, both silicon tetrahedra and free carbon in SiOC-2 material are amorphous structures.

[0081] The XPS image of the SiOC-2 material prepared in this comparative example is shown below. Figure 13 As shown, it can be seen that the silicon tetrahedron in the SiOC-2 material contains four components: SiO4, SiO3C, SiO2C2, and SiOC3.

[0082] The SiOC-2 material prepared in this comparative example was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown below. Figure 14 and 15 The battery achieved an initial coulombic efficiency of 46.9% at a current density of 1 A / g and a voltage window of 0.01-3 V, and a capacity retention of 62.9% after 500 cycles.

[0083] Example 2 10 mL of vinyltriethoxysilane, 20 mL of ethylene glycol, and 1.5 g of iodine were mixed thoroughly by stirring for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 180 °C for 12 hours. After the reaction was completed, precursor powder was obtained. The precursor powder was calcined at 800 °C for 3 hours under an argon atmosphere. During the calcination process, iodine sublimated upon heating to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining the I-SiOC-2 material.

[0084] The TEM and XRD images of the I-SiOC-2 material prepared in this embodiment are shown below. Figure 16 and 17 As shown, it can be seen that both silicon tetrahedra and free carbon in the I-SiOC-2 material prepared in this embodiment are amorphous structures.

[0085] The XPS image of the I-SiOC-2 material prepared in this embodiment is shown below. Figure 18 As shown in the figure, it can be seen that the silicon tetrahedron in the I-SiOC-2 material prepared in this embodiment contains only the SiO3C component.

[0086] The I-SiOC-2 material prepared in this embodiment was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown in the figure. Figure 19 and 20 It can be seen that the half-cell has an initial coulombic efficiency of 74.1% at a current density of 1 A / g and a voltage window of 0.01-3 V; and a capacity retention of 90.5% after 500 cycles.

[0087] Example 3 Take 10 mL of vinyltriethoxysilane, 20 mL of ethylene glycol, and 2 g of iodine, and stir for 4 hours to obtain a reaction solution. Place the reaction solution into a reaction vessel and perform a solvothermal reaction at 180 °C for 12 hours. After the reaction, a precursor powder is obtained. Calcine the precursor powder at 800 °C for 3 hours under an argon atmosphere. During calcination, iodine sublimates to form iodine vapor, which is carried out of the reaction system by continuously introduced argon gas, thus obtaining the I-SiOC-3 material.

[0088] The TEM and XRD images of the I-SiOC-3 material prepared in this embodiment are shown below. Figure 21 and 22 As shown, it can be seen that the silicon tetrahedrons and free carbon in the I-SiOC-3 material prepared in this embodiment are both amorphous structures, and the free carbon exhibits a graphite domain structure.

[0089] The XPS image of the I-SiOC-3 material prepared in this embodiment is shown below. Figure 23 As shown, the silicon tetrahedron in the I-SiOC-3 material prepared in this embodiment contains only the SiO3C component.

[0090] The I-SiOC-3 material prepared in this embodiment was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown in the figure. Figure 24 and 25 It can be seen that the half-cell has an initial coulombic efficiency of 84.1% at a current density of 1 A / g and a voltage window of 0.01-3 V; and a capacity retention of 99.6% after 500 cycles.

[0091] Example 4 10 mL of vinyltriethoxysilane, 20 mL of ethylene glycol, and 2.5 g of iodine were mixed thoroughly by stirring for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 180 °C for 12 hours. After the reaction was completed, precursor powder was obtained. The precursor powder was calcined at 800 °C for 3 hours under an argon atmosphere. During the calcination process, iodine sublimated upon heating to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining I-SiOC-4 material.

[0092] The TEM and XRD images of the I-SiOC-4 material prepared in this embodiment are shown below. Figure 26 and 27 As shown, it can be seen that the silicon tetrahedrons and free carbon in the I-SiOC-4 material prepared in this embodiment are both amorphous structures, and the free carbon exhibits a graphite domain structure.

[0093] The XPS image of the I-SiOC-4 material prepared in this embodiment is shown below. Figure 28 As shown in the figure, it can be seen that the silicon tetrahedron in the I-SiOC-4 material prepared in this embodiment contains only SiO3C component.

[0094] The I-SiOC-4 material prepared in this embodiment was used to fabricate a lithium half-cell according to the aforementioned steps, and its electrochemical performance was tested. The test results are shown in the figure. Figure 29 and 30 It can be seen that the half-cell has an initial coulombic efficiency of 83.9% at a current density of 1 A / g and a voltage window of 0.01-3 V; and a capacity retention of 95.1% after 500 cycles.

[0095] Example 5 10 mL of vinyltriethoxysilane, 10 mL of ethylene glycol, and 1.5 g of iodine were mixed thoroughly by stirring for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 160 °C for 15 hours. After the reaction was completed, precursor powder was obtained. The precursor powder was calcined at 900 °C for 2 hours under an argon atmosphere. During the calcination process, iodine sublimated upon heating to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining I-SiOC-5 material.

[0096] Example 6 10 mL of vinyltriethoxysilane, 30 mL of ethylene glycol, and 1.5 g of iodine were mixed thoroughly by stirring for 4 hours to obtain a reaction solution. The reaction solution was then placed in a reaction vessel and subjected to a solvothermal reaction at 170 °C for 10 hours. After the reaction was completed, precursor powder was obtained. The precursor powder was calcined at 1000 °C for 1 hour under an argon atmosphere. During the calcination process, iodine sublimated upon heating to form iodine vapor, which was carried out of the reaction system by the continuously introduced argon gas, thus obtaining I-SiOC-6 material.

[0097] Table 1 As can be seen from the data in Table 1, the SiOC-1 material prepared by the traditional sol-gel method in Comparative Example 1 contains four tetrahedral units: SiO4, SiO3C, SiO2C2, and SiOC3. The resulting half-cell exhibits an initial coulombic efficiency of only 47.8% and a capacity retention of only 61.0% after 500 cycles, indicating poor electrochemical performance. In contrast, the I-SiOC-1 material prepared by the iodine-assisted solvothermal method in Example 1 contains only a single SiO3C tetrahedral unit. The resulting half-cell exhibits an initial coulombic efficiency of 73.5% and a capacity retention of 82.0% after 500 cycles, both significantly improved compared to Comparative Example 1. In Comparative Example 2, a stepwise solvothermal method was used. First, iodine catalyzed the condensation of ethylene glycol to form a polyethylene glycol network, and then silane was added to react. Since the silane could not be uniformly embedded in the formed polymer network structure, the precursor components were uneven. The four tetrahedral units still coexisted in the resulting SiOC-2 material. The electrochemical performance of the assembled half-cell was similar to that of Comparative Example 1, but significantly worse than that of Example 1. This indicates that the way iodine is introduced is crucial to the directional regulation of the tetrahedral structure. If iodine catalyzes the condensation of ethylene glycol first and then introduces silane, it cannot play its structural guiding role, and the silane is difficult to distribute uniformly. The product is still a mixed phase structure.

[0098] In Examples 2-4, as the amount of iodine increased, the obtained I-SiOC materials all maintained a single SiO3C tetrahedral structure. The corresponding assembled half-cells had high initial coulombic efficiency and high capacity retention after cycling. Moreover, the initial coulombic efficiency and capacity retention showed a trend of first increasing and then decreasing.

[0099] The half-cells assembled with I-SiOC materials prepared in Examples 5 and 6 showed some fluctuation in initial coulombic efficiency and capacity retention after 500 cycles, but overall they exhibited excellent comprehensive electrochemical performance, significantly better than the comparative examples.

[0100] The above results demonstrate that the present invention successfully achieved the controllable construction of a single tetrahedral structure of SiO3C through an iodine-assisted directional synthesis strategy, eliminating the capacity loss and structural degradation problems caused by irreversible phases from the source. This is a key technical approach to achieve high initial coulombic efficiency and ultra-long cycle stability of SiOC materials.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing I-SiOC material, characterized in that, Includes the following steps: S1. Silane and ethylene glycol are used as silicon source and carbon source, respectively, and iodine is used as initiator. After stirring and mixing to dissolve the iodine, a reaction solution is obtained. The reaction solution is subjected to a solvothermal reaction to obtain the precursor. S2. After calcining the precursor in an inert atmosphere, I-SiOC material is obtained.

2. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S1, the silane is triethoxyvinylsilane, whose chemical structural formula is as follows: 。 3. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S1, the volume ratio of silane to ethylene glycol is 1:(1~3).

4. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of iodine to ethylene glycol is (1~2.5)g:(10~30)mL.

5. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S1, the temperature of the solvothermal reaction is 160~180°C, and the reaction time is 10~15h.

6. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

7. The method for preparing I-SiOC material according to claim 1, characterized in that, In step S2, the calcination temperature is 800~1000℃ and the calcination time is 1~4h.

8. An I-SiOC material, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 7.

9. A lithium battery, characterized in that, Includes the I-SiOC material as described in claim 8.

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