TiO2-x / SiOx heterostructure composite negative electrode material and preparation method thereof

Abstract

The invention discloses a TiO2-x / SiOx (0 < x < 2) heterostructure composite negative electrode material and a preparation method thereof. The preparation method comprises the following steps: firstly, coating TiO on SiOx by adopting a hydrolysis method to obtain a TiO2 / SiOx composite material; and then carrying out high-temperature reduction reaction on the TiO2 / SiOx composite material to prepare the TiO2-x / SiOx heterostructure composite material with the rambutan morphology. Oxygen vacancies exist in TiO2-x in the composite material with the specific morphology, the oxygen vacancies can induce formation of a local electronic state and generate an embedded electric field on a TiO2-x interface, the oxygen vacancies can provide additional channels for electron transmission and ion storage, and the embedded electric field further optimizes the electron and ion transmission performance of the composite material, so that the performance of the composite material is improved. Diffusion of electrons and lithium ions on an interface can be remarkably enhanced through the synergistic effect of oxygen vacancies and an embedded electric field, the conductivity of the lithium ions is greatly improved, and meanwhile the volume strain in the electrochemical cycle process is effectively relieved. When the composite material is prepared into an electrode, excellent cycling stability and rate capability are shown, and the cycle life is prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of electrode material preparation, and particularly relates to a TiO 2-x / SiO x heterostructure composite anode material and a preparation method thereof. Background Art

[0002] Silicon-based anode materials are considered promising candidates for lithium-ion batteries (LIBs) due to their theoretical capacity of about 4200 mAh / g. However, during charge and discharge processes, due to significant volume expansion, electrode cracking and poor cycle stability occur, which limit the practical application of silicon-based anode materials.

[0003] Silicon monoxide (SiO x , 0 < x < 2) has been studied due to its amorphous structure, which can reduce volume expansion to about 200%. In addition, stable by-products such as lithium oxide (Li2O) and lithium silicate (Li4SiO4) are formed during charge and discharge processes, further alleviating volume expansion and improving cycle stability.

[0004] However, SiO x still has problems such as poor ionic conductivity and large residual volume expansion in practical applications, which limit its application in high-performance requirements. In recent years, to solve the above problems, Ouyang et al. developed a gradient porous SiO x material with an eggshell structure to improve lithium storage capacity and cycle stability by providing additional buffer space and ion transport channels. However, due to the poor conductivity of SiO x , a conductive agent still needs to be added. Shen et al. developed a TiO2-Si-C composite anode material to reduce the volume expansion of silicon, but the initial Coulomb efficiency (82.51%) of this material is insufficient and still needs further optimization.

[0005] Rutile titanium dioxide (TiO2) has been widely studied due to its high conductivity (Li x TiO2, 0 ≤ x ≤ 1) during lithiation. However, due to its relatively low theoretical specific capacity, its application as an independent anode material is limited. Oxygen-deficient titanium dioxide (TiO 2-x ) is a titanium oxide rich in oxygen defects, which has a very wide spectral response range and good conductive properties.

[0006] In view of this, the present invention proposes to introduce TiO 2-x (0 < x < 2), by promoting the rapid diffusion of lithium ions on the (001) crystal plane, enhancing ionic conductivity, and obtaining a higher theoretical specific capacity; then by combining TiO 2-x with SiO xEffectively combining and fully utilizing their respective advantages can achieve improvements in cycle stability and energy density - this is crucial to promoting the performance improvement of lithium-ion batteries. Summary of the Invention

[0007] In view of the problems existing in the background technology, the purpose of the present invention is to provide a TiO 2-x / SiO x Heterostructure composite negative electrode material and preparation method thereof.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention is to provide a TiO 2-x / SiO x A method for preparing a heterostructure composite negative electrode material comprises the following steps:

[0010] S1, tetrapropoxytitanium (TBOT) and SiO x Add ethanol, stir, centrifuge, wash and dry to obtain TiO2 / SiO x Composite materials;

[0011] S2, TiO2 / SiO x The composite material was subjected to high temperature reduction treatment in H2 / Ar atmosphere to obtain TiO 2-x / SiO x Composite materials.

[0012] Preferably, in step S1, the SiO x The specific preparation steps are as follows: adding hexadecyloxyammonium bromide (HTAB) and vinyltriethoxysilane to an aqueous solution of ethanol; then adding ammonia water to adjust the pH to alkaline, and stirring at room temperature for 16-28 hours; after the reaction is completed, centrifugation and drying are performed to obtain SiO2; then the obtained SiO2 is calcined in a H2 / Ar atmosphere at 800-1000℃ for 1.5-2 hours to obtain SiO x ; wherein the ethanol aqueous solution is obtained by mixing anhydrous ethanol and deionized water in a volume ratio of 1:1.9~2, and the mass ratio of HTAB, vinyltriethoxysilane and ammonia water is 0.2-0.5:1.5-2.5:1.5-2.5.

[0013] Preferably, in step S1, the stirring treatment time is 20-24 hours.

[0014] Preferably, in step S1, the tetra-n-propoxytitanium and SiO x The dosage ratio is 1-1.8mL:0.5-1.2g.

[0015] Preferably, in step S2, the conditions for the high-temperature reduction treatment are: a heating rate of 6-10°C / min, a reduction treatment temperature of 900-1100°C, and a reduction treatment time of 1-3h.

[0016] The second aspect of the present invention is to provide a TiO 2-x / SiO x Heterostructure composite negative electrode materials.

[0017] The third aspect of the present invention is to provide a lithium ion battery negative electrode, the lithium ion battery negative electrode comprising the above-mentioned TiO 2-x / SiO x Heterostructure composite negative electrode materials.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention provides a TiO 2-x / SiO x Specifically, by first hydrolyzing SiO x Coated on TiO to obtain TiO2 / SiO x Composite material; then TiO2 / SiO x The composite material was placed in H2 / Ar atmosphere for high temperature reduction reaction to prepare TiO with rambutan-like morphology. 2-x / SiO x Heterogeneous structure (nanosphere) composite material. Among them, the partially reduced TiO 2-x Coating on SiO x A rigid core-shell structure is formed on the surface. This rigid core-shell structure has a high specific surface area and rich porosity, which can significantly optimize the diffusion channel of lithium ions and promote the transmission of lithium ions and electrons in the electrode. In addition, the porous structure relieves the mechanical stress caused by volume expansion, improves the stability of the electrode interface and the cycle performance; the outer TiO2 layer has high mechanical strength and can effectively inhibit the SiO x During the cycling process, the volume expands and the structure degrades; at the same time, the TiO 2-x / SiO x TiO in heterostructured composites 2-x The oxygen vacancies in TiO can induce the formation of localized electronic states and xThe interface generates an embedded electric field, in which oxygen vacancies provide additional channels for electron transport and ion storage, and the generated embedded electric field can further optimize the electronic and ion transport properties of the composite material. The synergistic effect of oxygen vacancies and embedded electric field significantly enhances the diffusion of electrons and lithium ions on the interface, greatly improves the conductivity of lithium ions, and effectively reduces the volume strain during the electrochemical cycle. Experimental results show that when the TiO 2-x / SiO x Heterostructured composite materials made of TiO 2-x / SiO x The electrode showed excellent cycle stability, excellent rate performance and extended cycle life. At a current density of 1C, the electrode maintained a capacity of 608.4mAh / g after 1000 cycles, with a capacity retention rate of 99.9%; at a high rate of 3C, it maintained a reversible capacity of 421.6mAh / g. Therefore, the TiO 2-x / SiO x Composite materials can serve as negative electrode materials for high-capacity, long-life lithium-ion batteries and have broad potential applications in electric vehicles and large-scale energy storage systems.

[0020] (2) The preparation method of the present invention has simple process steps, low cost of raw materials, easy to achieve large-scale production, and suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 TiO2 / SiO x and TiO 2-x / SiO x Synthesis route of composite materials;

[0023] Figure 2 The SiO prepared in Example 1 x , TiO2 / SiO x and TiO 2-x / SiO x SEM images of the composite material;

[0024] Figure 3 The TiO prepared in Example 1 -x / SiO x SAED patterns of the composite materials;

[0025] Figure 4 The TiO prepared in Example 1 -x / SiO x Element distribution map of composite materials;

[0026] Figure 5 The TiO prepared in Example 1 2-x / SiO x TEM images of the composite electrode before and after cycling;

[0027] Figure 6 (a) TiO -x / SiO x Composite materials, SiO x 、TiO2 / SiO x XRD patterns of (b, c) SiO x 、TiO2 / SiO x and TiO -x / SiO x Raman spectra and magnified images of the composite materials; (d) Si 2p spectrum; (e) Ti 2p spectrum; (f) SiO x 、TiO2 / SiO x and TiO 2-x / SiO x Nitrogen adsorption-desorption isotherms and pore size distribution of the composite material;

[0028] Figure 7 is: (a,b)Ar + TiO after sputtering for 60s and 180s 2-x / SiO x XPS analysis;

[0029] Figure 8 (a) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO x Cycling performance results of the electrode at a current density of 0.1C; (b) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO x The first charge-discharge curve of the electrode at a current density of 0.1C; (c) TiO 2-x / SiO x Cyclic voltammetry (CV) curves of the electrode at different scan rates (0.2-1.0 mV / s); (d, e) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO xElectrochemical impedance spectroscopy of the electrode before and after 1000 cycles; (f) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO x Rate performance results of the electrode; (g) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO x Cycling performance results of the electrode at 1C; (h) SiO x Electrode, TiO2 / SiO x Electrode, TiO 2-x / SiO x The average coulombic efficiency change results of the electrode; DETAILED DESCRIPTION

[0030] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may also be implemented in other embodiments without these specific details.

[0031] Example 1

[0032] Reference Figure 1 , a TiO 2-x / SiO x The method for preparing a heterogeneous structure composite material comprises the following steps:

[0033] (1)SiO x Synthesis: 0.32g HTAB and 1.8g vinyltriethoxysilane were added to a solution containing 51.6g anhydrous ethanol and 101.2g deionized water. 1.8g ammonia was then added to adjust the pH to alkaline, and the mixture was stirred at room temperature for 24h. After the reaction was complete, SiO2 powder was obtained by centrifugation and subsequent drying. The SiO2 powder was heated to 900°C and calcined in a H2 / Ar atmosphere at a heating rate of 10°C / min for 1.5h to obtain SiO2. x powder.

[0034] (2)TiO2 / SiO x Synthesis of composite materials: 1 mL of tetra-n-propoxytitanium (TBOT) and 0.6 g of SiO x The mixture was added to 200 mL of ethanol and stirred at room temperature for 24 h. Subsequently, the mixture was centrifuged and washed three times with anhydrous ethanol to remove unreacted substances. The mixture was dried under vacuum at 60 °C to obtain powdered TiO2 / SiO x Composite materials.

[0035] (3)TiO 2-x / SiO x Synthesis of composite materials: The obtained powdered TiO2 / SiO x The composite material was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min, and reduced in a H2 / Ar atmosphere for 100 min to obtain TiO 2-x / SiO x Composite materials.

[0036] Example 2

[0037] A TiO 2-x / SiO x The method for preparing a heterogeneous structure composite material comprises the following steps:

[0038] (1)SiO x Synthesis: 0.32 g HTAB and 1.8 g vinyltriethoxysilane were added to a solution containing 51.6 g anhydrous ethanol and 101.2 g deionized water. 1.8 g ammonia was then added to adjust the pH to alkaline, and the mixture was stirred at room temperature for 24 h. After the reaction was complete, SiO2 powder was obtained by centrifugation and subsequent drying. The SiO2 powder was heated to 900°C and calcined in a H2 / Ar atmosphere at a heating rate of 10°C / min for 1.5 h to obtain SiO2. x powder.

[0039] (2)TiO2 / SiO x Synthesis of composite materials: 1 mL of tetra-n-propoxytitanium (TBOT) and 0.6 g of SiO x The mixture was added to 200 mL of ethanol and stirred at room temperature for 24 h. Subsequently, the mixture was centrifuged and washed three times with anhydrous ethanol to remove unreacted substances. The mixture was dried under vacuum at 60 °C to obtain powdered TiO2 / SiO x Composite materials.

[0040] (3)TiO 2-x / SiO x Synthesis of composite materials: The obtained powdered TiO2 / SiO x The composite material was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min, and reduced in a H2 / Ar atmosphere for 100 min to obtain TiO 2-x / SiO x Composite materials.

[0041] Example 3

[0042] A TiO 2-x / SiO x The method for preparing a heterogeneous structure composite material comprises the following steps:

[0043] (1)SiO x Synthesis: 0.32g HTAB and 1.8g vinyltriethoxysilane were added to a solution containing 51.6g anhydrous ethanol and 101.2g deionized water. 1.8g ammonia was then added to adjust the pH to alkaline, and the mixture was stirred at room temperature for 24h. After the reaction was complete, SiO2 powder was obtained by centrifugation and subsequent drying. The SiO2 powder was heated to 900°C and calcined in a H2 / Ar atmosphere at a heating rate of 10°C / min for 1.5h to obtain SiO2. x powder.

[0044] (2)TiO2 / SiO x Synthesis of composite materials: 1 mL of tetra-n-propoxytitanium (TBOT) and 0.6 g of SiO x The mixture was added to 200 mL of ethanol and stirred at room temperature for 24 h. Subsequently, the mixture was centrifuged and washed three times with anhydrous ethanol to remove unreacted substances. The mixture was dried under vacuum at 60 °C to obtain powdered TiO2 / SiO x Composite materials.

[0045] (3)TiO 2-x / SiO x Synthesis of composite materials: The obtained powdered TiO2 / SiO x The composite material was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min, and reduced in a H2 / Ar atmosphere for 100 min to obtain TiO 2-x / SiO x Composite materials.

[0046] Example 4

[0047] A TiO 2-x / SiO x The method for preparing a heterogeneous structure composite material comprises the following steps:

[0048] (1)SiO x Synthesis: 0.32g HTAB and 1.8g vinyltriethoxysilane were added to a solution containing 51.6g anhydrous ethanol and 101.2g deionized water. 1.8g ammonia was then added to adjust the pH to alkaline, and the mixture was stirred at room temperature for 24h. After the reaction was complete, SiO2 powder was obtained by centrifugation and subsequent drying. The SiO2 powder was heated to 900°C and calcined in a H2 / Ar atmosphere at a heating rate of 10°C / min for 1.5h to obtain SiO2. x powder.

[0049] (2)TiO2 / SiO x Synthesis of composite materials: 1 mL of tetra-n-propoxytitanium (TBOT) and 0.6 g of SiOx The mixture was added to 200 mL of ethanol and stirred at room temperature for 24 h. Subsequently, the mixture was centrifuged and washed three times with anhydrous ethanol to remove unreacted substances. The mixture was dried under vacuum at 60 °C to obtain powdered TiO2 / SiO x Composite materials.

[0050] (3)TiO 2-x / SiO x Synthesis of composite materials: The obtained powdered TiO2 / SiO x The composite material was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min, and reduced in a H2 / Ar atmosphere for 100 min to obtain TiO 2-x / SiO x Composite materials.

[0051] Example 5

[0052] A TiO 2-x / SiO x The method for preparing a heterogeneous structure composite material comprises the following steps:

[0053] (1)SiO x Synthesis: 0.32g HTAB and 1.8g vinyltriethoxysilane were added to a solution containing 51.6g anhydrous ethanol and 101.2g deionized water. 1.8g ammonia was then added to adjust the pH to alkaline, and the mixture was stirred at room temperature for 24h. After the reaction was complete, SiO2 powder was obtained by centrifugation and subsequent drying. The SiO2 powder was heated to 900°C and calcined in a H2 / Ar atmosphere at a heating rate of 10°C / min for 1.5h to obtain SiO2. x powder.

[0054] (2)TiO2 / SiO x Synthesis of composite materials: 1 mL of tetra-n-propoxytitanium (TBOT) and 0.6 g of SiO x The mixture was added to 200 mL of ethanol and stirred at room temperature for 24 h. Subsequently, the mixture was centrifuged and washed three times with anhydrous ethanol to remove unreacted substances. The mixture was dried under vacuum at 60 °C to obtain powdered TiO2 / SiO x Composite materials.

[0055] (3)TiO 2-x / SiO x Synthesis of composite materials: The obtained powdered TiO2 / SiO x The composite material was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min, and reduced in a H2 / Ar atmosphere for 100 min to obtain TiO 2-x / SiO x Composite materials.

[0056] Material characterization

[0057] SiO x 、TiO / SiO x and TiO 2-x / SiO x The structural morphology of the composite material was characterized. Figure 2-6 .

[0058] Depend on Figure 2 The SEM results show that SiO x The nanoparticles exhibited uniform morphology with an average diameter of approximately 1 μm. x and TiO 2-x / SiO x The composite material showed TiO and TiO 2-x Uniformly coated on SiO x The surface is a typical spherical structure, showing the morphological characteristics of rambutan.

[0059] Depend on Figure 3 The results show a clear ring structure, confirming the crystallinity of TiO2. Figure 3 Two distinct lattice fringes were identified with spacings of 0.348 nm and 0.228 nm, corresponding to the (101) and (004) planes of TiO2, respectively.

[0060] Depend on Figure 4 The results of energy spectrum analysis (EDS) mapping show that silicon is mainly concentrated in the core area, while titanium is evenly coated around the silicon core, and oxygen is evenly distributed in the composite material. This distribution highlights the 2-x / SiO x Structural characteristics and compositional uniformity of composite materials.

[0061] In order to systematically study the SiO x 、TiO2 / SiO x and TiO 2-x / SiO x The present invention has conducted a comprehensive analysis of the three-dimensional morphology changes of the anode during the cycling process. HRTEM was used to analyze the SiO x The thickness of the SEI layer of the composite material was tested. After 100 cycles, the thickness of the SEI layer of the TiO 2-x / SiO x The initial thickness of the SEI layer on the anode is 10.0 nm and is unevenly distributed ( Figure 5 (a)). After 1000 cycles, its thickness increases to 11.6nm, and the distribution becomes more uniform, completely covering the surface ( Figure 5(b)). During the cycle, TiO2 / SiO x SEI cracks often occur, leading to the repeated formation of new SEI layers on the damaged surface. In contrast, TiO 2-x / SiO x The electrode can maintain a stable SEI layer thanks to the inherent rigidity of the material and the porosity caused by oxygen vacancies, which can effectively relieve mechanical stress.

[0062] Depend on Figure 6 The XRD results in (a) show that SiO x The characteristic diffraction peaks are shown at 2θ angles of approximately 28.0°, 47.0° and 56.2°. x / TiO2), the diffraction peaks of TiO2 (101) and (004) planes appeared, located at 25° and 38° respectively. x After the reduction of TiO2 with hydrogen, the above diffraction peaks shifted significantly, and the (101) and (004) planes showed obvious blue shifts, which confirmed that TiO 2-x The anatase phase is retained, further indicating that the (101) surface is TiO 2-x The main exposed crystal face.

[0063] Depend on Figure 6 (b) and Figure 6 (c) Raman spectroscopy results show that TiO2 / SiO x Composite material at 151cm -1 There is a characteristic anatase TiO2 peak at 2-x / SiO x Composite material at 190cm -1 A new peak appears nearby, indicating a significant blue shift, which can be attributed to the structural change caused by the oxygen vacancy.

[0064] Depend on Figure 6 (d) High-resolution Si 2p spectrum shows that the peaks at 104.7 eV, 103.6 eV, and 102.7 eV correspond to Si 4+ 、Si 3+ and Si 2+ oxidation state, which indicates that during the high temperature reduction process, part of Si 4+ Reduction to Si 3+ and Si 2+ .

[0065] Depend on Figure 6 (e) Ti 2p spectrum shows significant peaks at 464.8eV and 459.2eV, which indicates that Ti 4+ In TiO 2-x / SiOx 2p in 1 / 2 and 2p 3 / 2 Orbital state.

[0066] Depend on Figure 6 (f) The results show that SiO x The BET specific surface area is 8.7 m 2 / g, after coating TiO2, TiO2 / SiO x The specific surface area of ​​the composite material increased to 21.4m 2 / g, TiO 2-x / SiO x The specific surface area of ​​the composite material is 20.6m 2 / g, compared with TiO2 / SiO x Composite materials, TiO 2-x / SiO x The composite material shows a wider pore size distribution, with the pore size range being between 4-15 nm. 2-x / SiO x The composite material has a high specific surface area and rich porosity, which can improve the permeability of the electrolyte and promote the transmission of lithium ions and electrons within the electrode. In addition, the formation of the pore structure can also alleviate the mechanical stress caused by volume expansion, thereby improving the stability of the electrode interface and the cycle performance.

[0067] Electrochemical testing

[0068] 80 wt% of the active material (TiO 2-x / SiO x The working electrode was prepared by mixing TiO 2-x / SiO xThe composite material, 10wt% activated carbon, and PAA were dispersed in deionized water to form a uniform slurry, which was then coated on copper foil and dried in a vacuum. The dried electrode material was compacted and cut into discs with a diameter of 0.9cm, and then placed in a vacuum oven for final drying. The battery was assembled in a glove box filled with high-purity argon (H2O <0.05ppm, O2 <0.05ppm). Lithium foil was used as the counter electrode, and the electrolyte was 1.0M LiPF6 dissolved in a 1:1 EC / DEC solution with 10% FEC added. Celgard 2325 polymer membrane was used as the separator. The electrochemical performance was evaluated using the Blue Energy battery test system to test the cycle stability, rate performance, and self-discharge performance in a voltage range of 0.012V. Cyclic voltammetry (CV) tests were performed using a CHI Instruments electrochemical workstation (CHI660e) with a voltage range of 0.012 V and scan rates of 0.1, 0.2, 1.0, 2.0, and 3.0 mV / s. Electrochemical impedance spectroscopy (EIS) tests were performed using the same electrochemical workstation with a frequency range of 0.01 Hz to 100 kHz and a voltage amplitude of 5 mV. All electrochemical tests were performed in a temperature-controlled room at 25°C. The results are shown in Figure 7 and Figure 8 .

[0069] Depend on Figure 7 (a) It can be seen that for TiO2 / SiO x At the anode, the SEI layer is mainly composed of organic components, with about 50% LiF being heterogeneously distributed. Figure 7 (b) Obvious Li2O signal is observed. In contrast, after cycling, TiO 2-x / SiO x The electrode showed about 35% LiF and only 1% Li2O. These changes in LiF and Li2O concentrations highlight that, compared to TiO 2-x / SiO x Compared with the SEI layer on the electrode, TiO 2-x / SiO x The thinner the SEI layer on the electrode, the more stable it is during cycling. 2-x / SiO x The increase in Si-O peak intensity on the electrode is more obvious, further indicating that the SEI layer is thinner. The difference in SEI thickness between the two composites is related to their respective stability levels. During the cycling process, the TiO2 / SiO x SEI cracks often occur, leading to the repeated formation of new SEI layers on the damaged surface. In contrast, TiO 2-x / SiO xThe electrode can maintain a stable SEI layer thanks to the inherent rigidity of the material and the porosity caused by oxygen vacancies, which can effectively relieve mechanical stress.

[0070] Depend on Figure 8 (a) The results show that after 200 cycles, SiO x The specific capacity of the electrode decreased from 712.5 mAh / g to 600.9 mAh / g, and the capacity retention rate was 84.3%. x The specific capacity of the electrode is 784.5 mAh / g, and the capacity retention rate is 89.68%. 2-x / SiO x The electrode maintained a high specific capacity of 920.2 mAh / g after cycling, with a capacity retention rate of 92.4%, which shows its excellent cycling stability.

[0071] Depend on Figure 8 (b) The results show that SiO x The initial reversible specific capacity of the electrode is 1287.4 mAh / g, but under the action of TiO coating, the specific capacity is reduced to 1091.0 mAh / g. 2-x After addition, the specific capacity increased to 1176.2 mAh / g, showing a significant improvement compared to pure TiO. This improvement is attributed to the 2-x The oxygen vacancies in the electrolyte trigger the formation of an embedded electric field and promote the diffusion of lithium ions at the interface, thereby effectively improving the capacity and cycle stability.

[0072] Depend on Figure 8 (c) The results show that the broad reduction peak at about 0.5 V in the cathode region indicates the formation of the SEI layer. In the anode region, the oxidation peak at about 0.6 V corresponds to the Li x The other peak at about 2.0 V is attributed to the decomposition of the Si phase and TiO 2-x phase, indicating that it enhances the diffusion ability of lithium ions.

[0073] Depend on Figure 8 (d) and Figure 8 (e) The results show that SiO x 、TiO / SiO x and TiO 2-x / SiO x Nyquist plot of the electrode. All electrodes show compressed semicircles in the high-frequency region, representing the charge transfer resistance, while the oblique lines in the low-frequency region indicate the diffusion-controlled process. The EIS data were fitted by the equivalent circuit R1+R2 / CPE2+W0, where R1 represents the ohmic resistance, R2 represents the charge transfer resistance, CPE2 is the constant phase element, and W0 corresponds to the Warburg diffusion impedance. The fitting results show that TiO 2-x / SiO x The R2 value of the electrode is significantly lower than that of SiO x and TiO / SiO x , indicating that TiO 2-x / SiO x The charge transfer resistance of the composite material is low. After 1000 cycles, a new semicircle appears in the middle frequency region of the Nyquist diagram, which may be related to the interface impedance (R3) caused by the deposition products during the discharge process. It is worth noting that TiO 2-x / SiO x The lower R2 and R3 values ​​of the electrode indicate that the TiO 2-x The coating not only effectively inhibits volume expansion, but also promotes the formation of a thinner and more stable SEI layer. This combined effect effectively reduces charge transfer and interfacial impedance, thereby greatly enhancing the electrochemical performance of the electrode.

[0074] Figure 8 (f) shows SiO x 、TiO / SiO x and TiO 2-x / SiO x The rate performance of the electrode at different current densities. Figure 6 (f) The results show that TiO 2-x / SiO x The composite electrode provided a high specific capacity of 917.7 mAh / g at 0.1C and maintained 421.6 mAh / g at 3.0C. In particular, after the high rate test, when the current density was restored to 0.1C, the specific capacity recovered to 828.5 mAh / g, reflecting its excellent structural stability. The specific capacity of the TiO2 coated electrode dropped to 1091.0 mAh / g, while the TiO 2-x The application of TiO 2-x Key role in increasing capacity.

[0075] Figure 8 (g) and Figure 8 (h) shows SiO x 、TiO / SiO x and TiO 2-x Cycling performance of TiO / SiOx electrode at 1C current density. After 1000 cycles, 2-x / SiO x The electrode maintains a high capacity of 608.4 mAh / g and an average coulombic efficiency of 99.9%. x and TiO / SiO x In comparison, TiO 2-x / SiO xThe electrodes exhibit excellent specific capacity, low charge transfer resistance, enhanced rate capability, and outstanding cycling stability.

[0076] This is attributed to the partially reduced TiO 2-x Coating on SiO x A rigid core-shell structure is formed on the surface, which not only has a high specific surface area and rich porosity, but also greatly optimizes the diffusion path of lithium ions; the high mechanical strength of the outer layer TiO2 effectively inhibits the SiO x The volume expansion and structural degradation during the electrochemical cycle enhance the stability of the composite material; at the same time, TiO 2-x The oxygen vacancies in the TiO2 induce the formation of local electronic states, which, combined with the embedded electric field at the TiO2 interface, significantly improves the conductivity of lithium ions. This unique structural design and the synergistic effect of interface electronic regulation greatly improve the conductivity of TiO2. 2-x / SiO x Specific capacity and cycling stability of the composite materials.

[0077] The present invention is not limited to the above-mentioned specific implementation methods. Various changes made by ordinary technicians in this field based on the above-mentioned concept without creative work are all within the scope of protection of the present invention.

Claims

1. A TiO 2-x / SiO x The method for preparing a heterostructure composite negative electrode material is characterized in that: The following steps are involved: S1. Mix TBOT and SiO at room temperature. x Add ethanol, stir, centrifuge, wash and dry to obtain TiO2 / SiO x Composite materials; S2, TiO2 / SiO x The composite material was subjected to reduction heat treatment in H2 / Ar atmosphere to obtain TiO 2-x / SiO x Composite materials.

2. TiO according to claim 1 2-x / SiO x The method for preparing a heterostructure composite negative electrode material is characterized in that: In step S1, the SiO x The specific preparation steps are as follows: HTAB and vinyl triethoxysilane are added to an aqueous solution of ethanol; then ammonia water is added to adjust the pH to alkaline, and the mixture is stirred at room temperature for 16-28 hours. After the reaction is completed, the mixture is centrifuged and dried to obtain SiO2, and then the obtained SiO2 is calcined in a H2 / Ar atmosphere at 800-1000°C for 1.5-2 hours to obtain SiO x ; wherein the ethanol aqueous solution is obtained by mixing anhydrous ethanol and deionized water in a volume ratio of 1:1.9~2, and the mass ratio of HTAB, vinyltriethoxysilane and ammonia water is 0.2-0.5:1.5-2.5:1.5-2.

5.

3. TiO according to claim 1 2-x / SiO x The method for preparing a heterostructure composite negative electrode material is characterized in that: In step S1, the stirring treatment time is 20-24h, and the HTAB and SiO x The dosage ratio is 1-1.8mL:0.5-1.2g.

4. TiO according to claim 1 2-x / SiO x The method for preparing a heterostructure composite negative electrode material is characterized in that: In step S2, the conditions of the high-temperature reduction treatment are: a heating rate of 6-10°C / min, a reduction treatment temperature of 900-1100°C, and a reduction treatment time of 1-3h.

5. TiO prepared by the preparation method according to any one of claims 1 to 4 2-x / SiO x Heterostructure composite negative electrode materials.

6. A lithium ion battery negative electrode, characterized in that Containing the TiO as claimed in claim 5 2-x / SiO x Heterostructure composite negative electrode materials.

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