Germanium regulated silicon / carbon fiber composite material and preparation method and application thereof

Abstract

This invention discloses a germanium-regulated silicon / carbon fiber composite material, its preparation method, and its application. The preparation method of the Si / Ge@CNFs composite material is as follows: (1) GeO2 / F127 dispersion is added to silicon nanoparticle / P123 dispersion and stirred to obtain silicon / germanium precursor dispersion; (2) PVA is dissolved in silicon / germanium precursor dispersion and uniformly dispersed GeO2 / Si@PVA fiber composite material is prepared by electrospinning technology; (3) GeO2 / Si@PVA fiber composite material is heat-treated in a hydrogen-argon mixed atmosphere to reduce GeO2 to Ge nanoparticles and convert PVA fibers into carbon fibers to obtain Ge / Si@CNFs composite material. In this invention, the initial reaction potentials of silicon and germanium in the Ge / Si@CNFs composite material are different, which effectively releases the stress caused by volume change. The carbon fibers can alleviate the volume expansion of silicon and germanium and accelerate the Lithification process. + This method improves the lithium storage performance of Ge / Si@CNFs composites by increasing electron transfer rate. It is economical, efficient, and environmentally friendly, providing a simple and efficient approach for preparing germanium-silicon-carbon composite anodes.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to a germanium-regulated silicon / carbon fiber composite material and its preparation method and application. Background Technology

[0002] Lithium-ion batteries are characterized by high energy density, environmental friendliness, and long lifespan, and are widely used in power supplies for electric vehicles and portable devices. Over the past decade, group IV elements have been considered an attractive alternative to commercial graphite for lithium-ion battery anodes due to their high theoretical capacity. Among them, silicon boasts a theoretical capacity as high as 3579 mAh g⁻¹. -1 Silicon, with its low operating voltage and abundant reserves, has become a preferred candidate for anode materials. However, silicon's inherent low electronic conductivity, ion diffusion ability, and significant volume expansion hinder its further development as an anode material for lithium-ion batteries. Furthermore, germanium is not only noteworthy for its high capacity but also for its good electronic conductivity and fast lithium-ion mobility, exhibiting better rate performance and cycle performance. However, germanium's high price and low abundance impede its commercialization.

[0003] Compared to pure silicon electrodes, the Ge / Si structure offers several advantages: First, Ge doping into Si accelerates lithium transport kinetics, thereby improving rate performance; second, the different reaction initiation potentials of Si and Ge with lithium prevent simultaneous expansion, allowing for gradual release of strain stress; and finally, when lithium is inserted into one component, the other acts as a buffer, mitigating volume changes. However, despite these advantages, several challenges remain. During lithiation / delithiation, both Si and Ge undergo significant volume changes, leading to anode cracking, failure, and eventual capacity decay. Designing complex nanostructures with additional free space to accommodate volume expansion is an effective strategy for maintaining electrode structural integrity and cycle stability.

[0004] To overcome these challenges, new fabrication technologies are needed to improve production efficiency and reduce energy consumption. Simultaneously, in-depth research into the Ge / Si structure is required to further enhance its cycle stability and capacity. This includes exploring more suitable Ge / Si ratios, optimizing nanostructure design, and developing novel carbon sources. These advancements promise to bring progress to anode materials for lithium-ion batteries, meeting the demand for high-performance batteries in commercial devices such as electric vehicles. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a germanium-modulated silicon / carbon fiber composite material, its preparation method, and its applications. This method successfully prepares a Si / Ge@CNFs composite material with a three-dimensional core-shell structure through simple electrospinning and heat treatment steps. This composite material combines the high capacity of silicon with the excellent conductivity of germanium, and effectively buffers the problems of volume expansion and poor conductivity through carbon nanofibers, exhibiting excellent lithium storage performance and suitable for use as a negative electrode material in lithium-ion batteries.

[0006] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0007] A method for preparing germanium-controlled silicon / carbon fiber composite material includes the following steps:

[0008] Step 1, Preparation of GeO2 / Si dispersion

[0009] F127 was dissolved in deionized water to prepare an F127 solution. While stirring, GeO2 polycrystalline particles were added, and stirring was continued at room temperature for 1 hour to obtain a transparent GeO2 / F127 dispersion.

[0010] P123 was dissolved in deionized water, and Si nanoparticles were added to the P123 solution to obtain a Si / P123 dispersion.

[0011] The GeO2 / F127 dispersion was then added to the Si / P123 dispersion to obtain the GeO2 / Si dispersion, wherein the molar ratio of Ge to Si was 0.25-2:1.

[0012] Step 2, Preparation of GeO2 / Si@PVA fiber composite material

[0013] 0.5g of sucrose was added to the GeO2 / Si dispersion, and then stirred continuously on a heating stirrer for 2 hours. 2g of PVA was added under strong stirring, and the mass ratio of sucrose to PVA was ≥0.25:1 (sucrose maintained the fiber morphology after calcination). The mixture was stirred for another 12 hours to obtain the GeO2 / Si@PVA slurry as an electrospinning liquid. Electrospinning was then performed to obtain the GeO2 / Si@PVA fiber composite material.

[0014] Step 3, Preparation of Ge / Si@CNFs composite material

[0015] The GeO2 / Si@PVA fiber composite material was pre-oxidized in air at 150℃ for 2 hours, then carbonized and reduced in a hydrogen-argon atmosphere, and naturally cooled to room temperature to obtain the Ge / Si@CNFs composite material.

[0016] As an improvement, the concentration of the F127 solution in step 1 is 4 wt%, and the concentration of the P123 solution is 1.5 wt%.

[0017] As an improvement, the molar ratio of Ge to Si in step 1 is 1:1.

[0018] As an improvement, the mass ratio of (Ge+Si) to PVA in step 2 is 0.5:20-2:20.

[0019] A further improvement is that the mass ratio of (Ge+Si) to PVA in step 2 is 1:20.

[0020] As an improvement, in step 3, the heating rate for carbonization in a hydrogen-argon atmosphere is 3℃ / min, the carbonization temperature is 800℃, and the reduction time is 6h.

[0021] The germanium-regulated silicon / carbon fiber composite material prepared by the above preparation method includes silicon nanoparticles, germanium nanoparticles and a carbon fiber matrix, wherein the silicon nanoparticles and germanium nanoparticles are uniformly distributed in the carbon fiber matrix to form a three-dimensional core-shell structure.

[0022] The above-mentioned Ge / Si@CNFs composite material is used as a negative electrode material in lithium-ion batteries.

[0023] Beneficial effects:

[0024] Compared with the prior art, the germanium-controlled silicon / carbon fiber composite material of the present invention, its preparation method and application, have the following advantages:

[0025] Beneficial effects:

[0026] 1. Structural advantages: The Ge / Si@CNFs composite material prepared by this invention has a three-dimensional core-shell structure. Based on the different initial reaction potentials of silicon and germanium, and the uniform coating of silicon and germanium nanoparticles in carbon nanofibers, the stress caused by volume change can be effectively released, and the carbon fibers can alleviate the volume expansion of silicon and germanium.

[0027] 2. Excellent performance: The Ge / Si@CNFs composite material of this invention combines the high capacity of silicon with the excellent conductivity of germanium. At the same time, its structure can alleviate volume expansion, exhibiting excellent lithium storage performance, such as high specific capacity, long cycle stability and good rate performance.

[0028] 3. Simple method: The Ge / Si@CNFs composite material of this invention uses water as a solvent and PVA as a spinning polymer. The preparation method is simple, efficient and low cost, and is suitable for large-scale industrial production. Attached Figure Description

[0029] Figure 1 The image shows the XRD pattern of the Si / Ge@CNFs composite material prepared in Example 1.

[0030] Figure 2 The Raman spectrum of the Si / Ge@CNFs composite material prepared in Example 1.

[0031] Figure 3 Thermogravimetric curve of the Si / Ge@CNFs composite material prepared in Example 1.

[0032] Figure 4 The image shows a SEM image of the GeO2 / Si@PVA fiber composite material prepared in Example 1.

[0033] Figure 5 SEM image of the Si / Ge@CNFs composite material prepared in Example 1.

[0034] Figure 6 The image shows a TEM image of the Si / Ge@CNFs composite material prepared in Example 1.

[0035] Figure 7 The CV curve of the Si / Ge@CNFs composite material prepared in Example 1 in LIBs.

[0036] Figure 8 The charge-discharge curves of the Si / Ge@CNFs composite material prepared in Example 1 in LIBs are shown.

[0037] Figure 9 0.2Ag prepared in Example 1 -1 Cyclic performance of Si / Ge@CNFs composites at current density.

[0038] Figure 10 Rate performance of the Si / Ge@CNFs composite material prepared in Example 1 at different current densities.

[0039] Figure 11 0.5A g prepared in Example 1 -1 Long-cycle performance of Si / Ge@CNFs composites at current density.

[0040] Figure 12 Composite materials prepared under different parameters were used as anode materials in 0.2Ag. -1 Cyclic performance at current density.

[0041] Figure 13 The image shows a SEM image of the Ge / Si@CNFs-0.05 composite material prepared in Example 2.

[0042] Figure 14 The image shows a SEM image of the Ge / Si@CNFs-0.15 composite material prepared in Example 3.

[0043] Figure 15The image shows a SEM image of the Ge / Si@CNFs-0.2 composite material prepared in Example 4.

[0044] Figure 16 SEM image of the Ge@CNFs composite material prepared for Comparative Example 2. Detailed Implementation

[0045] Example 1

[0046] The preparation method of Ge / Si@CNFs composite material includes the following steps:

[0047] (1) Preparation of GeO2 / Si dispersion:

[0048] 0.8 g of F127 was dissolved in 20 mL of deionized water and stirred continuously at room temperature for 1 h to prepare a 4 wt% F127 solution. Under vigorous stirring, 0.09 g of GeO2 polycrystalline particles were added to the F127 solution and stirred continuously at room temperature for 1 h to obtain a transparent GeO2 / F127 dispersion.

[0049] 0.3 g of P123 was dissolved in 20 mL of deionized water, and 0.0375 g of Si nanoparticles were added to the P123 solution to prepare a Si / P123 dispersion.

[0050] The mixture was sonicated for 3 hours, and then the GeO2 / F127 dispersion was added to the Si / P123 solution to obtain the GeO2 / Si dispersion.

[0051] (2) Preparation of GeO2 / Si@PVA fiber composite material:

[0052] 0.5 g of sucrose was added to the GeO2 / Si dispersion and stirred continuously on a heated stirrer for 2 h. Then, 2 g of PVA was added under vigorous stirring and stirred continuously for 12 h to obtain a GeO2 / Si@PVA slurry. This slurry was used as the electrospinning liquid to prepare GeO2 / Si@PVA fiber composite materials.

[0053] (3) Preparation of Ge / Si@CNFs composite materials:

[0054] The GeO2 / Si@PVA fiber composite material was pre-oxidized in air at 150℃ for 2 hours, and then carbonized and reduced at 800℃ in a hydrogen-argon atmosphere for 6 hours (heating rate of 3℃ / min) to reduce GeO2 to germanium nanoparticles and convert PVA fibers into carbon fibers, thus obtaining the Ge / Si@CNFs composite material.

[0055] Ge / Si@CNFs composite material, carbon black, and sodium carboxymethyl cellulose were mixed in water at a mass ratio of 8:1:1 to form a slurry. This slurry was then coated onto copper foil and vacuum dried for 12 hours to produce a sample with an area of ​​1.0 cm². 2 The electrode disc has an active material loading of approximately 1.0 mg / cm³. -2 The material was used as the negative electrode material for lithium-ion batteries. Half-cells were assembled in an argon-filled glove box, and after standing for 24 hours, lithium storage performance was tested at a constant temperature of 25°C. Cyclic voltammetry curves were recorded using an electrochemical workstation within a voltage window of 0.01–3V. The electrochemical performance of the battery was recorded using a LAND CT2001A battery testing system.

[0056] Figure 1 The X-ray diffraction (XRD) pattern of the Ge / Si@CNFs composite material prepared in Example 1 shows that the diffraction peaks at 27.3°, 45.3°, 53.7°, 66.0°, and 72.8° correspond one-to-one with the (111), (220), (311), (400), and (331) crystal planes of cubic Ge (PDF#04-0545). This indicates that GeO2 was completely converted to Ge after high-temperature treatment in an Ar / H2 atmosphere. In addition to the diffraction peaks corresponding to Ge, other diffraction peaks are also shown in the spectrum, which correspond well to the standard card of Si (PDF#75-0589).

[0057] Figure 2 The Raman spectrum of the Ge / Si@CNFs composite material prepared in Example 1. 1359.6 cm⁻¹ -1 The broad peak at 1600.7 cm corresponds to the sample's structure and defect condition (D band), while the peak at 1600.7 cm corresponds to the sample's structure and defect condition (D band). -1 The broad peak at this point corresponds to the layering and topology (G-band) of the sample. The more disordered the carbon material structure and the higher the defect density, the stronger the D-band. The I-band of the Ge / Si@CNFs composite material... D / I G The ratio is 0.992, while the I of the Si@CNFs and Ge@CNFs composite material is... D / I G The ratios were 0.906 and 1.001, respectively. This indicates that the addition of Ge leads to an increase in defects in the composite material, making electron conduction easier and improving the cycle efficiency of the composite material.

[0058] Figure 3The thermal decomposition curve of the Ge / Si@CNFs composite material prepared in Example 1 is shown. Calculations indicate a carbon content of 25.7 wt%, and this low carbon content is beneficial for increasing energy density. In the Ge / Si@CNFs composite material, carbon is mainly present in the CNFs, while silicon and germanium are embedded in the carbon nanofibers as nanoparticles.

[0059] Figure 4 The image shows a SEM image of the GeO2 / Si@PVA composite material prepared in Example 1. The GeO2 / Si@PVA composite material exhibits a very uniform fiber morphology, with a compact and smooth surface, and the fiber diameter is 300-400 nm.

[0060] Figure 5 This is a SEM image of the Ge / Si@CNFs composite material prepared in Example 1. After pre-oxidation and carbonization treatment, the fiber morphology of the Ge / Si@CNFs composite material remained essentially unchanged.

[0061] Figure 6 The image shows a TEM image of the Ge / Si@CNFs composite material prepared in Example 1. The results indicate that Si and Ge nanoparticles are well coated by carbon nanofibers. This coating structure not only improves the structural stability of the material but also prevents severe volume expansion and contraction of Si and Ge during charge and discharge, thus avoiding performance degradation in the battery.

[0062] Figure 7 The CV curves for the first four cycles of the Ge / Si@CNFs composite electrode prepared in Example 1 are shown. In Li + During the initial embedding process, a weak and broad peak appeared at approximately 1.19 V, which disappeared in subsequent cycles, indicating that Li x GeO x A reduction reaction occurred. Subsequently, electrolyte decomposition and SEI film formation took place in the 0-0.5V range. Furthermore, the lithiation of Ge in the second cycle appeared at approximately 0.3V, while the peak at 0.19V was attributed to the lithiation of Si. The two oxidation peaks at 0.40V and 0.52V corresponded to Li… y Si and Li x The delithiation process of Ge. The curves of the third and fourth cycles match well, demonstrating that the electrode has good cycle stability.

[0063] Figure 8 The charge-discharge curves of the Ge / Si@CNFs composite electrode prepared in Example 1 are shown. The results indicate that the discharge and charge plateaus of the electrode are similar to those of the electrode prepared in Example 1. Figure 7The positions of the redox peaks correspond to those in the middle, further verifying the redox reactions that occur during charge and discharge. The initial discharge capacity of the composite material is 3525.6 mAh g. -1 and 2353.1mAh g -1 It exhibits an initial coulomb efficiency of 66.7%.

[0064] Figure 9 The Ge / Si@CNFs composite electrode prepared for Example 1 was compared with other comparative electrodes at 0.2 Ag. -1 The difference in cycle performance after 200 cycles at the current density. As shown in the figure, the specific discharge capacity of the Ge / Si@CNFs composite electrode is 1152 mAh g⁻¹. -1 After 200 cycles, there was almost no degradation. The excellent lithium storage performance is mainly attributed to the synergistic effect between silicon and germanium, which provide each other with buffer space, effectively mitigating the negative impact of volume expansion during charge and discharge. At the same time, the carbon fibers in the core-shell structure also play a key role, further mitigating volume expansion and improving the cycling stability of the material.

[0065] Figure 10 Rate performance of the Ge / Si@CNFs composite electrode prepared in Example 1 at different current densities. (0.1, 0.2, 0.5, 1.0, and 2.0 Ag) -1 At current densities of [values ​​missing], the stable reversible capacities of the Ge / Si@CNFs composite materials were 1997.5, 1697.7, 1518.5, 1425.5, and 1168.7 mAh g, respectively. -1 Although the reversible capacity of the Ge / Si@CNFs composite decreased slightly with increasing current density, it still maintained a relatively high capacity. When the current density was adjusted back to 0.1 Ag... -1 At that time, the reversible capacity of the Ge / Si@CNFs composite material reached 1731.4 mAh g. -1 The reversible capacity was well recovered, demonstrating that the material has good structural stability and reversible lithium storage.

[0066] Figure 11 The Ge / Si@CNFs composite electrode prepared in Example 1 was subjected to a 0.5Ag... -1 The long-term cycling performance under high current density was demonstrated. After 1000 cycles, the discharge capacity of the Ge / Si@CNFs composite material was 764.1 mAh g⁻¹. -1 The discharge capacity of the second cycle (1059.7 mAh g) -1 Compared to the previous method, the capacity retention rate was 72.1%, indicating that the Ge / Si@CNFs composite material has good long-term cycling stability.

[0067] Comparative Example 1

[0068] The difference from Example 1 is that the prepared composite material does not contain Ge, and the resulting material is denoted as Si@CNFs.

[0069] In the lithium storage performance test, the loading of composite material in a single electrode was 1.0 mg.

[0070] Si@CNFs composites have similar morphologies to Ge / Si@CNFs composites, but their properties differ significantly. Figure 12 The results show that the Si@CNFs composite electrode retains a capacity of 386.3 mAh g after 200 cycles. -1 The capacity was significantly lower than that of the Ge / Si@CNFs composite electrode after 200 cycles, indicating that the addition of germanium helps to improve the lithium storage performance of the Ge / Si@CNFs composite material.

[0071] Example 2

[0072] The difference from Example 1 is that the mass ratio of (Ge+Si) to PVA is 0.5:20, and the resulting material is denoted as Ge / Si@CNFs-0.05.

[0073] In the lithium storage performance test, the loading of composite material in a single electrode was 1.0 mg.

[0074] The Ge / Si@CNFs-0.05 composite material has a similar morphology to the Ge / Si@CNFs composite material, such as... Figure 13 As shown, but the performance is significantly different. From Figure 12 As can be seen, the Ge / Si@CNFs-0.05 composite electrode maintained a capacity of 835.8 mAh g after 200 cycles. -1 The capacity was significantly lower than that of the Ge / Si@CNFs composite electrode after 200 cycles, further indicating that the amount of germanium added has a significant impact on improving the lithium storage performance of the Ge / Si@CNFs composite material.

[0075] Example 3

[0076] The difference from Example 1 is that the mass ratio of (Ge+Si) to PVA is 1.5:20. The prepared material is denoted as Ge / Si@CNFs-0.15.

[0077] In the lithium storage performance test, the loading of composite material in a single electrode was 1.0 mg.

[0078] The morphology of the Ge / Si@CNFs-0.15 composite material is similar to that of the Ge / Si@CNFs composite material, such as... Figure 14As shown, but the performance is significantly different. Figure 12 As can be seen, the Ge / Si@CNFs-0.15 composite electrode maintained a capacity of 481.6 mAh g after 200 cycles. -1 The capacity was significantly lower than that of the Ge / Si@CNFs composite electrode after 200 cycles, indicating that adding too much germanium is not conducive to improving the lithium storage performance of the Ge / Si@CNFs composite material.

[0079] Example 4

[0080] The difference from Example 1 is that the mass ratio of (Ge+Si) to PVA is 2:20, and the resulting material is denoted as Ge / Si@CNFs-0.2.

[0081] In the lithium storage performance test, the loading of composite material in a single electrode was 1.0 mg.

[0082] The morphology of the Ge / Si@CNFs-0.2 composite material is similar to that of the Ge / Si@CNFs composite material, such as... Figure 15 As shown, but the performance is significantly different. From Figure 12 As can be seen, the Ge / Si@CNFs-0.2 composite electrode maintained a capacity of 388.3 mAh g after 200 cycles. -1 The capacity was significantly lower than that of the Ge / Si@CNFs composite electrode after 200 cycles, indicating that adding too much germanium is not conducive to improving the lithium storage performance of the Ge / Si@CNFs composite material.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that no Si nanoparticles were added, and the resulting material is denoted as Ge@CNFs.

[0085] In the lithium storage performance test, the loading of composite material in a single electrode was 1.0 mg.

[0086] Ge@CNFs composites have similar morphologies to Ge / Si@CNFs composites, such as... Figure 16 As shown, however, the performance differences are significant. From Figure 12 As can be seen, the Ge@CNFs composite electrode maintained a capacity of 333.1 mAh g after 200 cycles. -1 The capacity is significantly lower than that of the Ge / Si@CNFs composite electrode after 200 cycles.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that no sucrose was added in the preparation of the GeO2 / Si@PVA composite material, and the prepared material is denoted as Ge / Si@C.

[0089] Experimental results show that without the addition of sucrose, the GeO2 / Si@PVA composite material cannot maintain its fiber structure after high-temperature calcination.

[0090] Comparative Example 4

[0091] The difference from Example 1 is that the amount of sucrose added is 1.0g.

[0092] Experimental results show that the precursor slurry used for GeO2 / Si@PVA composite materials is viscous and cannot be spun.

[0093] In summary, this invention successfully prepared a Ge / Si@CNFs composite material with a three-dimensional core-shell structure using electrospinning technology. This material exhibits excellent cycle stability and high capacity in lithium-ion battery anodes, providing a new method for synthesizing high-performance silicon-carbon anode materials, and is expected to meet the demand for high-performance batteries in commercial devices such as electric vehicles.

[0094] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing germanium-controlled silicon / carbon fiber composite material, characterized in that, Includes the following steps: Step 1, Preparation of GeO2 / Si dispersion F127 was dissolved in deionized water to prepare an F127 solution. While stirring, GeO2 polycrystalline particles were added, and stirring was continued at room temperature for 1 h to obtain a transparent GeO2 / F127 dispersion. P123 was dissolved in deionized water, and Si nanoparticles were added to the P123 solution to obtain a Si / P123 dispersion. The GeO2 / F127 dispersion was then added to the Si / P123 dispersion to obtain the GeO2 / Si dispersion, wherein the molar ratio of Ge to Si was 0.25-2:

1. Step 2, Preparation of GeO2 / Si@PVA fiber composite material 0.5 g of sucrose was added to the GeO2 / Si dispersion, and then stirred continuously on a heating stirrer for 2 h. 2 g of PVA was added under strong stirring, and then stirred for 12 h to obtain the GeO2 / Si@PVA slurry as the electrospinning liquid. Electrospinning was then performed to obtain the GeO2 / Si@PVA fiber composite material. Step 3, Preparation of Ge / Si@CNFs composite material The GeO2 / Si@PVA fiber composite material was pre-oxidized in air at 150 °C for 2 h, then carbonized and reduced in a hydrogen-argon atmosphere, and naturally cooled to room temperature to obtain the Ge / Si@CNFs composite material. The Ge / Si@CNFs composite material includes silicon nanoparticles, germanium nanoparticles and a carbon fiber matrix, wherein the silicon nanoparticles and germanium nanoparticles are uniformly distributed in the carbon fiber matrix to form a three-dimensional network core-shell structure.

2. The method for preparing a germanium-controlled silicon / carbon fiber composite material according to claim 1, characterized in that, The concentration of the F127 solution in step 1 is 4 wt%, and the concentration of the P123 solution is 1.5 wt%.

3. The method for preparing a germanium-controlled silicon / carbon fiber composite material according to claim 1, characterized in that, In step 1, the molar ratio of Ge to Si is 1:

1.

4. The method for preparing a germanium-controlled silicon / carbon fiber composite material according to claim 1, characterized in that, In step 2, the mass ratio of (Ge+Si) to PVA is 0.5:20-2:

20.

5. The method for preparing a germanium-controlled silicon / carbon fiber composite material according to claim 4, characterized in that, In step 2, the mass ratio of (Ge+Si) to PVA is 1:

20.

6. The method for preparing a germanium-controlled silicon / carbon fiber composite material according to claim 1, characterized in that, In step 3, the heating rate for carbonization in a hydrogen-argon atmosphere is 3 °C / min, the carbonization temperature is 800 °C, and the reduction time is 6 h.

7. The germanium-controlled silicon / carbon fiber composite material prepared by the method of claim 1, characterized in that, The germanium-regulated silicon / carbon fiber composite material includes silicon nanoparticles, germanium nanoparticles, and a carbon fiber matrix, wherein the silicon nanoparticles and germanium nanoparticles are uniformly distributed in the carbon fiber matrix to form a three-dimensional network core-shell structure.

8. The application of the germanium-modulated silicon / carbon fiber composite material as a negative electrode material in lithium-ion batteries according to claim 7.

Images