A high-performance germanium-based anode material with carbon coating and silicon dioxide embedded porous germanium, its preparation method and application

Abstract

The application belongs to the technical field of lithium ion battery negative electrode materials, and discloses a high-performance germanium-based negative electrode material of carbon-coated and silicon dioxide-embedded porous germanium, and a preparation method and application thereof. The method is to prepare porous germanium (p-Ge) by reducing germanium dioxide with low-temperature hydrogen, then prepare silicon dioxide microspheres by hydrolyzing tetraethyl orthosilicate and embed the silicon dioxide microspheres into the pores of the p-Ge, and finally coat the p-Ge with carbon to obtain the high-performance germanium-based negative electrode material. The preparation process is environmentally friendly and low-polluted, has high production efficiency, and is controllable in the synthesis process. The high-performance germanium-based negative electrode material prepared by the method has the characteristics of good conductivity, good cycle stability and excellent rate performance as the lithium ion battery negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, and relates to a new method for preparing porous germanium using hydrogen thermal reduction, and for preparing silica microspheres embedded in porous germanium by carbon coating and tetraethyl orthosilicate hydrolysis, as well as the high-performance germanium-based anode material prepared therefrom, and its application as a high-performance lithium-ion battery anode material. Background Technology

[0002] The vigorous development of new energy electric vehicles has become a national strategic plan. To make pure electric vehicles mainstream, breakthroughs are essential in the key core technology of new energy vehicles—high-energy-density lithium-ion batteries. With breakthroughs in the research of ternary cathode materials, higher demands are being placed on the performance of anode materials. Although germanium's theoretical specific capacity (1600 mAh g / g) is... -1 Germanium is only half the size of silicon, and while it is more expensive, it exhibits smaller volume changes during electrochemical cycling, has 400 times higher ion diffusivity and four orders of magnitude higher electronic conductivity than silicon. Furthermore, germanium's density is more than twice that of silicon (Ge = 5.3 g / cm³). -3 Si is 2.33 g cm⁻¹ -3 Germanium stores more charge per volume than silicon, thus offering broader application prospects. However, the significant volume expansion (approximately 230%) of germanium during cycling can lead to electrode material pulverization and further battery failure. Therefore, the commercial application of germanium anode materials still faces numerous challenges. Currently, research on germanium anodes mainly focuses on mitigating the volume effect of germanium and improving the ionic and electronic conductivity of the material through carbon coating modification. Additionally, reducing the size of Ge particles to the nanoscale can reduce mechanical stress generated during cycling, thereby improving cycling performance. However, nanoscale germanium results in lower initial coulombic efficiency (ICE), poor tap density and volumetric properties, excessively high production costs, and complex processes.

[0003] Zhang et al. utilized the strong binding relationship between Ge and ZnS to successfully encapsulate dispersed Ge nanoparticles within a thin ZnS protective shell and a nitrogen-doped carbon layer by performing a two-step carbonization and sulfidation process on a polydopamine-coated Zn2GeO4 nanorod precursor. The synthesized Ge-ZnS@NC anode exhibited stable long-cycle performance and excellent rate performance. However, the above synthesis method is complex, has low production efficiency, and is difficult to achieve large-scale production (Zhonghua Zhang, Lingjie Li, Jing Liu, Xiaosong Guo, Kun Chao, Changming Mao, Guicun Li, Alleviated volume changes of germanium anode via facile chemical confinement strategy, Chemical Engineering Journal, 497, 2024, 154741).

[0004] Yan et al. investigated the morphology and lithium storage performance of nanoporous Ge (np-Ge), silver nanoparticle-embedded nanoporous Ge (Ag / np-Ge), and Ge nanoparticle-embedded nanoporous Ag (Ge / np-Ag). The results showed that a high proportion of Ge as the main active material ensured a high theoretical capacity, while the porous network structure provided sufficient space for volume expansion and contraction. Furthermore, the embedded Ag nanoparticles promoted the electron transfer rate. The results indicated that the Ag / np-Ge electrode exhibited the best cycling stability. However, the aforementioned preparation methods involve high costs, making commercial application difficult (Yonghui Yan, Yang Liu, Yongguang Zhang, Chunling Qin, Zhumabay Bakenov, Zhifeng Wang, Improving the cycling stability of three-dimensional nanoporous Ge anode by embedding Ag nanoparticles for high-performance lithium-ion battery, Journal of Colloid and Interface Science, 592, 2021, 103-115). Therefore, how to improve the application of germanium materials in lithium-ion battery anode materials in a more economical, environmentally friendly and effective way remains a problem that needs further research and development in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a novel, controllable, low-pollution, and high-efficiency high-performance germanium-based anode material, p-Ge / SiO2 / C composite material, with carbon coating and silica embedding in porous germanium, along with its preparation method and applications. The method is characterized by using inert SiO2 microspheres prepared by the hydrolysis of tetraethyl orthosilicate as pore fillers for porous germanium. These microspheres effectively pinnate the volume changes occurring during charge-discharge cycles, limiting further volume changes in germanium during subsequent cycles. The high-performance p-Ge / SiO2 / C composite material is then obtained by further coating with a carbon coating.

[0006] The technical solution of the present invention will be described in detail below.

[0007] This invention provides a method for preparing a high-performance germanium-based anode material with carbon coating and silicon dioxide embedding of porous germanium. The method uses hydrogen as a thermal reaction source to reduce germanium dioxide powder to porous germanium (p-Ge), followed by hydrolysis with tetraethyl orthosilicate under alkaline conditions to prepare silica microspheres, which are then embedded to fill the pores of the p-Ge. Finally, the silica microspheres are mixed with carbon materials and carbonized at high temperature to achieve carbon coating modification, resulting in a p-Ge / SiO2 / C composite material with long cycle stability and excellent rate performance. The specific preparation method includes the following steps:

[0008] S1. Germanium dioxide powder is subjected to a low-temperature thermal reduction reaction under a hydrogen atmosphere to obtain porous germanium material p-Ge material;

[0009] S2. Add p-Ge to a mixed solution of anhydrous ethanol and deionized water, then add surfactant and tetraethyl orthosilicate and stir until homogeneous. React under alkaline conditions.

[0010] S3. The above reaction products are carbon-coated to obtain p-Ge / SiO2 / C composite material.

[0011] Preferably, the particle size of the germanium dioxide powder in step S1 is 3 to 30 micrometers.

[0012] Preferably, in step S1, a layer of germanium dioxide powder is spread evenly in an alumina ceramic boat for a thermal reduction reaction; more preferably, the thickness of the spread layer is 2 mm. More preferably, the hydrogen atmosphere flow rate should be maintained at 50–200 ml / min. More preferably, the hydrogen atmosphere is high-purity hydrogen.

[0013] Preferably, the thermal reduction conditions in step S1 are thermal reduction at 400°C for more than 8 hours, more preferably 8 to 14 hours. If the temperature is too low, the reduction reaction is difficult to achieve. If the temperature is too high, the pores of the porous germanium will grow and close during the high-temperature reduction process, leading to a decrease in the corresponding electrochemical performance, and the higher temperature conditions will also exacerbate energy consumption.

[0014] Preferably, the volume ratio of deionized water to anhydrous ethanol in the mixed solution in step S2 should be 1:(1-5). By using anhydrous ethanol and water as a solvent system, ethanol can act as a solvent in the reaction, increasing the solubility of tetraethyl silicate, ensuring that the reactants can fully contact and react uniformly, and avoiding the uneven reaction that may occur if water is used directly as the reaction medium, which would affect the quality and yield of silica. At the same time, the addition of ethanol can also effectively control the reaction rate, preventing the reaction between tetraethyl silicate and water from being too vigorous, resulting in uneven silica particle size, and even potentially generating a large amount of heat and gas, posing a safety hazard.

[0015] Preferably, in step S2, after p-Ge is added to the solvent, it is stirred evenly by ultrasonication. More preferably, the ultrasonic power is 200W and the ultrasonication time is 30-60min.

[0016] Preferably, the surfactant in step S2 is hexadecyltrimethylammonium bromide.

[0017] Preferably, the mass ratio of p-Ge to surfactant added in step S2 should be 20:(0.1~2).

[0018] Preferably, the volume ratio of deionized water to tetraethyl orthosilicate added in step S2 should be 20:(0.1-2). Under these conditions, the hydrolysis rate of tetraethyl orthosilicate is more suitable.

[0019] Preferably, in step S2, the amount of p-Ge and tetraethyl orthosilicate fed is 0.2g:0.25-1mL.

[0020] Preferably, in step S2, the alkaline conditions are a pH of not less than 8 and a reaction time of not less than 18 hours. More preferably, ammonia or conventional alkaline solutions such as sodium hydroxide or potassium hydroxide are added dropwise to adjust the pH of the mixed solution system to 8-10, and the mixture is stirred for 24 hours.

[0021] Preferably, after the reaction in step S2 is completed, the product is washed by centrifugation with deionized water and anhydrous ethanol and dried in sequence, and the reaction product is collected; more preferably, the product is washed by centrifugation with deionized water and anhydrous ethanol 5 times each at a speed of 6000 rpm and dried at 80°C for 12 h.

[0022] Preferably, the carbon coating step in step S3 specifically involves: stirring and ultrasonically dispersing the reaction product and carbon material in deionized water, evaporating to remove water from the suspension, and then calcining at 600-900°C in an inert atmosphere for 2 hours. The carbon coating conditions of the present invention have the advantages of low cost, simple synthesis, and ease of implementation.

[0023] More preferably, the carbon material is one or a combination of several of sucrose, glucose, chitosan, citric acid and cellulose;

[0024] More preferably, the water is removed by evaporating the suspension at a temperature above 100°C for at least 1 hour; even more preferably, the water is removed by evaporating the suspension at a temperature of 120°C to 180°C for 2 hours.

[0025] More preferably, calcination is carried out at 700°C under an inert atmosphere for 2 hours;

[0026] More preferably, the inert atmosphere is at least one of nitrogen, helium, and argon.

[0027] The present invention also provides a high-performance germanium-based anode material p-Ge / SiO2 / C composite material prepared by any of the above preparation methods, which is carbon-coated and has silicon dioxide embedded in porous germanium.

[0028] The present invention also provides an application of the p-Ge / SiO2 / C composite material, a high-performance germanium-based anode material with carbon coating and silicon dioxide embedded porous germanium, as an anode material for lithium-ion batteries.

[0029] This invention provides a novel method for preparing high-performance germanium-based anode materials. First, porous germanium (p-Ge) is prepared by low-temperature hydrogen thermal reduction of germanium dioxide. Then, silica microspheres are prepared by hydrolysis with tetraethyl orthosilicate and embedded to fill the pores of the p-Ge. Finally, the material is modified with a carbon coating. The preparation process of this invention is environmentally friendly and low-pollution, with high production efficiency. The synthesis process is controllable, without introducing byproducts or side reactions. Furthermore, the pore filling rate of the porous germanium can be controlled by adjusting the amount of raw materials, enabling the synthesis of different products. The prepared p-Ge / SiO2 / C composite material exhibits excellent cycle stability and rate performance.

[0030] Compared with the prior art, the beneficial effects of this invention are mainly reflected in:

[0031] (1) This invention provides a new method for synthesizing p-Ge / SiO2 / C composite materials that is environmentally friendly and low-pollution, has a simple and controllable reaction, high production efficiency, no solid phase by-products generated, and can efficiently synthesize p-Ge / SiO2 / C composite materials.

[0032] (2) The high-performance germanium-based anode material p-Ge / SiO2 / C composite material provided by the present invention has the characteristics of good conductivity, good cycle stability and excellent rate performance as anode material for lithium-ion batteries. Attached Figure Description

[0033] Figure 1 XRD patterns of p-Ge, p-Ge / C, p-Ge / SiO2 and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5 and 6 of this invention;

[0034] Figure 2Scanning electron microscope (SEM) images of the p-Ge, p-Ge / C, p-Ge / SiO2 and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5 and 6 of this invention;

[0035] Figure 3 The p-Ge, p-Ge / C, p-Ge / SiO2, and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5, and 6 of this invention were subjected to oxidation at 0.5 Ag. -1 Cyclic performance at current density;

[0036] Figure 4 The p-Ge, p-Ge / C, p-Ge / SiO2, and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5, and 6 of this invention were subjected to a reaction at 1.0 Ag. -1 Cyclic performance at current density;

[0037] Figure 5 Rate performance diagrams of p-Ge, p-Ge / C, p-Ge / SiO2 and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5 and 6 of this invention at different current densities;

[0038] Figure 6 Impedance (EIS) diagrams of the p-Ge, p-Ge / C, p-Ge / SiO2 and p-Ge / SiO2 / C composite materials prepared in embodiments 1, 2, 3, 4, 5 and 6 of this invention. Detailed Implementation

[0039] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, and instruments used in the embodiments, unless otherwise specified, can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0041] Example 1:

[0042] Step 1: Preparation of p-Ge materials

[0043] S1. A 2 mm thick layer of germanium dioxide powder was spread in an alumina ceramic boat and placed in a tube furnace. Thermal reduction was performed at 400℃ for 10 h at a high-purity hydrogen flow rate of 100 ml / min. After furnace cooling, porous p-Ge material was obtained. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0044] Figure 1 The XRD diffraction pattern of the p-Ge material, compared with standard PDF card 04-0545, shows only the characteristic diffraction peaks of Ge.

[0045] Figure 2 The image shows a SEM image of the p-Ge material, which reveals a porous honeycomb structure.

[0046] Step 2: Fabrication of coin cell lithium-ion batteries

[0047] The active material (p-Ge material), SuperP, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8 g). The solution was dried in a vacuum oven at 120°C for 12 hours. The electrode sheet was then pressed using a roller press and cut into 12 mm diameter discs using a slicer to obtain the test electrode discs. CR2032 button half-cells were assembled in an argon-filled glove box. A lithium foil was used as the counter electrode, and a Cellgard 2500 film was used as the separator. The electrolyte consisted of 1 M LiPF6 mixed with EC / DEC / EMC (1:1:1, vol%), 5 vol% FEC, and 1 vol% VC.

[0048] Figure 3 The coin cell lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cycling performance at current density and within the voltage range of 0.01–2.0 V. The p-Ge material exhibits a sharp capacity decrease after 150 charge-discharge cycles, with the final discharge specific capacity remaining at only 405 mAh g⁻¹. -1 The capacity retention rate was only 25.5% (compared to the 4th cycle), indicating poor cycle stability.

[0049] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance under current density and voltage range of 0.01–2.0 V. The capacity of this material drops sharply after 150 charge-discharge cycles, with the final discharge specific capacity remaining at only 438 mAh g⁻¹. -1 The capacity retention rate was only 27.5% (compared to the 4th cycle), and the cycling stability under high current was poor.

[0050] Figure 5 This figure shows the rate performance of the coin cell lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, after cycling at different current densities, when the current density is finally maintained at 1.0 Ag... -1 After 120 cycles, the final discharge specific capacity was only 386 mAh g. -1 The capacity retention rate was only 25.9% (compared to the 31st cycle), demonstrating poor rate performance.

[0051] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin-type lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 33 Ω.

[0052] Example 2:

[0053] Step 1: Preparation of p-Ge / SiO2-0.25 composite material

[0054] S1. The preparation method is the same as in Example 1: a 2 mm thick layer of germanium dioxide powder is spread in an alumina ceramic boat and placed in a tube furnace. The powder is thermally reduced at 400°C for 10 h at a high-purity hydrogen flow rate of 100 ml / min. After cooling with the furnace, porous p-Ge material can be obtained.

[0055] S2. Add 0.2g of p-Ge to a mixture of 80ml of anhydrous ethanol and 20ml of deionized water, stir, and sonicate at 200W for 1 hour to homogenize the mixture. Then add 0.02g of hexadecyltrimethylammonium bromide and 0.25ml of tetraethyl orthosilicate, and stir for 30 minutes to homogenize.

[0056] S3. Add 2 ml of ammonia water to the above mixed solution until pH = 9 to trigger the hydrolysis of tetraethyl orthosilicate, and stir for 24 h. After the hydrolysis reaction is completed, wash the mixture five times each with deionized water and anhydrous ethanol at 6000 rpm, and dry it at 80℃ for 12 h to finally obtain the p-Ge / SiO2-0.25 composite material. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0057] Figure 1 The XRD diffraction pattern of the p-Ge / SiO2-0.25 composite material is shown. Referring to standard PDF card 04-0545, only characteristic diffraction peaks of Ge are present. The broad SiO2 peak near 22° is not prominent in the p-Ge / SiO2-0.25 composite material, which is due to the low SiO2 content.

[0058] Figure 2 The image shows a SEM image of the p-Ge / SiO2-0.25 composite material. As can be seen from the image, the p-Ge / SiO2-0.25 composite material exhibits a porous honeycomb structure similar to that of p-Ge material, with only a small amount of pores filled.

[0059] Step 2: Fabrication of coin cell lithium-ion batteries

[0060] The battery preparation method was the same as in Example 1, except for the active material: the active material (p-Ge / SiO2-0.25 composite material), Super P, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8g). The solution was dried in a vacuum oven at 120°C for 12 hours, and then the electrode sheet was pressed using a rolling mill. The electrode sheet was then cut into 12mm diameter discs using a slicer to obtain the electrode discs for testing. The CR2032 button half-cell was assembled in an argon-filled glove box, with a lithium sheet as the counter electrode, a Cellgard 2500 film as the separator, and an electrolyte consisting of 1M LiPF6 mixed in EC / DEC / EMC (1:1:1, vol%) with 5 vol% FEC and 1 vol% VC.

[0061] Figure 3 The coin cell lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cycling performance at current density and within the voltage range of 0.01–2.0 V. The p-Ge / SiO2-0.25 composite material exhibits a sharp capacity decrease after 150 charge-discharge cycles, with a final discharge specific capacity of 542 mAh g. -1 The capacity retention rate was 47.2% (compared to the 4th cycle), indicating poor cycle stability.

[0062] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance under current density and voltage range of 0.01–2.0 V. The capacity of this material drops sharply after 150 charge-discharge cycles, with the final discharge specific capacity remaining at only 332 mAh g⁻¹. -1 The capacity retention rate was only 27.5% (compared to the 4th cycle), and the cycling stability under high current was poor.

[0063] Figure 5 This figure shows the rate performance of the coin cell lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, after cycling at different current densities, when the current density is finally maintained at 1.0 Ag... -1 After 120 cycles, the final discharge specific capacity was only 319 mAh g. -1 The capacity retention rate was only 28.1% (compared to the 31st cycle), demonstrating poor rate performance.

[0064] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin-type lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 33 Ω.

[0065] Example 3:

[0066] Step 1: Preparation of p-Ge / SiO2-0.5 composite material (by changing the amount of tetraethyl orthosilicate added based on Example 2)

[0067] S1. Spread a 2 mm thick layer of germanium dioxide powder in an alumina ceramic boat and place it in a tube furnace. At a high purity hydrogen flow rate of 100 ml / min, perform thermal reduction at 400℃ for 10 h. After cooling with the furnace, a porous p-Ge material can be obtained.

[0068] S2. Add 0.2g of p-Ge to a mixture of 80ml of anhydrous ethanol and 20ml of deionized water, stir, and sonicate at 200W for 1 hour to homogenize the mixture. Then add 0.02g of hexadecyltrimethylammonium bromide and 0.5ml of tetraethyl orthosilicate, and stir for 30 minutes to homogenize.

[0069] S3. Add 2 ml of ammonia water to the above mixed solution until pH = 9 to trigger the hydrolysis of tetraethyl orthosilicate, and stir for 24 h. After the hydrolysis reaction is completed, wash the mixture five times each with deionized water and anhydrous ethanol at 6000 rpm, and dry it at 80℃ for 12 h to finally obtain the p-Ge / SiO2-0.5 composite material. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0070] Figure 1 The image shows the XRD diffraction pattern of the p-Ge / SiO2-0.5 composite material. Referring to standard PDF card 04-0545, only characteristic diffraction peaks of Ge are present. The broad SiO2 peak near 22° is not prominent in the p-Ge / SiO2-0.5 composite material, which is due to the low SiO2 content.

[0071] Figure 2The image shows a SEM image of the p-Ge / SiO2-0.5 composite material. As can be seen from the image, the p-Ge / SiO2-0.5 composite material exhibits a porous honeycomb structure similar to that of p-Ge material, but the pores are partially filled.

[0072] Step 2: Fabrication of coin cell lithium-ion batteries

[0073] The battery preparation method was consistent with that in Example 1, except for the active material: the active material (p-Ge / SiO2-0.5 composite material), SuperP, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8g). The mixture was dried in a vacuum oven at 120°C for 12 hours, and then the electrode sheet was pressed using a rolling mill. The electrode sheet was then cut into 12mm diameter discs using a slicer to obtain the electrode discs for testing. The CR2032 button half-cell was assembled in an argon-filled glove box, with a lithium sheet as the counter electrode, a Cellgard 2500 film as the separator, and an electrolyte consisting of 1M LiPF6 mixed in EC / DEC / EMC (1:1:1, vol%) with 5vol% FEC and 1vol% VC.

[0074] Figure 3 The coin cell lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cyclic performance graphs at current density and voltage range of 0.01–2.0 V. The p-Ge / SiO2-0.5 composite material retains a final discharge specific capacity of 659 mAh g after 150 charge-discharge cycles. -1 The capacity retention rate was as high as 80.7% (compared to the 4th round), but the final remaining capacity was not high.

[0075] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance under current density and voltage range of 0.01–2.0 V. The material retains a final discharge specific capacity of 552 mAh g after 150 charge-discharge cycles. -1 The capacity retention rate was 68.0% (compared to the 4th round), but the final remaining capacity was still not high.

[0076] Figure 5 This figure shows the rate performance of the coin cell lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, after cycling at different current densities, when the current density is finally maintained at 1.0 Ag... -1 After 120 cycles, the final discharge specific capacity remained at 611 mAh g. -1 The capacity retention rate is as high as 85.1% (compared to the 31st cycle), showing good rate performance, but the final remaining specific capacity is not high.

[0077] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin cell lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 36 Ω.

[0078] Example 4:

[0079] Step 1: Preparation of p-Ge / SiO2-1 composite material (by changing the amount of tetraethyl orthosilicate added based on Example 2)

[0080] S1. Spread a 2 mm thick layer of germanium dioxide powder in an alumina ceramic boat and place it in a tube furnace. At a high purity hydrogen flow rate of 100 ml / min, perform thermal reduction at 400℃ for 10 h. After cooling with the furnace, a porous p-Ge material can be obtained.

[0081] S2. Add 0.2g of p-Ge to a mixture of 80ml of anhydrous ethanol and 20ml of deionized water, stir, and sonicate at 200W for 1 hour to homogenize the mixture. Then add 0.02g of hexadecyltrimethylammonium bromide and 1ml of tetraethyl orthosilicate, and stir for 30 minutes to homogenize.

[0082] S3. Add 2 ml of ammonia water to the above mixed solution until pH = 9 to trigger the hydrolysis of tetraethyl orthosilicate, and stir for 24 h. After the hydrolysis reaction is completed, wash the mixture five times each with deionized water and anhydrous ethanol at 6000 rpm, and dry it at 80℃ for 12 h to finally obtain the p-Ge / SiO2-0.5 composite material. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0083] Figure 1 The image shows the XRD diffraction pattern of the p-Ge / SiO2-1 composite material. Referring to standard PDF card 04-0545, characteristic diffraction peaks of Ge are observed, with a distinct broad peak near 22°, indicating amorphous SiO2.

[0084] Figure 2 The image shows a SEM image of the p-Ge / SiO2-1 composite material. As can be seen from the image, the porous structure of the p-Ge / SiO2-1 composite material has almost disappeared, and obvious SiO2 microspheres have been exposed on the outer surface.

[0085] Step 2: Fabrication of coin cell lithium-ion batteries

[0086] The battery preparation method was consistent with that in Example 1, except for the active material: the active material (p-Ge / SiO2-1 composite material), SuperP, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8g). The mixture was dried in a vacuum oven at 120°C for 12 hours, and then the electrode sheet was pressed using a rolling mill. The electrode sheet was then cut into 12mm diameter discs using a slicer to obtain the test electrode discs. The CR2032 button half-cell was assembled in an argon-filled glove box, with a lithium sheet as the counter electrode, a Cellgard 2500 film as the separator, and an electrolyte consisting of 1M LiPF6 mixed in EC / DEC / EMC (1:1:1, vol%) with 5 vol% FEC and 1 vol% VC.

[0087] Figure 3 The coin cell lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cyclic performance graphs at current density and voltage range of 0.01–2.0 V. The p-Ge / SiO2-1 composite material retains a final discharge specific capacity of 558 mAhg after 150 charge-discharge cycles. -1 The capacity retention rate was as high as 95.7% (compared to the 4th cycle), but the final remaining capacity was low, making it difficult to meet the high capacity requirements for commercialization.

[0088] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance under current density and voltage range of 0.01–2.0 V. The material retains a final discharge specific capacity of 484 mAh g after 150 charge-discharge cycles. -1 The capacity retention rate was 85.4% (compared to the 4th round), but the final remaining capacity was still not high.

[0089] Figure 5 This figure shows the rate performance of the coin cell lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, after cycling at different current densities, when the current density is finally maintained at 1.0 Ag... -1 After 120 cycles, the final discharge specific capacity remained at 518 mAh g. -1 The capacity retention rate was as high as 93.8% (compared to the 31st cycle), showing good rate performance, but the final remaining specific capacity was still not high.

[0090] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin cell lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 36 Ω.

[0091] Example 5:

[0092] Step 1: Preparation of p-Ge / SiO2 / C composite materials

[0093] S1. Spread a 2 mm thick layer of germanium dioxide powder in an alumina ceramic boat and place it in a tube furnace. At a high purity hydrogen flow rate of 100 ml / min, perform thermal reduction at 400℃ for 10 h. After cooling with the furnace, a porous p-Ge material can be obtained.

[0094] S2. Add 0.2g of p-Ge to a mixture of 80ml of anhydrous ethanol and 20ml of deionized water, stir, and sonicate at 200W for 1 hour to homogenize the mixture. Then add 0.02g of hexadecyltrimethylammonium bromide and 0.25ml of tetraethyl orthosilicate, and stir for 30 minutes to homogenize.

[0095] S3. Add 2 ml of ammonia water to the above mixed solution until pH = 9 to trigger the hydrolysis of tetraethyl orthosilicate, and stir for 24 h. After the hydrolysis reaction is completed, wash the product 5 times each by centrifugation at 6000 rpm with deionized water and anhydrous ethanol, and dry it at 80 °C for 12 h to obtain the p-Ge / SiO2-0.25 composite material.

[0096] S4. Take 0.3g of p-Ge / SiO2-0.25 composite material and 0.2g of chitosan, stir and ultrasonically disperse in 8g of deionized water. Evaporate the water in the suspension at 150℃ for 2h, and then calcine at 700℃ under Ar atmosphere for 2h to finally obtain p-Ge / SiO2 / C composite material. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0097] Figure 1 The image shows the XRD diffraction pattern of the p-Ge / SiO2 / C composite material. Referring to standard PDF card 04-0545, characteristic diffraction peaks of Ge are observed, with a distinct broad peak appearing near 22°, representing the superposition of amorphous SiO2 and carbon peaks.

[0098] Figure 2 The image shows a SEM image of the p-Ge / SiO2 / C composite material. As can be seen from the image, the porous structure of the p-Ge / SiO2 / C composite material has almost disappeared, and the outer surface is covered by SiO2 microspheres and an amorphous carbon layer.

[0099] Step 2: Fabrication of coin cell lithium-ion batteries

[0100] The active material (p-Ge / SiO2 / C composite material), SuperP, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8 g). The coating was dried in a vacuum oven at 120°C for 12 h. The electrode sheet was then pressed using a roller press and cut into 12 mm diameter discs using a slicer to obtain the test electrode discs. The CR2032 button half-cell was assembled in an argon-filled glove box. A lithium foil was used as the counter electrode, and a Cellgard 2500 film was used as the separator. The electrolyte consisted of 1 M LiPF6 mixed with EC / DEC / EMC (1:1:1, vol%), 5 vol% FEC, and 1 vol% VC.

[0101] Figure 3 The coin-type lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cyclic performance graphs at current density and voltage range of 0.01–2.0 V. The p-Ge / SiO2 / C composite material retains a final discharge specific capacity of 730 mAhg after 150 charge-discharge cycles. -1 It has the highest remaining specific capacity, with a capacity retention of 78.2% (compared to cycle 4), and excellent cycle performance.

[0102] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance at current density and within a voltage range of 0.01–2.0 V. The material retains a final discharge specific capacity of 627 mAh g after 150 charge-discharge cycles. -1 It has the highest remaining specific capacity, with a capacity retention of 69.7% (compared to cycle 4), and excellent cycle performance.

[0103] Figure 5 This figure shows the rate performance of the coin-type lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, the material at 4Ag... -1 It also has 677mAh g at current density -1 The capacity. And after cycling at different current densities, when the current density is finally maintained at 1.0 A g. -1 After 120 cycles, the final discharge capacity remaining is 701 mAh g. -1 It achieved a capacity retention rate of up to 85.4% (compared to the 31st cycle), demonstrating the best rate performance.

[0104] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin-type lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 17 Ω, exhibiting the lowest impedance and best conductivity.

[0105] Example 6:

[0106] Step 1: Preparation of p-Ge / C composite materials

[0107] S1. Spread a 2 mm thick layer of germanium dioxide powder in an alumina ceramic boat and place it in a tube furnace. At a high purity hydrogen flow rate of 100 ml / min, perform thermal reduction at 400℃ for 10 h. After cooling with the furnace, a porous p-Ge material can be obtained.

[0108] S2. Take 0.3g of p-Ge material and 0.2g of chitosan, stir and ultrasonically disperse in 8g of deionized water, evaporate the water in the suspension at 150℃ for 2h, and then calcine at 700℃ under Ar atmosphere for 2h to finally obtain p-Ge / C composite material. Particle size and pore size data are shown in Table 1, and elemental percentages are shown in Table 2.

[0109] Figure 1 This is the XRD diffraction pattern of the p-Ge / C composite material. Referring to standard PDF card 04-0545, characteristic diffraction peaks of Ge are observed. No diffraction peaks were observed for carbon because the carbon content is low and the carbon is amorphous.

[0110] Figure 2 The image shows a SEM image of the p-Ge / C composite material. As can be seen from the image, the pore structure of the p-Ge / C composite material is not obvious, and the outer surface is covered by an amorphous carbon layer.

[0111] Step 2: Fabrication of coin cell lithium-ion batteries

[0112] The active material (p-Ge / C composite material), SuperP, and polyacrylic acid (PAA) were dissolved in deionized water at a mass ratio of 6:2:2 and then uniformly coated onto copper foil (coating amount: 0.8 g). The coating was dried in a vacuum oven at 120°C for 12 hours. The electrode sheet was then pressed using a roller press and cut into 12 mm diameter discs using a slicer to obtain the test electrode discs. The CR2032 button half-cell was assembled in an argon-filled glove box. A lithium foil was used as the counter electrode, and a Cellgard 2500 film was used as the separator. The electrolyte consisted of 1 M LiPF6 mixed with EC / DEC / EMC (1:1:1, vol%), 5 vol% FEC, and 1 vol% VC.

[0113] Figure 3 The coin-type lithium-ion battery assembled in this embodiment is at 0.5Ag -1 Cycling performance at current density and within the voltage range of 0.01–2.0 V. The p-Ge / C composite material exhibits a sharp capacity decrease after 150 charge-discharge cycles, with a final discharge specific capacity of 430 mAh g. -1The capacity retention rate was 31.2% (compared to the 4th cycle), indicating poor cycle stability.

[0114] Figure 4 The coin cell lithium-ion battery assembled for this embodiment is at 1.0 Ag. -1 Cycling performance under current density and voltage range of 0.01–2.0 V. The capacity of this material drops sharply after 150 charge-discharge cycles, with the final discharge specific capacity remaining at only 334 mAh g⁻¹. -1 The capacity retention rate was only 23.4% (compared to the 4th cycle), and the cycling stability under high current was poor.

[0115] Figure 5 This figure shows the rate performance of the coin cell lithium-ion battery assembled in this embodiment at different current densities. As can be seen from the figure, after cycling at different current densities, when the current density is finally maintained at 1.0 Ag... -1 After 120 cycles, the final discharge specific capacity was only 480 mAh g. -1 The capacity retention rate was only 36.6% (compared to the 31st cycle), demonstrating poor rate performance.

[0116] Figure 6 Electrochemical impedance spectroscopy (EIS) of the coin-type lithium-ion battery assembled in this embodiment was tested in the range of 1 MHz to 0.1 Hz. The charge transfer impedance (Rct value) of this material is approximately 23 Ω.

[0117] The average particle size and pore size data of the p-Ge, p-Ge / C, p-Ge / SiO2, and p-Ge / SiO2 / C composite materials prepared in Examples 1, 2, 3, 4, 5, and 6 of this invention are shown in Table 1:

[0118] Table 1. Average particle size and pore size data of materials in each embodiment.

[0119]

[0120] The elemental percentages of the p-Ge, p-Ge / C, p-Ge / SiO2, and p-Ge / SiO2 / C composite materials prepared in Examples 1, 2, 3, 4, 5, and 6 of this invention are shown in Table 2:

[0121] Table 2 Summary of elemental percentages of materials in each embodiment

[0122]

[0123] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for preparing a high-performance germanium-based anode material with carbon coating and silicon dioxide embedding porous germanium, characterized in that: The method comprises the following steps: S1, low-temperature thermal reduction of germanium dioxide powder in a hydrogen atmosphere to obtain porous germanium material p-Ge material, the thermal reduction condition being thermal reduction at 400 DEG C for 8 h or more; S2, adding p-Ge to a mixed solution of anhydrous ethanol and deionized water, then adding a surfactant and tetraethyl orthosilicate and stirring uniformly, and reacting under alkaline conditions; the mass ratio of p-Ge to the surfactant in step S2 should be 20:(0.1-2), the volume ratio of deionized water to tetraethyl orthosilicate should be 20:(0.1-2), the feeding amount of p-Ge and tetraethyl orthosilicate in step S2 should be 0.2 g:0.25-1 mL, the alkaline condition should be pH no less than 8, and the reaction time should be no less than 18 h; S3, carbon-coated high-performance germanium-based negative electrode material is obtained by coating the reaction product.

2. The method of claim 1, wherein the method of preparing a high-performance germanium-based anode material of carbon-coated and silicon dioxide-embedded porous germanium is characterized by: The particle size of the germanium dioxide powder in step S1 is 3-30 microns.

3. The method of claim 1, wherein the method is characterized by: The hydrogen gas flow in step S1 should be maintained at 50-200 mL / min.

4. The method of claim 1, wherein the method of preparing a high-performance germanium-based anode material of carbon-coated and silicon dioxide-embedded porous germanium is characterized by, The volume ratio of deionized water to anhydrous ethanol in the mixed solution in step S2 should be 1:(1-5).

5. The method of claim 1, wherein the method of preparing a high-performance germanium-based anode material of carbon-coated and silicon-embedded porous germanium is characterized by, The carbon coating step in step S3 is as follows: dispersing the reaction product and carbon material into deionized water, evaporating water in the suspension, and then calcining at 600-900 DEG C in an inert atmosphere for 2 h.

6. The carbon-coated and silica-embedded porous germanium high-performance germanium-based negative electrode material prepared by the preparation method of any one of claims 1-5.

7. Application of the carbon-coated and silica-embedded porous germanium high-performance germanium-based negative electrode material of claim 6 in the field of lithium ion battery negative electrode materials.

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