Preparation method of germanium-carbon nanocomposite material for lithium-ion batteries by hydrothermal method

Abstract

This invention belongs to the technical field of lithium-ion battery anode materials, specifically a method for preparing germanium-carbon nanocomposite materials for lithium-ion batteries using a hydrothermal method. The preparation method includes: adding germanium dioxide to a sodium hydroxide solution and stirring vigorously with a magnetic stirrer until the germanium dioxide is completely dissolved to obtain a clear sodium germanate solution; adding concentrated hydrochloric acid dropwise to the sodium germanate solution to form a white suspension, and then adding carbon nanotubes; placing the mixed solution in a hydrothermal reactor for hydrothermal reaction; repeatedly filtering and washing the material with anhydrous ethanol and ultrapure water; and finally vacuum drying to obtain the germanium-carbon nanocomposite material. This invention uses germanium dioxide and carbon nanotubes as raw materials to generate a nanostructured germanium-carbon composite material through a hydrothermal reaction. It does not use any binders or catalysts, has a simple and low-cost preparation process, and produces a material with stable performance, high energy density, and suitable for long-term storage, thus supporting the commercial application of germanium-based anode materials.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and relates to a method for preparing germanium-carbon nanocomposite materials for lithium-ion batteries using a hydrothermal method. Background Technology

[0002] With the advancement of technology and the rapid development of new energy technologies, the performance requirements for lithium-ion batteries are constantly increasing. As a crucial component of lithium-ion batteries, the performance of the anode material directly affects the battery's energy density, cycle life, and safety. An ideal lithium-ion battery anode material should possess the following characteristics: high discharge voltage; stable crystal structure; high reversible capacity; high lithium-ion diffusion coefficient; and high energy density.

[0003] Currently, the main commercially available lithium-ion battery anode material is graphite, but graphite's capacity (theoretical specific capacity of graphite is 372 mAh·g) is limited. -1 The limitations imposed by silicon on battery performance are significant. As research progressed, researchers discovered that silicon-based anode materials possess advantages such as high energy density, abundant reserves, low cost, and low delithiation potential (typically 0.3V-0.5V). However, silicon undergoes massive volume changes during charge and discharge (expansion exceeding 320%), leading to material structural cracking and battery performance degradation, as well as poor conductivity. Germanium, like carbon and silicon, belongs to Group IIV A elements and, compared to other lithium-ion battery anode materials, has the following advantages: 1) Higher energy density; the theoretical specific capacity of germanium-based anode materials can reach as high as 1650 mAh·g. -1 1) It enables the battery to store more electrical energy in the same volume; 2) High conductivity, germanium has a narrow band gap, which is conducive to the battery to achieve more efficient energy transfer and storage in high power and high current devices; 3) Faster lithium-ion diffusion rate, which improves the battery's charge and discharge rate and efficiency; 4) Isotropic lithiation behavior reduces the structural damage of the negative electrode material during charge and discharge, thereby improving the battery's cycle life and stability.

[0004] However, using metallic germanium as a lithium anode material presents several problems: 1) Under fully lithiated conditions, germanium-based materials undergo significant volume expansion, leading to cracking and fragmentation of the active material. 2) During charge-discharge cycles, the aggregation of active particles increases the resistance to lithium-ion insertion / extraction, generating an additional SEI layer. In recent years, with the continuous development of battery anode material modification technology, researchers have conducted in-depth studies on the modification of germanium-based anode materials through nano-sizing and composite techniques. Among these, carbon and germanium composite nanomaterials can effectively alleviate the expansion effect of germanium-based anodes and improve the structural stability and electrochemical performance of germanium-based anode materials, demonstrating broad prospects for the practical application of germanium-based anode materials in next-generation lithium-ion batteries. Summary of the Invention

[0005] This invention proposes a hydrothermal method for preparing germanium-carbon nanocomposite anode materials for lithium-ion batteries.

[0006] To achieve the above objectives, the present invention provides a hydrothermal method for preparing germanium-carbon nanocomposite materials for lithium-ion batteries, the specific preparation steps of which include:

[0007] Step 1: Add germanium dioxide to sodium hydroxide solution and stir vigorously with a magnetic stirrer until germanium dioxide is completely dissolved to obtain a clear sodium germanate solution;

[0008] Step 2: Add 36%-38% concentrated hydrochloric acid dropwise to the clear sodium germanate solution, stir vigorously with a magnetic stirrer to form a white suspension, then add carbon nanotubes to the white suspension and continue stirring for 3-5 hours to obtain a mixed solution.

[0009] Step 3: Place the mixed solution into a hydrothermal reactor and carry out the hydrothermal reaction for 5-8 hours;

[0010] Step 4: The material prepared in step 3 is repeatedly filtered and washed with anhydrous ethanol and ultrapure water, and finally vacuum dried to obtain germanium-carbon nanocomposite material.

[0011] Preferably, in step 1, the amount of germanium dioxide added is 0.8g-1.2g; the amount of sodium hydroxide solution added is 12-18mL, and the concentration is 1.5M.

[0012] Preferably, in step 1, the stirring temperature is set to 20-40℃, and the stirring is carried out continuously at a speed of 500-1000 rpm for 0.5-1h.

[0013] Preferably, the concentrated hydrochloric acid is added dropwise at a rate of 10-20 drops / minute in step 2.

[0014] Preferably, in step 2, the temperature for vigorous stirring is set to 20-30℃, and the stirring is continued at a speed of 500-1000 rpm for 15-30 minutes.

[0015] Preferably, the amount of carbon nanotubes added is 0.5g.

[0016] Preferably, in step 2, the stirring temperature is set to 20-30℃ and the speed is 500-800rpm.

[0017] Preferably, the hydrothermal reaction temperature in step 3 is 150°C.

[0018] Preferably, the drying temperature in step 4 is set to 80-100℃ and the time is 6-10h.

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

[0020] This invention uses germanium dioxide and carbon nanotubes as raw materials. Germanium dioxide reacts sequentially with sodium hydroxide and carbon nanotubes to generate water-insoluble germanic acid. The germanic acid is then reacted with carbon nanotubes in a hydrothermal reactor to produce a nanostructured germanium-carbon composite material. This invention does not use any binders or catalysts in its preparation process, is simple in steps, low in cost, and the resulting composite material exhibits stable performance, can be stored for a long time in a dry environment, and produces lithium-ion batteries with high energy density and good cycle stability, providing strong support for the commercial application of germanium-based anode materials. Attached Figure Description

[0021] Figure 1 This is a SEM image of the germanium-carbon composite material of Example 1 of the present invention;

[0022] Figure 2 This is a constant current charge-discharge diagram of the electrode material prepared in Example 1 of this invention;

[0023] Figure 3 Long-cycle diagram of the electrode material prepared in Example 1 of this invention;

[0024] Figure 4 Rate performance diagram of the electrode material prepared in Example 1 of this invention; Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The present invention discloses a hydrothermal method for preparing germanium-carbon nanocomposite materials for lithium-ion batteries, the specific preparation steps of which include:

[0027] Step 1: Add germanium dioxide to sodium hydroxide solution and stir vigorously with a magnetic stirrer until germanium dioxide is completely dissolved to obtain a clear sodium germanate solution;

[0028] Step 2: Add 36%-38% concentrated hydrochloric acid dropwise to the clear sodium germanate solution, stir vigorously with a magnetic stirrer to form a white suspension, then add carbon nanotubes to the white suspension and continue stirring for 3-5 hours to obtain a mixed solution.

[0029] Step 3: Place the mixed solution into a hydrothermal reactor and carry out the hydrothermal reaction for 5-8 hours;

[0030] Step 4: The material prepared in step 3 is repeatedly filtered and washed with anhydrous ethanol and ultrapure water, and finally vacuum dried to obtain germanium-carbon nanocomposite material.

[0031] In step 1, the amount of germanium dioxide added is 0.8g-1.2g; the amount of sodium hydroxide solution added is 12-18mL, and the concentration is 1.5M.

[0032] In step 1, the stirring temperature is set to 20-40℃, and the stirring is carried out continuously at a speed of 500-1000 rpm for 0.5-1h.

[0033] In step 2, the concentrated hydrochloric acid is added drop by drop at a rate of 10-20 drops / minute.

[0034] In step 2, the temperature for vigorous stirring is set to 20-30℃, and stirring is continued at a speed of 500-1000 rpm for 15-30 minutes.

[0035] The amount of carbon nanotubes added is 0.5g.

[0036] In step 2, the stirring temperature is set to 20-30℃ and the speed is 500-800 rpm.

[0037] The hydrothermal reaction temperature in step 3 is 150℃.

[0038] In step 4, the drying temperature is set to 80-100℃ and the time is 6-10h.

[0039] Example 1

[0040] A hydrothermal method for preparing germanium-carbon nanocomposites for lithium-ion batteries, the specific preparation steps of which include:

[0041] Step 1: Add 1.2g of germanium dioxide to 18mL of 1.5M sodium hydroxide solution, stir vigorously with a magnetic stirrer at 30℃ and 800rpm for 1h until the germanium dioxide is completely dissolved to obtain a clear sodium germanate solution.

[0042] Step 2: Add 37% concentrated hydrochloric acid dropwise to the clear sodium germanate solution at a rate of 15 drops / minute. Stir vigorously with a magnetic stirrer at 30°C and 600 rpm for 30 minutes to form a white suspension. Then add 0.5g of carbon nanotubes to the white suspension. Stir continuously at 30°C and 500 rpm for 4 hours to obtain a mixed solution.

[0043] Step 3: Place the mixed solution into a hydrothermal reactor and carry out a hydrothermal reaction at a temperature of 150℃ for 8 hours.

[0044] Step 4: The material prepared in step 3 is repeatedly filtered and washed with anhydrous ethanol and ultrapure water, and finally vacuum dried at a temperature of 100°C for 10 hours to obtain germanium-carbon nanocomposite material.

[0045] Example 2

[0046] The difference between this embodiment and Embodiment 1 is as follows:

[0047] The amount of germanium dioxide added was 1g, the amount of sodium hydroxide was 15mL, and the other conditions remained unchanged.

[0048] Example 3

[0049] The difference between this embodiment and Embodiment 1 is as follows:

[0050] The amount of germanium dioxide added was 0.8g, the amount of sodium hydroxide was 12mL, and the other conditions remained unchanged.

[0051] Comparative Example 1

[0052] Step 1: Add 0.4g of germanium dioxide to ultrapure water, then add 3ml of 1.5M sodium hydroxide solution, stir vigorously with a magnetic stirrer at 30℃ and 800rpm for 1 hour until the germanium dioxide is completely dissolved.

[0053] Step 2: Add 0.5g of carbon nanotubes to the mixed solution prepared in Step 1, stir vigorously with a magnetic stirrer at a temperature of 30℃ and a speed of 500rpm for 4 hours.

[0054] Step 3: Place the mixed solution prepared in step 2 into a hydrothermal reactor and react at 150°C for 8 hours;

[0055] Step 4: The material prepared in step 3 is repeatedly filtered and washed with anhydrous ethanol and ultrapure water, and finally vacuum dried at a temperature of 100°C for 10 hours to obtain germanium-carbon nanocomposite material.

[0056] The material has relatively large particles and uneven coating, yet its electrochemical capacity can reach 1000 mAh·g. -1 The above values ​​are not explicitly stated, but the degradation is rapid, quickly decreasing to 300 mAh·g after 70 weeks. -1 the following.

[0057] Application Example 1

[0058] Preparation of negative electrode sheet:

[0059] The material, carbon black and PVDF were mixed evenly in a mass ratio of 8:1:1 and coated onto copper foil (coating thickness of 200µm). After vacuum drying at 50℃ for 12h, the negative electrode sheet was cut.

[0060] The fabrication of lithium-ion batteries:

[0061] Using the aforementioned negative electrode as the test electrode and metallic lithium as the control electrode, a lithium-ion coin cell was installed in a glove box filled with argon gas, containing 1M of LiPF6 / EC:DMC:EMC (V:V:V=1:1:1) as the electrolyte.

[0062] A charge-discharge cycle test was conducted for 100 cycles, with a charge-discharge voltage range of 0.01~2V and a current density of 200mA·g. -1 The test temperature was room temperature; specific performance data are shown in Table 1.

[0063] Depend on Figure 1 The SEM images of the material show that the germanium-carbon composite material prepared in this invention has a relatively uniform distribution and shape. Even when magnified to 200KX, the shape and structure of the material can still be clearly seen. Figure 2 The constant current charge-discharge diagram of the electrode material shows that the lithium-ion germanium-carbon composite anode material prepared in this invention has a discharge specific capacity exceeding 2000 mAh / g in the first cycle and retains a discharge specific capacity of over 800 mAh / g after 100 charge-discharge cycles. Figure 3 As can be seen from the long-cycle graph of this electrode material, the coulombic efficiency of the lithium-ion germanium-carbon composite anode material prepared in this invention is above 95% from the 2nd to the 100th cycle, proving that the material has good stability as an anode for lithium-ion batteries.

[0064] Application Examples 2 and 3

[0065] The germanium-carbon nanocomposites from Examples 2 and 3 were fabricated into negative electrode sheets according to the method in Application Example 1, and assembled into lithium-ion coin cells; specific performance data are shown in Table 1.

[0066] Application Comparative Example 1

[0067] The difference between this comparative example and example 1 is that:

[0068] Charge-discharge cycle stability tests were conducted with a charge-discharge voltage range of 0.01~2V and a current density of 100mA·g. -1 200mA·g -1 500mA·g -1 1A·g -1 200mA·g -1 and 100mA·g -1 Below, the circuits were cycled 9 times, 8 times, 8 times, 8 times, 8 times, and 8 times respectively, with the test temperature at room temperature; for detailed performance data, please refer to [link to performance data]. Figure 4 .

[0069] Depend on Figure 4As can be seen from the rate performance graph of the electrode material, the germanium-carbon nanocomposite anode for lithium-ion batteries prepared in this invention achieves a rate performance of 100 mA·g. -1 200mA·g -1 500mA·g -1 and 1A·g -1 At current density, it provides 908 mAh·g -1 827mAh·g -1 798mAh·g -1 and 422mAh·g -1 The discharge capacity of the germanium-carbon nanocomposite anode for lithium-ion batteries prepared in this invention, after undergoing changes in current density, is [not specified] at 100 mA·g [not specified]. -1 At current density, the discharge capacity recovers to 612 mAh·g -1 .

[0070] Application Comparative Example 2

[0071] The difference between this comparative example and example 1 is that:

[0072] The material, carbon black, and PVDF were mixed evenly at a mass ratio of 8:1:1 and then coated onto copper foil (coating thickness of 150µm); specific performance data are shown in Table 1.

[0073] Application Comparative Example 3

[0074] The difference between this comparative example and example 1 is that:

[0075] The material, carbon black, and PVDF were mixed evenly at a mass ratio of 8:1:1 and then coated onto copper foil (coating thickness of 250µm); specific performance data are shown in Table 1.

[0076] Application Comparative Example 4

[0077] The difference between this comparative example and example 1 is that:

[0078] The electrolyte is a mixture of 1M LiTFSI / DMC:DOL (V:V=1:1); specific performance data are shown in Table 1.

[0079] Table 1 Performance data of lithium-ion button cells

[0080]

[0081] As shown in Table 1, compared with the comparative example, the germanium-carbon nanocomposite anode for lithium-ion batteries prepared in this invention has higher capacity and better cycle stability. After 100 charge-discharge cycles, it still has a coulombic efficiency of over 95%.

[0082] In summary, this invention employs a simple and low-cost method to prepare a germanium-carbon nanocomposite anode with high stability. The germanium-carbon nanocomposite anode of this invention effectively alleviates the expansion effect of germanium-based anode materials in lithium-ion batteries, thereby improving the capacity, conductivity, and cycle stability of lithium-ion batteries.

[0083] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing germanium-carbon nanocomposite material for lithium ion battery by hydrothermal method, characterized in that, The specific preparation steps include: Step 1: germanium dioxide is added into sodium hydroxide solution, and stirred intensively with a magnetic stirrer until the germanium dioxide is completely dissolved to obtain a clear sodium germanate solution; Step 2: 36%-38% concentrated hydrochloric acid is added dropwise into the clear sodium germanate solution, and stirred intensively with a magnetic stirrer to form a white suspension, then carbon nanotubes are added into the white suspension, and the stirring is continued for 3-5 hours to obtain a mixed solution; Step 3: the mixed solution is placed into a hydrothermal reactor for hydrothermal reaction for 5-8 hours; Step 4: the material prepared in Step 3 is repeatedly filtered and washed with anhydrous ethanol and ultrapure water, and finally vacuum dried to obtain a germanium-carbon nanocomposite material.

2. The method for preparing the Ge / C nanocomposite material for lithium ion battery by hydrothermal method according to claim 1, characterized in that: In Step 1, the addition amount of germanium dioxide is 0.8-1.2 g, and the addition amount of sodium hydroxide solution is 12-18 mL with a concentration of 1.5 M.

3. The method for preparing the Ge / C nanocomposite material for lithium ion battery by hydrothermal method according to claim 1, characterized in that: In Step 1, the stirring temperature is set to 20-40℃, and the stirring is continued for 0.5-1 hour at a speed of 500-1000 rpm.

4. The method for preparing the Ge / C nanocomposite material for lithium ion battery by hydrothermal method according to claim 1, characterized in that: In Step 2, the speed of adding concentrated hydrochloric acid dropwise is set to 10-20 drops per minute.

5. The method for preparing the Ge / C nanocomposite material for lithium ion battery by hydrothermal method according to claim 1, characterized in that: In Step 2, the temperature for intensive stirring is set to 20-30℃, and the stirring is continued for 15-30 minutes at a speed of 500-1000 rpm.

6. The method for preparing the Ge / C nanocomposite for lithium-ion batteries by hydrothermal method according to claim 1, characterized in that: The addition amount of carbon nanotubes is 0.5 g.

7. The method for preparing the Ge / C nanocomposite for lithium-ion batteries by hydrothermal method according to claim 1, characterized in that: In Step 2, the stirring temperature is set to 20-30℃, and the stirring speed is 500-800 rpm.

8. The method for preparing the Ge / C nanocomposite for lithium-ion batteries by hydrothermal method according to claim 1, characterized in that: In Step 3, the hydrothermal reaction temperature is 150℃.

9. The method for preparing the Ge / C nanocomposite material for lithium ion battery by hydrothermal method according to claim 1, characterized in that: In Step 4, the drying temperature is set to 80-100℃, and the drying time is 6-10 hours.

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