A high-performance composite negative electrode material based on bulk silicon nanocrystals and preparation and application thereof

Abstract

The application relates to a high-performance composite negative electrode material based on a bulk silicon nanocrystal and a preparation and application thereof, and the preparation method of the negative electrode material comprises the following steps: (1) weighing silicon monoxide powder, a lithium source additive and a heat conduction network material, grinding and mixing to obtain a precursor mixture; (2) placing the precursor mixture on a carrier, carrying out a high-temperature disproportionation reaction, and cooling to room temperature to obtain modified silicon monoxide composite powder, namely a target product. Compared with the prior art, the application can effectively relieve mechanical stress caused by volume expansion of the nanocrystal in a cycle process, avoid particle rupture, and significantly improve the cycle stability of the material and the like.

Description

Technical Field

[0001] This invention belongs to the field of silicon-based anode material technology, and relates to a high-performance composite anode material based on bulk silicon nanocrystals and its preparation and application. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, wearable electronic devices, and various mobile power devices, people's pursuit of their performance is no longer limited to high energy density. In today's fast-paced and efficient work and life environment, the ability to work normally and stably increase energy under high-rate fast charging and discharging conditions is the future trend of the next generation of lithium-ion batteries.

[0003] As a crucial component of batteries, the anode material's inherent specific capacity and structural stability directly determine the electrochemical performance of the entire battery system. While silicon-based anodes offer high specific capacity, their significant volume changes leading to poor cycle performance are a major challenge hindering their commercialization. Silicon suboxide, with its unique microstructure of randomly mixed nanoscale Si and SiO2 phases, can improve the cycle performance of silicon-based anodes. Currently, various stress-dissipation strategies have been employed to buffer volume expansion in silicon suboxide materials, such as nanostructure design, surface coating, and the development of efficient binders. However, nanostructure production is costly and energy-intensive (e.g., CN109244386A), surface coating and chemical etching processes are complex, uncontrollable, and energy-intensive (e.g., CN108987732A), while optimized binders are expensive and environmentally costly (e.g., CN116759581B). Therefore, efficient, controllable, and cost-effective methods for modifying silicon suboxide anodes are still needed. Summary of the Invention

[0004] The purpose of this invention is to provide a high-performance composite anode material based on bulk silicon nanocrystals, its preparation, and its application. This material can obtain silicon nanocrystals with small size and superior crystallinity while maintaining their active state, thereby effectively alleviating the mechanical stress caused by volume expansion of the nanocrystals during cycling, preventing particle breakage, and significantly improving the cycling stability of the material. Furthermore, this invention significantly improves Joule heat transfer efficiency by introducing a thermally conductive network material, further optimizing the energy utilization rate of the rapid heating and cooling heat treatment process.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing a high-performance composite anode material based on bulk silicon nanocrystals, comprising the following steps:

[0007] (1) Weigh out silicon suboxide powder, lithium source additive and thermally conductive network material, grind and mix them to obtain precursor mixture;

[0008] (2) The precursor mixture is placed on a carrier and subjected to a high-temperature disproportionation reaction in an inert atmosphere. After cooling to room temperature, modified silica-suboxide composite powder is obtained, which is the target product.

[0009] Furthermore, the lithium source additive is selected from one or more of LiOH·H2O, LiH, LiAlH4, and LiBH4. LiOH·H2O is preferred because it is stable at room temperature and has a high safety factor.

[0010] Furthermore, the thermally conductive network material is one or more of carbon nanotubes, boron nitride, diamond, or silicon carbide. Carbon nanotubes are preferred, as CNTs can uniformly disperse the precursor, overcoming the disadvantage of uneven heat transfer during thermal shock treatment; in addition, the interconnected filler network in CNTs provides more heat transfer channels, significantly improving Joule heat transfer efficiency.

[0011] Furthermore, the mass ratio of silicon suboxide powder, lithium source additive and thermal network material is (10-40):1:(0.05-2), preferably (15-35):1:(0.2-1).

[0012] Furthermore, the silica suboxide particles have a particle size of 1–20 μm, more preferably 5 μm.

[0013] Furthermore, the grinding and mixing time is 5–30 minutes. More preferably, the grinding time is 10 minutes. The solid powder should be ground until additive particles are barely visible to the naked eye.

[0014] Furthermore, the carrier is either a graphite sheet or carbon paper.

[0015] Furthermore, the heating method for the high-temperature disproportionation reaction is one or more of the following: laser-induced heating, magnetic induction heating, plasma heating, Joule thermal shock, and microwave heating.

[0016] Furthermore, when the heating method is microwave heating, the power of microwave heating is 900-1800W, and the heating time is 5s-3min;

[0017] When the heating method is Joule thermal shock, the number of Joule thermal shock treatments is 1 to 10, the duration of each treatment is 0.05 to 5 seconds, the temperature is 700 to 1800°C, and the time interval between two adjacent heating treatments is about 5 seconds.

[0018] Furthermore, the high-temperature disproportionation reaction is carried out in a vacuum environment.

[0019] In a second aspect, the present invention provides a high-performance composite anode material based on bulk silicon nanocrystals, which is prepared by the preparation method described above.

[0020] In a third aspect, the present invention provides an application of a high-performance composite anode material based on bulk silicon nanocrystals in the anode of lithium-ion batteries.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) This invention innovatively introduces materials such as lithium hydroxide and carbon nanotubes as disproportionation initiators. Lithium salts, including lithium hydroxide, can synergistically promote the formation of disproportionated silicon nanoparticles through thermal shock and increase the crystallinity of the generated silicon nanoparticles, thereby maximizing capacity. Materials such as carbon nanotubes act as both thermally and electronically conductive networks, improving heat transfer efficiency and mitigating volume expansion to some extent. This helps maintain the structural stability of the silicon suboxide anode, enabling stable long-cycle operation.

[0023] 2) The equipment for preparing silicon suboxide in this invention can use heating methods such as Joule thermal shock devices, which can precisely control and utilize the thermal reaction in both time and space dimensions. It is a high-efficiency, low-energy-consumption, and high-throughput preparation technology.

[0024] 3) This invention can control the size and strength of crystallization by using different thermal shock temperatures to obtain small-sized silicon nanocrystals with optimal crystallinity in a non-deactivated state. This is crucial for alleviating particle expansion and preventing particle pulverization, thereby achieving a more stable cycle. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the generation of bulk nano-silicon crystals by heat treatment disproportionation according to the present invention.

[0026] Figure 2 The X-ray diffraction pattern of the modified silicon suboxide anode material provided in Example 1 of this invention.

[0027] Figure 3 XPS spectra of the modified silicon suboxide anode materials provided in Comparative Example 1 and Example 1 of this invention.

[0028] Figure 4 Transmission electron microscope (TEM) images (b, c, d) and selected area electron diffraction (SED) images (e) of Comparative Example 1(a), Example 1, and Comparative Example 1 are provided for the present invention.

[0029] Figure 5 Differential capacitance curves of the modified silicon suboxide anode materials provided in Examples 1, 2, 3 and 4 of this invention.

[0030] Figure 6This is a comparison chart of the cycle performance of the modified silicon suboxide anode materials provided in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0031] Figure 7 The graph shows a comparison of the cycle performance of the modified silicon suboxide anode materials provided in Examples 1, 2, 3, 4 and Comparative Example 1 of this invention.

[0032] Figure 8 This is a comparison chart of the rate performance of the modified silicon suboxide anode materials provided in Example 1 and Comparative Examples 1 and 2 of the present invention.

[0033] Figure 9 This is a comparison chart of the cycle performance of the modified silicon suboxide anode materials provided in Examples 10, 1, and 3 of the present invention.

[0034] Figure 10 This is a comparison chart of the cycle performance of the modified silicon suboxide anode materials provided in Example 1 and Comparative Example 4 of the present invention.

[0035] Figure 11 This is a comparison chart of the cycle performance of the modified silicon suboxide anode materials provided in Example 1 and Comparative Example 5 of the present invention. Detailed Implementation

[0036] This invention discloses a modification and preparation method for a silicon suboxide anode material. The main synergistic precursors of this material include lithium hydroxide and carbon nanotubes. By optimizing the Joule thermal shock temperature, time, and frequency, the optimal heat treatment conditions were discovered to obtain controllable formation of highly crystalline, small-sized disproportionated silicon nanocrystals.

[0037] 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.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available; for example, carbon nanotubes were purchased from Shenzhen Defang Nanotechnology Co., Ltd., CN-10302.

[0039] Example 1:

[0040] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0041] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0042] S2. Place the precursor on the carrier carbon paper of the Joule thermal shock apparatus and connect it to the positive and negative electrodes respectively through wires. Vacuum treatment for 10 minutes, turn on the power supply in the Joule thermal treatment apparatus, set the current to 200A and the voltage to 40V, and perform high-temperature thermal shock treatment on the precursor on the carbon paper. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, the time interval between two adjacent thermal shocks is 5s, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0043] The disproportionated silica suboxide prepared in this embodiment was subjected to XRD analysis, and the detection chromatogram is shown in the figure. Figure 1 The XRD pattern of Example 1 shows the presence of a sharp Si peak, indicating that the disproportionation reaction was successfully achieved in the preparation method of this example. Furthermore, TEM characterization of this example was performed, and the morphology pattern is shown in […]. Figure 2 The TEM image of Example 1 shows that silicon nanocrystals with good crystallinity and an average size of about 2 nm were obtained.

[0044] Example 2

[0045] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0046] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0047] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to Joule thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1100℃ to obtain disproportionated silicon suboxide.

[0048] Example 3

[0049] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0050] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0051] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to Joule thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the temperature of Joule thermal shock treatment is 1000℃, to obtain disproportionated silicon suboxide.

[0052] Example 4

[0053] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0054] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0055] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 2s, the number of thermal shock treatments is 2, and the Joule thermal shock treatment temperature is 1600℃, to obtain disproportionated silicon suboxide.

[0056] Example 5

[0057] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0058] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0059] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 5s, the number of thermal shock treatments is 1, and the Joule thermal shock treatment temperature is 750℃, to obtain disproportionated silicon suboxide.

[0060] Example 6

[0061] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0062] S1. Weigh 0.3g of silicon suboxide, 0.009g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:3:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0063] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0064] Example 7

[0065] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0066] S1. Weigh 0.3g of silicon suboxide, 0.012g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:4:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0067] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0068] Example 8

[0069] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0070] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.006g of carbon nanotubes according to the mass ratio of 100:5:2, place them in a mortar and grind for 10min to mix evenly to obtain the precursor;

[0071] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0072] Example 9

[0073] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0074] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium aluminum hydride and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0075] S2. The precursor is placed on the carrier carbon paper of the Joule thermal shock apparatus and connected to the positive and negative electrodes respectively through wires. The vacuum treatment is carried out for 10 minutes. The power supply in the Joule thermal treatment apparatus is turned on, the current is set to 200A and the voltage is set to 40V, and the precursor on the carbon paper is subjected to thermal shock treatment. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0076] Example 10

[0077] The preparation method of disproportionated silicon suboxide in this embodiment includes the following steps:

[0078] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium aluminum hydride and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0079] S2. The precursor is placed in a microwave heating device and microwaved in a microwave oven for 60 seconds at a power of 1000W to obtain disproportionated silicon suboxide.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Experimental Example 1 is that the original silicon suboxide material is not treated in any way.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Experimental Example 1 is that silicon suboxide was prepared without the addition of a disproportionating initiator. The preparation method includes the following steps:

[0084] S1. Weigh 0.3g of silicon suboxide;

[0085] S2. Place silicon suboxide on the carrier carbon paper of the thermal shock device and connect it to the positive and negative electrodes respectively through wires. Evacuate for 10 minutes, turn on the power supply in the Joule heat treatment device, set the current to 200A and the voltage to 40V, and perform high-temperature thermal shock treatment on the precursor on the carbon paper. The single thermal shock treatment time is 0.1s, the number of thermal shock treatments is 3, and the Joule thermal shock treatment temperature is 1200℃ to obtain disproportionated silicon suboxide.

[0086] Comparative Example 3

[0087] The difference between this comparative example and Example 1 is that disproportionated silicon suboxide is prepared using a conventional heating method. The preparation method includes the following steps:

[0088] S1. Weigh 0.3g of silicon suboxide, 0.015g of lithium hydroxide and 0.003g of carbon nanotubes in a mass ratio of 100:5:1, place them in a mortar and grind for 10 minutes to mix evenly to obtain the precursor.

[0089] S2. The precursor is sintered in a nitrogen atmosphere, heated to 950°C at 5°C / min, held for 5 hours, and then cooled to obtain disproportionated silicon suboxide.

[0090] Comparative Example 4

[0091] The difference between this comparative example and Experimental Example 1 is that lithium hydroxide was omitted.

[0092] Comparative Example 5:

[0093] The difference between this comparative example and Experimental Example 1 is that the addition of carbon nanotubes was omitted.

[0094] Effect verification test case

[0095] 1. Assessment of whether disproportionation reaction occurs

[0096] Test samples: Example 1, Comparative Example 1

[0097] Test methods: XRD, XPS, TEM

[0098] Test results:

[0099] (1) X-ray diffraction pattern (e.g.) Figure 2 As can be seen, diffraction peaks of silicon crystals appeared at 28°, 47° and 56° in Example 1, proving the presence of silicon grains and the occurrence of disproportionation reaction.

[0100] (2) XPS graphs (e.g.) Figure 3 As can be seen, there are no Si nanocrystals on the surface of Comparative Example 1. After Joule thermal shock, Si nanocrystals were generated on the surface of the Sample 1, proving that the disproportionation reaction occurred.

[0101] (3) The TEM image of Comparative Example 1 shows no obvious crystalline particles, revealing a typical amorphous structure of silicon suboxide, such as... Figure 4 As shown in (a); and from Figure 4As can be observed in (be), Example 1 exhibits the formation of distinct small and dense silicon grains, approximately 2 nm in size, distributed within the amorphous silicon suboxide matrix. Furthermore, selected area electron diffraction (SED) images clearly show diffraction rings of Si(111)(002)(311).

[0102] 2. Evaluation of the crystallinity of silicon nanocrystals

[0103] Test samples: Example 1, Example 2, Example 3, Example 4;

[0104] Test method: The strength of crystallinity of silicon nanocrystals is evaluated by the peak intensity ratio of the differential capacitance curve. Figure 5 The (dQ / dV) curves for the first charge of the anode between 0.01 and 2 V are shown, with distinct peaks corresponding to specific lithiation stages. The peak in region I (0.1–0.3 V) corresponds to Li 3.5 The transition from Si to Li₂Si, with the peak in region I (0.3–0.6 V) corresponding to Li 2.0 The transformation from Si to Si. Therefore, the ratio of the peak intensity at 0.45V to 0.28V can be used as an evaluation of the crystallinity of the generated nano-silicon.

[0105] Table 1 Assessment of Crystallinity

[0106]

[0107]

[0108] As shown in Table 1 above, Example 1 exhibits the highest peak intensity ratio and the strongest silicon domain crystallinity. (The treatment in Example 5 resulted in the formation of crystalline SiO2, which has lost its electrochemical activity.)

[0109] 3. Half-cell electrochemical performance testing

[0110] Test samples: Example 1, Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2;

[0111] Test method: Prepare the negative electrode and button cell as follows:

[0112] (1) Modified silicon suboxide anode material: Super P:PAA = 80:10:10 was used to prepare a slurry with distilled water as solvent, and the slurry was coated on copper foil with a thickness of 100 micrometers.

[0113] (2) The electrode obtained in (1) was transferred to an oven and dried at 60°C for 12 hours;

[0114] (3) Cut the dried electrode sheets into 12mm diameter round pieces using a cutting machine, and transfer the round pieces to a glove box for lithium battery assembly. The assembly sequence from bottom to top is: CR2025 negative electrode shell, lithium sheet, separator, commercial electrolyte (formulation 1MLiPF6 in EC:EMC:DMC=1:1:1 10%FEC), electrode sheet, gasket, spring sheet, and CR2025 positive electrode shell. Electrochemical tests were performed on the button battery in the voltage range of [0.01V, 1.5V] at a current density of 0.1C (1C=1300mA / g), with the battery discharged first and then charged.

[0115] Test results:

[0116] The disproportionated silicon suboxide prepared according to this invention, when used as the negative electrode material, exhibits excellent comprehensive electrochemical performance, such as... Figure 6 As shown, Example 1 exhibits an initial charge-discharge efficiency of 72%, a capacity retention of 98.4% after 100 cycles, and a stable cycle capacity of 1450 mAh / g. In contrast, the anode material in Comparative Example 1 has an initial charge-discharge efficiency of 70% and a capacity retention of only 70.1% after 100 cycles. The anode material in Comparative Example 2 has an initial charge-discharge efficiency of 71%, a capacity retention of 88.6% after 100 cycles, and a stable cycle capacity of 1300 mAh / g. Compared to the examples, the comparative examples show a greater initial irreversible capacity loss and poorer cycle performance.

[0117] The chemical performance of the half-cells in Examples 1, 2, 3, and 4 was compared. Figure 7 As shown, the material heat-treated in Example 1 exhibits the best electrochemical performance, with a capacity retention of 88.6% after 100 cycles. Therefore, the cycle performance of the battery is closely related to the crystallinity of Si domains. Smaller initial size and stronger crystalline phases help reduce pulverization, achieve greater capacity utilization, and thus obtain more stable cycling.

[0118] In addition, the rate performance of Example 1 (see Figure 8 The specific capacity of Example 1 was significantly improved when the rate was increased. The capacity loss of Example 1 when the rate was increased was much smaller than that of Comparative Example 1. The specific capacity at 1C was still about 1400mAh / g, while that of Comparative Example 1 was less than 800mAh / g. Moreover, after the rate was restored to 0.1C, the specific capacity of Example 1 was very close to that of the initial 0.1C. In stark contrast, Comparative Example 1 showed obvious capacity decay, indicating that Example 1 did not experience significant structural damage or loss of active materials under high-rate charge and discharge, which is better than Comparative Example 1. Figure 1 and Figure 4This indicates that the Joule thermal shock modified silicon suboxide anode material forms tiny silicon grains inside the amorphous silicon suboxide bulk phase by initiating a controllable disproportionation reaction, thereby suppressing volume expansion during the charge and discharge process. In addition, the addition of carbon nanotubes can encapsulate the active particles and maintain in-situ stabilization during the lithium insertion and extraction process, effectively preventing particle breakage and shedding, thus significantly improving cycle and rate performance.

[0119] Figure 9 The half-cell data of Examples 10, 1, and 3 are compared, with Example 1 showing higher specific capacity and more stable cycling. This demonstrates that different heat treatment methods have a significant impact on the performance of silicon suboxide materials.

[0120] 4. Synergistic crystallization effect of lithium source additives

[0121] Test samples: Example 1, Comparative Example 4

[0122] Test methods: The crystallinity of silicon nanocrystals before and after the addition of lithium source additives was evaluated by the peak intensity ratio of differential capacitance curves; the electrochemical performance was evaluated by assembling half-cells.

[0123] Table 2 Evaluation of Crystallinity Before and After Adding Lithium Source Additive

[0124] condition 0.45 / 0.28 peak intensity ratio (mean) No lithium salt additives added 0.68665 Add lithium salt additive 0.71464

[0125] As shown in Table 2 above, the peak intensity ratio of Example 1 is higher than that of Comparative Example 4, indicating stronger silicon domain crystallinity.

[0126] The half-cell chemical performance of Example 1 and Comparative Example 4 was compared. Figure 10 As shown, in Example 1, the lithium salt additive and thermal shock have a synergistic effect, inducing the disproportionation reaction, making it easier to generate nano-silicon, thereby giving it a greater capacity advantage and better cycle stability.

[0127] 5. The role of the conductive network in CNTs

[0128] Test samples: Example 1, Comparative Example 5

[0129] Test method: Electrochemical performance was evaluated by assembling half-cells.

[0130] Test results: such as Figure 11 As shown, Example 1 exhibits higher capacity utilization and cycle stability. After adding CNTs, the half-cell capacity retention increased from 88.6% after 100 cycles to 98.4%. This is because, after adding CNTs, the nanotubes can encapsulate the active particles, maintaining in-situ stabilization during the lithium insertion / extraction process and effectively preventing particle breakage and detachment.

[0131] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance composite anode material based on bulk silicon nanocrystals, characterized in that, Includes the following steps: (1) Weigh out silicon suboxide powder, lithium source additive and thermal network material, grind and mix them to obtain precursor mixture; (2) The precursor mixture is placed on a support and subjected to a high-temperature disproportionation reaction. After cooling to room temperature, modified silica-suboxide composite powder is obtained, which is the target product. The lithium source additive is selected from one or more of LiOH·H2O, LiH, LiAlH4 and LiBH4; The heat-conducting network material is one or more of carbon nanotubes, boron nitride, diamond, or silicon carbide; The mass ratio of silicon suboxide powder, lithium source additive, and thermally conductive network material is (10~40):1:(0.05~2). The high-temperature disproportionation reaction is carried out in a vacuum environment; The heating method for the high-temperature disproportionation reaction is microwave heating, with a power of 900~1800W and a heating time of 5s~3min; Alternatively, the heating method for the high-temperature disproportionation reaction may be Joule thermal shock, with the number of Joule thermal shock treatments being 1 to 10, the duration of each treatment being 0.05 to 5 seconds, and the temperature being 700 to 1800 °C.

2. The method for preparing a high-performance composite anode material based on bulk silicon nanocrystals according to claim 1, characterized in that, The carrier is either a graphite sheet or carbon paper.

3. A high-performance composite anode material based on bulk silicon nanocrystals, which is prepared according to the preparation method described in claim 1 or 2.

4. The application of the high-performance composite anode material based on bulk silicon nanocrystals as described in claim 3 in the anode of lithium-ion batteries.

Images