Composite modified silicon negative electrode material and preparation method and application thereof

Abstract

This invention belongs to the field of lithium-ion battery materials, and discloses a composite modified silicon anode material, its preparation method, and its application. The composite modified silicon anode material includes Sb. x SiM y Nano-silicon and graphite, M being any one or both of V and Zr, 2≤x≤3, 4≤y≤5, and Sb x SiM y The nano-silicon and the graphite are uniformly distributed. Sb is added to the silicon anode material. x SiM y This reduces the thermal conductivity of the silicon anode, minimizing localized overheating and thus improving battery durability and safety. Graphite provides fundamental conductivity, cycle stability, and flexible buffering. x SiM y This enhances volume expansion suppression, ion transport, and interface stability, and the combination of these two aspects significantly improves the overall performance of silicon anodes.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, and relates to an anode material, specifically a composite modified silicon anode material and its preparation method and application. Background Technology

[0002] Lithium-ion batteries are widely used in 3C (computers, communications, and consumer electronics), energy storage, and power applications. As a key material in lithium-ion batteries, graphite currently dominates the anode material market, holding nearly 90% of the market share. However, the actual specific capacity of graphite anodes is nearing its limit (the theoretical specific capacity of graphite is 372 mAh / g), failing to meet market demand for high-energy-density lithium batteries. Silicon has a mass specific capacity and volumetric specific capacity approximately an order of magnitude higher than graphite. With increasing market demands for high-energy lithium-ion batteries, the application prospects of silicon-based anodes are improving.

[0003] In existing technologies, lithium is typically combined with silicon to form a series of lithium-silicon alloys (LiSi). x Lithium storage in silicon (Si) is achieved through a typical alloying reaction, belonging to a hybrid "intercalation-alloying" mechanism, with alloying as the primary process. The core of this process involves lithium ions reacting chemically with silicon atoms in the negative electrode material to form lithium-silicon alloy phases with varying stoichiometric ratios. During charging, lithium ions are deintercalated from the positive electrode, migrate through the electrolyte to the negative electrode surface, gain electrons, and are reduced to lithium atoms, which then diffuse into the silicon lattice. During discharging, the lithium-silicon alloy decomposes, lithium ions deintercalate and return to the positive electrode, and silicon reverts to elemental silicon (or a silicon-rich phase), thus releasing energy.

[0004] Silicon anodes based on alloyed lithium storage mechanisms have drawbacks such as significant volume expansion and poor conductivity, which can cause silicon particles to break and increase battery polarization. Furthermore, nano-silicon anodes have high thermal conductivity, which can easily lead to local overheating of the battery and thus affect battery durability. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the present invention provides, firstly, a composite modified silicon anode material; secondly, a method for preparing the above-mentioned composite modified silicon anode material; and thirdly, a battery.

[0006] In a first aspect, the present invention provides a composite modified silicon anode material, comprising Sb x SiM y Nano-silicon and graphite, M being any one or both of V and Zr, 2≤x≤3, 4≤y≤5, and Sb x SiM y The nano-silicon and the graphite are uniformly distributed.

[0007] Preferably, the graphite, the nano-silicon, and the Sb x SiM y The mass ratio is 1:1~2:0.05~0.1.

[0008] Preferably, the graphite is any one or more of the following: block graphite, flake graphite, amorphous graphite, and microcrystalline graphite.

[0009] Preferably, the D50 of the nano-silicon is 50~100nm.

[0010] Preferably, the Sb x SiM y It can be either Sb2SiV4 or Sb3SiZr5.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned composite modified silicon anode material, comprising: ball milling Sb x SiM y The composite modified silicon anode material is obtained by combining nano-silicon and graphite.

[0012] Preferably, the ball milling time is 1~6 hours and the ball milling speed is 300~500 rpm.

[0013] Preferably, Sb is prepared x SiM y When Sb-containing chloride, silicon trichloride, and M-containing chloride are mixed and reacted under a protective atmosphere and high temperature and pressure, the resulting solid particles are Sb. x SiM y .

[0014] Preferably, the Sb-containing chloride is any one or both of SbCl3 and SbCl5.

[0015] Preferably, the M-containing chloride is any one or more of VCl3, VCl4, VCl5, ZrCl4, and ZrCl2.

[0016] Preferably, the molar ratio of Sb in the Sb-containing chloride, Si in silicon trichloride, and M in the M-containing chloride is 2~3∶1∶4~5.

[0017] Preferably, the reaction temperature is 750~1000℃, the reaction pressure is 1~3MPa, and the reaction time is 10~30h.

[0018] Preferably, the gas providing the protective atmosphere is nitrogen or argon.

[0019] Thirdly, the present invention provides a battery comprising the above-described composite modified silicon anode material or the composite modified silicon anode material prepared by the above-described preparation method.

[0020] Compared with the prior art, the present invention has the following significant advantages:

[0021] (1) Adding Sb to silicon anode material x SiM y This reduces the thermal conductivity of the silicon anode, minimizing localized overheating and thus improving battery durability and safety. Graphite provides fundamental conductivity, cycle stability, and flexible buffering. x SiM y This enhances volume expansion suppression, ion transport, and interface stability, and the combination of these two aspects significantly improves the overall performance of silicon anodes.

[0022] (2) This invention directly synthesizes the intermetallic compound Sb by a one-step sintering method. x SiM y Sb was prepared by solid-state mixing with nano-silicon and graphite. x SiM y The Si / C anode material has a simple modification method and good modification effect, providing ideas for the further practical application of silicon anodes. Attached Figure Description

[0023] Figure 1 The XRD pattern of the solid particles Sb2SiV4 obtained in step 1 of Example 1 is shown.

[0024] Figure 2 Cycle curves of batteries assembled from the negative electrode materials obtained in Examples 1-3 and Comparative Examples 1-2;

[0025] Figure 3 This is a SEM image of the silicon-based negative electrode sheet after 50 cycles in Example 1;

[0026] Figure 4 This is a SEM image of the silicon-based negative electrode sheet after 50 cycles in Comparative Example 1. Detailed Implementation

[0027] The present invention provides the following specific technical solutions.

[0028] In a first aspect, the present invention provides a composite modified silicon anode material, comprising Sb x SiM y Nano-silicon and graphite, M being any one or both of V and Zr, 2≤x≤3, 4≤y≤5, and Sb x SiM y The nano-silicon and the graphite are uniformly distributed.

[0029] The inventors discovered through research that, firstly, graphite has an extremely low volume expansion rate (approximately 10%), and possesses a layered structure and good flexibility, making it suitable as a matrix framework for silicon particles to disperse the volumetric stress of silicon during lithium intercalation. Sbx SiM y With high structural strength and a low coefficient of thermal expansion, graphite can form a rigid buffer layer around silicon particles, further limiting the volume expansion of silicon. The flexibility of graphite is similar to that of Sb. x SiM y The rigidity of the graphite is complementary, which buffers some stress through the deformation of the graphite and prevents excessive expansion through the support of the silicide, thus maintaining the integrity of the electrode structure and reducing pulverization and shedding during cycling.

[0030] Second, graphite possesses excellent electronic conductivity and a continuous layered structure, which can serve as the main pathway for electron conduction in electrodes, thus solving the problem of poor conductivity inherent in silicon; Sb x SiM y Graphite fills the interlayer spaces between graphite layers or silicon particles, connecting isolated silicon particles to the graphite network, eliminating conductive islands, and providing additional diffusion channels for lithium ions. Graphite constructs a macroscopic conductive pathway, enabling Sb... x SiM y By optimizing the conductivity of the micro-interface, the two are combined to form a macro-micro multi-level conductive network, which significantly reduces electrode resistance and improves charge transfer efficiency and rate performance.

[0031] Third, graphite has high thermal conductivity, which can accelerate heat dissipation inside the electrode and avoid localized overheating; Sb x SiM y With high melting point and thermal stability, Sb x SiM y Forming a continuous or semi-continuous thermally conductive network can enhance the structural stability of the electrode at high temperatures and reduce the risk of thermal runaway. (Graphite and Sb) x SiM y By jointly optimizing the thermal conductivity and heat resistance of the electrodes, the problem of local heat accumulation during charging and discharging is alleviated, thereby improving the battery's durability and safety.

[0032] Graphite provides fundamental electrical conductivity, cycle stability, and flexible cushioning, while Sb x SiM y This enhances volume expansion suppression, ion transport, and interface stability, and the combination of these two aspects significantly improves the overall performance of silicon anodes.

[0033] Preferably, the graphite, the nano-silicon, and the Sb x SiM y The mass ratio is 1:1~2:0.05~0.1.

[0034] Preferably, the graphite is any one or more of the following: block graphite, flake graphite, amorphous graphite, and microcrystalline graphite.

[0035] Preferably, the D50 of the nano-silicon is 50~100nm.

[0036] The inventors discovered through research that Sb x SiM y The effect of thermal conductivity on silicon anodes is the result of the combined effects of structure, interface, and dispersion state. The optimal ratios provided by the inventors can balance the distribution and interface state of the anode material, regulate the morphology, content, and synergistic effects with other components of the composite phase, and leverage the combined properties of graphite, nano-silicon, and Sb. x SiM y The advantages of this technology can be further optimized to improve thermal conductivity and electrochemical performance.

[0037] Preferably, the Sb x SiM y It can be either Sb2SiV4 or Sb3SiZr5.

[0038] Secondly, the present invention provides a method for preparing the above-mentioned composite modified silicon anode material, comprising: ball milling Sb x SiM y The composite modified silicon anode material is obtained by combining nano-silicon and graphite.

[0039] Preferably, the ball milling time is 1~6 hours and the ball milling speed is 300~500 rpm.

[0040] Preferably, Sb is prepared x SiM y The method includes: mixing Sb-containing chlorides, silicon trichloride, and M-containing chlorides, and reacting them under a protective atmosphere and high temperature and pressure to obtain solid particles, which are Sb. x SiM y .

[0041] Preferably, the Sb-containing chloride is any one or two of SbCl3 and SbCl5; the M-containing chloride is any one or more of VCl3, VCl4, VCl5, ZrCl4, and ZrCl2.

[0042] Preferably, the molar ratio of Sb in the Sb-containing chloride, Si in silicon trichloride, and M in the M-containing chloride is 2~3∶1∶4~5.

[0043] Preferably, the reaction temperature is 750~1000℃, the reaction pressure is 1~3MPa, and the reaction time is 10~30h.

[0044] Preferably, the gas providing the protective atmosphere is nitrogen or argon.

[0045] Thirdly, the present invention provides a battery comprising the above-described composite modified silicon anode material or the composite modified silicon anode material prepared by the above-described preparation method.

[0046] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0049] Example 1

[0050] A method for preparing a composite modified silicon anode material includes the following steps:

[0051] Step 1: Mix 1 mol of SbCl3, 0.5 mol of silicon trichloride, and 2 mol of VCl3, and sinter at 880°C for 20 h under a nitrogen atmosphere. During sintering, the pressure in the reactor is 2 MPa. The resulting solid particles are Sb2SiV4.

[0052] Step 2: Take 0.8g of Sb2SiV4 obtained in Step 1, 15g of nano-silicon material (D50 is 80nm) and 10g of flake graphite and ball mill them together for 4h at a ball milling speed of 400rpm to obtain the composite modified silicon anode material.

[0053] Figure 1 The XRD pattern of the solid particles Sb₂SiV₄ obtained in step 1 of Example 1 is shown below. Figure 1 It can be seen that the preparation method provided by the present invention successfully prepared Sb2SiV4 material.

[0054] Comparative Example 1

[0055] A method for preparing a composite modified silicon anode material includes: taking 15g of nano-silicon material (D50 of 80nm) and 10g of flake graphite and ball milling them together for 4h at a ball milling speed of 400rpm, thereby obtaining the composite modified silicon anode material.

[0056] Comparative Example 2

[0057] A method for preparing a composite modified silicon anode material includes: taking 1.2g of Sb2SiV4 obtained in step 1 of Example 1 and 15g of nano-silicon material (D50 is 80nm) and ball milling them together for 4h at a ball milling speed of 400rpm, thereby obtaining the composite modified silicon anode material.

[0058] Example 2

[0059] A method for preparing a composite modified silicon anode material includes the following steps:

[0060] Step 1: Mix 1.5 mol of SbCl3, 0.5 mol of silicon trichloride, and 2.5 mol of ZrCl4, and sinter at 750°C for 30 h under a nitrogen atmosphere. During sintering, the pressure in the reactor is 1 MPa. The resulting solid particles are Sb3SiZr5.

[0061] Step 2: Take 0.5g of Sb3SiZr5 obtained in Step 1, 10g of nano-silicon material (D50 is 50nm) and 10g of block graphite and ball mill them together for 1h at a speed of 500rpm to obtain the composite modified silicon anode material.

[0062] Example 3

[0063] A method for preparing a composite modified silicon anode material includes the following steps:

[0064] Step 1: Mix 1 mol of SbCl5, 0.5 mol of silicon trichloride, and 2 mol of VCl5, and sinter at 1000℃ for 10 h under a nitrogen atmosphere. During sintering, the pressure in the reactor is 3 MPa. The resulting solid particles are Sb2SiV4.

[0065] Step 2: Take 2g of Sb2SiV4 obtained in Step 1, 20g of nano-silicon material (D50 is 80nm) and 20g of artificial graphite and ball mill them together for 4h at a speed of 300rpm to obtain the composite modified silicon anode material.

[0066] The negative electrode materials obtained in Examples 1-3 and Comparative Examples 1-2 were assembled into batteries in the following manner:

[0067] Using the silicon anode material powder obtained in Examples 1-3 and Comparative Example 1 as the active material, it was mixed with the conductive agent acetylene black (AB) and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1. N-methylpyrrolidone (NMP) was used as the solvent, and the mixture was stirred at 800 r / min for 2 hours in a small beaker to obtain a slurry. The slurry was coated onto a current collector aluminum foil using an automatic coating machine, laid flat on tempered glass, and dried in a vacuum drying oven at 85°C for 4 hours. After die-cutting to prepare electrode sheets with a diameter of 14 mm, the sheets were dried in a vacuum drying oven at 105°C for 4 hours. The sheets were then placed in a glove box filled with argon atmosphere for 4 hours to reduce the moisture adsorbed during transfer. Finally, the sheets were assembled into CR2032 coin cells in the glove box. The separator used in this battery was a porous polyethylene membrane of model Celgard 2300 with a diameter of 18 mm, and a lithium sheet was used as the counter electrode.

[0068] After the battery assembly was completed and aged for 12 hours, a 2C rate charge-discharge test was then conducted within a voltage range of 0.1~3.0V. Figure 2 Cycle curves of batteries assembled from the negative electrode materials obtained in Examples 1-3 and Comparative Examples 1-2.

[0069] Depend on Figure 2 As can be seen from the comparison between Example 1 and Comparative Example 1, if only graphite is added to the negative electrode material, the battery's cycle performance degradation is relatively high. Comparing Example 1 and Comparative Example 2, if only Sb₂SiV₄ is added to the negative electrode material, the battery's conductivity decreases significantly, and the corresponding electrochemical performance is also affected to some extent. In summary, the negative electrode material provided by this invention exhibits superior cycle performance, and it can be predicted that batteries assembled using the negative electrode material provided by this invention will have a longer lifespan.

[0070] The electrical conductivity and thermal conductivity of batteries assembled from the negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested. The test data are shown in Table 1.

[0071] Table 1. Electrical and thermal conductivity of batteries assembled from the negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2.

[0072]

[0073] Based on Table 1 Figure 2 It can be seen that graphite materials and Sb x SiM y The synergistic effect improves the electrical and thermal conductivity of silicon-based anode materials. Sb x SiM y Forming a continuous or semi-continuous thermally conductive network can enhance the structural stability of the electrode at high temperatures and reduce the risk of thermal runaway. (Graphite and Sb) x SiM y This collaborative approach optimizes the thermal conductivity and heat resistance of the electrodes, mitigating localized heat buildup during charging and discharging, thereby improving battery durability and safety. Graphite provides the fundamental electrical and thermal conductivity, while Sb... x SiM y This enhances volume expansion suppression, ion transport, and interface stability, and the combination of these two factors significantly improves the overall performance of the silicon anode. In contrast, the silicon-based anode material in Comparative Example 2, which lacks graphite, exhibits poor electrical and thermal conductivity, but these are still greater than the theoretical values ​​for elemental silicon. This indicates that Sb... x SiM y Single modification has limited effect on electrical and thermal conductivity; it needs to be combined with graphite materials to achieve the most effective modification results.

[0074] Figure 3This is a SEM image of the silicon-based negative electrode sheet after 50 cycles in Example 1. Figure 3 As can be seen, the surface of the silicon negative electrode sheet after cycling is smooth and intact, with no obvious expansion or cracks.

[0075] Figure 4 The image shows a SEM image of the silicon-based negative electrode after 50 cycles in Comparative Example 1. Figure 4 As can be seen, obvious cracks appeared on the surface of the silicon anode sheet after cycling. This is because the silicon anode surface underwent volume expansion and deformation after cycling, resulting in local cracks.

[0076] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite modified silicon anode material, characterized in that, Including Sb x SiM y Nano-silicon and graphite, M being any one or both of V and Zr, 2≤x≤3, 4≤y≤5, and Sb x SiM y The nano-silicon and the graphite are uniformly distributed.

2. The composite modified silicon anode material as described in claim 1, characterized in that, The graphite, the nano-silicon, and the Sb x SiM y The mass ratio is 1:1~2:0.05~0.

1.

3. The composite modified silicon anode material as described in claim 1, characterized in that, The graphite is any one or more of the following: block graphite, flake graphite, amorphous graphite, and microcrystalline graphite.

4. The composite modified silicon anode material as described in claim 1, characterized in that, The D50 of the nano-silicon is 50~100nm.

5. The composite modified silicon anode material as described in claim 1, characterized in that, The Sb x SiM y It can be either Sb2SiV4 or Sb3SiZr5.

6. A method for preparing the composite modified silicon anode material according to any one of claims 1 to 5, characterized in that, include: Ball milling Sb x SiM y The composite modified silicon anode material is obtained by combining nano-silicon and graphite.

7. The method for preparing the composite modified silicon anode material as described in claim 6, characterized in that, The ball milling time is 1~6 hours, and the ball milling speed is 300~500 rpm.

8. The method for preparing the composite modified silicon anode material as described in claim 6, characterized in that, Preparation of Sb x SiM y When Sb-containing chloride, silicon trichloride, and M-containing chloride are mixed and reacted under a protective atmosphere and high temperature and pressure, the resulting solid particles are Sb. x SiM y .

9. The method for preparing the composite modified silicon anode material as described in claim 8, characterized in that, The Sb-containing chloride is any one or two of SbCl3 and SbCl5; the M-containing chloride is any one or more of VCl3, VCl4, VCl5, ZrCl4, and ZrCl2; the molar ratio of Sb in the Sb-containing chloride, Si in silicon trichloride, and M in the M-containing chloride is 2~3∶1∶4~5; the reaction temperature is 750~1000℃, the reaction pressure is 1~3MPa, and the reaction time is 10~30h.

10. A battery, characterized in that, The composite modified silicon anode material includes the composite modified silicon anode material according to any one of claims 1 to 5 or the composite modified silicon anode material prepared by the preparation method according to any one of claims 6 to 9.

Images