Lithium battery silicon-carbon negative electrode material and production process thereof

Abstract

The application relates to a lithium battery silicon-carbon negative electrode material and a production process thereof, and belongs to the field of lithium battery silicon-carbon negative electrode material production and processing. The material is composed of silicon-carbon particles, carbon nanotubes, a conductive agent, a modified PAA elastic binder and trace metal lithium. A buffer layer is formed by dry in-situ winding of the carbon nanotubes on the surface of the silicon-carbon particles. Si-N-C covalent bonds are formed between the carbon nanotubes and the silicon-carbon particles through laser induction. The silicon-carbon particles are provided with sieve type pores and loaded with metal lithium to realize in-situ prelithiation. The production process comprises the steps of dry winding, laser induction, pore preparation, in-situ prelithiation and mixing and pulping. The application synchronously solves the core problems of volume expansion, interface cracking and low initial efficiency of the existing silicon-carbon negative electrode material, improves the cycle stability and energy density of the battery, simplifies the process, adapts to mass production, reduces the production cost, and has good industrial application value.

Description

Technical Field

[0001] This invention relates to the field of lithium battery silicon-carbon anode material production and processing technology, specifically to a lithium battery silicon-carbon anode material and its production process. Background Technology

[0002] With the rapid development of the new energy industry, lithium batteries, with their advantages of being environmentally friendly, having low self-discharge rates, and having no memory effect, are widely used in new energy vehicles, energy storage systems, and portable electronic devices. As a core component of lithium batteries, the performance of the anode material directly determines the energy density, cycle life, and safety performance of the battery. Among these, silicon-carbon anode materials, due to their theoretical specific capacity being far higher than that of traditional graphite anodes, have become a current research hotspot and mainstream development direction for lithium battery anode materials. Currently, the production process of silicon-carbon anode materials for lithium batteries mainly includes core steps such as raw material mixing, composite modification, molding, and drying. Conventional processes often employ wet mixing methods, mixing silicon-carbon particles, conductive agents, binders, and solvents to form a slurry, which is then coated and dried to obtain the anode material.

[0003] However, silicon-carbon anode materials prepared using existing production processes still face numerous unresolved technical challenges in practical applications, severely hindering their industrialization and application effectiveness. The primary problem is the significant volume effect; silicon expands by 170%-360% during charge and discharge, and repeated volume expansion and contraction easily lead to electrode pulverization, active material shedding, and damage to the internal conductive network, resulting in rapid capacity decay. Secondly, poor interfacial stability; the weak interfacial bonding between silicon-carbon particles and conductive agents and binders causes repeated volume expansion and contraction, leading to SEI film rupture and regeneration, continuously consuming electrolyte and lithium sources, and significantly reducing battery cycle performance. Thirdly, low initial efficiency; the SEI film thickens during the first charge and discharge cycle, resulting in low coulombic efficiency of only 70-85%, accompanied by increased electrolyte consumption and higher production costs. Furthermore, silicon-carbon materials themselves have poor thermal stability, posing certain safety hazards. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the purpose of this invention is to provide a silicon-carbon anode material for lithium batteries and its production process, so as to at least partially solve the problems mentioned in the background art.

[0005] Therefore, the purpose of this invention is to provide a silicon-carbon anode material for lithium batteries and its production process, which simultaneously solves the problems of volume expansion, low initial efficiency, and interface cracking, thereby improving the overall performance of the battery.

[0006] To achieve the above objectives, this invention proposes a silicon-carbon anode material for lithium batteries, comprising silicon-carbon particles, carbon nanotubes, and in-situ pre-lithiated loaded metallic lithium; at least a portion of the surface of the silicon-carbon particles is in-situ wrapped with carbon nanotubes to form an elastic buffer layer; Si-NC covalent bonds are induced between the carbon nanotubes and the silicon-carbon particles; the silicon-carbon particles include an internal sieve-type pore structure.

[0007] Furthermore, the amount of carbon nanotubes used is 3-8% of the mass of silicon-carbon particles, and they are uniformly wound around the surface of silicon-carbon particles; the mass of carbon nanotubes wound around the surface of a single silicon-carbon particle is 3-8% of the mass of the single silicon-carbon particle itself; the number of continuous windings of a single carbon nanotube on the surface of a single silicon-carbon particle is 3-15, and adjacent carbon nanotubes overlap each other to form a continuous three-dimensional conductive network.

[0008] Furthermore, it also includes a conductive agent and a modified PAA elastic binder, wherein the conductive agent is either carbon black or graphene, and the amount used is 2-5% of the mass of the silicon carbon particles; the amount of the modified PAA elastic binder is 5-10% of the mass of the silicon carbon particles.

[0009] Furthermore, the amount of metallic lithium used in the in-situ pre-lithiation loading is 0.5-2% of the mass of the silicon-carbon particles, and it is uniformly loaded inside the sieve-type channels.

[0010] Furthermore, the sieve-type pore structure consists of nanopore cavities and sub-nanometer pore openings.

[0011] Another object of the present invention is to provide a manufacturing process for silicon-carbon anode materials for lithium batteries, comprising the following steps: (1) Carbon nanotubes are wound in situ onto the surface of silicon carbon particles using a dry process to form an elastic buffer layer; (2) Constructing Si-NC covalent bonds between carbon nanotubes and silicon-carbon particles by laser guidance; (3) A sieve-type channel structure is prepared inside silicon-carbon particles using an etchant, and a trace amount of metallic lithium is loaded in the channel to achieve in-situ pre-lithiation; (4) The treated silicon carbon particles are mixed with conductive agent and modified PAA elastic binder to form a slurry, which is then coated and dried to obtain the silicon carbon anode material for lithium batteries.

[0012] Furthermore, in step (1), the dry process adopts a combination of mechanical stirring and ultrasonic dispersion. The mechanical stirring speed is 800-1500 r / min, the stirring time is 20-40 min, the ultrasonic dispersion power is 300-500 W, and the ultrasonic time is 10-20 min.

[0013] Furthermore, in step (2), the laser power of the laser-guided processing is 50-150W, the laser irradiation time is 5-15s, and the irradiation distance is 5-10cm.

[0014] Further, in step (3), the etchant is a dilute hydrofluoric acid solution, the etching temperature is 25-40℃, the etching time is 15-30min, the in-situ pre-lithiation temperature is 60-80℃, and the holding time is 30-60min.

[0015] Further, in step (4), the amount of deionized water added during mixing is 40-60% of the total mass of silicon-carbon composite particles. The slurry is coated on the copper foil current collector with a coating thickness of 100-200μm. After coating, it is placed in a vacuum drying oven for drying at a temperature of 80-120℃ for 2-4 hours.

[0016] Beneficial effects: 1. The elastic buffer layer formed by carbon nanotubes can directly buffer the volume expansion stress during silicon charging and discharging. Combined with the expansion space reserved by the sieve-type pore structure, the volume expansion is significantly suppressed under the dual effect. The precise winding of individual silicon carbon particles can provide a continuous and uniform radial elastic binding force when the silicon carbon particles expand / contract during charging and discharging. Combined with the three-dimensional continuous conductive network formed by the overlapping of adjacent carbon nanotubes, the full-dimensional conductive coverage of the silicon carbon particle surface is achieved. 2. Laser-induced Si-NC covalent bonds can enhance the interfacial bonding force between carbon nanotubes and silicon-carbon particles, prevent interfacial delamination, reduce the rupture and regeneration of the SEI film, reduce the consumption of electrolyte and lithium source, and improve battery cycle performance. 3. The trace amount of metallic lithium loaded in the sieve-type channel achieves in-situ pre-lithiation, which can compensate for the lithium source consumed by the formation of the SEI film during the first charge and discharge process, effectively improve the coulombic efficiency of the first cycle, and at the same time reduce electrolyte consumption and reduce production costs. 4. The dry process replaces the traditional wet process, eliminating the need for complex solvent treatment, simplifying the production process, reducing environmental pressure, and ensuring seamless coordination between each step to meet the needs of industrial mass production. At the same time, the modified PAA elastic binder can further enhance the electrode bonding performance and improve the overall stability and safety of the battery.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a TEM image of the sieve-type channel structure in an embodiment of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The following description, in conjunction with the accompanying drawings, illustrates the lithium-ion battery silicon-carbon anode material and its manufacturing process according to embodiments of the present invention.

[0021] Example 1 A silicon-carbon anode material for lithium batteries and its production process, with specific raw material amounts (by weight): 100 parts silicon-carbon particles, 5 parts carbon nanotubes, 3 parts conductive agent (carbon black), 7 parts modified PAA elastic binder, 1 part metallic lithium, and 50 parts deionized water.

[0022] The specific production steps are as follows: S1. Dry in-situ winding: 100 parts of silicon carbon particles and 5 parts of carbon nanotubes are added to a dry mixer. The mixture is stirred mechanically and dispersed ultrasonically. The mechanical stirring speed is 1200 r / min and the stirring time is 30 min. The ultrasonic dispersion power is 400 W and the ultrasonic time is 15 min. This allows the carbon nanotubes to be uniformly wound in-situ on the surface of the silicon carbon particles to form a complete elastic buffer layer. S2. Laser-induced covalent bonding: The above mixed particles are laid flat and treated with laser guidance. The laser power is 100W, the laser irradiation time is 10s, the irradiation distance is 8cm, and the laser is moved at a uniform speed (moving speed 5mm / s) to ensure that each particle is irradiated. This stably constructs Si-NC covalent bonds between carbon nanotubes and silicon carbon particles, enhances the interfacial bonding force, and prevents interfacial delamination. S3. Preparation of sieve-type channels: The particles treated above are chemically etched using a dilute hydrofluoric acid solution (concentration 5%) as the etchant, at an etching temperature of 30℃ and an etching time of 20min to prepare a sieve-type channel structure composed of nanopores and sub-nanopores. The pore diameter is 20nm and the pore volume accounts for 22% of the total volume of the silicon-carbon particles, leaving sufficient space for volume expansion during silicon charging and discharging, while controlling the lithium-ion transport rate. S4. In-situ pre-lithiation: The etched particles are placed in a vacuum furnace, 1 part of metallic lithium is added, the temperature is raised to 70°C, the holding time is 45 min, and the vacuum degree is 0.08 MPa, so that the metallic lithium is uniformly loaded inside the sieve-type channel to complete the in-situ pre-lithiation treatment and compensate for the consumption of lithium source during the first charge and discharge process. S5. Mixing and slurry preparation: Add the treated silicon-carbon composite particles, 3 parts carbon black, 7 parts modified PAA elastic binder to a mixer, add 50 parts deionized water, stir at 1500 r / min for 45 min to prepare a viscous slurry (viscosity 5000 mPa·s); coat the slurry evenly onto a copper foil current collector with a coating thickness of 150 μm, and then place it in a vacuum drying oven to dry at 100℃ for 3 h. After cooling to room temperature, cut it into the required size to obtain the silicon-carbon anode material for lithium batteries.

[0023] Example 2 A silicon-carbon anode material for lithium batteries and its production process are basically the same as those in Example 1 in terms of raw material dosage and production steps. The difference is that the laser-induced covalent bonding treatment in step 2 is omitted, and the carbon nanotubes and silicon-carbon particles are only bonded by dry winding without constructing Si-NC covalent bonds. The other raw material dosages and production conditions (stirring speed, etching parameters, pre-lithiation parameters, etc.) are the same as those in Example 1.

[0024] Example 3 A silicon-carbon anode material for lithium batteries and its production process are basically the same as those in Example 1 in terms of raw material usage and production steps. The difference is that the amount of carbon nanotubes used is 2 parts, which causes the carbon nanotubes to be unable to completely wrap around the silicon-carbon particles and not form a complete elastic buffer layer. The remaining raw material usage and production conditions are the same as those in Example 1.

[0025] Example 4 A silicon-carbon anode material for lithium batteries and its production process are basically the same as those in Example 1 in terms of raw material usage and production steps. The difference is that in the preparation of the sieve-type channel, the etching time is 10 min, the etching temperature is 20℃, the sieve-type channel diameter is 8 nm, and the pore volume accounts for 10% of the total volume of silicon-carbon particles, which cannot reserve sufficient space for silicon volume expansion. The remaining raw material usage and production conditions are the same as those in Example 1.

[0026] Example 5 A silicon-carbon anode material for lithium batteries and its production process are basically the same as those in Example 1 in terms of raw material usage and production steps. The difference is that the in-situ pre-lithiation treatment in step 4 is omitted, and the sieved channels are not loaded with metallic lithium. The remaining raw material usage and production conditions are the same as those in Example 1.

[0027] Comparative Example 1 A conventional lithium-ion battery silicon-carbon anode material and its production process, with the following specific raw material amounts (by mass): 100 parts silicon-carbon particles, 3 parts conductive agent (carbon black), 7 parts ordinary styrene-butadiene rubber binder, and 50 parts N-methylpyrrolidone (solvent).

[0028] Specific production steps: Using a traditional wet process, the above raw materials are added to a mixer at a stirring speed of 1500 r / min for 45 min to form a slurry. The slurry is then coated onto a copper foil current collector to a thickness of 150 μm, dried at room temperature and in a ventilated environment for 4 h, and cut into the required size to obtain the silicon-carbon anode material for lithium batteries. Carbon nanotube winding, laser-induced covalent bonding, sieved pores, and in-situ pre-lithiation treatment are not used; all other testing conditions are the same as in Example 1.

[0029] Comparative Example 2 A silicon-carbon anode material for lithium batteries and its production process are disclosed. The specific raw material dosage is the same as in Example 1. The difference in production steps is that only dry in-situ winding (5 parts carbon nanotubes) and mixing slurry steps are used. Laser-induced covalent bonding, sieve-type channel preparation and in-situ pre-lithiation treatment are not performed. Modified PAA elastic binder is used as the binder. The remaining production conditions are the same as in Example 1.

[0030] Performance test results: The lithium battery silicon-carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The test indicators included volume expansion rate (maximum volume expansion rate during charge and discharge), first-cycle coulombic efficiency, specific capacity (specific capacity during the first discharge), and capacity retention rate after 100 cycles. The test results are shown in the table below (all data are averages of 3 tests): Table 1:

[0031] Results Analysis: As shown in Table 1, the test results and implementation status of the core improvements demonstrate that this invention, through dry winding, laser induction, pore preparation, in-situ pre-lithiation, and mixed slurry preparation, can simultaneously solve the core problems of volume expansion, interface cracking, and low initial efficiency of silicon-carbon anode materials. Each improvement works synergistically and is indispensable. A detailed analysis follows: 1. Volume Expansion Issue: In Example 1, the complete buffer layer formed by carbon nanotubes, combined with the expansion space reserved by the sieve-type channels, effectively controlled the volume expansion rate at 85.2%, which is much lower than that of Comparative Example 1 (168.5%) and Comparative Example 2 (132.6%). In Example 3, the amount of carbon nanotubes was insufficient, the buffer layer was incomplete, and the volume expansion rate increased to 112.3%. In Example 4, the pore volume of the sieve-type channels was insufficient, and the expansion space was inadequate, resulting in a volume expansion rate of 125.7%. This fully demonstrates that the carbon nanotube buffer layer and the sieve-type channels are the key to solving the volume expansion problem and must meet the specified parameters.

[0032] 2. Low initial efficiency: Example 1 compensated for the lithium source consumed by SEI film formation during the first charge and discharge process through in-situ pre-lithiation, and the first-week coulombic efficiency reached 92.8%, which is much higher than Comparative Example 1 (74.5%) and Comparative Example 2 (77.2%). Example 5 lacked the in-situ pre-lithiation step, and the first-week coulombic efficiency dropped to 78.8%, which is close to that of the comparative example. This shows that in-situ pre-lithiation is the core to improve the low initial efficiency, and the amount used needs to be controlled within a reasonable range.

[0033] 3. Interface cracking problem: In Example 1, laser-induced Si-NC covalent bonding was used to enhance the interfacial bonding between carbon nanotubes and silicon-carbon particles, preventing interface delamination and reducing SEI film rupture and regeneration. The capacity retention rate reached 95.6% after 100 cycles. In Example 2, the laser-induced covalent bonding step was missing, resulting in insufficient interfacial bonding and a reduced cycle capacity retention rate of 88.9%. This indicates that laser-induced covalent bonding can significantly improve interface stability and solve the interface cracking problem.

[0034] 4. Overall Performance: Example 1 fully adopts the core improvement points, achieving the best performance in all aspects, with a specific capacity of 1820mAh / g, far exceeding that of the comparative example. This fully demonstrates that the integrated improvement scheme of the present invention can simultaneously solve multiple defects, improve specific capacity, and balance performance and mass production requirements. Comparative example 1 did not adopt any core improvement points, resulting in prominent issues such as volume expansion, interface cracking, and low first-efficiency, leading to the worst overall performance. Comparative example 2 only adopted some improvement points and did not achieve integrated synergy, resulting in limited performance improvement and failing to achieve the technical effect of the present invention.

[0035] Furthermore, the production process of Example 1 adopts a dry process, which does not require complex solvent treatment, simplifies the production process, reduces environmental pressure, and is suitable for industrial mass production needs, further demonstrating the practicality and advancement of the present invention.

[0036] In summary, this invention simultaneously solves the core problems of existing silicon-carbon anode materials, such as volume expansion, interface cracking, and low initial efficiency, improves battery cycle stability and energy density, simplifies the process, adapts to mass production, reduces production costs, and has good industrial application value.

[0037] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A silicon-carbon anode material for lithium batteries, characterized in that, The invention comprises silicon-carbon particles, carbon nanotubes, and in-situ pre-lithiated lithium metal; at least a portion of the surface of the silicon-carbon particles is in-situ wrapped with carbon nanotubes to form an elastic buffer layer; Si-NC covalent bonds are induced between the carbon nanotubes and the silicon-carbon particles; the silicon-carbon particles include an internal sieve-type pore structure.

2. The lithium-ion battery silicon-carbon anode material according to claim 1, characterized in that, The amount of carbon nanotubes used is 3-8% of the mass of silicon-carbon particles, and they are uniformly wound around the surface of silicon-carbon particles; the mass of carbon nanotubes wound around the surface of a single silicon-carbon particle is 3-8% of the mass of that single silicon-carbon particle; the number of continuous windings of a single carbon nanotube on the surface of a single silicon-carbon particle is 3-15, and adjacent carbon nanotubes overlap each other to form a continuous three-dimensional conductive network.

3. The lithium-ion battery silicon-carbon anode material according to claim 1, characterized in that, It also contains a conductive agent and a modified PAA elastic binder, wherein the conductive agent is either carbon black or graphene, and the amount used is 2-5% of the mass of the silicon carbon particles; the amount of the modified PAA elastic binder is 5-10% of the mass of the silicon carbon particles.

4. The lithium battery silicon-carbon anode material according to claim 1, characterized in that, The amount of metallic lithium used in the in-situ pre-lithiation loading is 0.5-2% of the mass of silicon-carbon particles, and it is uniformly loaded inside the sieve-type channels.

5. The lithium battery silicon-carbon anode material according to claim 4, characterized in that, The sieve-type pore structure consists of nanopores and sub-nanometer pores.

6. A production process for lithium-ion battery silicon-carbon anode material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Carbon nanotubes are wound in situ onto the surface of silicon carbon particles using a dry process to form an elastic buffer layer; (2) Constructing Si-NC covalent bonds between carbon nanotubes and silicon-carbon particles by laser guidance; (3) A sieve-type channel structure is prepared inside silicon-carbon particles using an etchant, and a trace amount of metallic lithium is loaded in the channel to achieve in-situ pre-lithiation; (4) The treated silicon-carbon particles are mixed with conductive agent and modified PAA elastic binder to form a slurry. After coating and drying, the silicon-carbon anode material for lithium batteries is obtained.

7. The production process of the lithium battery silicon-carbon anode material according to claim 6, characterized in that, In step (1), the dry process adopts a combination of mechanical stirring and ultrasonic dispersion. The mechanical stirring speed is 800-1500 r / min, the stirring time is 20-40 min, the ultrasonic dispersion power is 300-500 W, and the ultrasonic time is 10-20 min.

8. The production process of the lithium battery silicon-carbon anode material according to claim 6, characterized in that, In step (2), the laser power of the laser-guided processing is 50-150W, the laser irradiation time is 5-15s, and the irradiation distance is 5-10cm.

9. The production process of the lithium battery silicon-carbon anode material according to claim 6, characterized in that, In step (3), the etchant is a dilute hydrofluoric acid solution, the etching temperature is 25-40℃, the etching time is 15-30min, the in-situ pre-lithiation temperature is 60-80℃, and the holding time is 30-60min.

10. The production process of the lithium battery silicon-carbon anode material according to claim 6, characterized in that, In step (4), the amount of deionized water added during mixing is 40-60% of the total mass of silicon-carbon composite particles. The slurry is coated onto the copper foil current collector with a coating thickness of 100-200μm. After coating, it is placed in a vacuum drying oven for drying at a temperature of 80-120℃ for 2-4 hours.

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