Composite negative electrode material with long cycle life and preparation method thereof
By using a composite structure of porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder, the problem of irreversible expansion of lithium-ion battery anode materials during lithium intercalation was solved, achieving optimized electrochemical performance with high capacity and long cycle life.
Patent Information
- Application Number
- CN202511465431.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-14
- Publication Date
- 2026-01-23
AI Technical Summary
Existing lithium-ion battery anode materials, such as graphite, expand irreversibly during lithium intercalation, leading to cycle performance failure and making it difficult to meet the requirements of high capacity and long cycle life. Silicon materials undergo large volume changes during charging and discharging, affecting battery life.
A composite structure consisting of porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder is adopted. Through mechanical buffering, improved electrolyte wettability and interfacial bonding, a composite system with high capacity, high conductivity and high stability is formed.
It achieves high capacity and long cycle life of composite anode material, with a 20% increase in initial discharge specific capacity, a capacity retention rate of over 97% after 500 cycles, and a 7% increase in rate capacity retention rate.
Smart Images
Figure CN121394338A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery anode material technology, specifically to a composite anode material with long cycle life and its preparation method. Background Technology
[0002] Lithium-ion batteries possess advantages such as high energy density, high discharge voltage, low self-discharge, and no memory effect, and are widely used in electric vehicles, electronic products, and energy storage devices. As the demand for green energy continues to increase, higher requirements are being placed on the cycle life of lithium-ion batteries. Lithium-ion batteries require prolonged and intensive charging and discharging during operation; therefore, maintaining high energy density and good cycle stability is crucial throughout their operating life.
[0003] Currently, graphite is the most widely used anode material for lithium-ion batteries, but its theoretical capacity is only 372 mAh·g. -1 This makes it difficult to meet the high-capacity, high-power charging and discharging requirements of lithium-ion batteries in applications such as electric vehicles and aerospace. Furthermore, during lithium intercalation, lithium ions embed themselves from the end faces of the graphite layers, leading to an increase in the interlayer spacing. This expansion is irreversible. Simultaneously, the expansion of graphite materials is closely related to the cycle life of the battery. After multiple lithium intercalation / deintercalation reactions, irreversible expansion occurs in a certain direction, resulting in microcracks in the graphite material, rupture and remodeling of the SEI film, electrolyte consumption, and cycle performance failure.
[0004] The theoretical capacitance of silicon material is 4200 mAh·g. -1 Using silicon as a negative electrode material for lithium-ion batteries is an effective way to improve the capacity of lithium-ion batteries, which has attracted great attention from scholars at home and abroad and has become one of the research hotspots of lithium-ion battery negative electrode materials. However, silicon materials undergo large volume changes during charging and discharging, which leads to excessively rapid capacity decay of lithium-ion batteries and greatly affects battery life. Therefore, there is an urgent need to provide a composite negative electrode material with high capacity and long cycle life.
[0005] Application content
[0006] To overcome the aforementioned technical problems, one of the objectives of this application is to provide a composite anode material with high capacity and long cycle life, which effectively improves the electrochemical performance of the composite anode material by utilizing the interaction of porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder.
[0007] To achieve the above objectives, the adopted technical solution is a composite anode material with a long cycle life, comprising the following components by mass percentage.
[0008] The composition consists of 20%-30% porous nano-silicon, 30%-35% silicon carbide-doped graphene powder, and the remainder sulfonate-coated graphite powder.
[0009] The graphite / SiC framework of silicon carbide-doped graphene powder provides mechanical buffering, disperses the volumetric stress of porous nano-silicon, and reduces pulverization. Sulfonate improves electrolyte wettability and SEI uniformity, enhances the interfacial bonding between porous nano-silicon and the graphite matrix, and can synergistically improve the continuity of the conductive network and interfacial stability with silicon carbide-doped graphene powder. Utilizing the interaction between porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphene powder, the three components work synergistically to form a "high capacity-high conductivity-high stability" composite system, achieving comprehensive optimization of electrochemical performance.
[0010] As a further embodiment of the composite anode material with long cycle life proposed in this application: Preferably, the porous nano-silicon has a particle size of 10 nm to 20 nm, the silicon carbide-doped graphene powder has a particle size of 100 nm to 200 nm, and the sulfonate-coated graphite powder has a particle size of 50 nm to 80 nm.
[0011] Among them, porous silicon nanoparticles with a particle size of 10nm to 20nm have a high specific surface area and abundant pores, which can promote electrolyte penetration and shorten the lithium ion diffusion path. Silicon carbide doped graphene powder with a particle size of 100nm to 200nm prevents the tight stacking of graphene sheets and forms a more open porous structure, which is conducive to lithium ion transport. The sulfonate coating nano-sulfonate layer in graphite powder with a particle size of 50nm to 80nm can pre-form a thinner, more stable and denser protective film on the graphite surface, which can reduce subsequent side reactions with electrolyte and guide the formation of a better SEI film, thereby reducing lithium loss in the first cycle.
[0012] Preferably, the porous nano-silicon is 25%, the silicon carbide-doped graphene powder is 32%, and the sulfonate-coated graphite powder is 43%.
[0013] The composite anode material prepared by mixing the above proportions achieves optimal initial discharge specific capacity, capacity after 500 cycles, and rate capacity retention.
[0014] Preferably, the method for preparing the porous nano-silicon includes the following steps: S1: Mix silica fume with magnesium powder in a muffle furnace and calcine under an inert atmosphere to form a reduction product; S2: Disperse the reduction product in the first acid solution, keep for 30 seconds, and remove the remaining magnesium powder; S3: Filter and dry the silicon powder in the acid solution to form porous nano-silicon.
[0015] In the above preparation method, silica fume and magnesium powder are mixed and calcined at high temperature in an inert atmosphere (usually argon) in a muffle furnace. The magnesium powder vaporizes at high temperature and undergoes a redox reaction with solid silicon dioxide. Magnesium (Mg) acts as a reducing agent to reduce the silica (SiO2). In step S1, silicon (Si) is reduced and oxidized to magnesium oxide (MgO). The resulting silicon (Si) and magnesium oxide (MgO) intertwine to form a complex reduction product. This reduction product is dispersed in a first acid solution (such as HCl), which reacts with the magnesium oxide (MgO) generated in step S1 to form soluble magnesium chloride (MgCl₂). It is soluble in water. When MgO is etched, the space originally occupied by MgO is left with pores, thus obtaining a porous silicon structure that retains the original morphology of silica fume but is filled with nanoscale pores. This porous nano-silicon can accelerate lithium ion diffusion.
[0016] The added magnesium powder can act as a reducing agent. When heated to 650°C to 700°C in a muffle furnace under an inert atmosphere (such as argon), the magnesium powder will undergo a violent exothermic reaction with the silica fume to produce elemental silicon and magnesium oxide. The inert atmosphere can prevent the magnesium powder from being oxidized by oxygen in the air, thereby reducing the utilization rate of the raw materials. Then, the generated silicon powder is dispersed in the first acid solution to remove magnesium oxide and porous nano-silicon.
[0017] As a further technical solution for the preparation of porous nano-silicon: Preferably, in S1, the calcination temperature of the silica fume is 600-750℃, and the calcination time is 4h to 6h; In S2, the first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of hydrofluoric acid is 1%-3%, the mass concentration of hydrochloric acid is 5%-10%, and the volume ratio of hydrofluoric acid to hydrochloric acid is 1:2 to 1:3; the mass-volume ratio of silicon powder to the acid solution is 1g:2mL to 1g:3mL.
[0018] A mixed solution of hydrofluoric acid and hydrochloric acid can dissolve magnesium oxide and unreduced silicon oxide in silicon powder. Specifically, hydrochloric acid dissolves magnesium oxide and hydrofluoric acid dissolves silicon oxide, resulting in higher purity porous nano-silicon.
[0019] Preferably, the method for preparing the silicon carbide-doped graphene powder includes the following steps: Y1: Graphene powder, silicon carbide powder and silane coupling agent are mixed and ball-milled to obtain a mixture; Y2: Place the mixture in an inert atmosphere and heat it to 400-500℃, then keep it at that temperature for 3-4 hours; Y3: Cool and grind the mixture to form silicon carbide-doped graphene powder.
[0020] In the above preparation method, the silanol group (-Si-OH) of the silane coupling agent undergoes dehydration condensation with the hydroxyl group (-OH) on the surface of SiC to form a stable Si-O-Si covalent bond. The organic long chain of the silane coupling agent forms steric hindrance on the surface of graphene, preventing them from recombinizing into graphite and making it easier to disperse in the polymer.
[0021] As a further method for preparing silicon carbide-doped graphene powder: Preferably, in Y1, the mass ratio of graphene powder to silicon carbide powder is 1:0.1 to 1:0.3, the amount of silane coupling agent added is 5wt%-10wt% of the mass of graphene powder, the ball milling speed is 300-400 rpm, and the ball milling time is 1h to 2h; in Y2, the heating rate of the mixture is 10℃ / min to 20℃ / min.
[0022] The above method can be used to prepare silicon carbide-doped graphene powder with a particle size of 100nm to 200nm. This silicon carbide-doped graphene powder can effectively maintain conductivity, which matches the high conductivity of composite anode materials.
[0023] Preferably, the method for preparing the sulfonate-coated graphite powder includes the following steps: Z1: After immersing graphite powder in the second acid solution for 3 to 5 hours, the solid and liquid are separated and dried to obtain activated graphite powder; Z2: Mix activated graphite powder with organic sulfonate solution evenly, react at 140℃ to 150℃ for 4 to 6 hours, filter, and dry to form sulfonate-coated graphite powder.
[0024] The second acid solution can clean the surface of the graphite powder, increase the surface active sites of the graphite powder, and facilitate the subsequent firm coating of the graphite powder surface with sulfonates.
[0025] As a further method for preparing sulfonate-coated graphite powder: Preferably, in Z1, the second acid solution is a 45wt% to 60wt% hydrochloric acid solution; In Z2, the general structural formula of the organic sulfonate is R-SO3Na, where R is a lower alkyl group, hydroxyl group, aromatic group or -CX3 of C1-C4, and X is a halogen. The mass concentration of the organic sulfonate solution is 5% to 10%, and the mass-volume ratio of the activated graphite powder to the organic sulfonate solution is 1g:3mL-1g:5mL. More preferably, the organic sulfonate is sodium methanesulfonate, sodium hydroxysulfonate or sodium ethylsulfonate.
[0026] The above method can be used to prepare sulfonate-coated graphite powder with a particle size of 50 nm to 80 nm. The sulfonate-coated graphite powder improves electrolyte wettability and SEI uniformity, and enhances the interfacial bonding between porous nano-silicon and graphite matrix.
[0027] The second objective of this application is to provide a method for preparing the composite anode material with long cycle life as described in any one of the above claims, comprising the following steps: X1: Select porous nano-silicon, silicon carbide doped graphene powder and sulfonate coated graphite powder according to the design ratio, and mix them evenly to form a mixed base material; X2: Add a binder to the mixed base material and granulate to form a precursor for the negative electrode material; X3: Under an inert atmosphere, the precursor of the anode material is heated to 650-750℃ and sintered for 4 to 6 hours to form a composite anode material.
[0028] The above method can be used to prepare a composite anode material with three dielectrics: porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder. By utilizing the interaction between porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder, the electrochemical performance can be fully optimized.
[0029] As a further aspect of this application: In X2, the binder is poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate in a mass ratio of 1:1 to 1:1.2, and the amount of binder added is 3wt%-5wt% of the mass of the mixed base material. In X3, the heating rate of the negative electrode material precursor is 20℃ / min to 25℃ / min.
[0030] Poly(3,4-ethylenedioxythiophene) is a conjugated polymer whose main chain consists of alternating single and double bonds. Electrons can be delocalized throughout the conjugated system, thus possessing intrinsic conductivity. Sodium polystyrene sulfonate can be used as a dispersion stabilizer to stabilize the dispersion of three nanoparticles: porous silicon nanoparticles, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder, thereby improving the mixing and dispersion effect of the three.
[0031] The advantages of this invention compared to the prior art are as follows: (1) This invention provides a composite anode material with a long cycle life, comprising the following raw materials by mass percentage: 20%-30% porous nano-silicon, 30%-35% silicon carbide-doped graphene powder, and the balance sulfonate-coated graphene powder. The interaction between porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphene powder effectively improves the electrochemical performance of the composite anode material. Specifically, the graphite / SiC framework of the silicon carbide-doped graphene powder provides mechanical buffering, disperses the volumetric stress of the porous nano-silicon, and reduces pulverization. Sulfonates improve electrolyte wettability and SEI uniformity, enhance the interfacial bonding between porous nano-silicon and graphite matrix, and can synergistically improve the continuity of conductive network and interfacial stability when combined with silicon carbide-doped graphene powder. More importantly, sulfonate-coated graphite powder enhances ion conduction, porous nano-silicon accelerates lithium-ion diffusion, and silicon carbide-doped graphene powder effectively maintains conductivity. The three work synergistically to form a composite system of "high capacity, high conductivity, and high stability," achieving comprehensive optimization of electrochemical performance.
[0032] (2) The present invention provides a method for preparing a composite anode material with long cycle life. The composite anode material prepared by porous nano-silicon, silicon carbide doped graphene powder and sulfonate coated graphite powder has an initial discharge specific capacity of about 380 mAh / g, which is 20% higher; after 500 cycles, the capacity retention rate is more than 97%, which is about 7% higher; the rate capacity retention rate is more than 96%, which is also about 7% higher. This allows the composite anode material to simultaneously achieve high capacity and long cycle life. Attached Figure Description
[0033] The present application will be further described below with reference to the accompanying drawings.
[0034] Figure 1 This is a flowchart of a method for preparing a composite anode material with long cycle life according to this application; Figure 2 This is a flowchart of a method for preparing porous nano-silicon in a composite anode material with long cycle life according to this application; Figure 3 This is a flowchart of a method for preparing silicon carbide-doped graphene powder in a composite anode material with long cycle life according to this application. Figure 4 This is a flowchart of a method for preparing sulfonate-coated graphite powder in a composite negative electrode material with long cycle life according to this application. Detailed Implementation
[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0036] Preparation Example 1
[0037] like Figure 2 As shown, the preparation method of porous nano-silicon is as follows: 100g of silica fume and 120g of magnesium powder were mixed in a muffle furnace and calcined at 680℃ for 5 hours under an inert atmosphere (helium atmosphere) to form a reduction product. The reduction product was dispersed in 120mL of a first acid solution, stirred evenly, and kept for 30s. After filtration and drying, porous nano-silicon with a particle size of 18nm was obtained. It should be noted that the equipment used for filtration and drying should be selected by those skilled in the art based on the amount of material in the muffle furnace. The first acid solution was a mixture of 2wt% hydrofluoric acid solution and 8wt% hydrochloric acid solution in a volume ratio of 1:2.5. Preparation Example 2 like Figure 3 As shown, the preparation method of silicon carbide-doped graphene powder is as follows: 30g of graphene powder, 5g of silicon carbide powder, and 2g of silane coupling agent were mixed evenly and ball-milled at 350rpm for 2 hours to obtain a mixture. Existing ball mills were used; the specific specifications and type were selected by those skilled in the art based on the total mass of the materials. The mixture was then heated to 450℃ at a heating rate of 15℃ / min under an inert atmosphere and held at that temperature for 3.5 hours. After cooling, the mixture was ground, with natural cooling to room temperature. Existing grinding technology was suitable. The grinding time was adjusted according to the amount of material to obtain silicon carbide-doped graphene powder with a particle size of 150nm. Preparation Example 3 like Figure 4 As shown, the method for obtaining sulfonate-coated graphite powder is as follows: 50g of graphite powder was immersed in 120ml of 50wt% hydrochloric acid solution for 4h, and then separated from the hydrochloric acid solution by filtration and dried to obtain activated graphite powder. Under an inert atmosphere (helium atmosphere), the activated graphite powder was mixed evenly with 150mL of sodium methanesulfonate solution with a mass concentration of 7.5% and reacted at 145℃ for 5h. After filtration and drying, sulfonate-coated graphite powder with a particle size of 60nm was obtained.
[0038] Example 1
[0039] This embodiment provides a method for preparing a composite anode material with long cycle life, such as... Figure 1 As shown, the porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder obtained by the above method are used to prepare a composite anode material according to the following steps: Step 1: Weigh 25g of porous nano-silicon from Preparation Example 1, 32g of silicon carbide-doped graphene powder from Preparation Example 2, and 43g of sulfonate-coated graphite powder from Preparation Example 3, and mix them evenly. Step 2: Add 4g of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate, wherein the mass of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate is 2g each, or ensure that the mass ratio of poly(3,4-ethylenedioxythiophene) to sodium polystyrene sulfonate is in the range of 1:1 to 1:1.2. Granulate the mixture by spray drying or mechanical stirring to form spherical particles with D50 < 15μm, thus obtaining the precursor of the negative electrode material. Step 3: The obtained granular anode material precursor is heated to 700℃ at a heating rate of 25℃ / min and sintered for 5 hours to obtain the final composite anode material.
[0040] The composite anode material includes 25g of porous nano-silicon with a particle size of 18nm, 32g of silicon carbide-doped graphene powder with a particle size of 150nm, and 43g of sulfonate-coated graphite powder with a particle size of 60nm.
[0041] Example 2
[0042] This embodiment provides a method for preparing a composite anode material with long cycle life, such as... Figure 1 As shown, the porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder obtained by the above method are used to prepare a composite anode material according to the following steps: Step 1: Weigh 30g of porous nano-silicon from Preparation Example 1, 30g of silicon carbide-doped graphene powder from Preparation Example 2, and 40g of sulfonate-coated graphite powder from Preparation Example 3, and mix them evenly. Step 2: Add 4g of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate in a mass ratio of 1:1, and granulate by spray drying or mechanical stirring to form spherical particles with D50 < 15μm to obtain the precursor of the negative electrode material; Step 3: The obtained granular anode material precursor is heated to 700℃ at a heating rate of 25℃ / min and sintered for 5 hours to obtain the final composite anode material.
[0043] The composite anode material includes 30g of porous nano-silicon with a particle size of 20nm, 30g of silicon carbide-doped graphene powder with a particle size of 100nm, and 40g of sulfonate-coated graphite powder with a particle size of 80nm.
[0044] Example 3
[0045] This embodiment provides a method for preparing a composite anode material with long cycle life, such as... Figure 1 As shown, the porous nano-silicon, silicon carbide-doped graphene powder, and sulfonate-coated graphite powder obtained by the above method are used to prepare a composite anode material according to the following steps: Step 1: Weigh 20g of porous nano-silicon from Preparation Example 1, 35g of silicon carbide-doped graphene powder from Preparation Example 2, and 45g of sulfonate-coated graphite powder from Preparation Example 3, and mix them evenly. Step 2: Add 4g of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate in a mass ratio of 1:1, and granulate by spray drying or mechanical stirring to form spherical particles with D50 < 15μm to obtain the precursor of the negative electrode material; Step 3: The obtained granular anode material precursor is heated to 700℃ at a heating rate of 25℃ / min and sintered for 5 hours to obtain the final composite anode material.
[0046] The composite anode material comprises 20g of porous nano-silicon with a particle size of 10nm, 35g of silicon carbide-doped graphene powder with a particle size of 180nm, and 45g of sulfonate-coated graphene powder with a particle size of 50nm.
[0047] Comparative Example 1
[0048] The difference between this comparative example and Example 1 is that the silicon carbide-doped graphene powder is replaced with an equal amount of graphene powder, while other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0049] Comparative Example 2
[0050] The difference between this comparative example and Example 1 is that the sulfonate-coated graphite powder is replaced with an equal amount of graphite powder, while the other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0051] Comparative Example 3
[0052] The difference between this comparative example and Example 1 is that the composite anode material only includes 32g of silicon carbide-doped graphene powder with a particle size of 150nm and 43g of sulfonate-coated graphene powder with a particle size of 60nm. The other components and processes remain unchanged, and the specific preparation process will not be described here.
[0053] Comparative Example 4
[0054] The difference between this comparative example and Example 1 is that the composite negative electrode material only includes 25g of porous nano-silicon with a particle size of 18nm and 43g of sulfonate-coated graphite powder with a particle size of 60nm. The amount of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate added in a mass ratio of 1:1 is 2.72g. Other processes remain unchanged, and the specific preparation process will not be described here.
[0055] Comparative Example 5
[0056] The difference between this comparative example and Example 1 is that the composite negative electrode material only includes 25g of porous nano-silicon with a particle size of 18nm and 32g of silicon carbide-doped graphene powder with a particle size of 150nm. The amount of poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate added in a mass ratio of 1:1 is 2.28g. Other processes remain unchanged, and the specific preparation process will not be described here.
[0057] Comparative Example 6
[0058] The difference between this comparative example and Example 1 is that porous nano-silicon is replaced with an equal amount of silicon dioxide, while other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0059] Comparative Example 7
[0060] The difference between this comparative example and Example 1 is that the composite anode material consists of only 100g of 150nm silicon carbide-doped graphene powder, while the other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0061] Comparative Example 8
[0062] The difference between this comparative example and Example 1 is that the composite anode material consists of only 100g of 18nm porous nano-silicon, while the other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0063] Comparative Example 9
[0064] The difference between this comparative example and Example 1 is that the composite negative electrode material consists only of 100g of 60nm sulfonate-coated graphite powder, while the other components and processes remain unchanged. The specific preparation process will not be described in detail here.
[0065] The composite negative electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 9 were used as negative electrode active materials and assembled with lithium iron phosphate positive electrode active material, electrolyte and separator to form a 5Ah soft-pack lithium-ion battery; wherein the electrolyte is a 1mol / L lithium hexafluorophosphate solution and the solvent is EC, DMC and DEC in a volume ratio of 1:1:1; the separator is Celegard 2400 with a thickness of 18μm.
[0066] The pouch lithium-ion batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 9 were tested as follows: Cyclic performance test: The energy density of the battery was tested for 500 cycles at a charge / discharge rate of 1C / 1C, a voltage range of 2.5V-3.65V, and a temperature of 25±3℃. The test results are shown in Table 1.
[0067] Rate performance test: The battery capacity retention rate was tested at a charge / discharge rate of 3C / 1C, a voltage range of 2.5V-3.65V, and a temperature of 25±3℃. The test results are shown in Table 1.
[0068] Table 1
[0069] As shown in Table 1, compared to Comparative Examples 1-2, the soft-pack lithium-ion battery prepared using the composite anode material with long cycle life provided in Example 1 of this application exhibits better cycle performance and rate performance. After 500 cycles, the soft-pack lithium-ion battery prepared using the composite anode material with long cycle life provided in Example 1 of this application still retains 97.3% of its capacity, and its rate capacity retention is as high as 96.9%. This is because the graphite / SiC framework of silicon carbide-doped graphene powder provides mechanical buffering, disperses the volume stress of porous nano-silicon, and reduces pulverization; sulfonate improves electrolyte wettability and SEI uniformity, enhances the interfacial bonding between porous nano-silicon and the graphite matrix, and can also synergistically improve the continuity of the conductive network and the interfacial stability with silicon carbide-doped graphene powder. More importantly, sulfonate coating of graphite powder enhances ion conduction, porous nano-silicon accelerates lithium-ion diffusion, and silicon carbide-doped graphene powder can effectively maintain conductivity. The three components work synergistically to form a "high capacity-high conductivity-high stability" composite system, achieving comprehensive optimization of electrochemical performance.
[0070] The foregoing has provided a detailed description of one embodiment of this application, but the description is merely a preferred embodiment and should not be construed as limiting the scope of this application. All equivalent variations and improvements made within the scope of this application should still fall within the patent coverage of this application.
Claims
1. A composite anode material having a long cycle life, characterized in that, The composite negative electrode material comprises the following components in mass percentage: 20%-30% of porous nano-silicon, 30%-35% of silicon carbide doped graphene powder, and the rest of sulfonate coated graphite powder. 2.The composite negative material with long cycle life according to claim 1, characterized in that, The particle size of the porous nano-silicon is 10-20 nm, the particle size of the silicon carbide doped graphene powder is 100-200 nm, and the particle size of the sulfonate coated graphite powder is 50-80 nm. 3.The composite negative material with long cycle life according to claim 1, characterized in that, The preparation method of the porous nano-silicon comprises the following steps: S1: mixing silicon ash powder and magnesium powder in a muffle furnace and calcining under an inert atmosphere to form a reduction product; S2: dispersing the reduction product in a first acid solution to remove the rest of the magnesium powder; S3: filtering and drying the reduction product in the acid solution to form porous nano-silicon.
4. The composite anode material with long cycle life according to claim 3, characterized in that, In S1, the calcination temperature of the silicon ash powder is 600-750℃, and the calcination time is 4-6 h; In S2, the first acid solution is a mixed solution of hydrofluoric acid and hydrochloric acid, wherein the mass concentration of hydrofluoric acid is 1%-3%, the mass concentration of hydrochloric acid is 5%-10%, and the volume ratio of hydrofluoric acid to hydrochloric acid is 1:2-1:3; the mass-volume ratio of the silicon powder to the first acid solution is 1 g:2 mL-1 g:3 mL.
5. The composite anode material with long cycle life according to claim 1, characterized in that, The preparation method of the silicon carbide doped graphene powder comprises the following steps: Y1: mixing graphene powder, silicon carbide powder, and silane coupling agent, and obtaining a mixture after ball milling; Y2: placing the mixture in an inert atmosphere, heating to 400-500℃, and keeping the temperature for 3-4 h; Y3: cooling and grinding the mixture to obtain silicon carbide doped graphene powder.
6. The composite anode material with long cycle life according to claim 5, characterized in that, In Y1, the mass ratio of the graphene powder to the silicon carbide powder is 1:0.1-1:0.3, the addition amount of the silane coupling agent is 5%-10% of the mass of the graphene powder, the rotation speed of the ball milling is 300-400 rpm, and the ball milling time is 1-2 h; In Y2, the heating rate of the mixture is 10-20℃ / min. 7.The composite negative material with long cycle life according to claim 1, characterized in that, The preparation method of the sulfonate coated graphite powder comprises the following steps: Z1: immersing graphite powder in a second acid solution for 3-5 h, then performing solid-liquid separation and drying to obtain activated graphite powder; Z2: uniformly mixing the activated graphite powder with an organic sulfonate solution, reacting at 140-150℃ for 4-6 h, filtering, and drying to form sulfonate coated graphite powder. 8.The composite anode material with long cycle life according to claim 7, characterized in that, In Z1, the second acid solution is a 45-60 wt% hydrochloric acid solution; In Z2, the general structure of the organic sulfonate is R-SO3Na, wherein R is a C1-C4 lower alkyl group, a hydroxyl group, an aromatic group, or -CX3, wherein X is a halogen, and the mass concentration of the organic sulfonate solution is 5%-10%; the mass-volume ratio of the activated graphite powder to the organic sulfonate solution is 1 g:3 mL-1 g:5 mL.
9. A method of producing the composite negative electrode material having a long cycle life according to any one of claims 1 to 8, characterized by, The method comprises the following steps: X1: selecting porous nano-silicon, silicon carbide doped graphene powder, and sulfonate coated graphite powder according to the mass percentage of claim 1, and uniformly mixing to form a mixed base material; X2: adding a binder to the mixed base material and granulating to form a negative electrode material precursor; X3: the negative electrode material precursor is heated to 650-750 DEG C under an inert atmosphere and sintered for 4-6 hours to form the composite negative electrode material.
10. The method of claim 9, wherein the composite negative electrode material having a long cycle life is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. In X2, the binder is poly(3,4-ethylenedioxythiophene) and sodium polystyrene sulfonate at a mass ratio of 1:1 to 1:1.2, and the binder is added in an amount of 3-5% of the mass of the mixed base material; In X3, the heating rate of the negative electrode material precursor is 20-25 DEG C / min.