Self-repairing silicon-based lithium battery negative electrode material and preparation method and application thereof

Abstract

This invention provides a self-healing silicon-based lithium-ion battery anode material, its preparation method, and its application. The self-healing silicon-based lithium-ion battery anode material comprises a nano-silicon particle core and a self-healing cross-linked polymer coating the surface of the nano-silicon particle core. The self-healing cross-linked polymer is obtained by cross-linking a linear polymer with a thiol compound via a thiol-Michael addition reaction. The linear polymer is obtained by free radical copolymerization of acrylonitrile and allyl methacrylate. This invention uses the self-healing cross-linked polymer as a coating layer, utilizing its flexibility and self-healing ability to effectively alleviate the stress accumulation caused by the huge volume expansion of silicon-based materials during charging and discharging. It has outstanding advantages such as high initial coulombic efficiency and excellent cycle stability, which can significantly improve the energy density and lifespan of lithium batteries, making it suitable for the production and application of high-performance lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery electrode materials technology, specifically to a self-healing silicon-based lithium battery anode material, its preparation method, and its application. Background Technology

[0002] Silicon-based materials, with a theoretical specific capacity as high as 3579 mAh / g (nearly 10 times that of traditional graphite), a higher lithium-to-electric potential, and potentially superior fast-charging performance, have become an ideal choice for next-generation high-energy-density lithium-ion battery anode materials. However, silicon-based materials experience a massive volume expansion of over 300% during lithium insertion / extraction, leading to stress accumulation within the electrode, fragmentation and pulverization of active material particles, and separation failure between the active material and the current collector. Simultaneously, the drastic volume change causes repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, continuously consuming active lithium and electrolyte, resulting in excessive SEI film thickening, a continuous increase in electrochemical impedance, and ultimately, rapid decay of reversible capacity, deterioration of cycle performance, and shortened battery life.

[0003] In existing technologies, strategies such as core-shell structure coating and polymer coating have been adopted to address the above problems. While core-shell coating with rigid or ordinary elastomers can buffer some volume expansion, its effect is limited under long-term cycling and may restrict ion transport. Traditional polymer coating can temporarily improve interfacial contact, but it lacks sustained self-healing ability and cannot cope with cumulative mechanical damage during cycling. The preparation processes of existing self-healing material systems are often complex, and their interfacial bonding with silicon-based materials is generally insufficient, making it difficult to simultaneously meet the requirements of mechanical stability and good electrochemical performance for long-term cycling.

[0004] Therefore, developing a silicon-based anode material with a relatively simple preparation process, high efficiency in self-healing properties, and strong interfacial bonding ability has significant practical application value. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a self-healing silicon-based lithium battery anode material, its preparation method and application, aiming to solve the technical problems that silicon-based anode materials are prone to structural damage and SEI film damage due to volume expansion during cycling, as well as the poor self-healing ability of existing self-healing materials due to insufficient interfacial bonding with silicon-based materials.

[0006] In a first aspect, the present invention provides a self-healing silicon-based lithium battery anode material, comprising a nano-silicon particle core and a self-healing crosslinked polymer coated on the surface of the nano-silicon particle core; Self-healing crosslinking polymers are prepared by crosslinking linear polymers with thiols via a thiols-Michael addition reaction. The linear polymer is prepared by free radical copolymerization of acrylonitrile and allyl methacrylate.

[0007] Preferably, the mass ratio of nano-silicon particles to self-healing crosslinked polymer is 1:(1~3); the molar ratio of acrylonitrile to allyl methacrylate in the linear polymer is (30~50):1.

[0008] Secondly, this invention provides a method for preparing a self-healing silicon-based lithium battery anode material, comprising the following steps: S1. Under an inert atmosphere, acrylonitrile, allyl methacrylate, a first organic solvent, a free radical initiator, and a chain transfer agent are mixed and reacted at 60-80°C for 3-8 hours. After post-treatment, a linear polymer is obtained. S2. Dissolve the linear polymer in a second organic solvent, add a multifunctional thiol compound and a catalyst, and carry out a thiol-Michael addition reaction at 30~50℃ for 1~5 hours. After drying, a self-healing crosslinked polymer is obtained. S3. Prepare nano-silicon suspension, self-healing cross-linked polymer solution and surfactant solution respectively; add nano-silicon suspension and self-healing cross-linked polymer solution to surfactant solution, stir and emulsify, and then remove solvent to obtain self-healing silicon-based lithium battery anode material.

[0009] Preferably, in step S1, the molar ratio of acrylonitrile to allyl methacrylate is (30~50):1; the free radical initiator is 2%~5% of the total mass of acrylonitrile and allyl methacrylate; the chain transfer agent is 0.1%~0.3% of the total mass of acrylonitrile and allyl methacrylate; and the molar volume ratio of allyl methacrylate to the first organic solvent is 1 mol: (40~60) mL.

[0010] Preferably, in step S1, the free radical initiator is selected from at least one of azo compounds and organic peroxides; the chain transfer agent is an alkyl thiol or a thiol compound containing hydroxyl / carboxyl groups; and the first organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran.

[0011] Preferably, in step S2, the molar ratio of the linear polymer to the polyfunctional thiol compound is 1:(10~40); the amount of catalyst is 1~8wt% of the total mass of the linear polymer and the polyfunctional thiol compound; and the mass-volume ratio of the linear polymer to the second organic solvent is 1g:(8~15)mL.

[0012] Preferably, in step S2, the second organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; the polyfunctional thiol compound is an organic compound containing 2 to 4 thiol groups; and the catalyst includes an organic strong base or a photoinitiator.

[0013] Preferably, in step S3, the mass ratio of the nano-silicon particles to the self-healing crosslinking polymer and the surfactant is 1:(1~3):(1~3).

[0014] Preferably, in step S3, the nano-silicon suspension is obtained by dispersing nano-silicon particles in a third organic solvent; the third organic solvent is a non-polar or weakly polar organic solvent with a boiling point of 60~120℃. The self-healing cross-linking polymer solution is obtained by dissolving the self-healing cross-linking polymer in a fourth organic solvent; the fourth organic solvent is a polar aprotic solvent with a boiling point >150℃; The surfactant solution is obtained by dissolving the surfactant in a fifth organic solvent; the fifth organic solvent is a highly polar solvent with a dielectric constant >30; the surfactant is a nonionic surfactant with an HLB value of 12~30.

[0015] Thirdly, the present invention provides a lithium battery, the raw materials for which include the self-healing silicon-based lithium battery anode material described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The self-healing silicon-based lithium battery anode material provided by this invention uses nano-silicon as the core and a self-healing polymer containing dynamic covalent bonds as the coating layer. Through the high flexibility and intrinsic self-healing ability of this polymer layer, the destructive stress caused by the huge volume expansion of the silicon-based material is dynamically and effectively alleviated during charging and discharging. It actively repairs the resulting particle cracks and interface damage, thereby inhibiting the repeated rupture and uncontrolled growth of the SEI film and significantly improving the structural stability of the electrode. The material has extremely excellent electrochemical performance due to the suppression of side reactions and the improvement of interface stability by the coating layer. This invention provides a key material foundation for the development of high energy density and long life lithium batteries, and provides a new technical path and reliable material support for the development of high-performance lithium batteries. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the self-healing polymer-coated Si powder prepared in Example 1 of the present invention; Figure 2 The image shows an infrared comparison of the linear polymer and the self-healing polymer in Example 1 of this invention. Figure 3 This is a molecular weight detection graph of the linear polymer in Example 1 of the present invention. Detailed Implementation

[0018] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0019] To address the technical problems of structural damage and SEI film damage caused by volume expansion during cycling of silicon-based anode materials, as well as the poor self-healing ability of existing self-healing materials due to insufficient interfacial bonding with silicon-based materials, this invention provides a self-healing silicon-based lithium battery anode material, its preparation method, and its application. Specifically, by employing a self-healing crosslinked polymer containing dynamic covalent bonds as a coating layer, the high flexibility and intrinsic self-healing ability of this polymer layer effectively and dynamically alleviate the destructive stress caused by the massive volume expansion of the silicon-based material during charging and discharging. This actively repairs the resulting particle cracks and interfacial damage, thereby inhibiting repeated rupture and uncontrolled growth of the SEI film and significantly improving the structural stability of the electrode.

[0020] In a first aspect, embodiments of the present invention provide a self-healing silicon-based lithium battery anode material, comprising a nano-silicon particle core and a self-healing crosslinked polymer coated on the surface of the nano-silicon particle core; Self-healing crosslinking polymers are prepared by crosslinking linear polymers with thiols via a thiols-Michael addition reaction. The linear polymer is prepared by free radical copolymerization of acrylonitrile and allyl methacrylate.

[0021] In the technical solution of this invention embodiment, acrylonitrile and allyl methacrylate are selected as comonomers for the linear polymer based on the synergistic matching of their structures and properties: the cyano group (-CN) in the acrylonitrile (AN) molecule has strong polarity and can form hydrogen bonds with the hydroxyl groups on the surface of nano-silicon, thereby improving the interfacial bonding force between the polymer and the silicon core and reducing the problem of coating layer detachment during cycling; the conjugated structure of the cyano group gives the polymer good antioxidant degradation resistance and flame retardancy, which is suitable for the complex electrochemical environment of lithium batteries and prevents the coating layer from decomposing during charging and discharging; the rigid structure of the AN unit can enhance the mechanical strength of the polymer coating layer, balance flexibility and support, and better constrain the volume expansion of silicon particles. The allyl group (-CH=CH2) in the side chain of allyl methacrylate (AMA) is a highly efficient acceptor for the thiol-Michael addition reaction, enabling precise cross-linking with thiol compounds and providing the necessary functional group basis for the formation of dynamic covalent bonds. Furthermore, the ester group (-COO-) in the AMA unit and the allyl side chain increase the flexibility of the polymer chain, giving the coating layer good deformation capability and better buffering the volume changes of silicon particles. AN and AMA have similar copolymerization activity and can form a uniform linear polymer through free radical copolymerization, ensuring the consistency of subsequent cross-linking reactions and avoiding imbalances in repair performance due to uneven monomer distribution.

[0022] Linear polymers are crosslinked via thiol-Michael addition reaction to form self-healing polymers. The resulting CS bonds are typical dynamic covalent bonds, which can undergo reversible breakage and recombination under mechanical stress or mild thermal stimulation, providing the material with self-healing properties. Moreover, the crosslinking density remains basically stable during the exchange process, avoiding the deterioration of the material's mechanical properties. The crosslinked polymer network has suitable pore structure and polarity characteristics, which can improve electrolyte wettability, accelerate lithium-ion transport, and enhance battery rate performance.

[0023] The self-healing mechanism of the self-healing silicon-based lithium battery anode material of the present invention is as follows: (1) Damage-triggered bond breakage: When the volume expansion of silicon particles generates mechanical stress, the thiol-Michael addition crosslinking bonds in the polymer coating layer undergo reversible breakage under stress, releasing stress and preventing irreversible cracks from forming in the coating layer; (2) Dynamic bond recombination repair: The broken thiol end group (-SH) and allyl end group (-CH=CH2) can undergo a re-addition reaction without external stimulation to achieve dynamic bond recombination; if the damage is more severe, the bond exchange rate can be accelerated under mild thermal stimulation (such as the increase of battery operating temperature) to improve the repair efficiency; (3) The crosslinking density remains stable: Thiol-Michael addition belongs to the associative dynamic covalent exchange mechanism. Bond breaking and recombination occur simultaneously, and the overall density of the crosslinking network remains basically unchanged, ensuring that the mechanical and electrochemical properties of the repaired material do not significantly decrease; (4) SEI film synergistic repair: The self-repair of the coating layer can inhibit the repeated rupture and regeneration of the SEI film, reduce the growth of the SEI film thickness, and reduce the interfacial impedance. At the same time, the dynamic crosslinking structure can adapt to the slight deformation of the SEI film and improve the interfacial stability.

[0024] Furthermore, in some embodiments, the mass ratio of nano-silicon particles to self-healing crosslinked polymer is 1:(1~3); the molar ratio of acrylonitrile to allyl methacrylate in the linear polymer is (30~50):1.

[0025] Secondly, embodiments of the present invention provide a method for preparing a self-healing silicon-based lithium battery anode material, comprising the following steps: S1. Under an inert atmosphere, acrylonitrile, allyl methacrylate, a first organic solvent, a free radical initiator, and a chain transfer agent are mixed and reacted at 60-80°C for 3-8 hours. After post-treatment, a linear polymer is obtained. S2. Dissolve the linear polymer in a second organic solvent, add a multifunctional thiol compound and a catalyst, and carry out a thiol-Michael addition reaction at 30~50℃ for 1~5 hours. After drying, a self-healing crosslinked polymer is obtained. S3. Prepare nano-silicon suspension, self-healing cross-linked polymer solution and surfactant solution respectively; add nano-silicon suspension and self-healing cross-linked polymer solution to surfactant solution, stir and emulsify, and then remove solvent to obtain self-healing silicon-based lithium battery anode material.

[0026] In the technical solution of this invention embodiment, the thiol-Michael addition reaction is carried out under mild conditions of 30~50℃, without the need for high temperature and high pressure, which can avoid the aggregation or structural damage of nano-silicon particles during the crosslinking process.

[0027] Further, in some embodiments, in step S1, the molar ratio of acrylonitrile to allyl methacrylate is (30~50):1; the free radical initiator is 2%~5% of the total mass of acrylonitrile and allyl methacrylate; the chain transfer agent is 0.1%~0.3% of the total mass of acrylonitrile and allyl methacrylate; and the molar volume ratio of allyl methacrylate to the first organic solvent is 1 mol: (40~60) mL.

[0028] Furthermore, in some embodiments, in step S1, the free radical initiator is selected from at least one of azo compounds and organic peroxides.

[0029] In the technical solutions of the embodiments of the present invention, the free radical initiator includes, but is not limited to, azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), benzoyl peroxide (BPO), and dodecyl peroxide (LPO); more preferably, AIBN or ABVN, which have a suitable half-life in the range of 60~80°C, and can precisely control the polymerization rate and molecular weight distribution.

[0030] Furthermore, in some embodiments, in step S1, the first organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran.

[0031] Furthermore, in some embodiments, in step S1, the chain transfer agent is a sulfur-containing compound; preferably an alkyl thiol with 3 to 12 carbon atoms or a thiol compound containing hydroxyl / carboxyl groups.

[0032] In the technical solutions of the embodiments of the present invention, the chain transfer agent includes, but is not limited to, methyl 3-mercaptopropionate (CYS), n-dodecyl mercaptan (DDM), 3-mercaptopropionic acid (MPA), and 2-mercaptoethanol (ME); more preferably, CYS or MPA, whose polar groups (ester groups / carboxyl groups) can improve compatibility with the silicon interface.

[0033] Furthermore, in some embodiments, in step S1, the post-processing specifically involves adding ice-cold methanol to the reaction solution to precipitate the precipitate, followed by centrifugation, washing, and drying.

[0034] Furthermore, in some embodiments, in step S2, the second organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran.

[0035] Further, in some embodiments, in step S2, the molar ratio of the linear polymer to the polyfunctional thiol compound is 1:(10~40); the amount of catalyst is 1~8wt% of the total mass of the linear polymer and the polyfunctional thiol compound; and the mass-volume ratio of the linear polymer to the second organic solvent is 1g:(8~15)mL.

[0036] Furthermore, in some embodiments, in step S2, the multifunctional thiol compound is an organic compound containing 2 to 4 thiol groups (-SH), and its molecular structure includes an aliphatic chain, an ester group, and / or an ether bond-linked backbone.

[0037] In the technical solution of the present invention, the polyfunctional thiol compound is preferably a polyfunctional thiol compound with a functionality of 2 or 3; wherein the difunctional thiol is selected from any one of 1,6-hexanedithiol (HDT), 1,4-butanedithiol (BDT), 1,8-octanedithiol (ODT), and ethylene glycol di(3-mercaptopropionate) (EGDMP); and the trifunctional thiol is selected from trimethylolpropane tri(3-mercaptopropionate) (TMPMP).

[0038] Furthermore, in some embodiments, in step S2, the catalyst comprises a strong organic base or a photoinitiator.

[0039] In the technical solutions of this invention, the catalyst is preferably a compound containing a cyclic guanidine group or a phosphine imine structure, including but not limited to 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 7-methyl-TBD (MTBD), and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO).

[0040] Furthermore, in some embodiments, in step S3, the mass ratio of the nano-silicon particles to the self-healing crosslinking polymer and the surfactant is 1:(1~3):(1~3).

[0041] Furthermore, in some embodiments, in step S3, the nano-silicon suspension is obtained by dispersing nano-silicon particles in a third organic solvent; the third organic solvent is a non-polar or weakly polar organic solvent with a boiling point of 60~120℃; preferably toluene, cyclohexane or n-hexane.

[0042] Furthermore, in some embodiments, in step S3, the self-healing crosslinking polymer solution is obtained by dissolving the self-healing crosslinking polymer in a fourth organic solvent; the fourth organic solvent is a polar aprotic solvent with a boiling point >150°C, preferably N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP).

[0043] Further, in some embodiments, in step S3, the surfactant solution is obtained by dissolving the surfactant in a fifth organic solvent; the fifth organic solvent is a highly polar solvent with a dielectric constant >30, preferably formamide, DMSO or a glycerol-water mixture; the surfactant is a nonionic surfactant with an HLB value of 12 to 30, preferably a polyoxyethylene-polyoxypropylene block copolymer (Pluronic series) or a polyethylene glycol fatty acid ester (Tween series); more preferably a functionalized surfactant containing polymerizable groups (allyl, mercapto).

[0044] Furthermore, in some embodiments, in step S3, the solvent removal method includes rotary evaporation or freeze drying.

[0045] Thirdly, embodiments of the present invention provide a lithium battery, the raw materials for which include the self-healing silicon-based lithium battery anode material described in the first aspect.

[0046] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0047] Example 1 A self-healing silicon-based lithium battery anode material and its preparation method are described below: (1) Synthesis of linear polymer: A 250 mL three-necked flask was heated, evacuated, and purged with argon gas. 5.27 mL acrylonitrile, 0.212 mL allyl methacrylate (molar ratio = 50:1), 50 mL dimethyl sulfoxide, 0.0888 g azobisisobutyronitrile and 0.004 g methyl 3-mercaptopropionate were added to the flask. After purging with argon gas for 8 minutes, the flask was sealed and placed in an oil bath at 70 °C with magnetic stirring for 5 h. After the reaction was completed, the reaction solution was added dropwise to 250 mL of ice-cold methanol to precipitate flocculent precipitate. The product was collected by centrifugation at 3500 rpm for 10 min, washed 3 times with anhydrous ethanol, and dried under vacuum at 50 °C for 12 h to obtain the linear polymer. (2) Preparation of self-healing crosslinking polymer: 0.3g of linear polymer was completely dissolved in 3.2mL of N,N-dimethylformamide, transferred to a 100mL three-necked flask purged with argon, and 20μL of 1,6-hexanedithiol and 0.02g of TBD were added in sequence. After sealing, the mixture was magnetically stirred at 40℃ for 3h and then vacuum dried at 60℃ for 12h to obtain a brownish-yellow solid, which is the self-healing crosslinking polymer. (3) Preparation of polymer-coated nano-silicon: 100 mg of nano-silicon was dispersed in 10 mL of toluene and sonicated for 30 min (solution A); 200 mg of self-healing polymer was dissolved in 5 mL of DMF (solution B); 200 mg of Pluronic F108 was dissolved in 20 mL of formamide (solution C); under stirring at 1400 rpm, solutions A and B were added to solution C in sequence, emulsified for 40 min, and rotary evaporated at 80 °C for 4 h to obtain black polymer-coated Si powder; (4) Electrode preparation: Weigh the polymer-coated Si powder, PAA, acetylene black and CNT in a mass ratio of 70:15:12:3, stir for 6 hours to form a slurry, coat copper foil with a scraper, and vacuum dry at 80°C for 12 hours to obtain the self-healing silicon-based lithium battery anode material.

[0048] Figure 1This is a scanning electron microscope image of the self-healing polymer-coated Si powder prepared in this embodiment.

[0049] Figure 2 Infrared comparison images of linear polymers and self-healing polymers; linear polymers at 1630 cm⁻¹. -1 The allyl C=C stretching vibration peak that appeared at 1200 cm⁻¹ disappears in the self-healing polymer, and an overtone combination vibration peak of the carbonyl group (C=O) appears. Meanwhile, in the self-healing polymer, a peak at 1200 cm⁻¹ is observed. -1 The presence of stretching vibration peaks of CS bonds nearby confirms the successful occurrence of the thiol-Michael addition reaction, indicating that the linear polymer has formed a self-healing polymer network through dynamic covalent cross-linking.

[0050] Figure 3 This is a molecular weight test graph of the linear polymer obtained in this embodiment.

[0051] Example 2 A self-healing silicon-based lithium battery anode material and its preparation method are described below: (1) Synthesis of linear polymer: A 250 mL three-necked flask was heated, evacuated, and purged with argon gas. 5.27 mL acrylonitrile, 0.212 mL allyl methacrylate (molar ratio = 50:1), 50 mL dimethyl sulfoxide, 0.0888 g azobisisobutyronitrile and 0.004 g methyl 3-mercaptopropionate were added to the flask. After purging with argon gas for 8 minutes, the flask was sealed and placed in an oil bath at 70 °C with magnetic stirring for 5 h. After the reaction was completed, the reaction solution was added dropwise to 250 mL of ice-cold methanol to precipitate flocculent precipitate. The product was collected by centrifugation at 3500 rpm for 10 min, washed 3 times with anhydrous ethanol, and dried under vacuum at 50 °C for 12 h to obtain the linear polymer. (2) Preparation of self-healing crosslinked polymer: 0.3 g of linear polymer was completely dissolved in 3.2 mL of N,N-dimethylformamide, transferred to a 100 mL three-necked flask purged with argon, and 12 μL of 1,4-butanedithiol and 0.015 g of UDB were added sequentially. After sealing, the mixture was magnetically stirred at 40 °C for 3 h and then vacuum dried at 60 °C for 12 h to obtain the self-healing crosslinked polymer; (3) Preparation of polymer-coated nano-silicon: 100 mg of nano-silicon was dispersed in 10 mL of toluene and sonicated for 30 min (solution A); 200 mg of self-healing polymer was dissolved in 5 mL of DMF (solution B); 200 mg of the compound system of surfactant Span 80 (sorbitan monooleate) and Tween 80 (polyoxyethylene sorbitan monooleate) (mass ratio 1:2) was dissolved in 20 mL of glycerol / water mixed solvent (volume ratio 1:1) and recorded as solution C; solution A and solution B were added to solution C in sequence under stirring at 1400 rpm, emulsified for 40 min, and rotary evaporated at 50 °C for 4 h to obtain black polymer-coated Si powder; (4) Electrode preparation: Weigh the polymer-coated Si powder, PAA, acetylene black and CNT in a mass ratio of 70:15:12:3, stir for 6 hours to form a slurry, coat copper foil with a scraper, and vacuum dry at 80°C for 12 hours to obtain the self-healing silicon-based lithium battery anode material.

[0052] Example 3 A self-healing silicon-based lithium battery anode material and its preparation method are described below: (1) Synthesis of linear polymer: A 250 mL three-necked flask was heated, evacuated, and purged with argon gas. 5.27 mL acrylonitrile, 0.212 mL allyl methacrylate (molar ratio = 50:1), 50 mL dimethyl sulfoxide, 0.0888 g azobisisobutyronitrile and 0.004 g methyl 3-mercaptopropionate were added to the flask. After purging with argon gas for 8 minutes, the flask was sealed and placed in an oil bath at 70 °C with magnetic stirring for 5 h. After the reaction was completed, the reaction solution was added dropwise to 250 mL of ice-cold methanol to precipitate flocculent precipitate. The product was collected by centrifugation at 3500 rpm for 10 min, washed 3 times with anhydrous ethanol, and dried under vacuum at 50 °C for 12 h to obtain the linear polymer. (2) Preparation of self-healing crosslinked polymer: 0.3 g of linear polymer was completely dissolved in 3.2 mL of N,N-dimethylformamide, transferred to a 100 mL three-necked flask purged with argon, and 18 mg of TMPMP and 0.014 g of MTBD were added in sequence. After sealing, the mixture was magnetically stirred at 40 °C for 3 h and then vacuum dried at 60 °C for 12 h to obtain the self-healing crosslinked polymer. (3) Preparation of polymer-coated nano-silicon: 100 mg of nano-silicon was dispersed in 10 mL of toluene and sonicated for 30 min (solution A); 200 mg of self-healing polymer was dissolved in 5 mL of DMF (solution B); 200 mg of maleic anhydride-modified Pluronic F127 was dissolved in 20 mL of formamide (solution C); solution A was injected into solution C under stirring at 1000 rpm, and after mixing for 5 min, solution B was added. The mixture was stirred at 1000 rpm for 1 h to form an emulsion. The emulsion was frozen at -50℃ for 24 h and then freeze-dried at -80℃ / 0.1 Pa to obtain black polymer-coated Si powder. (4) Electrode preparation: Weigh the polymer-coated Si powder, PAA, acetylene black and CNT in a mass ratio of 70:15:12:3, stir for 6 hours to form a slurry, coat copper foil with a scraper, and vacuum dry at 80°C for 12 hours to obtain the self-healing silicon-based lithium battery anode material.

[0053] Example 4 A self-healing silicon-based lithium battery anode material and its preparation method are described below: (1) Synthesis of linear polymer: A 250 mL three-necked flask was heated, evacuated, and purged with argon gas. 5.27 mL acrylonitrile, 0.212 mL allyl methacrylate (molar ratio = 50:1), 50 mL dimethyl sulfoxide, 0.0888 g azobisisobutyronitrile and 0.004 g methyl 3-mercaptopropionate were added to the flask. After purging with argon gas for 8 minutes, the flask was sealed and placed in an oil bath at 70 °C with magnetic stirring for 5 h. After the reaction was completed, the reaction solution was added dropwise to 250 mL of ice-cold methanol to precipitate flocculent precipitate. The product was collected by centrifugation at 3500 rpm for 10 min, washed 3 times with anhydrous ethanol, and dried under vacuum at 50 °C for 12 h to obtain the linear polymer. (2) Preparation of self-healing crosslinking polymer: 0.3g of linear polymer was completely dissolved in 3.2mL of N,N-dimethylformamide, transferred to a 100mL three-necked flask purged with argon, and 22μL of EGDMP and 0.02g of TPO were added in sequence. Under nitrogen protection, the mixture was irradiated with 365nm UV light for 30min to obtain a brownish-yellow solid, which is the self-healing crosslinking polymer. (3) Preparation of polymer-coated nano-silicon: 100 mg of nano-silicon was dispersed in 10 mL of cyclohexane and sonicated for 30 min (solution A); 200 mg of self-healing polymer was dissolved in 5 mL of DMF (solution B); 200 mg of HS-PEG was added to the solution. 1000 -SH was dissolved in 20 mL of ethylene glycol (solution C); solution A and solution B were added to solution C in sequence while stirring at 1400 rpm; emulsification was carried out at 1000 rpm for 1 h in an ice-water bath at 15 °C; and rotary evaporation was carried out at 50 °C for 4 h to obtain black polymer-coated Si powder. (4) Electrode preparation: Weigh the polymer-coated Si powder, PAA, acetylene black and CNT in a mass ratio of 70:15:12:3, stir for 6 hours to form a slurry, coat copper foil with a scraper, and vacuum dry at 80°C for 12 hours to obtain the self-healing silicon-based lithium battery anode material.

[0054] Comparative Example 1 A silicon-based lithium battery anode material and its preparation method are disclosed, with the following specific steps: Nano-Si powder, PAA, acetylene black and CNT were weighed in a mass ratio of 70:15:12:3, stirred for 6 hours to form a slurry, coated with copper foil with a scraper, and vacuum dried at 80°C for 12 hours to obtain the silicon-based lithium battery anode material.

[0055] Comparative Example 2 A silicon-based lithium battery anode material and its preparation method are disclosed, with the following specific steps: (1) Preparation of polymer-coated silicon nanoparticles: 100 mg of silicon nanoparticles were dispersed in 10 mL of toluene and sonicated for 30 min (solution A); 200 mg of polyacrylonitrile (molecular weight Mw≈80 kDa) was dissolved in 5 mL of DMF (solution B); 200 mg of Pluronic F108 was dissolved in 20 mL of formamide (solution C); and solutions A and B were added to solution C in sequence under stirring at 1400 rpm, emulsified for 40 min, and rotary evaporated at 80 °C for 4 h to obtain black polymer-coated Si powder; (2) Electrode preparation: Weigh the polymer-coated Si powder, PAA, acetylene black and CNT in a mass ratio of 70:15:12:3, stir for 6 hours to form a slurry, coat copper foil with a scraper, and vacuum dry at 80°C for 12 hours to obtain the silicon-based lithium battery anode material.

[0056] Performance testing The silicon-based lithium battery anode materials prepared in each embodiment and comparative example were cut into pieces, assembled into button batteries, and the battery performance was tested.

[0057] Coin cell fabrication method: Silicon-based lithium battery anode material is cut into circular pieces with a diameter of less than 12 mm and transferred to a glove box with a high-purity argon environment for assembly of CR2016 model coin cells. The water and oxygen content in the glove box is below 0.01 ppm. In the coin cell, metallic lithium is used as the counter electrode of the silicon anode. The electrolyte is 1 mol / L lithium hexafluorophosphate dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1, and 10% by mass of fluoroethylene carbonate is added.

[0058] Electrochemical performance testing method: Constant current charge-discharge tests were conducted using the LAND CT3002A battery testing system under the following conditions: discharge current density of 200 mA / g, initial discharge cutoff voltage of 0.01 V; charging current density of 200 mA / g, initial charging cutoff voltage of 1.5 V; after three cycles, the coin cells were subjected to constant current charge-discharge tests at a current density of 1000 mA / g within a voltage range of 0.01 V to 1.5 V.

[0059] The performance test results of the button batteries assembled with the silicon-based lithium battery anode materials prepared in each embodiment and comparative example are shown in Table 1 below.

[0060] Table 1

[0061] Table 1 shows that the button batteries assembled using the self-healing silicon-based lithium battery anode material prepared in the embodiments of the present invention exhibit significant advantages in key electrochemical performance aspects such as initial discharge specific capacity, rate performance, cycle life, and interfacial impedance. Compared with Comparative Example 1 (pure nano-silicon anode) without self-healing polymer coating, the initial discharge specific capacity of Examples 1-4 is slightly lower than that of Comparative Example 1. However, in terms of rate performance, Comparative Example 1 has almost zero capacity at a high rate of 5C, while the embodiments show excellent high-rate charge-discharge capabilities. Regarding cycle stability, the capacity retention rate of Comparative Example 1 after 300 cycles is only 23.3%. Comparative Example 2, after being coated with ordinary polyacrylonitrile, shows improved cycle life, but it is still far lower than the capacity retention rate of over 70% in the embodiments. This indicates that the self-healing cross-linked polymer network can effectively alleviate the volume expansion of silicon material during charge and discharge, inhibit the damage to the electrode structure, and thus significantly improve cycle stability. In addition, the interfacial impedance of each embodiment is lower than that of Comparative Example 1 and Comparative Example 2, indicating that the self-healing polymer coating layer of the present invention helps to improve the interfacial compatibility between the electrode and the electrolyte.

[0062] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A self-healing silicon-based lithium battery anode material, characterized in that, It includes a nano-silicon particle core and a self-healing cross-linked polymer coating the surface of the nano-silicon particle core; The self-healing crosslinking polymer is prepared by crosslinking a linear polymer with a multifunctional thiol compound via a thiol-Michael addition reaction; The linear polymer is prepared by free radical copolymerization of acrylonitrile and allyl methacrylate.

2. The self-healing silicon-based lithium battery anode material according to claim 1, characterized in that, The mass ratio of the nano-silicon particles to the self-healing crosslinked polymer is 1:(1~3); the molar ratio of acrylonitrile to allyl methacrylate in the linear polymer is (30~50):

1.

3. The method for preparing the self-healing silicon-based lithium battery anode material as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Under an inert atmosphere, acrylonitrile, allyl methacrylate, a first organic solvent, a free radical initiator, and a chain transfer agent are mixed and reacted at 60-80°C for 3-8 hours. After post-treatment, a linear polymer is obtained. S2. Dissolve the linear polymer in a second organic solvent, add a multifunctional thiol compound and a catalyst, and carry out a thiol-Michael addition reaction at 30~50°C for 1~5 hours. After drying, a self-healing crosslinked polymer is obtained. S3. Prepare nano-silicon suspension, self-healing cross-linked polymer solution and surfactant solution respectively; add the nano-silicon suspension and the self-healing cross-linked polymer solution to the surfactant solution, stir and emulsify, and then remove the solvent to obtain self-healing silicon-based lithium battery anode material.

4. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S1, the molar ratio of acrylonitrile to allyl methacrylate is (30~50):1; And / or, the free radical initiator is 2% to 5% of the total mass of the acrylonitrile and the allyl methacrylate; And / or, the chain transfer agent is 0.1% to 0.3% of the total mass of the acrylonitrile and the allyl methacrylate; And / or, the molar volume ratio of the allyl methacrylate to the first organic solvent is 1 mol: (40~60) mL.

5. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S1, the free radical initiator is selected from at least one of azo compounds and organic peroxides; And / or, the chain transfer agent is an alkyl thiol or a thiol compound containing hydroxyl / carboxyl groups; And / or, the first organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran.

6. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S2, the molar ratio of the linear polymer to the polyfunctional thiol compound is 1:(10~40). And / or, the amount of the catalyst is 1-8 wt% of the total mass of the linear polymer and the polyfunctional thiol compound; And / or, the mass-to-volume ratio of the linear polymer to the second organic solvent is 1 g: (8~15) mL.

7. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S2, the second organic solvent is selected from any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran; And / or, the polyfunctional thiol compound is an organic compound containing 2 to 4 thiol groups; And / or, the catalyst comprises a strong organic base or a photoinitiator.

8. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S3, the mass ratio of the nano-silicon particles to the self-healing crosslinking polymer and the surfactant is 1:(1~3):(1~3).

9. The method for preparing the self-healing silicon-based lithium battery anode material according to claim 3, characterized in that, In step S3, the nano-silicon suspension is obtained by dispersing nano-silicon particles in a third organic solvent; the third organic solvent is a non-polar or weakly polar organic solvent with a boiling point of 60~120℃. And / or, the self-healing crosslinking polymer solution is obtained by dissolving the self-healing crosslinking polymer in a fourth organic solvent; the fourth organic solvent is a polar aprotic solvent with a boiling point >150℃; And / or, the surfactant solution is obtained by dissolving the surfactant in a fifth organic solvent; the fifth organic solvent is a highly polar solvent with a dielectric constant >30; the surfactant is a nonionic surfactant with an HLB value of 12~30.

10. A lithium battery, characterized in that, The raw materials used in the preparation include the self-healing silicon-based lithium battery anode material as described in any one of claims 1 to 2.

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