Negative electrode material with a hollow multi-core shell structure, preparation method thereof and application

Abstract

The present invention relates to a negative electrode material with a hollow multi-core shell structure, a preparation method thereof, and an application. The inner core of the negative electrode material is a composite sphere of a metal-doped nano-silicon-based material and a first carbon material. The composite sphere has a multi-pore structure. The outer shell is a composite of carbon black particles, carbon nanotubes and / or carbon fibers and a second carbon material. The inner core accounts for (70%, 95%] of the total mass of the negative electrode material, and the outer layer accounts for (5%, 30%] of the total mass of the negative electrode material. The general formula of the metal-doped nano-silicon-based material is SiMxOy, where 0 < x ≤ 10 and 0 ≤ y ≤ 10, and M is a metal doping element, including one or more of Mg, Ca, Ba, Ti, Li, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na, B. The precursor material of the first carbon material is a low-residual-carbon carbon source. The precursor material of the second carbon material is a high-residual-carbon carbon source.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium secondary batteries, and particularly relates to a negative electrode material with a hollow multi-nuclear shell structure, a preparation method thereof, and an application thereof. Background Art

[0002] Silicon, as a negative electrode material for lithium ion batteries, has a theoretical reversible capacity as high as 4200 mAh / g. However, due to the huge volume effect during the process of lithium deintercalation and intercalation, problems such as the collapse of the electrode material structure and the instability of the solid electrolyte interface (SEI) film occur in silicon materials, which greatly reduces the cycle performance of the battery. Currently, the modification work on silicon-based materials is continuously carried out. In the literature (H. Li, X. J. Huang, L. Q. Chen, Z. G. Wu, Y. Liang, Electrochem. and Solid-State Lett., 2, 547-549 (1999)), Li et al. prepared a negative electrode material using nanoscale silicon particles, which can reduce the volume effect, improve the cycle performance of the silicon-based negative electrode material, and maintain a relatively high reversible capacity (1700 mAh / g). Miyachi et al. found that doping 25% of Fe, Ti, or Ni can significantly increase the first Coulombic efficiency of SiO X to 84%-86%.

[0003] However, at present, silicon-based materials still have problems such as volume expansion during the process of lithium deintercalation and intercalation and poor cycle stability. The silicon-carbon negative electrode material with a hollow structure described in CN108258230A and the hollow core-shell structure composite material in CN107482188A utilize the difference in the residual carbon rate of the carbon source to provide a reserved space for the volume expansion of the silicon-based material. However, due to the volume change accompanied by the decomposition of the carbon source itself during the carbonization process, stress will be generated between the two mutually contacting carbon sources, resulting in damage to the structure itself during the carbonization process, such as uneven stress on the outer shell and reduced structural strength. These problems may cause damage to the overall structure during processes such as pulping, coating, and rolling. During the later charge-discharge cycle process, it cannot withstand the huge volume effect of the silicon-based material itself, resulting in the inability to achieve the expected good cycle stability. Summary of the Invention

[0004] An embodiment of the present invention provides a negative electrode material with a hollow multi-nuclear shell structure, a preparation method thereof, and an application thereof. The negative electrode material is used for the negative electrode of a lithium ion battery and has the advantages of stable structure, excellent cycle performance, and good rate performance.

[0005] In a first aspect, an embodiment of the present invention provides a negative electrode material having a hollow multi-capsule core-shell structure. The core of the negative electrode material is a composite sphere of a metal-doped nano-silicon-based material and a first carbon material. The composite sphere has a multi-capsule pore structure inside. The outer shell is a composite of carbon black particles, carbon nanotubes and / or carbon fibers and a second carbon material, and the diameter ranges from 20 μm to 200 μm.

[0006] The core accounts for (70%, 95%] of the total mass of the negative electrode material, and the outer layer accounts for (5%, 30%] of the total mass of the negative electrode material.

[0007] The general formula of the metal-doped nano-silicon-based material is SiMxOy, where 0 < x ≤ 10 and 0 ≤ y ≤ 10. M is a metal doping element, including one or more of Mg, Ca, Ba, Ti, Li, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na, B. The precursor material of the first carbon material is a low-residual-carbon carbon source, and the residual carbon rate at 900 °C is ≤ 20%. The nano-silicon-based material includes one or more combinations of silicon, silicon dioxide, and silicon suboxide. The particle size range of the composite sphere is from 1 μm to 30 μm.

[0008] The precursor material of the second carbon material is a high-residual-carbon carbon source, and the residual carbon rate at 900 °C is ≥ 40%. The diameter of the carbon black particles is ≤ 20 nm. The diameter of the carbon nanotubes is ≤ 1 μm, and the length is ≤ 50 μm. The diameter of the carbon fibers is ≤ 1 μm, and the length is ≤ 50 μm.

[0009] Preferably, the low-residual-carbon carbon source specifically includes: one or more of glucose, sucrose, and polyvinylpyrrolidone.

[0010] The high-residual-carbon carbon source specifically includes: one or more of phenolic resin, epoxy resin, and urea-formaldehyde resin.

[0011] Preferably, the high-residual-carbon carbon source and the low-residual-carbon carbon source are dissolved in different solvent systems.

[0012] In a second aspect, an embodiment of the present invention provides a preparation method of the negative electrode material having a hollow multi-capsule core-shell structure described in the first aspect. The preparation method includes:

[0013] Step 1: Inject the nano-silicon-based material and the simple substance or oxide of the metal doping element into the reactor at the same time, and perform heat treatment on the mixed powder of the nano-silicon-based material and the simple substance or oxide of the metal doping element under a protective atmosphere at 400 °C to 1200 °C for 1 hour to 10 hours, and then grind the obtained product into particles. The molar ratio of the nano-silicon-based material to the simple substance or oxide of the metal doping element is 1:0.001 to 1:10. The average particle size of the particles is from 1 nm to 1 μm.

[0014] Step 2: After mixing the particles obtained in Step 1 with the low-residual-carbon source at a mass ratio of 1:0.1 to 1:10, add a first solvent according to a solid-to-solvent mass ratio of 1:100 to 1:1000, stir until the low-residual-carbon source is dissolved, perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain first spray granulation particles, with the average particle size of the first spray granulation particles being in the range of 1 nm to 30 μm;

[0015] Step 3: Mix the first spray granulation particles obtained in Step 2 with carbon black, carbon nanotubes, and / or carbon fibers, and a high-residual-carbon source in a ratio of A:B:C:D; 0 < A ≤ 10, 0 < B ≤ 15, 0 < C ≤ 5, 0 < D ≤ 50; add a second solvent according to a solid-to-solvent mass ratio of 1:50 to 1:200, stir until the high-residual-carbon source is dissolved, perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain second spray granulation particles, with the average particle size of the second spray granulation particles being in the range of 20 nm to 300 μm; wherein, the second solvent does not dissolve the low-residual-carbon source;

[0016] Step 4: Heat the second spray granulation particles obtained in Step 3 from room temperature to 700 °C to 1300 °C at a rate of 1 °C / min to 10 °C / min in a protective atmosphere environment, and hold for 0.5 hour to 15 hours, so that the low-residual-carbon source undergoes carbonization to form a multi-cyst pore structure in the core, thereby obtaining the anode material with a hollow multi-cyst core-shell structure.

[0017] Preferably, the heat treatment is carried out in a vacuum environment or a protective atmosphere, and the protective atmosphere is a nitrogen atmosphere or an inert atmosphere.

[0018] Preferably, the first solvent is distilled water or ethanol; the second solvent includes one or a mixture of several of acetone, styrene, perchloroethylene, trichloroethylene, ethylene glycol ether, or triethanolamine.

[0019] Preferably, during the spray granulation in Step 2, the outlet temperature of the spray dryer is 130 - 200 °C, and the pressure is 3 - 4 MPa.

[0020] Preferably, during the spray granulation in Step 3, the outlet temperature of the spray dryer is 100 - 150 °C, and the pressure is 3 - 4 MPa.

[0021] In a third aspect, an embodiment of the present invention provides a use of the anode material with a hollow multi-cyst core-shell structure described in the first aspect above, and the anode material is used as the anode material of a lithium-ion battery.

[0022] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery with an anode material having a hollow multi-cyst core-shell structure.

[0023] The negative electrode material with a hollow multi-capsule core-shell structure proposed by the present invention has a composite sphere of a nano-silicon-based material and a carbon material as its inner core to ensure electrochemical performance. The pores left after carbonization of the low-residual-carbon carbon source in the inner core can provide a buffer space for the expansion of the silicon-based material, so as to eliminate the influence of volume expansion of the silicon-based material during the lithium insertion and extraction process. The outermost layer is a composite of carbon black particles, carbon nanotubes and / or carbon fibers and a carbon material, which plays a role in supporting the outer shell and increasing conductivity, ensuring the strength and stability of the overall structure during the processes of beating, coating, rolling and charge and discharge, and further ensuring the cycle stability of the material. At the same time, by using the difference in the residual carbon content of the carbon source, a process flow for constructing a core-shell structure by secondary spraying is adopted, so as to have better process stability in quantitative production, prevent the problem of incomplete coating of the silicon-based material, and effectively improve the cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0025] Figure 1 It is a schematic structural diagram of the negative electrode material with a hollow capsule-like core-shell structure provided by an embodiment of the present invention;

[0026] Figure 2 It is a scanning electron microscope (SEM) image of the negative electrode material with a hollow capsule-like core-shell structure provided by an embodiment of the present invention;

[0027] Figure 3 It is a flow chart of the preparation method of the negative electrode material with a hollow capsule-like core-shell structure provided by an embodiment of the present invention;

[0028] Figure 4 It is a full cell capacity retention graph of Embodiment 1, Embodiment 2 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below with reference to the drawings and specific embodiments, but it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0030] The negative electrode material with a hollow multi-capsule core-shell structure of the present invention is a composite material with a core-shell structure. The inner core is a composite sphere of a metal-doped nano-silicon-based material and a first carbon material, and the composite sphere has a multi-capsule pore structure. The outer shell is a composite of carbon black particles, carbon nanotubes and / or carbon fibers and a second carbon material, and the diameter range is 20um to 200um;

[0031] Among them, the inner core of the multi-cysts accounts for (70%, 95%] of the total mass of the anode material, and the outer layer accounts for (5%, 30%] of the total mass of the anode material;

[0032] In the inner core, the general formula of the metal-doped nano-silicon-based material is SiMxOy, where 0 < x ≤ 10 and 0 ≤ y ≤ 10. Here, M is a metal doping element, including one or more of Mg, Ca, Ba, Ti, Li, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na, B; the precursor material of the first carbon material is a low-residual-carbon carbon source, and the residual-carbon rate at 900 °C ≤ 20%; the nano-silicon-based material includes a combination of one or more of silicon, silicon dioxide, and silicon suboxide; the particle size range of the composite sphere is from 1 μm to 30 μm;

[0033] In the outer shell, the precursor material of the second carbon material is a high-residual-carbon carbon source, and the residual-carbon rate at 900 °C ≥ 40%; the diameter of the carbon black particles ≤ 20 nm; the diameter of the carbon nanotubes ≤ 1 μm and the length ≤ 50 μm; the diameter of the carbon fibers ≤ 1 μm and the length ≤ 50 μm.

[0034] In the present invention, the above-mentioned high-residual-carbon carbon source and low-residual-carbon carbon source are dissolved in different solvent systems.

[0035] Specifically, the low-residual-carbon carbon source may include: one or more of glucose, sucrose, and polyvinylpyrrolidone. The high-residual-carbon carbon source may include: one or more of phenolic resin, epoxy resin, and urea-formaldehyde resin.

[0036] Figure 1 It is a schematic structural diagram of the anode material with a hollow multi-cyst core-shell structure provided by an embodiment of the present invention. Among them, in the inner core, it can be seen: the metal-doped nano-silicon-based material 11, the first carbon material 12 obtained by carbonizing the low-residual-carbon carbon source, and the multi-cyst pores 13; in the outer shell, it can be seen: the second carbon material 21 obtained by carbonizing the high-residual-carbon carbon source, the carbon black particles 22, and the carbon nanotubes and / or carbon fibers 23.

[0037] The anode material of the present invention presents a hollow multi-cyst core-shell structure, as shown by scanning electron microscopy (SEM) Figure 2 shown.

[0038] In the present invention, through the composite sphere of the nano-silicon-based material and the carbon material in the inner core, the electrochemical performance of the material is guaranteed. The pores left after carbonizing the low-residual-carbon carbon source in the inner core can provide a buffer space for the expansion of the silicon-based material, eliminating the influence of the volume expansion of the silicon-based material during the lithium insertion and extraction process. The composite body of the carbon black particles, carbon nanotubes and / or carbon fibers and the carbon material in the outer layer plays a role in supporting the outer shell and increasing the conductivity, ensuring the strength and stability of the overall structure during pulping, coating, rolling, and charge and discharge processes, and further guaranteeing the cycle stability of the material.

[0039] The above-mentioned negative electrode material of the present invention can be prepared by the following preparation method. Its main process can be as Figure 3 shown, including:

[0040] Step 110: Inject the nano-silicon-based material and the simple substance or oxide of the metal doping element into the reactor at the same time, and heat-treat the mixed powder of the nano-silicon-based material and the simple substance or oxide of the metal doping element under a protective atmosphere at 400°C to 1200°C for 1 hour to 10 hours, and then grind the obtained product into particles;

[0041] Among them, the molar ratio of the nano-silicon-based material to the simple substance or oxide of the metal doping element is 1:0.001 to 1:10; the average particle size of the ground particles is 1 nm to 1 μm.

[0042] The above heat treatment is carried out in a vacuum environment or a protective atmosphere, and the protective atmosphere is a nitrogen atmosphere or an inert atmosphere.

[0043] Step 120, after mixing the obtained particles with the low-residual-carbon carbon source in a mass ratio of 1:0.1 to 1:10, add the first solvent according to a solid-to-solvent mass ratio of 1:100 to 1:1000, stir until the low-residual-carbon carbon source is dissolved, then perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain the first spray granulation particles;

[0044] Among them, the average particle size of the first spray granulation particles is 1 nm to 30 μm; the first solvent is distilled water or ethanol.

[0045] In the process of spray granulation in this step, the outlet temperature of the spray dryer is 130 to 200°C, and the pressure is 3 to 4 MPa.

[0046] Step 130, mix the first spray granulation particles with carbon black, carbon nanotubes and / or carbon fibers, and the high-residual-carbon carbon source in proportion, add the second solvent according to a solid-to-solvent mass ratio of 1:50 to 1:200, stir until the high-residual-carbon carbon source is dissolved, then perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain the second spray granulation particles;

[0047] Among them, the mixing ratio is A:B:C:D; 0 < A ≤ 10, 0 < B ≤ 15, 0 < C ≤ 5, 0 < D ≤ 50; the average particle size of the second spray granulation particles is 20 nm to 300 μm; the second solvent does not dissolve the low-residual-carbon carbon source; the second solvent includes: one or several mixtures of acetone, styrene, perchloroethylene, trichloroethylene, ethylene glycol ether or triethanolamine.

[0048] In the process of spray granulation in this step, the outlet temperature of the spray dryer is 100 to 150°C, and the pressure is 3 to 4 MPa.

[0049] Step 140: Heat the second spray granulation particles from room temperature to 700°C - 1300°C at a rate of 1°C / min - 10°C / min in a protective atmosphere environment, and hold for 0.5 - 15 hours, so that the low-residual carbon source undergoes carbonization to form a multi-cyst pore structure in the core. After cooling, a negative electrode material with a hollow multi-cyst core-shell structure is obtained.

[0050] The preparation method of the negative electrode material with a hollow cystic core-shell structure provided by the present invention is simple, easy to operate, highly safe, and easy for large-scale production. The negative electrode material prepared by this method is used for the negative electrode of a lithium-ion battery, and has the advantages of stable structure, excellent cycling performance, and good rate performance.

[0051] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process and application performance of preparing the negative electrode material by using the method provided in the above embodiments of the present invention.

[0052] Example 1

[0053] This example provides a method for preparing a negative electrode composite material with a hollow cystic core-shell structure, including:

[0054] (1) Take nano-silicon monoxide powder and nano-aluminum oxide powder and uniformly mix them in a molar ratio of 1:1 to form 1 kg of a mixture and inject it into a reactor. Heat-treat the mixture at 1200°C in a protective atmosphere and hold for 1 hour. Grind and screen the product to obtain aluminum-containing silicon oxide composite powder;

[0055] (2) After mixing the composite powder obtained in (1) with glucose in a mass ratio of 1:5, add distilled water according to a solid-to-solvent mass ratio of 1:300, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and use a spray dryer for spray granulation, with an outlet temperature of 150°C and a pressure of 3 MPa;

[0056] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10, add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and use a spray dryer for spray granulation, with an outlet temperature of 130°C and a pressure of 3 MP;

[0057] (4) Heat the composite powder obtained by spray granulation in (3) from room temperature to 900°C at a rate of 5°C / min in a protective atmosphere environment, and hold for 6 hours to obtain the composite negative electrode material with a hollow multi-cyst core-shell structure.

[0058] The prepared composite anode material is uniformly mixed with carbon black with a mass ratio of 2%, sodium carboxymethyl cellulose with a mass ratio of 2%, and styrene-butadiene rubber with a mass ratio of 3% in an aqueous solvent to form a battery anode slurry. The slurry is coated on a copper foil, dried and cut into 8*8 mm square pieces. After vacuum drying at 110 °C for 12 hours, a half-cell is assembled with a lithium sheet in a glove box to evaluate its electrochemical performance.

[0059] The electrochemical test mode is as follows: in the first week, it is discharged to 0.005 V at 0.1 C, discharged to 0.005 V at 0.05 C, discharged to 0.005 V at 0.02 C, then left standing for 5 s and charged to 1 V cutoff at 0.1 C. In subsequent cycles, it is discharged to 0.005 V at 0.5 C, discharged to 0.005 V at 0.2 C, discharged to 0.005 V at 0.05 C, discharged to 0.005 V at 0.02 C, left standing for 5 s and then charged to 1 V cutoff at 0.5 C.

[0060] The above discharge is the process of lithium insertion, corresponding to charging in the full cell; the charging is the process of lithium extraction, corresponding to discharging in the full cell.

[0061] After coating the obtained anode material on a copper foil according to the above ratio, a 1 Ah soft-pack battery is assembled with lithium cobaltate as the cathode to test its cycling performance at 0.5 C.

[0062] Example 2

[0063] This example provides a method for preparing a negative composite material with a hollow capsule-like core-shell structure, including:

[0064] (1) Take nano-silicon monoxide powder and nano-copper oxide powder and uniformly mix them in a molar ratio of 1:10 to form 1 kg of a mixture and inject it into a reactor. The mixture is heat-treated at 1200 °C under a protective atmosphere for 10 hours. The product is ground and sieved to obtain copper-containing silicon oxide composite powder;

[0065] (2) After mixing the composite powder obtained in (1) with glucose in a mass ratio of 1:10, add distilled water according to a solid-to-solvent mass ratio of 1:1000, stir until the glucose is completely dissolved, ultrasonically treat for 5 minutes, and perform spray granulation using a spray dryer with an outlet temperature of 150 °C and a pressure of 3 MPa;

[0066] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:15:3:50, add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, ultrasonically treat for 5 minutes, and perform spray granulation using a spray dryer with an outlet temperature of 120 °C and a pressure of 3 MP;

[0067] (4) Heat the composite powder obtained in (3) to 1300 °C at a rate of 10 °C / min in a protective atmosphere, and then hold for 15 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0068] Battery assembly and testing were carried out in the same manner as in Example 1.

[0069] To visually compare their cyclic capacity retention performance, the following compares Comparative Example 1 with Examples 1 and 2.

[0070] Comparative Example 1

[0071] This comparative example provides a method for a metal-doped silicon-carbon anode composite material, including:

[0072] (1) Take nano-sized silicon monoxide powder and nano-sized alumina powder, mix them evenly in a molar ratio of 1:1 to form 1 kg of a mixture, and inject it into a reactor. Heat-treat the mixture at 1200 °C in a protective atmosphere and hold for 1 hour. Grind and screen the product to obtain an aluminum-containing silicon oxide composite powder;

[0073] (2) Mix the composite powder obtained in (1) with glucose in a mass ratio of 1:5, then add distilled water according to a solid-to-solvent mass ratio of 1:300, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer with an outlet temperature of 150 °C and a pressure of 3 MPa;

[0074] (3) Heat the composite powder obtained in (2) to 1300 °C at a rate of 10 °C / min in a protective atmosphere, and then hold for 15 hours to obtain the metal-doped silicon-carbon anode composite material, which has no core-shell structure.

[0075] Battery assembly and testing were carried out in the same manner as in Example 1.

[0076] Cycling tests were carried out on the full cells assembled with the materials prepared in Examples 1 and 2 and Comparative Example 1 above. Figure 4 This is the full cell capacity retention graph of Example 1, Example 2 and Comparative Example 1 of the present invention. It can be seen from the comparison between Comparative Example 1 and Examples 1 and 2 that because the anode composite material with a hollow capsule-like core-shell structure in the examples has a larger and more reasonable internal buffer space layout, it can better ensure structural stability compared with Comparative Example 1, and thus improve the cycling stability. In particular, the cycling capacity retention rate after 150 cycles has a significant improvement compared with Comparative Example 1.

[0077] Example 3

[0078] This example provides a method for preparing an anode composite material with a hollow capsule-like core-shell structure, including:

[0079] (1) Take nano-silicon monoxide powder and nano-titanium oxide powder and uniformly mix them in a molar ratio of 1:5 to form 1 kg of a mixture, which is then injected into a reactor. Heat-treat the mixture under a protective atmosphere at 1100 °C for 6 hours. Grind and screen the product to obtain a titanium-containing silicon oxide composite powder;

[0080] (2) After mixing the composite powder obtained in (1) with polyvinylpyrrolidone (PVP) in a mass ratio of 1:10, add distilled water according to a solid-to-solvent mass ratio of 1:100, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer with an outlet temperature of 120 °C and a pressure of 3 MPa;

[0081] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10, add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer with an outlet temperature of 200 °C and a pressure of 3 MP;

[0082] (4) Heat the composite powder obtained in (3) in a protective atmosphere environment at a rate of 5 °C / min to 900 °C, and then hold for 8 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0083] Example 4

[0084] This example provides a method for preparing a negative electrode composite material with a hollow capsule-like core-shell structure, including:

[0085] (1) Take nano-silicon monoxide powder and nano-copper oxide powder and uniformly mix them in a molar ratio of 1:9 to form 1 kg of a mixture, which is then injected into a reactor. Heat-treat the mixture under a protective atmosphere at 400 °C for 10 hours. Grind and screen the product to obtain a copper oxide-containing silicon oxide composite powder;

[0086] (2) After mixing the composite powder obtained in (1) with PVP in a mass ratio of 1:10, add distilled water according to a solid-to-solvent mass ratio of 1:100, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer with an outlet temperature of 120 °C and a pressure of 3 MPa;

[0087] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10, add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer with an outlet temperature of 150 °C and a pressure of 3 MP;

[0088] (4) Heat the composite powder obtained in (3) to 900 °C at a rate of 5 °C / min in a protective atmosphere, and then hold for 8 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0089] Example 5

[0090] This example provides a method for preparing a negative composite material with a hollow capsule-like core-shell structure, including:

[0091] (1) Take nano-silicon monoxide powder and nano-copper oxide powder, mix them evenly at a molar ratio of 1:10 to form 1 kg of mixture, and inject it into the reactor. Heat-treat the mixture at 400 °C in a protective atmosphere and hold for 5 hours. Grind and screen the product to obtain a copper-containing oxide composite powder;

[0092] (2) Mix the composite powder obtained in (1) with PVP at a mass ratio of 1:10, then add distilled water at a solid-to-solvent mass ratio of 1:100, stir until glucose is completely dissolved, ultrasonically treat for 5 minutes, and perform spray granulation using a spray dryer with an outlet temperature of 120 °C and a pressure of 3 MPa;

[0093] (3) Mix the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin at a mass ratio of 1:5:2:10, then add acetone at a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, ultrasonically treat for 5 minutes, and perform spray granulation using a spray dryer with an outlet temperature of 130 °C and a pressure of 3 MP;

[0094] (4) Heat the composite powder obtained in (3) to 900 °C at a rate of 5 °C / min in a protective atmosphere, and then hold for 8 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0095] Example 6

[0096] This example provides a method for preparing a negative composite material with a hollow capsule-like core-shell structure, including:

[0097] (1) Take nano-silicon monoxide powder and nano-magnesium oxide powder, mix them evenly at a molar ratio of 1:10 to form 1 kg of mixture, and inject it into the reactor. Heat-treat the mixture at 800 °C in a protective atmosphere and hold for 8 hours. Grind and screen the product to obtain a magnesium-containing oxide composite powder;

[0098] (2) Mix the composite powder obtained in (1) with PVP at a mass ratio of 1:10, then add distilled water at a solid-to-solvent mass ratio of 1:100, stir until glucose is completely dissolved, ultrasonically treat for 5 minutes, and perform spray granulation using a spray dryer with an outlet temperature of 140 °C and a pressure of 3 MPa;

[0099] (3) Mix the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10. After that, add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer. The outlet temperature is 120 °C and the pressure is 3 MP;

[0100] (4) Heat the composite powder obtained in (3) to 900 °C at a rate of 5 °C / min in a protective atmosphere environment, and hold for 8 hours to obtain the composite anode material with a hollow multi-capsule core-shell structure.

[0101] Example 7

[0102] This example provides a method for preparing a negative electrode composite material with a hollow capsule-like core-shell structure, including:

[0103] (1) Take nano-silicon monoxide powder and nano-magnesium oxide powder and uniformly mix them in a molar ratio of 1:10 to form 1 kg of a mixture and inject it into a reactor. Heat-treat the mixture at 900 °C in a protective atmosphere and hold for 2 hours. Grind and screen the product to obtain a magnesium-containing oxidized composite powder;

[0104] (2) Mix the composite powder obtained in (1) with glucose in a mass ratio of 1:5. After that, add distilled water according to a solid-to-solvent mass ratio of 1:100, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer. The outlet temperature is 140 °C and the pressure is 3 MPa;

[0105] (3) Mix the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10. After that, add acetone according to a solid-to-solvent mass ratio of 1:100, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and carry out spray granulation using a spray dryer. The outlet temperature is 120 °C and the pressure is 3 MP;

[0106] (4) Heat the composite powder obtained in (3) to 900 °C at a rate of 5 °C / min in a protective atmosphere environment, and hold for 8 hours to obtain the composite anode material with a hollow multi-capsule core-shell structure.

[0107] Example 8

[0108] This example provides a method for preparing a negative electrode composite material with a hollow capsule-like core-shell structure, including:

[0109] (1) Take nano - silicon monoxide powder and nano - zinc oxide powder and uniformly mix them in a molar ratio of 1:10 to form 1 kg of a mixture, which is then injected into a reactor. Heat - treat the mixture under a protective atmosphere at 800 °C for 8 hours. Grind and screen the product to obtain zinc - containing oxide composite powder;

[0110] (2) After mixing the composite powder obtained in (1) with PVP in a mass ratio of 1:10, add distilled water according to a solid - to - solvent mass ratio of 1:100, stir until glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and then carry out spray granulation using a spray dryer with an outlet temperature of 140 °C and a pressure of 4 MPa;

[0111] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10, add acetone according to a solid - to - solvent mass ratio of 1:200, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and then carry out spray granulation using a spray dryer with an outlet temperature of 150 °C and a pressure of 4 MP;

[0112] (4) Heat the composite powder obtained in (3) from room temperature to 900 °C at a rate of 5 °C / min under a protective atmosphere, and then hold for 8 hours to obtain the composite anode material with a hollow multi - nuclear shell structure.

[0113] Example 9

[0114] This example provides a method for preparing a negative electrode composite material with a hollow - cyst - like core - shell structure, including:

[0115] (1) Take nano - silicon monoxide powder and nano - magnesium oxide powder and uniformly mix them in a molar ratio of 1:10 to form 1 kg of a mixture, which is then injected into a reactor. Heat - treat the mixture under a protective atmosphere at 800 °C for 8 hours. Grind and screen the product to obtain magnesium - containing oxide composite powder;

[0116] (2) After mixing the composite powder obtained in (1) with sucrose in a mass ratio of 1:10, add distilled water according to a solid - to - solvent mass ratio of 1:100, stir until glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and then carry out spray granulation using a spray dryer with an outlet temperature of 140 °C and a pressure of 3 MPa;

[0117] (3) After mixing the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:5:30, add acetone according to a solid - to - solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and then carry out spray granulation using a spray dryer with an outlet temperature of 120 °C and a pressure of 3 MP;

[0118] (4) Heat the composite powder obtained in (3) to 1000 °C at a rate of 5 °C / min in a protective atmosphere, and then hold for 6 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0119] Example 10

[0120] This example provides a method for preparing a composite anode material with a hollow cystic core-shell structure, including:

[0121] (1) Take nano-silicon monoxide powder and nano-titanium oxide powder and uniformly mix them in a molar ratio of 1:10 to form 1 kg of a mixture, which is then injected into a reactor. Heat-treat the mixture at 800 °C under a protective atmosphere and hold for 8 hours. Grind and screen the product to obtain a titanium-containing oxide composite powder;

[0122] (2) Mix the composite powder obtained in (1) with glucose in a mass ratio of 1:5, then add distilled water according to a solid-to-solvent mass ratio of 1:100, stir until the glucose is completely dissolved, perform ultrasonic treatment for 5 minutes, and use a spray dryer for spray granulation, with an outlet temperature of 140 °C and a pressure of 3 MPa;

[0123] (3) Mix the composite powder obtained in (2) with carbon black, carbon nanotubes, and phenolic resin in a mass ratio of 1:5:2:10, then add acetone according to a solid-to-solvent mass ratio of 1:300, stir until the phenolic resin is completely dissolved, perform ultrasonic treatment for 5 minutes, and use a spray dryer for spray granulation, with an outlet temperature of 100 °C and a pressure of 3 MP;

[0124] (4) Heat the composite powder obtained in (3) to 800 °C at a rate of 5 °C / min in a protective atmosphere, and then hold for 2 hours to obtain the composite anode material with a hollow multi-nuclear shell structure.

[0125] Assemble button cells according to the method of Example 1 for the above examples, and evaluate their electrochemical performance through testing, and the results are recorded in Table 1.

[0126]

[0127] Table 1

[0128] The negative electrode material with a hollow multi-core shell structure proposed by the present invention has a composite sphere of a nano-silicon-based material and a carbon material as its inner core to ensure electrochemical performance. The pores left after the carbonization of the low-residual-carbon carbon source in the inner core can provide a buffer space for the expansion of the silicon-based material, so as to eliminate the influence of the volume expansion of the silicon-based material during the lithium insertion and extraction process. The outermost layer is a composite of carbon black particles, carbon nanotubes, and / or carbon fibers and a carbon material, which plays a role in supporting the outer shell and increasing conductivity, ensuring the strength and stability of the overall structure during the processes of pulping, coating, rolling, and charging and discharging, and further ensuring the cycle stability of the material. At the same time, by utilizing the difference in the residual carbon amount of the carbon source, a process flow for constructing the core-shell structure by secondary spraying is adopted, so as to have better process stability in mass production, prevent the problem of incomplete coating of the silicon-based material, and effectively improve the cycle stability of the material.

[0129] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A negative electrode material with a hollow multi-core shell structure, characterized in that, The core of the negative electrode material is a composite sphere of a metal-doped nano-silicon-based material and a first carbon material. The composite sphere has a multi-cyst pore structure, and the outer shell is a composite of carbon black particles, carbon nanotubes and / or carbon fibers and a second carbon material, with a diameter range of 20 μm to 200 μm; Among them, the core accounts for (70%, 95%] of the total mass of the negative electrode material, and the outer shell accounts for (5%, 30%] of the total mass of the negative electrode material; The general formula of the metal-doped nano-silicon-based material is SiMxOy, where 0 < x ≤ 10 and 0 ≤ y ≤ 10. M is a metal doping element, including one or more of Mg, Ca, Ba, Ti, Li, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ge, Sn, Al, Na, B; the precursor material of the first carbon material is a low-residual-carbon carbon source, and the residual-carbon rate at 900 °C is ≤ 20%; the nano-silicon-based material includes one or more combinations of silicon, silicon dioxide, and silicon monoxide; the particle size range of the composite sphere is 1 μm to 30 μm; The precursor material of the second carbon material is a high-residual-carbon carbon source, and the residual-carbon rate at 900 °C is ≥ 40%; the diameter of the carbon black particles is ≤ 20 nm; the diameter of the carbon nanotubes is ≤ 1 μm and the length is ≤ 50 μm; the diameter of the carbon fibers is ≤ 1 μm and the length is ≤ 50 μm.

2. The negative electrode material according to claim 1, characterized in that, The low-residual-carbon carbon source specifically includes: one or more of glucose, sucrose, and polyvinylpyrrolidone; The high-residual-carbon carbon source specifically includes: one or more of phenolic resin, epoxy resin, and urea-formaldehyde resin.

3. The negative electrode material according to claim 1, wherein, The high-residual-carbon carbon source and the low-residual-carbon carbon source are dissolved in different solvent systems.

4. A method for preparing the anode material with a hollow multi-core shell structure according to any one of claims 1-3 above, characterized in that, The preparation method includes: Step 1: Inject the nano-silicon-based material and the metal doping element in the form of a single substance or an oxide into the reactor at the same time, and under a protective atmosphere at 400 °C to 1200 °C, heat-treat the mixed powder of the nano-silicon-based material and the metal doping element in the form of a single substance or an oxide, keep it warm for 1 hour to 10 hours, and then grind the obtained product into particles; the molar ratio of the nano-silicon-based material to the metal doping element in the form of a single substance or an oxide is 1:0.001 to 1:10; the average particle size of the particles is 1 nm to 1 μm; Step 2: After mixing the particles obtained in Step 1 with the low-residual-carbon carbon source in a mass ratio of 1:0.1 to 1:10, add a first solvent according to a solid-to-solvent mass ratio of 1:100 to 1:1000, stir until the low-residual-carbon carbon source is dissolved, then perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain first spray granulation particles, and the average particle size of the first spray granulation particles is 1 nm to 30 μm; Step 3: Mix the first spray granulation particles obtained in Step 2 with carbon black, carbon nanotubes, carbon fibers, and / or a high residual carbon source in a proportion of A:B:C:D; 0 < A ≤ 10, 0 < B ≤ 15, 0 < C ≤ 5, 0 < D ≤ 50; Add a second solvent according to a solid-to-solvent mass ratio of 1:50 to 1:200, stir until the high residual carbon source is dissolved, then perform ultrasonic treatment, and then use a spray dryer for spray granulation to obtain second spray granulation particles, the average particle size of the second spray granulation particles being 20 nm to 300 μm; wherein, the second solvent does not dissolve the low residual carbon source; Step 4: Heat the second spray granulation particles obtained in Step 3 from room temperature to 700 °C to 1300 °C at a rate of 1 °C / min to 10 °C / min in a protective atmosphere environment, and hold for 0.5 hour to 15 hours, so that the low residual carbon source undergoes carbonization to form a multi-pore structure in the core, thereby obtaining the negative electrode material having a hollow multi-core shell structure.

5. The preparation method according to claim 4, characterized in that, The heat treatment is a heat treatment carried out in a vacuum environment or a protective atmosphere, and the protective atmosphere is a nitrogen atmosphere or an inert atmosphere.

6. The preparation method according to claim 4, characterized in that, The first solvent is distilled water or ethanol; the second solvent includes one or a mixture of acetone, styrene, perchloroethylene, trichloroethylene, ethylene glycol ether, or triethanolamine.

7. The preparation method according to claim 4, wherein During the spray granulation in Step 2, the outlet temperature of the spray dryer is 130 to 200 °C, and the pressure is 3 to 4 MPa.

8. The preparation method according to claim 4, characterized in that, During the spray granulation in Step 3, the outlet temperature of the spray dryer is 100 to 150 °C, and the pressure is 3 to 4 MPa.

9. Use of the negative electrode material with a hollow multi-core shell structure according to any one of claims 1-3 above, characterized in that, The negative electrode material is used as the negative electrode material of a lithium-ion battery.

10. A lithium-ion battery comprising the negative electrode material having a hollow multi-core shell structure according to any one of claims 1-3 above.

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