Method of manufacturing silicon-based negative electrode active material and manufacturing apparatus for performing the method

Abstract

A method of manufacturing a silicon-based anode active material and a manufacturing apparatus for performing the method, the method of manufacturing a silicon-based anode active material first prepares a plurality of silicon-based particles. Each of the silicon-based particles is coated with a carbon film. Next, the method of the present invention immerses the plurality of silicon-based particles in a solvent solution of a carrier and heats to a first temperature for a first length of time to obtain a plurality of lithium-containing silicon-based particles. Next, the method of the present invention heats the plurality of lithium-containing silicon-based particles to a second temperature for a second length of time in an inert atmosphere to homogenize the plurality of lithium-containing silicon-based particles. Finally, the method of the present invention immerses the homogenized plurality of lithium-containing silicon-based particles in a passivation agent environment and heats to a third temperature for a third length of time to passivate the homogenized plurality of lithium-containing silicon-based particles, i.e., to obtain a silicon-based anode active material.

Description

TECHNICAL FIELD

[0001] The present application relates to a method of manufacturing silicon-based negative active material and manufacturing equipment for performing the method, and in particular to a method of manufacturing silicon-based negative active material with pre-lithium, homogenization and passivation of multiple silicon-based particles and manufacturing equipment for performing the method.

[0002] For the relevant technical background of the present application, please refer to the following technical literature:

[0003] [1] Casimir A, Zhang H, Ogoke O, Amine JC, Lu J, Wu G. Silicon-based anodes for lithium-ion batteries: Effectiveness of materials synthesis and electrode preparation. Nano Energy. 2016; 27: 359-376.

[0004] [2] Xing Y, Shen T, Guo T, Wang X, Xia X, Gu C, et al. A novel durable double-conductive core-shell structure applying to the synthesis of silicon anode for lithium ion batteries. Journal of Power Sources. 2018; 384: 207-213.

[0005] [3] Shang H, Zuo Z, Yu L, Wang F, He F, Li Y. Low-temperature growth of all-carbon graphdiyne on a silicon anode for high-performance lithium-ion batteries. Advanced Materials. 2018; 30: 1801459.

[0006] [4] Li Z, He Q, He L, Hu P, Li W, Yan H, et al. Self-sacrificed synthesis of carbon-coated SiO xNanowires for high capacity lithium ion battery anodes. Journal of Materials Chemistry A. 2017; 5: 4183-4189.

[0007] [5] Parimalam BS, Mac Intosh AD, Kadam R, Lucht BL. Decomposition reactions of anode solid electrolyte interphase (SEI) components with LiPF6. The Journal of Physical Chemistry C. 2017; 121: 22733-22738.

[0008] [6] Haruta M, Okubo T, Masuo Y, Yoshida S, Tomita A, Takenaka T, et al. Temperature effects on SEI formation and cyclability of Si nanoflake powder anode in the presence of SEI-forming additives. Electrochimica Acta. 2017; 224: 186-193.

[0009] [7] Elia GA, Hassoun J. A SiO x -based anode in a high-voltage lithium-ion battery. ChemElectroChem. 2017; 4: 2164-2168.

[0010] [8] Park E, Park MS, Lee J, Kim KJ, Jeong G, Kim JH, et al. A highly resilient mesoporous SiO x lithium storage material engineered by oil–water templating. ChemSusChem. 2015; 8: 688-694.

[0011] [9] Sun L, Su T, Xu L, Liu M, Du H-B. Two-dimensional ultra-thin SiO x (0 < x < 2) nanosheets with long-term cycling stability as lithium ion battery anodes. Chemical Communications. 2016; 52: 4341-4344.

[0012]

[10] Japanese Patent Application Publication No. JP2018511969A.

[0013] The following two articles are relevant to prelithiation:

[0014]

[11] Ming-Yan Yan, Ge Li, Juan Zhang, Yi-Fan Tian, Ya-Xia Yin, Chuan-Jian Zhang, Ke-Cheng Jiang, Quan Xu, Hong-Liang Li, and Yu-Guo Guo, Enabling SiOx / C Anode with High Initial Coulombic Efficiency through a Chemical Pre-Lithiation Strategy for High-Energy-Density Lithium-Ion Batteries, ACS Appl. Mater. Interfaces 2020, 12, 27202-27209. DOI: 10.1021 / acsami.0c05153.

[0015]

[12] Huancheng Yue, Shu Zhang, Tingting Feng, Cheng Chen, Haiping Zhou, Ziqiang Xu, and Mengqiang Wu, Understanding of the Mechanism Enables Controllable Chemical Prelithiation of Anode Materials for Lithium-Ion Batteries, ACS Appl. Mater. Interfaces 2021, 13, 53996-54004. DOI: 10.1021 / acsami.1c16842. BACKGROUND

[0016] High-purity silicon oxide particles have been used to manufacture many commercially valuable product fields, for example, in the production of hydrogen, in the manufacture of lithium-ion battery anodes, in the manufacture of silicon oxide and silicon carbide product fields, etc.

[0017] For example, lithium-ion batteries have been widely used in energy storage technology, which has the advantages of high energy density, high discharge voltage, small internal resistance, small self-discharge, no storage effect, environmental protection and no pollution. Lithium-ion batteries have been widely used in various products in life, such as mobile phones, notebook computers, hearing aids, camcorders, electric vehicles, etc. In addition, lithium-ion batteries are also widely used in modern high-tech fields such as torpedoes, aircraft, micro-electromechanical systems, etc. Therefore, lithium-ion batteries are the ideal new energy for human beings. However, the existing commercial lithium-ion batteries still have many shortcomings, which cannot meet the demand in the application of high specific energy power supply. Just for the anode, the currently commercialized lithium-ion batteries mostly use carbon materials such as graphite as the anode. Because the anode made of graphite has the advantages of good electrical conductivity and long cycle life. However, the specific capacity of the anode made of graphite is low (the theoretical specific capacity of graphite is only 372 mAh / g), which cannot meet the capacity demand of high specific energy power supply system. Therefore, the development of high-capacity and excellent performance anode materials has become a research hotspot.

[0018] Silicon material has a high theoretical lithium storage capacity, a low lithium extraction potential (0.2-0.3V vs. Li / Li + ), and silicon is an abundant element on earth. Therefore, silicon is considered to be the most likely alternative anode material to replace graphite. Silicon and lithium can form Li 12 Si7, Li7Si3, Li 13 Si4, and Li 22 Si5, etc. The theoretical capacity of various phase Li-Si alloys is as high as 4200 mAh / g, which is the highest theoretical capacity among various alloy anode materials currently studied. Moreover, the voltage of lithium insertion into silicon is low, and there is no co-insertion of solvent molecules during the insertion process, which is very suitable for use as an anode material for lithium-ion batteries [1-3]. However, the large volume expansion rate of silicon anode (~400%) leads to the degradation of silicon particles and the destruction of the solid electrolyte interface [4-6]. These problems will cause a sharp decline in the capacity and even the overall damage, thereby hindering the commercial application of silicon anodes in lithium-ion batteries.

[0019] Due to the improved cycle stability of silicon suboxides (SiO x , 0 < x < 2), they have attracted considerable research investment as potential alternatives to silicon. SiO xnot only exhibit a relatively small volume expansion rate, but also form Li2O and lithium silicates, which act as a buffer medium for Si during the first lithiation process [7-9]. As a result, SiO x exhibit better cycle performance than Si. In this regard, the silicon oxide particles referred to in the present invention have the chemical formula SiO x , 0 < x < 2.

[0020] The uniformity of the particle size distribution of the silicon oxide microparticles or nanoparticles can affect the properties of the negative electrode. The more uniform the particle size distribution, the better the properties of the negative electrode made from the silicon oxide particles. If the silicon oxide particles with a uniform particle size distribution can be produced, the commercial value of the silicon oxide particles can be increased.

[0021] To improve the capacity of the lithium ion battery using the negative electrode made from the silicon oxide particles and to improve the initial efficiency, the silicon oxide particles must be pre-lithiated. The prior art uses a pre-lithium solution containing lithium, and the silicon oxide particles are immersed in the pre-lithium solution containing lithium and heated to be pre-lithiated [10-12]. This pre-lithiation method is also referred to as chemical pre-lithiation. The pre-lithium solution used in the prior art contains one or more of biphenyl, terphenyl, and derivatives thereof, and the solvent is an ether-based solution. However, the prior art must first prepare a pre-lithium solution containing lithium, and the biphenyl, terphenyl, and derivatives thereof in the pre-lithium solution are carriers. The prior art has a molar ratio of lithium to carrier in the pre-lithium solution containing lithium less than 4, which increases the cost of separating the carrier from the lithium. Moreover, the pH value of the lithium-containing silicon oxide particles prepared by the prior art is about 12 or higher. Mixing the lithium-containing silicon oxide particles prepared by the prior art with a binder to form a negative electrode coating, the excessively high alkalinity causes the binder to deteriorate, the viscosity of the negative electrode coating decreases, and the solid content must be increased to complete the coating, and then the negative electrode is formed, but the adhesion of the binder decreases, and the strength of the negative electrode is easily deteriorated. Moreover, the chemical pre-lithiation method of the prior art is a staged process, including a stage of taking out, cleaning, and drying, which process cannot easily avoid air and moisture, and there is a risk of explosion. Obviously, the chemical pre-lithiation method of the prior art still has room for improvement.

[0022] In addition, the prior art using the chemical pre-lithiation method has not yet proposed a one-time treatment process and equipment, nor has it proposed a technology for significantly reducing the amount of carrier and recovering the carrier and solvent. SUMMARY

[0023] Therefore, the technical problem to be solved by the present invention is to provide a method for manufacturing silicon-based negative electrode active materials from pre-lithiated, homogenized, and passivated silicon-based particles and a manufacturing apparatus for performing the method.

[0024] The method for manufacturing silicon-based negative electrode active material according to a preferred embodiment of the present application first prepares a plurality of silicon-based particles. Each of the silicon-based particles is coated with a carbon film and has a chemical formula of C-SiO x Next, the method according to a preferred embodiment of the present application immerses the plurality of silicon-based particles and a lithium source into a carrier solution and heats the plurality of silicon-based particles to a first temperature and maintains the first temperature for a first length of time in an inert furnace atmosphere to obtain a plurality of lithium-containing silicon-based particles. The carrier solution is a mixture of a polycyclic aromatic hydrocarbon and a solvent. The molar ratio of the lithium source to the polycyclic aromatic hydrocarbon is equal to or greater than 5. The volume ratio of the solvent to the plurality of silicon-based particles is equal to or greater than 1. The polycyclic aromatic hydrocarbon can be biphenyl (BP), naphthalene (NP), a functional group-attached biphenyl, or a mixture of the above polycyclic aromatic hydrocarbons. The solvent is an ether or a ketone, which can be tetrahydrofuran (THF), methoxymethane, or N-methylpyrrolidone (NMP), or a mixture of the above organic compounds. The first temperature ranges from 50°C to 250°C. The first length of time ranges from 1 hour to 24 hours. Next, the method according to a preferred embodiment of the present application heats the plurality of lithium-containing silicon-based particles to a second temperature and maintains the second temperature for a second length of time in an inert furnace atmosphere to homogenize the plurality of lithium-containing silicon-based particles. The second temperature ranges from 550°C to 850°C. The second length of time ranges from 1 hour to 16 hours. Finally, the method according to a preferred embodiment of the present application places the homogenized plurality of lithium-containing silicon-based particles in a passivation solution or a passivation gas and heats the homogenized plurality of lithium-containing silicon-based particles to a third temperature and maintains the third temperature for a third length of time to passivate the homogenized plurality of lithium-containing silicon-based particles. The passivation solution can be a mixture of hexane and perfluorotriamylamine (FC70) or a mixture of second tetrahydrofuran and hydrofluoric acid. The first weight percentage of perfluorotriamylamine is equal to or less than 5 wt.%. The second weight percentage of hydrofluoric acid is equal to or less than 10 wt.%. The passivation gas can be nitrogen trifluoride or Freon. The third temperature ranges from 30°C to 250°C. The third length of time ranges from 10 minutes to 24 hours or even longer. The homogenized and passivated plurality of lithium-containing silicon-based particles is the silicon-based negative electrode active material manufactured by the method according to a preferred embodiment of the present application.

[0025] In an embodiment, the concentration of the carrier solution ranges from 0.025M to 2M.

[0026] In an embodiment, the molar ratio of the lithium source to the polycyclic aromatic hydrocarbon ranges from 5 to 100.

[0027] In an embodiment, the pH value of the silicon-based negative electrode active material is equal to or less than 12.

[0028] In one embodiment, phosphorus or boron is added in the step of homogenizing the plurality of lithium-containing silicon-based particles to form phosphorus oxide or boron oxide on the surface of the plurality of lithium-containing silicon-based particles, thereby reducing the pH of the silicon-based negative electrode active material. The amount of phosphorus or boron added is equal to or less than 10% of the third weight percentage of the plurality of lithium-containing silicon-based particles.

[0029] A manufacturing apparatus for manufacturing a silicon-based negative electrode active material according to a preferred embodiment of the present application includes a stirrable reaction chamber, an inert gas supply source, a solvent supply source, a first recovery device, and a second recovery device. A plurality of silicon-based particles, a lithium source, and a polycyclic aromatic hydrocarbon are placed in the reaction chamber. Each of the silicon-based particles is coated with a carbon film, and has a chemical formula of C-SiO x, 0 < x < 2. The reaction chamber is sealed. The polycyclic aromatic hydrocarbon can be biphenyl (BP), naphthalene (NP), biphenyl with a functional group, or a mixture of the above polycyclic aromatic hydrocarbons, etc. The inert gas supply source is in communication with the reaction chamber and stores the inert gas therein. The solvent supply source is in communication with the reaction chamber and contains the solvent therein. The solvent is an ether or a ketone, can be first tetrahydrofuran (THF), methoxymethane, N-methylpyrrolidone (NMP), or a mixture of the above organic compounds, etc. The passivation source supply source is in communication with the reaction chamber and contains a passivation solution or a passivation gas therein. The passivation solution can be a mixture of hexane and perfluorotriamylamine (FC70) or a mixture of second tetrahydrofuran and hydrofluoric acid. The first weight percentage of perfluorotriamylamine is equal to or less than 5 wt.%. The second weight percentage of hydrofluoric acid is equal to or less than 10 wt.%. The passivation gas can be nitrogen trifluoride or Freon. The first recovery device is in communication with the reaction chamber. The second recovery device is in communication with the reaction chamber. The solvent supply source supplies the solvent into the reaction chamber, wherein the polycyclic aromatic hydrocarbon is mixed with the solvent to form a carrier solution. The plurality of silicon-based particles and the lithium source are immersed in the carrier solution. The inert gas supply source supplies the inert gas into the reaction chamber to form an inert atmosphere in the reaction chamber. The reaction chamber is heated to a first temperature and maintained for a first length of time to obtain a plurality of lithium-containing silicon-based particles. The first temperature ranges from 50°C to 250°C. The first length of time ranges from 1 hour to 24 hours. The first recovery device recovers the carrier solution. The reaction chamber is heated to a second temperature and maintained for a second length of time under the inert atmosphere to homogenize the plurality of lithium-containing silicon-based particles. The second temperature ranges from 550°C to 850°C. The second length of time ranges from 1 hour to 16 hours. The passivation source supply source supplies the passivation solution or the passivation gas into the reaction chamber. The reaction chamber is heated to a third temperature and maintained for a third length of time to passivate the homogenized plurality of lithium-containing silicon-based particles. The third temperature ranges from 30°C to 250°C. The third length of time ranges from 10 minutes to 24 hours. The second recovery device recovers the passivation solution or the passivation gas. The homogenized and passivated plurality of lithium-containing silicon-based particles are the silicon-based negative electrode active material manufactured by the manufacturing apparatus of the present application.

[0030] In a specific embodiment, when the first recovery device recovers the carrier solution, the reaction chamber is heated to a temperature higher than the boiling point of the carrier solution.

[0031] Unlike the prior art of the chemical pre-lithiation method, the method according to the present application has a molar ratio of lithium to carrier equal to or greater than 5. Also, the pH value of the plurality of homogenized and passivated lithium-containing silicon-based particles prepared according to the method of the present application is equal to or less than 12, and the negative electrode is easily prepared. The manufacturing apparatus according to the present application performs a one-time process, and does not have a stage of taking out the dried or washed product during the process, so there is no risk of explosion. Also, the manufacturing apparatus according to the present application can significantly reduce the amount of carrier used, and perform recovery of the carrier and solvent.

[0032] The advantages and spirit of the present application can be further understood by the detailed description of the invention and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Flowchart of each procedure step of the method of manufacturing a silicon-based negative active material according to a preferred embodiment of the present application;

[0034] Figures 2 to 6 Schematic diagram of the architecture of the manufacturing apparatus according to a preferred embodiment of the present application at different manufacturing stages;

[0035] Figure 7 Data graphs of the charge and discharge capacity and the initial coulombic efficiency of the negative electrode prepared according to the example and the comparative example of the present application;

[0036] Figure 8 Data graphs of the thickness of the LiF layer formed on the surface of the lithium-containing silicon-based particles and the pH value of the lithium-containing silicon-based particles according to the example of the present application and the comparative example according to different passivation times;

[0037] Figure 9 Data graphs of the weight change measured as the length of time in air increases for the plurality of homogenized and passivated lithium-containing silicon-based particles according to the example of the present application and the plurality of homogenized and unpassivated lithium-containing silicon-based particles according to the comparative example.

[0038] SYMBOL DESCRIPTION

[0039] 1: method

[0040] S10-S16: procedure steps

[0041] 2: manufacturing apparatus

[0042] 20: reaction chamber

[0043] 202: stirring device

[0044] 204: heater

[0045] 21: first container

[0046] 22: inert gas supply source

[0047] 222: control valve

[0048] 24: solvent supply source

[0049] 242: control valve

[0050] 26: passivation source supply source

[0051] 262: control valve

[0052] 28: first recovery device

[0053] 282: control valve

[0054] 30: second recovery device

[0055] 302: control valve

[0056] 32: vacuum evacuation device

[0057] 34: vacuum evacuation device

[0058] 40: silicon-based particles

[0059] 42: lithium source

[0060] 44: polycyclic aromatic hydrocarbon

[0061] 46: solvent

[0062] 48: passivation solution

[0063] 50: carrier solution

[0064] 52: lithium-containing silicon-based particles

[0065] 54: homogenized lithium-containing silicon-based particles

[0066] 56: homogenized and passivated lithium-containing silicon-based particles DETAILED DESCRIPTION

[0067] Referring to Figure 1 , FIG. 1 is a flowchart of a method 1 for manufacturing a silicon-based negative electrode active material according to a preferred embodiment of the present invention.

[0068] As shown in Figure 1 , the method 1 according to the present invention first performs step S10 of preparing a plurality of silicon-based particles. Each of the silicon-based particles is coated with a carbon thin film, and has a chemical formula of C-SiO x , 0 < x < 2. There are many methods for preparing the C-SiO x particles, and thus a detailed description thereof will not be provided herein.

[0069] Next, the plurality of silicon-based particles and the lithium source (e.g., lithium foil) are immersed in a carrier solution and heated to a first temperature and maintained for a first length of time in an inert atmosphere (e.g., argon, neon, helium, etc.) to obtain a plurality of lithium-containing silicon-based particles according to the method 1 of the preferred embodiments of the present application. The plurality of silicon-based particles coated with a carbon film can somewhat prevent the decrease in conductivity caused by lithium intercalation.

[0070] The carrier solution is formed by mixing a polycyclic aromatic hydrocarbon with a solvent. The polycyclic aromatic hydrocarbon is the carrier. In particular, as the lithium source slowly dissolves in the carrier solution, the lithium source and the polycyclic aromatic hydrocarbon (i.e., the carrier) are in a molar ratio of equal to or greater than 5.

[0071] In one embodiment, the lithium source and the polycyclic aromatic hydrocarbon (i.e., the carrier) are in a molar ratio ranging from 5 to 100.

[0072] In one embodiment, the carrier solution has a concentration ranging from 0.025 M to 2 M.

[0073] The volume ratio of the solvent to the plurality of silicon-based particles is equal to or greater than 1. The polycyclic aromatic hydrocarbon can be biphenyl (BP), naphthalene (NP), a functional group-attached biphenyl, or a mixture of the above polycyclic aromatic hydrocarbons, etc. The solvent is an ether or a ketone, such as an ether like tetrahydrofuran (THF), methoxymethane, or a ketone like N-methylpyrrolidone (NMP), or a mixture of the above organic compounds, etc. The first temperature ranges from 50°C to 250°C. The first length of time ranges from 1 hour to 24 hours.

[0074] Next, the plurality of lithium-containing silicon-based particles are heated to a second temperature and maintained for a second length of time in an inert atmosphere to homogenize the plurality of lithium-containing silicon-based particles according to the method 1 of the preferred embodiments of the present application. The second temperature ranges from 550°C to 850°C. The second length of time ranges from 1 hour to 16 hours.

[0075] Finally, the homogenized plurality of lithium-containing silicon-based particles are placed in a passivation solution or a passivation gas and heated to a third temperature and maintained for a third length of time to passivate the homogenized plurality of lithium-containing silicon-based particles according to the method of the preferred embodiments of the present application. The homogenized and passivated plurality of lithium-containing silicon-based particles are the silicon-based negative electrode active material produced by the method of the present application.

[0076] The passivation solution can be a mixture of a non-polar solvent such as hexane and perfluorotriamylamine (FC70) or a mixture of a second tetrahydrofuran and hydrofluoric acid. The first weight percentage of perfluorotriamylamine is equal to or less than 5 wt.%. The second weight percentage of hydrofluoric acid is equal to or less than 10 wt.%. The passivation gas can be nitrogen trifluoride or a fluorocarbon such as Freon. The third temperature ranges from 30°C to 250°C. The third time length ranges from 10 minutes to 24 hours.

[0077] In one embodiment, the silicon-based negative electrode active material, i.e. the homogenized and passivated plurality of lithium-containing silicon-based particles, has a pH equal to or less than 12. The silicon-based negative electrode active material prepared by the method according to the present application is mixed with a binder to form a negative electrode coating having a high viscosity, which allows the coating to be completed without increasing the solid content, and thus the negative electrode is easily prepared. The weight percentage of the binder ranges from 5 to 15 wt.%.

[0078] In one embodiment, phosphorus or boron is added in the step of homogenizing the plurality of lithium-containing silicon-based particles to form phosphorus oxide or boron oxide on the surface of the plurality of lithium-containing silicon-based particles, thereby reducing the pH of the silicon-based negative electrode active material. The amount of phosphorus or boron added is equal to or less than 10% of the third weight percentage of the plurality of lithium-containing silicon-based particles.

[0079] Referring to Figures 2 to 6 , the drawings schematically illustrate the architecture of a manufacturing apparatus 2 for manufacturing a silicon-based negative electrode active material according to a preferred embodiment of the present application and at different manufacturing stages. In Figures 2 to 6 , some elements and devices are shown in cross-sectional view or in partial perspective view.

[0080] As shown in Figures 2 to 6 , the manufacturing apparatus 2 for manufacturing a silicon-based negative electrode active material according to a preferred embodiment of the present application comprises a stirrable reaction chamber 20, an inert gas supply source 22, a solvent supply source 24, a passivation source supply source 26, a first recovery device 28, and a second recovery device 30. The manufacturing apparatus 2 according to the present application further comprises a stirring device 202. The stirring device 202 is arranged to operate within the reaction chamber 20. The manufacturing apparatus 2 according to the present application further comprises a heater 204. The heater 204 is arranged to surround the reaction chamber 20.

[0081] The plurality of silicon-based particles 40, the lithium source 42 (e.g. lithium foil or aluminum particles), and the polycyclic aromatic hydrocarbon 44 are first placed into the reaction chamber 20, as shown in Figure 2 . Each silicon-based particle 40 is coated with a carbon film and has a chemical formula of C-SiO x, 0 < x < 2. The reaction chamber 20 is sealed. The oxidation amount of the lithium source 42 before being placed into the reaction chamber 20 can be ignored in the process of manufacturing the silicon-based anode active material performed by the manufacturing apparatus 2 according to the present invention. The polycyclic aromatic hydrocarbon 44 serves as a carrier. The polycyclic aromatic hydrocarbon 44 can be biphenyl (BP), naphthalene (NP), biphenyl with a functional group attached, or a mixture of the above polycyclic aromatic hydrocarbons, etc.

[0082] The inert gas supply source 22 is connected to the reaction chamber 20 and stores an inert gas (e.g., argon, neon, helium, etc.) therein. The manufacturing apparatus 2 according to the present invention further includes a control valve 222. The control valve 222 is installed between the reaction chamber 20 and the inert gas supply source 22.

[0083] The solvent supply source 24 is connected to the reaction chamber 20 and contains a solvent 46 therein. The solvent 46 can include ethers such as first tetrahydrofuran (THF), dimethyl ether (methoxymethane), or ketones such as N-methylpyrrolidone (NMP), or a mixture of the above organic compounds, etc. The manufacturing apparatus 2 according to the present invention further includes a control valve 242. The control valve 242 is installed between the reaction chamber 20 and the solvent supply source 24.

[0084] The passivation source supply source 26 is connected to the reaction chamber 20 and contains a passivation solution 48 (as Figures 2 to 6 shown) or a passivation gas therein. The passivation solution 48 can be formed by mixing a non-polar solvent such as hexane (Hexane) and perfluorotripentylamine (FC70) or by mixing second tetrahydrofuran and hydrofluoric acid. The first weight percentage of perfluorotripentylamine is equal to or less than 5 wt.%. The second weight percentage of hydrofluoric acid is equal to or less than 10 wt.%. The passivation gas can be nitrogen trifluoride or a fluorocarbon such as freon (Freon). The manufacturing apparatus 2 according to the present invention further includes a control valve 262. The control valve 262 is installed between the reaction chamber 20 and the passivation source supply source 26.

[0085] The first recovery device 28 is connected to the reaction chamber 20. The manufacturing apparatus 2 according to the present invention further includes a control valve 282 installed between the reaction chamber 20 and the first recovery device 28.

[0086] The second recovery device 30 is connected to the reaction chamber 20. The manufacturing apparatus 2 according to the present invention further includes a control valve 302 installed between the reaction chamber 20 and the second recovery device 30.

[0087] As Figure 3As shown, in the manufacturing process of silicon-based anode active material performed by the manufacturing apparatus 2 according to the present invention, valve 242 is then opened, and solvent 46 is supplied to the reaction chamber 20 by solvent supply source 24, wherein polycyclic aromatic hydrocarbon 44 is mixed with solvent 46 to form a carrier solution 50. Multiple silicon-based particles 40 and lithium source 42 are immersed in the carrier solution 50. Control valve 222 is opened, allowing inert gas supply source 22 to supply inert gas to the reaction chamber 20, creating an inert atmosphere within the reaction chamber 20. It should be emphasized that because lithium source 42 slowly dissolves into carrier solution 50, the molar ratio of lithium source 42 to polycyclic aromatic hydrocarbon 44 (i.e., the carrier) is equal to or greater than 5.

[0088] Similarly, Figure 3 As shown, the reaction chamber 20 can be heated to a first temperature and maintained for a first time length by the heater 204 to obtain multiple lithium-containing silicon-based particles 52. The first temperature ranges from 50°C to 250°C. The first time length ranges from 1 hour to 24 hours.

[0089] like Figure 4 As shown, the first recovery device 28 recovers the carrier solution 50. During the recovery process of the carrier solution 50, the control valve 282 is opened. The manufacturing apparatus 2 according to the invention also includes a vacuum pumping device 32. The vacuum pumping device 32 is connected downstream of the first recovery device 28. The vacuum pumping device 32 is used to create a vacuum environment inside the first recovery device 28 to recover the carrier solution 50.

[0090] In one specific embodiment, when the first recovery device 28 recovers the carrier solution 50, the reaction chamber 20 can be heated to a temperature higher than the boiling point of the carrier solution 50 by the heater 204.

[0091] Similarly, Figure 4 As shown, the reaction chamber 20 can be heated to a second temperature and maintained for a second time length by the heater 204 under an inert atmosphere, thereby homogenizing multiple lithium-containing silicon-based particles 52 into multiple homogenized lithium-containing silicon-based particles 54. The second temperature ranges from 550°C to 850°C. The second time length ranges from 1 hour to 16 hours.

[0092] like Figure 5 As shown, valve 262 is opened, allowing passivation source supply 26 to supply passivation solution 48 or passivation gas into reaction chamber 20. Reaction chamber 20 can be heated to a third temperature and maintained for a third time period by heater 204, thereby passivating multiple homogenized lithium-containing silicon-based particles 54 into multiple homogenized and passivated lithium-containing silicon-based particles 56. The third temperature ranges from 30°C to 250°C. The third time period ranges from 10 minutes to 24 hours.

[0093] like Figure 6As shown, the second recovery device 30 recovers the passivation solution 48 or the passivation gas. The passivation solution 48 or the passivation gas is recovered by the process, and the control valve 302 is opened. The manufacturing apparatus 2 according to the present application further comprises a vacuum pumping device 34. The vacuum pumping device 34 is connected after the second recovery device 30. The vacuum pumping device 34 is used to pump the second recovery device 30 into a vacuum environment, so as to recover the passivation solution 48 or the passivation gas.

[0094] The plurality of homogenized and passivated lithium-containing silicon-based particles 56 is the silicon-based negative electrode active material manufactured by the manufacturing apparatus according to the present application.

[0095] As shown, the manufacturing apparatus 2 according to the present application is a device for performing a one-time processing procedure. The manufacturing apparatus 2 according to the present application does not have a stage for taking out the drying or cleaning during the process of manufacturing the silicon-based negative electrode active material, so there is no risk of explosion. Moreover, the manufacturing apparatus 2 according to the present application can recover the carrier, the solvent and the passivation agent.

[0096] Two examples of the present application are: (1) 5 wt.% lithium, the second temperature is 750°C, and the second time length is 2 hours; (2) 10 wt.% lithium, the second temperature is 750°C, and the second time length is 2 hours; and a control process condition: 0 wt.% lithium, the second temperature is 750°C, the second time length is 2 hours, the third temperature is 160°C, and the third time length is 2 hours. The negative electrode materials manufactured by the three sets of process conditions are further manufactured into negative electrodes. The charge-discharge capacities and the first coulombic efficiencies of the half-cells of these electrodes are shown in Table 1. Figure 7 Figure 7 It is confirmed that the charge-discharge reversible capacities of the batteries with increased pre-lithium amounts are close, and the first coulombic efficiencies are also higher, in which the electrode with 10 wt.% lithium has the best first coulombic efficiency of more than 93%.

[0097] Several examples of the present application place the plurality of homogenized lithium-containing silicon-based particles in nitrogen trifluoride for passivation, and the passivation temperature is 160°C. The effects of different passivation time lengths on the thickness of the LiF layer formed on the surface of the lithium-containing silicon-based particles and the pH value of the lithium-containing silicon-based particles are shown in Table 2. Figure 8 Figure 8 As a control, the thickness of the LiF layer and the pH value of the plurality of homogenized lithium-containing silicon-based particles without passivation are also indicated in Table 2. Figure 8 It is confirmed that as the passivation time increases, the thickness of the LiF layer also increases, and the trend of the increase in the thickness of the LiF layer tends to be flat at a passivation time of 5 hours. Figure 8 Moreover, the pH value of the lithium-containing silicon-based particles without passivation is about 11.95, and as the passivation time increases, the pH value of the lithium-containing silicon-based particles also decreases, and the pH value of the lithium-containing silicon-based particles decreases to about 11.1 at a passivation time of 18 hours.​​

[0098] In two embodiments of this invention, multiple homogenized lithium-containing silicon-based particles are passivated in nitrogen trifluoride at a passivation temperature of 160°C for 3 hours and 18 hours, respectively, to obtain homogenized and passivated multiple lithium-containing silicon-based particles. The homogenized and passivated lithium-containing silicon-based particles from the above two embodiments are then oxidized in air. The measured weight changes as the exposure time in air increase are described in [reference needed]. Figure 9 As shown. As a control, multiple homogenized lithium-containing silicon-based particles that had not been passivated were oxidized in air; the measured weight change with increasing exposure time is also shown in the figure. Figure 9 . Figure 9 The study confirmed that passivated lithium-containing silicon particles are relatively stable in air. Multiple lithium-containing silicon particles passivated for 18 hours were more stable in air than those passivated for 3 hours.

[0099] Through the detailed description of the preferred embodiments above, it will be clear that the molar ratio of lithium to carrier according to the method of the present invention is equal to or greater than 5. Furthermore, the pH value of the homogenized and passivated lithium-containing silicon-based particles obtained according to the method of the present invention is equal to or less than 12, making them easy to fabricate as negative electrode electrodes. The manufacturing equipment according to the present invention performs a one-time processing procedure, eliminating the need for in-process drying and cleaning, thus eliminating the risk of explosion. Moreover, the manufacturing equipment according to the present invention can recover the carrier, solvent, passivating agent, etc.

[0100] The detailed description of the preferred embodiments above is intended to more clearly illustrate the features and spirit of the present invention, and is not intended to limit the scope of the invention to the preferred embodiments disclosed above. Rather, the aim is to cover various modifications and equivalent arrangements within the scope of the claims to be made. Therefore, the scope of the claims to be made should be interpreted in the broadest possible sense based on the foregoing description, so as to cover all possible modifications and equivalent arrangements.

Claims

1. A method for manufacturing a silicon-based anode active material, comprising the following steps: Prepare multiple silicon-based particles, each of which is coated with a carbon film and has a chemical formula of C-SiO x , where 0 < x < 2; Immerse the multiple silicon-based particles and a lithium source in a carrier solution and heat them to a first temperature in an inert furnace atmosphere and maintain the first time length to obtain multiple lithium-containing silicon-based particles, wherein the carrier solution is formed by mixing a polycyclic aromatic hydrocarbon and a solvent, the molar ratio of the lithium source to the polycyclic aromatic hydrocarbon is equal to or greater than 5, the volume ratio of the solvent to the multiple silicon-based particles is equal to or greater than 1, the polycyclic aromatic hydrocarbon is selected from one of the group consisting of biphenyl, naphthalene, biphenyl with a functional group attached, and mixtures of the above polycyclic aromatic hydrocarbons, the solvent is selected from one of the group consisting of first tetrahydrofuran, dimethyl ether, N-methylpyrrolidone, and mixtures of the above organic compounds, the range of the first temperature is from 50 °C to 250 °C, and the range of the first time length is from 1 hour to 24 hours; In the inert furnace atmosphere, the plurality of lithium-containing silicon-based particles are heated to a second temperature and maintained for a second time duration, thereby homogenizing the plurality of lithium-containing silicon-based particles, wherein the second temperature ranges from 550°C to 850°C, and the second time duration ranges from 1 hour to 16 hours; and The homogenized lithium-containing silicon-based particles are placed in a passivation solution or passivation gas and heated to a third temperature and maintained for a third time period to passivate the homogenized lithium-containing silicon-based particles. The passivation solution is a mixture of hexane and perfluorotripentylamine or a mixture of tetrahydrofuran and hydrofluoric acid. The first weight percentage of the perfluorotripentylamine is equal to or less than 5 wt.%, the second weight percentage of the hydrofluoric acid is equal to or less than 10 wt.%, and the passivation gas is nitrogen trifluoride or chlorofluorocarbon. The third temperature ranges from 30°C to 250°C, and the third time period ranges from 10 minutes to 24 hours. The multiple lithium-containing silicon-based particles that have been homogenized and passivated are the silicon-based anode active material.

2. The method according to claim 1, wherein the concentration range of the carrier solution is from 0.025M to 2M.

3. The method according to claim 2, wherein the molar ratio of the lithium source to the polycyclic aromatic hydrocarbon ranges from 5 to 100.

4. The method according to claim 3, wherein the pH value of the silicon-based negative electrode active material is equal to or less than 12.

5. The method according to claim 4, wherein in the step of homogenizing the plurality of lithium-containing silicon-based particles, phosphorus or boron is added to generate phosphorus oxide or boron oxide on the surface of the plurality of lithium-containing silicon-based particles, thereby reducing the pH value of the silicon-based negative electrode active material, wherein the amount of phosphorus or boron added is equal to or less than 10% of the third weight percentage of the plurality of lithium-containing silicon-based particles.

6. A manufacturing apparatus for producing silicon-based anode active materials, comprising: A stirrable reaction chamber, in which multiple silicon-based particles, a lithium source, and polycyclic aromatic hydrocarbons are placed in the reaction chamber, and each silicon-based particle is coated with a carbon film and has a chemical formula of C-SiO x , where 0 < x < 2, the reaction chamber is sealed, and the polycyclic aromatic hydrocarbon is selected from one of the group consisting of biphenyl, naphthalene, biphenyl with a functional group attached, and mixtures of the above polycyclic aromatic hydrocarbons. An inert gas supply source is connected to the reaction chamber and stores inert gas therein; A solvent supply source is connected to the reaction chamber and contains a solvent, wherein the solvent is selected from the group consisting of tetrahydrofuran, dimethyl ether, N-methylpyrrolidone, and mixtures of the above organic compounds; A passivation source supply is connected to the reaction chamber and contains a passivation solution or a passivation gas, wherein the passivation solution is a mixture of hexane and perfluorotripentylamine or a mixture of tetrahydrofuran and hydrofluoric acid, wherein the first weight percentage of the perfluorotripentylamine is equal to or less than 5 wt.%, the second weight percentage of the hydrofluoric acid is equal to or less than 10 wt.%, and the passivation gas is nitrogen trifluoride or chlorofluorocarbon. A first recovery device is connected to the reaction chamber; and A second recovery device is connected to the reaction chamber; The solvent supply source supplies the solvent into the reaction chamber, the polycyclic aromatic hydrocarbon is mixed with the solvent to form a carrier solution, and the plurality of silicon-based particles and the lithium source are immersed in the carrier solution. The inert gas supply source supplies inert gas into the reaction chamber, creating an inert atmosphere within the reaction chamber. The reaction chamber is heated to a first temperature and maintained for a first time duration to obtain multiple lithium-containing silicon-based particles. The first temperature ranges from 50°C to 250°C, and the first time duration ranges from 1 hour to 24 hours. The first recovery device recovers the carrier solution. The reaction chamber is heated to a second temperature and maintained for a second time under an inert furnace atmosphere, thereby homogenizing the plurality of lithium-containing silicon-based particles. The second temperature ranges from 550°C to 850°C, and the second time ranges from 1 hour to 16 hours. The passivation source supply supply provides the passivation solution or the passivation gas into the reaction chamber. The reaction chamber is heated to a third temperature and maintained for a third time duration, thereby passivating the homogenized plurality of lithium-containing silicon-based particles. The third temperature ranges from 30°C to 250°C, and the third time duration ranges from 10 minutes to 24 hours. The second recovery device recovers the passivation solution or the passivation gas. The multiple lithium-containing silicon-based particles, after homogenization and passivation, are the silicon-based anode active material.

7. The manufacturing apparatus according to claim 6, wherein when the first recovery device recovers the carrier solution, the reaction chamber is heated to a temperature above the boiling point of the carrier solution.

8. The manufacturing apparatus according to claim 7, wherein the concentration of the carrier solution ranges from 0.025M to 2M.

9. The manufacturing apparatus according to claim 8, wherein the molar ratio of the lithium source to the polycyclic aromatic hydrocarbon is in the range of 5 to 100.

10. The manufacturing apparatus according to claim 8, wherein the pH value of the silicon-based anode active material is equal to or less than 12.

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