Negative electrode for lithium-ion batteries and method for manufacturing the same

Abstract

Disclosed is a method of manufacturing an anode for a lithium ion battery, the method comprising milling a mixture of nanosilicon, one or more carbonaceous materials, and one or more solvents, wherein the mixture is maintained as a wet slurry during milling. The mixture is carbonized to produce a thin carbon-coated silicon (Si@C) material. A second mixture of the Si@C material, one or more graphites, one or more second carbonaceous materials, and one or more second solvents is further milled, wherein the second mixture is maintained as a second wet slurry during milling. The second mixture is carbonized to produce a Si@C / graphite / carbon material. The anode is formed from the Si@C / graphite / carbon material.

Description

[0001] Related applications

[0002] This application claims priority to Australian Provisional Patent Application No. 2019904719, filed on December 13, 2019, the contents of which are to be understood as incorporated herein by reference. Technical Field

[0003] This invention generally relates to electrochemical battery cells, and more particularly to batteries. In specific examples, the invention relates to electrodes used in batteries (e.g., lithium-ion batteries, i.e., lithium-ion battery cells), as well as methods for manufacturing electrodes and batteries. More specifically, exemplary embodiments relate to lithium-ion batteries, negative electrodes for lithium-ion batteries, methods for manufacturing negative electrodes and lithium-ion batteries, and / or methods for preparing components or materials for negative electrodes and lithium-ion batteries. Background Technology

[0004] Any discussion of prior art throughout the specification should not be construed as an admission that such prior art is well-known or constitutes part of the general knowledge in the field.

[0005] Lithium-ion batteries are an attractive energy source for a wide range of applications, partly due to their ability to provide relatively high energy and long cycle life. The performance characteristics of lithium-ion batteries (LIBs), such as total energy capacity, depend on the types of anodes and cathodes used in the LIB. In the realm of anode materials used in lithium-ion batteries, silicon, with a theoretical capacity of up to 4200 mAh / g, is considered a promising anode material for next-generation LIBs, such as an alternative to graphite. However, silicon typically undergoes a significant volume change (approximately 300%) during lithiation and delithiation, leading to the cracking and fragmentation of the active material, followed by anode disintegration and a rapid decline in capacity.

[0006] Some methods involving nanostructured silicon (nano-silicon) can alleviate the volume expansion of silicon to some extent; however, known synthesis processes involving nano-silicon are relatively complex, expensive, and difficult to industrialize.

[0007] To improve the performance of silicon-based anodes in LIBs (especially high-energy LIBs), key issues that need to be addressed may include: (a) uniform distribution of silicon particles in the conductive matrix; (b) the ability to mass-produce secondary silicon particles to achieve high gravimetric energy density, high volumetric energy density, and high first coulombic efficiency; and (c) excellent mechanical properties of the anode.

[0008] Chinese patent application CN108807861A from Amprius Nanjing Co., Ltd. discloses a method for manufacturing a negative electrode for lithium-ion batteries. The method includes the following steps: grinding a mixture of nano-silicon, one or more carbonaceous materials (

[0028] section), and one or more solvents, wherein the mixture remains a wet slurry during grinding; carbonizing the mixture at a carbonization temperature to generate a silicon (Si@C) material coated with carbon; grinding a second mixture of the Si@C material, one or more second carbonaceous materials, and one or more second solvents, wherein the second mixture remains a second wet slurry during grinding; carbonizing the second mixture at a second carbonization temperature to generate a Si@C / carbon material; and forming a negative electrode from the Si@C / carbon material. Although CN'861 describes silicon as "nano-silicon," the silicon used is approximately 3 μm to 4 μm in size.

[0009] More specifically, CN'861 Figure 1 A silicon-carbon composite material formed from irregularly shaped secondary particles obtained by the method described in CN'861 is shown. Figure 1 The diagram shows particles surrounded by a continuous amorphous carbon protective layer, the interior of which consists of multiple secondary particles composed of silicon material. The particles also contain conductive additives, such as carbon nanotubes, uniformly dispersed throughout the mixture. The silicon material and conductive filler are each surrounded by amorphous carbon filler, which is then surrounded by a continuous amorphous carbon protective layer. Therefore, CN'861 teaches that it is difficult to obtain a uniform, relatively thin nanocrystalline silicon coating. A uniform, relatively thin nanocrystalline silicon coating is expected to improve the cycle life of the resulting battery.

[0010] Zhou et al. (“Preparation and characterisation of core-shell structure Si / C composite with multiple carbon phases as anode materials for lithium ion batteries”, 2016, J. Alloys and Compounds, vol. 658, pp. 91-97) disclosed a lithium-ion battery anode comprising modified spherical graphite / silicon / sheet graphite / disordered carbon. The active material was prepared by mixing nano-silicon, sheet graphite, and citric acid, followed by carbonization to obtain Si@CFG. Modified spherical graphite (i.e., graphite and a second carbonaceous material) containing a coal tar pitch layer was then added, followed by a second carbonization step to generate the Si@CFG / spherical graphite / carbon material. Zhou et al. apparently did not teach that the second mixing step included grinding. Therefore, the anode structure and integrity were relatively coarse. Zhou et al. further taught that the silicon particles were not directly coated with carbon, causing the silicon particles to easily expand and undergo side reactions, leading to a decrease in conductivity. Summary of the Invention

[0011] The purpose of this invention is to overcome or improve at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0012] The object of a particularly preferred embodiment of the present invention is to provide new or improved lithium-ion batteries, negative electrodes for lithium-ion batteries, methods for manufacturing negative electrodes and / or lithium-ion batteries, and / or methods for preparing components or materials for negative electrodes and / or lithium-ion batteries.

[0013] Unless the context explicitly requires otherwise, throughout the specification and claims, the terms "comprise," "comprising," etc., shall be interpreted in an inclusive sense, rather than in an exclusive or exhaustive sense; that is, they shall mean "including but not limited to."

[0014] Although the invention will be described with reference to specific examples, those skilled in the art will understand that the invention may be implemented in many other forms.

[0015] This summary is provided to introduce, in a simplified form, a series of concepts that will be further described below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0016] According to a first aspect of the present invention, a method for manufacturing a negative electrode for a lithium-ion battery is provided, the method comprising the following steps:

[0017] A mixture of nano-silicon, one or more carbonaceous materials, and one or more solvents is ground, wherein the mixture remains as a wet slurry during grinding.

[0018] The mixture is carbonized at a carbonization temperature to produce a silicon (Si@C) material thinly coated with carbon;

[0019] A second mixture of Si@C material, graphite, one or more second carbonaceous materials, and one or more second solvents is ground, wherein the second mixture is maintained as a second wet slurry during grinding;

[0020] The second mixture is carbonized at a second carbonization temperature to produce a Si@C / graphite / carbon material; and

[0021] The negative electrode is formed from Si@C / graphite / carbon materials.

[0022] The Si@C “thin” coating on silicon is typically in the range of about 2 angstroms to about 500 angstroms. In particular, about 5-450, 10-400, 15-350, 20-300, 25-250, 30-200, 35-150, 40-100, or about 45-50 angstroms. For example, approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, or 500 angstroms.

[0023] In one embodiment, the method further includes the step of drying the wet slurry at a drying temperature before carbonizing the mixture.

[0024] In one embodiment, the method further includes the step of drying the second wet slurry at a second drying temperature before carbonizing the second mixture.

[0025] In one embodiment, the mixture is ground by wet ball milling.

[0026] In one embodiment, nano-silicon and one or more carbonaceous materials are mixed in a mass ratio equal to or from about 40:60 to about 70:30 (nano-silicon: carbonaceous material).

[0027] In one embodiment, nano-silicon and one or more carbonaceous materials are mixed in a mass ratio of about 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, about 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, about 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31 or about 70:30 (nano-silicon: carbonaceous material).

[0028] In one embodiment, the average particle size of the nano-silicon is equal to or about 50 nm to about 500 nm.

[0029] In one embodiment, the average particle size of the nano-silicon is about 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0030] In one embodiment, the average particle size of the nano-silicon is about 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, or 500 nm.

[0031] In one embodiment, one or more solvents are one or more inert solvents, such as ethylene glycol (EG), 1-pentanol, propylene glycol, and polyacrylic acid.

[0032] In one embodiment, one or more solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine, tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof.

[0033] In one embodiment, one or more carbonaceous materials are selected from the group consisting of functionalized graphene sheets, carbon nanotubes (CNTs), reduced graphene oxide (rGO), pyrolytic carbon derived from glucose, sucrose, or citric acid (CA) precursors, pitch, polyacrylonitrile (PAN), polyvinyl chloride (PVC), poly(diallyldimethylammonium chloride) (PDDA), poly(sodium 4-styrenesulfonate) (PSS), polydopamine (PDA), polypyrrole (PPy), and phenolic resins.

[0034] In one implementation, the graphite is flake graphite or graphite microspheres.

[0035] In one embodiment, the graphite microspheres have an average size of about 1 μm to about 20 μm.

[0036] In one embodiment, the graphite microspheres have an average size of about 1 μm, 5 μm, 10 μm, 15 μm, or 20 μm.

[0037] In one embodiment, the graphite microspheres have an average size of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 μm.

[0038] In one implementation, the wet slurry is vacuum dried in an oven.

[0039] In one embodiment, the drying temperature is equal to or equal to about 70°C to about 150°C.

[0040] In one embodiment, the drying temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0041] In one embodiment, the drying temperature is about 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C.

[0042] In one embodiment, one or more steps of carbonizing the mixture occur under an inert gas flowing in a tubular furnace.

[0043] In one embodiment, the inert gas is nitrogen, argon, or a mixture thereof. In one embodiment, the inert gas is argon.

[0044] In one embodiment, the carbonization temperature is equal to or equal to about 900°C to about 1200°C.

[0045] In one embodiment, the carbonization temperature is approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0046] In one embodiment, the carbonization temperature is approximately 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, or 1200°C.

[0047] In one embodiment, the carbonization time of the mixture at the carbonization temperature is equal to or equal to about 3 hours to about 8 hours.

[0048] In one embodiment, the mixture is carbonized at a carbonization temperature for approximately 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 hours.

[0049] In one embodiment, the mixture is held at a holding temperature below the carbonization temperature before reaching the carbonization temperature.

[0050] In one embodiment, the temperature is maintained at or above 300°C to about 500°C.

[0051] In one embodiment, the temperature is maintained at approximately 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or approximately 500°C.

[0052] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio equal to or about 10-30:40-80:10-30 (Si@C material: graphite: second carbonaceous material).

[0053] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio of about 10-30:40-80:10-30 (Si@C material: graphite: second carbonaceous material).

[0054] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio of about 10:80:10, about 10:70:20, about 10:60:30, about 20:70:10, about 20:60:20, about 20:50:30, about 30:60:10, about 30:50:20, or about 30:40:30 (Si@C material: graphite: second carbonaceous material).

[0055] In one embodiment, the second mixture is ground by wet ball milling.

[0056] In one embodiment, one or more second solvents are one or more inert solvents, such as ethylene glycol (EG), 1-pentanol, propylene glycol, and polyacrylic acid.

[0057] In one embodiment, one or more second solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof.

[0058] In one implementation, one or more second carbonaceous materials are the same as one or more carbonaceous materials.

[0059] In one implementation, one or more second carbonaceous materials are different from one or more carbonaceous materials.

[0060] In one embodiment, one or more second solvents are the same as one or more solvents.

[0061] In one embodiment, one or more second solvents are different from one or more solvents.

[0062] In one embodiment, the second drying temperature is equal to or equal to about 70°C to about 150°C.

[0063] In one embodiment, the second drying temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0064] In one embodiment, the second drying temperature is about 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C.

[0065] In one embodiment, the carbonization of the second mixture occurs under an inert gas flowing in a tubular furnace.

[0066] In one embodiment, the inert gas is nitrogen, argon, or a mixture thereof. In one embodiment, the inert gas is argon or nitrogen.

[0067] In one embodiment, the second carbonization temperature is equal to or equal to about 900°C to about 1200°C.

[0068] In one embodiment, the second carbonization temperature is about 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0069] In one embodiment, the second carbonization temperature is about 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, or 1200°C.

[0070] In one embodiment, the second mixture is carbonized at a second carbonization temperature for a period of approximately 3 hours to approximately 8 hours.

[0071] In one embodiment, the second mixture is carbonized at a carbonization temperature for 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 hours.

[0072] In one embodiment, the second mixture is held at a second holding temperature below the second carbonization temperature before reaching the second carbonization temperature.

[0073] In one embodiment, the second holding temperature is equal to or equal to about 300°C to about 500°C.

[0074] In one embodiment, the second holding temperature is about 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or about 500°C.

[0075] In one embodiment, the method further includes the step of grinding the Si@C / graphite / carbon material.

[0076] In one implementation, the grinding is performed using a dry ball mill.

[0077] In one embodiment, the method further includes the step of mixing the Si@C / graphite / carbon material with one or more polymer binders.

[0078] In one embodiment, one or more polymeric adhesives comprise one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

[0079] In one implementation, the negative electrode is formed through the following steps:

[0080] A slurry is generated by mixing Si@C / graphite / carbon materials with one or more polymer binders;

[0081] Apply the slurry to the metal component; and

[0082] The metal component coated with the slurry is dried to form the negative electrode.

[0083] According to a second aspect of the present invention, a method for manufacturing a negative electrode for a lithium-ion battery is provided, the method comprising the following steps:

[0084] Mixing microsilica with one or more inert solvents to form a wet slurry mixture; and

[0085] Milling a wet slurry mixture of microsilicon and one or more inert solvents yields nanosilicon, wherein the mixture remains a wet slurry during milling.

[0086] A mixture of nano-silicon, one or more carbonaceous materials, and one or more solvents is ground, wherein the mixture remains as a wet slurry during grinding.

[0087] The mixture is carbonized at a carbonization temperature to produce a silicon (Si@C) material coated with carbon;

[0088] A second mixture of Si@C material, graphite, one or more second carbonaceous materials, and one or more second solvents is ground, wherein the second mixture is maintained as a second wet slurry during grinding;

[0089] The second mixture is carbonized at the second carbonization temperature to produce Si@C / graphite / carbon material;

[0090] A slurry is generated by mixing Si@C / graphite / carbon materials, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

[0091] Apply the slurry to the metal component; and

[0092] The metal component coated with the slurry is dried to form the negative electrode.

[0093] In one embodiment, the mixture is ground by wet ball milling.

[0094] In one embodiment, nano-silicon and one or more carbonaceous materials are mixed in a mass ratio equal to or about 40:60 to about 70:30 (nano-silicon: carbonaceous material).

[0095] In one embodiment, nano-silicon and one or more carbonaceous materials are mixed in a mass ratio of about 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, about 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, about 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31 or about 70:30 (nano-silicon: carbonaceous material).

[0096] In one embodiment, the average particle size of the nano-silicon is equal to or about 50 nm to about 500 nm.

[0097] In one embodiment, the average particle size of the nano-silicon is about 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0098] In one embodiment, the average particle size of the nano-silicon is approximately 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, or 500 nm.

[0099] In one embodiment, one or more solvents are one or more inert solvents.

[0100] In one embodiment, one or more solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof.

[0101] In one embodiment, one or more carbonaceous materials are selected from the group consisting of functionalized graphene sheets, carbon nanotubes (CNTs), reduced graphene oxide (rGO), pyrolytic carbon derived from glucose, sucrose, or citric acid (CA) precursors, pitch, polyacrylonitrile (PAN), polyvinyl chloride (PVC), poly(diallyldimethylammonium chloride) (PDDA), poly(sodium 4-styrenesulfonate) (PSS), polydopamine (PDA), polypyrrole (PPy), and phenolic resins.

[0102] In one embodiment, the graphite is flake graphite or graphite microspheres.

[0103] In one embodiment, the graphite microspheres have an average size of about 1 μm to about 20 μm.

[0104] In one embodiment, the graphite microspheres have an average size of about 1 μm, 5 μm, 10 μm, 15 μm, or 20 μm.

[0105] In one embodiment, the graphite microspheres have an average size of about 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm.

[0106] In one implementation, the wet slurry is vacuum dried in an oven.

[0107] In one embodiment, the drying temperature is equal to or equal to about 70°C to about 150°C.

[0108] In one embodiment, the drying temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0109] In one embodiment, the drying temperature is about 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C.

[0110] In one embodiment, one or more steps of carbonizing the mixture occur under an inert gas flowing in a tubular furnace.

[0111] In one embodiment, the inert gas is argon, nitrogen, or a mixture thereof.

[0112] In one embodiment, the carbonization temperature is equal to or equal to about 900°C to about 1200°C.

[0113] In one embodiment, the carbonization temperature is approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0114] In one embodiment, the carbonization temperature is approximately 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, or 1200°C.

[0115] In one embodiment, the mixture is carbonized at a carbonization temperature for a period of approximately 3 to approximately 8 hours.

[0116] In one embodiment, the mixture is carbonized at a carbonization temperature for approximately 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 hours.

[0117] In one embodiment, the mixture is held at a holding temperature below the carbonization temperature before reaching the carbonization temperature.

[0118] In one embodiment, the temperature is maintained at or above 300°C to about 500°C.

[0119] In one embodiment, the temperature is maintained at approximately 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or approximately 500°C.

[0120] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio equal to or in the range of about 10-30:40-80:10-30 (Si@C material: graphite: second carbonaceous material).

[0121] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio of about 10-30:40-80:10-30 (Si@C material: graphite: second carbonaceous material).

[0122] In one embodiment, Si@C material, graphite, and one or more second carbonaceous materials are mixed in a mass ratio of about 10:80:10, about 10:70:20, about 10:60:30, about 20:70:10, about 20:60:20, about 20:50:30, about 30:60:10, about 30:50:20, or about 30:40:30 (Si@C material: graphite: second carbonaceous material).

[0123] In one embodiment, the second mixture is ground by wet ball milling.

[0124] In one embodiment, one or more second solvents are one or more inert solvents.

[0125] In one embodiment, one or more second solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof.

[0126] In one implementation, one or more second carbonaceous materials are the same as one or more carbonaceous materials.

[0127] In one implementation, one or more second carbonaceous materials are different from one or more carbonaceous materials.

[0128] In one embodiment, one or more second solvents are the same as one or more solvents.

[0129] In one embodiment, one or more second solvents are different from one or more solvents.

[0130] In one embodiment, the second drying temperature is equal to or equal to about 70°C to about 150°C.

[0131] In one embodiment, the second drying temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C.

[0132] In one embodiment, the second drying temperature is about 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C.

[0133] In one embodiment, the carbonization of the second mixture occurs under an inert gas flowing in a tubular furnace.

[0134] In one embodiment, the inert gas is argon, nitrogen, or a mixture thereof.

[0135] In one embodiment, the second carbonization temperature is equal to or equal to about 900°C to about 1200°C.

[0136] In one embodiment, the second carbonization temperature is about 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0137] In one embodiment, the second carbonization temperature is about 900°C, 925°C, 950°C, 975°C, 1000°C, 1025°C, 1050°C, 1075°C, 1100°C, 1125°C, 1150°C, 1175°C, or 1200°C.

[0138] In one embodiment, the second mixture is carbonized at a second carbonization temperature for a period of approximately 3 hours to approximately 8 hours.

[0139] In one embodiment, the second mixture is carbonized at a carbonization temperature for approximately 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 hours.

[0140] In one embodiment, the second mixture is held at a second holding temperature below the second carbonization temperature before reaching the second carbonization temperature.

[0141] In one embodiment, the second holding temperature is equal to or equal to about 300°C to about 500°C.

[0142] In one embodiment, the second holding temperature is about 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, or about 500°C.

[0143] In one embodiment, the method further includes the step of grinding the Si@C / graphite / carbon material.

[0144] In one implementation, the grinding is performed using a dry ball mill.

[0145] In one embodiment, the method further includes the step of mixing the Si@C / graphite / carbon material with one or more polymer binders.

[0146] In one embodiment, one or more polymeric adhesives comprise one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

[0147] In one implementation, the negative electrode is formed through the following steps:

[0148] A slurry is generated by mixing Si@C / graphite / carbon materials with one or more polymer binders;

[0149] Apply the slurry to the metal component; and

[0150] The metal component coated with the slurry is dried to form the negative electrode.

[0151] According to a third aspect of the present invention, a negative electrode for a lithium-ion battery is provided, which is manufactured by the method described in the first or second aspect of the present invention.

[0152] According to a fourth aspect of the present invention, a negative electrode for a lithium-ion battery is provided, comprising a Si@C / graphite / carbon material.

[0153] According to a fifth aspect of the present invention, a lithium-ion battery is provided, comprising:

[0154] The negative electrode as defined in the third or fourth aspect of the present invention;

[0155] Positive electrode; and

[0156] One or more electrolytes or mixtures thereof are disposed between the negative electrode and the positive electrode, and / or one or more diaphragms or mixtures thereof.

[0157] An exemplary non-limiting electrolyte comprises 1.15 M LiPF6 in a mixture of ethylene carbonate (EC) / ethyl carbonate (EMC) / ethyl propionate (EP) / fluoroethylene carbonate (FEC) in a weight ratio of 27:35:27:10 (ethylene carbonate (EC): ethyl methyl carbonate (EMC): ethyl propionate (EP): fluoroethylene carbonate (FEC)), and additives such as propylene sulfate (PS) and adiponitrile (AND).

[0158] As will be apparent to those skilled in the art, a separator is a physical barrier that separates the two sides of a battery while allowing only ion transfer. Non-limiting examples of separators include polymer separators, particularly multilayer polymer separators, and more particularly polyethylene multilayer polymer separators.

[0159] In other examples, the method further includes: drying the wet slurry at a drying temperature before carbonizing the mixture, and / or drying the second wet slurry at a second drying temperature before carbonizing the second mixture. In another example, the mixture is milled by wet ball milling, and / or the second mixture is milled by wet ball milling. Optionally, but preferably, one or more solvents and / or one or more second solvents are one or more inert solvents.

[0160] In other instances, one or more second carbonaceous materials are the same as one or more carbonaceous materials; one or more second carbonaceous materials are different from one or more carbonaceous materials; one or more second solvents are the same as one or more solvents; or one or more second solvents are different from one or more solvents.

[0161] In other instances, the mixture is held at a holding temperature below the carbonization temperature before reaching the carbonization temperature, and / or the second mixture is held at a second holding temperature below the second carbonization temperature before reaching the second carbonization temperature.

[0162] In another example, the obtained Si@C / graphite / carbon material is further ground, preferably by dry grinding. In another example, the Si@C / graphite / carbon material is mixed with one or more polymer binders during the manufacture of the negative electrode. In yet another example, the negative electrode is formed by the following steps: mixing the Si@C / graphite / carbon material with one or more polymer binders to generate a slurry; coating the slurry onto a metal component; and drying the slurry-coated metal component to form the negative electrode. In yet another example, the metal component is a metal foil, metal strip, or metal mesh. In yet another example, a conductive agent is mixed into the slurry.

[0163] Other aspects, features, and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, which are part of this disclosure and illustrate the principles of various embodiments by way of example. Attached Figure Description

[0164] Preferred embodiments of the invention will now be described, given only by way of example at least one non-limiting embodiment described in conjunction with the accompanying drawings.

[0165] Figure 1 A flowchart of an example method for producing nano-silicon from micro-silicon is shown.

[0166] Figure 2 A flowchart illustrating an example method for manufacturing a negative electrode comprising silicon / carbon / graphite materials for lithium-ion batteries is shown.

[0167] Figure 3 An exemplary representation of one embodiment of the Si@C / G / C structure of the present invention is shown.

[0168] Figure 4 An example lithium-ion battery, i.e. a lithium-ion battery cell, is shown, which includes a negative electrode manufactured according to one of the example methods disclosed herein.

[0169] Figure 5(a) shows the cycling performance of the example negative electrode (labeled Si@C / G / C-1), and Figure 5(b) shows the cycling performance of the example electrode (labeled Si / G-1); both use a standard industrial CMC / SBR binder. The Si@C / G / C-1 negative electrode provides an average reversible discharge capacity (i.e., specific capacity) of 522.17 mAh / g after 400 cycles. The initial CE is 80.56%, the CE exceeds 99.0% after 25 cycles, and the capacity is retained at 72.6% after 400 cycles. The Si / C / G-1 negative electrode provides an average discharge capacity of 510.17 mAh / g after 400 cycles, with a capacity retention of 70.67%. These results demonstrate that a dual-carbon coating (e.g., as used in Example 1) is beneficial to the electrochemical performance of the negative electrode.

[0170] Figure 6 The cycling performance of an example negative electrode (Example 3) labeled Si@C / G / C-2 is shown. The discharge capacity drops rapidly, and the retention capacity is very low. It is believed that dry ball milling (i.e., without the use of one or more solvents) results in uneven coating, thus exposing some silicon particles directly to the electrolyte. These uncoated silicon particles lead to reduced electrochemical performance and poorer cycling ability compared to Example 1.

[0171] Figure 7 The cycling performance of example anodes labeled Si / G-1 (Example 4) and Si-1 (Example 5) is shown. Both the Si / G-1 and Si-1 anodes provide high reversible capacity during the initial cycling period, but the reversible capacity decreases rapidly after further cycling. After 100 cycles, only 28.5% (Si / G-1 anode) and 8.3% (Si-1 anode) of the capacity are retained.

[0172] Figure 8 The cycling performance of example anodes labeled Si@C / G / C-3 (Example 6) and Si@C / G / C-4 (Example 7) is shown. Compared to the Si@C / G / C-1 anode (Example 1), the Si@C / G / C-3 and Si@C / G / C-4 anodes offer lower capacity retention, retaining 86.01% (Si@C / G / C-3 anode) and 81.47% (Si@C / G / C-4 anode) of capacity after 100 cycles, and 71.4% (Si@C / G / C-3 anode) and 40.65% (Si@C / G / C-4 anode) of capacity after 250 cycles.

[0173] Figure 9 A flowchart illustrating an example method for producing a multifunctional polymer adhesive is shown.

[0174] Figure 10A flowchart illustrating an example method for manufacturing a negative electrode for a lithium-ion battery is shown. Step 1010 includes mixing silicon / graphite / carbon materials, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to generate a slurry.

[0175] Figure 11 A flowchart illustrating an example method for manufacturing a negative electrode with a binder for lithium-ion batteries is shown.

[0176] Figure 12(a) shows the cycling performance of an example anode labeled Si@C / G / C-5 (Example 8). The Si@C / G / C-5 anode provides an average reversible discharge capacity of approximately 525.7 mAh / g after 250 cycles. The CE exceeds 99.0% after 13 cycles, retains 95.35% of the capacity after 100 cycles, and retains 89.2% of the capacity after 250 cycles, representing an improvement in electrochemical performance compared to the Si@C / G / C-1 anode (Example 1).

[0177] Figure 12(b) shows the cycling performance of an example anode (Example 8) using an LSCR binder, labeled Si@C / G / C-5 (i.e., “5:1”), after 400 cycles. It retains 82.8% of its capacity after 400 cycles, representing an improvement in electrochemical performance compared to the Si@C / G / C-1 anode after 400 cycles.

[0178] Figure 13 Cycling performance of Si@C / G / C-5 with various binders at 0.3C (200 mA / g) is shown. The Si@C / G / C-5 anode was prepared in the same manner as Si@C / G / C-1 (Example 1), except that neographite (natural graphite) was used in the composite. Si@C / G / C-5 using LSCR binder (#1) retained 88.0% of its capacity after 100 cycles, higher than the 72.8% of Si@C / G / C-5 with LSC (no SBR) binder (#2), higher than the 68.4% of Si@C / G / C-5 using CMC+SBR binder (#3), and higher than the 63.4% of Si@C / G / C-5 using CMC binder (#4). The results indicate that this binder of the present invention is beneficial to the capacity retention of the Si / C composite anode.

[0179] Figure 14 The rate performance of Si@C / G / C-5 with various binders at 0.3C (200 mA / g) is shown above. Figure 13The Si@C / G / C-5 anode was prepared in the same manner as Si@C / G / C-1 (Example 1), except that neographite (natural graphite) was used in the composite. The Si@C / G / C-5 using LSCR binder (#1) provided specific capacities of 606 mAh / g, 581 mAh / g, 559 mAh / g, 522 mAh / g, 376 mAh / g, and 241 mAh / g at 0.15C, 0.3C, 0.45C, 0.75C, 1.5C, and 3C, respectively. This is superior to electrodes using LSC binder (#2), CMC+SBR binder (#3), and CMC binder (#4), while the electrode using CMC binder (#4) had the lowest capacities at 1.5C and 3C, at 234 mAh / g and 146 mAh / g, respectively.

[0180] Figure 15 The cycling performance of Si@C / G / C-6, Si@C / G / C-7, and Si@C / G / C-8 is shown. These three anodes were prepared in a similar manner to Si@C / G / C-1 (Example 1), differing only in the use of different annealing temperatures and the use of virgin graphite (natural graphite). The annealing temperatures used during carbonization were as follows: 1000°C for Si@C / G / C-6, 900°C for Si@C / G / C-7, and 700°C for Si@C / G / C-8. Si@C / G / C-6 provided the highest capacity retention, maintaining 81.3% of its capacity after 100 cycles, while Si@C / G / C-7 and Si@C / G / C-8 retained only 77.8% and 68.9%, respectively.

[0181] Figure 16 SEM images of brand new and 100-cycle Si@C / G / C-5 anodes using different adhesives are shown. Figure 16 (a) and (b) refer to brand new and 100-cycle Si@C / G / C-5 anodes using CMC binder; (c) and (d) are CMC+SBR binders; (e) and (f) are LSC binders; (g) and (h) are LSCR binders. Figure 16 (b) and (d) show obvious microcracks on the entire electrode surface, while no obvious cracks were observed in the case of LSCR adhesive after 100 cycles, indicating that the electrode integrity is better after 100 charge / discharge cycles.

[0182] Figure 17 The viscosity of different adhesives was compared, and SBR adhesive showed the lowest viscosity, while LSCR adhesive showed the highest viscosity. This result demonstrates that LSCR adhesive is advantageous in withstanding the stress caused by volume changes during cycling and maintaining the integrity of the negative electrode. Detailed Implementation

[0183] To provide a more precise understanding of the subject matter of one or more embodiments, the following methods are described by way of example only. In the accompanying drawings incorporated to describe the features of the example embodiments, similar reference numerals are used to identify similar portions throughout the drawings.

[0184] In one example, a silicon / carbon / graphite (i.e., Si@C / G / C or Si / C / G) material is manufactured or formed for use as a negative electrode in a lithium-ion battery (LIB) (i.e., a lithium-ion battery cell). The silicon / carbon / graphite material can be formed using silicon and one or more carbonaceous materials as well as graphite. In various example methods of manufacturing the negative electrode, the silicon content and distribution in the composite material forming the negative electrode significantly affect the overall performance of the negative electrode. For example, a trade-off is made between the capacity and stability of the negative electrode. Therefore, the selection of the type and content ratio of carbonaceous raw materials (i.e., one or more carbonaceous materials), the selection of the type and content ratio of silicon, the selection of the graphite content ratio, the coating process, the mixing process, and other processes used are important aspects of achieving improved negative electrode performance for commercial LIB applications.

[0185] To obtain high-performance anodes, such as those formed from silicon / carbon / graphite materials, to replace known graphite anodes in LIBs, the inventors have addressed the following related issues: (a) achieving uniform distribution of silicon particles in a conductive matrix (e.g., graphite and carbon); (b) mass production of secondary silicon particles to achieve high gravimetric energy density, high volumetric energy density, and high initial coulombic efficiency; and / or (c) excellent mechanical properties of the anode, and in certain examples, long cycle life of the anode achieved through the use of viscous, elastic, conductive, and self-healing polymeric adhesives.

[0186] In the example implementation, a novel method is used to synthesize (i.e., manufacture) anodes formed from different silicon / carbon / graphite materials. For example, a novel method is used to manufacture anodes formed from "double carbon coated" silicon / carbon / graphite (i.e., Si@C / G / C) materials.

[0187] The terms Si / C / G and Si@C / G / C refer to "silicon / carbon / graphite" materials formed from or based on silicon (Si), carbon (C), and graphite (G). Si@C refers to carbon-coated silicon particles (i.e., silicon coated or covered with carbon materials). For example, in Si@C materials, a carbon shell or layer covers the silicon core, preventing direct contact between the silicon surface and the electrolyte. Specifically, Si@C / G / C refers to materials formed from or based on Si@C materials, graphite (G), and (C).

[0188] In another example embodiment, a method is provided for manufacturing a negative electrode for use in a lithium-ion battery, the negative electrode comprising a Si@C / G / C material, and the method includes:

[0189] Use nano-silicon:carbon materials within a specified weight ratio range;

[0190] Grinding, for example, wet ball milling of nano-silicon and carbonaceous materials together with one or more solvents (which may be one or more inert solvents);

[0191] During grinding, such as wet ball milling, the mixture is kept (i.e. maintained) as a wet slurry;

[0192] Dry the wet slurry at a drying temperature for a period of time;

[0193] The dried Si / C mixture is carbonized / sintered at a carbonization temperature within the carbonization temperature range to produce Si@C material (i.e., silicon particles coated with carbon).

[0194] Using (Si@C materials) within the specified weight ratio range: graphite: carbonaceous material;

[0195] Grinding (i.e., a second time), such as wet ball milling of Si@C material and graphite, along with a second carbonaceous material (which may be the same as or a different carbonaceous material used previously) together with one or more second solvents (which may be one or more second inert solvents, and one or more of the second solvents may be the same as or different from one or more solvents);

[0196] During grinding processes such as wet ball milling, the mixture of Si@C, graphite, and carbonaceous materials is kept (i.e., maintained) as a wet slurry.

[0197] The wet slurry is dried at the second drying temperature for the second drying time.

[0198] The Si@C / G / C mixture (i.e., the second mixture) is carbonized / sintered (i.e., the second time) at a second carbonization temperature within the second carbonization temperature range, wherein the second carbonization temperature may be the same as or different from the carbonization temperature, and the range of the second carbonization temperature may be the same as or different from the range of the carbonization temperature; and

[0199] The resulting Si@C / G / C material is used to form a negative electrode, for example, by compacting the Si@C / G / C material.

[0200] experiment

[0201] a) Preparation of nano-silicon

[0202] In one example, a method for producing nano-silicon from microsilicon includes grinding (e.g., sand milling or ball milling) the microsilicon with an inert solvent, and keeping the mixture as a wet slurry during the grinding of the microsilicon. Using an inert solvent avoids oxidation of the resulting nano-silicon.

[0203] refer to Figure 1 The figure illustrates a method 100 for producing nano-silicon from microsilicon. Step 110 includes mixing microsilicon and one or more inert solvents to generate a wet slurry mixture. Step 120 includes milling (preferably using a sand mill) the wet slurry mixture of microsilicon and one or more inert solvents. During step 120, the mixture is maintained as a wet slurry mixture (i.e., during milling).

[0204] In a specific example, the average particle size of the micro-Si is equal to or about 10 μm to about 100 μm. Preferably, the average particle size of the micro-Si is about 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. Most preferably, the average particle size of the micro-Si is about 10 μm.

[0205] Nano silicon is produced by grinding or ball milling (high-energy) microsilicon in the presence of at least one inert solvent, keeping the mixture as a wet slurry during the microsilicon milling process. The resulting nano silicon has an average particle size of about 50 nm to about 500 nm. Preferably, the average particle size of the obtained nano-silicon is about 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm, or 500nm. Most preferably, the average particle size of the nano-silicon is about 100 nm, for example, about 50 nm to 150 nm, 60 nm to 140 nm, 70 nm to 130 nm, 80 nm to 120 nm, or 90 nm to 110 nm.

[0206] Microsilicon is pulverized into nano-silicon by grinding (preferably by sand milling) in one or more inert solvents. The inert solvent may be one or more of ethylene glycol (EG), 1-pentanol, propylene glycol, polyacrylic acid, or the like.

[0207] Alternatively, the solvent can be selected from the group consisting of toluene, xylene, quinoline, pyridine and tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof. In this step, sand milling or high-energy ball milling is required because grinding microsilica requires extremely high grinding energy. During wet milling, the slurry is intentionally not allowed to dry to avoid agglomeration of silicon particles.

[0208] b) Manufacturing negative electrodes for lithium-ion batteries

[0209] An example negative electrode for a lithium-ion battery, comprising silicon / graphite / carbon materials, such as Si / C / G materials or Si@C / G / C materials, is manufactured by pyrolysis, sintering, or preferably by a mixture of silicon carbide particles, one or more carbonaceous materials, and graphite.

[0210] As previously described, nano-silicon is produced from microsilicon to obtain nano-silicon for later use, or commercially available nano-silicon can be used. The average particle size of the nano-silicon used is preferably equal to or about 50 nm to about 500 nm. The nano-silicon used may have an average particle size of approximately 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, or 500 nm. Most preferably, the average particle size of the nano-silicon used is about 100 nm, for example, about 50 nm to 150 nm, 60 nm to 140 nm, 70 nm to 130 nm, 80 nm to 120 nm, or 90 nm to 110 nm.

[0211] One or more carbonaceous materials are available for use. For example, one or more carbonaceous materials may be functionalized graphene sheets, carbon nanotubes (CNTs), reduced graphene oxide (rGO), pyrolytic carbon derived from precursors such as glucose, sucrose, or citric acid (CA), pitch, polyacrylonitrile (PAN), polyvinyl chloride (PVC), poly(diallyldimethylammonium chloride) (PDDA), poly(sodium 4-styrenesulfonate) (PSS), polydopamine (PDA), polypyrrole (PPy), or phenolic resins.

[0212] Graphite is obtained for later use; the graphite may be natural graphite and / or synthetic graphite. For natural graphite, spherical graphite is preferred, while for synthetic graphite, flake graphite is preferred. For example, graphite microspheres with an average size equal to or from about 1 μm to about 20 μm can be used. Preferably, the average size of the graphite microspheres is about 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 μm, or 20 μm. Most preferably, the average size of the graphite microspheres is about 5 μm.

[0213] refer to Figure 2 The figure illustrates a method 200 for manufacturing a negative electrode for lithium-ion batteries.

[0214] Step 210 includes grinding a mixture of nano-silicon, one or more carbonaceous materials, and one or more solvents, wherein the mixture remains a wet slurry during grinding.

[0215] Optionally, step 220 includes drying the wet slurry at a drying temperature for a drying time to produce a dried mixture / powder.

[0216] Step 230 includes carbonizing the mixture (or a dried mixture / powder if drying step 220 is used) at a carbonization temperature to produce a carbon-coated silicon (Si@C) material.

[0217] Step 240 includes grinding a second mixture of Si@C material, graphite, one or more second carbonaceous materials, and one or more second solvents, wherein the second mixture remains as a second wet slurry during grinding.

[0218] Optionally, step 250 includes drying the second wet slurry at a second drying temperature to produce a dried coarse “silicon@C” (Si@C) / graphite / carbon mixture / powder coated with carbon material.

[0219] Step 260 includes carbonizing the second mixture (or, if drying step 250 is used, a dried crude Si@C / graphite / carbon mixture / powder) at a second carbonization temperature to produce a Si@C / graphite / carbon material.

[0220] Step 270 includes grinding (preferably dry ball milling) the resulting "silicon" / graphite / carbon (i.e., Si@C / G / C) material coated with carbon material.

[0221] Finally, step 280 includes forming a negative electrode from a Si@C / graphite / carbon material.

[0222] The following provides steps for further non-limiting example methods of manufacturing a negative electrode for a lithium-ion battery according to the present invention.

[0223] Step 1: Weigh The mass ratio (nano-silicon:carbon material) is equal to or about 40:60 to about 70:30 for nano-silicon and at least one carbon material. Preferably, the mass ratio (nano-silicon:carbon material) is about 40:60, about 50:50, about 60:40 or about 70:30. More preferably, the ratio is about 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, about 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, about 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31, or about 70:30. Most preferably, the mass ratio (nano-silicon: carbonaceous material) is about 50:50.

[0224] Step 2: Nano-silicon and one or more carbonaceous materials are thoroughly mixed by grinding (preferably wet ball milling). One or more solvents (which may be one or more inert solvents) may be used during the wet ball milling process and may include, for example, toluene, xylene, quinoline, pyridine, tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethyl acetamide (DMA), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol (EG), propylene glycol, polyacrylic acid, or mixtures thereof. The volume of the desired solvent or more should be just sufficient to immerse the solid powder, keeping the mixture in a wet slurry rather than a diluted liquid or viscous state during the wet ball milling process. Sealing is required throughout the grinding process to prevent solvent evaporation.

[0225] The ball milling speed is preferably about 400 rpm, although the ball milling speed can be from about 300 rpm to about 600 rpm, for example, about 300 rpm, 325 rpm, 350 rpm, 375 rpm, 400 rpm, 425 rpm, 450 rpm, 475 rpm, 500 rpm, 525 rpm, 550 rpm, 575 rpm, or about 600 rpm. The ball milling duration is preferably about 6 hours, although the ball milling duration may be from about 3 to about 24 hours, for example, about 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours. The ball-to-weight ratio is preferably about 20:1, although the ball-to-weight ratio can be from about 10:1 to 40:1, for example, about 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or about 50:1.

[0226] Step 3: Put The mixture, as a wet slurry, is vacuum dried in an oven at a drying temperature for a period of time to produce a dry powder. For example, the temperature can be equal to or from about 70°C to about 150°C. Preferably, the temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C. Most preferably, the temperature is about 80°C. The drying time can be equal to or from about 2 hours to about 18 hours. Preferably, the drying time is about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 hours. Most preferably, the drying time is about 12 hours.

[0227] Step 4: Then The dried material (i.e., dried powder) is carbonized under an inert gas (preferably argon or nitrogen or a mixture thereof) flowing in a tube furnace, for example, and the resulting Si@C material (i.e., silicon particles coated with carbon material) is collected. Preferably, the carbonization process (characterized by high-temperature carbonization) includes the following steps:

[0228] The dried powder is heated to a holding temperature of approximately 400°C (or optionally, approximately 300°C to 500°C) in progressive increments of approximately 5°C per minute (or optionally equal to or equal to approximately 2°C to approximately 5°C per minute).

[0229] The dried powder is kept at about 400°C (or optionally equal to or about 300°C to about 500°C) for about 3 hours (or optionally equal to or about 2 hours to about 5 hours).

[0230] The dried powder is further heated to a carbonization temperature of approximately 1000°C (or optionally equal to or a carbonization temperature range of approximately 900°C to approximately 1200°C, for example, the carbonization temperature may be approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C) in progressive increments of approximately 8°C per minute (or optionally equal to or a carbonization temperature range of approximately 900°C to approximately 1200°C, for example, the carbonization temperature may be approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C).

[0231] The dried powder is held at the carbonization temperature for about 5 hours (or optionally equal to or for about 3 hours to about 8 hours), then

[0232] The Si@C material obtained by natural cooling to room temperature, during which the gas flow rate of argon (or nitrogen) remains stable.

[0233] Step 5: Next, the obtained Si@C material, graphite, and one or more second carbonaceous materials are weighed at a mass ratio equal to or between approximately 10-30:40-80:10-30 (Si@C material: graphite: second carbonaceous material). Preferably, the mass ratio (Si@C material: graphite: second carbonaceous material) is approximately 10:80:10, approximately 10:70:20, approximately 10:60:30, approximately 20:70:10, approximately 20:60:20, approximately 20:50:30, approximately 30:60:10, approximately 30:50:20, or approximately 30:40:30. Most preferably, the mass ratio (Si@C material: graphite: second carbonaceous material) is approximately 20:60:20. The one or more second carbonaceous materials used in this step are preferably the same as those previously used; however, different types of one or more second carbonaceous materials may also be used.

[0234] Step 6: The obtained Si@C material, graphite, and one or more second carbonaceous materials are thoroughly mixed into a second mixture by grinding (preferably wet ball milling). In this step, the Si@C material is bonded to the graphite and further coated by one or more second carbonaceous materials (for a second use). One or more second solvents (which may be one or more second inert solvents) are used during the grinding process and may be one or more of toluene, xylene, quinoline, pyridine, tetrahydrofuran, etc.

[0235] One or more second solvents are preferably the same as the previously used solvents, but they can also be different solvents. The volume of the required second solvents should be just sufficient to submerge the solid powder, keeping the second mixture as a wet slurry rather than a diluted liquid or viscous state during the grinding process by wet ball milling. Sealing is required throughout the grinding process to prevent evaporation of the second solvent.

[0236] The ball milling speed is preferably about 400 rpm, although it may be from about 300 rpm to about 600 rpm. The ball milling duration is preferably about 24 hours, although it may be from about 12 hours to about 48 hours. The ball-to-weight ratio is preferably about 20:1, although it may be from about 10:1 to 40:1.

[0237] Step 7: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] The obtained second mixture (as a second wet slurry) is vacuum-dried in an oven at a second drying temperature for a second drying time to produce dried coarse Si@C / G / C material (powder). For example, the temperature can be equal to or from about 70°C to about 150°C. Preferably, the temperature is about 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C. Most preferably, the temperature is about 80°C. The drying time can be equal to or from about 6 hours to about 18 hours. Preferably, the drying time is about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 hours. Most preferably, the drying time is about 12 hours.

[0238] Step 8: The dried crude Si@C / G / C material (powder) is then carbonized in a tube furnace, for example, under a flowing inert gas (preferably argon or nitrogen or a mixture thereof), and the resulting Si@C / G / C material is collected. Preferably, the carbonization process (characterized by high-temperature carbonization) includes the following steps:

[0239] The dried, crude Si@C / G / C powder is heated to a second holding temperature of approximately 400°C (or optionally, approximately 300°C to 500°C) in progressive increments of approximately 5°C per minute (or optionally equal to or equal to approximately 2°C to approximately 5°C per minute).

[0240] The Si@C / G / C powder at the second holding temperature is maintained at about 400°C (or optionally equal to or about 300°C to about 500°C) for about 3 hours (or optionally equal to or about 2 hours to about 5 hours).

[0241] The Si@C / G / C powder is further heated to a second carbonization temperature of approximately 1000°C (or optionally equal to or a second carbonization temperature range of approximately 900°C to approximately 1200°C, for example, the second carbonization temperature may be approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C) in progressive increments of approximately 8°C per minute (or optionally equal to or a second carbonization temperature range of approximately 5°C to approximately 10°C per minute). The second carbonization temperature may be the same as or different from the original carbonization temperature, and the range of the second carbonization temperature may be the same as or different from the original carbonization temperature range.

[0242] The Si@C / G / C powder is held at the second carbonization temperature for about 5 hours (or optionally equal to or about 3 hours to about 8 hours), and then...

[0243] The obtained Si@C / G / C material was naturally cooled to room temperature, during which time the argon gas flow rate remained stable.

[0244] Step 9: After final grinding (preferably dry ball milling), the final Si@C / G / C material is obtained. The ball milling speed is preferably about 400 rpm, although the dry ball milling speed can be from about 300 rpm to about 500 rpm. The dry ball milling duration is preferably about 24 hours, although the ball milling duration can be from about 12 hours to about 48 hours. Sufficient duration and speed are required to ensure the uniformity of the obtained material; the ball mill jar should be filled with an inert gas, such as argon, helium, nitrogen, etc.

[0245] Step 10: The Si@C / G / C material exhibits a microscale hierarchical structure in which carbon-coated Si nanoparticles are uniformly distributed on a graphite matrix, and a second carbon coating is formed throughout the structure to create a uniform conductive network. To form the negative electrode used in lithium-ion batteries, the Si@C / G / C material, one or more polymer binders (e.g., CMC+SBR), and a conductive agent (e.g., carbon black) are mixed in a ratio (e.g., 8:1:1), uniformly stirred in distilled water to form a homogeneous slurry, and coated onto a clean and flat metal component (e.g., copper foil). In the example discussed, a copper foil coated with the Si@C / G / C slurry is obtained.

[0246] Copper foil coated with Si@C / G / C slurry was heated and dried under vacuum for approximately 12 hours. The dried Si@C / G / C coated copper foil was then cut and pressed to form a Si@C / G / C anode used in lithium-ion batteries. An exemplary representation of the resulting Si@C / G / C structure is shown below. Figure 3 middle.

[0247] c) Example Lithium-ion Battery (LIB)

[0248] refer to Figure 4 The figure shows an example lithium-ion battery 300 (i.e., a lithium-ion battery) which includes a negative electrode manufactured according to one of the example methods disclosed herein.

[0249] Figure 4A coin-on-coin lithium-ion battery 300 is shown, having a first component 312 and a second component 314 made of conductive material and usable as electrical contacts. However, it should be noted that the battery 300 can be constructed according to any lithium-ion battery configuration known in the art. Within or attached to the first component 312 is a negative electrode 316 manufactured according to this embodiment, and within or attached to the second component 314 is a positive electrode 320. A separator 318 is disposed between the negative electrode 316 and the positive electrode 320.

[0250] Insulator 322 ensures that the negative electrode 316 is electrically connected only to the first component 312, and the positive electrode 20 is electrically connected only to the second component 314, thereby forming a closed circuit with the electrical contact of both the first component 312 and the second component 314, and allowing current to flow due to the electrochemical reaction at the negative electrode 316 and the positive electrode 320. Button-to-button lithium-ion battery configurations, as well as other electrode and component configurations, are well known in the art, and the negative electrode of the present invention can be readily configured into any type of lithium-ion battery configuration, as will be apparent to those skilled in the art.

[0251] In example lithium-ion battery configurations using electrolytes, various electrolytes can be used. An exemplary non-limiting electrolyte comprises 1.15 M LiPF6 in a mixture of ethylene carbonate (EC) / ethyl carbonate (EMC) / ethyl propionate (EP) / fluoroethylene carbonate (FEC) in a weight ratio of 27:35:27:10 (ethylene carbonate (EC): ethyl methyl carbonate (EMC): ethyl propionate (EP): fluoroethylene carbonate (FEC)), and additives such as propylene sulfate (PS) and adiponitrile (AND).

[0252] The following examples provide a more detailed discussion and are intended to be illustrative only and not to limit the scope of the invention.

[0253] For the following exemplary negative electrodes, the negative electrode is formed as a solid electrode from the material / powder generated in each embodiment. The electrode is manufactured using a slurry coating and drying method. To form the negative electrode, a mixture of active materials (e.g., Si@C / G / C, Si / C / G, Si / G, etc.), CMC, and SBR (as one or more polymer binders) and carbon black (as a conductive agent) is mixed in a ratio equal to or in the range of about 80-96:1-10:3-10, uniformly stirred in distilled water to form a homogeneous slurry, and coated onto a clean, flat copper foil to obtain a slurry-coated copper foil. The slurry-coated copper foil is dried by heating under vacuum for about 12 hours, and then the dried active material-coated copper foil is cut and pressed to form the negative electrode used in the example lithium-ion battery.

[0254] The resulting negative electrode is assembled into a lithium-ion battery (i.e., a lithium-ion battery cell), which is provided as a button-type semi-CR2032 battery. In Neware TM The battery testing system performed constant current charge-discharge tests at a constant current density of 200 mA / g within a voltage window of 10 mV to 1.5 V (vs Li+ / Li). The electrolyte used consisted of 1.15 M LiPF6 in a mixture of ethylene carbonate (EC) / methyl ethyl carbonate (EMC) / ethyl propionate (EP) / fluoroethylene carbonate (FEC) in a weight ratio of 27:35:27:10 (ethylene carbonate (EC): ethyl methyl carbonate (EMC): ethyl propionate (EP): fluoroethylene carbonate (FEC)), and additives including propylene sulfate (PS) and adiponitrile (AND).

[0255] Example 1

[0256] In the example implementation, a negative electrode (Example 1) was prepared, labeled as Si@C / G / C-1 negative electrode. The Si@C / G / C-1 negative electrode was prepared using 5.0 g of nano-silicon obtained by sand milling and 5.0 g of pitch (which were mixed together with 50 mL of THF (tetrahydrofuran) as a solvent by wet ball milling).

[0257] The THF solvent volumetrically covers the solid powder, and during wet ball milling, the mixture remains a wet slurry rather than a diluted liquid or viscous state. A seal is used during wet ball milling to prevent THF evaporation. The milling speed is 400 rpm, and the milling duration is 48 hours. The ball-to-weight ratio is approximately 20:1. The resulting slurry is then vacuum-dried overnight in an oven at 80°C for approximately 12 hours.

[0258] The dried powder was then carbonized in a tube furnace under flowing argon gas. During carbonization, the dried powder was first heated to a holding temperature of 400°C in incremental increments of 5°C per minute. The dried powder at the holding temperature was maintained at 400°C for 3 hours. The dried powder was then further heated to a final temperature of 1000°C in incremental increments of 8°C per minute. The dried powder at the final temperature was maintained at 1000°C for 5 hours, and then the resulting Si@C material was allowed to cool naturally to room temperature, during which time the argon gas flow rate remained stable. The resulting Si@C material was collected.

[0259] Then, 5.0 g of the obtained Si@C material, 15.0 g of graphite, and 5.0 g of pitch were wet-ball milled together with THF (50 mL) as a solvent. The volume of THF solvent completely submerged the solid powder mixture, maintaining the mixture as a wet slurry rather than a diluted liquid or viscous state during the wet ball milling process. A seal was used during the milling process to prevent evaporation of the THF solvent. The ball milling speed was 400 rpm, and the milling duration was approximately 48 hours. The ball-to-weight ratio was approximately 20:1. The resulting slurry was then vacuum-dried in an oven at 80°C for approximately 12 hours.

[0260] The collected, dried coarse Si@C / G / C powder was then carbonized in a tube furnace under flowing argon gas (second carbonization step). In the further carbonization process, the dried coarse Si@C / G / C powder was first heated to a holding temperature of 400°C in incremental increments of 5°C per minute. The Si@C / G / C powder at the holding temperature was held at 400°C for 3 hours. Then, the Si@C / G / C powder was further heated to a final temperature of 1000°C in incremental increments of 8°C per minute. The Si@C / G / C powder at the final temperature was held at 1000°C for 5 hours, and then the resulting Si@C / G / C material was allowed to cool naturally to room temperature, during which time the argon gas flow rate remained stable. The resulting Si@C / G / C material was collected.

[0261] The Si@C / G / C powder was homogenized by dry ball milling, and the resulting Si@C / G / C material (powder) was collected. The dry ball milling speed was 400 rpm, and the duration of dry ball milling was approximately 24 hours. The ball milling jar was filled with argon gas.

[0262] Figure 5 illustrates the cycling performance of the obtained Si@C / G / C-1 anode. Referring to Figure 5, the Si@C / G / C-1 anode provides an average reversible discharge capacity (i.e., specific capacity) of 522.17 mAh / g after 400 cycles. The initial coulombic efficiency (CE) is 80.56%, exceeding 99.0% after 25 cycles, and retaining 72.6% of the capacity after 400 cycles. This is advantageous, for example, compared to Figure 5 of CN108807861A (as described above), which achieved 83% capacity retention after 200 cycles.

[0263] Example 2

[0264] A comparative negative electrode (Example 2) was prepared, labeled as Si / C / G-1 negative electrode (coated with carbon only once). The Si / C / G-1 negative electrode was prepared using 2.5 g of nano-silicon obtained by sand milling, 15.0 g of graphite, and 7.5 g of pitch (which were completely mixed together with 50 mL of THF (tetrahydrofuran) as a solvent by wet ball milling), followed by vacuum drying of the resulting slurry. The collected coarse Si / C / G-1 powder was carbonized in a vacuum tube, and finally, the Si / C / G-1 powder was homogenized by dry ball milling.

[0265] Figure 5 further illustrates the cycling performance of the obtained Si / C / G-1 anode. Referring to Figure 5, the Si / C / G-1 anode provides an average discharge capacity of 487.56 mAh / g after 250 cycles, retaining 78.3% of its capacity. This result demonstrates that dual carbon coating (e.g., as used in Example 1) is beneficial to the electrochemical performance of the anode.

[0266] Example 3

[0267] A comparative negative electrode (Example 3) was prepared and labeled as Si@C / G / C-2 negative electrode (prepared without solvent during ball milling). The preparation of the Si@C / G / C-2 negative electrode was similar to that of Si@C / G / C-1 (Example 1), except that no solvent was used in the ball milling step and the wet slurry was not maintained during the ball milling process.

[0268] Figure 6 The cycling performance of the obtained Si@C / G-2 anode is shown. (Reference) Figure 6 The discharge capacity decreased rapidly, and the retention capacity was very low. It is believed that dry ball milling (i.e., without the use of one or more solvents) resulted in uneven coating, thus some silicon particles were directly exposed to the electrolyte. Compared with Example 1, these uncoated silicon particles led to reduced electrochemical performance and poor cycling ability.

[0269] Examples 4 and 5

[0270] A comparative negative electrode (Example 4) was prepared, labeled as Si / G-1 negative electrode (silicon without carbon coating but mixed with graphite). Another comparative negative electrode (Example 5) was prepared, labeled as Si-1 negative electrode (bare silicon without carbon coating and not mixed with graphite).

[0271] The Si / G-1 anode was prepared using 5.0 g of nano-silicon obtained by sand milling and 20.0 g of graphite (which were thoroughly mixed with ethylene glycol (50 mL) by wet ball milling), dried, and then heat-treated in a tube furnace to collect the coarse Si / G powder, similar to the carbonization step in Example 1. Finally, the Si / G powder was dry-ball-milled to achieve a homogeneous state. In contrast, the Si-1 anode was prepared by simply collecting the nano-silicon after sand milling.

[0272] Figure 7 The cycling performance of the obtained Si / G-1 anode and the obtained Si-1 anode are shown. (Reference) Figure 7 The Si / G-1 and Si-1 anodes provide high reversible capacity during the initial cycling phase, but the reversible capacity decreases rapidly after further cycling. After 100 cycles, only 28.5% (Si / G-1 anode) and 8.3% (Si-1 anode) of capacity are retained. It is believed that the rapid capacity decline of the Si-1 anode (bare silicon) is due to its excessive volume expansion. In contrast, for example, the Si / C / G-1 anode (Example 2) and Si / G-1 anode (Example 4), silicon coated with carbon effectively mitigates the volume expansion of silicon and extends the cycle life of the anode.

[0273] Examples 6 and 7

[0274] A comparative negative electrode (Example 6) was prepared and labeled as Si@C / G / C-3 negative electrode (at different annealing temperatures). Another comparative negative electrode (Example 7) was prepared and labeled as Si@C / G / C-4 negative electrode (at different annealing temperatures).

[0275] The preparation of Si@C / G / C-3 and Si@C / G / C-4 anodes is similar to that of Si@C / G / C-1 anode (Example 1), except that different annealing (i.e., sintering) temperatures are used.

[0276] As previously described in Example 1, the annealing temperature used during carbonization in the manufacturing of the Si@C / G / C-1 anode was 1000°C. In contrast, the annealing temperature used during carbonization in the manufacturing of the Si@C / G / C-3 anode was 800°C. In a further comparison, the annealing temperature used during carbonization in the manufacturing of the Si@C / G / C-4 anode was 600°C. Other process conditions used for manufacturing the different anodes were the same.

[0277] Figure 8 The cycle performance of the obtained Si@C / G / C-3 and Si@C / G / C-4 anodes is described. (Reference) Figure 8 Compared to the Si@C / G / C-1 anode (Example 1), the Si@C / G / C-3 and Si@C / G / C-4 anodes exhibited lower capacity retention, retaining 86.01% (Si@C / G / C-3 anode) and 81.47% (Si@C / G / C-4 anode) of capacity after 100 cycles, and 71.4% (Si@C / G / C-3 anode) and 40.65% (Si@C / G / C-4 anode) of capacity after 250 cycles. It is believed that insufficiently high annealing temperatures prevent complete carbonization of the carbonaceous material.

[0278] d) Multifunctional polymer adhesives

[0279] Multifunctional adhesives, particularly relatively low-cost multifunctional polymeric adhesives, have been designed and synthesized. These multifunctional polymeric adhesives possess a 3D network structure, improved conductivity, and self-healing properties. In one example application for the negative electrode in lithium-ion batteries, using a multifunctional polymeric adhesive as part of the negative electrode helps address the relatively poor conductivity and large volume expansion of negative electrodes (e.g., silicon-based negative electrodes), which would otherwise lead to rapid capacity decay. Those skilled in the art will understand that multifunctional polymeric adhesives may have a variety of other example applications.

[0280] refer to Figure 9 The figure illustrates a method 900 for producing a multifunctional polymer adhesive. Method 900 includes mixing one or more linear polymers 910, one or more conductive polymers 920, one or more self-healing polymers 930, and one or more rubber polymers 940 together to produce a multifunctional polymer adhesive 950.

[0281] The composition of the example multifunctional polymer adhesive includes:

[0282] One or more linear polymers, having a weight percentage equal to or from about 20 wt.% to about 60 wt.%. Preferably, the weight percentage of one or more linear polymers is about 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, or 60 wt.%. In a preferred example, the weight percentage of one or more linear polymers is about 50 wt.%.

[0283] One or more conductive polymers, wherein the weight percentage is equal to or is from about 5 wt.% to about 20 wt.%. Preferably, the weight percentage of one or more conductive polymers is about 5 wt.%, 10 wt.%, 15 wt.%, or 20 wt.%. In a preferred example, the weight percentage of one or more conductive polymers is about 10 wt.%.

[0284] One or more self-healing polymers, wherein the weight percentage is equal to or equal to about 10 wt.% to about 20 wt.%. Preferably, the weight percentage of the one or more self-healing polymers is about 10 wt.%, 15 wt.%, or 20 wt.%. In a preferred example, the weight percentage of the one or more self-healing polymers is about 10 wt.%; or

[0285] One or more rubber polymers, having a weight percentage equal to or from about 10 wt.% to about 40 wt.%. Preferably, the weight percentage of one or more rubber polymers is about 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, or 40 wt.%. In a preferred example, the weight percentage of one or more rubber polymers is about 30 wt.%.

[0286] Surprisingly, the inventors discovered that when the multifunctional binder described herein is mixed with silicon / graphite / carbon materials (e.g., Si@C / G / C) to manufacture anodes for lithium-ion batteries, it can increase at least one of the cycle life (cycle performance) of the silicon-containing anode and the coulombic efficiency of the resulting lithium-ion battery.

[0287] Without being bound by any particular theory, the inventors believe that the increase in cycle life and coulombic efficiency is due to the substantially uniform distribution of the multifunctional polymer binder of the present invention within the silicon / graphite / carbon material in the manufactured negative electrode. Without being bound by any particular theory, the inventors believe that the multifunctional polymer binder is miscible or compatible with the silicon / graphite / carbon material in the manufactured negative electrode, thereby resulting in a substantially uniform distribution and preventing SBR migration.

[0288] In specific examples, hydroxyl, amino, or carboxyl groups of linear polymers; imino or sulfonic acid groups of conductive polymers; and urea groups of self-healing polymers are crosslinked to form a 3D network of rigid-flexible chains, thereby improving the desired mechanical properties and adhesion of the negative electrode.

[0289] Without being bound by any particular theory, the inventors have also discovered that, in some embodiments, the addition of an organic acid (preferably citric acid) can improve the distribution of the adhesive of the present invention throughout the silicon / graphite / carbon material in the manufactured negative electrode by triggering the crosslinking of one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers when the slurry is heated. The crosslinked, multifunctional polymer adhesive prevents or improves the migration of rubber polymers to the electrode surface, thereby providing a more uniform three-dimensional structure.

[0290] Preferred linear polymers include, for example, sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), polyvinyl alcohol (PVA), citric acid (CA), sodium alginate (SA), 2-pentenoic acid, 2-methacrylic acid, or chitosan (CS).

[0291] Preferred conductive polymers include, for example, polyaniline (PANI), poly[9,9-bis(3-propionic acid)fluorosodium (PFCOONa), poly[(l-pyrene methyl)methacrylate-co-methacrylic acid) (PPyMAA), polypyrrole (PPY), or 3,4-ethylenedioxythiophene / polystyrene-4-sulfonate (PEDOT:PSS).

[0292] Preferred self-healing polymers include, for example, urea-pyrimidinone (UPy), dopamine methacrylamide (DMA), and dopamine (DA).

[0293] Preferred rubber polymers include, for example, styrene-butadiene rubber (SBR), chloroprene rubber, nitrile rubber, butyl silicone rubber, or polysulfide rubber. In a preferred embodiment, the rubber polymer is styrene-butadiene rubber (SBR) and its derivatives.

[0294] In some embodiments, the weight-average molecular weight of one or more linear polymers is from 20,000 to 1,000,000 Daltons. In some embodiments, the weight-average molecular weight is from 20,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is from 50,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is from 100,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is from 500,000 to 550,000 Daltons. In some embodiments, the weight-average molecular weight is 520,000 Daltons. In some embodiments, the weight-average molecular weight is from 50,000 to 150,000 Daltons. In some embodiments, the number-average molecular weight is from 100,000 to 200,000 Daltons.

[0295] In some embodiments, one or more conductive polymers have a weight-average molecular weight of 20,000 to 1,000,000 Daltons. In some embodiments, the weight-average molecular weight is 20,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 100,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 500,000 to 550,000 Daltons. In some embodiments, the weight-average molecular weight is 520,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 150,000 Daltons. In some embodiments, the number-average molecular weight is 100,000 to 200,000 Daltons.

[0296] In some embodiments, one or more self-healing polymers have a weight-average molecular weight of 20,000 to 1,000,000 Daltons. In some embodiments, the weight-average molecular weight is 20,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 100,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 500,000 to 550,000 Daltons. In some embodiments, the weight-average molecular weight is 520,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 150,000 Daltons. In some embodiments, the number-average molecular weight is 100,000 to 200,000 Daltons.

[0297] In some embodiments, one or more rubber polymers have a weight-average molecular weight of 20,000 to 1,000,000 Daltons. In some embodiments, the weight-average molecular weight is 20,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 100,000 to 600,000 Daltons. In some embodiments, the weight-average molecular weight is 500,000 to 550,000 Daltons. In some embodiments, the weight-average molecular weight is 520,000 Daltons. In some embodiments, the weight-average molecular weight is 50,000 to 150,000 Daltons. In some embodiments, the number-average molecular weight is 100,000 to 200,000 Daltons.

[0298] In some embodiments, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and / or one or more rubber polymers are block copolymers. In some embodiments, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and / or one or more rubber polymers are random copolymers.

[0299] e) Manufacturing a negative electrode with a binder for use in lithium-ion batteries

[0300] In another exemplary embodiment, the example negative electrode used in the lithium-ion battery also includes a multifunctional adhesive, such as, as disclosed herein, preferably a multifunctional polymer adhesive.

[0301] By improving the electrode structure, the electrochemical performance of the anode material prepared as described above was further improved. The multifunctional binder disclosed herein can be used as part of the anode. The multifunctional binder has a 3D network structure, improved conductivity, and self-healing properties, solving the problem of relatively poor conductivity and large volume expansion of silicon-based anodes for lithium-ion batteries (LIBs), which leads to rapid capacity decay.

[0302] refer to Figure 10 The figure illustrates a method 100 for manufacturing a negative electrode for a lithium-ion battery. Step 1010 includes mixing a silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers to generate a slurry. The silicon / graphite / carbon material can be previously disclosed examples, such as Si@C / G / C or Si / C / G powder materials, or it can be a mixture of raw silicon (Si), graphite (G), and carbon (C) (active material). Optionally, step 1010 may also include mixing a conductive agent as part of the slurry. For example, the conductive agent can be carbon black, carbon nanotubes, carbon nanofibers, or mixtures thereof as a conductive slurry. Step 1020 includes coating the slurry onto a metal component, such as a metal foil, metal strip, or metal mesh. Step 1030 includes drying the slurry-coated metal component to form the negative electrode.

[0303] The following is provided for reference. Figure 11 Another non-limiting example method 1100 is used to manufacture a negative electrode containing a multifunctional polymer binder for lithium-ion batteries.

[0304] Step 1110; Weigh one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers according to the weight percentages and mass ratios (linear polymer: conductive polymer: self-healing polymer: rubber polymer) described herein.

[0305] Step 1120: A silicon / graphite / carbon material (which may be, as previously disclosed examples, such as Si@C / G / C or Si / C / G powder, or may be a mixture of raw silicon (Si), graphite (G) and carbon (C) (active material)) is uniformly mixed with a conductive agent (e.g., carbon black, carbon nanotubes, carbon nanofibers or mixtures thereof, as a conductive paste) and a multifunctional polymer binder at a mass ratio equal to or in the range of about 80-96:1-10:3-10 (active material: conductive agent: multifunctional polymer binder). Preferably, the mass ratio (active material: conductive agent: multifunctional polymer binder) is about 80:10:10, about 85:10:5, about 85:9:6, about 85:8:7, about 85:7:8, about 85:6:9, about 85:5:10, about 90:7:3, about 90:6:4, about 90:5:5, about 90:4:6, about 90:3:7, about 90:2:8, about 90:1:9, about 95:2:3, about 95:1:4, or about 96:1:3. Most preferably, the mass ratio (active material: conductive agent: multifunctional polymer binder) is about 80:10:10.

[0306] In some embodiments, the multifunctional polymeric adhesive has sufficient electrical conductivity to eliminate the need for a conductive agent. In these embodiments, a mixture of silicon / graphite / carbon materials, and one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers is mixed together at a mass ratio of approximately 80-99:1-20, 85-99:1-15, 90-99:1-10, 95-99:1-5, 96:4, 97:3, 98:2, or 99:1 (silicon / graphite / carbon material:polymer mixture).

[0307] The mixing time can be equal to or from about 2 hours to about 5 hours. Preferably, the mixing time is about 2 hours, 3 hours, 4 hours or 5 hours. Most preferably, the mixing time is about 2 hours.

[0308] Step 1130: The resulting slurry is applied to a metal component, such as a metal foil, strip, or mesh, preferably a copper component provided as copper foil, which should be kept clean and flat. Other metal components may be made of, for example, nickel, zinc, aluminum, gold, or silver.

[0309] Step 1140: The resulting metal component (e.g., copper foil) coated with the negative electrode material slurry is dried in a vacuum furnace at a specified drying temperature for a specified drying time. For example, the drying temperature may be equal to or from about 100°C to about 180°C. Preferably, the temperature is about 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C. Most preferably, the temperature is about 100°C. The drying time may be equal to or from about 10 hours to about 18 hours. Preferably, the drying time is about 10, 11, 12, 13, 14, 15, 16, 17, or 18 hours. Most preferably, the drying time is about 12 hours.

[0310] Step 1150: The dried composite material is then compacted and used as the negative electrode in assembled lithium-ion batteries (i.e., lithium-ion battery cells).

[0311] Example 8

[0312] In the example implementation, a negative electrode (Example 8) was prepared and labeled as Si@C / G / C-5 negative electrode (i.e., "5:1" negative electrode with a multifunctional polymer binder).

[0313] The Si@C / G / C-5 anode was prepared using the same method as the Si@C / G / C-1 anode (Example 1), except that the Si@C / G / C-1 anode (Example 1) used a binder containing CMC (linear polymer) and SBR (semi-polymer), while the Si@C / G / C-5 anode (Example 8) used a multifunctional polymer binder containing CMC (linear polymer), PPY (conductive polymer), DA and / or UOAA (self-healing polymer), and SBR (semi-polymer). All other conditions for anode preparation were the same.

[0314] Si@C / G / C-5 anodes were prepared using a polymer mass ratio of 40:20:20:20 (CMC:PPY:DA / UOAA:SBR). The conductive agent used was the Swiss-made TIMCAL Graphite & Carbon product, traded under the name Super P. TM A type of carbon black was then used. The active material, conductive agent, and multifunctional polymer binder were mixed at a mass ratio of 80:10:10 (Si@C / G / C: conductive agent: multifunctional polymer binder) for 2 hours. The resulting slurry was coated onto a clean and flat copper foil. The copper foil coated with the negative electrode material slurry was dried in a vacuum oven at 100°C for 12 hours. The resulting dried composite material was then compacted and used as a negative electrode in an assembled lithium-ion battery.

[0315] Figure 12(a) shows the cycling performance of an example anode (Example 2) with LSCR binder, labeled Si@C / G / C-5. The Si@C / G / C-5 anode provides an average reversible discharge capacity of approximately 525.7 mAh / g after 250 cycles. The CE exceeds 99.0% after 13 cycles, retains 95.35% of the capacity after 100 cycles, and retains 89.2% of the capacity after 250 cycles, representing an improvement in electrochemical performance compared to the Si@C / G / C-1 anode (Example 1) using a standard CMC:SBR binder. Figure 12(b) shows the cycling performance of an example anode (Example 1) with LSCR binder, labeled Si@C / G / C-5, after 400 cycles. It retains 82.8% of the capacity after 400 cycles, representing an improvement in electrochemical performance compared to the Si@C / G / C-1 anode using an LSCR binder (Example 1) after 400 cycles.

[0316] Optional embodiments may also be referred to as broadly including the parts, elements, steps and / or features mentioned or specified herein, alone or in any combination of two or more parts, elements, steps and / or features, and specific objects mentioned herein that have known equivalents in the field to which this invention pertains are considered to be incorporated herein as separately listed.

[0317] While preferred embodiments have been described in detail, it should be understood that many modifications, alterations, substitutions, or changes will be apparent to those skilled in the art without departing from the scope of the invention.

Claims

1. A method for manufacturing a negative electrode for a lithium-ion battery, the method comprising the following steps: A mixture of nano-silicon, one or more carbonaceous materials, and one or more solvents is ground, wherein the mixture remains as a wet slurry during grinding. The mixture is carbonized at a carbonization temperature to produce a carbon-coated silicon material, wherein the carbonization temperature is equal to or between 1000°C and 1200°C. The second mixture of the carbon-coated silicon material, graphite, one or more second carbonaceous materials, and one or more second solvents is ground, wherein the second mixture remains as a second wet slurry during grinding. The second mixture is carbonized at a second carbonization temperature to produce a carbon-coated silicon / graphite / carbon material, wherein the second carbonization temperature is equal to or between 1000°C and 1200°C; and The negative electrode is formed from the carbon-coated silicon / graphite / carbon material.

2. The method of claim 1, further comprising the step of drying the wet slurry at a drying temperature of 70°C to 150°C before carbonizing the mixture.

3. The method according to claim 1 or 2, further comprising the step of drying the second wet slurry at a second drying temperature equal to or greater than 70°C to 150°C before carbonizing the second mixture.

4. The method according to any one of claims 1 to 3, wherein the mixture is ground by wet ball milling.

5. The method according to any one of claims 1 to 4, wherein the nano-silicon and the one or more carbonaceous materials are mixed in a mass ratio equal to or greater than 40:60 to 70:

30.

6. The method according to any one of claims 1 to 5, wherein the average particle size of the nano-silicon is equal to or has a particle size of 50 nm to 500 nm.

7. The method according to any one of claims 1 to 6, wherein the one or more solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine, tetrahydrofuran, diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol, propylene glycol, polyacrylic acid, and mixtures thereof.

8. The method according to any one of claims 1 to 7, wherein the one or more carbonaceous materials are selected from the group consisting of functionalized graphene sheets, carbon nanotubes, reduced graphene oxide, pyrolytic carbon derived from glucose, sucrose or citric acid precursors, pitch, polyacrylonitrile, polyvinyl chloride, poly(diallyldimethylammonium chloride), poly(sodium 4-styrenesulfonate), polydopamine, polypyrrole and phenolic resins.

9. The method according to any one of claims 1 to 8, wherein the graphite is synthetic flake graphite or graphite microspheres.

10. The method of claim 9, wherein the graphite microspheres have an average size equal to or greater than 1 μm to 20 μm.

11. The method of claim 2, wherein the wet slurry is vacuum dried in an oven.

12. The method according to any one of claims 1 to 11, wherein carbonization of the mixture occurs under an inert gas flowing in a tubular furnace.

13. The method according to any one of claims 1 to 12, wherein the mixture is carbonized at the carbonization temperature for a period of 3 to 8 hours.

14. The method according to any one of claims 1 to 13, wherein the mixture is held at a holding temperature below the carbonization temperature before reaching the carbonization temperature.

15. The method according to any one of claims 1 to 14, wherein the carbon-coated silicon material, the graphite, and the one or more second carbonaceous materials are mixed in a mass ratio equal to or in the range of 10-30:40-80:10-30 (carbon-coated silicon material: graphite: second carbonaceous material).

16. The method according to any one of claims 1 to 15, wherein the one or more second solvents are selected from the group consisting of toluene, xylene, quinoline, pyridine, tetrahydrofuran, diethyl ether, diisopropyl ether, methyl ethyl ether, dioxane, methanol, ethanol, 1-propanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, pentane, n-hexane, cyclohexane, acetonitrile, acetone, chloroform, dichloromethane, carbon tetrachloride, ethylene glycol, propylene glycol, polyacrylic acid, and mixtures thereof.

17. The method according to any one of claims 1 to 16, wherein carbonization of the second mixture occurs under an inert gas flowing in a tubular furnace.

18. The method according to any one of claims 1 to 17, wherein the second mixture is carbonized at the second carbonization temperature for a time equal to or equal to 3 to 8 hours.

19. The method according to any one of claims 1 to 18, wherein the second mixture is held at a second holding temperature below the second carbonization temperature before reaching the second carbonization temperature.

20. The method according to any one of claims 1 to 19, the method further comprising grinding the carbon-coated silicon / graphite / carbon material.

21. The method according to claims 1 to 20, further comprising mixing the milled carbon-coated silicon / graphite / carbon material with one or more polymer binders.

22. The method of claim 21, wherein the one or more polymeric adhesives comprise one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers.

23. The method of claim 22, wherein The one or more linear polymers mentioned are sodium carboxymethyl cellulose, polyacrylic acid, and combinations thereof; The one or more conductive polymers are polypyrrole, PEDOT:PSS and combinations thereof; The one or more self-healing polymers are dopamine, urea-oligoamide amine, and combinations thereof; and The one or more rubber polymers mentioned are styrene-butadiene rubber.

24. The method according to any one of claims 21-23, wherein the negative electrode is formed by the following steps: The carbon-coated silicon / graphite / carbon material is mixed with one or more polymer binders to generate a slurry; The slurry is applied to the metal component; and The metal component coated with the slurry is dried to form a negative electrode.

25. A method for manufacturing a negative electrode for a lithium-ion battery, the method comprising the following steps: Microsilica and one or more inert solvents are mixed to generate a wet slurry mixture; and Milling the microsilicon and the wet slurry mixture of one or more inert solvents yields nanosilicon, wherein the mixture remains a wet slurry mixture during milling. Grinding the nano-silicon, one or more carbonaceous materials and one or more solvents, wherein the mixture is kept as a wet slurry during grinding; The mixture is carbonized at a carbonization temperature to produce a carbon-coated silicon material, wherein the carbonization temperature is equal to or between 1000°C and 1200°C. The second mixture of the carbon-coated silicon material, graphite, one or more second carbonaceous materials, and one or more second solvents is ground, wherein the second mixture remains as a second wet slurry during grinding. The second mixture is carbonized at a second carbonization temperature to produce a carbon-coated silicon / graphite / carbon material, wherein the second carbonization temperature is equal to or between 1000°C and 1200°C. A slurry is generated by mixing the carbon-coated silicon / graphite / carbon material, one or more linear polymers, one or more conductive polymers, one or more self-healing polymers, and one or more rubber polymers. The slurry is applied to the metal component; and The metal component coated with the slurry is dried to form a negative electrode.

26. A negative electrode for a lithium-ion battery, said negative electrode being manufactured by any one of claims 1 to 25.

27. A lithium-ion battery, the lithium-ion battery comprising: The negative electrode as described in claim 26; positive electrode; and Electrolyte and / or membrane arranged between the negative and positive electrodes.

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