Graphite aggregate particles, methods for producing the same, and their use in electrochemical cells

Abstract

A method for producing graphite aggregate particles is provided, comprising the steps of i) providing a graphite fine slurry; ii) spray-drying the graphite fine slurry to form spray-dried re-aggregated graphite particles; and iii) heat-treating the spray-dried re-aggregated graphite particles to obtain graphite aggregate particles, wherein the graphite fine slurry comprises a binder, graphite fine particles, and a solvent. The graphite aggregate particles obtained using this method, as well as their use in electrode materials, electrodes, electrochemical cells, and electrochemical batteries, are also described.

Description

[Technical Field]

[0001] Related applications This application claims priority under applicable law to U.S. Provisional Application No. 63 / 491,614, filed on 22 March 2023, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0002] This invention generally relates to graphite aggregate particles, methods for producing them, and their use in electrochemical cells. [Background technology]

[0003] Graphite (whether natural or synthetic) has been used as a host structure for Li intercalation on the anode side since the commercialization of the first lithium-ion batteries (LIBs) due to its abundance, relatively low cost, high energy and power density, and long cycle life. + Operating voltage close to that of (approximately 0.1V vs Li / Li) + ), and in its fully lithium-ionized state, 372mAh.g -1 It has a theoretical capacity of 1 liter per 6 carbon atoms, which corresponds to one Li insertion (LiC6). Despite ongoing efforts to improve the performance of LIB anodes using high-capacity materials such as silicon or silicon oxide, graphite remains the optimal anode in current state-of-the-art LIBs, holding a dominant 98% market share. As of 2020, synthetic graphite and natural graphite accounted for 58% and 39% of the LIB anode market, respectively.

[0004] However, because the production of synthetic graphite is energy-intensive, time-consuming, and has a large environmental footprint, the demand for natural graphite is expected to grow by 2030 and become dominant in the graphite market. Natural graphite is further classified into three types: massive graphite, amorphous graphite, and flaky graphite, the latter being desirable for LIBs due to their high crystallinity, carbon content (80-95%), and good electrical conductivity.

[0005] After mining and separation from graphite ore, raw flaky graphite requires further processing to produce a material suitable for use in LIBs. One of the key steps is called spheroidization, in which flaky graphite is mechanically formed into nearly spherical particles (typically D50 = 10-25 μm) through sophisticated grinding techniques to reduce their surface area and increase material density. Furthermore, rounded particles offer easier processability during electrode manufacturing compared to flaky material. However, due to the use of a complex classifier mill cascade, which can consist of up to 30 classifier mills, required to obtain particles suitable for LIB anodes, conventional spheroidization processes can be time-consuming and energy-intensive, resulting in low yields of approximately 30-50%, meaning significant graphite loss in the process. The by-products mainly consist of fine, flaky graphite particles that are too fine (less than 10 μm) for the production of LIB anodes. It is known that fine particles with a large surface area result in a larger solid electrolyte interface (SEI) layer and higher irreversible capacity.

[0006] Therefore, many technical challenges still exist, and there is a need to develop new methods for recycling and reprocessing graphite powder. [Overview of the project]

[0007] In some aspects, embodiments of the technology described herein include the following: 1. A method for producing graphite aggregate particles, wherein the method is i) A step of providing a graphite powder slurry comprising multiple graphite powders, a solvent, and a binder, ii) A step of spray-drying a graphite fine powder slurry to form spray-dried re-aggregated graphite particles, iii) A method comprising the step of heat-treating spray-dried re-aggregated graphite particles to obtain graphite aggregate particles. 2. The method according to item 1, wherein the binder is a polymer binder. 3. The method according to item 1, wherein the polymer binder is selected from the group consisting of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), polylactic acid (PLA), cellulose, chitin, starch, polycaprolactone (PCL), polyhydroxybutyrate (PHB), and at least two combinations thereof. 4. The method according to item 3, wherein the polymer binder is carboxymethylcellulose (CMC). 5. The method according to any one of items 1 to 4, wherein the solvent is selected from the group consisting of water, methanol, acetone, ethanol, dichloromethane, tetrahydrofuran, ethyl acetate, chloroform, glycerin, dimethylformamide, dimethyl sulfoxide, and at least two miscible combinations thereof. 6. The method according to item 5, wherein the solvent is water. 7. The method according to any one of items 1 to 6, wherein the mass ratio of graphite powder to binder in the graphite powder slurry is approximately 4:1 to approximately 20:1 (including upper and lower limits). 8. The method according to item 8, wherein the mass ratio of graphite powder to binder in the graphite powder slurry is at least about 4:1, or at least about 5:1, or at least about 6:1, or at least about 7:1. 9. The method according to item 7 or 8, wherein the mass ratio of graphite powder to binder in the graphite powder slurry is at most about 20:1, at most about 15:1, at most about 10:1, or at most about 8:1. 10. The method according to any one of items 7-9, wherein the mass ratio of graphite powder to binder in the graphite powder slurry is approximately 6:1. 11. The method according to any one of items 1 to 10, wherein the graphite fine slurry contains approximately 14% to approximately 35% by weight (including upper and lower limits) of graphite fine. 12. The method according to item 11, wherein the graphite fine slurry contains at least about 14% by weight, or at least about 18% by weight, or at least about 21% by weight, or at least about 24% by weight of graphite fine. 13. The method according to item 11 or 12, wherein the graphite fine slurry contains at most about 35% by weight, at most about 33% by weight, at most about 30% by weight, or at most about 28% by weight of graphite fine. 14. The method according to any one of items 11-13, wherein the graphite fine slurry contains approximately 24% by weight of graphite fine. 15. The method according to any one of items 1 to 14, wherein the graphite fines in the graphite fine slurry are purified. 16. The method according to any one of items 1 to 15, wherein the purity of the graphite fine powder is approximately 99.70% to approximately 99.99% (including upper and lower limits). 17. The method according to item 16, wherein the purity of the graphite fine powder is at least about 99.70%, or at least about 99.8%, or at least about 99.90%, or at least about 99.95%. 18. The method according to item 16 or 17, wherein the purity of the graphite fine powder is at most about 99.99% or at most about 99.95%. 19. The method according to any one of items 16-18, wherein the purity of the graphite fine powder is approximately 99.95%. 20. Graphite fine powder D 50 However, the method according to any one of items 1 to 19, wherein the size is approximately 3 μm to approximately 10 μm (including upper and lower limits). 21. Graphite fine powder D 50 The method according to item 20, wherein the thickness is at least about 3 μm, or at least about 4 μm, or at least about 5 μm, or at least about 6 μm. 22. Graphite fine powder D 50 The method according to item 20 or 21, wherein the size is at most about 10 μm, at most about 9 μm, at most about 8 μm, or at most about 7 μm. 23. Graphite fine powder D 50 However, the method described in any one of items 20-22, which is approximately 7 μm. 24. The method according to any one of items 1 to 23, wherein the graphite fine slurry contains approximately 0.7% to approximately 6.0% by weight (including upper and lower limits) of a binder. 25. The method according to item 24, wherein the graphite fine slurry comprises at least about 0.7% by weight, or at least about 1.4% by weight, or at least about 2.5% by weight, or at least about 3.0% by weight of a binder. 26. The method according to item 24 or 25, wherein the graphite fine slurry contains at most about 6.0% by weight, or at most about 5.0% by weight, or at most about 4.5% by weight, or at most about 4.0% by weight of a binder. 27. The method according to any one of items 24-26, wherein the graphite fine slurry contains about 4.0% by weight of a binder. 28. The method according to any one of items 1 to 27, wherein the graphite fine slurry further comprises a crosslinking agent. 29. The method according to item 28, wherein the crosslinking agent is an organic crosslinking agent or an inorganic crosslinking agent. 30. The method according to item 29, wherein the crosslinking agent is an organic crosslinking agent. 31. The method according to any one of items 28 to 30, wherein the crosslinking agent is selected from the group consisting of citric acid, formic acid, acetic acid, oxalic acid, and at least two combinations thereof. 32. The method according to item 31, wherein the crosslinking agent is citric acid. 33. The method according to any one of items 28 to 32, wherein the graphite fine slurry contains approximately 0.5% to approximately 4.0% by weight (including upper and lower limits) of a crosslinking agent. 34. The method according to item 33, wherein the graphite fine slurry contains at least about 0.5% by weight, or at least about 1.0% by weight, or at least about 1.5% by weight, or at least about 2.0% by weight of a crosslinking agent. 35. The method according to item 32 or 34, wherein the graphite fine slurry contains at most about 4% by weight, at most about 3.5% by weight, at most about 3.0% by weight, or at most about 2.5% by weight of a crosslinking agent. 36. The method according to any one of items 32 to 35, wherein the graphite fine slurry contains approximately 3.0% by weight of a crosslinking agent. 37. The method according to any one of items 1 to 36, wherein the graphite fine slurry contains approximately 58% to approximately 83% by weight (including upper and lower limits) of solvent. 38. The method according to item 37, wherein the graphite fine slurry comprises at least about 53% by weight, or at least about 58% by weight, or at least about 62% by weight, or at least about 66% by weight, and / or at most about 83% w / w%, at most about 80% w / w%, at most about 72% w / w%, or at most about 69% w / w% of the solvent. 39. The method according to item 37 or 38, wherein the graphite fine slurry contains at most about 83% by weight, at most about 80% by weight, at most about 72% by weight, or at most about 69% by weight of solvent. 40. The method according to any one of items 37-39, wherein the graphite fine slurry contains approximately 69% by weight of solvent. 41. The method according to any one of items 28 to 40, wherein the graphite fine slurry comprises about 24% by weight of graphite fine, about 4.0% by weight of a binder, about 3.0% by weight of a crosslinking agent, and about 69% by weight of a solvent. 42. A method according to any one of items 1 to 41, which comprises providing a graphite fine powder slurry. 43. The method according to item 42, wherein the graphite fine powder slurry is prepared by combining graphite fine powder, a binder, optionally a crosslinking agent, and a solvent, and then mixing the components together. 44. The method according to item 43, wherein the graphite fine powder slurry is mixed by a resonant acoustic mixer. 45. The method according to item 44, wherein the graphite fine powder slurry is mixed at an acceleration of 50 G for about 30 minutes. 46. A method according to any one of items 1 to 45, wherein the graphite fine powder slurry further contains silicon particles. 47. The D of the silicon particles in the graphite fine powder slurry 50 is from about 50 nm to about 5 μm (including the upper and lower limits), according to the method of item 46. 48. The method according to item 46 or 47, wherein the content of the silicon particles in the graphite fine powder slurry is from about 0.42 wt% to about 11.55 wt% (including the upper and lower limits). 49. A method according to any one of items 1 to 48, wherein the graphite fine powder slurry further contains an additive selected from carbon black, graphite, graphene, carbon fiber, carbon nanotube, and combinations of at least two thereof. 50. The method according to item 49, wherein the additive is a carbon nanotube. 51. The method according to item 50, wherein the carbon nanotube is a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof. 52. The method according to any one of items 49 to 51, wherein the graphite fine powder slurry contains from about 0.1 wt% to about 3 wt% (including the upper and lower limits) of carbon nanotubes. 53. The supply rate of spray drying is from about 10 mL / min -1 to about 22 mL / min -1 (including the upper and lower limits), according to the method of any one of items 1 to 52. 54. The spray drying supply rate is at least approximately 10 mL / min. -1 , or at least about 12 mL. -1 , or at least about 14 mL. -1 , or at least about 16 mL. -1 The method described in item 53. 55. The spray drying supply rate is at most approximately 22 mL / min. -1 , or at most about 21 mL. -1 , or at most about 20 mL. -1 , or at most about 18 mL. -1 The method described in item 53 or 54. 56. The spray drying supply rate is approximately 20.3 mL / min. -1 The method described in any one of items 53-55. 57. The method according to any one of items 1 to 56, wherein the inlet temperature during the spray drying process is approximately 190°C to approximately 220°C (including upper and lower limits). 58. The method according to item 57, wherein the inlet temperature during the spray drying process is at least about 190°C or at least about 200°C. 59. The method according to item 57 or 58, wherein the inlet temperature during the spray drying process is at most about 220°C or at most about 210°C. 60. The method according to any one of items 57-59, wherein the inlet temperature during the spray drying process is approximately 210°C. 61. The air blow speed during the spray drying process is approximately 2.0 m 3 .minutes -1 ~about 2.5m 3 .minutes -1 A method according to any one of items 1 through 60, including upper and lower limits. 62. The method according to any one of items 1 to 61, wherein spray-dried re-aggregated graphite particles are heat-treated in the presence of a carbon precursor to obtain carbon-coated graphite aggregate particles. 63. The method according to item 62, wherein the carbon precursor is selected from petroleum pitch, coal tar pitch, biomass pitch, a combination of at least two of them, and any similar material. 64. The method according to item 63, wherein the carbon precursor is coal tar pitch. 65. The method according to any one of items 1 to 64, wherein the heat treatment step includes heating the spray-dried re-aggregated graphite particles at a temperature of approximately 550°C to approximately 1300°C (including upper and lower limits). 66. The method according to item 65, wherein the spray-dried re-aggregated graphite particles are heated to a temperature of at least about 550°C, or at least about 600°C, or at least about 700°C, or at least about 750°C. 67. The method according to item 65 or 66, wherein the spray-dried re-aggregated graphite particles are heated at a temperature of at most about 1300°C, at most about 1100°C, at most about 1000°C, or at most about 900°C. 68. The method according to any one of items 65-67, wherein spray-dried re-aggregated graphite particles are heated to a temperature of approximately 1000°C. 69. The method according to any one of items 1 to 68, wherein the spray-dried re-aggregated graphite particles formed in step (ii) are mixed with a carbon precursor, followed by a heat treatment step for the thermal decomposition of the carbon precursor. 70. The method according to item 69, wherein the carbon precursor is coal tar pitch. 71. Spray-dried re-aggregated graphite particles: The method according to item 69 or 70, wherein the mass ratio of the carbon precursor is about 9:1. 72. The method according to any one of items 69-71, wherein the mixing step is carried out by a resonant acoustic mixer. 73. The method according to item 72, wherein the mixing process is carried out at an acceleration of 50G for approximately 15 minutes. 74. The method according to any one of items 69 to 73, wherein spray-dried re-aggregated graphite particles and a carbon precursor are mixed together using wet or dry mixing. 75. The method according to any one of items 69 to 74, wherein the amount of carbon precursor in a mixture comprising spray-dried re-aggregated graphite particles and a carbon precursor is about 5% to about 30% by weight (including upper and lower limits). 76. The method according to item 75, wherein the amount of carbon precursor in the mixture is at least about 5% by weight, or at least about 10% by weight, or at least about 15% by weight. 77. The method according to item 75 or 76, wherein the amount of carbon precursor in the mixture is at most about 30% by weight, at most about 25% by weight, or at most about 20% by weight. 78. The method according to any one of items 75-77, wherein the amount of carbon precursor in the mixture is about 10% by weight. 79. A method according to any one of items 69-78, wherein the thermal decomposition of the carbon precursor and binder is carried out in a single-step heat treatment. 80. The method according to item 79, wherein the heat treatment is carried out as two sub-steps, the spray-dried re-aggregated graphite particles are first heat-treated to form graphite aggregate particles, the graphite aggregate particles are then mixed with a carbon precursor, and subsequently a second heat treatment for carbon coating is performed. 81. The method according to any one of items 1 to 80, further comprising subjecting the spray-dried re-aggregated graphite particles to a high-temperature heat treatment carried out at a temperature of approximately 2000°C to approximately 3000°C (including upper and lower limits). 82. Graphite aggregate particles manufactured using a method defined in any one of items 1 through 81. 83. The graphite aggregate particles described in item 82, wherein the graphite aggregate particles are spherical or substantially spherical. 84. D of the graphite aggregate particles 50 Graphite aggregate particles as described in item 82 or 83, which are approximately 18 μm to approximately 21 μm (including upper and lower limits). 85. D of the graphite aggregate particles 50 However, the graphite aggregate particles described in item 82 or 83 are approximately 20 μm to approximately 24 μm (including upper and lower limits). 86. D of the graphite aggregate particles 50 However, the graphite aggregate particles described in item 82 or 83 are approximately 13 μm to approximately 17 μm (including upper and lower limits). 87. The graphite aggregate particles described in any one of items 82 to 86, wherein the graphite aggregate particles are carbon-coated graphite aggregate particles. 88. Graphite aggregate particles according to any one of items 82 to 87, wherein the graphite aggregate particles are pitch-coated graphite aggregate particles. 89. Graphite aggregate particles, further containing silicon, as described in any one of items 82-88. 90. The graphite aggregate particles described in item 89, wherein the graphite aggregate particles contain more than 0% by weight of silicon. 91. The graphite aggregate particles according to item 90, wherein the graphite aggregate particles contain at least about 3% by weight of silicon. 92. Graphite aggregate particles according to item 90 or 91, wherein the graphite aggregate particles contain at most about 50% by weight or at most about 33% by weight of silicon. 93. Electrode material containing graphite aggregate particles as defined in any one of items 82-92. 94. Electrode materials as described in item 93, further comprising an electrically conductive material. 95. Electrode material according to item 94, wherein the electrically conductive material is selected from carbon black, graphite, graphene, carbon fiber, carbon nanotubes, and at least two combinations thereof. 96. Electrode materials as described in item 95, wherein the electrically conductive material is carbon black, carbon nanotubes, or a combination thereof. 97. Electrode material as described in item 96, wherein the carbon nanotubes are single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination thereof. 98. Any one of the electrode materials described in items 93-97, further comprising at least one additive. 99. An electrode material according to any one of items 93 to 98, further comprising at least one binder. 100. Electrode material according to item 99, wherein the binder is selected from polyether-type polymer binders, polycarbonate-type polymer binders, polyester-type polymer binders, fluorinated polymers, and water-soluble binders. 101. An electrode comprising electrode material defined by any one of items 93-100 applied to a current collector. 102. The electrode described in item 101, wherein the current collector is made of copper foil. 103. The electrode described in item 101 or 102, wherein the electrode is calendered. 104. One electrode from items 101-103, where the electrode is the anode. 105. An electrochemical cell comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and the cathode comprises an electrode material as defined in any one of items 93 to 100. 106. An electrochemical cell comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and cathode is an electrode as defined in any one of items 101 to 103. 107. An electrochemical battery comprising at least one electrochemical cell as defined in item 105 or 106. 108. The electrochemical battery described in item 107, wherein the electrochemical battery is a battery selected from lithium batteries, lithium-ion batteries, sodium batteries, sodium-ion batteries, magnesium batteries, and magnesium-ion batteries. 109. An electrochemical battery as described in item 107 or 108, wherein the electrochemical battery is a lithium-ion battery. 110. A method for producing graphene aggregate particles, i) A step of providing a graphene fine powder slurry comprising multiple graphene fine powders, a solvent, and a polymer binder, ii) A step of spray-drying a graphene fine powder slurry to form spray-dried re-aggregated graphene particles, iii) A method comprising the step of heat-treating spray-dried re-aggregated graphene particles to obtain graphene aggregate particles. [Brief explanation of the drawing]

[0008] [Figure 1] This is a flowchart of a method for producing graphite aggregate particles according to one embodiment. [Figure 2] This is a schematic diagram of a spray drying process according to one embodiment of the method defined herein. [Figure 3] a) Scanning electron microscopy (SEM) images of the raw material (graphite powder) and b) graphite aggregate particles obtained by one embodiment of the method defined herein are shown. [Figure 4] The following are shown: a) particle size distribution (PSD) curves and b) X-ray diffraction (XRD) patterns obtained for fine natural graphite (f-NG), unprocessed graphite, spray-dried re-aggregated graphite particles obtained by spray-drying according to one embodiment of the method defined herein, pitch-coated graphite aggregate particles obtained by spray-drying according to one embodiment of the method defined herein and then through a single HT step, and commercial PGPT102 graphite. [Figure 5] The images show SEM images of a) f-NG raw material, b) aggregated graphite particles obtained by spray drying followed by heat treatment, c) a single aggregated graphite particle and its surface details, d) a cross-section of an aggregated graphite particle, e) a pitch-coated graphite aggregate particle and its surface details, and f) a cross-section of a pitch-coated graphite aggregate particle. [Figure 6-1]The images show SEM images of the top and cross-section of electrodes, including a) uncalendared graphite aggregate particles, b) uncalendared pitch-coated graphite aggregate particles, c) calendared graphite aggregate particles, and d) calendared pitch-coated graphite aggregate particles, as well as FIB-SEM images of e) uncalendared graphite aggregate electrodes and f) calendared graphite aggregate electrodes. [Figure 6-2] The images show SEM images of the top and cross-section of electrodes, including a) uncalendared graphite aggregate particles, b) uncalendared pitch-coated graphite aggregate particles, c) calendared graphite aggregate particles, and d) calendared pitch-coated graphite aggregate particles, as well as FIB-SEM images of e) uncalendared graphite aggregate electrodes and f) calendared graphite aggregate electrodes. [Figure 7a] a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 7b] a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 7c]a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 7d] a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 7e] a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 7f] a) the first charge-discharge cycles of various electrodes, b) the differential capacitance curves of various electrodes, c) the specific discharge capacity and Coulomb efficiency of various electrodes, d) the capacity retention rate of graphite aggregate electrodes and conventional PGPT102 electrodes throughout 200 cycles, e) the charge-discharge cycles of various electrodes, and f) the differential capacitance curves of graphite aggregate electrodes and conventional PGPT102 electrodes in selected cycles. [Figure 8] This shows a comparison of the cumulative irreversible capacity of a graphite aggregated electrode and a conventional PGPT102 electrode. [Figure 9]The images show SEM images of a) a graphite aggregate electrode before cycling, b) a pitch-coated graphite aggregate particle (1-step HT) electrode before cycling, and c) a pitch-coated graphite aggregate particle (2-step HT) electrode before cycling, where (a', b', and c') show the corresponding electrodes after 200 cycles, and (a'', b'', and c'') show the corresponding cross-sectional images of the cycled electrodes. [Figure 10] The images show SEM images of graphite aggregate particles obtained by the method defined herein, having f-NG content of a) 14% by weight, b) 21% by weight, c) 28% by weight, and d) 33% by weight. [Figure 11] The images show SEM images of graphite aggregate particles obtained by the method defined herein for f-NG:CMC mass ratios of a) 50:1, b) 30:1, c) 10:1, and d) 6:1. [Figure 12] The images show SEM images of graphite aggregate particles obtained by the method defined herein at supply rates of a) 9.8 mL / min, b) 14.7 mL / min, and c) 20.3 mL / min. [Figure 13] The images show SEM images of graphite aggregate particles obtained by the method defined herein at inlet temperatures of a) 200°C, b) 210°C, and c) 220°C. [Figure 14] a) SEM images of graphite aggregate particles obtained by the method defined herein at air blow rates of 2.5 m³ / min and b) 2.0 m³ / min are shown. [Figure 15] This is a weighted Pareto chart used to determine the effect of slurry composition and spray drying parameters on the D50 of the resulting aggregated graphite particles, as defined herein. [Figure 16] The graphs show the PSD (Particle Size Derived) before (dotted line) and after (dashed line) the ball mill grinding process for agglomerated graphite particles, obtained using (a) no crosslinking agent and (b) 3% by weight of citric acid as a crosslinking agent. [Figure 17]The PSD comparison between pitch-coated graphite aggregate particles obtained through one-step HT and two-step HT is shown in accordance with the teachings disclosed herein. [Figure 18] This specification shows a comparison of the XRD patterns of pitch-coated graphite aggregate particles obtained through one-step HT and two-step HT in accordance with the teachings disclosed herein. [Figure 19] This shows the deconvolution of the (101) peak for various graphite materials to calculate the [A3R(101) / A2H(101)] mass ratio. [Figure 20] a) SEM image of commercially available PGPT102 graphite before spray drying and heat treatment, b) SEM image of commercially available PGPT102 graphite after spray drying and heat treatment, and c) high-magnification image of the graphite surface showing nanogranules formed due to carbonization of the binder. [Figure 21] The following are SEM images of pitch-coated graphite aggregate particles obtained through a two-step HT process in accordance with the teachings disclosed herein. [Figure 22] The specific discharge capacity and Coulomb efficiency during cycling are shown for uncalendared electrodes (white symbols) and calendared electrodes (black symbols) for a) conventional PGPT102, b) uncoated graphite aggregate particles, and c) pitch-coated graphite aggregate particles. [Figure 23] Differential capacitance curves comparing the first and fifth cycles of various electrodes in the potential range of 0.5V to 0.9V are shown to illustrate the cathode peak resulting from the formation of the SEI layer during the discharge in the first cycle. [Figure 24] This report describes the charging (delithiation) rate capability tests of electrodes containing f-NG, graphite aggregate particles, and conventional PGPT102. The discharge rate was fixed at C / 10, all electrodes were calendered, and their graphite mass load was 5 mg / cm². [Figure 25] A modular diagram of a control station for controlling the steps of the method described herein is shown. [Figure 26] The image shows a SEM image of graphite aggregate particles containing carbon nanotubes (CNTs) obtained by the method defined herein. [Figure 27] The image shows a cross-sectional SEM image of graphite aggregate particles containing CNTs obtained by the method defined herein. [Figure 28] a) SEM images of uncoated graphite aggregate particles containing CNTs, and b) SEM images of pitch-coated graphite aggregate particles containing CNTs. [Figure 29] This graph shows the PSD for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs. [Figure 30] The graph shows the discharge ratio capacity (mAh.g-1) as a function of the number of cycles. Results are shown for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs. [Figure 31] The graphs show the delithiation rate performance. Results are shown for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs. [Figure 32] The images show SEM images of a) raw graphite fine powder, b) microsilicon powder, c) nanosilicon powder, d) graphite aggregate particles, e) graphite-silicon composite aggregate particles (9% microsilicon by weight), and f) graphite-silicon composite aggregate particles (9% nanosilicon by weight). [Figure 33]a) XRD patterns and b) graphs showing the PSD of unprocessed graphite fine powder, microsilicon powder, nanosilicon powder, graphite aggregate particles, graphite-silicon composite aggregate particles (9% microsilicon by weight), and graphite-silicon composite aggregate particles (9% nanosilicon by weight) are shown. [Figure 34] The graphs of the discharge ratio capacity as a function of the number of cycles are shown. a) Results are shown for graphite aggregate particles, graphite-silicon composite aggregate particles (9 wt% nanosilicon) obtained by a resonant acoustic mixer, graphite-silicon composite aggregate particles (9 wt% microsilicon) obtained by spray drying, and graphite-silicon composite aggregate particles (9 wt% nanosilicon) obtained by spray drying. b) Results are shown for graphite aggregate particles, graphite-silicon composite aggregate particles (5 wt% nanosilicon), graphite-silicon composite aggregate particles (9 wt% nanosilicon), and graphite-silicon composite aggregate particles (15 wt% nanosilicon). [Figure 35] a) SEM image of graphite-silicon composite aggregate particles containing CNTs, and b) cross-section of a single graphite-silicon composite aggregate particle containing CNTs. [Figure 36] a) XRD patterns of unprocessed graphite fine powder, graphite nanosilicon composite aggregate particles without CNTs, nanosilicon powder, and graphite nanosilicon composite aggregate particles containing CNTs are shown, and b) graphs showing the PSD of unprocessed graphite fine powder, graphite nanosilicon composite aggregate particles without CNTs, and graphite nanosilicon composite aggregate particles containing CNTs are shown. [Figure 37] a) A graph of the discharge ratio capacity as a function of the number of cycles, and b) A graph of the capacity retention rate as a function of the number of cycles for graphite aggregate particles, graphite nanosilicon composite aggregate particles without CNTs, and graphite nanosilicon composite aggregate particles with CNTs. [Modes for carrying out the invention]

[0009] The following detailed description and examples are illustrative and should not be construed as further limiting the scope of the invention. In contrast, all possible alternative forms, modifications, and equivalents as defined herein are intended to be exhaustive. The purpose, advantages, and other features of the method will be more clearly and better understood by reading the following non-limiting description and references to the accompanying drawings.

[0010] Where applicable, embodiments can be described using process flow diagrams, but the present invention is not limited to such drawings or corresponding descriptions. Furthermore, for the sake of brevity and clarity, i.e., to avoid placing an excessive burden on the diagrams with processes, reactants, equipment, and / or products, not all diagrams include all processes, reactants, equipment, and / or products. Some processes, reactants, and / or products may be found in only one diagram, and the processes, reactants, equipment, and / or products of this disclosure illustrated in other diagrams can be readily inferred from there.

[0011] All technical and scientific terms and expressions used herein have the same definitions as those commonly understood by those skilled in the art when relating to this art. Nevertheless, for the sake of clarity, definitions of some terms and expressions used herein are provided below.

[0012] In this specification, when the term "approximately" is used, it means "about," "nearly," or "around." When the term "approximately" is used in reference to a number, it modifies the number by, for example, a variation of 5% or 10% above or below its nominal value. The term may also take into account, for example, the rounding of the number or probability of random errors in experimental measurements due to instrument limitations.

[0013] Where a range of values ​​is referred to in this application, the lower and upper limits of the range are always included in its definition unless otherwise indicated. Where a range of values ​​is referred to in this application, it is intended to include all intermediate and partial ranges, as well as the individual values ​​included within the range.

[0014] Throughout this specification, where the article “a” is used to introduce an element, it is worth noting that it means “one or more,” not “only one.” Where this specification describes a process, component, feature, or characteristic as “may be included,” “might be included,” “can be included,” or “could be included,” it should be understood that the particular component, feature, or characteristic is not necessarily included. Unless otherwise indicated, the terms “comprising,” “having,” “including,” and “containing” should be interpreted as open-ended terms (i.e., “not limited to, but including”).

[0015] In this specification, the term "particle size" is described by the distribution of particle size dx. Here, the value d x x% of the particles are d x This represents the diameter for particles with a diameter less than d. For example, d 10 The value indicates that 10% of all particles have a particle size smaller than that value. The d90 value indicates that 90% of all particles have a particle size smaller than that value. Therefore, d 50 The value represents the median particle size, meaning that 50% of all particles are larger than this value, and 50% are smaller than this value.

[0016] In this specification, when the term "slurry" is used, it refers to an "emulsion," "solution," "suspension," or "semi-liquid mixture" containing fine material (fine powder) in a solvent.

[0017] All methods described herein may be carried out in any preferred order, unless otherwise indicated herein or unless otherwise clearly contradicted by the context.

[0018] Any and all examples or illustrative phrases (e.g., "etc.") provided herein are used solely to better illustrate the teachings presented herein and, unless otherwise claimed, do not impose any limitations on scope protection.

[0019] Nothing in this specification should be construed as indicating any unclaimed element that is essential to the practice of the invention.

[0020] The various methods described herein relate to the recycling and resource recovery of by-product graphite fine powder through agglomeration. For example, agglomerated graphite produced by the methods described herein can be used as an anode material in LIBs.

[0021] This technology relates to graphite aggregate particles, methods and systems for producing them, and electrode materials, electrodes, electrochemical cells, and batteries containing said graphite aggregate particles.

[0022] Method for producing graphite aggregate particles This technology relates to a method for producing graphite aggregate particles. For a more detailed understanding of this disclosure, first refer to Figure 1, which provides a flowchart of the method according to possible embodiments.

[0023] A method for producing graphite aggregate particles is: (i) A step of providing a graphite powder slurry comprising multiple graphite powders, a solvent, and a binder, (ii) A step of spray-drying the graphite fine slurry to form spray-dried re-aggregated graphite particles, (iii) The process includes a step of heat-treating the spray-dried re-aggregated graphite particles to obtain graphite aggregate particles.

[0024] Those skilled in the art will understand that graphite aggregate particles, graphene aggregate particles, or aggregate particles containing both graphite and graphene can be produced using the methods defined herein. In other words, the methods and various variations thereof presented throughout this disclosure can be adapted to completely or partially replace graphite fines with graphene fines. Those skilled in the art will readily understand that slurries can contain graphite fines, graphene fines, or both graphite fines and graphene fines. Graphite fine slurry can be replaced with graphene fine slurry. A method for producing graphene aggregate particles is: (i) A step of providing a graphene powder slurry comprising multiple graphene powders, a solvent, and a binder, (ii) A step of spray-drying the graphene fine powder slurry to form spray-dried re-aggregated graphene particles, (iii) It is understood that the step includes heat treatment of the spray-dried re-aggregated graphene particles to obtain graphene aggregate particles.

[0025] For the sake of brevity and clarity, it should be understood that whenever graphite is referred to in this specification, graphene is also intended.

[0026] In some embodiments, the methods defined herein enable the recycling and resource recovery of graphite powder. For example, graphite powder may be obtained as a by-product of other processes such as spheroidization.

[0027] The graphite powder slurry comprises graphite powder, a solvent, a binder, and optionally at least one crosslinking agent and / or at least one additional component. The graphite powder, and any additional component, may be homogeneously dispersed in a solution comprising the solvent, binder, and optionally the crosslinking agent.

[0028] In some embodiments, the binder may be carboxymethylcellulose (CMC). Graphite fines, and any additional components, may be homogeneously dispersed in a solution comprising the solvent, CMC, and a crosslinking agent (e.g., citric acid). For example, the presence of a crosslinking agent may promote the formation of intermolecular crosslinks rather than intramolecular crosslinks, thereby improving the mechanical properties of the graphite aggregate particles. While not to be constrained by theory, this may be due to electrostatic repulsion between charged macromolecules, resulting in very few hydroxyl groups available for reaction at the most reactive position, C6. In the presence of a crosslinking agent, cyclic anhydride intermediates can be formed at sufficiently high temperatures, which can esterify hydroxyl groups present on adjacent polymer chains, resulting in crosslink formation. It is understood that the aggregation process can be initiated when a slurry containing graphite fines, a binder, and a crosslinking agent is supplied to a spray dryer.

[0029] A spray drying process generally comprises three stages: (i) atomization, (ii) droplet-to-particle conversion (or particle formation), and (iii) particle collection. In the atomization stage, a spray nozzle (or atomizer) is used to convert the feed solution (i.e., graphite fine slurry) into substantially fine droplets via atomization. Those skilled in the art will understand that atomizing the feed solution into atomized droplets can substantially increase the surface area of ​​the liquid, thereby optimizing heat and mass transfer between the heated drying gas and the liquid particles in subsequent stages. In the droplet-to-particle conversion stage, the atomized droplets are exposed to a heated drying medium (e.g., a heated drying gas such as heated air) within a drying chamber, causing the solvent to substantially evaporate. Those skilled in the art will understand that the temperature of the drying medium and the residence time of the atomized droplets inside the drying chamber can be optimized to sufficiently evaporate the solvent while substantially or completely avoiding thermal decomposition of the particles. While we do not wish to be bound by theory, when in contact with a heated drying medium, the temperature of the droplet increases from its initial temperature to its equilibrium evaporation temperature. The drying process can be carried out at a constant evaporation rate. During the drying process, the droplet surface remains sufficiently cool to be saturated with moisture, thereby maintaining its temperature at a substantially constant wet-bulb temperature. Solvent evaporation occurs at a substantially constant rate until a critical value of the droplet's moisture content is reached, forming a thin shell on the droplet's surface, thereby slowing down the evaporation process. In the particle collection stage, the newly formed spray-dried re-aggregated graphite particles are then separated from the drying medium and collected.

[0030] In some embodiments, the heat treatment may be carried out for a period of time and at a temperature sufficient to cure or crosslink the binder and subsequently carbonize it.

[0031] (i) Provide a graphite fine powder slurry. As mentioned earlier, the graphite powder slurry comprises graphite powder, a solvent, a binder, and optionally, at least one crosslinking agent and / or additional components.

[0032] The method is not limited by any particular graphite powder. The graphite powder can be any conventional graphite powder known in the art. In some embodiments, the graphite powder can be a by-product obtained by a conventional spheroidizing process. In some embodiments, the graphite powder has a substantially small particle size (e.g., less than 10 μm).

[0033] As mentioned earlier, the graphite fine slurry contains a binder and, optionally, a crosslinking agent. The binder can bind the graphite fine particles during the spray-drying process, while the crosslinking agent can improve the mechanical strength of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles through crosslinking.

[0034] Any known equivalent binder is intended. In some embodiments, the binder is a polymer binder, e.g., a polar polymer binder. Non-limiting examples of polymer binders include CMC, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), biodegradable polymers including, but not limited to, polysaccharides (e.g., cellulose, chitin, starch, glycogen, and pectin), polycaprolactone (PCL), polylactic acid (PLA), polyhydroxybutyrate (PHB), and at least two combinations thereof. In some other embodiments, the binder is a non-polymer binder. Non-limiting examples of non-polymer binders include glycerin, pentaerythritol, monosaccharides, disaccharides (e.g., sucrose), other similar compounds, and at least two combinations thereof. In some embodiments of interest, the binder is CMC.

[0035] Any known equivalent crosslinking agent is intended. For example, the crosslinking agent may be an organic crosslinking agent or an inorganic crosslinking agent. In some embodiments of interest, the crosslinking agent is an organic crosslinking agent. Non-limiting examples of organic crosslinking agents include citric acid, formic acid, acetic acid, oxalic acid, and at least two combinations thereof. Non-limiting examples of inorganic crosslinking agents include Cu 2+ Zn 2+ Mg 2+ Ca 2+ Examples include divalent metal ions and at least two combinations thereof. In some embodiments of interest, the crosslinking agent is citric acid.

[0036] Any known equivalent solvent is intended. For example, the solvent can be any equivalent solvent conventionally used in spray drying. For example, the solvent can be an aqueous solvent. Non-limiting examples of solvents include water, methanol, acetone, ethanol, dichloromethane, tetrahydrofuran, ethyl acetate, chloroform, glycerin, dimethylformamide, dimethyl sulfoxide, and at least two miscible combinations thereof. In some embodiments of interest, the solvent is water.

[0037] The mass ratio of graphite fine powder to binder can be optimized to obtain aggregated graphite particles having desired properties (e.g., size). Those skilled in the art will understand that by decreasing the mass ratio of graphite fine powder to binder in the graphite fine powder slurry, the granular size of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles can be increased. If the mass ratio of graphite fine powder to binder falls below a certain threshold, binder solubility may be an issue, while if the mass ratio of graphite fine powder to binder exceeds a certain threshold, there may be insufficient binder, meaning that aggregation of graphite particles may not occur or may not occur sufficiently. In some embodiments, the mass ratio of graphite fine powder to binder in the graphite fine powder slurry is about 4:1 to about 20:1 (including upper and lower limits). In some embodiments, the mass ratio of graphite particles to binder in the graphite particle slurry is at least about 4:1, or at least about 5:1, or at least about 6:1, or at least about 7:1. In some embodiments, the mass ratio of graphite particles to binder in the graphite particle slurry is at most about 20:1, or at most about 15:1, or at most about 10:1, or at most about 8:1. In some embodiments of interest, the mass ratio of graphite particles to binder in the graphite particle slurry is about 6:1.

[0038] D of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50Since the amount of graphite fines generally increases with the amount of graphite fines, the content of graphite fines in a graphite fines slurry can play a role in the granular size of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles. In some embodiments, the weight concentration (wt / wt% or w / w%) of graphite fines in the graphite fines slurry is about 14% to about 35% by weight (including upper and lower limits). In some embodiments, the graphite fines slurry contains at least about 14% by weight, or at least about 18% by weight, or at least about 21% by weight, or at least about 24% by weight of graphite fines. In some embodiments, the graphite fines slurry contains at most about 35% by weight, or at most about 33% by weight, or at most about 30% by weight, or at most about 28% by weight of graphite fines. In some embodiments of interest, the graphite fines slurry contains about 24% by weight of graphite fines.

[0039] The mass ratio of graphite powder to binder can affect the amount of graphite powder or binder that can be used to form a slurry. For example, if the graphite powder content is high and the graphite powder to binder mass ratio is low, there may be too much binder that does not dissolve sufficiently in the solvent. On the other hand, a lower graphite powder content (e.g., 18 wt%) may allow for a lower graphite powder to binder mass ratio (e.g., 4:1) without substantially having problems with binder dissolution. In light of the above, in some embodiments of interest, a graphite powder content of about 14 wt% can be combined with a graphite powder to binder mass ratio lower than about 10:1, while a graphite powder content of about 35 wt% can be combined with a graphite powder to binder mass ratio higher than about 8:1. Therefore, the graphite powder slurry may contain 14% by weight of graphite powder or a graphite powder to binder mass ratio of 20:1, the former preferably combined with a lower graphite powder to binder mass ratio (e.g., 10:1 or less), while the latter preferably combined with a higher graphite powder content (e.g., 21% by weight or more). In some embodiments of interest, the graphite powder slurry may contain about 1.4% by weight of binder, about 14% by weight of graphite powder, and a graphite powder to binder mass ratio of about 10:1.

[0040] The graphite fines can be purified or unpurified. In some embodiments of interest, the graphite fines are purified, and the method may further include a step of purifying the graphite fines. The purification step may be carried out by any known equivalent purification method.

[0041] In some embodiments, the purity of the graphite powder is approximately 99.70% to approximately 99.99% (including upper and lower limits). In some embodiments, the purity of the graphite powder is at least approximately 99.70%, or at least approximately 99.8%, or at least approximately 99.9%, or at least approximately 99.95%. In some embodiments, the purity of the graphite powder is at most approximately 99.99%, or at most approximately 99.95%. In some embodiments of interest, the purity of the graphite powder is approximately 99.95%, which is a generally accepted purity level for battery applications.

[0042] Graphite fine powder D 50 This can play a role in the granular size of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles. Those skilled in the art will know that the D of spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50 D of the graphite fine powder constituting the spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50 Since it cannot be made lower than the D of spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50 D of graphite fine powder 50 You will understand that it can be increased along with the graphite powder D 50 The size is approximately 3 μm to approximately 10 μm (including upper and lower limits). In some embodiments, the graphite fine powder D 50 The diameter is at least about 3 μm, or at least about 4 μm, or at least about 5 μm, or at least about 6 μm. In some embodiments, the graphite fine powder D 50 The size is at most about 10 μm, or at most about 9 μm, or at most about 8 μm, or at most about 7 μm. In some embodiments of interest, the D of the graphite powder 50 Its diameter is approximately 7 μm.

[0043] D of the resulting graphite aggregate particles 50The graphite aggregate particles can be optimized based on their intended use. In some embodiments, the graphite aggregate particles are used in small batteries, and the D 50 The size can be approximately 18 μm to approximately 21 μm (including upper and lower limits). In some other embodiments, the graphite aggregate particles are used in large batteries (such as batteries for use in electric vehicles), and the D of the graphite aggregate particles 50 The size can be approximately 20 μm to approximately 24 μm (including upper and lower limits). In some other embodiments, the graphite aggregate particles are used in medium-sized batteries (such as batteries for use in hybrid electric vehicles), and the D of the graphite aggregate particles 50 This can be approximately 13 μm to approximately 17 μm (including upper and lower limits).

[0044] The D50 of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles can be increased along with the amount of binder in the graphite fine slurry. This may be due to the resulting viscosity of the graphite fine slurry, which can reduce the atomization energy available to produce droplets. It is understood that the amount of binder sufficient to bind the graphite fine particles can be limited by the solubility of the binder in the solvent, while the binder is present in the graphite fine slurry up to an upper limit. In some embodiments, the graphite fine slurry contains about 0.7% to about 6.0% by weight (including upper and lower limits) of binder. In some embodiments, the graphite fine slurry contains at least about 0.7% by weight, or at least about 1.4% by weight, or at least about 2.5% by weight, or at least about 3.0% by weight of binder. In some embodiments, the graphite powder slurry contains at most about 6.0% by weight, at most about 5.0% by weight, at most about 4.5% by weight, or at most about 4.0 w / w% of a binder. In some embodiments of interest, the graphite powder slurry contains about 4.0% by weight of a binder.

[0045] D of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50 The amount of crosslinking agent can increase with the amount of crosslinking agent when present in the graphite fine slurry, presumably because the crosslinking agent can promote a higher degree of polymerization. In some embodiments, the graphite fine slurry contains about 0.5% to about 4.0% by weight (including upper and lower limits) of crosslinking agent. In some embodiments, the graphite fine slurry contains at least about 0.5% by weight, or at least about 1.0% by weight, or at least about 1.5% by weight, or at least about 2.0% by weight of crosslinking agent. In some embodiments, the graphite fine slurry contains at most about 4% by weight, or at most about 3.5% by weight, or at most about 3.0% by weight, or at most about 2.5% by weight of crosslinking agent. In some embodiments, the graphite fine slurry contains about 3.0% by weight of crosslinking agent.

[0046] D of the resulting spray-dried re-aggregated graphite particles and / or graphite aggregate particles 50 The amount of solvent in the graphite fine slurry can decrease, presumably because the solvent can dilute the graphite fine content in the graphite fine slurry, and therefore reduce the amount of graphite fine available for agglomeration. In some embodiments, the graphite fine slurry contains about 58% to about 83% by weight (including upper and lower limits) of solvent. In some embodiments, the graphite fine slurry contains at least about 53% by weight, or at least about 58% by weight, or at least about 62% by weight, or at least about 66% by weight of solvent. In some embodiments, the graphite fine slurry contains at most about 83% by weight, or at most about 80% by weight, or at most about 72% by weight, or at most about 69% by weight of solvent. In some embodiments, the graphite fine slurry contains about 69% by weight of solvent.

[0047] Those skilled in the art will understand that the optimal amount of solvent in a graphite powder slurry can depend on different parameters. For example, if the graphite powder content is about 35% by weight and the graphite powder to binder mass ratio is about 4:1, a small amount of solvent, about 53% by weight, may be effective. However, in such an example, the resulting binder content would be 8.7% by weight, and if CMC is the binder, it may be impossible to dissolve it in only about 53% by weight of solvent (assuming the solvent is water). Conversely, a combination of about 35% by weight graphite powder content and about 8:1 graphite powder to binder mass ratio may be possible with a solvent content of 58% by weight (if the binder is CMC and the solvent is water).

[0048] In some embodiments of interest, the graphite powder slurry comprises about 24% by weight of graphite powder, about 4.0% by weight of a binder, about 3.0% by weight of a crosslinking agent, and about 69% by weight of a solvent.

[0049] In some embodiments, providing a graphite fine slurry involves preparing a graphite fine slurry. In some embodiments of interest, the graphite fine slurry is prepared by combining graphite fine, a binder, a solvent, optionally a crosslinking agent, and optionally additional components, and then mixing the components together. The mixing step may be carried out by any known equivalent mixing method, for example, the mixing step may be carried out using a mixer. In some embodiments of interest, the mixing step may be carried out using a resonant acoustic mixer. For example, the mixing step may be carried out for an acceleration and duration sufficient to substantially homogeneously disperse the graphite fine. For example, the mixing step may be carried out using a resonant acoustic mixer at an acceleration of about 50 G for about 30 minutes.

[0050] In some embodiments, the graphite fine slurry may further contain silicon particles. In such embodiments, the spray-dried re-aggregated graphite particles resulting from the spray-drying process and the graphite aggregate particles resulting from the heat treatment process may also contain the silicon particles.

[0051] D of silicon particles in graphite slurry 50 The particle size can be approximately 50 nm to approximately 5 μm (including upper and lower limits). In some embodiments, the silicon particle content in the graphite fine slurry can be approximately 0.0014% by weight to approximately 17.5% by weight (including upper and lower limits). For example, these can correspond to a silicon content of approximately 0.01% by weight and approximately 50% by weight in the resulting aggregates, respectively, when the graphite fine slurry contains a minimum of approximately 14% by weight and a maximum of approximately 35% by weight of the active material (graphite fine / silicon particles).

[0052] In some embodiments, the graphite fine slurry may further contain graphene particles and / or graphite fine particles. In such embodiments, the spray-dried re-aggregated graphite particles resulting from the spray-drying step and the aggregated graphite particles resulting from the heat treatment step include both graphite and graphene aggregate particles.

[0053] The D50 of graphene particles in the slurry can be approximately 50 nm to approximately 20 μm (including upper and lower limits). For example, the D50 of graphene particles in the slurry can be approximately 50 nm to approximately 18 μm, or approximately 50 nm to approximately 16 μm, or approximately 50 nm to approximately 14 μm, or approximately 50 nm to approximately 12 μm, or approximately 50 nm to approximately 10 μm, or approximately 50 nm to approximately 8 μm, or approximately 50 nm to approximately 6 μm, or approximately 50 nm to approximately 5 μm (including upper and lower limits).

[0054] In some embodiments, the graphite fine slurry may further include an electrically conductive material. For example, the electrically conductive material can be a carbon source. Non-limiting examples of electrically conductive materials include carbon black (e.g., Ketjen® Carbon and Super P® Carbon), acetylene black (e.g., Shawinigan Carbon and Denka® Carbon Black), carbon fibers (e.g., vapor-grown carbon fiber, VGCF), carbon nanofibers, CNTs (e.g., single-walled carbon nanotubes, SWCNTs, multi-walled carbon nanotubes, MWCNTs, and combinations thereof), and at least two combinations thereof. In some embodiments of interest, the graphite fine slurry further includes CNTs. In some embodiments, the graphite fine slurry contains about 0.1% to about 3.0% by weight (including upper and lower limits) of CNTs. For example, graphite fine slurry can be approximately 0.1% to 2.8% by weight, or approximately 0.1% to 2.6% by weight, or approximately 0.1% to 2.4% by weight, or approximately 0.1% to 2.2% by weight, or approximately 0.1% to 2.0% by weight, or approximately 0.1% to 1.8% by weight, or approximately 0.1% to 1.6% by weight, or approximately 0.1% to 1.4% by weight, or approximately 0.1% to The material contains approximately 1.2% by weight, or approximately 0.2% to approximately 1.0% by weight, or approximately 0.3% to approximately 1.0% by weight, or approximately 0.4% to approximately 1.0% by weight, or approximately 0.5% to approximately 1.0% by weight, or approximately 0.6% to approximately 1.0% by weight, or approximately 0.7% to approximately 1.0% by weight, or approximately 0.8% to approximately 1.0% by weight, or approximately 0.9% to approximately 1.0% by weight (including upper and lower limits). In some embodiments of interest, the graphite powder slurry contains approximately 0.8% to approximately 1.1% by weight (including upper and lower limits) of CNTs.

[0055] In some embodiments of interest, the graphite powder slurry may further contain both an electrically conductive material and silicon particles. In some preferred embodiments, the graphite powder slurry may further contain both CNTs and silicon particles.

[0056] (ii) Spray drying process The spray drying process involves spray drying a graphite fine slurry to obtain spray-dried re-aggregated graphite particles. Any equivalent spray drying system is intended.

[0057] Those skilled in the art will understand that by optimizing several spray drying parameters, it is possible to obtain spray-dried re-aggregated graphite particles and subsequent graphite aggregate particles having desired properties (e.g., particle size, size distribution, and morphology). For example, by optimizing key process parameters, including the feed rate of the graphite fine slurry, the humidity and temperature at the inlet and outlet, and / or the flow rate of the heated drying medium, spray-dried re-aggregated graphite particles and subsequent graphite aggregate particles having desired properties can be obtained. In some embodiments, these key process parameters can be the same as those used in conventional spray drying processes. Those skilled in the art will readily understand that these key process parameters can be adapted to suit specific situations (e.g., laboratory-scale spray drying processes typically utilize different process parameters than commercial-scale spray drying processes). For clarity, the following paragraphs considering the feed rate, inlet temperature, and flow rate of the heated drying medium generally refer to laboratory-scale spray drying process parameters. However, those skilled in the art will find it easy to adjust these process parameters for commercial-scale spray drying processes.

[0058] D of the resulting spray-dried re-aggregated graphite particles and graphite aggregate particles 50This can be increased along with the feed rate of the graphite fine slurry in the spray drying step (ii). While we do not wish to be bound by theory, at a constant atomization pressure, increasing the feed rate of the graphite fine slurry increases the droplet size, which results in a decrease in outlet temperature because the nozzle (or atomizer) must atomize more liquid with the same energy. In some embodiments, the feed rate of the graphite fine slurry is approximately 10 mL.min -1 ~Approx. 22mL.min -1 (Including upper and lower limits). In some embodiments, the graphite fine slurry feeding rate is at least about 10 mL.min. -1 , or at least about 12 mL. -1 , or at least about 14 mL. -1 , or at least about 16 mL. -1 In some embodiments, the graphite fine slurry supply rate is at most about 22 mL / min. -1 , or at most about 21 mL. -1 , or at most about 20 mL. -1 , or at most about 18 mL. -1 In some embodiments of interest, the feed rate of the graphite fine slurry is approximately 20.3 mL / min. -1 That is the case.

[0059] D of the resulting spray-dried re-aggregated graphite particles and graphite aggregate particles 50 The temperature decreases with the inlet temperature of the spray drying process (ii), presumably because the inlet temperature increases the dryer's evaporation capacity and thermal efficiency and reduces residual moisture. In some embodiments, the inlet temperature is about 190°C to about 220°C (including upper and lower limits). In some embodiments, the inlet temperature is at least about 190°C, or at least about 200°C. In some embodiments, the inlet temperature is at most about 220°C, or at most about 210°C. In some embodiments of interest, the inlet temperature is about 210°C.

[0060] In some embodiments, the flow rate of the heated drying medium is approximately 2.0 m³ 3 .minutes-1 ~about 2.5m 3 .minutes -1 (Including upper and lower limits.)

[0061] Herein, we refer to Figure 2, which provides a schematic diagram of a spray dryer system (and process) for the aggregation of graphite fines according to possible embodiments. In some embodiments, graphite fines, a binder (e.g., CMC), optionally a crosslinking agent (e.g., citric acid), optionally at least one additional component (e.g., graphene particles, graphene fines, silicon particles, electrically conductive materials (e.g., CNTs), and at least two combinations thereof), and a solvent (e.g., water) can be mixed in a feed tank (1) using a mixer (e.g., a resonant acoustic mixer) (2). The resulting mixture can then be supplied to an atomizer nozzle (6) via a pump (e.g., a peristaltic pump) (5). The atomizer can then disperse the liquid flow into controlled droplet-sized sprays, which can then be rapidly dried in a drying chamber (7) with a heated drying medium (e.g., heated air) provided by a pump (3) and a drying medium heater (e.g., an air heater) (4). Fine dry particles may then fall into a dust collector (8), while larger particles (spray-dried re-agglomerated graphite particles) pass through a separator (e.g., a cyclone separator) (9) driven by the dry medium flow, where they can be collected into a product collection container (10) using, for example, centrifugal force. The heated medium can then be extracted via an extraction fan (11).

[0062] (iii) Heat treatment process The next step (iii) is to heat-treat the spray-dried re-aggregated graphite particles to obtain graphite aggregate particles. Any equivalent heat treatment method is intended. By heat-treating the spray-dried re-aggregated graphite particles, at least a portion of the volatile substances are removed therefrom.

[0063] Optionally, spray-dried re-aggregated graphite particles obtained by spray-drying a graphite fine slurry can be mixed with a carbon precursor before heat treatment to produce carbon-coated graphite aggregate particles. The carbon coating may be performed or omitted depending on the desired final product. For example, if the user desires uncoated graphite aggregate particles, the carbon coating will be completely omitted. Conversely, if the user desires carbon-coated graphite aggregate particles, heat treatment may be performed using the carbon precursor. The properties of each of these final products (and the properties of electrodes produced therefrom), including how their properties vary with the parameters presented herein, will be described in more detail throughout this specification.

[0064] Any equivalent carbon precursor is intended. For example, the carbon precursor can be any carbon precursor conventionally used to coat particles with a carbon material via heat treatment. Non-limiting examples of carbon precursors include petroleum pitch, coal tar pitch, biomass pitch, a combination of at least two of them, and any similar equivalent material. In some embodiments of interest, the carbon precursor is coal tar pitch. When pitch, for example coal tar pitch, is used, the resulting graphite aggregate particles are pitch-coated graphite aggregate particles.

[0065] The carbon material can form a homogeneous coating layer on the surface of the graphite aggregate particles. For example, the carbon material can form a substantially uniform coating layer on the surface of the graphite aggregate particles. Alternatively, the carbon material can form a coating layer on at least a portion of the surface of the graphite aggregate particles. For example, the carbon material can be heterogeneously dispersed on the surface of the graphite aggregate particles.

[0066] Graphite aggregate particles will be approximately the same size as heat-treated, spray-dried, re-aggregated graphite particles. However, it is understood that coating graphite aggregate particles with a carbon material will naturally produce graphite aggregate particles with a slightly increased diameter compared to the corresponding spray-dried, re-aggregated graphite particles, due to the presence of the coating layer.

[0067] In some embodiments, the heat treatment is carried out for a temperature and duration sufficient to decompose the binder and, if present, the crosslinker. Those skilled in the art will understand that the heat treatment conditions (e.g., temperature, duration, heating rate, heating time, etc.) can be optimized to substantially or completely decompose the binder and, if present, the crosslinker. It will be understood that the heat treatment conditions can be optimized based on the sample size and / or properties of the binder and, if present, the properties of the crosslinker. In some embodiments, substantial or complete decomposition of the binder can be achieved at a temperature of about 1100°C. In some embodiments, the heat treatment step (iii) is carried out by heating the spray-dried re-aggregated graphite particles at a temperature of about 550°C to about 1300°C (including upper and lower limits). In some embodiments, the spray-dried re-aggregated graphite particles are heated to a temperature of at least about 550°C, or at least about 600°C, or at least about 700°C, or at least about 750°C. In some embodiments, the spray-dried re-aggregated graphite particles are heated to a temperature of at most about 1300°C, at most about 1100°C, at most about 1000°C, or at most about 900°C. In some embodiments of interest, the spray-dried re-aggregated graphite particles are heated to a temperature of about 1000°C.

[0068] Any equivalent heat treatment method is intended. For example, heat treatment step (iii) can be carried out using a conventional heat treatment method for natural graphite. In some embodiments, heat treatment step (iii) is carried out in a laboratory furnace (e.g., a tubular furnace) or an industrial furnace. For example, heat treatment step (iii) can be carried out in an inert atmosphere, for example, heat treatment step (iii) can be carried out under an inert gas flow such as an argon (Ar) or nitrogen (N2) flow. In some embodiments, the heat treatment profile consists of a heating gradient from room temperature to about 400°C (gradient of 2.00°C / min), isothermal heating at about 400°C for about 2 hours, a second heating gradient from about 400°C to about 900°C (gradient of 2.00°C / min), followed by isothermal heating at about 900°C for about 2 hours. In some embodiments, the sample comprises CMC as a binder and citric acid as a crosslinking agent, and the CMC / CA mass loss due to carbonization during the heat treatment step (iii) is approximately 80%, which can account for approximately 18% of the total heat-treated mass.

[0069] If carbon-coated graphite aggregate particles are desired, any equivalent coating method is considered. For example, any conventional technique used to coat graphite particles with a carbon material via heat treatment can be used. For example, spray-dried re-aggregated graphite particles and a carbon precursor can be mixed using a wet or dry mixing method. In some embodiments, the spray-dried re-aggregated graphite particles obtained in step (ii) are mixed with petroleum pitch (ZL250M) (e.g., mass ratio 9:1) using a resonant acoustic mixer (e.g., with an acceleration of about 50 G for about 15 minutes), followed by a heat treatment for the thermal decomposition of the petroleum pitch. In some embodiments, the heat treatment profile consists of a single temperature gradient from room temperature to about 1000°C (a gradient of 2.00°C / min), followed by isothermal heating at about 1000°C for about 30 minutes. The thermal decomposition can be carried out under an inert gas flow such as argon (Ar) or nitrogen (N2) flow.

[0070] In some embodiments, the carbon precursor is added to the spray-dried re-aggregated graphite particles in an amount sufficient to coat the entire surface of the spray-dried re-aggregated graphite particles. In some embodiments, the carbon precursor is mixed with the spray-dried re-aggregated graphite particles such that the carbon precursor represents about 5% to about 30% by weight (including upper and lower limits) of the mixture containing the spray-dried re-aggregated graphite particles and the carbon precursor. In some embodiments, the amount of carbon precursor in the mixture containing the spray-dried re-aggregated graphite particles and the carbon precursor is at least about 5% by weight, or at least about 10% by weight, or at least about 15% by weight. In some embodiments, the amount of carbon precursor in the mixture containing the spray-dried re-aggregated graphite particles and the carbon precursor is at most about 30% by weight, or at most about 25% by weight, or at most about 20% by weight. In some embodiments of interest, the amount of carbon precursor in the mixture containing the spray-dried re-aggregated graphite particles and the carbon precursor is about 10% by weight.

[0071] In some embodiments, binder carbonization and carbon coating can be carried out via a single heat treatment process (hereinafter referred to as one-step HT). In some embodiments, the mass loss of the CMC / citric acid / carbon precursor due to decomposition in one-step HT may be about 69%, which may account for about 21% of the total heat-treated mass. In some alternative embodiments, binder carbonization and carbon coating can be carried out via a two-step process in which spray-dried re-aggregated graphite particles are first heat-treated to form graphite aggregate particles, and then these graphite aggregate particles are mixed with a carbon precursor. Subsequently, a second heat treatment step for carbon coating (hereinafter referred to as two-step HT) is carried out. In some embodiments, the mass loss of the carbon precursor (e.g., pitch) due to carbonization via two-step HT may be about 47% (i.e., about 4.7% of the total heat-treated mass).

[0072] Those skilled in the art will understand that the parameters (or process conditions) used in the heat treatment step (iii) may affect the properties of the resulting graphite aggregate particles. For example, in some embodiments, the graphite aggregate particles may include nanogranules having a diameter of about 20 nm to about 200 nm (including upper and lower limits). Nanogranules may be arranged on the surface of the graphite aggregate particles. The presence of these nanogranules may be due to the carbonization of a binder (e.g., CMC) and, if present, a crosslinking agent (e.g., citric acid), which may result in the formation of nano- and micro-sized granules and spheres. On the other hand, in some embodiments, carbon-coated graphite aggregate particles obtained through a one-step HT may exhibit a smoother surface compared to their uncoated counterparts, while still conforming to the overall shape of the graphite aggregate particles. In some embodiments, the presence of nanogranules may be substantially reduced by the carbon coating. However, in some embodiments, nanogranules may still be present on the surface of carbon-coated graphite aggregate particles obtained through a two-step HT.

[0073] It is worth mentioning that carbon coating (both one-step and two-step HT) can reduce the surface area of ​​graphite aggregate particles (e.g., less than 10 nm) due to pore coating, which may be a desired effect of surface modification by carbon coating.

[0074] In some embodiments of interest, the heat treatment is preferably carried out using a one-step HT in the presence of a carbon precursor (e.g., coal pitch tar).

[0075] For clarity, the expression “spray-dried re-aggregated graphite particles” refers to the product obtained from the spray-drying process (ii), while the expression “graphite aggregate particles” refers to the product obtained through the heat treatment process (iii) as defined herein. As mentioned above, the properties of the graphite aggregate particles (e.g., carbon-coated vs. uncoated) will depend on whether or not carbon coating is performed and on the parameters (or process conditions) of the heat treatment (e.g., one-step HT or two-step HT).

[0076] Those skilled in the art will understand that the methods presented herein include a heat treatment step, which can be carried out discontinuously from other steps (i.e., at separate locations or by different entities). Thus, in certain embodiments, steps (i) and (ii) of the method can be carried out by a first entity, and the product (i.e., spray-dried re-aggregated graphite particles) can then be sold or transferred to another entity after which step (iii) is carried out (e.g., at a different location).

[0077] As mentioned above, Figure 1 illustrates one embodiment of the method as defined herein. In the embodiment shown in Figure 1, a binder (e.g., CMC) and, optionally, a crosslinking agent (e.g., citric acid) are dissolved in a solvent (e.g., water), followed by the addition of graphite powder (raw material). The resulting graphite powder slurry is then spray-dried to produce substantially spherical spray-dried reaggregated graphite particles having a median particle size of about 17 μm. As illustrated in Figure 1, the next step of the method may include mixing the spray-dried reaggregated graphite particles with a carbon precursor (e.g., coal tar pitch) in a mass ratio of 9:1, and heat-treating the mixture in an inert atmosphere at a temperature of about 1000°C for simultaneous binder carbonization and particle coating with carbon. For example, coating the particles with carbon can substantially reduce the surface reactivity of the graphite aggregate particles with the electrolyte of an electrochemical cell, thereby improving its electrochemical performance. Since these two processes (binder charring and particle coating with carbon) can be achieved in a single heat treatment step, the overall efficiency of the method can be increased.

[0078] In some embodiments, the spray-dried re-aggregated graphite particles are further subjected to high-temperature heat treatment carried out at temperatures of approximately 2000°C to approximately 3000°C (including upper and lower limits). This can be done, for example, to convert amorphous carbon coatings and / or binders into more graphitized materials.

[0079] The graphite aggregate particles obtained by the method presented herein will be described in more detail in the following paragraphs. Figure 3 shows SEM images of graphite powder (raw material) and graphite aggregate particles obtained by one embodiment of the method disclosed herein.

[0080] Graphite aggregate particles This technology also relates to graphite aggregate particles containing aggregated graphite fine powder. For example, graphite aggregate particles can be produced using the methods defined herein.

[0081] In some embodiments of interest, the graphite aggregate particles are spherical or nearly spherical particles (meaning they have a pseudo-spherical morphology).

[0082] As mentioned earlier, the D of graphite aggregate particles 50 This may vary depending on the intended application of the graphite aggregate particles. For example, in small batteries, a preferred D 50 The thickness is approximately 18 μm to approximately 21 μm (including upper and lower limits). For large-scale batteries (such as batteries for use in electric vehicles), the preferred D 50 The thickness is approximately 20 μm to approximately 24 μm (including upper and lower limits). For medium-sized batteries (such as batteries for use in hybrid electric vehicles), the preferred D 50 The size range is approximately 13 μm to 17 μm (including the upper and lower limits).

[0083] In some embodiments, the graphite aggregate particles may contain graphite having a Bernal (2H) phase, a rhombohedral (3R) phase, or both the 2H and 3R phases, and may retain the crystalline structure of the graphite fine powder raw material. In some embodiments of interest, the graphite aggregate particles contain graphite having both the 2H and 3R phases. Therefore, in some embodiments, the methods described herein do not substantially alter the crystalline structure of the graphite fine powder used to produce the graphite aggregate particles.

[0084] In some embodiments, the graphite aggregate particles may be carbon-coated graphite aggregate particles. For example, the graphite aggregate particles may be pitch-coated graphite aggregate particles.

[0085] As mentioned earlier, in some embodiments, the graphite aggregate particles are optionally subjected to further high-temperature heat treatment carried out at temperatures ranging from about 2000°C to about 3000°C (including upper and lower limits). Those skilled in the art will understand that when such high temperatures are used, the crystalline structure of the graphite may be slightly more modified compared to embodiments of the method that omit the additional high-temperature heat treatment step (i.e., embodiments of the method that use lower temperatures).

[0086] In some embodiments, the graphite aggregate particles may further contain silicon particles. In some embodiments, the silicon content in the graphite aggregate particles is greater than 0% by weight. In some embodiments, the silicon content in the graphite aggregate particles is at least about 3% by weight. In some embodiments, the silicon content in the graphite aggregate particles is at most about 50% by weight, or at most about 33% by weight.

[0087] In some other embodiments, the teachings presented herein with respect to graphite aggregate particles can be modified by substituting at least a portion of the graphite fine powder with silicon particles. Thus, the teachings presented herein may be applicable when using silicon content as high as at least about 35% by weight, or at least about 95% by weight, or about 100% by weight.

[0088] In some embodiments, the graphite aggregate particles may further comprise an electrically conductive material (such as the electrically conductive material defined earlier). In some embodiments of interest, the graphite aggregate particles further comprise carbon nanotubes (CNTs).

[0089] In some embodiments of interest, the graphite aggregate particles may further comprise both electrically conductive material and silicon particles. In some preferred embodiments, the graphite aggregate particles may further comprise both CNTs and silicon particles.

[0090] Applications of graphite aggregate particles This technology also relates to the use of graphite aggregate particles (for example, manufactured by the methods defined herein) in electrode materials, electrodes, electrochemical cells, and batteries.

[0091] Graphite aggregate particles (carbon coated or not) as defined herein constitute an electrode material. In some embodiments, the electrode material comprises graphite aggregate particles as defined herein and at least one additional component. In some other embodiments, the electrode material is made of graphite aggregate particles as defined herein. In some embodiments of interest, the graphite aggregate particles as defined herein are present in the electrode material at a weight concentration (wt / wt%) ranging from about 70% to about 100% by weight (including upper and lower limits).

[0092] In some embodiments, the electrode material as defined herein may further include an electrically conductive material. Non-limiting examples of electrically conductive materials include carbon sources such as carbon black (e.g., Ketjen® Carbon and Super P® Carbon), acetylene black (e.g., Shawinigan Carbon and Denka® Carbon Black), graphite, graphene (e.g., graphene nanoparticles), carbon fibers (e.g., VGCF), carbon nanofibers, CNTs (e.g., SWCNTs, MWCNTs, and combinations thereof), and at least two combinations thereof. In some embodiments of interest, the electrically conductive material includes carbon black, CNTs, or combinations thereof. In some embodiments of interest, the electrically conductive material is present in the electrode material at a weight concentration (wt / wt%) ranging from about 0.05% to about 10% (including upper and lower limits).

[0093] In some embodiments, the electrode material as defined herein may further include at least one additive. The additive can be selected from inorganic ion conductive materials, inorganic materials, glass, glass-ceramics, ceramics including nanoceramics (e.g., Al2O3, TiO2, SiO2, and other similar compounds), salts (e.g., lithium salts), and at least two combinations thereof. In some embodiments of interest, the additive may be hard carbon.

[0094] In some embodiments, the electrode material as defined herein may further include a binder. The binder may be selected for its compatibility with various elements of the electrochemical cell. Any known equivalent binder is intended. For example, the binder may be selected from polyether, polycarbonate or polyester type polymer binders, fluorinated polymers, and water-soluble binders. In some embodiments, the binder is a fluorinated polymer such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). In some other embodiments, the binder is a water-soluble binder such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (HNBR), epichlorohydrin rubber (CHR), or acrylate rubber (ACM), and optionally includes a thickener such as CMC, or a polymer such as poly(acrylic acid) (PAA), poly(methyl methacrylate) (PMMA), or at least two combinations thereof. In some other embodiments, the binder is a polyether-type polymer binder. For example, polyether-type polymer binders are linear, branched, and / or crosslinked and optionally contain crosslinkable units based on poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), or combinations thereof (e.g., EO / PO copolymer). In some embodiments of interest, the binder includes CMC and SBR as binders (e.g., in a mass ratio of about 30:70). In some embodiments of interest, the binder is present in the electrode material at a weight concentration (wt / wt%) ranging from about 1% to about 20% by weight (including upper and lower limits).

[0095] In some embodiments of interest, the electrode material is the anode material.

[0096] Electrodes comprising the electrode material defined herein, applied to a current collector (e.g., aluminum or copper foil), are also considered. Alternatively, the electrode may be a freestanding electrode. In some embodiments of interest, the electrode defined herein is an anode. For example, the electrode material defined herein can act as an active material when the electrode is used in an electrochemical cell or battery.

[0097] The electrodes may or may not be calendered. In some embodiments of interest, the electrodes are calendered.

[0098] In some embodiments, electrodes prepared using graphite aggregate particles as defined herein (e.g., manufactured by the methods defined herein) exhibit electrochemical properties comparable to those obtained using conventional electrodes prepared using conventional graphite. Therefore, electrodes prepared using graphite aggregate particles as defined herein (e.g., manufactured by the methods defined herein) can be used in any equivalent electrochemical cell or battery, such as a conventional LIB.

[0099] In some embodiments, electrodes prepared using graphite aggregate particles as defined herein (e.g., manufactured by the method defined herein) have a capacitance of 418±13 / 351±9 mAh.g -1 410±4 / 351±6mAh.g -1 , or 415±4 / 350±2mAh.g -1This can include the initial discharge / charge capacity, which translates to an initial Coulomb efficiency of 84%, 86%, or 84% for graphite aggregate particles, pitch-coated graphite aggregate particles (1-step HT), and pitch-coated graphite aggregate particles (2-step HT), respectively.

[0100] In some embodiments, the electrodes are obtained using carbon-coated graphite aggregate particles as defined herein (preferably obtained using a previously defined one-step HT). Those skilled in the art will understand that the carbon coating can act as a protective layer to suppress volume expansion of the graphite during cycling (e.g., during lithium intercalation) and / or to stabilize the SEI layer.

[0101] In some embodiments, compared to conventional graphite electrodes such as those containing commercially available PGPT102 graphite, the cathode peak on electrodes obtained using carbon-coated graphite aggregate particles as defined herein may be observed at a higher positive potential, while the anode peak may appear at a slightly lower positive potential, which can indicate better electrical conductivity of these electrodes. In addition, electrodes obtained using uncoated graphite aggregate particles as defined may exhibit slightly lower capacity retention (calculated from the second cycle) compared to the one-step HT and two-step HT carbon-coated counterparts. In some embodiments, the capacity retention of such electrodes is 94.4±2.2%, 95.1±0.4%, and 94.5±0.8%, respectively.

[0102] Those skilled in the art will understand that the type of graphite aggregate particles used can affect the properties of the resulting electrode. For example, the presence of a carbon coating can help contain the volume expansion of the graphite aggregate particles and / or significantly maintain the electrical conductivity of the electrode. Furthermore, the carbon coating can reduce the irreversible capacity in each cycle, especially when the electrode contains graphite aggregate particles obtained by a one-step HT method, which allows for more reversible intercalation comparable to that of commercially available graphite.

[0103] In addition, the graphite aggregate particles defined herein, being heat-treated, can exhibit higher initial Coulombic efficiency compared to raw materials, despite having a relatively large surface area due to the carbonization of the binder, and can exhibit cycling performance comparable to commercially available natural graphite exceeding 100 cycles. Overall, the carbon-coated graphite aggregate particles defined herein generally exhibit improved electrochemical and / or mechanical properties, especially when obtained through a one-step heat treatment (HT).

[0104] The electrodes can be prepared by any equivalent method known in the art. For example, a slurry containing the electrode material as defined herein can be prepared by mixing all the components described above. Any known equivalent mixing method is intended. In some embodiments of interest, a mixture of about 6.5 wt% CMC and SBR (e.g., in a mass ratio of about 30:70) as a binder, about 92.5 wt% of graphite aggregate particles (carbon-coated or uncarbonized) as defined herein as an active material, and about 1 wt% carbon black (e.g., SuperC65) as an electrically conductive material can be mixed (e.g., by a resonant acoustic mixer at an acceleration of about 50 G for about 15 minutes). The slurry thus obtained can then be coated onto a current collector (e.g., aluminum or copper foil). Any equivalent coating method is intended. For example, the coating process can be carried out by at least one of the following: a doctor blade coating method, a comma coating method, a reverse comma coating method, a printing method such as gravure coating, or a slot die coating method. In some embodiments of interest, the coating process is carried out by a doctor blade coating method. In some embodiments of interest, the slurry can be coated onto copper foil (e.g., 25 μm thick) using a doctor blade film applicator. For example, the blade gap can be about 5 mg / cm². -2 To obtain the graphite area mass loading, it can be set to approximately 200 μm. The coating can then be dried. In some embodiments, the coating is air-dried at room temperature for approximately 24 hours. An electrode disc (e.g., 10 mm in diameter) can then be punched out from the electrode thus obtained. It should be understood that the method described herein is for laboratory-scale testing and can be adapted to commercial scale.

[0105] An electrochemical cell is also contemplated, comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and cathode comprises an electrode material as defined herein. In some embodiments of interest, the anode comprises an electrode material as defined herein.

[0106] An electrochemical cell is also contemplated, comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and cathode is an electrode as defined herein. In some embodiments of interest, the anode is an electrode as defined herein.

[0107] The cathode can be any known electrochemically active material, including electrochemically active materials that can be selected for their electrochemical compatibility with various elements of an electrochemical cell as defined herein. For example, the electrochemically active material of the cathode can be selected for its electrochemical compatibility with the material of the anode as defined herein. Non-limiting examples of electrochemically active cathode materials include metal oxides (e.g., lithium metal oxide), metal phosphates (e.g., lithium metal phosphate), titanates (e.g., lithium titanate), metal fluorophosphates (e.g., lithium metal fluorophosphate), metal oxyfluorophosphates (e.g., lithium metal oxyfluorophosphate), metal sulfates (e.g., lithium metal sulfate), metal halides (e.g., lithium metal halides), and at least two combinations thereof. For example, the metal of the electrochemically active material can be selected from the group consisting of titanium, iron, magnesium, manganese, vanadium, nickel, cobalt, aluminum, chromium, copper, antimony, zirconium, zinc, niobium, and, if equivalent, at least two combinations thereof. In some embodiments of interest, the electrochemically active cathode material is metallic lithium oxide or metallic lithium phosphate. More specifically, the electrochemically active cathode material can be selected from lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4 or LFP), and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC).

[0108] The electrolyte can be selected for compatibility with different elements of the electrochemical cell. Any type of equivalent electrolyte is intended. In some embodiments, the electrolyte is a liquid electrolyte containing a salt in a solvent. In some other embodiments, the electrolyte is a gel electrolyte containing a salt in a solvent and, optionally, a solvating polymer. In some other embodiments, the electrolyte is a solid polymer electrolyte containing a salt in a solvating polymer. In some other embodiments, the electrolyte comprises an inorganic solid electrolyte material; for example, the electrolyte may be a ceramic type solid electrolyte. In some other embodiments, the electrolyte is a polymer-ceramic hybrid solid electrolyte.

[0109] In some embodiments, the salt, when present in an electrolyte, may be an ionic salt such as a lithium salt. Non-limiting examples of lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium 2-trifluoromethyl-4,5-dicyanoimidazolate (LiTDI), lithium 4,5-dicyano-1,2,3-triazolate (LiDCTA), lithium bis(pentafluoroethylsulfonyl)imide (LiBETI), lithium difluorophosphate (LiDFP), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium nitrate (LiNO3), and lithium chloride (lithium Lithium chloride (LiCl), lithium bromide (LiBr), lithium fluoride (LiF), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiSO3CF3) (LiOTf), lithium fluoroalkyl phosphate Li[PF3(CF2CF3)3] (LiFAP), lithium tetrakis(trifluoroacetoxy)borate Li[B(OCOCF3)4] (LiTFAB), lithium bis(1,2-benzenediolate(2-)-O,O')borate Li[B(C6O2)2] (LiBBB), lithium difluoro(oxalato)borate (LiBF2(C2O4)) (LiFOB), formula LiBF2O4R x (In the formula, R x Examples include salts of C2-4 alkyl groups and at least two combinations thereof. In some embodiments of interest, the lithium salt is LiPF6.

[0110] In some embodiments, the solvent may be a non-aqueous solvent if present in the electrolyte. Non-limiting examples of solvents include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC); dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), and dipropyl carbonate (Dipropyl Examples of solvents include acyclic carbonates such as carbonate (DPC); lactones such as γ-butyrolactone (γ-BL) and γ-valerolactone (γ-VL); acyclic ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME), trimethoxymethane, and ethyl monoglyme; cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and dioxolane derivatives; and other solvents such as dimethyl sulfoxide, formamide, acetamide, dimethylformamide, acetonitrile, propylnitrile, nitromethane, triesters phosphate, sulfolane, methylsulfolane, propylene carbonate derivatives, and combinations of at least two thereof. In some embodiments of interest, the solvent is a mixture of EC and DMC (50 / 50; v / v).

[0111] In some embodiments, the gel electrolyte or liquid electrolyte defined above may also be impregnated into a separator such as a polymer separator or a glass microfiber membrane. Examples of separators, but not limited to, include polyethylene (PE), polypropylene (PP), cellulose, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polypropylene-polyethylene-polypropylene (PP / PE / PP) separators. For example, the separator may be a Whatman® grade GF / D glass microfiber membrane.

[0112] Electrochemical batteries comprising at least one electrochemical cell as defined herein are also contemplated. In some embodiments of interest, the electrochemical battery is a battery selected from lithium batteries, lithium-ion batteries, sodium batteries, sodium-ion batteries, magnesium batteries, and magnesium-ion batteries. In some embodiments of interest, the battery is a lithium-ion battery.

[0113] Given that lithium-ion batteries (LIBs) have become a prominent energy storage solution and essential tool in modern society, the application of graphite aggregate particles as battery-grade graphite to LIBs is particularly advantageous. For 30 years in the market, LIB technology has achieved remarkable commercial success and currently dominates the energy storage market due to its high energy per unit mass, high power-to-weight ratio, and low self-discharge compared to other types of rechargeable systems such as lead-acid and nickel-metal hydride batteries. Demand for LIBs is expected to increase further in the future, driven by the popularity of consumer portable electronic devices and, more importantly, the growth of the commercialization of electric and hybrid electric vehicles.

[0114] It should be noted that electrodes may not be prepared using only graphite aggregate particles as defined herein (e.g., manufactured by the methods defined herein). For example, electrodes may be prepared using a slurry containing graphite aggregate particles as defined herein (e.g., manufactured by the methods defined herein) and conventional battery-grade graphite.

[0115] Potential benefits Those skilled in the art will readily understand certain advantages upon reading this disclosure. Furthermore, in certain embodiments, the methods, graphite aggregate particles, electrode materials, electrodes, electrochemical cells, and / or electrochemical batteries as defined herein may further present one or more of the following advantages: The methods defined herein can enable the recycling and reprocessing of graphite powder. For example, graphite powder can be a by-product of the spheroidization of flaky natural graphite and can be recycled and reprocessed by the methods defined herein.

[0116] The structural integrity of graphite aggregate particles as defined herein may not be substantially impaired by the calendering process.

[0117] The methods defined herein may be relatively simple and / or relatively inexpensive.

[0118] The use of binders and spray-drying processes can easily extend the methods defined herein and / or reduce their relatively low cost.

[0119] The method as defined herein may be suitable for continuous, low-cost, and / or large-scale manufacturing.

[0120] The method defined herein is comparable to commercially available battery-grade natural graphite. 50This makes it possible to manufacture spherical or nearly spherical graphite aggregate particles having [a certain characteristic].

[0121] The graphite aggregate particles as defined herein can exhibit sufficient mechanical strength to withstand the calendering process, which is a standard procedure in the manufacture of anodes for LIBs.

[0122] Despite having a relatively large surface area due to the carbonization of the binder (due to the heat treatment process (iii)), the graphite aggregate particles as defined herein can yield higher initial Coulomb efficiency compared to the raw material and / or exhibit cycling performance comparable to that of commercially available natural graphite for more than 100 cycles.

[0123] Optional surface modification of graphite aggregate particles by carbon coating can further improve the electrochemical and / or mechanical properties of electrode materials as defined herein.

[0124] The method can enable the recovery and reintegration of waste or by-product graphite powder into the production chain for battery-grade natural graphite and anodes for LIBs. This can result in improved waste recycling and / or increased productivity and economic benefits for any producer of battery-grade natural graphite.

[0125] Considering that single-step heat treatment can transform a single-step heat treatment in the manufacturing chain into a more efficient overall process, one-step heat treatment can have positive effects not only in terms of electrochemical performance but also in terms of industrial manufacturing feasibility.

[0126] Here, we refer to Figure 25, which shows a logical modular representation of an exemplary system 2000 comprising a control station 2100. The control station 2100 comprises a memory module 2160, a processor module 2120, a process control module 2130, and a network interface module 2170. The control station 2100 may also include a sensor module 2150.

[0127] System 2000 may include a storage system 2300 for storing and accessing long-term (i.e., non-temporary) data, and may further record data while the control station 2100 is in use. Figure 25 shows examples of the storage system 2300 as a separate database system 2300A, a separate module 2300C of the control station 2100, or a submodule 2300B of the memory module 2160 of the control station 2100. The storage system 2300 may be distributed across different systems A, B, and C. The storage system 2300 may include one or more logical or physical hard disk drives, as well as local or remote hard disk drives (or arrays thereof). The storage system 2300 may further include a local or remote database made accessible to the control station 2100 by a standardized or proprietary interface, or via a network interface module 2170.

[0128] The network interface module 2170 represents at least one physical interface that can be used to communicate with other network nodes. The network interface module 2170 can be made visible to other modules of the control station 2100 through one or more logical interfaces. The actual stack of protocols used by the physical network interface and / or logical network interfaces 2172-2178 of the network interface module 2170 does not affect the teachings of the present invention.

[0129] The processor module 2120 may represent a single processor having one or more processor cores, or an array of processors, each having one or more processor cores. The memory module 2160 may contain various types of memory (different standardized or different types of random access memory modules, memory cards, read-only memory modules, programmable read-only memory, etc.).

[0130] Bus 2180 is depicted as an example of a means for exchanging data between different modules of the control station 2100. The teachings presented herein are not affected by the manner in which the different modules exchange information. For example, the memory module 2160 and the processor module 2120 can be connected by a parallel bus, but can also be connected by a continuous connection or include an intermediate module (not shown) without affecting the teachings of the present invention.

[0131] The process control module 2130 provides process-related services to the control station 2100. The process control module 2130 may be used to exchange information with parts of industrial equipment (not shown) through one or more dedicated interfaces 2152 of the network interface module 2140 and / or the sensor module 2150. More specifically, the control station 2100 may communicate directly or indirectly with different devices involved in the method for producing graphite aggregate particles as defined herein. Depending on the manner in which the method for producing graphite aggregate particles as defined herein is to be carried out, different control parameters may be calculated (for example, by the process control module 2130 using the processor module 2120). For example, referring to Figure 2, the control station 2100 may be configured to fully or partially control the operation of one or more of the following: a supply tank (1), a mixer (2), a pump (3), a drying medium heater (4), a pump (5), an atomizer nozzle (6), a drying chamber (7), a dust collector (8), a separator (9), a product collection container (10), and an extraction fan (11) in order to carry out a method for producing graphite aggregate particles as defined herein. Devices (1) to (11) may be further selectively interconnected to facilitate the automation of a method for producing graphite aggregate particles as defined herein. The interconnection devices may take different forms (conveyors, pipes, vents, etc.) depending on the role of devices (1) to (11) within them. Furthermore, some of devices (1) to (11) may not be involved in some of the processes and / or may be involved in one or more additional positions and operated by one or more additional entities. Control station 2100 may further communicate with another control station 2100' (e.g., via network 2000) if the method for producing graphite aggregate particles is carried out at multiple locations and / or if providing two or more control stations is better suited to completing the method for producing graphite aggregate particles (e.g., large plant, multi-site project, etc.).

[0132] Variations of the processor module 2120, memory module 2160, and network interface module 2170 that can be used in the context of the present invention will be readily apparent to those skilled in the art. Similarly, even if there is no explicit reference to the process control module 2130, memory module 2160, sensor module 2150, and / or processor module 2120 throughout this description of the embodiment, those skilled in the art will readily recognize that such modules may be used in conjunction with other modules of the control station 2100 to implement the conventional and innovative elements presented herein.

[0133] In the context of this invention, various network links may be used implicitly or explicitly. A link may be described as a wireless link, but it can also be implemented as a wired link using coaxial cable, optical fiber, Category 5 cable, etc. Wired or wireless access points (not shown) may be present between links. Similarly, any number of routers (not shown) may be present and may be part of a link, which may further extend over the Internet. [Examples]

[0134] The following embodiments are for illustrative purposes only and should not be construed as further limiting the scope of the invention as intended. These embodiments will be better understood by referring to the accompanying drawings.

[0135] Specifically, graphite aggregate particles were manufactured using the method defined herein. Various parameters of the resulting graphite aggregate particles and electrodes fabricated therefrom were measured and compared with those of conventional graphite electrodes.

[0136] Unless otherwise indicated, all figures used herein to represent quantities, preparation conditions, concentrations, properties, etc., of components shall be understood in all cases to be modified by the term “approximately.” At a minimum, each numerical parameter should be interpreted by applying a general rounding technique in light of the number of significant figures reported. Thus, unless otherwise indicated, the numerical parameters described herein are approximations that may vary depending on the desired properties. Despite the fact that the ranges of the numerical values ​​and parameters defining the scope of the embodiments are approximations, the numerical values ​​presented in the following examples are reported as accurately as possible. However, any numerical value inherently contains certain errors arising from variations in experiments, test measurements, statistical analyses, etc.

[0137] Example 1: Graphite aggregate particles - Experimental conditions and method a) Reagents Fine powdered natural graphite (f-NG) (carbon content = 99.7%, D) obtained as a by-product of spheroidization of purified natural flake graphite. 50 Approximately 7 μm was used without further purification. Petroleum pitch (ZL250M) (RUETGERS Germany GmbH) was used without further purification. Carboxymethylcellulose sodium (average molecular weight M W Approximately 90,000 (degree of substitution = 0.7), lithium foil (1 mm thick, 99.9%), and battery-grade LP30 (LiPF6 solution in EC and DMC containing 1 M concentration of LiPF6 in EC / DMC (50 / 50, v / v)) were purchased from Sigma. Citric acid (over 99.5%) was purchased from Alfa Aesar. SBR (50% solid content) and Super C65 conductive carbon black were purchased from MTI Corporation. PGPT102 natural graphite (battery grade) was purchased from Targray.

[0138] b) Agglomeration of f-NG onto spray-dried, re-aggregated graphite particles The aggregation of f-NG onto spray-dried re-aggregated graphite particles was achieved using a spray dryer (Pilotech, Mini Spray Dryer YC-015) with CMC as a binder. Preliminary spray-drying studies were conducted to evaluate the effects of parameters such as the f-NG / CMC mass ratio, f-NG content, feed rate, inlet temperature, and air blow rate on the particle size of the resulting product. The results of these studies are reported in Tables 4-8. Briefly, slurries containing selected f-NG:CMC ratios and f-NG content were prepared, and after graphite aggregation and subsequent heat treatment of the resulting product, particle size distribution (PSD) analysis was performed to obtain preliminary D 50 Data was obtained. This data was processed using Minitab® software to determine the importance of various parameters. Through a weighted Pareto chart (Figure 15), the f-NG content was identified as the parameter with the greatest influence on the particle size of the resulting aggregates, followed by the f-NG / CMC mass ratio. The optimal f-NG content and f-NG:CMC mass ratio were found to be approximately 24 wt% and 6:1, respectively. The feed rate, inlet temperature, and air blow rate parameters were found to have a more limited influence on particle size, with the optimal values ​​being approximately 20.3 mL / min each. -1 Approximately 210°C, and approximately 2.5m 3 .minutes -1 Additionally, 3% by weight of citric acid was incorporated into the slurry to improve the mechanical strength of the spray-dried re-aggregated graphite particles and the subsequent graphite aggregate particles through a cross-linking reaction with CMC. The effect of citric acid was evaluated by measuring the PSD of the graphite aggregate particles before and after a ball milling process performed for approximately 30 minutes using a 15 mL IKA® dispersion tube with three glass balls driven by an IKA® ULTRA-TURRAX® Tube Drive (Figure 16). 50Experienced a greater decrease compared to graphite aggregate particles containing 3 wt% citric acid, so PSD analysis suggested more severe particle breakage during ball milling. Thus, in some examples, the final composition of the slurry to achieve the desired D 50 was composed of approximately 4 wt% CMC, approximately 3 wt% citric acid, approximately 24 wt% f-NG, and approximately 69 wt% water. All slurries for spray drying described in this paragraph were mixed for approximately 30 minutes at an acceleration of approximately 50G using a Resonant Acoustic Mixer (RAM, ResoDyn LabRam).

[0139] c) Spray drying studies Findings from preliminary spray drying studies are reported in Tables 1 to 5. Experiments revealed that the particle size increased with a decrease in the f-NG:CMC ratio, but the latter was ultimately limited by the viscosity of the slurry. As mentioned above, the optimal f-NG:CMC mass ratio was found to be approximately 6:1. Since the D of the resulting aggregates increases with the amount of raw graphite, the f-NG content also plays an important role in the particle size. The optimal f-NG content was determined to be approximately 24 wt%, while the feed rate, inlet temperature, and air blow rate parameters were found to have a more limited effect on the particle size, and the optimal values were approximately 20.3 mL.min 50 , approximately 210 °C, and approximately 2.5 m -1 , respectively. 3 .min -1

[0140]

Table 1

[0141]

Table 2

[0142]

Table 3

[0143] [Table 4]

[0144] [Table 5]

[0145] d) Heat treatment Heat treatment was performed on spray-dried powder (i.e., spray-dried re-aggregated graphite particles) under an inert Ar flow in a tubular furnace (Thermo Scientific®, Thermolyne® F21125). The heat treatment consisted of a heating gradient from room temperature to approximately 400°C (2.00°C / min gradient), isothermal heating at approximately 400°C for approximately 2 hours, followed by a second heating gradient from approximately 400°C to approximately 900°C (2.00°C / min gradient), and isothermal heating at approximately 900°C for approximately 2 hours. The mass loss of CMC / citric acid due to carbonization during heat treatment was approximately 80%, which accounts for approximately 18% of the total heat-treated mass. The carbonized powder was sieved using an ultrasonic sieve (GilSonic AutoSiever® Sonic Sifter, GA-6) with a stainless steel mesh having a 45 μm opening. The percentage of particles removed was approximately 10% by weight.

[0146] e) Pitch coating Pitch-coated graphite aggregate particles were obtained through a dry method consisting of mixing spray-dried re-aggregated graphite particles with coal tar pitch (ZL250M) (9:1 w / w ratio) using a resonant acoustic mixer (at an acceleration of approximately 50 G for approximately 15 minutes), followed by heat treatment for thermal decomposition of the coal tar pitch. The heat treatment profile consisted of a single temperature gradient of 2.00°C / min from room temperature to approximately 1000°C under an inert Ar stream, followed by isothermal heating at approximately 1000°C for approximately 30 minutes. In this way, binder carbonization and pitch coating were carried out in a single step (hereinafter referred to as 1-step HT). The mass loss of CMC / citric acid / pitch due to decomposition during heat treatment was approximately 69%, which accounts for approximately 21% of the total heat-treated mass. For comparative purposes, an alternative strategy (2-step HT) was evaluated, in which graphite aggregate particles were mixed with coal tar pitch and then subjected to a second heat treatment for pitch coating. In this case, the mass loss of pitch due to carbonization was approximately 47% (about 4.7% of the total heat-treated mass). The pitch-coated particles were sieved as described above. The percentage of particles removed was approximately 15% by weight.

[0147] f) Evaluation of material characteristics The morphology of uncoated and pitch-coated graphite aggregate particles was characterized using a TESCAN VEGA3 instrument for SEM, while cross-sectional images of individual aggregate particles were obtained using a focused ion beam (FIB)-SEM with a TESCAN LYRA3 instrument equipped with a Ga ion source (FIB). Post-verification SEM top view images of the electrodes were acquired after 200 cycles, in conjunction with a vacuum transfer chamber to avoid contact between the sample and air. After dispersing the powder in water, the PSD of all materials was measured using a Bettersizer ST laser particle size analyzer. Their crystal structures were determined by XRD using a Bruker D8 Advance diffractometer equipped with a Cu Kα source (λ=0.15406nm, 40kV, 40mA). All diffraction patterns were acquired in continuous scan mode with a 0.02° 2θ angle step size and an acquisition time of 2 seconds per step. Tap density was measured using a Quantachrome Dual Autotap instrument. The specific surface area of ​​the sample was determined from N2 adsorption isotherms using a TriStar II Plus Micromeritics™ analyzer, based on the Brunauer-Emmet-Teller (BET) theory.

[0148] g) Calculation of the porosity of graphite electrodes The graphite-based electrodes used in this study contain an active material (graphite), carbon black (Super C65), and binders (CMC and SBR).

[0149] Assuming an electrode without pores, the true or theoretical density of the electrode (ρ theo ) is the mass fraction ρ of each electrode component. m,i and true density ρ i Therefore, the calculation was performed according to the following formula.

[0150]

number

[0151] [Number] and ρ SBR φ estimated to be 1.99 with ρ SBR = 0.94 m,SBR = 4.55%

[0152] Next, the porosity (P) of the electrode was estimated using the following equation,<于 <于

[0153] <于 [[ID=2——4]]<于 [Number]<于 <于 <于 <于 where ρ<于 meas is the measured density of the electrode calculated from the measured weight and thickness (excluding the Cu current collector).<于 <于

[0154] <于 h) Preparation of the electrode and cell assembly<于 [[ID=—38]]A slurry containing approximately 6.5 wt% CMC SBR (30:70 mass ratio) as a binder, approximately 92.5 wt% graphite aggregate particles (pitch-coated or not) as an active material, and approximately 1 wt% carbon black Super C65 as an electrically conductive material was mixed using a resonant acoustic mixer at an acceleration of approximately 50 G for approximately 15 minutes. The slurry was coated onto a copper foil (25 μm thick) using a doctor blade film applicator with a blade gap set to 200 μm to obtain approximately 5 mg.cm<于 -2 It should be noted that there are some tags like <于 etc. which seem to be in a non-standard format. If this is a special encoding or specific notation in a particular system, it might need further clarification for a more accurate translation. The above translation is done based on the best understanding of the provided text.A graphite area mass load was obtained. The coating was air-dried at room temperature for approximately 24 hours, and then 10 mm diameter electrode disks were punched out from the dried coated Cu sheet. To study the effect of the coating's porosity and density on its electrochemical performance, the electrodes were calendered using a rolling cylinder press (MSK-HRP-MR100DC, Zhengzhou CY Scientific Instruments). The thickness of the electrodes before and after compression was measured at the center of each disk using a digital micrometer (Mitutoyo, 293-240-30, with a resolution of 1 μm, assuming that the Cu current collector was not deformed (confirmed from cross-sectional SEM images of the electrodes)). Before use, all electrodes were dried under vacuum at a temperature of approximately 100°C for approximately 2 hours. The working electrode was mounted in a Swagelok® type cell in a two-electrode configuration, facing a 10 mm diameter lithium metal electrode that acted as both the reference electrode and the counter electrode. The graphite electrode and lithium electrode were separated by a borosilicate glass fiber (WhatmanGF / D) membrane, immersed in approximately 350 μL of LP30 electrolyte, and the entire assembly was compressed by a spring on the lithium side to ensure proper contact. The cell was assembled in an Ar-filled glove box (H2O and O2 concentration of 0.5 ppm or less) and tightened with a torque of approximately 50 Nm.

[0155] i) Electrode cycling At room temperature, 10mV to 1V vs. Li / Li + The graphite electrodes were cycled using the Neware BTS4000 series Battery Testing System in constant current mode. Before cycling, the cells were left at open-circuit voltage for 1 hour, and after each discharge and charge, they were left for 1 second and 35 seconds, respectively. For the first two cycles, a C / 20 C rate was applied (1C = 372mAg). -1The graphite electrodes were subjected to a C / 9 discharge rate for all subsequent cycles. Speed ​​performance tests were also conducted while varying the charge (delithiation) C rate from C / 20 to 2C, while the discharge C rate was fixed at C / 10. All electrodes were evaluated three times, and the results were compared with commercially available PGPT102 graphite electrodes. Capacity was expressed as mAh per gram of graphite and averaged from the three cycling tests.

[0156] Example 2: Characterization of graphite aggregate particles a) Evaluation of physicochemical characteristics Figure 4a shows the PSD curves obtained for f-NG raw material, graphite aggregate particles, and pitch-coated graphite aggregate particles obtained through a one-step HT process, with commercial PGPT102 graphite used as a reference material. Analysis revealed that after spray drying, D 50 The value increased from approximately 7.3 μm to approximately 16.5 μm, confirming successful aggregation of flake-like graphite. Furthermore, the resulting graphite aggregate particles exhibited PSD(D) comparable to that of PGPT102 graphite. 50 It exhibits a particle size of approximately 16.1 μm, which demonstrates the slurry composition and spray drying parameters. On the other hand, in the pitch-coated (1-step HT) sample, due to the additional pitch-assisted re-aggregation of graphite particles, D 50 =A slightly larger PSD of approximately 19.9 μm was obtained. In pitch-coated graphite aggregate particles through a two-step HT process, a similar PSD (D 50 (Approximately 19.6) was obtained (Figure 17).

[0157] The XRD patterns of all samples are shown in Figure 4b. The XRD diffraction pattern of the commercially available PGPT102 graphite shows peaks of hexagonal 2H structure graphite containing (002), (100), (101), (004), and (110) planes at 2θ = 26.4°, 42.3°, 44.6°, 54.6°, and 77.5°, respectively, in the ABAB stacking order (JCPDS card, No. 41-1487). However, in the f-NG raw material and derived graphite aggregate particles, in addition to the 2H structure peaks, signals attributable to rhombohedral 3R structure graphite are also observed. The peaks at 2θ = 43.4°, 46.1°, 56.5°, and 63.4° are indexed to the (101), (012), (104), and (015) planes, respectively, of rhombohedral 3R graphite (JCPDS card, No. 26-1079) in which the graphene layers are stacked in an ABCABC arrangement. This indicates that the graphite aggregate particles are composed of graphite having both 2H and 3R phases, and that they substantially retain the crystalline structure of the raw material. The XRD diffraction patterns of pitch-coated graphite aggregate particles obtained through one-step HT and two-step HT are substantially identical (Figure 18). To determine the relative concentrations of the 2H and 3R phases in the sample, the area under peaks 3R(101) and 2H(101) from the deconvolution of the (101) peak in the range of 42° to 47° is used, as shown in Figure 19. 3R(101) / A 2H(101) The ratio was calculated for PGPT102, f-NG, graphite aggregate particles, and 1-step HT and 2-step HT pitch-coated graphite aggregate particles. 3R(101) / A 2H(101)The values ​​were 0.15, 0.37, 0.41, 0.46, and 0.40, respectively. As expected from the XRD diffraction patterns, PGPT102 has the smallest amount of rhombohedral 3R structure, followed by the f-NG raw material. Since the carbonization of the CMC / citric acid binder and coal tar pitch in these materials results in the formation of amorphous / disordered carbon, it is not surprising that the 3R phase graphite content is higher in the uncoated graphite aggregate particle samples and the pitch-coated graphite aggregate particle samples. Furthermore, the intensities of the (002) and (004) peaks in the uncoated graphite aggregate particles and the pitch-coated graphite aggregate particles are reduced compared to the PGPT102 and f-NG samples, which is also a result of their higher disordered carbon content. Interlayer distance d for all samples 002 and d 100 These values ​​are 0.336 nm and 0.213 nm, respectively, which are consistent with the values ​​for crystalline graphite.

[0158] Figure 5a shows an SEM image of the f-NG raw material as received, where distinctly different shaped flake-like graphite is observed. In contrast, after aggregation of the flake-like graphite by spray drying and subsequent heat treatment, particles with a considerably more homogeneous appearance and nearly spherical morphology were obtained, as shown in Figure 5b. Figure 5c shows an SEM image of a single aggregated particle, where a better defined edge is observed than that of the flake-like material that fits the aggregate. During higher magnification analysis, nanogranules with a diameter of approximately 20–200 nm, as shown in the inset of Figure 5c, were observed on virtually the entire surface of the aggregated particles. Carbonization with CMC and citric acid has been reported to result in the formation of nano and micro-sized granules and spheres. To investigate the origin of these features, commercial PGPT102 graphite was subjected to spray drying and heat treatment under the same conditions as the f-NG raw material. SEM images of the obtained powder (Figure 20) show the same type of nanogranules on the PGPT102 surface as observed on the graphite aggregate particles, thus confirming their properties as forms of carbon resulting from CMC and citrate carbonization. On the other hand, pitch-coated graphite aggregate particles obtained through one-step HT (Figure 5e) exhibit a smoother surface compared to their uncoated counterparts, while following the overall shape of the aggregates, which is the expected effect of pitch coating. However, a more detailed examination of the particle surface (inset in Figure 5e) revealed that the presence of nanogranules, CMC, and citrate carbonization products was substantially reduced by the pitch coating. Interestingly, nanogranules are still observed on the surface of pitch-coated particles obtained through two-step HT (Figure 21), suggesting that the absence of these features is due to something beyond a mere coating effect. Considering that the carbonization of CMC / citric acid and the thermal decomposition of pitch occur simultaneously in the material obtained by a single-step heat treatment, the formation of nanogranules may be completely mitigated by side reactions in the presence of pitch. The nature of the interaction between CMC / citric acid and pitch during heat treatment remains uninvestigated.FIB-SEM cross-sectional images of uncoated graphite aggregate particles and pitch-coated graphite aggregate particles, shown in Figures 5d and 5f, respectively, revealed voids within the material resulting from the folding of irregularly sized and shaped flake-like graphite particles that conform to the aggregates. These voids within the aggregate particles are most likely the reason for their lower tap density compared to commercially available PGPT102 graphite. Specifically, the tap densities of uncoated graphite aggregate particles and pitch-coated graphite aggregate particles (1-step HT and 2-step HT) were approximately 0.471 g.cm³, respectively. -3 , about 0.450g.cm -3 , and approximately 0.444 g.cm -3 This is because the tap density of commercially available PGPT102 graphite is (1.070 g.cm³). -3 It is approximately 2.3 times lower than [uncoated]. The similarity in internal structure and tap density between uncoated graphite particles and pitch-coated graphite particles suggests that the effect of pitch is limited to the surface of the aggregate.

[0159] Figure 22 shows the N2 adsorption isotherm of the sample, and the BET specific surface area and micropore area calculated from the adsorption isotherm are reported in Table 6. Analysis revealed that the BET surface area of ​​the graphite aggregated particles was higher than that of the unprocessed f-NG, which was contrary to the expected result. The increase in specific surface area after aggregation can be attributed to the carbonization of the CMC / citric acid binder, which formed micropores in the sample, as evidenced by the micropore area in the t-plots reported in Table 6. This was confirmed by surface area analysis of commercially available PGPT102 graphite that had undergone spray drying and heat treatment. After processing, the specific surface area of ​​PGPT102 was approximately 2.1 m². 2 .g -1 ~approximately 7.8m 2 .g -1 While it increased to that extent, the micropore area was approximately 0.07 m². 2 .g -1 ~Approximately 5.1m 2 .g -1increased up to. On the other hand, pitch coating (1-step HT and 2-step HT) reduced the surface area of graphite aggregate particles due to the coating of pores less than 10 nm, which is the desired effect of surface modification by pitch.

[0160]

Table 6

[0161] b) Electrode Morphology To evaluate the behavior of uncoated graphite aggregate particles and pitch-coated graphite aggregate particles after compression, the electrodes were calendared and compared with their uncalendered counterparts. The top and cross-sectional SEM images of the uncalendered graphite aggregate electrode and the pitch-coated graphite aggregate (1-step HT) electrode, presented in Figures 6a and 6b respectively, show a coating thickness of approximately 100 μm. The areal mass loading of the electrode is 5.1 ± 0.1 mg.cm -2 and the electrode (coating) density is 0.63 ± 0.01 g.cm -3 which results in a porosity of approximately 70%. The SEM images of the compressed graphite aggregate electrode and the coated graphite aggregate electrode are shown in Figures 6c and 6d respectively. The thickness of the calendared electrode is approximately 45 μm, which gives an electrode density of 1.32 ± 0.02 g.cm -3While the density increases, the porosity decreases to approximately 30%. Top and cross-sectional images of the electrodes show good overall structural integrity after calendering for both the uncoated and pitch-coated graphite materials. However, to further investigate the effect of compression at the aggregate particle level, uncoated and calendered uncoated graphite aggregate electrodes were analyzed using FIB-SEM techniques. Cross-sections of aggregate particles located on the surface of the uncalendered electrode (Figure 6e) exhibit the same structural characteristics as their powder form (Figure 5d), indicating that the material remains substantially unchanged after deposition on the copper foil. On the other hand, FIB-SEM images of the calendered electrode (Figure 6f), obtained to substantially the depth of the coating layer, reveal substantial particle deformation and a significant reduction in voids within the graphite aggregate particles. However, despite considerable morphological changes, individual aggregate particles can still be distinguished, so no obvious aggregate fracture is observed. Therefore, the structural integrity of the graphite aggregate particles is not compromised by the calendering process.

[0162] c) Electrochemical performance A preliminary short cycling test was conducted to evaluate the effect of calendering on electrode performance. Figure 23 compares the specific discharge capacity and Coulomb efficiency of uncoated graphite aggregate electrodes, pitch-coated graphite aggregate electrodes, and PGPT102 electrodes before and after calendering. Compression of the aggregate electrodes does not adversely affect their electrochemical performance, at least for short cycle periods (23 cycles) at the applied moderate C rate (C / 20 in the first cycle and C / 9 in subsequent cycles). Therefore, all subsequent cycling tests were performed using calendered electrodes.

[0163] Figure 7a shows the first cycle discharge / charge curves for flaky graphite electrodes, aggregated graphite electrodes, and PGPT102 graphite electrodes, performed at a C / 20 rate. The potential profiles of all electrodes show a series of Li between the graphene layers in the graphite host, resulting in the formation of LiC6. + This is consistent with a well-known staging mechanism characterized by intercalation. All curves exhibit potential plateaus due to staging in graphite, however, these occur at slightly different potentials at each electrode. The potentials at which these processes occur can be observed more clearly in the differential capacitance plot shown in Figure 7b. At the initial discharge, all electrodes are approximately 0.7V vs. Li / Li + It shows an irreversible cathode peak (Figure 24), which is due to the formation of the SEI layer. + 0.3V vs Li / Li resulting from intercalation and deintercalation + Three reversible cathode peaks below 0.18V, 0.10V, and 0.07V vs. Li / Li are observed in all curves. + These peaks found correspond to the transitions from diluted Stage I to Stage IV, Stage III to Stage II, and Stage II to Stage I, respectively. During the initial charging process, the corresponding reverse processes are approximately 0.11V, 0.15V, and 0.23V vs. Li / Li + This produces three anode peaks. All processes occur at very similar potential values ​​for the graphite aggregate electrode and the PGPT102 graphite electrode, demonstrating the desirable electrochemical behavior of the graphite aggregate electrode. Interestingly, the cathode peaks on both pitch-coated graphite aggregate electrodes are observed at a more positive potential, while the anode peaks appear at a slightly lower positive potential, which may be due to better electrical conductivity on these electrodes. Based on three cycling tests with each formulation, the initial discharge / charge capacity was 416±10 / 336±5mAh.g -1 418±13 / 351±9mAh.g -1 410±4 / 351±6mAh.g-1 415±4 / 350±2mAh.g -1 , and 388±3 / 354±6mAh.g -1 These values ​​translate to initial Coulomb efficiencies of 80%, 84%, 86%, 84%, and 91% for f-NG, graphite aggregates, pitch-coated aggregates (1-step HT), pitch-coated aggregates (2-step HT), and PGPT102, respectively. The relatively low initial Coulomb efficiencies may be due to the formation of the SEI layer, an irreversible process. The capacity contribution from SEI formation is more clearly observed in Figure 7e. Nevertheless, apart from f-NG, the Coulomb efficiencies of the electrodes increased rapidly, reaching over 99% by the third cycle (Table 7). As expected, the f-NG electrode exhibited the lowest initial Coulomb efficiency, which increased after aggregation. However, it remained lower than that of the PGPT102 electrode. Furthermore, the pitch coating only slightly reduced the irreversible capacity of the graphite aggregate particles. These unexpected results are likely due to the high surface area and microporosity / mesoporosity (Table 6) generated by the carbonization of CMC and citric acid in the spray-dried powder. Various reports have indicated that the properties of the initial graphite material affect the degree of pitch coating effectiveness. The minimal effect of pitch coating on the initial Coulomb efficiency suggests that 10 wt% pitch may not effectively coat the entire surface of the graphite aggregate particles, and therefore the pitch coating procedure may be further optimized.

[0164] As shown in Figures 7c and 7d, the PGPT102 electrodes exhibited the highest overall discharge capacity and capacity retention rates, respectively, throughout the 200-cycle test, while the graphite aggregate electrodes showed comparable behavior for the first approximately 100 cycles. Subsequently, a steady decrease in capacity was observed, which became steeper in the uncoated graphite aggregate electrodes, particularly after 150 cycles. This translated to slightly lower capacity retention rates for the uncoated graphite aggregate particles at the end of the test (calculated from the second cycle), compared to the one-step HT and two-step HT pitch-coated counterparts, at 94.4±2.2%, 95.1±0.4%, and 94.5±0.8%, respectively (Figure 7d). However, this trend appears to indicate better cycling stability for the pitch-coated electrodes.

[0165] Figure 7e shows the degree of performance loss for each material by comparing the discharge / charge curves for the first, 5th, 100th, and 200th cycles, and the differential capacitance plots for selected cycles shown in Figure 7f provide better insight into the capacitance degradation of the electrodes. In all electrodes, the potential at which the electrochemical processes occur changes over time as the cycle progresses, with the cathode peak experiencing a potential shift to a lower value, while the anode peak experiences a shift to a more positive potential. However, in the PGPT102 electrode, the change was minimal, as expected from its high cycling stability, whereas in the aggregated electrode, particularly in the uncoated graphite aggregates, the potential shift was larger. The increase in overpotential for all electrochemical reactions in the aggregated material is likely a result of decreased electrical conductivity within the electrode, while the decrease in capacitance suggests decay of the active site on the electrode. The continuous volume changes caused by the lithiation process can lead to the breakdown of aggregate particles and deterioration of contact between the graphite and the current collector. Initially, the pitch coating appeared to have little effect on electrochemical performance, but differential capacitance analysis revealed that it may play a long-term role in preserving the electrical conductivity of the electrodes by involving the volume expansion of aggregate particles. Furthermore, the cumulative irreversible capacitance plot shown in Figure 8 demonstrates the favorable effect of the pitch coating, which reduces the irreversible capacitance in each cycle, particularly in materials obtained by the one-step HT method, enabling more reversible intercalation comparable to that of commercially available graphite. This is a desirable effect not only in terms of electrochemical performance but also in terms of industrial manufacturability, considering that a single heat treatment in the manufacturing chain is transformed into a more efficient process overall. Table 7 compares the indices of merit extracted from Figure 8.

[0166] To rapidly evaluate the charging rate capabilities of graphite aggregates versus f-NG raw materials and commercially available PGPT102 graphite, electrochemical cycling tests were conducted using C rates ranging from C / 20 to 2C during the charging (delithiation) process, with the discharge C rate fixed at C / 10. The study presented in Figure 24 shows that the charging rate capability of graphite aggregates is equivalent to that of PGPT102, with slightly lower charging capacity from C / 20 to 1C, but similar capacity retention. The decrease in charging capacity is observed only at 2C, but this decay is very limited (approximately 2%). More importantly, the performance of the aggregates is superior to that of the raw materials, exhibiting significantly higher capabilities throughout the experiment.

[0167] [Table 7]

[0168] d) Post-event analysis To further investigate electrode degradation during cycling and the effects of pitch coating, a post-test analysis was performed on the aggregated electrode at the end of the 200-cycle test and compared with the electrode before cycling. Figures 9a, 9b, and 9c show top SEM images of the graphite aggregate electrode, pitch-coated graphite aggregate (1-step HT) electrode, and pitch-coated graphite aggregate (2-step HT) electrode before cycling, respectively. Images (a', b', c') show the top view of the corresponding electrode after 200 cycles, while (a'', b'', c'') feature the corresponding cross-sectional image of the cycled electrode. Insets of the top view images are high-magnification visualizations of the corresponding electrodes. Aggregate particles on the surface of electrodes that were flattened due to the calendering process but not cycled can be easily identified, as shown in the insets of Figures 9a, 9b, and 9c. However, after 200 cycles, the surface of the uncoated graphite aggregates did not show clear boundaries between aggregate particles due to the formation of the SEI layer and swelling of the particles on the electrode (Figure 9a'). Furthermore, higher magnification images (inset in Figure 9a') revealed numerous cracks on the SEI layer, which were caused by volume changes of the graphite aggregate particles during intercalation. Similarly, in the cross-sectional images of the cycled electrodes (Figure 9a"), the aggregate particles could not be distinguished; instead, a high-density structure with smooth regions was observed. In stark contrast, the cycled pitch-coated graphite (1-step HT and 2-step HT) aggregate electrodes (Figures 9b' and 9c', respectively) retained the characteristics they exhibited in their uncycled state. As shown in the insets of Figures 9b' and 9c', the aggregate particles remained well defined after 200 cycles, despite the presence of the SEI layer on the electrode surface. Furthermore, no apparent degradation of the SEI layer was observed. In a similar manner, the cross-sectional images of these electrodes (Figures 9b'' and 9c'') resembled those in their initial state (Figures 6c and 6d).As shown in Table 8, which compares mass and thickness (measured in the glove box) before and after cycling, electrodes fabricated with pitch-coated graphite, particularly those obtained through a single-step HT process, experienced a significantly smaller thickness increase (23%) after 200 cycles compared to uncoated graphite aggregate electrodes (36%). The remarkable difference between uncoated and pitch-coated graphite aggregate electrodes after cycling supports the effectiveness of the pitch coating as a protective layer by suppressing the volume expansion of graphite during lithium intercalation and stabilizing the SEI layer.

[0169] [Table 8]

[0170] The graphite fine powder, a by-product from the spheroidization of flaky natural graphite, can be recycled and repurposed using relatively simple and inexpensive methods such as spray drying and heat treatment, demonstrating the successful re-aggregation of fine graphite into graphite aggregate particles. Preliminary spray drying studies have shown that by fine-tuning the slurry composition and spray drying parameters, it is possible to obtain nearly spherical spray-dried re-aggregated graphite particles and graphite aggregate particles with a D50 comparable to commercially available battery-grade natural graphite. The resulting aggregates exhibited sufficient mechanical strength to withstand the calendering process, a standard step in the production of anodes for LIBs. Despite having a relatively large surface area due to the carbonization of the binder, the graphite aggregate particles yielded higher initial Coulombic efficiency compared to the raw material and exhibited cycling performance comparable to commercially available natural graphite for over 100 cycles. Surface modification of the aggregates by pitch coating further improved the electrochemical and mechanical properties of the material, particularly as reflected in the cumulative irreversible capacity and post-verification SEM images after 200 cycles. The favorable effect of pitch coating was more evident in the material obtained through a single heat treatment process. The reasons behind the different properties of the pitch-coated aggregate materials obtained through one and two heat treatment processes remain uninvestigated. Overall, the proposed strategy has the potential for successful recycling and reintegration of by-product graphite into the manufacturing chain anodes for LIBs, which could result in increased productivity and economic benefits for battery-grade natural graphite producers.

[0171] Example 3: Graphite aggregate particles containing CNTs - Experimental conditions and method a) Reagents Fine powdered natural graphite (f-NG) (carbon content = 99.7%, D) obtained as a by-product of spheroidization of purified natural flake graphite. 50Approximately 7 μm was used without further purification. Petroleum pitch (ZL250M) (RUETGERS Germany GmbH) was used without further purification. Carboxymethylcellulose sodium (average molecular weight M W Approximately 90,000 (degree of substitution = 0.7), lithium foil (1 mm thick, 99.9%), and battery-grade LP30 (LiPF6 solution in EC and DMC containing 1 M concentration of LiPF6 in EC / DMC (50 / 50, v / v)) were purchased from Sigma. Citric acid (over 99.5%) was purchased from Alfa Aesar. SBR (50% solid content) and Super C65 conductive carbon black were purchased from MTI Corporation. PGPT102 natural graphite (battery grade) was purchased from Targray. SWCNT dispersion (TUBALL® BATT H2O, 0.4% CNT, 0.6% CMC, 99% H2O) was purchased from OCSiAl.

[0172] b) Preparation of graphite aggregate particles containing CNTs by spray drying The method for re-aggregating the graphite fine powder was the same as that described in Example 1(b). The addition of CNTs to the graphite aggregate particles was achieved by directly adding a commercially available CNT dispersion to the feed material for spray drying. Considering the composition of the CNT dispersion, the slurry was designed to obtain aggregate particles with a CNT content of approximately 1% by weight.

[0173] The slurry for spray drying consisted of 78% by weight deionized water, 2% by weight CMC, 19.8% by weight graphite fine powder, and 0.2% by weight CNT. Therefore, the composition of the spray-dried powder was 90% by weight graphite fine powder, 0.91% by weight CNT, and 9.09% by weight CMC.

[0174] c) Heat treatment For the carbonization of the binder under an inert Ar (99.998%) flow, the spray-dried powder was heat-treated in a tubular furnace (Thermo Scientific™, Thermolyne™ F21125). The heat treatment profile included a heating gradient from room temperature to about 1100 °C (at a gradient of 2.00 °C / min), an isothermal heating at about 1100 °C for about 2 hours, and natural cooling to room temperature. The mass loss due to carbonization during the heat treatment was about 8.8%. Assuming that only CMC undergoes thermal decomposition, the composition of the resulting powder is approximately 98.7 wt% graphite, 1.0 wt% CNT, and 0.3 wt% amorphous carbon from the decomposition of CMC.

[0175] d) Alternative heat treatment for producing pitch-coated graphite aggregate particles containing CNT Alternatively, to obtain pitch-coated graphite aggregate particles containing CNT, the spray-dried powder described above was mixed with coal tar pitch at a mass ratio of 9:1 (graphite aggregate particles containing CNT: coal tar pitch) and subjected to the same heat treatment as described in Example 3d. Due to the thermal decomposition of both coal tar pitch and CMC binder, the mixture was subjected to a single heat treatment, and the total mass loss after heat treatment was about 11.6%. As a result, the composition of the obtained powder is about 91.6 wt% graphite, 0.9 wt% CNT, and 7.4 wt% amorphous carbon.

[0176] Example 4: Graphite Aggregate Particles Containing CNT - Characterization a) Physicochemical Characterization Figure 26 shows a top SEM image of graphite aggregate particles containing CNT, and Figure 27 shows a cross-sectional SEM image of the same material. CNT can be observed on the surface of the particles and inside the aggregates.

[0177] Figure 28 shows SEM images of (a) uncoated graphite aggregate particles containing CNTs and (b) pitch-coated graphite aggregate particles containing CNTs. Figure 28 demonstrates that the addition of pitch does not significantly alter the surface characteristics of the particles due to the thin nature of the pitch coating, and therefore the CNTs remain visible.

[0178] Figure 29 is a graph showing the PSD for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs.

[0179] b) Electrochemical properties Electrodes containing graphite aggregate particles with CNTs as the active material were prepared by the method described in Example 1(h). Swagelok® type cells equipped with these electrodes were assembled using the protocol described in Example 1(h). These cells were cycled using the protocol described in Example 1(i).

[0180] Figure 30 shows a graph of the discharge ratio capacity as a function of the number of cycles. Results are shown for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs. Figure 30 shows that the cycling stability of graphite aggregate particles was significantly improved by the addition of CNTs.

[0181] Figure 31 shows a graph of delithiation rate performance. It presents results for conventional PGPT102, graphite aggregate particles, pitch-coated graphite aggregate particles, graphite aggregate particles containing CNTs, and pitch-coated graphite aggregate particles containing CNTs. The rate performance test (Figure 31) shows a significant improvement, particularly at 4C, when CNTs were added (84% capacity retention compared to 64% with graphite alone). Furthermore, pitch-coated graphite aggregate particles containing CNTs achieved a capacity retention of 95%, demonstrating the best performance at 4C.

[0182] Example 5: Graphite-silicon composite aggregate particles containing and not containing CNTs - Experimental conditions and methods a) Reagents Fine powdered natural graphite (f-NG) (carbon content = 99.7%, D) obtained as a by-product of spheroidization of purified natural flake graphite. 50 Approximately 7 μm was used without further purification. Petroleum pitch (ZL250M) (RUETGERS Germany GmbH) was used without further purification. Carboxymethylcellulose sodium (average molecular weight M WApproximately 90,000 (degree of substitution = 0.7), potassium hydroxide (KOH) (85%), lithium foil (1 mm thick, 99.9%), battery-grade LP30 (LiPF6 solution in EC and DMC containing 1 M concentration of LiPF6 in EC / DMC (50 / 50, v / v)), and fluoroethylene carbonate (FEC) (99%) were purchased from Sigma. Citric acid (over 99.5%) was purchased from Alfa Aesar. SBR (50% solid content) and Super C65 conductive carbon black were purchased from MTI Corporation. PGPT102 natural graphite (battery grade) was purchased from Targray. Microsilicon powder (APS 1-5 microns, 99.9% (metal-based)) was purchased from Alfa Aesar, while nanosilicon powder (APS 50 nm, less than 97%) was purchased from Trunnano. I purchased a SWCNT dispersion (TUBALL® BATT H2O, 0.4% CNT, 0.6% CMC, 99% H2O) from OCSiAl.

[0183] b) Preparation of graphite-silicon composite aggregate particles by spray drying Aggregation of graphite fines and silicon was achieved by spray drying (Pilotech, Mini Spray Dryer YC-015) in a manner similar to that described in Example 1(b). The graphite content in the composition was adjusted to accommodate the incorporation of silicon fines into the mixture. The feedstock for spray drying was a slurry containing 72 wt% water, 4 wt% CMC, and 24 wt% graphite fines. The latter included selected mass ratios of graphite fines to silicon (micro and nano) powders (100:0, 95:5, 91:9, and 85:15), which were further used to evaluate the effects of silicon size and nanosilicon content on the cycle life of the material.

[0184] c) Preparation of spherical graphite-silicon composite aggregate particles containing CNTs Inclusion of 1% by weight of CNTs in graphite-silicon composite aggregate particles was carried out by spray drying. Similarly, slurries were designed considering the composition of the CNT dispersion to obtain composite aggregate particles having a content of 15% by weight of nanosilicon and 1% by weight of CNTs.

[0185] A slurry containing 78.0% by weight water, 2.0% by weight CMC, 16.8% by weight graphite powder, 3.0% by weight nanosilicon powder, and 0.2% by weight CNTs was spray-dried for the synthesis of spherical graphite-silicon composite aggregate particles containing CNTs. Therefore, the composition of the spray-dried powder was 76.5% by weight graphite powder, 13.6% by weight nanosilicon, 0.9% by weight CNTs, and 9.0% by weight CMC.

[0186] All slurries were mixed using a resonant acoustic mixer at an acceleration of approximately 50 G for approximately 30 minutes. The supply rate, inlet temperature, and air blow rate spray drying parameters were set to approximately 20.3 mL / min each. -1 Approximately 210°C, and approximately 2.5m 3 .minutes -1 I set it to that.

[0187] 2.4. Heat Treatment For binder carbonization under a flow of inert Ar (99.998%), the spray-dried powder was heat-treated in a tubular furnace (Thermo Scientific®, Thermolyne® F21125). The heat treatment profile included a heating gradient from room temperature to approximately 1100°C (2.00°C / min gradient), isothermal heating at approximately 1100°C for approximately 2 hours, and natural cooling to room temperature.

[0188] Assuming that only CMC undergoes thermal decomposition, the mass loss due to binder carbonization during heat treatment of CNT-free materials is approximately 11.5%, which accounts for approximately 80.5% of the CMC. As a result, the heat-treated powders contain approximately 3.1% by weight of residual carbon, with graphite content of 92.1% by weight, 88.1% by weight, and 82.3% by weight, corresponding to silicon content of 4.8% by weight, 8.8% by weight, and 14.6% by weight, and are hereafter referred to as G95Si5, G91Si9, and G85Si15, respectively.

[0189] Similarly, the mass loss of the graphite-silicon composite aggregate particles containing CNTs was approximately 9.7%, which accounted for approximately 87.7% of the CMC, resulting in a powder composition of 82.7% by weight of graphite, 14.8% by weight of silicon, and 1% by weight of CNTs.

[0190] The heat-treated powder was sieved using an ultrasonic sieve (GilSonic AutoSiever® Sonic Sifter, GA-6) with a stainless steel mesh having a 45 μm opening. The percentage of particles removed was less than 10% by weight.

[0191] Example 6: Characterization of graphite-silicon composite aggregate particles without CNTs a) Evaluation of physicochemical characteristics Figure 32 shows SEM images of a) raw graphite fine powder, b) microsilicon powder, c) nanosilicon powder, d) graphite aggregate particles, e) graphite-silicon composite aggregate particles (9% by weight of microsilicon), and f) graphite-silicon composite aggregate particles (9% by weight of nanosilicon).

[0192] Figure 33 shows graphs of a) XRD patterns and b) PSDs of raw graphite fine powder, microsilicon powder, nanosilicon powder, graphite aggregate particles, graphite-silicon composite aggregate particles (9% by weight of microsilicon), and graphite-silicon composite aggregate particles (9% by weight of nanosilicon).

[0193] b) Electrochemical properties Electrodes containing graphite-silicon composite aggregate particles without CNTs as the active material were prepared by the method described in Example 1(h). Swagelok® type cells equipped with these electrodes were assembled using the protocol described in Example 1(h). These cells were cycled using the protocol described in Example 1(i).

[0194] Figure 34 shows the short-term cycling performance of the composite material obtained by spray drying and the mixture of graphite fine powder and nanosilicon powder obtained by a resonant acoustic mixer in a). The rapid volume decline of the latter demonstrates that the silicon nanoparticles are not embedded in the graphite aggregates, which demonstrates the effectiveness of the spray drying technique for integrating silicon powder into graphite aggregates, as shown in Figure 32. The considerable volume decay observed over 50 cycles in the composite material containing microsilicon may be due to its significant volume expansion, which is in contrast to the moderate expansion of nanosilicon and is a well-known phenomenon that results in improved cycling stability.

[0195] Figure 34 shows the effect of different nanosilicon content in graphite aggregates in b). Compared to pure graphite, 5 wt% nanosilicon increased the capacity by approximately 23% with relatively good stability over 200 cycles, resulting in a loss of less than 10% of the capacity. However, 9 wt% nanosilicon increased the specific capacity by more than 60%, but most of it was lost at the end of 200 cycles. Furthermore, 15 wt% nanosilicon did not significantly improve either the specific capacity or the capacity retention rate. The results indicate that nanosilicon expansion is significant at 9 wt% and 15 wt% content. For this reason, the addition of CNTs was evaluated as a means to stabilize the nanosilicon expansion, preserve structural integrity, and / or maintain the electrical conductivity of the composite particles.

[0196] Example 7: Characterization of graphite-silicon composite aggregate particles containing CNTs a) Evaluation of physicochemical characteristics Figure 35 shows a) an SEM image of graphite-silicon composite aggregate particles containing CNTs, and b) a cross-section of a single graphite-silicon composite aggregate particle containing CNTs. CNTs can be observed on the surface of the particles (inset in Figure 35a). The cross-sectional image makes it possible to observe nanosilicon aggregates inside the aggregated composite particles. CNTs are not observed at this magnification, but in Example 4(a) (Figure 27), it was demonstrated that CNTs can also be found inside the aggregate particles.

[0197] Figure 36 shows graphs of a) XRD patterns of raw graphite fine powder, graphite nanosilicon composite aggregate particles without CNTs, nanosilicon powder, and graphite nanosilicon composite aggregate particles containing CNTs, and b) PSDs of raw graphite fine powder, graphite nanosilicon composite aggregate particles without CNTs (graphite:nanosilicon mass ratio (85:15)), and graphite nanosilicon composite aggregate particles containing CNTs (graphite:nanosilicon:CNT mass ratio (84:15:1)).

[0198] b) Electrochemical properties Electrodes containing graphite-silicon composite aggregate particles, with and without CNTs, as active materials were prepared by the method described in Example 1(h). Swagelok® type cells equipped with these electrodes were assembled using the protocol described in Example 1(h). These cells were cycled using the protocol described in Example 1(i).

[0199] Figure 37 shows a) a graph of the discharge ratio capacity as a function of the number of cycles, and b) a graph of the capacity retention rate as a function of the number of cycles for graphite aggregate particles, graphite nanosilicon composite aggregate particles without CNTs, and graphite nanosilicon composite aggregate particles with CNTs.

[0200] More specifically, this figure compares the cycling performance of graphite nanosilicon composite aggregate particles with and without CNTs. For reference, the cycling performance of graphite aggregate particles alone is shown. The tests show that CNTs delay and / or slow down the capacity decay of the graphite nanosilicon composite aggregate particles, resulting in a capacity retention rate of approximately 95% after 200 cycles, while that of the composite without CNTs dropped to 60% (Figure 37b).

[0201] Numerous modifications can be made to any of the embodiments described above without departing from the intended scope of the present invention. References, patents, or scientific documents referred to herein are incorporated herein by reference in their entirety for all purposes.

Claims

1. A method for producing graphite aggregate particles, wherein the method is i) A step of providing a graphite powder slurry comprising multiple graphite powders, a solvent, and a binder, ii) A step of spray-drying the graphite fine slurry to form spray-dried re-aggregated graphite particles, iii) A method comprising the step of heat-treating the spray-dried re-aggregated graphite particles to obtain graphite aggregate particles.

2. The method according to claim 1, wherein the binder is a polymer binder.

3. The method according to claim 1, wherein the polymer binder is selected from the group consisting of carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), polylactic acid (PLA), cellulose, chitin, starch, polycaprolactone (PCL), polyhydroxybutyrate (PHB), and at least two combinations thereof.

4. The method according to claim 3, wherein the polymer binder is carboxymethylcellulose (CMC).

5. The method according to any one of claims 1 to 4, wherein the solvent is selected from the group consisting of water, methanol, acetone, ethanol, dichloromethane, tetrahydrofuran, ethyl acetate, chloroform, glycerin, dimethylformamide, dimethyl sulfoxide, and at least two miscible combinations thereof.

6. The method according to claim 5, wherein the solvent is water.

7. The method according to any one of claims 1 to 6, wherein the mass ratio of graphite fine powder to the binder in the graphite fine powder slurry is about 4:1 to about 20:1 (including upper and lower limits).

8. The method according to claim 8, wherein the mass ratio of graphite fine powder to the binder in the graphite fine powder slurry is at least about 4:1, or at least about 5:1, or at least about 6:1, or at least about 7:

1.

9. The method according to claim 7 or 8, wherein the mass ratio of graphite fine powder to the binder in the graphite fine powder slurry is at most about 20:1, at most about 15:1, at most about 10:1, or at most about 8:

1.

10. The method according to any one of claims 7 to 9, wherein the mass ratio of graphite fine powder to the binder in the graphite fine powder slurry is about 6:

1.

11. The method according to any one of claims 1 to 10, wherein the graphite powder slurry contains about 14% to about 35% by weight (including upper and lower limits) of graphite powder.

12. The method according to claim 11, wherein the graphite powder slurry contains at least about 14% by weight, or at least about 18% by weight, or at least about 21% by weight, or at least about 24% by weight of graphite powder.

13. The method according to claim 11 or 12, wherein the graphite fine powder slurry contains at most about 35% by weight, at most about 33% by weight, at most about 30% by weight, or at most about 28% by weight of graphite fine powder.

14. The method according to any one of claims 11 to 13, wherein the graphite fine powder slurry contains about 24% by weight of graphite fine powder.

15. The method according to any one of claims 1 to 14, wherein the graphite fine powder in the graphite fine powder slurry is purified.

16. The method according to any one of claims 1 to 15, wherein the purity of the graphite fine powder is about 99.70% to about 99.99% (including upper and lower limits).

17. The method according to claim 16, wherein the purity of the graphite fine powder is at least about 99.70%, or at least about 99.8%, or at least about 99.90%, or at least about 99.95%.

18. The method according to claim 16 or 17, wherein the purity of the graphite fine powder is at most about 99.99% or at most about 99.95%.

19. The method according to any one of claims 16 to 18, wherein the purity of the graphite fine powder is about 99.95%.

20. Graphite fine powder D ５０ The method according to any one of claims 1 to 19, wherein the particle size is approximately 3 μm to approximately 10 μm (including upper and lower limits).

21. The graphite fine powder D ５０ The method according to claim 20, wherein the thickness is at least about 3 μm, or at least about 4 μm, or at least about 5 μm, or at least about 6 μm.

22. The graphite fine powder D ５０ The method according to claim 20 or 21, wherein the thickness is at most about 10 μm, or at most about 9 μm, or at most about 8 μm, or at most about 7 μm.

23. The graphite fine powder D ５０ The method according to any one of claims 20 to 22, wherein the thickness is approximately 7 μm.

24. The method according to any one of claims 1 to 23, wherein the graphite fine powder slurry contains about 0.7% to about 6.0% by weight (including upper and lower limits) of the binder.

25. The method according to claim 24, wherein the graphite fine slurry contains at least about 0.7% by weight, or at least about 1.4% by weight, or at least about 2.5% by weight, or at least about 3.0% by weight of the binder.

26. The method according to claim 24 or 25, wherein the graphite fine slurry contains at most about 6.0% by weight, at most about 5.0% by weight, at most about 4.5% by weight, or at most about 4.0% by weight of the binder.

27. The method according to any one of claims 24 to 26, wherein the graphite fine slurry contains about 4.0% by weight of the binder.

28. The method according to any one of claims 1 to 27, wherein the graphite fine powder slurry further comprises a crosslinking agent.

29. The method according to claim 28, wherein the crosslinking agent is an organic crosslinking agent or an inorganic crosslinking agent.

30. The method according to claim 29, wherein the crosslinking agent is an organic crosslinking agent.

31. The method according to any one of claims 28 to 30, wherein the crosslinking agent is selected from the group consisting of citric acid, formic acid, acetic acid, oxalic acid, and at least two combinations thereof.

32. The method according to claim 31, wherein the crosslinking agent is citric acid.

33. The method according to any one of claims 28 to 32, wherein the graphite fine powder slurry contains about 0.5% to about 4.0% by weight (including upper and lower limits) of the crosslinking agent.

34. The method according to claim 33, wherein the graphite fine powder slurry contains at least about 0.5% by weight, or at least about 1.0% by weight, or at least about 1.5% by weight, or at least about 2.0% by weight of the crosslinking agent.

35. The method according to claim 32 or 34, wherein the graphite fine powder slurry contains at most about 4% by weight, at most about 3.5% by weight, at most about 3.0% by weight, or at most about 2.5% by weight of the crosslinking agent.

36. The method according to any one of claims 32 to 35, wherein the graphite fine powder slurry contains about 3.0% by weight of the crosslinking agent.

37. The method according to any one of claims 1 to 36, wherein the graphite fine slurry contains the solvent in an amount of about 58% to about 83% by weight (including upper and lower limits).

38. The method according to claim 37, wherein the graphite fine slurry contains at least about 53% by weight, or at least about 58% by weight, or at least about 62% by weight, or at least about 66% by weight, and / or at most about 83 w / w%, at most about 80 w / w%, at most about 72 w / w%, or at most about 69 w / w% of the solvent.

39. The method according to claim 37 or 38, wherein the graphite fine slurry contains at least about 83% by weight, at least about 80% by weight, at least about 72% by weight, or at least about 69% by weight of the solvent.

40. The method according to any one of claims 37 to 39, wherein the graphite fine slurry contains about 69% by weight of the solvent.

41. The method according to any one of claims 28 to 40, wherein the graphite fine slurry comprises about 24% by weight of graphite fine, about 4.0% by weight of the binder, about 3.0% by weight of the crosslinking agent, and about 69% by weight of the solvent.

42. The method according to any one of claims 1 to 41, wherein providing the graphite fine slurry comprises preparing the graphite fine slurry.

43. The method according to claim 42, wherein the graphite fine slurry is prepared by combining the graphite fine, the binder, optionally the crosslinking agent, and the solvent, and then mixing the components together.

44. The method according to claim 43, wherein the graphite fine powder slurry is mixed by a resonant acoustic mixer.

45. The method according to claim 44, wherein the graphite fine slurry is mixed at an acceleration of 50 G for about 30 minutes.

46. The method according to any one of claims 1 to 45, wherein the graphite fine slurry further comprises silicon particles.

47. The D of the silicon particles in the graphite fine powder slurry ５０ The method according to claim 46, wherein the range is approximately 50 nm to approximately 5 μm (including upper and lower limits).

48. The method according to claim 46 or 47, wherein the content of silicon particles in the graphite fine powder slurry is about 0.42% by weight to about 11.55% by weight (including upper and lower limits).

49. The method according to any one of claims 1 to 48, wherein the graphite fine slurry further comprises an additive selected from carbon black, graphite, graphene, carbon fibers, carbon nanotubes, and at least two combinations thereof.

50. The method according to claim 49, wherein the additive is a carbon nanotube.

51. The method according to claim 50, wherein the carbon nanotube is a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof.

52. The method according to any one of claims 49 to 51, wherein the graphite fine powder slurry contains about 0.1% to about 3% by weight (including upper and lower limits) of carbon nanotubes.

53. The supply rate for the aforementioned spray drying is approximately 10 mL / min. －１ ~Approx. 22mL. minutes －１ The method according to any one of claims 1 to 52, including upper and lower limits.

54. The supply rate before the spray drying is at least about 10 mL / min －１ or at least about 12 mL / min －１ or at least about 14 mL / min －１ or at least about 16 mL / min －１ The method according to claim 53, wherein the supply rate is as above.

55. The supply rate for the spray drying is at most about 22 mL / min. －１ or at most about 21 mL. －１ or at most about 20 mL. －１ or at most about 18 mL. －１ The method according to claim 53 or 54.

56. The supply rate for the spray drying is approximately 20.3 mL / min. －１ The method according to any one of claims 53 to 55.

57. The method according to any one of claims 1 to 56, wherein the inlet temperature during the spray drying step is approximately 190°C to approximately 220°C (including upper and lower limits).

58. The method according to claim 57, wherein the inlet temperature during the spray drying step is at least about 190°C or at least about 200°C.

59. The method according to claim 57 or 58, wherein the inlet temperature during the spray drying step is at most about 220°C or at most about 210°C.

60. The method according to any one of claims 57 to 59, wherein the inlet temperature during the spray drying process is approximately 210°C.

61. The air blow speed during the aforementioned spray drying process is approximately 2.0 m ３ .. minutes －１ ~about 2.5m ３ .. minutes －１ The method according to any one of claims 1 to 60, including upper and lower limits.

62. The method according to any one of claims 1 to 61, wherein the spray-dried re-aggregated graphite particles are heat-treated in the presence of a carbon precursor to obtain carbon-coated graphite aggregate particles.

63. The method according to claim 62, wherein the carbon precursor is selected from petroleum pitch, coal tar pitch, biomass pitch, at least two combinations thereof, and any similar material.

64. The method according to claim 63, wherein the carbon precursor is coal tar pitch.

65. The method according to any one of claims 1 to 64, wherein the heat treatment step includes heating the spray-dried re-aggregated graphite particles at a temperature of about 550°C to about 1300°C (including upper and lower limits).

66. The method according to claim 65, wherein the spray-dried re-aggregated graphite particles are heated to a temperature of at least about 550°C, or at least about 600°C, or at least about 700°C, or at least about 750°C.

67. The method according to claim 65 or 66, wherein the spray-dried re-aggregated graphite particles are heated at a temperature of at most about 1300°C, at most about 1100°C, at most about 1000°C, or at most about 900°C.

68. The method according to any one of claims 65 to 67, wherein the spray-dried re-aggregated graphite particles are heated at a temperature of about 1000°C.

69. The method according to any one of claims 1 to 68, wherein the spray-dried re-aggregated graphite particles formed in step (ii) are mixed with a carbon precursor, and subsequently a heat treatment step is performed for the thermal decomposition of the carbon precursor.

70. The method according to claim 69, wherein the carbon precursor is coal tar pitch.

71. The method according to claim 69 or 70, wherein the mass ratio of the spray-dried re-aggregated graphite particles to the carbon precursor is about 9:

1.

72. The method according to any one of claims 69 to 71, wherein the mixing step is carried out by a resonant acoustic mixer.

73. The method according to claim 72, wherein the mixing step is performed at an acceleration of 50G for about 15 minutes.

74. The method according to any one of claims 69 to 73, wherein the spray-dried re-aggregated graphite particles and the carbon precursor are mixed together using wet mixing or dry mixing.

75. The method according to any one of claims 69 to 74, wherein the amount of carbon precursor in the mixture containing the spray-dried re-aggregated graphite particles and the carbon precursor is about 5% by weight to about 30% by weight (including upper and lower limits).

76. The method according to claim 75, wherein the amount of the carbon precursor in the mixture is at least about 5% by weight, or at least about 10% by weight, or at least about 15% by weight.

77. The method according to claim 75 or 76, wherein the amount of the carbon precursor in the mixture is at most about 30% by weight, at most about 25% by weight, or at most about 20% by weight.

78. The method according to any one of claims 75 to 77, wherein the amount of the carbon precursor in the mixture is about 10% by weight.

79. The method according to any one of claims 69 to 78, wherein the thermal decomposition of the carbon precursor and the binder is carried out in a single-step heat treatment.

80. The method according to claim 79, wherein the heat treatment is carried out as two sub-steps, the spray-dried re-aggregated graphite particles are first heat-treated to form graphite aggregate particles, the graphite aggregate particles are then mixed with the carbon precursor, and subsequently a second heat treatment for carbon coating is performed.

81. The method according to any one of claims 1 to 80, wherein the heat treatment further comprises subjecting the spray-dried re-aggregated graphite particles to a high-temperature heat treatment carried out at a temperature of about 2000°C to about 3000°C (including upper and lower limits).

82. Graphite aggregate particles manufactured using a method defined in any one of claims 1 to 81.

83. The graphite aggregate particles according to claim 82, wherein the graphite aggregate particles are spherical particles or substantially spherical particles.

84. D of the graphite aggregate particles ５０ The graphite aggregate particles according to claim 82 or 83, wherein the particle size is approximately 18 μm to approximately 21 μm (including upper and lower limits).

85. The graphite aggregate particles ５０ The graphite aggregate particles according to claim 82 or 83, wherein the particle size is approximately 20 μm to approximately 24 μm (including upper and lower limits).

86. The graphite aggregate particles ５０ The graphite aggregate particles according to claim 82 or 83, wherein the particle size is approximately 13 μm to approximately 17 μm (including upper and lower limits).

87. The graphite aggregate particles according to any one of claims 82 to 86, wherein the graphite aggregate particles are carbon-coated graphite aggregate particles.

88. The graphite aggregate particles according to any one of claims 82 to 87, wherein the graphite aggregate particles are pitch-coated graphite aggregate particles.

89. Graphite aggregate particles according to any one of claims 82 to 88, further comprising silicon.

90. The graphite aggregate particles according to claim 89, wherein the graphite aggregate particles contain more than 0% by weight of silicon.

91. The graphite aggregate particles according to claim 90, wherein the graphite aggregate particles contain at least about 3% by weight of silicon.

92. The graphite aggregate particles according to claim 90 or 91, wherein the graphite aggregate particles contain at most about 50% by weight, or at most about 33% by weight, of silicon.

93. An electrode material comprising graphite aggregate particles as defined in any one of claims 82 to 92.

94. The electrode material according to claim 93, further comprising an electrically conductive material.

95. The electrode material according to claim 94, wherein the electrically conductive material is selected from carbon black, graphite, graphene, carbon fiber, carbon nanotubes, and at least two combinations thereof.

96. The electrode material according to claim 95, wherein the electrically conductive material is carbon black, carbon nanotubes, or a combination thereof.

97. The electrode material according to claim 96, wherein the carbon nanotube is a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof.

98. The electrode material according to any one of claims 93 to 97, further comprising at least one additive.

99. The electrode material according to any one of claims 93 to 98, further comprising at least one binder.

100. The electrode material according to claim 99, wherein the binder is selected from a polyether-type polymer binder, a polycarbonate-type polymer binder, a polyester-type polymer binder, a fluorinated polymer, and a water-soluble binder.

101. An electrode comprising an electrode material defined in any one of claims 93 to 100, applied to a current collector.

102. The electrode according to claim 101, wherein the current collector is a copper foil.

103. The electrode according to claim 101 or 102, wherein the electrode is calendered.

104. The electrode according to any one of claims 101 to 103, wherein the electrode is an anode.

105. An electrochemical cell comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and the cathode comprises an electrode material as defined in any one of claims 93 to 100.

106. An electrochemical cell comprising an anode, a cathode, and an electrolyte, wherein at least one of the anode and the cathode is an electrode as defined in any one of claims 101 to 103.

107. An electrochemical battery comprising at least one electrochemical cell as defined in claim 105 or 106.

108. The electrochemical battery according to claim 107, wherein the electrochemical battery is a battery selected from lithium batteries, lithium-ion batteries, sodium batteries, sodium-ion batteries, magnesium batteries, and magnesium-ion batteries.

109. The electrochemical battery according to claim 107 or 108, wherein the electrochemical battery is a lithium-ion battery.

110. A method for producing graphene aggregate particles, i) A step of providing a graphene fine powder slurry comprising multiple graphene fine powders, a solvent, and a polymer binder, ii) A step of spray-drying the graphene fine powder slurry to form spray-dried re-aggregated graphene particles, iii) A method comprising the step of heat-treating the spray-dried re-aggregated graphene particles to obtain graphene aggregate particles.

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