Graphite from sustainable sources and methods for making same - Patents.com

Abstract

Graphite prepared from raw materials of renewable or sustainable sources, methods for making them, and batteries containing them.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 399,047, filed August 18, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Demand for lithium-ion battery materials is expected to increase significantly over the next decade, primarily due to the expected increase in demand for electric vehicles. Meeting that demand will require not only scaling up current materials production methods, but also developing new ways to produce these materials.

[0003] Graphite is the most common anode material in lithium-ion batteries. There are two types of graphite: synthetic and natural. Synthetic graphite is traditionally produced by graphitizing petroleum coke, while natural graphite is mined and then refined using various processes. There is a need in the art for a process that can efficiently prepare graphite from renewable, recyclable, or sustainable resources. Summary of the Invention

[0004] Most carbonaceous materials processed at high temperatures without a catalyst simply carbonize to form disordered amorphous carbon materials, ordered soft carbon materials with cross-linked domains, or ordered soft carbon materials with graphitic domains. See Sagues, et al., “A simple method for producing bio-based anode materials for lithium-ion batteries,” Green Chem., 2020, 22, 7093. The present inventors have surprisingly discovered a method for graphitizing feedstocks derived from renewable and sustainable sources without the use of coke, calcination, or graphitization catalysts.

[0005] One embodiment of a non-catalytic graphitization process includes: (a) providing a feedstock comprising at least one aromatic compound, wherein the feedstock is derived from a sustainable or renewable source; (b) coking the feedstock at a temperature ranging from 300°C to 650°C to obtain a coke; (c) calcining the coke at a temperature ranging from 900°C to 1500°C to obtain a calcined coke; and (d) graphitizing the calcined coke at a temperature ranging from 2200°C to 3200°C.

[0006] Also described is graphite prepared by the disclosed non-catalytic graphitization method. 002 ) interlayer spacing and the c-axis direction (L c ) crystallite size independent of the graphitization method disclosed.

[0007] Also described is a lithium-ion battery having an anode containing graphite prepared by the disclosed graphitization method, or an anode having the above properties regardless of how the material is graphitized, along with a cathode and an electrolyte disposed between the anode and cathode.

[0008] The foregoing summary, as well as the following description of the present disclosure, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present disclosure, the drawings illustrate some, but not all, alternative embodiments. The disclosure is not limited to the precise arrangements and instrumentalities shown. The following figures, which are incorporated in and constitute a part of this specification, help to explain the principles of the present disclosure. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a plot illustrating the graphitization process from a feedstock that was residue from a biomass pyrolysis process. [Figure 2] 1 shows an overlaid powder X-ray diffraction pattern of bio-graphite compared to a pattern from Birla Carbon's synthetic graphite, BCG18. [Figure 3] 1 shows a photograph of one embodiment of crushed bio-graphite prepared according to the method of the present disclosure. [Figure 4] 1 shows a particle size distribution graph of one embodiment of bio-graphite. [Figure 5] Electrochemical data obtained from a cell utilizing bio-graphite as part of the anode material is shown. [Figure 6] A plot of voltage versus specific capacity shows that the bio-graphite exhibited the expected lithium intercalation chemistry of typical graphite. See, e.g., Allart et al., “Model of Lithium Intercalation into Graphite by Potentiometric Analysis with Equilibrium and Entropy Change Curves of Graphite Electrode,” Journal of the Electrochemical Society, 165 (2) A380-A387 (2018). [Figure 7] Electrochemical data from an NMC532 full cell (coin cell) constructed with bio-graphite is shown. [Figure 8] We present additional data collected from an NMC532 bio-graphite full-cell coin cell, showing impressive rate performance with 70.8% capacity retention at 2 °C. [Figure 9] 1 is a plot showing the results of further electrochemical testing of an NMC811 full cell, showing a first cycle coulombic efficiency of 78.5%. A reference non-bio-graphite-based cell is shown to the right of the plot. DETAILED DESCRIPTION OF THE INVENTION

[0010] In one embodiment, a method for producing graphite includes obtaining a feedstock comprising at least one aromatic compound, wherein the feedstock is derived from a sustainable or renewable source, coking the feedstock at a temperature ranging from 300° C. to 650° C. to obtain coke, calcining the coke at a temperature ranging from 900° C. to 1500° C. to obtain calcined coke, and graphitizing the calcined coke at a temperature ranging from 2200° C. to 3200° C. The process in some embodiments does not involve the use of a catalyst in any portion of the process, including the calcination and graphitization steps.

[0011] "Sustainable or renewable sources" refers to resources that are persistent or renewable, e.g., that can be replenished, recycled, etc., naturally or otherwise, and will not eventually be completely depleted. Examples include biomass, biomass-derived oils, and manufacturing materials such as plastics, among others.

[0012] In one embodiment, the coking step can be carried out at a temperature ranging from 300°C to 650°C to obtain coke. In a further embodiment, the coking step can be carried out at a temperature ranging from 400°C to 600°C. In a further embodiment, the coking step can be carried out at a temperature ranging from 450°C to 500°C. In a further embodiment, the coking step can be carried out at a temperature of about 500°C. When the word "about" precedes a numerical value herein and elsewhere in this application, the value can vary by plus or minus 10%, unless otherwise specified. In one particular embodiment, the coking step can be carried out at a temperature of about 500°C for about 5 hours in an inert atmosphere, such as nitrogen. As discussed above, the coking step can be carried out without the use of any catalyst, including an aromatization catalyst.

[0013] Coke can generally be calcined at a temperature ranging from 900°C to 1500°C to obtain calcined coke. In one embodiment, the coke can be calcined at a temperature ranging from 1000°C to 1400°C. In a further embodiment, the coke can be calcined at a temperature ranging from 1100°C to 1300°C. In a further embodiment, the coke can be calcined at a temperature of about 1200°C in a furnace under an inert gas, such as nitrogen. As discussed above, the calcination step can be carried out without the use of any catalyst, including an aromatization catalyst.

[0014] Calcined coke can generally be graphitized at a temperature ranging from 2200°C to 3200°C. In one embodiment, calcined coke can be graphitized at a temperature ranging from 2300°C to 3100°C. In a further embodiment, calcined coke can be graphitized at a temperature ranging from 2400°C to 3000°C. In a further embodiment, calcined coke can be graphitized at a temperature ranging from 2500°C to 2900°C. In a further embodiment, calcined coke can be graphitized at a temperature ranging from 2600°C to 2800°C. In a further embodiment, calcined coke can be graphitized at a temperature of about 2700°C in a furnace under an inert atmosphere, such as helium.

[0015] In one aspect, the feedstock comprises a residual oil remaining from a process comprising pyrolyzing biomass and recovering at least one of the aromatic fractions of the pyrolyzed biomass: benzene, toluene, or xylenes. The oil or bio-oil, in one aspect, can be derived by subjecting a biomass feedstream to a cracking catalyst to obtain a hydrocarbon vapor fraction. The vapor fraction can be separated from other oxygen-containing organic compounds and the cracking catalyst, and then the vapor fraction can be converted to products containing aromatic compounds using an aromatization catalyst, such as a zeolite catalyst. The desired aromatic compounds can then be removed, leaving a bio-oil residue. This bio-oil residue can, in some aspects, be a feedstock for the disclosed graphitization method. It should be understood that while the feedstock can be catalytically pyrolyzed or aromatized, embodiments of the method for graphitizing the feedstock do not involve the use of any catalyst.

[0016] A biomass pyrolysis process for preparing and recovering aromatic compounds, particularly benzene, toluene, and xylenes, is further described in U.S. Patent Publication No. 2017 / 0247617 A1 by Schenk et al. A similar plastic pyrolysis process for preparing similar aromatic compounds is described in U.S. Patent Publication No. 2022 / 0195310 A1 by Schenk et al. Both the '617 and '310 patent publications are incorporated by reference in their entireties into this application as they teach pyrolysis processes that leave bio-oil or other residues suitable for use as sustainable or renewable feedstocks for the disclosed graphitization processes.

[0017] As further understood with reference to the '617 application, in some embodiments, the biomass for the pyrolysis process can be lignocellulosic biomass, such as plants or wood, including softwoods such as pine. In further embodiments, the biomass for the pyrolysis process can include agricultural waste, plants, wood, or combinations thereof.

[0018] The present inventors have surprisingly discovered that bio-oil derived from the residue remaining from the biomass pyrolysis process described above results in a bio-oil having a degree of aromaticity and character such that no catalyst (e.g., aromatization catalyst) is needed to further aromatize the bio-oil feedstock or otherwise catalyze either the calcination or graphitization steps. In some embodiments, the at least one aromatic compound in the feedstock constitutes at least 60 wt.% of the feedstock, e.g., at least 65 wt.%, at least 70 wt.%, at least 75 wt.%, at least 80 wt.%, at least 85 wt.%, at least 90 wt.%, or at least 95 wt.% or more of the amount of the feedstock is one or more aromatic compounds.

[0019] In one embodiment, the feedstock comprises at least one of xylene, toluene, o-xylene, trimethylbenzene, benzene, naphthalene, ethylbenzene, or indene. In a further embodiment, the feedstock comprises one or more of xylene, toluene, or benzene. In yet a further embodiment, the feedstock comprises xylene, toluene, and benzene. In another embodiment, the feedstock comprises at least one of xylene, toluene, o-xylene, trimethylbenzene, benzene, naphthalene, ethylbenzene, or indene, with xylene present in the feedstock in amounts up to 80% by weight of the feedstock, toluene up to 80% by weight, o-xylene up to 25% by weight, trimethylbenzene up to 25% by weight, benzene up to 80% by weight, naphthalene up to 25% by weight, ethylbenzene up to 25% by weight, and indene up to 5% by weight. The feedstock may also comprise other aromatic or non-aromatic compounds. In one embodiment, the feedstock is a liquid or oil at 25°C.

[0020] In one aspect, the feedstock is anthracene-free. In another aspect, the feedstock is methylated anthracene-free. In a further aspect, the feedstock is aromatic oxygen-free. In a further aspect, the coke prepared from the feedstock is anthracene-free. In another aspect, the coke prepared from the feedstock is methylated anthracene-free. In a further aspect, the coke prepared from the feedstock is aromatic oxygen-free. In another aspect, the calcined coke is anthracene-free. In a further aspect, the calcined coke is methylated anthracene-free. In a further aspect, the calcined coke is aromatic oxygen-free. In some aspects, these aromatic species can be formed in conventional graphitization processes utilizing certain aromatization catalysts.

[0021] Also disclosed is graphite prepared by any of the disclosed methods. In one aspect, the graphite is "biographite," which refers to graphite derived from carbon of biological origin, such as biomass. In one aspect, the graphite prepared by the graphitization method has a 002 plane (d 002) interlayer spacing and the c-axis direction (L c In a further embodiment, the graphite prepared by the graphitization method has a charge capacity greater than 315 mAh / g, e.g., greater than 320 mAh / g, greater than 325 mAh / g, or greater than 330 mAh / g.

[0022] Also disclosed is a lithium-ion battery (LiB) having an anode comprising graphite produced by the disclosed graphitization method, a cathode, and an electrolyte disposed between the anode and the cathode. In one embodiment, the electrolyte comprises a vinylene carbonate additive. In a further embodiment, the LiB can achieve a first cycle coulombic efficiency of at least 90% with a charge capacity greater than 330 mAh / g.

[0023] Also disclosed is graphite derived from sustainable or renewable sources, independent of any disclosed graphitization method, the graphite having a 002 plane (d 002 ) interlayer spacing and the c-axis direction (L c ) crystallite size. In one embodiment, the graphite has a charge capacity greater than 315 mAh / g. In a further embodiment, the graphite is derived from biomass. In a further embodiment, the graphite is derived from lignocellulosic biomass. Also disclosed is a lithium-ion battery (LiB) having an anode comprising graphite derived from sustainable or renewable feedstocks and having a c-axis interlayer spacing and crystallite size, a cathode, and an electrolyte disposed between the anode and cathode. In one embodiment, the electrolyte includes a vinylene carbonate additive.

[0024] A. Working Example The following examples further illustrate the present disclosure. The scope of the present disclosure and claims are not limited by the scope of the following examples.

[0025] Residual oil from a biomass pyrolysis process, which is a liquid oil at room temperature and contains a mixture of aromatic compounds including one or more of xylene, toluene, o-xylene, trimethylbenzene, benzene, naphthalene, ethylbenzene, and indene, was first coked in a ceramic boat in a tube furnace at 500°C for 5 hours under nitrogen. The resulting coke was calcined at 1200°C under nitrogen in the furnace. The calcined coke was graphitized at 2700°C under helium in the furnace to prepare bio-graphite.

[0026] Graphitization of the coke was evidenced from the x-ray diffraction data shown in Figure 1. The yields from calcination and graphitization are shown in Table 1. The (002) d-spacing and L c Data are presented in Table 2 with reference to BCG 18, a synthetic graphite produced by Birla Carbon (Marietta, GA, USA). [Table 1] [Table 2]

[0027] The powder x-ray diffraction pattern of the bio-graphite compared to the pattern from Birla's BCG18 is shown in Figure 2. A photograph of the crushed bio-graphite is shown in Figure 3. The particle size of the bio-graphite was similar to that of typical battery-grade graphite. A particle size distribution graph is shown in Figure 4. Particle size distribution data, along with specific capacity and first cycle coulombic efficiency data achieved with the bio-graphite in electrochemical half-cells, are shown in Table 3. [Table 3]

[0028] As shown in Table 3, bio-graphite from biomass pyrolysis residue achieved a capacity of 332 mAh / g and a first-cycle coulombic efficiency of 90.3%. Additional electrochemical data are shown in Figure 5. In comparison, bio-graphite produced using catalytic graphitization achieved a specific capacity of 335 mAh / g but a first-cycle coulombic efficiency of only 68.5%. Carbon coating the catalytically produced bio-graphite improved the first-cycle coulombic efficiency to 87.9% but reduced the specific capacity to 301 mAh / g. The relatively low first-cycle coulombic efficiency of uncoated bio-graphite is most likely due to the relatively small particle size to which the material was milled. This property was significantly improved by increasing the particle size using a carbon coating, but it could alternatively be assumed that the graphite had a DV of 10-20 microns without the carbon coating. 50 This can be achieved by optimizing the grinding parameters. Carbon coating is primarily done to increase electrical conductivity, but coulombic efficiency benefits may also result from increasing particle size. In general, the specific capacitance should increase as the temperature at which the bio-calcined coke is graphitized increases. The degree of graphitization and specific capacitance are directly correlated.

[0029] Bio-graphite prepared according to one embodiment of the disclosed method exhibited the expected lithium intercalation chemistry of graphite typically used in lithium batteries, as shown in FIG.

[0030] NMC532 full cells (coin cells) were constructed using bio-graphite, and the electrochemical data from these cells is shown in Figure 7. The NMC532 bio-graphite full-cell coin cells exhibited impressive rate capability with a capacity retention of 70.8% at 2 °C, as shown in Figure 8. Further electrochemical testing showed that bio-graphite performed well as an anode material, as shown in Figure 9. It is believed that the performance of bio-graphite as an anode material can be further improved by using an electrolyte containing vinylene carbonate as an additive.

[0031] The features and advantages of the present disclosure are apparent from the detailed description, and the appended claims cover all such features and advantages. Many variations will occur to those skilled in the art, and any variations equivalent to those described in this disclosure fall within the scope of the present disclosure. Those skilled in the art will appreciate that the concepts on which the present disclosure is based may be used as a basis for designing other methods and systems for carrying out some of the purposes of the present disclosure. Consequently, the scope of the claims should not be considered limited by the description or examples.

Claims

1. 1. A method for producing graphite, comprising: a) providing a feedstock comprising at least one aromatic compound, wherein the feedstock is derived from a sustainable or renewable source; b) coking the feedstock at a temperature in the range of 300°C to 650°C to obtain coke; c) calcining the coke at a temperature in the range of 900°C to 1500°C to obtain calcined coke; d) graphitizing the calcined coke at a temperature in the range of 2200°C to 3200°C; The method does not involve the use of a calcination catalyst or a graphitization catalyst.

2. 10. The method of claim 1, wherein the feedstock comprises bottoms remaining from a process comprising pyrolyzing biomass and recovering at least one of benzene, toluene, or xylenes from an aromatized fraction thereof.

3. The method of claim 2 , wherein the biomass is lignocellulosic biomass.

4. 4. The method of claim 2 or 3, wherein the biomass comprises agricultural waste, plants, wood, or a combination thereof.

5. The method according to any one of claims 1 to 4, wherein the raw material does not contain anthracene.

6. The method according to any one of claims 1 to 5, wherein the raw material does not contain methylated anthracene.

7. The method of any one of claims 1 to 6, wherein the feedstock is free of aromatic oxygenates.

8. The method of any of claims 1 to 7, wherein said at least one aromatic compound comprises at least 60 wt% of said feedstock.

9. The method of any one of claims 1 to 8, wherein the feedstock comprises at least one of xylene, toluene, o-xylene, trimethylbenzene, benzene, naphthalene, ethylbenzene, or indene.

10. The method according to any one of claims 1 to 9, wherein the raw material is a liquid or oil at 25°C.

11. Graphite prepared by the method according to any one of claims 1 to 10.

12. A lithium ion battery (LiB) comprising an anode comprising the graphite of any one of claims 1 to 11, a cathode, and an electrolyte disposed between the anode and the cathode.

13. 13. The battery of claim 12, wherein the electrolyte comprises a vinylene carbonate additive.

14. Graphite derived from sustainable or renewable sources, having a 002 plane (d 002 ) interlayer spacing and a c-axis direction (L c ) Graphite, characterized by its crystal size.

15. 15. The graphite of claim 14 having a charge capacity greater than 315 mAh / g.

16. Graphite according to claim 14 or 15, derived from biomass.

17. 17. The graphite of claim 16, derived from lignocellulosic biomass.

18. A lithium-ion battery (LiB) comprising an anode comprising the graphite of any one of claims 14 to 17, a cathode, and an electrolyte disposed between the anode and the cathode.

19. 20. The battery of claim 18, wherein the electrolyte comprises a vinylene carbonate additive.

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