Claims:1. A battery (100) comprising:
a cathode (102);
an anode (104), wherein the anode (104) and the cathode (102) disposed on opposite sides of a separator (106) are soaked with an electrolyte (108), wherein the anode is a carbonized synthetic anode made from demineralized coal material.
2. The battery (100) as claimed in the claim 1, wherein the demineralized coal material is selected from any one of low-ash clean coal or ultra-low ash clean coal.
3. A method (300) of preparing the synthetic anode material from demineralized coal material as claimed in the claim 1, the method (300) comprising:
mixing the demineralized coal with a catalyst to obtain an admixture;
pyrolyzing the admixture at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product; and
grinding or pulverizing the pyrolysis product to obtain a prefinal product which is sieved to obtain a final product having predetermined size.
4. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 3, wherein the demineralized coal is selected from any one of low-ash clean coal or ultra-low ash clean coal.
5. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 3, wherein the catalyst is selected from any one of coal tar pitch and iron acetate.
6. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 5, wherein the catalyst is mixed with demineralized coal at 0.1%.
7. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 3, wherein the admixture is pyrolyzed at the first predetermined temperature in the range of 900°C – 1300°C for the first predetermined time in the range of 1 to 3 hours.
8. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 7, wherein the admixture is pyrolyzed at the first predetermined temperature of 900°C for the first predetermined time of 3 hours.
9. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 7, wherein the admixture is pyrolyzed at the first predetermined temperature of 900°C-1300°C at a rate of 2°C/min to 5°C/min.
10. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 9, wherein the admixture is pyrolyzed at the first predetermined temperature of 900°C at a rate of 2°C/min.
11. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 9, wherein the admixture is pyrolyzed at the first predetermined temperature of 900°C at a rate of 5°C/min.
12. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 3, wherein the admixture is pyrolyzed in a nitrogen gas atmosphere.
13. The method (300) of preparing the synthetic anode material from demineralized coal as claimed in the claim 12, wherein the nitrogen gas atmosphere has a flow rate of 2-3 ml/min.
14. A method (400) of preparing the low-ash clean coal as claimed in claim 4, wherein the low-ash clean coal is prepared from high-ash coal waste, the method (400) comprising:
mixing high-ash coal waste with water in 1:1 ratio to obtain an admixture;
grinding the admixture in a planetary ball mill for a time duration of 30-45 minutes at 300-350 rpm to obtain ultrafine size coal-water slurry;
mixing the ultrafine size coal-water slurry with water in 1:1 ratio to obtain a dilute coal-water slurry, wherein the ultrafine size coal-water slurry is mixed with water to lower the pulp density;
separating via a centrifuge the dilute coal-water slurry to obtain a soft layer of coal, wherein the centrifuge is rotated at 10,000 rpm for 3 minutes; and
collecting the soft layer of coal to obtain the low-ash clean coal.
15. The method (400) of preparing the low-ash clean coal from high-ash coal waste as claimed in the claim 14, wherein grinding of the admixture in the planetary ball mill is performed for a time duration of 30 minutes at 350 rpm to obtain the ultrafine size coal-water slurry.
16. The method (400) of preparing the low-ash clean coal from high-ash coal waste as claimed in the claim 14, wherein the low-ash clean coal has 16-18% ash content.
17. A method (500) of preparing the ultra-low ash clean coal as claimed in claim 4, wherein the ultra-low ash clean coal is prepared from high-ash coal waste, the method (500) comprising:
mixing high-ash coal waste with dilute NaOH solution in 1:1 ratio to obtain an admixture;
heating the admixture at a 200°C temperature and 25 bar N2 pressure for a time duration of 60 minutes in a high-pressure reaction;
cooling the mixture and filtering to obtain a filter cake;
washing the filter cake with water till pH of wash water is lower than 8;
washing the filter cake with wash water at a temperature of 60°C to obtain washed filter cake, wherein washing the filter cake with wash water at a temperature of 60°C removes residual reagent;
mixing the washed filter cake with 10%(w/w) HCL solution in 1:1 ratio to obtain a slurry;
heating the slurry at a temperature of 60°C for 30 minutes;
cooling down the slurry and filtering to obtain a pre-final filter cake; and
washing the pre-final filter cake with water till pH of wash water is greater than 6.5 to obtain ultra-low ash clean coal.
18. The method (500) of preparing the ultra-low ash clean coal from high-ash coal waste as claimed in the claim 17, wherein the ultra-low ash clean coal has 5-7% ash content.
19. The battery (100) having synthetic anode prepared from ultra-low-ash coal as claimed in the claims 1, 3, and 17, wherein the ultra-low-ash coal is pyrolyzed at 900°C at 2°C/min with the help of coal tar pitch as catalyst, exhibits a high initial discharge capacity of 514 mAh/g at 0.1C rate and a reversible capacity of 286 mAh/g after 100 cycles at 0.1C rate.
20. The battery (100) having synthetic anode prepared from ultra-low-ash coal as claimed in the claims 1, 3, and 17, wherein the ultra-low-ash coal is pyrolyzed at 900°C at 2°C/min with the help of iron acetate as catalyst, exhibits a high initial discharge capacity of 354 mAh/g at 0.1C rate and a reversible capacity of 83 mAh/g after 100 cycles at 0.1C rate.
21. The battery (100) having synthetic anode as claimed in the claims 19 and 20, wherein the improved initial discharge capacity is due to the improved crystallinity of synthetic anode material with the help of catalyst.
22. A method (200) of preparing the synthetic anode material from demineralized coal as claimed in the claim 1, the method (200) comprising:
pyrolyzing demineralized coal at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product; and
grinding or pulverizing the pyrolysis product to obtain a prefinal product which is sieved to obtain a final product having predetermined size.
23. The method (200) of preparing the synthetic anode material from demineralized coal as claimed in the claim 22, wherein the demineralized coal is selected from any one of low-ash clean coal or ultra-low ash coal.
24. The battery (100) having synthetic anode prepared from low-ash clean coal as claimed in the claims 1, 14, and 22, wherein the low-ash clean coal is pyrolyzed at 900°C at 5°C/min exhibits an initial discharge capacity of 414 mAh/g at 0.1C rate and a reversible capacity of 228 mAh/g after 100 cycles at 0.1C rate.
25. The battery (100) having synthetic anode prepared from ultra-low-ash coal as claimed in the claims 1, 17, and 22, wherein the ultra-low-ash coal is pyrolyzed at 900°C at 2°C/min exhibits a high initial discharge capacity of 421 mAh/g at 0.1C rate and a reversible capacity of 290 mAh/g after 70 cycles at 0.1C rate.
26. The battery (100) having synthetic anode as claimed in the claim 25, wherein the improved initial discharge capacity and stability is due to the reduction of insulating silica material in the ultra-low-ash coal.
, Description:FIELD OF INVENTION
[0001] The present invention relates to a method for preparing a synthetic anode material from demineralized coal, and more particularly to the method of preparing synthetic anode material from demineralized coal for a battery application.

BACKGROUND
[0002] Electrochemical energy storage technologies are fast growing with high momentum, which can provide clean energy for a sustainable world. Several chargeable and rechargeable cells are already existing in the market. Among all electrochemical energy storage systems available, a rechargeable lithium-ion battery (LIB) is capturing the market because of its higher energy density and longer cycle life compared to other existing battery systems. The market size of Lithium-Ion batteries is estimated to grow at 16.4%.
[0003] Lithium-ion battery includes an anode (negative electrode), a cathode (positive electrode) and an electrolyte. The two electrodes (anode and cathode) are capable of reversibly hosting lithium in ionic form. Common candidates for the cathode are lithiated metal oxides and carbonaceous materials for the anode. Presently, carbonaceous material such as graphite is being used as anode material for intercalating lithium ions in rechargeable LIB due to its well-defined layered structure, low operating potential, and remarkable interfacial stability. With the increase in market demand for Li-ion batteries, the demand for anode materials is predicted to be 34.9 billion USD by year 2025. Since the availability of flake-like natural graphite is limited, a high demand-supply gap is predicted. Therefore, development of synthetic anode materials has gained importance to cater to the market demand.
[0004] Previous works show, different carbon materials have been investigated for their utilization in the preparation of synthetic anode materials. However, developing a synthetic anode material from other carbon materials have challenges in achieving high capacity, enhanced lithium-ion diffusion, long cycling life, and high cycling stability.
[0005] Metallurgical grade coals are suitable precursor materials for the preparation of carbonaceous anode materials due to their plastic behavior upon heating. This enables the material to get a porous structure with high percentage of micro-pores during devolatilization and re-solidification stages of pyrolysis. Therefore, a method is developed to prepare synthetic anode material from abundant high ash coals for their application in Li-ion battery.
OBJECTIVE OF INVENTION
[0006] It is an object of the invention to solve the aforementioned problems of the prior art and to provide a method of preparing a synthetic anode material from demineralized coal and evaluate its properties for its application as anode in lithium-ion batteries.
[0007] Another objective of the present invention is to develop synthetic anode materials having excellent reversible capacity and cycle-efficiency in a Li-ion battery.
[0008] Another objective of the present invention is to develop a method of preparing the synthetic anode from the high-ash coal waste obtained during froth-flotation of run-of-mine coal.
[0009] It is further another objective of the present invention meet the latest requirement of market to product further.
SUMMARY OF INVENTION
[0010] This summary is provided to introduce concepts related to a method for preparing synthetic anode material from demineralized coal for battery application. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0011] In one aspect of the present invention, a battery is provided. The battery comprises a cathode and an anode. The anode and the cathode disposed on opposite sides of a separator are soaked with an electrolyte. The anode is a carbonized synthetic anode made from demineralized coal material.
[0012] In an embodiment, the demineralized coal material is selected from any one of low-ash clean coal or ultra-low ash clean coal.
[0013] In an embodiment, a method of preparing the synthetic anode material from demineralized coal material is provided. The method comprising mixing the demineralized coal with a catalyst to obtain an admixture. The method also comprising pyrolyzing the admixture at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product. The method further comprising grinding or pulverizing the pyrolysis product to obtain a prefinal product which is sieved to obtain a final product having predetermined size.
[0014] In an embodiment, the catalyst is selected from any one of coal tar pitch and iron acetate. In an embodiment, the catalyst is mixed with demineralized coal at 0.1%.
[0015] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature in the range of 900°C – 1300°C for the first predetermined time in the range of 1 to 3 hours.
[0016] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature of 900°C for the first predetermined time of 3 hours.
[0017] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature of 900°C-1300°C at a rate of 2°C/min to 5°C/min.
[0018] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature of 900°C at a rate of 2°C/min.
[0019] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature of 900°C at a rate of 5°C/min. In an embodiment, the admixture is pyrolyzed in a nitrogen gas atmosphere.
[0020] In an embodiment, the nitrogen gas atmosphere has a flow rate of 2-3 ml/min.
[0021] In an embodiment, a method of preparing the low-ash clean coal is provided. The low-ash clean coal is prepared from high-ash coal waste. The method comprising mixing high-ash coal waste with water in 1:1 ratio to obtain an admixture. The method also comprising grinding the admixture in a planetary ball mill for a time duration of 30-45 minutes at 300-350 rpm to obtain ultrafine size coal-water slurry. The method further comprising mixing the ultrafine size coal-water slurry with water in 1:1 ratio to obtain a dilute coal-water slurry. The ultrafine size coal-water slurry is mixed with water to lower the pulp density. The method comprising separating via a centrifuge the dilute coal-water slurry to obtain a soft layer of coal. The centrifuge is rotated at 10,000 rpm for 3 minutes. The method also comprising collecting the soft layer of coal to obtain the low-ash clean coal.
[0022] In an embodiment, grinding of the admixture in the planetary ball mill is performed for a time duration of 30 minutes at 350 rpm to obtain the ultrafine size coal-water slurry. In an embodiment, the low-ash clean coal has 16-18% ash content.
[0023] In an embodiment, a method of preparing the ultra-low ash clean coal is provided. The ultra-low ash clean coal is prepared from high-ash coal waste. The method comprising mixing high-ash coal waste with dilute NaOH solution in 1:1 ratio to obtain an admixture. The method also comprising heating the mixture at a 200°C temperature and 25 bar N2 pressure for a time duration of 60 minutes in a high-pressure reaction. The method further comprising cooling the mixture and filtering to obtain a filter cake. The method comprising washing the filter cake with water till pH of wash water is lower than 8. The method also comprising washing with wash water at a temperature of 60°C to remove residual reagent to obtain washed filter cake. The method further comprising mixing the washed filter cake with 10% HCL solution in 1:1 ratio to obtain a slurry. The method comprising heating the slurry at a temperature of 60°C for 30 minutes. The method comprising cooling down the slurry and filtering to obtain a pre-final filter cake. The method also comprising washing the pre-final filter cake with water till pH of wash water is greater than 6.5 to obtain ultra-low ash clean coal.
[0024] In an embodiment, the ultra-low ash clean coal has 5-7% ash content.
[0025] In an embodiment, the ultra-low-ash coal is pyrolyzed at 900°C at 2°C/min with the help of coal tar pitch as catalyst, exhibits a high initial discharge capacity of 514 mAh/g at 0.1C rate and a reversible capacity of 286 mAh/g after 100 cycles at 0.1C rate.
[0026] In an embodiment, the ultra-low-ash coal is pyrolyzed at 900°C at 2°C/min with the help of iron acetate as catalyst, exhibits a high initial discharge capacity of 354 mAh/g at 0.1C rate and a reversible capacity of 83 mAh/g after 100 cycles at 0.1C rate.
[0027] In an embodiment, the improved initial discharge capacity is due to the improved crystallinity of synthetic anode material with the help of catalyst.
[0028] In an embodiment, a method of preparing the synthetic anode material from demineralized coal is provided. The method comprising pyrolyzing demineralized coal at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product. The method also comprising grinding or pulverizing the pyrolysis product to obtain a prefinal product which is sieved to obtain a final product having predetermined size. In an embodiment, the demineralized coal is selected from any one of low-ash clean coal or ultra-low ash coal.
[0029] In an embodiment, the battery having synthetic anode prepared from low-ash clean coal pyrolyzed at 900°C at 5°C/min exhibits an initial discharge capacity of 414 mAh/g at 0.1C rate and a reversible capacity of 228 mAh/g after 100 cycles at 0.1C rate.
[0030] In an embodiment, the battery having synthetic anode prepared from ultra-low-ash coal pyrolyzed at 900°C at 2°C/min exhibits a high initial discharge capacity of 421 mAh/g at 0.1C rate and a reversible capacity of 290 mAh/g after 70 cycles at 0.1C rate.
[0031] In an embodiment, the improved initial discharge capacity and stability is due to the reduction of insulating silica material in the ultra-low-ash coal.
[0032] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Figure 1 illustrates a schematic configuration of a battery having a cathode and a synthetic anode prepared from demineralized coal, according to an embodiment of the present invention;
[0034] Figure 2 illustrates a flow chart of a demineralization methodology to generate low ash clean coal (demineralized coal) from high-ash coal waste, according to an embodiment of the present invention;
[0035] Figure 3 illustrates a flow chart of a demineralization methodology to generate ultra-low ash clean coal (demineralized coal) from high-ash coal waste, according to an embodiment of the present invention;
[0036] Figure 4a, illustrates a flow chart of a method of preparing the synthetic anode from demineralized coal with a catalyst, according to an embodiment of the present invention;
[0037] Figure 4b, illustrates a flow chart of a method of preparing the synthetic anode from demineralized coal without a catalyst, according to another embodiment of the present invention;
[0038] Figure 5 illustrates a graph showing rate capability of the battery with synthetic anode material LGC_ (16_5_900), according to an embodiment of the present invention;
[0039] Figure 6 illustrates a graph showing rate capability of the battery with synthetic anode material LGC_ (5_2_900), according to an embodiment of the present invention; and
[0040] Figure 7 illustrates a graph showing rate capability of the battery with synthetic anode material C_LGC_P (5_2_900), according to an embodiment of the present invention.
[0041] The drawings referred to in this description are not to be understood as being drawn to scale except if specifically noted, and such drawings are only exemplary in nature.

DETAILED DESCRIPTION
[0042] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0043] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0044] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0045] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0046] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0047] Referring to Figure 1, a schematic view of a battery (100), according to embodiment of the present invention is illustrated. The battery (100) is a secondary battery which converts stored chemical energy into electrical energy during discharge and converts electrical energy into stored chemical energy during recharge. The battery (100) described herein embodies an electrochemical cell (herein after alternatively referred to as electrochemical cell (100)). Plurality of these batteries (100) may be connected in series or parallel or any combination thereof to produce a greater voltage output and current, without limiting the scope of the invention.
[0048] The battery (100) comprises a cathode (102), an anode (104), a separator (106), and electrolyte (108). The battery (100) may further include additional components such as casing, terminals, tabs etc. know in the art, that are generally associated with batteries, without limiting the scope of the invention. In the preferred embodiment, the battery (100) is a lithium-ion battery.
[0049] The battery (100) may be connected to a load device (not shown) via an interruptible external circuit (not) that connects the anode (104) and the cathode (102). The battery (100) supports the load device that is operatively connected to the external circuit. The load device receives electrical energy from the battery (100) during the discharge cycle. The load device may be electric motor, a laptop, a phone, a light bulb etc. The load device may also be a power-suppling or power-generating apparatus which charges the battery (100), without any limitations.
[0050] Referring further to Figure 1, the anode (104) and the cathode (102) are disposed on opposite sides of a separator (106). The separator (106) may be made with nonwoven fabrics, cellulose natural fibers, or one or more synthetic fibers selected from the group consisting of polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), Glass fiber (GF) and polyvinylidene fluoride (PVDF), without limiting the scope of the invention.
[0051] In the illustrated example, the cathode (102) is a lithium iron phosphate cathode. In the illustrated example, the electrolyte is lithium hexafluorophosphate. In the illustrated example, the anode (104) is made of synthetic anode material prepared from demineralized coal material. The demineralized coal material is selected from any one of low-ash clean coal or ultra-low ash clean coal prepared from high-ash coal waste.
[0052] Referring to Figure 2, an exemplary method (400) of preparing low-ash clean coal (demineralized coal) from high-ash coal waste is illustrated. At step (402), high-ash coal waste is mixed with water in 1:1 ratio to obtain an admixture.
[0053] At step (404), the admixture is grinded in a planetary ball mill for a time duration of 30-45 minutes at 300-350 rpm to obtain ultrafine size (<100 µm) coal-water slurry. In the preferred embodiment, the admixture is grinded in the planetary ball mill for a time duration of 30 minutes at 350 rpm to obtain the ultrafine size coal-water slurry. Wet-grinding helps is achieving the homogeneous particle size in water medium.
[0054] At step (406), the ultrafine size coal-water slurry is mixed with water in 1:1 ratio to obtain a dilute coal-water slurry. The ultrafine size coal-water slurry is mixed with water to lower the pulp density. At step (408), the dilute coal-water slurry is separated via a centrifuge to obtain a soft layer of coal. In the preferred embodiment, the centrifuge is rotated at 10,000 rpm for 3 minutes.
[0055] At step (410), the soft layer of coal is collected to obtain the low-ash clean coal. In the preferred embodiment, the low-ash clean coal has 16-18% ash content.
[0056] Referring to Figure 3, an exemplary method (500) of preparing ultra-low ash clean coal (demineralized coal) from high-ash coal waste is illustrated. At step (502), high-ash coal waste is mixed with dilute NaOH solution in 1:1 ratio to obtain an admixture. At step (504), the mixture is heated at a 200°C temperature and 25 bar N2 pressure for a time duration of 60 minutes in a high-pressure reaction. At step (506), the mixture is cooled and filtered to obtain a filter cake. In the preferred embodiment, the reagents are cooled to atmospheric temperature and filtered.
[0057] At step (508), the filter cake is washed with water till pH of wash water is lower than 8. At step (510), the filter cake is further washed with wash water kept at a temperature of 60°C to obtain washed filter cake. Washing the filter cake with wash water removes residual solvents.
[0058] At step (512), the washed filter cake is mixed with 10%(w/w) HCL solution in 1:1 ratio to obtain a slurry. At step (514), the slurry is heated at a temperature of 60°C for 30 minutes. At step (516), the heated slurry is cooled and filtered to obtain a pre-final filter cake. At step (518), the pre-final filter cake is washed with water till pH of wash water is greater than 6.5 to obtain ultra-low ash clean coal without any chemical impurities. In the preferred embodiment, the ultra-low ash clean coal has 5-7% ash content.
[0059] One of the low-ash clean coal ((demineralized coal)) having 16-18% ash content prepared using the method (400) or the ultra-low ash clean coal having 5-7% ash content prepared using the method (500) is used to prepare the synthetic anode material.
[0060] Referring to Figures 4a and 4b, exemplary methods (300, 200) of preparing the synthetic anode material from demineralized coal material are illustrated respectively. The demineralized coal material is selected from any one of low-ash clean coal having 16-18% ash content or ultra-low ash clean coal having 5-7% ash content. The method (300) is a method for preparing the synthetic anode material from demineralized coal material with utilization of a catalyst, whereas the method (200) is a method of preparing the synthetic anode material from demineralized coal material without utilization of a catalyst.
[0061] Referring to Figure 4a, the method (300) of preparing the synthetic anode material from demineralized coal material using a catalyst is illustrated. At step (302), demineralized coal is mixed with a catalyst to obtain an admixture. The demineralized coal material is selected from any one of low-ash clean coal or ultra-low ash clean coal. In an example, the catalyst is selected from any one of coal tar pitch (a by-product of coal tar distillation) and iron acetate. In the illustrated example, the catalyst is mixed with demineralized coal at 0.01%. Catalyst is mixed with the coal in 1:1000 ratio.
[0062] At step (304), the admixture is pyrolyzed at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product. In an embodiment, the admixture is pyrolyzed at the first predetermined temperature in the range of 900°C – 1300°C for the first predetermined time in the range of 1 to 3 hours. More preferably, the admixture is pyrolyzed at the first predetermined temperature of 900°C for the first predetermined time of 3 hours.
[0063] In an embodiment, the admixture is pyrolyzed at the first predetermined temperature of 900°C-1300°C at a rate of 2°C/min to 5°C/min. In the illustrated example, the admixture is pyrolyzed in a nitrogen gas atmosphere having a flow rate of 2-3 ml/min.
[0064] At step (306), the pyrolysis product obtained in the step (304) is grinded or pulverized to obtain a prefinal product which is sieved to obtain a final product having predetermined size. In the preferred embodiment, the pyrolysis product material is grinded to 150µm.
[0065] Referring to Figure 4b, the method (200) of preparing the synthetic anode material from demineralized coal material without a catalyst is illustrated. At step (202), demineralized coal is pyrolyzed at a first predetermined temperature for a first predetermined time in an inert atmosphere having a predetermined flow rate to obtain pyrolysis product. In an embodiment, the demineralized coal material is pyrolyzed at the first predetermined temperature in the range of 900°C – 1300°C for the first predetermined time in the range of 1 to 3 hours. More preferably, the demineralized coal material is pyrolyzed at the first predetermined temperature of 900°C for the first predetermined time of 3 hours.
[0066] In an embodiment, the demineralized coal material is pyrolyzed at the first predetermined temperature of 900°C-1300°C at a rate of 2°C/min to 5°C/min. In the illustrated example, the demineralized coal material is pyrolyzed in a nitrogen gas atmosphere having a flow rate of 2-3 ml/min.
[0067] At step (204), the pyrolysis product obtained in the step (202) is grinded or pulverized to obtain a prefinal product which is sieved to obtain a final product having predetermined size. In the illustrate example, the pyrolysis product material is grinded to 150µm.
[0068] The final products having predetermined size obtained using methods (300, 200) are used to make the synthetic anodes (104) of the battery (100).
[0069] Electrochemical Characterization
[0070] The anodic performance of the final products (carbonaceous materials) obtained from the method (200) (herein after alternatively referred to as pyrolysis) and the method (300) (herein after alternatively referred to as catalytic pyrolysis) of low-ash coal and ultra-low-ash coal are summarized below.
[0071] The final products (carbonaceous materials) obtained from the pyrolysis and catalytic pyrolysis of low-ash coal with various operating parameters are designated as LGC (X_Y_Z) and C_LGC_A (X_Y_Z) where, X denotes the ash content, Y is heat rate (°C/min) and Z is the heat treatment temperature, and A is the catalyst for catalytic pyrolysis (Iron acetate or Coal tar pitch).
[0072] A slurry is prepared with active carbon material, conductive carbon black additive and binder Polyvinylidene fluoride (PVDF) in the 8:1:1 ratio in the presence of N-Methyl-2-pyrrolidone. Then the slurry is coated on to Cu foil and dried in vacuum oven at 90° C for 24 hours. Later, the dried electrode is cut into 12 mm circular discs and used as anode in coin cell CR 2032 assembly. The prepared coin cells with the working electrodes are connected to rate capability studies from 0.1 C to 1 C-rate, where the current rate is increased after every 10 cycles. After that, the current rate was swapped back to 0.1 C-rate to examine the long cyclic performance.
[0073] Case-1: Pyrolysis (method (200)) of low-ash clean coal without catalyst:
LGC (16_5_900): The low-ash coal with 16-17% ash content is pyrolyzed at 900°C at 5°C/min. As synthesized material is packed as an anode in a coin cell to evaluate its electrochemical performance. It is observed that the LGC (16_5_900) has shown an initial coulombic efficiency of 71.9% with a high initial discharge capacity of 414 mAh/g at 0.1C rate. The material has also delivered reversible capacities of 246 mAh/g, 203 mAh/g, 162 mAh/g, and 124 mAh/g at 0.1C (after 10 cycles), 0.2 C (after 20 cycles), 0.5C (after 30 cycles) and 1C rates (after 40 cycles), respectively. Later, during the long cyclic stability test, the electrodes has delivered a reversible capacity of 228 mAh/g after 100 cycles at 0.1C rate.
[0074] Case-2: Pyrolysis (method (200)) of ultra-low-ash clean coal without catalyst:
LGC (5_2_900): The ultra-low-ash coal with 5-7% ash content is pyrolyzed at 900°C at 2°C/min. As synthesized material is packed as an anode in a coin cell to evaluate its electrochemical performance. It is observed that the LGC (5_2_900) has shown an excellent initial coulombic efficiency of 86.5% with a high initial discharge capacity of 421 mAh/g at 0.1C rate. The material has also delivered reversible capacities of 340 mAh/g, 300 mAh/g, 251 mAh/g, and 214 mAh/g at 0.1C (after 10 cycles), 0.2 C (after 20 cycles), 0.5C (after 30 cycles) and 1C rates (after 40 cycles), respectively. Later, during the long cyclic stability test, the electrodes has delivered a reversible capacity of 290 mAh/g after 70 cycles at 0.1C rate. The improved initial discharge capacity is due to the reduction in the ash content. It was observed that, metal oxides present in the ash are inert in the electro-chemical cell.
[0075] Case-3: Pyrolysis (method (300)) of ultra-low-ash clean coal with catalyst:
C_LGC_P (5_2_900): The ultra-low-ash coal with 5-7% ash content is catalytically pyrolyzed at 900°C at 2°C/min with pitch as catalyst with 0.1% loading. As synthesized material is packed as an anode in a coin cell to evaluate its electrochemical performance. It is observed that the C_LGC_P (5_2_900) has shown an initial coulombic efficiency of 81.8 % with an outstanding initial discharge capacity of 514mAh/g at 0.1C rate, current density.
[0076] The coulombic efficiency is better in case of ultra-low-ash coal because the presence of insulating silica content is reduced. The material has also delivered reversible capacities of 321mAh/g, 257mAh/g, 221mAh/g, and 177mAh/g at 0.1C (after 10 cycles), 0.2 C (after 20 cycles), 0.5C (after 30 cycles) and 1C rates (after 40 cycles), respectively. Later, during the galvanostatic charge-discharge long cyclic stability test, the electrodes has delivered a reversible capacity of 286 mAh/g after 100 cycles at 0.1C rate. Here, the catalyst played an important role to improve the crystallinity of the sample and thereby improving electrode stability during rate capability test.
[0077] Electrochemical performance of other catalytic pyrolysis products from demineralized coal is illustrated in the below table:
Sample ICE, % IDC (mAh/g) at 0.1C rate Reversible capacity (mAh/g) at various current rates
0.1C rate 0.2C rate 0.5C rate 1C rate 0.1 C rate
(100 cycles)
CPC-A-900-2-P 81.8 514 321 257 221 177 276
CPC-B-900-5-P 77.5 248 148 117 84 65 72
CPC-A-1300-5-P 82.3 373 299 268 223 189 249
CPC-B-1300-2-P 79.8 305 202 155 114 94 139
CPC-B-900-5-Fe 69.6 536 320 223 185 142 144
CPC-B-1300-2-Fe 75.9 216 149 132 104 77 145
CPC-A-1300-5-Fe 88.3 305 260 226 181 152 175
CPC-A-900-2-Fe 83.3 354 227 136 87 57 83

A- ULTRA-LOW ASH CLEAN COAL
B- LOW-ASH CLEAN COAL
900/1300: TEMPERATURE
2/5: HEATING RATE
Pitch (Coal tar pitch)/Fe (Iron acetate): CATALYST
[0078] The present invention relates to the method (200, 300) for preparing synthetic anode material from demineralized coal. The demineralized coal material is selected from any one of low-ash clean coal or ultra-low ash clean coal. The present invention also provides methods (400, 500) of preparing low-ash clean coal or ultra-low ash clean coal from high-ash coal waste. Further, as the anodes made from carbonaceous material have high capacity, lithium-ion diffusion, long cycling life, high cycling stability, and no safety issues, these anodes are suitable for replacing conventional graphite anodes. Furthermore, as coal tar (which is a by-product) is being used to make these anode material, protection of environment, energy conservation and emission reduction, and sustainable economic development can be achieved.
[0079] Furthermore, the terminology used herein is for describing embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0080] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0081] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.