FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
“A GREEN PROCESS FOR SYNTHESIZING HARD CARBON AND APPLICATIONS THEREOF”
RELIANCE INDUSTRIES LIMITED., an Indian Company of 3rd Floor, Maker Chamber-IV, 222, Nariman Point, Mumbai - 400 021, Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
The present disclosure generally relates to the field of polymer science. Particularly, the present disclosure provides a green process of synthesizing hard carbon using a biomass-based precursor and a polymer resin precursor. The hard carbon prepared by the said process is employed as an anode material in a sodium ion battery. The present disclosure therefore also relates to the use and further applications of the hard carbon for preparing sodium ion batteries.
BACKGROUND OF THE DISCLOSURE
[0001] The demand for rechargeable batteries has increased in recent years and technology has begun to expand from lithium-ion batteries to sodium ion (Na-ion) batteries. Additionally, Na-ion batteries have gained much interest in recent years owing to the technological challenges faced by lithium-ion batteries in terms of resources and costs. Further, as sodium and lithium belong to the same group in the periodic table, they have certain similar physical and chemical properties. Lastly, sodium is found much more abundantly than lithium and thus, sodium ion batteries are being considered as an alternative for applications in mass storage energy systems.
[0002] As is known, energy generation from renewable sources has been increasing in the current scenario due to shortage of fossil fuels. Additionally, environmental concerns relating to the exploitation of fossil sources invite alternative means of energy generation. Biomass sources of energy are renewable and provide a better replacement for fossil fuels which are generated with lower carbon elements.
[0003] Hard carbon is used as an anode material in sodium ion batteries and is generally synthesized from PVC as a polymer precursor which is easily available and low in cost. Literature discloses that the high cost and low initial coulomb efficiencies of conventionally prepared hard carbon limits its large-scale application.
Considering the limitations associated with fossil fuels and with the view to provide better coulomb efficiency than conventionally prepared hard carbons, there is a need to replace the dependency on fossil fuels and provide simple, green, easily scalable and cost-efficient process for hard carbon synthesis which can be used in the preparation of high-performance anode material for sodium ion batteries. The present disclosure addresses this need of the prior art.

SUMMARY OF THE DISCLOSURE
[0004] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiments and is not intended to the full description of the disclosure. A full appreciation of the various aspects of the preferred embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
[0005] The present disclosure relates to a process for synthesis of hard carbon by combining a pre-treated biomass-based first precursor with a polymer resin based second precursor followed by a 2-step thermal treatment to obtain the hard carbon.
[0006] In some embodiments, the present disclosure provides a green process which is devoid of any chemical treatment in the process of preparing the hard carbon.
[0007] In some embodiments, the present disclosure provides a process for preparing a hard carbon wherein the biomass-based first precursor is preferably coffee waste powder.
[0008] In some embodiments, the coffee waste powder is pretreated with demineralized water.
[0009] In some embodiments, the present invention provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 600-1600ºC to obtain the hard carbon, wherein the first and the second precursor are in a ratio of about 30-70:70-30.
[0010] In some embodiments, the first precursor and the second precursor are in a ratio of about 30:70, 50:50 or 70:30.

[0011] In some embodiments, the polymer resin is selected from a group comprising polyvinyl chloride, polyethylene and polypropylene, or any combination thereof.
[0012] In some embodiments, the polymer resin is preferably polyvinyl chloride or a precursor.
[0013] In some embodiments, the polymer resin based second precursor is in the range of about 10 wt.% to 95 wt. %.
[0014] In some embodiments, the biomass-based first precursor is selected from a group comprising coffee powder, almond shell powder, ground nutshell powder or husk and sugarcane bagasse, or any combination thereof; and wherein the biomass-based precursor is in the range of about 5 wt.% to 90 wt.%.
[0015] In some embodiments, the biomass-based first precursor is coffee powder in the form of coffee grounds.
[0016] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating the biomass with demineralized water for about 3-4 hours to remove impurities.
[0017] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating with demineralized water at a temperature range of about 70ºC-95ºC.
[0018] In some embodiments, the biomass-based first precursor is pretreated with demineralized water for about 4 hours.
[0019] In some embodiments, the biomass-based first precursor is pretreated with demineralized water at about 90℃ for about 4 hours.

[0020] In some embodiments, the pretreated biomass-based first precursor is dried at a temperature of about 80℃-120℃ for about 3-6 hours prior to combining it with the polymer resin based second precursor.
[0021] In some embodiments, the heating in step (iii) is done at a temperature of about 200ºC to 250ºC.
[0022] In some embodiments, the heating in step (iii) is performed for about 2-4 hours at a ramping rate of about 2-15℃/min.
[0023] In some embodiments, the pyrolysis performed in step (iv) is performed at a temperature of about 700-1300 ºC.
[0024] In some embodiments, the pyrolysis performed in step (iv) is performed for about 1-5 hours at a ramping rate of about 5-15℃/min.
[0025] In some embodiments, the pyrolysis performed in step (iv) is performed under nitrogen atmosphere.
[0026] In some embodiments, after the pyrolysis, the hard carbon is allowed to cool down to room temperature, re-washed with distilled water to remove ash and water-soluble impurities, and dried at about 90℃ for about 8 hours.
[0027] The present disclosure also provides the hard carbon obtained by the process of the present invention, having a d-spacing value of more than or equal to about 3.6 Å.
[0028] In some embodiments, the hard carbon obtained by the method of the present invention has an Id/Ig ratio of about 0.8 to about 1.1.
[0029] In some embodiments, an anode material is provided comprising the hard carbon obtained by the present invention.
5

[0030] In some embodiments, the anode material has a coulombic efficiency of about 99.99% till 80th cycle.
[0031] In some embodiments of the present disclosure, the hard carbon obtained by the process of the present invention is employed as an anode in sodium ion batteries.
[0032] Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples while indicating the preferred embodiments of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure. The disclosure itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
[0033] Figure 1 provides the XRD and Raman spectrum of hard carbon obtained from PVC and coffee waste in 1:1 ratio at 700℃.
[0034] Figure 2 provides the XRD and Raman spectrum of hard carbon obtained from PVC and coffee waste in 70:30 ratios at 700℃.
[0035] Figure 3 provides the XRD and Raman spectrum of hard carbon obtained from PVC and coffee waste in 30:70 ratio at 700℃.
[0036] Figure 4 provides the XRD and Raman spectrum of hard carbon obtained from PVC and coal in 50:50 ratio at 700℃.
[0037] Figure 5 provides the X-ray diffraction (XRD) and Raman spectrum of hard carbon obtained at 700℃.
6

[0038] Figure 6 provides the XRD and Raman spectrum of hard carbon obtained at 1300℃.
[0039] Figure 7 provides Electrochemical performance: (a) first cycle charge-discharge profile (b) 2nd and 80th cycle charge-discharge profile (c) cycle-life vs performance plot and (d) Cyclic-voltammetry profile.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0040] The details of one or more embodiments of the disclosure are set forth in the accompanying description below including specific details of the best mode contemplated by the inventors for carrying out the disclosure, by way of example. It will be apparent to one skilled in the art that the present disclosure may be practiced without limitation to these specific details.
Abbreviations Used PVC- polyvinyl chloride XRD- X-ray diffraction
[0041] The foregoing broadly outlines the summary and features of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying the disclosed methods or for carrying out the same purpose as that of the present disclosure.
[0042] The process for synthesizing hard carbon comprises the steps of pre-treating a biomass-based first precursor and then combining it with a polymer resin based second precursor to form a mixture followed by two-step thermal treatment.
[0043] In some embodiments, the process for synthesizing hard carbon as described in the embodiments above comprises heating the mixture of a pretreated biomass-based first precursor and a polymer resin based second precursor to a temperature of about 150 ºC to 400ºC for 2-4 hours to obtain a solid and allowing the said solid to cool to ambient temperature followed by subjecting the cooled mixture to pyrolysis at a temperature of about 600-1600 ºC for 1-5 hours to obtain the hard carbon.
7

[0044] In some embodiments, the process for synthesizing hard carbon as described in the embodiments above, comprises heating the mixture of a pretreated biomass-based first precursor and a polymer resin based second precursor to a temperature of about 200ºC to 250ºC for 2-4 hours to obtain a solid and allowing the said solid to cool to ambient temperature followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700-1300 ºC for 1-5 hours to obtain the hard carbon.
[0045] In some embodiments, the process for synthesizing hard carbon as described in the embodiments above, comprises heating the mixture of a pretreated biomass-based first precursor and a polymer resin based second precursor to a preferable temperature of about 200ºC for 2 hours to obtain a solid and allowing the said solid to cool to ambient temperature followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700ºC for 1 hour to obtain the hard carbon.
[0046] In some embodiments, the process for synthesizing hard carbon comprises the steps of pretreating a biomass-based first precursor and then combining it with a polymer resin based second precursor to form a mixture followed by heating the mixture to a temperature of about 150 ºC to 400ºC to obtain a solid and allowing the said solid to cool to ambient temperature followed by subjecting the cooled mixture to pyrolysis at a temperature of about 600-1600 ºC to obtain the hard carbon wherein the first and second precursor are in a ratio of about 30-70:70-30.
[0047] In some embodiments, the process for synthesizing hard carbon comprises the steps of pretreating a biomass-based first precursor and then combining it with a polymer resin based second precursor to form a mixture followed by heating the mixture to a temperature of about 200 ºC to 250ºC to obtain a solid and allowing the said solid to cool to ambient temperature followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700-1300 ºC to obtain the hard carbon wherein the first and second precursor are in a ratio of about 30-70:70-30.
[0048] In some embodiments, the process for synthesizing hard carbon as described in the embodiments above, comprises heating the mixture to a temperature of about 150 ºC, 200 ºC, 250 ºC, 300 ºC, 350 ºC or 400 ºC including all values and ranges therein between.

[0049] In some embodiments, the process for synthesizing hard carbon as described in the embodiments above, comprises subjecting the cooled mixture to pyrolysis at a temperature of about 600 ºC, 650 ºC, 700 ºC, 750 ºC, 800 ºC, 850 ºC, 900 ºC, 950 ºC, 1000 ºC, 1050 ºC, 1100 ºC, 1150 ºC, 1200 ºC, 1250 ºC, 1300 ºC, 1350 ºC, 1400 ºC, 1450 ºC, 1500 ºC, 1550 ºC or 1600 ºC including all values and ranges therein between.
[0050] In some embodiments, the process for synthesizing hard carbon is a green process which is devoid of any chemical treatments.
[0051] In some embodiments, the polymer resin based second precursor is selected from a group comprising polyvinyl chloride, polyethylene and polypropylene, or any combination thereof.
[0052] In some embodiments, the polymer resin based second precursor is preferably polyvinyl chloride.
[0053] In some embodiments, the polymer resin based second precursor is in the range of about 10 wt.% to 95 wt.%.
[0054] In some embodiments, the process for synthesizing hard carbon comprises employing the polymer resin based second precursor in the range of about 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.% or 95 wt.% including values and ranges therein between.
[0055] In some embodiments, the biomass-based first precursor is selected from a group comprising coffee powder, almond shell powder, ground nutshell powder or husk and sugarcane bagasse, or any combination thereof.
[0056] In some embodiments, the biomass-based first precursor is coffee powder in the form of coffee grounds.
[0057] In some embodiments, the biomass-based first precursor is in the range of about 5 wt.% to 90 wt.%.
[0058] In some embodiments, the biomass-based first precursor is in the range of about 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60

wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.% or 90 wt.% including values and ranges therein between.
[0059] In some embodiments, the first and second precursor are in a preferable ratio of 30:70, 50:50 or 70:30.
[0060] In some embodiments, the first and second precursor are in a ratio of about 30:70.
[0061] In some embodiments, the first and second precursor are in a ratio of about 50:50.
[0062] In some embodiments, the first and second precursor are in a ratio of about 70:30.
[0063] In some embodiments, the first and second precursor are in a ratio of about 30-70:70-30 including 30:70, 35:65; 40:60, 50:50, 55:45, 60:40, 65:35, 70:30 and values and ranges therein between.
[0064] Accordingly, in some embodiments, the present disclosure provides a process for
synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5
wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about
10 wt.% to 95 wt.% to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture
to pyrolysis at a temperature of about 600-1600ºC to obtain the hard carbon.
[0065] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5
wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about
10 wt.% to 95 wt.% to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and

iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon.
[0066] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon.
[0067] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating with demineralized water for about 3-4 hours to remove impurities at a temperature range of about 70℃-95℃.
[0068] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating with demineralized water for about 3-4 hours to remove impurities at a temperature range of about 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃ including values and ranges therein between.
[0069] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating with demineralized water for about 4 hours to remove impurities at a temperature range of about 90℃.
[0070] In some embodiments, the pretreatment of the biomass-based first precursor comprises treating with demineralized water at about 90℃ for about 4 hours.
[0071] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor;

ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 600-1600ºC to obtain the hard carbon. wherein the biomass-based first precursor is pretreated with demineralized water at a temperature range of 70℃-95℃ for about 3-4 hours.
[0072] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon wherein the biomass-based first precursor is pretreated with demineralized water at a temperature range of 90℃ for about 4 hours.
[0073] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor, preferably coffee waste powder; ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon;

wherein the biomass-based first precursor, preferably coffee waste powder is pretreated with demineralized water at a temperature range of 90℃ for about 4 hours.
[0074] In some embodiments, the pretreated biomass-based first precursor is dried at a temperature of about 80℃-120℃ for about 3-6 hours prior to combining it with the polymer resin based second precursor.
[0075] In some embodiments, the pretreated biomass-based first precursor is dried by conventional drying methods such as using a vacuum drying oven at a temperature of about 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃ including values and ranges therein between.
[0076] In some embodiments, the pretreated biomass-based first precursor is dried for about 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours including values and ranges therein between.
[0077] In some embodiments, the mixture of pretreated biomass-based first precursor and polymer resin based second precursor is heated at 600-1600℃ for about 2-4 hours at a ramping rate of about 2-15℃/min.
[0078] In some embodiments, the mixture of pretreated biomass-based first precursor and polymer resin based second precursor is heated at 700-1300℃ for about 2-4 hours at a ramping rate of about 2-15℃/min.
[0079] In some embodiments, the mixture of pretreated biomass-based first precursor and polymer resin based second precursor is heated at 600-1600℃ for about 2-4 hours at a ramping rate of about 10℃/min.
[0080] In some embodiments, the mixture of pretreated biomass-based first precursor and polymer resin based second precursor is heated at 700-1300℃ for about 2-4 hours at a ramping rate of about 10℃/min.
[0081] In some embodiments, the mixture of pretreated biomass-based first precursor and polymer resin based second precursor is heated at a ramping rate of about 2℃/min, 3℃/min, 4℃/min, 5℃/min, 6℃/min, 7℃/min, 8℃/min, 9℃/min, 10℃/min, 11℃/min, 12℃/min, 13℃/min, 14℃/min or 15℃/min including values and ranges therein between.
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[0082] In some embodiments, the pyrolysis is performed for about 1-5 hours at a ramping rate of about 5-15℃/min.
[0083] In some embodiments, the pyrolysis is performed for about 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours including values and ranges therein between.
[0084] In some embodiments, the pyrolysis is performed at a ramping rate of about 5℃/min, 6℃/min, 7℃/min, 8℃/min, 9℃/min, 10℃/min, 11℃/min, 12℃/min, 13℃/min, 14℃/min or 15℃/min including values and ranges therein between.
[0085] In some embodiments, the pyrolysis is performed for about 1 hour at a ramping rate of about 5℃/min.
[0086] In some embodiments, the pyrolysis is performed under an inert atmosphere such as that provided by inert gases selected from a group comprising helium, neon, argon, xenon, radon, krypton and nitrogen.
[0087] In some embodiments, the inert gas employed for pyrolysis is nitrogen.
[0088] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 150-400ºC at a ramping rate of
2-15 ºC/min to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 600-1600ºC at a ramping rate of 5-15 ºC/min to obtain the hard carbon.
[0089] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
14

i. pretreating a biomass-based first precursor; ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5
wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about
10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200-250ºC for 2-4 hours at a
ramping rate of 2-15 ºC/min to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture
to pyrolysis at a temperature of about 700-1300ºC for 1-5 hours at a ramping rate of 5-15
ºC/min to obtain the hard carbon.
[0090] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of, i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based precursor of step (i) at a concentration of about 5 wt.% to 90 wt.% with a polymer resin based second precursor at a concentration of about 10 wt.% to 95 wt.% to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200ºC for 2 hours at a ramping
rate of 2-15 ºC/min to obtain a solid; and iv. allowing the solid formed in step (iii) to cool, followed by subjecting the cooled mixture to pyrolysis at a temperature of about 700ºC for 1 hour at a ramping rate of 5-15 ºC/min to obtain the hard carbon.
[0091] In some embodiments, after the pyrolysis, the hard carbon is allowed to cool down to room temperature, re-washed with distilled water to remove ash and water-soluble impurities, and dried at about 90℃- 100℃ for about 6-10 hours.
[0092] In some embodiments, after the pyrolysis, the hard carbon is allowed to cool down to room temperature, re-washed with distilled water to remove ash and water-soluble impurities, and dried at about 90℃ for about 8 hours.
Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,

i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 600-1600ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 30-70:70-30.
[0093] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 30:70.
[0094] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon,

wherein the first and the second precursor are in a ratio of about 50:50.
[0095] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 70:30.
[0096] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 30-70:70-30.
[0097] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
17

iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 30:70.
[0098] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 50:50.
[0099] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon,
wherein the first and the second precursor are in a ratio of about 70:30.
[00100] Now that the process for synthesis of hard carbon has been described above, the present disclosure also relates to the hard carbon per se that is obtained from the said process.

[00101] Accordingly, the present disclosure also describes the hard carbon obtained by employing the process provided in the above embodiments, having a d-spacing value of more than or equal to about 3.6 Å.
[00102] In some embodiments, the hard carbon obtained by employing the process enumerated in the above embodiments has an Id/Ig ratio of about 0.8 to about 1.1.
[00103] In some embodiments, the hard carbon obtained by employing the steps enumerated in the above embodiments has an Id/Ig ratio of about 0.8, about 0.9, about 1.0, or about 1.1 including values and ranges therein between.
[00104] Accordingly, in some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor; ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 600-1600ºC to obtain the hard
carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of
about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 30-70:70-30.
[00105] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor; ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard
19

carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 30:70.
[00106] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and
v. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 50:50.
[00107] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
iv. pretreating a biomass-based first precursor;
v. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
vi. heating the mixture of step (ii) to a temperature of about 200-250ºC to obtain a solid; and
vi. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700-1300ºC to obtain the hard
carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of
about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 70:30.

[00108] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 30-70:70-30.
[00109] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 30:70.
[00110] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
21

iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 50:50.
[00111] In some embodiments, the present disclosure provides a process for synthesis of hard carbon comprising the steps of,
i. pretreating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture;
iii. heating the mixture of step (ii) to a temperature of about 200ºC to obtain a solid; and
iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subjecting
the cooled mixture to pyrolysis at a temperature of about 700ºC to obtain the hard carbon having a d-spacing value of more than or equal to about 3.6 Å and an Id/Ig ratio of about 0.8 to about 1.1,
wherein the first and the second precursor are in a ratio of about 70:30.
[00112] In some embodiments, the hard carbon obtained by employing the steps enumerated in the above embodiments can be further utilized in an anode material.
[00113] In some embodiments, the anode material comprising the hard carbon obtained by employing the steps enumerated in the above embodiments has a coulombic efficiency of about 99.99% till 80th cycle.
[00114] In some embodiments, the anode material comprising the hard carbon obtained by employing the steps enumerated in the above embodiments can be incorporated in rechargeable batteries such as sodium ion battery or a lithium-ion battery.
ADVANTAGES

[00115] The present disclosure has the following advantages:
- Provides a green process for the synthesis of hard carbon
- Provides improved d-spacing values which can accommodate a larger number of sodium ions.
- Provides an energy efficient process by saving on usage of fossil fuels
- Provides an environmental friendly and cost effective process for preparing hard carbon by utilizing coffee waste powder and other biomass precursors.
[00116] While the present disclosure is susceptible to various modifications and alternative forms, specific aspects thereof have been shown by way of examples (and drawings) described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention as defined by the appended claims. The present disclosure is therefore further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner.
EXAMPLES
Experimental example 1
10gm of coffee waste powder was collected from coffee machine after use and pretreated with 40ml of demineralized (DM) water at 90℃ for 4 hours to remove impurities. Treated coffee waste powder was dried in a vacuum oven at 80-120℃ for 3-6 hours. Dried coffee waste powder was then used for hard carbon synthesis.
10gm of PVC K67-01 resin and 10gm of pretreated coffee waste powder were taken in a 50:50 ratio in a silica crucible. The mixture was kept in a muffle furnace at 200℃ for 2 hours at ramping rate of 10℃/min. Chlorine from PVC and moisture present in coffee waste were expected to release in this step. The solid formed was cooled and kept for pyrolysis in a muffle furnace at a temperature of 700℃ for 1 hour with ramping rate of 5℃/min under nitrogen. 5.9 gm of hard carbon was obtained at the final stage and was cooled down to room temperature. The final yield of hard carbon obtained was 29.5%.
23

After cooling, the hard carbon obtained above was washed with distilled water several times to remove ash and other water-soluble impurities from the hard carbon. It was later dried in vacuum oven at 90℃ for 8 hours. After drying, the obtained hard carbon was washed with water and dried completely. The dried product was powdered in mortar and pestle into fine powder. XRD spectrum showed d-spacing of 0.37 nm and Raman analysis showed Id/Ig ratio of 1.008 (Figure 1).
Experimental example 2
Coffee waste powder was pretreated as per experimental example 1. 14gm of PVC K67-01 resin and 6gm of pretreated coffee waste powder were taken in a 70:30 ratio in a silica crucible. The mixture was kept in a muffle furnace at 200℃ for 2 hours at a ramping rate of 10℃/min. Chlorine from PVC and moisture present in coffee waste were expected to release in this step.
The solid formed was allowed to cool and was kept for pyrolysis in a muffle furnace at a temperature of 700℃ for 1 hour with a ramping rate of 5℃/min under nitrogen. Hard carbon obtained at the final stage was allowed to cool down at room temperature. After cooling down, the hard carbon was washed several times with distilled water to remove ash and other water-soluble impurities. It was further dried in a vacuum oven at 90℃ for 8 hours. After drying, 4 gm of hard carbon was obtained. This was then powdered in mortar and pestle into fine powder which was then analysed by various analytical techniques. The final yield of hard carbon obtained was 20%. XRD analysis showed d-spacing of 0.36 nm and Raman analysis gave an Id/Ig ratio of 0.84 (Figure 2).
Experimental example 3
Coffee waste powder was pretreated as per experimental example 1. 6gm of PVC K67-01 resin and 14gm of washed coffee waste powder were taken in a 30:70 ratio in a silica crucible. The mixture was kept in a muffle furnace at 200℃ for 2 hours at a ramping rate of 10℃/min. Chlorine from PVC and moisture present in coffee waste were expected to release in this step. The solid formed was allowed to cool and was kept for pyrolysis in a muffle furnace at a temperature of 700℃ for 1 hour with ramping rate of 5℃/min under nitrogen. About 10.2 gm of hard carbon obtained at the final stage was allowed to cool down at room temperature.

After cooling down, the hard carbon was washed several times with distilled water to remove ash and other water-soluble impurities. It was further dried in vacuum oven at 90℃ for 8 hours. After drying, 10.2gm of the product was obtained which was then powdered in a mortar and pestle into a fine powder which were analysed by various analytical techniques. The final yield of hard carbon obtained was 51%. X-ray diffraction study showed d-spacing of 0.37 nm and Raman analysis gave an Id/Ig ratio of 0.87 (Figure 3).
Comparative example 1
10gm of PVC K67-01 resin and 10gm of powdered coal were taken in a 50:50 ratio in silica crucible. The mixture was kept in a muffle furnace at 200℃ for 2 hours at ramping rate of 10℃/min. Chlorine from PVC and moisture if present in coal were expected to release in this step. Solid formed was allowed to cool and kept for pyrolysis in a muffle furnace at a temperature of 700℃ for 1 hour with ramping rate of 5℃/min under nitrogen. 2.8 gm of hard carbon obtained at the final stage was allowed to cool down at room temperature. After cooling down, the hard carbon was washed several times with distilled water to remove ash and other water-soluble impurities. It was further dried in vacuum oven at 90℃ for 8 hours. After drying, 2.8gm of the product was powdered in mortar and pestle into a fine powder which was then analysed by various analytical techniques. The final yield of hard carbon obtained was 14%. X-ray diffraction study showed d-spacing of 0.37 nm and Raman analysis gave an Id/Ig ratio of 0.81 (Figure 4).
Comparative Example 2
20gm of PVC K67-01 resin was taken in a silica crucible and kept in a vacuum oven at 200℃ for 2 hours. A release of chlorine atoms was expected in this step. Pyrolysis of the partially thermally treated PVC was conducted in a muffle furnace at temperatures ranging from 700℃ for a time period of 1 hour under nitrogen at the ramping rate of 5℃/min.
2.8gm of hard carbon was obtained at final step was allowed to cool down to room temperature/ambient temperature. The final yield of hard carbon obtained was 14%. The hard carbon obtained above was then made into fine powder by using mortar and pastel and ball mill operation. X-ray diffraction of hard carbon synthesized at 700℃ showed d-spacing of 0.351 nm and Raman spectroscopy showed Id/Ig ratio of 0.95 (Figure 5).

Comparative Example 3
20gm of PVC K67-01 resin was taken in a silica crucible and kept in a vacuum oven at 200℃ for 2 hours. A release of chlorine atoms was expected in this step. Pyrolysis of the partially thermally treated PVC was carried out in muffle furnace at temperature 700℃ for time period of 1 hour under nitrogen at the ramping rate of 10℃/min. Remaining of the chlorine present in PVC was released at temperature of about 600℃.
Hard carbon obtained at this stage was further kept for pyrolysis in a quartz tube muffle furnace at 1300℃ for 1 hour at ramping rate of 5℃/min. 3.2gm of hard carbon formed was allowed to cool down to room temperature/ambient temperature and then made into fine powder in mortar and pastel followed by ball milling. The final yield of hard carbon obtained was 16%. X-ray diffraction showed d-spacing of 0.35 nm and Raman spectroscopy showed Id/Ig ratio of 1.05 (Figure 6).
Table 1: Properties of synthesized hard carbon.

Sr. no. Sample D-spacing (nm) Id/Ig Crystallite size (Å) Av. Particle
(Ball milled)
size (µm)
1 Experimental
example 1: PV-CW-50:50 0.37 1.008 10 10
2 Experimental
example 2: PV-CW-70:30 0.36 0.84 12 6
3 Experimental
example 3: PV-CW-30:70 0.37 0.87 10 2.5
4 Comparative example 1: PV-Coal -50:50 0.37 0.81 9 9

5 Comparative example 2: PV-700 0.35 0.95 18.5 2
6 Comparative example 3: PV-1300 0.35 1.05 30 10
The d-spacing value and crystallite size of hard carbon are inversely proportional to each other. Accordingly, in comparative example 2 and 3, the higher crystallite size gives a d-spacing value of below 0.36.
Also, the d-spacing value and particle size of hard carbon are important properties since they play a significant role in the performance of hard carbon as an electrode material in sodium ion batteries. The average particle size of commercial hard carbon falls in the range of 2-20 micron which falls in the range of the hard carbon as prepared by the present invention.
Performance analysis
Performance analysis of synthesized PVC and coffee waste based hard carbon prepared in accordance with experimental examples 1-3, as anode material was carried out. Coulombic efficiency for Experimental example 3 was found very high for synthesized hard carbon. It can be observed from Figure 6 that very high coulombic efficiencies remained i.e. 99.99% till 80th cycle.
This indicates that the hard carbon material from PVC and coffee waste is a promising anode candidate for Na-ion batteries. The Synthesized hard carbon also showed promising initial discharge and reversible capacity (Figure 7).
Experimental results prove that a combination of a biomass based first precursor and polymer resin based second precursor in a defined ratio when reacted together in accordance with the method of the present invention results in good yield of hard carbon which can be used as a high-performance anode material for sodium ion batteries.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Thus, while considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Similarly, terms such as “include” or “have” or “contain” and all their variations are inclusive and will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The terms "about" or “approximately” are used herein to mean approximately, in the region of, roughly, or around. When the term "about" is used in conjunction with a numerical value/range, it modifies that value/range by extending the boundaries above and below the numerical value(s) set forth. In general, the term "about" is used herein to modify a numerical value(s) or a measurable value(s) such as a parameter, an amount, a temporal duration, and the like, above and below the stated value(s) by a variance of +/-20% or less, +/-10% or less, +/-5% or less, +/-1% or less, and +/-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention, and achieves the desired results and/or advantages as disclosed in the present disclosure. It is to be understood that the value to which the modifier “about” or “approximately” refers is itself also specifically, and preferably, disclosed.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. As used in this specification and the appended claims, the singular forms “a,” “an” and “the” includes both singular and plural references unless the content clearly dictates otherwise. The use of the expression ‘at least’ or ‘at least one’ suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. As such, the terms “a” (or “an”), “one or more”, and “at least one” can be used interchangeably herein.
Numerical ranges stated in the form ‘from x to y’ include the values mentioned and those values that lie within the range of the respective measurement accuracy as known to the skilled person. If several preferred numerical ranges are stated in this form, of course, all the ranges formed by a combination of the different end points are also included.
As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D,

G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.
Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
All references, articles, publications, general disclosures etc. cited herein are incorporated by reference in their entireties for all purposes. However, mention of any reference, article, publication etc. cited herein is not, and should not be taken as, an acknowledgment or any form of suggestion that they constitute valid prior art or form part of the common general knowledge in any country in the world.

We Claim:
1. A process for synthesis of hard carbon comprising the steps of,
i. pre-treating a biomass-based first precursor;
ii. combining the pretreated biomass-based first precursor of step (i) with a polymer resin
based second precursor to form a mixture; iii. heating the mixture of step (ii) to a temperature of about 150-400ºC to obtain a solid; and iv. allowing the solid formed in step (iii) to cool at room temperature, followed by subj ecting
the cooled mixture to pyrolysis at a temperature of about 600-1600ºC to obtain the hard
carbon,
wherein the first and the second precursor are in a ratio of about 30-70:70-30.
2. The process as claimed in claim 1, wherein the process for synthesis of hard carbon is a green process and devoid of any chemical treatment.
3. The process as claimed in any of claim 1 or 2, wherein the polymer resin is selected from a group comprising polyvinyl chloride, polyethylene and polypropylene, or any combination thereof.
4. The process as claimed in any of claims 1 -3, wherein the polymer resin is preferably polyvinyl chloride or a precursor thereof.
5. The process as claimed in any one of claims 1 to 3, wherein the polymer resin based second precursor is in the range of about 10 wt.% to 95 wt. %.
6. The process as claimed in any one of claims 1 to 4, wherein the biomass-based first precursor is selected from a group comprising coffee powder, almond shell powder, ground nutshell powder or husk and sugarcane bagasse, or any combination thereof; and wherein the biomass-based precursor is in the range of about 5 wt.% to 90 wt.%.
7. The process as claimed in any one of claims 1 to 6, wherein the biomass-based first precursor is coffee waste powder in the form of coffee grounds.
8. The process as claimed in claim 1 or 7, wherein the pretreatment of the biomass-based first precursor comprises treating with demineralized water for about 3-4 hours to remove impurities.
9. The process as claimed in claim 8, wherein the pretreatment of the biomass-based first precursor comprises treating with demineralized water at a temperature range of about 70℃-95℃.
31

10. The process as claimed in claim 1 or 7, wherein the biomass-based first precursor is pretreated
with demineralized water for about 4 hours.
11. The process as claimed in claim 1, wherein the biomass-based first precursor is pretreated with
demineralized water at about 90℃ for about 4 hours.
12. The process as claimed in any one of claims 9 to 11, wherein the pretreated biomass-based first precursor is vacuum dried at a temperature of about 80℃-120℃ for about 3-6 hours prior to combining it with the polymer resin based second precursor.
13. The process as claimed in claim 1, wherein the heating in step (iii) is done at a temperature of about 200ºC to 250ºC.
14. The process as claimed in claim 1, wherein the heating in step (iii) is performed for about 2-4 hours at a ramping rate of about 2-15℃/min.
15. The process as claimed in claim 1, wherein the pyrolysis performed in step (iv) is performed at a temperature of about 700-1300 ºC.
16. The process as claimed in claim 1, wherein the pyrolysis performed in step (iv) is performed for about 1-5 hours at a ramping rate of about 5-15℃/min.
17. The process as claimed in claim 1, wherein the pyrolysis performed in step (iv) is performed under nitrogen atmosphere.
18. The process as claimed in any one of claims 1 to 17, wherein the first precursor and the second precursor are in a ratio of about 30:70, 50:50 or 70:30.
19. The process as claimed in any one of claims 1 to 18, wherein after the pyrolysis, the hard carbon is allowed to cool down to room temperature, re-washed with distilled water to remove ash and water-soluble impurities, and dried at about 90℃ for about 8 hours.
20. Hard carbon obtained by the process of claim 1, wherein said hard carbon has a d-spacing value of more than or equal to about 3.6 Å.
21. The hard carbon as claimed in claim 20, having Id/Ig ratio of about 0.8 to about 1.1.
22. An anode material comprising the hard carbon as claimed in claim 19.
23. The anode material as claimed in claim 22, having coulombic efficiency of about 99.99% till 80th cycle.
24. A sodium ion battery comprising the anode material as claimed in claim 23.
Dated this 30 day of April, 2024.