Nanoporous carbon for energy storage, a method for production thereof, and an energy storage device

Abstract

The present disclosure provides a nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 μm to about 50 μm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w. The present disclosure also provides a method for the production of nanoporous carbon. The nanoporous carbon of the present disclosure is particularly suited for energy storage for example, for the production of battery, capacitor, and the like.

Description

NANOPOROUS CARBON FOR ENERGY STORAGE, A METHOD FOR PRODUCTION THEREOF, AND AN ENERGY STORAGE DEVICETECHNICAL FIELD

[0001] The present disclosure provides nanoporous carbon particularly suited for energy storage for example, for the production of battery, capacitor, and the like. The present disclosure also provides a method for the production of nanoporous carbon. Aspects of the present disclosure also provide an energy storage device and a method of fabrication thereof.BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] There is a strong need to move towards the development of sustainable and renewable energy resources because of diminishing conventional resources such as fossil fuels. A considerable amount of research has been done in this direction such as production of biofuels, solar energy, use of biomass for energy production in the form of biofuels, etc.

[0004] In recent years, waste-to-energy / -resource conversion has received considerable attention in response to a substantial increase in the utilization of natural resources and the amount of solid wastes generated, caused by rapid population growth. For example, the total amount of municipal solid waste (MSW) generated globally was 2000 million tons. Utilization of MSW for producing new resources, especially for environmental remediation, is attractive because it (i) offers solutions for solid waste management, (ii) reduces the cost of raw materials required for the production of valuable chemicals and commercial products and (iii) addresses global environmental issues in the context of sustainability.

[0005] Products such as porous carbon obtained from such wastes are being explored for a wide range of applications such as removal of heavy metals from contaminated water, removal of contaminants from flue gas, CO2 capture, hydrogen storage, heterogeneous catalysis, photocatalysis, bio-imaging, drug delivery, and energy storage. For this, a variety of batteries, capacitors, and hybrid capacitors are used as energy storage material. However, these suffer the drawbacks of large-scale storage, such as low power density, limited life span, and low energy density. Electrode quality plays a major role in the overall performanceof any energy storage device. Due to its eco-friendly nature and low cost, activated / nanoporous carbon has been the preferred choice of electrode material.

[0006] Activated / nanoporous carbons are versatile adsorbents due to their high surface area and therefore find applications in many fields such as the separation of environmental contaminants and purification of gases, resource recovery, catalysis, etc. Activated carbon or activated charcoal, is a form of carbon that is processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions. Enhancement of the porosity of these activated carbons is highly desirable. This is usually achieved by employing different chemical activating agents, optimizing the activation conditions such as temperature, ramp rate, and gas flow rate, and pre-treatment methods including soaking or stirring. However, the existing state of the art suffers several drawbacks such as high cost, low capacitance, and use of hazardous chemicals.

[0007] There is, therefore, a need in the art of nanoporous carbon particularly suited for energy storage, for example, for the production of battery, capacitor, and the like, which alleviates one or more shortcomings of the conventional approaches. The need is also felt for a method for the production of nanoporous carbon. The need is also felt for an energy storage device and a method of fabrication thereof, which alleviates one or more shortcomings of the conventional approaches. The disclosure of the instant application meets, at least in part, the long-standing need in the art and provides nanoporous carbon and a method for the production thereof.OBJECTS

[0008] An object of the present disclosure is to provide nanoporous carbon particularly suited for energy storage.

[0009] Another object of the present disclosure is to provide a nanoporous carbon that has very low impurities.

[0010] Further object of the present disclosure is to provide a method for the production of nanoporous carbon.

[0011] Further object of the present disclosure is to provide an energy storage device that exhibits superior energy density.

[0012] Still further object of the present disclosure is to provide a method of fabrication of an energy storage device that is facile and economical.SUMMARY

[0013] The present disclosure provides nanoporous carbon particularly suited for energy storage for example, for the production of battery, capacitor, and the like. The present disclosure also provides a method for the production of nanoporous carbon. Aspects of the present disclosure also provide an energy storage device and a method of fabrication thereof.

[0014] An aspect of the present disclosure relates to a nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w.

[0015] In some embodiments, the nanoporous carbon has BET area in the range from 1400 to 1500. In some embodiments, the nanoporous carbon has a pore volume in the range of 2.4 to 2.6. In some embodiments, the nanoporous carbon has particle size (Dv90) ranging from 15 pm to 20 pm. In some embodiments, the nanoporous carbon has Fe content ranging from 1 to 20 ppm, and ash content ranging from 0.02% to 0.1%.

[0016] Another aspect of the present disclosure relates to a process for purification of crude nanoporous carbon, said process comprising the steps of: (i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon; (ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon; (iii) subjecting the dried crude nanoporous carbon to particle size reduction; and (iv) exposing the crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss.

[0017] In some embodiments, the inert material comprises one or more polymeric materials. In some embodiments, the corrosion-resistant alloy comprises one or more nickel- based alloys. In some embodiments, the step of drying comprises exposing the treated crude nanoporous carbon to a temperature ranging from 90°C to 150°C for a time period ranging from 30 minutes to 48 hours.

[0018] Still another aspect of the present disclosure relates to a process for obtaining nanoporous carbon for energy storage, the process comprising the steps of: (a) pre-treating a raw material to obtain a char, the pre-treatment of the raw material being done using a chemical oxidant in presence of oxygen at a temperature of 50°C to 350°C for a first time period; (b) treating the char using a pore forming agent followed by washing; (c) optionally,effecting a successive thermal treatment to obtain a crude nanoporous carbon; and subjecting the crude nanoporous carbon to a purification process to obtain the nanoporous carbon, said purification process comprising: (i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon; (ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon; (iii) subjecting the dried crude nanoporous carbon to particle size reduction; and (iv) exposing the crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss.

[0019] In some embodiments, the raw material is a biomass waste comprising one or a combination of: saw dust, sugarcane bagasse, palm kernel shells, almond shells, coconut shell, coconut husks, municipal sludge, chicken poop, human hair, and lignin powder. In some embodiments, the nanoporous carbon has BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w.

[0020] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiment / s, along with the accompanying drawing figures in which numerals represent components.BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 illustrates an exemplary Dynamic light scattering (DLS) curve for the nanoporous carbon realized in accordance with an embodiment of the present disclosure.

[0022] FIG. 2A illustrates an exemplary galvanostatic charge-discharge (V vs C) of Li / CSC half-cell graph at different cycle for nanoporous carbon realized in accordance with an embodiment of the present disclosure.

[0023] FIG. 2B illustrates an exemplary capacity vs. Cycle number plot of Li / CSC halfcell graph for nanoporous carbon realized in accordance with an embodiment of the present disclosure.

[0024] FIG. 3A illustrates an exemplary galvanostatic charge-discharge (V vs C) of Li / CSC half-cell graph at different cycle for nanoporous carbon realized in accordance with an embodiment of the present disclosure.

[0025] FIG. 3B illustrates an exemplary capacity vs. cycle number plot of Li / CSC halfcell graph for nanoporous carbon realized in accordance with an embodiment of the present disclosure.

[0026] FIG. 4A-4E illustrates exemplary Eceii vs. time plot of CSC / Graphite LIC at varying temperature realized in accordance with an embodiment of the present disclosure.

[0027] FIG. 4F illustrates an exemplary ragone plot of CSC / Graphite LIC comparing energy density and power density at different temperatures realized in accordance with an embodiment of the present disclosure.

[0028] FIG. 5 illustrates an exemplary long-term cycling performance of LiCe / CSC LIC graph at a current density of 0.75 A g1at room temperature conditions realized in accordance with an embodiment of the present disclosure.

[0029] FIG. 6 illustrates exemplary long term cycling performance of LiCe / CSC LIC curve at varying temperature realized in accordance with an embodiment of the present disclosure.

[0030] FIG. 7A-7E illustrates exemplary Eceii vs. time plot of CSC / LTO LIC curves at varying temperatures, in accordance with embodiments of the present disclosure.

[0031] FIG. 7F illustrates an exemplary ragone plot of CSC / LTO LIC comparing energy density and power density at different temperatures, in accordance with embodiments of the present disclosure.

[0032] FIG. 8 illustrates an exemplary long-term cycling performance of CSC / LTO LIC at a current density of 1.5 A g'1at room temperature, in accordance with embodiments of the present disclosure.

[0033] FIG. 9 illustrates an exemplary long-term cycling performance of CSC / LTO LIC at varying temperatures, in accordance with embodiments of the present disclosure.DETAILED DESCRIPTION

[0034] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered 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.

[0035] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitationsspecified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0036] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0037] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0038] The present disclosure provides nanoporous carbon particularly suited for energy storage for example, for the production of battery, capacitor, and the like. The present disclosure also provides a method for the production of nanoporous carbon. Aspects of the present disclosure also provide an energy storage device and a method of fabrication thereof.

[0039] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0040] The present disclosure is, at least in part, on the premise of surprising observations by inventors of the instant application that employing nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, Pore volume in the range of 2 to 2.8 cm3 / g, Particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w affords unprecedented maximum energy density to the tune of about 192 Wh / kg when used for fabrication of an electrochemical storage device. It was also surprising to note that the amount of impurities, particularly, Fe and Ash content, present in the nanoporous carbon plays a pivotal role, and reduction in the amount of impurities present in the nanoporous carbon dramatically improves the maximum energy density of the electrochemical storage device.

[0041] Accordingly, an aspect of the present disclosure relates to a nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w.

[0042] In some embodiments, the nanoporous carbon has BET area in the range of 1200 to 1700 m2 / g, for example, ranging from 1300 to 1600 or from 1400 to 1500. The nanoporous carbon having BET area ranging from 1400 to 1500 is preferred.

[0043] In some embodiments, the nanoporous carbon has pore volume in the range of 2 to 2.8 cm3 / g, for example, ranging from 2.2 to 2.4 or from 2.4 to 2.6. The nanoporous carbon having a pore volume ranging from 2.4 to 2.6 is preferred.

[0044] In some embodiments, the nanoporous carbon has particle size (Dv90) ranging from about 5 pm to about 50 pm, for example, ranging from 5 to 20 or from 15 to 20. The nanoporous carbon having particle size (Dv90) ranging from 15 to 20 is preferred.

[0045] In some embodiments, the nanoporous carbon has Fe content less than about 20 ppm, for example, ranging from 1 to 20 ppm or ranging from 1 to 19 ppm or ranging from 5 to 20 ppm or from 1 to 10 ppm. The nanoporous carbon having Fe content less than about 10 ppm is preferred. The nanoporous carbon having Fe content less than about 7 ppm is particularly preferred.

[0046] In some embodiments, the nanoporous carbon has ash content less than about 0.2% w / w, for example, ranging from 0.02% to 0.2%, or from 0.02% to 0.1%. The nanoporous carbon having ash content less than about 0.05% is preferred.

[0047] In some embodiments, the nanoporous carbon comprises nanoporous carbon derived from one or a combination of: saw dust, sugarcane bagasse, palm kernel shells, almond shells, coconut shell, coconut husks, municipal sludge, chicken poop, human hair, and lignin powder. In an embodiment, the nanoporous carbon comprises coconut shell derived nanoporous carbon.

[0048] The present disclosure is also, at least in part, on the premise of surprising observations by inventors of the instant application that purification of crude nanoporous carbon by a process inclusive of the steps: (i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with of a corrosion resistant alloy to obtain treated crude nanoporous carbon; (ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon; (iii)subjecting the dried crude nanoporous carbon to particle size reduction; and (iv) exposing the crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss to 15,000 Gauss affords nanoporous carbon having Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w, which is particularly suited for energy storage applications.

[0049] Accordingly, another aspect of the present disclosure relates to a process for purification of crude nanoporous carbon, said process comprising the steps of: (i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon; (ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon; (iii) subjecting the dried crude nanoporous carbon to particle size reduction; and (iv) exposing the crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss. It has been observed that the process affords a reduction in the amount of impurities in the nanoporous carbon and aids in dramatically improving the performance characteristics of the electrode fabricated therefrom.

[0050] In some embodiments, the inert material comprises one or more polymeric materials. In some embodiments, the inert material comprises an ethylene -based copolymer. In some embodiments, the inert material comprises ethylene-tetrafluoroethylene (ETFE) copolymer (for example, Tefzel™ ETFE resin).

[0051] In some embodiments, the corrosion-resistant alloy comprises one or more nickel- based alloys, such as Hastelloy®.

[0052] In some embodiments, the step of drying comprises exposing the treated crude nanoporous carbon to a temperature ranging from 90°C to 150°C, preferably, ranging from 100°C to 125°C for a time period ranging from 30 minutes to 48 hours, preferably, ranging from 4 hours to 48 hours and more preferably, ranging from 10 hours to 36 hours. In some embodiments, the step of drying is effected in a furnace.

[0053] In some embodiments, the step of particle size reduction is effected in a ball mill. In some embodiments, the ball mill is rubber-lined. In some embodiments, the ball mill comprises zirconia balls having a diameter of about 8 mm.

[0054] In some embodiments, the step of particle size reduction is effected in a ball mill keeping the ball to crude nanoporous carbon mass ratio within the range of 25: 1 to 2: 1, preferably, ranging from 20: 1 to 5: 1, and more preferably, ranging from 15: 1 to 5: 1.

[0055] In some embodiments, the crude nanoporous carbon subjected to the step of particle size reduction is passed through a size of 325 mesh size to obtain the crude nanoporous carbon of the desired particle size.

[0056] In some embodiments, the step of exposing the crude nanoporous carbon of desired particle size to a magnetic flux comprises exposing the crude nanoporous carbon of desired particle size to magnets having magnetic flux in the range of 10,000 Gauss and 15,000 Gauss, preferably, in the range of 10,000 Gauss to 14,000 Gauss, and more preferably, in the range of 10,000 Gauss to 12,000 Gauss. In some embodiments, the magnets are NdFeB Magnets.

[0057] In some embodiments, the crude nanoporous carbon comprises crude nanoporous carbon derived from one or a combination of: saw dust, sugarcane bagasse, palm kernel shells, almond shells, coconut shell, coconut husks, municipal sludge, chicken poop, human hair, and lignin powder. In an embodiment, the crude nanoporous carbon comprises coconut shell-derived crude nanoporous carbon.

[0058] In some embodiments, the resultant nanoporous carbon has Fe content less than about 20 ppm, for example, ranging from 1 to 20 ppm or ranging from 1 to 19 ppm or ranging from 5 to 19 ppm or ranging from 1 to 9 ppm or from 1 to 8 ppm or from 1 to 7 ppm. The nanoporous carbon having Fe content less than about 7 ppm is preferred.

[0059] In some embodiments, the resultant nanoporous carbon has ash content less than about 0.2% w / w, for example, ranging from 0.02% to 0.2%, or from 0.02% to 0.1%. The nanoporous carbon having ash content less than about 0.05% is preferred.

[0060] Further aspect of the present disclosure relates to a process for obtaining nanoporous carbon for energy storage. The process comprises the steps of: (a) pre-treating a raw material to obtain a char, the pre-treatment of the raw material being done using a chemical oxidant in presence of oxygen at a temperature of 50°C to 350°C for a first time period; (b) treating the char using a pore forming agent followed by washing; (c) optionally, effecting a successive thermal treatment to obtain a crude nanoporous carbon; and subjecting the crude nanoporous carbon to a purification process to obtain the nanoporous carbon, said purification process comprising: (i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon; (ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon; (iii) subjecting the dried crude nanoporous carbon to particle size reduction; and (iv) exposing the crudenanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss to obtain the nanoporous carbon for energy storage.

[0061] In some embodiments, the raw material is a biomass waste comprising one or a combination of: saw dust, sugarcane bagasse, palm kernel shells, almond shells, coconut shell, coconut husks, municipal sludge, chicken poop, human hair, and lignin powder.

[0062] In some embodiments, the chemical oxidant is hydrogen peroxide.

[0063] In some embodiments, the first time period ranges from 1 hour to 10 hours, for example, from 1.5 hours to 8 hours, or from 2 hours to 8 hours, or from 2.5 hours to 7 hours, or from 3.5 hours to 6 hours. In one embodiment, the first time period ranges from 3 hours to 6 hours.

[0064] In some embodiments, the pre-treatment of the raw material is effected at a temperature ranging from 70°C to 350°C, for example, from 90°C to 325°C, or from 100°C to 300°C, or from 130°C to 300°C, or from 150°C to 250°C. In one embodiment, the pretreatment of the raw material is effected at a temperature ranging from 130°C to 250°C.

[0065] In some embodiments, the pore-forming agent comprises a zinc salt.

[0066] In some embodiments, the char is treated using the pore-forming agent at a temperature ranging from 150°C to 400°C, preferably, ranging from 150°C to 350°C and more preferably, ranging from 150°C to 250°C for a second time period.

[0067] In some embodiments, the second time period ranges from 5 hours to 30 hours, preferably, ranging from 5 hours to 25 hours, and more preferably, ranging from 5 hours to 15 hours.

[0068] In some embodiments, the char treated using the pore-forming agent is subjected to a thermal treatment by exposing it to a temperature ranging from 400°C to 900°C, for example, from 450°C to 850°C, or from 500°C to 800°C, or from 550°C to 800°C, or from 600°C to 800°C. In one embodiment, the char is subjected to the thermal treatment at a temperature ranging from 600°C to 800°C.

[0069] In some embodiments, the crude nanoporous carbon is subjected to washing followed by treatment with an acid before subjecting it to the purification process. In some embodiments, the crude nanoporous carbon is washed with water followed by treatment with an acid for a time period ranging from about 6 hours to about 36 hours, preferably, ranging from about 10 hours to about 30 hours and more preferably, ranging from 12 hours to 24 hours.

[0070] Further aspect of the present disclosure provides an electrochemical energy storage device comprising: an anode comprising electrochemically prelithiated graphite orlithium titanate; a cathode comprising the nanoporous carbon realized in accordance with embodiments of the present disclosure; a porous separator; and an electrolyte comprising Lithium hexafluorophosphate (LiPF6) dissolved in a solvent.

[0071] In some embodiments, the electrolyte comprises 1 M LiPF6dissolved in 1: 1 v / v mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC).

[0072] In some embodiments, the anode comprises lithium titanate - Li4Ti50i2 (LTO).

[0073] In some embodiments, the anode comprises a graphite / Lithium titanate ( L^Ti O 12 )- conductive carbon, and binder in the ratio of 8: 1 : 1.

[0074] In some embodiments, the cathode comprises the nanoporous carbon, conductive carbon, and binder in the ratio of 8: 1 : 1.

[0075] In some embodiments, the conductive carbon is selected from acetylene black or Super P.

[0076] In some embodiments, the binder is selected from polyvinylidene fluoride or teflonized acetylene black (TAB-2).

[0077] In some embodiments, the porous separator is selected from Whatman paper or polypropylene sheet. However, porous separator made from any other material can also be used.

[0078] In some embodiments, the electrochemical energy storage device is a Lithium-ion capacitor (LIC).

[0079] Still further aspect of the present disclosure relates to a method of fabrication of an electrochemical energy storage device, said method comprising the steps of: (i) preparing a calendered anode and a calendered cathode on a substrate, said calendered cathode comprising the nanoporous carbon realized in accordance with embodiments of the present disclosure; (ii) fabricating half-cell of calendered anode and calendered cathode; (iii) activating the anodic half-cell electrochemically; (iv) disassembling the anodic half-cell after electrochemical activation; and (v) fabricating the electrochemical energy storage device by employing the electrochemically activated anode and mass-balanced cathode.

[0080] In some embodiments, the step of preparing the calendered anode and the calendered cathode on the substrate comprises: (a) preparing slurries of electrode materials comprising an anodic active material or a cathodic active material, conductive carbon, and binder with a solvent; (b) spreading the slurry into a film employing a doctor blade and drying at 50-70°C; and (c) pressing by calendering to make the calendered anode and the calendered cathode.

[0081] In some embodiments, the anodic active material comprises lithium titanate - Li4Ti50i2 (LTO).

[0082] In some embodiments, the slurry of anode materials comprises a graphite / Lithium titanate (L4Ti50i2), conductive carbon, and binder in the ratio of 8: 1 : 1.

[0083] In some embodiments, the cathodic active material comprises the nanoporous carbon realized in accordance with the embodiments of the present disclosure.

[0084] In some embodiments, the slurry of cathode materials comprises the nanoporous carbon realized in accordance with the embodiments of the present disclosure, conductive carbon, and binder in the ratio of 8: 1 : 1.

[0085] In some embodiments, the conductive carbon is selected from acetylene black or Super P.

[0086] In some embodiments, the binder is selected from polyvinylidene fluoride or teflonized acetylene black (TAB-2).

[0087] In some embodiments, the step of fabricating half-cells of calendered anode and calendered cathode comprises the steps of: cutting the calendered anode and the calendered cathode, and fabricating a half-cell by employing Li-metal as the counter or reference electrode.

[0088] In some embodiments, the step of activating the anodic half-cell electrochemically comprises the steps of: carrying out electrochemical activation of the half-cell of the anode by running one or more cycles of charge and discharge of the half-cells, wherein the electrochemical pre-treatment of the graphitic anode is carried out under current density of about 0. 1 A g1and voltage ranges from 0.005 to 2 V vs. Li and the LTO anode is carried out under current density of 0. 1 A g1and voltage ranges from 1 to 3 V.

[0089] In some embodiments, the step of disassembling the anodic half-cell after electrochemical activation comprises: retrieving the activated anode after disassembling the half-cell in a lithiated state (LiCe).

[0090] In some embodiments, the mass-balanced cathode is obtained by carrying out the mass-balancing using the following equation:M1C1= M2C2where Mi, M2are anodic and cathodic masses, and Ci, C2 are anodic and cathodic capacities, respectively.

[0091] In some embodiments, the step of fabricating the electrochemical energy storage device comprises physically separating the electrochemically activated anode and the mass- balanced cathode by a porous separator and an electrolyte.

[0092] In some embodiments, the porous separator is selected from the Whatman paper or polypropylene sheet.

[0093] In some embodiments, the electrolyte comprises 1 M Lithium hexafluorophosphate (LiPF6) dissolved in 1 : 1 v / v mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC).

[0094] In some embodiments, the electrochemical energy storage device is a Lithium-ion capacitor (LIC).

[0095] 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.EXAMPLES

[0096] EXAMPLE 1: PREPARATION OF NANOPOROUS CARBON

[0097] Coconut shells were used as a raw material for carbon production. The coconut shells were crushed & sieved to obtain 500-1000 pm size (using mesh sizes of 10 and 20 mesh). The shells were then oxidized using oxygen and H2O2 at temperatures of about 170°C and at an ambient pressure of about 1 atm for about 4 hours to obtain a hydrochar, wherein the coconut shells and H2O2 were in a ratio of 0.3: 1 (w / v). The hydrochar was soaked in zinc chloride for about 3 hours at 200°C and 3 hours at 230°C to obtain a mixture. The mixture was then thermally processed in a furnace by increasing the temperature at a rate of 4°C / min till it reaches 700°C. The mixture was kept at 700°C for about 2 hours under an inert atmosphere (N2 flow). The furnace was cooled down and the mixture was washed with deionized water followed by soaking with HC1 for 24 hours afterwards zinc chloride was recovered up to 50%. Successive washings were carried out using an Agitated Neutsche Filter (ANF) with dilute acids / bases like HC1 and NH40H to remove the unreacted chemicals and calcined ash. The mixture was dried in an oven at 115°C for about 24 hours. After this, the mixture was grounded using a rubber-lined ball mill. Ball to carbon mass ratio used was 10: 1 and Zirconia balls of 8 mm size were used. Ball milling was carried out for 4 hours and then sieved to 325 mesh size. The final mixture was then subjected to 2 layers of magnetic separation (at a magnetic flux of 11000 Gauss and 12000 Gauss) using high-intensity NdFeB magnets to remove the impurities to obtain the final product i.e. nanoporous carbon which isparticularly suitable for energy storage. The final product was stored in a dry box (cool & dry).

[0098] Characterization and analysis

[0099] The nanoporous carbon material prepared above was subjected to characterization and analysis, details wherefore are provided below:

[0100] Particle size analysisThe particle size analysis for nanoporous carbon prepared above is provided in FIG. 1.

[0101] BET surface analysisBET surface analysis for nanoporous carbon prepared above is provided in Table 2 below:Table 2: BET surface analysis

[0102] Impurity Profiling

[0103] Preparation of Lithium-ion capacitors (LICs)

[0104] The electrodes were prepared by separately casting slurries composed of active materials (graphite / Li4Ti5Oi2(LTO) / nanoporous carbon (CSC)), conductive carbon (acetylene black), and binder (teflonized acetylene black, TAB-2) in the weight ratio of 8: 1: 1 over current collectors. The electrodes of 12 / 14 mm diameter were punched out and paired with the lithium metal for the half-cell studies.

[0105] For the fabrication of the full-cell with graphite anode (C) and CSC cathode, the steps were as follows:1) Prelithiation of Li / C: Initially, the graphite electrode was paired with Li metal, and a half cell was fabricated. This was cycled for a few cycles to remove the initial irreversibility that was caused due to the solid electrolyte interface (SEI) layer formation. After running for a few cycles, the cell was terminated at a discharged state to obtain the lithium-inserted graphite or pre-lithiated graphite (LiC6).2) Fabrication of CSC / LiC6 full cell: The prelithiated Li / graphite half cell was dismantled inside the glove box and paired with the mass-balanced CSC cathode to obtain the full cell (LiC6 / / CSC).The Li / C cell was subjected to electrochemical pre-lithiation before the LIC fabrication, whereas the LTO electrodes were directly paired with the CSC electrode. The LIC was assembled by sandwiching the electrolyte-soaked Whatmann separator between the electrochemically pretreated C or LTO electrode and CSC electrode in a lab-scale exemplary coin-cell (CR 2016) set up in the inert condition. The electrolyte used was 1 M LiPF6dissolved in a 1: 1 v / v mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The fabricated CSC / C and CSC / LTO-based LICs were tested at different current rates in the voltage window of 1.9 to 4.4 V and 1 to 3 V, respectively.For the half-cell study, the CSC electrode was paired with the metallic lithium. The aforementioned electrolyte and Whatmann separator were used as other cell components. The Li / CSC half-cell was tested in the potential window of 2 to 4.5 V vs. Li at a current density of 0.1 A g '. The Lithium metal battery (Li / CSC) subjected to galvanostatic charge-discharge studies at a potential range of 2 to 4.5 V vs. Li delivered initial discharge / reversible capacityof 94 mAh g1(as shown in Fig. 2A) and maintained a specific capacity of ~98 mAh g1after 500 cycles at a current density of 0.1 A g1(as shown in FIG. 2B).

[0106] For another half-cell study, the Lithium metal battery (Li / CSC) was subjected to galvanostatic charge-discharge studies at a potential window of 3 to 4.5 V vs. Li, in which the cell delivered an initial reversible capacity of ~52 mAh g respectively (as shown in FIG. 3 A), and maintained a specific capacity of ~ 42 mAh g1after 1300 cycles at a current density of 0.1 A g1(as shown in FIG. 3B).

[0107] A Lithium-ion capacitor (LIC) was fabricated with electrochemically prelithiated graphite as anode, CSC as cathode, and a 1: 1 v / v mixture of 1 M LiPFe in ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolyte, tested at the voltage window of 1.9 to 4.4 V for galvanostatic charge-discharge studies under the balanced mass loading condition. The LIC tested at different current rates (0.1 to 2.5 A g '). and different temperature conditions delivered an excellent energy / power density value of 191.7 Wh kg ' / 8.7 kW kg1. respectively (as shown in FIG. 4A-4F).

[0108] The LIC was also subjected to charge-discharge for more than 12,000 cycles, for which >80% of the capacity was retained after cycling (as shown in FIG. 5), which is one of the prerequisites for practical application. In addition, the LIC exhibited a capacity retention of greater than or close to 80% even after 1000 cycles of charge-discharge at varying temperatures (as shown in FIG. 6). At higher temperatures, it was observed that the electrolytes get activated, which increases inevitable side reactions leading to degradation upon cycling.

[0109] For full-cell study, a LIC was fabricated using Li4Ti50i2 (LTO) as an anode, CSC as a cathode, and a 1: 1 v / v mixture of 1 M LiPF6in ethylene carbonate and dimethyl carbonate as an electrolyte, tested at the voltage window of 1 to 3 V for galvanostatic chargedischarge studies under the balanced mass loading condition. The full-cell tested at the different current rates (0.1 to 2.5 A g ') exhibited a superior energy density and power density value of 67.8 Wh kg and 5.1 kW kg respectively (as shown in FIG. 7A-7F), at room temperature conditions. However, the maximum energy and power density values were observed at 50 °C (Energy density: 71.1 Wh kg Power density: 5.8 kW kg '). In addition, the full displayed capacity retention was >80% after 4500 cycles of charge-discharge (as shown in FIG. 8). The performance of the LIC was also studied at different temperature conditions (-10, 0, 10, 25, and 50 °C). Except at 50 °C, the LIC retained an excellent capacity of >97 % after 1900 cycles at all temperatures (as shown in FIG. 9).

[0110] In all the above examples, the performance of the CSC was compared with commercial activated carbon (YP 80F Kuraray, Japan; surface area: 2100 m2g-1, pore volume: 0.97 mb g-1), wherein it was noted that the CSC delivers superior results compared with commercial activated carbon. The energy capability and power of the LIC were evaluated with two different anodic combinations with the CSC. The energy density value, evaluated from LIC with graphitic anode, was far better than that of the commercial activated carbon as a cathode. The CSC / LTO-based LIC also displayed an excellent power density value. It was noted and concluded that the CSC is an excellent cathode material for the lithium-ion capacitor application as it exhibits superior energy density, power density, cyclic stability, etc. than commercially available activated carbon.

Claims

We Claim:

1. A nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w.

2. The nanoporous carbon as claimed in claim 1, wherein the nanoporous carbon has BET area in the range of 1400 to 1500, pore volume in the range of 2.4 to 2.6, particle size (Dv90) ranging from about 5 pm to about 20 pm, Fe content ranging from 1 to 20 ppm, and ash content ranging from 0.02% to 0.2%.

3. A process for purification of crude nanoporous carbon, said process comprising the steps of:(i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon;(ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon;(iii) subjecting the dried crude nanoporous carbon to particle size reduction; and(iv) exposing the crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss to obtain the nanoporous carbon.

4. The process as claimed in claim 3, wherein the inert material comprises one or more polymeric materials.

5. The process as claimed in claim 3, wherein the corrosion-resistant alloy comprises one or more nickel-based alloys.

6. The process as claimed in claim 3, wherein the step of drying comprises exposing the treated crude nanoporous carbon to a temperature ranging from 90°C to 150°C for a time period ranging from 30 minutes to 48 hours.

7. A process for obtaining nanoporous carbon for energy storage, said process comprising the steps of:(a) pre-treating a raw material to obtain a char, the pre-treatment of the raw material being done using a chemical oxidant in presence of oxygen at a temperature of 50°C to 350°C for a first time period;(b) treating the char using a pore-forming agent followed by washing;(c) optionally, effecting a successive thermal treatment to obtain a crude nanoporous carbon; and(d) subjecting the crude nanoporous carbon to a purification process to obtain the nanoporous carbon, said purification process comprising:(i) treating the crude nanoporous carbon with dilute acid(s) and / or base(s) in an Agitated Neutsche Filter (ANF), said Agitated Neutsche Filter (ANF) being internally lined with an inert material and having a stirrer made of or lined with a corrosion resistant alloy to obtain treated crude nanoporous carbon;(ii) subjecting the treated crude nanoporous carbon to drying to obtain a dried crude nanoporous carbon;(iii) subjecting the dried crude nanoporous carbon to particle size reduction; and(iv) exposing the dried crude nanoporous carbon of desired particle size to a magnetic flux in the range of 10,000 Gauss and 15,000 Gauss.

8. The process as claimed in claim 7, wherein the raw material is a biomass waste comprising one or a combination of: saw dust, sugarcane bagasse, palm kernel shells, almond shells, coconut shell, coconut husks, municipal sludge, chicken poop, human hair, and lignin powder.

9. The process as claimed in claim 8, wherein the nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w.

10. An electrochemical energy storage device comprising: an anode comprising electrochemically prelithiated graphite or lithium titanate; a cathode comprising the nanoporous carbon, said nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w; a porous separator; and an electrolyte comprising Lithium hexafluorophosphate (LiPF6) dissolved in a solvent.

11. The electrochemical energy storage device as claimed in claim 10, wherein the anode comprises a graphite / Lithium titanate (L4Ti50i2), conductive carbon, and binder in the ratio of 8: l:l.

12. The electrochemical energy storage device as claimed in claim 10, wherein the cathode comprises the nanoporous carbon, conductive carbon, and binder in the ratio of 8: 1 : 1.

13. The electrochemical energy storage device as claimed in any of claims 11 and 12, wherein the conductive carbon is selected from: acetylene black and Super P, and wherein the binder is selected from: polyvinylidene fluoride and teflonized acetylene black (TAB-2).

14. The electrochemical energy storage device as claimed in any of claims 10 to 13, wherein the electrolyte comprises 1 M LiPF6dissolved in 1: 1 v / v mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC).

15. The electrochemical energy storage device as claimed in any of claims 10 to 14, wherein the electrochemical energy storage device is a Lithium-ion capacitor (LIC).

16. A method of fabrication of an electrochemical energy storage device, said method comprising the steps of:(i) preparing a calendered anode and a calendered cathode on a substrate, said calendered cathode comprising nanoporous carbon having BET area in the range of 1200 to 1700 m2 / g, pore volume in the range of 2 to 2.8 cm3 / g, particle size (Dv90) ranging from about 5 pm to about 50 pm, Fe content less than about 20 ppm, and Ash content less than about 0.2% w / w;(ii) fabricating half-cell of calendered anode and calendered cathode;(iii) activating the anodic half-cell electrochemically;(iv) disassembling the anodic half-cell after electrochemical activation; and(v) fabricating the electrochemical energy storage device by employing the electrochemically activated anode and mass-balanced cathode.

17. The method as claimed in claim 16, wherein the step of fabricating half-cells of calendered anode and calendered cathode comprises: cutting the calendered anode and the calendered cathode; and fabricating half-cell by employing Li-metal as the counter or reference electrode.

18. The method as claimed in any of claims 16 or 17, wherein the step of activating the anodic half-cell electrochemically comprises: carrying out electrochemical activation of the half-cell of the anode by running one or more cycles of charge and discharge of the half-cells, wherein the electrochemical pre-treatment of the graphitic anode is carried out under currentdensity of about 0. 1 A g1and voltage ranging from 0.005 to 2 V vs. Li and the LTO anode is carried out under current density of 0.1 A g1and voltage ranges from 1 to 3 V.

19. The method as claimed in any of claims 16 to 18, wherein the step of disassembling the anodic half-cell after electrochemical activation comprises retrieving the activated anode after disassembling the half-cell in a lithiated state (LiCe).

20. The method as claimed in any of claims 16 to 19, wherein the mass-balanced cathode is obtained by carrying out the mass-balancing using the equation:where Mi and M2 represent anodic and cathodic masses, respectively, and Ci and C2 represent anodic and cathodic capacities, respectively.

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