CARBON ELECTRODE FROM SPENT WALNUT SHEL^ FOR AQUEOUS AND NON-AQUEOUS SUPERCAPACITORS AND LITHIUM-JON BATTERY
FIELD OF INVENTION
The invention relates to energy storage devices and in particulai"to Supercapacitor devices and lithium-ion battery. Further, the invention relates to the use off naturally available materials such as spent wainut shell and the activated carbon derived frpm il used as lithium insertion anode material for lithium-ion battery and as electrodes for ultracapacit0*5 (Supercapacitors) in aqueous and non-aqueous electrolytes.
BACKGROUND OF INVENTION
The development of energy storage devices in general has g^ined significance to meet the energy demands of the modem-life. ln particular, energy stora#e devices and their production from recyclable sources have gained particular attention. The usage of lithium-ion battery is increasing for everyday applications and are widely used in the portable consumer electronics. The lithium-ion batteries have a very dominant usage in certain application areas.
As with the.characteristic of the ever-evolving market requirements, the battery manufacturers are continuously working on developing batteries with high energy density, power density and long cycle-life with short charging time. Thus, it is indisperisable to develop high energy density energy storage devices which are also capable of d^vermS Pea^ power demand. Supercapacitors are capable of delivering peak power deman^s. The most desirable energy storage device for various consumer electronics applications mUst nave features of the batteries and that of the supercapacitors in a single platform.
However, almost all the commercial Li-ion batteries utilize graphitic'carbon as the anode material and as electrodes for ultracapacitor in aqueous and non-aqueous electrolyte owing to the favourable properties such as high conductivity, low voltage hysteresis, good rate capability etc. The objective of the invention is to propose a novel and $ustainable waste as source for generation of carbon electrodes for energy storage devices. Yet another object of the invention is to propose the manufacturing of the aforesaid Lithium-ion batterv and Ultracapacitor energy

storage devices having improved performance with the use of natura! resources such as organic . waste/agricultural waste.
A further object of the invention is to propose sustainable approach for generating carbon electrode materials from the spent walnut shell. The activated carbon derived from the spent walnut shell is used as anode material for lithium-ion battery and as electrodes for ultracapacitor in aqueous and non-aqueous electrolytes.
SUMMARY OF THE INVENTION
Energy storage devices with higher performance potentials are disclosed. In some embodiments, the energy storage devices comprise identical two carbon electrodes in aqueous or non-aqueous ultracapacitor and Li-ion battery using commercial LiCo02 as positive electrode, and the activated carbon derived by carbonizing spent walnut shell material as anode are disclosed. Fabrication processes for manufacturing both the energy storage devices are disclosed.
The other objectives and advantages of the device of the present disclosure will be further appreciated and understood when considered in combination with the following description and accompanying drawings. While the following description may contain specific details describing particular embodiments of the devices of the present disclosure, this should not be construed as limitations to the scope of the device of the present disclosure but rather as an exemplificatiori of preferable embodiments. For each aspect of the device of the present disclosure, many variations are possible as suggested herein that are known to those of ordinary skill in the art. A variety of changes and modifications may be made within the scope of the present disclosure without departing from the spirit thereof.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is the XRD pattern recorded for the spent walnut shell-derived activated carbon.
FIG. 2 is the Raman spectrum recorded for the spent walnut shell-derived activated carbon obtained at different temperature.
FIG. 3 (a-d) are the SEM images recorded for the spent walnut shell-derived precarbonized carbon sampicaf 300 °G.

FIG. 4 (a-i) are the SEM images recorded for (a-c) 500 °C, (d-f) 600 °C and (g-i) 700 °C the activated carbon from spent walnut shell.
FIG. 5 (a-i) are the CV curves at different scan rates, Charge-discharge profiles at different currents for the 500 °C, 600 °C and 700 °C activated carbon samples in three electrode.
FIG. 6 is the comprasion of specific capacitance for the spent walnut shell-derived activated carbon samples generated at different activation temperatures.
FIG. 7 (a-c) are the CV curves at different scan rate, Charge-discharge profiles at different currents, Columbic efficiency-cum-cycle life recorded for aqueous prototype symmetric supercapacitor in IMH2SO4.
FIG. 8 (a-f) are the CV curves at different potential windows at a scan rate of 10 m V s"1, CV curves of different scan rates, Charge-discharge profiles at different currents and Columbic efficiency-cum-cycle life recorded for non-aqueous prototype lithium-ion ultracapacitor. Inset: Photographs of glowing LED powered using the lithium-ion capacitor.
Fig.9. (a, b) Ragone plots recorded for the aqueous (1M H2SO4) and the non-aqueous symmetry (1M LiPFe) ultracapacitor devices containing the walnut-derived activated carbon electrodes. Inset: Schematic of the devices.
FIG. 10 is the Charge-discharge profiles and Rate capability cum-cycle life test obtained for the coin-type 2032 half-cell containing 500 °C activated carbon anode and Li metal counter electrode.
FIG. 11 is the Charge-discharge profiles and Rate capability cum-cycle life test obtained for the coin-type 2032 half-cell containing 600 °C activated carbon anode at and Li metal counter electrode.
FIG. 12 is the Charge-discharge profiles and Rate capability cum-cycle life test obtained for the coin-type 2032 half-cell containing 700 °C activated carbon anode at and Li metal counter electrode.
FIG. 13 is the Charge-discharge profile of the CR-2032 prototype full cell lithium-ion battery containing 700 °C activated carbon anode and.commercial LiCo02.cathode. Inset: Photograph of glowing LED powered by the CR-2032 type full cell lithium-ion battery.

DETAILED DESCRIPTION OF THE INVENTION
The invention aims to solve the technical problem of improving the perforriiances of energy storage devices and to explore the readily available natural waste materials as the alternate carbon sources. The energy storage devices of the invention comprise an aqueous, non-aqueous ultracapacitors and Li-ion battery. Ultracapacitor comprising of two identical carbon electrodes derived from the spent walnut shell in aqueous (1M H2SO4) and non-aqueous (1M LiPF6 in EC/DEC) electrolytes. The lithium-ion battery consists of commercial LiCo02 cathode and carbon anode extracted from carbonizing spent walnut shell material, are disclosed. Provided herein are carbon and LiCoCh-based materials, fabrication processes, ultracapacitor devices and Li-ion battery devices with improved performance.
In particular, the concept of intercalation/de-intercalation of Li ions paved the way for the use of the carbon-based anode material in place of the Li metal. All the available commercial Li-ion battery utilize graphitic carbon as the anode material and there is a need to explore alternate carbon resources that can be derived from naturally occurring materials.
For achieving the above-identified objectives, carbon electrode has been designed and the fabrication process of the same is disclosed. Activated carbon derived from carbonizing spent walnut shell material and its use as electrodes are disclosed. The spent walnut shell was collected, cleaned and dried. For carbonization process, a portion of the cleaned walnut shell was initially precarbonized in a muffle furnace in a temperature range of about 200- 400 °C for a time period of about two hours. Then, the precarbonized sample was homogeneously mixed with the requisite amount of KOH and in the subsequent step, the mixture was transferred into an alumina boat and kept in.tubular furnace at a temperature range of about 400 - 800 °C in Ar atmosphere f or a time period of about four to six hours for activation. After the treatment, the obtained sample was washed several times subjected to acidic (HC1) and distilled water treatment. The samples then are dried in vacuum desiccator to obtain the final activated carbon.
In this context, few embodiments of the invention are described in detail and it is to be understood that the invention is not limited in its application to the details of construction, arrangements of the components, the steps by which a particular device is manufactured and the analysis techniques as set forth in the following description or illustrated in the drawings. It is entirely possible that the invention is capable of other embodiments and of being practiced

and carried out in various other ways. Also, the phrases and terminologies as used hereinare for the purpose of the description and should not be regarded as limiting.
The following steps explains in detail, the energy storage devices, their components and fabrication in detail:
Energy Storage Device Components and Fabrication
Activated carbon generation and characterization
Spent walnut shells were collected and cleaned. For carbonization process, a portion of the cleaned walnut shell was initially precarbonized in a muffle furnace at a temperature range of about 200- 400 °C for about two to three hours. Then, the precarbonized sample was homogeneously mixed with K.OH and in the subsequent step, the mixture was transferred into an alumina boat and kept in tubular furnace at a range of about 400 - 800 °C in Ar atmosphere for a time period of about four to six hours for activation. After the treatment, the obtained sample was washed several times with 1M HC1 and distilled water. The samples then are dried in vacuum desiccator to obtain the final activated carbon. Three samples of such activated carbon were prepared with activation temperature of 500, 600 and 700 °C.
The obtained activated carbons were characterized by using powder X-ray diffraction (Bruker D8 advance Da vinci) employing Cu Ka radiation source (a = 1.5417Å), Raman spectroscopy (Witec Confocal Raman instrument with Ar ion laser 718 nm CRM200) and scanning electron microscope (SEM, Hitachi, Model: S-3400N). High-resolution transmission electron microscope (HR-TEM, JEOL JEM 2100) analysis of the prepared sample was carried at an operating voltage of 200 kV.
Ultracapacitor Characterization
The ultracapacitor studies of the activated carbon were done initially in a three-electrode cell comprising the derived activated carbon as the working electrode, platinum (Pt) as counter electrode and Ag/AgCl as reference electrode in 1M H2SO4. Then, proto-type symmetric ultracapacitor devices were fabricated using identical two activated carbon electrodes in the form of CR-2032-coin cell using Wattman filter paper as separator. The working electrode for this characterization study was prepared using the mixture of the activated carbon (80 wt.%), carbon black (10 wt.%) and polyvinylidene fluoridone (PVDF) (10 wt.%). The PVDF was used as the binder in electrode fabrication to bind the electrode material on to the surface of carbon cloth current collector. N-methyl-2-pyrrolid6ne (fWtP) was used as a*so1véhfi:o obtain slurry.

The slurry thus obtained was pasted on to the carbon cloth (1 cm x 1 cm) and dried at a temperature range of about 80-120°C for overnight. The masses of the coated and uncoated electrodes were measured. The total mass loading of the electrode was calculated by measuring the difference between the mass of the coated and uncoated electrodes. The active mass of the electrode was found to be 2 mg cm"2. The cyclic voltammetry (CV) and galvanostatic charge-discharge studies were carried out in a three-electrode cell using the aforementioned electrochemical Workstation. The ultracapactive performances of proto-type symmetric devices were evaluated in 1M H2SO4 (aqueous) and 1M LiPF6 (non-aqueous lithium-ion capacitor) in ethylene carbonate (EC)/ dimethyl carbonate (DEC) (1:1 in voiume).
Lithium-ion storage characterization:
Lithium-ion storage performance of the spent walnut shell-derived activated carbon was examined by fabricating a prototype, a CR2032-type coin cell. The working electrode for this prototype was prepared by mixing the carbon active material, super P carbon and polyvinylidene difluoride (PVDF) binder in a weight ratio of 70:15:15. N-methyl-2-pyrrolidone (NMP) was used as a solvent to prepare the slurry. The slurry thus prepared was coated on a copper foil (9 um thickness) by doctor blade method and dried-at a temperature range of anout 60-150 °C for a time period of about 8-15 h under vacuum. After this, the coin cells were assembled in an Ar-filled glovebox (NICHWELL a-1500u) using the Li-metal disc as the counter electrode and the activated carbon as anode for the Li half-cell. For Li-ion full cell, commercial lithium cobalt oxide (LCO)-coated on an aluminium foil as the cathode and the"activated carbon on the copper foil as the anode were used. In both these cases, the electrolyte used was 1M LiPFe in ethylene carbonate (EC)/ dimethyl carbonate (DEC) (1:1 in voiume). The cyclic voltammetry (CV) studies were carried out using electrochemical Workstation (Biologic, SP-150) on the coin cells in the potential range of 0-3 V at a scan rate of 0.01 mV/s. The galvanostatic charge-discharge cyclings on the coin cells at different current rates were performed using the battery analyzer Neware (CT-4008). The potential window for the half-cell was 0-3 V and that for the full cell was 2.8-4.2 V.
Results and Discussion
Crvstal Structure and Morphology
Figure 1. (a) shows XRD patterns recorded for the spent walnut shell-derived activated carbon along with the precarbonized sample. The set of Bragg peaks. located at the diffraction angles (2G),'25.4'8 andt43.1o fårtnS fcårnples arelndexesd tp granhitic carbomas.t>er the JCPDS PDF#

01-075-2078. It is apparent that the XRD pattern is characterized with well-defined high intense Bragg peaks corresponding to the graphitic carbon and the absence of other noticeable peaks indicating that the material is devoid of any other impurities. To substantiate the XRD result, Raman spectral analysis was carried out for the activated carbon. The Raman shifts displayed in Figure 2 are for the samples exhibiting two broad peaks centred at about 1310 and 1590 cm"1, corresponding to the D and G bands of carbon, respectively. The D band corresponds to the disorder graphitic domains, while the G band is attributed to the Eig mode of sp2 domain of the graphéne carbon. The estimated (ID/IG) ratio for the prepared samples are 0.99, 1.09 and 1.29 which is almost equal or greater than one (1.0) which clearly indicates the existence of highly disordered graphitic carbon.
SEM analysis was done to explore the surface morphology of the spent walnut shell-derived activated carbon. Figure 3 and Figure 4 show the SEM images of pre-carbonized sample and the activated carbons, respectively. It is obvious from Figure 3 that the surface of the pre-carbonized sample has singularly smooth solid matrix without significant pores. Undoubtedly, the micrographs of the activated carbon demonstrate the complete transformation of the smooth surface to highly etched surface with noticeable pores (Figure 4). The presence of such nanosized pores is expected to facilitate rapid diffusion of ions during the electrochemical testing.
Performance Characteristies:
Double laver capacitance of walnut shell-derived carbon:
• The spent walnut shell-derived activated carbon was examined for ultracapacitor application in aqueous and non-aqueous (lithium-ion capacitor) electrolytes. Initially, the charge storage properties of the activated carbons were examined in three electrdde configurations in 1M H2SO4. Figure 5 (a-c) shows the CV curves recorded in the potential range of 0 - 0.8 V Vs Ag/AgCl in 1M H2SO4. The CV curves are nearly rectangular in shape, implying that the charge storage takes place by means of electrical double-layer formation. It can be noted that the 600 °C activated carbon seems large amount of charge during charge/discharge process. It is evidently seen that the current response increases with the increase of scan rate, suggesting that the electrode is possessing exceilent rate capability. It is noted that with increase of current response as the scan rate is increased, a pronounced anodic peak is seen in all the CV curves at about 0.4 V, indicating existence of minor pseudo capacitåhe*etøue'to^the ocCufrénéé bTFaradie réaetiOiFat thetårbbn élecVodé sWace where

oxygen functional groups present. It has been well documented that the OH or NH containing carbon materials are demonstrated to exhibit such minor pseudo capacitance owing to the redox reaction promoted by the lone pair electrons associated with the heteroatoms.
Further, the charge storage features of the carbon electrode were investigated by means of galvanostatic charge-discharge studies. Figure 5. (d-f) shows charge-discharge profiles of the activated carbon electrode recorded at various current densities in the potential range of 0-0.8 V. It is apparent that at each current density, the charge-discharge curves display nearly symmetrical which further confirms that the charge storage is highly reversible with high Cotumbic efficiency. From the charge-discharge profiles, the specific capacitance was calculated at each current density using the following equation:
C= (I*t)/(V*m) Fg'1 (1)
where, C is specific capacitance (F g"1), I is discharge current (A), t is discharge time (s), V is potential window (V) and m is active surface of the electrode (g). The obtained specific capacitance values are compared in Fig 6. It is observed that at low current density, higher specific capacitance is delivered owing to the effective utilization of the active mass of the electrode, while a low specific capacitance is obtained at higher current density due to the fast charge-discharge rates which lead to poor utilization of the active surface. It is seen from Fig. 6 that the sample 600 °C-activated carbon exhibits high specific capacitance of 321 F g"1 at a current density of 0.5 A g"1 compared with that of 500 °C-activated carbon (171 F g"1) and retains to 150 F g"1 even at a high current density of 10 A g"1. Interestingly, among the three-walnut shell-derived activated carbon electrodes, sample-600 exhibits the highest specific capacitance. This may be due to the presence of extensive external surface with quite a number of pores which would have facilitated more charge accommodations.
Performances of aqueous (Carbon I H?SOd | Carbon) and non-aqueous (Carbon 1 LiPFfi 1 Carbon) proto-tvpe ultracapacitor devices:
The aforesaid high capacitance of the spent walnut shell-derived carbon electrode encouraged us to further investigate its performance in the form of laboratory proto-type symmetric ultracapacitor devices. Thus, the symmetric ultracapacitor device in the form of CR-2032-coin cell was constructed using identical two carbon electrodes in aqueous (1M thSCH) and non-aqueous (1M LiPFé) electrolyte. It is pertinent to note that, Fig. 7 & % shows that thelc6rrrfortablfe worKing voitagé fange could'bé fixéd fo'0-1.4'V for'aqueous and 0-3.2 V

for non-aqueous, beyond which, the decomposition of electrolyte takes place. It is apparent that the CV curves (Fig. 7(a) and 8(b)) of the symmetric device shows characteristic nearly rectangular shape. The appearance of rectangular shape curves implies dominance of double layer mechanism for charge storage, as has already verified in three electrode configuration. The CV curves of aqueous and non-qaqueous symmetric devices show unperturbed rectangular shape even at higher scan rates, suggesting an excellent electrochemical reversibility of the symmetric ultracapacitors with appreciable charge storage.
Further, the charge storage features of the ultracapacitor was characterized by examining galvanostatic charge-discharge cycling at various current densities in the respective potential windows of 0-1.4 V (aqueous) and 0-3.2 V (non-aqueous). The obtained profiles are displayed in Figure 7(b) and 8(c). The symmetric devices possess an excellent reversibility, as the charge-discharge profiles are nearly symmetrical, in particular beyond 1 Ag"1 current density, implying a rapid current-voltage response as well as excellent Coulombic efficiency.
One of the vital features of the practical ultracapacitor, is its long-term stability. Hence, cycling stability of the symmetric devices in aqueous and non-aqueous electrolytes were carried out for 5000 and 10000 cycles and the obtained results are given in Fig. 7 (c) and 8(d). The unperturbed nearly 100% Columbic efficiency for the examined long cycles suggests robustness stability of the proto-type devices. Thus, from the above results, it is concluded that the proto-type ultracapacitor performed well in 1M LiPF6 electrolyte and possess great promise for practical energy storage device. To verify this, the proto-type device was examined for their practical implementation in powering an LED bulb. For this, the non-aqueous symmetric devices (CR-2032 coin cell) was charged to 3.2 V, then, the device was connected to the LED bulb. The photograph of prototype device connected and powering the red LED for about 35 min in single charge is shown in inset Fig. 8(d).
The energy density and power density of the devices were calculated from the charge/di scharge profiles using the following Eqs.:
E= 1/7.2 CV2 Wh kg'1 (2)
P = E><3600/At W kg-1 (3)
where, E is energy density (Wh kg"'), C is specific capacitance (F g"1), V is device voltage (V), P is power density (W kg"1) and At is discharge time (s). The calculated energy density and the power density are displayed in Ragone plots for aqueous and non-aqueous symmetric device are shown in Fig. 9(a, b), The Ragone plot of the symmetric device in non-aqueous electrolyte

shows a maximum energy density of 42 Wh kg-1 at a power density of 402 W kg"1, whereas the aqueous dévice delivers an energy density of 35 Wh kg-1 at a power density of 700 W kg-1. At an energy density of 18 Wh kg'1, the symmetric non-aqueous device delivers power density of 4750 W kg-1. It is seen that the-energy density and power density observed in the present work is much higher than those reported so far. The present symmetrical devices showed a commendable performances, demonsIrating suitable for real life application. For all practical purposes, non-aqueous system is preferred due to it is environmental compatibility.
Performance of lithium-ion half-cell and full cell containinp; spent walnut-derived carbon anode:
To evaluate lithium storage features, electrochemical activity of the fabricated CR-2032 half-cell comprising the walnut shell-derived activated carbon samples at different temperature as anode and Li metal counter electrode, was initially examined by means of galvanostatic charge/discharge (GCD) studies.
Figure 10-13 shows the representative cycle charge/discharge profiles recorded at 0.2 C-rate in the potential range of 0.01 -3 V for the half-cell containing the activated carbon anode generated at 500,600, 700 °C and Lithium metal as counter electrode. In all case, it is seen that the plateau observed about at 0.6 V in the first cycle discharge profile corresponds LC insertion. It is seen that the initial discharge capacity is 2200 and 900 mA h g*1 for in the sample 500 and sample 600, respectively with low Coulombic efficiency of 76 %. Such a low Coulombic efficiency in the first cycle is ascribed to the formation of SEI and subsequent transformation of the pristine carbon electrode to a highly active Li storage host. In the second cycle, the carbon anode delivers a discharge capacity of 800 mA h g"1 with excellent Coulombic efficiency as high as 99 %, indicating stabilizcd reversible capacity. Thus, from the aforementioned half-cell data, the walnut-derived carbon anodes are demonstrated to be excellent insertion electrode.
Undoubtedly, the high Coulombic efficiency confirms that the Walnut shell-derived activated carbon is highly susceptible for efficient Li+ insertion/re-insertion, demonstrating suitability for practical use. It is noticeable that beyond 3rd cycle, the carbon anode maintained almost a stable lithiation capacity and Coulombic efficiency as high as 95%. The rate capability of the carbon anodes was examined by means of galvanostatic charge:discharge cyclings at different C-rates from 0.2 to 1C. The obtained data are also shown Fig 10-12. The carbon electrode possess excellent rate capability.

By the way, for all practical purpose, full cell is required. This, the CR-2032 coin type laboratory prototype lithium-ion full cell comprising of the walnut-derived carbon anode (700 °C activated) and commercial lithium cobalt oxide (L1C0O2) cathode using LiPF6 in EC/DEC as electrolyte was fabricated. Then, the full cell was subjected to charging-discharging studies. It is seen that the full cell consisting of the activated carbon anode and the LCO cathode exhibits a discharge capacities of 275 mA h g"1'. This capacity is much better than the commercial Lithium-ion battery. The obtained a representative cyclic charge-discharge plot is shown Fig 13. Then, the fabricated full cell was examined for powering a consumer electronics, namely . commercial green LED bulb. For this, the full cell was subjected to galvanostatic charging up to 4.2 V at 0. lC-rate. Then, the green LED bulb was connected to the charged coin cell. It was found that on a single charge, the coin cell could power the LED for more than 3 h. Thus, the walnut-derived activated carbon can be a practical insertion anode for Lithium-ion battery with high capacity.
In conclusion, the instant invention provides an excellent energy storage device,. a supercapacitor and a lithium ion battery. The development of energy storage device with high energy (20-50 Wh kg"1) and power densities (7-11 kW kg"1) and when connected in series or alone can power a wide variety of consumer electronics. Further, the aqueous and non-aqueous electrolyte provides a wide potential window for the device operation and potential electrode material coated with carbon helps in reducing the capacity fading and thus improving the performance. More important is the fact that the potential electrode materials for ultracapacitor and Li-ion battery are derived from agricultural wastes and hence provides an excellent alternative for sustainability.
Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural reférences unless the context clearly dictates otherwise. Any reference to "or" herein is intended to encompass "and/or" unless otherwise stated..
While the preferable embodiments of the current invention have been discussed and described as appropriate, it will be obvious to a person skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions are possible without départing from the scope of the present disclosure. Various alternatives to the embodiments of the present disclosure described herein may be employed while practicing the

disclosure of the current invention. Further, it is intended that the following claims define the scope of the present disclosure and that methods and structures within the scope of these claims and their equivalents be covered thereby.
Also, throughout the disclosure of "the current invention, the numerical features are presented in a way of range format. The description in range format is merely for suitability and convenience and should not be construed as an inflexible limitation on the scope of any of the embodiments of the current invention. Accordingly, the description of a range mentioned is to be considered as disclosing all the possible subranges as well as individual numerical values within that range to the tenth of the unit of the lower limit unless the context clearly dictates otherwise. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed subranges .such as from 1 to 2, from 1 to 3, from 1 to 4, from.2.to 4, from 2 to 3, and from 3 to 4, as well as individual* values within that range, for example, 1.1, 2, 2.3, 4, and 4.9. This applies regardless of the breadth of the range. The upper and lower limits of these intervening ranges may independently be included in the smaller ranges, and are also encompassed within the present disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the present disclosure, unless the context clearly dictates otherwise.

CLAIMS
1. A method of fabricating energy storage device comprising:
a) carbonization of the spent walnut shells
b) collecting the carbonized spent walnut shells and processing it to activated carbon on copper foil as the anode
c) using lithium cobalt oxide (LCO) coated on an aluminium foil and/or Li-metal discs as the cathode
d) fabricating the device comprising activated carbon on copper foil or discs as the negative electrode or anode, lithium cobalt oxide (LCO) coated on an aluminium foil and/or Li-metal discs, as the positive electrode or the cathode along with other components such as separators
2. The method of claim 1, wherein the processing of spent walnut shells to obtain activated
carbon comprises;
a) washing and drying the spent walnut shells
b) pre-carboriizing the washed walnut shells in a muffle furnace at a temperature range of 200-400 9C for atime period of at least two to-three hours
c) mixing the pre carbonized sample with the requisite amount of KOH, subjecting the mixture to be transferred into an alumina boat and kept in tubular furnace at a temperature range of 400 - 800 °C in Ar atmosphere for a time period of about four to six hours
d) subjecting the obtained sample to be washed several times with acid (HG) and distilled water
e) sample drying in vacuum desiccator to obtain activated carbon.
3. A ultracapacitor with the electrodes extracted by processing the spent walnut shells
comprising:
a) using a mixture of activated carbon and carbon black, with a binder such as polyvinylidene difluoride (PVDF), Polytetrafluoroethylene (PTFE), polysodium acrylate (PAA); and a conductive additive such as -sp carbon, acetylene black, activated carbon;

b) slurry was prepared by adding a solvent such as NMP, ethanol, water and coated on a current collector such as carbon cloth, nickel foam, stainless steel, copper foil and the slurry paste of the said electrodes applied on a substrate
c) separator between the negative electrode and the positive electrode
d) H2SO4 for aqueous symmetric capacitor or LiPF6 for non-aqueous symmetric capacitor as the electrolyte
4. A Li-ion battery with the activated carbon anode extracted from the spent walnut shell
material comprising:
a) lithium cobalt oxide (LCO) coated on an aluminium foil and/or Li-metal discs, the cathode comprising a binder such as polyvinylidene difluoride (PVDF), Polytetrafluoroethylene (PTFE), polysodium acrylate (PAA); and a conductive additive such as sp carbon, acetylene black, activated carbon
b) slurry was prepared by adding a solvent such as NMP, ethanol, water and coated on a current collector such as carbon cloth, nickel foam, stainless steel, copper foil and the slurry paste of the said electrodes applied on a substrate
c) activated carbon derived from spent walnut shell materials used as anode, and a separator between the anode and the cathode
d) LiPF4 in EC/DEC as the electrolyte

5. The ultracapacitor of claim3, having a high energy density in the range of 10-50 Wh kg"1 for both aqueous/non-aqueous symmetric capacitors and power density in the range of 2-7 kW kg"' for both aqueous/non-aqueous symmetric capacitors
6. The Lithium-ion battery of claim 4, having a storage capacity in the range of 130 mAh g"1 to2p0mAh/g'1