AU2020102999A4

AU2020102999A4 - Electrochemical energy storage device and a process thereof

Info

Publication number: AU2020102999A4
Application number: AU2020102999A
Authority: AU
Inventors: D. Geetha; P. S. Ramesh
Original assignee: Geetha D Dr; Ramesh P S Dr
Current assignee: Geetha D Dr; Ramesh P S Dr
Priority date: 2020-10-24
Filing date: 2020-10-24
Publication date: 2020-12-24
Anticipated expiration: 2028-10-24

Abstract

An electrochemical energy storage device, the device comprising: a porous capacitive electrode comprising an electrochemical capacitor to store electrochemical energy through non-faradic reaction; an electrolyte containing ions for non-faradic and faradic reactions, wherein the capacitive electrode is suspended inside the electrolyte that promotes flow of current from electrolyte to a load; at least two conducting plates attached with the capacitive electrode to transfer the current from electrode to the load, wherein the conducting plates comprises a positive plate and a negative plate; and a nanoporous transition metal sulphide fabricated on the capacitive electrode to make the capacitive electrode porous to improve the ion diffusion and thereby enhance the capacitive behavior of the capacitive electrode. 0 to c 0 4-J U 0 04-J 4-J ) 0-.. 4-U N W = U >U0 Uu 4-J U H. (-I_____ 0oo

Description

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ELECTROCHEMICAL ENERGY STORAGE DEVICE AND A PROCESS THEREOF FIELD OF THE INVENTION

The present disclosure relates to energy storage devices. More specifically, the present disclosure relates to an electrochemical energy storage device anda process thereof.

BACKGROUND OF THE INVENTION

In the modern era electrical energy is a basic need of humans. In today's world, almost every work is related to electrical energy from small mobile to machines running in the factories. The generation of electrical energy improved vigorously from direct current to alternating current. The direct current is easy to store, but tough and expensive to transmit. The direct current is used to store in batteries, capacitors or the like.

The Battery acted as a main source of electrical energy before the development of electric generators and electrical grids. Improvements in battery technology facilitated major electrical advances, from early scientific studies to the rise of telegraphs and telephones, eventually leading to portable computers, mobile phones, electric cars, and many other electrical devices.

Currently, the batteries that stores large amount of electrical energy are bulky in size and the batteries that are of smaller size stores less electrical energy. Development in the field of electrical and electronics needs to discover and design highly efficient batteries and other energy storage devices to fulfil the requirement of our society.

However, the existing solutions are less efficient due to occurring of charge separation at the interface between electrode and electrolyte, which leads to limited specific capacitance. The poor electrical and ionic conductivity of the existing solutions have active materials of transition- metal oxides, which generally decreases the capacitor performance, especially at high rates

In view of the foregoing discussion, there exists a need to have an electrochemical energy storage device and a process for producing the electrochemical energy storage device based on fabrication of nanosheets.

SUMMARY OF THE INVENTION

The present disclosure seeks to provide an electrochemical energy storage device and a process for producing the electrochemical energy storage device based on fabrication of nanosheets using hydrothermal method.

In an embodiment, an electrochemical energy storage device is provided. The device comprises a porous capacitive electrode comprising an electrochemical capacitor to store electrochemical energy through non-faradic reaction. The device comprises an electrolyte containing ions for non-faradic and faradic reactions, wherein the capacitive electrode is suspended inside the electrolyte that promotes flow of current from electrolyte to a load.

The device comprises, at least two conducting plates attached with the capacitive electrode to transfer the current from electrode to the load, wherein the conducting plates comprises a positive plate and a negative plate. The device further comprises a nanoporous transition metal sulphide fabricated on the capacitive electrode to make the capacitive electrode porous to improve the ion diffusion and thereby enhance the capacitive behavior of the capacitive electrode.

In an embodiment, a process for producing a nanoporous transition metal sulphide for fabricating the capacitive electrode of electrochemical energy storage device is disclosed. The process includes dissolving a copper nitrate trihydrate, a thiourea and a cetyl trimethyl ammonium bromide (CTAB) in a predetermined proportion into a solvent of ethylene glycol to produce a transition metal doped nano structured solution.

The process includes adding multiple proportions of cadmium nitrate trihydrate and stirring the solution for 30 minutes to 1 hour to eliminate the surface defects and thereby convert a cubic structure of the solution into a hexagonal structured solution. The multiple proportions of cadmium nitrate trihydrate includes 0.05, 0.15 and 0.30 millimole. The ethylene glycol act as, both reaction media and dispersion media can efficiently absorb and stabilize surface of the particles and favors producing transition metal doped nano structures with smaller size.

The process includes synthesizing Cd-CuS nanostructures at low hydrothermal temperature of 130 degree Celsius for reaction time of at least 10 hours to prepare a black colored precipitate of transition metal sulphide nanostructures.

The process includes washing precipitate to remove impurities and thereby drying the precipitate at a temperature of 50 to 80 degree Celsius for 5 to 10 hours to produce a black colored precipitate of nanoporous transition metal sulphide.

The process includes fabricating the black colored precipitate on the capacitive electrode of the electrochemical energy storage device to improve the ion exchange diffusion to enhance the capacitive behavior of the capacitive electrode and thereby to increase the storage capacity of the electrochemical energy storage device.

In an embodiment, a composition for producing a nanoporous transition metal sulphide, the composition comprising a 1 mM of copper nitrate trihydrate, a 2mM of thiourea, 40 ml of ethylene glycol, a cetyl trimethyl ammonium bromide, multiple proportions of cadmium nitrate trihydrate, an ethanol and a de-ionized water.

In an embodiment, a process growth is significant when time temperature is lowered, wherein synthesizing Cd-CuS nanostructures at low hydrothermal temperature 130-degree Celsius for keeping reaction time in 10 hours is performed. The CdS changes a cubic structure of CuS into a hexagonal structure upon adding of Cd ions into the solution mixture, wherein a structural alteration within the crystal lattice of the CuS is achieved due to the replacement of bigger size Cd2+ ions (1.71Ao) by the smaller Cu2+ ions (1.28Ao).

In an embodiment, the average sizes of CuS and Cd-CuS particles are found to be 14 nm, 9, 15, 17 nm for concentration of Cd doped CuS respectively, and decreased when Cd2+ ions occupied the place of Cu2+ ions. A phase transitions in CdS is reported due to a plurality of parameters includes particle size, concentration of S2- and Cd2+, stacking faults, presence of CTAB and other foreign materials present in the solution mixture also underwent phase transition.

In an embodiment, the CTAB plays a vital role in the morphological transformation of the CuS and Cd-CuS nanostructures, the transformation process comprising combining a head group of CTAB with Cd-CuS nanosheets and detaching outwards and projecting a tail group of CTAB to the neighboring Cd-CuS nanosheets for creating regular structure of a heaped up nanosheets.

An object of the present disclosureis todevelop an electrochemical energy storage device.

Another object of the present disclosure is to develop a cadmium doped CuS nanostructures prepared via a sample hydrothermal process at 130 C.

Another object of the present disclosure is to improve the stability of electrode materials by focusing on the other part of doping material.

Another object of the present disclosure is to fabricate materials with chemical, thermal and mechanical stabilities.

Another object of the present disclosure is to synthesize Cd-CuS by mild hydrothermal method with CTAB as template material and study to morphological, structural and electrochemical properties.

Yet another object of the present invention is to deliver an eco-friendly and cost effectiveprocess for producing a nanoporous transition metal sulphide for fabricating the capacitive electrode of electrochemical energy storage device.

To further clarify advantages and features of the present disclosure, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustratesa schematic block diagram of an electrochemical energy storage device in accordance with an embodiment of the present disclosure;

Figure 2 illustrates a flow chart of a process for producing a nanoporous transition metal sulphide for fabricating the capacitive electrode of electrochemical energy storage device in accordance with an embodiment of the present disclosure;

Figure 3 illustrates a plurality of graphs of intensity versus degree profile of XRD patterns of the CuS and different concentrations of Cd-CuS nanostructures in accordance with an embodiment of the present disclosure;

Figure 4 illustrates a plurality of scanning electron microscopy (SEM) images and respective graphs of corresponding CuS and CdS in accordance with an embodiment of the present disclosure;

Figure 5 illustrates a plurality of transmission electron microscopy (TEM) images of Cd doped CuS nanostructure in accordance with an embodiment of the present disclosure;

Figure 6 illustrates a plurality of graphs of transmittance versus wavenumber profile of CTAB stabilized Cd doped CuS structure in accordance with an embodiment of the present disclosure;

Figure 7 illustratesa plurality of graphs of intensity versus binding energy profile of XPS spectra of CTAB stabilized CuS doped with Cd in accordance with an embodiment of the present disclosure; and

Figure 8 illustratesa plurality of graphs of electrochemical characterization profile of two modified electrodes CuS and Cd-CuS in accordance with an embodiment of the present disclosure.

A

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.

Referring to Figure 1, a schematic block diagram of an electrochemical energy storage device is illustrated in accordance with an embodiment of the present disclosure. The systemlOO includes a porous capacitive electrode 102 comprising an electrochemical capacitor 104 to store electrochemical energy through non-faradic reaction. The porous capacitive electrode 102 comprises a capacitive material, a binder, and a conductive additive, wherein the binder can be organic or inorganic. The conductive additive may be any substance with high electric conductivity. Specifically, the conductive additive is selected from carbon black, acetylene black, activated carbon, carbon nanowires, carbon nanotubes, graphite, graphene, and metal particles including copper, silver, nickel, titanium, aluminum, and conducting polymers. The capacitive material is selected from an electro-inert material, an electro-active material, and its combination. The electro-inert material is selected from amorphous, semi-crystalline, or crystalline carbonaceous materials.

In an embodiment, the semi-crystalline carbonaceous material comprises of crystallinity in the range of 1% to 99%, <1%, and >99%. The carbonaceous material includes activated carbons, carbon fibers, multi-wall carbon nanotubes, double-wall carbon nanotubes, single wall carbon nanotubes, graphene, carbon nanocrystals, carbon nanoparticles, microporous carbons with pore size <2 nm, mesoporous carbons with pore size 2 nm-50 nm, macroporous carbons with pore size >50 nm, carbon nanocages, carbon nano-onions, carbon black, and fluorinated carbons.

In an embodiment, the electro-active material is selected from material which does not dissolve as ions during the cycling. The selection of a capacitive material relies on reactivity and stability in a specific electrolyte system. Composites of electro-inert materials and electro-active materials is used to improve the cycling stability of the electro-active materials. The air catalyst comprises oxygen reduction catalyst and oxygen evolution catalyst that has been studied for fuel cells and metal-air batteries.

In an embodiment, an electrolyte 106 containing ions is used for non-faradic and faradic reactions. The capacitive electrode 102 is suspended inside the electrolyte 106 that promotes flow of current from electrolyte 106 to a load 112. The electrolyte 106 includes aqueous and non-aqueous solutions, gels, polymers, semi-solids, and solids.

In an embodiment, at least two conducting plates 108 is attached with the capacitive electrode 102 to transfer the current from electrode to the load 112, wherein the conducting plates 108 comprises a positive plate and a negative plate. The positive plate consisting of a current collector and a catalyst or catalysts that effectively reduces oxygen during the discharge process and facilitate oxygen evolution during the charge process. The negative plate consisting of a porous material or materials that stores charge at the electrode/electrolyte 106 interface.

In an embodiment, a nanoporous transition metal sulphide 1Ois fabricated on the capacitive electrode 102 to make the capacitive electrode 102 porous to improve the ion diffusion and thereby enhance the capacitive behavior of the capacitive electrode 102. The nanoporous transition metal sulphide 110 includes cadmium sulphide (CdS), which is an excellent semiconductor with a direct band gap of 2.42ev at room temperature with many outstanding physio-chemical properties. The physio-chemical properties have promising applications in multiple technical field such as solar cells, photo catalysis, light-emitting diodes for flat-panel displays.

In an embodiment, a composition of a nanoporous transition metal sulphide 110 comprises copper nitrate trihydrate (Cu (N03).3H20), thiourea (Tu,Sc(NH2)2, ethylene glycol (EG), cetyl trimethyl ammonium bromide (CTAB) and cadmium nitrate trihydrate (Cd(N03).3H20), ethanol and de-ionized water.

Figure 2 illustrates a flow chart of a process for producing a nanoporous transition metal sulphide for fabricating the capacitive electrode of electrochemical energy storage device in accordance with an embodiment of the present disclosure.At step 202, the process 200 includes dissolving a copper nitrate trihydrate, a thiourea and a cetyl trimethyl ammonium bromide (CTAB) in a predetermined proportion into a solvent of ethylene glycol to produce a transition metal doped nano structured solution. The predetermined proportion of the cetyl trimethyl ammonium bromide (CTAB) is selected from 0.1mM.

At step 204, the process 200 includes adding multiple proportions of cadmium nitrate trihydrate and stirring the solution for 30 minutes to 1 hour to eliminate the surface defects and thereby convert a cubic structure of the solution into a hexagonal structured solution. The multiple proportions of cadmium nitrate trihydrate includes 0.05, 0.15 and 0.30 millimole. The ethylene glycol act as, both reaction media and dispersion media, which can efficiently absorb and stabilize surface of the particles and favors producing transition metal doped nano structures with smaller size.

At step 206, the process 200 includes synthesizing Cd-CuS nanostructures at low hydrothermal temperature of 130 degree Celsius for reaction time of at least 10 hours to prepare a black colored precipitate of transition metal sulphide nanostructures.

At step 208, the process 200 includes washing precipitate to remove impurities and thereby drying the precipitate at a temperature of 50 to 80 degree Celsius for 5 to 10 hours to produce a black colored precipitate of nanoporous transition metal sulphide 110.

At step 210, the process 200 includes fabricating the black colored precipitate on the capacitive electrode 102 of the electrochemical energy storage device to improve the ion exchange diffusion to enhance the capacitive behavior of the capacitive electrode 102 and thereby to increase the storage capacity of the electrochemical energy storage device.

.7

In an embodiment, a composition for producing a nanoporous transition metal sulphide 110, the composition comprising a 1 mM of copper nitrate trihydrate, a 2mM of thiourea, 40 ml of ethylene glycol, a cetyl trimethyl ammonium bromide, multiple proportions of cadmium nitrate trihydrate, an ethanol and a de-ionized water.

In an embodiment, a process growth is significant when time temperature is lowered, wherein synthesizing Cd-CuS nanostructures at low hydrothermal temperature 130-degree Celcius for keeping reaction time in 10 hours is performed. The CdS changes a cubic structure of CuS into a hexagonal structure upon adding of Cd ions into the solution mixture. A structural alteration within the crystal lattice of the CuS is achieved due to the replacement of bigger size Cd2+ ions (1.7lAo) by the smaller Cu2+ ions (1.28Ao).

In an embodiment, the average sizes of CuS and Cd-CuS particles are found to be 14 nm, 9, , 17 nm for concentration of Cd doped CuS respectively, and decreased when Cd2+ ions occupied the place of Cu2+ ions. A phase transitions in CdS is reported due to a plurality of parameters includes particle size, concentration of S2- and Cd2+, stacking faults, presence of CTAB and other foreign materials present in the solution mixture also underwent phase transition.

In an embodiment, the CTAB plays a vital role in the morphological transformation of the CuS and Cd-CuS nanostructures, the transformation process comprising combining a head group of CTAB with Cd-CuS nanosheets and thereupon detaching outwards and projecting a tail group of CTAB to the neighboring Cd-CuS nanosheets for creating regular structure of a heaped up nanosheets.

In an embodiment, a TEM image of the Cd- CuS nanostructures shows that the Cd- CuS nanostructures are composed of sheet like Cd-CuS nanoparticles. The TEM image shows that the size of the spherical nanoparticle is about 20 nm, resulting from an interference of a surfactant the Cd-CuS smaller nanoparticles are governed by the porous sheet-like structures.

In an embodiment, a specific capacitance (Cs) of CTAB stabilized CuS and Cd-CuS are 328.26 and 458 Fg-1 respectively. The Cs of CTAB/Cd doped CuS electrode is high, indicating that the capacitive electrode 102 has a better discharge capacity than another sample.

Figure 3 illustrates a plurality of graphs of intensity versus degree profile of XRD patterns of the CuS and different concentrations of Cd-CuS nanostructures in accordance with an embodiment of the present disclosure.Figure 3 includes four graphs (a), (b), (c) and (d)

Graph (a) illustrates the intensity versus degree profile of the crystalline CuS. The quality of a CuS crystalline is observed in diffraction patterns with degree (20) values at 23 degree, 27 degree, 29 degree, 31 degree, 32 degree, 47 degree, 52 degree and 59 degree corresponding to the planes of (100), (101), (102), (103), (106), (110), (108), and (116) respectively.

Graphs(b), (c) and (d) illustrate the intensity versus degree profiles of the crystallineCuS nanostructures at various concentrations of cadmium (Cd). The quality of the crystalline is observed in diffraction patterns with degree (20) values at 27.53degree, 29.72degree, 31.97degree, 48.13degree, 52.27degree and 59.41degree corresponding to the planes of (101), (102), (103), (110), (108) and (116) of covellite Cd-CuS nanostructures. The diffraction peaks of CdS originated from a different set of planes includes (100), (200), (101), (102), (110), (103) and (112), wherein diffraction peaks of the CdS matches with the standard JCPDS Code 01-073, corresponding to cubic phase of CdS. The occurrence of peak at 20=21 degree is attributed to the presence of CTAB in the sample. The JCPDS (05-0640) confirms the Cd phase with face-centered crystal structure to the Bragg position for reflections like (111) for Cd-CuS nanostructures.

The cubic structure of the crystalline CuS changes into hexagonal structure of CdS upon adding of Cd ions to a solution of CuS. The structural change within the crystal lattice is due to the replacement of the bigger Cd2+ ions (1.7lAo) by the smaller Cu2+ ions (1.28Ao), but the diffraction peaks are more intense in 0.05mM of Cd doped CuS. The structure of Cd2+ is controlled by the concentration of the nanoparticles.

In an embodiment, average sizes of CuS and Cd-CuS particles are found to be 14 nm, 9, 15, 17 nm for concentration of Cd doped CuS respectively, and decreased when Cd2+ ions occupied the place of Cu2+ ions. The average particle size is calculated using the Scherrer's formula.

kA D =lOS #3cosO

In an embodiment, the comparison of X-ray diffraction (XRD) patterns indicates that a structural phase transformation from cubic phase to hexagonal phase of the CdS is achieved. The phase transformation is attributed to the intercalation ofcetyl trimethyl ammonium bromide (CTAB) into the crystal structure of CdS. The phase transitions in CdS is reported due to variousparametersincluding particle size, concentration of S2- and Cd2+, stacking faults and due to the presence of CTAB.

Figure 4 illustrates a plurality of scanning electron microscopy (SEM) images and respective graphs of corresponding CuS and CdS in accordance with an embodiment of the present disclosure.Figure 4 includes two sections, wherein a first section contains eight SEM images of CuS and CdS whereas a second part contains four degree versus intensity graphs of the corresponding CuS and CdS crystalline.The eight SEM images are differentiated as a, b, d, e, g, h, j and k, whereas the four degree versus intensity graphs are differentiated as c, f, i, and 1. The eight SEM images illustrateintercalation of 0.1mM CTAB into the structure of pure CuS by image a and b, 0.05mM Cd-CuS by d and e, 0.15mM Cd-CuS by g and h, and 0.30mM Cd-CuS nanostructures by j and k.

In an embodiment, the SEM images a-k of CuS and Cd-CuS delineate the surface morphology and the porosity. The Micrograph of Cd-CuS exposes the globular particles in some concentrations. The formation of the global morphology is due to the metal charge transfer transitions of the sample. The increase in quantity of Cd changes the spherical structure of the crystallineinto hemispherical structures. The interpretation of the structural transformation is that the interaction of Cd-CuS results the highly porous nanosheets. The interconnected uniform 3D nanosheet of Cd-CuS nanostructures are of the size of 40 nm.

In an embodiment, the graphsc, f, i,1 illustrates the Energy-dispersive X-ray spectroscopy (EDS) results of the CuS and Cd-CuS samples that indicates the elemental composition of Cd, Cu and S alone in Cd-CuS nanostructure.The EDS spectra of Cd doped CuS nanostructuresconfirms Cd+ entry into the crystal matrix of CuS. The Cd+ ions capable of replacing the S2- ions instead of occupying an interstitial site of the CuS crystal. The elemental compositions present in the samples are estimated. The agglomeration of particles is explained in a common way to minimize their surface free energy. The obtained elements of CuS and Cd doped CuS samples are tabulated in table 1.

Table 1 In EDS, percentage of individual elements for CuS and Cd-CuS: Sr. No. Samples Present Weight % Atomic

% Elements 1. CuS Cu, S Cu=79.25 1.45 Cu=81.57 1.50 S=20.75 0.27 S=18.43 0.55 2. 0.05mM Cd-CuS Cu,S, Cd Cu=68.72 1.45 Cu=71.46 1.50 S=6.90 0.27 S=14.21 0.55 Cd=24.38 0.56 Cd=14.33 0.33 3. 0.15mM Cd-CuS Cu, S, Cd Cu=62.34 1.45 Cu=68.25+1.50 S=7.12 0.27 S=12.21 0.55 Cd=30.54 0.56 Cd=19.54 0.33 4. 0.30mM Cd-CuS Cu, S, Cd Cu=55.12 1.45 Cu=66.18 1.50 S=5.34 0.27 S=11.45 0.55 Cd=39.54 0.56 Cd=22.37 0.33

In an embodiment, the Table 1 depicts percentage of individual elements for CuS and Cd CuS. The sample CuS is having Cu and S elements with weight percentage of Cu=79.25± 1.45 & S=20.75 0.27, and atomic percentage of Cu=81.57 1.50 & S=18.43 0.55. The 0.05mM Cd-CuS is having Cu, S and Cd elements with weight percentage of Cu=68.72± 1.45, S=6.90 0.27 & Cd=24.38 0.56, and atomic percentage of Cu=71.46 1.50, S=14.21 ±0.55 & Cd=14.33 0.33. The 0.15mM Cd-CuS is having Cu, S and Cd elements with weight percentage ofCu=62.34 1.45, S=7.12 0.27 & Cd=30.54 0.56, and atomic percentage of Cu=68.25+1.50, S=12.21 0.55 and Cd=19.54 0.33. The 0.30mM Cd-CuS is having Cu, S and Cd elements with weight percentage ofCu=55.12 1.45, S=5.34 0.27 and Cd=39.54 0.56, and atomic percentage of Cu=66.18 1.50, S=11.45 0.55 and Cd=22.37 +0.33.

i

In an embodiment, the complex hierarchical architecture has a diameter ranging from 1 m to 0.5pm and is of uniform morphology. Graph d indicates that each crystal is composed of multiple curved nanosheets of few tens of nanometer. The vertical arrangements of these nanosheets are observed in a crisscrossed manner in which the gap is measured between 100 and 200 nm.

Figure 5 illustrates a plurality of transmission electron microscopy (TEM) images of Cd doped CuS nanostructure in accordance with an embodiment of the present disclosure. Figure includes four transmission electron microscopy (TEM) images, which are differentiated by a, b, c, and d. The information of CdS architecture is derived by the TEM images a, d, and c. The TEM images a, b, and c show that the nanosheets are composed of a large number of nanoparticles. Furthermore, the TEM image shows that the size of individual nanoparticle is about 15nm, which is blended with the contiguous nanoparticle having a common crystallographic orientation. The TEM is performed to examine the surface morphology of the Cd-CuS for super capacitor applications. The TEM images a, b, and c illustrates distinctive TEM images of the 0.05mM Cd-CuSnanosheets. The image b depicts that the length of Cd-CuS nanosheets ranges from 90-110nm, which explains the capability for high performance. The TEM image d shows that the selected area electron diffraction (SAED) pattern is obtained from TEM images of the Cd-CuS crystal samples. The CTAB plays a vital role in the morphological transformation of the CuS and Cd-CuS nanostructures. A head group of CTAB combines with Cd-CuS nanosheets and detaches outwards, whereas a tail group of (CTAB) project from the neighboring Cd-CuS nanosheets. The heaped up nanosheets eventually creates the rectangular structure. The TEM images of the Cd- CuS nanostructures show that samples are composed of sheet like Cd-CuS nanoparticles. The TEM image shows that the size of the spherical nanoparticle is about 20 nm, resulting from the interference of the surfactant the smaller nanoparticles are governed by the porous sheet like structures.

Figure 6 illustrates a plurality of graphs of transmittance versus wavenumber profile of CTAB stabilized Cd doped CuS structure in accordance with an embodiment of the present disclosure.Figure 6 comprises four graphs differentiated as a, b, c, and d, wherein the graphs depict fourier-transform infrared spectroscopy (FTIR) spectra of0.1mM CTAB stabilized CuS doped with Cd. The four graphs a, b, c, and d are differentiated by doping of Cd, wherein graph a depicts 0.00mM doping, graph b depicts 0.05mM doping, graphic depicts 0.15mM doping and graph d depicts 0.30 mM doping.

In an embodiment, a broad curve in the range 3000-3500 cm-i is due to bending vibration of H20. A triplet is observed at 1397 cm-1, 1239 cm-i and 1097 cm-1. The peaks observed at 1725 cm-1, 1673 cm-i and 1615 cm-lare because of bending vibration of Cd2+. A weak absorbent band is observed at 2764 cm-i and 2679 cm-i due to Cu-O vibrations. The tripled sulphate considerably reduces intensity and FTIR confirms that the vibration of CuS causes a broad band at 619 cm-1.

Figure 7 illustrates a plurality of graphs of intensity versus binding energy profile of XPS spectra of CTAB stabilized CuS doped with Cd in accordance with an embodiment of the present disclosure.Figure 7comprises four graphs of XPS spectra of 0.1mM CTAB stabilized CuS doped with Cd. The four graphs are differentiated by a, b, c and d, wherein the graph a depicts full spectrum, graph b depicts Cu 2p, graph c depicts Cd 2p and graph d depicts S 2p in nanostructures. The X-ray photoelectron spectroscopy (XPS) spectra are employed to evaluate the chemical nature of the Cd-CuS nanostructures.

In an embodiment, graph a shows full spectrum, which mainly contain Cls (as reference), Cd 2p, Cu 2p, and S 2p four core-level peaks. Graph b depicts the high-resolution of Cu 2p spectrum, the two main peaks Cu 2p3/2 and Cu 2pl/2 at 932.07 and 952.10 eV are. Graph c depicts the high-resolution of S2p spectrum, wherein S2p spectrum comprises two sulfur contributions.The element S at 162.7 eV shows metal-sulfide bonds in metal sulfide, wherein another peak placed at 163.9 eV corresponds to sulfide defect states with low sulfur coordination. Graph d depicts the high-resolution Cd 2p lines, whereinthe Cd 3d5/2 main peak is located at 405.7eV and the Cd 3d3/2 main peak is located at 411.6eV respectively. This main peaks further confirms that the pure Cd-CuS phase exists in the nanostructures.

Figure 8 illustrates a plurality of graphs of electrochemical characterization profile of two modified electrodes CuS and Cd-CuS in accordance with an embodiment of the present disclosure.Figure 8 comprises four graphs a, b, c, and d. Graph a depicts current versus potential profile of CTAB/CuS.Graph b depicts current versus potential profile of CTAB/Cd(0.05mM)-CuS electrode at different scan rates.Graph c depicts specific capacitance calculated from the CV curves as a function of scan rate. Graphd is a Nyquist plots of modified CuS and Cd (0.05mM)-CuS electrode. The Electrochemical test is employed to find the potential of the materials for supercapacitor applications. Graphs a and b depict the typical cyclic voltammetry (CV) curves of the CuS and Cd-CuS electrode respectively in 2M KOH electrolyte 106. A distinct pair of reduction and oxidation peaks at 0.lvolts, 0.25volts and 0.30volts are obtained in a cyclic voltammogram. The current versus voltage curves demonstrate that increase in the scan rate of 5-50 mVs-1 increases the cathodic and anodic current, which depicts the lower resistance in the reaction. Graph c depicts that the Cs of CuS and Cd-CuS electrodes at 5-50 mVs-1 scan rates in 2M KOH.

The specific capacitance of CuS and Cd-Cus electrodes is quantified using the formula:

Cs = AV.m

Where, Cs represents the specific capacitance, Q is an anodic and a cathodic charge on each scanning, m is the mass of the active material (g) in the electrodes and AV is an applied voltage window of the voltammetry curve (mVs-1).

1,

The Cs of CTAB stabilized CuS and Cd-CuS are 328.26 and 458 Fg-1 respectively. As expected, the Cs of CTAB/Cd doped CuS electrode is high, indicating that the electrode has a better discharge capacity than another sample. The shape of the CV curve of the Cd-CuS nanosheet electrode mainly result from pseudo-capacitance, which indicates that the capacitance characteristic is different from that of electric double layer capacitance. The comparison of specific capacitance for synthesized CuS and Cd-CuS electrode materials with earlier electrode materialsisdescribed in table 2.

Table 2:Comparison of specific capacitance for synthesized CuS and Cd-CuS electrode materials with earlier electrode materials.

Sr. No. Electrode Materials Specific capacitance (Fg-1) 1. CuCo2S4 90.6 @2 A g-I 2. CuCoS 518@ 1 A g-i 3. CuS-carbon nanotube 114 @2mV s-1 4. CuS 597@ 1 A g-i 5. CuS-MWCNTs 2831@ 1 Ag-i 6. CuS 925 @ 1 Ag-i 7. CoS 508 @ 5mA/cm2 8. CuS 328 @ 5 mV s-i 9. Cd-CuS 458@ 5 mV s-I

In an embodiment, the comparison of specific capacitance for synthesized CuS and Cd-CuS electrode materials with earlier electrode materials is illustrated in Table 2, the CuCo2S4 offers the specific capacitance of 90.6 @2 A g-i. The CuCoS offers the specific capacitance of 518 @ I A g-. The CuS-carbon nanotube offers the specific capacitance of 114 @ 2mV s-i. The CuS offers the specific capacitance of 597 @ I A g-. The CuS-MWCNTs offers the specific capacitance of 2831@ 1 Ag-i. The CuS offers the specific capacitance of 925 @ I Ag-i. The CoS offers the specific capacitance of 508 @ 5mA/cm2. The CuS offers the specific capacitance of 328 @ 5 mV s-i. The Cd-CuS offers the specific capacitance of 458@ 5 mV s-i. The elevation by the specific electrolytein the sample is feasible since it contains uniform pore distribution which ultimately elevates the capacitance, wherein the feasibility helps to exhibit good impedance properties.

In an embodiment, a Nyquist plot of CuS and Cd-CuS electrodes is depicted in graph d, wherein a higher frequency region and a mid-frequency region refers to the electrolyte's properties and electrode/electrolyte interface processes respectively. A lower frequency region where close linear EIS plots are found is a characteristic of Warburg impedance, where the resistance behavior is assumed to arise from the diffusion of the OH- ion inside the pores of Cd-CuS electrode during redox reaction. For the curve of the graph d, the solution resistance (Rs) and charge transfer resistance (RCT) intercept at the point at high frequency and mid frequency with the real axis respectively. Both modified materials have ideal capacitor behavior. Also, the electrochemical impedance spectra analyzed by Nyquist plot confirmed the capacitance behavior.

In an embodiment, the electrochemical energy storage (EES) in the form of supercapacitor is generally used for powering the portable electronic devices for the electrification of the transportation sector. The multiple challenges are faced in finding materials for EES that improvesthe storing and delivering huge amount of energy. The disclosed process results in production of supercapacitor based electrochemical energy storage device using materials available in abundant amount, are nontoxic, lower in price and enhances the security of EES devices in stationary power. According to charge-storage mechanism, two varieties of capacitors are mentioned including EDLS and pseudo-capacitors for EES devices.

In an embedment, the charge separation occurs at the interface between electrode and electrolyte 106 in EDLS, which leads to limited specific capacitance. However, pseudo capacitors with transition metal oxides (NiO, C0304 and MnO2) may yield higher specific capacitances due to its redox faradic reaction. Unfortunately, the poor electrical and ionic conductivity of the active materials of transition- metal oxides in pseudo-capacitors decreases the capacitor performance, especially at high rates.

The Chalcogenides (PhS,ZnS,CdS,CuS) are inorganic materials with unique properties, wherein CuS is one of the crystal structures that can vary the structure from orthogonal to hexagonal showing five different stoichiometric forms such as covellite (CuS), anilite (Cul.75S), digenite (Cul.8S), djurleite (Cul.95S) and chalcocite (Cu2S) that are known to be stable at room temperature. The presence of copper vacancies in CuS makes act as P- type semiconductors with either direct or indirect band gaps. The percentage of Cu controls the band gap of CuS, the CuS must be weaved with the appropriate measure of Cu to yield more specific capacitance. The Cadmium sulphide (CdS) is an excellent semiconductor with a direct band gap of 2.42ev at room temperature with variousphysio-chemical properties. The Cadmium sulphide has promising applications in multiple technical fields including, solar cells, photo catalysis, light-emitting diodes for flat-panel displays. The CdS nanostructures with divergent morphologiescomprising nanorods, dendrites, spheres and sea-urchin. The characteristics such as soft-template effect, capability to modify the chemical kinetics and easy manoeuvrability of the surfactants help to control the nanostructure or the morphology. Few frequently used surfactants in the preparation of Cd-CuS nanostructures areselected from the group of PVP, Tween-80 and ethylene diamine SDC as soft templates for synthesis of the Cd-CuS nanostructures. An Ostwald ripening and oriented attachments (OA) are two kinds of mechanism in the growth of nanostructure. The Oriented attachment mechanism is the formation of a single crystal from two particles by sharing common crystallographic orientation. This crystallographic orientation is dominant at nanometer due to direct modification of the nanoparticle surface.

In an embodiment, the CuS and CdS can be synthesized separately in the form of powder, but the problem of capping is observed in separate synthesis, which should be solved to avoid the change in electrochemical properties. The stability of electrode materials is improved by

1A focusing on the other part of a doping material. The binary composite sulphides, for example, Cd-CuS is important to fabricate materials with chemical, thermal and mechanical stabilities. However, the binary composites have relatively high surface area than oxide materials. The surface region and morphology of the electrode materials play vital role in regard to the stored energy to a greater extent. The nanostructure electrode materials with high surface area as well as good porosity offers an all-encompassing contact area with the electrolyte 106 ions promotes in decreasing of the resistance. Hence, the objective of the work is to synthesize Cd-CuS by mild hydrothermal method with CTAB as template material and to study the morphological, structural and electrochemical properties of the Cd-CuS.

In an embedment, a characterization of Cd-CuS is performed using anX-ray diffractometer to study the crystallographic structure at a scan rate of 1 degree per minute in the 20 range of 10 degree Celsius -70 degree Celsius. The FTIR determines the functional groups using a Perkin Elmer spectrometer range from 400-4000 cm-1. The SEM scrutinizes the surface morphology (JEOL-JSM - 5610 LV with INCA EDS) and the elements are analyzed by EDS, in combination with SEM and TEM-CM-200. Electrochemical behavior of CuS and Cd-CuS is examined in an electrochemical workstation (CHI 660C, USA) by cyclic voltammetry (CV) and electron impedance spectroscopy (EIS).

In an embodiment, the capacitive electrode 102 preparation is achieved using the mechanism Cu2++ mTu + nEG -> [Cu (Tu) m (EG) n] 2+ Hydrothermal

[Cu(Tu)m(EGn)]2 0 CuSA 130°C The Ethylene glycol acting as both reaction media and dispersion media, which isable to efficiently absorb and stabilize the surface of the particles and therebyfavors producing transition metal doped nano structures with smaller size.

In an embodiment, the cetyl trimethyl ammonium bromide (CTAB) is a common cationic surfactant with the molecular formula C19H42BrN. The CTAB is a molecule with trimethyl ammonium, as a head group witha tail groupare a long chain of alkyl group. The CTAB interacts with the surrounding medium through the head group as well as tail group. The CTAB is used in many applications including rare metal nanostructures and fabrication of nanostructures comprising palladium nanocubes, 3D hierarchical structure of Sr2Sb2O7, dendrite silver crystals, nanofibers of BaMoO4, copper-indium sulphide hollow nanospheres, polyaniline nanotubes, gold nanoplates, and the like. TheVanderwal interaction seem to be balanced, which is the cause of the self- assemblies of nanoparticles in bottom up methodologies. Synthesis of Cd-CuS nanostructures by hydrothermal process is preferred to efficiently yield Cd-CuS nanostructure with different morphologies.

In an embodiment, a reaction condition is optimized after examining at elevated temperatures. At this temperature fabrication of inorganic substance is feasible to be formed. The size and shape are difficult to be controlled as the disclosed method involves rapid nucleation and growth. The growth process is significant when time temperature is lowered.

1r.

In the disclosed method, an attempt has been made to synthesize Cd-CuS nanostructures at low hydrothermal temperature (130°C) for keeping reaction time in 10 hours.

In an embodiment, anelectrochemical energy storage deviceis today's need for present and in future utility, where high energy and power density are combined in the same material. The supercapacitors offer high energy density at high charge-discharge rates. The transition metal sulphides 110are used as a new type of electrode materials for supercapacitor and good performance is achieved. The cadmium doped CuS nanostructures is prepared via a sample hydrothermal process at 1300C. The nanocomposite of cadmium doped CuS have been the main focus due to their potential applications in diverse fields. The nanostructures are characterized by XRD, FTIR, SEM/ EDS and TEM. The XRD pattern reveals that the Cd nanoparticle incorporated CuS shows crystallite nature and crystallinity increases with the addition of cadmium on CuS.The electrochemical analysis is performed using a 2M KOH electrolyte 106by the technique called CV and EIS study, wherein Cd-CuS exhibits hexagonal architecture and the specific capacitance is calculated as 458 F/g at 5mV/s scan rate. The high utility of pseudo-capacitive Cd-CuS is achieved only at highest doping concentration of cadmium on CuS. Therefore, the Cd-CuS electrode material may get wide utility range in future energy storage devices.

In an embodiment, a simple hydrothermal techniqueis selected to fabricate CuS and Cd-CuS nanostructures at130degree Celsius for 10 hours. A Cationic surfactant varies the morphology of the Cd-CuS nanostructures. The cationic surfactant introduces a phase transition and eliminates the surface defects, which results change of cubical structure into hexagonal structure. The changing of cubical structure into hexagonal structure implies that cationic surfactant acts as an outstanding structural cum morphological director in Cd- CuS nanostructures.

In an embodiment, the conclusions drawn from the characterization resultsthe pure CuS has distinct (101), (102), (103), (110), (108) and (116) planes that confirms the covellite. The Cd CuS has additional peaks at (100), (200), (101), (102) and (112) plane, which confirms that the hexagonal structure and average size of CuS is 14 nm and for Cd (0.05mM)-CuS is 9 nm.

In an embodiment, disclosure discloses that a novel hierarchal interconnected Cd-CuS nanosheets is fabricated using mild hydrothermal technique for superior supercapacitor. The nanosheet like nanostructure of the Cd-CuS electrode had Cs of 458 Fg-1 at a scan rate mVs-1, low solution resistance.

The device made in accordance with the present disclosure are improved at storing and delivering huge amount of energy. The disclosure facilitates abundant materials to store electrochemical energy. The nontoxic and low-cost device is produced to enhance the security of EES equipment in stationary power. The device is eco-friendly and very light weighted that promotes easy movement.

The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

Claims

WE CLAIM 1. An electrochemical energy storage device, the device comprising:

a porous capacitive electrode comprising an electrochemical capacitor to store electrochemical energy through non-faradic reaction; an electrolyte containing ions for non-faradic and faradic reactions, wherein the capacitive electrode is suspended inside the electrolyte that promotes flow of current from electrolyte to a load; at least two conducting plates attached with the capacitive electrode to transfer the current from electrode to the load, wherein the conducting plates comprises a positive plate and a negative plate; and a nanoporous transition metal sulphide fabricated on the capacitive electrode to make the capacitive electrode porous to improve the ion diffusion and thereby enhance the capacitive behavior of the capacitive electrode.

2. A process for producing a nanoporous transition metal sulphide for fabricating the capacitive electrode of electrochemical energy storage device, the process comprising:

dissolving a copper nitrate trihydrate, a thiourea and a cetyl trimethyl ammonium bromide (CTAB) in a predetermined proportion into a solvent of ethylene glycol to produce a transition metal doped nano structured solution; adding multiple proportions of cadmium nitrate trihydrate and stirring the solution for 30 minutes to 1 hour to eliminate the surface defects and thereby convert a cubic structure of the solution into a hexagonal structured solution; synthesizing Cd-CuS nanostructures at low hydrothermal temperature of 130 degree Celsius for reaction time of at least 10 hours to prepare a black colored precipitate of transition metal sulphide nanostructures; washing precipitate to remove impurities and thereby drying the precipitate at a temperature of 50 to 80 degree Celsius for 5 to 10 hours to produce a black colored precipitate of nanoporous transition metal sulphide; and fabricating the black colored precipitate on the capacitive electrode of the electrochemical energy storage device to improve the ion exchange diffusion to enhance the capacitive behavior of the capacitive electrode and thereby to increase the storage capacity of the electrochemical energy storage device.

3. The process as claimed in claim 2, comprising a composition for producing a nanoporous transition metal sulphide, the composition comprising:

a 1 mM of copper nitrate trihydrate, a 2mM of thiourea, 40 ml of ethylene glycol, a cetyl trimethyl ammonium bromide, multiple proportions of cadmium nitrate trihydrate, an ethanol and a de-ionized water.

4. The process as claimed in claim 3, wherein the multiple proportions of cadmium nitrate trihydrate includes 0.05, 0.15 and 0.30 millimole.

5. The process as claimed in claim 2, wherein an ethylene glycol act as, both reaction media and dispersion media can efficiently absorb and stabilize surface of the particles and favors producing transition metal doped nano structures with smaller size.

6. The process as claimed in claim 2, wherein a process growth is significant when time temperature is lowered, wherein synthesizing Cd-CuS nanostructures at low hydrothermal temperature 130degree Celcius for keeping reaction time in 10 hours is performed.

7. The process as claimed in claim 2, wherein the CdS changes a cubic structure of CuS into a hexagonal structure upon adding of Cd ions into the solution mixture, wherein a structural alteration within the crystal lattice of the CuS is achieved due to the replacement of bigger size Cd2+ ions (1.7lAo) by the smaller Cu2+ ions (1.28Ao).

8. The process as claimed in claim 2 and 7, wherein the average sizes of CuS and Cd-CuS particles are found to be 14nm, 9nm, 15nm, l7nm for concentration of Cd doped CuS respectively, and decreased when Cd2+ ions occupied the place of Cu2+ ions.

9. The process as claimed in claim 2, wherein a phase transitions in CdS is reported due to a plurality of parameters includes particle size, concentration of S2- and Cd2+, stacking faults, presence of CTAB and other foreign materials present in the solution mixture also underwent phase transition.

10. The process as claimed in claim 2, wherein the CTAB plays a vital role in the morphological transformation of the CuS and Cd-CuS nanostructures, the transformation process comprising:

combining a head group of CTAB with Cd-CuS nanosheets and detaching outwards; and projecting a tail group of CTAB to the neighboring Cd-CuS nanosheets for creating regular structure of a heaped up nanosheets.

Capacitive Electrochemical Electrode 102 Capacitor 104

Electrolyte 106 At Least Two Conducting Plates 108

Nanoporous Load 112 Transition Metal Sulphide 110

Figure 1

202 dissolving a copper nitrate trihydrate, a thiourea and a cetyl trimethyl ammonium bromide (CTAB) in a predetermined proportion into a solvent of ethylene glycol to produce a transition metal doped nano structured solution

204 adding multiple proportions of cadmium nitrate trihydrate and stirring the solution for 30 minutes to 1 hour to eliminate the surface defects and thereby convert a cubic structure of the solution into a hexagonal structured solution

206 synthesizing Cd-CuS nanostructures at low hydrothermal temperature of 130 degree Celsius for reaction time of at least 10 hours to prepare a black colored precipitate of transition metal sulphide nanostructures

208 washing precipitate to remove impurities and thereby drying the precipitate at a temperature of 50 to 80 degree Celsius for 5 to 10 hours to produce a black colored precipitate of nanoporous transition metal sulphide

210 fabricating the black colored precipitate on the capacitive electrode of the electrochemical energy storage device to improve the ion exchange diffusion to enhance the capacitive behavior of the capacitive electrode and thereby to increase the storage capacity of the electrochemical energy storage device

Figure 2

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