FeSe2 BASED COMPOSITE MATERIAL FOR ALUMINUM BATTERIES

Abstract

The present disclosure relates to FeSe2 decorated porous nitrogen and sulfur-doped carbon spheres (FSPNSCS) composite material as cathode for the aluminium ionic battery (AIB) or aluminium aqueous battery. The present invention also relates to a process of preparation of said composite material comprising FeSe2 with nitrogen and sulphur co-doped porous carbon spheres. The invention also relates to aluminium aqueous batteries containing FeSe2 material as cathode.

Description

[0001] FeSe2BASED COMPOSITE MATERIAL FOR ALUMINUM BATTERIES

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to FcSci decorated porous nitrogen and sulfur-doped carbon spheres (FSPNSCS) composite material as cathode for the aluminium ionic battery (AIB) or aluminium aqueous battery. The present invention also relates to a process of preparation of said composite material comprising FcSci with nitrogen and sulphur co-doped porous carbon spheres. The invention also relates to aluminium aqueous batteries containing FcSci material as cathode.

[0004] BACKGROUND OF THE INVENTION

[0005] There is an increasing demand in alternative energy storage technologies, separate from those reliant on lithium-ion. Adopting these new solutions will help to reduce the costs and geopolitical issues associated with Li-ion-based storage technology. Sodium-ion-based systems have been experiencing significant growth and are emerging as strong contenders among various storage technologies, including batteries and supercapacitors. At the same time, multivalent ion batteries (Mg2+, Ca2+, Zn2+, Al3+) are viable alternatives to lithium. Multivalent ions are capable of carrying more than one electron, resulting in a high theoretical capacity and energy density.

[0006] Aluminium (Al) is particularly significant for multivalent ion candidates. An Al anode has a specific volumetric capacity of up to 8046 mAh cm'3, about four times higher than Li (2062 mAh cm'3), and a gravimetric capacity of 2980 mAh g'1, equivalent to Li metal's 3860 mAh g' f Al is abundant in earth’s crust, accounting for approximately 8% of the earth's crust. Furthermore, because Al metal has higher air stability than Li, the possible safety danger is reduced, which increases the ease of handling in an ambient environment.

[0007] With increasing interest in developing multivalent batteries, there is a need for new electrode materials that can be harnessed to achieve high-capacity Al ion batteries. In aluminum-ion batteries (AIBs), it is anticipated that Al ions (Al3+) possessing a smaller ionic radius of 53.5 pm will function as guest cations, in a manner analogous to the intercalation chemistry observed in lithium-ion batteries. However, the greater hydrated radius limits insertion and extraction into and from the host electrode. Furthermore, Al3+s strong electrostatic interactions with the host structure, as well as its high charge density, impede the insertion / extraction process, resulting in sluggish kinetics, a large overpotential, and the host structure's final collapse. The greater electrochemical redox potentials and lower gravimetric specific capacities than lithium metal as anode result in a lower discharge plateau. These limitations reduce the gravimetric energy density of a complete cell. The selection of cathode materials will determine the future direction of rechargeable aqueous AIBs. Hence, altering the current materials and creating new materials is imperative.

[0008] FeSe2 features high theoretical capacity values hence it is well studied for the Li and Na battery system. Transition metal compounds, such as oxides, sulfides, and selenides, have been studied for quick charge / discharge and extended cycle life. FeSe2, a transition metal selenide with a narrow band gap of 1.0 eV and high electrical conductivity of 10'4mScm'1, is a promising option due to its higher rate capacity and lower internal resistance compared to oxides and sulfides. At the same time it is well suited in the aqueous electrolyte.

[0009] Changhuan Zhang, Liran Zhang, Nianwu Li and Xiuqin Zhang, Energies 2020, 13(17), 4375; ( pgAdoi org / lO 390 / en 13174375) reports the Mg-Li Hybrid Batteries based on the dualion electrolyte. Hybrid ion batteries are a different concept from Aluminum ion batteries. Hence, it will not be applicable for the instant case.

[0010] Considering the above-mentioned drawbacks, the current inventors have developed a FcSci decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite as cathode material obtained from 2 step hydrothermal method for aqueous Al battery.

[0011] OBJECTIVE OF THE INVENTION

[0012] An objective of the present disclosure is to provide a FcSci decorated porous nitrogen, sulfur- doped carbon spheres (FSPNSCS) composite as cathode material.

[0013] Another objective of the present disclosure is to provide a process of preparation of said composite material comprising FcSci with nitrogen and sulphur co-doped porous carbon spheres.

[0014] Still another objective of the invention is to provide a cathode with a high capacity of 60 mAh g1at 200 mA g1,which is comparable with the reported cathode with stable coulombic efficiency of more than 80%.

[0015] Still another objective of the invention is to provide an aluminium aqueous battery containing FeSei material as cathode.

[0016] Still another objective of the invention is to provide a battery with improved electrochemical performance.

[0017] Still another objective of the invention is to provide a cathode material as well as battery that is cost effective and environmentally friendly. SUMMARY OF THE INVENTION

[0018] The aspects of the present disclosure relate to FcSci decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite as cathode material for the aluminium ionic battery (AIB) or aluminium aqueous battery.

[0019] In an aspect, the present disclosure relates to an aluminium battery comprising: a) cathode based on FcSci-dccoratcd porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite material, b) anode; and c) electrolyte

[0020] In an embodiment, the anode is selected from pristine aluminium foil, aluminium zinc alloy, and aluminium eutectic alloy.

[0021] In an embodiment, the electrolyte is selected from mixture of l-ethyl-3-methylimidazolium chloride and aluminium chloride [(EMIm)Cl and AlCh], aluminium nitrate [A1(NO3)3], aluminium trifluoromethanesulfonate [Al(0TF)3], and aluminium chloride.

[0022] In an embodiment, the ratio of l-ethyl-3-methylimidazolium chloride and aluminium chloride electrolyte is 1.3-1.5: 1.

[0023] In an embodiment, the concentration of aluminium nitrate as electrolyte is in the range of 0.5-

[0024] 2 M.

[0025] In an embodiment, the concentration of aluminium trifluoromethanesulfonate as electrolyte is in the range of 0.5-2 M.

[0026] In an embodiment, the concentration of aluminium chloride as electrolyte is in the range of 0.5-

[0027] 3 M.

[0028] In an embodiment, the aluminium battery is an aluminium ionic battery (AIB) or an aluminium aqueous battery.

[0029] In an embodiment, the FSPNSCS composite material is in shape of micro-flowers.

[0030] In another aspect, the present disclosure relates to a process for the preparation of said FSPNSCS composite material, comprising the steps of: a) dissolving a sugar in a solvent under stirring, followed by the addition of an amino acid to obtain a solution; b) hydrothermally heating the solution of step a) at temperature in the range of 160 to 200 °C for a time period of 20 to 26 hours, followed by cooling the solution to 25 °C to 30°C; c) washing the solution of step b) with a solvent under vacuum filtration, followed by drying at a temperature in range of 70°C -100°C for a time period of 8 to 14 h; d) annealing the dried material of step c) at a temperature in range of 780 to 820 °C for time period of 1-1.30 h to obtain a Nitrogen and Sulfur-doped carbon spheres (NSCS); e) subjecting the NSCS of step d) with a KOH solution to obtain a mixture, followed by thermally activating the mixture at a temperature in range of 780 to 820 °C with ramp rate of 5 °C for time period of 1 h; f) cooling the mixture of step e) at temperature ranging from 25-30 °C, followed by removing KOH through filtration to obtain porous NSCS (PNSCS) particles; g) drying the PNSCS particles of step f) at temperature in range of 70-90 °C in an oven for time period of 10-14 h; h) mixing and stirring iron ammonium sulphate, selenium powder, citric acid and the dried PNSCS of step g) in the solvent for a time period of 20 to 45 minutes; i) adding dropwise hydrazine hydrate to the mixture of step h) under stirring for time period of 20 to 40 minutes followed by sonication at 20-35 °C for time period of 45 to 90 minutes; j) autoclaving the solution of step i) followed by heating at temperature in the range of 160 to 200°C for time period of 10 to 14 hrs; and k) washing the solution of step j) with the solvent to obtain a clear solution, followed by drying the solution at temperature in the range of 60 to 100 °C for a time period of 10 to 14 hrs to obtain FSPNSCS composite material.

[0031] In an embodiment, the solvent is selected from deionized water, and ethanol or a mixture thereof.

[0032] In an embodiment, the amino acid is selected from cysteine, glycine, alanine, and glutamine or a mixture thereof.

[0033] In an embodiment, the nitrogen and sulfur-doped carbon spheres (NSCS) and KOH solution in step (e) are mixed at a ratio in the range of 1:2 to 1:4.

[0034] In an embodiment, the present disclosure relates to a process for preparation of the cathode comprising: coating or fabricating FSPNSCS composite material onto a metal substrate electrode.

[0035] In an embodiment, the metal substrate electrode is selected from graphite sheet, molybdenum, tantalum, and tungsten. Another aspect of the present disclosure relates to an aq. or ionic AIB battery comprising said FSPNSCS composite material as a cathode material, anode, electrolyte, etc.

[0036] In another aspect of the present disclosure, the aluminium battery comprises the FSPNSCS composite material as a cathode, pristine aluminium foil as anode and [EMIm]Cl : A1C13 (1.3: 1) as electrolyte.

[0037] Another aspect of the present disclosure relates to an aq. AIB battery comprising said FcSci material as a cathode material, anode, electrolyte, etc.

[0038] Another aspect of the present disclosure relates to a process of preparation of cathode material for aluminium batteries comprising coating or fabricating FeSe2@PNSCS micro-flowers composite material onto substrate electrodes under specific conditions, wherein the substrate electrode is made of metal.

[0039] In another aspect of the present disclosure, the substrate electrode is selected from Grafoil (graphite sheet), Molybdenum, Tantalum, and Tungsten.

[0040] In another aspect of the present disclosure, the working electrode is prepared by mixing the active material (FSPNSCS, FeSe?, or PNSCS) with a conducting additive and PVDF binder (8:1: 1 weight ratio) in N-methylpyrrolidone NMP to form a slurry, coating it onto a 1 x 1 cm2Grafoil sheet, and drying at 70°C under vacuum overnight.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.

[0043] The features and advantages of the present disclosure will become more apparent from the following detailed description along with the accompanying figures, which forms a part of this application and in which:

[0044] Figure 1 illustrates the Rietveld refinement of powder X-ray diffraction data for FSPNSCS; Simulated crystal structure obtained from the Rietveld refinement.

[0045] Figure 2 illustrates the a, b. ESEM images of PNSCS and c,d. FSPNSCS.

[0046] Figure 3 illustrates the Survey and Deconvoluted XPS Spectra of FSPNSCS.

[0047] Figure 4 illustrates the (a) CV Profiles at different scan rates; (b) Nyquist plot before and after CV; (c) log(i) vs log(v) Plot; (d) Peak current vs v1 / 2; (e) CV Profile at 1 mV s’1; (f) Separation of the capacitive and diffusion currents.

[0048] Figure 5 illustrates the Galvanostatic Charge Discharge Study (a) Rate Study (b) Stability. Figure 6 illustrates the Galvanostatic Charge-Discharge comparison of controlled samples at 500 mA g’1.

[0049] Figure 7 illustrates the (a) schematic Pouch cell setup with FSPNSCS cathode, and b) Schematic Pouch cell setup with FcSci cathode covering aqueous Al battery.

[0050] Figure 8 illustrates the (a) CV Profile at 1 mV s’1,(b) Nyquist plot before and after CV.

[0051] Figure 9 illustrates the Galvanostatic Charge-Discharge study at 500mAg-1.

[0052] Figure 10 illustrates the (a) schematic three electrode system setup with FSPNSCS cathode and (b) schematic three electrode system setup with FcSci as cathode.

[0053] Figure 11 illustrates the synthesis of porous nitrogen, sulfur carbon spheres (PNSCS).

[0054] Figure 12 illustrates the synthesis of synthesis of FeSe2 decorated porous nitrogen, sulfur carbon spheres (FSPNSCS)

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] The following is a detailed description of embodiments of the disclosure. 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.

[0057] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0058] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0059] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0060] 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.

[0061] 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.

[0062] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0063] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.

[0064] 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.

[0065] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.

[0066] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.

[0067] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention. The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0068] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0069] The term "or", as used herein, is generally employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0070] The present invention provides FcSci decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite as cathode material.

[0071] The FeSe2 decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite as cathode material is obtained from the 2-step hydrothermal method for aqueous AIB. Comprehensive characterization techniques were employed, including X-ray Diffraction (XRD) analysis to confirm the crystalline structure, XPS and Scanning Electron Microscopy (ESEM) to reveal the unique composite morphology.

[0072] Some of the advantages of the FSPNSCS composite or FcSci material as cathode in the aluminum battery are:

[0073] 1. FSPNSCS composite or FcSci has a high theoretical capacity, which is important for making batteries with a high capacity;

[0074] 2. FeSei is noted for its comparatively high electrical conductivity;

[0075] 3. Efficient electron movement inside the cathode material is critical to the battery’s overall performance, including charge and discharge rates; 4. The conductivity of FSPNSCS composite is improved in the battery’s electrochemical performance;

[0076] 5. FSPNSCS composite is suitable for aqueous electrolytes, which are typically considered safer than non-aqueous electrolytes (e.g. ionic electrolytes).

[0077] Another aspect of the present disclosure relates to a process of preparation of said composite material comprising FcSci with nitrogen and sulphur co-doped porous carbon spheres.

[0078] Another aspect of the present disclosure relates to a process of preparation of said composite material, comprising the steps of: a) stirring and dissolving a sugar in a solvent followed by addition of an amino acid; b) hydrothermally heating the solution of step a) at temperature in the range of 160 to 200 °C for a time period of 20 to 26 hrs followed by cooling down the solution at temperature of 25 to 30 °C; c) washing the solution of step b) with the solvent under a vacuum filtration followed by drying at a temperature in range of 70-100°C for a time period of 8 to 14 hrs; d) annealing the material of step c) at a temperature in range of 780 to 820 °C for time period of 1-1.30 hrs to obtain a N and S doped carbon spheres (NSCS); e) subjecting the NSCS of step d) with a KOH solution at a ratio in the range of 1:2 to 1:4 to obtain mixture; f) thermally treating the mixture of step e) at a temperature in range of 780 to 820 °C with ramp rate of 5 °C for time period of 1 hr; g) cooling down the mixture of step f) at temperature ranging from 25-30 °C followed by removing KOH through a filtration to obtain porous NSCS (PNSCS) particles; h) drying the PNSCS particles of step g) at temperature in range of 70-90 °C in an oven for time period of 10-14 hrs; i) adding and stirring a mixture comprising an iron ammonium sulphate, a Se powder, a citric acid and said dried PNSCS of step h) in the solvent for a time period of 20 to 45 minutes; j) drop wise adding a hydrazine hydrate to the mixture of step i) under stirring for time period of 20 to 40 minutes followed by sonication for time period of 45 to 90 minutes; k) autoclaving the solution of step j) followed by heating at temperature in the range of 160 to 200°C for time period of 10 to 14 hrs; and l) washing the solution of step k) with the solvent to obtain a clear solution followed by drying the solution at temperature in the range of 60 to 100 °C for a time period of 10 to 14 hrs to obtain FSPNSCS composite. In another aspect of the present disclosure, the solvent is selected from deionised water, ethanol or a mixture thereof.

[0079] In another aspect of the present disclosure, the amino acid is selected from cysteine, glycine, alanine, glutamine or a mixture thereof.

[0080] Another aspect of the present disclosure relates to an aq. or ionic AIB battery comprising said FSPNSCS composite material as a cathode material, anode, electrolyte, etc.

[0081] Another aspect of the present disclosure relates to an aq. AIB battery comprising said FcSci material as a cathode material, anode, electrolyte, etc (Figure 10b).

[0082] In some embodiments, the current collector (substrate on which slurry is coated) is selected from Grafoil (graphite sheet), Molybdenum, Tantalum, and Tungsten in the aqueous as well as the ionic Aluminum ion battery.

[0083] The main function of the current collector is to collect and facilitate the flow of electrical current between the electrochemically active substances (active material) in the electrodes and the external circuit. The Al ion battery electrolytes of the prevent invention contain Cl’ which is corrosive in nature, and hence, the current collector must be selected that is corrosion resistant or can withstand the electrolyte without getting corroded. Mo, W, Ni (to a certain extent) are non-corrosive in chloroaluminate electrolytes and hence can be used as a current collector. Grafoil current collector for aqueous system and Mo current collector for the ionic system are used in the present invention.

[0084] In some embodiments, the working electrode was prepared by mixing the active material (FSPNSCS or FcSci or PNSCS), conducting additive and poly-vinylidene fluoride (PVDF) binder at a weight ratio 8: 1: 1 in N-methylpyrrolidone (NMP) to form a homogeneous slurry. Then the slurry was uniformly spread over a 1 x 1 cm2area of grafoil sheet and dried at 70°C in a vacuum oven overnight.

[0085] Another aspect of the present disclosure relates to an aq. or ionic AIB battery comprising said FSPNSCS composite material as a cathode material, anode, electrolyte, etc.

[0086] Another aspect of the present disclosure relates to a process of preparation of cathode material for aluminium battery comprising coating or fabricating FeSe2@PNSCS micro-flowers composite material onto substrate electrodes under specific conditions, wherein the substrate electrode is made of metal (Figure 10b).

[0087] In some embodiments, the inventors have tested the FSPNSCS as cathode material for an aqueous Aluminum ion battery in 3 electrode system wherein Grafoil was used as a current collector for the working electrode, Pt as the counter electrode, and Ag / AgCl as a reference electrode (Figure 10a). In some embodiments, gold, glassy carbon, or any inert electrode may be used. In some embodiments, reference electrodes may be selected from Saturated Calomel Electrode (SCE), Ag / Ag2SO4, Ag / AgBr, etc.

[0088] In some embodiments, in the ionic Aluminum ion battery, testing was done in a pouch cell in which active material was coated on Mo foil to use as a working electrode and pristine Al foil was used as anode with [EMIm]Cl : AlCh (1.3: 1) as ionic electrolyte (Figure 7).

[0089] The present invention also relates to aqueous Al ion battery comprising the cathode, FcSci deposited onto electrode, working electrode, reference electrode, anode material, electrolyte, etc.

[0090] In some embodiments, in the aqueous Aluminum ion battery testing, 3 electrode system was used which consists of the working electrode (slurry coated on grafoil), counter electrode (Pt), and reference electrode (Ag / AgCl) in IM AlCh as electrolyte.

[0091] In some embodiments, the inventors have tested the FeSe2 as cathode material for an aqueous Aluminum ion battery in 3 electrode system wherein Grafoil was used as a current collector for the working electrode, Pt as the counter electrode, and Ag / AgCl as a reference electrode with IM AICI3 as electrolyte.

[0092] Methods reported in literature covers Al battery based on FeSe2 in ionic electrolyte showing a good capacity at higher current when compared with the present battery covering composite material in aqueous conditions.

[0093] As it would be apparent to a person skilled in the art, direct comparison between aqueous and ionic electrolyte systems is not possible as many parameters are completely different from one another. The above-mentioned literature reports the study in ionic electrolyte systems; hence, comparisons between aqueous electrolytes will not apply. If we consider the performance of FSPNSCS in aqueous and ionic electrolytes in the present invention, then we can comment that in the aqueous system, the stability and capacity values are better than ionic.

[0094] It is noted that the composite material containing the battery in aqueous conditions gives better results than an ionic battery. The same is also applied to FeSe2 material which gives better or improved capacity values than ionic batteries as disclosed in said reference.

[0095] In some embodiments, FSPNSCS showed around 25 to 30 mAhg-1capacity at 500 mA g1current density after 500 cycles in an aqueous electrolyte system. In some embodiments, in an ionic electrolyte in a pouch cell the capacity was around 10 to 15 mAhg1at 500 mA g1current density.

[0096] In the case of only FeSe2 mentioned in the EES paper, it has shown specific capacity of 21 mAh g1at 1 A g1with rapid capacity decay within 100 cycles. However, the comparison of FeSei and FSPNSCS in respect of capacity retention, FSPNSCS has shown superior performance in an aqueous system.1

[0097] In some embodiments, the inventors have conducted the comparative study for the FcSci, PNSCS and FSPNSCS to get a better idea in terms of overall comparison of the data. Above plot shows the stability data for FcSci. PNSCS and FSPNSCS at 500 mA g1current density in an aqueous system (Figure 6). Composite FSPNSCS clearly shows better performance compared to PNSCS and FcSci. PNSCS shows better coulombic efficiency, but capacity decay can be observed, which can be seen in the figure 6. Overall FSPNSCS shows a better capacity value with coulombic efficiency maintained around 90%.

[0098] In an embodiment, the present disclosure provides a cathode comprising FeSei decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) with a high capacity of 60 mAh g1at 200 mA g1, with stable coulombic efficiency of more than 80%, aluminium-ion battery (AIB) comprising such an electrode, with improved electrochemical performance, a cathode material as well as battery that is cost effective and environmentally friendly.

[0099] Galvanostatic charge-discharge study for FcSci, PNSCS, and FSPNSCS conducted at 500 mA g1current density shows the improvement of discharge capacity for FSPNSCS compared to FeSe2 and PNSCS in aqueous system (Figure 9). At the same time coulombic efficiency and capacity retention for the FSPNSCS after 500 cycles show promising numbers as the coulombic efficiency is maintained at 90 % with capacity retention of almost 100%, which gives the edge over FeSei and PNSCS. Further the performance of FSPNSCS was studied at various current densities to establish the performance of the cathode at various electrochemical conditions (Figure 8). Only a few reports mention FeSe2@rGO composite for ionic AIB. However, till now, there are no reports of FeSe2 material used in an aqueous Aluminum ion battery.

[0100] EXAMPLES

[0101] Materials and Method: All the chemicals were used as received without purification. Sucrose and L-cysteine, Se powder, and hydrazine hydrate were obtained from Sigma-Aldrich. Hydrochloric acid (35%), sulphuric acid (98%), and potassium hydroxide pellets were procured from Thomas Bakers (chemicals) Pvt. Ltd. India.

[0102] Example 1: Synthesis of porous nitrogen, sulfur carbon spheres (PNSCS):

[0103] The porous nitrogen and sulfur co-doped carbon was made using the hydrothermal method, followed by activating it with KOH. 10 g of saccharose was mixed with 120 ml of deionized water. It was then mixed with 2 g of L-cysteine. The solution was then put into a stainless-steel autoclave sealed with Teflon and heated at 180°C for 24 hours. The result was cooled to room temperature, filtered, and washed several times with deionised water and ethanol. It was then left to dry overnight. The hydrochar material is mixed with KOH in a weight ratio 1 :3 and heated at 800°C for 1 hour under an Argon flow at a rate of 5°C / min to make it porous. Inorganic elements formed during the activation process were removed by rewashing the material with 2 M hydrochloric acid (HC1). Then, the water was deionised until the pH of the filtrate was equal to 7. The residue was left to dry overnight to get active porous carbon spheres doped with N and S (PNSCS). (Figure 11)

[0104] Example 2: Synthesis of FeSez decorated porous nitrogen, sulfur carbon spheres (FSPNSCS):

[0105] Typical synthesis of FSPNSCS consists of mixing Fe(NH4)2(SO4)2 6H2O (2 mmol, 0.7843 g), Se (4 mmol, 0.3158 g), and citric acid (CA) (20.8 mmol, 4 g) and dried PNSCS into 44 mL of deionized water. After that, 16 mL of hydrazine hydrate was added to the liquid drop by drop. The solution was mixed well and sonicated for one hour. It was then put into a Teflon-lined stainless-steel autoclave that was sealed and heated to 180 °C for 12 hours. The autoclave was opened once it had cooled to room temperature. The suspension that was made was centrifuged, and distilled water and 100% ethanol were used to wash the precipitate very well. (Figure 12)

[0106] Materials Characterization:

[0107] The synthesized product was characterized by various techniques such as powder X-ray diffraction measurements using a Philips X’Pert PRO diffractometer with nickel -filtered Cu Ka radiation, field emission scanning electron microscopy (FE-SEM) with Hitachi S-4200 apparatus and transmission electron microscopy (TEM, FEI Tecnai F20 FEG with 200 kV), X Ray photoelectron spectroscopy using (XPS; Phi 5000 VersaProbe II, Physical Electronics, ULVAC PHI) equipped with monochromatic Al Ka (1= 1486.6 eV) X-ray radiation and a hemispherical analyzer.

[0108] Figure 1 illustrates the XRD data of synthesised FSPNSC. Rietveld refinement of powder X- ray diffraction data for FSPNSCS and simulated crystal structure obtained from the Rietveld refinement, showing an orthorhombic Pnnm space group. Obtained material was characterized by XRD, XPS, and ESEM. Phase confirmation of FSPNSCS was done with XRD matching with Rietveld refinement as shown in Figure 1. Further Figure 2. c,d, show SEM images showed the FeSe2 grown on the carbon spheres. XPS analysis was performed to further confirm the FeSe2 phase. Figure 3 presents the Fe 2p spectrum with two characteristic 2p3 / 2 and 2pl / 2 peaks located at 711.9 and 725.5 eV, corresponding to the chemical valence of Fe2+. The 3d5 / 2 and 3d3 / 2 peaks of Se are centred at 54.8 and 55.7 eV, respectively, and the peak at 59.3 eV from Se-0 bonds is ascribed to the surface oxidation state of selenium species.

[0109] Table 1 confirms the elemental composition of the composite material, as provided below.

[0110] Example 3: Electrochemical characterization

[0111] In aqueous AIB testing was conducted in three electrodes system, platinum was used as the counter electrode and Ag / AgCl as reference and FSPNSCS coated on grafoil was used as the working electrode with IM AlCh as electrolytes for the study. Working electrode was prepared by using a slurry consisting of 80 wt % FSPNSCS, 10 wt % Conducting additive, and 10 wt % PVDF using NMP as solvent. The obtained slurry was uniformly coated on a grafoil with and then dried in a vacuum drying oven. Active loading of the electrodes was maintained in range 1 to 1.5 mg. Cyclic voltammetry and galvanostatic charge discharge were performed on a Biologic workstation at the scan rates and current densities.

[0112] Application of FSPNSCS as cathode material for aqueous Aluminum ion battery

[0113] Electrochemical characterizations were carried out using a three-electrode setup using IM AlCh as electrolyte. The working electrode was prepared by coating a slurry of active material (FSPNSCS), conducting additive, and binder in a ratio of 8: 1 : 1. Cyclic Voltammetry was performed at various scan rates to study the kinetics of the reaction occurring during charge and discharge.

[0114] Figure 4a shows the cyclic voltammogram recorded at various scan rates. The relationship between the faradaic peak currents (i) and scan rates (v) can be expressed using the following formula, i = avblog i = log a + b logv where a and b are adjustable variables. The observed relationship between log(i) and log(v) demonstrates a linear correlation (Figure 4c), characterized by a slope denoted as "b" The slope, denoted as b, carries the essential information pertaining to the storage kinetics of charges. b=l indicates the presence of a capacitive-controlled faradaic redox process, while a value of b= 0.5 shows a diffusion-controlled faradaic redox reaction. The obtained value of 0.68 indicated that the FSPNSCS electrode shows redox -type behavior. This behavior is controlled by both surface-controlled capacitive process and diffusion-controlled battery -like behavior. Further to check cycling performance of the cells was evaluated at various charge-discharge rates of 200mA g'1, 300mA g'1, 400mA g'1, 500mA g'1, 600mA g'1which showed stable performance in range 60 mAh g'1to 28 mAh g’1. While long-term cycling study showed the coulombic efficiency maintained above 85%.

[0115] Cycling testing is done for the composite in the range of 50-200 cycles, showing said higher capacity values and until 98% coulombic efficiency.

[0116] The FSPNSCS composite shows the capacity to be 60mAh g-1 at 200mA g-1 also the capacity retention is above 95% maintained even after 500 cycles at 500 mA g-1 current density.

[0117] FSPNSCS shows the compatibility as a cathode material for aqueous AIB, demonstrated energy storage capabilities, delivering a reversible capacity of 60 mAh g'1at a current density of 200 mAg'1, while maintain the coulombic efficiency above 85% at 500 mAh g'1(Figure 5a-b). This remarkable performance was retained after 500 charge-discharge cycles, underlining its stability and cyclability.

[0118] ADVANTAGES OF THE PRESENT INVENTION i. The present disclosure provides a FcSci decorated porous nitrogen, sulfur-doped carbon spheres (FSPNSCS) composite as cathode material. ii. The present disclosure provides a process of preparation of said composite material comprising FeSe2 with nitrogen and sulphur co-doped porous carbon spheres. iii. The present disclosure provides a cathode with a high capacity of 60 mAh g1at 200 mA g1,which is comparable with the reported cathode with stable coulombic efficiency of more than 80%. iv. The present disclosure provides a battery with improved electrochemical performance. v. The present disclosure provides a cathode material as well as battery that is cost effective and environmentally friendly. vi. Although the present invention has been described with reference to preferred embodiments, it is submitted that various modifications can be made to the exemplary embodiments without departing from the spirit and scope of the invention.

Claims

We Claim1. An aluminium battery comprising: a) cathode based on FcSci-dccoratcd porous nitrogen, sulfur-doped carbon spheres FSPNSCS composite material, b) anode; and c) electrolyte.

2. The aluminium battery as claimed in claim 1, wherein the anode is selected from pristine aluminium foil, aluminium zinc alloy, and aluminium eutectic alloy; and the electrolyte is selected from mixture of l-ethyl-3-methylimidazolium chloride and aluminium chloride [(EMIm)Cl and AlCh], aluminium nitrate [A1(NO3)3], aluminium trifluoromethanesulfonate [A1(OTF)3], and aluminium chloride.

3. The aluminium battery as claimed in claim 2, wherein the ratio of l-ethyl-3- methylimidazolium chloride and aluminium chloride electrolyte is 1.3- 1.5: 1.

4. The aluminium battery as claimed in claim 1, wherein the aluminium battery is an aluminium ionic battery (AIB) or an aluminium aqueous battery.

5. A process for preparation of FSPNSCS composite material as claimed in claim 1, comprising the steps of: a) dissolving a sugar in a solvent under stirring, followed by the addition of an amino acid to obtain a solution; b) hydrothermally heating the solution of step a) at temperature in the range of 160 to 200 °C for a time period of 20 to 26 hours, followed by cooling the solution to 25°C to 30°C; c) washing the solution of step b) with the solvent under vacuum filtration, followed by drying at a temperature in range of 70°C -100°C for a time period of 8 to 14 h; d) annealing the dried material of step c) at a temperature in range of 780 to 820 °C for time period of 1-1.30 h to obtain a Nitrogen and Sulfur-doped carbon spheres (NSCS);e) subjecting the NSCS of step d) with a KOH solution to obtain a mixture, followed by thermally activating the mixture at a temperature in range of 780 to 820 °C with ramp rate of 5 °C for time period of 1 h; f) cooling the mixture of step e) at temperature ranging from 25-30 °C, followed by removing KOH through filtration to obtain a porous NSCS (PNSCS) particles; g) drying the PNSCS particles of step f) at temperature in range of 70-90 °C in an oven for time period of 10-14 h; h) mixing and stirring iron ammonium sulphate, selenium powder, citric acid and the dried PNSCS of step g) in the solvent for a time period of 20 to 45 minutes; i) adding dropwise hydrazine hydrate to the mixture of step h) under stirring for time period of 20 to 40 minutes followed by sonication at 20-35 °C for time period of 45 to 90 minutes; j) autoclaving the solution of step i) followed by heating at temperature in the range of 160 to 200°C for time period of 10 to 14 hrs; and k) washing the solution of step j) with the solvent to obtain a clear solution, followed by drying the solution at temperature in the range of 60 to 100 °C for a time period of 10 to 14 hrs to obtain FSPNSCS composite material.

6. The process as claimed in claim 5, wherein the solvent is selected from deionized water, and ethanol or a mixture thereof.

7. The process as claimed in claim 5, wherein the amino acid is selected from cysteine, glycine, alanine, and glutamine or a mixture thereof.

8. The process as claimed in claim 5, wherein the nitrogen and sulfur-doped carbon spheres (NSCS) and KOH solution in step (e) are mixed at a ratio in the range of 1:2 to 1:4.

9. A process for preparation of cathode as claimed in claim 1 comprising: coating or fabricating FSPNSCS composite material onto a metal substrate electrode.

10. The process as claimed in claim 9, wherein the metal substrate electrode is selected from graphite sheet, molybdenum, tantalum, and tungsten.

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