A dual ion water-in-salt hybrid electrolyte composition for zinc-ion battery and a zinc-ion battery thereof

Abstract

The present invention provides a dual ion water-in-salt hybrid electrolyte composition and a low-cost scalable cathode for zinc ion battery. The cathode is fabricated from commercially available V₂O₅ and oxidizing agent. Additionally, a dual-ion water-in-salt hybrid electrolyte composition comprises zinc salt, lithium salt, co-solvent and water. This electrolyte, comprising co-solvent and water, supports stable cycling and excellent Zn plating / stripping behaviour, maintaining performance for over 1986 hours in Zn symmetric cells at a current density of 2 mA cm⁻². Furthermore, the zinc-ion battery demonstrates exceptional cycling life, with Coulombic efficiency (CE) sustaining over 10000 cycles when the electrolyte composition is optimized with a 50:50 water:co-solvent ratio. These advancements result in a zinc-ion battery with improved stability, efficiency, and long-term cycling performance, making it suitable for practical energy storage applications.

Description

[0001] A DUAL ION WATER-IN-SALT HYBRID ELECTROLYTE COMPOSITION FOR ZINC-ION BATTERY AND A ZINC-ION BATTERY THEREOF FIELD OF DISCLOSURE

[0002] The present invention relates to a dual ion water-in-salt hybrid electrolyte composition for zinc-ion battery and a zinc-ion battery thereof. More particularly, the present invention provides a dual ion water-in-salt hybrid electrolyte composition for a zincion battery comprising a co-solvent and a low-cost scalable cathode which is fabricated from V2O5 and oxidizing agents for a zinc-ion battery.

[0003] BACKGROUND

[0004] The performance and durability of zinc (Zn) anodes in aqueous electrolytes are often compromised due to the undesired occurrence of hydrogen evolution, which exacerbates dendritic growth and leads to the formation of inactive Zn deposits. In typical dilute electrolytes, Zn2+ions primarily coordinate with water molecules, forming a hydrated solvation structure. This interaction between Zn2+and water induces electronic polarization, weakening O-H bonds and facilitating partial water dissociation. As a result, proton reduction is triggered, initiating the hydrogen evolution reaction (HER) and accelerating electrolyte degradation.

[0005] The extensive hydrogen-bonding network within bulk water further promotes rapid 20 proton transport, amplifying HER activity. The continuous release of hydrogen gas not only depletes the electrolyte but also generates internal pressure, which can damage the electrode integrity. These factors collectively reduce Coulombic efficiency, limit reversibility, and hinder the long-term cycling stability of Zn-based batteries. Therefore, addressing these challenges is crucial for advancing Zn-based aqueous energy storage systems.

[0006] To mitigate hydrogen evolution and enhance the stability of Zn anodes, electrolyte engineering has concentrated on reducing water reactivity and modifying the Zn2+solvation structure. One prominent strategy involves the use of highly concentrated electrolytes (HCEs) or water-in-salt electrolytes (WiSEs), where the higher salt-towater ratio reduces the presence of free water molecules. This disruption of thebulk hydrogen-bonding network alters Zn2+coordination dynamics, leading to the inclusion of anions (such as SO42, Cl", or TFSI ) in the solvation shell.

[0007] By replacing a portion of water molecules with anions, the modified solvation structure limits proton availability, thereby reducing hydrogen evolution pathways. Moreover, anion-rich environments promote more uniform Zn deposition, which helps reduce dendritic growth and improves Zn plating / stripping efficiency. As a result, Zn anodes in such electrolyte systems exhibit enhanced reversibility, higher Coulombic efficiency, and extended cycle life, thereby addressing critical challenges in Zn-based aqueous battery technologies.

[0008] Increasing the concentration of Zn salts in electrolytes has been shown to shift the reduction potential of Zn2+to a more favourable range, effectively suppressing hydrogen evolution and expanding the electrochemical stability window. The higher overpotential required for HER on Zn metal further reduces parasitic side reactions, enhancing Zn plating efficiency. However, the solubility limits of Zn salts in aqueous environments restrict the maximum achievable concentration, necessitating the use of co-salts, such as lithium bistrifluoromethanesulfonimide (LiTFSI) or potassium acetate (KAc), to create highly concentrated electrolyte systems.

[0009] Various reported water-in-salt electrolyte (WiSE) formulations, such as 1 m Zn(TFSI)2+ 20 m LiTFSI, 1 m Zn(Ac)2+ 31 m KAc, and 0.5 m Zn(C104)2+ 18 m NaCICL, have relatively low Zn2+concentrations (2-8% of the total salt content), resulting in higher overpotentials (>0.1 V) for Zn electrodeposition. Low Zn2+concentrations in WiSEs may cause kinetic bottlenecks, localized heating, and uneven Zn nucleation, promoting dendrite formation. Additionally, the high viscosity of these electrolytes exacerbates mass transport limitations, leading to concentration polarization that restricts ion diffusion, impairs charge transfer, and raises cell impedance. Despite considerable research on water content and solvation structure in Zn-based electrolytes, the direct relationship between Zn salt concentration and Zn anode stability in WiSEs remains inadequately understood, warranting further investigation.Vanadium oxide-based cathodes offer significant advantages in aqueous Zn-ion batteries (AZIBs) due to their high theoretical capacity and ability to host multiple ions during charge and discharge cycles, which enhances the overall energy density. Their unique structural properties, including layered and tunnel-like architectures, facilitate efficient ion diffusion and electron transport, making them suitable for applications that require rapid charge and discharge. Additionally, these cathodes exhibit good redox reversibility, contributing to stable cycling performance. However, a critical challenge arises from the dissolution of vanadium species in aqueous electrolytes, which can lead to capacity degradation over time. Therefore, maintaining the structural integrity of the cathode throughout multiple chargedischarge cycles is essential for ensuring long-term cyclic performance.

[0010] EP3896762A1 discloses metal perchlorate-based aqueous electrolytes a secondary aqueous battery featuring a cathode material composed of graphene, metal oxides, and carbon nanotubes. It further highlights an electrolyte composition containing zinc perchlorate Zn (C1O4)2 and lithium perchlorate Li (CICL), which collectively contribute to Coulombic efficiency.

[0011] US11245133B2 relates non-aqueous electrolyte secondary energy storage cells. The invention further relates to a lithium rich cathode comprising a layered or spinel oxide material and a lithium metal anode. The invention also discloses a non - aqueous liquid electrolyte comprising an organic solvent and at least one lithium imide salt. The invention includes a high energy density, high power lithium metal anode rechargeable battery and a liquid and / or solid electrolyte, capable of discharging faster than 1 C at room temperature, and more than 200 cycles until 80 % capacity retention.

[0012] In addressing the challenges associated with Zn anode stability and vanadium dissolution, in the present invention, a hybrid organic / inorganic electrolyte has been formulated that minimizes free solvent molecules, alters the Zn anode surface chemistry, controls Zn deposition behaviour, and mitigates vanadium dissolution in vanadium oxide-based cathodes with layered graphene analogue’s structure.Developing long-term, high-performance aqueous zinc batteries (AZBs) suitable for large-scale energy storage remains a challenging task. A key factor in achieving this goal is the integration of electrode material innovation with electrolyte compatibility. To address the issue of vanadium dissolution in the battery system, a dual-ion electrolyte has been developed to stabilize the solvation structure and minimize vanadium solubility. This innovative electrolyte design incorporates Zn2+and Li+ions to form anion-rich solvation networks that preferentially coordinate with Zn2+. This approach effectively reduces the dissolution of vanadium and improves the stability of the electrolyte, thereby protecting the cathode material and suppressing side reactions that could degrade the battery’s performance.

[0013] An additional improvement in electrolyte safety involves the incorporation of flameretardant co-solvents or additives. While organic phosphates, such as trimethyl phosphate (TMP) and triethyl phosphate (TEP), have been used to improve thermal stability in lithium-ion batteries, their excessive use can lead to unwanted passivation layers on the anode, thereby hindering battery performance. To overcome this issue, blending water with a fire-retardant solvent mitigates localized thermal effects caused by high Li salt concentrations. This electrolyte composition also reduces the availability of free water molecules, which helps minimize vanadium dissolution and suppress hydrogen evolution reactions (HER). As a result, Zn anode stability is enhanced, cycling life is prolonged, and Coulombic efficiency is improved. Furthermore, the modified electrolyte enhances the redox kinetics of the vanadiumbased cathode, leading to more efficient charge and discharge cycles and better capacity retention. These improvements collectively contribute to a longer battery lifespan and greater reliability.

[0014] This dual-ion electrolyte features a precisely controlled Zn salt concentration of x mol and a Li salt concentration in a 1 :2 ratio, optimized for enhanced performance. The system incorporates a balanced mixture of 50% water and 50% fire-retardant solvent, ensuring a stable solvation structure and minimizing side reactions. The adjusted Zn2+molar ratio improves ion transport kinetics, facilitates uniform Zndeposition, and reduces dendrite formation, thereby improving cycling performance.

[0015] This approach systematically explores the relationship between Zn2+concentration, electrolyte composition, and anode cycling stability, with a focus on optimizing water content. By fine-tuning solvation dynamics and electrolyte properties, this research aims to establish a strategic framework for designing advanced Zn-based aqueous batteries that balance high energy density, rapid charge-discharge capabilities, and extended operational lifespans.

[0016] The optimized dual-ion electrolyte with a blended solvent not only stabilizes the Zn anode and vanadium oxide cathode materials but also ensures the long-term efficiency and performance of Zn-ion batteries.

[0017] OBJECTIVE OF THE INVENTION

[0018] One object of the present invention is to provide a dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery. More particularly the objective of the present invention is to provide a dual ion water-in-salt hybrid electrolyte composition comprising zinc and lithium salt dissolved in solvent mixture. The solvent mixture herein is mixture of water and co-solvent and wherein co-solvent is trimethyl phosphate (TMP). Said co-solvent enhance ionic conductivity and charge transport.

[0019] Another object of the present invention is to provide a cathode for zinc-ion battery fabricated from V2O5 and oxidizing agent. The oxidizing agent is selected from group consisting of TEMPO, hydrogen peroxide and mixture thereof.

[0020] Yet another object of the present invention is to provide a Zn ion battery with atleast one cathode that is synthesized using commercial V2O5 and at least one oxidizing agent and wherein an electrolyte composition comprises of zinc and lithium salts dissolved in solvent mixture. The solvent mixture herein is mixture of water and atleast one cosolvent.

[0021] Another object of the present invention is to provide a zinc-ion battery showing excellent Zn plating / stripping behaviour, maintaining stable cycling for 1986 hours wherein Zn / / Zn symmetric cells cycled at a current density of 2 mA cm2.Another objective of the present invention is to provide a zinc-ion battery where cycle life extends to about 10000 cycles with a Coulombic efficiency (CE) of 100% when water:TMP is in 50:50 ratio and Zn:Li is in 2:4 ratio in the dual ion water-in-salt hybrid electrolyte composition for said zinc-ion battery.

[0022] SUMMARY OF THE INVENTION

[0023] In one aspect of the invention, the present invention provides a dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery, comprising: a) zinc salt; b) lithium salt; c) a co-solvent; and d) water. The dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery employs trimethyl phosphate (TMP) as the cosolvent. The dual ion water-in-salt hybrid electrolyte composition of the present invention discloses series of water: trimethyl phosphate percent ratio. The percent ratio of 50:50 of water and co-solvent in the composition is able to demonstrate the best performance, with redox peaks at 0.42 / 0.72 V and 0.89 / 1.06 V, indicating optimal ion transport and stability. This electrolyte balanced the solvation dynamics of Zn2+with rapid ionic conductivity, minimizing polarization and overpotential. In this electrolyte with a Zn / Li salt ratio of 2:4, electrode achieved a high specific capacity upto 445 mAh / g at a current density of 0.5 A / g, demonstrating superior electrochemical stability and performance. This observation highlights the superiority of the TMP-50 electrolyte in improving Zn-ion mobility, reducing polarization, and enhancing cycling stability, making it a promising candidate for high-performance Zn-ion batteries.

[0024] In another aspect of the invention, there is provided a low-cost cathode fabricated from V2O5 and oxidizing agent. The oxidizing agent is selected from group consisting of TEMPO, hydrogen peroxide and mixture thereof. More particularly, the oxidizing agent is selected from group consisting of TEMPO and hydrogen peroxide. In another embodiment, TEMPO is tetramethylpiperidin-l-oxyl or 2,2,6,6-tetramethylpiperidinl-yl)oxidanyl.

[0025] Said cathode enables monoclinic layered structure resulting in improve conductivity and facilitate phase transitions. Flaky nanosheets that are uniformly stacked, forming an interconnected network with an average thickness of 10.5 nm.This well-defined sheet-like structure increases the surface area and exposure of active sites, benefiting electrochemical applications, particularly for Zn-ion batteries. The surface-controlled mechanism, where Zn2+ions interact with the electrode material via fast surface redox reactions, supports high-rate performance and rapid charge / discharge kinetics, making low-cost cathode of the present invention is ideal for high-power applications.

[0026] In yet another aspect of the present invention, there is provided a method of preparation of a dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery and a low-cost scalable cathode for zinc-ion battery fabricated from V2O5 and oxidizing agent.

[0027] In yet another aspect the present invention provides a Zn-ion battery comprising a) one zinc anode b) one cathode and c) an electrolytic composition. The cathode is synthesized using commercial V2O5 and at least one oxidizing agent and wherein an electrolyte composition comprises of dissolving zinc and lithium salts in water and atleast one co-solvent and wherein the co-solvent is trimethyl phosphate. The zinc-ion battery of the present invention shows excellent Zn plating / stripping behaviour in Zn / / Zn symmetrical cells with a duration of 1986 hours at a current density of 2 mA / cm2 and assembled full cell using cathode maintaining stable cycle life of 10000 cycles and Coulombic efficiency (CE) of 100% at a current density of 5A / g.

[0028] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 shows the XRD patterns of VOT and VOH samples.

[0031] Fig. 2 shows the Raman spectroscopic studies of VOH and VOT samples.

[0032] Fig. 3 shows XPS Spectroscopic studies (a) and (b) V2p and Ols spectra of VOH respectively; (c) and (d) V2p and Ols spectra of VOT samples respectively.Fig. 4 shows SEM micrographs: (a) and (b) VOH; (c) and (d) VOT; (e) VOM and (f) Cycled VOT

[0033] Fig. 5 shows (a) Comparison CV profiles of VOT Cathode in various electrolytes at 1 mV / s (b) Charge discharge profiles of VOT cathode in various electrolytes at 0.5 A / g (c) Comparison of CD curves obtained at 0.5 A / g for VOH and VOT cathodes in TMP 50 electrolyte (2:4 ratio of Zn / Li salt) respectively, & CD curves of VOT cathode obtained in 1:1 ratio of Zn / Li salt, (d) and (e) CV curves obtained for VOT in TMP50 at various scan rates and Log ip vs. log (scan rate) graph respectively, (f) EIS spectra of VOT sample in various electrolytes.

[0034] Fig. 6 shows the charge-discharge profiles of VOT cathode in various electrolytes at various current densities (a) TMP50, (b) TMP30 (c) Zn(OTf)2 and (d) ZnSO4. Fig.7 shows the rate capability profiles of VOT cathode in various electrolytes. Fig.8 shows cycle life stability and coulombic efficiency performance of VOT cathode in different electrolytes, (a) Cycle life performance (b) Coulombic efficiency (CE).

[0035] Fig.9 shows the (a) Energy density vs Power density plot using VOT cathode, (b) Galvanostatic charge-discharge profiles of Zn / / Zn symmetric cells obtained for TMP50, Zn(OTf)2 and ZnSO4 at current density of 2 mA cm-2

[0036] Fig. 10 shows the LSV curves of VOT.

[0037] Fig. 11 SEM images of cycled zinc anodes after 50 cycles (a)TMP 50 (b) ZnSO4 (c) Zn(OTf)2

[0038] DESCRIPTION OF THE INVENTION

[0039] Definitions

[0040] For convenience, before further description of the present invention, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0041] The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.

[0042] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps. The term “binder” refers to the polymeric substance that provides adhesion and mechanical integrity to some extent, to the active material when loaded on a current collector to obtain an electrode. In the present invention, binder includes but not limited to polytetrafluoroethylene (PTFE), fluoroethylene vinyl ether (FEVE), polyvinylidene fluoride (PVDF).

[0043] The term “cathode” refers to a positive electrode which is a battery electrode comprising: (a) at least one active material; (b) at least one primary conductive carbon having (c) at least one conductive additive (d) at least one binder.

[0044] The term “conductive carbon” refers to the carbon-based additive added to an electrode composition to enhance the conductivity of the electrode. In the present invention, the conductive carbon is selected from group comprising of multi-walled carbon nanotubes (MWCNTs), Ketjen black, carbon black or acetylene black. The term “conductive additive” refers to the carbon-based additive added to an electrode composition to enhance the conductivity of the electrode in addition to the multi-walled carbon nanotubes. In the present invention, the conductive carbon is selected from group comprising of Super P or KS6L.

[0045] The term “conductive carbon mixture” refers to the mixture of carbon-based additive added to an electrode composition to enhance the conductivity of the electrode. In the present invention, the conductive carbon mixture is mixture of multi -walled carbon nanotubes (MWCNTs) and Super P. The conductive carboncomposition coated on the electrode surface, gives better contact between the particles.

[0046] The term “oxidizing agent” refers to compounds that oxidise other substances and participates in the chemical reactions. In the present invention the oxidizing agents is catalyst selected from the group consisting of TEMPO, hydrogen peroxide and mixture thereof. More preferably in the present invention the oxidizing agents are catalyst selected from the group consisting of TEMPO and hydrogen peroxide. In another embodiment, TEMPO is tetramethylpiperidin-l-oxyl or 2, 2, 6, 6-tetramethylpiperidinl-yl)oxidanyl. In the present invention, morphology and size of the nanosheets in active materials were carefully tailored by varying the oxidizing agents during the hydrothermal reaction. Said compound regioselectively oxidize the sample and the resultant hydrogel sample.

[0047] The term “VOT” refers to cathode active material of the present invention that is synthesized using commercial V2O5 and, TEMPO and H2O2 as oxidizing agent / catalyst via a hydrothermal method.

[0048] The term “VOH” refers to cathode active material of the present invention that is synthesized using commercial V2O5 and H2O2 as oxidizing agent / catalyst via a hydrothermal method.

[0049] The term “co-solvent” refers to flame-retardant additives in the electrolyte composition. In the present invention blending water with a fire-retardant solvent helps to inhibit localized thermal effects caused by high Li salt concentrations. The present invention provides an optimized dual-ion electrolyte with blended solvent enhances both Zn anode and vanadium oxide cathode performance by preventing material degradation, stabilizing electrochemical reactions, and ensuring the longterm efficiency of Zn-ion batteries. The co-solvent used in the present invention is trimethyl phosphate (TMP).

[0050] The term “TMP50” refers to the dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery wherein the composition has water: trimethyl phosphate ratios in the proportions of 50:50 and labelled as TMP 50. The trimethyl phosphate is employed as a cosolvent to restructure hydrogen bonds with water.This selection is driven by TMP's advantageous properties, including low viscosity, fire resistance, and a high Gutmann donor number, which collectively enhance ion transport stability, solubility, and overall electrochemical performance.

[0051] The term “TMP30” refers to the dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery wherein the composition has water: trimethyl phosphate ratios in the proportions of 70:30 and labelled as TMP30.

[0052] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

[0053] The term “Coulombic efficiency” (CE), also called faradaic efficiency or current efficiency, describes the charge efficiency by which electrons are transferred in batteries. CE is the ratio of the total charge extracted from the battery to the total charge put into the battery over a full cycle. It is generally measured in percentage (%).

[0054] The term “cycle number” indicates that if capacity falls by a set value (10 % or 20 % is customary), the actual number of cycles indicates the cycle-life of the capacitor. In general, commercial capacitors can be cycled for hundreds of thousands of cycles.

[0055] As discussed in the background section, there is a need in the art to develop efficient battery electrode exhibits high conductivity, better performance in aspects of improved discharge capacity, initial coulombic efficiency, capacity retention, and improved performance at high C rates. In conventional system the longevity of Zn anodes in aqueous electrolytes are often hindered by undesired hydrogen evolution, which exacerbates dendritic growth and leads to the formation of inactive Zn deposits and a hydrated solvation structure. This process promotes proton reduction, triggering the hydrogen evolution reaction (HER) and accelerating electrolyte degradation. The persistent release of hydrogen gas not only depletesthe electrolyte but also generates internal pressure, which can compromise electrode integrity. These effects ultimately reduce Coulombic efficiency, limit reversibility, and hinder the long-term cycling stability of Zn-based batteries. Addressing these challenges is crucial for the practical advancement of Zn-based aqueous energy storage systems.

[0056] Accordingly, the present invention provides a dual ion water-in-salt hybrid electrolyte composition, a low-cost scalable cathode for zinc-ion battery fabricated from V2O5 and oxidizing agent and method of producing the same and a zinc-ion battery comprising at least one cathode synthesized using commercial V2O5 and at least one oxidizing agent and dual ion water-in-salt hybrid electrolyte composition. Said electrolyte composition further comprises of Zn and Li salts dissolved in solvent wherein said solvent is mixture of water and atleast one co-solvent.

[0057] Strategies for Enhancing Zn Anode Stability

[0058] To suppress hydrogen evolution and enhance the stability of Zn anodes, electrolyte engineering has focused on reducing water reactivity and restructuring the Zn2+solvation environment. A key approach involves the adoption of highly concentrated electrolytes (HCEs) or water-in-salt electrolytes (WiSEs), where an increased salt-to water ratio minimizes the presence of free water molecules. This disruption of the bulk hydrogen-bonding network alters Zn2+coordination dynamics, leading to the integration of anions (e.g., SO42, CL, TFSI ) within the solvation shell.

[0059] By replacing a fraction of the water molecules with anions, this modified solvation structure reduces proton availability, thereby limiting hydrogen evolution pathways. Additionally, anion-rich environments facilitate more uniform Zn deposition, mitigating dendritic growth and improving Zn plating / stripping efficiency. Consequently, Zn anodes in such electrolyte systems demonstrate enhanced reversibility, higher Coulombic efficiency, and extended cycle life, addressing key challenges in aqueous Zn-based battery technologies.

[0060] Influence of Electrolyte Composition on Zn DepositionEnhancing Zn salt concentration in electrolytes has been found to shift Zn2+reduction to a more favourable potential, effectively suppressing hydrogen evolution and broadening the electrochemical stability window. The increased overpotential required for HER on-Zn metal further reduces parasitic side reactions, thereby improving Zn plating efficiency. A low Zn2+concentration in WiSEs can introduce kinetic bottlenecks, induce localized heating, and promote uneven Zn nucleation, which accelerates dendrite formation.

[0061] Vanadium oxide-based cathodes demonstrate good redox reversibility, which contributes to their stable cycling performance. Their unique structural properties, such as layered and tunnel-like architectures, promote efficient ion diffusion and electron transport, making them suitable for applications requiring fast charge and discharge capabilities. However, a key challenge is the dissolution of vanadium species in aqueous electrolytes, which can lead to capacity degradation over time. So, maintaining the cathode’s structure over multiple charge-discharge cycles is also essential to obtain long term cyclic performance. It requires a well -integrated approach that balances electrode material development with electrolyte compatibility.

[0062] To tackle the issue of vanadium dissolution, a dual-ion electrolyte system has been engineered to stabilize the solvation structure and minimize vanadium solubility. The strategic incorporation of Zn2+and Li+ions encourage the formation of anion-rich solvation networks that preferentially coordinate with Zn2+, effectively restricting vanadium dissolution and enhancing electrolyte stability. This approach not only protects the cathode material but also suppresses side reactions that could compromise battery performance.

[0063] One effective strategy to enhance electrolyte safety is incorporating flame-retardant cosolvents or additives. In lithium-ion batteries, organic phosphates have been utilized to improve thermal stability. However, excessive use of phosphate-based solvents, such as trimethyl phosphate (TMP) and triethyl phosphate (TEP), has been found to hinder battery performance by forming unwanted passivation layers on the anode.Additionally, blending water with a fire-retardant solvent helps to inhibit localized thermal effects caused by high Li salt concentrations. The electrolyte composition also reduces free water molecule availability, thereby limiting vanadium dissolution and mitigating hydrogen evolution reactions (HER). This suppression of side reactions enhances Zn anode stability, prolongs cycling life, and improves Coulombic efficiency. Moreover, the modified electrolyte promotes faster redox kinetics in the vanadiumbased cathode, leading to more efficient charge / discharge cycles and superior capacity retention. These advancements collectively contribute to extended battery lifespan and reliability.

[0064] In essence, an optimized dual-ion electrolyte with blended solvent enhances both Zn anode and vanadium oxide cathode performance by preventing material degradation, stabilizing electrochemical reactions, and ensuring the long-term efficiency of Zn-ion batteries.

[0065] Optimized Dual-Ion Electrolyte for Enhanced Zn Anode Stability

[0066] To address the challenges associated with Zn anode stability and vanadium dissolution effects, a concentrated and hybrid organic / inorganic electrolytes have shown potential in reducing free solvent molecules, altering Zn anode surface chemistry, controlling Zn deposition behaviour and vanadium dissolution in layered graphene analogues vanadium oxide-based cathode.

[0067] The present invention provides a dual-ion electrolyte formulation with a precisely controlled Zn salt concentration of x mol and a Li salt concentration in a 1 :2 ratio. This electrolyte system incorporates a balanced mixture of 50% water and 50% fire-retardant solvent, providing a stable solvation structure while minimizing side reactions. The carefully adjusted Zn2+molar ratio enhances ion transport kinetics and facilitates uniform Zn deposition, effectively reducing dendrite formation and improving cycling performance.

[0068] This study systematically explores the interplay between Zn2+concentration, electrolyte composition, and anode cycling stability, with a particular emphasis on optimizing water content. By fine-tuning solvation dynamics and electrolyte properties, the present invention aims to establish a strategic framework fordesigning advanced Zn-based queous batteries that achieve an optimal combination of high energy density, rapid charge-discharge capability, and prolonged operational lifespan.

[0069] Accordingly, in one embodiment, the invention provides a dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery, comprising:

[0070] a) zinc salt ;

[0071] b) lithium salt ;

[0072] c) a co- solvent; and

[0073] d) water.

[0074] In one embodiment, the dual ion water-in-salt hybrid electrolyte composition comprises of zinc salt. In another embodiment, said zinc salt is zinc perchlorate hexahydrate.

[0075] Yet in another embodiment, the dual ion water-in-salt hybrid electrolyte composition comprises of lithium salt. In another embodiment, said lithium salt is lithium perchlorate salt.

[0076] In one embodiment, the dual ion water-in-salt hybrid electrolyte composition comprises of Zn: Li ratio is 2:4.

[0077] In another embodiment, the dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery comprises of water and co-solvent.

[0078] In a preferred embodiment, said co-solvent is trimethyl phosphate (TMP).

[0079] In one embodiment, in hybrid electrolyte water: TMP ratios is in the proportions of 50 / 50. In another embodiment, the hybrid electrolyte water: TMP ratios is in the proportions of 70 / 30.

[0080] In yet another embodiment, said hybrid electrolytes with water: TMP ratios in the proportions of 50 / 50 is labelled as TMP50. In another embodiment, the hybrid electrolytes water:TMP ratios in the proportions of 70 / 30 is labelled as TMP30. In one embodiment, the TMP based hybrid electrolytes labelled as TMP 50 exhibited superior battery performance compared to TMP30, maintaining a stable liquid state without phase separation. Thus, the optimised TMP -based dual ionhybrid electrolyte demonstrates significant potential as a high-performance electrolyte for zinc-ion batteries.

[0081] According to one aspect, the present invention provides a method of preparation of dual ion water-in-salt hybrid electrolyte composition, comprising steps;

[0082] a) preparing a solvent mixture of water and trimethyl phosphate;

[0083] b) dissolving Zinc perchlorate hexahydrate with lithium perchlorate salts in solvent mixture of step a) maintaining a stable liquid state without phase separation to obtain the electrolyte for zinc ion battery.

[0084] In another embodiment, the method of preparation of dual ion water-in-salt hybrid electrolyte comprises zinc perchlorate salts and lithium perchlorate salts.

[0085] In another embodiment, the method of preparation of dual ion water-in-salt hybrid electrolyte comprises zinc perchlorate hexahydrate and lithium perchlorate.

[0086] In another embodiment, the zinc perchlorate hexahydrate in said electrolyte composition ranges from 0.5 M to 5M. In another embodiment, the concentration of lithium perchlorate salts ranges from IM to 10M.

[0087] In another embodiment, the concentration of zinc perchlorate hexahydrate is 2M and the concentration of lithium perchlorate is 4M.

[0088] Yet in another preferred embodiment, dual ion water-in-salt hybrid electrolyte has Zn: Li ratio of 2:4.

[0089] In another embodiment, the method of preparation of dual ion water-in-salt hybrid electrolyte comprises dissolving zinc perchlorate hexahydrate and lithium perchlorate in the solvent mixture of water and trimethyl phosphate (TMP).

[0090] In one exemplary embodiment, the water: TMP ratios is in the proportions of 50 / 50 (labelled as TMP50). In another exemplary embodiment, the hybrid electrolytes water:TMP ratios is in the proportions of 70 / 30 (labelled as TMP30).

[0091] In one embodiment, the dual ion water-in-salt hybrid electrolyte with water: trimethyl phosphate ratio of 50:50 (TMP50) exhibits higher discharge capacity, indicating efficient Zn2+transport and favourable electrolyte-cathode interactions.In another embodiment, the dual ion water-in-salt hybrid electrolyte TMP50 exhibit enhanced performance in both charge and discharge cycles suggesting that its optimized solvation structure enhances Zn-ion mobility, improves charge transfer efficiency, and mitigates undesirable side reactions. This distinct electrochemical behaviour observed across different electrolytes underscores the importance of electrolyte selection in stabilizing Zn-ion intercalation / extraction processes and prolonging battery lifespan.

[0092] In another aspect of the present invention, there is provided a low-cost scalable cathode for zinc-ion battery.

[0093] In one embodiment, a low-cost scalable cathode for zinc-ion battery is Grapheneanalogous hydrated vanadium oxide (GA-V2O5 nEEO). In another embodiment, said low-cost scalable cathode for zinc-ion battery is fabricated from V2O5 and catalyst. In another embodiment, the catalyst is an oxidizing agent. In yet another embodiment, the oxidizing agent of the low-cost cathode is selected from group consisting of TEMPO, hydrogen peroxide (H2O2) and mixture thereof. In yet another embodiment, the oxidizing agent of the low-cost cathode is TEMPO. In an exemplary embodiment, TEMPO is 2,2,6,6-tetramethylpiperidin-l-oxyl. In yet another embodiment, the oxidizing agent is H2O2.

[0094] In yet another embodiment, the oxidizing agent of the low-cost cathode is a mixture of TEMPO andH2O2.

[0095] In an exemplary embodiment, the low-cost cathode having 2, 2,6,6-tetramethylpiperidin-l-oxyl and H2O2 as oxidizing agent is labelled as VOT. In another exemplary embodiment, VOT has optimized composition of TEMPO and H2O2. In another exemplary embodiment, the optimized composition is prepared by mixing TEMPO in H2O2.

[0096] In another exemplary embodiment, the low-cost cathode prepared using hydrogen peroxide as oxidizing agent is labelled as VOH. In yet another embodiment, VOH is made from optimized composition of H2O2.

[0097] In another embodiment, the H2O2 in optimized composition for VOT and VOH is 30% H2O2In another embodiment, the concentration range of TEMPO in optimized composition for VOT preparation is between 2 - 200 mg. In another embodiment, the concentration of H2O2 in optimized composition for VOT preparation ranges from 5-15 ml of 30% H2O2.

[0098] In another embodiment, the concentration of H2O2 in optimized composition for VOH preparation ranges from 5-15 ml of 30% H2O2.

[0099] In another embodiment, the optimized composition for preparing VOT is made from 100 mg TEMPO and 5 ml of 30% H2O2. In another embodiment, the optimized composition for preparing VOH is made 15 ml of 30% H2O2.

[0100] According to another aspect, the invention provides a method of preparation of a lowcost cathode, comprising steps;

[0101] a) dissolving commercial V2O5 powder in deionized (DI) water with constant stirring, sonicating the solution for 30 minutes and yielding a yellowish orange solution;

[0102] b) adding to the solution of step a) to previously dissolved oxidizing agent in deionized (DI) water and homogenizing the solution;

[0103] c) adding the solution of step b) to a base solution under continuous stirring under ambient conditions to obtain a dark red wine solution;

[0104] d) subjecting the solution of step c) to hydrothermal treatment at 200 °C for 8 hours in a muffle furnace to obtain a hydrogel sample;

[0105] e) collecting the hydrogel sample of step d) upon cooling to room temperature and aging said hydrogel for 12 hrs;

[0106] f) washing the resultant product of step e) successively with solvent, using filtration and centrifugation techniques to ensure thorough purification to obtain a green coloured product;

[0107] g) drying the product of step f) in a vacuum oven at 80 °C for 12 hours;

[0108] h) mixing product of step g) with 15% of multi -walled carbon nanotubes (MWCNTs) + 10% Super P and subjecting to ultrasonication for 90 minutes; i) drying and optimizing the product of step h) in the presence of a binder.wherein the solvent in step f) is water and ethanol.

[0109] In one embodiment, the oxidizing agent employed in the method of preparation of the low-cost cathode is selected from group consisting of TEMPO, hydrogen peroxide and mixture thereof.

[0110] In yet another embodiment, the oxidizing agent is TEMPO. In an exemplary embodiment, TEMPO is tetramethylpiperidin-l-oxyl.

[0111] In yet another embodiment, the oxidizing agent employed in the method of preparation of the low-cost cathode is hydrogen peroxide (H2O2).

[0112] In yet another embodiment, the oxidizing agent is mixture of TEMPO and H2O2. In an exemplary embodiment, the low-cost cathode prepared using 2, 2,6,6-tetramethylpiperidin-l-oxyl and H2O2 as oxidizing agent is labelled as VOT. In another exemplary embodiment, VOT has optimized composition of TEMPO and H2O2. In another exemplary embodiment, the optimized composition is prepared by mixing TEMPO in H2O2.

[0113] In another exemplary embodiment, the low-cost cathode prepared using hydrogen peroxide as oxidizing agent is labelled as VOH. In another embodiment, VOH is made from optimized composition of H2O2.

[0114] In another embodiment, the H2O2 in optimized composition for VOT and VOH is 30% H2O2.

[0115] In another embodiment, the concentration range of TEMPO in optimized composition for VOT preparation is between 2 - 200 mg. In another embodiment, the concentration of H2O2 in optimized composition for VOT preparation ranges from 5-15 ml of 30% H2O2.

[0116] In another embodiment, the concentration of H2O2 in optimized composition for VOH preparation ranges from 5-15 ml of 30% H2O2.

[0117] In another embodiment, the optimized composition for preparing VOT is made from 100 mg TEMPO and 5 ml of 30% H2O2. In another embodiment, the optimized composition for preparing VOH is made from 15 ml of 30% H2O2.In a preferred embodiment, the method of preparing the low-cost cathode involves varying the constituent ratios, with the active material ratio ranging from 60 % to 80%, the primary carbon additive ratio ranging from 5% to 25%, the secondary carbon additive ratio ranging from 1% to 10% and the binder ratio ranging from 5% to 10%.

[0118] In another exemplary embodiment, the primary carbon additive is MWCNTs and the secondary carbon additive is Super P.

[0119] In yet another exemplary embodiment, the binder is polyvinylidene fluoride (PVDF).

[0120] According to the present invention, the low-cost cathode is prepared by adding 65 % of active material, 15% of primary carbon additive, 10 % of the secondary carbon additive and 10 % of binder.

[0121] In another embodiment, the optimized final electrode obtained has 65% of active material, 25% of conductive carbon mixture (MWCNTs 15% + Super P 10%) and 10% of binder. The resulting electrode exhibits enhanced ion transport and reactivity, potentially improving the material’s performance in energy storage and catalytic applications in Zn-ion batteries.

[0122] According to one aspect, the present invention provides a Zn-ion battery comprising;

[0123] a) one zinc anode;

[0124] b) one cathode and

[0125] c) an electrolytic composition

[0126] wherein at least one cathode is synthesized using commercial V2O5 and at least one oxidizing agent and wherein an electrolyte composition comprises of zinc perchlorate hexahydrate and lithium perchlorate dissolved in solvent mixture. In one embodiment, the solvent mixture is water and atleast one co-solvent.

[0127] In another embodiment, the oxidizing agent is selected form group consisting of TEMPO, hydrogen peroxide (H2O2) and mixture thereof.In yet another embodiment, the oxidizing agent is TEMPO. In an exemplary embodiment, TEMPO is 2,2,6,6-tetramethylpiperidin-l-oxyl.

[0128] In yet another embodiment, the oxidizing agent is H2O2.

[0129] In yet another embodiment, the oxidizing agent is mixture of TEMPO and H2O2. In an exemplary embodiment, the low-cost cathode prepared using 2, 2,6,6-tetramethylpiperidin-l-oxyl and H2O2 as oxidizing agent is labelled as VOT. In another exemplary embodiment, VOT is made from optimized composition of TEMPO and H2O2. In another exemplary embodiment, the optimized composition is prepared by mixing TEMPO in H2O2.

[0130] In another exemplary embodiment, the low-cost cathode prepared using hydrogen peroxide as oxidizing agent is labelled as VOH. In another exemplary embodiment, VOH is made from optimized composition of H2O2.

[0131] In another embodiment, the H2O2 in optimized composition for VOT and VOH is 30% H2O2.

[0132] In another embodiment, the concentration range of TEMPO in optimized composition for VOT is between 2 - 200 mg. In another embodiment, the concentration of H2O2 in optimized composition for VOT ranges from 5-15 ml of 30% H2O2.

[0133] In another embodiment, the concentration of H2O2 in optimized composition for VOH ranges from 5-15 ml of 30% H2O2.

[0134] In another exemplary embodiment, the optimized composition for VOT is made from lOOmg of TEMPO in 5 ml of 30% H2O2. In another embodiment, the optimized composition for VOH is made from 15 mL of 30% H2O2.

[0135] In an exemplary embodiment, the electrolyte composition has water: co-solvent ratio of 50:50. In yet another exemplary embodiment, the electrolyte composition has water: co-solvent ratio of 70:30.

[0136] In yet another exemplary embodiment, the co-solvent is trimethyl phosphate. In yet another embodiment, the electrolyte composition has Zn:Li ratio of 2:4.In one embodiment, the zinc-ion battery when water: trimethyl phosphate is in 50:50 ratio the Zn / / Zn symmetric cells at a current density of 2 mA cm2shows excellent Zn plating / stripping behaviour, maintaining stable cycling for over 1986 hours.

[0137] In another embodiment, the zinc-ion battery when water: trimethyl phosphate is in 50:50 ratio and Zn:Li is in 2:4 ratio the cycling life is extended to 10000 cycles with a Coulombic efficiency (CE) of 100%.

[0138] EXAMPLES

[0139] Example 1: Preparation of cathode material

[0140] The invention provides a low-cost scalable preparation method for V10O24.12H2O. The characteristic features show Graphene-analogous hydrated vanadium oxide (GAV2O5 nEEO) which was synthesized using commercial V2O5, 2, 2, 6, 6- tetramethylpiperidin-l-oxyl (TEMPO) and / or H2O2 via a hydrothermal method. In the initial synthesis stage, 0.8 g of commercial V2O5 powder was dissolved in 50 mL of deionized (DI) water with constant stirring and sonication for 30 minutes, yielding a yellowish-orange solution characteristic of V2O5. Subsequently, 0.1 g of TEMPO was added to 10 mL of DI water followed by 5 mL of 30% H2O2 and homogenized. The TEMPO solution was then added to the base solution, which played a crucial role in influencing the morphology of the V2O5 nanosheets. Continuous stirring under ambient conditions resulted in a homogeneous mixture, accompanied by a distinct colour change to dark red wine. The prepared solution was then transferred to a Teflon-lined autoclave with 60-70% of its 100 mL volume capacity and subjected to hydrothermal treatment at 200 °C for 8 hours in a muffle furnace. The use of TEMPO as a catalyst regioselectively oxidize the sample and the resultant hydrogel sample was collected upon cooling to room temperature and aged for 12 hrs. The resulting product underwent successive washing with deionized water and ethanol, using filtration and centrifugation techniques to ensure thorough purification. The final product, exhibiting a green coloration, was dried in a vacuum oven at 80 °C for 12 hours and labelled as VOT. Similarly, the VOM sample is prepared to identify morphologicalchanges using 0.1 g of TEMPO alone. Additionally, for comparison the synthesis of the sample with 15 mL of 30% H2O2 as oxidizing agent was also carried out through similar procedure. The obtained product was dried overnight in vacuum drier and the sample is labelled as VOH.

[0141] Example 2: Preparation of Electrode

[0142] For electrode preparation multi-walled carbon nanotubes (MWCNTs) were incorporated to enhance the electrical conductivity of VOT and VOH samples. The VOT or VOH samples were mixed with 15% of MWCNTs + 10% Super P and subjected to ultrasonication for 90 minutes. The final material was obtained by drying the mixture overnight in vacuum yielding a conductive sample suitable for further applications.

[0143] Table 1 : Electrode preparation using VOT / VOH cathode material

[0144] Components VOT VOH MWCNTs Super P Binder (PVDF)) Concentration 65% 65% 15% 10 % 10%

[0145] (%)

[0146]

[0147] Table 2 : Optimized final electrode

[0148] Components VOT VOH Conductive carbon mixture Binder MWCNTs Super P (PVDF) (15%) (10%) Concentration in the final 65% 65% 25% 10% product (% )

[0149]

[0150] The final electrodes were optimized to have 65% VOT (or) VOH, 25% conductive carbon mixture (15% of MWCNTs + 10% Super P) and 10% binder.

[0151]

[0152] 3:

[0153] The invention provides the optimized electrolyte chemistry which effectively addresses critical challenges, such as water solidification and solid-electrolyte interphase (SEI)- related kinetic limitations. The electrolyte of the present inventionis designed where trimethyl phosphate (TMP) was employed as a cosolvent to restructure hydrogen bonds with water. This selection was driven by TMP's advantageous properties, including low viscosity, fire resistance, and a high Gutmann donor number, which collectively enhance ion transport stability, solubility, and overall electrochemical performance. A series of TMP / water-in-salt hybrid electrolytes was utilized in this study. Zinc perchlorate hexahydrate and lithium perchlorate salts were dissolved in water to induce strong ion-water interactions that disrupt the hydrogen-bond network, effectively preventing water solidification. Additionally, the perchlorate ion (CIO4 ), with its chemical stability, enables the electrolyte to operate within an extended voltage range without decomposition, thus enhancing battery performance. The zinc metal component mitigates dendrite growth, while Li+ions improve ionic conductivity and regulate the electrolyte's interaction with water. To prepare the formulation 2 M zinc perchlorate hexahydrate and 4 M lithium perchlorate was dissolved in water, with varying volume ratios of TMP. Among the tested formulations, TMP based hybrid electrolytes with WaterTMP ratios in the proportions of 50 / 50 and 70 / 30 labelled as TMP 50 and TMP30 respectively exhibited superior battery performance, maintaining a stable liquid state without phase separation. In contrast, other high concentration of TMP with water: TMP of 30 / 70 compositions experienced crystallization or solidification issues. Further it was also identified that the Zn:Li ratio is optimized to 2:4 gave the best result. Thus, the optimised TMP -based dual ion hybrid electrolyte demonstrates significant potential as a high-performance electrolyte for zinc-ion batteries.

[0154] Table 3: Electrolyte compositions

[0155] Water 1 %) triniethyl phosphate zinc lithium perchlorate (TMP) (%) perchlorate

[0156] hexahydrate

[0157] TMP50 50 50 2M 4M

[0158] TMP30 70 30 2.M 4M.

[0159] 2M ZnSO< (aq.) 100 0 0 0

[0160] 3M ZnfOtfp (aq ) 100 0 0 0

[0161]

[0162] Preparation of ZnSO4 and Zn(OTf)2 electrolyte is widely available in the art. For the purpose of present invention, the ZnSO4 and Zn(OTf)2 electrolytes were prepared by the method known in the art.

[0163] Example 4: Electrochemical measurements

[0164] Cyclic voltammetry (CV) curves, Galvanostatic charge-discharge profiles and electrochemical impedance data were acquired using electrochemical workstations (POTENTIOSTAT, AMETEK- Versa STAT 3). Cycle life tests were conducted utilizing NEW ARE battery testing systems (BTS4000 5V6A, Shenzhen, China). All GCD measurements for VOT / / Zn cells were performed within a voltage window of 0.20-1.60 V vs. Zn / Zn2+.

[0165] RESULTS

[0166] 1. X-ray diffraction analysis

[0167] Figure 1 shows the XRD patterns of VOT and VOH samples. The crystal structure and phase composition of the synthesized vanadium oxide were characterized using powder X-ray diffraction (PXRD). The diffraction peaks at 29 values of 6.5°, 13°, 15.5°, 19.3°, 25.6°, 25.9°, 30.8°, 31.3°, 33.2°, 34°, 34.5°, 46.8°, 49.8°, 50.2°, 59.9°, 61.3°, and 61.7° were indexed to the crystallographic planes (002), (004), (-202), (006), (110), (111), (- 402), (0010), (-406), (-310), (311), (510), (-518), (-3113), (-422), (-3117), and (-716), respectively. These results confirm the monoclinic layered structure of Bariandite, belonging to the C2 / c space group. Furthermore, the diffraction pattern aligns closely with the JCPDS standard file No. 25-1006. The dominant (002) reflection indicates a preferential growth orientation of the synthesized material along the (002) plane, exhibiting a widened and broadened profile with an interlayer spacing of 13.5 A for VOT sample whereas the interplanar spacing for the VOH sample is 11.5 A. The broad peak, associated with low crystallinity, is highly conducive to the insertion and extraction of Zn2+ions, facilitating rapid diffusion of intercalated zinc ions within the Zn-ion battery system.

[0168] 2. Raman spectroscopic studies of VOH and VOT samplesThe Raman spectral analysis of the synthesized VOT and VOH samples (Figure 2) exhibits characteristic peaks at 146, 288, 409, 546, 690, and 992 cm ', corresponding to distinct V-0 bond vibrations. These features can be categorized into two regions based on frequency. The low-frequency region (<200 cm ') is dominated by vanadium atom displacements, with a prominent peak at 149 cm1attributed to the in-phase oscillation of vanadium, 0(2), and 0(3) atoms along the b-axis, representing the Bsg shear-like distortion mode. In the mid- and high-frequency region (200-900

[0169]

[0170] cm peaks at 290, 413, and 691 cm1are observed. The 290 cm1peak corresponds to the Big ladder-like distortion mode, characterized by in-phase oscillation of vanadium and 0(2) atoms combined with out-of-phase oscillation of 0(3) atoms along the b-axis. The 413 cm1and 546 cm1peak arises from the bending vibrations of bridging V-O-V bonds and from the vibration of the V-O2 linkages, while the 691 cm1peak is associated with stretching vibrations of V-0 bonds. Finally, the high-frequency peak at 992 cm1is attributed to the tensile stretching mode of the V=O double bond, confirming the layered structure of V2O5. These Raman features, along with the presence of oxygen vacancies, suggest enhanced voids and nucleation centers that facilitate phase transitions. The findings are consistent with XPS analysis, indicating mixed valence states (V4+ / V5+), which improve the material’s conductivity.

[0171] 3. XPS Spectroscopic studies of VOH and VOT samples

[0172] Results demonstrated in Figure 3 shows XPS spectra: (a) and (b) V2p and Ols spectra of VOH respectively; (c) and (d) V2p and Ols spectra of VOT samples respectively. The XPS spectrum of the VOH sample (Fig. a) exhibits a weak shoulder peak at -515.4 eV, assigned to the V2ps / 2 signal of V4+, likely originating from VO2 like species within the mixed-valence structure. The dominant peaks at -516.7 eV and -517.0 eV correspond to V5+, indicating two distinct chemical environments. In contrast, the XPS spectrum of the VOT sample (Fig. c) suggests that the material synthesized via TEMPO oxidation predominantly consists of V5+species, with a notable contribution from V4+. These findings are consistent with the Raman data, reinforcing the presence of mixedvalence vanadium species. The splitting of the V5+peak into two components (-516.7 eV and -517.0 eV) can beattributed to differences in local coordination environments and hydration effects. In hydrated vanadium oxides, V5+can adopt both octahedral and distorted tetrahedral geometries, leading to small variations in binding energy. The poly oxovanadate framework of Vw024 12ILO accommodates both V5+and V4+, with structural defects, water incorporation, and surface hydroxylation contributing to the observed XPS features. Additionally, hydrothermal synthesis can induce subtle shifts in binding energy due to oxygen vacancies or defect states, further influencing the electronic structure. The V 2piA region, which arises due to spinorbit coupling, also supports this oxidation state distribution. It exhibits two deconvoluted peaks at -522.2 eV (V4+) and -524.0 eV (V5+), consistent with the mixed-valence nature of the material. The -7.5-7.8 eV spin-orbit splitting between the V 2ps / 2 and V 2piA levels confirms the presence of vanadium in oxidation states ranging from +4 to +5, with the higher binding energy of V5+reflecting its more oxidized coordination environment. In the O Is region from Fig (b) and (d), the primary peak at -529.4 eV corresponds to V-0 bonding in vanadium oxides, while a minor peak at -530.5 eV is attributed to chemisorbed -OH, C=O species from atmospheric exposure, or residual organic oxygenates. Additionally, the peak at -532.0 eV corresponds to interlayer water molecules. A comparison of peak intensities indicates that the VOT sample exhibits a higher concentration of defects than the VOH sample. These defects, likely oxygen vacancies or hydroxylated surface species, may enhance ion transport and reactivity, potentially improving the material’s performance in energy storage and catalytic applications.

[0173] 4. Morphological studies

[0174] Figure 4 demonstrates the SEM micrographs for VOH (Fig. 4(a) and 4(b)) and VOT (Fig. 4(c) and 4(d)). The morphology and size of the VOH and VOT nanosheets were carefully tailored by varying the oxidizing agent / catalyst during the hydrothermal reaction. In the TEMPO-assisted hydrothermal process with regulated concentration of H2O2, the SEM images (Fig. (c) and (d)) reveal thin, flaky nanosheets that are uniformly stacked, forming an interconnected network with an average thickness of 10.5 nm. This well-defined sheet-like structurefacilitates enhanced surface area and exposure of active sites, which can be beneficial for electrochemical applications.

[0175] In contrast, the VOH sample synthesized using an ILCh-based reagent exhibits a more aggregated morphology (Fig (a) and (b)), where the nanosheets are less uniformly distributed and appear to be densely packed. These nanosheets show an increased average thickness of 13.8 nm, suggesting a variation in the nucleation and growth mechanism under different oxidation conditions. The increased stacking and aggregation in the FhCh-based sample could potentially affect ion transport and electrolyte accessibility, influencing its functional properties. Fig. 4(e) displays granulated particles along with flaky sheets, indicating the impact of TEMPO treatment alone. Meanwhile, Fig. 4(f) illustrates the surface morphology of the cycled VOT cathode, which appears uniform and free from significant stress-related damage. The incorporation of CNTs likely contributes to mechanical stability, preventing structural degradation during cycling.

[0176] 5. Electrochemical characterizations: VOT cathode performance comparison using hybrid dual ion electrolyte and various zinc ion-based electrolytes The CV curve comparison of VOT in various electrolytes reveals distinct shifts in the redox peak positions. These shifts provide valuable insights into the ion storage mechanism in different environments, highlighting variations in behaviour across the electrolytes. Comparative CV analysis of VOT in different Electrolytes is shown in Figure 5(a)

[0177] Table 4 - Comparative CV analysis of VOT in different ElectrolytesElectrolyte Reduction Oxidation Peaks Key Observation*

[0178] Peaks (V) (V)

[0179] ZnSO'. 0.52, 0.86 0.74, 1 07 Strong Zn?' solvation

[0180] leads to higher

[0181] crveipotential

[0182] Zti(OTfh 047, 0.90 0.67, 1.05 Weaker Zir's

[0183] solvauoti reduces

[0184] oveipotential.

[0185] TMP-50 0.42, 0.89 0.72, 1.06 Best ion transport & (Li'-fZMT stability, optimal 50:50 TMP / vvater ratio.

[0186] TMPV-ater)

[0187] TMP-30 0.43, 0.90 Q.69. 1.03 Higher water content

[0188] (Li’tZir*, slightly weakens 30:70 kinetics.

[0189] TMP'walerl

[0190]

[0191] The cyclic voltammetry (CV) curves of VOT exhibit two distinct pairs of redox peaks in all electrolytes, confirming multiple Zn2+insertion / extraction processes. In the ZnSO4 electrolyte, the redox peaks at 0.52 / 0.74 V and 0.86 / 1.07 V (vs. Zn2+ / Zn) indicate strong Zn2+interaction with the vanadium oxide framework. The higher reduction potential suggests that Zn2+solvation is more pronounced in this electrolyte due to the high charge density of SO42, making Zn2+de-solvation before intercalation more energy-intensive. This results in increased overpotential and slower reaction kinetics. In contrast, in the Zn(OTf)2 electrolyte, the redox peaks shift to 0.47 / 0.67 V and 0.90 / 1.05 V (vs. Zn2+ / Zn), indicating slightly weaker Zn2+solvation compared to ZnSCk The triflate (OTf ) anion has a lower charge density, reducing Zn2+solvation strength and facilitating easier Zn2+de-solvation. Consequently, Zn(OTf)2 shows improved Zn2+insertion / extraction kinetics and reduced polarization.

[0192] Trimethyl phosphate (TMP) plays a crucial role in Zn2+solvation and de-solvation dynamics. TMP has a lower dielectric constant than water, which weakens Zn2+solvation and allows easier Zn2+de-solvation before intercalation. While water enables fast ion transport, excessive water content increases Zn2+solvation energy, leading to higher overpotential and reduced efficiency. TMP-50 (50:50 TMP / H2O) exhibits redox peaks at 0.42 / 0.72 V and 0.89 / 1.06 V (vs. Zn2+ / Zn), indicating an optimal balance between Zn2+de-solvation (due to TMP) and fast ionic conductivity(due to water). This balance enhances electrochemical kinetics and reduces polarization, improving reaction efficiency and stability. The smaller peak separation (AV) signifies lower charge transfer resistance and superior redox reversibility. Additionally, Li+incorporation modifies the local electronic environment, lowering the energy barrier for Zn2+insertion and further stabilizing the redox behaviour.

[0193] In contrast, TMP-30 (30:70 TMP / H2O) exhibits redox peaks at 0.43 / 0.69 V and 0.90 / 1.03 V (vs. Zn2+ / Zn), suggesting slightly slower kinetics due to the higher water content. Increased water content enhances Zn2+solvation, making desolvation before intercalation more energy-intensive. This results in a larger peak separation and slightly higher overpotential. The peak shifts in TMP-30 also reflect a weaker interaction between Zn2+and the vanadium oxide structure, reducing electrochemical efficiency.

[0194] The superior performance of TMP-50 can be attributed to its optimized Zn2+desolvation, which reduces the solvation barrier while maintaining fast ionic conductivity. The lower charge transfer resistance, as evidenced by the smaller peak separation, suggests improved electron and ion transport. The presence of Li+stabilizes the vanadium oxide framework and enhances redox reversibility. Furthermore, TMP-50 minimizes water-induced parasitic reactions, improving long-term cycling stability.

[0195] Overall, TMP-50 outperforms TMP-30 due to its optimized solvent ratio, which facilitates Zn2+de-solvation, reduces overpotential, and enhances stability. The peak shifts in TMP-30 result from its higher water content, which increases Zn2+solvation strength, slowing insertion / extraction kinetics. With lower charge transfer resistance, improved redox reversibility, and enhanced Zn2+ / Li+intercalation, TMP-50 demonstrates superior electrochemical performance.

[0196] The Charge discharge profiles of VOT cathode in various electrolytes

[0197] The charge-discharge (CD) profiles in the figure illustrate the electrochemical behaviour of the VOT-based cathode in different electrolyte compositions (Figure 5(b)) The characteristic CD curves exhibit a multi-step voltage profile, reflectingthe sequential Zn-ion intercalation / de-intercalation process within the layered vanadate framework. During the discharge, an initial rapid voltage drop occurs, followed by a distinct plateau region and a gradual voltage recovery. This suggests a multi-phase reaction mechanism, involving Zn2+insertion into interlayer sites and structural reorganization of the vanadate framework. The steady-state region corresponds to Zn2+intercalation, while the voltage recovery phase indicates partial structural relaxation or re-equilibration of the cathode. Notably, the electrolyte composition significantly affects the voltage profile. TMP50 (black curve) exhibits a well-defined plateau and higher discharge capacity, indicating efficient Zn2+transport and favourable electrolyte-cathode interactions. ZnSCh (green curve) shows an earlier voltage decay, suggesting higher polarization, side reactions, or slower Zn-ion diffusion kinetics which lead to least specific capacity. Zn(OTf)2 (red curve) and TMP30 (blue curve) display intermediate behaviour, implying varying Zn-ion solvation structures and charge transfer kinetics. Further during the charging, the Zn2+extraction (deintercalation) process occurs in multiple steps, reflected by distinct voltage plateaus or sloped regions. The gradual voltage increase suggests a diffusion-controlled Zn-ion extraction process, influenced by electrolyte composition and electrode structure. The higher charge voltage in ZnSO4 suggests increased over potential, possibly due to poor Zn-ion transport and increased charge transfer resistance. The TMP50 electrolyte exhibits a more reversible charge process, with minimal polarization and a well-defined voltage profile, indicating better electrolyte-cathode compatibility. The absence of severe voltage hysteresis in TMP50 further suggests improved Zn-ion kinetics and lower interfacial resistance. The superior performance of TMP50 in both charge and discharge cycles suggests that its optimized solvation structure enhances Zn-ion mobility, improves charge transfer efficiency, and mitigates undesirable side reactions. This distinct electrochemical behaviour observed across different electrolytes underscores the importance of electrolyte selection in stabilizing Zn-ion intercalation / extraction processes and prolonging battery lifespan. The findings emphasize that electrolyte engineering is crucial for improving Zn / VOT battery performance. Hybrid electrolytes like TP50 enhance charge-discharge efficiency,reduce polarization, and improve cycle stability, making them promising candidates for high-performance Zn-ion batteries.

[0198] Charge-discharge profiles of the VOT sample in TMP -50 electrolyte

[0199] Figure 5 (c) presents the charge-discharge profiles of the VOT sample in the TMP-50 electrolyte, as well as an electrolyte formulated using zinc perchlorate and lithium perchlorate in a 1 : 1 molar ratio, dissolved in a 50:50 vol% mixture of TMP and water.

[0200] The results indicate that the VOT electrode in the TMP-50 electrolyte, with a Zn / Li salt concentration ratio of 2:4, delivers a high specific capacity of 445 mAh / g. In comparison, the electrolyte containing Zn / Li salts in a 1:1 ratio exhibits a lower specific capacity of 390 mAh / g. Additionally, the VOH electrode in the bestperforming TMP50 electrolyte achieves only 366 mAh / g, with significantly higher overpotential and polarization resistance, which likely hinders charge transfer kinetics and reduces overall electrochemical performance. This suggests that the optimized Zn / Li ratio in the TMP-50 electrolyte may enhances ionic conductivity and electrochemical stability.

[0201] Cyclic voltammetry curves or cyclo-voltammograms (CV) curves of VOT at various scan rates

[0202] Figure 5(d) shows the cyclic voltammetry (CV) curves of hydrated vanadium oxide (VOT) recorded at various scan rates (0.2, 0.4, 0.6, 0.8, and 1 mV / s). These curve reveal multiple redox peaks, which confirm the presence of Zn2+insertion / extraction processes in the electrode material. As the scan rate increases, the peak currents (i) also increase, and a slight shift in the peak potentials is observed. This shift can be attributed to the increased polarization at higher scan rates, which affects the electrochemical kinetics.

[0203] To further understand the charge storage mechanism, a log-log relationship between the peak current (i) and the scan rate (v) is analyzed (Fig 5(e)) using the power-law equation:

[0204] 1

[0205]

[0206] - a V6where i is the peak current, v is the scan rate, a is a constant, and b is the exponent that provides insight into the charge storage mechanism. The value of b can be determined from the slope of the linear fit in the plot of log(i) versus log(v).

[0207] The b-values calculated for the four redox peaks are 0.91, 1.00, 0.87, and 0.86. These values are all close to 1, suggesting that the electrochemical reaction is predominantly surface-controlled. A b-value of 1 typically indicates a capacitive or pseudocapacitive charge storage mechanism, where charge accumulation occurs primarily through fast surface redox reactions rather than slow bulk diffusion. The near-surface-controlled behaviour implies that Zn2+ions interact with the electrode material via rapid surface adsorption / desorption and interfacial redox processes rather than undergoing deep intercalation into the bulk lattice. This characteristic is advantageous for achieving high-rate performance, as surface-dominated reactions generally enable faster charge / discharge kinetics compared to bulk diffusion-controlled processes.

[0208] Additionally, the relatively stable peak positions across different scan rates further indicate that the charge storage mechanism remains consistent, reinforcing the conclusion that the redox reactions in VOT are predominantly governed by surface-controlled kinetics. This behaviour makes hydrated vanadium oxide a promising material for applications requiring high-power density and rapid charge / discharge capabilities, such as zinc-ion batteries and super capacitors.

[0209] EIS Spectroscopic studies

[0210] From the Nyquist plot (Figure 5 (f)), the electrochemical behaviour of the VOT-Zn system varies with electrolyte composition, influencing charge transfer resistance and ion diffusion. The hybrid electrolyte, TMP50 (black curve), shows a semicircle followed by a diffusion tail, indicating moderate charge transfer resistance. Despite slightly higher charge transfer resistance, TMP5 than TMP30 balances ion transport and charge transfer, improving Zn2+diffusion and electrochemical stability. Its mixed organic-aqueous nature reduces passivation, lowers solution resistance, and improves wettability, leading to better Zn deposition morphology. The incorporation of Li+alongside Zn2+further enhances solvation control, acceleratesdesolvation, and promotes a more uniform Zn plating / stripping process. Li+also improves ionic conductivity and reaction kinetics, enhancing cyclability. On the other hand, ZnSO4 and Zn(OTf)2 exhibit lower initial charge transfer resistance due to their dissociated Zn2+, their performance is limited by poor ion transport, Zn2+solvation, and uncontrolled Zn deposition, leading to high polarization, dendrite formation, and shorter cycle life.

[0211] Although TMP50 has higher viscosity than aqueous electrolytes, which can increase charge transfer resistance, its optimized solvation structure, dual-ion system, and cosolvents enhance ionic conductivity and charge transport. Improved wettability ensures uniform ion distribution, reducing polarization effects. These factors allow TMP50 to sustain higher current densities and faster charge / discharge rates, outperforming purely aqueous electrolytes and making it a promising candidate for advanced energy storage applications.

[0212] The variation in Warburg slopes for different electrolytes reveals the transition from capacitive-dominated charge storage to diffusion-controlled behaviour. A nearvertical slope (90°) indicates surface-controlled ion adsorption / desorption, characteristic of capacitive charge storage. Zn(OTf)2 exhibits a slightly lower slope, suggesting a fast charge transfer process with minor diffusion limitations due to its weaker Zn2+solvation, facilitating easier de-solvation and intercalation. ZnSC , with stronger Zn2+solvation, shows a further decrease in slope, implying moderate diffusion constraints. TMP30 (30:70 TMP / water) increases the diffusion-controlled contribution due to higher water content, which enhances Zn2+solvation and raises the energy required for de-solvation, slowing Zn2+insertion / extraction. TMP50 (50:50 TMP / water) exhibits a Warburg slope close to 45°, signifying classical semiinfinite diffusion behaviour. The optimized TMP-to-water ratio in TMP50 balances Zn2+de-solvation and ionic transport, resulting in improved charge transfer kinetics but bulk diffusion-dominated storage.

[0213] Overall, these trends highlight how electrolyte composition affects electrochemical performance, with Zn(OTf)2 favouring fast capacitive storage and TMP50 promoting bulk Zn2+intercalation, making it suitable for long-term cycling stability.6. Electrolyte-Dependent Charge-Discharge Behaviour at Various Current Densities

[0214] The charge-discharge (CD) profiles of the VOT cathode were evaluated in different electrolytes (TMP50, TMP30, Zn(OTf)2, and ZnSO4) at current densities ranging from 0.5 A / g to 10 A / g to assess their influence on Zn-ion storage, transport kinetics, and electrochemical performance.

[0215] TMP50 electrolyte (Hybrid Electrolyte, High Performance)

[0216] The VOT cathode in TMP50 electrolyte demonstrates a high specific capacity of 440 mAh / g at 0.5 A / g, with minimal capacity fading across all current densities (Figure 6(a)). The charge-discharge curves show well-defined voltage plateaus, indicating stable Zn2+intercalation / deintercalation kinetics and strong electrolytecathode compatibility. At the highest current density (10 A / g), the capacity retains at 345 mAh / g, suggesting fast Zn-ion diffusion, low polarization, and efficient charge transfer. The minimal voltage hysteresis even at higher current densities highlights the optimized Zn2+solvation structure, which enables smooth ion transport and reduced internal resistance.

[0217] TMP30 Electrolyte (Intermediate Performance)

[0218] The charge-discharge profiles in TMP30 electrolyte exhibit relatively stable voltage plateaus but with moderate polarization effects as current density increases (Figure 6(b)). At 0.5 A / g, the specific capacity is 400 mAh / g, which is slightly lower than TMP50 but still superior to aqueous-based electrolytes. As the current density increases to 10 A / g, the capacity decreases gradually to 335 mAh / g, suggesting moderate charge transfer limitations and slightly restricted Zn2+transport compared to TMP50. The capacity retention remains good, but the increase in overpotential at high current densities suggests slower ion diffusion kinetics, making TMP30 a slightly less efficient electrolyte than TMP50.

[0219] Zn(OTf)2 Electrolyte (Moderate Performance)

[0220] The initial specific capacity in Zn(OTf)2 electrolyte is 385 mAh / g at 0.5 A / g, which is lower than both TMP50 and TMP30 (Figure 6(c)). The electrochemical profile remains stable, but higher overpotentials are observed as current density increases,indicating moderate Zn-ion transport kinetics. At the highest current density (10 A / g), the specific capacity drops to 330 mAh / g, which is lower than TMP50 and TMP30, implying increased internal resistance and reduced charge storage efficiency. The broader voltage hysteresis at higher rates suggests that the Zn2+solvation and mobility in Zn(OTf)2 electrolyte are not as optimized, leading to slightly increased charge transfer resistance.

[0221] ZnSO4 Electrolyte (Lowest Performance, Severe Polarization)

[0222] The ZnSCL electrolyte exhibits the lowest electrochemical performance, with an initial capacity of 410 mAh / g at 0.5 A / g (Figure 6(d)). The charge-discharge profiles show irregular voltage plateaus, particularly at higher current densities, indicating sluggish Zn-ion transport and increased polarization. As the current density increases, the capacity drops drastically, reaching only 108 mAh / g at 10 A / g, which is significantly lower than the other electrolytes. Severe polarization effects and voltage instability suggest poor Zn-ion transport, high electrolyte resistance, and possible structural degradation of the VOT cathode. The significant capacity decay may be attributed to electrolyte decomposition, side reactions, or Zn dendrite formation, leading to reduced battery efficiency and cycle life.

[0223] 7. Rate-capability performance of VOT cathode in various electrolytes The results in Figure 7 illustrates the rate capability of the cathode in various electrolytes. As the current density increases from 0.5 A / g to 10 A / g, the specific capacity varies as follows:

[0224] • TMP50 electrolyte: Capacity decreases from 444 mAh g1to 350 mAh g but recovers to 447 mAh g1when the current density is reduced back to 0.5 A / g.

[0225] • TMP30 electrolyte: Capacity varies from 400 mAh g1to 338 mAh g with a recovery to 398 mAh g1at 0.5 A / g.

[0226] • Zn(OTf)2 electrolyte: Capacity ranges from 386 mAh g1to 333 mAh g retaining 356 mAh g1upon returning to 0.5 A / g.

[0227] • ZnSCL electrolyte: Capacity drops significantly from 302 mAh g1to 122 mAh g with only partial recovery to 227 mAh g1at 0.5 A / g.The rate performance results indicate that the electrolyte compositions of the present invention, TMP50 and TMP30, exhibit superior capacity retention, demonstrating enhanced Zn-ion transport kinetics and improved electrode stability compared to conventional electrolytes.

[0228] 8. Cycle life stability and Coulombic efficiency performance of VOT cathode in different electrolytes

[0229] The cycle life stability of the VOT cathode was evaluated at 5A / g in different electrolytes (TMP50, TMP30, Zn(OTf)2, and ZnSO4), revealing significant variations in capacity retention and long-term electrochemical performance. The observed differences arise due to electrolyte-cathode interactions, Zn2+solvation structures, side reactions, and structural stability of the electrode material.

[0230] I. Cycle life performance

[0231] TMP50 Electrolyte - Exceptional Long-Term Stability

[0232] The initial capacity of the electrode is -for first 20 cycles is gradually increased to 350 mAh / g and a steep increment to 380 mAh / g over the first 300 cycles due to an activation phase that enhances Zn-ion intercalation sites and improves electrochemical reversibility. Over the long term, the capacity stabilizes at 337 mAh / g after 10000 cycles, retaining nearly 100% of the initial capacity, demonstrating exceptional electrochemical stability. This superior performance is attributed to an optimized Zn2+solvation structure that enhances ion transport while minimizing unwanted side reactions, strong cathode-electrolyte compatibility that prevents electrode degradation, and minimal dendrite formation and electrolyte decomposition, leading to high reversibility and prolonged cycle life.

[0233] TMP30 Electrolyte - Moderate Stability (2000 Cycles)

[0234] The initial capacity of the cell is 290 mAh / g, but it gradually declines to 278 mAh / g after 2000 cycles, after which the cell fails. This capacity fading occurs due to moderate Zn-ion diffusion and charge transfer limitations over repeated cycles. Additionally, the cell exhibits higher internal resistance compared to TMP50, leading to increased polarization during prolonged cycling. Another contributing factor is the structural instability of the cathode, as repeated Zn2+intercalation anddeintercalation result in the loss of active material, ultimately compromising the cell’s performance.

[0235] Zn(OTf)2 Electrolyte - Limited Cycle Life (300 Cycles)

[0236] The (OTf)? electrolyte exhibits a limited cycle life of 300 cycles. Initially, it delivers a capacity of 329 mAh / g, which declines to 300 mAh / g after 300 cycles before failure occurs. This capacity fading is primarily attributed to moderate Zn-ion transport kinetics, which hinder long-term performance. Additionally, increased overpotential and sluggish Zn-ion mobility lead to higher electrochemical polarization, further exacerbating the degradation. Over time, electrolyte decomposition and the formation of irreversible byproducts contribute to reduced stability, ultimately limiting the lifespan of the electrolyte.

[0237] ZnSO4 Electrolyte - Severe Capacity Loss (5000 Cycles)

[0238] The initial capacity of the battery is 360 mAh / g; however, it experiences an abrupt decay, dropping below 200 mAh / g within 100 cycles and further declining to just 22 mAh / g at 5000 cycles, ultimately leading to failure. This rapid capacity degradation is primarily attributed to poor Zn2+transport kinetics, which hinder efficient ion movement. Additionally, severe electrolyte decomposition and side reactions generate insulating by products that obstruct ion transport. The formation of Zn dendrites further accelerates cell failure by causing short circuits and electrolyte depletion. Moreover, excessive Zn2+insertion and continuous side reactions lead to the structural collapse of the cathode, resulting in irreversible capacity loss.

[0239] Conclusion: TMP50 demonstrates outstanding stability, achieving an exceptionally high cycle life of 10000 cycles due to optimized Zn2+transport, minimal side reactions, and excellent cathode stability. In contrast, TMP30 performs moderately, lasting 200 cycles but exhibiting increasing polarization and capacity fading over time. Zn(OTf)2 has a relatively short cycle life, failing after 300 cycles due to moderate Zn-ion transport limitations and electrolyte degradation. ZnSCL performs the worst, experiencing severe capacity fading within 100 cycles and ultimately failing after 500 cycles due to poor Zn-ion mobility, electrolyte decomposition, and Zn dendrite formation. The results are demonstrated in Figure8(a). These findings underscore the critical role of electrolyte formulation in determining Zn-ion battery stability and longevity, highlighting the necessity of hybrid electrolytes like TMP50 for high-performance applications.

[0240] II. Coulombic efficiency (CE)

[0241] The coulombic efficiency (CE) of ZnSO4, Zn(OTf)2, TMP-30, and TMP-50 demonstrates varying stability across cycling Figure 8(b). ZnSO4 exhibits significant fluctuations in CE throughout the cycling process before the cell ultimately fails at approximately 5000 cycles. In contrast, Zn(OTf)2 maintains a relatively stable CE of -97-98%; however, the cell undergoes premature failure, lasting only around 300 cycles, likely due to electrode degradation or side reactions. TMP-30 and TMP-50 exhibit the highest CE of -99-100%, with superior long-term cycling stability. Specifically, TMP-30 retains stable performance up to -2000 cycles, while TMP-50 extends cycling life beyond 10000 cycles. The initially observed CE above 100% is likely due to electrolyte-mediated side reactions, capacitive contributions, or nonuniform Zn stripping, which stabilize over cycling. The near-ideal CE of 99-100% in TMP-30 and TMP-50 suggests enhanced Zn plating / stripping reversibility, effective suppression of side reactions, and the formation of a stable solid-electrolyte interphase (SEI), contributing to prolonged cycling stability.

[0242] 9. Electrochemical performance of zinc ion battery

[0243] Regone Plot

[0244] The Ragone plot (Figure 9 (a)) for the fabricated zinc ion battery demonstrates the energy-power trade-off, highlighting its electrochemical performance across different charge / discharge rates. At low power densities (350-1400 W / kg), the cathode delivers high energy densities (310-295.4 Wh / kg), indicating efficient Zn2+intercalation with minimal polarization losses. As power density increases beyond 2100 W / kg, the energy density gradually decreases (289.1 277.2 Wh / kg), suggesting kinetic limitations due to ionic transport resistance and electrode polarization. Despite this decline, the VOT cathode retains reasonable energy density even at ultra-high-power densities (>3500 W / kg), indicating possible pseudocapacitive contributions that enhance charge storage at high rates. Thisbehaviour suggests that surface-controlled charge storage mechanisms supplement bulk intercalation, enabling faster Zn2+transport and improved rate capability. Overall, the VOT / / Zn system exhibits a favorable balance of energy and power density, making it a promising candidate for high-energy aqueous Zn-ion batteries. Zinc / / Zinc Symmetrical cells in various electrolytes

[0245] The cycling performance of Zn symmetric cells was evaluated at a current density of 2 mA cm2(Figure 9(b)). The Zn / / Zn cells using the novel TMP electrolyte showed excellent Zn plating / stripping behaviour, maintaining stable cycling for over 1986 hours. Voltage-time profiles were used to compare polarization effects between the best performing TMP 50 electrolyte and conventional aqueous electrolytes (Zn(OTf)2- and ZnSO4) electrolytes exhibited unstable overpotentials, leading to short cycle lifetimes of 300 and 40 hr., respectively. In contrast, the TMP50 electrolyte provided the longest cycling stability. The improved performance of the TMP50 electrolyte is due to its balanced composition. Water ensures high Zn2+solubility, while the organic solvent reduces water activity, limiting unwanted side reactions. A small amount of free water in TMP50 enables fast ion exchange between C1O4 , water, and Li+, maintaining high ionic conductivity. In the TMP50 electrolytes, Zn2+ions are fully hydrated by dipolar water molecules, forming [Zn(OH2)<>]2. This interaction weakens the O-H bond in water, causing partial deprotonation and resulting in an acidic electrolyte (TMP50, pH -1). This is consistent with the slightly acidic nature of Zn(C104)2 (pH -5) and the hydration effect of Li+ . Moreover, the TMP50 electrolyte effectively reduces side reactions such as hydrogen evolution, corrosion, and passivation, which can interfere with Zn plating / stripping. These results highlight the TMP electrolyte potential to improve the stability of Zn-based batteries.

[0246] 10. Study of hydrogen evolution reaction (HER) process

[0247] The linear sweep voltammetry (LSV) curves for hydrogen evolution reaction (HER) in different electrolytes reveal distinct electrochemical behaviours based on their solvent compositions and ionic interactions (Figure 10). TMP-50, with a maximum current density of -10.5 mA / cm2, exhibits the lowest HER activity among the tested electrolytes. This is due to its balanced solvent ratio, which reduces wateractivity and limits proton availability for hydrogen evolution. The presence of TMP weakens Zn2+solvation, optimizing Zn plating / stripping but simultaneously suppressing HER. In contrast, TMP-30, with a slightly higher water content, shows a slightly greater HER current density of -13 mA / cm2. The increased availability of free water molecules enhances proton reduction, making HER more pronounced compared to TMP-50, yet still lower than in fully aqueous systems due to TMP’s influence.

[0248] ZnSO4, as a pristine aqueous electrolyte, facilitates a higher HER current density of - 15 mA / cm2. Without TMP, water remains fully available for proton reduction, leading to more significant hydrogen evolution. This increased HER activity is characteristic of conventional Zn2+electrolytes, where uncoordinated water molecules contribute to undesired side reactions, including HER and dendrite formation. However, the most aggressive HER is observed in the zinc tritiate electrolyte, reaching -43 mA / cm2. The tritiate anion alters the solvation structure and influences interfacial electrochemistry, promoting an environment where water molecules are more readily available for HER. The strong proton reduction kinetics in zinc tritiate lead to rapid hydrogen evolution, significantly increasing current density.

[0249] Overall, the trend in HER activity follows the order of TMP-50 < TMP-30 < ZnSO4 < Zn tritiate, where increasing water activity and changes in electrolyte solvation structure play a key role in determining HER kinetics. TMP -based electrolytes effectively suppress HER by limiting free water content, while aqueous ZnSO4 and triflate-based systems enhance HER due to stronger proton availability and interfacial effects.

[0250] Figure 11 shows the morphological studies on zinc anode after cycling. In Zn(OTf)2, where HER is most pronounced, SEM images depict large dendritic structures with vertically oriented flaky zinc sheets. This morphology suggests rapid and irregular zinc deposition, likely due to increased HER, which disrupts uniform plating and encourages high-surface-area structures. The high water content in Zn(OTf)2 contributes to intensified HER, further promoting dendritegrowth. For ZnSO4, which exhibits moderate HER activity, the deposition pattern shifts to mossy dendrites. This suggests a somewhat more controlled zinc growth compared to Zn(OTf)2, but HER-induced disturbances still lead to non-uniform deposition. The sulfate anions in the electrolyte affect solvation dynamics and ion transport, resulting in a different structural outcome. In contrast, TMP-50, associated with the lowest HER activity, exhibits homogeneous growth of zinc. The absence of significant dendritic or mossy structures suggests a more regulated plating process, attributed to reduced HER and optimized solvation effects. The TMP -based electrolyte alters the solvation environment, restricting free water activity and thereby minimizing HER, which supports smooth and uniform zinc deposition.

[0251] These findings emphasize the significant role of electrolyte composition in shaping HER kinetics and zinc deposition behaviour. Controlling HER can lead to more uniform zinc plating, reducing dendrite formation and enhancing the long-term stability of Znbased batteries.

Claims

I Claim:

1. A dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery, comprising of:a) zinc salt;b) lithium salt;c) a co-solvent; andd) waterwherein the co-solvent is trimethyl phosphate (TMP).

2. The electrolyte composition as claimed in claim 1, wherein the zinc salt is zinc perchlorate hexahydrate.

3. The electrolyte composition as claimed in claim 1, wherein the lithium salt is Lithium perchlorate salts.

4. The electrolyte composition as claimed in claim 1, wherein the percent ratio of Water and co-solvent is 50:50.

5. The electrolyte composition as claimed in claim 1, wherein the percent ratio of Water and co-solvent is 70:30.

6. The electrolyte composition as claimed in claim 1, wherein Zn: Li ratio is to 2:4.

7. A low-cost scalable cathode for zinc-ion battery fabricated from V2O5 and oxidizing agent.

8. The low-cost scalable cathode as claimed in claim 7, wherein the oxidizing agent is selected from TEMPO and hydrogen peroxide or a mixture thereof.

9. The low-cost scalable cathode as claimed in claim 8, wherein the TEMPO is tetramethylpiperidin-l-oxyl or 2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl.

10. A method for the preparation of a low-cost cathode, comprising the steps of;a) dissolving V2O5 powder in deionized (DI) water with constant stirring, b) sonicating the solution of step (a) for 30 minutes to obtain a yellowish-orange solution;c) dissolving oxidizing agent mixture in deionized (DI) water;d) adding solution of step (b) to the solution of step (c) and homogenizing the solution;e) adding the solution of step (d) to a base solution under continuous stirring under ambient conditions to obtain a dark red wine solution;f) subjecting the solution of step (e) to hydrothermal treatment at 200 °C for 8 hours in a muffle furnace to obtain a hydrogel sample;g) collecting the hydrogel sample of step (f) upon cooling to room temperature and aging said hydrogel for 12 hrs;h) washing the resultant product of step (g) successively with solvent, using filtration and centrifugation techniques to ensure thorough purification to obtain a green coloured product;i) drying the product of step (h) in a vacuum oven at 80 °C for 12 hours; j) mixing product of step (i) with 15% of multi -walled carbon nanotubes (MWCNTs) + 10% Super P and subjecting to ultrasonication for 90 minutes; and k) drying and optimizing the product of step (j) in the presence of a binder, wherein the solvent in step (h) is water and ethanol.

11. The method as claimed in claim 10, wherein the oxidizing agent is optimized concentration of TEMPO and H2O2 and wherein the optimized concentration is lOOmg TEMPO and 5mL of 30% H2O2.

12. The method as claimed in claim 10, wherein TEMPO is 2, 2,6,6- tetramethylpiperidin- 1-oxyl or 2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl.

13. The method as claimed in claim 10, wherein the oxidizing agent is TEMPO or hydrogen peroxide or a mixture of TEMPO and hydrogen peroxide.

14. The method as claimed in claim 10, wherein the product of step (K) has 65% of product of step (i), 25% conductive carbon mixture (15% of MWCNTs + 10% Super P) and 10% binder.

15. The method as claimed in claim 10, wherein said low-cost cathode is capable of retaining reasonable energy density of -277 Wh / Kg at ultra-high-power densities upto -3500 W / kg and wherein the maximum energy density of 315 Wh / Kg is retained at a power density of 350 W / Kg.

16. A method of preparing the dual ion water-in-salt hybrid electrolyte composition for a zinc-ion battery wherein the preparation of said electrolyte comprises the steps of;a) preparing a solvent mixture of water and trimethyl phosphate;b) dissolving Zinc perchlorate hexahydrate with lithium perchlorate salts in solvent mixture of step a) maintaining a stable liquid state without phase separation to obtain the electrolyte for zinc ion battery.

17. The method as claimed in claim 16, wherein water: trimethyl phosphate ratio is 50:50.

18. The method as claimed in claim 16, wherein water: trimethyl phosphate ratio is 70:30.

19. The method as claimed in claim 16, wherein the concentration of Zinc perchlorate hexahydrate ranges from 0.5 M to 5M and the concentration of lithium perchlorate salts is IM to 10M.

20. The method as claimed in claim 16, wherein the concentration of Zinc perchlorate hexahydrate is 2M and the concentration of lithium perchlorate salts is 4M.

21. The method as claimed in claim 16, wherein the ratio of Zn: Li is 2:4.

22. A zinc-ion battery, comprising:a) one zinc anode;b) one cathode; andc) an electrolytic composition,wherein at least one cathode is synthesized using commercial V2O5 and at least one oxidizing agent, wherein an electrolyte composition comprises of zinc perchlorate hexahydrate and lithium perchlorate salts dissolved in solvent wherein the solvent comprises of water and atleast one co-solvent.

23. The zinc-ion battery as claimed in claim 22, wherein oxidizing agent is selected from TEMPO and hydrogen peroxide or a mixture of TEMPO and hydrogen peroxide.

24. The zinc-ion battery as claimed in claim 22, wherein oxidizing agent is optimized concentration of TEMPO and H2O2 and wherein the optimized concentration is lOOmg TEMPO and 5mL of 30% H2O2.

25. The zinc-ion battery as claimed in claim 22, wherein TEMPO is tetramethylpiperidin- 1-oxyl or 2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl.

26. The zinc-ion battery as claimed in claim 22, wherein co-solvent is trimethyl phosphate.

27. The zinc-ion battery as claimed in claim 22, wherein when water: trimethyl phosphate is in 50:50 ratio the Zn symmetric cells at a current density of 2 mA cm2show excellent Zn plating / stripping behavior, maintaining stable cycling for over 1986 hours.

28. The zinc-ion battery as claimed in claim 22, wherein when water: trimethyl phosphate is in 50:50 ratio and Zn: Li ratio is in 2:4 ratio the Coulombic efficiency (CE) extends cycling life beyond 10000 cycles.

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